CN118420430A - A method for preparing mesitylene by hydroisomerization of trimethylol - Google Patents

Abstract

The present invention relates to a method for preparing mesitylene by hydroisomerization of paratrimethylbenzene, which is characterized in that: in a fixed bed reactor, a raw material containing paratrimethylbenzene is subjected to hydroisomerization reaction by a catalyst containing Cu/HMOR in the presence of hydrogen to generate a product containing mesitylene. The preparation of the catalyst containing Cu/HMOR comprises the steps of treating the raw powder of MOR molecular sieve with a silicon-aluminum ratio of 10 to 30 with an organic base, an inorganic base, molding, ammonium exchange, metal Cu loading and activation treatment. The loading amount of Cu is 2 to 10 wt%. The catalyst prepared by the scheme of the present invention has excellent isomerization activity, and the yield and selectivity of mesitylene can reach 33.11% and 75.94%.

Description

A method for preparing mesitylene by hydroisomerization of trimethylol

Technical Field

The invention belongs to the technical field of preparation of mesitylene, and relates to a method for preparing mesitylene by hydroisomerization of paratrimethylol. Specifically, in a fixed bed reactor, raw materials containing paratrimethylol are subjected to isomerization reaction with a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper to prepare mesitylene.

Background technique

In recent years, the construction of a large number of aromatics joint units, ethylene units and the development of modern coal chemical industry have made the sources of heavy aromatics more diversified, and the amount of by-product heavy aromatics has increased day by day. How to effectively utilize this resource is of great significance to the development of the petrochemical industry and the development of the national economy and energy. C9 heavy aromatics are mainly a mixture of polyalkylbenzenes, and there are two main sources: one is the by-product fraction of steam cracking to produce ethylene, which accounts for about 10% to 20% of the total product of the ethylene unit; the other is the bottom oil of the xylene tower from the reforming unit of the refinery. Its composition is mainly composed of partial trimethylbenzene, mesitylene, and methyl ethylbenzene. Among them, mesitylene is widely used due to its high value and its unique properties, including the intermediates for the synthesis of various dyes such as trimesic acid and benzoic anhydride, as well as the production of antioxidants, high-efficiency wheat field herbicides, polyester resin curing agents, stabilizers, alkyd resin plasticizers, etc. In addition, mesitylene can also be used to produce 2,4,6-trimethylphenol as an anti-ultraviolet oxidation stabilizer for rubber, plastics, and liquid wax.

The production methods of mesitylene can be divided into two categories: synthesis method and direct separation and purification method of C9 aromatics. The synthesis method mainly includes the isomerization method of para-trimethylbenzene and the alkylation of para-trimethylbenzene to produce mesitylene and tetramethylbenzene; the separation and purification method includes extraction distillation, complex separation, molecular sieve adsorption separation, deep cold crystallization, extraction, alkylation separation, etc. At present, the production methods of mesitylene in China are mainly based on alkylation separation and para-trimethylbenzene isomerization. The alkylation separation method requires the consumption of olefins as alkylating agents (Chinese patent application CN1775714A). The isomerization method usually uses mixed C9 or para-trimethylbenzene produced by catalytic reforming as raw materials, and generates mesitylene through hydroisomerization or non-hydroisomerization reaction under gas phase or liquid phase conditions. The hydroisomerization technology effectively improves the catalyst's anti-coking ability under hydrogen conditions; the non-hydroisomerization technology has simple reaction operation and low equipment requirements.

Chinese patent CN115770611B discloses a method for preparing a catalyst for preparing mesitylene by isomerization of unsymmetrical trimethylbenzene, using a MCM-22 molecular sieve catalyst modified with three-step ammonium salt, unsymmetrical trimethylbenzene (95-99%) as a raw material, a reaction temperature of 260-300°C, a pressure of 1.0-3.0 MPa, and a mass space velocity of 0.6-1.4 h ^-1 . With nitrogen as a carrier gas and a nitrogen flow rate of 2-20 ml/min, the unsymmetrical trimethylbenzene conversion rate is 40.16%, the mesitylene selectivity is 64.09%, and the mesitylene yield is 25.74%.

Chen Yanjie of Tianjin University (Chen Yanjie. Research on the production process of mesitylene [D]. Tianjin University, 2004.) used M-2 composite mordenite catalyst, high-purity trimethylolbenzene as raw material, and under non-hydrogen conditions, at a reaction temperature of 300℃~320℃, a reaction pressure of 1.0~1.5MPa, and a volume space velocity of 1.5~2.0h ^-1 , the single-pass conversion rate of trimethylolbenzene was about 38%, the selectivity of trimethylolbenzene was 70%, and the yield of trimethylolbenzene was about 26.6%.

Wang Shenjiang of Tianjin University (Wang Shenjiang. Research on the process of synthesizing mesitylene by non-hydrogen isomerization [D]. Tianjin University, 2007.) used unisotrilene (98.66%) as raw material and M-2 composite mordenite treated by charcoal burning. Under the conditions of reaction temperature of 353℃, pressure of 3.2MPa and volume space velocity of 0.9h ^-1 , the one-way conversion rate of unisotrilene was 45.97%, the one-way yield of mesitylene was 20.69% and the selectivity was 47.05%.

Chinese patent CN116173963B discloses a method for preparing mesitylene from isomerized trimethylol. A nano _-Al2O3 - _NiO composite catalyst is prepared by using a nano-initiator. At a reaction temperature of 280°C, a mass space velocity of 5h ^-1 , and a reaction time of 2h under normal pressure, the conversion rate of trimethylol is as high as 99%, and the yield of mesitylene is as high as 97%. It is worth noting that the catalyst prepared by the patented technical solution has a trimethylol conversion rate of nearly 100% and a mesitylene yield of nearly 100%, which exceeds the reasonable range of chemical equilibrium. According to the thermodynamic equilibrium data of trimethylol (Ye Zhaojian, Ben Yuchang, Li Huimin, et al. Liquid phase isomerization of trimethylol to prepare mesitylene [J]. Petrochemicals, 1991 (08): 521-526), the equilibrium composition of trimethylol in the reaction system under normal pressure and 280°C is: trimethylol 61.53%, mesitylene 25.68%, and trimethylol 12.80%.

The above technical report uses non-hydrogen isomerization technology. The isomerization of trimethylol to mesitylene is an acid-catalyzed mechanism. Under non-hydrogen conditions, the catalyst is prone to carbon deposition and deactivation, making it difficult to achieve the needs of industrial continuous reaction operations. Therefore, the development of trimethylol hydroisomerization technology suitable for industrial application is still an important direction of people's attention.

Zhou Ting from Nanjing University of Technology (Zhou Ting, Chen Xiaorong, Chen Changlin. Isomerization of unsatisfactory trimethylbenzene over modified WO ₃ /ZrO ₂ catalyst [J]. Journal of Nanjing University of Technology (Natural Science Edition), 2008 (03): 21-25.) used WO ₃ /ZrO ₂ solid strong acid catalyst, loaded with Ni and doped with alkaline earth metals (Mg, Ca, Sr, Ba), first activated at 450℃ (air atmosphere) for 3h, then treated at 300℃ for 3h (hydrogen atmosphere) in a fixed bed reactor, at a reaction temperature of 270℃ and a volume space velocity of 1h ^-1 . The unsatisfactory trimethylbenzene conversion rate was 59.1%, the selectivity of mesitylene was only 31.6%, and the single-pass yield of mesitylene was 18.7%.

Chinese patent application CN111039741A discloses a method for isomerizing trimethylbenzene to prepare mesitylene. Two metals (Pt and Pd) of group VIII elements and a metal modification (Mo) of group VIB elements are used as active components, and a hydrogen-type EUO-type structure catalyst (containing a ten-membered ring straight-through channel) is used as a carrier. Using high-purity trimethylbenzene (96-99wt%) as a raw material, at 350-370°C, 0.3-0.6MPa, 2.5-3.5h ^-1 (WHSV), and a hydrogen-to-oil volume ratio of 500-700v/v, the trimethylbenzene conversion rate is 43.62%, the mesitylene selectivity is 55.73%, and the yield is 24.31%.

Chinese patent application CN115869994A discloses a method for preparing a Pd-Ni-Co/NaOH-Hβ catalyst. Using Pd-Ni/NaOH-Hβ catalyst, using a mixed C9 enriched solution (9.82-10.54% of unisex trimethylol, 37.49-39.84% of trimethylol and 49.62-50.91% of heavy components) as raw material, reaction temperature 290-310°C, pressure 1.3-1.8 MPa, mass space velocity 0.6-1.4 h ^-1 , hydrogen-to-oil ratio 8-12:1, the conversion rate of trimethylol is 89.18%, the total yield of unisex trimethylol and mesitylene is 64.50%, and the actual yield of mesitylene is not given.

Chinese patent application CN116786158A discloses a method for preparing a catalyst for catalyzing the production of mesitylene from unsymmetrical trimethylbenzene. A multi-level pore β zeolite molecular sieve is prepared by modification with NaOH solution, and the multi-level pore β and hydrogen-type mordenite molecular sieve form a composite molecular sieve catalyst, which is modified by two or more of the metals Ni, La, Zr, and W. Using unsymmetrical trimethylbenzene (purity 98%) as raw material, under the conditions of reaction temperature 260-300°C, pressure 1.2-1.4MPa, mass space velocity 0.8-1.3h ^-1 , hydrogen-oil ratio 500-800v/v, the unsymmetrical trimethylbenzene conversion rate is 47.74%, and the mesitylene selectivity and yield are 58.19% and 27.78% respectively.

Chinese patent CN102746091B discloses a method for producing BTX aromatics and trimethylbenzenes from heavy aromatics. The method uses hydrogen-type binderless ten-membered ring zeolite (ZSM-5, ZSM-11) loaded with 0.005-0.5% platinum and palladium as a catalyst, uses hydrogen and heavy aromatics as raw materials for hydrocracking treatment, and under the conditions of reaction temperature of 320-450°C, reaction pressure of 2.0-4.0MPa, mass space velocity of 10-4.0h ^-1 , and hydrogen/hydrocarbon raw material ratio of 3-10:1 in mole, the production of BTX aromatics can be increased and trimethylbenzene and trimethylbenzene can be separated and produced, wherein the content of xylene reaches 27.47% and the content of trimethylbenzene is only 5.26%.

Chinese patent CN1102360B discloses a method for preparing an alkyl aromatic hydrocarbon isomerization catalyst. A composite carrier of ZSM-5 zeolite and mordenite loaded with Group VIII noble metal element platinum is used as a catalyst. Using high-purity trimethylolbenzene (99.12 wt%) as a raw material, under the reaction conditions of 430°C, 0.8 MPa, 3.1 h ^-1 (volume space velocity), and a hydrogen-to-oil molar ratio of 1.5, the trimethylolbenzene conversion rate is 40.45%, the selectivity of trimethylolbenzene is 49.11%, and the yield is only 19.86%.

Feng Jianlin (Feng Jianlin, Zhao Kaipeng. Study on the isomerization performance of trimethylolene with high-silicon mordenite [J]. Chemical Industry Times, 2000 (06): 11-14.) from the Refinery Research Institute of Jinling Petrochemical Company used high-purity trimethylolene (＞99%) as raw material, water glass and aluminum salt, synthesized under the conditions of inorganic ammonia, and high-silicon mordenite with a silicon-aluminum ratio of 15-30 as catalyst. Under the conditions of 1.2 MPa, 320℃, volume space velocity of 1.0 h ^-1 and hydrogen-to-oil ratio (molar ratio) of 10, the gas phase isomerization reaction in the presence of hydrogen was carried out. The trimethylolene conversion rate was 47.9%, and the selectivity and single-pass yield of mesitylene were 51.6% and 24.7%.

Wang Yan from Tianjin University (Wang Yan, Wang Ming, Zhang Xubin, et al. Study on the isomerization performance of trimethylolene on Ni-Mo/HM [J]. Chemical Industry and Engineering, 2016, 33(01): 35-39.) prepared a mordenite catalyst loaded with Mo and Ni by an equal volume impregnation method. When the content of metal Ni in the mordenite catalyst was 5wt% and the content of metal Mo was 1.25wt%, under the conditions of 260℃, 1.2MPa, mass space velocity 1.0h ^-1 and hydrogen-to-oil ratio (molar ratio) 5, the conversion rate of trimethylolene was 49.17%, and the yield and selectivity of mesitylene were 23.10% and 46.98%, respectively.

The above report adopts the hydroisomerization technology, and improves the anti-coking ability of the catalyst under hydrogen conditions by loading precious metals (Pt, Pd) or non-precious metals (Mo, Ni, W) on acidic carriers. Generally speaking, supported metal catalysts can not only activate (dissociate) _H2 during the hydrogenation reaction, but also dissociate or isomerize other chemical bonds in the reactant molecules. However, the catalyst performance in the above report is not good, the selectivity of mesitylene is not higher than 60%, and the yield is not higher than 28%. Due to the low content of mesitylene in the product, separation is difficult, and the separation cost is still at a high level. Therefore, it is urgent to develop a mesitylene isomerization catalyst with high isomerization performance and can be applied to long-term stable industrial use, focusing on improving the isomerization selectivity of the catalyst to mesitylene, inhibiting the occurrence of side reactions, so as to obtain a higher mesitylene yield.

Summary of the invention

In view of the problems existing in the above-mentioned prior art, the present invention provides a method for isomerizing unsemanated trimethylolene to prepare mesitylene under hydrogen conditions, so as to achieve high selectivity and high yield production of mesitylene and reduce production costs.

The isomerization reaction mechanism of trimethylolbenzene is acid-catalyzed. Trimethylolbenzene and the catalyst form an active δ-complex through the donation and acceptance of protons. Due to the different stabilities of different isomers of the δ-complex, mutual transformation will occur. When the methyl group of trimethylolbenzene moves within the benzene ring position (within the molecule), an isomerization reaction occurs. In addition, under the action of a solid acid catalyst, trimethylolbenzene is also prone to side reactions such as disproportionation, alkyl transfer, and dealkylation. Therefore, it is necessary to improve the preparation method of the catalyst, design and regulate its structure and acid properties, in order to improve the isomerization performance and inhibit the occurrence of side reactions. The isomerization of trimethylolbenzene to produce mesitylene is a skeletal isomerization reaction of aromatic hydrocarbons. Molecular sieve catalysts are used, and their catalytic activity mainly depends on the relatively independent surface On the other hand, due to the large molecular size of trimethylol and mesitylene, in order to allow the reactant and product molecules to fully contact the acidic active center of the catalyst, a solid acid catalyst with larger pores and channels is required. Mordenite (MOR) has a unique pore structure and special acid center distribution, which makes it exhibit good catalytic performance in reactions such as aromatic alkylation, aromatic isomerization, toluene disproportionation and carbonylation.

MOR molecular sieve has a stable skeleton structure, but because the size of its twelve-membered ring pore (0.67nm×0.70nm) is comparable to the molecular size of trimethylolbenzene (0.7～0.8nm), the diffusion of reactant molecules in the pore is limited by the configuration diffusion effect. Usually, the solid acid catalyst is treated with alkali to remove part of the skeleton silicon, expand the pore opening of the molecular sieve or form secondary pores, and increase the mesoporous structure; at the same time, a large number of intracrystalline mesopores are generated, which improves the diffusion characteristics of the molecular sieve and effectively increases the diffusion rate of the reactant molecules. However, the inventors have found through a lot of research that when mordenite is treated with alkali, on the one hand, excessive desiliconization can easily destroy the skeleton structure of the molecular sieve; on the other hand, the amorphous Si and Al components removed after strong alkali treatment can easily block the pores. In addition, the desiliconization process may also increase the density and strength of the acid center of the molecular sieve, causing a significant increase in the rate of side reactions, so the conditions for alkali treatment of MOR need to be strictly controlled. Through in-depth research, the inventors found that under mild hydrothermal conditions, the use of organic bases to treat mordenite can produce a protective mechanism of "first desiliconization and then silicon replenishment", causing a certain degree of rearrangement of the MOR surface structure. That is, the organic base removes part of the non-framework silicon and framework silicon, and forms a silicon-rich layer on the surface of the molecular sieve through a recrystallization process; on this basis, a stronger inorganic base is used for treatment, and the tolerance of MOR is greatly improved. Not only can the pores be expanded and modified to obtain a stable multi-level pore MOR molecular sieve carrier, but the properties and strength of the surface acid center can also be adjusted, which is beneficial to the isomerization reaction of trimethylolbenzene. In addition, for metal bifunctional catalysts, especially at low metal dispersion, the diffusion of reactant molecules will be restricted during the catalytic isomerization reaction of aromatics. Since the catalytic reaction only occurs at the pore mouth, most of the active sites are not fully utilized. The new pores generated by alkali treatment and desiliconization can minimize this defect.

As is known to all, copper-supported catalysts are generally used for ammonia selective catalytic reduction, dimethyl ether carbonylation, and oil hydrogenation reactions with good performance, but there are few reports on the use of copper-supported catalysts for isomerization reactions of aromatics. The inventors found that the HMOR catalyst loaded with metallic copper exhibited excellent isomerization activity after activation and reduction, and the synergistic catalytic effect between the highly dispersed copper component and B acid after activation and reduction greatly improved the isomerization selectivity of the Cu/HMOR catalyst.

Usually, when preparing copper-loaded catalysts, acidic copper salt solutions such as copper nitrate solutions are often used as impregnation solutions. Impregnation in an acidic environment can easily cause partial skeleton dealumination of the mordenite carrier, resulting in an increase in L acid centers. For the isomerization reaction of trimethylbenzene, the isomerization reaction is a unimolecular reaction and requires an independent B acid center, and the synergistic effect of the B acid center and the L acid center will make the catalyst surface disproportionation reaction more active. Therefore, the present invention uses a mixed solution of copper nitrate and copper ammonia complex as a copper source impregnation solution to carry out copper loading. The ammonium ions in the copper ammonia complex provide a weak alkaline environment, and the metal ions are precipitated on the porous molecular sieve carrier in the form of basic salts, while protecting the molecular sieve structure. The copper species are uniformly dispersed on the catalyst surface. In the step of metal loading, the inventor adopts a method of step-by-step ultrasonic impregnation, three-stage program temperature control drying and two-stage program temperature roasting. Step-by-step ultrasonic impregnation of metal components is conducive to the uniform dispersion of Cu on the surface of the catalyst; the three-stage program control drying process can avoid excessively high temperature and excessive evaporation of water, so that the metal components aggregate to form large grains. Since the thermal decomposition temperature of copper nitrate is 170°C and the thermal decomposition temperature of copper ammine complex is 650°C, a two-stage programmed temperature rise calcination method is adopted to achieve two-step pyrolysis. First, the temperature is raised to about 170°C to make copper nitrate decompose preferentially and evenly distribute on the catalyst surface. Since the copper ammine ion [Cu(NH ₃ ) ₄ ] ²⁺ in the copper ammine complex has a large steric hindrance effect and there is a strong interaction between ammonium ions and molecular sieves, it is pyrolyzed in the second stage, which can avoid the direct temperature rise calcination causing a large amount of copper components to be thermally transferred and form clusters.

In addition, the inventors also found that since microwave heating technology not only has the advantages of fast heating speed, high efficiency, energy saving and uniform heating, metal ion impregnation under microwave heating conditions is beneficial to the migration and dispersion of copper salt components on the catalyst surface, and the obtained bifunctional catalyst has better performance.

The technical solution of the present invention is as follows:

The invention provides a method for preparing mesitylene by hydroisomerization of paratrimethylbenzene. The raw material containing paratrimethylbenzene is passed through a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper in the presence of hydrogen to undergo an isomerization reaction to generate a product containing mesitylene.

The preparation method of the Cu/HMOR comprises the following steps: the multi-level porous HMOR is obtained by loading metal Cu; the loading amount of Cu in the Cu/HMOR is 2-10 wt%.

The multi-level pore HMOR is obtained by using MOR molecular sieve raw powder with a silicon-aluminum ratio of 10 to 30 through organic base modification, inorganic base modification, molding, and ammonium exchange.

The preparation of the above-mentioned Cu/HMOR-containing catalyst mainly includes the following steps:

(1) Organic base modification: The MOR molecular sieve raw powder is mixed with an organic base solution with a mass concentration of 0.5-4.0 wt% at a solid-liquid mass ratio of 1: (10-15), placed in a hydrothermal kettle, stirred at 70-110° C. for 1-5 h, washed, filtered, dried, and calcined at 400-550° C. for 3-8 h to obtain an organic base-modified MOR molecular sieve; the organic base solution is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethyleneimine and piperidine solution;

(2) Inorganic base modification: The organic base-modified MOR molecular sieve is added to an inorganic base sodium hydroxide solution with a mass concentration of 0.5-5.0 wt% at a solid-liquid mass ratio of 1: (10-15), stirred at 60-90°C for 1-3 h, washed, filtered, dried, and calcined at 350-600°C for 3-8 h to obtain a two-step base-modified multi-level pore MOR molecular sieve;

(3) Forming and ammonium exchange: The two-step alkali-modified multi-level pore MOR molecular sieve is kneaded with boehmite, sesbania powder and dilute nitric acid to obtain a slurry, which is extruded into strips with a diameter of 3 to 6 mm, and then subjected to ammonium exchange modification with one or more of ammonium sulfate, ammonium chloride and ammonium citrate for 1 to 3 times after drying and calcining, and then washed, dried and calcined to obtain a multi-level pore HMOR carrier;

(4) Metal loading: placing the multi-level porous HMOR carrier in a mixed solution of copper nitrate and copper ammine complex, wherein the molar ratio of copper nitrate:copper ammine complex is 1:(2.3-14), and impregnating it under ultrasonic conditions for 20-60 minutes, and then controlling the drying process by programmed temperature rise; repeating the above steps, after at least two ultrasonic impregnations and drying, controlling the calcination process by programmed temperature rise conditions, to obtain a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper.

In step (3), the amount of boehmite added is 10-40wt% of the slurry mass; the amount of sesbania powder added is 1-10wt% of the slurry mass; the mass concentration of dilute nitric acid is 2-8wt%. The mass ratio of the two-step alkali-modified multi-level pore MOR molecular sieve, boehmite and sesbania powder to nitric acid is 1:(1-2).

In the mixed solution of copper nitrate and copper ammonia complex in step (4), the molar ratio of copper nitrate to copper ammonia complex is 1:(3-8).

The drying process described in step (4) adopts three-stage programmed temperature control steps: the first stage: 30-60°C maintained for 2-4 hours; the second stage: 70-90°C maintained for 3-6 hours; the third stage: 100-120°C maintained for 8-12 hours.

The calcination process described in step (4) adopts two stages of programmed temperature control steps: the first stage: heating to 170-200°C at 1-4°C/min and maintaining for 2-5h; the second stage: heating to 550-650°C at 3-6°C/min and maintaining for 5-8h.

In the above step (4), the impregnation under ultrasonic conditions is replaced by impregnation under microwave heating, and the multi-level porous HMOR impregnated with the mixed solution of copper nitrate and copper ammine complex is treated under microwave power of 400-1000W for 3-10 minutes.

The preferred loading amount of Cu in the above Cu/HMOR is 2 to 6 wt %.

The method for catalytically hydroisomerizing trimethylol to produce mesitylene comprises pumping trimethylol as a raw material into a fixed bed reactor filled with a catalyst of multi-level porous mordenite Cu/HMOR containing copper and porcelain balls for reaction, with hydrogen as the reaction atmosphere.

The catalyst containing copper-loaded hierarchical mordenite Cu/HMOR is activated and reduced by hydrogen, and the raw material containing mesitylene is isomerized to produce a product containing mesitylene at a reaction temperature of 265-305°C, a pressure of 0.6-1.6 MPa, a mass space velocity of mesitylene of 0.6-1.4 h ^-1 , and a hydrogen-to-oil ratio of 4-10.

The invention has the following advantages: using a catalyst containing copper-loaded multi-level mordenite Cu/HMOR to catalyze the hydroisomerization reaction of trimethylolbenzene, the yield of trimethylolbenzene reaches 33.11% and the selectivity of trimethylolbenzene reaches 75.94% at a relatively low reaction temperature. When trimethylolbenzene is hydroisomerized to produce trimethylolbenzene, the catalyst prepared by the invention has strong anti-coking ability, thus having stable activity and long service life, and can meet the needs of industrialized continuous reaction production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an XRD diagram of a comparative example and an embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the embodiments given here are only used to explain the present invention patent, and are not used to limit the scope of the present invention patent.

1. Calculation of catalytic performance indicators

The hydroisomerization reaction of trimethylolbenzene is carried out on a small fixed bed device, and the reactant composition is 98.84wt% high-purity trimethylolbenzene. The calculation formulas for each performance index are:

Example 1

Take 15g of MOR molecular sieve powder, add 150g of 2.4wt% tetraethylammonium hydroxide solution, mix, place in a hydrothermal kettle, stir at 90℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and roast at 550℃ for 6h to obtain organic base modified MOR molecular sieve. Take 10g of organic base modified MOR molecular sieve, add 100g of 3.2wt% sodium hydroxide solution, mix, stir at 80℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and roast at 550℃ for 6h to obtain two-step base modified multi-level pore MOR molecular sieve.

6g of two-step alkali-modified multi-level porous MOR molecular sieve was kneaded with 2.57g of boehmite, 0.26g of sesbania powder, and 14.73g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain a multi-level porous MOR carrier. 5g of the multi-level porous MOR carrier was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain a multi-level porous HMOR carrier, which was crushed into particles of 20-40 mesh.

Take 0.6g of copper sulfate and dissolve it in 20g of deionized water, and add 1g of 25% ammonia water to the solution to obtain a copper ammonia complex solution. Take 0.03g of copper nitrate trihydrate and add it to 2.16g of copper ammonia complex solution and mix it evenly. Add 3g of two-step alkali-modified multi-level porous HMOR carrier for ultrasonic impregnation for 30min. Put the obtained multi-level porous HMOR carrier impregnated in the mixed solution of copper nitrate and copper ammonia complex into a 45℃ oven for 3h, then heat it to 80℃ for 3h, heat it to 110℃, and keep it for 12h, repeat twice. Then put it into a muffle furnace and heat it to 170℃ at 2℃/min, keep it for 3h; then heat it to 650℃ at 4℃/min and keep it for 6h to obtain a catalyst containing Cu/HMOR.

1.0 g of catalyst was loaded into a small fixed bed reactor. 15 ml/min hydrogen was introduced at 350°C and 1.2 MPa for activation for 8 h. The catalytic performance was evaluated at a reaction temperature of 295°C, a reaction pressure of 1.2 MPa, a mass space velocity of trimethylol of 1.0 h ^-1 , and a hydrogen-to-oil molar ratio of 4.8. The results are shown in Table 2.

Example 2

Take 15g of MOR molecular sieve powder, add 150g of 3.2wt% tetramethylammonium hydroxide solution, mix, place in a hydrothermal kettle, stir at 90℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain organic base modified MOR molecular sieve. Take 10g of organic base modified MOR molecular sieve, add 100g of 0.8wt% sodium hydroxide solution, mix, stir at 80℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain two-step base modified multi-level pore MOR molecular sieve.

6g of two-step alkali-modified multi-level porous MOR molecular sieve was kneaded with 2.57g of boehmite, 0.26g of sesbania powder, and 14.73g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain a multi-level porous MOR carrier. 5g of the multi-level porous MOR carrier was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain a multi-level porous HMOR carrier, which was crushed into particles of 20-40 mesh.

Take 1.8g of copper sulfate and dissolve it in 20g of deionized water, and add 3g of 25% ammonia water to the solution to obtain a copper ammonia complex solution. Take 0.09g of copper nitrate trihydrate and add it to 2.48g of copper ammonia complex solution and mix it evenly. Add 3g of two-step alkali-modified multi-level porous HMOR carrier and ultrasonically impregnate it for 30min. Put the obtained multi-level porous HMOR carrier impregnated in the mixed solution of copper nitrate and copper ammonia complex into a 45℃ oven for 3h, then heat it to 80℃ for 3h, heat it to 110℃, and keep it for 12h, repeat twice. Then put it into a muffle furnace and heat it to 170℃ at 2℃/min, keep it for 3h; then heat it to 650℃ at 4℃/min and keep it for 6h to obtain a catalyst containing Cu/HMOR.

1.0 g of catalyst was loaded into a small fixed bed reactor. The catalytic performance was evaluated at 350°C, 1.2 MPa, 15 ml/min hydrogen for activation for 8 h, reaction temperature 295°C, reaction pressure 1.2 MPa, unsymmetrical trimethylol mass space velocity 1.0 h ^-1 , hydrogen to oil molar ratio 4.8. The results are shown in Table 2.

Example 3

Take 15g of MOR molecular sieve powder, add 150g of 2.4wt% tetraethylammonium hydroxide solution, mix, place in a hydrothermal kettle, stir at 90℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain organic base modified MOR molecular sieve. Take 10g of organic base modified MOR molecular sieve, add 100g of 2.4wt% sodium hydroxide solution, mix, stir at 80℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain two-step base modified multi-level pore MOR molecular sieve.

6g of two-step alkali-modified multi-level porous MOR molecular sieve was kneaded with 2.57g of boehmite, 0.26g of sesbania powder, and 14.73g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain a multi-level porous MOR carrier. 5g of the multi-level porous MOR carrier was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain a multi-level porous HMOR carrier, which was crushed into particles of 20-40 mesh.

Take 1.2g of copper sulfate and dissolve it in 20g of deionized water, and add 2g of 25% ammonia water to the solution to obtain a copper ammonia complex solution. Take 0.06g of copper nitrate trihydrate and add it to 2.32g of copper ammonia complex solution and mix it evenly. Add 3g of two-step alkali-modified multi-level porous HMOR carrier for ultrasonic impregnation for 30min, and put the obtained multi-level porous HMOR carrier impregnated in the mixed solution of copper nitrate and copper ammonia complex into a 45℃ oven for 3h, then heat it to 80℃ for 3h, heat it to 110℃, and keep it for 12h, repeat twice. Then put it into a muffle furnace and heat it to 170℃ at 2℃/min, keep it for 3h; then heat it to 650℃ at 4℃/min and keep it for 6h to obtain a catalyst containing Cu/HMOR.

1.0 g of catalyst was loaded into a small fixed bed reactor. 15 ml/min hydrogen was introduced at 350°C and 1.2 MPa for activation for 8 h. The catalytic performance was evaluated at a reaction temperature of 295°C, a reaction pressure of 1.2 MPa, a mass space velocity of trimethylol of 1.0 h ^-1 , and a hydrogen-to-oil molar ratio of 4.8. The results are shown in Table 2.

Example 4

Take 15g of MOR molecular sieve powder, add 150g of 0.6wt% tetraethylammonium hydroxide solution, mix, place in a hydrothermal kettle, stir at 90℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain organic base modified MOR molecular sieve. Take 10g of organic base modified MOR molecular sieve, add 100g of 1.6wt% sodium hydroxide solution, mix, stir at 80℃ for 2h, wash with deionized water to neutrality, filter, dry at 110℃ for 12h, and calcine at 550℃ for 6h to obtain two-step base modified multi-level pore MOR molecular sieve.

6g of two-step alkali-modified multi-level porous MOR molecular sieve was kneaded with 2.57g of boehmite, 0.26g of sesbania powder, and 14.73g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain a multi-level porous MOR carrier. 5g of the multi-level porous MOR carrier was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain a multi-level porous HMOR carrier, which was crushed into particles of 20-40 mesh.

Take 1.2g of copper sulfate and dissolve it in 20g of deionized water, and add 2g of ammonia water with a mass fraction of 25% to the solution to obtain a copper ammonia complex solution. Take 0.06g of copper nitrate trihydrate and add it to 2.32g of copper ammonia complex solution and mix it evenly. Add 3g of two-step alkali-modified multi-level porous HMOR carrier and immerse it for 6min under the heating condition of microwave power of 600W. The drying process is the same as Example 3 and repeated twice. Then put it into a muffle furnace and heat it to 170℃ at 2℃/min and keep it for 3h; then heat it to 650℃ at 4℃/min and keep it for 6h to obtain a catalyst containing Cu/HMOR. As shown in Figure 1XRD, the Cu species in the catalyst prepared by mixing copper nitrate and copper ammonia complex and impregnating it multiple times is highly dispersed, which has obvious advantages over Comparative Examples 2 and 3; the characterization results of its texture properties are shown in Table 1.

1.0g of catalyst was taken and loaded into a small fixed bed reactor. 15ml/min hydrogen was introduced at 350℃ and 1.2MPa for activation for 8h. The catalytic performance was evaluated under the conditions of reaction temperature of 295℃, reaction pressure of 1.2MPa, mass space velocity of mesitylene of 1.0h ^-1 , and hydrogen-oil molar ratio of 4.8. The results are shown in Table 2. After a long operation of 200h, the selectivity and yield of mesitylene were still as high as 75.67% and 30.84% respectively, showing excellent catalytic stability.

Comparative Example 1

10g of MOR molecular sieve raw powder was kneaded with 4.29g of boehmite, 0.44g of sesbania powder, and 24.55g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain MOR molecular sieve. 5g of MOR molecular sieve was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain HMOR catalyst, which was broken into 20-40 mesh particles. The characterization results of its texture properties are shown in Table 1.

1.0 g of the catalyst was loaded into a small fixed bed reactor. The catalytic performance was evaluated under the conditions of reaction temperature of 295°C, reaction pressure of 1.2 MPa, mass space velocity of trimethylol 1.0 h ^-1 , and hydrogen to oil molar ratio of 4.8. The results are shown in Table 2.

Comparative Example 2

Take 10g of MOR molecular sieve powder, knead it with 4.29g of boehmite, 0.44g of sesbania powder, and 24.55g of dilute nitric acid with a concentration of 5wt%, and then extrude it into strips, dry it in the shade for 12h, dry it at 110℃ for 6h, and calcine it at 550℃ for 6h to obtain MOR carrier. Take 5g of MOR carrier and add 50g of 0.4mol/L ammonium sulfate solution, exchange it at 90℃ for 2h, exchange it twice, wash it with deionized water to neutrality, dry it at 120℃ for 12h, and calcine it at 550℃ for 8h to obtain HMOR carrier, which is crushed into 20-40 mesh particles.

0.92 g of copper nitrate trihydrate was dissolved in 2.27 g of water, 3.0 g of HMOR carrier was added and ultrasonically impregnated for 30 min, the HMOR carrier impregnated in the copper nitrate solution was placed in a 45 ° C oven for 3 h, then heated to 80 ° C for 3 h, heated to 110 ° C for 12 h, and then placed in a muffle furnace and heated to 550 ° C at 4 ° C/min for calcination for 6 h to obtain a catalyst containing Cu/HMOR.

1.0 g of catalyst was loaded into a small fixed bed reactor. The catalytic performance was evaluated at 350°C, 1.2 MPa, 15 ml/min hydrogen for activation for 8 h, reaction temperature 295°C, reaction pressure 1.2 MPa, unsymmetrical trimethylol mass space velocity 1.0 h ^-1 , hydrogen to oil molar ratio 4.8. The results are shown in Table 2.

Comparative Example 3

Take 10g of MOR molecular sieve raw powder, add it into 100g of 2.4wt% sodium hydroxide solution, stir it at 80℃ for 2h, wash it with deionized water until it is neutral, filter it, dry it at 110℃ for 12h, and calcine it at 550℃ for 6h to obtain the inorganic base modified MOR molecular sieve.

6g of MOR molecular sieve modified with inorganic base was kneaded with 2.57g of boehmite, 0.26g of sesbania powder, and 14.73g of dilute nitric acid with a concentration of 5wt%, and then extruded into strips, naturally dried in the shade for 12h, dried at 110℃ for 6h, and calcined at 550℃ for 6h to obtain a MOR carrier. 5g of MOR carrier was added with 50g of 0.4mol/L ammonium sulfate solution, exchanged at 90℃ for 2h, exchanged twice, washed with deionized water to neutrality, dried at 120℃ for 12h, and calcined at 550℃ for 8h to obtain a HMOR carrier, which was crushed into 20-40 mesh particles. The characterization results of its texture properties are shown in Table 1.

0.46 g of copper nitrate trihydrate was dissolved in 2.27 g of water, 3.0 g of HMOR carrier was added and ultrasonically impregnated for 30 min, the HMOR carrier impregnated in the copper nitrate solution was placed in a 45 ° C oven for 3 h, then heated to 80 ° C for 3 h, heated to 110 ° C for 12 h, and then placed in a muffle furnace and heated to 550 ° C at 4 ° C/min for calcination for 6 h to obtain a catalyst containing Cu/HMOR.

1.0 g of catalyst was loaded into a small fixed bed reactor. The catalytic performance was evaluated at 350°C, 1.2 MPa, 15 ml/min hydrogen for activation for 8 h, reaction temperature 295°C, reaction pressure 1.2 MPa, unsymmetrical trimethylol mass space velocity 1.0 h ^-1 , hydrogen to oil molar ratio 4.8. The results are shown in Table 2.

Table 1 Texture properties of comparative examples and examples

Table 2 Catalytic isomerization evaluation results of Examples and Comparative Examples

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

Claims (10)

1. A method for preparing mesitylene by hydroisomerization of paratrimethylbenzene, characterized in that a raw material containing paratrimethylbenzene is passed through a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper in the presence of hydrogen to undergo an isomerization reaction to generate a product containing mesitylene. 2. The method according to claim 1, wherein the preparation method of Cu/HMOR comprises using HMOR with multi-level pores to load metal Cu, and the loading amount of Cu in Cu/HMOR is 2-10wt%. 3. The method according to claim 1 or 2, characterized in that the preparation method of the catalyst containing Cu/HMOR adopts the following steps: (1) Organic base modification: The MOR molecular sieve raw powder is mixed with an organic base solution with a mass concentration of 0.5-4.0 wt% at a solid-liquid mass ratio of 1: (10-15), placed in a hydrothermal kettle, stirred at 70-110° C. for 1-5 h, washed, filtered, dried, and calcined at 400-550° C. for 3-8 h to obtain an organic base-modified MOR molecular sieve; the organic base solution is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethyleneimine and piperidine solution; (2) Inorganic base modification: The organic base-modified MOR molecular sieve is added to an inorganic base sodium hydroxide solution with a mass concentration of 0.5-5.0 wt% at a solid-liquid mass ratio of 1: (10-15), stirred at 60-90°C for 1-3 h, washed, filtered, dried, and calcined at 350-600°C for 3-8 h to obtain a two-step base-modified multi-level pore MOR molecular sieve; (3) Forming and ammonium exchange: The two-step alkali-modified multi-level pore MOR molecular sieve is kneaded with boehmite, sesbania powder and dilute nitric acid to obtain a slurry, which is extruded into strips with a diameter of 3 to 6 mm, and then subjected to ammonium exchange modification with one or more of ammonium sulfate, ammonium chloride and ammonium citrate for 1 to 3 times after drying and calcining, and then washed, dried and calcined to obtain a multi-level pore HMOR carrier; (4) Metal loading: placing the multi-level porous HMOR carrier in a mixed solution of copper nitrate and copper ammine complex, wherein the molar ratio of copper nitrate:copper ammine complex is 1:(2.3-14), and impregnating it under ultrasonic conditions for 20-60 minutes, and then controlling the drying process by programmed temperature rise; repeating the above steps, after at least two ultrasonic impregnations and drying, controlling the calcination process by programmed temperature rise conditions, to obtain a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper. 4. The method according to claim 3, characterized in that: the amount of boehmite added in step (3) is 10-40wt% of the slurry mass; the amount of sesbania powder added is 1-10wt% of the slurry mass; the mass concentration of dilute nitric acid is 2-8wt%; the mass ratio of the two-step alkali-modified multi-level pore MOR molecular sieve, boehmite and sesbania powder to nitric acid is 1:(1-2). 5. The method according to claim 3, characterized in that: in the mixed solution of copper nitrate and copper ammonia complex in step (4), the molar ratio of copper nitrate:copper ammonia complex is 1:(3-8). 6. The method as claimed in claim 3 is characterized in that: the drying process described in step (4) adopts three-stage programmed temperature control steps: the first stage: 30-60°C maintained for 2-4 hours; the second stage: 70-90°C maintained for 3-6 hours; the third stage: 100-120°C maintained for 8-12 hours. 7. The method as claimed in claim 3 is characterized in that: the roasting process described in step (4) adopts two stages of programmed temperature control steps: the first stage: heating to 170-200°C at 1-4°C/min and maintaining for 2-5h; the second stage: heating to 550-650°C at 3-6°C/min and maintaining for 5-8h. 8. The method according to claim 3, characterized in that: the impregnation under ultrasonic conditions in step (4) is replaced by impregnation under microwave heating, and the multi-level porous HMOR impregnated with a mixed solution of copper nitrate and copper ammine complex is treated under a microwave power of 400 to 1000 W for a treatment time of 3 to 10 minutes. 9. The method according to claim 2, characterized in that the loading amount of Cu in the Cu/HMOR is 2-6 wt%. 10. The method according to claim 1, characterized in that: a catalyst containing multi-level porous mordenite Cu/HMOR loaded with copper is activated and reduced by hydrogen, and a raw material containing trimethylol is isomerized to generate a product containing mesitylene at a reaction temperature of 265-305°C, a pressure of 0.6-1.6 MPa, a mass space velocity of trimethylol of 0.6-1.4 h ^-1 , and a hydrogen-to-oil ratio of 4-10.