Benzene and carbon dioxide alkylation reaction method

Abstract

The invention discloses a method for alkylation reaction of benzene and carbon dioxide. Comprising the following steps: contacting and reacting a raw material containing benzene and carbon dioxide with a catalyst to obtain a product containing xylene, the catalyst is a composite catalyst of a metal-based catalyst and a ZSM-11 molecular sieve. The metal catalyst is a copper-based catalyst, a zinc-based catalyst and the like. The combined catalyst shows relatively high xylene selectivity, namely relatively high secondary methylation efficiency, and product distribution can be modulated by changing the acid property of ZSM-11.

Description

Technical Field

[0001] The present application relates to a method for alkylation reaction of benzene with carbon dioxide, belonging to the field of catalysts. Background Art

[0002] In recent years, with the worsening of the greenhouse effect, CO2 emission reduction has become an urgent problem to be solved by the international community. How to utilize the emitted CO2 and produce high value-added chemicals is an important research direction at present. CO2 hydrogenation to methanol is an important way to reduce carbon emissions, but due to thermodynamic limitations, its equilibrium conversion rate is low. Coupling the CO2 hydrogenation to methanol process with the aromatic alkylation process can not only pull the reaction equilibrium and improve the CO2 conversion rate, but also produce high value-added aromatic compounds. It is of great value in solving the CO2 utilization problem and easing the supply of aromatics. It is a route with broad application prospects. This route uses carbon dioxide and hydrogen as raw materials to replace methanol. Compared with the traditional aromatic methanol alkylation method, it can avoid the methanol to olefin side reaction caused by improper methanol / aromatic feed ratio, and improve the production efficiency of aromatic products; at the same time, it can inhibit the isomerization reaction of aromatic products and improve the selectivity of specific products.

[0003] With the increasing attention paid to the capture and utilization of carbon dioxide and the increasing demand for the selective production of aromatic compounds in recent years, this route has shown its unique advantages. Researchers have begun to focus on the conversion of CO2 and H2 as methylation raw materials for aromatic substances, including the methylation of various substrates such as benzene, toluene, and naphthalene to produce high-value-added aromatics. The catalyst for the coupling of carbon dioxide hydrogenation to benzene alkylation requires the combination of hydrogenation catalysts and molecular sieve catalysts. By screening different metal hydrogenation active sites and different molecular sieve combinations, a highly active and selective catalyst combination is selected; the currently reported catalyst systems are mainly Re-based-zeolite and Zn-based-zeolite, and the selected molecular sieves are mainly ZSM-5, MOR, and Beta.

[0004] Both ZSM-11 and ZSM-5 molecular sieves are Pentasil molecular sieves with two-dimensional pore systems, but their pore structures are different. ZSM-5 is a molecular sieve with MFI topological structure, and its pore system consists of elliptical ten-membered ring straight pores. and sinusoidal pores The ZSM-11 is a molecular sieve with MEL topology, and its pore system is composed of two-dimensional straight pores of elliptical ten-membered rings. The diffusion resistance in the straight pores of ZSM-11 molecular sieve is significantly smaller than that of ZSM-5 molecular sieve, and it exhibits excellent catalytic performance in some catalytic reactions. Summary of the invention

[0005] ZSM-11 molecular sieve shows excellent activity and stability in the alkylation reaction of benzene and ethanol. ZSM-11 molecular sieve is a potential alkylation catalyst for the coupling reaction of CO2 hydrogenation and aromatic alkylation.

[0006] This patent aims to develop a highly selective catalyst, especially a catalyst with high xylene selectivity, in order to solve the problem of poor controllability of product selectivity in the process of coupling CO2 hydrogenation and benzene alkylation to produce toluene and xylene.

[0007] According to one aspect of the present application, a method for alkylation reaction of benzene with carbon dioxide is provided, comprising the following steps:

[0008] The raw material containing benzene and carbon dioxide is contacted with a catalyst to react and obtain a product containing xylene;

[0009] The catalyst is a composite catalyst of a metal-based catalyst and a ZSM-11 molecular sieve.

[0010] The compounding method is selected from at least one of powder mixing, particle mixing, and segmented filling.

[0011] The metal-based catalyst is obtained by the following steps:

[0012] The metal nitrate, the precipitant and water are mixed, aged and calcined to obtain the metal-based catalyst;

[0013] The metal nitrate is selected from at least one of copper nitrate, zinc nitrate, chromium nitrate and ruthenium nitrate.

[0014] The precipitant is selected from at least one of sodium carbonate and ammonium carbonate;

[0015] The molar ratio of the metal nitrate to the precipitant is 1:1 to 5;

[0016] The concentration of the metal nitrate is 0.2 to 2M;

[0017] The aging temperature is 40 to 80°C;

[0018] The aging time is 1 to 12 hours;

[0019] The calcination temperature is 300-550°C;

[0020] The calcination time is 1 to 6 hours.

[0021] Specifically, the metal-based catalyst is obtained by the following steps:

[0022] The CuO / ZnO / Al2O3 (CZA) catalyst was prepared by co-precipitation method: 100 mL of Cu(NO3)2·3H2O, Zn(NO3)2·6H2O and Al(NO3)3·9H2O were configured into a 1 M metal solution with Cu:Zn:Al=6:3:1, mixed with 200 mL of 1 M Na2CO3 solution, stirred vigorously to pH=8, and then treated at 65°C for 2 h. The obtained precursor was washed, dried, and calcined at 350°C for 2 h.

[0023] The ZnZrOx catalyst was prepared by coprecipitation method: 0.6g Zn(NO3)2·6H2O and 5.8g Zr(NO3)4·5H2O were dissolved in 100mL water, which was recorded as solution A, and 3.06(NH4)2CO3 solution was dissolved in 100mL water, which was recorded as solution B. Under vigorous stirring, solution B was added to solution A at a rate of 3mL / min, then treated at 70℃ for 2h, aged at room temperature for 2h after cooling, then washed, dried, and calcined at 500℃ for 3h.

[0024] The ZSM-11 molecular sieve is selected from H-type ZSM-11 molecular sieve and / or metal ion type ZSM-11 molecular sieve.

[0025] The ZSM-11 molecular sieve is prepared by the following steps:

[0026] A silicon source, an aluminum source, a template agent and water are mixed, crystallized, calcined and exchanged in a closed container to obtain the ZSM-11 molecular sieve.

[0027] The silicon source is selected from at least one of white carbon black, silica gel, tetraethyl orthosilicate and silica sol;

[0028] The aluminum source is selected from at least one of sodium aluminate, aluminum sol, pseudo-boehmite, and alumina;

[0029] The alkali is selected from at least one of sodium hydroxide and potassium hydroxide;

[0030] The template agent is selected from at least one of tetrabutylammonium hydroxide and tetrabutylammonium bromide;

[0031] The molar ratio of the silicon source to the aluminum source is 1:0.01-0.05;

[0032] The molar ratio of the silicon source to the template is 1:0.05-0.8;

[0033] The molar ratio of the silicon source to the water is 1:5-50;

[0034] The molar ratio of the silicon source to the base is 1:0.01-0.5;

[0035] The molar amount of the silicon source is based on the molar amount of silicon dioxide therein;

[0036] The molar amount of the aluminum source is based on the molar amount of the aluminum element therein;

[0037] The crystallization temperature is 130-180°C;

[0038] The crystallization time is 24 to 120 hours;

[0039] The stirring rate of the crystallization is 20 to 100 rpm;

[0040] The calcination temperature is 350-550°C;

[0041] The calcination time is 1 to 6 hours.

[0042] The exchange includes exchanging with ammonium nitrate to obtain H-type ZSM-11 molecular sieve and / or exchanging with metal salt to obtain metal ion type ZSM-11 molecular sieve.

[0043] Optionally, a silicon source, an aluminum source, a template, a base, and water are mixed, crystallized, calcined, and exchanged in a closed container to obtain the ZSM-11 molecular sieve;

[0044] The base is selected from sodium hydroxide.

[0045] The molar ratio of the silicon source to the base is 1:0.01-0.5;

[0046] The molar amount of the silicon source is based on the molar amount of silicon dioxide therein.

[0047] Specifically, the ZSM-11 molecular sieve can be prepared as follows:

[0048] A certain amount of sodium aluminate and sodium hydroxide are added to a reactor with a polytetrafluoroethylene liner in sequence, deionized water is added and stirred until fully dissolved, and then a certain amount of template (including tetrabutylammonium hydroxide, tetrabutylammonium bromide) and white carbon black are added in sequence, and the mixture is fully stirred and mixed. The molar composition of the formed gel is: 1.0SiO2 / a Na2O / b Al2O3 / cTBAOH / d H2O (a=0.01-0.5, b=0.01-0.05, c=0.05-0.8, d=5-50). The reactor is sealed and crystallized for a certain time at a crystallization temperature of 130-180°C, autogenous pressure and stirring (20-100 rpm). The reaction is then quenched with deionized water. The solid product is separated by centrifugation, washed with deionized water until the liquid is close to neutral, and dried overnight at 120°C.

[0049] The reaction temperature is 200-400°C;

[0050] The reaction pressure is 0.5-4 MPa.

[0051] The gas space velocity of the reaction is 1000-10000h -1 ;

[0052] The space velocity of benzene is 0.5-10h -1 ;

[0053] The molar ratio of the benzene to the carbon dioxide is 1:0.1-10.

[0054] The beneficial effects of this application include:

[0055] The present invention develops a method for preparing a catalyst for the alkylation reaction of benzene with carbon dioxide, wherein the catalyst is a combination catalyst of a metal oxide and a molecular sieve, wherein the metal catalyst is a copper-based, zinc-based or other catalyst, and the molecular sieve is a ZSM-11 molecular sieve. This combination catalyst exhibits a higher xylene selectivity, i.e., a higher secondary methylation efficiency, and the product distribution can be adjusted by changing the acid properties of ZSM-11. DETAILED DESCRIPTION

[0056] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0057] Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources.

[0058] The CuO / ZnO / Al2O3 (CZA) catalyst was prepared by co-precipitation method: 100 mL of Cu(NO3)2·3H2O, Zn(NO3)2·6H2O and Al(NO3)3·9H2O were configured into a 1 M metal solution with Cu:Zn:Al=6:3:1, mixed with 200 mL of 1 M Na2CO3 solution, stirred vigorously to pH=8, and then treated at 65°C for 2 h. The obtained precursor was washed, dried, and calcined at 350°C for 2 h.

[0059] ZnZrO x The catalyst was prepared by coprecipitation method: 0.6g Zn(NO3)2·6H2O and 5.8g Zr(NO3)4·5H2O were dissolved in 100mL water, which was recorded as solution A, and 3.06(NH4)2CO3 solution was dissolved in 100mL water, which was recorded as solution B. Under vigorous stirring, solution B was added to solution A at a rate of 3mL / min, then treated at 70℃ for 2h, aged at room temperature for 2h after cooling, then washed, dried, and calcined at 500℃ for 3h.

[0060] ZSM-11 molecular sieve can be prepared as follows:

[0061] Add a certain amount of sodium aluminate and sodium hydroxide to a reactor lined with polytetrafluoroethylene in turn, add deionized water and stir until fully dissolved, then add a certain amount of tetrabutylammonium hydroxide and white carbon black in turn, stir and mix thoroughly. The molar composition of the gel formed is: 1.0SiO2 / a N a2 O / b Al2O3 / c TBAOH / d H2O (a=0.05, b=0.02, c=0.4, d=10). The reactor was sealed and crystallized for a certain time at a crystallization temperature of 140°C, autogenous pressure and stirring (30 rpm). The reaction was then quenched with deionized water. The solid product was separated by centrifugation, washed with deionized water until the liquid was close to neutral, and dried at 120°C overnight.

[0062] Exchange with ammonium nitrate to obtain H-type ZSM-11 molecular sieve;

[0063] The metal ion type ZSM-11 molecular sieve is obtained by exchanging with metal salt.

[0064] The catalysts used in the subsequent examples were all obtained by the method of Preparation Example 1.

[0065] Example 1

[0066] CuO / ZnO / Al2O3 and H-ZSM-11 were granulated and sieved to obtain particles with a particle size of 40-60 mesh, and then 0.5 g of each was taken and mixed evenly to obtain a combined catalyst.

[0067] Example 2

[0068] ZnZrO x The catalyst was mixed with H-ZSM-11 in a mass ratio of 1:1, and then granulated and sieved to obtain particles with a particle size of 40-60 mesh to obtain a combined catalyst.

[0069] Example 3

[0070] Take H-ZSM-11 and exchange it with Mg(NO3)2 solution, dry it and roast it to obtain modified H-ZSM-11. Granulate CuO / ZnO / Al2O3 and modified H-ZSM-11 separately, sieve them to obtain particles with a particle size of 40-60 mesh, and then take 0.5g of each and mix them evenly to obtain a combined catalyst.

[0071] Example 4

[0072] Take H-ZSM-11 and exchange it with NaNO3 solution, dry it and roast it to obtain modified H-ZSM-11. Mix CuO / ZnO / Al2O3 and modified H-ZSM-11 in a mass ratio of 1:1, then granulate and sieve to obtain particles with a particle size of 40-60 mesh to obtain a combined catalyst.

[0073] Application Example 1

[0074] A high-pressure continuous fixed-bed reactor was used to evaluate the catalyst performance, and gas chromatography was used to analyze the product components.

[0075] 1 g of the combined catalyst provided in Examples 1 to 4 was taken respectively and placed in the middle of a reaction tube, and first reduced in hydrogen at 350° C. for 1 h to obtain an active catalyst; a mixed gas of carbon dioxide, hydrogen, benzene and nitrogen (wherein the volume fraction of nitrogen is 1 to 50%, used as an internal standard) was introduced at a space velocity of 9000 mL / g / h / , wherein the molar ratio of hydrogen to carbon dioxide was 3:1, and the molar ratio of carbon dioxide to gaseous benzene was 4:1, and the reaction was carried out at 350° C. and a pressure of 3.0 MPa; the reaction products were divided and then entered into a gas chromatograph (GC) equipped with a flame ionization detector (FID) and a thermal conductivity cell detector (TCD) for online analysis, and the carbon dioxide conversion rate and the reaction product selectivity were calculated using the C-based normalization method, and the results are shown in Table 1.

[0076] Table 1 Reaction performance of each example

[0077]

[0078]

[0079] As can be seen from the table, by changing the acid properties of the ZSM-11 molecular sieve by ion exchange with different metal cations, the benzene conversion rate, toluene selectivity and xylene selectivity of the reaction can be significantly changed. In particular, the catalyst used in Example 3 has a very high secondary methylation efficiency.

[0080] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for the alkylation reaction of benzene with carbon dioxide, characterized in that: The following steps are involved: The raw material containing benzene and carbon dioxide is contacted with a catalyst to react and obtain a product containing xylene; The catalyst is a composite catalyst of a metal-based catalyst and a ZSM-11 molecular sieve.

2. The method according to claim 1, characterized in that The compounding method is selected from at least one of powder mixing, particle mixing, and segmented filling.

3. The method according to claim 1, characterized in that The metal-based catalyst is obtained by the following steps: The metal nitrate, the precipitant and water are mixed, aged and calcined to obtain the metal-based catalyst; The metal nitrate is selected from at least one of copper nitrate, zinc nitrate, chromium nitrate and ruthenium nitrate.

4. The method according to claim 1, characterized in that: The precipitant is selected from at least one of sodium carbonate and ammonium carbonate; The molar ratio of the metal nitrate to the precipitant is 1:1 to 5; The concentration of the metal nitrate is 0.2 to 2M; The aging temperature is 40 to 80°C; The aging time is 1 to 12 hours; The calcination temperature is 300-550°C; The calcination time is 1 to 6 hours.

5. The method according to claim 1, characterized in that The ZSM-11 molecular sieve is selected from H-type ZSM-11 molecular sieve and / or metal ion type ZSM-11 molecular sieve.

6. The method according to claim 1, characterized in that The ZSM-11 molecular sieve is prepared by the following steps: A silicon source, an aluminum source, a template agent and water are mixed, crystallized, calcined and exchanged in a closed container to obtain the ZSM-11 molecular sieve.

7. The method according to claim 6, characterized in that The silicon source is selected from at least one of white carbon black, silica gel, tetraethyl orthosilicate and silica sol; The aluminum source is selected from at least one of sodium aluminate, aluminum sol, pseudo-boehmite, and alumina; The alkali is selected from at least one of sodium hydroxide and potassium hydroxide; The template agent is selected from at least one of tetrabutylammonium hydroxide and tetrabutylammonium bromide; The molar ratio of the silicon source to the aluminum source is 1:0.01-0.05; The molar ratio of the silicon source to the template is 1:0.05-0.8; The molar ratio of the silicon source to the water is 1:5-50; The molar ratio of the silicon source to the base is 1:0.01-0.5; The molar amount of the silicon source is based on the molar amount of silicon dioxide therein; The molar amount of the aluminum source is based on the molar amount of the aluminum element therein; The crystallization temperature is 130-180°C; The crystallization time is 24 to 120 hours; The stirring rate of the crystallization is 20 to 100 rpm; The calcination temperature is 350-550°C; The calcination time is 1 to 6 hours.

8. The method according to claim 6, characterized in that The exchange includes exchanging with ammonium nitrate to obtain H-type ZSM-11 molecular sieve and / or exchanging with metal salt to obtain metal ion type ZSM-11 molecular sieve.

9. The method according to claim 1, characterized in that: The reaction temperature is 200-400°C; The reaction pressure is 0.5-4 MPa.

10. The method according to claim 1, characterized in that The gas space velocity of the reaction is 1000-10000h -1 ; The space velocity of benzene is 0.5-10h -1 ; The molar ratio of the benzene to the carbon dioxide is 1:0.1-10.

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