阅读说明：本技术 一种用于苯与甲醇烷基化的纳米zsm-5催化剂及其制备方法 (Nano ZSM-5 catalyst for alkylation of benzene and methanol and preparation method thereof ) 是由 李建伟 张艳君 郭丹 张佳瑾 陈标华 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种苯与甲醇烷基化的改性分子筛催化剂,该方法以正硅酸乙酯(TEOS)、异丙醇铝(AIP)为硅源、铝源,以四丙基氢氧化铵(TPAOH)为模板剂,γ-氨丙基三乙氧基硅烷(APTES)为硅烷偶联剂,制备纳米分子筛催化剂,制得催化剂硅铝比(nSiO<Sub>2</Sub>/Al<Sub>2</Sub>O<Sub>3</Sub>)为50～200,分别负载镍、磷的氧化物为活性组分改性剂,经过浸渍、烘干、焙烧,在苯、甲醇烷基化制甲苯、对二甲苯的反应中,苯的单程转化率可达59％以上,甲苯和二甲苯选择性可达95％以上,消除了副产物丙苯,并大大减少乙苯、甲乙苯等副产物的含量,该催化剂具有活性好,择形选择性高等特点。(The invention discloses a modified molecular sieve catalyst for alkylation of benzene and methanol, which is prepared by taking Tetraethoxysilane (TEOS) and Aluminum Isopropoxide (AIP) as a silicon source and an aluminum source, tetrapropylammonium hydroxide (TPAOH) as a template agent and gamma-Aminopropyltriethoxysilane (APTES) as a silane coupling agent to prepare a nano molecular sieve catalyst, wherein the catalyst has a silicon-aluminum ratio (nSiO) 2 /Al 2 O 3 ) 50-200 of nickel and phosphorus respectively loaded oxide as active componentThe catalyst has the characteristics of good activity, high shape selective selectivity and the like, and can be used for preparing toluene and p-xylene through dipping, drying and roasting, wherein the conversion per pass of benzene can reach more than 59%, and the selectivity of toluene and xylene can reach more than 95%, so that a byproduct, namely propyl benzene is eliminated, and the content of byproducts, namely ethylbenzene, methyl ethylbenzene and the like is greatly reduced.)

1. A modified nanometer ZSM-5 molecular sieve catalyst is characterized in that: taking nano ZSM-5 as a matrix, the silicon-aluminum ratio (nSiO) of the ZSM-5₂/Al₂O₃) 50-200, the particle size is 100-300nm, chemical modification of Ni and P elements is adopted, the content of Ni element is 0.2-2% by simple substance based on the catalyst, and the P element is P₂O₅The content is 3-15%.

2. The catalyst of claim 1, wherein: the preparation method of the nano ZSM-5 molecular sieve raw powder comprises the steps of taking Tetraethoxysilane (TEOS) and Aluminum Isopropoxide (AIP) as a silicon source and an aluminum source, taking tetrapropylammonium hydroxide (TPAOH) as a template agent, and taking gamma-ammoniaPropyltriethoxysilane (APTES) as silane coupling agent, according to n (SiO)₂)：n(Al₂O₃)：n(TPAOH)：n(APTES)：n(NaOH)：n(H₂O) ═ 1: 0.005-0.2: 0.15-0.4: x: 0.01: 25(x is 0, 0.05, 0.1) preparing materials.

3. The catalyst of claim 2, wherein: the preparation method of the nano ZSM-5 molecular sieve comprises the following steps:

according to the raw material proportion, firstly mixing the template agent M with part of water, uniformly stirring, adding NaOH, uniformly mixing, continuously adding an aluminum source after stirring and dissolving, and stirring until the raw materials are completely hydrolyzed to obtain a solution A;

dropwise adding a silicon source into the solution A, and after the hydrolysis is completed, continuously refluxing the obtained solution for 10-24h in a three-neck flask in a water bath at the temperature of 80-90 ℃ to obtain a seed crystal solution; adding the silane coupling agent Q into the seed crystal solution, continuously stirring for 4-8h under the water bath condition after rinsing, transferring the obtained material into a high-pressure hydrothermal synthesis kettle with a polytetrafluoroethylene lining, and crystallizing for 3-5 days at the temperature of 180 ℃ under 160-;

standing the crystallized product, cooling to room temperature, taking out the crystallized product, washing with deionized water until the pH value is 7, performing centrifugal separation, taking the product, drying at the temperature of 100 ℃ and 120 ℃, and roasting at the temperature of 550 ℃ for 4 hours to obtain the Na-type nano ZSM-5 molecular sieve; and carrying out ion exchange on the Na-type nano ZSM-5 molecular sieve and 0.8mol/L ammonium nitrate solution to obtain the H-type nano ZSM-5 molecular sieve.

4. A catalyst according to claim 1, 2 or 3, characterized in that: the catalyst modification steps are as follows: h-type nano ZSM-5 with certain solubility of Ni (NO)₃Solution and/or (NH)₄)₂HPO₄Soaking the solution in the same volume so that the content of Ni element is calculated as simple substance, and the content of P element is calculated as P₂O₅The content is 3-15%, after being evenly stirred, the nano ZSM-5 molecular sieve is soaked for 24 hours, then dried for 1 hour at the temperature of 60 ℃, further dried for 12 hours at the temperature of 120 ℃, and then roasted for 4 hours at the temperature of 550 ℃ in the air atmosphere, thus obtaining the Ni and/or P modified nano ZSM-5 molecular sieve.

5. A catalyst according to claim 1, 2 or 3, characterized in that: the crystal grains of the nano ZSM-5 are spherical under an electron microscope, and are agglomerated into 200-300nm spherical particles by 20-30nm round spheres, and the particles are uniform and dispersed to reach the nano size.

6. The catalyst of claim 4, wherein the Ni modified nano ZSM-5 molecular sieve catalyst has a specific surface area of 297.5661-367.8702m²Per g, total pore volume V_total ^aIs 0.2085-0.2253m³Volume of micropores V_mecoIs 0.0943-0.1142m³(ii) in terms of/g. The mesoporous size range of the Ni modified nano ZSM-5 molecular sieve is 20nm to 120nm, and the distribution is uniform. The total acid quantity of the Ni modified nano ZSM-5 molecular sieve is 0.8426-0.9567mmol/g, and the weak acid/strong acid ratio B/L is 0.1097-0.1385.

7. The catalyst of claim 4, the P-modified nano ZSM-5 molecular sieve catalyst having a specific surface area of 237.6186-342.9235m²Per g, total pore volume V_totalIs 0.1470-0.2443m³G, micropore volume V_mecoIs 0.0562 to 0.1080m³/g。

8. The method for producing a catalyst according to any one of claims 1 to 4, characterized in that:

(1) mixing the template agent M with a part of water, adding NaOH to be uniformly mixed after uniformly stirring, continuously adding an aluminum source after stirring and dissolving, and stirring until the raw materials are completely hydrolyzed to obtain a solution A; dropwise adding a silicon source into the solution A, and after the solution A is completely hydrolyzed, continuously stirring the obtained solution for 10-24 hours in a water bath at the temperature of 80-90 ℃ to obtain a seed crystal solution; adding the silane coupling agent Q into the seed crystal solution, continuously stirring for 4-8h, transferring the obtained material into a high-pressure hydrothermal synthesis kettle with a polytetrafluoroethylene lining, and crystallizing at 160-180 ℃ for 3-5 days to obtain a crystallized product; standing the crystallized product, cooling to room temperature, taking out the crystallized product, washing with deionized water until the pH value is 7, performing centrifugal separation, taking the product, drying at the temperature of 100 ℃ and 120 ℃, and roasting at the temperature of 550 ℃ for 4 hours to obtain the Na-type nano ZSM-5 molecular sieve; carrying out ion exchange on the Na-type nano ZSM-5 molecular sieve and 0.8mol/L ammonium nitrate solution to obtain an H-type nano ZSM-5 molecular sieve;

(2) using Ni (NO) with certain concentration for the H-type nano ZSM-5 molecular sieve obtained in the step (1)₃)₂·6H₂O solution and/or (NH)₄)₂HPO₄Soaking the solution in the same volume to obtain Ni content and P content₂O₅The contents of the components are 0.2-2% and 3-15%, respectively, after stirring uniformly, dipping for 12-36h, drying the fully dipped product for 1h at 60 ℃, then drying for 12h at 120 ℃, and roasting the dried product in the air atmosphere to obtain the Ni and P modified nano ZSM-5 molecular sieve catalyst.

9. The method of claim 8, wherein the silicon source is tetraethyl orthosilicate (TEOS), the aluminum source is Aluminum Isopropoxide (AIP), the templating agent is tetrapropylammonium hydroxide (TPAOH), and the silane coupling agent is gamma-Aminopropyltriethoxysilane (APTES).

10. Use of the catalyst of any one of claims 1-5, wherein the modified nano ZSM-5 molecular sieve catalyst is used in the alkylation of benzene with methanol. The catalyst is activated for 5 hours at 400 ℃ before alkylation reaction, then the reaction temperature is 450-650 ℃ under the conditions of no carrier gas and normal pressure, and the reaction space velocity is kept at 1-6 hours^-1The molar ratio of benzene to methanol is 0.5-5: 1.

Technical Field

The invention relates to a nano catalyst and a preparation method thereof, in particular to a modified nano ZSM-5 molecular sieve catalyst for alkylation of benzene and methanol and a preparation method thereof.

Background

In recent years, the yield of pure benzene in China is gradually increased, and the situation of excess benzene productivity is slowly presented; with the development of coal chemical industry, a serious surplus of methanol also appears. However, toluene and xylene are important organic chemical raw materials, are widely applied to the fields of materials, textiles, medicines, daily chemicals and the like, and are in short supply at home. In particular to Paraxylene (PX), which is one of the basic organic raw materials in petrochemical industry, has wide application in chemical fiber, medicine, pesticide, synthetic resin, plastic, medicine and other chemical production fields. 2008, 2012, the yield of p-xylene is increased from 464 ten thousand tons/year to 750 ten thousand tons/year, and the apparent consumption is increased from 760 ten thousand tons/year to 1637.2 ten thousand tons/year. The annual average increase rate of the apparent consumption in 2008-2013 is 23.1%, and the external dependence rate of the product is about 55%.

At present, the industrial production process of paraxylene mainly comprises four processes: (1) catalytically reforming naphtha; (2) toluene disproportionation and transalkylation processes; (3) separating coal tar; (4) a process for preparing p-xylene from toluene and methanol. Wherein naphtha catalytic reforming is hydrogenated, and the mass fraction of paraxylene in the catalytic reforming product is about 22%; the toluene disproportionation and transalkylation process is to selectively convert toluene into benzene and xylene, wherein 2 tons of toluene are consumed for producing each ton of p-xylene (PX), a large amount of benzene is produced as a byproduct, and the economy is poor; when the coal tar separation technology is used for processing the paraxylene, the mass fraction of the xylene in the coal tar is 5 percent, the separation process is complex, the energy consumption is high, and the yield and the purity of the xylene are low; when the toluene methanol alkylation process is adopted, about 1 ton of toluene is consumed for producing each ton of p-xylene (PX), the benzene production amount is small, and the economy is good, so that the toluene methanol alkylation for preparing p-xylene becomes a hot spot of recent research.

Methanol alkylation reactions involve methylation of benzene with methanol, methanol self-reaction, benzene self-reaction, carbon deposition reaction, and the like. The molecular sieve catalyst has micropores, so that the diffusion rate of reaction raw materials and product molecules on the surface and in the pores of the catalyst is low, the molecular sieve catalyst has long retention time in the pore channels, and a part of active sites of the catalyst cannot be exposed, so that the benzene conversion rate of the toluene and methanol alkylation reaction in the prior art is low, and the selectivity of xylene is also low.

The surface of the ZSM-5 molecular sieve contains a large number of B acid and L acid sites, and the acid amount, the acid strength and the ratio of the B acid to the L acid of the molecular sieve can be changed along with the change of a synthesis method and the structure of the molecular sieve. However, there are still few research documents and patents on molecular sieve catalysts for benzene and methanol alkylation at home and abroad.

CN102964201A discloses a method for applying ZSM-5, USY, MCM-22 and EU-1 molecular sieves loaded with metal oxides of Mo, Ni or La to alkylation reaction of benzene and methanol, wherein toluene is introduced as a raw material, the conversion rate of benzene reaches 45.77%, and the selectivity of xylene is lower than 74.35%.

CN102688771A zeolite H MCM-56 and gamma-or eta-Al₂O₃The catalyst is a composite carrier and is formed by loading one or more of molybdenum, nickel, magnesium, lanthanum, boron or oxides thereof, the conversion rate of benzene reaches more than 50%, the selectivity of toluene and xylene is more than 90%, the resources of benzene and methanol are fully utilized, the production cost of toluene and xylene is relatively reduced, but the preparation process of the catalyst is complex, and a plurality of byproducts are generated.

The patent CN105214714A of Shaanxi coal chemical engineering center Limited company discloses a catalyst for preparing p-xylene by benzene and methanol alkylation and a preparation method thereof, wherein the active component of the catalyst is a sodium type or hydrogen type ZSM-5 molecular sieve, and the modified component is a siloxane-based compound and alkaline earth metal. The active component, the matrix material and the binder are mixed, sprayed and formed, and modified by the modifying component to prepare the fluidized bed catalyst for the alkylation reaction of benzene and methanol, the conversion per pass of the benzene reaches more than 55 percent, the isomerization process is not needed, the obtained main product is p-xylene, the selectivity of the p-xylene in isomers reaches more than 95 percent, but the modification process is complex, a large amount of waste liquid is generated and is difficult to recover, and the industrialization is not facilitated.

Chinese patent CN102101818A applied by China Petroleum gas GmbH discloses a method for synthesizing xylene from benzene and methanol, which adopts a modified HMCM-56 molecular sieve as a catalyst, loads metal Mo or Ni, and has a single-pass conversion rate of benzene up to 45% and a toluene xylene selectivity up to 89%.

The Chinese patent CN101624327A applied by Shanxi Hengyang science and technology Limited company and Huishen engineering (China) Limited company uses benzene and methanol as raw materials under the action of acidic molecular sieve catalyst, and rectifies, recycles and recycles the benzene which is used for reaction to prepare toluene and xylene products, and is characterized in that the selectivity of toluene and xylene can be conveniently adjusted when the reaction temperature is lower (400 ℃). However, under high temperature conditions (>500 ℃), methanol is easy to generate self-conversion reaction to generate short-chain and long-chain alkane and olefin, which causes the generation of byproducts ethylbenzene, methyl ethylbenzene, propyl benzene, trimethyl benzene and tetramethyl benzene, greatly increases the industrial separation cost, and is not suitable for industrial production.

In summary, although the prior art is not replete with methods for modifying ZSM-5 molecular sieves, the geometric size of the pores in the porous molecular sieve material, diffusion constraints, and the nature of the acid on the catalyst surface are generally important factors in determining the methylation catalytic activity and selectivity. Only through continuously and deeply researching the shape-selective methylation reaction mechanism, continuously exploring and developing new catalytic materials, and combining with a specific reaction process, the bottleneck of the MTPX technology is expected to be broken through. If a new process route for producing toluene and xylene by alkylating benzene and methanol can be realized, the shortage of PX supply in China can be relieved, the problem of excess production capacity of benzene and methanol can be solved, and meanwhile, the generated mixed aromatic hydrocarbon can also be used as a blending component of high-octane gasoline, so that the gasoline octane number is improved, and the method has important significance. However, the catalyst in the prior art has various disadvantages for the reaction of benzene and methanol alkylation gasification toluene and xylene, and cannot meet the requirement of large-scale industrial production, so that the provision of a catalyst suitable for the reaction of benzene and methanol alkylation preparation toluene and xylene becomes a technical problem to be solved urgently.

Disclosure of Invention

Aiming at the technical defects of generally low yield of p-xylene, low benzene conversion rate, more byproducts and the like in the prior art, the invention provides a nano ZSM-5 molecular sieve catalyst for alkylating benzene and methanol and a preparation method thereof. The conversion rate of benzene and the selectivity of toluene and xylene in reaction products are improved by the shape selectivity of the catalyst and the addition of the modifying active agent. The invention provides a nano ZSM-5 molecular sieve catalyst for alkylating benzene and methanol, which takes a nano ZSM-5 molecular sieve as a parent body and realizes the modification of the nano ZSM-5 molecular sieve through chemical modification of Ni element and P element, wherein n (SiO) of the parent body₂)/n(Al₂O₃) Is 50-200, the particle size is 100-300 nm; in the modified nano ZSM-5 molecular sieve catalyst, the content of Ni element is 0.2-2% by simple substance and the P element is P₂O₅The content is 3-15%. The invention realizes the performance modulation and optimization of the nano ZSM-5 molecular sieve catalyst by introducing Ni element and P element.

Furthermore, the specific surface area of the Ni modified nano ZSM-5 molecular sieve catalyst is 297.5661-367.8702m²Per g, total pore volume V_total ^aIs 0.2085-0.2253m³Volume of micropores V_mecoIs 0.0943-0.1142m³(ii) in terms of/g. The mesoporous size range of the Ni modified nano ZSM-5 molecular sieve is 20nm to 120nm, and the distribution is uniform. The total acid quantity of the Ni modified nano ZSM-5 molecular sieve is 0.8426-0.9567mmol/g, and the weak acid/strong acid ratio B/L is 0.1097-0.1385.

The specific surface area of the P modified nano ZSM-5 molecular sieve catalyst is 237.6186-342.9235m²Per g, total pore volume V_total ^aIs 0.1470-0.2443m³G, micropore volume V_mecoIs 0.0562 to 0.1080m³/g。

Further, the crystal grain of the modified nano ZSM-5 molecular sieve catalyst is spherical under an electron microscope, and is agglomerated into 200-3 parts by 20-30nm round spheresSpherical particles of 00 nm. Further, in the modified nano ZSM-5 molecular sieve catalyst, the content of Ni element is 0.4-0.8% by taking the catalyst as a percentage standard, and the content of P element is P element₂O₅The content is 3-7%.

Furthermore, after Ni modification is adopted, the selectivity of the target products toluene and xylene is improved, and the selectivity of the byproduct ethylbenzene is reduced by one order of magnitude. After P is modified, the molecular sieve has better stability and better xylene selectivity, and the xylene selectivity is improved by 2 wt%.

Further, the Ni modified nano ZSM-5 molecular sieve catalyst is adopted to carry out benzene and methanol alkylation reaction, so that a byproduct of propyl benzene is eliminated, the content of ethylbenzene is reduced to 0.05 wt%, and the content of methyl ethyl benzene is reduced to 0.03 wt%.

The invention also provides a preparation method of the modified nano ZSM-5 molecular sieve catalyst, which comprises the following steps:

step (1) preparation of catalyst raw powder

The raw materials comprise a silicon source, an aluminum source, a template agent M, a silane coupling agent Q, NaOH and water according to a molar ratio of n (SiO)₂)： n(Al₂O₃)：n(M)：n(Q)：n(NaOH)：n(H₂O) ═ 1: 0.005-0.2: 0.15-0.4: x: 0.01: 25(x is 0, 0.05, 0.1), preparing each raw material; mixing the template agent M with a part of water, adding NaOH to be uniformly mixed after uniformly stirring, continuously adding an aluminum source after stirring and dissolving, and stirring until the raw materials are completely hydrolyzed to obtain a solution A;

dropwise adding a silicon source into the solution A, and after the hydrolysis is completed, continuously refluxing the obtained solution for 10-24h in a three-neck flask in a water bath at the temperature of 80-90 ℃ to obtain a seed crystal solution; adding the silane coupling agent Q into the seed crystal solution, continuously stirring for 4-8h under the water bath condition after rinsing, transferring the obtained material into a high-pressure hydrothermal synthesis kettle with a polytetrafluoroethylene lining, and crystallizing for 3-5 days at the temperature of 180 ℃ under 160-; standing the crystallized product, cooling to room temperature, taking out the crystallized product, washing with deionized water until the pH value is 7, performing centrifugal separation, taking the product, drying at the temperature of 100 ℃ and 120 ℃, and roasting at the temperature of 550 ℃ for 4 hours to obtain the Na-type nano ZSM-5 molecular sieve; carrying out ion exchange on the Na-type nano ZSM-5 molecular sieve and 0.8mol/L ammonium nitrate solution to obtain an H-type nano ZSM-5 molecular sieve;

step (2) modification of the catalyst

Using Ni (NO) with certain concentration for the H-type nano ZSM-5 molecular sieve obtained in the step (1)₃)₂·6H₂O solution and/or (NH)₄)₂HPO₄Soaking the solution in the same volume to obtain Ni content and P content₂O₅The contents of the components are 0.2-2% and 3-15%, respectively, after stirring uniformly, dipping for 12-36h, drying the fully dipped product for 1h at 60 ℃, then drying for 12h at 120 ℃, and roasting the dried product in the air atmosphere to obtain the Ni and P modified nano ZSM-5 molecular sieve catalyst.

Further, in the step (1), after the silane coupling agent Q is added, stirring is continued for 6 hours.

Further, in the step (1), the ion exchange condition is that stirring is carried out in water bath at 80 ℃ for 2h, ion exchange is carried out for 3 times, washing is carried out until the solution is neutral, the operation is repeated for 3 times, and then centrifugation, washing, drying and roasting are carried out.

Further, in the step (2), the dipping time is 24 h.

Further, in the step (2), the roasting temperature is 550-. Further, in the step (1), the silica-alumina ratio (nSiO) of the H-type nano ZSM-5 molecular sieve₂/Al₂O₃) Is 50 to 200.

The invention provides a method for producing methylbenzene and dimethylbenzene by adopting alkylation of methanol and benzene, which is a method for carrying out benzene and methanol alkylation reaction by adopting a modified nano ZSM-5 molecular sieve catalyst prepared by the method, wherein a fixed bed continuous flow micro-reactor is adopted in the reaction process, and the reaction airspeed is kept at 1-6 h at the reaction temperature of 450-650 ℃ under the conditions of no carrier gas and normal pressure^-1Wherein the molar ratio of benzene to methanol in the reaction raw materials is (0.5-5.0): 1.0.

further, the reaction temperature is 500-550 ℃, and the reaction space velocity is 1-2 h^-1The molar ratio of benzene to methanol in the reaction raw materials is (0.5-1): 1;

further, the alkylation reaction was carried out in a fixed bed continuous flow microreactor having an internal diameter of 12 mm;

further, the catalyst was activated for 5h before feeding, the activation conditions being 400 ℃.

The modified nanometer ZSM-5 molecular sieve catalyst is adopted to carry out the reaction of benzene and methanol alkylation for preparing dimethylbenzene, the catalyst activity is high, the single-pass conversion rate of the benzene can reach more than 59%, the selectivity of the toluene and the dimethylbenzene can be higher than 95%, the byproduct propylbenzene obtained by the reaction of other catalysts in the prior art is eliminated, the ethylbenzene content is reduced to 0.05%, and the methylethylbenzene content is reduced to 0.03%.

Alkylation reaction conditions also have some effect on the yield of the target product, the occurrence of side reactions and the formation of by-products. In addition to the carbon deposition reaction, the other reactions are exothermic, so the temperature of the benzene/methanol alkylation reaction cannot be too high. It can be obtained that the alkylation reaction temperature cannot be too high, since high temperatures will be detrimental to the main reaction, wherein the soot reaction rate will be much faster. The reaction temperature is generally low and is 380-500 ℃, and methanol is easy to generate self-conversion reaction due to overhigh high temperature, so that byproducts of ethylbenzene, methyl ethylbenzene, propyl benzene, trimethyl benzene and tetramethyl benzene are generated, and the industrial separation cost is greatly increased. The pressure is generally atmospheric conditions, since a suitable increase favors conversion but disfavors selectivity and increases costs. The airspeed is controlled to be 2-10 h^－1Too low space velocity, too long residence time of the reactants, increased by-products and too low production efficiency; too high a space velocity results in too low a conversion. A suitable molar ratio of benzene to methanol alkylation in the feed is about 1, since the conversion of benzene decreases with increasing molar ratio.

The invention has the beneficial effects that:

1. the invention utilizes the benzene and the methanol with excessive and cheap products to generate the toluene and the xylene which are target products, and the toluene and the xylene are directly used for carrying out mild alkylation reaction under the conditions of high temperature (up to 650 ℃), normal pressure and no carrier gas by the loading of a high-efficiency catalyst and a modified active component without high-temperature steam or polymer modification, thereby improving the conversion rate and the selectivity of the toluene and the xylene, reducing the alkylation byproducts of the benzene and the methanol, inspecting the change rules of the conversion rate and the selectivity under different process conditions and selecting the optimal process conditions.

2. The catalyst synthesized by the method is used for carrying out the benzene and methanol alkylation reaction, the operation conditions of normal pressure and no carrier gas can be adopted, the production cost can be saved, and the method is suitable for large-scale industrial production.

3. The modified molecular sieve catalyst is suitable for the alkylation reaction process of benzene and methanol, the activity of the catalyst is high, the conversion per pass of the benzene can reach more than 59%, the selectivity of the product toluene and xylene can reach 95%, the content of the byproduct propylbenzene is completely eliminated, the content of the byproduct ethylbenzene is reduced to 0.05%, and the content of the methylethylbenzene is reduced to 0.03%.

4. The modified molecular sieve catalyst prepared by the invention is spherical particles of 200-300nm agglomerated by 20-30nm spheres, and has the characteristics of controllable morphology, good dispersibility, high stability and the like by introducing modified metal.

5. According to the invention, through optimizing the shape selectivity of the molecular sieve catalyst and adding the modified metal, the conversion rate of benzene and the selectivity of toluene and xylene in reaction products are greatly improved.

6. The method adopts segmented drying, firstly drying at 60 ℃, and then drying at 120 ℃, so that the method is favorable for forming a multilevel pore channel, improving the specific surface area and pore volume of the catalyst, reducing side reaction active sites, and being favorable for forming a molecular sieve micro-mesoporous structure.

7. The method effectively controls the particle size of molecules by limiting the proportion of raw materials and the adding sequence of the template agent, the silicon source, the aluminum source and the silane coupling agent, enables round spheres with the particle size of 20-30nm to be agglomerated into 200-300nm spherical particles, and then uses Ni and P to prepare the spherical particles₂O₅The modification of the catalyst can further reduce the surface acidity of the catalyst, improve the pore volume size, improve the diffusion efficiency and reduce the occurrence of side reactions. The mild reaction is carried out under the conditions of high temperature (450-650 ℃), normal pressure and no carrier gas, the conversion per pass of the obtained benzene can reach more than 59 percent, and the toluene and the xylene can be obtainedThe selectivity of toluene can reach more than 95 percent, and the content of by-products is eliminated.

Drawings

FIG. 1 TPD data for Ni-modified ZSM-5 and nano-ZSM-5

FIG. 2 XRD patterns of Ni/nano ZSM-5 with different loading amounts

FIG. 3 NH of different loaded Ni/nanometer ZSM-5₃TPD diagram

FIG. 4 XRD patterns of P/nano ZSM-5 with different loadings

FIG. 5 NH of P/nano ZSM-5 with different loading amounts₃-TPD spectrum

FIG. 6 Effect of starting material benzyl alcohol ratio on 5% P/Nano ZSM-5 alkylation Performance

Examples

The invention is illustrated in detail below with reference to examples: