Three-way catalyst and application thereof in catalyzing hydrogenation of carbon dioxide to prepare p-xylene

Abstract

The invention provides a three-way catalyst and application of the three-way catalyst in catalyzing hydrogenation of carbon dioxide to prepare p-xylene. The three-way catalyst comprises a metal oxide, zeolite ZSM-5 and a molecular sieve, wherein the molecular sieve is selected from a molecular sieve S-1-OH or a molecular sieve SAPO-34; the metal oxide is selected from ZnCrOx; the mass ratio of the metal oxide to the zeolite ZSM-5 to the molecular sieve is 1: 1: 1. In the reaction for preparing p-xylene (a main product) through carbon dioxide hydrogenation by adopting the three-way catalyst, when the reaction pressure is 3-4MPa, the reaction temperature is 240-450 DEG C, the molar ratio of hydrogen to carbon dioxide in the reaction raw materials is 3: 1, and the space velocity of the reaction raw materials is 500-50000mL / (h.gcat), the volume of p-xylene in the product is not less than 60% and can reach 70% at most, the conversion rate of carbon dioxide reaches 40%, and the conversion rate of p-xylene in the product can reach 90% at most. Efficient conversion of carbon dioxide and high-selectivity PX generation are realized, and the method has relatively high economic utilization value.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts and preparation thereof, and in particular to a three-way catalyst and application thereof in catalyzing carbon dioxide hydrogenation to produce p-xylene. Background Art

[0002] Paraxylene (PX) is mainly based on crude oil refining. However, the depletion of fossil fuel reserves, the instability of crude oil prices and the concept of carbon neutrality have prompted researchers to develop green chemical raw materials from renewable resources or sustainable routes. Therefore, how to obtain paraxylene with high selectivity and orientation has become a pain point in the industry. In recent years, research on the preparation of chemicals by hydrogenation of carbon dioxide has received increasing attention. As a greenhouse gas, the resource utilization of carbon dioxide not only helps to reduce carbon emissions, but also provides a new source of raw materials for the chemical industry. However, the conversion of carbon dioxide into high-value chemicals, such as PX, still faces many challenges, including the selectivity of catalysts and the optimization of reaction conditions.

[0003] Molecular sieves have the advantages of easy acidity adjustment, strong hydrothermal stability, and pore size close to that of aromatic molecules. After coupling with metal oxide-zeolites, they perform well in the catalytic reaction of carbon dioxide hydrogenation to produce high-value-added chemicals. However, the products generated by the metal oxide-zeolite catalytic system are mainly heavy aromatics, such as C9 and C10 aromatics, and the selectivity of the high-value benzene-toluene-xylene mixture (BTX) is generally less than 15%. Summary of the invention

[0004] Based on the above problems, the present invention provides a three-way catalyst and its application in catalytic hydrogenation of carbon dioxide to produce paraxylene. The application adopts a three-way composite catalyst to carry out catalytic hydrogenation of carbon dioxide under optimized reaction conditions, thereby achieving efficient conversion of carbon dioxide and highly selective PX generation.

[0005] The specific content of the invention is as follows: In a first aspect, the present invention provides a three-way catalyst, comprising a metal oxide, a zeolite ZSM-5 and a molecular sieve; wherein: The molecular sieve is selected from molecular sieve S-1-OH or molecular sieve SAPO-34; The metal oxide is selected from ZnCrO x ; The mass ratio of the metal oxide, zeolite ZSM-5 and molecular sieve is 1:1:1.

[0006] Optionally, the three-way catalyst is formed by mixing the metal oxide, zeolite ZSM-5 and molecular sieve by stirring or layering.

[0007] Optionally, the molecular sieve S-1-OH is obtained by the following method: Dissolve the template, silicon source, diethoxymethylsilane and urea in a molar ratio of 3:2:0.1:1.5 in deionized water to form a mixed system; The mixed system is transferred to a hydrothermal kettle and reacted at 180°C for 72 hours. The obtained product is washed and dried, then placed in a muffle furnace and calcined at 500-600°C for 6-10 hours. After being taken out and cooled, the molecular sieve S-1-OH is obtained.

[0008] Optionally, the template is tetrapropylammonium hydroxide; The silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate and silica sol.

[0009] Optionally, the washing and drying comprises: washing the obtained product with deionized water for 3-5 times, and then transferring it to a 100° C. oven and drying it for 6-10 h.

[0010] Optionally, the molecular sieve SAPO-34 is obtained by the following method: Dissolving the template and the aluminum source in deionized water to form a mixed system; Adding a proper amount of phosphorus source dropwise to the mixed system, stirring sufficiently, further adding a proper amount of silicon source dropwise, stirring sufficiently to form a reaction system; The reaction system is transferred to a hydrothermal reactor and reacted at 200°C for 72 h. The obtained product is washed and dried, and then placed in a muffle furnace and calcined at 500-600°C for 6h-10h. After being taken out and cooled, the molecular sieve SAPO-34 is obtained. Wherein, the molar ratio of the template, the aluminum source, the phosphorus source and the silicon source is (0.5-10): (0.2-3): (0.2-3): (0.05-10).

[0011] Optionally, the template is one or more of diethylamine, triethylamine, morpholine and tetraethylammonium hydroxide; and / or The aluminum source is one or more of activated alumina, pseudo-boehmite and aluminum isopropoxide; and / or The phosphorus source is phosphoric acid; and / or The silicon source is one or more of silica sol, tetraethyl orthosilicate or active silicon dioxide.

[0012] In a second aspect, the present invention provides an application of the three-way catalyst described in the first aspect, wherein the three-way catalyst is used for catalyzing the hydrogenation of carbon dioxide to produce p-xylene, comprising: After the three-way catalyst is loaded into a fixed bed reactor, the pressure in the fixed bed reactor is controlled to be 3-4 MPa and the temperature is 240-450° C., and then hydrogen and carbon dioxide are introduced at a molar ratio of 3:1 for catalytic reaction to obtain light aromatics containing para-xylene; The space velocity of hydrogen and carbon dioxide is 500-50000 mL / (h·gcat); Among the light aromatic hydrocarbons, the volume of p-xylene is not less than 60%; The conversion rate of the carbon dioxide reaches 40%.

[0013] Optionally, before the catalytic reaction, the three-way catalyst is subjected to activation treatment, the activation treatment atmosphere is hydrogen, and the activation temperature is 300-400°C.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention provides a three-way catalyst, comprising a metal oxide, a zeolite ZSM-5 and a molecular sieve; wherein the molecular sieve is selected from a molecular sieve S-1-OH or a molecular sieve SAPO-34; and the metal oxide is selected from ZnCrO x ; The mass ratio of the metal oxide, zeolite ZSM-5 and molecular sieve is 1:1:1. In the reaction of hydrogenating carbon dioxide to produce p-xylene (main product) using the above-mentioned ternary catalyst, when the reaction pressure is 3-4MPa, the reaction temperature is 240-450°C, the molar ratio of hydrogen to carbon dioxide in the reaction raw material is 3:1, and the space velocity of the reaction raw material is 500-50000mL / (h·gcat), the volume of p-xylene in the product is not less than 60%, and can reach up to 70%, and the conversion rate of carbon dioxide reaches 40%, achieving efficient conversion of carbon dioxide and highly selective generation of PX, and having high economic utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 The flowchart of the preparation method of the molecular sieve S-1-OH provided in the embodiment of the present invention is shown; Figure 2 The flowchart of the preparation method of the molecular sieve SAPO-34 provided in the embodiment of the present invention is shown. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0018] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0019] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0020] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0021] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The specific implementation methods of the present invention are as follows: In the first aspect, the present invention provides a three-way catalyst, which is specifically composed of a metal oxide, a zeolite ZSM-5 and a molecular sieve; the molecular sieve is selected from a molecular sieve S-1-OH or a molecular sieve SAPO-34; the metal oxide is selected from ZnCrO x ; wherein the mass ratio of the metal oxide, zeolite ZSM-5 and molecular sieve is 1:1:1.

[0023] In specific implementation, the ternary catalyst provided by the present invention is formed by mixing metal oxide, zeolite ZSM-5 and molecular sieve; on the basis of the metal oxide-zeolite catalytic system, the embodiment of the present invention adds a certain amount of molecular sieve S-1-OH or molecular sieve SAPO-34 to the metal oxide and zeolite ZSM-5, so that the newly formed ternary catalyst, in the product of catalytic hydrogenation of carbon dioxide to produce high-value-added chemicals, reduces the proportion of heavy aromatics (such as C9 and C10 aromatics), and improves the selectivity of BTX (benzene-toluene-xylene mixture) with higher value, thereby achieving efficient conversion of carbon dioxide and highly selective generation of PX.

[0024] In specific implementation, the metal oxide can be selected from ZnCrO x ; Molecular sieve is molecular sieve S-1-OH or molecular sieve SAPO-34; The mixing method can be mechanical stirring mixing or layered mixing; The preferred mixing method in the embodiment of the present invention is mechanical stirring mixing; The preferred mechanical stirring mixing maintains the particle size of the three-way catalyst at 100 mesh.

[0025] Figure 1 The flow chart of the preparation method of the molecular sieve S-1-OH provided in the embodiment of the present invention is shown as follows: Figure 1 As shown, the molecular sieve S-1-OH component constituting the three-way catalyst is specifically obtained by the following preparation method: S11, dissolving a template agent, a silicon source, diethoxymethylsilane and urea in a molar ratio of 3:2:0.1:1.5 in deionized water to form a mixed system; S12, transferring the mixed system into a hydrothermal kettle, reacting at 180°C for 72 h, washing and drying the obtained product, placing it into a muffle furnace, calcining it at 500-600°C for 6h-10h, taking it out and cooling it to obtain the molecular sieve S-1-OH.

[0026] In specific implementation, the template agent is selected from tetrapropylammonium hydroxide; the silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate and silica sol; as an example, a molecular sieve S-1-OH provided in this embodiment can be obtained by hydrothermal reaction and calcination of tetrapropylammonium hydroxide, tetraethyl silicate, diethoxymethylsilane and urea, wherein tetrapropylammonium hydroxide (TPAOH) is a quaternary ammonium compound, which is used as a template agent in the synthesis of molecular sieves. It can guide the molecular sieve to form a specific structure and pores, which is crucial for the synthesis of molecular sieves with specific properties; tetraethyl silicate (TEOS) is used as a silicon source for synthesizing molecular sieves, and it will undergo hydrolysis reaction under hydrothermal conditions to generate silicic acid, which is further condensed to form a silicon-oxygen tetrahedral structure, which is the basic component unit of the molecular sieve framework; diethoxymethylsilane is used as a silicon source or structure-directing agent, which modifies the structure during the synthesis of the molecular sieve and participates in the construction of the molecular sieve framework; urea helps to form a specific pore structure and control the particle size function of the molecular sieve S-1-OH.

[0027] It should be noted that the entire hydrothermal reaction process is a complex chemical reaction process, involving the interaction of multiple substances and the control of reaction conditions. The present invention successfully synthesized the molecular sieve S-1-OH by controlling the molar ratio of the template and the silicon source to 3:2, and further controlling the reaction temperature, reaction time, and calcination temperature and other factors.

[0028] Further, Figure 2 The flow chart of the preparation method of the molecular sieve SAPO-34 provided in the embodiment of the present invention is shown as follows: Figure 2 As shown, the preparation method of molecular sieve SAPO-34 is as follows: S21, dissolving the template and the aluminum source in deionized water to form a mixed system; S22, adding a proper amount of phosphorus source dropwise to the mixed system, stirring sufficiently, further adding a proper amount of silicon source dropwise, stirring sufficiently to form a reaction system; S23, transferring the reaction system to be reacted into a hydrothermal kettle, reacting at 200°C for 72 h, washing and drying the obtained product, placing it into a muffle furnace, calcining it at 500-600°C for 6h-10h, taking it out and cooling it to obtain the molecular sieve SAPO-34.

[0029] In a specific implementation, the template is one or more of diethylamine, triethylamine, morpholine and tetraethylammonium hydroxide; the aluminum source is one or more of activated alumina, pseudo-boehmite and aluminum isopropoxide; the phosphorus source is phosphoric acid; the silicon source is one or more of silica sol, tetraethyl orthosilicate or activated silicon dioxide; the molar ratio of the template, the aluminum source, the phosphorus source and the silicon source is (0.5~10): (0.2~3): (0.2~3): (0.05~10).

[0030] In a second aspect, the present invention provides an application of the three-way catalyst described in the first aspect, wherein the three-way catalyst is used for catalyzing the hydrogenation of carbon dioxide to produce para-xylene, comprising: after the three-way catalyst is loaded into a fixed bed reactor, the pressure in the fixed bed reactor is controlled to be 3-4 MPa and the temperature to be 240-450° C., and then hydrogen and carbon dioxide are introduced at a molar ratio of 3:1 for catalytic reaction to obtain light aromatics containing para-xylene; wherein the space velocity of the hydrogen and carbon dioxide is 500-50000 mL / (h·gcat); Among the light aromatic hydrocarbons, the volume of p-xylene is not less than 60%; The conversion rate of the carbon dioxide reaches 40%.

[0031] The ternary catalyst provided in the embodiment of the present invention is used in the process of catalyzing the hydrogenation of carbon dioxide to produce p-xylene. First, the metal oxide in the ternary catalyst is used to convert carbon dioxide and hydrogen into intermediate products such as formaldehyde, methanol, and ketene. After the intermediate products diffuse to the surface of zeolite ZSM-5 and molecular sieve (molecular sieve S-1-OH or molecular sieve SAPO-34), alcohol-aldehyde condensation occurs to generate C2-5 olefins. Some C2-5 olefins are oligomerized to generate C6 and above olefins. Cycloalkanes are generated through hydrogen transfer and cyclization. Cycloalkanes are cyclized through hydrogen transfer to obtain aromatics. The molecular sieve S-1-OH and molecular sieve SAPO-34 have stronger chemical adsorption capacity for light aromatics than ZSM-5, and their surfaces cannot provide activity for methylation reaction, so light aromatics can be selectively generated, thereby improving the BTX yield and thus improving the p-xylene yield.

[0032] The present invention uses the above-mentioned three-way catalyst to carry out the reaction of hydrogenating carbon dioxide to produce p-xylene (main product), and the reaction pressure is 3-4MPa, the reaction temperature is 240~450℃, the reaction raw material space velocity is 500~50000mL / (h·gcat), and the molar ratio of hydrogen to carbon dioxide in the reaction raw material is 3:1. Under the conditions, polymerization, isomerization, cyclodehydrogenation, hydrogen transfer and aromatization reactions are carried out to obtain light aromatic hydrocarbon products. Light aromatic hydrocarbons include carbon benzene, toluene, o-xylene, m-xylene, and p-xylene, of which p-xylene accounts for more than 60%. By adjusting the reaction conditions and the content of the catalyst component, the embodiment of the present invention can controllably change the content of each component in the product, thereby meeting the demand for the product to the greatest extent. Finally, the carbon dioxide conversion rate is achieved to be more than 40%, and the p-xylene yield can reach up to 70%. Compared with the prior art, the technical effect is significant and has a high economic utilization value.

[0033] It should be noted that before the catalytic reaction, the catalyst needs to be activated for 1 hour at a temperature of 300-400 °C and in a hydrogen atmosphere; after the catalyst bed temperature and pressure reach the requirements of the catalytic reaction, a combination of carbon dioxide and hydrogen is introduced to react.

[0034] In some embodiments, after the catalytic reaction is completed, the product obtained by the reaction is first passed through a hot trap at a temperature of 260°C to collect the hot trap product, and then the uncondensed product enters a cold trap to collect the cold trap product, and the final tail gas enters a chromatogram for online analysis. This avoids the condensation and retention of heavy oil phase products in the system, realizes direct and effective separation of the product and the catalyst, simplifies the process flow, and reduces production costs.

[0035] In order to enable those skilled in the art to more clearly understand the present invention, the ternary catalyst of the present invention and its application in catalyzing the hydrogenation of carbon dioxide to para-xylene are now described in detail through the following examples.

[0036] Embodiment 1: (1) Preparation of S-1-OH molecular sieve Weigh 12.07 g of tetrapropylammonium hydroxide (TPAOH), dissolve it in 15.3 g of deionized water and stir it on a stirrer at 300 rpm / min for 30 min to obtain a white transparent solution; Weigh 7.57 g of tetraethyl silicate (TEOS), 0.301 g of diethoxymethylsilane (DEMS), and 1.95 g of urea, dissolve them in the solution, and stir on a stirrer at 300 rpm / min for 12 h (the molar ratio of tetrapropylammonium hydroxide, tetraethyl silicate, diethoxymethylsilane, and urea is 3:2:0.1:1.5); The solution was taken out and placed into a hydrothermal reactor, and reacted at 180° C. for 72 hours; After washing three times with water, it was placed in a 100°C oven to dry for 7 h, and finally placed in a muffle furnace to be calcined at 550°C for 6 h. After cooling, it was collected to obtain the S-1-OH molecular sieve.

[0037] (2) Preparation of ternary catalyst Weigh the metal oxide ZnCrO x 0.5 g, 0.5 g ZSM-5 and 0.5 g S-1-OH were mixed uniformly by mechanical stirring.

[0038] (3) Catalytic hydrogenation of carbon dioxide to produce p-xylene 1 g of the ternary mixed catalyst obtained in step (2) was loaded into a fixed bed, nitrogen was introduced to a pressure of 3 MPa, and the temperature was raised to 350°C under nitrogen flow protection. Then, carbon dioxide and hydrogen were introduced at a space velocity of 0.2 h / min. -1 .

[0039] The reaction tail gas was analyzed online using an Agilent 7890A gas chromatograph, and the results are shown in Table 1. As shown in Table 1, the conversion rate of the raw gas was 44%. The yield of aromatics was 85%, of which p-xylene accounted for 78%.

[0040] Table 1 Reaction results in Example 1

[0041] Embodiment 2: (1) Preparation of SAPO-34 molecular sieve Weigh 2.1423 g of aluminum isopropoxide and place it in a screw-cap bottle. Add an appropriate amount of 4.3 ml of tetraethylammonium hydroxide and 3 mL of deionized water. Stir at room temperature for 40 min to mix the solution evenly to form a mixed system. 0.679 mL of phosphoric acid was added dropwise to the mixed system and stirred for 2 h, and then 0.6 g of silica sol was slowly added dropwise and stirred for 2 h to form a reaction system (the molar ratio of aluminum isopropoxide, tetraethylammonium hydroxide, phosphoric acid and silica sol was 0.1:0.2:0.4:0.07); The reaction system was transferred to a reactor and reacted at 200 °C for 72 h. The obtained product was centrifugally washed with water and dried at 60°C for 12 h. The dried product was calcined at 600°C for 6 h to obtain SAPO-34 catalyst.

[0042] (2) Preparation of ternary catalyst Weigh the metal oxide ZnCrO x 0.5 g of quartz, 0.5 g of ZSM-5 and 0.5 g of molecular sieve SAPO-34 were mixed uniformly by mechanical stirring.

[0043] (3) Catalytic hydrogenation of carbon dioxide to produce p-xylene 1 g of the ternary mixed catalyst obtained in step (2) was loaded into a fixed bed, nitrogen was introduced to a pressure of 3 MPa, and the temperature was raised to 350°C under nitrogen flow protection. Then, carbon dioxide and hydrogen were introduced at a space velocity of 0.2 h / min. -1 .

[0044] The reaction tail gas was analyzed online using an Agilent 7890A gas chromatograph, and the results are shown in Table 2. As can be seen from Table 2, the conversion rate of the raw gas was 48%. The yield of aromatics was 81%, of which p-xylene accounted for 72%.

[0045] Table 2 Reaction results in Example 2

[0046] Comparative Example 1: Metal oxide-zeolite binary mixed catalyst without molecular sieve addition is used for CO2 hydrogenation to produce p-xylene: ZnCrO x , ZSM-5 are mixed uniformly with mechanical stirring at a mass ratio of 1:1 to form a binary mixed catalyst; 1.0 g of the obtained ternary mixed catalyst was loaded into a fixed bed, nitrogen was introduced to a pressure of 3 MPa, and the temperature was raised to 350° C. under nitrogen flow protection. Then, CO 2 and H 2 were introduced at a space velocity of 600 ml / g / h.

[0047] The reaction tail gas was analyzed online using an Agilent 7890A gas chromatograph, and the results are shown in Table 3; Table 3 shows that the conversion rate of the raw gas is 33%. The yield of aromatics is 48%, of which p-xylene accounts for 31%.

[0048] Table 3. Reaction results in Comparative Example 1

[0049] Comparative Example 2 S-1-OH molecular sieve, metal oxide and zeolite are layered and assembled for CO2 hydrogenation to produce p-xylene: A method for synthesizing all components of aviation kerosene using CO2 and H2 as raw materials, firstly, ZnCrOx and ZSM-5 are mechanically mixed at a mass ratio of 1:1 and placed in the lower layer of a reaction tube, denoted as A, then S-1-OH molecular sieve is filled, and quartz wool is filled between A and the molecular sieve to separate them; 1.0g of the obtained ternary mixed catalyst is loaded into a fixed bed, nitrogen is passed to a pressure of 3MPa, and the temperature is raised to 350°C under nitrogen flow protection. Then, CO2 and H2 are passed in at an air velocity of 600 ml / g / h.

[0050] The reaction tail gas was analyzed online using an Agilent 7890A gas chromatograph. The results are shown in Table 4.

[0051] As shown in Table 4, the conversion rate of the raw gas is 39%, the yield of aromatics is 62%, of which paraxylene accounts for 49%.

[0052] Table 4. Reaction results in Comparative Example 2

[0053] Comparative Example 3 SAPO-34 molecular sieve, metal oxides and zeolites are layered and assembled for CO2 hydrogenation to produce p-xylene: ZnCrOx and ZSM-5 were mechanically mixed in a mass ratio of 1:1 and placed in the lower layer of the reaction tube, denoted as A, and then filled with SAPO-34 molecular sieve, and quartz wool was filled between A and the molecular sieve to separate them; 1.0g of the obtained ternary mixed catalyst was loaded into the fixed bed, nitrogen was passed to a pressure of 3MPa, and the temperature was raised to 350°C under nitrogen flow protection. Then, CO2 and H2 were introduced at a space velocity of 600ml / g / h.

[0054] The reaction tail gas was analyzed online using an Agilent 7890A gas chromatograph. The results are shown in Table 5.

[0055] As shown in Table 5, the conversion rate of the raw gas is 39%, and the yield of aromatics is 71%, of which p-xylene accounts for 60%.

[0056] Table 5 Reaction results in Comparative Example 2

[0057] In summary, when the molecular sieve-metal oxide-zeolite ternary mixed catalyst prepared in Examples 1-2 of the present application is used to synthesize para-xylene using a mixed gas of CO2 and H2 as a raw material, the CO2 conversion rate reaches more than 40% under matching reaction conditions, and the para-xylene yield reaches more than 70%.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0059] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0060] The above is a detailed introduction to a ternary catalyst provided by the present invention and its application in catalytic hydrogenation of carbon dioxide to produce para-xylene. Specific examples are used herein to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for a person skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A three-way catalyst, characterized in that: Including metal oxides, zeolite ZSM-5 and molecular sieves; among which, The molecular sieve is selected from molecular sieve S-1-OH or molecular sieve SAPO-34; The metal oxide is selected from ZnCrO x ; The mass ratio of the metal oxide, zeolite ZSM-5 and molecular sieve is 1:1:

1.

2. The three-way catalyst according to claim 1, characterized in that: The three-way catalyst is formed by mixing the metal oxide, zeolite ZSM-5 and molecular sieve through stirring or layering.

3. The three-way catalyst according to claim 1, characterized in that: The molecular sieve S-1-OH is obtained by the following method: Dissolve the template, silicon source, diethoxymethylsilane and urea in a molar ratio of 3:2:0.1:1.5 in deionized water to form a mixed system; The mixed system is transferred to a hydrothermal kettle and reacted at 180°C for 72 h. The obtained product is washed and dried, then placed in a muffle furnace and calcined at 500-600°C for 6h-10h. After being taken out and cooled, the molecular sieve S-1-OH is obtained.

4. The three-way catalyst according to claim 3, characterized in that: The template agent is tetrapropylammonium hydroxide; The silicon source is selected from one or more of methyl orthosilicate, ethyl orthosilicate and silica sol.

5. The three-way catalyst according to claim 3, characterized in that: The washing and drying comprises: washing the obtained product with deionized water for 3-5 times, and then transferring it to a 100° C. oven and drying it for 6-10 hours.

6. The three-way catalyst according to claim 1, characterized in that: The molecular sieve SAPO-34 is obtained by the following method: Dissolving the template and the aluminum source in deionized water to form a mixed system; Adding a proper amount of phosphorus source dropwise to the mixed system, stirring sufficiently, further adding a proper amount of silicon source dropwise, stirring sufficiently to form a reaction system; The reaction system is transferred to a hydrothermal reactor and reacted at 200°C for 72 h. The obtained product is washed and dried, and then placed in a muffle furnace and calcined at 500-600°C for 6h-10h. After being taken out and cooled, the molecular sieve SAPO-34 is obtained. Wherein, the molar ratio of the template, the aluminum source, the phosphorus source and the silicon source is (0.5-10): (0.2-3): (0.2-3): (0.05-10).

7. The three-way catalyst according to claim 6, characterized in that: The template agent is one or more of diethylamine, triethylamine, morpholine and tetraethylammonium hydroxide; and / or The aluminum source is one or more of activated alumina, pseudo-boehmite and aluminum isopropoxide; and / or The phosphorus source is phosphoric acid; and / or The silicon source is one or more of silica sol, tetraethyl orthosilicate or active silicon dioxide.

8. An application of the three-way catalyst according to any one of claims 1 to 7, characterized in that: The three-way catalyst is used for catalyzing the hydrogenation of carbon dioxide to produce p-xylene, and comprises: After the three-way catalyst is loaded into a fixed bed reactor, the pressure in the fixed bed reactor is controlled to be 3-4 MPa and the temperature is 240-450° C., and then hydrogen and carbon dioxide are introduced at a molar ratio of 3:1 for catalytic reaction to obtain light aromatics containing para-xylene; The space velocity of introducing hydrogen and carbon dioxide is 500 to 50000 mL / (h·gcat).

9. The use according to claim 8, characterized in that: Among the light aromatic hydrocarbons, the volume of p-xylene is not less than 60%; The conversion rate of the carbon dioxide reaches 40%.

10. The use according to claim 9, characterized in that: Before the catalytic reaction, the three-way catalyst is activated in an atmosphere of hydrogen at an activation temperature of 300-400°C.

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