Composite catalyst for directly preparing aromatic hydrocarbon from carbon dioxide and preparation method and application thereof

Abstract

The present application relates to a kind of composite catalyst for directly preparing aromatic hydrocarbon from carbon dioxide, it is characterized in that, by metal oxide and HZSM-5 molecular sieve coupling mass ratio is (1-3):1 mechanically mixed to be made, wherein metal oxide main active component is iron oxide, metal oxide auxiliary is at least one of manganese oxide and copper oxide, sodium oxide, potassium oxide, manganese auxiliary is introduced when preparing iron oxide, other metal auxiliary is introduced after preparing iron manganese metal oxide, the content of auxiliary accounts for 10%-40% of the total mass of composite metal oxide.There is the advantage that carbon dioxide conversion rate is improved, methane, C2-C4 alkane class selectivity is reduced, high selectivity of carbon dioxide is realized to prepare aromatic hydrocarbon, C5 + hydrocarbon product selectivity and C5 + mid-aromatic hydrocarbon selectivity are improved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a composite catalyst for the direct production of aromatics from carbon dioxide, its preparation method, and its application. Background Technology

[0002] Aromatic hydrocarbons are important chemical raw materials in the organic chemical industry, with wide applications in plastics, rubber and fiber synthesis, fine chemical synthesis, military industry, explosives, pesticides, and organic solvent synthesis, resulting in a large market demand. Utilizing hydrogenation technology to convert CO2 into high-value-added aromatic hydrocarbons allows CO2 to be stored in the form of hydrocarbon chemicals, which can both realize the utilization of CO2 carbon resources and reduce CO2 emissions, providing strong technical support for carbon peaking and carbon neutrality strategic decisions.

[0003] Currently, the technical routes for producing aromatics from carbon dioxide can be divided into the methanol route and the Fischer-Tropsch synthesis route. The methanol route involves hydrogenating carbon dioxide to synthesize methanol, which is then aromatized to obtain aromatics. The Fischer-Tropsch synthesis route involves converting carbon dioxide to carbon monoxide via reverse water-gas shift (RWGS), then using the carbon monoxide to synthesize the CxHy intermediate via the Fischer-Tropsch reaction, and finally aromatizing it to obtain aromatics.

[0004] Significant progress has been made in the domestic carbon dioxide-to-aromatics route technology. Liu Zhongmin et al. from the Dalian Institute of Chemical Physics used a ZnAlOx / HZSM-5 composite catalyst to catalyze the hydrogenation of carbon dioxide to produce aromatics, achieving a total aromatics selectivity of 73.9%, while the methane byproduct selectivity was only 0.4%. Li Can's research group (CN110743606B) disclosed a ZnZrO / HZSM-5 catalyst with a carbon dioxide conversion rate of 14% and an aromatics selectivity (carbon-based selectivity) of up to 80% in the hydrocarbon products. The carbon monoxide byproduct selectivity was also relatively high at 44%. Sun Jian and Ge Qingjie's research group (CN107840778B) disclosed a method for preparing aromatics by carbon dioxide hydrogenation, using a composite catalyst composed of an iron-based low-carbon olefin catalyst and a modified or unmodified aromatics synthesis catalyst molecular sieve. On this catalyst, the carbon dioxide conversion rate was 33%, the carbon monoxide selectivity was 10%, and the total aromatics selectivity in the liquid phase products was 63%. Xiamen University researchers, including Duan Xinping et al. (CN109621996B), disclosed a catalyst composed of transition metal phosphides and auxiliary phosphides. The auxiliary phosphides are one or more of Cu3P2, Ni2P, CoP, and FeP. The selectivity for aromatics can reach 68.3%, and the product does not contain CO. Xiamen University researchers, including Wang Ye et al., prepared a composite catalyst of ZnO-ZrO2 aerogel and HZSM-5, achieving a single-pass carbon dioxide conversion rate of 16% and an aromatics selectivity of 76%. The Shanghai Advanced Research Institute of the Chinese Academy of Sciences researchers, including Gao Peng et al. (CN108160104A), disclosed a ZnZrOx catalyst. The composite catalyst with chain-like HZSM-5 achieved a carbon dioxide conversion rate of 17.5% and a carbon monoxide selectivity reduced to 23.8%. Furthermore, by adjusting the b-axis length of the HZSM-5 nanocrystals, the aromatic selectivity could reach up to 75%. Qiao Minghua et al. from Fudan University (CN109942359A) disclosed a dual-bed composite catalyst. The first bed uses three-dimensional honeycomb graphene as a support to load catalytically active components such as iron and potassium, catalyzing the generation of low-carbon olefin intermediates from CO2. The second bed uses an acidic molecular sieve catalyst to catalyze the aromatization reaction of low-carbon olefins.On this dual-bed catalyst, the composition of aromatics can be flexibly controlled by adjusting the catalyst ratio, and the selectivity of the aromatic products is high, but the carbon dioxide conversion rate is not high. Liu Dianhua et al. of East China University of Science and Technology (CN111229303A) disclosed a catalyst with a three-layer porous core-shell structure, the inner layer being a metal-modified metal oxide, the middle layer being a microporous SiO2 thin layer coated with metal-modified metal oxide, and the outer layer being an HZSM-5 molecular sieve layer. Hu Bairui of Northwest University studied the Fe-K / a-Al2O3&P / HZSM-5 bifunctional catalyst, which achieved a CO2 conversion rate of 36.4%, an aromatic selectivity of 35.5%, and a CO by-product selectivity of 10.2%. In March 2021, the world's first 10,000-ton-level carbon dioxide to aromatics industrial pilot project, jointly developed and designed by Inner Mongolia Jiutai Group, China Chengda and Tsinghua University, held a commencement meeting. It adopts the one-step production of aromatics from fluidized syngas (FSTA) and the production of dienes from fluidized oxidative dehydrogenation (FODH). PetroChina Petrochemical Research Institute has developed a highly active Na-FeMnOx / HZSM-5 bifunctional catalyst with a CO2 conversion rate of 44.49% and a liquid-phase aromatics selectivity of 76.3%.

[0005] In 2018, Tsubaki et al. from Toyama University in Japan prepared a Cr2O3 / H-ZSM-5 / SiO2 composite catalyst. The HZSM-5 was coated with an inert SiO2 shell and mechanically mixed with Cr2O3 oxide powder to catalyze the hydrogenation reaction of CO2. The conversion rate reached 34.5% and the selectivity of aromatics was 76%. Compared with the uncoated catalyst, the conversion rate and selectivity were significantly improved. However, the selectivity of carbon monoxide was still very high, and there was still room for improvement in the conversion rate of carbon dioxide. Summary of the Invention

[0006] In view of the deficiencies of the above-mentioned technology, the first objective of the present invention is to provide a composite catalyst for the direct production of aromatics from carbon dioxide.

[0007] The second objective of this invention is to provide a method for preparing a composite catalyst for the direct production of aromatics from carbon dioxide.

[0008] A third objective of this invention is to provide an application of a composite catalyst for the direct production of aromatics from carbon dioxide.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] The first aspect of the present invention provides a composite catalyst for the direct production of aromatics from carbon dioxide, which is prepared by mechanically mixing metal oxide and HZSM-5 molecular sieve in a coupling mass ratio of (1-3):1. The main active component of the metal oxide is iron oxide, and the metal oxide promoter is composed of manganese oxide and at least one of copper oxide, sodium oxide and potassium oxide. The manganese promoter is introduced during the preparation of iron oxide, and the other metal promoters are introduced after the preparation of iron-manganese metal oxide. The content of the promoter accounts for 10%-40% of the total mass of the composite metal oxide.

[0011] Preferably, the main forms of iron-based metal oxides are Fe2O3 and Fe3O4, the main forms of manganese-based metal oxides are Mn2O3, Mn3O4 and MnO2, the main form of sodium-based metal oxides is Na2O, the main form of potassium-based metal oxides is K2O, and the main form of copper-based metal oxides is CuO.

[0012] Preferably, in the metal oxide, the molar ratio of manganese to iron is (0.1-10):1, the molar ratio of sodium to iron is (0-10):1, the molar ratio of potassium to iron is (0-10):1, and the molar ratio of copper to iron is (0-5):1.

[0013] Preferably, the metal oxide is an amorphous particle with a particle size of 10-1000 μm and a pore volume of 0.05-0.50 cm³. 3 / g, BET specific surface area is 30-200m² 2 / g, with an average pore size of 2-100nm; the pore volume of the HZSM-5 molecular sieve is 0.05-100cm³. 3 / g, BET specific surface area is 100-550m² 2 / g, with an average pore size of 0.5-50nm and a silicon-to-aluminum ratio of 10-400.

[0014] A second aspect of the present invention provides a method for the direct production of aromatics from carbon dioxide using a composite catalyst, comprising the following steps:

[0015] (1) Preparation of metal-modified metal oxides

[0016] Iron nitrate and manganese nitrate in a molar ratio of (1-10):1 are dissolved in 100mL-400mL of deionized water. The solution is heated and stirred until completely dissolved. An alkaline precipitant is slowly added dropwise at 70-80℃. When the pH reaches 4-13, the titration endpoint is reached and the addition of the alkaline precipitant is stopped. Stirring is continued, and the solution is aged for 0.5-3h. The solution is then filtered, washed, and the alkali metal ion content and pH of the filter cake are adjusted. The solution is then dried at 60-120℃ for 6-24h.

[0017] One of copper metal oxide, sodium metal oxide, and potassium metal oxide is loaded onto the precursor using an excess impregnation method: the mass of the corresponding carbonate solution is calculated according to the amount of metal oxide required, and a salt solution is prepared. The precursor is impregnated in the salt solution, and after impregnation, it is allowed to stand for 8-24 hours, dried at 60-120℃ for 5-18 hours, and calcined at 350-550℃ for 2-10 hours to obtain a composite metal oxide.

[0018] (2) Preparation of HZSM-5 molecular sieve by phase transfer method

[0019] Sodium hydroxide was dissolved in deionized water and stirred for 5 min to 1 h. Tetrapropylammonium hydroxide was then added dropwise and mixed thoroughly. Aluminum isopropoxide was added and stirred for 1 to 6 h. Tetraethyl orthosilicate was added dropwise and stirred for 3 to 24 h. Toluene was added and stirred for 0.5 to 6 h. Trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) was added dropwise and stirred for 2 to 6 h. The precursor was then transferred to a hydrothermal reactor for crystallization and crystallized at 80 to 180 °C for 12 to 72 h. After cooling to room temperature, the product was centrifuged and washed several times with deionized water or ethanol until the washing solution was neutral. The product was dried at 60 to 120 °C for 5 to 24 h and calcined at 200 to 600 °C for 1 to 10 h to obtain Na-type ZSM-5 molecular sieve.

[0020] Na-type ZSM-5 molecular sieves were subjected to ion exchange with 0.1-2 mol / L ammonium chloride solution for 1-6 h at a temperature of 40-80℃. The concentration of Na-type ZSM-5 molecular sieves dissolved in ammonium chloride solution was 0.1-10 mol / L. This process was repeated 2-4 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at a temperature of 80-120℃ for 5-18 h and calcined at a temperature of 200-600℃ for 1-6 h to obtain nano-HZSM-5 molecular sieves.

[0021] (3) The metal oxide and HZSM-5 molecular sieve are mechanically mixed at a coupling mass ratio of (1-3):1 to obtain the composite catalyst.

[0022] Preferably, in step (1) of the preparation method, the iron nitrate is iron nitrate, the manganese nitrate is a 50wt% manganese nitrate solution, the alkaline precipitant is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and ammonia water, prepared into an aqueous solution with a concentration of 0.01-10 mol / L, the auxiliary agent is composed of manganese oxide and one of copper, sodium, and potassium oxides, and the heating and stirring to completely dissolve it is at a temperature of 40-90℃ for 5-60 min.

[0023] The third aspect of the present invention provides an application of a composite catalyst for the direct production of aromatics from carbon dioxide, the application comprising the following steps: pressing the composite catalyst into tablets, grinding it into 40-60 mesh particles, mixing 0.5g of each of the two catalysts evenly, loading it into the isothermal section of a fixed-bed tubular reactor, and evaluating the carbon dioxide hydrogenation reaction after pretreatment.

[0024] Preferably, the reaction evaluation conditions are as follows: the composite catalyst is loaded into the isothermal section of a fixed-bed tubular reactor, and the temperature is increased from room temperature to the reduction temperature at a rate of 1-10℃ / min under nitrogen atmosphere. Then, it is reduced under H2, N2 or pure hydrogen atmosphere. After reduction, it is carbonylated under a mixed gas of CO and N2 or pure CO atmosphere. After completion, the temperature is adjusted to the reaction temperature, and the reducing gas is switched to the reaction feed gas for activity evaluation.

[0025] Preferably, the pretreatment conditions include: a two-step H2-CO pretreatment, first at 250–500°C, 0.01–5.0 MPa, in an atmosphere containing H2 and N2, with a space velocity of 1000–50000 ml·h. -1 ·gCat -1 Catalyst reduction was carried out for 2–30 hours under CO and N2 atmospheres at 250–450 °C, 0.01–5.0 MPa, and a gas space velocity of 500–50000 ml·h. -1 ·gCat -1 The process involves catalytic carbonylation for 3–50 hours under specific conditions.

[0026] Preferably, the proportion of hydrogen in the H2 and N2 mixture of the pretreatment gas is 5%-100%, and the proportion of CO in the CO and N2 mixture is 10%-100%. The volume ratio of H2 to CO2 in the reaction feed gas is 1-6. The reaction temperature is 250-380℃, the reaction pressure is 2-5MPa, and the space velocity is 500-10000 ml·h. -1 ·gCat -1 .

[0027] The beneficial effects of this invention are:

[0028] The preparation method disclosed in this invention obtains a metal oxide with uniformly dispersed active components by combining precipitation and ultrasonic impregnation. A special pretreatment method is used (using hydrogen to reduce iron in oxide state to elemental iron, and then using CO to carbonize elemental iron to Fe5C2, and the active species for the hydrogenation of carbon dioxide to produce low-carbon olefins is Fe5C2) so that the metal oxide can improve the carbon dioxide conversion rate, reduce the selectivity of C2-C4 alkanes, and improve the selectivity of C2-C4 olefins during the catalytic carbon dioxide activation process. At the same time, it has the advantage of high selectivity of carbon dioxide to directly produce aromatics. The reason for this effect is that (1) the reaction process of carbon dioxide to produce aromatics can be described as the process of carbon dioxide and hydrogen reverse water conversion and Fischer-Tropsch reaction to produce low-carbon olefins, and the low-carbon olefins undergo olefin aromatization reaction on molecular sieves to produce aromatics. The C2-C4 alkanes generated on the metal oxide do not react on the molecular sieve. Therefore, the lower the selectivity of C2-C4 alkanes generated on the metal oxide, the lower the selectivity of the final product C2-C4 hydrocarbons in the reaction system. 5+ The selectivity of hydrocarbons and aromatics is also higher; (2) The present invention uses the phase transfer method to prepare a molecular sieve with abundant intercrystalline mesopores to catalyze the carbon dioxide to aromatics reaction. Through abundant intercrystalline mesopores and suitable molecular sieve pore size, the selectivity of the product aromatics is improved. Attached Figure Description

[0029] none Detailed Implementation

[0030] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0031] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and compounds are commercially available.

[0032] Example 1

[0033] The first step, the preparation method of copper-modified iron-manganese bimetallic oxide, includes the following steps:

[0034] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0035] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0036] Prepare 10 ml of a 0.0435 mol / L copper carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the copper carbonate solution. After sonication for 50 min, let it stand for 12 h to soak. Transfer the mixture to an oven and dry it at 120℃ for 12 h, then calcine it at 400℃ for 4 h to obtain copper-modified iron-manganese metal oxide. Grind, press, and sieve to 40-60 mesh for later use.

[0037] The copper-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the copper-modified iron-manganese bimetallic oxide is 0.27 cm³. 3 / g, BET specific surface area is 69.88m² 2 / g, with an average pore size of 3.16nm;

[0038] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of copper to iron is 0.012:1.

[0039] The second step, the preparation method of HZSM-5 molecular sieve, includes the following steps:

[0040] First, sodium hydroxide is dissolved in deionized water and stirred for 20 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:4:15:8:2500:500:5.

[0041] The product was crystallized at 170℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0042] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 2 mol / L ammonium chloride solution at 60℃ for 3 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 110℃ for 6 h and calcined at 500℃ for 5 h to obtain nano-HZSM-5 molecular sieve.

[0043] The pore volume of HZSM-5 molecular sieve is 0.45 cm³. 3 / g, BET specific surface area is 420m² 2 / g, with an average pore size of 3.8nm and a silicon-to-aluminum ratio of 25.

[0044] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0045] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0046] Step 4: The application of the catalyst includes the following steps:

[0047] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions: at atmospheric pressure and 350°C, with a reducing atmosphere of pure H2 and a reducing atmosphere space velocity of 1000 ml·h. -1 ·gCat -1 Reduction for 4 hours under normal pressure and CO atmosphere at 300℃ for 500 ml / h -1 ·gCat -1 After 4 hours of pretreatment, the temperature was adjusted to the reaction temperature, and the reaction gas was switched to the reaction conditions: the volume ratio of H2 to CO2 in the reactant gas was 3, the temperature was 320℃, the pressure was 3MPa, and the space velocity was 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0048] Example 2

[0049] The first step, the preparation method of copper-modified iron-manganese bimetallic oxide, includes the following steps:

[0050] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0051] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0052] Prepare 10 ml of a 0.2416 mol / L copper carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the copper carbonate solution. After sonication for 50 min, let it stand for 12 h to soak. Transfer the mixture to an oven and dry it at 120℃ for 12 h, then calcine it at 400℃ for 4 h to obtain copper-modified iron-manganese metal oxide. Grind, press, and sieve to 40-60 mesh for later use.

[0053] The copper-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the copper-modified iron-manganese bimetallic oxide is 0.32 cm³. 3 / g, BET specific surface area is 72.35m² 2 / g, with an average pore size of 2.86nm;

[0054] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of copper to iron is 0.067:1.

[0055] The second step and subsequent methods are the same as in Example 1.

[0056] Example 3

[0057] The first step, the preparation method of copper-modified iron-manganese bimetallic oxide, includes the following steps:

[0058] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0059] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0060] Prepare 10 ml of a 0.3508 mol / L copper carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the copper carbonate solution. After sonication for 50 min, let it stand for 12 h to soak. Transfer the mixture to an oven and dry it at 120℃ for 12 h, then calcine it at 400℃ for 4 h to obtain copper-modified iron-manganese metal oxide. Grind, press, and sieve to 40-60 mesh for later use.

[0061] The copper-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the copper-modified iron-manganese bimetallic oxide is 0.27 cm³. 3 / g, BET specific surface area is 69.88m² 2 / g, with an average pore size of 3.16nm;

[0062] In metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of copper to iron is 0.1:1.

[0063] The second step and subsequent methods are the same as in Example 1.

[0064] Example 4

[0065] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0066] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0067] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0068] Prepare 10 ml of a 0.174 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the sodium carbonate solution. Sonicate for 50 min, then let it stand for 12 h to soak. Transfer the mixture to an oven and dry at 120 °C for 12 h, then calcine at 400 °C for 4 h to obtain sodium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0069] The sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-modified iron-manganese bimetallic oxide is 0.21 cm³. 3 / g, BET specific surface area is 65.78m² 2 / g, with an average pore size of 5.99nm;

[0070] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of sodium to iron is 0.046:1.

[0071] The second step, the preparation method of HZSM-5 molecular sieve, includes the following steps:

[0072] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:4:15:8:2500:500:5.

[0073] The product was crystallized at 160℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0074] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 2 mol / L ammonium chloride solution at 80℃ for 6 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 120℃ for 8 h and calcined at 550℃ for 6 h to obtain nano-HZSM-5 molecular sieve.

[0075] The pore volume of HZSM-5 molecular sieve is 0.6 cm³. 3 / g, BET specific surface area is 480m² 2 / g, average pore size is 3nm, silicon-to-aluminum ratio is 25.

[0076] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0077] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0078] Step 4: The application of the catalyst includes the following steps:

[0079] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions were: 1.0 MPa, 370 °C, reducing atmosphere (20% H₂, 80% N₂, volume ratio), and reducing atmosphere space velocity (HSV) of 2000 ml·h⁻¹. -1 gCat -1 Reduction for 8 hours under the following conditions; followed by reduction at 1 MPa and 300℃ in an atmosphere (20% CO, 80% N2 by volume) at 4000 ml / h. 1 ·gCat -1 After 8 hours of treatment; after pretreatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: the volume ratio of H2 to CO2 in the reactant gas is 2, the temperature is 320℃, the pressure is 3MPa, and the space velocity is 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0080] Example 5

[0081] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0082] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0083] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0084] Prepare 10 ml of a 0.348 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the sodium carbonate solution. Sonicate for 50 min, then let it stand for 12 h. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain sodium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0085] The sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-modified iron-manganese bimetallic oxide is 0.22 cm³. 3 / g, BET specific surface area is 63.53m² 2 / g, with an average pore size of 5.42nm;

[0086] In the metal oxides, the molar ratio of iron to manganese is 1:0.3, and the molar ratio of sodium to iron is 0.093:1.

[0087] The second step, the preparation method of HZSM-5 molecular sieve, includes the following steps:

[0088] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:4:20:10:2500:500:5.

[0089] The product was crystallized at 170℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0090] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 1 mol / L ammonium chloride solution at 80℃ for 6 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 120℃ for 12 h and calcined at 550℃ for 6 h to obtain nano-HZSM-5 molecular sieve.

[0091] The pore volume of HZSM-5 molecular sieve is 0.68 cm³. 3 / g, BET specific surface area is 415m² 2 / g, average pore size is 4nm, silicon-to-aluminum ratio is 25.

[0092] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0093] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0094] Step 4: The application of the catalyst includes the following steps:

[0095] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions were: 2.0 MPa, 350 °C, reducing atmosphere (10% H₂, 90% N₂, volume ratio), and reducing atmosphere space velocity (4000 ml·h⁻¹). -1 ·gCat -1Reduction for 16 hours under the following conditions; followed by reduction at 2 MPa, 300 °C, and an atmosphere of (20% CO, 80% N2, by volume) at 4000 ml / h. -1 gCat -1 After 8 hours of treatment; after pretreatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: the volume ratio of H2 to CO2 in the reactant gas is 3, the temperature is 350℃, the pressure is 3MPa, and the space velocity is 3000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0096] Example 6

[0097] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0098] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0099] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 8 hours to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0100] Prepare 10 ml of a 0.696 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the sodium carbonate solution. Sonicate for 60 min, then let it stand for 12 h to soak. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain sodium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0101] The sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-modified iron-manganese bimetallic oxide is 0.21 cm³. 3 / g, BET specific surface area is 62.73m² 2 / g, with an average pore size of 5.01nm;

[0102] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of sodium to iron is 0.186:1.

[0103] The second step, the preparation method of HZSM-5 molecular sieve, includes the following steps:

[0104] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:4:20:10:2500:500:5.

[0105] The product was crystallized at 160℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0106] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 1 mol / L ammonium chloride solution at 80℃ for 3 h, and the process was repeated 4 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 110℃ for 6 h and calcined at 500℃ for 5 h to obtain nano-HZSM-5 molecular sieve.

[0107] The pore volume of HZSM-5 molecular sieve is 0.8 cm³. 3 / g, BET specific surface area is 450m² 2 / g, with an average pore size of 3.5nm and a silicon-to-aluminum ratio of 25.

[0108] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0109] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0110] Step 4: The application of the catalyst includes the following steps:

[0111] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions: at atmospheric pressure and 350°C, with a reducing atmosphere of pure H2 and a reducing atmosphere space velocity of 1000 ml·h. -1 ·gCat-1 Reduction for 4 hours under normal pressure and CO atmosphere at 300℃ for 500 ml / h -1 ·gCat -1 After 4 hours of treatment; once reduction is complete, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: H2 to CO2 volume ratio in the reactant gas is 3, temperature is 320℃, pressure is 3MPa, and space velocity is 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0112] Example 7

[0113] The first step, the preparation method of potassium-modified iron-manganese bimetallic oxide, includes the following steps:

[0114] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0115] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0116] Prepare 10 ml of a 1.4 mol / L potassium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the potassium carbonate solution. Sonicate for 60 min and then let it stand for 18 h. Transfer the mixture to an oven and dry at 120 °C for 12 h, then calcine at 400 °C for 4 h to obtain potassium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0117] The potassium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the potassium-modified iron-manganese bimetallic oxide is 0.19 cm³. 3 / g, BET specific surface area is 59.31m² 2 / g, with an average pore size of 4.77nm;

[0118] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of potassium to iron is 0.373:1.

[0119] The second step, the preparation method of HZSM-5 molecular sieve, includes the following steps:

[0120] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:4:15:10:2500:500:5.

[0121] The product was crystallized at 170℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0122] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 1 mol / L ammonium chloride solution at 60℃ for 6 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 120℃ for 12 h and calcined at 450℃ for 6 h to obtain nano-HZSM-5 molecular sieve.

[0123] The pore volume of HZSM-5 molecular sieve is 0.62 cm³. 3 / g, BET specific surface area is 460m² 2 / g, with an average pore size of 3.9nm and a silicon-to-aluminum ratio of 25.

[0124] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0125] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0126] Step 4: The application of the catalyst includes the following steps:

[0127] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions: 3 MPa pressure, 350 °C, reducing atmosphere (5% H2, 95% N2, volume ratio), and reducing atmosphere space velocity 6000 ml·h.-1 ·gCat -1 Reduction for 24 hours under the following conditions; then subjected to 3 MPa, 300℃, and an atmosphere of (10% CO, 90% N2, by volume) at 2000 ml / h. -1 ·gCa -1 After 24 hours of treatment; after pretreatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: the volume ratio of H2 to CO2 in the reactant gas is 3, the temperature is 320℃, the pressure is 3MPa, and the space velocity is 1000ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0128] Example 8

[0129] The first step, the preparation method of potassium-modified iron-manganese bimetallic oxide, includes the following steps:

[0130] First, dissolve 30.3g of ferric nitrate nonahydrate and 8.0529g of manganese nitrate solution in 180ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0131] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried overnight at 110°C to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0132] Prepare 10 ml of a 0.696 mol / L potassium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the potassium carbonate solution. Sonicate for 50 min, then let it stand for 12 h. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain potassium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0133] The potassium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the potassium-modified iron-manganese bimetallic oxide is 0.27 cm³. 3 / g, BET specific surface area is 61.8m² 2 / g, with an average pore size of 5.23nm;

[0134] In the metal oxides, the molar ratio of iron to manganese is 1:0.3, and the molar ratio of potassium to iron is 0.186:1.

[0135] The second step, the preparation method of HZSM-5 (Si / Al=60) molecular sieve, includes the following steps:

[0136] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:1.66:20:10:2500:500:5.

[0137] The product was crystallized at 170℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0138] Na-type ZSM-5 molecular sieve was subjected to ion exchange with 1 mol / L ammonium chloride solution at 80℃ for 6 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at 110℃ for 12 h and calcined at 550℃ for 5 h to obtain nano-HZSM-5 molecular sieve.

[0139] The pore volume of HZSM-5 molecular sieve is 0.61 cm³. 3 / g, BET specific surface area is 496m² 2 / g, with an average pore size of 3.1nm and a silicon-to-aluminum ratio of 60.

[0140] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0141] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0142] Step 4: The application of the catalyst includes the following steps:

[0143] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions were: 2.0 MPa, 370 °C, reducing atmosphere (25% H₂, 75% N₂, volume ratio), and reducing atmosphere space velocity (4000 ml·h⁻¹). -1 ·gCat -1 Reduction was carried out under the following conditions for 8 hours: 2.0 MPa, 320 °C, and an atmosphere of (15% CO, 85% N2, by volume) at 4000 ml / h. -1 ·gCat -1 After 10 hours of treatment; following the pretreatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: H2 to CO2 volume ratio in the reactant gas is 2, temperature is 350℃, pressure is 4MPa, and space velocity is 5000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0144] Example 9

[0145] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0146] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0147] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 8 hours to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0148] Prepare 10 ml of a 0.696 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the sodium carbonate solution. Sonicate for 60 min, then let it stand for 12 h to soak. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain sodium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0149] The sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-modified iron-manganese bimetallic oxide is 0.21 cm³.3 / g, BET specific surface area is 62.73m² 2 / g, with an average pore size of 5.01nm;

[0150] In the metal oxides, the molar ratio of iron to manganese is 1:0.3, and the molar ratio of sodium to iron is 0.186:1.

[0151] The second step, the preparation method of HZSM-5 (Si / Al=200) molecular sieve, includes the following steps:

[0152] First, sodium hydroxide is dissolved in deionized water and stirred for 10 minutes. Then, tetrapropylammonium hydroxide is added dropwise. After the mixture is homogeneous, aluminum isopropoxide is added and stirred for 3 hours. Then, tetraethyl orthosilicate is added dropwise to the solution and stirred for 12 hours. Then, toluene is added to the solution and stirred for 3 hours. Then, trimethoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyltrimethoxysilane (HTS) is added dropwise. After stirring for 3 hours, the precursor is transferred to a hydrothermal reactor for crystallization. The molar ratio of tetraethyl orthosilicate, aluminum isopropoxide, tetrapropylammonium hydroxide, sodium hydroxide, deionized water, toluene, and trimethoxy[3-(phenylamino)propyl]silane or hexadecyltrimethoxysilane is 100:0.5:20:10:2500:500:5.

[0153] The product was crystallized at 170℃ for 48 hours, during which the hydrothermal crystallization vessel was rotated at a rate of 90 r / min. The crystallized product was filtered and washed, dried at 100℃ for 12 hours, and then calcined in air at 550℃ for 5 hours to obtain Na-type HZSM-5.

[0154] Na-type ZSM-5 molecular sieves were subjected to ion exchange with 1.5 mol / L ammonium chloride solution at a temperature of 40-80℃ for 6 h, and the process was repeated 3 times. The resulting product was centrifuged and washed with deionized water until neutral. The filter cake was dried at a temperature of 110℃ for 12 h and calcined at a temperature of 550℃ for 5 h to obtain nano-HZSM-5 molecular sieves.

[0155] The pore volume of HZSM-5 molecular sieve is 0.58 cm³. 3 / g, BET specific surface area is 521m² 2 / g, with an average pore size of 2.8nm and a silicon-to-aluminum ratio of 200.

[0156] The third step involves the preparation of a composite catalyst for the direct production of high-value aromatics from carbon dioxide, including the following steps:

[0157] 0.5g of the metal oxide prepared in the first step and 0.5g of the HZSM-5 molecular sieve prepared in the second step are mechanically mixed evenly to obtain the composite catalyst for the direct production of high-value aromatics from carbon dioxide.

[0158] Step 4: The application of the catalyst includes the following steps:

[0159] The homogeneously mixed catalyst was packed into the isothermal section of a fixed-bed tubular reactor for evaluation of carbon dioxide hydrogenation reaction. Pretreatment conditions: at atmospheric pressure and 350°C, with a reducing atmosphere of pure H2 and a reducing atmosphere space velocity of 1000 ml·h. -1 ·gCat -1 Reduction for 4 hours under normal pressure and CO atmosphere at 300℃ for 500 ml / h -1 ·gCat -1 After 4 hours of treatment; once reduction is complete, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: H2 to CO2 volume ratio in the reactant gas is 3, temperature is 320℃, pressure is 3MPa, and space velocity is 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0160] Comparative Example 1

[0161] (The oxide is an iron-manganese bimetallic oxide, without the addition of a third component, and the molecular sieve preparation and pretreatment methods are the same as in Example 4)

[0162] The first step, the method for preparing sodium-free iron-manganese bimetallic oxide, includes the following steps:

[0163] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0164] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 L of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110 °C for 12 h and calcined at 400 °C for 4 h to obtain iron-manganese bimetallic oxide, which was then ground and sieved to 40-60 mesh for later use.

[0165] The iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the iron-manganese bimetallic oxide is 0.18 cm³. 3 / g, BET specific surface area is 52.14m² 2 / g, with an average pore size of 5.11nm;

[0166] In metal oxides, the molar ratio of iron to manganese is 5:1.

[0167] Step 2: The preparation method of HZSM-5 molecular sieve, the catalyst pretreatment method, and the reaction conditions for carbon dioxide hydrogenation to aromatics are the same as in Example 4.

[0168] Comparative Example 2

[0169] (The oxides were prepared using a co-precipitation method, and the molecular sieve preparation and pretreatment methods were the same as in Example 4.)

[0170] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide by co-precipitation, includes the following steps:

[0171] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh 10.92g of sodium carbonate and dissolve it in water to prepare a precipitant with a concentration of 1mol / L. Under constant temperature conditions of 70℃, slowly add sodium carbonate solution (at a rate of one drop every four seconds) to the precursor solution while stirring until the alkaline solution is completely added. Allow the precipitate to age for 60 minutes.

[0172] The precipitate was then separated by filtration, and the filter cake was dried at 110°C for 12 hours and calcined at 400°C for 4 hours to obtain sodium-modified iron-manganese bimetallic oxide, which was then ground and sieved to 40-60 mesh for later use.

[0173] Sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-modified iron-manganese bimetallic oxide is 0.15 cm³. 3 / g, BET specific surface area is 54.32m² 2 / g, with an average pore size of 4.83nm;

[0174] In the metal oxides, the molar ratio of iron to manganese is 5:1, and the molar ratio of sodium to iron is 0.186:1.

[0175] Step 2: The preparation method of HZSM-5 molecular sieve, the catalyst pretreatment method, and the reaction conditions for carbon dioxide hydrogenation to aromatics are the same as in Example 4.

[0176] Comparative Example 3

[0177] (Manganese oxide and sodium additives were impregnated separately; the molecular sieve preparation and pretreatment methods were the same as in Example 4.)

[0178] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0179] First, dissolve 30.3g of ferric nitrate nonahydrate in 150ml of deionized water and heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a precipitant with a concentration of 1mol / L. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0180] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 8 hours and ground into powder for subsequent preparation processes.

[0181] Weigh 5.3686 g of manganese nitrate solution, add the above precursor powder into the manganese nitrate solution, and let it stand for 12 h. Transfer the mixture to an oven at 110 °C and dry for 12 h to obtain the iron-manganese bimetallic precursor, and grind it into powder.

[0182] Prepare 10 ml of a 0.696 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic precursor powder and add it to the sodium carbonate solution. After sonication for 60 min, let it stand for 12 h to soak. Transfer the mixture to an oven and dry it at 120 °C for 12 h, then calcine it at 400 °C for 4 h to obtain sodium-modified metal oxides. Sieve the oxides to 40-60 mesh for later use.

[0183] The sodium-modified iron-manganese bimetallic oxide is an amorphous powder with a particle size of approximately 14 μm. The pore volume of the sodium-manganese-modified iron oxide is 0.11 cm³. 3 / g, BET specific surface area is 40.13m² 2 / g, with an average pore size of 3.27nm;

[0184] In the metal oxides, the molar ratio of iron to manganese is 5:1, and the molar ratio of sodium to iron is 0.186:1.

[0185] Step 2: The preparation method of HZSM-5 molecular sieve, the catalyst pretreatment method, and the reaction conditions for carbon dioxide hydrogenation to aromatics are the same as in Example 4.

[0186] Comparative Example 4

[0187] The catalyst was prepared in the same manner as in Example 4, except that a one-step pretreatment with pure hydrogen was used.

[0188] Pretreatment conditions: At atmospheric pressure and 350℃, the reducing atmosphere is pure H2, and the reducing atmosphere space velocity is 1000 ml·h. -1 ·gCat -1The reduction was carried out for 4 hours under the following conditions: after reduction, the temperature was adjusted to the reaction temperature, and the reaction gas was switched to the reaction conditions: the volume ratio of H2 to CO2 in the reactant gas was 3, the temperature was 320℃, the pressure was 3MPa, and the space velocity was 1000ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0189] Comparative Example 5

[0190] The catalyst was prepared in the same manner as in Example 4, but the pretreatment was performed using pure CO in a one-step process.

[0191] Pretreatment conditions: At normal pressure, CO atmosphere, 300℃, 500ml·h -1 ·gCat -1 After 4 hours of treatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: H2 to CO2 volume ratio in the reactant gas is 3, temperature is 320℃, pressure is 3MPa, and space velocity is 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0192] Comparative Example 6

[0193] The catalyst was prepared in the same way as in Example 3, but the pretreatment was carried out in one step using a mixture of hydrogen and nitrogen.

[0194] Pretreatment conditions: at 2.0 MPa and 350 °C, with a reducing atmosphere (10% H2, 90% N2, volume ratio) and a reducing atmosphere space velocity of 4000 ml·h. -1 ·gCat -1 The reduction was carried out for 16 hours under the following conditions: after reduction, the temperature was adjusted to the reaction temperature, and the reaction gas was switched to the following conditions: the volume ratio of H2 to CO2 in the reactant gas was 3, the temperature was 350℃, the pressure was 3MPa, and the space velocity was 3000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0195] Comparative Example 7

[0196] The catalyst was prepared in the same way as in Example 3, except that the pretreatment was performed in one step using a mixture of carbon monoxide and nitrogen.

[0197] Pretreatment conditions: 2 MPa, 300 °C, atmosphere (20% CO, 80% N2, volume ratio), 4000 ml / h -1 ·gCa -1After 8 hours of treatment; after pretreatment, adjust the temperature to the reaction temperature and switch to the reaction gas. Reaction conditions: the volume ratio of H2 to CO2 in the reactant gas is 3, the temperature is 350℃, the pressure is 3MPa, and the space velocity is 3000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0198] Comparative Example 8

[0199] The catalyst was prepared in the same manner as in Example 2, but the pretreatment was carried out in one step using a mixture of hydrogen and nitrogen.

[0200] Pretreatment conditions: at 1.0 MPa and 370 °C, with a reducing atmosphere (20% H2, 80% N2 by volume) and a reducing atmosphere space velocity of 2000 ml·h. -1 ·gCat -1 The reaction was carried out under the following conditions for 8 hours: after pretreatment, the temperature was adjusted to the reaction temperature, and the reaction gas was switched to the following conditions: the volume ratio of H2 to CO2 in the reaction feed gas was 2, the temperature was 320℃, the pressure was 3MPa, and the space velocity was 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0201] Comparative Example 9

[0202] The catalyst was prepared in the same manner as in Example 2, but the pretreatment was carried out in one step using a mixture of carbon monoxide and nitrogen.

[0203] Pretreatment conditions: 1 MPa, 300℃, atmosphere (20% CO, 80% N2, volume ratio), 4000 ml / h -1 ·gCat -1 The pretreatment process lasted 8 hours. After pretreatment, the temperature was adjusted to the reaction temperature, and the reaction gas was switched to the reaction conditions: the volume ratio of H2 to CO2 in the reactant gas was 2, the temperature was 320℃, the pressure was 3MPa, and the space velocity was 1000 ml·h. -1 ·gCat -1 The reaction time is 48 hours.

[0204] Comparative Example 10

[0205] The preparation of metal oxides and catalyst pretreatment are the same as in Example 4. Commercially available molecular sieves are used, and they are ground and pressed into tablets of 40-60 mesh for later use.

[0206] The pore volume of HZSM-5 molecular sieve is 0.23 cm³. 3 / g, BET specific surface area is 320m² 2 / g, with an average pore size of 1.25nm and a silicon-to-aluminum ratio between 20 and 30.

[0207] Comparative Example 11

[0208] The preparation method of copper-modified iron-manganese bimetallic oxide includes the following steps:

[0209] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0210] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0211] Prepare 10 ml of a 0.7016 mol / L copper carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the copper carbonate solution. Sonicate for 50 min, then let it stand for 12 h. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain copper-modified iron-manganese metal oxide. Grind, press into tablets, and sieve to 40-60 mesh for later use.

[0212] The molar ratio of iron to manganese in the metal oxide is 1:0.2, and the molar ratio of copper to iron is 0.2:1.

[0213] The preparation and pretreatment of molecular sieves are the same as in Example 1.

[0214] Comparative Example 12

[0215] The first step, the preparation method of sodium-modified iron-manganese bimetallic oxide, includes the following steps:

[0216] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0217] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0218] Prepare 10 ml of a 0.87 mol / L sodium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the sodium carbonate solution. Sonicate for 50 min, then let it stand for 12 h. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain sodium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0219] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of sodium to iron is 0.23:1.

[0220] The preparation and pretreatment of molecular sieves are the same as in Example 4.

[0221] Comparative Example 13

[0222] The first step, the preparation method of potassium-modified iron-manganese bimetallic oxide, includes the following steps:

[0223] First, dissolve 30.3g of ferric nitrate nonahydrate and 5.3686g of manganese nitrate solution in 150ml of deionized water. Heat and stir in a constant temperature water bath until completely dissolved. Weigh out sodium hydroxide and dissolve it in water to prepare a 1mol / L precipitant. Under constant temperature conditions of 70℃, slowly add sodium hydroxide solution dropwise (at a rate of one drop every four seconds) to the precursor solution while stirring. Monitor the pH of the solution with a pH meter. When the pH reaches 8.5-9.5, stop adding sodium hydroxide solution. Keep the temperature constant and continue stirring to allow the precipitate to age for 60 minutes.

[0224] The precipitate was then separated by vacuum filtration. The resulting filter cake was washed with 1000 ml of deionized water and separated by vacuum filtration again. The filter cake was then dried at 110°C for 12 h to obtain the iron-manganese bimetallic oxide precursor, which was ground into powder for subsequent preparation processes.

[0225] Prepare 10 ml of a 1.88 mol / L potassium carbonate solution. Weigh 4 g of the above-mentioned iron-manganese bimetallic oxide precursor powder and add it to the potassium carbonate solution. Sonicate for 60 min and then let it stand for 18 h. Transfer the mixture to an oven and dry at 120℃ for 12 h, then calcine at 400℃ for 4 h to obtain potassium-modified iron-manganese metal oxide. Grind, compress, and sieve to 40-60 mesh for later use.

[0226] In the metal oxides, the molar ratio of iron to manganese is 1:0.2, and the molar ratio of potassium to iron is 0.5:1.

[0227] The preparation and pretreatment of molecular sieves are the same as in Example 7.

[0228] Table 1 lists the activity evaluation data of the catalysts synthesized in Examples 1-9 and Comparative Examples 1-13.

[0229] Table 1

[0230]

[0231]

[0232] Table 1 shows the activity evaluation data of the composite catalyst, where CO2conv. represents the CO2 conversion rate, CO sel. represents the selectivity of CO among all products, and hydrocarbon product sel. represents the selectivity of each hydrocarbon among the total hydrocarbons, CH4, C2-C4, C 5+ They represent methane, C2-C4 hydrocarbons, and C... 5+ Selectivity of hydrocarbons in total hydrocarbons, C 5+ Aromatic hydrocarbons (sel.) represent various C atoms. 5+ Hydrocarbons in C 5+ Selectivity in total hydrocarbons.

[0233] As shown in Table 1, the metal oxide prepared by this invention is coupled with HZSM-5 molecular sieve and combined with special pretreatment technology to achieve direct and highly selective production of aromatics from carbon dioxide, thereby improving the carbon dioxide conversion rate.

[0234] Compared with the iron-manganese oxide in Comparative Example 1, the sodium-modified iron-manganese bimetallic oxide prepared in this invention has a higher carbon dioxide conversion rate and a lower selectivity for carbon monoxide byproducts. At the same time, the selectivity for aromatics is also significantly increased, indicating that sodium modification enhances the catalytic activity of the metal oxide and can promote Fischer-Tropsch synthesis while reducing the chain growth ability of the catalyst.

[0235] Compared with Comparative Example 2, the sodium-modified iron-manganese bimetallic oxide obtained by the impregnation method has a higher carbon dioxide conversion rate and aromatic selectivity. Compared with the internal sodium prepared by the co-precipitation method, the sodium on the catalyst surface has a more prominent and crucial effect on improving the performance of the catalyst.

[0236] In Comparative Example 3, sodium and manganese were both loaded onto the surface of the metal oxide by impregnation. The performance of the metal oxide decreased significantly, indicating that the coupling distance between sodium and manganese is too close, which is not conducive to the performance improvement of the metal oxide.

[0237] In Comparative Example 4, the pretreatment used a one-step reduction with pure hydrogen. In contrast, the two-step H2-CO pretreatment technology of this invention can achieve a higher carbon dioxide conversion rate, reduce the selectivity of by-product CO, and improve C2 conversion efficiency. 5+ Selectivity of aromatic hydrocarbons.

[0238] In Comparative Example 5, the pretreatment used pure carbon monoxide reduction. Compared to this, the two-step H2-CO pretreatment technology of the present invention can achieve a higher carbon dioxide conversion rate, reduce C2-C4 hydrocarbon selectivity, and improve C2-C4 hydrocarbon selectivity. 5+ Selectivity of aromatic hydrocarbons.

[0239] In Comparative Examples 6 and 8, the pretreatment used a one-step pretreatment with a mixture of hydrogen and nitrogen. Compared with this, the two-step H2-CO pretreatment technology of the present invention can achieve a higher carbon dioxide conversion rate, reduce the selectivity of by-product CO, and improve C 5+ Selectivity of aromatic hydrocarbons.

[0240] In Comparative Examples 7 and 9, the pretreatment used a one-step pretreatment with a mixture of carbon monoxide and nitrogen. Compared with this, the two-step H2-CO pretreatment technology of the present invention can achieve a higher carbon dioxide conversion rate, reduce the selectivity of CO and C2-C4 hydrocarbons, and increase the C2-C4 hydrocarbon conversion rate. 5+ Selectivity of aromatic hydrocarbons.

[0241] Comparative Example 10 uses commercially available molecular sieves. It can be seen that the molecular sieve prepared in this invention has higher selectivity for aromatics, indicating that the prepared molecular sieve has a more optimized structure and abundant mesopores, resulting in stronger product shape selectivity.

[0242] Comparative Examples 11, 12, and 13 show that when the metal molar ratio exceeds the optimal molar ratio range, the catalyst performance decreases significantly.

[0243] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the present invention.

Claims

1. A composite catalyst for direct production of aromatic hydrocarbons from carbon dioxide, characterized by comprising a metal oxide and a metal complex. The composite catalyst is prepared by mechanically mixing metal oxides and HZSM-5 molecular sieves in a coupling mass ratio of (1-3):1, wherein the main active component of the metal oxides is iron oxide, the metal oxide additive is composed of manganese oxide and at least one of copper oxide, sodium oxide and potassium oxide, the manganese additive is introduced during the preparation of the iron oxide, and the other metal additives are introduced after the preparation of the iron-manganese metal oxide, and the content of the additive accounts for 10%-40% of the total mass of the composite metal oxide; The preparation method of the composite catalyst comprises the following steps: (1) preparing metal-modified metal oxides Iron nitrate and manganese nitrate in a molar ratio of (1-10):1 are dissolved in 100-400 mL of deionized water under heating and stirring until completely dissolved, and then a basic precipitator is slowly added dropwise under the condition of 70-80 ℃, when the pH reaches 4-13, the titration endpoint is reached and the addition of the basic precipitator is stopped, and then the stirring is continued, aging for 0.5-3 h, and then filtration, washing, adjusting the content of alkali metal ions in the filter cake and the pH of the filter cake, and drying at 60-120 ℃ for 6-24 h are carried out; One of copper metal oxide, sodium metal oxide and potassium metal oxide is loaded on the precursor by an excess impregnation method: the mass of the corresponding carbonate solution is calculated according to the amount of the required metal oxide, and then the salt solution is prepared, the above-mentioned precursor is immersed in the salt solution, and then after the immersion is completed, it is placed for 8-24 h, dried at 60-120 ℃ for 5-18 h, and calcined at 350-550 ℃ for 2-10 h to obtain the composite metal oxide; (2) preparing HZSM-5 molecular sieves by phase transfer method Sodium hydroxide is dissolved in deionized water, and then tetrapropylammonium hydroxide is added dropwise after stirring for 5 min-1 h, and then aluminum isopropoxide is added after the mixture is uniformly mixed, and then stirring is carried out for 1-6 h, and then tetraethyl orthosilicate is added dropwise and stirring is carried out for 3-24 h, and then toluene is added and stirring is carried out for 0.5-6 h, and then tri-methoxy[3-(phenylamino)propyl]silane (TPPS) or hexadecyl trimethoxysilane (HTS) is added dropwise, and then stirring is carried out for 2-6 h, and then the precursor is transferred to a hydrothermal kettle for crystallization under the condition of 80-180 ℃ for 12-72 h, and then the product is centrifuged, washed with deionized water or ethanol several times until the washing liquid is neutral, and then dried at 60-120 ℃ for 5-24 h, and then calcined under the condition of a temperature of 200-600 ℃ for 1-10 h to obtain Na-type ZSM-5 molecular sieves; The Na-type ZSM-5 molecular sieves are ion-exchanged with 0.1-2 mol / L ammonium chloride solution under the condition of a temperature of 40-80 ℃ for 1-6 h, the concentration of the Na-type ZSM-5 molecular sieves dissolved in the ammonium chloride solution is 0.1-10 mol / L, the ion-exchange is repeated for 2-4 times, the obtained product is centrifuged and washed with deionized water until neutral, the filter cake is dried at a temperature of 80-120 ℃ for 5-18 h, and then calcined under the condition of a temperature of 200-600 ℃ for 1-6 h to obtain nano HZSM-5 molecular sieves; (3) the metal oxides and the HZSM-5 molecular sieves are mechanically mixed in a coupling mass ratio of (1-3):1 to obtain the composite catalyst.

2. The composite catalyst of claim 1, wherein The main forms of the iron-based metal oxide in the metal oxide are Fe2O3 and Fe3O4, the main forms of the manganese-based metal oxide are Mn2O3, Mn3O4 and MnO2, the main form of the sodium-based metal oxide is Na2O, the main form of the potassium-based metal oxide is K2O, and the main form of the copper-based metal oxide is CuO.

3. The composite catalyst of claim 2, wherein In the metal oxide, the molar ratio of manganese to iron is (0.1-10):1, the molar ratio of sodium to iron is (0-10):1, the molar ratio of potassium to iron is (0-10):1, and the molar ratio of copper to iron is (0-5):

1.

4. The composite catalyst of claim 3, wherein the metal oxide is selected from the group consisting of titanium oxide, zirconium oxide, and mixtures thereof. The metal oxide is amorphous particles, particle size is 10-1000 μm; pore volume is 0.05-0.50 cm 3 / g, BET specific surface area is 30-200 m 2 / g, average pore size is 2-100 nm; The HZSM-5 molecular sieve has a pore volume of 0.05-100 cm 3 / g, a BET specific surface area of 100-550 m 2 / g, an average pore diameter of 0.5-50 nm, and a silicon / aluminum ratio of 10-400.

5. The composite catalyst of claim 1, wherein In step (1), the iron nitrate is ferric nitrate, the manganese nitrate is a 50wt% manganese nitrate solution, the alkaline precipitant is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate and ammonia water, which is configured into an aqueous solution with a concentration of 0.01-10mol / L, and the auxiliary agent is composed of one of manganese oxide and copper, sodium and potassium oxides; The temperature for complete dissolution of the heating and stirring is 40-90℃, and the time is 5-60min.

6. Use of the composite catalyst according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: loading the composite catalyst into a constant temperature section of a fixed bed tubular reactor, and performing a carbon dioxide hydrogenation reaction evaluation after pretreatment.

7. Use according to claim 6, characterized in that, The reaction evaluation conditions are as follows: loading the composite catalyst into a constant temperature section of a fixed bed tubular reactor, heating from room temperature to a reduction temperature at a rate of 1-10℃ / min under a nitrogen atmosphere, then reducing under an H2, N2 or pure hydrogen atmosphere, after reduction, carbonylating under a CO and N2 mixed gas or pure CO atmosphere, after the end of the reaction, adjusting the temperature to the reaction temperature, and switching the reduction gas to the reaction raw material gas to perform an activity evaluation.

8. Use according to claim 7, characterized in that, The pre-treatment conditions include: H2-CO two-step pre-treatment, under the conditions of 250-500℃, 0.01-5.0 MPa, containing H 2、 Under N2 atmosphere, space velocity is 1000-50000 ml·h -1 ·g Cat -1 The catalyst reduction is carried out for 2-30 hours, and then the catalyst carbonylation is carried out for 3-50 hours under the conditions of CO, N2 atmosphere, 250-450℃, 0.01-5.0 MPa, gas space velocity is 500-50000 ml·h -1 ·g Cat -1 ​ 9. Use according to claim 8, characterized in that, The volume ratio of hydrogen in the mixed gas of H2 and N2 is 5% to 100%, the volume ratio of CO in the mixed gas of CO and N2 is 10% to 100%, the volume ratio of H2 to CO2 in the reaction raw material gas is 1 to 6, the reaction temperature is 250 to 380℃, the reaction pressure is 2 to 5MPa, and the space velocity is 500 to 10000ml·h -1 ·g Cat -1 .

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