阅读说明：本技术 一种生产均四甲苯的催化剂的合成方法及应用 (Synthetic method and application of catalyst for producing durene ) 是由 王刃 王相珣 张伶超 徐连海 宋芳芳 于 2019-09-12 设计创作，主要内容包括：本发明提供一种生产均四甲苯的催化剂的合成方法及应用,以晶粒尺寸为210nm～300nm间可调的小晶粒ZSM-5分子筛做载体,再经过碱处理、铵交换、挤条成型、酸处理、金属盐溶液浸渍,焙烧得到生产均四甲苯催化剂,所合成的催化剂具有表面酸性增强、高表面积、高择形性、高活性、高稳定性的特点,应用于甲醇和二甲苯制备均四甲苯中,反应温度低,均四甲苯收率为30％～38.2％,均四甲苯在产物中的纯度能达到94％～97.1％。(The invention provides a synthetic method and application of a catalyst for producing durene, wherein a small crystal grain ZSM-5 molecular sieve with adjustable crystal grain size of 210-300 nm is used as a carrier, and the small crystal grain ZSM-5 molecular sieve is subjected to alkali treatment, ammonium exchange, extrusion molding, acid treatment, metal salt solution impregnation and roasting to obtain the catalyst for producing durene, the synthesized catalyst has the characteristics of enhanced surface acidity, high surface area, high shape selectivity, high activity and high stability, and is applied to the preparation of durene from methanol and xylene, the reaction temperature is low, the yield of the durene is 30-38.2%, and the purity of the durene in the product can reach 94-97.1%.)

1. A preparation method of a catalyst for producing durene is characterized by comprising the following steps:

s1, uniformly mixing a silicon source, an aluminum source, an alkali source, n-butylamine, deionized water and ZSM-5 seed crystals to form a mixed solution, crystallizing the mixed solution at 40-190 ℃ for 12-120 h, and washing, drying and roasting a solid product obtained by crystallization to obtain a ZSM-5 molecular sieve carrier;

s2, carrying out alkali treatment, ammonium exchange, extrusion molding, acid treatment and metal salt solution impregnation on the ZSM-5 molecular sieve carrier, and then roasting to obtain the durene catalyst;

OH in the step S1 Mixed liquid System (crystallization reaction System)^-:SiO₂:A1₂O₃The molar ratio of n-butylamine to water is 2-4:7-15:0.1-1:0.5-5: 300-1100.

2. The method according to claim 1, wherein step S1 is performed in the presence of a mixture system (S) (i.e., a mixture system of (i) and (ii) a catalyst for durene productionCrystallization reaction system) OH^-:SiO₂:A1₂O₃The molar ratio of n-butylamine to water is 2.3-3.5:10-13.5:1:2.5-5.5: 250-.

3. The method of claim 1, wherein the source of silicon is one or a mixture of tetraethyl orthosilicate, silica sol, and water glass; the aluminum source is one or more of aluminum sulfate, aluminum isopropoxide and sodium metaaluminate; the alkali source is at least one of sodium hydroxide and potassium hydroxide.

4. The method of claim 1, wherein the amount of seed crystals added in step S1 is 1-8% of the yield of durene-producing catalyst.

5. The method of claim 1, wherein the crystallization temperature in step S1 is 140 ℃ to 190 ℃ and the crystallization time is 12h to 120 h.

6. The method of claim 1, wherein the alkali treatment in step S2 is to impregnate the ZSM-5 molecular sieve support with an alkali solution at 60-90 ℃ for 15-200min, wherein the alkali solution is one or both of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 0.05-0.3 mol/L.

7. The method of claim 1, wherein the ammonium exchange in step S2 is performed by ion-exchanging the base-treated ZSM-5 molecular sieve support with ammonium nitrate at 60-90 ℃ for 30-200min, and the concentration of the ammonium nitrate solution is 0.05-0.3 mol/L.

8. The method according to claim 1, wherein the acid treatment in step S2 is to soak the ZSM-5 molecular sieve support subjected to ion exchange and extrusion molding with an acid solution at 60-80 ℃ for 1-5 hours, wherein the acid solution is one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, and acetic acid, and the concentration of the acid solution is 0.1-2.0 mol/L; in the step S2, the metal salt solution is copper nitrate, magnesium nitrate and zinc nitrate, and the mass fraction of the metal salt after impregnation is 0.01-0.05%.

9. A durene-producing catalyst prepared according to the process of claim 1, wherein: the catalyst comprises a ZSM-5 molecular sieve carrier and active metal, wherein the crystal grain size of the ZSM-5 molecular sieve carrier is 210 nm-300 nm, the active metal is one or more of zinc, iron, magnesium, calcium and rare earth elements, and the mass fraction of the active metal is 0.1-2.0%.

10. The application of the catalyst for producing durene according to claim 9, wherein methanol and xylene are used as raw materials, the methanol is fed into the reactor in a side-stream multistage feeding mode, the reaction temperature is 250-400 ℃, the pressure is 0.5-2.0 MPa, and the mass space velocity of the xylene is 0.2-2.0 h^-1The mass space velocity of the methanol is 0.2-1.0 h^-1The mixed hydrocarbon component rich in durene is processed by an oil-water separator, a liquefied gas removal tower and a product separation tower to obtain heavy aromatic hydrocarbon rich in durene, and the heavy aromatic hydrocarbon rich in durene is processed by a multi-stage freezing crystallization and centrifugal separation squeezing system to obtain solid durene; the feedstock may also be methanol and mixed aromatics containing xylenes.

Technical Field

The invention belongs to the technical field of durene catalyst materials, and relates to a synthesis method and application of a catalyst for producing durene.

Background

Durene (1,2,4, 5-tetramethylbenzene) is commonly known as durene, the English name is 1,2,4, 5-tetramethyl-bezene or durene, and the durene is an important organic chemical raw material and is mainly used for producing pyromellitic dianhydride (1,2,4, 5-benzoic dianhydride or pyromellitic anhydride, PMDA).

In recent years, the use of pyromellitic dianhydride has been expanding, and polyimide can be synthesized by reacting pyromellitic dianhydride with 4, 4-diaminodiphenyl ether. Polyimide is a novel synthetic material which is resistant to high temperature, low temperature, radiation and impact and has excellent electrical and mechanical properties, and has important applications which cannot be replaced by other engineering plastics in the aviation and electromechanical industries. With the increasing market usage of polyimide, durene is used as the main raw material for synthesizing polyimide, and the demand is increasing.

Many technologists at home and abroad explore a series of durene preparation processes and develop different process routes. Separation and synthesis methods can be broadly classified: the separation method comprises₁₀Rectifying heavy aromatic hydrocarbon fraction, freezing and crystallizing, and purifying by fractional crystallization; ethanol refining method; c₁₀Heavy aromatic fraction distillation, adsorption separation and the like. The synthesis method comprises the alkylation of trimethyl benzyl alcohol; chloromethylating trimethyl benzene; isomerizing and disproportionating trimethylbenzene; then carrying out hydrocracking to obtain durene and pseudocumene; synthesizing durene from methanol and pseudocumene on a shape-selective zeolite catalyst; tetramethylbenzene isomerization, and the like. But the process is not mature and does not form a certain industrial production scale.

In conclusion, durene has wide application and high added value, and is an important fine chemical raw material. Therefore, the method has potential and huge social and economic benefits by improving the quality of durene, increasing the yield of durene, developing a durene synthesis process route and a catalyst with high yield and high conversion rate; but also can meet the requirements of the aerospace industry of China on novel engineering materials, and has extremely important strategic significance on the economic and national defense construction of China.

Disclosure of Invention

In order to solve the technical problems, the invention provides a synthesis method and application of a catalyst for producing durene, and provides a high-efficiency catalyst with high reaction activity and good stability for a new synthesis process. The invention successfully adopts a cheap template agent to prepare the small-crystal-grain ZSM-5 molecular sieve carrier with high crystallinity, uniform size and adjustable crystal grain size between 210nm and 300nm, and the ZSM-5 catalyst for producing durene is obtained through a series of modifications. The catalyst can catalyze methanol and xylene or methanol and mixed aromatic hydrocarbon containing xylene to prepare durene, has good activity and stability in the synthesis reaction of catalyzing durene, and has good industrial application prospect.

The technical scheme of the invention is as follows:

a preparation method of a catalyst for producing durene comprises the following steps:

s1, uniformly mixing a silicon source, an aluminum source, an alkali source, n-butylamine, deionized water and ZSM-5 seed crystals to form a mixed solution, adding the mixed solution into a stirring kettle, adjusting the stirring speed to be 100r/min-400r/min, crystallizing the mixed solution at 40-190 ℃ for 12-120 h, washing, drying and roasting a solid product obtained by crystallization to obtain a ZSM-5 molecular sieve carrier;

s2, carrying out alkali treatment, ammonium exchange, extrusion molding, acid treatment, metal salt solution impregnation and roasting on the ZSM-5 molecular sieve carrier in the step S1 to obtain the durene catalyst;

OH in the step S1 Mixed liquid System (crystallization reaction System)^-:SiO₂:A1₂O₃The molar ratio of n-butylamine to water is 2-4:7-15:0.1-1:0.5-5: 300-1100.

Preferably OH in the mixed liquid system (crystallization reaction system) of step S1^-:SiO₂:A1₂O₃The molar ratio of n-butylamine to water is 2.3-3.5:10-13.5:1:2.5-5.5: 250-.

In step S1, the silicon source, the alkali source and the water are mixed uniformly, and then the silicon source, the n-butylamine and the ZSM-5 seed crystal are sequentially added and mixed uniformly to form a mixed solution.

In step S2, the ZSM-5 molecular sieve carrier is washed with water and dried before being subjected to alkali treatment.

The silicon source is one or a mixture of tetraethyl orthosilicate, silica sol and water glass; the aluminum source is one or more of aluminum sulfate, aluminum isopropoxide and sodium metaaluminate; the alkali source is at least one of sodium hydroxide and potassium hydroxide.

Preferably, the seed crystal is added in the step S1 in an amount of 1-8% of the yield of the durene-producing catalyst.

Preferably, the crystallization temperature in the step S1 is 140-190 ℃, and the crystallization time is 12-120 h.

In the step S2, the alkali treatment is to soak the ZSM-5 molecular sieve carrier with an alkali solution at 60-90 ℃ for 15-200min, wherein the alkali solution is one or two of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 0.05-0.3 mol/L.

In the step S2, the ammonium exchange is to carry out ion exchange on the ZSM-5 molecular sieve carrier treated by the alkali for 30-200min at the temperature of 60-90 ℃ by using ammonium nitrate, and the concentration of the ammonium nitrate solution is 0.05-0.3 mol/L.

In the step S2, the acid treatment is to soak the ZSM-5 molecular sieve carrier subjected to ion exchange and extrusion molding with an acid solution at 60-80 ℃ for 1-5h, wherein the acid solution is one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid and acetic acid, and the concentration of the acid solution is 0.1-2.0 mol/L.

In the step S2, the metal salt solution is one or more of copper nitrate, magnesium nitrate and zinc nitrate, and the mass fraction of the impregnated metal salt is 0.01-0.05%.

The invention also provides a catalyst for producing durene, which comprises a ZSM-5 molecular sieve carrier and active metal, wherein the grain size of the ZSM-5 molecular sieve carrier is 210 nm-300 nm, the active metal is one or more of zinc, iron, magnesium, calcium and rare earth elements, and the mass fraction of the active metal is 0.1-2.0%.

The invention also provides an application of the catalyst for producing durene, wherein methanol and dimethylbenzene are used as raw materials, the methanol enters a reactor in a side-line multistage feeding mode, the reaction temperature is 250-400 ℃, the pressure is 0.5-2.0 MPa, and the mass space velocity of the dimethylbenzene is 0.2-2.0 h^-1The mass space velocity of the methanol is 0.2-1.0 h^-1Strip ofConverting the mixture into a mixed hydrocarbon component rich in durene under a condition of conversion; the mixed hydrocarbon component rich in durene passes through an oil-water separator, a liquefied gas removal tower and a product separation tower (components with boiling points lower than that of durene are separated), heavy aromatic hydrocarbon rich in durene is obtained, and the heavy aromatic hydrocarbon rich in durene is subjected to multistage freezing crystallization and centrifugal separation squeezing systems to obtain solid durene; the feedstock may also be methanol and mixed aromatics containing xylenes.

The invention has the beneficial effects that: the invention adopts the means of adjusting the mixture ratio to synthesize the small crystal grain ZSM-5 molecular sieve carrier with the adjustable crystal grain size of 210 nm-300 nm, the activity of the catalyst can be increased by adjusting and controlling the crystal grain size, the acidity of the molecular sieve catalyst is improved by alkali treatment, ammonium exchange and acid treatment, strong acid is enhanced, then alkali metal is loaded, the shape selectivity of the catalyst can be improved, and the service life is prolonged. The ZSM-5 molecular sieve carrier with small crystal grains is synthesized by the mixture ratio of the materials, the crystal grains have small size, the surface area of the catalyst can be improved, and the reaction is more thorough. By synthesizing the molecular sieve with small crystal grains and subsequent modification treatment, the surface area of the catalyst is increased, the acidity and shape selectivity of the catalyst are enhanced, and the yield and purity of durene can be greatly improved. Still further, the alkali treatment aims to remove the aluminum element in the ZSM-5 molecular sieve carrier, so that the subsequent acid treatment is facilitated. The catalyst prepared by the invention is applied to the preparation of durene from methanol and xylene or methanol and mixed aromatic hydrocarbon containing xylene, the reaction temperature is low, the durene yield is 30-38.2 percent (calculated by the xylene), and the purity of the durene in the product can reach 97 percent after multi-stage cooling.

Drawings

FIG. 1 is a schematic diagram of a transmission electron microscope of a ZSM-5 molecular sieve support obtained in example 3 of the present invention;

FIG. 2 is a schematic scanning electron microscope of a ZSM-5 molecular sieve support obtained in example 3 of the present invention.

Detailed Description

Comparative example 1

0.30g of sodium metaaluminate, 0.52g of sodium hydroxide and 30g of deionized water are used as raw materialsUniformly mixing water, adding 10g of silica sol, uniformly mixing, adding 4.3g of ethylenediamine, uniformly mixing, adding 0.10g of ZSM-5 crystal seeds to form a mixed solution, adding the mixed solution into a stirring kettle, adjusting the stirring speed to 80r/min, heating to 170 ℃, crystallizing for 72 hours to obtain a ZSM-5 molecular sieve carrier, synthesizing the ZSM-5 molecular sieve carrier with the grain size of 400nm, taking 5g of the obtained ZSM-5 molecular sieve carrier, soaking for 2 hours at 80 ℃ by using a sodium hydroxide solution with the mass fraction of 0.5%, exchanging for 2 hours by using an ammonium nitrate solution with the concentration of 0.5M, and extruding and molding. Treating a ZSM-5 carrier formed by extruding strips for 4 hours at 40 ℃ by using a hydrofluoric acid solution with the concentration of 0.2M, soaking the ZSM-5 carrier for 24 hours by using zinc nitrate with the mass fraction of 0.05%, roasting the zinc nitrate at 550 ℃ for 6 hours to obtain a ZSM-5 catalyst, applying the catalyst to the reaction of methanol and dimethylbenzene, taking the methanol and the dimethylbenzene as raw materials, feeding the methanol into a reactor in a lateral line multi-section feeding mode, and feeding the methanol into the reactor at the reaction temperature of 400-420 ℃ and the mass airspeed of the dimethylbenzene of 0.5 hour^-1The mass space velocity of the methanol is 0.8h^-1The heavy aromatic hydrocarbons containing durene are converted into mixed hydrocarbon components containing durene, the mixed hydrocarbon components containing durene pass through an oil-water separator, a liquefied gas removal tower and a product separation tower to obtain heavy aromatic hydrocarbons containing durene, and the heavy aromatic hydrocarbons containing durene pass through a multi-stage freezing crystallization and centrifugal separation squeezing system to obtain solid durene; the yield of durene obtained was 30.8% and the purity in the product was 92.6%.

Comparative example 2

Uniformly mixing 0.48g of sodium metaaluminate, 0.21g of sodium hydroxide and 27g of deionized water serving as reaction raw materials, adding 10g of silica sol, uniformly mixing, adding 0.8g of n-butylamine, uniformly mixing, adding 0.06g of ZSM-5 seed crystal, uniformly mixing to form a mixed solution, adding the mixed solution into a stirring kettle, adjusting the stirring speed to 240r/min, heating to 170 ℃, crystallizing for 72 hours to obtain a ZSM-5 molecular sieve carrier, wherein the grain size of the ZSM-5 molecular sieve carrier is about 380nm, taking 5g of the obtained ZSM-5 molecular sieve carrier, soaking the ZSM-5 molecular sieve carrier by using a sodium hydroxide solution with the mass fraction of 0.5% at the temperature of 80 ℃ for 2 hours, exchanging for 2 hours by using an ammonium nitrate solution with the concentration of 0.5M, and extruding and forming. Treating extruded ZSM-5 with 0.2M hydrofluoric acid solution at 40 deg.C for 4 hr, soaking in 0.05% zinc nitrate solution for 24 hr, and calcining at 550 deg.C for 6 hr to obtain ZSM-5 catalystThe catalyst is applied to the reaction of methanol and xylene, the methanol and the xylene are used as raw materials, the methanol enters a reactor in a lateral line multi-section feeding mode, the reaction temperature is 370-390 ℃, and the mass space velocity of the xylene is 0.5h^-1The mass space velocity of the methanol is 0.8h^-1The heavy aromatic hydrocarbons containing durene are converted into mixed hydrocarbon components containing durene, the mixed hydrocarbon components containing durene pass through an oil-water separator, a liquefied gas removal tower and a product separation tower to obtain heavy aromatic hydrocarbons containing durene, and the heavy aromatic hydrocarbons containing durene pass through a multi-stage freezing crystallization and centrifugal separation squeezing system to obtain solid durene; the yield of durene obtained was 27.6% and the purity in the product was 91.3%.