A catalyst for synthesizing olefins by hydrogenation of co2 and a method for preparing the same

Abstract

The application provides a CO2 hydrogenation synthesis olefin catalyst and a preparation method thereof, and the preparation method comprises the following steps: (1) dissolving iron nitrate and zinc nitrate in water to obtain an iron salt and zinc salt mixed solution; (2) adding the iron salt and zinc salt mixed solution and anhydrous sodium carbonate aqueous solution into a reaction container to perform an aging reaction, and obtaining a suspension liquid, wherein the aging reaction is performed under the following conditions: the pH of the aging reaction is maintained at 8-10, and the reaction is stirred at 20-90 DEG C for 6-24 hours; (3) performing solid-liquid separation on the suspension liquid; (4) drying the separated solid; (5) immersing the dried solid in anhydrous sodium carbonate aqueous solution; (6) calcining the immersed solid to obtain a catalyst precursor; and (7) activating the catalyst precursor to obtain the activated CO2 hydrogenation synthesis olefin catalyst, wherein the activation is performed under the following conditions: in a pure hydrogen atmosphere, at 200-400 DEG C for 1-5 hours.

Description

Technical Field

[0001] This application relates to the field of catalyst technology, and in particular to a catalyst for the synthesis of olefins by CO2 hydrogenation and a method for preparing the same. Background Technology

[0002] The massive emissions of greenhouse gases, represented by CO2, are causing global climate change, a significant global issue. CO2 capture, utilization, and storage (CCUS) technology is crucial for achieving green energy development and replacing fossil fuels with green chemical industries. A major obstacle to the development of CO2 utilization is the high conversion cost, while the value of the products is low, resulting in low economic benefits.

[0003] Hydrogenating CO2 to synthesize olefins is one approach to developing CO2 utilization. Short-chain olefins such as ethylene and propylene are important basic chemical raw materials, widely used in various chemical synthesis and the preparation of polyolefins. Long-chain olefins are mainly obtained industrially from short-chain olefins through oligomerization, and have higher value, used in the synthesis of thermoplastic elastomers, higher alcohols, surfactants, and other high-end chemicals. The CO2 hydrogenation process can produce methane, methanol, low-carbon alkanes, oils, olefins, and higher alcohols. Among these, olefins have higher industrial value than alkanes and methanol, and their synthesis is more feasible than that of higher alcohols, achieving relatively higher conversion rates and selectivity. Unfortunately, there is currently no large-scale industrialized CO2 hydrogenation process for olefin production. Furthermore, research on CO2 hydrogenation for olefin production in academia suffers from low CO2 conversion rates, high byproduct selectivity, and low selectivity for higher olefins, hindering industrial-scale development and resulting in low economic efficiency. Summary of the Invention

[0004] The purpose of this application is to provide a catalyst for CO2 hydrogenation to olefins and its preparation method, so as to improve the reaction conversion rate, olefin selectivity, and olefin space-time yield of CO2 hydrogenation to olefins, reduce the selectivity of lower-value products such as CO and CH4, and achieve long-term stable operation for more than 500 hours. The specific technical solution is as follows:

[0005] The first aspect of this application provides a method for preparing a catalyst for CO2 hydrogenation to olefins, which includes the following steps:

[0006] (1) Dissolve ferric nitrate and zinc nitrate in water to obtain a mixture of ferric and zinc salts;

[0007] (2) The iron salt and zinc salt mixture and anhydrous sodium carbonate aqueous solution are added to the reaction vessel to carry out an aging reaction to obtain a suspension. The conditions for the aging reaction are: maintaining the pH of the aging reaction at 8 to 10 and stirring the reaction at 20°C to 90°C for 6 to 24 hours.

[0008] (3) The suspension is subjected to solid-liquid separation;

[0009] (4) Dry the separated solids;

[0010] (5) The dried solid is immersed in the anhydrous sodium carbonate aqueous solution;

[0011] (6) The impregnated solid is calcined to obtain a catalyst precursor;

[0012] (7) The catalyst precursor is activated to obtain the activated CO2 hydrogenation to olefin synthesis catalyst; the activation conditions are: activation at 200℃~400℃ for 1h~5h in a pure hydrogen atmosphere.

[0013] In some embodiments of this application, the molar ratio of ferric nitrate to zinc nitrate is (2-0.5):1, the concentration of the ferric salt-zinc salt mixture is 0.1 mol / L to 2.5 mol / L, and the concentration of the anhydrous sodium carbonate aqueous solution is 0.1 mol / L to 2.5 mol / L.

[0014] In some embodiments of this application, the drying conditions are: drying at 40℃ to 150℃ for 2h to 24h, and the impregnation time is 3h to 24h.

[0015] In some embodiments of this application, the calcination conditions are as follows: in an air atmosphere, the temperature is increased to 300°C to 500°C at a rate of 2°C / min to 10°C / min, and held at that temperature for 1 hour to 12 hours.

[0016] The second aspect of this application provides a CO2 hydrogenation catalyst for olefin synthesis prepared using the preparation method provided in the first aspect of this application.

[0017] In some embodiments of this application, the CO2 hydrogenation to olefins catalyst comprises zinc, iron, and sodium, wherein the mass percentage of zinc is 25% to 60%, the mass percentage of iron is 35% to 70%, and the mass percentage of sodium is 0.01% to 5%, based on the mass of the CO2 hydrogenation to olefins catalyst.

[0018] In some embodiments of this application, the main crystalline phase of the CO2 hydrogenation catalyst for olefin synthesis includes zinc oxide and α-iron, and the catalyst also includes sodium ions.

[0019] The third aspect of this application provides the use of the CO2 hydrogenation synthesis olefin catalyst provided in the second aspect of this application for catalyzing the CO2 hydrogenation synthesis olefin reaction.

[0020] The beneficial effects of this application are:

[0021] This application provides a catalyst for CO2 hydrogenation to olefins and its preparation method. This method allows for more precise control of the component content in the catalyst and enables repeated scale-up preparation by adjusting aging reaction conditions and impregnation treatment. Furthermore, by activating the catalyst precursor under a pure hydrogen atmosphere, the catalyst structure changes, which is beneficial for improving the catalyst's reactivity and olefin selectivity. The catalyst prepared using this method can improve the reaction conversion, olefin selectivity, and olefin space-time yield of CO2 hydrogenation to olefins, reduce the selectivity of lower-value products such as CO and CH4, and achieve long-term stable operation for over 500 hours, resulting in higher overall potential economic benefits. This application provides guidance for the industrialization of CO2 hydrogenation to olefins processes and promotes the development of CO2 resource utilization processes.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0024] Figure 1a The XRD pattern of the catalyst after CO hydrogenation reaction reported in the paper of Comparative Example 1 of this application;

[0025] Figure 1b The in-situ XRD pattern of the catalyst reported in the paper of Comparative Example 1 of this application during the hydrogen temperature programmed process;

[0026] Figure 1c The XRD characterization pattern of the catalyst prepared in Example 1 of this application after the CO hydrogenation reaction;

[0027] Figure 1d The XRD pattern of the catalyst prepared in Example 1 of this application after activation in a pure hydrogen atmosphere;

[0028] Figure 2a This is a carbon number distribution diagram of hydrocarbon products generated by the catalyst prepared in Example 1 of this application in the catalytic CO2 hydrogenation to olefin synthesis reaction;

[0029] Figure 2b The evaluation results of CO2 hydrogenation at different temperatures for the catalyst prepared in Example 1 of this application in the catalytic CO2 hydrogenation to olefin synthesis reaction;

[0030] Figure 2cThe evaluation results of the catalyst prepared in Example 1 of this application in the CO2 hydrogenation reaction at different reaction pressures in the catalytic CO2 hydrogenation to olefin synthesis reaction;

[0031] Figure 2d The results of evaluating the catalyst prepared in Example 1 of this application in the CO2 hydrogenation reaction at different reaction space velocities in the catalytic CO2 hydrogenation to olefin synthesis reaction;

[0032] Figure 2e The results show the long-term stability evaluation of the catalyst prepared in Example 1 of this application in the catalytic CO2 hydrogenation to olefin synthesis reaction. Detailed Implementation

[0033] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0034] The surge in emissions of greenhouse gases such as CO2 has caused global warming and other problems. Utilizing CO2 as a cheap carbon resource can not only help reduce net emissions but also replace the use of traditional fossil fuels in chemical production. Currently reported CO2 hydrogenation to olefins processes suffer from low CO2 conversion rates and low olefin selectivity, resulting in a large amount of unused feedstock gas, hindering industrial-scale development and limiting economic benefits. Therefore, this application provides a CO2 hydrogenation catalyst for olefin synthesis and its preparation method, which can improve CO2 conversion rate and olefin selectivity, resulting in high economic benefits.

[0035] The first aspect of this application provides a method for preparing a catalyst for CO2 hydrogenation to olefins, which includes the following steps:

[0036] (1) Dissolve ferric nitrate and zinc nitrate in water to obtain a mixture of ferric and zinc salts;

[0037] (2) Add the iron salt and zinc salt mixture and anhydrous sodium carbonate aqueous solution to the reaction vessel to carry out the aging reaction and obtain a suspension. The conditions for the aging reaction are: maintain the pH of the aging reaction at 8 to 10 and stir the reaction at 20℃ to 90℃ for 6 to 24 hours.

[0038] (3) Perform solid-liquid separation on the suspension;

[0039] (4) Dry the separated solids;

[0040] (5) Immerse the dried solid in anhydrous sodium carbonate aqueous solution;

[0041] (6) The impregnated solid is calcined to obtain a catalyst precursor;

[0042] (7) Activate the catalyst precursor to obtain the activated CO2 hydrogenation to olefin synthesis catalyst; the activation conditions are: in a pure hydrogen atmosphere, at 200℃~400℃ for 1h~5h.

[0043] In step (2), the pH of the aging reaction can be 8, 8.5, 9, 9.5, 10, or any two of these numbers; the temperature of the aging reaction can be 20℃, 30℃, 45℃, 60℃, 70℃, 80℃, 90℃, or any two of these numbers; the aging reaction time can be 6h, 8h, 10h, 12h, 15h, 18h, 21h, 24h, or any two of these numbers. If the aging time is too short, the catalyst will be uneven and contain impurities, resulting in poor reaction stability; if the aging time is too long, the catalyst size will be too large, reducing its activity.

[0044] In step (3), the suspension can be separated into solid and liquid by vacuum filtration, and a filter cake is obtained after vacuum filtration.

[0045] In step (7), the activation temperature can be 200℃, 240℃, 270℃, 300℃, 350℃, 400℃ or any two of these numbers; the activation time can be 1h, 2h, 3h, 4h, 5h or any two of these numbers.

[0046] The preparation method provided in this application, on the one hand, allows for more precise control of the component content in the catalyst by adjusting the aging reaction conditions and performing impregnation treatment before calcination, and enables repeated scale-up preparation, laying the foundation for industrial production. On the other hand, by activating the catalyst precursor under a pure hydrogen atmosphere, the structure of the catalyst changes, which is beneficial to improving the catalyst's reactivity and olefin selectivity.

[0047] In some embodiments of this application, the molar ratio of ferric nitrate to zinc nitrate is (2–0.5):1, the concentration of the ferric-zinc salt mixture is 0.1 mol / L to 2.5 mol / L, and the concentration of the anhydrous sodium carbonate aqueous solution is 0.1 mol / L to 2.5 mol / L. For example, the molar ratio of ferric nitrate to zinc nitrate can be 2:1, 1.5:1, 1:1, 0.5:1, or any range of two such numbers; the concentration of the ferric-zinc salt mixture can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or any range of two such numbers; and the concentration of the anhydrous sodium carbonate aqueous solution can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or any range of two such numbers. By controlling the concentrations of the iron-zinc salt mixture and the anhydrous sodium carbonate aqueous solution within the above-mentioned ranges, the aging reaction can be promoted, allowing the iron and zinc ions in the iron-zinc salt mixture to precipitate completely and age into shape.

[0048] In this application, zinc nitrate, ferric nitrate, and anhydrous sodium carbonate are all commercially available conventional substances. This application does not have any particular restrictions on their sources, as long as they can achieve the purpose of this application.

[0049] In some embodiments of this application, the drying conditions are: drying at 40℃ to 150℃ for 2h to 24h, and impregnation time for 3h to 24h. For example, the drying temperature can be 40℃, 80℃, 110℃, 150℃, or any two of these numbers; the drying time can be 2h, 7h, 12h, 16h, 20h, 24h, or any two of these numbers; and the impregnation time can be 3h, 8h, 12h, 15h, 18h, 21h, 24h, or any two of these numbers. By controlling the drying conditions within the above range to ensure complete drying of the solid, and then impregnating the dried solid with a 0.1mol / L to 2.5mol / L anhydrous sodium carbonate aqueous solution for the impregnation time within the above range, it is possible not only to precisely control the content of each component in the catalyst and to achieve repeated scale-up preparation of the catalyst, but also to ensure the stability of the catalyst's conversion rate, selectivity, and other properties.

[0050] In some embodiments of this application, the calcination conditions are as follows: under an air atmosphere, the temperature is increased to 300℃ to 500℃ at a rate of 2℃ / min to 10℃ / min, and held for 1h to 12h. For example, the heating rate can be 2℃ / min, 5℃ / min, 7℃ / min, 10℃ / min, or any combination of two of these numbers; the temperature can be increased to 300℃, 350℃, 400℃, 450℃, 500℃, or any combination of two of these numbers; the holding time can be 1h, 4h, 6h, 9h, 12h, or any combination of two of these numbers. Controlling the heating rate, temperature, and calcination time within the above ranges allows for the complete decomposition of the aged and formed mixed carbonate and hydroxide precipitate containing sodium ions, resulting in a catalyst precursor with a uniform composition. Simultaneously, it results in a smaller active size of the subsequently activated catalyst, which is beneficial for improving the CO2 hydrogenation conversion rate.

[0051] The second aspect of this application provides a CO2 hydrogenation catalyst for olefin synthesis prepared using the preparation method provided in the first aspect of this application.

[0052] The CO2 hydrogenation catalyst for olefin synthesis provided in this application achieves a smaller active size by controlling the calcination conditions, and improves the CO2 hydrogenation conversion and reduces the selectivity of CO and CH4 byproducts through the interaction of zinc oxide and sodium ions with active iron. Under suitable catalytic reaction conditions, the olefin-alkane ratio is >8, while simultaneously achieving high C2. 4+ ＝ (C 4+ This catalyst, with a carbon atom count of 4 or higher, exhibits olefin selectivity and can achieve long-term stable operation exceeding 500 hours, resulting in higher overall potential economic benefits. The catalyst in this application effectively improves the feedstock utilization efficiency and high-value olefin selectivity in the CO2 hydrogenation to olefins process, laying the foundation for the industrial development of the CO2 hydrogenation to olefins process.

[0053] In this application, the active size of the CO2 hydrogenation catalyst for olefin synthesis prepared by the method of this application is about 30 nm to 40 nm.

[0054] In some embodiments of this application, the CO2 hydrogenation catalyst for olefin synthesis comprises zinc, iron, and sodium. Based on the mass of the CO2 hydrogenation catalyst, the mass percentage of zinc is 25%–60%, the mass percentage of iron is 35%–70%, and the mass percentage of sodium is 0.01%–5%. For example, the mass percentage of zinc can be 25%, 30%, 34%, 38%, 43%, 50%, 55%, 60%, or any range of two such numbers; the mass percentage of iron can be 35%, 37%, 42%, 48%, 55%, 60%, 65%, 70%, or any range of two such numbers; and the mass percentage of sodium can be 0.01%, 0.05%, 1%, 1.4%, 1.9%, 2.4%, 3%, 3.5%, 4.2%, 5%, or any range of two such numbers. Controlling the mass percentages of zinc, iron, and sodium within the aforementioned range helps to ensure sufficient dispersion of active species, thereby improving catalyst activity and stability.

[0055] In some embodiments of this application, the main crystalline phase of the CO2 hydrogenation catalyst for olefin synthesis includes zinc oxide and α-iron, and the catalyst also includes sodium ions. By activating the catalyst precursor under a pure hydrogen atmosphere, the iron phase in the catalyst precursor is rarely oxidized and mainly exists in the form of α-iron phase. This is beneficial to improving the degree of carbonization of the catalyst under the conditions of CO2 hydrogenation for olefin synthesis, thereby improving the CO2 hydrogenation conversion and olefin selectivity.

[0056] In this application, sodium ions in the catalyst exist in the form of sodium carbonate and / or sodium bicarbonate.

[0057] The third aspect of this application provides the use of the CO2 hydrogenation synthesis olefin catalyst provided in the second aspect of this application for catalyzing the CO2 hydrogenation synthesis olefin reaction.

[0058] In this application, the activated CO2 hydrogenation catalyst prepared above can be placed in a CO2 hydrogenation reactor to catalyze the CO2 hydrogenation reaction to olefins; alternatively, the activated CO2 hydrogenation catalyst prepared above can be placed in a CO2 hydrogenation reactor while SiC is added to the reactor; alternatively, the catalyst precursor prepared above can be directly placed in a CO2 hydrogenation reactor for activation, and the activated catalyst can be directly used to catalyze the CO2 hydrogenation reaction to olefins after cooling; or alternatively, the catalyst precursor prepared above can be directly placed in a CO2 hydrogenation reactor while SiC is added, followed by activation, and the activated catalyst can be directly used to catalyze the CO2 hydrogenation reaction to olefins after cooling. The added SiC has high thermal conductivity, which helps to disperse the heat of the reaction system and improve the stability of the catalyst. This application does not have a particular limitation on the amount of SiC used, as long as the purpose of this application is achieved.

[0059] Example

[0060] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0061] Test methods and equipment:

[0062] Determination of elemental content in CO2 hydrogenation catalyst for olefin synthesis:

[0063] A mixed hydrochloric acid and nitric acid solution was prepared using 10 ml of hydrochloric acid and nitric acid solution. The concentrations of hydrochloric acid and nitric acid used were 3 mol / L and 1 mol / L, respectively, with a volume ratio of 1:1. 20 mg of CO2 hydrogenation synthesis olefin catalyst sample was thoroughly dissolved to obtain a solution containing the catalyst component. To meet the requirements of inductively coupled plasma optical emission spectrometry (ICP-OES), the expected concentration of the solution containing the catalyst component was diluted to approximately 5 μg / ml. An ICP-OES instrument, Prodigy 7, manufactured by Leeman, Inc., was used for the analysis of Fe... 3+ Zn 2+ and Na +The solution was analyzed. The above-mentioned mixed hydrochloric acid and nitric acid solution without sample was used as the blank control. A standard solution containing three metal elements was prepared. According to the standard curve, the concentrations of Fe (using the spectral line at 259.94 nm), Zn (using the spectral line at 206.2 nm), and Na (using the spectral line at 589.592 nm) in the solution dissolving the catalyst components were analyzed. Based on the mass of the sample used, the mass fractions of the three elements in the catalyst sample were further obtained.

[0064] X-ray diffraction test (XRD)

[0065] An X-ray diffractometer, model D8 powder diffractometer, produced by Bruker Company in Germany, was used. The set parameters were 35 kV, 40 mA, continuous mode, scanning step size of 0.04°, integration time of 0.4 s, scanning range of 20 - 100°, and Co target was used for testing. The crystal phase was analyzed based on the JCPDS database.

[0066] Example 1

[0067] <Preparation of CO2 hydrogenation to olefin catalyst and testing of catalyst catalytic performance>

[0068] Equal amounts of ferric nitrate and zinc nitrate were dissolved in water to prepare a 1 mol / L mixed solution of iron salt and zinc salt, and anhydrous sodium carbonate was prepared into a 2 mol / L aqueous solution. 50 mL of the above-mentioned mixed solution of iron salt and zinc salt and 60 mL of the anhydrous sodium carbonate aqueous solution were respectively placed in two constant-pressure funnels, and were slowly dropped into a three-neck flask placed in an 80°C water bath under the stirring of a magnetic stirrer. At the same time, a pH meter was used to control the pH value of the system to be maintained at about 9.0. After the dropping was completed, stirring reaction was continued at this temperature for 12 h to obtain a suspension. The suspension was filtered by suction and washed thoroughly with deionized water to obtain a filter cake, and the filter cake was dried at 80°C for 12 h. Then, the dried filter cake was immersed in a 2 mol / L anhydrous sodium carbonate aqueous solution for 12 h, and the impregnated filter cake was heated in a muffle furnace to 350°C at a heating rate of 2°C / min and calcined for 4 h to obtain a catalyst precursor.

[0069] The CO2 hydrogenation to olefins catalytic reaction was carried out in a three-channel high-pressure fixed-bed reactor. Before the reaction, 1g of calcined catalyst precursor was granulated to 40-60 mesh and mixed with 3g of SiC, then added to the high-pressure fixed-bed reactor. The reactor was heated to 350℃ for 4 hours under a pure hydrogen atmosphere to obtain 0.8g of activated CO2 hydrogenation to olefins catalyst. The catalyst contained 43% zinc, 37% iron, and 1% sodium by mass. After activation, the system was cooled to 50℃. The atmosphere was switched to a reaction gas with a CO2:H2:Ar molar ratio of 24:72:4, and the reactor back pressure was 2MPa. The reaction system was then heated to 340℃ and maintained at this temperature, with a reaction space velocity of 12000 ml·gcat. -1 ·h -1 The products generated in the reaction were separated using a cold trap and a hot trap. The temperature of the cold trap was set at approximately 0°C, and the temperature of the hot trap was set at approximately 160°C, yielding gaseous products, liquid products, and high-boiling-point solid products. During the reaction, the composition of the gaseous products was analyzed using an online gas chromatograph (model: Agilent 7890) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) to obtain the selectivity of the gaseous products. For the liquid products, the reaction liquid was collected in a sample vial in the cold trap, weighed, and its composition was analyzed using an offline gas chromatograph (model: Agilent 7890) equipped with an FID detector to obtain the selectivity of the liquid products. For the high-boiling-point products, which are solid at room temperature, the product selectivity was obtained by gravimetric analysis.

[0070] Example 2

[0071] Except for the aging time of 24 hours, it is the same as in Example 1. The catalyst contains 43% zinc, 37% iron, and 1% sodium by mass.

[0072] Example 3

[0073] Except for the filter cake, which was soaked in a 1 mol / L anhydrous sodium carbonate aqueous solution for 3 hours and then dried, the catalyst was identical to that in Example 1. The catalyst contained 43% zinc, 37% iron, and 1% sodium by mass.

[0074] Example 4

[0075] Except for the aging time of 6 hours, the catalyst is identical to that in Example 1. The catalyst contains 43% zinc, 37% iron, and 1% sodium by mass.

[0076] Example 5

[0077] Except for the filter cake, which was impregnated in a 0.1 mol / L anhydrous sodium carbonate aqueous solution for 24 hours and then dried, the catalyst was identical to that in Example 1. The catalyst contained 43% zinc, 37% iron, and 0.4% sodium by mass.

[0078] Comparative Example 1

[0079] The catalyst was prepared according to the method reported in the paper by Peng Zhai, Ding Ma* et al. Angew. Chem. Int. Ed. 2016, 55, 9902. Specifically:

[0080] Ferric nitrate and zinc nitrate were dissolved in water to prepare a 1 mol / L iron-zinc salt mixture, and anhydrous sodium carbonate was prepared into a 2 mol / L aqueous solution. 50 mL of the iron-zinc salt mixture and 50 mL of the anhydrous sodium carbonate solution were placed in two constant-pressure funnels, respectively, and slowly added dropwise to a three-necked flask placed in an 80°C water bath with magnetic stirring. The pH of the system was maintained at approximately 9.0 using a pH meter. After the addition was complete, the reaction was continued at this temperature with stirring for 5 hours to obtain a suspension. The suspension was filtered and thoroughly washed with deionized water to obtain a filter cake. The filter cake was calcined in a muffle furnace at a rate of 2°C / min to 350°C and held at this temperature for 4 hours to obtain the catalyst precursor.

[0081] The CO2 hydrogenation to olefins catalytic reaction was carried out in a three-channel high-pressure fixed-bed reactor. Before the reaction, 0.2 g of calcined catalyst precursor was granulated to 40-60 mesh and mixed with 0.6 g of SiC, then added to the high-pressure fixed-bed reactor. The catalyst was treated at 300°C for 4 h under a 10% H2 / Ar atmosphere to obtain the activated catalyst. The catalyst performance testing conditions were the same as in Example 1.

[0082] Comparative Example 2

[0083] The results of CO2 hydrogenation to olefins reported in the paper by Yao Xu, Ding Ma* et al., Angew. Chem. Int. Ed. 2020, 59, 21736, were compared.

[0084] The performance parameters of each embodiment and comparative example are shown in Table 1.

[0085] Table 1

[0086]

[0087] Results analysis:

[0088] As can be seen from Examples 1 to 3 and Comparative Examples 1 and 2 in Table 1, the CO2 hydrogenation catalyst prepared in this application has good catalytic activity, which can improve the reaction conversion rate, olefin selectivity and olefin space-time yield of CO2 hydrogenation to olefins, and reduce the selectivity of lower value products such as CO and CH4.

[0089] Figure 1a The XRD pattern of the catalyst after CO hydrogenation reaction reported in the paper of Comparative Example 1 is shown. Figure 1b The in-situ XRD pattern of the catalyst reported in the paper of Comparative Example 1 during the hydrogen temperature-programmed process. Figure 1c The XRD characterization pattern of the catalyst prepared in Example 1 of this application after the CO hydrogenation reaction; Figure 1d The image shows the XRD pattern of the catalyst prepared in Example 1 of this application after activation in a pure hydrogen atmosphere. As can be seen from the figure, the catalyst reported in Comparative Example 1 mainly consists of three phases after the CO hydrogenation reaction: ZnO, Fe3O4, and Fe5C2. Under a 10% H2 / Ar atmosphere and treatment at 300°C for 4 hours, the activated catalyst produces the Fe3O4 phase. In contrast, the catalyst prepared in Example 1 of this application, after the CO hydrogenation reaction, consists of three phases: ZnO, Fe5C2, and Fe2C, with the Fe phase being rarely oxidized. Under a pure hydrogen atmosphere and treatment at 350°C for 4 hours, the activated catalyst mainly consists of the α-iron phase, with the ZnO phase also present. Therefore, although the elemental composition and catalyst precursor preparation methods are similar, the structure of the catalyst in this application after activation and reaction is significantly different from the catalyst reported in Comparative Example 1.

[0090] Figure 1a and Figure 1b Both figures were tested using Cu target XRD, while Figure 1c and Figure 1d Both figures show tests conducted using a Co target. The diffraction angles obtained by the two testing methods will differ, but both can be used to perform phase analysis using standard samples from the corresponding X-ray sources.

[0091] The catalyst prepared in Example 1 underwent a CO hydrogenation reaction under essentially the same process and conditions as reported in Comparative Example 1. Specifically, the catalyst precursor prepared in Example 1 was activated in a three-channel high-pressure fixed-bed reactor under the activation conditions described in Example 1. Subsequently, the reaction gas was switched to a CO:H2:Ar = 32:64:4 composition at 50°C, with a reactor back pressure of 2 MPa and a reaction rate of 18000 ml·gcat. -1 ·h -1 The reactor was reacted at space velocity for 60 hours. After cooling and depressurization, the reactor was transferred to a glove box and then transferred for structural characterization tests.

[0092] Figures 2a to 2e The results show the catalytic performance evaluation of the catalyst prepared in Example 1 under different reaction conditions in the catalytic CO2 hydrogenation to olefin synthesis reaction. Figure 2a The catalyst was tested at 340°C, reactor back pressure 2 MPa, and the reactant gases were a mixture of CO2:H2:Ar = 24:72:4, with a reaction space velocity of 12000 ml·gcat. -1 ·h -1 Carbon number distribution of the generated hydrocarbon products under the given conditions; Figure 2b The catalyst was tested at a reactor back pressure of 1 MPa and a reaction space velocity of 12000 ml·gcat. -1 ·h -1 Evaluation results of CO2 hydrogenation under different reaction temperatures while keeping other conditions constant. Figure 2c and Figure 2d The conditions were respectively 340℃, 2MPa, 12000ml·gcat -1 ·h -1 The evaluation results of CO2 hydrogenation were obtained by changing different reaction pressures and reaction space velocities while keeping other reaction conditions constant, based on the reaction conditions. Figure 2e In order to be in Figure 2a The results of the long-term stability evaluation of the catalyst under the reaction conditions. From Figures 2a to 2d As can be seen, using the catalyst of this application to catalyze the CO2 hydrogenation to olefins reaction results in a high proportion of high-value olefins in the reaction products and a low proportion of methane as a byproduct. Changing the reaction conditions of the CO2 hydrogenation to olefins reaction can adjust the CO2 conversion rate and the selectivity of the target olefin in the reaction process. Figure 2e It can be seen that the catalyst of this application can achieve stable operation for more than 500 hours.

[0093] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a catalyst for the hydrogenation of CO2 to olefins, comprising the following steps: (1) Dissolve ferric nitrate and zinc nitrate in water to obtain a mixture of ferric and zinc salts; (2) The iron salt and zinc salt mixture and anhydrous sodium carbonate aqueous solution are added to the reaction vessel to carry out an aging reaction to obtain a suspension. The conditions for the aging reaction are: maintaining the pH of the aging reaction at 8 to 10 and stirring the reaction at 20°C to 90°C for 6 to 24 hours. (3) The suspension is subjected to solid-liquid separation; (4) Dry the separated solids; (5) The dried solid is impregnated in the anhydrous sodium carbonate aqueous solution; (6) The impregnated solid is calcined to obtain a catalyst precursor; (7) The catalyst precursor is activated to obtain the activated CO2 hydrogenation to olefin synthesis catalyst. The activation conditions are: activation at 200℃~400℃ for 1h~5h in a pure hydrogen atmosphere.

2. The production method according to claim 1, wherein The molar ratio of ferric nitrate to zinc nitrate is (2-0.5):1, the concentration of the iron-zinc salt mixture is 0.1 mol / L to 2.5 mol / L, and the concentration of the anhydrous sodium carbonate aqueous solution is 0.1 mol / L to 2.5 mol / L.

3. The production method according to claim 1, wherein The drying conditions are: drying at 40℃~150℃ for 2h~24h, and the impregnation time is 3h~24h.

4. The production method according to claim 1, wherein The calcination conditions are as follows: under an air atmosphere, the temperature is increased to 300℃ to 500℃ at a rate of 2℃ / min to 10℃ / min, and held at that temperature for 1h to 12h.

5. A catalyst for the synthesis of olefins via CO2 hydrogenation, prepared by any one of claims 1 to 4.

6. The CO2 hydrooxygenation to olefins catalyst of claim 5, wherein, The CO2 hydrogenation catalyst for olefin synthesis comprises zinc, iron, and sodium. Based on the mass of the CO2 hydrogenation catalyst for olefin synthesis, the mass percentage of zinc is 25%–60%, the mass percentage of iron is 35%–70%, and the mass percentage of sodium is 0.01%–5%.

7. The CO2 hydrooxygenation to olefins catalyst of claim 6, wherein, The main crystalline phase of the CO2 hydrogenation catalyst for olefin synthesis includes zinc oxide and α-iron, and the catalyst also includes sodium ions.

8. The use of the CO2 hydrogenation to olefins catalyst according to claim 5 for catalyzing the CO2 hydrogenation to olefins reaction.

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