A preparation method of a catalyst for preparing metaxylene by isomerization of pseudo-xylene

Abstract

This invention provides a method for preparing a catalyst for the isomerization of pseudotrimethylbenzene to mesitylene, comprising: alkali-modifying a mordenite molecular sieve to obtain an alkali-modified molecular sieve; kneading and extruding the alkali-modified molecular sieve with a binder, followed by drying and calcination, acid treatment, and then ammonium exchange to obtain a hierarchical porous HMOR support; using a mixed solution of copper nitrate and copper ammonia complex for metal support, followed by ultrasonic impregnation, drying, and calcination to obtain a copper-loaded catalyst precursor; and then performing weak acid washing to obtain a Cu / HMOR catalyst. This invention employs a step-by-step synergistic modification strategy of "alkali modification + acid treatment + metal support + weak acid washing" to precisely control the pore structure and acidity distribution of the mordenite support, optimizing the metal-support interaction. The catalyst prepared by this method, when used in the hydroisomerization reaction of pseudotrimethylbenzene, simultaneously improves the conversion and selectivity of pseudotrimethylbenzene, increases the yield of mesitylene, and exhibits good stability, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to a method for preparing a catalyst for the hydroisomerization of trimesene to produce mesitylene. Background Technology

[0002] Mesitylene is an important C9 aromatic hydrocarbon, widely used in the synthesis of high-performance resins, specialty dyes, pharmaceutical intermediates, and antioxidants, among other high-value-added products. Pseudotrimethylbenzene is a relatively abundant component of C9 heavy aromatic hydrocarbons, and its selective isomerization to mesitylene is a crucial pathway for the efficient utilization of heavy aromatic hydrocarbon resources. Currently, pseudotrimethylbenzene isomerization technologies are mainly divided into two categories: hydrogen-dependent and non-hydrogen-dependent.

[0003] Chinese patent CN115770611B discloses a method for preparing a catalyst for the non-hydroisomerization of pseudotrimethylbenzene to mesitylene. The method uses a three-step ammonium salt modified MCM-22 molecular sieve catalyst, with pseudotrimethylbenzene (95-99%) as the raw material. The reaction temperature is 260-300℃, the pressure is 1.0-3.0 MPa, and the mass hourly space velocity (WHSV) is 0.6-1.4 h⁻¹. -1 With nitrogen as the carrier gas and a nitrogen flow rate of 2-20 ml / min, the conversion rate of pseudotrimethylbenzene was 40.16%, the selectivity of mesitylene was 64.09%, and the yield of mesitylene was 25.74%.

[0004] Chen Yanjie (Chen Yanjie. Research on the Production Process of Mesitylene [D]. Tianjin University, 2004.) used M-2 type composite mordenite zeolite catalyst, with high-purity metatrimethylbenzene as raw material, under non-hydrogen-dependent conditions, at a reaction temperature of 300℃~320℃, a reaction pressure of 1.0~1.5MPa, and a volume hourly space velocity of 1.5~2.0h⁻¹. -1 Under these conditions, the single-pass conversion of mesitylene is approximately 38%, the selectivity of mesitylene is 70%, and the yield of mesitylene is approximately 26.6%.

[0005] Zhang Pengfei et al. from Tianjin University (Zhang Pengfei, Wang Cong, Chi Hongwei, Chen Yanjie. Study on the process of producing mesitylene by non-hydroisomerization of pseudotrimethylbenzene [J]. Petrochemical Technology, 2005(05):441-444.) used M-2 type composite mordenite zeolite catalyst at a reaction temperature of 320℃, a reaction pressure of 1.0~2.0MPa, and a volume hourly space velocity of 1.0~1.5h⁻¹. -1 Under the given conditions, the single-pass conversion of pseudotrimethylbenzene was approximately 39%, the single-pass yield of mesitylene was 25.49%, and the selectivity of mesitylene was 66.29%.

[0006] Wang Shenjiang (Wang Shenjiang. Study on the process of synthesizing mesitylene by non-hydroisomerization [D]. Tianjin University, 2007.) used pseudotrimethylbenzene (98.66%) as raw material and adopted M-2 type composite mordenite zeolite that had undergone carbonization regeneration treatment. The reaction was carried out at a reaction temperature of 353℃, a pressure of 3.2MPa, and a volume hourly space velocity of 0.9h. -1 Under the given conditions, the single-pass conversion of pseudotrimethylbenzene was 45.97%, the single-pass yield of mesitylene was 20.69%, and the selectivity was 47.05%.

[0007] Liu Rui et al. (Liu Rui, Tan Juan, Liu Jing, et al. Catalysis of non-hydrogen-dependent isomerization of pseudotrimethylbenzene by mesoporous molecular sieve catalyst [J]. Acta Petrolei Sinica (Petroleum Processing), 2024, 40(6): 1516-1527.) prepared a mesoporous HMCM-22 molecular sieve catalyst by alkali modification. Under non-hydrogen-dependent conditions, the reaction temperature was 310℃, the pressure was 3.0MPa, and the mass hourly space velocity was 0.8h. -1 The conversion rate of metatrimethylbenzene was 37.57%, the selectivity of mesitylene was 63.29%, and the yield was 23.78%.

[0008] Chinese patent CN202410542468.7 discloses a method for isomerizing pseudotrimethylbenzene to synthesize mesitylene. The method uses a heteroatom EWT molecular sieve with a framework containing aluminum atoms and heteroatoms (boron, iron, titanium, gallium, germanium) as a catalyst. The reaction is carried out under gas-phase non-hydrogen-dependent conditions at a temperature of 240–450 °C, a pressure of 0.1–2.0 MPa, a nitrogen flow rate of 10–20 mL / min, and a pseudotrimethylbenzene mass hourly space velocity (WHSV) of 0.5–3.5 h⁻¹. -1 The selectivity and yield of mesitylene were higher than those of [Si,Al]-EWT molecular sieves without heteroatoms, and the byproducts such as tetramethylbenzene and xylene were significantly reduced.

[0009] Chinese patent CN202410542471.9 discloses a method for synthesizing mesitylene via gas-phase non-hydroisomerization of pseudotrimethylbenzene. The method uses an EWT-structured molecular sieve with a total pore volume of 0.20–0.51 cm³ / g and a mesopore volume of 0.11–0.37 cm³ / g as a catalyst. The reaction is carried out at a temperature of 240–400 °C, a pressure of 0.1–1.2 MPa, a nitrogen flow rate of 5–50 mL / min, and a pseudotrimethylbenzene mass hourly space velocity of 0.5–1.0 h⁻¹. -1 Under the given conditions, the conversion rate of mesitylene was 45-50%, the selectivity of mesitylene was 50-65%, the yield of mesitylene was 17-35%, and the yield of mesitylene remained above 20% even after 90 hours of continuous reaction with the catalyst.

[0010] Although the above-mentioned non-hydroisomerization technology has achieved high selectivity for mesitylene under certain conditions, the catalyst is prone to carbonization and deactivation during the reaction process, making it difficult to guarantee stability. In addition, the reaction temperature is relatively high (300~360℃), which leads to an increase in the content of thionylene in the product and limits the yield of mesitylene.

[0011] Chinese patent CN1102360A discloses an alkyl aromatic hydrocarbon isomerization catalyst, using a composite zeolite composed of ZSM-5 zeolite and mordenite, along with alumina, as a support, and loaded with the Group VIII noble metal platinum. This catalyst can be used to isomerize C9 aromatic hydrocarbons to produce mesitylene via the isomerization of pseudotrimethylbenzene, at a reaction temperature of 430℃, a pressure of 0.8 MPa, and a volume hourly space velocity of 3.1 h⁻¹. -1 Under the condition of a hydrogen-to-hydrocarbon molar ratio of 1.5, the conversion rate of pseudotrimethylbenzene was 40.45%, the selectivity of mesitylene was only 49.11%, and the yield was only 19.86%.

[0012] Chinese patent CN111039741A discloses a method for isomerizing trimethylbenzene to produce mesitylene, using a hydrogen-form EUO molecular sieve as a support and loading platinum, palladium, and molybdenum as active components. High-purity pseudotrimethylbenzene (96-99 wt%) is used as raw material, and the process is carried out at 350-370℃, 0.3-0.6 MPa, and a mass hourly space velocity (WHSV) of 2.5-3.5 h⁻¹. -1 Under the conditions of a hydrogen-to-oil volume ratio of 500-700 v / v, the conversion rate of pseudotrimethylbenzene was 43.62%, the selectivity of mesitylene was 55.73%, and the yield was 24.31%.

[0013] Chinese patent CN102746091B discloses a method for producing BTX aromatics and trimethylbenzene from heavy aromatics. The method uses a hydrogen-form binderless ten-membered ring zeolite (ZSM-5, ZSM-11) with a loading percentage of 0.005~0.5% platinum and palladium as a catalyst, and operates at a reaction temperature of 320~450℃, a reaction pressure of 2.0~4.0 MPa, and a mass hourly space velocity of 10~4.0 h⁻¹. -1 Under conditions where the hydrogen / hydrocarbon feed ratio is 3 to 10:1 in molar terms, the content of mesitylene is only 5.26%, which is far from achieving the ideal isomerization effect.

[0014] Feng Jianlin et al. from the Refinery Research Institute of Jinling Petrochemical Company (Study on the isomerization performance of high-silica mordenite zeolite [J]. Chemical Industry Times, 2000(06):11-14.) used high-purity pseudotrimethylbenzene (>99%) as raw material and high-silica mordenite zeolite with a silica-to-alumina ratio of 15-30 synthesized from water glass and aluminum salt as catalyst, at 1.2 MPa, 320℃, and a volume hourly space velocity of 1.0 h⁻¹. -1 Under conditions of a hydrogen-to-oil ratio (molar ratio) of 10, the hydrogen-to-oil gas-phase isomerization reaction was carried out, with a conversion of 47.9% for paratrimethylbenzene and selectivity and single-pass yield of 51.6% and 24.7% for mesitylene, respectively.

[0015] Zhou Ting et al. from Nanjing University of Technology (Isomerization of parabens on modified WO3 / ZrO2 catalyst [J]. Journal of Nanjing University of Technology (Natural Science Edition), 2008(03):21-25.) used WO3 / ZrO2 solid strong acid catalyst, supported with Ni and alkaline earth metals (Mg, Ca, Sr, Ba), at a reaction temperature of 270℃ and a volume hourly space velocity of 1 h⁻¹. -1 Under these conditions, the conversion rate of pseudotrimethylbenzene was 59.1%, the selectivity of mesitylene was only 31.6%, and the single-pass yield was 18.7%.

[0016] Wang Yan et al. (Study on the isomerization performance of tricresylbenzene on Ni-Mo / HM [J]. Chemical Industry and Engineering, 2016, 33(01):35-39.) prepared mollusken zeolite catalysts supported on Mo and Ni by an equal-volume impregnation method. When the content of metallic Ni was 5wt% and the content of metallic Mo was 1.25wt%, the catalysts were successfully prepared at 260℃, 1.2MPa, and a mass hourly space velocity of 1.0h⁻¹. -1 Under the condition of a hydrogen-to-oil ratio (molar ratio) of 5, the conversion of pseudotrimethylbenzene was 49.17%, and the yield and selectivity of mesitylene were 23.10% and 46.98%, respectively.

[0017] Chinese patent CN116786158B discloses a method for preparing and applying a catalyst for the production of mesitylene from pseudotrimethylbenzene. First, a hierarchical porous Hβ zeolite molecular sieve is prepared. Then, the hierarchical porous Hβ is mixed with a hydrogen-form mordenite molecular sieve and a binder, extruded into strips, dried and calcined, and then impregnated and reduced with hydrogen to obtain the pseudotrimethylbenzene isomerization catalyst. Using pseudotrimethylbenzene (98% purity) as raw material, the reaction is carried out at a temperature of 260–300 °C, a pressure of 1.2–1.4 MPa, and a mass hourly space velocity of 0.8–1.3 h⁻¹. -1 Under the conditions of a hydrogen-to-oil ratio of 500-800 v / v, the conversion rate of pseudotrimethylbenzene was 47.74%, and the selectivity and yield of mesitylene were 58.19% and 27.78%, respectively.

[0018] Wang Fushan et al. (Preparation of Ag / HZSM-5 catalyst and its hydroisomerization performance of pseudotrimethylbenzene [J]. Petrochemical Technology and Application, 2023, 41(6):425-429.) used Ag-modified HZSM-5 catalyst. The reaction was carried out at a temperature of 280℃, a pressure of 1.6 MPa, and a mass hourly space velocity of 1.0 h⁻¹. -1 Under the condition of a hydrogen-to-oil molar ratio of 5, the conversion rate of pseudotrimethylbenzene was 33.80%, the selectivity of mesitylene was 71.34%, and the yield was 24.90%.

[0019] Chinese patent CN119368227A discloses a catalyst for preparing mesitylene and its preparation method. The catalyst consists of the following components: 65%–80% molecular sieve, 15%–30% γ-Al₂O₃, and 0.25%–2.5% metal element. The molecular sieve is an MFI type and / or MOR type molecular sieve, and the metal element is selected from one or more of Group VIII, Group I, or lanthanides. Using this catalyst for the isomerization reaction of mesitylene, the selectivity and yield of mesitylene are 67% and 24.5%, respectively.

[0020] Chinese patent CN118420430A discloses a method for preparing mesitylene via hydroisomerization of pseudotrimethylbenzene. A hierarchical porous mordenite zeolite modified in two steps using organic and inorganic bases is used as a support to prepare a Cu / HMOR catalyst loaded with copper. The reaction is carried out at a temperature of 265–305 °C, a pressure of 0.6–1.6 MPa, and a mass hourly space velocity of 0.6–1.4 h⁻¹. -1 Under conditions of a hydrogen-to-oil ratio of 4 to 10, the conversion rate of pseudotrimethylbenzene is 43.61%, the yield of mesitylene can reach 33.11%, and the selectivity is as high as 75.94%.

[0021] Chinese patent CN202410830238.0 discloses a method for producing mesitylene from C9 heavy aromatics. The method involves mixing C9 heavy aromatics with hydrogen and then feeding the mixture into a dealkylation isomerization reactor containing a zeolite catalyst loaded with non-precious metal elements (Ni, W, Mo, P). The reaction is carried out at 340–400 °C, 1.0–3.0 MPa, and a mass hourly space velocity (WHSV) of 1–4 h⁻¹. -1 The reaction is carried out under conditions where the molar ratio of hydrogen to C9 heavy aromatics is 3~6:1. The product does not contain propylbenzene, the content of methylbenzene is <0.2%, and the single-pass yield of mesitylene is ≥12%.

[0022] The aforementioned report employed hydroisomerization technology, improving the catalyst's resistance to coking under hydrothermal conditions by loading noble metals (Pt, Pd) or non-noble metals (Mo, Ni, W, Cu) onto an acidic support. However, a comprehensive analysis of these technologies reveals a common "seesaw effect" in existing hydroisomerization catalysts, where activity and selectivity are difficult to balance. On one hand, some catalysts achieve high conversion rates, such as the Ni-Mo / HM catalyst at 49.17% and the WO3 / ZrO2 catalyst at 59.1%, but their mesitylene selectivity is less than 50%, resulting in low yields of the target product. On the other hand, while alkali modification combined with a metal loading strategy (such as CN118420430A) can increase mesitylene selectivity to 75.94% and yield to 33.11%, the mesitylene conversion is only 43.61%, indicating significant room for improvement. Therefore, current technologies have not yet achieved the goal of significantly increasing conversion while maintaining high selectivity.

[0023] In summary, while non-hydroisomerization processes are simple to operate, the catalysts are prone to coking and deactivation, resulting in poor stability. Hydroisomerization technology can effectively suppress coking and improve catalyst stability, thus becoming the mainstream direction for industrial applications. However, existing hydroisomerization catalysts generally suffer from the problem of balancing activity and selectivity. Current modification techniques cannot simultaneously obtain catalysts with high selectivity and high conversion rates, limiting the improvement of mesitylene yield and the extension of catalyst single-pass life. How to overcome this trade-off and develop hydroisomerization catalysts with both high conversion and high selectivity, while improving catalyst single-pass life, remains a key technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0024] To address the technical problems of existing hydroisomerization catalysts for pseudotrimethylbenzene, which suffer from difficulty in balancing activity and selectivity and low conversion rates, this invention provides a method for preparing a catalyst for the isomerization of pseudotrimethylbenzene to mesitylene. This method employs a step-by-step synergistic modification strategy of "alkali modification + acid treatment + metal support + weak acid washing," which significantly improves conversion rates while maintaining high selectivity, resulting in a substantial increase in mesitylene yield and further extending the catalyst's single-pass lifespan. In industrial applications, the extended catalyst lifespan can effectively reduce regeneration frequency, lower operating energy consumption and costs, improve the continuous operation cycle and production efficiency of the unit, and provide more economical and stable technical support for the high-value utilization of C9 heavy aromatics resources.

[0025] Through in-depth research, the inventors discovered the root cause of the "activity-selectivity" seesaw effect in existing technologies: While single-base modification can improve diffusion performance by constructing hierarchical channels through desilication, it often leads to a decrease in conversion rate due to the reduction in the total number of acid sites; while single-acid treatment can increase mesopores and improve conversion rate through dealumination, excessive strong acids exacerbate side reactions such as disproportionation, severely deteriorating selectivity; conventional metal loading methods easily cause framework dealumination, affecting acidity distribution, and the interaction between the metal and the support needs optimization. Based on this, the present invention proposes a multi-step synergistic modification strategy, the technical principle of which is as follows: (1) Alkali modification: MOR (mordenite molecular sieve) is treated with organic alkali + inorganic alkali for mild desilication treatment, selectively removing non-framework and part of the framework silicon. While clearing the pores and constructing a multi-level pore structure, it effectively suppresses the number of strong acid centers, laying the foundation for selective optimization.

[0026] (2) Acid treatment: After the alkali-modified molecular sieve is formed, it is treated with acid solutions such as nitric acid. Nitric acid treatment can further remove amorphous species that block the pores during alkali treatment and forming process, precisely control the type of acid center, especially enrich Lewis acid sites that are beneficial to isomerization, reconstruct a synergistic acidic microenvironment, and provide multi-mode activation sites for reactants.

[0027] (3) Metal support: A mixed solution of copper nitrate and copper ammonia complex was used as the copper source for loading. The ammonium ions in the copper ammonia complex provide a weakly alkaline environment, allowing the metal ions to precipitate on the porous molecular sieve support in the form of basic salts, thus protecting the molecular sieve structure while ensuring uniform dispersion of copper species. High dispersion and stable anchoring of copper species were achieved through stepwise ultrasonic impregnation, three-stage programmed temperature drying, and two-stage programmed temperature calcination.

[0028] (4) Weak acid washing: The copper-supported catalyst precursor is subjected to weak acid washing. This step can selectively remove unstable or weakly bound copper species on the surface, retain active copper species that strongly interact with the support, further optimize the metal-support interaction, and at the same time, the surface acidity is controlled by mild modification of the catalyst surface by weak acid, thereby creating conditions for improving the conversion rate while maintaining high selectivity.

[0029] The step-by-step synergistic modification sequence described in this invention is crucial. The "base-acid" modification sequence enables targeted, step-by-step optimization of the support's "pore-acidity" relationship; the "metal-supported followed by weak acid washing" sequence ensures precise control of active metal species. These four synergistic steps ultimately construct a highly synergistic catalytic system of "pore-acidity-metal sites".

[0030] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a catalyst for the isomerization of pseudotrimethylbenzene to mesitylene includes the following steps: (1) Modification with organic base + inorganic base: MOR molecular sieve raw powder is mixed with an alkaline solution at a solid-liquid mass ratio of 1:(8~20), stirred at 50~120℃ for 1~6h, and then washed, filtered, dried and calcined to obtain alkaline-modified MOR molecular sieve; the alkaline solution is a mixed solution of organic base and inorganic base, wherein the organic base is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethyleneimine and piperidine; the inorganic base is one or more of ammonium carbonate, sodium hydroxide and potassium hydroxide; (2) Acid treatment: The alkali-modified MOR molecular sieve obtained in step (1) is kneaded with boehmite, guar gum powder and dilute nitric acid to obtain a slurry, which is extruded into strips, dried and calcined, and mixed with an acid solution with a mass concentration of 0.3~6.0wt%. The mixture is stirred at 50~100℃ for 0.5~6h, washed, dried and calcined to obtain an acid-modified molding carrier; the acid-modified molding carrier is then subjected to ammonium exchange modification 1~3 times with one or more of ammonium sulfate, ammonium chloride and ammonium citrate, washed, dried and calcined to obtain a multi-level porous HMOR carrier; the acid solution is one or more of nitric acid, hydrochloric acid, sulfuric acid and phosphoric acid; (3) Metal support: The hierarchical porous HMOR support obtained in step (2) is placed in a mixed solution of copper nitrate and copper ammonia complex, wherein the molar ratio of copper nitrate to copper ammonia complex is 1:(2~12), and is immersed in ultrasonic conditions for 15~60 min and then dried; the above steps are repeated at least twice for ultrasonic immersion and drying, and then calcined to obtain a copper-loaded catalyst precursor; (4) Weak acid washing: The copper-supported catalyst precursor obtained in step (3) is mixed with a weak acid solution with a mass concentration of 0.1~1.5wt%, and stirred at 20~70℃ for 0.2~2h. After washing, drying and calcining, the copper-supported modified mordenite catalyst Cu / HMOR is obtained; the weak acid is one or more of acetic acid, citric acid and oxalic acid.

[0031] The mass concentrations of organic base and inorganic base in the alkaline solution in step (1) are 0.2~1.0wt% and 0.5~3.0wt%, respectively.

[0032] In step (1), the stirring temperature is 70~90℃ and the processing time is 2~4h.

[0033] In step (1), the roasting temperature is 400~600℃ and the roasting time is 3~8h.

[0034] In step (2), the amount of boehmite added is 20-30 wt% of the slurry mass, the amount of guar gum added is 3-6 wt% of the slurry mass, and the mass concentration of dilute nitric acid is 4-6 wt%.

[0035] The acid solution is a nitric acid solution with a mass concentration of 2-3 wt%.

[0036] In step (2), the stirring temperature is 60~80℃ and the processing time is 2~3h.

[0037] In step (2), the roasting temperature is 400~600℃ and the roasting time is 3~8h.

[0038] In step (3), the molar ratio of copper nitrate to copper ammonia complex in the mixed solution is 1:(4~6).

[0039] The drying process described in step (3) adopts a three-stage temperature control step: first stage: 30~60℃ for 2~5h; second stage: 70~90℃ for 3~6h; third stage: 100~120℃ for 8~12h.

[0040] The roasting process employs a two-stage programmed temperature control step: the first stage involves increasing the temperature at 1~4℃ / min to 170~200℃ and holding it for 2~5 hours; the second stage involves increasing the temperature at 3~6℃ / min to 550~650℃ and holding it for 5~8 hours.

[0041] The weak acid mentioned in step (4) is citric acid with a mass concentration of 0.5~1.5wt%.

[0042] In step (4), the stirring temperature is 35~45℃ and the processing time is 0.2~1h.

[0043] The Cu loading in the Cu / HMOR catalyst is 2-10 wt%.

[0044] The present invention has the following advantages: (1) Breaking the trade-off between activity and selectivity: This invention utilizes a step-by-step synergistic modification strategy of "alkali modification + acid treatment + metal support + weak acid washing" to regulate the pore structure and acidity distribution of mordenite support. Alkali modification constructs hierarchical pores and suppresses strong acids, optimizing mass transfer and reducing side reactions; acid treatment further optimizes the pores and enriches Lewis acids, reconstructing a synergistic acidic environment; metal support introduces highly dispersed copper species; and weak acid washing selectively removes unstable copper, optimizing the metal-support interaction. This four-step synergistic approach successfully breaks through the technical bottleneck of the difficulty in balancing activity and selectivity in traditional catalysts.

[0045] (2) Significantly improved catalytic performance: The catalyst prepared by the method of this invention can significantly improve the conversion rate while maintaining high selectivity when used in the hydroisomerization reaction of mesitylene. Compared with the prior art, the catalyst of this invention improves both conversion rate and selectivity under hydroisomerization conditions, and the yield of mesitylene can reach more than 31%. Its comprehensive performance is significantly better than the single modification system reported in the prior art.

[0046] (3) Good stability and long life: Thanks to the optimized multi-level pore structure and optimized metal-support interaction, the catalyst of this invention has good anti-coking ability under hydrogen conditions. During a long-term operation of 300 hours, the yield of mesitylene can be stably maintained at more than 30%, showing excellent industrial application potential.

[0047] (4) The preparation process is highly controllable: The step-by-step modification method of the present invention has mild process conditions, simple operation steps, and is easy to scale up. The parameters of each step can be optimized and adjusted according to actual needs, providing a feasible path for the industrial production of high-performance hydroisomerization catalysts. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. It should be understood that the embodiments given herein are only for explaining this invention and are not intended to limit the scope of this invention.

[0049] I. Calculation of Catalytic Performance Indicators The hydroisomerization reaction of p-trimethylbenzene was carried out on a small fixed-bed apparatus, and the reactant composition was 98.84%. wt % high-purity pseudotrimethylbenzene. The formulas for calculating each performance indicator are as follows:

[0050]

[0051]

[0052] Example 1 Take 20g of MOR molecular sieve raw powder and add it to 200g of mixed alkaline solution, wherein the mixed alkaline solution contains 1.2g of tetraethylammonium hydroxide, 6g of ammonium carbonate, and the remainder is deionized water. Stir at 80℃ for 3h, wash with deionized water until neutral, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain alkali-modified molecular sieve powder.

[0053] Take 6g of the above-mentioned alkali-modified molecular sieve powder, mix it with 2.57g of boehmite and 0.26g of guar gum powder, add 14.73g of 5wt% dilute nitric acid, knead, extrude into strips, air-dry naturally for 12h, dry at 110℃ for 6h, and calcine at 550℃ for 6h to obtain the molded carrier. Mix the molded carrier with 150g of 2wt% nitric acid solution, stir at 80℃ for 2h, wash until neutral, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain the acid-modified molded carrier. Take 5g of the acid-modified molded carrier and add 50g of 5wt% ammonium sulfate solution, exchange at 90℃ for 2h, exchange twice, wash with deionized water until neutral, dry at 120℃ for 12h, and calcine at 550℃ for 8h to obtain the hierarchical porous HMOR carrier.

[0054] Dissolve 0.72 g of copper sulfate in 20 g of deionized water, and add 1.2 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain a copper-supported catalyst precursor.

[0055] The copper-loaded catalyst precursor was mixed with 100 g of a 1.5 wt% citric acid solution, stirred at 40 °C for 0.2 h, washed until neutral, dried at 110 °C for 12 h, and calcined at 550 °C for 6 h to obtain the Cu / HMOR catalyst, with a calculated Cu loading of 6 wt%.

[0056] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under the condition of a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1.

[0057] Example 2 Take 20g of MOR molecular sieve raw powder and add it to 200g of mixed alkaline solution. The mixed alkaline solution contains 0.8g of tetraethylammonium hydroxide, 2g of ammonium carbonate, and the remainder is deionized water. Stir at 80℃ for 3h, wash with deionized water until neutral, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain alkali-modified molecular sieve powder.

[0058] Take 6g of the above-mentioned alkali-modified molecular sieve powder, mix it with 2.57g of boehmite and 0.26g of guar gum powder, add 14.73g of 5wt% dilute nitric acid, knead, extrude into strips, air-dry naturally for 12h, dry at 110℃ for 6h, and calcine at 550℃ for 6h to obtain the molded carrier. Mix the molded carrier with 150g of 3wt% nitric acid solution, stir at 80℃ for 2h, wash until neutral, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain the acid-modified molded carrier. Take 5g of the acid-modified molded carrier and add 50g of 5wt% ammonium sulfate solution, exchange at 90℃ for 2h, exchange twice, wash with deionized water until neutral, dry at 120℃ for 12h, and calcine at 550℃ for 8h to obtain the hierarchical porous HMOR carrier.

[0059] Dissolve 0.21 g of copper sulfate in 20 g of deionized water, and add 0.35 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain the copper-supported catalyst precursor.

[0060] The copper-loaded catalyst precursor was mixed with 100 g of 0.5 wt% citric acid solution, stirred at 40 °C for 0.5 h, washed until neutral, dried at 110 °C for 12 h, and calcined at 550 °C for 6 h to obtain the Cu / HMOR catalyst, with a calculated Cu loading of 2 wt%.

[0061] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under the condition of a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1.

[0062] Example 3 Take 20g of MOR molecular sieve raw powder and add it to 200g of mixed alkaline solution. The mixed alkaline solution contains 0.8g of tetraethylammonium hydroxide, 4g of ammonium carbonate, and the remainder is deionized water. Stir at 80℃ for 3h, wash with deionized water until neutral, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain alkali-modified molecular sieve powder.

[0063] Take 6g of the above-mentioned alkali-modified molecular sieve powder, mix it with 2.57g of boehmite and 0.26g of guar gum powder, add 14.73g of 5wt% dilute nitric acid, knead, extrude into strips, air-dry naturally for 12h, dry at 110℃ for 6h, and calcine at 550℃ for 6h to obtain the molded carrier. Mix the molded carrier with 150g of 2.5wt% nitric acid solution, stir at 80℃ for 2h, wash until neutral, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain the acid-modified molded carrier. Take 5g of the acid-modified molded carrier and add 50g of 5wt% ammonium sulfate solution, exchange at 90℃ for 2h, exchange twice, wash with deionized water until neutral, dry at 120℃ for 12h, and calcine at 550℃ for 8h to obtain the hierarchical porous HMOR carrier.

[0064] Dissolve 0.6 g of copper sulfate in 20 g of deionized water, and add 1 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain the copper-supported catalyst precursor.

[0065] The copper-loaded catalyst precursor was mixed with 100 g of a 1.0 wt% citric acid solution, stirred at 40 °C for 0.3 h, washed until neutral, dried at 110 °C for 12 h, and calcined at 550 °C for 6 h to obtain the Cu / HMOR catalyst, with a calculated Cu loading of 4 wt%.

[0066] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1. After 200 h of continuous operation, the conversion rate of pseudotrimethylbenzene still reached 46.24%, and the yield of mesitylene reached 31.69%. After 300 h of operation, the conversion rate and yield remained at 40.08% and 30.02%, respectively, showing excellent catalytic stability.

[0067] Comparative Example 1 MOR molecular sieve raw powder was used to prepare a molding carrier according to the molding method in step (2) of Example 1, but without the alkali modification in step (1) and the acid treatment in step (2). Specifically, the MOR raw powder was kneaded and extruded with boehmite, guar gum powder and dilute nitric acid, and then dried and calcined to obtain the molding carrier. 5 g of the molding carrier was added to 50 g of 5wt% ammonium sulfate solution, exchanged at 90℃ for 2 h, exchanged twice, washed with deionized water until neutral, dried at 120℃ for 12 h, and calcined at 550℃ for 8 h to obtain the HMOR carrier.

[0068] Dissolve 0.6 g of copper sulfate in 20 g of deionized water, and add 1 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain the copper-supported catalyst precursor.

[0069] The copper-loaded catalyst precursor was mixed with 100g of 1.0wt% citric acid solution, stirred at 40℃ for 2h, washed until neutral, dried at 110℃ for 12h, and calcined at 550℃ for 6h to obtain the Cu / HMOR catalyst, with a calculated Cu loading of 4wt%.

[0070] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under the condition of a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1.

[0071] Comparative Example 2 Take 20g of MOR molecular sieve raw powder and add it to 200g of mixed alkaline solution, wherein the mixed alkaline solution contains 1g of tetraethylammonium hydroxide and 3g of ammonium carbonate, with the remainder being deionized water. Stir at 80℃ for 3h, wash with deionized water until neutral, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain alkali-modified molecular sieve powder.

[0072] Take 6g of the above-mentioned alkali-modified molecular sieve powder, mix it with 2.57g of boehmite and 0.26g of guar gum powder, add 14.73g of 5wt% dilute nitric acid, knead, extrude into strips, air-dry naturally for 12h, dry at 110℃ for 6h, and calcine at 550℃ for 6h to obtain the molded carrier. Mix the molded carrier with 150g of 2wt% nitric acid solution, stir at 80℃ for 2h, wash until neutral, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain the acid-modified molded carrier. Take 5g of the acid-modified molded carrier and add 50g of 5wt% ammonium sulfate solution, exchange at 90℃ for 2h, exchange twice, wash with deionized water until neutral, dry at 120℃ for 12h, and calcine at 550℃ for 8h to obtain the hierarchical porous HMOR carrier.

[0073] Dissolve 0.6 g of copper sulfate in 20 g of deionized water, and add 1 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain a Cu / HMOR catalyst with a calculated Cu loading of 4 wt%.

[0074] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under the condition of a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1.

[0075] Comparative Example 3 Take 15 g of MOR molecular sieve raw powder, add 150 g of 2.4 wt% tetraethylammonium hydroxide solution and mix. Place the mixture in a hydrothermal reactor and stir at 90 ℃ for 2 h. Wash with deionized water until neutral, filter, dry at 110 ℃ for 12 h, and calcine at 550 ℃ for 6 h to obtain organic base modified MOR molecular sieve. Take 10 g of organic base modified MOR molecular sieve, add 100 g of 2.4 wt% sodium hydroxide solution and mix. Stir at 80 ℃ for 2 h, wash with deionized water until neutral, filter, dry at 110 ℃ for 12 h, and calcine at 550 ℃ for 6 h to obtain two-step base modified hierarchical porous MOR molecular sieve.

[0076] Six g of two-step alkali-modified hierarchical porous MOR molecular sieve was kneaded with 2.57 g of boehmite, 0.26 g of guar gum powder, and 14.73 g of 5 wt% dilute nitric acid. The mixture was then extruded into strips, naturally air-dried for 12 h, dried at 110 ℃ for 6 h, and calcined at 550 ℃ for 6 h to obtain a hierarchical porous MOR support. Five g of the hierarchical porous MOR support was added to 50 g of 5 wt% ammonium sulfate solution, exchanged at 90 ℃ for 2 h, and repeated twice. The mixture was washed with deionized water until neutral, dried at 120 ℃ for 12 h, and calcined at 550 ℃ for 8 h to obtain a hierarchical porous HMOR support.

[0077] Dissolve 0.6 g of copper sulfate in 20 g of deionized water, and add 1 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain a Cu / HMOR catalyst with a calculated Cu loading of 4 wt%.

[0078] 1.0 g of the above catalyst was loaded into a small fixed-bed reactor. Activation was performed at 350 °C and 1.2 MPa with hydrogen gas at a flow rate of 15 ml / min for 8 h. Catalytic performance was evaluated under the following conditions: reaction temperature 295 °C, reaction pressure 1.2 MPa, p-xylene mass hourly space velocity 1.0 h⁻¹, and hydrogen-to-oil molar ratio 4.8. The results are shown in Table 1. After 180 h of continuous operation, the p-xylene conversion decreased to 39.52%, and the yield of mesitylene was 29.16%.

[0079] Comparative Example 4 Take 20g of MOR molecular sieve raw powder and add it to 200g of mixed alkaline solution. The mixed alkaline solution contains 0.8g of tetraethylammonium hydroxide, 4g of ammonium carbonate, and the remainder is deionized water (i.e., 0.4wt% of tetraethylammonium hydroxide and 2wt% of ammonium carbonate). Stir at 80℃ for 3h, wash with deionized water until neutral, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain alkali-modified molecular sieve powder.

[0080] Take 6g of the above-mentioned alkali-modified molecular sieve powder, mix it with 2.57g of boehmite and 0.26g of guar gum powder, add 14.73g of 5wt% dilute nitric acid, knead, extrude into strips, air-dry naturally for 12h, dry at 110℃ for 6h, and calcine at 550℃ for 6h to obtain the molded carrier. Take 5g of the molded carrier and add 50g of 5wt% ammonium sulfate solution, exchange at 90℃ for 2h, exchange twice, wash with deionized water until neutral, dry at 120℃ for 12h, and calcine at 550℃ for 8h to obtain the hierarchical porous HMOR carrier.

[0081] Dissolve 0.6 g of copper sulfate in 20 g of deionized water, and add 1 g of 25% ammonia solution dropwise to obtain a copper-ammonia complex solution. Add 0.03 g of copper nitrate trihydrate, mix well, add 3 g of the above-mentioned hierarchical porous HMOR support, sonicate for 30 min, place in an oven at 45 °C for 3 h, raise the temperature to 80 °C and hold for 3 h, then raise the temperature to 110 °C and hold for 12 h. Repeat the above impregnation-drying steps once. Then raise the temperature to 170 °C at 2 °C / min and hold for 3 h, then raise the temperature to 650 °C at 4 °C / min and hold for 6 h to obtain the copper-supported catalyst precursor.

[0082] The copper-loaded catalyst precursor was mixed with 100g of 1.0wt% citric acid solution, stirred at 40℃ for 2h, washed until neutral, dried at 110℃ for 12h, and calcined at 550℃ for 6h to obtain the Cu / HMOR catalyst, with a calculated Cu loading of 4wt%.

[0083] Take 1.0 g of the above catalyst and load it into a small fixed-bed reactor. Activate the reactor for 8 h at 350 °C and 1.2 MPa by introducing hydrogen gas at a rate of 15 ml / min. The reaction temperature is 295 °C, the reaction pressure is 1.2 MPa, and the mass hourly space velocity (WHSV) of p-xylene is 1.0 h⁻¹. -1 Catalytic performance was evaluated under the condition of a hydrogen-to-oil molar ratio of 4.8, and the results are shown in Table 1.

[0084] Table 1. Evaluation results of catalytic isomerization in the examples and comparative examples. composition raw material Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Benzene, Toluene / % 0 0.15 0.19 0.08 0.12 0.11 0.06 0.05 Xylene / % 0.11 4.50 5.92 3.15 3.64 3.88 4.29 4.64 Trimethylbenzene / % Trimethylbenzene 98.84 54.09 50.26 57.50 53.84 51.08 47.87 49.14 Trimethylbenzene 0.23 26.35 29.54 30.27 30.99 31.36 32.25 33.64 Trimethylbenzene 0.27 3.50 4.08 4.62 4.73 4.95 5.31 6.84 o-methylethylbenzene / 0.34 0.12 0.11 0.13 0.14 0.16 0.17 0.18 <![CDATA[Other C9 + / %]]> 0.21 11.29 9.90 4.25 6.54 8.46 10.05 5.51 Trimethylbenzene conversion rate / % - 45.28 49.15 41.83 45.53 48.32 51.57 50.28 Trimethylbenzene yield / % - 26.43 29.65 30.39 31.12 31.50 32.40 33.80 Trimethylbenzene selectivity / % - 58.37 60.33 72.67 68.36 65.18 62.82 67.22

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for the hydroisomerization of pseudotrimethylbenzene to mesitylene, characterized in that, Includes the following steps: (1) Modification with organic base + inorganic base: MOR molecular sieve raw powder is mixed with an alkaline solution at a solid-liquid mass ratio of 1:(8~20), stirred at 50~120℃ for 1~6h, and then washed, filtered, dried and calcined to obtain alkali-modified MOR molecular sieve; the alkaline solution is a mixed solution of organic base and inorganic base, wherein the organic base is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethyleneimine and piperidine; and the inorganic base is one or more of ammonium carbonate, sodium hydroxide and potassium hydroxide. (2) Acid treatment: The alkali-modified MOR molecular sieve obtained in step (1) is kneaded with boehmite, guar gum powder and dilute nitric acid to obtain a slurry, which is then extruded into strips, dried and calcined, and mixed with an acid solution with a mass concentration of 0.3~6.0wt%. The mixture is stirred at 50~100℃ for 0.5~6h, washed, dried and calcined to obtain an acid-modified molding carrier; the acid-modified molding carrier is then subjected to ammonium exchange modification 1~3 times with one or more of ammonium sulfate, ammonium chloride and ammonium citrate, and washed, dried and calcined to obtain a multi-level porous HMOR carrier; the acid solution is one or more of nitric acid, hydrochloric acid, sulfuric acid and phosphoric acid; (3) Metal support: The hierarchical porous HMOR support obtained in step (2) is placed in a mixed solution of copper nitrate and copper ammonia complex, wherein the molar ratio of copper nitrate to copper ammonia complex is 1:(2~12). After being immersed in ultrasonic conditions for 15~60 min, it is dried. The above steps are repeated at least twice, and then calcined to obtain a copper-loaded catalyst precursor. (4) Weak acid washing: The copper-supported catalyst precursor obtained in step (3) is mixed with a weak acid solution with a mass concentration of 0.1~1.5wt%, and stirred at 20~70℃ for 0.2~2h. After washing, drying and calcining, the copper-supported modified mordenite catalyst Cu / HMOR is obtained; the weak acid is one or more of acetic acid, citric acid and oxalic acid.

2. The method for preparing the catalyst according to claim 1, characterized in that, The mass concentrations of organic and inorganic bases in the alkaline solution in step (1) are 0.2~1.0wt% and 0.5~3.0wt%, respectively; and / or, the stirring temperature in step (1) is 70~90℃ and the treatment time is 2~4h.

3. The method for preparing the catalyst according to claim 1, characterized in that, The roasting temperature in step (1) is 400~600℃ and the roasting time is 3~8h.

4. The method for preparing the catalyst according to claim 1, characterized in that, In step (2), the amount of boehmite added is 20-30 wt% of the slurry mass, the amount of guar gum added is 3-6 wt% of the slurry mass, and the mass concentration of dilute nitric acid is 4-6 wt%; and / or, the acid solution in step (2) is a nitric acid solution with a mass concentration of 2-3 wt%; and / or, the stirring temperature in step (2) is 60-80℃, and the processing time is 2-3 h.

5. The method for preparing the catalyst according to claim 1, characterized in that, The roasting temperature in step (2) is 400~600℃ and the roasting time is 3~8h.

6. The method for preparing the catalyst according to claim 1, characterized in that, In step (3), the molar ratio of copper nitrate to copper ammonia complex in the mixed solution is 1:(4~6).

7. The method for preparing the catalyst according to claim 1, characterized in that, The drying process described in step (3) adopts a three-stage temperature control step: the first stage: 30~60℃ for 2~5h; the second stage: 70~90℃ for 3~6h; the third stage: 100~120℃ for 8~12h; and / or, the roasting process adopts a two-stage temperature control step: the first stage: heating to 170~200℃ at 1~4℃ / min and holding for 2~5h; the second stage: heating to 550~650℃ at 3~6℃ / min and holding for 5~8h.

8. The method for preparing the catalyst according to claim 1, characterized in that, The weak acid mentioned in step (4) is citric acid with a mass concentration of 0.5~1.5wt%; and / or, the stirring temperature in step (4) is 35~45℃ and the processing time is 0.2~1h.

9. The method for preparing the catalyst according to claim 1, characterized in that, The Cu loading in the Cu / HMOR catalyst is 2-10 wt%.

10. The use of the catalyst according to claim 1 in the hydroisomerization of pseudotrimethylbenzene to produce mesitylene.

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