DIBC-free H2O2 used in the production of propylene oxide

Abstract

The present invention relates in a first aspect to a method for preparing propylene oxide, comprising: (i) providing a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide; (ii) contacting the reaction mixture provided in (i) with an epoxidation catalyst comprising a zeolite material having a framework structure containing Si, O and Ti in an epoxidation zone, and subjecting the reaction mixture to epoxidation reaction conditions in the epoxidation zone to obtain a mixture comprising propylene oxide, water and an organic solvent in the epoxidation zone; (iii) removing a discharge stream from the epoxidation zone, the discharge stream comprising propylene oxide, water and an organic solvent; wherein the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. In a second aspect, the invention further relates to a reaction mixture for preparing propylene oxide, comprising propylene, water, an organic solvent, and hydrogen peroxide, wherein the reaction mixture contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg / kg of hydrogen peroxide contained in the reaction mixture. In a third aspect, the invention relates to a system comprising an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O, and Ti, and the system further comprising the reaction mixture comprising propylene, water, and an organic solvent as described in the second aspect. In a fourth aspect, the invention relates to the use of an aqueous hydrogen peroxide solution as an epoxidizing agent in the presence of an organic solvent and an epoxidation catalyst for preparing propylene oxide, wherein the epoxidation catalyst comprises a zeolite material having a framework structure containing Si, O, and Ti, wherein the aqueous hydrogen peroxide solution comprises at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution.

Description

[0001] The present invention relates in a first aspect to a method for preparing propylene oxide, comprising: (i) providing a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide; (ii) contacting the reaction mixture provided in (i) with an epoxidation catalyst comprising a zeolite material having a framework structure containing Si, O and Ti in an epoxidation zone, and subjecting the reaction mixture to epoxidation reaction conditions in the epoxidation zone to obtain a mixture comprising propylene oxide, water and an organic solvent in the epoxidation zone; (iii) removing a discharge stream from the epoxidation zone, the discharge stream comprising propylene oxide, water and an organic solvent; wherein the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. In a second aspect, the invention further relates to a reaction mixture for preparing propylene oxide, the reaction mixture comprising propylene, water, an organic solvent, and hydrogen peroxide, wherein the reaction mixture contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg / kg of hydrogen peroxide contained in the reaction mixture. In a third aspect, the invention relates to a system comprising an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O, and Ti, and the system further comprising the reaction mixture comprising propylene, water, and an organic solvent as described in the second aspect. In a fourth aspect, the invention relates to the use of an aqueous hydrogen peroxide solution as an epoxidizing agent in the presence of an organic solvent and an epoxidation catalyst for preparing propylene oxide, the epoxidation catalyst comprising a zeolite material having a framework structure containing Si, O, and Ti, wherein the aqueous hydrogen peroxide solution comprises at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution.

[0002] Propylene oxide is an important intermediate in the chemical industry. A suitable method for preparing propylene oxide is to use propylene as a raw material, hydrogen peroxide (H₂O₂) as an oxidant, and a solvent and a titanium-containing zeolite epoxidation catalyst. Hydrogen peroxide is usually prepared in aqueous solution, and different methods are known. One widely used method is the so-called anthraquinone process ("AO process," see Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Vol. A, 13 (1989), pp. 443-466). The hydrogen peroxide solution produced by the anthraquinone process is obtained by extracting a so-called oxidizing working solution with water. The oxidizing working solution is a mixture containing a solvent, anthraquinone, tetrahydroanthraquinone, and H₂O₂, obtained by oxidizing a reducing working solution, which is itself a mixture containing a solvent, anthraquinone, tetrahydroanthraquinone, and oxygen (O₂). The resulting aqueous solution can be used directly for the epoxidation reaction of propylene. Alternatively, the solution can be concentrated by partially evaporating water to obtain a higher concentration of H₂O₂ solution. This solution always contains organic impurities from the working solution. These impurities can be components of the working solution or products formed by reactions unwanted by these components, such as oxidation or hydrolysis products. The exact nature of all organic impurities contained in aqueous H₂O₂ solutions is generally unknown, and current technology provides little or no information in this regard. Typically, the content of organic matter is given only as a TOC value (total organic carbon), which usually ranges from 100 to 1000 ppm (mg of organic carbon per kilogram of H₂O₂ solution). However, it is expected that the nature of the impurities contained in aqueous H₂O₂ solutions will depend considerably on the solvent system and the nature of the anthraquinones used. Working solutions are typically composed of a mixture of two solvents to retain anthraquinone and anthraquinone forms, as well as tetrahydroanthraquinone and tetrahydroanthraquinone forms, in solution. These two solvents are selected from quinone solvents and hydroquinone solvents, such as those disclosed in Ullmann's Encyclopedia of Industrial Chemistry, page 447, cited above, including ureas, particularly as quinone solvents.

[0003] Methods for removing organic impurities from aqueous H2O2 solutions are known in the art, for example in the production of electronic-grade H2O2, but such methods are very expensive, and the resulting aqueous H2O2 solutions are too costly to be economically viable for the epoxidation of propylene.

[0004] Regarding specific impurities, aqueous solutions of hydrogen peroxide containing amines such as dibutylamine (see EP 1 546 035A1, Evonik) are known to be unsuitable for propylene epoxidation catalyzed by titanium silicates such as titanium silicalite-1 (TS-1) in methanol. Since dibutylamine is produced from tetrabutylurea, which is commonly used as a solvent in industrial production, the prior art suggests using hydrogen peroxide derived from methods that do not use solvents capable of forming amines. Other organic impurities present in commercial hydrogen peroxide solutions have been mentioned. However, apart from amines derived from solvents (such as tetraalkylurea), such organic impurities have never been reported to affect the epoxidation reaction. Furthermore, WO 99 / 40024 A1 (Solvay SA) and WO 2013 / 160163 A1 (Solvay SA) specifically mention that diisobutylmethanol is a suitable polar solvent for the production of hydrogen peroxide via the AO process (see WO 99 / 40024 A1, page 7, line 14 and WO 2013 / 160163A1, page 29, line 30). Therefore, it can be concluded that compounds like diisobutylmethanol have never been considered detrimental to the AO process and therefore will not be detrimental to subsequent reactions such as the epoxidation of propylene. Industrial-grade "diisobutylmethanol" (DIBC) comprises two isomers: 2,6-dimethyl-4-heptanol and 4,6-dimethyl-2-heptanol.

[0005] However, given the importance of propylene oxide in industrial-scale production, it is desirable to utilize hydrogen peroxide for epoxidation reactions as efficiently as possible.

[0006] Therefore, the object of the present invention is to provide an economically advantageous method for preparing propylene oxide in an organic solvent using propylene and hydrogen peroxide, which can improve the efficiency of the epoxidation reaction.

[0007] Surprisingly, it was found that aliphatic oxygen-containing compounds with 8 to 10 carbon atoms contained in commercial hydrogen peroxide solutions have a negative impact on the efficiency of propylene epoxidation, particularly on the catalytic performance of epoxidation catalysts during propylene oxide formation.

[0008] Therefore, in a first aspect, the present invention relates to a method for preparing propylene oxide, comprising:

[0009] (i) Provide a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide;

[0010] (ii) In the epoxidation zone, the reaction mixture provided in (i) is contacted with an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the reaction mixture is subjected to epoxidation reaction conditions in the epoxidation zone to obtain a mixture containing propylene oxide, water and an organic solvent.

[0011] (iii) Remove the effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, water and organic solvent;

[0012] The reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0013] It goes without saying that the order of steps (i), (ii), and (iii) means that step (ii) is performed after step (i), preferably directly after step (i), and step (iii) is performed after step (ii), preferably directly after step (ii). "Directly after" means that there are no intermediate steps between (i) and (ii) or between (ii) and (iii).

[0014] The statement "The reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture" means that the reaction mixture contains only one or more aliphatic oxygen-containing compounds having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. In other words, the reaction mixture provided in (i) and subjected to (ii) contains one or more aliphatic oxygen-containing compounds having 8 to 10 carbon atoms, in an amount of ≤500 mg per kg of hydrogen peroxide contained in reaction mixture (i). This also applies to the definitions below, which include specific ranges.

[0015] Preferably, the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of 0 to 500 mg per kg of hydrogen peroxide contained in the reaction mixture, preferably 0 to 400 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 300 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 200 mg per kg of hydrogen peroxide contained in the reaction mixture, and more preferably 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0016] Surprisingly, the performance of the epoxidation catalysts improved with decreasing concentrations of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms. When the concentration of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms exceeded 500 mg / kg hydrogen peroxide, much higher temperatures (and therefore higher temperatures of the cooling medium) were required in the epoxidation zone to maintain a hydrogen peroxide conversion of ≥90%. However, at these high concentrations, the selectivity was far below 85%. It was also found that excessively high concentrations of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms exceeding 500 mg / kg hydrogen peroxide negatively impacted different types of TS-1 zeolite catalysts, regardless of their preparation methods and properties. This finding is somewhat surprising, as different types of TS-1 zeolite catalysts typically react differently when impurities are taken into account. Experiments further show that only when the concentration of at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is maintained at or below the threshold of 500 ppm can a high hydrogen peroxide conversion rate of ≥98% and high selectivity be achieved over a meaningful period of time, i.e., more than 200 hours.

[0017] The at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms

[0018] Generally, there are no specific limitations on the properties of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms. The expression "having 8 to 10 carbon atoms" means that each aliphatic oxygen-containing compound has 8, 9, or 10 carbon atoms. Preferably, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is selected from secondary monohydric alcohols C10, where n is an integer from 8 to 10. n H 2n+2 O, where m is an integer from 8 to 10, a monoketone C m H 2m O, where p is an integer from 8 to 10, of the diol C p H 2p+2 O2, and mixtures of two or more of these compounds; preferably selected from secondary monohydric alcohols C9H 20 O, monoketone C9H 18O, Diol C9H 20 O2 and mixtures of two or more of these compounds. Diols C9H 20 O2 preferably has one secondary hydroxyl group and one tertiary hydroxyl group, more preferably selected from 2,6-dimethylheptane-2,4-diol, 4,6-dimethylheptane-2,4-diol, 2,4-dimethylheptane-2,6-diol, and mixtures of two or more of these diols, each having one secondary hydroxyl group and one tertiary hydroxyl group. More preferably, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is selected from secondary monohydric alcohols C9H. 20 O, monoketone C9H 18 O and secondary monohydric alcohol C9H 20 O and a monoketone C9H 18 A mixture of O. More preferably, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is selected from diisobutylmethanol and diisobutyl ketone, and mixtures of diisobutylmethanol and diisobutyl ketone, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms more preferably includes at least diisobutylmethanol (C9H). 19 OH).

[0019] In one embodiment, based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms contains 95 to 99.5% by weight of diisobutylmethanol, preferably 96 to 99% by weight. In one embodiment, based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms contains 95 to 99.5% by weight of diisobutylmethanol and contains diisobutyl ketone (C9H). 18The amount of diisobutylmethanol (DIBC) is 1.0 to 0.01% by weight. Preferably, the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms comprises 96 to 99% by weight of diisobutylmethanol and 0.9 to 0.05% by weight of diisobutyl ketone, each based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms. The balance adds up to 100% by weight, the balance typically being ≤1% by weight, including compounds such as methylheptane-3-ol, isomers of methylheptane-3-ol, and smaller fragments such as C4-C6 alcohols and ketones. "Diisobutylmethanol" (DIBC) includes two isomers: 2,6-dimethyl-4-heptanol and 4,6-dimethyl-2-heptanol. Based on the total weight of diisobutylmethanol, preferably ≥95% by weight, more preferably ≥96% by weight, and even more preferably ≥80% by weight, the diisobutylmethanol comprises 2,6-dimethyl-4-heptanol and 4,6-dimethyl-2-heptanol. In one embodiment, based on the total weight of diisobutylmethanol, the DIBC comprises 80 to 90% by weight, preferably 82 to 89% by weight, more preferably 84 to 88% by weight, of 4,6-dimethyl-2-heptanol and 10 to 20% by weight, preferably 11 to 18% by weight, more preferably 12 to 16% by weight, of 4,6-dimethyl-2-heptanol. "Diisobutyl ketone" includes both isomers: 2,6-dimethyl-4-heptanone and 4,6-dimethyl-2-heptanone.

[0020] According to step (i) of the method for preparing propylene oxide, a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide is provided.

[0021] Typically, it is conceivable to use pure or substantially pure propylene as a starting material and as part of the reaction mixture provided in (i). A mixture of propylene and propane is preferred. Most preferably, technical-grade propylene conforming to international standards (e.g., ASTM D5273 or DIN 51622) is used. If a mixture of propylene and propane is used as part of the reaction mixture provided in (i), the propylene:propane weight ratio is preferably at least 7:3. For example, commercially available propylene can be used, which may be polymer-grade or chemical-grade propylene. Typically, polymer-grade propylene has a propylene content between 99 and 99.8% by weight and a propane content between 0.2 and 1% by weight. Chemical-grade propylene typically has a propylene content between 92 and 98% by weight and a propane content between 2 and 8% by weight. According to a preferred embodiment of the invention, a mixture of propylene and propane is used, wherein the propylene content is in the range of 99 to 99.8% by weight and the propane content is in the range of 0.2 to 1% by weight.

[0022] The organic solvent is preferably an organic epoxidizing solvent, more preferably selected from alcohols, acetonitrile, tert-butanol, propionitrile, and mixtures of two or more thereof; even more preferably selected from alcohols, acetonitrile, and mixtures of alcohols and acetonitrile; even more preferably, the organic solvent contains at least one alcohol. "The organic solvent contains at least one alcohol" means that, based on the total weight of the organic solvent, at least 90% by weight, preferably at least 95% by weight, more preferably at least 98% by weight, and even more preferably at least 99% by weight of the organic solvent is composed of the alcohol. The alcohol is preferably a C1 to C5 monohydric alcohol or a mixture of two or more C1 to C5 alcohols, more preferably the alcohol contains at least methanol, and even more preferably the alcohol is methanol. According to a preferred embodiment, the organic solvent is methanol.

[0023] There are no restrictions on the water used in the reaction mixture. For example, water treated with NH3 can be used, but untreated water can also be used. Deionized water is preferred for the reaction mixture. Deionized water can be obtained by ion exchange using condensate. Typical grades of deionized water are defined in ISO 3696 (1987), and all grades described therein are applicable within the scope of this invention. The water may also contain trace amounts of corrosion inhibitors, such as ammonia, hydrazine, or hydroxylamine; in this case, its pH should be between 7 and 9 (measured using a calibrated glass electrode). Preferably, the water used does not contain corrosion inhibitors.

[0024] Typically, the reaction mixture comprising propylene, water, an organic solvent, and hydrogen peroxide can be provided in (i) by any conceivable method. Preferably, the reaction mixture comprising propylene, water, an organic solvent, and hydrogen peroxide or a hydrogen peroxide source provided in (i) is prepared from two or more streams. More preferably, the reaction mixture is provided in (i) by combining at least three separate streams, wherein the first stream comprises hydrogen peroxide or a hydrogen peroxide source, optionally an aqueous solution, the second stream comprises propylene and optionally propane, and the third stream comprises an organic solvent and optionally water.

[0025] Preferably, in the reaction mixture provided in (i), the weight ratio (w / w) of propylene to hydrogen peroxide is in the range of 1:1 to 6:1, more preferably in the range of 1:1 to 2:1 or in the range of 3:1 to 5:1. Preferably, in the reaction mixture provided in (i), the weight ratio of organic solvent to hydrogen peroxide (w / w) is in the range of 15:1 to 5:1, more preferably in the range of 12:1 to 6:1, and even more preferably in the range of 11:1 to 8:1. Preferably, in the reaction mixture provided in (i), the weight ratio of organic solvent to propylene (w / w) is in the range of 10:1 to 1:0.1, more preferably in the range of 9:1 to 1:1, even more preferably in the range of 9:1 to 7:1 or in the range of 1.5:1 to 1:1.

[0026] Preferably, the reaction mixture provided in (i) comprises

[0027] (i.1) Provide an aqueous solution of hydrogen peroxide;

[0028] (i.2) The aqueous hydrogen peroxide solution provided in (i.1) is mixed with propylene and an organic solvent to obtain a reaction mixture;

[0029] The aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0030] It goes without saying that the order of steps (i.1) and (i.2) means that step (i.2) is performed after step (i.1), preferably directly after step (i.1). "Directly after" means that no intermediate steps are performed between (i.1) and (i.2). It can be understood that this also means that the complete sequence of steps is preferably (i.1), (i.2), (ii), and (iii), wherein preferably no intermediate steps are performed between (i.2) and (ii) and between (ii) and (iii).

[0031] Hydrogen peroxide aqueous solution

[0032] Preferably, the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of 0 to 500 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, preferably 0 to 400 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, more preferably 0 to 300 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, more preferably 0 to 200 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, and even more preferably 0 to 100 mg / kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution. "The reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture" means that the reaction mixture contains only one or more aliphatic oxygen-containing compounds having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture—the total amount of all aliphatic oxygen-containing compounds having 8 to 10 carbon atoms contained in the reaction mixture is up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. This also applies to the definitions above that include specific quantity ranges.

[0033] Preferably, the total organic carbon (TOC) content of the hydrogen peroxide aqueous solution provided in (i.1) and subjected to (i.2) is 100 to 800 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, more preferably 120 to 750 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, and more preferably 150 to 700 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, as determined as described in Example 5.

[0034] Generally, there are no specific limitations on the pH value of the hydrogen peroxide aqueous solution and the amount of hydrogen peroxide contained in the solution, as long as the epoxidation reaction of propylene can be carried out effectively. Preferably, the pH value of the hydrogen peroxide aqueous solution provided in (i.1) and subjected to (i.2) is in the range of 0 to 3.0, more preferably in the range of 0.1 to 2.5, and more preferably in the range of 0.5 to 2.3, as determined with reference to Example 4. Preferably, the hydrogen peroxide aqueous solution provided in (i.1) and subjected to (i.2) comprises 20 to 80% by weight, more preferably 30 to 70% by weight, and more preferably 40 to 60% by weight of hydrogen peroxide relative to the total weight of the hydrogen peroxide aqueous solution.

[0035] Generally, there are no specific restrictions on the source of the aqueous hydrogen peroxide solution, as long as the epoxidation of propylene can be carried out effectively. Preferably, the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is obtained or available from the anthraquinone process.

[0036] According to one embodiment of the invention, an aqueous solution of hydrogen peroxide is preferably used, which is obtained as a crude hydrogen peroxide solution by extraction of a mixture produced by a process called the anthraquinone process (see, for example, Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Volume A, 13 (1989), pp. 443-466). The anthraquinone solution used contains an alkyl group preferably having 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2, 5, or 6 carbon atoms. The solvent used is typically a mixture of at least two different solvents. Preferably, a mixture of two solvents or a mixture of three solvents is used. Preferably, the solvents used in the anthraquinone process are not nitrogen-containing substances. This anthraquinone solution is commonly referred to as the working solution. In this method, the hydrogen peroxide formed in the anthraquinone process is typically separated from the working solutions by extraction after a hydrogenation / reoxidation cycle. The extraction can preferably be carried out with essentially pure water, yielding a crude aqueous solution of hydrogen peroxide. The crude aqueous solution of hydrogen peroxide thus obtained can typically be further purified and / or concentrated by distillation. A crude aqueous solution of hydrogen peroxide that has not been distilled and / or concentrated can be used, as well as a distilled and / or concentrated aqueous solution of hydrogen peroxide. Furthermore, the crude aqueous solution of hydrogen peroxide can typically undergo a further extraction stage, in which a suitable extractant, preferably an organic solvent, is used. More preferably, the organic solvent used in this further extraction stage is the same solvent used in the anthraquinone process. It is preferred to use only one solvent from the working solution for extraction, and most preferably only the most nonpolar solvent in the working solution. If the crude aqueous solution of hydrogen peroxide undergoes such a further extraction stage, a so-called crude washed hydrogen peroxide solution is obtained. According to a preferred embodiment of the invention, the crude washed hydrogen peroxide solution is used as the aqueous solution of hydrogen peroxide in (i.1). For example, the production of the crude solution is described in European Patent Application EP 1 122 249 A1. Regarding the term "basically pure water," refer to paragraph 10 on page 3 of EP 1 122 249 A1, which is incorporated herein by reference. Hydrogen peroxide can also be treated to remove trace metals, for example, before use as described in WO 2015 / 049327 A1.

[0037] It is understood that hydrogen peroxide is prepared in situ from hydrogen and oxygen in the epoxidation zone, preferably in the presence of a suitable noble metal catalyst contained in the epoxidation zone according to (ii). Suitable noble metal catalysts preferably include one or more of palladium, platinum, silver, gold, rhodium, iridium, ruthenium, and osmium. Preferably, the noble metal catalyst includes palladium. The noble metal catalyst is preferably supported on a support, wherein the support preferably includes SiO2, Al2O3, B2O3, GeO2, Ga2O3, ZrO2, TiO2, MgO, carbon, and one or more zeolites, preferably one or more titanium zeolites. More preferably, the support comprises an epoxidation catalyst containing titanium zeolites. If hydrogen peroxide is prepared in situ from hydrogen and oxygen in the epoxidation zone according to (ii), the reaction mixture provided in (i) includes propylene, hydrogen, oxygen, water, and an organic solvent.

[0038] (ii) Reaction conditions for epoxidation

[0039] According to step (ii) of the method for preparing propylene oxide, the reaction mixture provided in (i) is contacted in an epoxidation zone with an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the reaction mixture is subjected to epoxidation reaction conditions in the epoxidation zone to obtain a mixture containing propylene oxide, water and an organic solvent.

[0040] Generally, there are no specific restrictions on the conditions for contact between the reaction mixture and the epoxidation catalyst in the epoxidation zone, as long as the epoxidation reaction of propylene can be carried out effectively. Preferably, the epoxidation reaction conditions according to (ii) include trickle bed conditions or fixed bed conditions, with fixed bed conditions being more preferred. Preferably, these conditions are applied in a reactor in which the catalyst is present in a fixed bed. "Trickle bed conditions" preferably refer to a reaction that is preferably carried out at a temperature and pressure in which the reaction mixture is partially liquid and partially gaseous, with the catalyst present in a fixed bed. In embodiments with fixed bed conditions, the reaction is preferably carried out at a temperature and pressure in which the reaction mixture in the epoxidation zone is liquid and no gaseous phase is present, wherein two or more liquid phases may be present, with the catalyst present in a fixed bed. Preferably, the contact between the reaction mixture provided in (i) and the epoxidation catalyst according to (ii) in the epoxidation zone is carried out at an absolute pressure of 0.5 to 5.0 MPa, preferably 1.5 to 3.0 MPa, more preferably 1.8 to 2.8 MPa in the epoxidation zone.

[0041] Generally, the contact between the reaction mixture provided in (i) and the epoxidation catalyst in (ii) in the epoxidation zone can be carried out in any suitable manner. Thus, for example, it can be carried out in a batch reactor, or in at least one semi-continuous reactor, or in at least one continuous reactor. Continuous operation is preferred, wherein at least (ii) is preferably carried out continuously, wherein at least (ii) and (iii) are more preferred, and (i), (ii), and (iii) are even more preferred to be carried out continuously.

[0042] Preferably, the reaction mixture provided in (i) is contacted with the epoxidation catalyst in the epoxidation zone according to (ii) in at least one preferably continuously operating reactor, such as a tubular reactor or a tube bundle reactor, which preferably includes at least one cooling jacket surrounding at least one tube. A cooling medium flows through the cooling jacket. The nature of the cooling medium is not particularly limited, as long as it is sufficient to regulate the temperature of the epoxidation zone. For example, the cooling medium includes water, and may also include additives such as aliphatic C2 to C5 monohydric alcohols, aliphatic C2 to C5 dihydric alcohols, and mixtures of two or more thereof. Preferably, based on the total weight of the cooling medium, ≥90% by weight, more preferably ≥95% by weight, of the cooling medium is water. The temperature of the cooling medium is the temperature of the cooling medium used in (ii) to regulate the temperature of the reaction mixture in the epoxidation zone, wherein the temperature is preferably regulated by passing the cooling medium through the cooling jacket, wherein the temperature of the cooling medium is preferably the temperature of the cooling medium before regulating the temperature of the reaction mixture, and preferably the temperature of the cooling medium at the inlet of the cooling jacket.

[0043] Preferably, the contact between the reaction mixture provided in (i) and the epoxidation catalyst according to (ii) in the epoxidation zone is carried out at a temperature in the epoxidation zone ranging from 33 to 73°C, more preferably from 38 to 63°C, and even more preferably from 53 to 63°C. The temperature of the epoxidation zone is measured using ten thermocouples, i.e., ten thermal elements. The epoxidation zone is defined as the area where the reaction of hydrogen peroxide and propylene to produce propylene oxide still occurs in a detectable amount (≥10 ppm propylene oxide). Preferably, the epoxidation zone exists along the entire length of the catalyst bed, i.e., the area where the epoxidation catalyst is preferably present within the reactor (epoxidation zone = catalyst bed). Hot spots, i.e., the areas where the maximum reaction occurs, are typically located in the front half of the catalyst bed, preferably with ≥6 of the ten thermal elements located in the front half of the catalyst bed.

[0044] The temperature of the epoxidation zone is the average temperature determined by the temperature values ​​measured by all the thermal elements located in the front half of the catalyst bed. Typically, the temperature values ​​measured by these thermal elements differ from each other within the range of 6-10°C.

[0045] Preferably, the temperature of the cooling medium is the temperature of the cooling medium entering the reactor inlet. Preferably, the temperature of the cooling medium is in the range of 25 to 65°C, more preferably in the range of 30 to 55°C, and even more preferably in the range of 345 to 55°C. The optimal temperature range for the cooling medium is 45 to 55°C. Temperatures below 45°C are associated with the start-up phase of the epoxidation reaction and are too low for effective tempering during the epoxidation reaction. Above 55°C, the decomposition of hydrogen peroxide and the formation of oxygen increase exponentially. Within the cooling medium temperature range of 45 to 55°C, the optimal temperature range for the epoxidation zone is 53 to 63°C to achieve maximum selectivity and optimal activity.

[0046] Epoxidized region

[0047] According to step (ii) of the method for preparing propylene oxide, the reaction mixture provided in (i) is contacted in an epoxidation zone with an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the reaction mixture is subjected to epoxidation reaction conditions in the epoxidation zone to obtain a mixture containing propylene oxide, water and an organic solvent.

[0048] Generally, there are no specific limitations on the design of the epoxidation zone, as long as it is suitable for carrying out a preferred continuous epoxidation reaction. Preferably, the epoxidation zone according to (ii) comprises one or more epoxidation subzones, wherein a given epoxidation subzone preferably consists of one or more epoxidation reactors, wherein there are no specific limitations on the design of the one or more epoxidation reactors, as long as the reactors are suitable for carrying out a preferred continuous epoxidation reaction.

[0049] Preferably, the epoxidation zone according to (ii) comprises a first epoxidation section consisting of one or more epoxidation reactors A. The term "first epoxidation section" as used in the context of this invention refers to the epoxidation section to which the reaction mixture provided in (i) is fed, wherein the epoxidation zone in (ii) may include other epoxidation sections arranged downstream of the first epoxidation section. If the first epoxidation section comprises two or more epoxidation reactors A, it is preferred that the two or more epoxidation reactors A are arranged in parallel. In this case, it is preferable that in (ii), the reaction mixture provided in (i) is fed into at least one epoxidation reactor A. For example, when the reaction mixture provided in (i) is fed into at least one epoxidation reactor A, it is possible to stop the operation of at least one reactor A, for example for maintenance purposes and / or regeneration of the catalyst contained in at least one reactor A. If the first epoxidation section comprises two or more epoxidation reactors A, the operating reactors operate substantially identically, such that in each operating epoxidation reactor A, the given epoxidation conditions in each reactor are within the same range. For example, the temperature of the epoxidation zone is within the same range in each reactor.

[0050] The temperature of the cooling medium is used to regulate the temperature of the reaction mixture in the first epoxidation reaction zone according to (ii), wherein the temperature is preferably regulated by passing the cooling medium through the cooling jacket of one or more epoxidation reactors A, wherein the temperature of the cooling medium is preferably the temperature of the cooling medium before regulating the temperature of the reaction mixture, and preferably the temperature of the cooling medium at the inlet of the cooling jacket of one or more epoxidation reactors A. If the first epoxidation zone comprises two or more epoxidation reactors A, the temperature of the cooling medium is related to a given reactor A in operation within the first epoxidation zone.

[0051] According to a first preferred embodiment of the invention, the epoxidized region according to (ii) is composed of a first epoxidized partition.

[0052] According to a second preferred embodiment of the invention, the epoxidation zone according to (ii) further includes a second epoxidation section consisting of one or more epoxidation reactors B, wherein if the second epoxidation section includes two or more epoxidation reactors B, the two or more epoxidation reactors B are arranged in parallel, and the second epoxidation section is arranged downstream of the first epoxidation section. In this case, it is preferable that the discharge stream obtained from the first epoxidation section, optionally after appropriate intermediate treatment, is fed into at least one epoxidation reactor B. For example, when the discharge stream obtained from the first epoxidation section, optionally after appropriate intermediate treatment, is fed into at least one epoxidation reactor B, it is possible to stop the operation of at least one reactor B, for example for maintenance purposes and / or regeneration of the catalyst contained in at least one reactor B. If the second epoxidation section includes two or more epoxidation reactors B, the reactors in operation operate substantially identically, such that the given epoxidation conditions in each reactor in each operating epoxidation reactor B are within the same range. Generally, it can be understood that, in addition to the first and second epoxidation sections, the epoxidation zone according to (ii) includes at least one additional epoxidation section arranged downstream of the second epoxidation section. Preferably, according to a second preferred embodiment of the invention, the epoxidized region according to (ii) consists of a first epoxidized zone and a second epoxidized zone.

[0053] Preferably, the temperature of the reaction mixture in the second epoxidation reaction zone is not regulated by passing a cooling medium through the cooling jacket of the one or more epoxidation reactors B. More preferably, the second epoxidation zone is a substantially adiabatic epoxidation zone. More preferably, the second epoxidation zone is an adiabatic epoxidation zone.

[0054] Epoxidation catalyst

[0055] According to step (ii) of the method for preparing propylene oxide, the reaction mixture provided in (i) is contacted in an epoxidation zone with an epoxidation catalyst comprising an epoxidation catalyst having a framework structure containing Si, O, and Ti. Generally, there are no specific limitations on the epoxidation catalyst comprising an epoxidation catalyst having a framework structure containing Si, O, and Ti. Preferably, 95-100 wt%, more preferably 98-100 wt%, more preferably 99-100 wt%, more preferably 99.5-100 wt%, more preferably 99.9-100 wt% of the zeolite material is composed of Si, O, Ti, and optionally H. Preferably, the zeolite material contains 0.2 to 5 wt% Ti, more preferably 0.5 to 4 wt%, more preferably 1.0 to 3 wt%, more preferably 1.2 to 2.5 wt%, more preferably 1.4 to 2.2 wt%, calculated in elemental Ti and based on the total weight of the zeolite material.

[0056] Preferably, the zeolite material containing a Si, O, and Ti framework structure in the epoxidation catalyst is a zeolite material with the following properties: 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, GIS, GIU, GME, GON, GOO, H EU,IFR,ISV,ITE,ITH,ITQ,ITW,IWR,IWW,JBW,KFI,LAU,LEV,LIO,LOS,LOV,LTA,LTL,LTN,MA R,MAZ,MCM-22(S),MCM-36,MCM-56,MEI,MEL,MEP,MER,MIT-1,MMFI,MFS,MON,MOR,MSE,MSO,M TF,MTN,MTT,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 Titanium zeolites with framework structures of SFO, SGT, SOD, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WEI, WEN, YUG, ZON, SVR, SVY, or a mixture of two or more of these framework structure types. Framework structure types such as MCM-22(S), MCM-56, IEZ-MWW, ITQ (delaminated MWW), MIT-1, and MCM-36 are titanium zeolites with framework structures associated with MWW framework structures, obtained or obtainable from them or from corresponding two-dimensional precursors through, for example, layer expansion and / or post-modification.Preferably, the zeolite material comprising a Si, O, and Ti framework structure in the epoxidation catalyst is a titanium zeolite having an MFI framework, MEL framework, MWW framework, MCM-22(S) framework, MCM-56 framework, IEZ-MWW framework, MCM-36 framework, ITQ framework, BEA framework, MOR framework, or a mixture of two or more of these framework types. More preferably, it has an MFI framework or MWW framework, and even more preferably, the zeolite material with a Si, O, and Ti framework structure has an MFI framework. More preferably, the zeolite material with a Si, O, and Ti framework structure is titanium silicate zeolite-1 (TS-1).

[0057] Epoxidation catalysts comprising zeolite materials with a Si, O, and Ti framework structure can be used in various conceivable forms, including powders, micropowders, preferably spray-dried powders, as powder-containing molded bodies, or as micropowder-containing, preferably spray-dried powder-containing molded bodies. Preferably, the epoxidation catalyst comprising zeolite materials with a Si, O, and Ti framework structure is used as a powder or micropowder-containing, preferably spray-dried powder-containing molded body, more preferably as a micropowder-containing, preferably spray-dried powder-containing molded body. More preferably, the epoxidation catalyst comprising zeolite materials with a Si, O, and Ti framework structure exists as a molded body in the epoxidation zone, preferably as a fluidized bed catalyst or a fixed bed catalyst, more preferably as a fixed bed catalyst.

[0058] According to a preferred embodiment, the epoxidation catalyst further includes a binder. Preferably, the epoxidation catalyst is in the form of a molded article, preferably an extrusion or granules, wherein the molded article preferably comprises a zeolite material and a binder. Preferably, 95 to 100 wt%, more preferably 98 to 100 wt%, more preferably 99 to 100 wt%, more preferably 99.5 to 100 wt%, more preferably 99.9 to 100 wt%, of the molded article is composed of the zeolite material and the binder. Preferably, 95 to 100 wt%, more preferably 98 to 100 wt%, more preferably 99 to 100 wt%, more preferably 99.5 to 100 wt%, more preferably 99.9 to 100 wt%, of the binder contained in the molded article is composed of Si and O.

[0059] Preferably, the epoxidation catalyst (preferably a molded body) includes a binder, calculated as SiO2, in an amount between 2 and 90 wt%, more preferably between 5 and 70 wt%, more preferably between 10 and 50 wt%, more preferably between 15 and 30 wt%, more preferably between 20 and 25 wt%, based on the total weight of the epoxidation catalyst, preferably based on the total weight of the molded body, and / or wherein the epoxidation catalyst (preferably a molded body) includes zeolite material in an amount between 10 and 98 wt%, preferably between 30 and 95 wt%, more preferably between 50 and 90 wt%, more preferably between 70 and 85 wt%, more preferably between 75 and 80 wt%, based on the total weight of the epoxidation catalyst, preferably based on the total weight of the molded body.

[0060] Other methods and steps

[0061] Following steps (i), (ii), and (iii), the method for preparing propylene oxide may include...

[0062] (iv) Separate propylene oxide from the discharge stream obtained in (iii), optionally after separating propylene, to obtain a stream S1 containing propylene oxide and a stream S2 containing water and organic solvent.

[0063] Preferably, (iv) includes

[0064] (iv-1) Separate propylene from the discharge stream obtained in (iii), and preferably at least a portion of the separated propylene, optionally after processing, is recovered to the epoxidation zone according to (ii) to obtain a feed stream S1a containing propylene oxide, water and organic solvent and leaning towards propylene compared to the discharge stream; (iv-2) Separate propylene oxide from the feed stream S1a obtained according to (iv-1) to obtain a feed stream S1b containing propylene oxide and leaning towards water and organic solvent compared to the discharge stream and feed stream S1a, respectively, and a feed stream S2 containing water and organic solvent and leaning towards propylene oxide compared to the discharge stream and S1a, respectively.

[0065] Following steps (i), (ii), (iii), and (iv), the method for preparing propylene oxide may include

[0066] (v) The organic solvent is separated from the stream S2 obtained according to (iv) or (iv-2) by distillation to obtain a stream S3 rich in organic solvent compared with stream S2, and preferably at least a portion of S3 is optionally recovered to the epoxidation zone according to (ii) after processing.

[0067] It goes without saying that the following of (i), (ii), and (iii) means that step (iv) is performed after step (iii), preferably directly after step (iii). "Directly after" means that no intermediate steps are performed between (iii) and (iv). It is understood that this also means that the complete order of the steps is preferably in the order of (i), (ii), (iii), and (iv), wherein preferably no intermediate steps are performed between (i) and (ii), between (ii) and (iii), and between (iii) and (iv), and this also applies to step (v).

[0068] The second aspect – reaction mixture

[0069] In a second aspect, the present invention relates to a reaction mixture for preparing propylene oxide, wherein the reaction mixture comprises propylene, water, an organic solvent and hydrogen peroxide, wherein the reaction mixture contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. The statement “the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture” means that the reaction mixture contains only one or more aliphatic oxygen-containing compounds having 8 to 10 carbon atoms in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture, i.e., the total amount of all aliphatic oxygen-containing compounds having 8 to 10 carbon atoms contained in the reaction mixture is up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture. This also applies to the definitions of specific quantity ranges given below. In this second aspect, the content of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in the reaction mixture is preferably 0 to 500 mg / kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 440 mg / kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 300 mg / kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 200 mg / kg of hydrogen peroxide contained in the reaction mixture, and more preferably 0 to 100 mg / kg of hydrogen peroxide contained in the reaction mixture. The further details disclosed above in the method for preparing propylene oxide according to the first aspect of the invention also apply to the reaction mixture for preparing propylene oxide according to the second aspect. The reaction mixture is preferably obtained or acquired by a method comprising (i) as defined in the first aspect above, preferably composed of (i). Therefore, the invention also relates to a method for preparing a reaction mixture according to the second aspect, wherein the reaction mixture comprises (i) as defined in the first aspect above, preferably composed of (i).

[0070] The third aspect – catalytic epoxidation system

[0071] In a third aspect, the present invention relates to a system comprising an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O, and Ti, and the system further comprising a reaction mixture comprising propylene, water, and an organic solvent according to the second aspect above. The catalytic epoxidation system is preferably obtained or acquired by a method comprising providing a reaction mixture according to the second aspect and contacting the reaction mixture with a zeolite material having a framework structure containing Si, O, and Ti. The reaction mixture comprises, and preferably consists of, (i) as defined in the first aspect above. Therefore, the present invention also relates to a method for preparing a catalytic epoxidation system comprising providing a reaction mixture according to the second aspect and contacting the reaction mixture with a zeolite material having a framework structure containing Si, O, and Ti.

[0072] Fourth aspect – Application

[0073] In a fourth aspect, the present invention relates to the use of an aqueous hydrogen peroxide solution as an epoxidizing agent in the presence of an organic solvent and an epoxidation catalyst to prepare propylene oxide, wherein the epoxidation catalyst comprises a zeolite material having a framework structure containing Si, O and Ti, wherein the aqueous hydrogen peroxide solution comprises at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, the content of which is up to 500 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution.

[0074] The invention is further illustrated by the following set of embodiments and combinations of embodiments derived from the shown dependencies and references. In particular, it should be noted that whenever a scope of embodiments is referred to, for example in the context of terms such as “any one of embodiments 1 to 4…”, each embodiment within that scope is intended to be clearly disclosed to a person skilled in the art, that is, the wording of the term should be understood by a person skilled in the art to be synonymous with “any one of embodiments 1, 2, 3, and 4…”. Furthermore, it should be clearly pointed out that the following set of embodiments is not a claim defining the scope of protection, but rather represents an appropriate component of the description relating to the general and preferred aspects of the invention.

[0075] 1. A method for preparing propylene oxide, comprising:

[0076] (i) Provide a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide;

[0077] (ii) In the epoxidation zone, the reaction mixture provided in (i) is contacted with an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the reaction mixture is subjected to epoxidation reaction conditions in the epoxidation zone to obtain a mixture containing propylene oxide, water and an organic solvent.

[0078] (iii) Remove the effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, water and organic solvent;

[0079] The reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0080] 2. The method of embodiment 1, wherein the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of 0 to 500 mg per kg of hydrogen peroxide contained in the reaction mixture, preferably 0 to 400 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 300 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 200 mg per kg of hydrogen peroxide contained in the reaction mixture, and more preferably 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0081] 3. The method of embodiment 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is selected from secondary monohydric alcohols C10 where n is an integer from 8 to 10. n H 2n+2 O, where m is an integer from 8 to 10, a monoketone C m H 2m O, where p is an integer from 8 to 10, of the diol C p H 2p+2 O2, and mixtures of two or more of these compounds; preferably selected from secondary monohydric alcohols C9H 20 O, monoketone C9H 18 O, Diol C9H 20 O2 and mixtures of two or more of these compounds; more preferably selected from secondary monohydric alcohols C9H 20 O, monoketone C9H 18 O and secondary monohydric alcohol C9H 20 O and a monoketone C9H 18 A mixture of O; more preferably selected from diisobutylmethanol and diisobutyl ketone and mixtures of diisobutylmethanol and diisobutyl ketone; wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms more preferably includes at least diisobutylmethanol.

[0082] 4. The method of any one of embodiments 1 to 3, wherein the reaction mixture provided in (i) comprises

[0083] (i.1) Provide an aqueous solution of hydrogen peroxide;

[0084] (i.2) The aqueous hydrogen peroxide solution provided in (i.1) is mixed with propylene and an organic solvent to obtain a reaction mixture;

[0085] The aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0086] 5. The method of embodiment 4, wherein the hydrogen peroxide aqueous solution provided in (i.1) and subjected to (i.2) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms in an amount of 0 to 500 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, preferably 0 to 400 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, more preferably 0 to 300 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, more preferably 0 to 200 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, and more preferably 0 to 100 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution.

[0087] 6. The method of embodiment 4 or 5, wherein the total organic carbon (TOC) content of the hydrogen peroxide aqueous solution provided in (i.1) and subjected to (i.2) is 100 to 800 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, preferably 120 to 750 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, more preferably 150 to 700 mg per kg of hydrogen peroxide contained in the hydrogen peroxide aqueous solution, as determined with reference to Example 5.

[0088] 7. The method of any one of embodiments 4 to 6, wherein the pH value of the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is in the range of 0 to 3.0, preferably in the range of 0.1 to 2.5, more preferably in the range of 0.5 to 2.3, as determined with reference to Example 4.

[0089] 8. The method of any one of embodiments 4 to 7, wherein the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) contains 20 to 80% by weight, preferably 30 to 70% by weight, more preferably 40 to 60% by weight relative to the total weight of the aqueous hydrogen peroxide solution.

[0090] 9. The method of any one of embodiments 4 to 8, wherein the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is obtained or is available by the anthraquinone process.

[0091] 10. The method of any one of embodiments 1 to 9, wherein the contact between the reaction mixture provided in (i) and the epoxidation catalyst according to (ii) in the epoxidation zone is carried out under conditions where the absolute pressure of the epoxidation zone is 0.5 to 5.0 MPa, preferably 1.5 to 3.0 MPa, more preferably 1.8 to 2.8 MPa.

[0092] 11. The method of any one of embodiments 1 to 10, wherein the reaction mixture provided in (i) is contacted with the epoxidation catalyst according to (ii) in the epoxidation zone at a temperature in the epoxidation zone in the range of 33 to 73°C, preferably in the range of 38 to 63°C, and more preferably in the range of 53 to 63°C.

[0093] 12. The method of any one of embodiments 1 to 11, wherein a cooling medium is used to adjust the temperature of the epoxidation zone, wherein the temperature of the cooling medium is preferably in the range of 25 to 65°C, more preferably in the range of 30 to 55°C, and even more preferably in the range of 345 to 55°C.

[0094] 13. The method of any one of embodiments 1 to 12, wherein the weight ratio (w / w) of propylene to hydrogen peroxide in the reaction mixture provided in (i) is in the range of 1:1 to 6:1, preferably in the range of 1:1 to 2:1 or in the range of 3:1 to 5:1.

[0095] 14. The method of any one of embodiments 1 to 13, wherein the weight ratio (w / w) of organic solvent to hydrogen peroxide in the reaction mixture provided in (i) is in the range of 15:1 to 5:1, preferably in the range of 12:1 to 6:1, and more preferably in the range of 11:1 to 8:1.

[0096] 15. The method of any one of embodiments 1 to 14, wherein the weight ratio (w / w) of organic solvent to propylene in the reaction mixture provided in (i) is in the range of 10:1 to 1:0.1, preferably in the range of 9:1 to 1:1, more preferably in the range of 9:1 to 7:1 or in the range of 1.5:1 to 1:1.

[0097] 16. The method of any one of embodiments 1 to 15, wherein the epoxidation reaction conditions according to (ii) include trickle bed conditions.

[0098] 17. The method of any one of embodiments 1 to 16, wherein the epoxidation reaction conditions according to (ii) include fixed-bed conditions.

[0099] 18. The method of any one of embodiments 1 to 17, wherein 95 to 100% by weight, more preferably 98 to 100% by weight, more preferably 99 to 100% by weight, more preferably 99.5 to 100% by weight, more preferably 99.9 to 100% by weight, is composed of Si, O, Ti and optionally H.

[0100] 19. The method of any one of embodiments 1 to 18, wherein the zeolite material contains Ti in an amount of 0.2 to 5 wt%, preferably 0.5 to 4 wt%, more preferably 1.0 to 3 wt%, more preferably 1.2 to 2.5 wt%, more preferably 1.4 to 2.2 wt%, calculated in elemental Ti and based on the total weight of the zeolite material.

[0101] 20. The method of any one of embodiments 1 to 19, wherein the zeolite material is titanium silicate zeolite-1 (TS-1).

[0102] 21. The method of any one of embodiments 1 to 20, wherein the epoxidation catalyst further comprises a binder.

[0103] 22. The method of embodiment 21, wherein the epoxidation catalyst is in the form of a molded article, preferably in the form of an extrusion or granules.

[0104] 23. The method of embodiment 21 or 22, wherein 95 to 100% by weight, preferably 98 to 100% by weight, more preferably 99 to 100% by weight, more preferably 99.5 to 100% by weight, and more preferably 99.9 to 100% by weight of the molded article is composed of the zeolite material and the binder.

[0105] 24. The method of any one of embodiments 21 to 23, wherein the adhesive contained in the molded body comprises 95 to 100% by weight, preferably 98 to 100% by weight, more preferably 99 to 100% by weight, more preferably 99.5 to 100% by weight, and more preferably 99.9 to 100% by weight of Si and O.

[0106] 25. The method of embodiment 24, wherein the epoxidation catalyst (preferably the molded body) comprises the binder, calculated as SiO2, in an amount ranging from 2 to 90 wt%, more preferably from 5 to 70 wt%, more preferably from 10 to 50 wt%, more preferably from 15 to 30 wt%, more preferably from 20 to 25 wt%, based on the total weight of the epoxidation catalyst, preferably based on the total weight of the molded body, and / or wherein the epoxidation catalyst (preferably the molded body) comprises the zeolite material in an amount ranging from 10 to 98 wt%, preferably from 30 to 95 wt%, more preferably from 50 to 90 wt%, more preferably from 70 to 85 wt%, more preferably from 75 to 80 wt%, based on the total weight of the epoxidation catalyst, preferably based on the total weight of the molded body.

[0107] 26. The method of any one of embodiments 1 to 25, wherein at least (ii) is carried out continuously, wherein preferably at least (ii) and (iii), more preferably (i), (ii) and (iii) are carried out continuously.

[0108] 27. The method of any one of implementation schemes 1 to 26, further including

[0109] (iv) Separate propylene oxide from the discharge stream obtained in (iii), optionally after separating propylene, to obtain a stream S1 containing propylene oxide and a stream S2 containing water and organic solvent.

[0110] 28. The method of implementing scheme 27, wherein (iv) includes

[0111] (iv-1) Separate propylene from the discharge stream obtained in (iii), and preferably at least a portion of the separated propylene, optionally after processing, is recovered to the epoxidation zone according to (ii) to obtain a feed stream S1a containing propylene oxide, water and organic solvent and leaning towards propylene compared to the discharge stream; (iv-2) Separate propylene oxide from the feed stream S1a obtained according to (iv-1) to obtain a feed stream S1b containing propylene oxide and leaning towards water and organic solvent compared to the discharge stream and feed stream S1a, respectively, and a feed stream S2 containing water and organic solvent and leaning towards propylene oxide compared to the discharge stream and S1a, respectively.

[0112] 29. The method of implementing Implementation 27 or 28, including

[0113] (v) The organic solvent is separated from the stream S2 obtained according to (iv) or (iv-2) by distillation to obtain a stream S3 rich in organic solvent compared with stream S2, and preferably at least a portion of S3 is optionally recovered to the epoxidation zone according to (ii) after processing.

[0114] 30. The method of any one of embodiments 1 to 29, wherein the organic solvent is an organic epoxidizing solvent, preferably selected from alcohols, acetonitrile, tert-butanol, propionitrile, and mixtures of two or more thereof; more preferably selected from alcohols, acetonitrile, and mixtures of alcohols and acetonitrile, and even more preferably the organic solvent comprises at least one alcohol.

[0115] 31. A reaction mixture for preparing propylene oxide, comprising propylene, water, an organic solvent and hydrogen peroxide, wherein the reaction mixture contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0116] 32. The reaction mixture of embodiment 31, wherein the content of at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is 0 to 500 mg per kg of hydrogen peroxide contained in the reaction mixture, preferably 0 to 440 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 300 mg per kg of hydrogen peroxide contained in the reaction mixture, more preferably 0 to 200 mg per kg of hydrogen peroxide contained in the reaction mixture, and more preferably 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture.

[0117] 33. The reaction mixture of embodiment 31 or 32, which can be obtained or acquired by a method comprising (i) as defined in any one of embodiments 1 to 9, preferably a method consisting of (i).

[0118] 34. A method for preparing a reaction mixture according to any one of embodiments 31 to 33, wherein the reaction mixture comprises (i) as defined in any one of embodiments 1 to 9, preferably consisting of (i).

[0119] 35. A catalytic epoxidation system for preparing propylene oxide, the catalytic epoxidation system comprising an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the catalytic epoxidation system further comprising a reaction mixture containing propylene, water and an organic solvent according to any one of embodiments 31 to 34.

[0120] 36. The catalytic epoxidation system of embodiment 35 is obtainable or acquired by a method comprising providing a reaction mixture according to any one of embodiments 31 to 34 and contacting said reaction mixture with a zeolite material having a framework structure containing Si, O and Ti.

[0121] 37. A method for preparing a catalytic epoxidation system according to embodiment 35, comprising providing a reaction mixture according to any one of embodiments 31 to 34, and contacting the reaction mixture with a zeolite material having a framework structure containing Si, O and Ti.

[0122] 38. Use of an aqueous hydrogen peroxide solution as an epoxidizing agent in the preparation of propylene oxide in the presence of an organic solvent and an epoxidizing catalyst, wherein the epoxidizing catalyst comprises a zeolite material having a framework structure containing Si, O and Ti, wherein the aqueous hydrogen peroxide solution comprises at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of up to 500 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution.

[0123] It should be clearly pointed out that the above set of embodiments is not a claim that defines the scope of protection, but rather represents an appropriate part of the description of the general and preferred aspects of the invention.

[0124] The present invention is further illustrated by the following reference examples, comparative examples and embodiments. Example

[0125] Refer to Example 1—Experimental Apparatus

[0126] In a continuous epoxidation reactor, 15g of the corresponding TS-1 catalyst in the form of a strand as described in the reference examples below is loaded into a vertically arranged tubular reactor (length: 1.4m, outer diameter: 10mm, inner diameter: 4mm; material: 1.4571 austenitic stainless steel) equipped with a cooling jacket for thermal stabilization. The area within the reactor covered by the inscribed strand is called the catalyst bed. The remaining reactor volume is filled with inert material (2mm diameter talc balls) to a height of approximately 5cm from the bottom of the reactor and the remaining portion at the top. The temperature of the epoxidation zone (i.e., the catalyst bed) is measured using ten thermocouples (ten heating elements, each made of 1.4571 austenitic stainless steel). Six of the ten heating elements are located in the front half of the catalyst bed.

[0127] A feed stream is provided for all starting materials: methanol, propylene, and hydrogen peroxide (as an aqueous solution of hydrogen peroxide with a hydrogen peroxide content of 40% or 60% by weight). Initially, all feed streams contain less than 0.1% by weight of an aliphatic oxygen-containing compound having 8 to 10 carbon atoms. An aliphatic oxygen-containing compound having 9 carbon atoms is added to the hydrogen peroxide feed stream, as detailed in the examples below.

[0128] The feed streams are combined and fed into the reactor. The combination of all feed streams is called the "reaction mixture".

[0129] By circulating a cooling medium with a temperature ranging from 45 to 55°C through the cooling jacket, the temperature of the epoxidation zone is regulated to a range of 53 to 63°C, so that the hydrogen peroxide conversion rate, measured based on the effluent leaving the reactor, remains substantially constant at a predetermined value. The pressure inside the reactor is maintained constant at 21 bar (absolute pressure).

[0130] The reactor effluent downstream of the pressure control valve was collected, weighed, and analyzed. Hydrogen peroxide content was determined colorimetrically using the titanium oxysulfate method. All other components were quantified by gas chromatography. The selectivity of propylene oxide (S(H2O2) vs. PO) relative to the hydrogen peroxide (H2O2) determination was calculated as 100 times the ratio of the number of moles of propylene oxide in the effluent (mol(PO generated)) to the number of moles of hydrogen peroxide in the feed (mol(H2O2 in the feed)), as shown below:

[0131]

[0132] The aliphatic oxygen-containing compound with nine carbon atoms added to the hydrogen peroxide stream is mainly composed of diisobutylmethanol (DIBC), with the following detailed composition: 85.8 wt% 2,6-dimethyl-4-heptanol, 12.8 wt% 4,6-dimethyl-2-heptanol, and 0.2 wt% 2,6-dimethyl-4-heptanone, with the remaining residue totaling 100 wt% being impurities.

[0133] The composition of aliphatic oxygen-containing compounds with 9 carbon atoms was determined by GC / MS according to Analytical Sciences Standard Operating Procedure MS-SOP-004.00. A tenth (0.1) μL (nominal volume) aliquots of pure sample were analyzed on a Finnigan SSQ 7000 GC / MS system in electron impact (EI) mode. Tenth (0.1) μL (nominal volume) aliquots of pure sample were also analyzed on the same instrument in positive ion chemical ionization (PCI) mode. Ammonia (NH3) was used as the reactant gas in the PCI analysis, present at an ion source pressure of approximately 1300 mTorr. Representative analytical conditions are listed below:

[0134] Column: J&W Scientific 60m x 0.32mm x 1.0μm DB-1

[0135] Temperature: Column: 100℃ to 260℃ at 10℃ / minute, hold for 5 minutes

[0136] Inlet temperature: 260℃, Ion source temperature: 150℃

[0137] Transmission line: 260℃, Manifold: 70℃; Detector: EMULT: 900V (EI), 950V (PCI)

[0138] Preamplifier: 10-7A / V

[0139] Conv.Dyn.: (±)15kV, Mode: +Q1MS, CENT

[0140] ELEN:70V(EI),200V(PCI),ECURR:1.3mA(EI),1.0mA(PCI)

[0141] Scan: 35-650 amu (EI), Scan: 65-650 amu (PCI), Rate: 0.5 s / scan; Injection volume (nominal): 0.1 μL (EI), 0.1 μL (PCI)

[0142] Flow split ratio: 300 / 1

[0143] FT

[0144] Given that the two isomers of diisobutylmethanol constitute more than 98.5% by weight of an aliphatic oxygenated compound with nine carbon atoms, the latter will be referred to as “DIBC” below.

[0145] Reference Example 2—TS-1 Catalyst 1

[0146] Titanium silicate zeolite-1 (TS-1 catalyst 1) powder was prepared according to the following formulation: 300 kg of tetraethyl orthosilicate (TEOS) was added to a stirred reactor at room temperature and stirring was started (100 rpm). In a second container, 60 kg of TEOS and 13.5 kg of TEOT (tetraethyl orthosilicate) were first mixed, and then added to the TEOS in the first container. Subsequently, another 360 kg of TEOS was added to the mixture in the first container. The contents of the first container were then stirred for 10 minutes, and 950 g of TPAOH (tetrapropylammonium hydroxide) was added. Stirring continued for 60 minutes. The ethanol released by hydrolysis was separated by distillation at a bottom temperature of 95°C. Then, 300 kg of water was added to the contents of the first container, and an amount of water equivalent to the amount of distillate was further added. The resulting mixture was stirred for 1 hour. Crystallization was carried out at 175°C and autogenous pressure for 12 hours. The obtained titanium silicate zeolite-1 crystals were separated, dried, and calcined in air at 500°C for 6 hours. The Ti content of the obtained zeolite material particles is 1.9% by weight, calculated as elemental Ti.

[0147] Zeolite material particles and carboxymethyl cellulose (4.0 g; Walocel™, Mw = 15,000 g) were mixed in a kneader for 5 minutes. Then, an aqueous polystyrene dispersion (100.7 g; 33.7 g polystyrene) was continuously added. After 10 minutes, polyethylene oxide (1.33 g) was added. After 10 minutes, an aqueous colloidal silica binder precursor (70 g; 40 wt% SiO2) was added. AS-40). After another 10 minutes, add 20 ml of water. The total kneading time is 35 minutes. Under a pressure of 100 bar, extrude the kneaded formable material with a plasticity of 3321 N through a matrix with a circular orifice of 1.9 mm in diameter. The resulting stock is air-dried in an oven at 120°C for 4 hours and then calcined in air at 490°C for 5 hours. The crushing strength of the stock determined above is 1.6 N.

[0148] The 36g of these strands were divided into four portions, each containing 9g and 180g of deionized water. The resulting mixture was heated to 145°C in an autoclave for 8 hours. Afterward, the water-treated strands were separated and sieved through a 0.8mm sieve. The resulting strands were then washed with deionized water and subjected to a nitrogen stream at ambient temperature. Each washed strand was subsequently air-dried at 120°C for 4 hours and then calcined in air at 450°C for 2 hours. The resulting material had a TOC of less than 0.1g / 100g, a Si content of 44g / 100g, and a Ti content of 1.5g / 100g.

[0149] Refer to Example 3—TS-1 catalyst 2

[0150] TS-1 catalyst 2 was synthesized according to Example 5 of EP 1 138 387 A1. A 2 mm extrudate was prepared using silica sol as a binder.

[0151] Reference Example 4 - pH Measurement

[0152] According to AM7160, pH is measured using a pH-sensitive glass electrode. The pH should be understood as being measured using a pH-sensitive glass electrode in an inert atmosphere, which avoids, for example, contact between the liquid aqueous system and atmospheric carbon dioxide, which, if absorbed by the liquid aqueous system, would lower the pH value.

[0153] Reference Example 5 – Determination of Total Organic Carbon (TOC)

[0154] Total organic carbon (TOC) content was determined according to DIN EN 1484.

[0155] Determination of the adsorption / desorption isotherm of N2 in Example 6

[0156] The adsorption / desorption isotherm of nitrogen was determined at 77 K according to the method disclosed in DIN 66131. ​​The isotherm was determined at liquid nitrogen temperature using a Micrometrics ASAP 2020M and a Tristar system.

[0157] Example 1 – Propylene epoxidation reaction using different concentrations of diisobutylmethanol (DIBC)

[0158] The epoxidation of propylene was carried out according to Reference Example 1. A 40% by weight aqueous solution of H2O2 was used as the hydrogen peroxide feed stream, which contained less than 0.1% by weight of an aliphatic oxygen-containing compound having 8 to 10 carbon atoms based on H2O2, and had a TOC value of 700 mg per kg of hydrogen peroxide as determined according to Reference Example 5, and a pH value of 2 as determined according to Reference Example 4.

[0159] DIBC was added to the H2O2 aqueous solution, and the concentration of DIBC relative to the H2O2 aqueous solution feed stream and the hydrogen peroxide in the reaction mixture at the start of the epoxidation reaction is shown in Table 1.

[0160] In the reactor, the starting feedstocks were fed at the following flow rates: methanol (77.8 g / h); hydrogen peroxide (7.6 g / h; used as a 40% by weight aqueous solution of hydrogen peroxide, i.e., the flow rate of the aqueous solution of hydrogen peroxide was 19.4 g / h); propylene (10.8 g / h; polymer grade). The combined feed flow rate was 108 g / h.

[0161] The TS-1 catalyst 1 of Reference Example 2 was used as the epoxidation catalyst.

[0162] The average temperature of the epoxidation zone was regulated to 60–70 °C by a cooling medium flowing through the cooling jacket, so that the hydrogen peroxide conversion, measured based on the effluent leaving the reactor, remained substantially constant at ≥90%. The pressure within the reactor was maintained at a constant 21 bar (absolute pressure), and the reaction mixture—except for the fixed-bed catalyst—consisted of a single liquid phase. The epoxidation reaction was carried out for 550 hours.

[0163] The selectivity to propylene oxide (PO) (S(H2O2) to PO, calculated according to Reference Example 1), the temperature of the cooling medium, and the average temperature of the epoxidation zone, derived from data measured at the end of epoxidation (at 550 hours), are shown in Table 1.

[0164] Table 1

[0165] Propylene epoxidation in the presence of different concentrations of DIBC yields propylene oxide.

[0166]

[0167] *Comparison Example

[0168] Experiments i to v show that catalyst performance improves with decreasing DIBC concentration. Based on H₂O₂, the most significant improvement in selectivity occurs when the DIBC concentration decreases from 0.1 wt% to 0.05 wt%. The reaction yields optimal results when the DIBC concentration is ≤0.1 wt%. When the DIBC concentration exceeds 500 mg DIBC per kg of hydrogen peroxide, significantly higher temperatures are required in the epoxidation zone to maintain a hydrogen peroxide conversion of ≥90% (and therefore, a much higher temperature for the cooling medium). However, at these high DIBC concentrations, the selectivity is far below 85%.

[0169] Example 2 – Propylene epoxidation reaction using TS-1 catalyst 2

[0170] The experiment was conducted according to Experiment No. v of Example 1, but using TS-1 catalyst 2 from Reference Example 3, with a 40% by weight aqueous solution of H2O2. The concentration of DIBC in the hydrogen peroxide feed stream and in the reaction mixture at the start of the epoxidation reaction, the selectivity of the resulting effluent to propylene oxide (PO) (S(H2O2) to PO, calculated according to Reference Example 1), the temperature of the cooling medium, and the average temperature of the epoxidation zone are listed in Table 2.

[0171] Table 2

[0172] Propylene epoxidation reaction using TS-1 catalyst 2

[0173]

[0174] *Comparison Example

[0175] The results of Experiment viii are comparable to those of Experiment No. v in Example 1: excessively high DIBC concentrations exceeding 500 mg / kg hydrogen peroxide—1000 mg / kg hydrogen peroxide in this case—have a negative impact on different types of TS-1 zeolite catalysts, regardless of their preparation method and characteristics.

[0176] Example 3—Propylene epoxidation reaction without temperature adjustment

[0177] According to Example 1, propylene epoxidation was carried out using 40% by weight of H2O2 aqueous solution and TS-1 catalyst 1 as epoxidation catalyst; an aliphatic oxygen-containing compound having 9 carbon atoms was added to the hydrogen peroxide feed stream at the concentrations shown in Table 4 as in Example 1.

[0178] By circulating a cooling medium through the cooling jacket, the temperature of the epoxidation zone is regulated to the range of 53 to 63°C at the start of the epoxidation reaction, so that the hydrogen peroxide conversion rate, measured based on the effluent leaving the reactor, remains substantially constant at ≥98%, i.e., the cooling medium temperature is set within the range of 45 to 55°C. After the epoxidation reaction begins, the temperature of the epoxidation zone is no longer further regulated by the cooling medium. The epoxidation reaction is carried out until the temperature of the epoxidation zone exceeds 63°C (and correspondingly, the temperature of the cooling medium exceeds 55°C), and then the reaction is stopped. The time from the start to the stop of the epoxidation reaction is measured.

[0179] The selectivity of propylene oxide (PO) in the resulting effluent (S(H2O2) to PO, calculated according to Reference Example 1) and the time until the reaction stops, determined based on data measured at the time the epoxidation reaction stops, are shown in Table 3.

[0180] Table 3

[0181] The epoxidation reaction of propylene is carried out in a cooling medium with a temperature range of 45 to 55°C.

[0182]

[0183] *Comparison Example

[0184] Experiments x and xi show that only when the concentration of DIBC is maintained at or below the threshold of 500 ppm can a high hydrogen peroxide conversion rate of ≥98% and high selectivity (optimal temperature window) be achieved over a meaningful period of time, i.e., more than 200 hours.

[0185] References

[0186] -Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, Volume A, 13 (1989), pp. 443-466

[0187] -EP 1 546 035 A1

[0188] -WO 99 / 40024 A1

[0189] -WO 2013 / 160163 A1

[0190] -EP 1 122 249 A1

[0191] -WO 2015 / 049327 A1

[0192] -Stallmach et al., Annual Reports on NMR Spectroscopy, 2007, Vol. 61, pp. 51-131.

Claims

1. A method for preparing propylene oxide, comprising: (i) Provide a reaction mixture comprising propylene, water, an organic solvent and hydrogen peroxide; (ii) In the epoxidation zone, the reaction mixture provided in (i) is contacted with an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, and the reaction mixture is subjected to epoxidation reaction conditions in the epoxidation zone to obtain a mixture containing propylene oxide, water and an organic solvent. (iii) Remove the effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, water and organic solvent; The reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture; The at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms includes at least diisobutylmethanol; Wherein (i) the provided reaction mixture includes (i.1) Provide an aqueous solution of hydrogen peroxide; (i.2) The aqueous hydrogen peroxide solution provided in (i.1) is mixed with propylene and an organic solvent to obtain a reaction mixture; in, The aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture; The total organic carbon (TOC) content of the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is 100 to 800 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, wherein the TOC is determined according to DIN EN 1484; The material with a framework structure containing Si, O and Ti is titanium silicate zeolite-1 (TS-1); The organic solvent contains at least one alcohol, and the at least one alcohol contains methanol.

2. The method according to claim 1, wherein the organic solvent is methanol.

3. The method according to claim 1 or 2, wherein the total organic carbon content (TOC) of the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is 120 to 750 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, wherein the TOC is determined according to DIN EN 1484.

4. The method according to claim 1 or 2, wherein the total organic carbon content (TOC) of the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is 150 to 700 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, wherein the TOC is determined according to DIN EN 1484.

5. The method according to claim 1 or 2, wherein the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is obtained or is available by the anthraquinone process.

6. The method according to claim 1 or 2, wherein the epoxidation reaction conditions according to (ii) include trickle bed conditions or wherein the epoxidation reaction conditions according to (ii) include fixed bed conditions.

7. The method according to claim 1 or 2, wherein at least (ii) is carried out continuously.

8. The method according to claim 1 or 2, wherein at least (ii) and (iii) are performed sequentially.

9. The method according to claim 1 or 2, wherein (i), (ii) and (iii) are performed sequentially.

10. The method according to claim 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms is diisobutylmethanol.

11. The method according to claim 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms comprises 95 to 99.5% by weight of diisobutylmethanol, based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms.

12. The method according to claim 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms comprises 96 to 99% by weight of diisobutylmethanol, based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms.

13. The method according to claim 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms comprises 95 to 99.5% by weight of diisobutylmethanol and 1.0 to 0.01% by weight of diisobutyl ketone (C9H12H2O). 18 O), based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms.

14. The method according to claim 1 or 2, wherein the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms comprises 96 to 99% by weight of diisobutylmethanol and 0.9 to 0.05% by weight of diisobutyl ketone, each based on the total weight of the at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms.

15. The method according to claim 1 or 2, wherein the balance in 100% by weight comprises compounds such as methylheptane-3-ol, isomers of methylheptane-3-ol, and smaller fragments such as C4-C6 alcohols and ketones.

16. The method according to claim 1 or 2, wherein diisobutylmethanol comprises two isomers: 2,6-dimethyl-4-heptanol and 4,6-dimethyl-2-heptanol.

17. The method according to claim 13 or 14, wherein the diisobutyl ketone comprises two isomers: 2,6-dimethyl-4-heptanone and 4,6-dimethyl-2-heptanone.

18. A reaction mixture for preparing propylene oxide, comprising propylene, water, an organic solvent and hydrogen peroxide, wherein the reaction mixture provided in (i) and subjected to (ii) contains at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms, in an amount of 0 to 100 mg per kg of hydrogen peroxide contained in the reaction mixture; The at least one aliphatic oxygen-containing compound having 8 to 10 carbon atoms includes at least diisobutylmethanol; The organic solvent comprises at least one alcohol, the at least one alcohol comprising methanol, wherein the total organic carbon content (TOC) of the aqueous hydrogen peroxide solution provided in (i.1) and subjected to (i.2) is 100 to 800 mg per kg of hydrogen peroxide contained in the aqueous hydrogen peroxide solution, wherein the TOC is determined according to DIN EN 1484; The material with a framework structure containing Si, O and Ti is titanium silicate zeolite-1 (TS-1); The reaction mixture is obtained or acquired by a method comprising (i) as defined in any one of claims 1 to 17.

19. The reaction mixture for preparing propylene oxide according to claim 18, wherein the reaction mixture is obtained or acquired by the method comprising (i).

20. A catalytic epoxidation system for preparing propylene oxide, the catalytic epoxidation system comprising an epoxidation catalyst containing a zeolite material having a framework structure containing Si, O and Ti, wherein the material having a framework structure containing Si, O and Ti is titanium silicate zeolite-1 (TS-1), and the catalytic epoxidation system further comprising a reaction mixture containing propylene, water and an organic solvent according to claim 18 or 19.

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