A method for isomerization of o-cresol and the catalyst used

Abstract

This invention relates to a method for the isomerization of o-cresol and the catalyst used therein. The catalyst used in this method is prepared by a process comprising the following steps: a silicon source, a quaternary ammonium base, and a compound containing a dopant element are subjected to a crystallization reaction in water under heating conditions to obtain a molecular sieve containing a quaternary ammonium cation; the molecular sieve is then mixed with a solution of a modified compound and a silane coupling agent, shaped, and calcined to obtain the catalyst. The modified compound is a water-soluble compound containing element M, which is selected from one or more combinations of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P, and Zn. Using this method, both the conversion rate and the selectivity of the target product are significantly improved, and the catalyst exhibits good wear resistance.

Description

Technical Field

[0001] This invention relates to a method for isomerizing o-cresol and the catalyst used therein. Background Technology

[0002] Cresol is widely used in pharmaceuticals, pesticides, fragrances, coatings, animal feed, antioxidants, polymerization inhibitors, UV absorbers, fuel additives, rubber additives, and synthetic materials, and is an important fine chemical intermediate in industrial production. Cresol has three isomers: o-cresol, m-cresol, and p-cresol. o-cresol is relatively easy to synthesize, has a higher yield, and lower cost. m-cresol and p-cresol are more difficult to synthesize and have lower yields.

[0003] Industrially, m-p-cresol (a mixture of m-cresol and p-cresol) can be prepared using traditional natural separation methods, which are physical methods involving the extraction of m-p-cresol from coal tar. However, coal tar resources are limited, and the separation process is complex, so this method is rarely used. Another method is chemical synthesis. Several industrially viable chemical synthesis methods include: toluene sulfonation with alkaline solution, toluene chlorination and hydrolysis, phenol alkylation, isopropyltoluene, m-toluidine hydrolysis, and o-cresol isomerization. Among these, o-cresol isomerization is widely used due to its high selectivity, low byproduct production, minimal environmental pollution, and readily available and inexpensive raw materials. This method requires a catalyst to catalyze the isomerization reaction of o-cresol, and the catalyst significantly affects the selectivity and conversion rate of the reaction.

[0004] Currently, most o-cresol isomerization catalysts are based on molecular sieves, and their catalytic performance is improved through various modification methods. For example, Chinese patent CN116060104A discloses an o-cresol isomerization catalyst modified by multiple elements after being formed by mixing molecular sieve and alumina. When the molecular sieve is HEU-1 and the modifying element is La, the o-cresol conversion rate is 56.28%, the m- and p-cresol yield is 54.09%, and the phenol yield is 1.83%. However, the o-cresol conversion rate still needs to be improved, and the preparation process of this catalyst is too complex.

[0005] For example, Chinese patent CN103341363A provides a moving bed catalyst for the isomerization of o-cresol. This catalyst is formed by stepwise impregnation of HZSM-5 molecular sieve with clay, metal oxides, and organosilanes to create a spherical catalyst. At 380℃, the conversion rate of o-cresol is 66.76%, the yield of m- and p-cresol is 46.24%, and the yield of phenol is 10.26%. Such catalysts are often prepared through multiple impregnation or calcination methods, which may damage the original pore structure of the molecular sieve, leading to increased byproducts and insufficient reaction selectivity. Furthermore, multiple impregnation or calcination processes prolong the catalyst preparation process, increase energy consumption, and make catalyst preparation more complex. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an isomerization method for o-cresol in order to address the shortcomings and deficiencies of the prior art. Using this method, the conversion rate of o-cresol is improved, and the selectivity of p-cresol (a mixture of m-cresol and p-cresol) among the target products is significantly improved. At the same time, the process is simple and the cost is low.

[0007] To solve the above technical problems, the present invention adopts the following technical solution:

[0008] A method for isomerizing o-cresol involves using o-cresol as a raw material and carrying out an isomerization reaction in the presence of a catalyst to prepare p-cresol and m-cresol. The catalyst is prepared by a method comprising the following steps: crystallizing a silicon source, a quaternary ammonium base, and a compound containing a dopant element in water under heating conditions to obtain a molecular sieve containing a quaternary ammonium cation; mixing the molecular sieve with a solution of a modified compound and a silane coupling agent, molding, and calcining to obtain the catalyst. The modified compound is a water-soluble compound containing an element M, wherein the element M is selected from one or more combinations of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P, and Zn.

[0009] In this invention, silicon source refers to a raw material capable of forming the silicon framework of a molecular sieve. Quaternary ammonium base refers to a compound containing quaternary ammonium cations and hydroxide anions. Dopant element refers to an element other than silicon in the molecular sieve framework. Crystallization reaction refers to the chemical reaction process that forms molecular sieve crystals.

[0010] In some embodiments, the quaternary ammonium base has the molecular formula R4N. + OH - , where R is independently a C1-C16 alkyl or cycloalkyl group.

[0011] In some embodiments, R is independently methyl, ethyl, propyl, butyl, hexadecyl, or adamantyl.

[0012] In some embodiments, the quaternary ammonium base is selected from one or more combinations of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, diethyldimethylammonium hydroxide, trimethyladamantylammonium hydroxide, and hexadecyltrimethylammonium hydroxide.

[0013] In some embodiments, the silicon source is selected from one or more combinations of silica sol, silica fume, and tetraethyl silicate. The silica gel may be fine silica gel, etc.

[0014] In some embodiments, the doping element is selected from one or more combinations of Al, B, Ga, and Ge.

[0015] In some embodiments, when the dopant element is Al, the compound containing the dopant element is selected from one or more combinations of Al(NO3)3, Al2(SO4)3, Al(OH)3, and aluminum isopropoxide; or, when the dopant element is B, the compound containing the dopant element is selected from boric acid and boron oxide; or, when the dopant element is Ga, the compound containing the dopant element is Ga(NO3)3; or, when the dopant element is Ge, the compound containing the dopant element is GeO2.

[0016] In some embodiments, when element M is selected from one or more combinations of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P, and Zn, the modified compound is selected from one or more combinations of nitrates, acetates, chlorides, and oxygen-containing salts of element M; when element M is B, the modified compound is boric acid or boron oxide; when element M is P, the modified compound is selected from one or more combinations of phosphoric acid, dihydrogen phosphate, or dihydrogen phosphate.

[0017] Oxygen-containing salts are oxoacid salts of the corresponding elements, such as ammonium vanadate (NH4VO3).

[0018] In some embodiments, the M element is selected from one or more of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P and Zn.

[0019] In some embodiments, the molecular sieve is selected from one or more combinations of ZSM-5 molecular sieve, ZSM-48 molecular sieve, ZSM-35 molecular sieve, MCM-41 molecular sieve, Beta molecular sieve, MOR molecular sieve, and Y molecular sieve. When a combination of these is selected, it can be a physical mixture of multiple molecular sieves or a composite molecular sieve thereof; physical mixing refers to mixing two or more molecular sieves by physical mixing; composite molecular sieves are crystal configurations in which a single molecular sieve crystal contains multiple molecular sieves.

[0020] In some embodiments, the silane coupling agent is selected from one or more combinations of tetraalkoxysilanes, vinyl-containing silanes, amino-containing silanes, and epoxy-containing silanes.

[0021] In some embodiments, the silane coupling agent is selected from one or more combinations of vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, tetraethoxysilane, 3-aminopropyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, and acryloyloxypropyltrimethoxysilane.

[0022] In some embodiments, the solvent in the solution of the modified compound is ethanol, water, or a mixture of ethanol and water.

[0023] In some embodiments, the volume ratio of water to ethanol in the mixture is 1:0.2 to 1:1.

[0024] In some embodiments, the molar ratio of the silicon source, quaternary ammonium base, compound containing doped elements, and water is 1:0.4-0.6:0.02-0.1:15-30.

[0025] In some embodiments, the mass ratio of the molecular sieve to the volume of the modified compound solution is 0.01-0.1 g / mL.

[0026] In some embodiments, the molar concentration of the solution of the modified compound is 0.01-0.5 mol / L.

[0027] In some embodiments, the mass of the silane coupling agent is 0.5-2% of the mass of the molecular sieve.

[0028] In some embodiments, the crystallization reaction is carried out at 120-160°C.

[0029] In some embodiments, the crystallization reaction takes 2-6 days.

[0030] In some embodiments, the preparation method of the catalyst further includes the steps of filtering, washing, and drying after the crystallization reaction to obtain the molecular sieve.

[0031] In some embodiments, the composite molecular sieve is prepared by adding one type of synthesized, uncalcined molecular sieve to the synthesis system of another type of molecular sieve, so that a single crystal contains two or more crystal structures.

[0032] In some embodiments, the mixing is performed under ultrasound.

[0033] In some embodiments, the molding process includes the steps of adding binder and lubricant, mixing, kneading, aging, extruding, and drying.

[0034] In some embodiments, the power of the ultrasound is 100-500W.

[0035] In some implementations, the mixing time is 10-60 minutes.

[0036] In some embodiments, the stirring is carried out at 60-120°C.

[0037] In some embodiments, the kneading is carried out in a vacuum ply mill.

[0038] In some implementations, the aging time is 1-3 days.

[0039] In some embodiments, the aging is carried out at room temperature and 30%-70% humidity.

[0040] In some embodiments, the extrusion is performed in an extrusion molding machine.

[0041] In some embodiments, the drying temperature is 50-150°C.

[0042] In some embodiments, the drying time is 12-48 hours.

[0043] In some embodiments, the binder is selected from one or more combinations of carboxymethyl cellulose, guar gum, polyvinyl alcohol, and polyethylene glycol.

[0044] In some embodiments, the polyethylene glycol (PEG) is PEG-2000.

[0045] In some embodiments, the lubricant is selected from one or more combinations of glycerin, oxalic acid, propylene glycol, and stearic acid.

[0046] In some embodiments, the mass of the binder is 0.5-5% of the mass of the molecular sieve.

[0047] In some embodiments, the mass of the lubricant is 0.1-2% of the mass of the molecular sieve.

[0048] In some embodiments, the calcination temperature is 350-600°C.

[0049] In some embodiments, the roasting time is 2-6 hours.

[0050] In some embodiments, the isomerization reaction is carried out continuously in a fixed-bed reactor, in which the catalyst is packed.

[0051] In some embodiments, the isomerization reaction is carried out at 300-450°C.

[0052] In some embodiments, the feed space velocity of the o-cresol is 0.4-1.2 h⁻¹. -1 .

[0053] In some embodiments, the isomerization reaction uses hydrogen or nitrogen as a carrier gas.

[0054] In some embodiments, the space velocity of the carrier gas is 40-150 h⁻¹. -1 .

[0055] In some embodiments, the raw material is replaced by o-cresol with a mixture containing o-cresol, said mixture further containing one or more phenolic compounds selected from xylenol, p-cresol, m-cresol, and phenol. That is, the present invention can also use a mixture of phenolic compounds in which o-cresol is the predominant component, as this type of raw material is more inexpensive and readily available.

[0056] Furthermore, the mass percentage of o-cresol in the mixture is 70% or more.

[0057] The present invention also provides the aforementioned catalyst, which can improve the conversion rate and reaction selectivity when used to catalyze the isomerization reaction of o-cresol. The catalyst has high mechanical strength and wear resistance, and the preparation process is simple and low cost.

[0058] Compared with the prior art, the present invention has the following advantages:

[0059] Using the o-cresol isomerization method of the present invention, when a continuous reaction is carried out in a fixed-bed reactor, the conversion rate of o-cresol can reach 71.2% and the selectivity of m-p-cresol can reach as high as 99.6% after a reaction time of 1000 hours. Even after a reaction time of 1000 hours, the conversion rate of o-cresol can still reach 70.5% and the selectivity of m-p-cresol can still reach as high as 99.4%. Compared with the prior art, the o-cresol isomerization method of the present invention significantly improves both the conversion rate of o-cresol and the selectivity of m-p-cresol target products, and the catalyst can operate stably under conditions of high conversion rate and selectivity.

[0060] The catalyst of this invention can operate efficiently and stably when used to catalyze the isomerization reaction of o-cresol.

[0061] The catalyst of this invention has high mechanical strength and wear resistance, with an wear index as low as 0.4%h. -1 Moreover, the preparation process is simple, requiring no multiple impregnations or calcinations, resulting in low production costs. Detailed Implementation

[0062] This invention provides an isomerization method for o-cresol, which uses o-cresol as a raw material and carries out an isomerization reaction in the presence of a catalyst to prepare p-cresol and m-cresol. The catalyst is prepared by a method including the following steps: crystallizing a silicon source, a quaternary ammonium base, and a compound containing a dopant element in water under heating conditions to obtain a molecular sieve containing a quaternary ammonium cation; mixing the molecular sieve with a solution of a modified compound and a silane coupling agent, molding, and calcining to obtain the catalyst. The modified compound is a water-soluble compound containing an element M, where the element M is selected from one or more combinations of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P, and Zn.

[0063] The main innovation of this invention lies in using a molecular sieve containing quaternary ammonium cations as the modification basis. A quaternary ammonium base is added during the molecular sieve synthesis, acting as a structure-directing agent to give the molecular sieve obtained from the crystallization reaction a specific spatial structure. Furthermore, this invention does not calcine the molecular sieve after synthesis, ensuring that it still contains quaternary ammonium cations (corresponding anions in the molecular sieve framework). These quaternary ammonium cations can occupy the internal pores of the molecular sieve. When modifying the molecular sieve with a modifying compound, the modifying compound cannot enter the internal pores, thus preventing blockage. The modifying compound only modifies the surface of the molecular sieve without affecting its internal pore structure. After the modification is complete, the final calcination process decomposes and releases the quaternary ammonium cations from the molecular sieve pores, exposing the internal pore structure. Therefore, in the catalyst of the present invention, the internal pores of the molecular sieve will not be occupied or blocked by the modified compound, and its internal pores are still very suitable for isomerization substrate o-cresol. As a result, when the catalyst of the present invention is used for o-cresol isomerization reaction, the reaction selectivity is significantly improved, the mass transfer efficiency of the material is improved, the conversion rate of the reaction substrate is improved, and the stability of the catalyst is greatly improved.

[0064] Another innovation of this invention lies in the use of specific modifying compounds to modify the molecular sieve. The modifying compounds of this invention can improve the acidity of the molecular sieve surface, reduce the content of acidic centers on the molecular sieve surface, and thus improve the conversion rate and selectivity of the isomerization reaction. After final calcination, the modified compounds of this invention may form oxides of the corresponding elements.

[0065] Another innovation of this invention lies in the simultaneous modification of the molecular sieve with a modifying compound and the addition of a silane coupling agent. The silane coupling agent acts as a coupling agent between the molecular sieves, forming a three-dimensional network structure. This prevents the decomposition of the quaternary ammonium cation directing agent during the final calcination process, which could lead to catalyst structural breakage. Consequently, the catalyst of this invention exhibits good mechanical strength and wear resistance. Furthermore, the silane coupling agent introduces a small amount of silicon onto the surface of the molecular sieve, reducing the content of acidic sites on the catalyst surface, improving the selectivity for m-cresol, and reducing the formation of byproducts such as phenol and xylenol.

[0066] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0067] All reagents and raw materials used in the following examples are commercially available.

[0068] Example 1

[0069] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0070] 1) Synthesis of molecular sieve: Tetrapropylammonium hydroxide, fine silica gel, aluminum nitrate and water are mixed evenly, wherein the molar ratio of tetrapropylammonium hydroxide, fine silica gel, aluminum nitrate and water is 0.5:1:0.03:20; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Al-ZSM-5 molecular sieve, which contains tetrapropylammonium cation.

[0071] 2) Synthesis of catalyst: Take 800 mL of deionized water, 200 mL of ethanol and 2.564 g of Mg(NO3)2·6H2O, stir and mix to dissolve to obtain Mg salt solution.

[0072] Weigh 10g of the uncalcined Al-ZSM-5 molecular sieve and add it to the Mg salt solution. Stir well, then add 0.05g of vinyltriethoxysilane and sonicate for 10 minutes using a KQ-500DE ultrasonic cleaner at 500W power. After sonication, place the solid-liquid mixture in a water bath and stir at 60°C until it reaches a slurry consistency. Then add 0.5g of carboxymethyl cellulose and 0.2g of glycerol and continue stirring to obtain a gel-like slurry.

[0073] The above-mentioned colloidal mud was kneaded in a vacuum ply mill at 0.5 MPa for 10 minutes, and then aged at room temperature with 70% humidity for 3 days to obtain plastic mud. The plastic mud was extruded into cylindrical preforms using a SY-6217 extruder and cut, then dried at 50℃ for 48 hours. The dried preforms were calcined at 500℃ for 5 hours to obtain the Mg / Al-ZSM-5 catalyst. The abrasion index of the catalyst was measured using an ISPF-1 abrasion index meter according to the following method, and the result was 0.6%h. -1 : Place a 10kg sample into the wear index measuring device and blow it for five hours at a constant air speed. Discard the sample blown out in the first hour and collect the sample blown out in the last four hours. Calculate the average wear percentage per hour as the wear index of the sample.

[0074] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.0 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 120 h⁻¹. -1The isomerization reaction temperature was controlled at 400℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h. The conversion rates of o-cresol and the selectivity of m-cresol at the time points of 100 h and 1000 h (determined by chromatography) are shown in Table 1 below.

[0075] Example 2

[0076] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0077] 1) Synthesis of molecular sieve: Tetraethylammonium hydroxide, silica sol (silica gel mass fraction is 30%), boric acid and water are mixed evenly, wherein the molar ratio of tetraethylammonium hydroxide, silica sol, boric acid and water is 0.4:1:0.04:15; then the mixture is placed in an oven at 120℃ for crystallization for 6 days. After crystallization, it is filtered, washed and dried to obtain uncalcined B-Beta molecular sieve, which contains tetraethylammonium cation.

[0078] 2) Synthesis of catalyst: Take 500 mL of deionized water, 500 mL of ethanol, 7.986 g of Cu(CH3COO)2·H2O and 16.866 g of CoSO4·7H2O, stir and mix to dissolve, and obtain Cu-Co salt solution.

[0079] Weigh 100g of the uncalcined Beta molecular sieve and add it to the Cu-Co salt solution. Stir well, then add 0.5g of 3-glycidoxypropyltrimethoxysilane and sonicate for 30 minutes using a KQ-500DE ultrasonic cleaner at 300W power. After sonication, place the solid-liquid mixture in a water bath and stir at 100℃ until it reaches a slurry consistency. Then add 0.5g of polyvinyl alcohol (PVA) and 0.1g of stearic acid and continue stirring to obtain a gel-like slurry.

[0080] The above-mentioned colloidal mud was kneaded in a vacuum ply mill at 0.3 MPa for 30 minutes, and then aged at room temperature with 50% humidity for 1 day to obtain plastic mud. The plastic mud was extruded into cylindrical preforms using a SY-6217 extruder and cut, then dried at 100°C for 36 hours. The dried preforms were calcined at 450°C for 4 hours to obtain the Cu-Co / B-Beta catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0081] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, using a mixture of 80 wt% o-cresol and 20 wt% p-cresol as the reactants, with a feed space velocity of 0.8 h⁻¹. -1 Nitrogen gas was used as the carrier gas, with a space velocity of 60 h⁻¹. -1The isomerization reaction temperature was controlled at 360℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0082] Example 3

[0083] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0084] 1) Synthesis of molecular sieve: Tetrapropylammonium hydroxide, fine silica gel, gallium nitrate and water are mixed evenly, wherein the molar ratio of tetrapropylammonium hydroxide, fine silica gel, gallium nitrate and water is 0.6:1:0.02:22; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Ga-ZSM-5 molecular sieve, which contains tetrapropylammonium cation.

[0085] 2) Synthesis of catalyst: Take 70 mL of deionized water, 30 mL of ethanol, 2.001 g of AlCl3 and 10.409 g of Zn(NO3)2·6H2O, stir and mix to dissolve, and obtain Al-Zn salt solution.

[0086] Weigh 10g of uncalcined Ga-ZSM-5 molecular sieve and add it to the above Al-Zn salt solution. Stir well, then add 0.1g of 3-aminopropyltriethoxysilane and 0.1g of tetraethoxysilane, and sonicate for 60min using a KQ-500DE ultrasonic cleaner at 100W power. After sonication, place the solid-liquid mixture in a water bath at 120℃ and stir until it reaches a slurry consistency. Then add 0.3g of guar gum powder, 0.2g of PEG-2000, and 0.2g of oxalic acid and continue stirring to obtain a gel-like slurry.

[0087] The above-mentioned colloidal mud was kneaded in a vacuum ply mill at 0.1 MPa for 60 minutes, and then aged at room temperature with 30% humidity for 1 day to obtain plastic mud. The plastic mud was extruded into sheet-like preforms using a SY-6217 extruder, and then dried at 150°C for 12 hours. The dried preforms were calcined at 350°C for 6 hours to obtain the Al-Zn / Ga-ZSM-5 catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0088] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 0.4 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 80 h⁻¹. -1The isomerization reaction temperature was controlled at 350℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0089] Example 4

[0090] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0091] 1) Synthesis of molecular sieve: Tetrapropylammonium hydroxide, fine silica gel, GeO2 and water are mixed evenly, wherein the molar ratio of tetrapropylammonium hydroxide, fine silica gel, GeO2 and water is 0.5:1:0.03:25; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Ge-ZSM-5 molecular sieve, which contains tetrapropylammonium cation.

[0092] 2) Synthesis of catalyst: Take 400 mL of deionized water, 600 mL of ethanol, 5.549 g of CaCl2, 18.968 g of TiCl4 and 5.830 g of NH4VO3 and stir to obtain Ca-Ti-V salt solution.

[0093] Weigh 100g of uncalcined Ge-ZSM-5 molecular sieve and add it to the above Ca-Ti-V salt solution. Stir, then add 1.2g of 3-aminopropyltrimethoxysilane and sonicate at 200W for 40min using a KQ-500DE ultrasonic cleaner. After sonication, place the solid-liquid mixture in a water bath at 120℃ and stir until it reaches a slurry consistency. Then add 1g of carboxymethyl cellulose, 0.2g of PEG-2000, and 0.1g of propylene glycol and continue stirring to obtain a gel-like slurry.

[0094] The above-mentioned colloidal sludge was kneaded in a vacuum ply mill at 0.2 MPa for 20 minutes, and then aged at room temperature with 60% humidity for 2 days to obtain plastic sludge. The plastic sludge was extruded into ring-shaped preforms using a SY-6217 extruder, and then dried at 80°C for 24 hours. The dried preforms were calcined at 550°C for 3 hours to obtain the Ca-Ti-V / Ge-ZSM-5 catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0095] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, using a mixture of 70 wt% o-cresol and 30 wt% xylenol as the reactants, with a feed space velocity of 0.6 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 40 h⁻¹. -1The isomerization reaction temperature was controlled at 380℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0096] Example 5

[0097] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0098] 1) Synthesis of molecular sieve: Diethyldimethylammonium hydroxide, fine silica gel, aluminum nitrate and water are mixed evenly, wherein the molar ratio of diethyldimethylammonium hydroxide, fine silica gel, aluminum nitrate and water is 0.6:1:0.04:30; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Al-ZSM-48 molecular sieve, which contains diethyldimethylammonium cation.

[0099] Hexadecyltrimethylammonium hydroxide, fine silica gel, aluminum nitrate, and water were mixed evenly, with the molar ratio of hexadecyltrimethylammonium hydroxide, fine silica gel, aluminum nitrate, and water being 0.4:1:0.03:25. The mixture was then placed in an oven at 150°C for crystallization for 4 days. After crystallization, the mixture was filtered, washed, and dried to obtain uncalcined Al-MCM-41 molecular sieve, which contains hexadecyltrimethylammonium cations.

[0100] 2) Synthesis of catalyst: Take 900 mL of deionized water, 100 mL of ethanol, 36.764 g of Mn(CH3COO)2·4H2O and 40.400 g of Fe(NO3)2·9H2O and stir to obtain Mn-Fe salt solution.

[0101] 80g and 20g of uncalcined Al-ZSM-48 and Al-MCM-41 molecular sieves were weighed and added to the above Mn-Fe salt solution and stirred. Then, 1.2g of 3-aminopropyltrimethoxysilane was added, and the mixture was ultrasonically cleaned using a KQ-500DE ultrasonic cleaner at 200W power for 40 minutes. After ultrasonication, the solid-liquid mixture was placed in a water bath at 80℃ and stirred until it reached a slurry consistency. Then, 0.8g of guar gum powder, 1g of PVA, and 0.3g of stearic acid were added, and stirring continued to obtain a gel-like slurry.

[0102] The above-mentioned colloidal mud was kneaded in a vacuum ply mill at 0.4 MPa for 40 minutes, and then aged at room temperature with 70% humidity for 2 days to obtain plastic mud. The plastic mud was extruded into ring-shaped preforms using a SY-6217 extruder, and then dried at 100°C for 24 hours. The dried preforms were calcined at 500°C for 4 hours to obtain the Mn-Fe / Al-ZSM-48 / Al-MCM-41 catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0103] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, using a mixture of 80 wt% o-cresol, 10 wt% phenol, and 10 wt% xylenol as the reaction feedstock, with a feed space velocity of 0.4 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 80 h⁻¹. -1 The isomerization reaction temperature was controlled at 390℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0104] Example 6

[0105] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0106] 1) Synthesis of molecular sieve: Tetrabutylammonium hydroxide, fine silica gel, aluminum nitrate and water are mixed evenly, wherein the molar ratio of tetrabutylammonium hydroxide, fine silica gel, aluminum nitrate and water is 0.6:1:0.1:15; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Al-Y molecular sieve, which contains tetrabutylammonium cation.

[0107] Trimethyladamantane ammonium hydroxide, fine silica gel, aluminum nitrate, and water were mixed evenly, with the molar ratio of trimethyladamantane ammonium hydroxide, fine silica gel, aluminum nitrate, and water being 0.4:1:0.05:20. The mixture was then placed in an oven at 150°C for crystallization for 4 days. After crystallization, the mixture was filtered, washed, and dried to obtain uncalcined Al-MOR molecular sieve containing trimethyladamantane ammonium cations.

[0108] 2) Synthesis of catalyst: Take 400 mL of deionized water, 600 mL of ethanol, 9.981 g of Cu(CH3COO)2·H2O, 14.540 g of Ni(NO3)2·6H2O and 9.684 g of Ce(NO3)2·6H2O and stir to obtain Cu-Ni-Ce salt solution.

[0109] 70g and 30g of uncalcined Al-Y and Al-MOR molecular sieves were weighed and added to the above Cu-Ni-Ce salt solution and stirred. Then, 1.5g of methacryloxypropyltrimethoxysilane was added, and the mixture was ultrasonically cleaned using a KQ-500DE ultrasonic cleaner at 200W power for 40 minutes. After ultrasonication, the solid-liquid mixture was placed in a water bath at 80℃ and stirred until it reached a slurry consistency. Then, 0.5g of carboxymethyl cellulose, 0.8g of guar gum powder, and 1.5g of glycerol were added, and stirring was continued to obtain a gel-like slurry.

[0110] The above-mentioned colloidal sludge was kneaded in a vacuum ply mill at 0.5 MPa for 10 minutes, and then aged at room temperature with 50% humidity for 1 day to obtain a plastic sludge. The plastic sludge was extruded into a honeycomb preform using a SY-6217 extruder, and then dried at 70°C for 36 hours. The dried preform was calcined at 600°C for 2 hours to obtain a Cu-Ni-Ce / Al-Y / Al-MOR catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0111] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.2 h⁻¹. -1 Nitrogen gas was used as the carrier gas, with a space velocity of 150 h⁻¹. -1 The isomerization reaction temperature was controlled at 410℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0112] Example 7

[0113] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0114] 1) Synthetic molecular sieve: Same as in Example 1.

[0115] 2) Synthesis of catalyst: basically the same as in Example 1, except that Mg(NO3)2·6H2O was replaced with boric acid, and finally B / Al-ZSM-5 catalyst was obtained. The wear index of the catalyst was determined using the same method as in Example 1. The results are shown in Table 1 below.

[0116] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.0 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 120 h⁻¹. -1 The isomerization reaction temperature was controlled at 400℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0117] Example 8

[0118] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0119] 1) Synthetic molecular sieve: Same as in Example 1.

[0120] 2) Synthesis of catalyst: basically the same as in Example 1, except that Mg(NO3)2·6H2O was replaced with diammonium hydrogen phosphate, and P / Al-ZSM-5 catalyst was finally obtained. The wear index of the catalyst was determined using the same method as in Example 1. The results are shown in Table 1 below.

[0121] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.0 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 120 h⁻¹. -1 The isomerization reaction temperature was controlled at 400℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0122] Example 9

[0123] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0124] 1) Synthesis of molecular sieve: Tetrapropylammonium hydroxide, fine silica gel, boric acid, aluminum nitrate and water are mixed evenly, wherein the molar ratio of tetrapropylammonium hydroxide, fine silica gel, boric acid, aluminum nitrate and water is 0.5:1:0.01:0.03; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined B-Al-ZSM-5 molecular sieve, which contains tetrapropylammonium cation.

[0125] 2) Synthesis of catalyst: Take 800 mL of deionized water, 200 mL of ethanol and 2.564 g of Mg(NO3)2·6H2O, stir and mix to dissolve to obtain Mg salt solution.

[0126] Weigh 100g of the uncalcined B-Al-ZSM-5 molecular sieve and add it to the Mg salt solution. Stir well, then add 0.05g of vinyltriethoxysilane and sonicate for 10 minutes using a KQ-500DE ultrasonic cleaner at 500W power. After sonication, place the solid-liquid mixture in a water bath and stir at 60℃ until it reaches a slurry consistency. Then add 0.5g of carboxymethyl cellulose and 0.2g of glycerol and continue stirring to obtain a gel-like slurry.

[0127] The above-mentioned colloidal mud was placed in a vacuum ply mill and kneaded at 0.5 MPa for 10 minutes, followed by aging at room temperature with 70% humidity for 3 days to obtain plastic mud. The plastic mud was extruded into cylindrical preforms using a SY-6217 extruder and cut, then dried at 50°C for 48 hours. The dried preforms were calcined at 500°C for 5 hours to obtain the Mg / B-Al-ZSM-5 catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0128] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.0 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 120 h⁻¹. -1 The isomerization reaction temperature was controlled at 400℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0129] Example 10

[0130] This embodiment provides a method for isomerizing o-cresol, the specific steps of which are as follows:

[0131] 1) Synthesis of molecular sieve: Tetrapropylammonium hydroxide, fine silica gel, aluminum nitrate and water are mixed evenly, wherein the molar ratio of tetrapropylammonium hydroxide, fine silica gel, aluminum nitrate and water is 0.5:1:0.03:20; then the mixture is placed in an oven at 150℃ for crystallization for 4 days. After crystallization, it is filtered, washed and dried to obtain uncalcined Al-ZSM-5 molecular sieve, which contains tetrapropylammonium cation.

[0132] Tetrabutylammonium hydroxide, fine silica gel, aluminum nitrate, and water were mixed evenly, with a molar ratio of 0.5:1:0.03:20. The synthesized Al-ZSM-5 molecular sieve was then added to the solution and stirred, with the amount of molecular sieve added being 60% of the mass of the fine silica gel. The mixture was then placed in an oven at 150°C for crystallization for 4 days. After crystallization, the mixture was filtered, washed, and dried to obtain uncalcined Al-ZSM-5-Y composite molecular sieve containing tetrabutylammonium and tetrapropylammonium cations.

[0133] 2) Synthesis of catalyst: Take 800 mL of deionized water, 200 mL of ethanol and 2.564 g of Mg(NO3)2·6H2O, stir and mix to dissolve to obtain Mg salt solution.

[0134] Weigh 100g of the uncalcined Al-ZSM-5-Y molecular sieve and add it to the Mg salt solution. Stir well, then add 0.05g of vinyltriethoxysilane and sonicate for 10 minutes using a KQ-500DE ultrasonic cleaner at 500W power. After sonication, place the solid-liquid mixture in a water bath and stir at 60℃ until it reaches a slurry consistency. Then add 0.5g of carboxymethyl cellulose and 0.2g of glycerol and continue stirring to obtain a gel-like slurry.

[0135] The above-mentioned colloidal mud was kneaded in a vacuum ply mill at 0.5 MPa for 10 minutes, and then aged at room temperature with 70% humidity for 3 days to obtain plastic mud. The plastic mud was extruded into cylindrical preforms using a SY-6217 extruder and cut, then dried at 50°C for 48 hours. The dried preforms were calcined at 500°C for 5 hours to obtain the Mg / Al-ZSM-5-Y catalyst. The attrition index of the catalyst was determined using the same method as in Example 1, and the results are shown in Table 1 below.

[0136] 3) Isomerization of o-cresol: The above catalyst was packed into a fixed-bed reactor, and o-cresol was used as the reactant with a feed space velocity of 1.0 h⁻¹. -1 Hydrogen was used as the carrier gas, with a space velocity of 120 h⁻¹. -1 The isomerization reaction temperature was controlled at 400℃. Under these conditions, the catalyst underwent isomerization reactions for 100 h and 1000 h, and the conversion rate of o-cresol and the selectivity of m-cresol are shown in Table 1 below.

[0137] Comparative Example 1

[0138] This comparative example provides an isomerization method for o-cresol, with the specific steps being basically the same as in Example 1, except that in step 1), after drying, the molecular sieve is calcined at 550°C for 4 hours to obtain a calcined Al-ZSM-5 molecular sieve that does not contain tetrapropylammonium cations. This calcined Al-ZSM-5 molecular sieve replaces the uncalcined Al-ZSM-5 molecular sieve in step 2). The resulting comparative catalyst, with its attrition index, o-cresol conversion rate, and m-cresol selectivity during the catalytic reaction, are shown in Table 1 below.

[0139] Comparative Example 2

[0140] This comparative example provides an isomerization method for o-cresol, with the specific steps being basically the same as in Example 1, except that in step 1), tetrapropylammonium hydroxide is replaced with NaOH during the synthesis of the molecular sieve, resulting in an uncalcined Al-ZSM-5 molecular sieve that does not contain tetrapropylammonium cations. This uncalcined Al-ZSM-5 molecular sieve is then used to replace the uncalcined Al-ZSM-5 molecular sieve in step 2). The resulting comparative catalyst, with its attrition index, o-cresol conversion rate, and m-cresol selectivity during the catalytic reaction, are shown in Table 1 below.

[0141] Comparative Example 3

[0142] This comparative example provides an isomerization method for o-cresol, with the specific steps being basically the same as in Example 1, except that: in step 1), aluminum nitrate is not added during the synthesis of the molecular sieve, and the all-silica ZSM-5 molecular sieve is used to replace the uncalcined Al-ZSM-5 molecular sieve in step 2). The resulting comparative catalyst, with its attrition index, o-cresol conversion rate, and m-cresol selectivity during the catalytic reaction, are shown in Table 1 below.

[0143] Comparative Example 4

[0144] This comparative example provides an isomerization method for o-cresol, with the specific steps being basically the same as in Example 1, except that vinyltriethoxysilane is not added in step 2). The resulting comparative catalyst, along with its attrition index, o-cresol conversion rate, and m-cresol selectivity during the catalytic reaction, are shown in Table 1 below.

[0145] Comparative Example 5

[0146] This comparative example provides an isomerization method for o-cresol, with the specific steps being basically the same as in Example 1, except that Mg salt solution is not added in step 2). The resulting comparative catalyst, along with its attrition index, o-cresol conversion rate, and m-cresol selectivity during the catalytic reaction, are shown in Table 1 below.

[0147] Table 1. Reaction performance and catalyst attrition index of each example and comparative example.

[0148]

[0149] As can be seen, this invention uses molecular sieves containing quaternary ammonium cations as the modification basis, modifies the molecular sieves with specific modifying compounds, and adds coupling agents, which can significantly improve the conversion rate of o-cresol and the selectivity of the reaction between target products and o-cresol in the isomerization reaction of the catalyst. Moreover, the catalyst has good stability, and the catalytic effect remains basically unchanged after 1000 hours of catalysis.

[0150] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for isomerizing o-cresol, using o-cresol as a raw material, and carrying out an isomerization reaction in the presence of a catalyst to prepare p-cresol and m-cresol, characterized in that: The catalyst is composed of The catalyst is prepared by a method comprising the following steps: a silicon source, a quaternary ammonium base, and a compound containing a dopant element are subjected to a crystallization reaction in water under heating conditions to obtain a molecular sieve containing a quaternary ammonium cation; the molecular sieve is mixed with a solution of a modified compound and a silane coupling agent, shaped, and calcined to obtain the catalyst; the modified compound is a water-soluble compound containing an element M, wherein the element M is selected from one or more combinations of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, B, P, and Zn; and the dopant element is selected from one or more combinations of Al, B, Ga, and Ge.

2. The isomerization method of o-cresol according to claim 1, characterized in that: The quaternary ammonium base has a molecular formula of R4N + OH - wherein R is independently a C1-C16 alkyl or cycloalkyl group; and / or the silicon source is selected from the group consisting of one or more of silica gel, fumed silica, tetraethyl orthosilicate.

3. The isomerization method of o-cresol according to claim 2, characterized in that: R is independently methyl, ethyl, propyl, butyl, hexadecyl, or adamantyl; and / or, when the dopant element is Al, the compound containing the dopant element is selected from one or more combinations of Al(NO3)3, Al2(SO4)3, Al(OH)3, and aluminum isopropoxide; or, when the dopant element is B, the compound containing the dopant element is selected from boric acid and boron oxide; or, when the dopant element is Ga, the compound containing the dopant element is Ga(NO3)3; or, when the dopant element is Ge, the compound containing the dopant element is GeO2.

4. The isomerization method of o-cresol according to claim 1, characterized in that: When element M is selected from one or more of Mg, Al, Ca, Ti, V, Mn, Cu, Fe, Co, Ni, Ce, La, and Zn, the modified compound is selected from one or more of nitrates, acetates, chlorides, and oxygen-containing salts of element M; when element M is B, the modified compound is one of boric acid and boron oxide; when element M is P, the modified compound is selected from one or more of phosphoric acid, dihydrogen phosphate, or dihydrogen phosphate.

5. The isomerization method of o-cresol according to claim 1, characterized in that: The quaternary ammonium base is selected from one or more combinations of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, diethyldimethylammonium hydroxide, trimethyladamantylammonium hydroxide, and hexadecyltrimethylammonium hydroxide.

6. The isomerization method of o-cresol according to claim 1, characterized in that: The molecular sieve is selected from one or more combinations of ZSM-5 molecular sieve, ZSM-48 molecular sieve, ZSM-35 molecular sieve, MCM-41 molecular sieve, Beta molecular sieve, MOR molecular sieve and Y molecular sieve; and / or, the silane coupling agent is selected from one or more combinations of tetraalkoxysilane, vinyl-containing silane, amino-containing silane and epoxy-containing silane.

7. The isomerization method of o-cresol according to claim 1, characterized in that: The silane coupling agent is selected from one or more combinations of vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, tetraethoxysilane, 3-aminopropyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, and acryloyloxypropyltrimethoxysilane.

8. The isomerization method of o-cresol according to claim 1, characterized in that: The solvent in the solution of the modified compound is ethanol, water, or a mixture of both; and / or the molar ratio of the silicon source, quaternary ammonium base, compound containing dopant element, and water is 1:0.4-0.6:0.02-0.1:1-30.

9. The isomerization method of o-cresol according to claim 8, characterized in that: The volume ratio of water to ethanol in the mixture is 1:0.2-1:

1.

10. The isomerization method of o-cresol according to claim 1, characterized in that: The mass ratio of the molecular sieve to the volume of the modified compound solution is 0.01-0.1 g / mL; and / or, the molar concentration of the modified compound solution is 0.01-0.5 mol / L; and / or, the mass of the silane coupling agent is 0.5-2% of the mass of the molecular sieve.

11. The isomerization method of o-cresol according to claim 1, characterized in that: The crystallization reaction is carried out at 120-160°C; and / or the crystallization reaction takes 2-6 days; and / or the catalyst preparation method further includes the steps of filtering, washing, and drying after the crystallization reaction to obtain the molecular sieve.

12. The isomerization method of o-cresol according to claim 1, characterized in that: The mixing is carried out under ultrasound; and / or the molding includes the steps of adding binder and lubricant, stirring, kneading, aging, extruding, and drying.

13. The isomerization method of o-cresol according to claim 12, characterized in that: The ultrasonic power is 100-500W; and / or the mixing time is 10-60min; and / or the stirring is carried out at 60-120℃; and / or the kneading is carried out in a vacuum pumice machine.

14. The isomerization method of o-cresol according to claim 12, characterized in that: The aging time is 1-3 days; and / or the aging is carried out at room temperature and 30%-70% humidity; and / or the drying temperature is 50-150℃; and / or the drying time is 12-48 h.

15. The isomerization method of o-cresol according to claim 12, characterized in that: The binder is selected from one or more combinations of carboxymethyl cellulose, guar gum, polyvinyl alcohol and polyethylene glycol; and / or, the lubricant is selected from one or more combinations of glycerin, oxalic acid, propylene glycol and stearic acid; and / or, the mass of the binder is 0.5-5% of the mass of the molecular sieve; and / or, the mass of the lubricant is 0.1-2% of the mass of the molecular sieve.

16. The isomerization method of o-cresol according to claim 1, characterized in that: The calcination temperature is 350-600℃; and / or the calcination time is 2-6 h.

17. The isomerization method of o-cresol according to claim 1, characterized in that: The isomerization reaction is carried out continuously in a fixed-bed reactor, in which the catalyst is packed; and / or, the isomerization reaction is carried out at 300-450°C.

18. The isomerization method of o-cresol according to claim 17, characterized in that: The ortho-cresol has a feed space velocity of 0.4-1.2 h -1 ; and / or the isomerization reaction is carried out with hydrogen or nitrogen as carrier gas, the carrier gas has a feed space velocity of 40-150 h -1 .

19. The isomerization method of o-cresol according to claim 1, characterized in that: It is also feasible to replace the raw material with o-cresol with a mixture containing o-cresol, wherein the mixture also contains one or more phenolic compounds selected from xylenol, p-cresol, m-cresol, and phenol.

20. A catalyst according to any one of claims 1-19 in the isomerization method.

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