Regeneration method of titanium zeolite catalyst for propylene epoxidation

Abstract

The present invention relates to a process for the regeneration of a catalyst comprising a titanium-containing zeolite as catalytically active material, comprising introducing a feed stream comprising propylene, hydrogen peroxide or a hydrogen peroxide source and an organic solvent into a reactor containing a catalyst comprising a titanium-containing zeolite, subjecting the feed stream in the reactor to epoxidation conditions in the presence of a catalyst, removing a product stream comprising propylene oxide and an organic solvent from the reactor, stopping introduction of the feed stream, washing the catalyst with a liquid aqueous system, and calcining the washed catalyst.

Description

[0001] This application is a divisional application of a Chinese patent application filed on February 12, 2016, with application number 201680020837.X and invention name “Regeneration method of titanium zeolite catalyst for propylene epoxidation”.

[0002] The present invention relates to a method for regenerating a catalyst comprising a titanium-containing zeolite as catalytically active material, a regenerated catalyst and a continuous process for preparing propylene oxide.

[0003] In the past few years, a variety of titanium-containing zeolites have been developed which can be used to catalyze organic reactions such as the conversion of olefins to epoxides. For example, WO 98 / 55229 A1 discloses the preparation and use of titanium-containing zeolites for the epoxidation of olefins.

[0004] Titanium-containing zeolites are of great industrial interest and, in this context, economic and environmental considerations are of great importance. In the catalysis of organic reactions, efficient regeneration of such zeolites for subsequent reuse is highly preferred over replacement with fresh catalyst.

[0005] EP 1 221 442 A1 discloses the regeneration of a titanium zeolite catalyst for the epoxidation of olefins with hydrogen peroxide, the method comprising carrying out an epoxidation reaction, wherein the regeneration of the spent catalyst is carried out with hydrogen peroxide in the presence of the olefin, whereby the epoxidation reaction continues, and wherein the regeneration is achieved by reversing the feed direction of the hydrogen peroxide. Hydrogen peroxide is also a valuable starting material and is difficult to handle itself due to its tendency to spontaneously decompose.

[0006] WO 2005 / 000827 A1 discloses the regeneration of a titanium silicalite catalyst after a process of continuous epoxidation of propylene with hydrogen peroxide. The catalyst is periodically regenerated with a methanol solvent at a temperature of at least 100° C. Methanol is a valuable organic compound which requires expensive and time-consuming recovery. After regeneration, the epoxidation must be restarted at a higher temperature than with fresh catalyst in WO 2005 / 000827 A1.

[0007] WO 2007 / 013739 A1 discloses the regeneration of a titanium-containing molecular sieve catalyst, wherein after pre-treating the spent catalyst with water or ethanol, the catalyst thus pre-treated is contacted with a mixture comprising hydrogen peroxide, water and ethanol. Thus, the method comprises two mandatory and subsequent steps, wherein the spent catalyst is contacted with two different solutions. In addition, a mixture comprising hydrogen peroxide, water and ethanol needs to be treated.

[0008] It is therefore an object of the present invention to provide a simple and cost-effective process for the regeneration of a catalyst comprising a titanium-containing zeolite as catalytically active material for the epoxidation of olefins. Another object of the present invention is to provide a regenerated catalyst comprising a titanium-containing zeolite as catalytically active material which can be easily reused for the epoxidation of olefins.

[0009] The present invention therefore relates to a method for the regeneration of a catalyst comprising a titanium-containing zeolite as catalytically active material, comprising

[0010] (i) A stage comprising the following steps:

[0011] (a) continuously preparing propylene oxide, comprising

[0012] (a1) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0013] (a2) subjecting the feed stream of (a1) to epoxidation conditions in a reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0014] (a3) removing a product stream comprising propylene oxide and an organic solvent from the reactor;

[0015] (b) stopping the introduction of the feed stream into the reactor;

[0016] (c) washing the catalyst with a liquid aqueous system;

[0017] Stage (i) further comprises repeating the process of steps (a) to (c) n times, wherein n is an integer and is at least 1; the method for regeneration further comprises

[0018] (ii) a stage of calcining the catalyst obtained in (c) after repeating the sequence of steps (a) to (c) n times;

[0019] The process of stages (i) to (ii) is optionally repeated m times, wherein m is an integer and is at least 1, and wherein n is the same or different in each repetition of the process of stages (i) to (ii).

[0020] Surprisingly, according to the process of the present invention, regeneration of a catalyst comprising a titanium-containing zeolite as catalytically active material for the epoxidation of olefins can be achieved by washing the catalyst at least once with a liquid aqueous system in step (c) of stage (i) without subsequent calcination, wherein after said washing the catalyst exhibits the same or at least substantially the same catalytic activity as a corresponding fresh catalyst which has not been subjected to a calcination step, and wherein the result of the regeneration can even be enhanced by calcining the catalyst according to stage (ii) after one or more further washing steps.

[0021] Stage (i)

[0022] Stage (i) of the method of the invention comprises

[0023] (a) continuously preparing propylene oxide, comprising

[0024] (a1) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0025] (a2) subjecting the feed stream of (a1) to epoxidation conditions in a reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0026] (a3) removing a product stream comprising propylene oxide and an organic solvent from the reactor;

[0027] (b) stopping the introduction of the feed stream into the reactor;

[0028] (c) washing the catalyst with a liquid aqueous system;

[0029] Stage (i) further comprises repeating the process of steps (a) to (c) n times, wherein n is an integer and is at least 1.

[0030] Step (a1)

[0031] The feed stream of (a1) comprises propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent.

[0032] Hydrogen peroxide or a source of hydrogen peroxide

[0033] Both hydrogen peroxide and a source of hydrogen peroxide can be used as the epoxidizing agent in the feed stream of (a1).

[0034] In case hydrogen peroxide is used, it is preferred that the hydrogen peroxide is an aqueous hydrogen peroxide solution, wherein the solution preferably comprises 30 to 50% by weight of hydrogen peroxide, relative to the total amount of water.

[0035] It is also possible that hydrogen peroxide is formed in situ from hydrogen and oxygen in the reaction mixture in the presence of a suitable catalyst or catalyst system, for example in the presence of a titanium-containing zeolite which additionally comprises one or more noble metals or in the presence of a titanium-containing zeolite and a further catalyst comprising one or more noble metals, for example a noble metal supported on a suitable support such as charcoal or a suitable inorganic oxide or mixture of inorganic oxides.

[0036] For the preparation of hydrogen peroxide in the feed stream of (a1), the anthraquinone process can be used. This method is based on the catalytic hydrogenation of anthraquinone compounds to form corresponding anthrahydroquinone compounds, which are then reacted with oxygen to form hydrogen peroxide and then the hydrogen peroxide formed is extracted. The cycle is completed by the rehydrogenation of the anthraquinone compounds that have been formed again in the oxidation. A review of the anthraquinone process is given in "Ullmann's Encyclopedia of Industrial Chemistry" 5th edition, volume 13, pages 447 to 456. As an alternative, hydrogen peroxide can be obtained by anodic oxidation of sulfuric acid while releasing hydrogen at the cathode to produce peroxydisulfuric acid. The hydrolysis of peroxydisulfuric acid first forms peroxysulfuric acid, then forms hydrogen peroxide and sulfuric acid, which are then recovered. In another alternative, hydrogen peroxide can be directly obtained from elemental hydrogen and oxygen.

[0037] Preferably, hydrogen peroxide is used in the feed stream to (a1).

[0038] Organic solvents

[0039] The organic solvent used in (a1) is in principle all known solvents for this purpose. Preferred organic solvents are alcohols, nitriles and mixtures thereof, optionally also water. Preferably, the organic solvent is selected from methanol and acetonitrile. More preferably, the organic solvent is acetonitrile.

[0040] Feed flow (a1)

[0041] In general, the feed stream of (a1) can be prepared according to any conceivable method. Thus, the feed stream in (a1) can be prepared by mixing a stream comprising propylene, a stream comprising hydrogen peroxide or a source of hydrogen peroxide, and a stream comprising an organic solvent, which comprises sequentially mixing, i.e. mixing a stream comprising propylene with a stream comprising an organic solvent and mixing the resulting stream with a stream comprising hydrogen peroxide or a source of hydrogen peroxide.

[0042] Generally, the feed stream of (a1) has no limitation on the molar ratio of propylene to hydrogen peroxide or one equivalent of hydrogen peroxide produced by a hydrogen peroxide source. Preferably, the propylene in the feed stream of (a1) is present in a molar excess relative to the hydrogen peroxide or one equivalent of hydrogen peroxide produced by a hydrogen peroxide source. Preferably, the molar ratio of propylene to hydrogen peroxide or one equivalent of hydrogen peroxide produced by a hydrogen peroxide source in the feed stream of (a1) is from 1 to 1.6, more preferably from 1.1 to 1.55, more preferably from 1.2 to 1.5, more preferably from 1.40 to 1.45.

[0043] Typically, the feed stream of (a1) comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent has no restrictions as to the other components comprised in the feed stream. Thus, the feed stream of (a1) may further comprise at least one additional component, such as at least one potassium-containing salt.

[0044] Containing potassium salt

[0045] There are no particular restrictions on the chemical nature of the at least one potassium salt. Preferably, the at least one potassium salt is selected from at least one inorganic potassium salt, at least one organic potassium salt and a combination of at least one inorganic potassium salt and at least one organic potassium salt.

[0046] Preferred inorganic salts containing potassium include, but are not limited to, potassium halides such as potassium chloride or potassium bromide, potassium nitrate, potassium sulfate, potassium hydrogen sulfate, potassium hydroxide, potassium perchlorate, phosphorus-containing potassium salts such as potassium dihydrogen phosphate or dipotassium hydrogen phosphate or potassium phosphate or potassium pyrophosphate such as monobasic potassium pyrophosphate or dibasic potassium pyrophosphate or tribasic potassium pyrophosphate or tetrabasic potassium pyrophosphate or potassium etidronate such as monobasic potassium etidronate or dibasic potassium etidronate or tribasic potassium etidronate or tetrabasic potassium etidronate, potassium cyanate, potassium oxide (K2O) or potassium superoxide (KO2) or potassium peroxide (K2O2).

[0047] Preferred organic salts containing potassium include, but are not limited to, potassium carbonate (K2CO3), potassium bicarbonate, potassium salts of aliphatic saturated carboxylic acids such as potassium salts of monocarboxylic acids preferably having 1 to 6, more preferably 1 to 5, more preferably 1 to 4, more preferably 1 to 3 carbon atoms such as formic acid, acetic acid, propionic acid, potassium salts of dicarboxylic acids preferably having 2 to 6, more preferably 2 to 4 carbon atoms such as oxalic acid, maleic acid, succinic acid, tartaric acid, potassium salts of tricarboxylic acids preferably having 6 to 10 carbon atoms such as citric acid or isocitric acid or propane-1,2,3-tricarboxylic acid or tetracarboxylic acid. Preferably, the organic potassium salt is selected from potassium salts of aliphatic saturated monocarboxylic acids preferably having 1, 2, 3, 4, 5 or 6 carbon atoms, potassium carbonate and potassium bicarbonate. More preferably, the organic potassium salt is selected from potassium formate, potassium acetate, potassium propionate, potassium carbonate and potassium bicarbonate. More preferably, the organic potassium salt is selected from potassium formate, potassium acetate, potassium carbonate and potassium bicarbonate.

[0048] Therefore, the potassium-containing salt is preferably selected from: at least one inorganic potassium salt selected from the following: potassium hydroxide, potassium halide, potassium nitrate, potassium sulfate, potassium hydrogen sulfate, potassium perchlorate, potassium dihydrogen phosphate or dipotassium hydrogen phosphate or potassium phosphate or potassium pyrophosphate such as monobasic potassium pyrophosphate or dibasic potassium pyrophosphate or tribasic potassium pyrophosphate or tetrabasic potassium pyrophosphate, or potassium etidronate such as monobasic potassium etidronate or dibasic potassium etidronate or tribasic potassium etidronate or tetrabasic potassium etidronate; at least one organic potassium salt selected from the following: potassium salts of aliphatic saturated monocarboxylic acids, preferably having 1, 2, 3, 4, 5 or 6 carbon atoms, potassium carbonate and potassium bicarbonate; and a combination of at least one of the at least one inorganic potassium salt and at least one of the at least one organic potassium salt.

[0049] More preferably, the potassium-containing salt is selected from: at least one inorganic potassium salt selected from potassium dihydrogen phosphate or dipotassium hydrogen phosphate or potassium phosphate, potassium hydroxide, potassium halide, potassium nitrate, potassium sulfate, potassium hydrogen sulfate, potassium perchlorate, at least one organic potassium salt selected from potassium formate, potassium acetate, potassium propionate, potassium carbonate and potassium bicarbonate, and a combination of at least one of the at least one inorganic potassium salt and at least one of the at least one organic potassium salt.

[0050] Particularly preferably, the potassium-containing salt is potassium dihydrogen phosphate, dipotassium hydrogen phosphate or potassium formate. Therefore, if a single potassium salt is used, the potassium-containing salt is most preferably potassium dihydrogen phosphate, dipotassium hydrogen phosphate or potassium formate. If two or more potassium-containing salts are used, one potassium salt is potassium dihydrogen phosphate, dipotassium hydrogen phosphate or potassium formate.

[0051] There are no particular restrictions regarding the concentration of the potassium-containing salt in the feed stream. Preferably, the concentration of the potassium-containing salt in the feed stream is at least 10% of the solubility limit of the potassium-containing salt in the feed stream, preferably in the range of 10 to 100%, preferably 20 to 100%, more preferably 30 to 100%, more preferably 40 to 100%. The term "solubility limit of at least one potassium salt in the liquid feed stream" as used in the context of the present invention refers to the saturation concentration of the potassium-containing salt in the liquid feed stream, wherein when more potassium-containing salt is added, the concentration of the potassium-containing salt as a solute in the mixture does not increase, and the potassium-containing salt will begin to precipitate. The solubility limit of the potassium-containing salt in the feed stream depends on the composition and conditions of the mixture, such as the temperature and pressure at which the feed stream is provided. Determining the solubility limit of the potassium-containing salt in the mixture is an easy and straightforward task for a person skilled in the art who knows the conditions and the composition of a given mixture. A simple procedure for assessing whether the amount of potassium-containing salt added is above the solubility limit is to pass the feed stream through a filter before being subjected to the epoxidation conditions in (a2) and measure the pressure drop across the filter. If the pressure drop across the filter increases over time and potassium-containing salts are found on the filter when taken off the line, the amount of potassium-containing salt added has been above the solubility limit.

[0052] Preferably, in (a1), the molar ratio of potassium contained in the potassium-containing salt relative to hydrogen peroxide contained in the feed stream or one equivalent of hydrogen peroxide produced by the hydrogen peroxide source is in the range of 10×10 -6 :1 to 1500x10 -6 :1, preferably 20x10 -6 :1 to 1300x10 -6 :1, preferably 30x10 -6 :1 to 1000x10 -6 :1. If two or more potassium-containing salts are used, the molar amount of potassium contained in the potassium-containing salt refers to the total molar amount of potassium contained in all potassium-containing salts used in (a1).

[0053] Further preferably, in (a1), the molar ratio of potassium to hydrogen peroxide in the feed stream or one equivalent of hydrogen peroxide produced by the hydrogen peroxide source is in the range of 10×10 -6 :1 to 5000x10 -6 :1, preferably 15x10 -6 :1 to 2500x10 -6 :1, preferably 20x10 -6 :1 to 1,500x10 -6 :1, preferably 25x10 -6 :1 to 1,300x10 -6 :1, preferably 30x10 -6 :1 to 1,000x10 -6 :1.

[0054] Preferably, the feed stream of (a1) does not contain ammonium dihydrogen phosphate. More preferably, the feed stream of (a1) does not contain ammonium phosphate, ammonium hydrogen phosphate and ammonium dihydrogen phosphate. More preferably, the feed stream of (a1) does not contain ammonium carbonate, ammonium bicarbonate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate, ammonium hydrogen pyrophosphate, ammonium pyrophosphate, ammonium chloride, ammonium nitrate and ammonium acetate. More preferably, the feed stream of (a1) does not contain ammonium salts. As used herein, the term "free of" means that the concentration of the corresponding compound is at most 2 ppm by weight, preferably at most 1 ppm by weight, based on the total weight of the feed stream.

[0055] Preferably, the feed stream of (a1) has a molar ratio of sodium to hydrogen peroxide or one equivalent of hydrogen peroxide produced by a hydrogen peroxide source in the range of 1×10 -6 :1 to 250x10 -6 :1. 5x10 is preferred -6 :1 to 50x10 -6:1 contains sodium. Preferably, the mixture, preferably the feed stream of (a1), contains no dissolved sodium dihydrogen phosphate (NaH2PO4), more preferably contains neither dissolved sodium dihydrogen phosphate nor dissolved sodium dihydrogen phosphate (Na2HPO4), more preferably contains neither dissolved sodium dihydrogen phosphate nor dissolved sodium dihydrogen phosphate nor dissolved sodium phosphate (Na3PO4).

[0056] In case the feed stream of (a1) further comprises at least one potassium-containing salt, the liquid feed stream is preferably prepared by combining at least four separate streams. Preferably, the aqueous stream comprising at least one dissolved potassium-containing salt is combined with a stream comprising propylene, or with a stream comprising hydrogen peroxide or a source of hydrogen peroxide, or with a stream comprising an organic solvent, or with a mixed stream of two or three of these streams, preferably with a stream comprising hydrogen peroxide or a source of hydrogen peroxide, or with a stream comprising an organic solvent, or with a mixed stream thereof.

[0057] The feed stream comprising propylene can additionally comprise propane, wherein preferably at least 98 wt %, more preferably at least 99 wt %, more preferably at least 99.5 wt %, more preferably at least 99.9 wt % of the feed stream is composed of propylene and propane. Preferably, the weight ratio of propylene in the feed stream relative to propane is at least 7:3. For example, commercially available propylene can be used, which can be polymer grade propylene or chemical grade propylene. Typically, the propylene content of polymer grade propylene ranges from 99 to 99.8 wt %, and the propane content ranges from 0.2 to 1 wt %. Chemical grade propylene typically has a propylene content and a propane content range of 2 to 8 wt % in the range of 92 to 98 wt %. Preferably, a feed stream having a propylene content range of 99 to 99.8 wt % and a propane content range of 0.2 to 1 wt % is used.

[0058] The stream containing hydrogen peroxide or a source of hydrogen peroxide can be prepared according to various conceivable methods. It is conceivable that sulfuric acid is converted into peroxydisulfuric acid by anodic oxidation while releasing hydrogen at the cathode to obtain a stream containing hydrogen peroxide. Peroxydisulfuric acid is then hydrolyzed via peroxysulfuric acid to produce hydrogen peroxide and sulfuric acid, thereby obtaining sulfuric acid. It is also conceivable that hydrogen peroxide is prepared from elements. According to the specific preparation method, the stream containing hydrogen peroxide can be, for example, an aqueous or water / methanol hydrogen peroxide stream, preferably an aqueous hydrogen peroxide stream. In the case of using an aqueous hydrogen peroxide stream, the content range of hydrogen peroxide in the stream is generally 3 to 85% by weight, preferably 25 to 75% by weight, more preferably 30 to 50% by weight, such as 30 to 40% by weight or 35 to 45% by weight or 40 to 50% by weight. Preferably, at least 25% by weight, more preferably at least 30% by weight, more preferably at least 35% by weight of the stream containing hydrogen peroxide is composed of water and hydrogen peroxide. Preferred ranges are 30 to 80 wt % or 35 to 75 wt % or 40 to 70 wt %.

[0059] In order to provide adequate hydrogen peroxide stability during extraction with water, preferably with substantially pure water, suitable stabilizers are usually added to the water, preferably substantially pure water. In particular, strong mineral acids and / or chelating agents are mentioned. According to a preferred extraction method, small amounts of nitrates and / or phosphates and pyrophosphates are added as stabilizers, in the form of acid or sodium salts, respectively. These stabilizers are usually added in such amounts that the crude aqueous hydrogen peroxide solution contains 50 to 400 ppm by weight of sodium cations, 100 to 700 ppm by weight of phosphorus (in the form of phosphate (PO4)), and 100 to 700 ppm by weight of sodium cations. 3- ) calculated), and 50 to 400 weight ppm of nitrate anions, in each case calculated relative to the hydrogen peroxide contained in the crude aqueous hydrogen peroxide solution. Preferred ranges are, for example, 50 to 200 weight ppm or 50 to 100 weight ppm of sodium cations, 100 to 500 weight ppm or 100 to 300 weight ppm of phosphorus, and 50 to 200 weight ppm or 50 to 100 weight ppm of nitrate. In addition, it is also conceivable to use other stabilizers, such as sodium stannate (Na2SnO2) and / or organic phosphonic acids, in particular organic diphosphonic acids such as etidronic acid. Preferably, the aqueous hydrogen peroxide stream has a molar ratio of sodium to hydrogen peroxide in the range of 1×10 -6 :1 to 250x10 -6 :1. More preferably 5x10 -6 :1 to 50x10 -6 :1Contains sodium.

[0060] Typically, the molar ratio of water to organic solvent in the feed stream provided in (a1) is not subject to any particular restrictions. Preferably, in particular when the organic solvent is acetonitrile, the molar ratio of water to organic solvent is at most 1:4, more preferably in the range of 1:50 to 1:4, preferably 1:15 to 1:4.1, more preferably 1:10 to 1:4.2.

[0061] Catalyst (a1)

[0062] Typically, the titanium-containing zeolites used as catalytically active materials may have a zeolite framework structure type that conforms to the following three-letter codes: ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, G IS, GIU, GME, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MMFI, MFS, MON, MOR, MSO, MTF, MTN, MT T, MTW, MWW, NAB, NAT, NEES, NON, NPO, OBW, OFF, OSI, OSO, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZON or a mixture of two or more of these framework structures. For three-letter codes and their definitions, see "Atlas of Zeolite Framework Types", 5th edition, Elsevier, London, England (2001).

[0063] Preferably, the titanium-containing zeolite has an MFI framework structure, a MEL framework structure, an MWW framework structure, an MWW-type framework structure or a mixed structure of two or more of these framework structures, preferably an MFI framework structure, an MWW framework structure or an MWW-type framework structure, more preferably an MWW framework structure or an MWW-type framework structure. More preferably, the titanium-containing zeolite is a zeolite called "TS-1" (titanium silicate-1) or "TiMWW".

[0064] Preferably, in particular when the titanium-containing zeolite is TiMWW, the titanium-containing zeolite comprises one or more of Al, B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, Cd, preferably one or more of B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, Cd, more preferably Zn.

[0065] The term "titanium zeolite of MWW-type framework structure" as used in the context of the present invention - also referred to as "TiMWW" - refers to a zeolite of framework structure MWW comprising titanium as an isomorphous substitution element in the zeolite framework. Preferably, the zeolite framework is substantially free of aluminum and consists essentially of silicon, titanium and oxygen. Preferably, at least 99% by weight, more preferably at least 99.5% by weight, more preferably at least 99.9% by weight of the zeolite framework consists of silicon, titanium and oxygen. Optionally, the titanium zeolite of MWW-type framework structure may contain extra-framework titanium, which is understood to be various titanium species that are not part of the MWW zeolite framework. The preparation of TiMWW catalysts is described, for example, in US2007043226 A1, in particular in Examples 3 and 5 therein.

[0066] The titanium content of the MWW-type framework-structured titanium zeolite is not subject to any particular restrictions. Preferably, the titanium content of the MWW-type framework-structured titanium zeolite contained in the catalyst in (a1) - calculated as elemental titanium - is 0.1 to 5% by weight, more preferably 0.2 to 4% by weight, more preferably 0.5 to 3% by weight, more preferably 1 to 2% by weight, based on the total weight of the MWW-type framework-structured titanium zeolite. Therefore, the present invention relates to a method as described above, wherein the titanium content of the MWW-type framework-structured titanium zeolite contained in the catalyst in (a1) - calculated as elemental titanium - is 0.1 to 5% by weight, preferably 1 to 2% by weight, silicon, based on the total weight of the MWW-type framework-structured titanium zeolite.

[0067] In addition to titanium, the titanium zeolite of the MWW framework structure can also include at least one other element except titanium, silicon and oxygen. Generally, it is conceivable that this at least one other element is the isomorphous substitution element of a part of the MWW zeolite framework structure. Preferably, this at least one other element is not an isomorphous substitution element. This other element that is not an isomorphous substitution element can be applied to the zeolite by, for example, spraying, wet impregnation (such as incipient wetness process) or any other suitable method. Preferably, the at least one other element is selected from Al, B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, Cd and two or more combinations, preferably selected from B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, Cd and two or more combinations. More preferably, the titanium zeolite of the MWW-type framework structure comprises zinc as the other element in addition to titanium, silicon and oxygen. More preferably, the titanium zeolite of the MWW-type framework structure comprises zinc as the only other element in addition to titanium, silicon and oxygen. More preferably, the titanium zeolite of the MWW-type framework structure comprises zinc as the only other element in addition to titanium, silicon and oxygen, wherein at least 99% by weight, more preferably at least 99.5% by weight, more preferably at least 99.9% by weight of the zeolite framework structure consists of silicon, titanium and oxygen. More preferably, in the case where the titanium zeolite of the MWW-type framework structure comprises zinc as the only other element, at least 99% by weight, more preferably at least 99.5% by weight, more preferably at least 99.9% by weight of the titanium zeolite of the MWW-type framework structure consists of zinc, titanium, silicon and oxygen; the titanium zeolite of the MWW-type framework structure comprising zinc as the only other element is also referred to as "ZnTiMWW".

[0068] ZnTiMWW Catalyst

[0069] The zinc content of the titanium zeolite of the MWW-type framework structure is not subject to any particular restrictions. Preferably, the zinc content of the titanium zeolite of the MWW-type framework structure contained in the catalyst in (a1) - calculated as elemental zinc - is 0.1 to 5% by weight, more preferably 0.2 to 4% by weight, more preferably 0.5 to 3% by weight, more preferably 1 to 2% by weight, based on the total weight of the titanium zeolite of the MWW-type framework structure. Therefore, the present invention relates to a method as described above, wherein the zinc content of the titanium zeolite of the MWW-type framework structure contained in the catalyst in (a1) - calculated as elemental zinc - is 0.1 to 5% by weight, preferably 1 to 2% by weight, based on the total weight of the titanium zeolite of the MWW-type framework structure.

[0070] Therefore, preferably, the titanium-containing zeolite contained in the catalyst in (a1) has an MWW framework structure, contains zinc, and has a titanium content - calculated as elemental titanium - of 0.1 to 5% by weight, preferably 1 to 2% by weight, based on the total weight of the titanium-containing zeolite, and a zinc content - calculated as elemental zinc - of 0.1 to 5% by weight, preferably 1 to 2% by weight, based on the total weight of the titanium-containing zeolite.

[0071] The catalyst of (a1) comprising a titanium zeolite of an MWW-type framework structure may be composed of a titanium zeolite of an MWW-type framework structure, preferably of said TiMWW or ZnTiMWW. In this case, the catalyst may be a titanium zeolite of an MWW-type framework structure in the form of a zeolite powder that may be shaped into the following forms: for example, particles, microspheres such as microspheres obtained by spray drying or by spray granulation, shaped bodies having shapes such as pills, flakes, cylinders, wheels, stars or spheres.

[0072] Preferably, the catalyst (a1) comprising a titanium zeolite of the MWW type framework structure, preferably TiMWW or ZnTiMWW, is prepared as a shaped body comprising a titanium zeolite of the MWW type framework structure, preferably TiMWW or ZnTiMWW, which is prepared by appropriately mixing a titanium zeolite of the MWW type framework structure with at least one binder and / or with at least one binder precursor, and optionally at least one pore former and / or at least one plasticizer. The shaped body can be formed into any conceivable geometric shape, such as, for example, strands with a rectangular, triangular, hexagonal, square, oval or circular cross section, stars, sheets, spheres, hollow cylinders, etc. Examples of the binder are metal oxides, such as SiO2, Al2O3, TiO2, ZrO2 or MgO or clays or mixtures of two or more of these oxides, or mixed oxides of at least two of Si, Al, Ti, Zr and Mg, preferably SiO2. Pore ​​formers such as mesopore formers include polymeric vinyl compounds, for example polyalkylene oxides such as polyethylene oxide, polystyrene, polyacrylates, polymethacrylates, polyolefins, polyamides and polyesters. Pasting agents include organic, especially hydrophilic polymers, such as carbohydrates such as cellulose, cellulose derivatives such as methylcellulose, and starches such as potato starch, wallpaper plaster, polyacrylates, polymethacrylates, polyvinyl alcohol, polyvinyl pyrrolidone, polyisobutylene or polytetrahydrofuran. It may also be mentioned that water, alcohols or glycols or mixtures thereof, for example mixtures of water and alcohols or water and glycols, for example mixtures of water and methanol or water and ethanol or water and propanol or water and propylene glycol are used as binders. Preferably, the catalyst of (a1) is used as a shaped body in the shape of an extrudate, preferably an extrudate having a length of preferably 1 to 10 mm, more preferably 1 to 7 mm, more preferably 1 to 5 mm and a diameter of preferably 0.1 to 5 mm, more preferably 0.2 to 4 mm, more preferably 0.5 to 2 mm. In particular, with regard to the preferred catalyst of (a1), comprising ZnTiMWW, it is preferred to use this catalyst in the form of a micropowder or in the form of a shaped body, wherein the shaped body preferably comprises the micropowder.

[0073] Preferred features of the catalyst in micronized form comprising ZnTiMWW of (a1) are the following features and embodiments including combinations of the given dependent embodiments:

[0074] 1. A micropowder, the particles of which have a Dv10 value of at least 2 micrometers, the micropowder comprising mesopores with an average pore diameter (4V / A) in the range of 2 to 50 nm, determined by the Hg porosimetry method according to DIN 66133, and comprising at least 95% by weight of microporous aluminum-free zeolitic material of MWW type structure containing titanium and zinc (ZnTiMWW), based on the weight of the micropowder. The Dv10 value is understood to be determined according to Reference Example 8 of WO 2013 / 117536.

[0075] 2. The micropowder of embodiment 1, whose Dv10 value ranges from 2 to 5.5 microns, preferably from 3 to 5.5 microns.

[0076] 3. The micropowder of embodiment 1 or 2, having a Dv50 value ranging from 7 to 25 microns, and optionally a Dv90 value ranging from 26 to 85 microns. The Dv50 and Dv90 values ​​are understood to be determined according to Reference Example 8 of WO 2013 / 117536.

[0077] 4. The micropowder according to any one of embodiments 1 to 3, wherein the average pore size (4V / A) of the mesopores is from 10 to 50 nm, preferably from 15 to 40 nm, more preferably from 20 to 30 nm, as determined by the Hg porosimetry method according to DIN 66133.

[0078] 5. The micropowder according to any one of embodiments 1 to 4, further comprising macropores with an average pore size (4V / A) in the range of greater than 50 nm, preferably having an average pore size in the range of 0.05 to 3 micrometers, as determined by Hg porosimetry according to DIN 66133.

[0079] 6. The micropowder according to any one of embodiments 1 to 5, wherein the micropores of the ZnTiMWW have an average pore diameter in the range of 1.0 to 1.2 nanometers, as determined by the nitrogen adsorption method according to DIN 66135.

[0080] 7. The micropowder according to any one of embodiments 1 to 6, comprising at least 99% by weight, preferably at least 99.7% by weight, of ZnTiMWW, based on the weight of the micropowder.

[0081] 8. The micropowder according to any one of embodiments 1 to 7, wherein the ZnTiMWW comprises zinc in an amount of 1.0 to 2.0 wt. %, preferably 1.2 to 1.9 wt. %, calculated as Zn and based on the weight of ZnTiMWW.

[0082] 9. The micropowder according to any one of embodiments 1 to 8, wherein the ZnTiMWW comprises titanium in an amount of 1.0 to 2.0 wt. %, preferably 1.2 to 1.8 wt. %, calculated as Ti and based on the weight of ZnTiMWW.

[0083] 10. The micropowder according to any one of embodiments 1 to 9, having a crystallinity of at least (80+ / -10)%, preferably at least (85+ / -10)%, as determined by X-ray diffraction (XRD) analysis. The crystallinity is understood to be determined according to reference example 10 of WO 2013 / 117536.

[0084] 11. The micropowder according to any one of embodiments 1 to 10, comprising less than 0.001% by weight, preferably less than 0.0001% by weight, of a noble metal, based on the total weight of the micropowder and calculated as the element, the noble metal being preferably selected from the group consisting of gold, silver, platinum, palladium, iridium, ruthenium, osmium and mixtures of two or more thereof, more preferably selected from the group consisting of gold, platinum, gold and mixtures of two or more thereof.

[0085] 12. The micropowder according to any one of embodiments 1 to 11, comprising less than 0.1% by weight, preferably less than 0.01% by weight, of boron, based on the total weight of the micropowder and calculated as element.

[0086] 13. The micropowder according to any one of embodiments 1 to 12, which has a bulk density ranging from 80 to 100 g / ml.

[0087] 14. The micropowder according to any one of embodiments 1 to 13, which is a spray powder, preferably obtainable or obtained by spray drying.

[0088] Furthermore, the catalyst in the form of shaped bodies comprising ZnTiMWW of (a1) is preferably characterized by the following features and embodiments, including combinations of the given dependent embodiments:

[0089] 1. A shaped body comprising a microporous aluminum-free zeolite material (ZnTiMWW) containing titanium and zinc of an MWW type structure, the shaped body preferably comprising at least 95% by weight of a microporous aluminum-free zeolite material (ZnTiMWW) containing titanium and zinc of an MWW type structure, based on the weight of the micropowder, the shaped body more preferably comprising the micropowder of any one of the micropowder embodiments 1 to 14 described above, the shaped body preferably further comprising at least one binder, preferably a silica binder.

[0090] 2. The shaped body according to embodiment 1, which comprises mesopores with an average pore diameter in the range from 4 to 40 nm, preferably from 20 to 30 nm, as determined by the Hg porosimetry method in accordance with DIN 66133.

[0091] 3. The shaped body according to embodiment 1 or 2, which has a crystallinity of at least (55+ / -10)%, preferably in the range of ((55 to 75)+ / -10)%, determined by XRD analysis. The crystallinity is understood to be determined according to reference example 10 of WO 2013 / 117536.

[0092] 4. The shaped body according to any one of embodiments 1 to 3, comprising the micropowder in an amount of 70 to 80% by weight and the silica binder in an amount of 30 to 20% by weight, the micropowder together with the silica binder making up at least 99% by weight of the shaped body, wherein the concentration of silanol groups in the shaped body is at most 6%, preferably at most 3%, relative to the total number of Si atoms, according to 29 Si MAS NMR determination. The concentration of silanol groups is understood to be determined according to Reference Example 3 of WO 2013 / 117536.

[0093] 5. The shaped body according to any one of embodiments 1 to 4, which is a strand having a circular cross section and a diameter in the range of 1.5 to 1.7 mm and a crushing strength of at least 5 N, preferably 5 to 20 N, more preferably 12 to 20 N, the crushing strength being measured by a crushing strength tester Z2.5 / TS1S according to the method described in Reference Example 2 of WO 2013 / 117536.

[0094] 6. The shaped body according to any one of embodiments 1 to 5, wherein 29 The Si-NMR spectrum contains six peaks at the following positions:

[0095] Peak 1 at -98 + / - x ppm,

[0096] Peak 2 at -104+ / -x ppm,

[0097] Peak 3 at -110 + / - x ppm,

[0098] Peak 4 at -113+ / -x ppm,

[0099] Peak 5 at -115+ / -x ppm,

[0100] Peak 6 at -118+ / -x ppm,

[0101] wherein x in any one of the peaks is 1.5, preferably 1.0, more preferably 0.5,

[0102] where Q is defined as

[0103] Q=100*{[a1+a2] / [a4+a5+a6]} / a3

[0104] is at most 2.5, preferably at most 1.6, preferably at most 1.4, wherein [a1+a2] is the sum of the peak areas of Peaks 1 and 2, and [a4+a5+a6] is the sum of the peak areas of Peaks 4, 5 and 6, and a3 is the peak area of ​​Peak 3. 29The Si-NMR characteristics are understood to be determined according to Reference Example 4 of WO 2013 / 117536.

[0105] 7. The shaped body according to any of embodiments 1 to 6, which has a water absorption in the range of 3 to 8% by weight, preferably 4 to 7% by weight. Water absorption is understood to be determined according to Reference Example 6 of WO 2013 / 11 536.

[0106] 8. The shaped body according to any one of embodiments 1 to 7, wherein the infrared spectrum of the shaped body comprises (3700-3750) + / - 20 cm -1 Band in the area, and (3670-3690) + / - 20cm -1 The belt in the area where (3700-3750) + / - 20cm -1 The band in the area is relative to (3670-3690) + / - 20cm -1 The intensity ratio of the bands in the region is at most 1.5, preferably at most 1.4. These IR characteristics are understood to be determined according to Reference Example 5 of WO 2013 / 117536.

[0107] Furthermore, a preferred process for preparing the catalyst of (a1) in the form of fine powders and / or shaped bodies comprising ZnTiMWW is characterized by the following features and embodiments, including combinations of the given dependent embodiments:

[0108] 1. A method comprising:

[0109] (a) providing a suspension comprising a microporous aluminum-free zeolite material containing titanium and zinc of an MWW-type structure (ZnTiMWW);

[0110] (b) spray drying the suspension provided in (a) to obtain a micro powder;

[0111] (c) optionally calcining the fine powder obtained in (b),

[0112] Among them, in (b) or (c), the fine powder obtained in (c) is preferably the fine powder of any one of the fine powder embodiments 1 to 14 as described above.

[0113] 2. The method of embodiment 1, wherein the solid content of the suspension provided in (a) is in the range of 5 to 25% by weight, preferably 10 to 20% by weight, and the suspension is preferably an aqueous suspension.

[0114] 3. The process of embodiment 1 or 2, wherein the ZnTiMWW of (a) comprises zinc in an amount of 1.0 to 2.0 wt. %, preferably 1.2 to 1.9 wt. %, calculated as Zn, and titanium in an amount of 1.0 to 2.0 wt. %, preferably 1.2 to 1.8 wt. %, calculated as Ti and based on the weight of the ZnTiMWW.

[0115] 4. The process according to any of embodiments 1 to 3, wherein in (b), a spray device, preferably a spray tower, is used for spray drying the suspension, the device having at least one nozzle, preferably at least one two-component nozzle, having a diameter in the range of 3.5 to 4.5 mm.

[0116] 5. The process according to any of embodiments 1 to 4, wherein in (b), a spraying device, preferably a spray tower, is used for spray drying the suspension, the device being operated with a nozzle gas having a temperature in the range of 20 to 50° C., preferably 20 to 30° C., and a drying gas having a temperature in the range of 250 to 350° C., preferably 275 to 325° C., the nozzle gas being preferably an inert gas, more preferably technical nitrogen, and the drying gas being preferably an inert gas, more preferably nitrogen.

[0117] 6. The method of any one of embodiments 1 to 5, wherein in (c), the fine powder is calcined at a temperature ranging from 600 to 700° C. for a time of 0.5 to 6 h.

[0118] 7. The method according to any one of embodiments 1 to 6, further comprising

[0119] (d) shaping the fine powder obtained in (b) or (c) to obtain a molded product;

[0120] (e) optionally drying and / or calcining the molded article obtained in (d).

[0121] 8. The method of embodiment 7, wherein the forming of (d) comprises

[0122] (aa) mixing a fine powder with a binder or a binder precursor, preferably a silica binder or a silica binder precursor, wherein the weight ratio of ZnTiMWW contained in the fine powder to the silica contained in or produced from the silica binder is in the range of 3:7 to 1:4, to obtain a mixture;

[0123] (bb) shaping the mixture obtained in (aa) to obtain a shaped body, said shaping preferably comprising extruding the mixture obtained in (aa), preferably obtaining therefrom strands having a diameter in the range of preferably 1.0 to 2.0 mm, more preferably 1.5 to 1.7 mm.

[0124] 9. The method according to embodiment 8, wherein in (aa), carbohydrates and / or water are added as binders.

[0125] 10. The process according to embodiment 8 or 9, wherein the mixing in (aa) is carried out for a period of 15 to 60 min, preferably 30-55 min, more preferably 40 to 50 min.

[0126] 11. The process according to any one of embodiments 7 to 10, wherein in (d), no mesopore former selected from the group consisting of polyalkylene oxides such as polyethylene oxide, polystyrene, polyacrylates, polymethacrylates, polyolefins, polyamides and polyesters is added.

[0127] 12. The process according to any one of embodiments 7 to 11, wherein in (e), the shaped body is dried at a temperature in the range of 100 to 150° C. for a period of 10 to 20 h and calcined at a temperature in the range of 500 to 600° C. for a period of 0.5 to 2 h.

[0128] 13. The method according to any one of embodiments 7 to 12, further comprising

[0129] (f) subjecting the molded body obtained in (d) or (e), preferably in (e), to water treatment;

[0130] (g) optionally drying and / or calcining the water-treated shaped body,

[0131] Among them, the molded body obtained in (f) or (g), preferably in (g), is preferably a molded body of any one of the molded body embodiments 1 to 8 as described above.

[0132] 14. The method of embodiment 13, wherein in (f), the water treatment comprises treating the shaped body with liquid water in an autoclave under autogenous pressure at a temperature in the range of 100 to 200°C, preferably 125 to 175°C, more preferably 140 to 150°C, for a period of 2 to 24 hours, preferably 6 to 10 hours.

[0133] 15. The process according to embodiment 13 or 14, wherein in (f), the weight ratio of the shaped body to water is in the range of 0.02 to 0.08, preferably 0.03 to 0.07, more preferably 0.04 to 0.06.

[0134] 16. The process according to any of embodiments 13 to 15, wherein in (g), the water-treated shaped body is dried at a temperature in the range of 100 to 150° C. for a period of 10 to 20 h and calcined at a temperature in the range of 400 to 500° C. for 1 to 3 h.

[0135] 17. The process according to any of embodiments 7 to 16, wherein the shaped bodies are not subjected to steam treatment.

[0136] Regarding the preferred method for preparing the catalyst in the form of a micropowder and / or a shaped body comprising ZnTiMWW as described in embodiments 1 to 17 above (a1), the ZnTiMWW (based on which the suspension in embodiment 1. (a) is provided) can be prepared according to all conceivable methods. For example, a microporous aluminum-free titanium-containing MWW-type structured zeolite material (TiMWW) can be prepared, and the TiMWW is subjected to a suitable treatment to obtain ZnTiMWW. In addition, an aluminum-free MWW-type structured zeolite material (MWW) can be prepared, and the MWW is subjected to a suitable treatment to obtain ZnTiMWW, wherein, for example, both Zn and Ti are appropriately incorporated into the MWW. In addition, it is conceivable to prepare an aluminum-free MWW-type structured zeolite material, wherein during the synthesis of the MWW-type framework, Ti is introduced and the resulting material is subjected to a suitable treatment to introduce Zn, or Zn is introduced and the resulting material is subjected to a suitable treatment to introduce Ti, or both Zn and Ti are introduced. As conceivable methods for preparing TiMWW, mention may be made of the methods described, for example, in US 6,114,551 or in Wu et al., "Hydrothermal Synthesis of a novel Titanosilicate with MWW Topology", Chemistry Letters (2000), pages 774-775. Preferably, in a first stage, an aluminum-free, Ti-containing zeolitic material of MWW-type structure (TiMWW) is prepared, while in a second stage, TiMWW is appropriately treated to obtain ZnTiMWW. More preferably, ZnTiMWW is prepared according to a method comprising the following steps:

[0137] (I) preparing an aluminum-free boron-containing zeolite material of MWW type structure (B-MWW);

[0138] (II) deboronating B-MWW to obtain an aluminum-free MWW-type structured zeolite material (MWW);

[0139] (III) incorporating titanium (Ti) into MWW to obtain an aluminum-free Ti-containing MWW-type structured zeolite material (TiMWW);

[0140] (IV) preferably acid-treated TiMWW;

[0141] (V) The TiMWW is impregnated with zinc (Zn) to obtain ZnTiMWW.

[0142] Preferably, in stage (I), B-MWW is prepared by a process whose preferred steps and conditions are defined by the following embodiments 1 to 28 and the corresponding dependent embodiments shown:

[0143] 1. A boron-containing zeolite material for preparing aluminum-free MWW framework structure

[0144] (B-MWW) method, comprising

[0145] (a) hydrothermally synthesizing a B-MWW precursor from a synthesis mixture comprising water, a silicon source, a boron source, and a MWW template compound in a mother liquor thereof to obtain a B-MWW precursor, wherein the pH of the mother liquor is higher than 9;

[0146] (b) adjusting the pH value of the mother solution containing the B-MWW precursor obtained in (a) to 6 to 9;

[0147] (c) separating the B-MWW precursor from the pH-adjusted mother liquor obtained in (b) by filtration in a filtration device.

[0148] 2. The process of embodiment 1, wherein in (a), at least 95% by weight, preferably at least 99% by weight, more preferably at least 99.9% by weight of the synthesis mixture consists of water, a silicon source, a boron source and a template compound.

[0149] 3. The method described in embodiment 1 or 2, wherein in (a), the silicon source is selected from calcined silica, colloidal silica and mixtures thereof, and the silicon source is preferably colloidal silica, and more preferably ammonia-stabilized silica; the boron source is selected from boric acid, borates, boron oxide and mixtures of two or more thereof, and the boron source is preferably boric acid; and the MWW template compound is selected from piperidine, hexamethyleneimine, N,N,N,N',N',N'-hexamethyl-1,5-pentanediammonium ion, 1,4-bis(N-methylpyrrolidinium)butane, octyltrimethylammonium hydroxide, heptyltrimethylammonium hydroxide, hexyltrimethylammonium hydroxide, N,N,N-trimethyl-1-adamantylammonium hydroxide and mixtures of two or more thereof, and the MWW template compound is preferably piperidine.

[0150] 4. The method of any one of embodiments 1 to 3, wherein in (a), the synthesis mixture comprises a boron source (calculated as elemental boron) with respect to a silicon source (calculated as elemental silicon) in a molar ratio ranging from 0.4:1 to 2.0:1, preferably from 0.6:1 to 1.9:1, more preferably from 0.9:1 to 1.4:1, a water with respect to the silicon source (calculated as elemental silicon) in a molar ratio ranging from 1:1 to 30:1, preferably from 3:1 to 25:1, more preferably from 6:1 to 20:1; and a template compound with respect to the silicon source (calculated as elemental silicon) in a molar ratio ranging from 0.4:1 to 2.0:1, preferably from 0.6:1 to 1.9:1, more preferably from 0.9:1 to 1.4:1.

[0151] 5. The method of any one of embodiments 1 to 4, wherein in (a), the hydrothermal synthesis is carried out at a temperature in the range of 160 to less than 180° C., preferably 170 to 175° C., for a time of 1 to 72 h, preferably 6 to 60 h, more preferably 12 to 50 h.

[0152] 6. The process according to any one of embodiments 1 to 5, wherein in (a), the hydrothermal synthesis is carried out at least partially under stirring.

[0153] 7. The process according to any one of embodiments 1 to 6, wherein in (a), the synthesis mixture further comprises a seed material, preferably a zeolitic material comprising a framework structure MWW, more preferably a boron-containing zeolitic material comprising a framework structure MWW.

[0154] 8. The method of embodiment 7, wherein the weight ratio of the seed material contained in the synthesis mixture to the silicon source is in the range of 0.01:1 to 1:1, preferably 0.02:1 to 0.5:1, more preferably 0.03:1 to 0.1:1, calculated as the amount of seed material (in kg) relative to the silicon contained in the silicon source (calculated as silicon dioxide, in kg).

[0155] 9. The process according to any one of embodiments 1 to 8, wherein the pH of the mother liquor obtained from (a) is higher than 10, preferably in the range of 10.5 to 12, more preferably 11 to 11.5.

[0156] 10. The process according to any one of embodiments 1 to 9, wherein in (b), the pH value of the mother liquor obtained in (a) is adjusted to 6.5 to 8.5, preferably 7 to 8.

[0157] 11. The method of any one of embodiments 1 to 10, wherein in (b), the pH is adjusted by a method comprising the steps of:

[0158] (aa) adding an acid to the mother liquor comprising the B-MWW precursor obtained from (a), wherein said adding is preferably carried out at least partly under stirring.

[0159] 12. The process of embodiment 1, wherein in (aa), the adding is carried out at a temperature in the range of 20 to 70°C, preferably 30 to 65°C, more preferably 40 to 60°C.

[0160] 13. The process of embodiment 11 or 12, wherein in (aa), the acid is an inorganic acid, preferably an aqueous solution comprising an inorganic acid.

[0161] 14. The method of embodiment 13, wherein the inorganic acid is selected from phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid and a mixture of two or more thereof, and the inorganic acid is preferably nitric acid.

[0162] 15. The method according to any one of embodiments 11 to 14, further comprising

[0163] (bb) stirring the mother liquor to which the acid was added according to (aa), wherein during (bb), no acid was added to the mother liquor.

[0164] 16. The process of embodiment 15, wherein in (bb), the stirring is carried out at a temperature in the range of 20 to 70°C, preferably 25 to 65°C, more preferably 30 to 60°C.

[0165] 17. The method of any one of embodiments 1 to 16, wherein in (b), the size of the particles contained in the mother liquor - represented by the corresponding Dv10, Dv50 and Dv90 values ​​- increases by at least 2%, preferably at least 3%, more preferably at least 4.5% with respect to Dv10, increases by at least 2%, preferably at least 3%, more preferably at least 4.5% with respect to Dv50, and increases by at least 5%, preferably at least 6%, more preferably at least 7% with respect to Dv90.

[0166] 18. The process of any one of embodiments 1 to 17, wherein the solids content of the pH-adjusted mother liquor obtained from (b) is from 1 to 10 wt.%, preferably from 4 to 9 wt.%, more preferably from 7 to 8 wt.%, based on the total weight of the pH-adjusted mother liquor obtained from (b).

[0167] 19. The method according to any one of embodiments 1 to 18, wherein the filtration resistance of the pH-adjusted mother liquor obtained from (b) is in the range of 10 to 50 mPa*s / m 2 , preferably 15 to 45 mPa*s / m 2 , more preferably 20 to 40 mPa*s / m 2 .

[0168] 20. The method of any one of embodiments 1 to 19, further comprising

[0169] (d) washing the B-MWW precursor obtained from (c), preferably the filter cake obtained from (c), wherein the washing is preferably carried out using water as a washing agent.

[0170] 21. The method of embodiment 20, wherein in (d), the filter cake obtained from (c) has a washing resistance of 10 to 50 mPa·s / m 2 , preferably 15 to 45 mPa·s / m 2 , more preferably 20 to 40 mPa·s / m 2 .

[0171] 22. The process according to embodiment 20 or 21, wherein the washing is carried out until the conductivity of the filtrate is at most 300 microSiemens / cm, preferably at most 250 microSiemens / cm, more preferably at most 200 microSiemens / cm.

[0172] 23. The method of any one of embodiments 1 to 22, further comprising

[0173] (e) drying the B-MWW precursor obtained from (c), preferably from (d), at a temperature in the range of 20 to 50°C, preferably 20 to 40°C, more preferably 20 to 30°C, wherein the drying is preferably carried out by subjecting the B-MWW to a gas flow, preferably a nitrogen flow.

[0174] 24. The process according to any one of embodiments 1 to 23, wherein the residual moisture of the B-MWW precursor obtained from (c), preferably from (d), more preferably from (e) is in the range of 80 to 90 wt.-%, preferably from 80 to 85 wt.-%.

[0175] 25. The method of any one of embodiments 1 to 24, further comprising

[0176] (f) preparing a suspension, preferably an aqueous suspension, comprising the B-MWW precursor obtained from (c), preferably from (d), more preferably from (e), and having a solids content in the range of 10 to 20 wt. %, preferably from 12 to 18 wt. %, more preferably from 14 to 16 wt. %;

[0177] (g) spray drying the suspension containing the B-MWW precursor obtained in (f) to obtain a spray powder;

[0178] (h) calcining the spray powder comprising a B-MWW precursor obtained in (g), preferably at a temperature in the range of 500 to 700° C., more preferably 550 to 650° C., more preferably 575 to 625° C., for a period of 1 to 24 h, preferably 2 to 18 h, more preferably 6 to 12 h, to obtain a spray powder, at least 99% by weight, more preferably at least 99.5% by weight, consisting of B-MWW.

[0179] 26. The process according to embodiment 25, wherein in (h) the calcination is carried out in a continuous mode, preferably in a rotary calciner, preferably with a throughput of 0.5 to 20 kg of spray powder per hour.

[0180] 27. The process according to embodiment 25 or 26, wherein the B-MWW contained in the spray powder obtained from (h) has a crystallinity of at least (75±5)%, preferably at least (80±5)%, as determined by XRD.

[0181] 28. The process according to any one of embodiments 25 to 27, wherein the B-MWW contained in the spray powder obtained by (h) has a BET specific surface area of ​​at least 300 m 2 / g, preferably 300 to 500m 2 / g, determined according to DIN 66131.

[0182] Preferably, stage (II) is carried out by a method whose preferred steps and conditions are defined by the following embodiments 1 to 7 and the corresponding dependent embodiments shown:

[0183] 1. A method for preparing a zeolite material, comprising:

[0184] (a) providing a boron-containing zeolitic material of MWW-type structure (B-MWW) obtained according to stage (I);

[0185] (b) deboronating B-MWW by treating B-MWW with a liquid solvent system to obtain a deboronated B-MWW (MWW);

[0186] The liquid solvent system is selected from water, monohydric alcohol, polyhydric alcohol and mixtures of two or more thereof, and the liquid solvent system does not contain an inorganic or organic acid or a salt thereof, and the acid is selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid and tartaric acid.

[0187] 2. The method of embodiment 1, wherein the liquid solvent system does not contain an inorganic or organic acid or a salt thereof.

[0188] 3. The method of embodiment 1 or 2, wherein the liquid solvent system is selected from water, methanol, ethanol, propanol, ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol, propane-1,2,3-triol, and a mixture of two or more thereof, preferably water.

[0189] 4. The process of any one of embodiments 1 to 3, wherein the treatment of (b) is carried out at a temperature in the range of 50 to 125°C.

[0190] 5. The method according to any one of embodiments 1 to 4, wherein the treatment of (b) is carried out for a period of 6 to 20 h.

[0191] 6. The process according to any of embodiments 1 to 5, wherein the treatment of (b) is carried out in at least two separate steps, wherein the MWW is dried between at least two treatment steps, preferably at a temperature in the range of 100 to 150° C.

[0192] 7. The method according to any one of embodiments 1 to 6, further comprising

[0193] (c) post-treating the MWW obtained by (b) by a method comprising the following steps:

[0194] (c.1) separating MWW from the liquid solvent system;

[0195] (c.2) preferably drying the separated MWW, preferably by spray drying;

[0196] (c.3) Optionally calcining the MWW obtained from (c.1) or (c.2), preferably at a temperature in the range of 500 to 700°C.

[0197] As far as stage (III) is concerned, a suitable starting mixture, preferably an aqueous mixture, comprising MWW and a Ti-containing precursor and preferably containing at least one suitable micropore former is preferably subjected to hydrothermal crystallization under autogenous pressure. It is conceivable to use at least one suitable seed material. As suitable Ti-containing precursors, tetraalkyl orthotitanates such as tetrabutyl orthotitanate may be mentioned. As suitable micropore formers, for example, piperidine, hexamethyleneimine or a mixture of piperidine and hexamethyleneimine may be mentioned. Preferably, the crystallization time is 4 to 8 days, more preferably 4 to 6 days. During the hydrothermal synthesis, the crystallization mixture may be stirred. The temperature range used during crystallization is preferably 160 to 200° C., more preferably 160 to 180° C. After the hydrothermal synthesis, the resulting crystalline zeolite material TiMWW is preferably suitably separated from the mother liquor. All methods for separating TiMWW from the mother liquor are conceivable. These methods include, for example, filtration, ultrafiltration, diafiltration and centrifugation methods, or, for example, spray drying methods and spray granulation methods. A combination of two or more of these methods may be applied. According to the present invention, TiMWW is preferably separated from its mother liquor by filtration to obtain a filter cake, which is washed, preferably with water. Subsequently, the filter cake (optionally further treated to obtain a suitable suspension) is spray-dried or ultrafiltered. Before separating TiMWW from its mother liquor, the TiMWW content of the mother liquor can be increased by concentrating the suspension. If washing is used, the washing process is preferably continued until the conductivity of the washing water is less than 1,000 microsiemens / cm, more preferably less than 900 microsiemens / cm, more preferably less than 800 microsiemens / cm, more preferably less than 700 microsiemens / cm. After the separation of TiMWW from its mother liquor is preferably achieved by filtration, and after washing, the washed filter cake containing TiMWW is preferably pre-dried, for example by subjecting the filter cake to a suitable gas flow (preferably a nitrogen flow) for 4 to 10 hours, more preferably 5 to 8 hours. Subsequently, the predried filter cake is preferably dried at a temperature in the range of 100 to 300° C., more preferably 150 to 275° C., more preferably 200 to 250° C. in a suitable atmosphere such as industrial nitrogen, air or rarefied air, preferably in air or rarefied air. This drying can be accomplished, for example, by spray drying. After drying, the TiMWW is calcined at a temperature in the range of 500 to 700° C., more preferably 550 to 675° C., more preferably 600 to 675° C. in a suitable atmosphere such as industrial nitrogen, air, or rarefied air, preferably in air or rarefied air. Preferably, no calcination is performed according to (III).

[0198] Preferably, stages (III) and (IV) are carried out by a process whose preferred steps and conditions are defined by the following embodiments 1 to 27 and the corresponding dependent embodiments shown:

[0199] 1. A method for preparing a titanium-containing zeolite material having an MWW framework structure, comprising:

[0200] (a) providing the deboronated crystalline zeolitic material MWW obtained according to stage (II);

[0201] (b) incorporating titanium into the zeolite material provided in (a), comprising

[0202] (b.1) preparing an aqueous synthesis mixture comprising the zeolite material provided in (i), a MWW template compound and a titanium source, wherein the molar ratio of the MWW template compound relative to Si (calculated as SiO2 and contained in the zeolite material provided in (a)) ranges from 0.5:1 to 1.4:1;

[0203] (b.2) hydrothermally synthesizing a titanium-containing zeolite material having an MWW-type framework structure from the aqueous synthesis mixture prepared in (b.1) to obtain a mother liquor containing a titanium-containing zeolite material having an MWW-type framework structure;

[0204] (c) spray drying the mother solution containing the titanium-containing zeolite material having an MWW-type framework structure obtained in (b.2).

[0205] 2. The method of embodiment 1, wherein in (b.1), the MWW template compound is selected from piperidine, hexamethyleneimine, N,N,N,N',N',N'-hexamethyl-1,5-pentanediammonium ion, 1,4-bis(N-methylpyrrolidinium)butane, octyltrimethylammonium hydroxide, heptyltrimethylammonium hydroxide, hexyltrimethylammonium hydroxide and a mixture of two or more thereof, and the MWW template compound is preferably piperidine.

[0206] 3. The method of embodiment 1 or 2, wherein in (b.1), the titanium source is selected from tetrabutyl orthotitanate, tetraisopropyl orthotitanate, tetraethyl orthotitanate, titanium dioxide, titanium tetrachloride, titanium tert-butoxide, and a mixture of two or more thereof, and the titanium source is preferably tetrabutyl orthotitanate.

[0207] 4. The method of any one of embodiments 1 to 3, wherein in the aqueous synthesis mixture in (b.1), the molar ratio of Ti (calculated as TiO2 and contained in the titanium source) to Si (calculated as SiO2 and contained in the zeolite material having a molar ratio of B2O3:SiO2 of up to 0.02:1) ranges from 0.005:1 to 0.1:1, preferably from 0.01:1 to 0.08:1, and more preferably from 0.02:1 to 0.06:1.

[0208] 5. The process according to any one of embodiments 1 to 4, wherein in the aqueous synthesis mixture in (b.1), the molar ratio of H2O to Si (calculated as SiO2 and contained in the zeolite material having a molar ratio of B2O3:SiO2 of at most 0.02:1) is in the range of 8:1 to 20:1, preferably 10:1 to 18:1, more preferably 12:1 to 16:1.

[0209] 6. The method of any one of embodiments 1 to 5, wherein in the aqueous synthesis mixture in (b.1), the molar ratio of the MWW template compound relative to Si (calculated as SiO2 and contained in the zeolite material provided in (i)) ranges from 0.5:1 to 1.7:1, preferably from 0.8:1 to 1.5:1, more preferably from 1.0:1 to 1.3:1.

[0210] 7. The process according to any one of embodiments 1 to 6, wherein in (b.2), the hydrothermal synthesis is carried out at a temperature in the range of 80 to 250°C, preferably 120 to 200°C, more preferably 160 to 180°C.

[0211] 8. The process according to any one of embodiments 1 to 7, wherein in (b.2), the hydrothermal synthesis is carried out for a time of 10 to 100 h, more preferably 20 to 80 h, more preferably 40 to 60 h.

[0212] 9. The process according to any one of embodiments 1 to 8, wherein in (b.2), the hydrothermal synthesis is carried out in a closed system under autogenous pressure.

[0213] 10. The process according to any of embodiments 1 to 9, wherein during (b.2), and after (b.2) and before (c), the titanium-containing zeolitic material having an MWW framework structure is not separated from its mother liquor.

[0214] 11. The method of any one of embodiments 1 to 10, wherein the mother liquor comprising the titanium-containing zeolite material having an MWW framework structure subjected to (c) has, after optional concentration or dilution, a solid content in the range of 5 to 25 wt.%, more preferably 10 to 20 wt.%, based on the total weight of the mother liquor comprising the titanium-containing zeolite material.

[0215] 12. The process according to any one of embodiments 1 to 11, wherein during spray drying in (c), the drying gas inlet temperature ranges from 200 to 350°C, and the drying gas outlet temperature ranges from 70 to 190°C.

[0216] 13. The process according to any one of embodiments 1 to 12, wherein the zeolitic material having an MWW framework structure obtained by (c) has an Si content of 30 to 40 wt.-% (calculated as elemental Si), a total organic carbon content (TOC) in the range of 0 to 14 wt.-%, and a Ti content of 2.1 to 2.8 wt.-% (calculated as elemental titanium), in each case based on the total weight of the zeolitic material.

[0217] 14. The method of any one of embodiments 1 to 13, further comprising

[0218] (d) treating the titanium-containing zeolitic material having an MWW framework structure obtained in (iii) with an aqueous solution having a pH of at most 5.

[0219] 15. The process of embodiment 14, wherein after (c) and before (d), the spray-dried titanium-containing zeolitic material having an MWW framework structure obtained from (c) is not calcined.

[0220] 16. The method of embodiment 14 or 15, wherein in (d), the weight ratio of the aqueous solution to the titanium-containing zeolitic material having an MWW framework structure ranges from 10:1 to 30:1, preferably from 15:1 to 25:1, more preferably from 18:1 to 22:1.

[0221] 17. The method according to any one of embodiments 14 to 16, wherein in (d), the aqueous solution comprises an inorganic acid, which is preferably selected from phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid and a mixture of two or more thereof, and the aqueous solution preferably comprises nitric acid.

[0222] 18. The method according to any one of embodiments 14 to 17, wherein in (d), the pH of the aqueous solution is from 0 to 5, preferably from 0 to 3, more preferably from 0 to 2.

[0223] 19. The process according to any of embodiments 14 to 18, wherein in (d) the titanium-containing zeolitic material having an MWW framework structure is treated with an aqueous solution at a temperature of 50 to 175°C, preferably 70 to 125°C, more preferably 95 to 105°C.

[0224] 20. The process according to any of embodiments 14 to 19, wherein in (d), the titanium-containing zeolitic material having an MWW-type framework structure is treated with the aqueous solution for a time of 0.1 to 6 h, preferably 0.3 to 2 h, more preferably 0.5 to 1.5 h.

[0225] 21. The process according to any one of embodiments 14 to 20, wherein the treatment of (d) is carried out in a closed system under autogenous pressure.

[0226] 22. The method according to any one of embodiments 14 to 21, further comprising

[0227] (e) separating the titanium-containing zeolite material having an MWW framework structure obtained in (d) from the aqueous solution, and optionally subsequently washing the separated titanium-containing zeolite material having an MWW framework.

[0228] 23. The process of embodiment 22, wherein (e) comprises drying the isolated and optionally washed titanium-containing zeolitic material having an MWW framework structure.

[0229] 24. The method according to any one of embodiments 14 to 23, further comprising

[0230] (f) preparing a suspension, preferably an aqueous suspension comprising the titanium-containing zeolitic material having an MWW framework structure obtained by (d), preferably by (e), the solids content of the suspension preferably being from 5 to 25 wt. %, more preferably from 10 to 20 wt. %, based on the total weight of the suspension, and spray drying the suspension.

[0231] 25. The process of embodiment 24, wherein during spray drying, the drying gas inlet temperature ranges from 200 to 330° C., and the drying gas outlet temperature ranges from 120 to 180° C.

[0232] 26. The method according to any one of embodiments 14 to 25, further comprising

[0233] (g) calcining the titanium-containing zeolitic material having an MWW framework structure obtained from (d), preferably from (e), more preferably from (f), wherein the calcination is preferably carried out at a temperature in the range of 400 to 800°C, more preferably 600 to 700°C.

[0234] 27. The process of embodiment 26, wherein in (vii), the calcination is carried out in a continuous mode, preferably at a rate of 0.2 to 2.0 kg of zeolitic material per hour, more preferably at a rate of 0.5 to 1.5 kg of zeolitic material per hour.

[0235] According to stage (V), the TiMWW preferably obtained according to stage (IV) is subjected to a suitable Zn treatment to obtain a ZnTiMWW for preparing the suspension of (a). Generally, as far as (V) is concerned, there are no particular restrictions, as long as the preferred ZnTiMWW defined above with the preferred Zn and Ti contents can be obtained. Most preferably, stage (V) comprises at least one suitable impregnation stage, more preferably at least one wet impregnation stage. Regarding the impregnation stage, the TiMWW preferably obtained according to (IV) is preferably contacted with at least one suitable Zn-containing precursor in at least one suitable solvent, most preferably water (wet impregnation). As suitable Zn-containing precursor, water-soluble Zn salts are particularly preferred, particularly preferably zinc acetate dihydrate. It is further preferred to prepare a solution of the Zn-containing precursor, preferably an aqueous solution, and to suspend the TiMWW in this solution. It is further preferred that the impregnation is carried out at a temperature elevated relative to room temperature, preferably at a temperature in the range of 75 to 125° C., more preferably 85 to 115° C., for a period of 3.5 to 5 h, more preferably 3 to 6 h. The suspension is preferably stirred during the impregnation. After impregnation, the obtained ZnTiMWW is preferably suitably separated from the suspension. All methods for separating ZnTiMWW from the suspension are conceivable. Particularly preferably, separation is carried out by filtration, ultrafiltration, diafiltration or centrifugation. A combination of two or more of these methods can be applied. According to the present invention, ZnTiMWW is preferably separated from the suspension by filtration to obtain a filter cake, which is preferably washed, preferably with water. If washing is used, the washing process can preferably be continued until the conductivity of the washing water is less than 1,000 microsiemens / cm, more preferably less than 900 microsiemens / cm, more preferably less than 800 microsiemens / cm, more preferably less than 700 microsiemens / cm. Subsequently, the preferably washed filter cake is pre-dried, for example by subjecting the filter cake to a suitable gas flow, preferably a nitrogen flow, preferably for 5 to 15 hours, more preferably 8 to 12 hours.

[0236] If TiMWW or ZnTiMWW is used as the catalytically active material according to the invention, the organic solvent is preferably acetonitrile.

[0237] Generally, the preferred ZnTiMWW catalysts can be prepared according to the specific teachings disclosed in WO 2013 / 117536 A2, the entire contents of which are incorporated herein by reference.

[0238] TS-1 Catalyst

[0239] According to the present invention, a titanium silicalite-1 catalyst, preferably a fixed bed titanium silicalite-1 catalyst, can be used as a catalyst. Titanium silicalite-1 is a microporous zeolite of MFI type structure that does not contain aluminum, and in which the Si(IV) in the silicate lattice is partially replaced by titanium as Ti(IV). The term "microporous" used in the context of the present invention refers to pores with a pore size of less than 2 nm, measured according to DIN 66134.

[0240] The titanium silicalite-1 zeolite of the catalyst can in principle be prepared by any conceivable method. Typically, the synthesis of at least one titanium zeolite of the present invention is carried out in a hydrothermal system comprising a combination of a silicon oxide active source and a titanium source (e.g. titanium oxide) and at least one template compound capable of forming the desired titanium zeolite in an aqueous suspension (e.g. in an alkaline suspension). Typically, an organic template is used. Preferably, the synthesis is carried out at an elevated temperature, for example at a temperature in the range of 150 to 200° C., preferably in the range of 160 to 180° C.

[0241] In principle, any suitable compound can be used as a source of silicon oxide. Typical sources of silicon oxide (SiO2) include silicates, silica hydrogels, silicic acid, colloidal silica, fumed silica, tetraalkoxysilanes, silicon hydroxide, precipitated silica and clays. Both so-called "wet process" silica and so-called "dry process" silica can be used. In these cases, the silica is particularly preferably amorphous, with the size of the silica particles ranging from, for example, 5 to 100 nm and the surface area of ​​the silica particles ranging from, for example, 50 to 500 m 2 / g. Colloidal silica is especially commercially available as or "Wet process" silica is especially commercially available as or "Dry process" silica is especially commercially available as or It is also within the scope of the present invention to use a silicon dioxide precursor compound as a silicon oxide source. For example, tetraalkoxysilanes, such as tetraethoxysilane or tetrapropoxysilane, may be mentioned as precursor compounds.

[0242] As template, any template suitable for providing the desired MFI zeolite structure can be used. In particular, tetrapropylammonium hydroxide is used, more preferably tetra-n-propylammonium hydroxide. In a preferred embodiment of the process of the invention, the at least one pore former is removed in a subsequent step by calcination, as described below.

[0243] Typically, the synthesis of titanium silicalite-1 is carried out batchwise in an autoclave so that the reaction suspension is subjected to autogenous pressure for several hours or days until titanium silicalite-1 is obtained. According to a preferred embodiment of the present invention, the synthesis is typically carried out at elevated temperatures, wherein the temperature during the hydrothermal crystallization step is typically in the range of 150 to 200° C., preferably 160 to 180° C. Typically, the reaction is carried out for several hours to several days, preferably 12 h to 48 h, more preferably 20 to 30 h. It is also conceivable to add seeds to the synthesis batch.

[0244] According to one embodiment of the present invention, the obtained crystalline titanium silicalite-1 is separated from the reaction suspension (ie from the mother liquor), optionally washed and dried.

[0245] All known methods for separating crystalline titanium silicalite-1 from suspensions can be used. Mention should be made in particular of filtration, ultrafiltration, diafiltration and centrifugation methods.

[0246] In the case of washing the obtained crystalline titanium silicalite-1, the washing step can be carried out using any suitable washing substance, such as water, an alcohol such as methanol, ethanol, or methanol and propanol, or ethanol and propanol, or methanol and ethanol and propanol, or a mixture of water and at least one alcohol, such as water and ethanol or water and methanol, or water and ethanol or water (eater) and propanol, or water and methanol and ethanol, or water and methanol and propanol, or water and ethanol and propanol, or water and ethanol and methanol and propanol. A mixture of water or water and at least one alcohol (preferably water and ethanol) is used as the washing substance.

[0247] The drying of the crystalline titanium silicalite-1 is usually carried out at a temperature of 80 to 160°C, preferably 90 to 145°C, particularly preferably 100 to 130°C.

[0248] Instead of the above-mentioned separation methods such as filtration, ultrafiltration, diafiltration and centrifugation methods, the suspension can also be subjected to a spraying method according to a further alternative embodiment, such as spray granulation and spray-drying.

[0249] If the separation of crystalline titanium silicalite-1 is carried out by a spray method, the separation and drying steps can be combined into a single step. In this case, the reaction suspension itself or a concentrated reaction suspension can be used. In addition, suitable additives, such as at least one suitable adhesive and / or at least one pore former, can be added to the suspension before spray drying or spray granulation - or to the reaction suspension itself or the concentrated suspension. Suitable adhesives are described in detail below. As pore formers, all of the above-mentioned pore formers can be used. In the case where the suspension is spray dried, the pore former (if added) can be added in two ways. First, the pore former can be added to the reaction mixture before spray drying. However, it is also possible to add a portion of the pore former to the reaction mixture before spray drying, while the remaining pore former is added to the spray-dried material.

[0250] In the case where the suspension is first concentrated to increase the content of tiranite-1 in the suspension, the concentration can be achieved, for example, by evaporation, for example evaporation under reduced pressure, or by cross-flow filtration. Likewise, the suspension can be concentrated by dividing the suspension into two parts, wherein the solids contained in one of the two parts are separated by filtration, diafiltration, ultrafiltration or centrifugation and suspended in the other part of the suspension after an optional washing step and / or drying step. The concentrated suspension as thus obtained is then subjected to a spraying method, such as spray granulation and spray drying.

[0251] According to an alternative embodiment, the concentration is achieved by separating the at least one titanium zeolite from the suspension and resuspending the titanium zeolite, optionally together with at least one suitable additive as described above, wherein the titanium zeolite may be subjected to at least one washing step and / or at least one drying step before resuspension. The resuspended titanium zeolite may then be used for a spray process, preferably spray drying.

[0252] Spray drying is a direct method of drying a slurry, suspension or solution by feeding a well-dispersed liquid-solid slurry, suspension or solution, which usually also contains a binder, into an atomizer and then rapidly drying it in a hot air stream. Atomizers can be of several different types. The most common is wheel atomization, which uses a high-speed rotating wheel or disk to break up the slurry into droplets, which are rotated out of the wheel into the chamber and are rapidly dried before hitting the chamber wall. Atomization can also be achieved by a single fluid nozzle that relies on hydrostatic pressure to force the slurry through a small nozzle. Multi-fluid nozzles are also used, in which gas pressure is used to force the slurry through the nozzle. The spray material obtained using spray drying and spray granulation methods (e.g., fluidized bed drying) can contain solids and / or hollow spheres, and can be essentially composed of such spheres, whose diameter ranges from, for example, 5 to 500 μm, 5 to 300 μm. Single-component or multi-component nozzles can be used. It is also conceivable to use a rotary atomizer. Possible inlet temperatures of the carrier gas used range, for example, from 200 to 600° C., preferably from 300 to 500° C. The outlet temperature of the carrier gas ranges, for example, from 50 to 200° C. Mention may be made as carrier gas of air, rarefied air or an oxygen-nitrogen mixture with an oxygen content of up to 10% by volume, preferably up to 5% by volume, more preferably less than 5% by volume, for example up to 2% by volume. The spraying process can be carried out in countercurrent or cocurrent.

[0253] Preferably, the titanium silicalite-1 is separated from the reaction suspension by conventional filtration or centrifugation, optionally dried and / or calcined and resuspended, preferably in a mixture, preferably an aqueous mixture of at least one binder material and / or a pore former. The resulting suspension is then preferably spray-dried or spray-granulated. The obtained spray material may be subjected to an additional washing step, which is carried out as described above. The optionally washed spray material is then dried and calcined, wherein the drying and calcining are preferably carried out as described above.

[0254] According to an alternative, the crystallization of titanium silicalite-1 is not carried out before the above suspension has been spray-dried. Therefore, first a suspension is formed comprising a silica source (preferably silica), a titanium oxide source and a template compound capable of forming titanium silicalite-1. The suspension is then spray-dried, wherein an optional additional pore-forming agent is subsequently added to the spray-dried titanium silicalite-1.

[0255] The spray-dried titanium silicalite-1 obtained according to the above process may optionally be subjected to at least one washing process. If at least one washing process is carried out, it is preferably followed by at least one drying step and / or at least one calcining step.

[0256] The titanium silicalite-1 optionally obtained by the spraying process can further undergo at least one calcination step, which is carried out according to a preferred embodiment of the present invention after the drying step, or instead of the drying step. The at least one calcination step is generally carried out at a temperature in the range of 350 to 750° C., preferably 400 to 700° C., particularly preferably 450 to 650° C.

[0257] The calcination of titanium silicalite-1 can be carried out under any suitable gas atmosphere, wherein air and / or rarefied air are preferred. In addition, the calcination is preferably carried out in a muffle furnace, a rotary cone and / or a belt calcining furnace, wherein the calcination is generally carried out for more than 1 hour, for example 1 to 24 hours or 4 to 12 hours. In the method of the present invention, the titanium silicalite-1 can be calcined once, twice or more times, for at least 1 hour in each case, for example 4 to 12 hours in each case, preferably 4 to 8 hours, wherein the temperature during the calcination step can be kept constant, or the temperature can be changed continuously or discontinuously. If the calcination is carried out twice or more, the calcination temperature in each step can be different or the same.

[0258] Therefore, a preferred embodiment of the present invention relates to a process as described above, wherein the titanium silicalite-1 separated from the suspension, for example by filtration or spray drying, is washed with a suitable washing substance and subsequently subjected to at least one drying step. Drying is generally carried out at a temperature in the range of 80 to 160° C., preferably 90 to 145° C., particularly preferably 100 to 130° C. Most preferably, after drying, a calcination step is carried out. This step is generally carried out at a temperature in the range of 350 to 750° C., preferably 400 to 700° C., particularly preferably 450 to 650° C.

[0259] The titanium silicalite-1 prepared as described above can usually be used directly as the catalyst in stages (i) and (iii). However, it is particularly preferred to use a fixed bed catalyst in both stages (i) and (iii), i.e. not to use the crystalline zeolite material itself as catalyst, but to process the crystalline material into a shaped body comprising titanium silicalite-1. Therefore, according to a preferred embodiment, a shaped body comprising titanium silicalite-1 as described above is used as the catalyst.

[0260] In general, when using shaped bodies as catalysts, the catalyst may contain, in addition to the titanium silicalite 1 according to the invention, all conceivable further compounds, such as, in particular, at least one binder and / or at least one pore former. Furthermore, the catalyst may also contain at least one binder instead of the at least one binder and / or at least one pore former or in addition to the at least one binder and / or the at least one pore former.

[0261] As binders, all compounds are suitable which provide adhesion and / or cohesion between the titanium silicalite-1 to be formed, which exceeds the physical adsorption without the binder. Examples of such binders are metal oxides, such as SiO2, Al2O3, TiO2, ZrO2 or MgO or clays or mixtures of two or more of these compounds. Clay minerals and naturally occurring or synthetically produced aluminas, such as α-, β-, γ-, δ-, η-, κ-, χ- or θ-aluminas and their inorganic or organometallic precursor compounds, such as gibbsite, bayerite, boehmite or pseudoboehmite or trialkoxyaluminates, such as aluminum triisopropoxide, are particularly preferably Al2O3 binders. Further preferred binders are amphiphilic compounds having polar and nonpolar parts and graphite. Other binders are, for example, clays, such as montmorillonite, kaolin, metakaolin, hectorite, bentonite, halloysite, dickite, nacrite or anaxite.

[0262] These adhesives can be used per se. It is also within the scope of the present invention to use compounds that form adhesives in at least one other step of manufacturing the molded body. Examples of such adhesive precursors are tetraalkoxysilanes, tetraalkoxy titanates, tetraalkoxy zirconates or a mixture of two or more different tetraalkoxy silanes, or a mixture of two or more different tetraalkoxy titanates, or a mixture of two or more different tetraalkoxy zirconates, or a mixture of at least one tetraalkoxy silane and at least one tetraalkoxy titanate, or a mixture of at least one tetraalkoxy silane and at least one tetraalkoxy zirconate, or a mixture of at least one tetraalkoxy titanate and at least one tetraalkoxy zirconate, or a mixture of at least one tetraalkoxy silane and at least one tetraalkoxy titanate and at least one tetraalkoxy zirconate.

[0263] In the context of the present invention, very particular preference is given to binders which completely or partially contain SiO2 or which are precursors of SiO2 (from which SiO2 is formed in at least one further step). In this context, colloidal silicon dioxide and so-called "wet process" silicon dioxide and so-called "dry process" silicon dioxide can be used. Particularly preferably, the silicon dioxide is amorphous silicon dioxide, the diameter of the silicon dioxide particles being, for example, 5 to 100 nm and the surface area of ​​the silicon dioxide particles being 50 to 500 m 2 / g.

[0264] Colloidal silica is commercially available, preferably as alkaline and / or ammoniacal solution, more preferably as ammoniacal solution, in particular, for example or "Wet process" silicas are commercially available, especially e.g. or "Dry process" silica is commercially available, especially e.g. or In particular, ammonia solutions of colloidal silicon dioxide are preferred in the present invention. Therefore, the present invention also describes a catalyst comprising a shaped body as described above, which comprises titanium silicalite-1 as described above and additionally comprises SiO2 as a binder material, wherein the binder used according to (I) is a binder comprising or forming SiO2. Generally, the titanium zeolite can also be shaped without the use of a binder.

[0265] The present invention therefore also relates to a process wherein in stages (i) and (iii) the titanium silicalite-1 catalyst is obtained by shaping the titanium silicalite-1 to give a shaped body comprising titanium silicalite-1 and preferably at least one binder, in particular a silica binder.

[0266] If necessary, a mixture of titanosilicate-1 and at least one binder or at least a binder precursor can be added at least on the pore former to further process and form a catalyst shaped body to be used as a fixed bed catalyst. With respect to the prepared shaped body, the pore former that can be used is a compound that provides a specific pore size and / or a specific pore size distribution and / or a specific pore volume. In particular, with respect to the prepared shaped body, the pore former provides micropores and / or micropores, in particular mesopores and micropores.

[0267] The present invention therefore also relates to a process wherein in stages (i) and (iii), the titanium silicalite-1 catalyst is obtained by shaping the titanium silicalite-1 to give a shaped body comprising titanium silicalite-1 and preferably at least one binder, in particular a silica binder, which shaped body has, in particular, micropores and mesopores.

[0268] As for examples of pore formers that can be used, reference can be made to the pore formers already mentioned above. Preferably, the pore former used in the forming method of the present invention is a polymer that is dispersible, suspendable or emulsifiable in water or in an aqueous solvent mixture. Particularly preferred polymers are polymeric vinyl compounds, such as polyalkylene oxides, such as polyethylene oxide, polystyrene, polyacrylates, polymethacrylates, polyolefins, polyamides and polyesters; carbohydrates, such as cellulose or cellulose derivatives, such as methylcellulose, or sugars or natural fibers. Other suitable pore formers are, for example, pulp or graphite.

[0269] If necessary, a mixture of two or more pore formers can be used to achieve a pore size distribution. In a particularly preferred embodiment of the method of the present invention, the pore former is removed by calcination to obtain a porous catalyst shaped body as described below. Preferably, a pore former providing mesopores and / or micropores, particularly preferably mesopores, is added to a mixture of at least one binder and the titanium silicalite-1 used to shape the titanium silicalite-1. Generally, it is also possible to shape the titanium silicalite-1 to obtain a catalyst shaped body without using a pore former.

[0270] Besides the binder and optionally the pore former, further components, for example at least one bonding agent, may also be added to the mixture used for shaping the shaped catalyst bodies.

[0271] If at least one binder is used, the binder is either used to replace at least one pore former or to use the binder in addition to at least one pore former. In particular, compounds that also serve as pore formers can be used as binders. The binders that can be used are all known compounds suitable for this purpose. These are preferably organic, in particular hydrophilic polymers, such as cellulose, cellulose derivatives, such as methylcellulose and starches such as potato starch, wallpaper plaster, polyacrylates, polymethacrylates, polyvinyl alcohol, polyvinyl pyrrolidone, polyisobutylene or polytetrahydrofuran. It can be mentioned that water, alcohol or glycol or a mixture thereof, such as a mixture of water and alcohol, or a mixture of water and glycol, such as water and methanol or water and ethanol or water and propanol or water and propylene glycol are used as binders. Preferably, a mixture of two or more of cellulose, cellulose derivatives, water and these compounds, such as water and cellulose or a mixture of water and cellulose derivatives, is used as a binder. In a particularly preferred embodiment of the method of the present invention, the at least one binder is removed by calcination as further described below to obtain a shaped body.

[0272] According to another embodiment of the present invention, at least one acidic additive can be added to the mixture for forming the shaped body. If an acidic additive is used, an organic acidic compound that can be removed by calcination is preferred, and in this article, carboxylic acids such as formic acid, oxalic acid and / or citric acid can be mentioned. Two or more of these acidic compounds can also be used.

[0273] The order in which the components are added to the mixture for forming the shaped body is not critical. For example, if a combination of a binder, a pore former, a binder and optionally at least one acidic compound is used, the at least one binder can be added first, then the at least one pore former, the at least one acidic compound and finally the at least one binder, and the order of the at least one binder, the at least one pore former, the at least one acidic compound and the at least one binder can also be interchanged.

[0274] After adding at least one binder and / or at least one adhesive and / or at least one pore former and / or at least one acidic additive to the mixture comprising titanium silicalite-1, the mixture is usually homogenized for 10 to 180 minutes. In particular, a kneader, an edge grinder or an extruder is particularly preferably used for homogenization. The mixture is preferably kneaded. On an industrial scale, grinding in an edge grinder is preferred for homogenization. Homogenization is usually carried out at a temperature in the range of about 10° C. to the boiling point of the binder and at atmospheric pressure or slightly above atmospheric pressure. Optionally, at least one of the above-mentioned compounds can then be added. The mixture thus obtained is homogenized, preferably kneaded, until an extrudable plastic material is formed.

[0275] The homogenized mixture is then shaped to obtain a shaped body. All known suitable shaping methods can be used, such as extrusion, spray drying, spray granulation, briquetting (i.e. mechanical compression with or without the addition of an additional binder) or granulation (i.e. compaction by circular and / or rotary motion).

[0276] Preferred forming methods are those forming methods in which a conventional extruder is used to form a mixture comprising titanium silicalite-1. Thus, for example, extrudates with a diameter of 1 to 10 mm, and preferably 2 to 5 mm, are obtained. In addition to using an extruder, an extruder can also be used to prepare a shaped body. The shape of the shaped body prepared according to the invention can be selected as required. In particular, a sphere, an ellipse, a cylinder or a sheet is possible. Similarly, for example, hollow structures such as a hollow cylinder or a honeycomb-like structure or a star-shaped geometry can be mentioned.

[0277] The forming can be carried out at ambient pressure or at a pressure above ambient pressure, for example at a pressure in the range of 1 bar to several hundred bars. Furthermore, the compaction can be carried out at ambient temperature or at a temperature above ambient temperature, for example at a temperature in the range of 20 to 300° C. If drying and / or calcination is part of the forming step, temperatures up to 600° C. are contemplated. Finally, the compaction can be carried out in an ambient atmosphere or in a controlled atmosphere. A controlled atmosphere is, for example, an inert gas atmosphere, a reducing atmosphere and / or an oxidizing atmosphere.

[0278] Preferably, the shaping step is followed by at least one drying step. The at least one drying step is carried out at a temperature in the range of typically 80 to 160° C., preferably 90 to 145° C. and particularly preferably 100 to 130° C., for typically more than 6 h, for example 6 to 24 h. However, shorter drying times, for example about 1, 2, 3, 4 or 5 h, are also possible, depending on the moisture content of the material to be dried.

[0279] Before and / or after the drying step, the extrudates preferably obtained can, for example, be comminuted. Preferably, granules or fragments having a particle size of 0.1 to 5 mm, in particular 0.5 to 2 mm, are thereby obtained.

[0280] According to a preferred embodiment of the present invention, the drying of the shaped bodies is preferably followed by at least one calcination step. Calcination is carried out at a temperature in the range of generally 350 to 750° C., preferably 400 to 700° C., particularly preferably 450 to 50° C. Calcination can be carried out under any suitable gas atmosphere, preferably air and / or rarefied air. In addition, calcination is preferably carried out in a muffle furnace, a rotary kiln and / or a belt calciner, wherein the duration of calcination is generally more than 1 h, for example 1 to 24 h, or 3 to 12 h. In the method of the present invention, the catalyst shaped body can therefore be calcined, for example, at least once, twice or more times, in each case for at least 1 h, for example in each case for 3 to 12 h, wherein the temperature during the calcination step can be kept constant or continuously or discontinuously changed. If calcination is carried out twice or more, the calcination temperature in each step can be different or the same.

[0281] According to a particularly preferred embodiment, the catalyst shaped body is subjected to hydrothermal treatment. Any suitable method known to those skilled in the art can be used for hydrothermal treatment. Therefore, the catalyst or shaped catalyst is usually contacted with water or water vapor. Usually, the hydrothermal treatment is carried out by adding the catalyst or according to the present invention together with water into an autoclave, and the slurry is heated to a temperature of 100 to 200 ° C, preferably 120 to 150 ° C for a period of 1 to 48 hours, preferably 24 to 48 hours at a pressure of 1.5 to 5 bar, preferably 2 to 3 bar. At least one washing step is usually carried out subsequently, preferably used as a washing substance. After being treated with water, the catalyst is preferably dried and / or calcined, wherein drying and calcining are carried out as described above. According to a preferred embodiment, the hydrothermal treatment is carried out by stirring the catalyst shaped body in an autoclave, wherein the stirring rate is adjusted to a stirring rate that avoids wear as much as possible. However, if the catalyst is used in the form of a cylindrical extrudate, some wear is required to achieve a cylindrical extrudate with a rounded edge. Using extrudates with rounded edges, higher packing densities can be achieved, for example using the extrudates as fixed bed catalysts in tubular reactor R1 and / or axial reactor R2. In addition, dust formation of the catalyst in the epoxidation process in stages (i) and (iii) is reduced.

[0282] Furthermore, in the epoxidation process of the present invention, a titanium silicalite-1 catalyst as described above is used, which has micropores and mesopores and contains 49.5 to 80% by weight, preferably 69.5 to 80% by weight, of titanium silicalite catalyst, based on the total weight of the catalyst, and 19.5 to 50% by weight, preferably 19.5 to 30% by weight, of at least one binder, preferably a silica binder, based on the total weight of the catalyst shaped body.

[0283] If TS-1 is used as the catalytically active material of the present invention, the organic solvent is preferably methanol.

[0284] Step (a2)

[0285] According to (a2), the feed stream of (a1) is subjected to epoxidation conditions in a reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent.

[0286] The reactor used in (a2) can be operated isothermally or adiabatically, wherein preferably the reactor in (a2) is an isothermally operated reactor.

[0287] Generally, the conversion of the starting materials can be controlled by adjusting the temperature, pressure, WHSV, etc. of the starting materials. For example, the reaction temperature can be adjusted so that at least 90% of the epoxidant is converted. The amount of starting material present in the reaction mixture before and after the epoxidation reaction can be analyzed by any suitable technique, such as chromatography.

[0288] In general, the continuous epoxidation reaction in (a2) can be carried out in any suitable vessel or reactor. Preferably, the reaction in (a2) is carried out in at least one continuously operated reactor such as a tubular reactor or a tube bundle reactor, which preferably comprises at least one cooling jacket surrounding the at least one tube, wherein the temperature of the reaction mixture is isothermally controlled using a heat transfer medium, preferably by passing the heat transfer medium through the jacket of the reactor. If the reaction in (a2) is carried out in such a reactor comprising at least one cooling jacket, the term "epoxidation reaction temperature" as used herein is defined as the temperature of the heat transfer medium before controlling the temperature of the reaction mixture, preferably as the temperature of the heat transfer medium at the jacket inlet of the isothermal reactor.

[0289] Preferably, at least one of the reactors in which the reaction of (a2) is carried out is a tubular reactor or a tube bundle reactor.

[0290] The catalyst comprising the titanium-containing zeolite can be used in every conceivable form as described above, including powder, micropowder, preferably spray powder, as a shaped body comprising powder, or as a shaped body comprising micropowder, preferably spray powder. Preferably, the catalyst comprising the titanium-containing zeolite is used as a shaped body comprising powder or micropowder, preferably spray powder, more preferably as a shaped body comprising micropowder, preferably spray powder.

[0291] The catalyst used in step (a2) of the present invention can be arranged in the reactor in every conceivable way. Preferably, the catalyst is arranged as a fluidized bed or a fixed bed, more preferably as a fixed bed.

[0292] Preferably, the epoxidation conditions in (a2) include an epoxidation reaction temperature ranging from 20 to 100°C, more preferably from 25 to 80°C, more preferably from 25 to 60°C, more preferably from 30 to 60°C.

[0293] Preferably, the epoxidation conditions in (a2) include an epoxidation reaction pressure of 5 to 100 bar, more preferably 10 to 32 bar, more preferably 15 to 25 bar, wherein the epoxidation reaction pressure is defined as the pressure at the outlet of the isothermal reactor.

[0294] Therefore, the epoxidation conditions of (A2) preferably include an epoxidation reaction temperature of 20 to 100° C. and an epoxidation reaction pressure of 5 to 100 bar, more preferably an epoxidation reaction temperature range of 25 to 60° C. and an epoxidation reaction pressure range of 10 to 32 bar, more preferably an epoxidation reaction temperature of 30 to 60° C. and an epoxidation reaction pressure of 15 to 25 bar.

[0295] The term "epoxidation conditions" as used in the context of the present invention refers to the epoxidation reaction in step (a2), wherein for at least 98%, preferably at least 99%, more preferably at least 99.9% of the total reaction time, the reaction temperature and pressure are within the ranges defined above. The term "total reaction time" as used in the context of the present invention refers to the reaction time of a given catalyst bed used before disposal or regeneration. In particular at the beginning of the epoxidation reaction (a2), when the catalyst is fresh, i.e. at the start of the epoxidation reaction in (a2), the reaction temperature or pressure or both may be outside the above ranges for a short time. Preferably, the flow rate of the heat transfer medium is selected so that the temperature difference between its inlet temperature and outlet temperature is at most 3K, more preferably at most 2K, more preferably at most 1K.

[0296] Preferably, the epoxidation reaction of step (a2) according to the present invention is carried out with a substantially constant conversion of the epoxidizing agent, preferably of hydrogen peroxide. Preferably, in order to determine the hydrogen peroxide conversion, the molar flow rate of hydrogen peroxide in the effluent stream removed in (a3) ​​(referred to herein as m out ) and the molar flow rate of hydrogen peroxide in the feed stream provided in (a1) (referred to herein as m in ) compared to, and wherein the hydrogen peroxide conversion is defined as 100x(1-m out / m in). Preferably, the inlet temperature of the above-mentioned heat transfer medium is adjusted within the above-mentioned preferred range so as to keep the hydrogen peroxide conversion rate substantially constant at 80 to 100%, more preferably 90 to 100%, more preferably 95 to 100%, more preferably 99 to 100%, more preferably 99.5 to 100%, more preferably 99.9 to 100%. The term "epoxidation conditions comprising" as used in the context of the present invention refers to the epoxidation reaction in step (a2), wherein the hydrogen peroxide conversion rate is within the above-mentioned range for at least 98%, preferably at least 99%, more preferably at least 99.9% of the total reaction time. The term "total reaction time" as used in the context of the present invention refers to the reaction time of a given catalyst bed used before disposal or regeneration. In particular at the beginning of the epoxidation reaction (a2), when the catalyst is fresh, i.e. at the start of the epoxidation reaction (a2), the hydrogen peroxide conversion rate may exceed the above-mentioned range for a short time. Preferably, the reaction temperature is not kept constant during the reaction, but is adjusted continuously or stepwise to allow a constant hydrogen peroxide conversion rate. Typically, due to a certain catalyst deactivation, the reaction temperature is increased continuously or stepwise. Preferably, the reaction temperature is increased continuously or stepwise by at most 1 K / d (Kelvin / day), more preferably by less than 1 K / d.

[0297] Preferably, the reaction mixture present in the reactor in (a2) is liquid under the epoxidation conditions. Preferably, the reaction mixture consists of a single liquid phase, two liquid phases or more than three liquid phases. Preferably, the reaction mixture in the reactor in (a2) consists of a single liquid phase or two liquid phases, more preferably consists of a single liquid phase.

[0298] Typically, the reactor used in step (a2) of the present invention can be arranged horizontally or vertically. Preferably, the reactor is arranged vertically. In the preferably vertically arranged reactor, the feed stream provided in (a1) can be passed in an upflow mode or a downflow mode, preferably an upflow mode. Preferably, the heat transfer medium passes through the jacket in a co-current mode compared to the flow direction of the feed stream.

[0299] Typically, the epoxidation reaction in (a2) can be carried out in one or more reactors, wherein these reactors can be arranged in parallel or in series. Preferably, the reaction in (a2) is carried out in one reactor or at least two reactors arranged in series, preferably two reactors arranged in series, wherein between the two reactors arranged in series, suitable intermediate treatment can be carried out. If the reaction is carried out in two reactors arranged in series, it is preferred that the first reactor is operated as described above, i.e., operated as an isothermal reactor, and the second reactor, i.e., the downstream reactor, is operated as an adiabatic or substantially adiabatic reactor. The term "reactor" as used herein also includes two or more reactors arranged in parallel, wherein the feed stream passing through is divided into two or more substreams, each substream enters the reactor, and the effluent stream removed from the reactor is combined to obtain a total effluent stream. Therefore, the epoxidation reaction can be carried out in at least one first reactor, such as two or more first reactors, such as 2,3,4 first reactors, the first reactors are arranged in parallel and are preferably isothermal reactors, and in at least one second reactor, such as two or more second reactors, such as 2,3,4 second reactors, the second reactors are arranged in parallel and are preferably adiabatic or substantially adiabatic reactors.

[0300] If the epoxidation reaction of (a2) is carried out in two reactors arranged in series, it is preferably carried out in the first reactor, which is preferably an isothermally operated reactor, the hydrogen peroxide conversion being essentially maintained in the range of 80 to 99%, preferably 85 to 98%, more preferably 90 to 97%, and in the second reactor, which is preferably designed as an adiabatic or essentially adiabatic reactor, the total hydrogen peroxide conversion (i.e. the hydrogen peroxide conversion taking into account the conversions in the first and second reactors) reaching a value of more than 99%, preferably at least 99.5%, more preferably at least 99.9%.

[0301] Step (a3)

[0302] According to step (a3), a product stream comprising propylene oxide and an organic solvent is removed from the reactor. The product stream is usually subjected to at least one post-treatment step to separate propylene oxide from the product stream. In addition, the organic solvent, which usually comprises a by-product of the epoxidation reaction, is preferably subjected to one or more post-treatment steps to allow the recycling of the organic solvent, preferably acetonitrile, preferably after one or more purification steps before entering step (a1). In the following reference examples 2 and Figure 1 and 2 A preferred post-processing step procedure is described in .

[0303] Step (b)

[0304] According to (b), the introduction of the feed stream into the reactor according to (a1) is stopped.

[0305] Preferably, step (b) further comprises separating the reaction mixture comprising propylene oxide and an organic solvent from a catalyst comprising a titanium-containing zeolite as a catalytically active material. This separation of the reaction mixture from the spent catalyst comprising a titanium-containing zeolite can be achieved in any suitable manner, such as pumping, slurry decanting, decantation, filtering, etc. Optionally, (b) further comprises drying the catalyst before performing the washing in (c), wherein the catalyst is preferably not dried before performing the washing in (c). If drying is performed, it is preferred that the drying comprises contacting the catalyst with a gas stream comprising nitrogen, preferably contacting at a temperature in the range of 40 to 200° C., more preferably 55 to 150° C., more preferably 70 to 100° C. The separation can be further achieved by flushing the reactor with an organic solvent, preferably acetonitrile.

[0306] Therefore, in a preferred embodiment, by replacing the feed stream of (a1) with a stream consisting essentially of an organic solvent (preferably acetonitrile), the hydrogen peroxide, propylene and propylene oxide in the reactor are flushed out until the reactor is substantially free of hydrogen peroxide, propylene and propylene oxide, and the reactor is optionally depressurized and emptied. For example, the stream consisting essentially of an organic solvent, preferably acetonitrile, contains at least 60% by weight, preferably at least 70% by weight, more preferably at least 75% by weight, more preferably at least 80% by weight of organic solvent, and optionally contains at least one other liquid, preferably water. Therefore, preferably at least 95% by weight, more preferably at least 98% by weight, more preferably at least 99% by weight of the stream consisting essentially of an organic solvent, preferably acetonitrile, consists of an organic solvent, preferably acetonitrile and water, wherein at least 60% by weight, preferably at least 70% by weight, more preferably at least 75% by weight, more preferably at least 80% by weight of the stream consists of an organic solvent, preferably acetonitrile. The flushing is preferably carried out at a temperature of the stream consisting essentially of the organic solvent, preferably acetonitrile, in the range of 20 to 90°C, more preferably 25 to 80°C, more preferably 30 to 70°C.

[0307] In an alternative preferred embodiment, the process of the present invention further comprises preparing the feed stream in (a1) by mixing a stream comprising propylene, a stream comprising hydrogen peroxide or a source of hydrogen peroxide and a stream comprising an organic solvent, wherein step (b) comprises

[0308] (b1) stopping a stream comprising hydrogen peroxide or a source of hydrogen peroxide;

[0309] (b2) stopping the stream comprising propylene and the stream comprising the organic solvent;

[0310] (b3) optionally depressurizing and evacuating the reactor,

[0311] The step (b2) is preferably performed at least 30 minutes, more preferably at least 60 minutes after the step (b1).

[0312] Step (c)

[0313] According to step (c), the catalyst is washed with a liquid aqueous system.

[0314] The possible components of the liquid aqueous system of (c) and the corresponding amounts described below are to be understood as the liquid aqueous system used in (c) prior to addition to the catalyst comprising the titanium-containing zeolite.

[0315] Typically, the liquid aqueous system of (c) is not limited with respect to the amount of water contained therein. Thus, the liquid aqueous system may comprise, for example, at least 50% by weight, or at least 75% by weight, or at least 85% by weight of water, based on the total weight of the liquid aqueous system. Preferably, the liquid aqueous system of (c) comprises at least 95% by weight, more preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system.

[0316] The water used in (c) can be obtained from any suitable source. Preferably, the water used in (c) is deionized water or condensed water.

[0317] Preferably, the liquid aqueous system of (c) comprises only small amounts of methanol, and preferably is free or at least substantially free of methanol. Preferably, the liquid aqueous system of (c) comprises at most 5 wt.-%, more preferably 1 wt.-%, more preferably 0.1 wt.-%, more preferably 0.01 wt.-%, more preferably 0.001 wt.-%, more preferably 0.0001 wt.-% methanol, based on the total weight of the liquid aqueous system.

[0318] Preferably, the liquid aqueous system of (c) comprises only small amounts of hydrogen peroxide, while preferably being free or at least substantially free of methanol. Preferably, the liquid aqueous system of (c) comprises at most 0.1 wt.-%, preferably 0.01 wt.-%, more preferably 0.001 wt.-%, more preferably 0.0001 wt.-% hydrogen peroxide, based on the total weight of the liquid aqueous system.

[0319] Preferably, the pH of the liquid aqueous system of (c) is from 4 to 10, preferably from 7 to 9, as measured with a pH electrode.

[0320] Particularly preferably, the liquid aqueous system of (c) consists of water.

[0321] The washing in (c) can be carried out in any conceivable container. Thus, the washing can be carried out, for example, in a reactor containing the catalyst or in any other suitable container in the case where the catalyst is removed from the reactor for the washing in (c). Preferably, the washing in (c) is carried out in a reactor containing the catalyst.

[0322] Therefore, the washing in (c) is preferably carried out in a reactor comprising the catalyst, wherein the liquid aqueous system of (c) comprises at least 95% by weight, preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system.

[0323] The washing in (c) can be carried out in batch mode or continuous mode. In the case of washing in batch mode, the catalyst contacts the liquid aqueous system of a specific amount once or several times. Therefore, washing can be carried out by immersing the catalyst in the liquid aqueous system. During washing, the liquid aqueous system can be stirred together with the catalyst. It is conceivable that when the washing in (c) is carried out in batch mode, the liquid aqueous system can be replaced once or multiple times.

[0324] In the case of washing in a continuous mode, the catalyst is continuously contacted with the stream of the liquid aqueous system. In the case where the reactor containing the catalyst is arranged vertically and the washing is carried out in the reactor or the washing is carried out outside the reactor in any other suitable vertically arranged container, the washing can be carried out in an upflow mode or a downflow mode, preferably a downflow mode. Preferably, the washing in (c) is carried out in a continuous mode. More preferably, the washing in (c) is carried out in a continuous mode in the reactor containing the catalyst.

[0325] Therefore, the washing in (c) is preferably carried out in a continuous mode in a reactor comprising the catalyst, wherein the liquid aqueous system of (c) comprises at least 95% by weight, preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system.

[0326] Preferably, the washing in the continuous mode is carried out in a tubular reactor or a tube bundle reactor with a liquid aqueous system, wherein the liquid hourly space velocity (LHSV) of the liquid aqueous system is from 1 to 20 m / h, more preferably from 5 to 15 m / h, more preferably from 5 to 10 m / h. The liquid hourly space velocity LHSV in (c) is defined as, in the case of a tube bundle reactor, the volume flow rate of the liquid aqueous system (in cubic meters per hour) divided by the total cross-sectional area (in square meters) of one empty tube of the reactor or several empty tubes of the reactor, wherein one tube has a constant diameter over its entire length, and several tubes have a constant diameter over their entire lengths, respectively.

[0327] Therefore, the washing in (c) is preferably carried out in a continuous mode in a tubular reactor or a tube bundle reactor comprising the catalyst, wherein the liquid aqueous system comprises at least 95% by weight, preferably at least 99% by weight, preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system, and is carried out using a liquid aqueous system having a LHSV in the range of 1 to 20 m / h, more preferably 5 to 15 m / h, more preferably 5 to 10 m / h.

[0328] The washing in (c) may be carried out at any suitable temperature of the liquid aqueous system. Preferably, the washing in (c) is carried out at a temperature of the liquid aqueous system in the range of 30 to 90°C, preferably 40 to 80°C.

[0329] The washing in (c) can be carried out for any time required to achieve sufficient washing of the catalyst used in (a2). Preferably, the washing in (c) is carried out for 1 to 25 hours, preferably 1.5 to 20 hours, more preferably 2 to 12 hours, more preferably 2.5 to 9 hours, more preferably 3 to 6 hours.

[0330] Therefore, the washing in (c) is preferably carried out at a temperature of the liquid aqueous system in the range of 30 to 90°C for 2.5 to 9 hours, more preferably at a temperature of the liquid aqueous system in the range of 40 to 80°C for 3 to 6 hours.

[0331] Therefore, the washing in (c) is preferably carried out in a continuous mode in a tubular reactor or a tube bundle reactor comprising the catalyst, wherein the liquid aqueous system comprises at least 95% by weight, preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system, and using a liquid aqueous system with an LHSV in the range of 5 to 15 m / h, at a liquid aqueous system temperature in the range of 30 to 90° C. for 2.5 to 9 hours, more preferably using 5 to 10 m / h of the liquid aqueous system, at a liquid aqueous system temperature in the range of 40 to 80° C. for 3 to 6 hours.

[0332] According to the present method, the washing in (c) is usually monitored by the total organic carbon concentration of the liquid aqueous system after contact with the catalyst, and the washing in (c) is preferably carried out until the liquid aqueous system after contact with the catalyst reaches a specific total organic carbon concentration. Since the total organic carbon concentration passes through a maximum value during the washing in (c), the specific concentration preferably reached refers to the value reached after passing the maximum value.

[0333] Preferably, the washing in (c) is carried out until the total organic carbon concentration of the liquid aqueous system after contact with the catalyst is less than 25%, preferably less than 20%, preferably less than 15%, preferably less than 10%, more preferably less than 5%, more preferably less than 4%, more preferably less than 3%, more preferably less than 2%, more preferably less than 1% of the maximum total organic carbon concentration detected during the washing in (c), wherein the total volume of the liquid aqueous system is equal to or greater than the internal volume of the reactor. The total organic carbon concentration is to be understood as being determined in accordance with DIN EN 1484.

[0334] The selection of the point in time at which the performance of step (b) is stopped and the introduction of the feed stream into the reactor is stopped to allow the washing in (c) to be performed is preferably based on the decrease in the selectivity of propylene oxide formation in (a2) relative to the average selectivity of the reaction in (a2) during the first 100 hours of the performance of step (a). In the context of the process of the present invention, the selectivity of propylene oxide formation in (a2) is understood to be the selectivity of propylene oxide formation in (a2) calculated as shown in Comparative Example 1 based on hydrogen peroxide. Thus, for example, step (b) can be performed when the selectivity of propylene oxide formation in (a2) relative to the average selectivity of the reaction in (a2) during the first 100 hours of the performance of step (a) decreases by less than 15%, less than 10%, or less than 6%. Preferably, step (b) is performed when the selectivity of propylene oxide formation in (a2) relative to the average selectivity of the reaction in (a2) during the first 100 hours of the performance of step (a) decreases by less than 4%, preferably less than 3%, more preferably less than 2%.

[0335] Phase (i) further comprises repeating the procedure of steps (a) to (c) n times, wherein n is an integer and is at least 1. Thus, the procedure of steps (a) to (c) is repeated at least once before carrying out phase (ii). Preferably, n is from 1 to 10 and is therefore 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. More preferably, n is from 1 to 6 and is therefore 1, 2, 3, 4, 5 or 6. More preferably, n is from 1 to 4 and is therefore 1, 2, 3 or 4.

[0336] According to the present process, the catalyst obtained from (b) is preferably washed only with water comprising at least 95% by weight, more preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight, based on the total weight of the liquid aqueous system. The washing is preferably carried out in a continuous mode. Thus, preferably, in addition to the liquid aqueous system comprising at least 95% by weight, more preferably at least 99% by weight, more preferably at least 99% by weight (based on the total weight of the liquid aqueous system) of water, the catalyst is not treated with other liquid systems between step (b) and stage (ii). Thus, preferably, no pretreatment or posttreatment with a different liquid aqueous system, preferably any different liquid system, is carried out, wherein this preferred embodiment does not exclude rinsing the reactor with an organic solvent, preferably acetonitrile, in (b).

[0337] According to the present process, the catalyst obtained from (b) is preferably not treated with a gas stream consisting of (preferably comprising) ozone.

[0338] Optionally, (c) further comprises drying the washed catalyst, and if drying is performed, preferably said drying comprises contacting the catalyst with a gas stream comprising nitrogen, preferably at a temperature of said gas stream in the range of 40 to 200° C., more preferably 55 to 150° C., more preferably 70 to 100° C. According to the present invention, it is preferred that said drying is not performed after a washing step (c) which is not followed by a calcination, i.e., it is performed immediately after a washing step (c) of stage (ii) is performed.

[0339] Phase (ii)

[0340] The method for regeneration also includes

[0341] (ii) A stage comprising calcining the catalyst obtained in (c) after repeating the procedure of steps (a) to (c) n times.

[0342] Preferably, the calcination in (ii) is carried out at a catalyst bed temperature in the range of 300 to 600°C, preferably 350 to 550°C, more preferably 400 to 500°C.

[0343] The calcination in (ii) can be carried out in a static ambient gas atmosphere or in a gas stream in contact with the catalyst. Preferably, the calcination in (ii) is carried out in a gas stream. Generally, the gas stream has no restrictions on the components present therein. Preferably, the gas stream comprises oxygen, preferably oxygen and nitrogen. Generally, the gas stream comprising oxygen, preferably oxygen and nitrogen has no restrictions on the source of the oxygen, preferably oxygen and nitrogen used. Preferably, air, rarefied air or a mixture thereof, more preferably air or rarefied air is used as the source. Therefore, the calcination in (ii) is preferably carried out in a gas stream comprising oxygen, preferably oxygen and nitrogen, wherein the gas stream comprising oxygen, preferably oxygen and nitrogen is preferably air, rarefied air or a mixture thereof, more preferably air or rarefied air.

[0344] Therefore, the calcination in (ii) is preferably carried out at a temperature of the catalyst bed in the range of 300 to 600° C., preferably 350 to 550° C., more preferably 400 to 500° C., in a gas stream comprising oxygen, preferably oxygen and nitrogen, wherein the gas stream comprising oxygen, preferably oxygen and nitrogen is preferably air, dilute air or a mixture thereof, more preferably air or dilute air.

[0345] The calcination in (ii) can be carried out for any time required to achieve sufficient calcination of the catalyst in the process of the present invention for catalyst regeneration. Preferably, the calcination in (ii) is carried out for 1 to 15 hours, preferably 2 to 10 hours, more preferably 3 to 7 hours.

[0346] Therefore, the calcination in (ii) is preferably carried out in a gas stream comprising oxygen, preferably oxygen and nitrogen, at a temperature of the catalyst bed in the range of 300 to 600° C. for 1 to 15 hours, more preferably at 350 to 550° C. for 2 to 10 hours, more preferably at 400 to 500° C. for 3 to 7 hours, wherein the gas stream comprising oxygen, preferably oxygen and nitrogen, is preferably air, dilute air or a mixture thereof, more preferably air or dilute air.

[0347] The calcination in (ii) can be carried out in any conceivable container. Thus, the calcination in (ii) can be carried out, for example, in a reactor containing the catalyst or, in the case of removing the catalyst from the reactor for the calcination in (ii), in any other suitable container. Preferably, the calcination in (ii) is carried out in a reactor containing the catalyst.

[0348] The steps of stages (i) and (ii) of the process of the invention for catalyst regeneration can be repeated m times before the catalyst is discarded, wherein m is an integer and is at least 1, wherein n is the same or different in each repetition of the steps of stages (i) and (ii). Thus, the steps of stages (i) and (ii) are repeated at least once, wherein n is the same or different in each repetition of the steps of stages (i) and (ii). Preferably, m is from 1 to 10 and is therefore 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. More preferably, m is from 1 to 6 and is therefore 1, 2, 3, 4, 5 or 6. More preferably, m is from 1 to 4 and is therefore 1, 2, 3 or 4.

[0349] Preferably, m is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 and n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, more preferably 1, 2, 3, 4, 5 or 6, more preferably 1, 2, 3 or 4. More preferably, m is 1, 2, 3, 4, 5 or 6 and n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, more preferably 1, 2, 3, 4, 5 or 6, more preferably 1, 2, 3 or 4. More preferably, m is 1, 2, 3 or 4 and n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, more preferably 1, 2, 3, 4, 5 or 6, more preferably 1, 2, 3, or 4.

[0350] Regeneration catalyst

[0351] The present invention also relates to a regenerated catalyst comprising, as catalytically active material, a titanium-containing zeolite obtainable or obtained by the process of the present invention as described above.

[0352] Preferably, the catalyst regenerated according to the invention exhibits a differential conversion temperature of at most 5 K, preferably at most 2 K, more preferably at most 1 K in the process for preparing propylene oxide, wherein the differential conversion temperature is defined as the absolute difference between the following temperatures:

[0353] (A1) a temperature at which a predetermined hydrogen peroxide conversion rate is achieved in the process for preparing propylene oxide, wherein a regenerated catalyst is used as a catalyst, and

[0354] (B1) A temperature at which a predetermined hydrogen peroxide conversion rate is achieved in the method for preparing propylene oxide, wherein a corresponding fresh catalyst is used as a catalyst under otherwise identical epoxidation reaction conditions.

[0355] After a certain operating time, a decrease in the catalytic activity of the catalyst comprising a titanium-containing zeolite as the catalytically active material is observed in the epoxidation reaction. The reduced catalytic activity is directly related to the reduced conversion of at least one starting material, i.e. olefin and / or epoxidant, which can be compensated by increasing the overall reaction temperature. This means that, as the catalyst continues to operate, the reaction temperature needs to be gradually increased relative to the starting temperature, so that the epoxidation process becomes gradually ineffective.

[0356] However, by subjecting the catalyst comprising the titanium-containing zeolite consumed in the epoxidation reaction to the regeneration method according to the invention, its initial catalytic activity can be restored. The initial catalytic activity here refers to the catalytic activity of the freshly prepared catalyst. Since the catalytic activity is conveniently directly related to the reaction temperature under otherwise identical reaction conditions, the regeneration efficiency of the consumed catalyst can be inferred from the reaction temperature required to maintain a set conversion. In this case, the catalyst regenerated according to the invention advantageously exhibits a conversion temperature in the process for preparing olefin oxides which deviates from the conversion temperature of the fresh catalyst under otherwise identical epoxidation conditions by at most 5 K, preferably at most 2 K, more preferably at most 1 K.

[0357] It is further preferred that the catalyst regenerated according to the process of the invention exhibits a selectivity difference of at most 1 in a process for preparing propylene oxide, wherein the selectivity difference is defined as the absolute difference in percentage points between the following selectivities:

[0358] (A2) selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a regenerated catalyst is used as catalyst, and

[0359] (B2) The selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a corresponding fresh catalyst is used as the catalyst under otherwise identical epoxidation reaction conditions, wherein the selectivity based on hydrogen peroxide is defined as the number of moles of propylene oxide produced divided by the number of moles of hydrogen peroxide consumed×100.

[0360] The quality of the catalyst comprising a titanium-containing zeolite regenerated according to the process of the invention can also be quantified by comparing the selectivity of the regenerated catalyst with the selectivity of the fresh catalyst under otherwise identical epoxidation conditions. After prolonged use, a decrease in the selectivity of the catalyst is generally observed. Advantageously, in this case, the selectivity of the catalyst comprising a titanium-containing zeolite, having been subjected to the regeneration process of the invention, differs by at most 1 percentage point from the selectivity of the fresh catalyst under otherwise identical epoxidation reaction conditions.

[0361] Continuous process for preparing propylene oxide

[0362] According to the present invention, preferably the epoxidation reaction is carried out in more than one reactor, for example in at least two reactors, three reactors or four reactors, which are operated in parallel. According to the method design, preferably during the regeneration of the catalyst in a given reactor, the epoxidation reaction is carried out in one or more of the remaining reactors. Thus, propylene oxide can be prepared in a continuous manner and the regeneration according to the present invention can be carried out at the same time. Preferably, according to the method design, the epoxidation reaction in the at least two reactors is started sequentially with an appropriate delay between the corresponding starts.

[0363] The present invention also relates to a continuous process for preparing propylene oxide, comprising

[0364] (i') A stage comprising the following steps

[0365] (a') continuously preparing propylene oxide in a first reactor, comprising

[0366] (a1′) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a first reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0367] (a2') subjecting the feed stream of (a1') to epoxidation conditions in a first reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0368] (a3') removing a product stream comprising propylene oxide and an organic solvent from the first reactor;

[0369] (b') stopping the introduction of the feed stream into the first reactor;

[0370] (c') washing the catalyst with a liquid aqueous system;

[0371] Stage (i') further comprises repeating steps (a') to (c') n' times, wherein n' is an integer and is at least 1; the method for preparing propylene oxide further comprises

[0372] (ii') a stage comprising calcining the catalyst obtained from (c') after repeating the sequence of steps (a') to (c') n' times;

[0373] wherein the steps of stages (i') to (ii') are optionally repeated m' times, wherein m' is an integer and is at least 1, wherein in each repetition of the steps (i') to (ii'), n' is the same or different;

[0374] The method for preparing propylene oxide further comprises the following steps:

[0375] (i") The stage comprising the following steps

[0376] (a") continuously preparing propylene oxide in a second reactor, comprising

[0377] (a1") introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a second reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0378] (a2") subjecting the feed stream of (a1") to epoxidation conditions in a second reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0379] (a3") removing a product stream comprising propylene oxide and an organic solvent from the second reactor;

[0380] (b") stopping the introduction of the feed stream into the second reactor;

[0381] (c") washing the catalyst with a liquid aqueous system;

[0382] Stage (i") further comprises repeating steps (a") to (c") n" times, wherein n" is an integer and is at least 1; the method for preparing propylene oxide further comprises

[0383] (ii") a stage comprising calcining the catalyst obtained in (c") after repeating the sequence of steps (a") to (c") n" times;

[0384] wherein the steps (i") to (ii") are optionally repeated m" times, wherein m" is an integer and is at least 1, and wherein in each repetition of the steps (i") to (ii"), n" is the same or different;

[0385] wherein during at least one of steps (b') and (c') or at least one of steps (b'), (c') and (ii'), propylene oxide is prepared according to (a")

[0386] The present invention is further characterized by the following individual embodiments and combinations of embodiments as indicated by the corresponding dependent embodiments:

[0387] 1. A method for regenerating a catalyst comprising a titanium-containing zeolite as a catalytically active material, comprising:

[0388] (i) A stage comprising the following steps:

[0389] (a) continuously preparing propylene oxide, comprising

[0390] (a1) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0391] (a2) subjecting the feed stream of (a1) to epoxidation conditions in a reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0392] (a3) removing a product stream comprising propylene oxide and an organic solvent from the reactor;

[0393] (b) stopping the introduction of the feed stream into the reactor;

[0394] (c) washing the catalyst with a liquid aqueous system;

[0395] Stage (i) further comprises repeating the process of steps (a) to (c) n times, wherein n is an integer and is at least 1; the method for regeneration further comprises

[0396] (ii) a stage comprising calcining the catalyst obtained in (c) after repeating the sequence of steps (a) to (c) n times;

[0397] The process of stages (i) to (ii) is optionally repeated m times, wherein m is an integer and is at least 1, and wherein n is the same or different in each repetition of the process of stages (i) to (ii).

[0398] 2. The process of embodiment 1, comprising preparing the feed stream of (a1) by mixing a stream comprising propylene, a stream comprising hydrogen peroxide or a source of hydrogen peroxide, and a stream comprising an organic solvent.

[0399] 3. The process of embodiment 2, wherein the feed stream of (a1) further comprises at least one potassium-containing salt.

[0400] 4. The method of embodiment 2, wherein the at least one potassium-containing salt is one or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium formate.

[0401] 5. The process of embodiment 3 or 4, wherein the preparation of the feed stream according to (a1) comprises combining the aqueous stream comprising at least one dissolved potassium salt with a stream comprising propylene, or with a stream comprising hydrogen peroxide or a source of hydrogen peroxide, or with a stream comprising an organic solvent, or with a mixed stream of two or three of these streams, preferably with a stream comprising hydrogen peroxide or a source of hydrogen peroxide, or with a stream comprising an organic solvent, or with a mixed stream thereof.

[0402] 6. The process according to any one of embodiments 1 to 5, wherein the organic solvent is methanol or acetonitrile, preferably acetonitrile.

[0403] 7. The process of any one of embodiments 1 to 6, wherein the molar ratio of propylene in the feed stream of (a1) relative to hydrogen peroxide or hydrogen peroxide produced by a source of hydrogen peroxide ranges from 1:1 to 1.6:1, preferably from 1.1:1 to 1.55:1, more preferably from 1.2:1 to 1.5:1, more preferably from 1.30:1 to 1.45:1.

[0404] 8. The process according to any one of embodiments 1 to 7, wherein the reactor of (a2) is an isothermally operated reactor.

[0405] 9. The process according to any of embodiments 1 to 8, wherein according to (a2), the temperature of the reaction mixture is isothermally controlled using a heat transfer medium, preferably by passing the heat transfer medium through the jacket of the reactor.

[0406] 10. The process of embodiment 9, wherein the epoxidation conditions of (a2) include an epoxidation reaction temperature in the range of 20 to 100°C, preferably 25 to 80°C, more preferably 30 to 60°C, wherein the epoxidation reaction temperature is defined as the temperature of the heat transfer medium prior to controlling the temperature of the reaction mixture, preferably the temperature of the heat transfer medium at the jacket inlet of an isothermally operated reactor.

[0407] 11. The process of any one of embodiments 1 to 10, wherein the epoxidation conditions in (a2) comprise an epoxidation reaction pressure of 5 to 100 bar, preferably 10 to 32 bar, more preferably 15 to 25 bar, wherein the epoxidation reaction pressure is defined as the pressure at the outlet of the isothermally operated reactor.

[0408] 12. The method of any one of embodiments 1 to 11, wherein the titanium-containing zeolite has an MFI framework structure, a MEL framework structure, an MWW framework structure, an MWW-type framework structure, or a mixed structure of two or more of these framework structures, preferably an MFI framework structure, an MWW-type framework structure or an MWW-type framework structure, more preferably an MWW framework structure or an MWW-type framework structure.

[0409] 13. The process according to any of embodiments 1 to 12, wherein at least 99% by weight, preferably at least 99.5% by weight, more preferably at least 99.9% by weight, of the framework structure of the titanium-containing zeolite consists of silicon, titanium and oxygen.

[0410] 14. The method of any one of embodiments 1 to 13, wherein the titanium-containing zeolite comprises one or more of Al, B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, and Cd, preferably one or more of B, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Pb, Pd, Pt, Au, and Cd, and more preferably Zn.

[0411] 15. The method of embodiment 14, wherein the titanium-containing zeolite contained in the catalyst of (a2) has an MWW framework structure, contains zinc, and contains titanium (calculated as elemental titanium) in an amount of 0.1 to 5 weight %, preferably 1 to 2 weight %, based on the total weight of the titanium-containing zeolite, and contains zinc (calculated as elemental zinc) in an amount of 0.1 to 5 weight %, preferably 1 to 2 weight %, based on the total weight of the titanium-containing zeolite.

[0412] 16. The process according to any of embodiments 1 to 15, wherein the catalyst comprising the titanium-containing zeolite is present in the reactor as a fixed bed catalyst.

[0413] 17. The process according to any one of embodiments 1 to 16, wherein the catalyst comprising the titanium-containing zeolite is present in the reactor as a shaped body comprising the titanium-containing zeolite, wherein the shaped body preferably comprises a content of 70 to 80 wt.-% of the titanium-containing zeolite and a content of 30 to 20 wt.-% of a binder, based on the total weight of the shaped body, wherein the binder is preferably a silica binder.

[0414] 18. The process of any one of embodiments 1 to 17, comprising preparing the feed stream of (a1) by mixing a stream comprising propylene, a stream comprising hydrogen peroxide or a source of hydrogen peroxide, and a stream comprising an organic solvent, wherein in order to stop introducing the feed stream into the reactor according to (b), preparing the feed stream of (a1) comprises

[0415] (a11) stopping the stream comprising hydrogen peroxide or a source of hydrogen peroxide and maintaining mixing the stream comprising propylene and the stream comprising an organic solvent to obtain a feed stream;

[0416] (a12) stopping a stream comprising propylene and a stream comprising an organic solvent;

[0417] wherein (a11) is preferably carried out at least 30 min, more preferably at least 60 min after (a12), and wherein after (a12), the reactor is optionally depressurized and emptied.

[0418] 19. The method of any one of embodiments 1 to 18, wherein the liquid aqueous system of (c) comprises at least 95% by weight, preferably at least 99% by weight, more preferably at least 99.9% by weight, more preferably at least 99.99% by weight of water, based on the total weight of the liquid aqueous system.

[0419] 20. The process of any one of embodiments 1 to 19, wherein the liquid aqueous system of (c) comprises at most 5 wt.-%, preferably at most 1 wt.-%, more preferably at most 0.1 wt.-%, more preferably at most 0.01 wt.-%, more preferably at most 0.001 wt.-%, more preferably at most 0.0001 wt.-%, based on the total weight of the liquid aqueous system, of methanol.

[0420] 21. The process according to any one of embodiments 1 to 20, wherein the liquid aqueous system of (c) comprises at most 0.1 wt.-%, preferably at most 0.01 wt.-%, more preferably at most 0.001 wt.-%, more preferably at most 0.0001 wt.-% hydrogen peroxide, based on the total weight of the liquid aqueous system.

[0421] 22. The process according to any one of embodiments 1 to 21, wherein according to (c), the washing of the catalyst is carried out in a reactor comprising the catalyst.

[0422] 23. The process according to any one of embodiments 1 to 22, wherein the total volume of the liquid aqueous system used according to (c) is equal to or greater than the internal volume of the reactor.

[0423] 24. The process of any one of embodiments 1 to 23, wherein the washing of (c) is performed in a continuous mode.

[0424] 25. The method of embodiment 24, wherein the reactor of (a) is a tubular reactor or a tube bundle reactor, and the washing with the liquid aqueous system of (c) is carried out at a liquid hourly space velocity (LHSV) in the range of 1 to 20 m / h, preferably 5 to 15 m / h, more preferably 5 to 10 m / h.

[0425] 26. The process according to any one of embodiments 1 to 25, wherein the washing of (c) is carried out at a temperature of the liquid aqueous system in the range of 30 to 90°C, preferably 40 to 80°C.

[0426] 27. The process according to any one of embodiments 1 to 26, wherein the washing of (c) is carried out for 1 to 25 hours, preferably 1.5 to 20 hours, more preferably 2 to 12 hours, more preferably 2.5 to 9 hours, preferably 3 to 6 hours.

[0427] 28. The method of any one of embodiments 1 to 27, wherein the washing of (c) is carried out until the total organic carbon concentration of the liquid aqueous system after contact with the catalyst is at most 25%, preferably at most 20%, preferably at most 15%, preferably at most 10%, more preferably at most 5%, more preferably at most 1%, of the maximum total organic carbon concentration detected during the washing in (c).

[0428] 29. The process of any one of embodiments 1 to 28, wherein the steps (b) and (c) are carried out when the selectivity of the epoxidation reaction of (a2) decreases by 4%, preferably 3%, more preferably 2% relative to the average selectivity of the epoxidation reaction of (a2) during the first 100 hours of carrying out step (a), wherein the selectivity of the epoxidation reaction is defined as the molar amount of propylene oxide obtained in (a2) relative to the molar amount of hydrogen peroxide converted in (a2).

[0429] 30. The process according to any one of embodiments 1 to 29, wherein n is from 1 to 10, preferably from 1 to 6, more preferably from 1 to 4.

[0430] 31. The process according to any of embodiments 1 to 30, wherein the calcination of stage (ii) is carried out at a catalyst temperature in the range of 300 to 600°C, preferably 350 to 550°C, more preferably 400 to 500°C.

[0431] 32. The process according to any of embodiments 1 to 31, wherein the calcination in stage (ii) is carried out using a gas stream comprising oxygen, preferably oxygen and nitrogen, wherein the gas stream is preferably air, dilute air or a mixture thereof, more preferably air or dilute air.

[0432] 33. The process according to any of embodiments 1 to 32, wherein the calcination in stage (ii) is carried out for 1 to 15 hours, preferably 2 to 10 hours, more preferably 3 to 7 hours.

[0433] 34. The process according to any of embodiments 1 to 33, wherein the calcination of stage (ii) is carried out in a reactor comprising the catalyst.

[0434] 35. The process according to any one of embodiments 1 to 34, wherein the procedures of stages (i) to (ii) are repeated m times, wherein m is an integer from 1 to 10, preferably from 1 to 6, more preferably from 1 to 4.

[0435] 36. A regenerated catalyst comprising a titanium-containing zeolitic material as catalytically active material, obtainable or obtained by the process of any one of embodiments 1 to 35.

[0436] 37. The regenerated catalyst of embodiment 36, wherein the titanium-containing zeolite has an MWW framework structure, wherein at least 99 weight %, preferably at least 99.5 weight %, more preferably at least 99.9 weight % of the framework structure of the titanium-containing zeolite is composed of silicon, titanium and oxygen, wherein the titanium-containing zeolite preferably contains Zn, and wherein the titanium-containing zeolite contains titanium (calculated as elemental titanium) in an amount of 0.1 to 5 weight %, preferably 1 to 2 weight %, based on the total weight of the titanium-containing zeolite, and preferably contains zinc (calculated as elemental zinc) in an amount of 0.1 to 5 weight %, preferably 1 to 2 weight %, based on the total weight of the titanium-containing zeolite.

[0437] 38. The regenerated catalyst of embodiment 36 or 37, wherein the regenerated catalyst is a shaped body comprising a titanium-containing zeolite, wherein the shaped body preferably comprises a titanium-containing zeolite in an amount of 70 to 80 wt. %, and a binder in an amount of 30 to 20 wt. %, based on the total weight of the shaped body, wherein the binder is preferably a silica binder.

[0438] 39. The regenerated catalyst according to any one of embodiments 36 to 38, which exhibits a conversion temperature difference of at most 5 K, preferably at most 2 K, more preferably at most 1 K in a process for preparing propylene oxide, wherein the conversion temperature difference is defined as the absolute difference between the following temperatures:

[0439] (A1) a temperature at which a predetermined hydrogen peroxide conversion rate is achieved in the process for preparing propylene oxide, wherein a regenerated catalyst is used as a catalyst, and

[0440] (B1) A temperature at which the predetermined hydrogen peroxide conversion is achieved in a process for preparing propylene oxide, wherein a corresponding fresh catalyst is used as a catalyst under otherwise identical epoxidation reaction conditions.

[0441] 40. The regenerated catalyst of any one of embodiments 36 to 39, which exhibits a selectivity difference of at most 1 in a process for preparing propylene oxide, wherein the selectivity difference is defined as the absolute difference, in percentage points, between the following selectivities:

[0442] (A2) selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a regenerated catalyst is used as catalyst, and

[0443] (B2) The selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a corresponding fresh catalyst is used as the catalyst under otherwise identical epoxidation reaction conditions, wherein the selectivity based on hydrogen peroxide is defined as the number of moles of propylene oxide produced divided by the number of moles of hydrogen peroxide consumed×100.

[0444] 41. A continuous process for preparing propylene oxide, comprising

[0445] (i') A stage comprising the following steps

[0446] (a') continuously preparing propylene oxide in a first reactor, comprising

[0447] (a1′) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a first reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0448] (a2') subjecting the feed stream of (a1') to severe epoxidation conditions in a first reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0449] (a3') removing a product stream comprising propylene oxide and an organic solvent from the first reactor;

[0450] (b') stopping the introduction of the feed stream into the first reactor;

[0451] (c') washing the catalyst with a liquid aqueous system;

[0452] Stage (i') further comprises repeating steps (a') to (c') n' times, wherein n' is an integer and is at least 1; the method for preparing propylene oxide further comprises

[0453] (ii') a stage comprising calcining the catalyst obtained from (c') after repeating the sequence of steps (a') to (c') n' times;

[0454] The steps of stage (i') to (ii') are optionally repeated m' times, wherein m' is an integer and is at least 1, and wherein in each repetition of the steps (i') to (ii'), n' is the same or different;

[0455] The method for preparing propylene oxide further comprises:

[0456] (i") The stage comprising the following steps

[0457] (a") continuously preparing propylene oxide in a second reactor, comprising

[0458] (a1") introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a second reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material;

[0459] (a2") subjecting the feed stream of (a1") to epoxidation conditions in a second reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent;

[0460] (a3") removing a product stream comprising propylene oxide and an organic solvent from the second reactor;

[0461] (b") stopping the introduction of the feed stream into the second reactor;

[0462] (c") washing the catalyst with a liquid aqueous system;

[0463] Stage (i") further comprises repeating steps (a") to (c") n" times, wherein n" is an integer and is at least 1; the method for preparing propylene oxide further comprises

[0464] (ii") a stage comprising calcining the catalyst obtained in (c") after repeating the sequence of steps (a") to (c") n" times;

[0465] wherein the steps (i") to (ii") are optionally repeated m" times, wherein m" is an integer and is at least 1, and wherein in each repetition of the steps (i") to (ii"), n" is the same or different;

[0466] wherein during at least one of steps (b') and (c') or at least one of steps (b'), (c') and (ii'), propylene oxide is prepared according to (a")

[0467] The present invention is further illustrated by the following figures, reference examples, examples and comparative examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0468] Figure 1 A block diagram of a method according to Reference Example 2 is shown. Figure 1 The letters and numbers have the following meanings:

[0469] A Epoxidation unit A

[0470] B Epoxidation unit B

[0471] C Distillation Unit

[0472] D Distillation Unit

[0473] E Distillation Unit

[0474] F Partial Stream Distillation Unit

[0475] G Mixer-settler unit

[0476] H Acetonitrile Recovery Unit

[0477] I Acetonitrile circulation unit

[0478] (1)-(20) According to a particularly preferred process as described in the examples

[0479] S0, S01, S02, S1, S2, S3, S4, S4b, S5, L1, L2, TL1, TL2, TL2, BL2

[0480] The feed stream according to a preferred process as described in the general description and in the examples is

[0481] Figure 2 Shows Figure 1 Detailed block diagram of the partial stream distillation F. Figure 2 The letters and numbers have the following meanings:

[0482] F1 Partial stream distillation unit F first fractionation

[0483] F2 Second fractionation unit of part stream distillation unit F

[0484] (13), (13a), (14), (15), (15a), (15b), (15c), (16), (19), (20)

[0485] The feed stream according to a particularly preferred process as described in the examples

[0486] S1, S2, S3, S4, S4a, S4b, S4c, S5, TL2

[0487] The feed stream according to a preferred process as described in the general description and in the examples is Example

[0488] Reference Example 1: Preparation of a shaped body comprising ZnTiMWW spray powder

[0489] The catalyst in the form of a shaped body was prepared as described in Example 5 of WO 2013 / 117536 A2, in particular in Examples 5.1-5.6 on pages 83-99. The characterization method of the shaped body involved in Examples 5.1-5.6 is described in Reference Examples 2-10 on pages 66-71 of WO 2013 / 17536 A2. The characteristic properties of the catalyst are shown in Figures 20-27 of WO 2013 / 117536 A2 and the corresponding description of the drawings on page 104 of WO 2013 / 117536 A2.

[0490] Reference Example 2: Epoxidation Reaction Setup

[0491] For abbreviations, see Figure 1 and Figure 2 The scheme is generally described in the "Description of the Figures" section. All pressures given are absolute pressures.

[0492] 1.1 Preparation of Stream S0 (Step (a))

[0493] a) Epoxidation in the epoxidation main reactor (epoxidation unit A)

[0494] Main reactor A is a vertically mounted tube bundle reactor with 5 tubes (tube length: 12m, inner tube diameter: 38mm), each tube is equipped with an axially placed multi-point thermocouple, which has 10 equally spaced measuring points encapsulated in a suitable thermocouple sleeve with a diameter of 18 mm. Each tube is loaded with 17.5kg of ZnTiMWW catalyst molded bodies (post-treated molded bodies) prepared according to Reference Example 1. The remaining free space is filled with talc balls (diameter 3mm). The heat of reaction is removed by circulating a constant temperature heat transfer medium (water / ethylene glycol mixture) on the side of the shell and flowing to the feed. The flow rate of the heat transfer medium is adjusted so that the temperature difference between the inlet and the outlet does not exceed 1°C. The reaction temperature referred to below is defined as the temperature of the heat transfer medium entering the reactor shell. At the reactor outlet, the pressure is controlled by a pressure regulator and kept constant at 20 bar.

[0495] A liquid single-phase stream (1) is fed from below the reactor. Stream (1) is prepared by mixing four streams (2), (3), (3a) and (4). The temperature of stream (1) is not actively controlled, but is typically in the range of 20 to 40°C:

[0496] - The flow rate of stream (2) is 85 kg / h. At least 99.5% by weight of stream (2) consists of acetonitrile, propene and water. This stream (2) comes from the bottom of the acetonitrile recycle distillation unit (I).

[0497] - Stream (3) with a flow rate of 15 kg / h is an aqueous solution of hydrogen peroxide with a hydrogen peroxide concentration of 40% by weight (from Solvay's "crude / wash" grade, TOC 100 to 400

[0498] The aqueous hydrogen peroxide solution was supplied from a storage tank to allow continuous feeding and was fed using a suitable metering pump.

[0499] - Stream (3a) is an aqueous stream containing dissolved potassium formate. A further stream is supplied from a storage tank to allow continuous feeding and is fed using a suitable metering pump. The concentration of potassium formate is 2.5% by weight and the feed rate of stream (S3a) is 370 g / h. Stream (3a) is thoroughly mixed with stream (3) and the combined stream is then mixed with the stream obtained by mixing streams (2) and (4).

[0500] - Stream (4) is a make-up stream of pure acetonitrile (chemical grade, from Ineos, purity about 99.9%, containing 70-180 wt. ppm propionitrile, 5-20 wt. ppm acetamide and less than 100 wt. ppm water as impurities).

[0501] Sufficient fresh acetonitrile is added to compensate for losses in the process. Under conventional conditions, an average of 100 to 150 g / h of make-up acetonitrile is added.

[0502] The output stream (5) leaving the epoxidation unit A is sampled every 20 minutes to determine the hydrogen peroxide concentration using the titanyl sulfate method and to calculate the hydrogen peroxide conversion. The hydrogen peroxide conversion is defined as 100×(1-m out / m in ), where m in is the molar flow rate of H2O2 at the reactor feed port and m out is the molar flow rate of H2O2 at the reactor outlet. Based on the respectively obtained hydrogen peroxide conversion value, the inlet temperature of the heat transfer medium is adjusted so that the hydrogen peroxide conversion is essentially kept in the range of 90 to 92%. At the start of a given run with a fresh batch of epoxidation catalyst, the inlet temperature of the heat transfer medium is set to 30°C and, if necessary, the temperature is increased to keep the hydrogen peroxide conversion in the above range. The required temperature increase is usually less than 1 K / d.

[0503] The output stream (5) leaving the epoxidation unit A is passed through a heat exchange unit. The stream leaving the heat exchange unit (stream (6), S0) is fed to the epoxidation unit B.

[0504] b) Epoxidation in the finishing reactor (epoxidation unit B)

[0505] Refining reactor B is a fixed bed reactor of adiabatic operation. In this case, the term "adiabatic" refers to an operating mode in which active cooling is not performed, and according to the operating mode, the refining reactor is properly insulated to minimize heat loss. The length of refining reactor B is 4m, and the diameter is 100mm. The reactor is filled with 9kg of the same epoxidation catalyst as used in the main epoxidation reactor A. The remaining space is filled with talc balls (diameter 3mm). The operating pressure of refining reactor B is 10 bar, which is kept constant by a suitable pressure regulator at the reactor outlet. The output of refining reactor B is sampled every 20 minutes to measure the hydrogen peroxide concentration using the titanyl sulfate method.

[0506] The effluent from finishing reactor B (stream (6)) is depressurized into a flash tank, and both liquid and gas from this tank are fed to a light boiler separation column (distillation unit C).

[0507] Stream (6) (stream S0) has on average an acetonitrile content of 69 to 70% by weight, a propylene oxide content of 9 to 11% by weight, for example 9.8% by weight, a water content of 17% by weight, a propylene content of about 3% by weight, a propane content of about 0.05% by weight, a hydrogen peroxide content of about 250 ppm by weight, a propylene glycol content of about 0.1% by weight and an oxygen content of about 150% by weight-ppm.

[0508] 1.2 Separation of propylene oxide from stream S0 to obtain stream S1 (step (b))

[0509] a) Separating light boilers from stream (6) (stream S0) to obtain stream (8) (stream S01)

[0510] Stream (6) is fed to a light boiler separation column (distillation unit C) operated at 1.1 bar. The distillation column has a length of 8.5 m, a diameter of 170 mm and is equipped with 40 bubbling trays, an evaporator at the bottom and a condenser at the top. The column is operated as a mixed washing / distillation column. As washing agent, part of the bottom stream of distillation unit D (stream 11, about 20-30 kg / h) is taken off, cooled to 10° C. and introduced into the top of the column. The liquid and gas inlet streams are introduced into the column at different points. The feed point for the liquid part of stream (6) is above the bubbling tray 37; the gaseous part of stream (6) is introduced into the column above the bubbling tray 28 (calculated from the top). The gas stream (7) leaving the cooling device at the top of the column mainly contains propene, propane (which is contained as an impurity in the polymer-grade propene used), oxygen formed as a by-product and small amounts of other light boilers (acetonitrile (1-2% by volume)), propionaldehyde (about 200 ppm by volume), acetone (about 100 ppm by volume), H2 (about 400 ppm by volume), CO2 (about 400 ppm by volume) and acetaldehyde (about 100 ppm by volume)), and is essentially free of propylene oxide (less than 300 ppm by volume). This top stream is sent to a flare for treatment. The bottom stream of the light boiler separation column (stream (8), i.e., stream S01) at a temperature of 70° C. has a propene content of 100 to 200 ppm by weight.

[0511] b) Separating propylene oxide from stream (8) (stream S01) to obtain stream S02

[0512] The stream S01 obtained according to section 1.2a) above is introduced into a distillation column (distillation unit D) to separate propylene oxide from the stream S01. The column has a height of 50 m, a diameter of 220 mm and is equipped with a packing (Sulzer BX64) with a total packing length of 27.5 m, which is divided into 8 beds with a length of 3060 mm each and two beds with a length of 1530 mm each. An intermediate flow distributor is installed between each bed. The column is operated at a top pressure of 750 mbar. The feed point of the stream S01 is located below the fourth packed bed (counted from the top). The top stream of the column is condensed and partly returned to the column as reflux (reflux ratio of about 5:1). The remainder (stream (9)) has a flow rate of 10.1 kg / h as the top product and consists essentially of propylene oxide with a purity of more than 99.9% by weight. The bottom evaporator is operated in such a way that the propylene oxide concentration in the bottom stream is less than 100 ppm by weight. The resulting temperature of the bottom stream is about 69° C. The stream S02 is then divided into two parts. The main part thereof (stream (10), with a flow rate of about 85 kg / h) is fed to the next distillation column (distillation unit E). The remainder (stream (11), 20-30 kg / h) is cooled and recycled to the top of the light boiler separation column (distillation unit C) as a washing agent as described in section 1.2a) above. The acetonitrile content of the stream S02 is about 80% by weight, the propylene oxide content is less than 100 ppm by weight, the water content is about 20% by weight, the propylene glycol content is about 0.1% by weight, and the hydroxypropanol content is about 0.1% by weight.

[0513] c) Separating light boiling compounds from stream (10) (stream S02) to obtain stream (13) (stream S1)

[0514] The stream S02 obtained according to the above section 1.2b) is introduced into the light component separation column (distillation unit E). The light component separation column has a height of 8 m, a nominal diameter of 150 mm and is equipped with 35 bubble trays. The column is operated at a top pressure of 2 bar and the stream S02 is introduced above the bubble column No. 7 (calculated from the bottom). The top stream obtained (stream (12), flow rate of about 1 kg / h) leaves the column at a temperature of 40 to 45° C. and does not condense when the column is operated without internal reflux. In addition to acetonitrile (6500 volume ppm), the top stream comprises predominantly nitrogen, which serves to keep the operating pressure of the column at a value of 2 bar, and small amounts of light boilers (acetaldehyde (900 volume ppm), oxygen (300 volume ppm) and propionaldehyde (320 volume ppm). The top stream is sent to the flare for treatment. The tank evaporator is operated by feeding saturated steam at a pressure of 16 bar in a constant amount (5 kg / h). The bottom temperature is 100° C. The bottom stream (stream S1) consists predominantly of acetonitrile and water, the remainder being high boilers. The acetonitrile content of stream S1 is about 80% by weight and the water content is about 20% by weight.

[0515] 1.3 Separation of stream S1 into streams S2 and S3 (step (c))

[0516] In step (c), the material stream S1 with a flow rate of 86 kg / h obtained according to the above 1.2c) is divided into two material streams, material stream S2 ( Figure 1 of stream 13a) and S3( Figure 1 Stream S2 has a flow rate of 84 kg / h, and stream S3 has a flow rate of 2 kg / h. Stream S3, 2.3% of stream S1, enters the partial distillation unit F (partial stream distillation column).

[0517] 1.4 Distillation of Partial Stream of Stream S1 (Step (d))

[0518] The first fractionation unit, i.e. the first distillation column F1, has a height of 9.5 m, a diameter of 85 m and is equipped with a 6.5 m metal structure of Rombopak 9M packing installed on three identical beds. Above the first bed of structured packing (calculated from the top), stream S3 ((stream 14)) is introduced into the first distillation column. The temperature of the stream S3 is 60±3° C. The first distillation column is operated at a top pressure of about 1.4 bar and a bottom temperature of 92±5° C. No reflux is applied. The amount of steam fed to the bottom evaporator of the first fractionation unit is controlled so that the acetonitrile concentration at the bottom is in the range of 10 to 25% by weight. A bottom stream S4b is removed (stream (15b), about 3% of stream S3). This stream consists mainly of water (72-85% by weight) and acetonitrile (10-24% by weight). The sum of all analyzed high-boiling components (27 components) varies in the range of 2-10% by weight. The top stream, the vapor fraction stream S4a (stream 15a), having a temperature of 85±3° C., is not condensed and is passed to the bottom of the second fractionation unit, the second distillation column F2. S4a enters above the last bed of structured packing (calculated from the top). F2 has a height of 9.5 m, a diameter of 85 mm and is equipped with 6.5 m of metal structured Rombopak 9M packing installed in 3 identical beds. The second distillation column is operated at a top pressure of about 1.25 bar and a bottom temperature of 85±5° C. The top stream, the vapor fraction stream S4c (stream (15c), up to 1% of stream S4a) is passed via an external overhead condenser ( Figure 2 The condensed liquid stream (not shown) is completely condensed and applied substantially completely to use the condensed liquid stream as reflux to the second distillation column. The liquid bottom stream S4 (stream 15) is removed and passed to the next step (recycling of stream S4). The acetonitrile content of stream S4 is about 80% by weight and the water content is about 20% by weight.

[0519] 1.5 Recycling of Stream S4 (Step (4))

[0520] a) Preparation of liquid stream S5

[0521] The material stream S4 ( Figure 1 and Figure 2 of stream 15) and stream S2 ( Figure 1 and Figure 2 Stream S4 is thus pumped back into the bulk process acetonitrile solvent stream. Mixing is performed at a point downstream of where stream S3 is diverted from stream S1. The combined stream at a flow rate of 86 kg / h is mixed with liquid stream P (at Figure 1 and Figure 2Stream S5 is obtained by mixing the combined stream of S2 and S4 with two further streams: the first of these streams is Figure 1 A stream (16) is obtained from the top of the distillation unit H. The second of these streams is Figure 1 The stream (19) is obtained from the acetonitrile recovery unit I. The streams (16) and (19) are described in detail below.

[0522] b) Adjusting the temperature of stream S5 and separating the liquid phases L1 and L2

[0523] The stream S5 with a flow rate of 130 kg / h±10 kg / h is then fed to a mixer-settler unit operated at 18 bar and a temperature in the range of 15±5° C. The volume of the sedimentation tank is 5.3 liters. Two liquid phases L1 and L2, an aqueous phase L2 and an organic phase L1, are obtained. The upper organic phase L1 is removed from the sedimentation tank as stream (17), and the lower aqueous phase L2 is removed from the sedimentation tank as stream (18). The flow rate of stream (17) is in the range of 110 kg / h±11 kg / h. Stream (17) is then passed to the acetonitrile recycling unit I, and stream (18) is passed to the acetonitrile recovery unit H, from which the above-mentioned stream (16) is obtained. The acetonitrile content of the stream (17) thus obtained is about 45-51% by weight, the propylene content is about 49-55% by weight, and the water content is about 2 to 5% by weight. The stream (18) thus obtained has an acetonitrile content of about 19 to 21% by weight, a water content of about 79 to 81% by weight and a propene content of less than 0.5% by weight.

[0524] c) Acetonitrile recovery (acetonitrile recovery unit H)

[0525] In order to recover as much solvent as possible and to minimize acetonitrile losses, stream (18) is introduced into a distillation column, from which stream (16) (also referred to as stream TL2) is obtained as a top stream, which in turn is recycled into the solvent stream as described above. For this purpose, a distillation column with a height of 9.5 m and a diameter of 100 mm is used, which is equipped with 50 bubble trays. The column is operated at a top pressure of 1.5 bar and a return flow ratio of 1:4. Stream (18) is fed to the column above the bubble tray 26 (calculated from the bottom). The bottom temperature is about 113° C., and the bottom product consists mainly of water containing high-boiling by-products. The typical composition of the bottom stream is as follows (given in brackets in % by weight): water (>99.0), propylene glycol (0.5), acetonitrile (up to 0.001), dipropylene glycol (0.06), acetamide (0.01), acetic acid (0.03), TOC (2.4)). After optional metering and analysis, this stream is discarded. The top product (stream (16) = stream TL2) has the following typical composition range (given in brackets in wt. %): acetonitrile (75-80), water (15-20), low boilers (e.g. propene, 1). As described above, stream (16) is recycled into the feed stream which is fed to the mixer-settler unit.

[0526] d) Acetonitrile recovery (Acetonitrile recovery unit I)

[0527] For the recycling of acetonitrile, the stream (17) obtained from the mixer-settler unit G is introduced into a distillation column with a height of 10 m and a nominal diameter of 200 mm, equipped with 40 bubble trays. The column is operated at a top pressure of 18 bar and a reflux ratio of 1:4. The stream (17) is fed to the column above the bubble tray 26 (calculated from the top). The top product (stream (19)), which mainly comprises propylene (about 97% by volume) and a small amount of propane (about 1-3% by volume), is also referred to as stream TL1, and is returned to the feed of the mixer-settler unit G as described above. Therefore, excess propylene is removed from the steam (17) and recycled. The temperature range of the bottom stream (stream (2), also referred to as stream BL1) is from 106 to 110° C. The precise operating parameters of the column (such as the energy input in the water tank) are adjusted so that the amount of propylene returned to the reactor with stream (2) is within a range such that the molar ratio of propylene to hydrogen peroxide in stream (1) is about 1:1.43. For the above-mentioned feed rate of 15 kg / h of aqueous hydrogen peroxide, this means that the conditions need to be adjusted so that the flow rate of propylene in stream (2) is about 9.7 kg / h. Before the feed of stream (2) to the main epoxidation reactor A, acetonitrile (stream (4) from Ineos, chemical grade, purity about 99.9%, containing 70-180 wt ppm propionitrile, 5-20 wt ppm acetamide and <100 wt ppm water as impurities) is optionally added to compensate for possible solvent losses.

[0528] The exact amount of additional acetonitrile required depends on the outlet stream and by-product losses, and also on the number of samples for analysis. Typical amounts of additional acetonitrile for the above process design may range from 100 to 150 g / h.

[0529] Example 1: Primary ZnTiMWW catalyst regeneration

[0530] Partial regeneration of the ZnTiMWW catalyst was performed based on the epoxidation reaction set-up as described in Reference Example 2 above. The ZnTiMWW catalyst of Reference Example 1 was loaded into the reactor. The epoxidation reaction was run continuously until the selectivity of (a2) based on hydrogen peroxide for the formation of propylene oxide was reduced by 2% relative to the average selectivity of (a2) based on hydrogen peroxide for the formation of propylene oxide during the first 100 hours of step (a). The reaction was then stopped and H2O2, propylene and propylene oxide were flushed out of the reactor. After decompression and evacuation, the reactor was flushed at 70°C with deionized water from top to bottom at a LHSV of about 7 m / h (LHSV based on the cross-section of the empty pipe) for at least 3 hours. Thereafter, the liquid aqueous system leaving the reactor showed that its total organic carbon concentration was less than 0.1% of the maximum value detected, and the total volume of the liquid aqueous system obtained from the reactor during the washing process was greater than the volume of the reactor. Then, the reactor was emptied and restarted. The continuous operation of Reference Example 2 was resumed and carried out for about 1500 hours until the reaction temperature again reached the value it had before regeneration.

[0531] Comparative Example 1: Continuous operation according to Reference Example 2 without regeneration

[0532] As a comparative example, the method of Reference Example 2 was carried out for 2500 hours without regenerating the catalyst.

[0533] Results of Example 1 and Comparative Example 1

[0534] The results of Example 1 and Comparative Example 1 are discussed below and are shown in Table 1. The inlet temperature of the heat transfer medium of the epoxidation unit A in both Example 1 and Comparative Example 1 was adjusted during the continuous operation of Reference Example 2 so that the hydrogen peroxide conversion rate was substantially maintained in the range of 90 to 92% (Reference Example 2, Section 1.1a). The resulting temperature of the heat transfer medium (cooling water) of the epoxidation unit A after a total operating time of 2500 h is shown in Table 1 for both Comparative Example 1 and Example 1. In addition, the deactivation rate is the ratio of the temperature difference of the heat transfer medium at the inlet at the end of the experiment and the temperature difference at the beginning of the experiment divided by the total operating time of 2500 h, expressed in ° C / day. In addition, the selectivity S of the hydrogen peroxide-based epoxidation reaction after a total operating time of 2500 h is provided in Table 1. Selectivity S / %=(n(PO) / n(H2O2))×100, where n(PO) is the molar amount of propylene oxide detected directly downstream of unit B and n(H2O2) is the molar amount of hydrogen peroxide converted in the epoxidation reaction.

[0535] Table 1

[0536]

[0537] It is clearly shown in Table 1 that the process of the invention allows the operation of the epoxidation unit A at a significantly reduced temperature of the cooling water after a total operating time of 2500 h, i.e. the catalyst shows a significantly better performance compared to Comparative Example 1. Furthermore, the deactivation rate (Δ(T) / Δ(t)) is also different for the two experiments and is significantly lower for the inventive example. Furthermore, the process of the invention provides a significantly higher selectivity than Comparative Example 1 after a total operating time of 2,500 h.

[0538] The regenerated catalyst of Example 1 exhibited a conversion temperature difference of 1 K, wherein the conversion temperature difference is defined as the absolute difference between (A1) the temperature at which a hydrogen peroxide conversion of 90-92% is achieved when the regenerated catalyst is used as a catalyst, and (B1) the temperature at which the said determined hydrogen peroxide conversion is achieved when the corresponding fresh catalyst is used under otherwise identical epoxidation reaction conditions. In addition, the regenerated catalyst of Example 1 exhibited a selectivity difference of 0.3 percentage points, wherein the selectivity difference is defined as the absolute difference (in percentage points) between (A2) the selectivity based on hydrogen peroxide in an epoxidation process using the regenerated catalyst as a catalyst, and (B2) the selectivity based on hydrogen peroxide in said epoxidation process using the corresponding fresh catalyst as a catalyst under otherwise identical epoxidation reaction conditions.

[0539] Example 2.1: Regeneration of the ZnTiMWW catalyst according to the invention comprising three washing steps

[0540] Partial ZnTiMWW catalyst regeneration was performed based on the epoxidation reaction setup as described in Reference Example 2 above.

[0541] Epoxidation

[0542] Partial regeneration of the ZnTiMWW catalyst was performed based on the epoxidation setup as described in Reference Example 2 above. The main reactor was charged with the ZnTiMWW catalyst according to Reference Example 1. The epoxidation reaction was run continuously for about 1300 hours until the "epoxidation temperature" reached 50°C, and the "epoxidation temperature" was defined as the temperature of the heat transfer medium at the jacket inlet of the main reactor, which had an initial value of 30°C at the start of the epoxidation reaction. At this point in time, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene continued to flow until the epoxidation in the tube was complete. The H2O2, propylene and propylene oxide in the reactor were then flushed out by passing a mixture of acetonitrile and water (80 wt% acetonitrile, 20 wt% water) through the reactor, wherein the temperature of the mixture was 50°C, and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0543] First washing step

[0544] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0545] Epoxidation

[0546] Continuous operation according to Reference Example 2 was resumed and carried out for about 1400 h until the reaction temperature reached 50° C. again. At this point, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene were allowed to flow continuously until the epoxidation in the tube was complete. H2O2, propylene and propylene oxide were then flushed out of the reactor by passing a mixture of acetonitrile and water (80% by weight acetonitrile, 20% by weight water) through the reactor, wherein the temperature of the mixture was 50° C., and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0547] Second washing step

[0548] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0549] Epoxidation

[0550] Continuous operation according to Reference Example 2 was resumed and carried out for about 1200 hours until the reaction temperature reached 50° C. again. At this point in time, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene were allowed to flow continuously until the epoxidation in the tube was complete. H2O2, propylene and propylene oxide were then flushed out of the reactor by passing a mixture of acetonitrile and water (80% by weight acetonitrile, 20% by weight water) through the reactor, wherein the temperature of the mixture was 50° C., and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0551] Residual amounts of acetonitrile and water were removed from the reactor by passing nitrogen through the catalyst bed at a nitrogen temperature of 70°C.

[0552] Third washing step

[0553] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0554] Calcination step

[0555] Then, at an initial nitrogen temperature of 70° C., nitrogen was passed through the catalyst bed for about 60 hours, the temperature being raised at 10 K / h to a value of 100° C. Subsequently, the catalyst was calcined by passing a gas mixture of air and nitrogen through the catalyst bed at a flow rate of 0.58 kg / s. The temperature of the mixture was further continuously raised at 10 K / h from its initial value of 100° C. to a final value of 450° C. and then kept substantially constant at 450° C. for 6 hours. At the start of the calcination, the oxygen content of the gas mixture entering the reactor was 4% by volume. Once 450° C. was reached, the oxygen content was adjusted to a value of 21% by volume. After calcination at 450° C., the reactor was cooled to a temperature of about 30° C.

[0556] Epoxidation

[0557] The continuous operation according to Reference Example 2 was resumed and carried out for about 1000 h.

[0558] Example 2.2: Regeneration of the ZnTiMWW catalyst according to the invention comprising two washing steps

[0559] Partial ZnTiMWW catalyst regeneration was performed based on the epoxidation reaction setup as described in Reference Example 2 above.

[0560] Epoxidation

[0561] The main reactor was charged with the ZnTiMWW catalyst according to Reference Example 1. The epoxidation reaction was run continuously for about 1200 hours until the "epoxidation temperature" reached 50°C, which was defined as the temperature of the heat transfer medium at the jacket inlet of the main reactor, which was 30°C at the start of the epoxidation reaction. At this point in time, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene continued to flow until the epoxidation in the tube was complete. The H2O2, propylene and propylene oxide in the reactor were then flushed out by passing a mixture of acetonitrile and water (80 wt% acetonitrile, 20 wt% water) through the reactor, wherein the temperature of the mixture was 50°C, and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0562] First washing step

[0563] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0564] Epoxidation

[0565] Continuous operation according to Reference Example 2 was resumed and carried out for about 1300 hours until the reaction temperature reached 50° C. again. At this point, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene were allowed to flow continuously until the epoxidation in the tube was complete. H2O2, propylene and propylene oxide were then flushed out of the reactor by passing a mixture of acetonitrile and water (80% by weight acetonitrile, 20% by weight water) through the reactor, wherein the temperature of the mixture was 50° C., and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0566] Residual amounts of acetonitrile and water were removed from the reactor by passing nitrogen through the catalyst bed at a nitrogen temperature of 70°C.

[0567] Second washing step

[0568] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0569] Calcination step

[0570] Then, at an initial nitrogen temperature of 70° C., nitrogen was passed through the catalyst bed for about 60 hours, the temperature being raised at 10 K / h to a value of 100° C. Subsequently, the catalyst was calcined by passing a gas mixture of air and nitrogen through the catalyst bed at a flow rate of 0.58 kg / s. The temperature of the mixture was further continuously raised at 10 K / h from its initial value of 100° C. to a final value of 450° C. and then kept substantially constant at 450° C. for 6 hours. At the start of the calcination, the oxygen content of the gas mixture entering the reactor was 4% by volume. Once 450° C. was reached, the oxygen content was adjusted to a value of 21% by volume. After calcination at 450° C., the reactor was cooled to a temperature of about 30° C.

[0571] Epoxidation

[0572] The continuous operation according to Reference Example 2 was resumed and carried out for about 1000 h.

[0573] Comparative Example 2: Regeneration of ZnTiMWW Catalyst Including a Washing Step

[0574] Epoxidation

[0575] The ZnTiMWW catalyst regeneration was performed based on the epoxidation setup as described in Reference Example 2 above. The main reactor was loaded with the ZnTiMWW catalyst according to Reference Example 1. The epoxidation reaction was run continuously for about 2200 hours until the "epoxidation temperature" reached 50°C, the "epoxidation temperature" being defined as the temperature of the heat transfer medium at the jacket inlet of the main reactor, which had a starting value of 30°C at the start of the epoxidation reaction. At this point in time, the epoxidation reaction was stopped by stopping the flow of hydrogen peroxide; acetonitrile and propylene continued to flow until the epoxidation in the tube was complete. The H2O2, propylene and propylene oxide in the reactor were then flushed out by passing a mixture of acetonitrile and water (80 wt% acetonitrile, 20 wt% water) through the reactor, wherein the temperature of the mixture was 50°C, and then the main part of the mixture of acetonitrile and water was discharged from the reactor.

[0576] Residual amounts of acetonitrile and water were removed from the reactor by passing nitrogen through the catalyst bed at a nitrogen temperature of 70°C.

[0577] Washing steps

[0578] Subsequently, the reaction tube was filled from below with water at a temperature of 70°C, and then water at a temperature of 70°C was passed through the tube from the top downward for about 6 hours. The water wash was stopped as soon as the conductivity of the outflowing water was below 200 microSiemens. The water was then drained from the reactor.

[0579] Calcination step

[0580] Then, at an initial nitrogen temperature of 70° C., nitrogen was passed through the catalyst bed for about 60 hours, the temperature being raised at 10 K / h to a value of 100° C. Subsequently, the catalyst was calcined by passing a gas mixture of air and nitrogen through the catalyst bed at a flow rate of 0.58 kg / s. The temperature of the mixture was further continuously raised at 10 K / h from its initial value of 100° C. to a final value of 450° C. and then kept substantially constant at 450° C. for 6 hours. At the start of the calcination, the oxygen content of the gas mixture entering the reactor was 4% by volume. Once 450° C. was reached, the oxygen content was adjusted to a value of 21% by volume. After calcination at 450° C., the reactor was cooled to a temperature of about 30° C.

[0581] Epoxidation

[0582] The continuous operation according to Reference Example 2 was resumed and carried out for about 1000 h.

[0583] Results of Examples 2.1 and 2.2 and Comparative Example 2

[0584] The results of Examples 2.1 and 2.2 and Comparative Example 2 are explained below and are shown in the following Table 2. The inlet temperature of the heat transfer medium of the epoxidation unit A in Examples 2.1 and 2.2 and Comparative Example 2 was adjusted during the continuous operation of Reference Example 2 so that the hydrogen peroxide conversion remained substantially constant at about 96%. The selectivity S of the hydrogen peroxide-based epoxidation reaction provided in Table 2 is defined as (n(PO) / n(H2O2)) x 100, where n(PO) is the molar amount of propylene oxide detected directly downstream of unit B, and n(H2O2) is the molar amount of hydrogen peroxide converted in the epoxidation reaction.

[0585] Table 2

[0586]

[0587] Table 2 clearly shows that the process according to the invention, in which one washing step (Example 2.2) and two washing steps (Example 2.1) are carried out without a subsequent calcination step, leads to a slight but still present increase in selectivity (1000 hours after calcination) compared to the conventional process (Comparative Example 2) in which calcination is carried out directly after the (single) washing step. The remarkable results are achieved despite a higher (300 hours increase for Example 2.2) or even significantly higher (1700 hours increase for Example 2.1) total epoxidation time before the calcination step. It is thus convincingly shown that the concept according to the invention of partial regeneration in stage (i), which avoids a calcination step after each washing step and thus represents a significantly less complicated process, surprisingly leads to improved results even with regard to the most important parameter, in particular for industrial-scale processes, namely the selectivity of the product of value.

[0588] References

[0589] -WO 98 / 55229A1

[0590] -EP 1 221 442 A1

[0591] - WO 2005 / 000827 A1

[0592] - WO 2007 / 013739 A1

[0593] -Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Volume 13, pages 447-456

[0594] -Atlas of Zeolite Framework Types, 5th Edition, Elsevier, London, England (2001)

[0595] -US2007043226 A1

[0596] -US 6,114,551

[0597] -Wu et al., “Hydrothermal Synthesis of a novel Titanosilicate with MWW Topology”, Chemistry Letters (2000), pp. 774 - 775

[0598] -WO 2013 / 117536 A2

Claims

1. A method for regenerating a catalyst comprising a titanium-containing zeolite as a catalytically active material, comprising: (i) A stage comprising the following steps: (a) continuously preparing propylene oxide, comprising (a1) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a reactor containing a catalyst comprising a titanium-containing zeolite as a catalytically active material; (a2) subjecting the feed stream of (a1) to epoxidation conditions in a reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent; (a3) removing a product stream comprising propylene oxide and an organic solvent from the reactor; (b) stopping the introduction of the feed stream into the reactor; (c) washing the catalyst with a liquid aqueous system; Stage (i) further comprises repeating the process of steps (a) to (c) n times, wherein n is an integer and is at least 1; the method for regeneration further comprises (ii) a stage comprising calcining the catalyst obtained in (c) after repeating the sequence of steps (a) to (c) n times; The process of stages (i) to (ii) is optionally repeated m times, wherein m is an integer and is at least 1, and wherein n is the same or different in each repetition of the process of stages (i) to (ii).

2. The method of claim 1, wherein the organic solvent is methanol or acetonitrile.

3. The process of claim 1 or 2, wherein the titanium-containing zeolite has an MFI framework structure or an MWW framework structure, and wherein at least 99% by weight of the framework structure of the titanium-containing zeolite consists of silicon, titanium and oxygen.

4. The process of claim 1 or 2, wherein the titanium-containing zeolite comprises Zn.

5. The process of claim 1 or 2, wherein the catalyst comprising the titanium-containing zeolite is present in the reactor as a fixed bed catalyst.

6. The method of claim 1 or 2, wherein the liquid aqueous system of (c) comprises at least 95% by weight water, based on the total weight of the liquid aqueous system.

7. The process of claim 1 or 2, wherein according to (c), the washing of the catalyst is carried out in a continuous mode in a reactor comprising the catalyst.

8. The process of claim 7, wherein the reactor of (a) is a tubular reactor or a tube bundle reactor, and the washing with the liquid aqueous system of (c) is carried out at a liquid hourly space velocity (LHSV) of 1 to 20 m / h.

9. The process of claim 1 or 2, wherein the washing of (c) is carried out at a temperature of the liquid aqueous system in the range of 30 to 90°C.

10. The process of claim 1 or 2, wherein the washing in (c) is carried out until the total organic carbon concentration of the liquid aqueous system after contact with the catalyst is at most 5% of the maximum total organic carbon concentration detected during the washing in (c).

11. The process of claim 1 or 2, wherein the steps (b) and (c) are performed when the selectivity of the epoxidation reaction of (a2) decreases by 4% relative to the average selectivity of the epoxidation reaction of (a2) during the first 100 hours of performing step (a), wherein the selectivity of the epoxidation reaction is defined as the molar amount of propylene oxide obtained in (a2) relative to the molar amount of hydrogen peroxide converted in (a2).

12. The method of claim 1 or 2, wherein n is 1 to 6.

13. The process of claim 1 or 2, wherein the calcination in stage (ii) is at a catalyst temperature in the range of 300 to 600°C.

14. The process of claim 1 or 2, wherein the calcination of stage (ii) is carried out in a reactor comprising the catalyst.

15. The method of claim 1 or 2, wherein the procedure of steps (i) to (ii) is repeated m times, wherein m is an integer from 1 to 6.

16. A regenerated catalyst comprising a titanium-containing zeolitic material as catalytically active material, obtainable or obtained by the process according to any one of claims 1 to 15.

17. The regenerated catalyst of claim 16, which exhibits a conversion temperature difference of at most 5 K in a process for preparing propylene oxide, wherein the conversion temperature difference is defined as the absolute difference between: (A1) a temperature at which a predetermined hydrogen peroxide conversion rate is achieved in the process for preparing propylene oxide, wherein a regenerated catalyst is used as a catalyst, and (B1) A temperature at which the predetermined hydrogen peroxide conversion rate is achieved in the method for preparing propylene oxide, wherein a corresponding fresh catalyst is used as the catalyst under otherwise identical epoxidation reaction conditions. and / or, it exhibits a selectivity difference of at most 1 in a process for preparing propylene oxide, wherein the selectivity difference is defined as the absolute difference, expressed in percentage points, between the following selectivities: (A2) selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a regenerated catalyst is used as catalyst, and (B2) The selectivity based on hydrogen peroxide in the process for preparing propylene oxide, wherein a corresponding fresh catalyst is used as the catalyst under otherwise identical epoxidation reaction conditions, wherein the selectivity based on hydrogen peroxide is defined as the number of moles of propylene oxide produced divided by the number of moles of hydrogen peroxide converted×100.

18. A continuous process for preparing propylene oxide, comprising (i') A stage comprising the following steps: (a') continuously preparing propylene oxide in a first reactor, comprising (a1′) introducing a feed stream comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent into a catalyst containing a titanium-containing zeolite as a catalytically active material. In a reactor; (a2') in the presence of a catalyst, the feed stream of (a1') is passed through a first reactor subjecting the mixture to epoxidation conditions to obtain a reaction mixture comprising propylene oxide and an organic solvent; (a3') removing a product stream comprising propylene oxide and an organic solvent from the first reactor; (b') stopping the introduction of the feed stream into the first reactor; (c') washing the catalyst with a liquid aqueous system; Stage (i') further comprises repeating steps (a') to (c') n' times, wherein n' is an integer and is at least 1; the method for preparing propylene oxide further comprises (ii') a stage comprising calcining the catalyst obtained from (c') after repeating the sequence of steps (a') to (c') n' times; wherein the steps of stages (i') to (ii') are optionally repeated m' times, wherein m' is an integer and is at least 1, wherein in each repetition of the steps (i') to (ii'), n' is the same or different; The method for preparing propylene oxide further comprises: (i") a stage comprising the following steps: (a") continuously preparing propylene oxide in a second reactor, comprising (a1") comprising propylene, hydrogen peroxide or a source of hydrogen peroxide and an organic solvent The feed stream is introduced into a catalyst containing a titanium-containing zeolite as the catalytically active material. In the second reactor; (a2") subjecting the feed stream of (a1") to epoxidation conditions in a second reactor in the presence of a catalyst to obtain a reaction mixture comprising propylene oxide and an organic solvent; (a3") removing a product stream comprising propylene oxide and an organic solvent from the second reactor; (b") stopping the introduction of the feed stream into the second reactor; (c") washing the catalyst with a liquid aqueous system; Stage (i") further comprises repeating steps (a") to (c") n" times, wherein n" is an integer and is at least 1; the method for preparing propylene oxide further comprises (ii") a stage comprising calcining the catalyst obtained in (c") after repeating the sequence of steps (a") to (c") n" times; wherein the steps (i") to (ii") are optionally repeated m" times, wherein m" is an integer and is at least 1, and wherein in each repetition of the steps (i") to (ii"), n" is the same or different; wherein during at least one of steps (b') and (c') or at least one of steps (b'), (c') and (ii'), propylene oxide is prepared according to (a")

Images