Metal oxide-molecular sieve bifunctional catalyst for preparing low-carbon olefin through carbon dioxide hydrogenation, preparation method and application

Abstract

The invention provides a metal oxide-molecular sieve bifunctional catalyst for preparing low-carbon olefin through carbon dioxide hydrogenation, a preparation method and application, the metal oxide is M1M2Ox, M1 is one metal element selected from Zn, Ga and In, and M2 is one metal element selected from Zr, Cr and Al; the two metal elements M1 or M2 are complexed with a water-soluble template agent and then calcined to form a metal oxide. The prepared composite catalyst composed of the metal oxide and the molecular sieve shows excellent catalytic performance in a reaction for preparing low-carbon olefin through carbon dioxide hydrogenation, effectively inhibits a reverse water-gas shift reaction under medium and high temperature reaction conditions, and reduces the generation of an unexpected by-product CO (the CO selectivity is as low as 27%); the activity is improved (the conversion rate of CO2 can reach 15.5%); meanwhile, the yield of the target product low-carbon olefin is greatly improved (nearly 10%).

Description

Technical Field

[0001] The present invention belongs to the technical field of heterogeneous catalysis, and specifically relates to a preparation method and application of a metal oxide component in a bifunctional catalyst for the reaction of hydrogenating carbon dioxide to produce light olefins. Background Art

[0002] Abnormal global climate change caused by excessive carbon emissions has become a major ecological and environmental issue facing humanity. Furthermore, CO₂ is the world's most abundant and inexpensive C₁ resource, offering enormous potential for development and utilization. Among the numerous CO₂ treatment and disposal methods, converting CO₂ into high-value-added chemicals (ethylene, propylene, and butenes) through a one-step catalytic hydrogenation reaction, a viable carbon resource, is crucial for energy conservation, emission reduction, and economic benefits. Currently, light olefins are primarily derived from naphtha cracking. With rising crude oil prices and increasingly severe environmental challenges, the development of a single-step, short-process, low-water-consumption CO₂ catalytic hydrogenation process (CO₂ + H₂ → C₂H₄ + C₃H₆ + C₄H₄) to produce light olefins has attracted widespread attention in the field, aiming to completely break free from dependence on carbon-containing mineral resources. The key to this research lies in developing efficient, highly selective, and highly stable catalysts for producing light olefins from CO₂ as a feedstock.

[0003] At present, with the advancement of academic research and development, the bifunctional catalytic system composed of metal oxides and molecular sieves separates the two processes of CO2 activation and CC bond formation. The methanol intermediate-dominated pathway can break through the selectivity limitations of traditional Fischer-Tropsch synthesis and achieve highly selective production of light olefins.

[0004] Commonly used inexpensive transition metal active components include solid solution oxides composed of Zn, Zr, In, Ga, and Cr, which enable the first step of CO2 hydrogenation to a methanol intermediate. Molecular sieves, such as SAPO-34 and SSZ-13, are typically used with relatively low acidity to select small molecules for the MTO reaction after carbon-carbon coupling while preventing over-hydrogenation to light alkanes. A paper (ACS Catalysis 7.12 (2017): 8544-8548) reported a bifunctional catalyst coupled with ZnZrOx and SAPO-34 for CO2 hydrogenation. At a CO2 conversion of 12.6%, the selectivity for light olefins in the hydrocarbons was 80%, and the selectivity for the byproduct CO was 47%. When the CO conversion rate reached 27.6%, the ZnO-Y2O3 composite SAPO-34 bifunctional catalyst achieved a selectivity of 83.9% for light olefins among hydrocarbons, but the byproduct CO selectivity was as high as 85.0% (Catalysis Communications 129(2019): 105711). After three reaction cycles, the CO selectivity of the GaZrOx / H-SSZ-13 composite catalyst increased from an initial 40% to 50%, ultimately exceeding 70%. The RWGS reaction gradually became dominant after each cycle, with activity decreasing while CO selectivity continued to increase with reaction time (Nature Catalysis 5.11(2022): 1038-1050). Currently reported CO2 hydrogenation reactions generally suffer from the bottleneck of high CO selectivity. The production of light olefins competes with the reverse water-gas shift (RWGS) reaction, significantly limiting the yield of light olefins. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation to light olefins. The catalyst prepared by this method can improve the reaction activity of CO2 hydrogenation to light olefins while inhibiting the RWGS reaction and reducing the generation of undesirable by-product CO, thereby improving the yield of the target product light olefins.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation to light olefins. The metal oxide is M1M2Ox, where M1 is a metal element selected from Zn, Ga, and In, and M2 is a metal element selected from Zr, Cr, and Al. The metal elements M1 or M2 are complexed with a water-soluble template and then calcined to form the metal oxide. Light olefins are C2H4, C3H6, and C4H8.

[0007] Preferably, the water-soluble template is one of polyvinyl pyrrolidone, polyethylene imine, polyethylene microspheres, ethylenediamine, vinyl pyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyethylene oxide-polypropylene oxide ether, polyvinyl alcohol, polyethylene glycol, sodium alginate, polyethylene imine, polystyrene sulfonic acid, polyaspartic acid, glucose, citric acid, and urea.

[0008] Preferably, the molar ratio of the M1 metal element to the M2 metal element is any value among 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, 5:1, 1:0, or any range therebetween.

[0009] Preferably, the metal oxide is M1M2Ox, when M1 is Zn, M2 is Zr; when M1 is Ga, M2 is Zr; when M1 is In, M2 is Zr; the water-soluble template is one of polyvinyl pyrrolidone, polyethylene imine, polyethylene microspheres, ethylenediamine, and vinyl pyrrolidone.

[0010] Preferably, the molecular sieve includes SAPO-34, SAPO-18 silicoaluminophosphate molecular sieve or SSZ-13 silicoaluminophosphate molecular sieve.

[0011] Preferably, the preparation method uses a metal oxide-molecular sieve catalyst bifunctional catalyst, wherein the metal oxide is M1M2Ox, M1 is a metal element among Zn, Ga, and In, and M2 is a metal element among Zr, Cr, and Al; the two metal elements M1 or M2 are complexed with a water-soluble template and then calcined to form a metal oxide.

[0012] Preferably, the preparation method of the metal oxide-molecular sieve catalyst bifunctional catalyst comprises the following steps: (1) A metal M1 nitrate precursor or a metal M1 carbonate precursor or a metal M1 sulfate precursor is mixed with a metal M2 nitrate precursor or a metal M2 carbonate precursor or a metal M2 sulfate precursor at a molar ratio of any value selected from 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, 1:0, or any range between the two; (2) Preparation of a water-soluble template solution: Weigh a water-soluble template solution of the same mass as the total mass of the metal nitrate precursor, metal carbonate precursor, or metal sulfate precursor in step (1); mix the solution in step (1) with the solution in step (2); (3) After vacuum freeze drying, grinding, calcination, and coupling with molecular sieve to form granules, a metal oxide-molecular sieve bifunctional catalyst is obtained.

[0013] Preferably, the calcination in step (3) is carried out using a static air method, and the calcination procedure is as follows: a heating rate of 1 °C / min from room temperature to 500 °C, a calcination temperature of 500 °C maintained for 360 min, and a pressure of 0.1 MPa; The vacuum freezing process is to first cool the vessel to -60°C for 1 hour, then evacuate the vessel for 48 hours, and finally defrost the vessel to room temperature.

[0014] Preferably, the molecular sieve includes SAPO-34, SAPO-18 silicoaluminophosphate molecular sieve or SSZ-13 silicoaluminophosphate molecular sieve.

[0015] The conditions for the CO2 hydrogenation reaction are preferably as follows: the reaction gas is a mixture of CO2 and H2, wherein the molar ratio of H2:CO2 is 3:1, and the volume space velocity of the reactor is 3000 h -1 , the reaction temperature is 355 °C, and the reaction pressure is 3 MPa.

[0016] Preferably, the active component is one of the metal elements Zn, Ga, and In and an expandable transition metal element such as Zr, and the molar ratio of one of the metal elements Zn, Ga, and In to Zr is any value among 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, 5:1, 1:0, or a range between any two values; the template is one of polyvinyl pyrrolidone (PVP), polyethylene imine (PEI), polyethylene microspheres (PS), ethylenediamine (EDA), and vinyl pyrrolidone (NVP); A method for preparing metal oxides for CO2 hydrogenation to olefins is preferably implemented according to the following steps: (1) Weighing zinc nitrate hexahydrate, gallium nitrate hydrate, indium nitrate pentahydrate, and zirconium nitrate nonahydrate, and mixing them in a molar ratio of any value selected from 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, 5:1, and 1:0, or a range between any two of them; (2) Preparation of water-soluble template solution: Weigh a powder of one of PVP, PEI, PS, EDA, and NVP equal to the total mass of the metal nitrates in step (1) and disperse it evenly in deionized water, stirring evenly with a magnetic stirrer; (3) pouring the metal nitrate weighed in step (1) into the template solution prepared in step (2); (4) The mixed solution of step (3) was stirred at room temperature for 6 to 12 hours until a transparent liquid appeared; (5) The mixed solution obtained in step (4) was dripped dropwise into a centrifuge tube filled with excess liquid nitrogen and sealed with a filter membrane; (6) The solid mixture obtained in step (5) was transferred to a vacuum freeze dryer and freeze-dried for 48 hours to obtain an anhydrous block solid; (7) Grind the solid block obtained in step (6) for 5-10 minutes to obtain a powder solid; (8) The powder solid obtained in step (7) was transferred to a muffle furnace for calcination using a static air method. The calcination procedure was as follows: a heating rate of 1 °C / min from room temperature to 500 °C, and the calcination temperature was maintained at 500 °C for 360 min at a pressure of 0.1 MPa.

[0017] In step (4), a magnetic stirrer is used to stir the metal salt or acid of the active component so as to mix the mixture thoroughly and evenly.

[0018] In step (5), excess liquid nitrogen is added drop by drop to quickly freeze the liquid, which can quickly turn from liquid to solid. At the same time, the uniform small droplets can expose more draining sites, making the water removal more thorough.

[0019] In step (6), the freeze-drying step in the freeze dryer is to first cool the trap to -60°C for 1 hour, then evacuate the container for 48 hours, and finally defrost the container to room temperature.

[0020] The metal oxide obtained in step (8) is used for the CO2 hydrogenation reaction to produce light olefins. The molecular sieve used is a standard SAPO-34 without any modification, Si / Al=0.075, which forms a bifunctional catalyst with the metal oxide obtained in step (8). Before the catalytic evaluation, it needs to be ground and granulated to 20~40 mesh (380~830μm), and then pretreated in a pure hydrogen atmosphere at 400℃ for 2h. The conditions for the catalyst to be used in the vertical high-pressure fixed-bed reactor for the CO2 hydrogenation reaction are: the reaction gas is a mixture of CO2 and H2, wherein the molar ratio of H2: CO2=3:1, and the volume space velocity of the reactor is 3000 h -1 , the reaction temperature is 355 °C, and the reaction pressure is 3 MPa.

[0021] In the present invention, the activity of the catalyst for CO2 hydrogenation reaction is measured by the volume variation coefficient η N2 , CO2 conversion rate, CO selectivity, light olefin selectivity and light olefin yield index evaluation: (1)

[0022] (2)

[0023] (3)

[0024] (4)

[0025] (5)

[0026] Beneficial effects: (1) This bifunctional catalyst is based on the regulation of the molar ratio of one of the active components Zn, Ga, and In to the transition metal Zr and the expansion of PVP, PEI, PS, EDA, and NVP as template agents. The performance of metal oxide-molecular sieve bifunctional catalysts is explored, and the types of binary metal oxides used in CO2 hydrogenation reactions to produce light olefins are expanded; (2) The freeze-dried metal oxide-molecular sieve bifunctional catalyst of the present invention has the ability to reduce the RWGS competitive reaction and has good and stable catalytic activity within 10 hours at a high space velocity. It can achieve a CO2 conversion rate of up to 15.5% and a light olefin selectivity of 84.4%. At the same time, the by-product CO selectivity is as low as 26.9%, making the light olefin yield as high as 9.6%.

[0027] (3) The binary metal oxide reported in the present invention not only has a simple one-step preparation method that can be expanded and has a significant catalytic effect, but also has low cost and excellent effect as the raw materials based on transition metal nitrates and water-soluble templates, and can be used for industrial CO2 conversion treatment.

[0028] (4) This patent proposes a novel method for preparing binary metal oxides, coupled with a low-acid-loaded and stable silicon-phosphorus-aluminum-based molecular sieve, to construct a bifunctional catalyst for CO2 hydrogenation to light olefins. The preparation method is simple and scalable, and exhibits high CO2 conversion and light olefin selectivity. Furthermore, it inhibits the RWGS reaction and reduces the formation of the undesirable byproduct CO. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 High-resolution transmission electron microscopy (HR-TEM) images of representative catalysts prepared in Example 4 and Comparative Examples 1, 4, and 7; Figure 2 X-ray diffraction (XRD) patterns of the catalysts prepared in Example 4, Comparative Example 1, Comparative Example 4, and Comparative Example 7 Figure 3 The CO2 conversion rate, CO selectivity curve, and hydrocarbon product distribution percentage stacked combination graph of the CO2 hydrogenation reaction lasting 10 hours for the representative catalysts prepared in Example 4 and Comparative Examples 1, 4, and 7; Figure 4 The light olefin yields of the representative catalysts prepared in Example 4 and Comparative Examples 1, 4, and 7 in the 10th hour; Figure 5 This is the light olefin product distribution diagram of the representative catalyst prepared in Example 4 and Comparative Examples 1, 4, and 7 in the 10th hour. DETAILED DESCRIPTION

[0030] Vacuum freeze drying (VFD) method: Weigh a certain amount of zinc nitrate hexahydrate and zirconium nitrate nonahydrate; and weigh a certain amount of one of PVP, PEI, PS, EDA, and NVP; and disperse them in deionized water. The resulting mixed solution is stirred on a magnetic stirrer for 6–12 hours until it becomes a transparent liquid. Excess liquid nitrogen is then added dropwise to the thoroughly stirred mixed solution to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block is thoroughly ground and calcined. After pretreatment with molecular sieves and pelletization, a metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation is obtained. The resulting catalyst is designated ZnZrOx-VFD / SAPO.

[0031] Sol-gel method (SG): A certain amount of zinc nitrate hexahydrate, zirconium nitrate nonahydrate, and glucose (D-glucose) were weighed and dispersed in deionized water. The resulting mixed solution was placed in a constant-temperature water bath at 80°C and stirred with magnetic stirring for 6 hours until foaming and dryness occurred. After drying overnight, the resulting solid block was thoroughly ground and calcined. After pretreatment with molecular sieves through granulation, a metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation was obtained. The resulting catalyst is designated ZnZrOx-SG / SAPO.

[0032] Co-precipitation (CP) method: A certain amount of zinc nitrate hexahydrate and zirconium nitrate nonahydrate were dissolved in deionized water (CP1 solution); a certain amount of ammonium carbonate was dissolved in deionized water (CP2 solution). The CP1 solution was placed in a 70°C water bath, and the CP2 solution was slowly added dropwise to the CP1 solution. After the addition was complete, the mixture was stirred and cooled to room temperature. The mixture was filtered, washed, and dried overnight. The resulting solid block was thoroughly ground and calcined, and then pretreated with a molecular sieve by granulation to obtain a metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation. The resulting catalyst was designated ZnZrOx-CP / SAPO.

[0033] Hydrothermal synthesis (HT): A certain amount of zinc nitrate hexahydrate, zirconium nitrate nonahydrate, and ethylenediamine are weighed and dissolved in deionized water. After thorough stirring, the mixture is transferred to a polytetrafluoroethylene tube. Crystallization is performed in a stainless steel autoclave, followed by centrifugation and washing with deionized water. The resulting solid is then dried in a vacuum oven. The resulting solid is thoroughly ground and calcined, and then pretreated with a molecular sieve by pelletization to produce a metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation. This catalyst is designated ZnZrOx-HT / SAPO.

[0034] The prepared oxide catalyst was used in the CO2 hydrogenation reaction performance test. The activity of the catalyst was evaluated by CO2 conversion rate, CO selectivity, light olefin selectivity, and light olefin yield. CO2, CO, CH3OH, CH4, C2H4, C2H6, C3H6, C3H8, C4H8, and C4H 10 、C5H 10 、C5H 12 Volume concentration was measured and analyzed using a gas chromatograph. The default test conditions were as follows: CO2 hydrogenation performance was tested in a vertical high-pressure fixed-bed quartz tube reactor. The bifunctional catalyst was prepared by mixing equal weights of metal oxide and molecular sieve powders (M / Z = 1 / 1) and granulating them into 20-40 mesh (380-830 μm) pellets with a loading of 150 mg. First, it was reduced and activated in a 100% H2 gas atmosphere at 400℃ and a flow rate of 30mL / min for 2h, with a heating rate of 5℃ / min and a pressure of 0.1MPa. Then, without removing the reduced and activated catalyst, a constant temperature long-term test was carried out at a reaction temperature of 355℃. The concentration of CO2 in the raw gas was 0.24mol / mol, the concentration of the reducing gas H2 was 0.72mol / mol, the concentration of the balance gas N2 was 0.04mol / mol, the total amount of reaction gas was 15mL / min, the pressure was 3MPa, and the reactor was a quartz tube with an inner diameter of 7mm. The real-time reaction temperature environment was provided by a vertical tubular heating furnace with a temperature control system.

[0035] The present application is described in detail below in conjunction with the examples, but the present application is not limited to the embodiments. Unless otherwise specified, the raw materials in the examples of the present application are purchased from commercial channels. Except for the metal oxides synthesized by vacuum freeze-drying, the molecular sieves and metal oxides involved in the present application are prepared according to the currently available synthesis methods. The following examples 1 to 34 are divided into Group A, Group B, and Group C, as shown in Table 1; Comparative Examples 1 to 9 are established as Group D to perform a preferred comparison of catalysts as shown in Table 1. The purpose of establishing Group A is to optimize the types and proportions of bimetallic oxide catalysts, the purpose of establishing Group B is to optimize the template used in the vacuum freeze-drying method; the purpose of establishing Group C is to optimize the optimal reaction conditions of the ZnZrOx / SAPO-34 (Si / Al = 0.075) composite catalyst for the hydrogenation of carbon dioxide to produce light olefins. The purpose of establishing Group D is to compare the performance of metal oxides prepared by advanced preparation methods in the carbon dioxide hydrogenation to produce olefins reaction under the optimal reaction conditions with those reported in the literature.

[0036] Table 1 shows the preferred grouping of catalysts prepared by vacuum freeze-drying method in Examples 1 to 34 and other methods in Comparative Examples 1 to 9; Table 1 Preferred grouping of catalysts prepared by vacuum freeze-drying method in Examples 1-34 and other methods in Comparative Examples 1-9

[0037] Example 1 5.950 g of zinc nitrate hexahydrate and 5.950 g of PVP were weighed and dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C was obtained using the static air method, with a heating rate of 1°C / min from room temperature to 500°C, then maintained at 500°C for 360 minutes under a pressure of 0.1 MPa.

[0038] Example 2 Weigh 0.541g of zinc nitrate hexahydrate, 7.806g of zirconium nitrate nonahydrate, and 8.347g of PVP, dissolve them in 40mL of deionized water and stir them thoroughly for 6-12h to obtain a transparent mixed solution; add excess liquid nitrogen dropwise to the stirred mixed solution to quickly freeze it, freeze it in a vacuum freeze dryer, and then grind the resulting block solid thoroughly; use the static air method, and the calcination procedure is: from room temperature to 500℃ at a heating rate of 1°C / min, the calcination temperature is maintained at 500℃ for 360min, and the pressure is 0.1MPa. The sample obtained after calcination at 500℃ is Zn1Zr 10 Ox-VFD catalyst.

[0039] Example 3 0.992 g of zinc nitrate hexahydrate, 7.155 g of zirconium nitrate nonahydrate, and 8.147 g of PVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn1Zr5Ox-VFD catalyst.

[0040] Example 4 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 7.708 g of PVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn2Zr4Ox-VFD catalyst.

[0041] Example 5 2.975 g of zinc nitrate hexahydrate, 4.293 g of zirconium nitrate nonahydrate, and 7.268 g of PVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn3Zr3Ox-VFD catalyst.

[0042] Example 6 3.967 g of zinc nitrate hexahydrate, 2.862 g of zirconium nitrate nonahydrate, and 6.829 g of PVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn4Zr2Ox-VFD catalyst.

[0043] Example 7 4.958 g of zinc nitrate hexahydrate, 1.431 g of zirconium nitrate nonahydrate, and 6.389 g of PVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn5Zr1Ox-VFD catalyst.

[0044] Example 8 8.586 g of zirconium nitrate nonahydrate and 8.586 g of PVP were weighed and dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the ZrOx-VFD catalyst.

[0045] Example 9 1.705g of hydrated gallium nitrate, 5.724g of zirconium nitrate nonahydrate, and 7.429g of PVP were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the GaZrO-VFD catalyst.

[0046] Example 10 2.006g of indium nitrate pentahydrate, 5.724g of zirconium nitrate nonahydrate, and 7.730g of PVP were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the In2Zr4Ox-VFD catalyst.

[0047] Table 2 is a data analysis table of CO2 conversion, CO selectivity curve, and hydrocarbon product distribution percentage of the CO2 hydrogenation reaction of the catalysts prepared in Examples 1 to 10 of Group A for the 10th hour; Table 2 Data analysis of carbon dioxide conversion, carbon monoxide selectivity, light olefin selectivity and light olefin yield of Examples 1-10 in Group A Table 2 shows the CO conversion, CO selectivity, light olefin selectivity, and light olefin yield of composite catalysts prepared by freeze-drying ZnZrOx, a bimetallic oxide with different element combinations, coupled with SAPO-34 (Si / Al = 0.075) at varying Zn / Zr molar ratios, for the CO hydrogenation to light olefins. The results show that a Zn / Zr ratio of 2 / 4 achieves the highest CO conversion. Excluding the oxides ZnOx and ZrOx, a Zn / Zr ratio of 1 / 5 achieves the lowest CO selectivity, while a Zn / Zr ratio of 4 / 2 achieves the highest light olefin selectivity. Considering light olefin yields, a Zn / Zr ratio of 2 / 4 is the optimal metal molar ratio for the ZnZr bimetallic oxide. GaZrOx exhibits high CO selectivity and light olefin selectivity, but its lower CO conversion results in a lower light olefin yield than ZnZr. InZrOx exhibits high CO conversion, but the CO methanation reaction is more vigorous, with a CH selectivity of 20% in the product. ZnZrOx has a high carbon dioxide conversion rate and can effectively inhibit the reverse water gas reaction. Due to its relatively mild hydrogenation ability, it can also obtain a higher selectivity for light olefins, thereby obtaining a higher light olefin yield.

[0048] Example 11 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 7.708 g of polyethylene terephthalate (PEI) were dissolved in 40 mL of deionized water and stirred for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn2Zr4Ox-VFD(PEI) catalyst.

[0049] Example 12 1.705g of hydrated gallium nitrate, 5.724g of zirconium nitrate nonahydrate, and 7.429g of polyethylene terephthalate (PEI) were dissolved in 40mL of deionized water and stirred for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the GaZrO-VFD(PEI) catalyst.

[0050] Example 13 2.006g of indium nitrate pentahydrate, 5.724g of zirconium nitrate nonahydrate, and 7.730g of polyethylene terephthalate (PEI) were dissolved in 40mL of deionized water and stirred for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the In2Zr4Ox-VFD(PEI) catalyst.

[0051] Example 14 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 7.708 g of PS were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the Zn2Zr4Ox-VFD(PS) catalyst.

[0052] Example 15 1.705g of hydrated gallium nitrate, 5.724g of zirconium nitrate nonahydrate, and 7.429g of PS were dissolved in 40mL of deionized water and stirred for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the Ga2Zr4Ox-VFD(PS) catalyst.

[0053] Example 16 2.006g of indium nitrate pentahydrate, 5.724g of zirconium nitrate nonahydrate, and 7.730g of PS were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample was calcined using the static air method: from room temperature to 500°C at a heating rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the In2Zr4Ox-VFD(PS) catalyst.

[0054] Example 17 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 7.708 g of EDA were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn2Zr4Ox-VFD(EDA) catalyst.

[0055] Example 18 1.705g of hydrated gallium nitrate, 5.724g of zirconium nitrate nonahydrate, and 7.429g of EDA were dissolved in 40mL of deionized water and stirred for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was heated from room temperature to 500°C at a rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the GaZrO-VFD(EDA) catalyst.

[0056] Example 19 2.006g of indium nitrate pentahydrate, 5.724g of zirconium nitrate nonahydrate, and 7.730g of EDA were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample was calcined using the static air method: from room temperature to 500°C at a heating rate of 1°C / min, held at 500°C for 360 minutes, and held at a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the In2Zr4Ox-VFD(EDA) catalyst.

[0057] Example 20 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 7.708 g of NVP were dissolved in 40 mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was: a heating rate of 1°C / min from room temperature to 500°C, then held at 500°C for 360 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the Zn2Zr4Ox-VFD(NVP) catalyst.

[0058] Example 21 1.705g of hydrated gallium nitrate, 5.724g of zirconium nitrate nonahydrate, and 7.429g of NVP were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was: a heating rate of 1°C / min from room temperature to 500°C, then held at 500°C for 360 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the GaZrO-VFD(NVP) catalyst.

[0059] Example 22 2.006g of indium nitrate pentahydrate, 5.724g of zirconium nitrate nonahydrate, and 7.730g of NVP were dissolved in 40mL of deionized water and stirred thoroughly for 6-12 hours to obtain a clear mixture. Excess liquid nitrogen was added dropwise to the stirred mixture to rapidly freeze it. After freeze-drying in a vacuum freeze dryer, the resulting solid block was thoroughly ground. The sample obtained after calcination at 500°C using the static air method was: a heating rate of 1°C / min from room temperature to 500°C, then held at 500°C for 360 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the In2Zr4Ox-VFD(NVP) catalyst.

[0060] Table 3 is a data analysis table of CO2 conversion, CO selectivity curve, and hydrocarbon product distribution percentage of the CO2 hydrogenation reaction of the catalysts prepared in Examples 11 to 22 of Group B for the 10th hour; Table 3 Data analysis of carbon dioxide conversion, carbon monoxide selectivity, light olefin selectivity and light olefin yield of Group B Examples 11 to 22

[0061] Table 3 shows the application of five templates in the preparation of metal oxides with ZnZr, GaZr and InZr as active components. The bulk phases are all single homogeneous tetragonal zirconium dioxide, reflecting the one-step scalable advantage of the vacuum freeze-drying method. Among them, after ZnZr, GaZr and InZr were synthesized by vacuum freeze-drying using five templates, the activity and target product selectivity of Examples 4, 9 and 10 using PVP as the template were the highest, with yields of 9.6%, 7.7% and 8.5% respectively. This is because the ultra-thin two-dimensional layered structure formed after calcination allows the oxide to expose more active sites. The advantages of PVP as a template in catalytic synthesis are mainly reflected in its precise control of the two-dimensional structure of the catalyst, and its improvement in the dispersibility, stability and specific surface area of the metal precursor. In addition, compared with the other four organic water-soluble templates, its green and environmentally friendly characteristics and wide applicability make it have great application potential in heterogeneous catalysis.

[0062] Example 23 The same composite catalyst as in Example 4 was used, and the reaction temperature in the default reaction conditions was changed to 300° C., while the rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-300° C. catalyst.

[0063] Example 24 The same composite catalyst as in Example 4 was used, and the reaction temperature in the default reaction conditions was changed to 330° C., while the rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-330° C. catalyst.

[0064] Example 25 The same composite catalyst as in Example 4 was used, and the reaction temperature in the default reaction conditions was changed to 370° C., while the rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-370° C. catalyst.

[0065] Example 26 The same composite catalyst as in Example 4 was used, and the reaction temperature in the default reaction conditions was changed to 380° C., while the rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-380° C. catalyst.

[0066] Example 27 The same composite catalyst as in Example 4 was used, and the reaction pressure in the default reaction conditions was changed to 1 MPa. The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-1 MPa catalyst.

[0067] Example 28 The same composite catalyst as in Example 4 was used, and the reaction pressure in the default reaction conditions was changed to 2 MPa. The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-2 MPa catalyst.

[0068] Example 29 The same composite catalyst as in Example 4 was used, and the reaction pressure in the default reaction conditions was changed to 4 MPa. The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-4 MPa catalyst.

[0069] Example 30 The same composite catalyst as in Example 4 was used, and the mixing ratio of the oxide and the molecular sieve in the default reaction conditions was changed to M / Z=1 / 2. The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-M / Z=2 / 1 catalyst.

[0070] Example 31 The same composite catalyst as in Example 4 was used, and the mixing ratio of the oxide and the molecular sieve in the default reaction conditions was changed to M / Z=2 / 1. The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-M / Z=1 / 2 catalyst.

[0071] Example 32 The same composite catalyst as in Example 4 was used, and the molecular sieve in the default reaction conditions was changed to SSZ-13 (Si / Al=50). The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-SSZ-13 catalyst.

[0072] Example 33 The same composite catalyst as in Example 4 was used, and the molecular sieve in the default reaction conditions was changed to SAPO-18 (Si / Al=0.05). The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-SAPO-18 catalyst.

[0073] Example 34 The same composite catalyst as in Example 4 was used, and the molecular sieve in the default reaction conditions was changed to RUB-13 (Si / Al=200). The rest remained the same as in Example 4, and was recorded as ZnZrOx-VFD-RUB-13 catalyst.

[0074] Table 4 is a data analysis table of CO2 conversion, CO selectivity curve, and hydrocarbon product distribution percentage of the CO2 hydrogenation reaction of the catalysts prepared in Examples 23 to 34 of Group C for the 10th hour; Table 4 Data analysis of carbon dioxide conversion, carbon monoxide selectivity, light olefin selectivity and light olefin yield of Examples 23 to 34 of Group C

[0075] Table 4 shows the -1 The carbon dioxide conversion rate, carbon monoxide selectivity, light olefin selectivity and light olefin yield under different reaction temperatures, reaction pressures and metal oxide to molecular sieve mixing ratios were investigated at different space velocities. The above results determined that the optimal reaction conditions for the ZnZrOx / SAPO-34 (Si / Al = 0.075) composite catalyst for the hydrogenation of carbon dioxide to light olefins reaction were the following default reaction conditions: reaction temperature: 355°C, reaction pressure: 3 MPa, metal oxide to molecular sieve mixing ratio M / Z = 1 / 1, and SAPO-34 (0.075) was selected as the molecular sieve type; the experimental parameters were also used as the default reaction conditions for the subsequent performance investigation of the CO2 hydrogenation to light olefins reaction in Comparative Examples 1 to 9.

[0076] Comparative Example 1 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 12.011 g of glucose were dissolved in 100 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to an 80°C water bath and stirred for 6 h to obtain a dry, foamy solid. The solid was then dried in a 100°C oven overnight and thoroughly ground. The resulting solid was then calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the ZnZrOx-SG catalyst.

[0077] Comparative Example 2 1.705 g of hydrated gallium nitrate, 5.724 g of zirconium nitrate nonahydrate, and 12.011 g of glucose were dissolved in 100 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to an 80°C water bath and stirred for 6 h to obtain a dry, foamy solid. The solid was then dried overnight in a 100°C oven and thoroughly ground. The resulting solid was then calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the GaZrOx-SG catalyst.

[0078] Comparative Example 3 2.006 g of indium nitrate pentahydrate, 5.724 g of zirconium nitrate nonahydrate, and 12.011 g of glucose were dissolved in 100 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to an 80°C water bath and stirred for 6 h to obtain a dry, foamy solid. The solid was then dried overnight in a 100°C oven and thoroughly ground. The resulting solid was then calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the InZrOx-SG catalyst.

[0079] Comparative Example 4 Weigh 1.983g of zinc nitrate hexahydrate and 5.724g of zirconium nitrate nonahydrate, dissolve in 100mL of deionized water, and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP1 solution. Weigh 4.6g of ammonium carbonate, dissolve in 100mL of deionized water, and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP2 solution. Place the CP1 solution in a 70℃ water bath, and add the CP2 solution dropwise to the CP1 solution at 3mL / min. After the addition is complete, continue stirring for 2h. Cool to room temperature, filter, and rinse repeatedly with deionized water three times, then dry at 100℃ overnight. The resulting solid block was thoroughly ground and calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5°C / min, held at 300°C for 1 hour, then raised to 500°C at a heating rate of 3.5°C / min, and held at 500°C for 180 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the ZnZrOx-CP catalyst.

[0080] Comparative Example 5 Weigh 1.705g of hydrated gallium nitrate and 5.724g of zirconium nitrate nonahydrate, dissolve in 100mL of deionized water, and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP1 solution. Weigh 4.6g of ammonium carbonate and dissolve in 100mL of deionized water, and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP2 solution. Place the CP1 solution in a 70℃ water bath, and add the CP2 solution dropwise to the CP1 solution at 3mL / min. After the addition is complete, continue stirring for 2h. Cool to room temperature, filter, and rinse repeatedly with deionized water three times, then dry at 100℃ overnight. The resulting solid block was thoroughly ground and calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5°C / min, then held at 300°C for 1 hour, then raised to 500°C at a heating rate of 3.5°C / min, and held at 500°C for 180 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the GaZrOx-CP catalyst.

[0081] Comparative Example 6 Weigh 2.006g of indium nitrate pentahydrate and 5.724g of zirconium nitrate nonahydrate, dissolve in 100mL of deionized water and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP1 solution. Weigh 4.6g of ammonium carbonate and dissolve in 100mL of deionized water and stir thoroughly for 0.5h to obtain a clear mixed solution, recorded as CP2 solution. Place the CP1 solution in a 70℃ water bath, and add the CP2 solution dropwise to the CP1 solution at 3mL / min. After the addition is complete, continue stirring for 2h. Cool to room temperature, filter and rinse repeatedly with deionized water three times, and then dry at 100℃ overnight. The resulting solid block was thoroughly ground and calcined in the absence of oxygen. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5°C / min, then held at 300°C for 1 hour, then raised to 500°C at a heating rate of 3.5°C / min, and held at 500°C for 180 minutes under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C was the InZrOx-CP catalyst.

[0082] Comparative Example 7 1.983 g of zinc nitrate hexahydrate, 5.724 g of zirconium nitrate nonahydrate, and 5.84 mL of anhydrous ethylenediamine were dissolved in 70 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to a polytetrafluoroethylene tube and crystallized in a stainless steel autoclave in a rotary oven at 120°C for 15 min. The mixture was then centrifuged, washed three times with deionized water, and dried in a vacuum oven at 80°C for 6 h. The resulting solid was thoroughly ground and calcined in an oxygen-free atmosphere. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the ZnZrOx-HT catalyst.

[0083] Comparative Example 8 1.705 g of hydrated gallium nitrate, 5.724 g of zirconium nitrate nonahydrate, and 5.84 mL of anhydrous ethylenediamine were dissolved in 70 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to a polytetrafluoroethylene tube and crystallized in a stainless steel autoclave in a rotary oven at 120°C for 15 min. The mixture was then centrifuged, washed three times with deionized water, and dried in a vacuum oven at 80°C for 6 h. The resulting solid was thoroughly ground and calcined in an oxygen-free atmosphere. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the GaZrOx-HT catalyst.

[0084] Comparative Example 9 2.006 g of indium nitrate pentahydrate, 5.724 g of zirconium nitrate nonahydrate, and 5.84 mL of anhydrous ethylenediamine were dissolved in 70 mL of deionized water and stirred thoroughly for 0.5 h. The mixture was then transferred to a polytetrafluoroethylene tube and crystallized in a stainless steel autoclave in a rotary oven at 120°C for 15 min. The mixture was then centrifuged, washed three times with deionized water, and dried in a vacuum oven at 80°C for 6 h. The resulting solid was thoroughly ground and calcined in an oxygen-free environment. The calcination procedure was as follows: from room temperature to 300°C at a heating rate of 2.5 °C / min, held at 300°C for 1 h, then raised to 500°C at a heating rate of 3.5 °C / min, and held at 500°C for 180 min under a pressure of 0.1 MPa. The sample obtained after calcination at 500°C is the InZrOx-HT catalyst.

[0085] Table 5 is a data analysis table of CO2 conversion, CO selectivity curve, and hydrocarbon product distribution percentage of the CO2 hydrogenation reaction of the catalysts prepared in Comparative Examples 1 to 9 of Group D for the 10th hour; Table 5 Data analysis of carbon dioxide conversion, carbon monoxide selectivity, light olefin selectivity and light olefin yield of comparative examples 1 to 9 in group D

[0086] Table 5 shows the CO2 hydrogenation to light olefins reaction performance of ZnZr, GaZr, and InZr metal oxides prepared by different preparation methods. In general, the hydrothermal synthesis method (HT) has the lowest performance, the coprecipitation method (CP) and the sol-gel method (SG) have similar performance, and the SG method has higher performance. The vacuum freeze drying method (VFD) can achieve a light olefin yield of up to 9.6% under the same metal ratio and reaction conditions, which is at least 3.0% higher than other methods; and the selectivity of by-product CO is generally lower than that of other methods, which effectively inhibits the occurrence of reverse water gas shift (RWGS) reaction, reflecting the superiority of this method in the reaction activity of CO2 hydrogenation to light olefins and the precise guidance of the target product.

[0087] Representative catalysts were selected from the four activity test results in Tables 2 to 5 above for further visualization mapping to intuitively demonstrate the advantages of the vacuum freeze-drying method used in this application in the CO2 hydrogenation to light olefins reaction.

[0088] Figure 1 and Figure 2 The morphological structure diagrams and X-ray crystal diffraction patterns of the catalyst ZnZrOx prepared by Example 4 and Comparative Examples 1, 4 and 7 are respectively taken by high-resolution transmission electron microscopy. Analysis of the images shows that the representative catalyst of Example 4 prepared by vacuum freeze-drying method is a uniform ultra-thin nanosheet material compared with the representative catalyst prepared by the comparative example. It can expose more active sites in the subsequent CO2 hydrogenation reaction, reflecting a higher CO2 adsorption activation efficiency; and the preparation method is simple and has high repeatability and operability; and different templates all show a single-phase solid solution of tetragonal zirconia, reflecting that the method has good scalability. Further XRD tests were performed on the ZnZrOx oxides prepared by different methods. The bulk phase results show that different synthesis methods all show a single-phase solid solution of tetragonal zirconia, without obvious phase separation or phase change, but there are differences in the half-peak width, reflecting different grain sizes, which is consistent with the differences in the morphological results of HR-TEM.

[0089] Depend on Figure 3It can be seen that Example 4 has faster and more stable catalytic activity within 10 hours at a higher space velocity at a test temperature of 355°C, and can achieve a CO2 conversion rate of up to 15.5%, a light olefin selectivity of 84.4%, and a by-product CO selectivity as low as 26.9%; compared with other traditional commonly used metal oxide preparation methods, when the CO2 conversion rate is close to or even slightly higher, the problem of generating a large amount of undesirable by-product CO in the RWGS reaction at medium and high temperatures is alleviated, the light olefins are more accurately directed, and the catalytic performance is improved.

[0090] Depend on Figure 4 From the calculation of the yield of light olefins, it can be seen that the vacuum freeze-drying method adopted in Example 4 further achieves excellent performance with lower CO selectivity under the evaluation indicators of CO2 conversion rate and light olefin selectivity that are almost the same as or slightly higher than those of Comparative Examples 1, 4, and 7. Therefore, the yield of Example 4 can reach higher, which improves the bottleneck problem of traditional binary oxides that are difficult to suppress the RWGS reaction to generate by-product CO at medium and high temperatures, and proves the excellent performance of preparing metal oxides by vacuum freeze-drying method using PVP as template.

[0091] Depend on Figure 5 The light olefin product distribution diagram shows that the molecular sieves used in Example 4, Comparative Examples 1, 4, and 7 perform consistently. After carbon-carbon coupling, they selectively select C2-C4 small molecules for the MTO reaction without excessive hydrogenation, eliminating the interference of molecular sieve deactivation on CO selectivity. Furthermore, Example 4 exhibits the highest light olefin to light alkane ratio (O / P), demonstrating that the molecular sieve bifunctional catalyst combined with Example 4 can achieve more precise targeting of light olefin target products while reducing the formation of undesirable byproducts such as light alkanes and CO. The preparation method of Example 4 provides an important reference for catalytic reaction mechanism research and industrial application optimization.

[0092] The above description is only a preferred embodiment of the present invention, and does not constitute the scope of the present invention. Any equivalent changes made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

[0093] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent replacements and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention should be included in the scope of protection of the invention.

Claims

1. A metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation to light olefins, characterized in that: The metal oxide is M1M2Ox, where M1 is a metal element selected from Zn, Ga, and In, and M2 is a metal element selected from Zr, Cr, and Al. The metal elements M1 or M2 are complexed with a water-soluble template and then calcined to form the metal oxide.

2. The metal oxide-molecular sieve bifunctional catalyst according to claim 1, characterized in that: The water-soluble template is one of polyvinyl pyrrolidone, polyethylene imine, polyethylene microspheres, ethylenediamine, vinyl pyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyethylene oxide-polypropylene oxide ether, polyvinyl alcohol, polyethylene glycol, sodium alginate, polyethylene imine, polystyrene sulfonic acid, polyaspartic acid, glucose, citric acid, and urea.

3. The metal oxide-molecular sieve bifunctional catalyst according to claim 1, characterized in that: The molar ratio of the M1 metal element to the M2 metal element is any value among 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, 5:1, 1:0 or any range between them.

4. The metal oxide-molecular sieve bifunctional catalyst according to claim 1, characterized in that: The metal oxide is M1M2Ox, when M1 is Zn, M2 is Zr; when M1 is Ga, M2 is Zr; when M1 is In, M2 is Zr; the water-soluble template is one of polyvinyl pyrrolidone, polyethylene imine, polyethylene microspheres, ethylenediamine, and vinyl pyrrolidone.

5. The metal oxide-molecular sieve bifunctional catalyst according to any one of claims 1 to 4, characterized in that The molecular sieve includes SAPO-34, SAPO-18 silicoaluminophosphate molecular sieve or SSZ-13 silicoaluminophosphate molecular sieve.

6. A method for preparing a metal oxide-molecular sieve catalyst bifunctional catalyst, characterized in that: The metal oxide is M1M2Ox, where M1 is a metal element selected from Zn, Ga, and In, and M2 is a metal element selected from Zr, Cr, and Al. The metal elements M1 or M2 are complexed with a water-soluble template and then calcined to form the metal oxide.

7. The preparation method according to claim 6, characterized in that The preparation method comprises the following steps: A metal M1 nitrate precursor, a metal M1 carbonate precursor, or a metal M1 sulfate precursor is mixed with a metal M2 nitrate precursor, a metal M2 carbonate precursor, or a metal M2 sulfate precursor at a molar ratio of any value selected from 0:1, 1:10, 1:5, 2:4, 3:3, 4:2, and 1:0, or any range between the two; (2) mixing the solution of step (1) with a water-soluble template solution, wherein the water-soluble template has the same total mass as the metal nitrate precursor, metal carbonate precursor, or metal sulfate precursor of step (1); (3) The mixed solution of step (2) is subjected to vacuum freeze drying, grinding, and calcination, and then coupled with molecular sieve to form granules, thereby obtaining a metal oxide-molecular sieve bifunctional catalyst.

8. The preparation method according to claim 7, characterized in that The step (3) is calcined using a static air method, and the calcination procedure is as follows: a heating rate of 1 °C / min from room temperature to 500 °C, a calcination temperature of 500 °C maintained for 360 min, and a pressure of 0.1 MPa; The vacuum freezing process is to first cool the vessel to -60°C for 1 hour, then evacuate the vessel for 48 hours, and finally defrost the vessel to room temperature.

9. The preparation method according to any one of claims 6 to 8, characterized in that The molecular sieve includes SAPO-34, SAPO-18 silicoaluminophosphate molecular sieve or SSZ-13 silicoaluminophosphate molecular sieve.

10. A metal oxide-molecular sieve bifunctional catalyst for CO2 hydrogenation to light olefins according to any one of claims 1 to 5, characterized in that: The conditions for the CO2 hydrogenation reaction are as follows: the reaction gas is a mixture of CO2 and H2, wherein the molar ratio of H2:CO2 is 3:1, and the volume space velocity of the reactor is 3000 h -1 , the reaction temperature is 355 °C, and the reaction pressure is 3 MPa.

Images