Method for preparing cresols from ditolyl ether

Abstract

The present invention relates to a novel process for preparing cresols from ditolyl ethers.

Description

[Technical Field]

[0001] The present invention relates to a novel method for producing cresols from ditolyl ethers. [Background technology]

[0002] For example, it is known in (US Pat. No. 5,629,499) that the C-O bond of aromatic ethers can be cleaved by hydrolysis or hydrogenolysis in the presence of radioactive thorium oxide, but this is not possible for industrial applications.

[0003] The use of nickel / nickel compounds on various substrates such as carbon or aluminum oxide / silicon oxide in the hydrogenolysis of the C-O bond of diaryl ethers in the presence of relatively large amounts of a sterically bulky strong base such as NaOtBu or potassium hexamethyldisilazide is also known, see (Non-Patent Document 1). Disadvantages include long reaction times, a high proportion of transition metal nickel, and, furthermore, the need to use a sterically bulky strong base which requires expensive and complicated separation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. A2604474 [Non-patent literature]

[0005] [Non-Patent Document 1] Gao et al.Applied Chem.Int.Ed.2016,55,1474-1478 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, one object of the present invention is to provide an improved process for producing cresol from ditolyl ether, which can easily produce cresol in high yield and high selectivity. [Means for solving the problem]

[0007] It has now surprisingly been found that this object can be achieved when ditolyl ether and water are reacted in the presence of a catalyst containing at least two oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and / or tungsten oxide.

[0008] Subject of the Invention The present invention provides a method for producing cresol from ditolyl ether and water in the presence of a catalyst containing at least 85% by weight of at least two of the oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, and / or tungsten oxide.

[0009] It is preferred if catalysts consisting of at least two of the oxides titanium oxide, zirconium oxide and tungsten oxide and / or catalysts from the group of zeolites containing at least 85% by weight of at least two oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and tungsten oxide are used.

[0010] In the context of the present invention, cresol includes o-cresol, m-cresol, and p-cresol as individual compounds and as mixtures, which can contain o-, m-, and p-cresol in any desired ratio.

[0011] In the context of the present invention, ditolyl ethers include 2,2'-, 2,3'-, 2,4'-, 3,3'-, 3,4'-, and / or 4,4'-ditolyl ethers as individual compounds and as mixtures of two or more of these individual said compounds.

[0012] The use of mixtures of 2,2'-, 2,3'-, 2,4'-, 3,3'-, 3,4'-, and 4,4'-ditolyl ethers, obtained, for example, in the alkaline hydrolysis of chlorotoluene, is preferred (see H. Fiege, Cresols and Xylenols, Ullmann's Encyclopedia of Industrial Chemistry, page 427, vol. 10, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2012).

[0013] In the context of the present invention, water preferably comprises demineralized water.

[0014] In the context of the present invention, catalyst should be understood to mean that a catalyst is used which contains at least 85% by weight, preferably 90 to 100% by weight, of at least two oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and tungsten oxide.

[0015] In one preferred embodiment, the catalyst consists of at least two of the oxides titanium oxide, zirconium oxide and tungsten oxide and / or of the group of zeolites containing at least 85% by weight of at least two of the oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and tungsten oxide.

[0016] In one preferred embodiment, the catalyst from the group of the zeolites contains silicon oxide, aluminum oxide, titanium oxide, and / or zirconium oxide.

[0017] If the catalyst preferably contains silicon oxide and aluminum oxide, the molar ratio of silicon to aluminum is preferably from 3:1 to 300:1, particularly preferably from 5:1 to 250:1, very particularly preferably from 30:1 to 90:1.

[0018] In a particularly preferred embodiment, the catalyst has a zeolite structure. In the context of the present invention, zeolite is preferably understood to mean a microporous material whose structure is characterized by a framework of tetrahedrons connected at their vertices. Each tetrahedron generally consists of four oxygen atoms surrounding one cation. The preferred cations of these tetrahedra are preferably selected from aluminum and silicon. The zeolite structure preferably consists of oxygen-aluminum tetrahedra and oxygen-silicon tetrahedra.

[0019] As is well known, the cell structure of all zeolites is characterized by a three-letter code by the Structure Committee of the International Zeolite Association (IZA).

[0020] Zeolites are particularly preferably of the framework type: LTA = Linde type A (e.g., Zeolite A); MFI = Mobil Five (e.g., ZSM-5, Zeolite Socony Mobil-5), MOR = mordenite; BEA = Beta zeolite, and / or FAU = Faujasite (e.g., Zeolite X, Y) It is a mixture of aluminum oxide and silicon oxide.

[0021] Very particularly preferred framework types are MFI and MOR.

[0022] Zeolites can be used as powders or as shaped bodies. When shaped into shaped bodies, the zeolites are mixed with a binder material, preferably 5 to 70% by weight, based on aluminum or silicon, and various inorganic and organic additives, such as nitric acid, citric acid, acetic acid, methylcellulose, glycerol, polyethylene glycol, sugar, and / or starch, and then processed. In this case, the processing includes the steps of shaping, for example, by pressing, and heating at a temperature in the range of 350°C to 900°C.

[0023] In the process according to the invention, preferably from the group of the MFI zeolites, commercially available ZSM-5 zeolites (Zeolite Socony Mobil-5) and MFI zeolites, for example from Clariant Produkte (Deutschland) GmbH, are used.

[0024] The host structures of ZSM-5 and MFI are preferably characterized by 10-membered rings that form a three-dimensional intersecting pore system, and, as is typical of "high silica" and pentasil zeolites, there are many 5-membered rings (in addition to a few 4-, 6-, 7-, and 8-membered rings).

[0025] A typical chemical composition of the zeolite group, in the case of Al oxides and Si oxides, is e.g.: M n+ x / n [(AlO2) - x (SiO2) y ]·zH2O As shown in the figure, M n+ is a cation, preferably H + , Na + and / or NH4 + where n represents the charge of the cation, preferably 1 or 2. Cation Mn + are generally not part of the aluminum-oxygen and silicon-oxygen tetrahedra that define the structure, but are located within the channels or voids of the zeolite for charge balancing purposes. In preferred embodiments, H, as can be characterized by the designations H-ZSM-5 and H-MFI, + is used as the cation. The type of cation can be reversibly changed by chemical derivatization, for example by an ion exchange reaction.

[0026] The molar ratio of oxygen-silicon tetrahedra to oxygen-aluminum tetrahedra (abbreviated as SI / Al) is called the modulus and is represented by the quotient y / x. In a preferred embodiment, y / x is 3 to 300, and particularly preferably 30 to 90. This quotient can be characterized by the notation H-MFI-y / x, i.e., for example, H-MFI-90.

[0027] Catalysts that can be used in the process according to the invention include commercially available mixed oxide catalysts, preferably in the form of spheres or extrudates. Examples of such catalysts include ZrO2 / WO3 and ZrO2 / SiO2 from Saint-Gobain Ceramic Materials GmbH, and Al2O3 / SiO2 mixtures from Shell Catalysts & Technologies Leuna GmbH. Usable Al2O3 / SiO2 mixtures also include commercially available zeolites, preferably in the form of spheres or extrudates. Examples of commercially available zeolites include extrudates of MFI zeolite, MOR zeolite, BEA zeolite, e.g., from Clariant Produkte (Deutschland) GmbH, and FAU zeolite, e.g., from Zeolyst International.

[0028] The process according to the invention is preferably carried out at temperatures between 250°C and 450°C, preferably between 270°C and 400°C, particularly preferably between 300°C and 370°C.

[0029] The process according to the invention is preferably carried out at a pressure of from 0.5 bar to 300 bar, particularly preferably from 0.9 bar to 50 bar, very particularly preferably from 1 bar to 10 bar.

[0030] The process according to the invention is preferably carried out in a reactor.

[0031] Usable reactors include all vessels in which gas can be added and in which the catalyst is in the form of a fixed bed, such as fixed-bed reactors, and those in which the catalyst is moved by a reactant feed or agitation device, such as entrained-flow reactors, fluidized-bed reactors, or batch reactors. The reactants can be added in gaseous or liquid form. In a preferred embodiment, the reactants are added as gases to a fixed-bed reactor having a fixed catalyst bed. The process according to the invention can be carried out continuously or discontinuously.

[0032] The total amount of catalyst based on ditolyl ether (DTE) can be selected as desired for a continuously operated reactor or a discontinuously operated reactor. In the case of a continuously operated reactor, the amount is preferably 0.01 to 1,000 g DTE / (g catalyst x h), particularly preferably 0.01 to 100 g DTE / (g catalyst x h). In the case of a discontinuously operated reactor, the amount is preferably 0.1 to 10,000 g DTE / g cat.

[0033] The molar ratio of ditolyl ether to water is preferably from 10:1 to 1:40, particularly preferably from 1:1 to 1:20, very particularly preferably from 1:5 to 1:15.

[0034] In addition to ditolyl ether and water, further gases, preferably inert gases such as nitrogen or argon, can be added. The amount of standard liters L required to achieve a proportion of 0 to 95% by volume, particularly preferably 0 to 40% by volume, based on the total volume, can be added. n It is preferred to add nitrogen or argon.

[0035] Nitrogen in the context of the present invention preferably has a purity of more than 99% by volume.

[0036] In this embodiment, the process for producing cresols from ditolyl ether and water in the presence of a catalyst can also be referred to as the hydrolytic cleavage of ditolyl ether.

[0037] In this preferred embodiment of the invention, it is preferred to carry out the process in a continuous manner as follows: The catalyst is first placed in a fixed-bed reactor and heated to 300-370°C. A mixture of ditolyl ether and water in a molar ratio of 1:5 to 1:15, preheated to at least 250°C, and mixed with up to 40% by volume of nitrogen, is added at a rate of 0.1-5 g of ditolyl ether per g of catalyst per hour. The reaction product is recovered, containing the cresols formed in high yield.

[0038] In a further preferred embodiment of the present invention, the production of cresols from ditolyl ethers is carried out by hydrogenolysis by reaction in the presence of water, hydrogen and a catalyst which further contains at least one metal from the group of platinum metals (Ru, Rh, Pd, Os, Ir, Pt).

[0039] One of the advantages of the hydrogenolysis production of cresols from ditolyl ether is the co-production of toluene.

[0040] In this preferred embodiment of the invention, reference is made to the above definitions and embodiments regarding cresol, ditolyl ether, and water.

[0041] In the context of the present invention, hydrogen preferably has a purity of more than 99% by volume.

[0042] A catalyst in the context of the present invention for hydrocracking should be understood to mean that a catalyst is used which contains at least 85% by weight, preferably 90 to 99.9% by weight, of at least two oxides selected from aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and tungsten oxide, and which further contains at least one element from the group of platinum metals.

[0043] In one preferred embodiment, the catalyst contains silicon oxide and aluminum oxide or zirconium oxide and tungsten oxide, and further contains at least one element from the group of platinum metals.

[0044] It is preferred if the molar ratio of silicon oxide to aluminium oxide is preferably 3:1 to 300:1, particularly preferably 5:1 to 250:1, very particularly preferably 30:1 to 90:1.

[0045] In one particularly preferred embodiment, the catalyst has a zeolite structure. Regarding the definition of zeolite in the context of the present invention, reference is made to the above.

[0046] Zeolites are particularly preferably of the framework type: LTA = Linde type A (e.g., Zeolite A); MFI = Mobil Five (e.g., ZSM-5, Zeolite Socony Mobil-5), MOR = mordenite; BEA = Beta zeolite, and / or FAU = Faujasite (e.g., Zeolite X, Y) It is a mixture of aluminum oxide and silicon oxide.

[0047] Very particularly preferred framework types are MFI and MOR.

[0048] In the case of an element from the group of platinum metals, a proportion of 0.1 to 10% by weight, based on the total amount of catalyst, is preferred, and in the case of an element from the group of platinum metals, a proportion of 0.5 to 5% by weight is particularly preferred.

[0049] It is further preferred if the metal from the group of platinum metals is platinum and / or rhodium.

[0050] Platinum metal-containing catalysts can be produced by commonly used processes for producing precious metal-containing catalysts. This can be done, for example, by contacting the catalyst support with a metal salt solution of the precious metal by impregnation or spraying. Impregnation can be performed as immersion-impregnation when the volume of the aqueous solution is greater than the liquid absorption capacity of the catalyst support to be coated, or as dry impregnation when the volume of the aqueous solution is equal to or less than the liquid absorption capacity of the catalyst support to be coated. The same applies to spraying the precious metal solution onto the catalyst support. It is also possible to perform an ion exchange process to add the precious metal to the catalyst by repeatedly adding a diluted metal salt solution of the precious metal onto the catalyst support. Following impregnation, spraying, or ion exchange, the precious metal-containing catalyst is dried, preferably at an elevated temperature, preferably 60°C to 200°C, in an air stream for 0.5 to 10 hours. Optionally, calcination can be performed at an elevated temperature, preferably 200°C to 1000°C, for 10 minutes to 24 hours.

[0051] The process according to the invention is particularly preferably carried out at temperatures between 250°C and 450°C, preferably between 270°C and 400°C, particularly preferably between 300°C and 370°C.

[0052] The process according to the invention is preferably carried out at a pressure of from 0.5 bar to 300 bar, particularly preferably from 0.9 bar to 50 bar, very particularly preferably from 1 bar to 10 bar.

[0053] The process according to the invention is preferably carried out in a reactor.

[0054] Usable reactors include all vessels in which gas can be added and in which the catalyst is in the form of a fixed bed, such as fixed-bed reactors, and those in which the catalyst is moved by a reactant feed or agitation device, such as entrained-flow reactors, fluidized-bed reactors, or batch reactors. The reactants can be added in gaseous or liquid form. In a preferred embodiment, the reactants are added as gases to a fixed-bed reactor having a fixed catalyst bed. The process according to the invention can be carried out continuously or discontinuously.

[0055] The total amount of catalyst based on ditolyl ether (DTE) can be selected as desired for a continuously operated reactor or a discontinuously operated reactor. In the case of a continuously operated reactor, the amount is preferably 0.01 to 1,000 g DTE / (g catalyst x h), particularly preferably 0.01 to 100 g DTE / (g catalyst x h). In the case of a discontinuously operated reactor, the amount is preferably 0.1 to 10,000 g DTE / g cat.

[0056] The molar ratio of ditolyl ether to water is preferably from 10:1 to 1:40, particularly preferably from 1:1 to 1:20, very particularly preferably from 1:5 to 1:15.

[0057] The molar ratio of ditolyl ether to hydrogen is preferably from 10:1 to 1:100, particularly preferably from 1:1 to 1:50, very particularly preferably from 1:5 to 1:40.

[0058] In addition to ditolyl ether, water, and hydrogen, further gases, preferably inert gases such as nitrogen or argon, can be added. The amount of standard liters L required to achieve a ratio of 0 to 95% by volume, particularly preferably 0 to 40% by volume, based on the total volume, can be added. n It is preferred to add nitrogen or argon.

[0059] Usable reactors include all vessels in which gas can be added and in which the catalyst is in the form of a fixed bed, such as fixed-bed reactors, and those in which the catalyst is moved by a reactant feed or agitation device, such as entrained-flow reactors, fluidized-bed reactors, or batch reactors. Reactants can be added in gaseous or liquid form. In a preferred embodiment, reactants are added as gases to a fixed-bed reactor having a fixed catalyst bed.

[0060] In this preferred embodiment of the present invention as hydrocracking, it is preferred to carry out the following process in a continuous manner:

[0061] The catalyst is first placed in a fixed-bed reactor and heated to 300-370°C. A mixture of ditolyl ether, water, and hydrogen heated to at least 250°C, with a molar ratio of ditolyl ether to water ranging from 1:5 to 1:15 and a molar ratio of ditolyl ether to hydrogen ranging from 1:5 to 1:40, mixed with up to 40% by volume of nitrogen, is added at a rate of 0.1-5 g of ditolyl ether per g of catalyst per hour. The reaction product formed is recovered, as it contains the cresols formed in high yield.

[0062] The process according to the invention is illustrated by the following non-limiting examples. [Example]

[0063] The experiments specified below were carried out in a steel tube with a perforated bottom plate as a reactor. The catalyst type and manufacturer information for each experiment are reported in Tables 1 and 2. A gas mixture of ditolyl ether, water, and nitrogen and / or hydrogen in the ratios reported in Tables 3 and 4 was introduced into the reactor. After the reaction, the product mixture was cooled to room temperature, and acetone was added to obtain a single-phase mixture, which was analyzed by gas chromatography using flame ionization. The results are listed in Tables 3 and 4.

[0064] [Table 1]

[0065] The precious metals in the precious metal-containing catalysts (see Examples 8(I)-15(I)) were applied by dry impregnation / ion exchange as described below. The amounts and nature are apparent from Table 2.

[0066] For dry impregnation, the precious metal source specified in Table 2 was dissolved in demineralized water and added to the carrier. The amount of demineralized water corresponded to 98% of the absorption capacity of the respective carrier (see Table 2). After complete absorption of the solution, the impregnated carrier was dried in a hot air stream at 120°C for 1 hour and calcined in a static oven at temperatures between 300°C and 500°C for 12 to 16 hours, except for Example 16(C). In the case of Example 16(C), the dry impregnation and drying were repeated three times to ensure that the entire amount of precious metal solution was applied.

[0067] For ion exchange, the noble metal doping solution was added to the support in a glass tube with a glass fritted bottom, and the solution was recirculated over the support for 24 hours, during which time the support was constantly covered with liquid.

[0068] [Table 2]

[0069] [Table 3]

[0070] Runs 2-7, performed using water according to the method of the present invention, showed higher conversion, higher selectivity, and higher yield compared to comparative example 1(C).

[0071] [Table 4]

[0072] It was found that Runs 8(I) to 13(I) and 15(I) performed by the method of the present invention using a platinum-containing catalyst, and Example 14(I) using a rhodium-containing catalyst, achieved higher conversions based on ditolyl ether, and higher selectivities and yields based on cresol and toluene, compared to Comparative Examples 16(C) and 17(C).

[0073] Comparative Example 16(C) also shows that the prior art use of nickel without the addition of a strong base results in very low conversions and much lower selectivities and yields than catalysts 8(I) to 15(I) of the present invention, which contain at least one element of the platinum group.

Claims

1. A process for producing cresol from ditolyl ether and water in the presence of a catalyst, characterized in that a catalyst from the group of zeolites of the LTA, MFI, MOR, BEA, FAU type is used, containing at least 85% by weight of an oxide selected from aluminum oxide and silicon oxide.

2. 2. The process of claim 1, wherein the catalyst from said group of zeolites has a silicon to aluminum molar ratio of from 3:1 to 300:

1.

3. 3. The process according to claim 1, wherein the catalyst further contains at least one element from the group of platinum metals and the reaction is carried out in the presence of hydrogen.

4. 4. The method of claim 3, wherein the proportion of said element from said group of platinum metals is 0.1 to 10% by weight, based on the total amount of said catalyst.

5. 5. A method according to claim 3 or 4, characterized in that said metal from the group of platinum metals is platinum and / or rhodium.

6. 6. A method according to any one of claims 1 to 5, characterized in that it is carried out at a temperature of between 250°C and 450°C.

7. 6. The method according to any one of claims 1 to 5, characterized in that it is carried out at a pressure of from 0.5 bar to 300 bar.

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