Molybdenum oxide catalyst, preparation method thereof and application of molybdenum oxide catalyst in reverse water vapor shift reaction

Abstract

The invention discloses a molybdenum oxide catalyst, a preparation method thereof and application of the molybdenum oxide catalyst in reverse water vapor shift reaction. The molybdenum oxide catalyst comprises molybdenum oxide and a metal additive, the molybdenum oxide is molybdenum trioxide and / or molybdenum dioxide; the metal additive exists in a metal state form. After the catalyst is subjected to reduction pretreatment, carbon dioxide and hydrogen can be converted into carbon monoxide and water. Compared with a traditional assistant doping method, the assistant doped by the high-temperature quenching method is obviously different in chemical state, and mainly exists in a metal state instead of an oxidation state, so that the catalytic activity of the molybdenum oxide catalyst is remarkably improved. According to the high-temperature quenching method, the catalyst containing the active component, the metal additive and the carrier can be prepared in one step, the utilization rate of the metal additive is remarkably increased, and the dosage of precious metal and the cost of the catalyst are reduced.

Description

Technical Field

[0001] The present application relates to a molybdenum oxide catalyst, a preparation method thereof and an application in a reverse water vapor shift reaction, belonging to the field of catalysis. Background Art

[0002] The continued excessive emission of carbon dioxide (CO), a greenhouse gas, has placed severe pressure on global ecosystems, leading to a series of ecological crises such as increased extreme weather events, ocean acidification, and rising global temperatures, exacerbating climate change. Therefore, reducing CO emissions and developing technologies for its sustainable utilization and conversion are urgent. The reverse water-gas shift (RWGS) reaction, which produces carbon monoxide via the hydrogenation of CO, is considered one of the most promising CO conversion technologies. Its product, CO, can serve as an important industrial feedstock for Fischer-Tropsch synthesis and other syngas conversion technologies, used to synthesize methanol, olefins, aromatics, gasoline, and other products. Therefore, the development of new RWGS processes and catalysts is crucial for the future efficient utilization of CO.

[0003] RWGS is an endothermic reaction, which is more conducive to the reaction at high temperatures. However, excessively high reaction temperatures not only place high demands on reactor equipment, but also pose a great challenge to the design of catalysts. For example, common Cu-based catalysts have excellent catalytic performance for RWGS reactions, but Cu catalysts are prone to aggregation and sintering under high temperature reaction conditions, resulting in poor catalyst stability (Publication No. CN107497439A). On the other hand, the design of RWGS catalysts requires high selectivity for CO, as the RWGS reaction is often accompanied by CO2 methanation reaction. For example, catalysts such as Ni and Co have low CO selectivity in RWGS reactions, and the reaction process is often accompanied by the production of a large amount of CH4 by-products (Publication No. CN107570162A; Publication No. CN106268893B), which requires the addition of subsequent separation technology to remove CH4, resulting in an increase in the cost of the CO2 conversion process. In addition, precious metal catalysts such as Pd and Pt have good catalytic performance in RWGS reactions, but the scarcity and high cost of precious metals themselves limit their development and application in RWGS.

[0004] In recent years, molybdenum-based catalysts have attracted widespread attention due to their excellent catalytic performance. In particular, the common molybdenum carbide and molybdenum nitride catalysts have both demonstrated high catalytic activity and selectivity, as well as good stability in RWGS (ACS Catal, 2017, 7, 912-918; Nature Communication, 2022, 13, 5800). However, the preparation of molybdenum carbide and molybdenum nitride requires carbonization and amination at high temperatures (700-800°C), respectively, which consumes large amounts of carbon source (methane, ethane, and other hydrocarbons) or nitrogen source (nitrogen-containing compounds such as ammonia). This not only places high demands on the corrosion resistance of the equipment, but also the long-term high-temperature treatment makes the process energy-intensive and the catalyst preparation costly. As a result, molybdenum carbide and molybdenum nitride catalysts have been rarely used in RWGS reactions. Therefore, the development of highly active and stable molybdenum-based oxide catalysts for RWGS reactions is extremely important for the catalytic conversion of carbon dioxide in actual industrial production. Summary of the Invention

[0005] The purpose of this application is to provide a metal-assisted modified molybdenum oxide catalyst and a preparation method thereof. The catalyst is prepared by mixing an auxiliary metal precursor and a molybdenum precursor and adopting a one-step high-temperature quenching technology. The technical advantages of this application are reflected in: (1) The metal-assisted modified molybdenum oxide catalyst prepared by this method can replace molybdenum carbide to catalyze the RWGS reaction, reducing the cost of catalyst preparation. (2) Compared with the traditional method, the auxiliary prepared by this method is significantly different in chemical state. The auxiliary introduced by the traditional impregnation method exists in the form of an oxidized state on the surface of molybdenum oxide, while the auxiliary introduced by this method is dispersed in the molybdenum oxide in a metallic state. The results show that the metallic auxiliary can more effectively improve the performance of the molybdenum oxide catalyst. (3) This method pre-mixes the molybdenum precursor with the auxiliary metal precursor, significantly improving the utilization rate of the metal auxiliary and reducing the amount of precious metal and catalyst cost.

[0006] In one aspect of the present application, a molybdenum oxide catalyst is provided, wherein the main component of the catalyst is molybdenum oxide, contains a small amount of metal additive, and may or may not have a carrier, and the carrier is a single metal oxide material and a composite metal oxide material.

[0007] Optionally, the molybdenum oxide catalyst comprises molybdenum oxide and a metal promoter;

[0008] The molybdenum oxide is molybdenum trioxide and / or molybdenum dioxide;

[0009] The metal adjuvant exists in a metallic form.

[0010] Optionally, in the molybdenum oxide catalyst, the mass fraction of molybdenum oxide is 30% to 99.98%;

[0011] In the molybdenum oxide catalyst, the mass fraction of the metal additive is 0.02% to 5%.

[0012] Optionally, in the molybdenum oxide catalyst, the mass fraction of the metal additive is 0.02% to 0.5%.

[0013] Optionally, in the molybdenum oxide catalyst, the mass fraction of molybdenum oxide is independently selected from any value among 30%, 50%, 75%, 99.98% or a range between any two of the above.

[0014] Optionally, in the molybdenum oxide catalyst, the mass fraction of the metal additive is independently selected from any value among 0.02%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 3%, 5% or a range between any two of the above.

[0015] Optionally, the metal additive is at least one of Ir, Pt, and Pd.

[0016] Optionally, the molybdenum oxide catalyst further includes a carrier;

[0017] The carrier is a metal oxide;

[0018] The metal oxide contains a metal element X;

[0019] The metal element X is selected from at least one of Zn, Ce, Zr, Mg, Ti, La, Si, and Al.

[0020] Another aspect of the present application provides a method for preparing the above-mentioned molybdenum oxide catalyst, the preparation method comprising:

[0021] According to the composition ratio of the molybdenum oxide catalyst, a mixed solution containing a molybdenum precursor and a metal additive precursor is subjected to a high-temperature quenching method to prepare the molybdenum oxide catalyst.

[0022] Optionally, the molybdenum precursor is selected from at least one of molybdic acid, molybdenum acetylacetonate, molybdenum acetate, and ammonium molybdate;

[0023] The metal auxiliary agent precursor is selected from at least one of acetylacetonate, acetate, and oxalate containing a metal auxiliary agent element, wherein the metal auxiliary agent element is selected from at least one of Ir, Pt, and Pd.

[0024] Optionally, the high temperature quenching method includes:

[0025] The mixed solution is pumped into a nozzle, sprayed out of the nozzle, dispersed into droplets by a dispersion gas, and the droplets are introduced into a flame for combustion to obtain composite oxide particles. The composite oxide particles leave the flame zone driven by the dispersion gas to obtain the molybdenum oxide catalyst.

[0026] Optionally, the pumping speed is 0.1 to 20 ml / min.

[0027] Optionally, the combustion gas required for flame combustion is a mixture of methane and oxygen, and the flow rates of methane and oxygen in the mixture are both 0.1 to 10 L / min.

[0028] Optionally, the pumping speed is independently selected from any value among 0.1 ml / min, 1 ml / min, 5 ml / min, 10 ml / min, 15 ml / min, 20 ml / min or a range between any two of the above values.

[0029] Optionally, in the mixed gas, the flow rate of methane is independently selected from any value among 0.1 L / min, 1 L / min, 5 L / min, 8 L / min, 10 L / min, or a range between any two of the above values.

[0030] Optionally, in the mixed gas, the flow rate of oxygen is independently selected from any value among 0.1 L / min, 1 L / min, 5 L / min, 8 L / min, 10 L / min, or a range between any two of the above values.

[0031] Optionally, the mixed solution further includes a carrier precursor;

[0032] The carrier precursor is selected from at least one of acetylacetonate, acetate, and oxalate containing a metal element X, wherein the metal element X is selected from at least one of Zn, Ce, Zr, Mg, Ti, La, Si, and Al.

[0033] As a specific embodiment, the preparation method of the molybdenum oxide catalyst includes:

[0034] (1) mixing and dissolving precursor compounds of molybdenum, a metal promoter, and a carrier in an organic solvent in a ratio required for the composition of the catalyst to form a mixed solution;

[0035] (2) The mixed solution is pumped into a nozzle, and the solution is sprayed out of the nozzle and dispersed into droplets by a dispersion gas. The droplets burn in a high-temperature flame. The composite oxides obtained after combustion are carried out of the high-temperature area of ​​the flame by a high-speed airflow and are quickly quenched. Finally, the prepared catalyst powder is collected through a collection net.

[0036] Another aspect of the present application provides an application of the above-mentioned molybdenum oxide catalyst in a reverse water gas shift reaction, wherein the application includes:

[0037] The reaction atmosphere contacts and reacts with the pretreated molybdenum oxide catalyst;

[0038] The reaction atmosphere includes hydrogen and carbon dioxide.

[0039] Optionally, the pretreatment atmosphere is hydrogen.

[0040] Optionally, the pretreatment temperature is 200-600°C.

[0041] Optionally, the pretreatment temperature is 350-450°C.

[0042] Optionally, the pretreatment temperature is independently selected from any value of 200° C., 350° C., 400° C., 450° C., 600° C., or a range between any two of the above values.

[0043] Optionally, the pretreatment time is 0.5 to 10 hours.

[0044] Optionally, the pretreatment time is 1 to 3 hours.

[0045] Optionally, the pretreatment time is independently selected from any value of 0.5h, 1h, 2h, 3h, 5h, 8h, 10h or a range between any two of the above values.

[0046] Optionally, in the reaction atmosphere, the volume ratio of hydrogen to carbon dioxide is 1 to 5.

[0047] Optionally, in the reaction atmosphere, the volume ratio of hydrogen to carbon dioxide is 2 to 4;

[0048] Optionally, in the reaction atmosphere, the volume ratio of hydrogen to carbon dioxide is independently selected from any value among 1, 2, 3, 4, 5, or a range between any two of the above.

[0049] Optionally, the total concentration of hydrogen and carbon dioxide in the reaction atmosphere is 0.1 to 100%;

[0050] Optionally, the reaction pressure is 0.1-5.0 MPa.

[0051] Optionally, the reaction pressure is 0.1-0.5 MPa;

[0052] Optionally, the reaction pressure is independently selected from any value among 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 1.5 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, or a range between any two of the above values.

[0053] Optionally, the reaction temperature is 300-700°C.

[0054] Optionally, the reaction temperature is 500-600°C;

[0055] Optionally, the reaction temperature is independently selected from any value among 300°C, 400°C, 500°C, 600°C, 700°C or a range between any two of the above values.

[0056] Optionally, the volume space velocity of the reaction atmosphere is 10 to 1000 L / (g·h).

[0057] Optionally, the volumetric space velocity of the reaction atmosphere is independently selected from any value among 10L / (g·h), 100L / (g·h), 300L / (g·h), 500L / (g·h), 800L / (g·h), 1000L / (g·h) or a range value between any two of the above.

[0058] The beneficial effects of this application include:

[0059] 1. Compared with the traditional method of introducing additives, the high-temperature quenching method in this application can increase the dispersion of additives and improve the utilization efficiency of additives. The modification effect of high-content (2-5%) additives can be achieved by using a lower content (0.02-0.5%) of metal additives, thereby reducing the amount of precious metal additives used and saving catalyst costs.

[0060] 2. While the additive introduced by the traditional impregnation method exists in an oxidized state on the molybdenum oxide surface, this method introduces the additive in a metallic state dispersed throughout the molybdenum oxide. Compared to the molybdenum oxide catalyst modified with the oxidized additive, the molybdenum oxide catalyst modified with the metallic additive exhibited significantly improved RWGS activity, with a 37.8% increase in CO yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Activity and selectivity evaluation diagram of the catalysts obtained in Example 1 and Comparative Example 1 - influence of preparation method;

[0062] Figure 2 Stability evaluation diagram of the catalysts obtained in Example 1 and Comparative Example 1 - the effects of different methods of doping auxiliary agents;

[0063] Figure 3 EXAFS graphs of the Ir element on the catalysts in Example 1 and Comparative Example 1, and comparisons with standard graphs of iridium foil and iridium dioxide;

[0064] Figure 4 Comparative graph of the activity of the catalysts in Examples 1 to 4 - the influence of the metal doping content and type;

[0065] Figure 5 Comparative diagram of the activity on the catalysts in Example 1 and Examples 5-6 - Effect of pretreatment reduction temperature. DETAILED DESCRIPTION

[0066] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0067] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0068] The analysis method in the examples of this application is as follows:

[0069] The concentrations of CO2, CO and CH4 in the exhaust gas at the outlet were analyzed using a gas chromatograph (Shimadzu GC-8A) equipped with a TDX-01 carbon molecular sieve column.

[0070] The conversion rate and selectivity in the examples of this application are calculated as follows:

[0071] CO2 conversion rate ( The calculation formula of in%) is as follows:

[0072]

[0073] CO selectivity (S CO ,in%) is calculated as follows:

[0074]

[0075] [CO2] out , [CO] out and [CH4] out are the concentrations of CO2, CO and CH4 at the reactor outlet, respectively.

[0076] Example 1

[0077] (1) Molybdenum oxide was prepared by high-temperature quenching method. Specifically, 3.94g of molybdenum acetylacetonate was dissolved in 60ml of benzyl alcohol and ultrasonically stirred at room temperature for about 1h to mix it evenly. The mixture was named as solution A. Then, 0.0153g of iridium acetate was added to about 5ml of water and ultrasonically stirred at room temperature for about 10min to dissolve it. Then, 55ml of ethanol was added and ultrasonically stirred for more than 0.5h to mix it evenly. The mixture was named as solution B. The above two solutions A and B were mixed and ultrasonically stirred at room temperature for more than 1h to mix the solutions as evenly as possible to prepare a mixed precursor solution. The prepared solution was pumped into the flame at a rate of 5ml / min using a syringe. The flame combustion gas was a mixture of methane (0.6L / min) and oxygen (1.9L / min), and the mixture was sprayed from a nozzle with a diameter of 2mm. The catalyst particles obtained by combustion were collected using glass fiber filter paper. The prepared catalyst was recorded as FSP-0.5% IrMoO3.

[0078] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 400°C for 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 300-700°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0079] Example 2

[0080] (1) Molybdenum oxide was prepared by high-temperature quenching method. Specifically, 3.94g of molybdenum acetylacetonate was dissolved in 60ml of benzyl alcohol, and ultrasonically stirred at room temperature for about 1h to mix it evenly, and named it solution A. Then, 3.5ml of 0.1mgIr / ml iridium acetate solution was added to about 57ml of ethanol, and ultrasonically stirred for more than 0.5h to mix it evenly, and named it solution B. The above two solutions A and B were mixed, and ultrasonically stirred at room temperature for more than about 1h to mix the solutions as evenly as possible to prepare a mixed precursor solution; the prepared solution was pumped into the flame at a speed of 5ml / min using a syringe. The flame combustion gas was a mixture of methane (0.6L / min) and oxygen (1.9L / min), and the mixture was sprayed from a nozzle with a diameter of 2mm. The catalyst particles obtained by combustion were collected using glass fiber filter paper. The prepared catalyst was recorded as FSP-0.02% IrMoO3.

[0081] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 400°C for 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 300-700°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0082] Example 3

[0083] (1) Molybdenum oxide was prepared by high-temperature quenching method. Specifically, 3.94g of molybdenum acetylacetonate was dissolved in 60ml of benzyl alcohol and ultrasonically stirred at room temperature for about 1h to mix it evenly. The mixture was named as solution A. Then, 0.153g of iridium acetate was added to about 5ml of water and ultrasonically stirred at room temperature for about 10min to dissolve it. Then, 55ml of ethanol was added and ultrasonically stirred for more than 0.5h to mix it evenly. The mixture was named as solution B. The above two solutions A and B were mixed and ultrasonically stirred at room temperature for more than 1h to mix the solutions as evenly as possible to prepare a mixed precursor solution. The prepared solution was pumped into the flame at a rate of 5ml / min using a syringe. The flame combustion gas was a mixture of methane (0.6L / min) and oxygen (1.9L / min), and the mixture was sprayed from a nozzle with a diameter of 2mm. The catalyst particles obtained by combustion were collected using glass fiber filter paper. The prepared catalyst was recorded as FSP-5% IrMoO3.

[0084] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 400°C for 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 300-700°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0085] Example 4

[0086] (1) Molybdenum oxide was prepared by high temperature quenching method. The specific operation was to dissolve 3.94g of molybdenum acetylacetonate in 60ml of benzyl alcohol, and stir ultrasonically at room temperature for about 1h to mix it evenly, and named it solution A. Then, 0.87ml of 0.01g Pt / mL solution (chloroplatinic acid solution), add 60ml of ethanol, ultrasonicate for more than 0.5h to mix evenly, named solution B. Mix the above two solutions A and B, and ultrasonicate at room temperature for more than about 1h to mix the solutions as evenly as possible to make a mixed precursor solution; use a syringe to pump the prepared solution into the flame at a rate of 5ml / min. The flame combustion gas is a mixture of methane (0.6L / min) and oxygen (1.9L / min), and the mixed gas is sprayed from a nozzle with a diameter of 2mm. The catalyst particles obtained by combustion are collected using glass fiber filter paper. The prepared catalyst is recorded as FSP-0.5% PtMoO3.

[0087] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 400°C for 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 600°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0088] Example 5

[0089] (1) Molybdenum oxide was prepared by high temperature quenching method. The specific operation was the same as that in Example 1.

[0090] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 200°C, 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 600°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0091] Example 6

[0092] (1) Molybdenum oxide was prepared by high temperature quenching method. The specific operation was the same as that in Example 1.

[0093] (2) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 600°C for 2 hours, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 600°C, pressure 0.1 MPa, reaction gas composition 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0094] Comparative Example 1

[0095] (1) Molybdenum oxide was prepared by high-temperature quenching method. The specific operation is to dissolve 19.7g of molybdenum acetylacetonate in 100ml of benzyl alcohol, ultrasonically stir at room temperature for about 1h to mix it evenly, then add 100ml of diethylhexanoic acid (EHA) to the solution, ultrasonically stir at room temperature for more than 1h to mix the solution as evenly as possible to prepare a 0.5mol / L mixed precursor solution; use a syringe to pump the prepared solution into the flame at a rate of 5ml / min. The flame combustion gas is a mixture of methane (0.6L / min) and oxygen (1.9L / min), and the mixture is sprayed from a nozzle with a diameter of 2mm. The catalyst particles obtained by combustion are collected using glass fiber filter paper.

[0096] (2) Introduce the additive by impregnation. Take 0.009g of iridium acetate, add about 1ml of water to dissolve it, then add 1g of the sample obtained in step (1), and then add about 1ml of water or ethanol, and stir thoroughly. Let the sample stand for 6h, and evaporate it in an 80℃ water bath for 2h. The prepared catalyst is recorded as IM-0.5% IrMoO3.

[0097] (3) Catalyst evaluation in RWGS. Reduction pretreatment conditions: 400°C for 1 hour, H₂ flow rate 30 ml / min; Reaction conditions: reaction temperature 300-600°C, pressure 0.1 MPa, reaction gas composition: 24% CO₂ / 72% H₂ / 4% N₂ (v / v / v), volumetric space velocity 300 L / (g·h).

[0098] Test Case

[0099] (1) The activity and selectivity of the catalysts obtained in Example 1 (high temperature quenching method) and Comparative Example 1 (impregnation method) were analyzed respectively. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that both catalysts achieve 100% CO selectivity at reaction temperatures above 500°C. The molybdenum oxide catalyst prepared in Example 1 exhibits superior activity, particularly at reaction temperatures between 500°C and 700°C. The CO2 conversion rates of Example 1 at 500°C, 600°C, and 700°C are 27.8%, 42.6%, and 55.7%, respectively, while those of Comparative Example 1 at 500°C, 600°C, and 700°C are 22.9%, 32.8%, and 41.5%, respectively.

[0100] (2) The stability of the catalysts obtained in Example 1 and Comparative Example 1 was evaluated. Figure 2 As shown. Figure 2 It can be seen that at 600 ° C, 300 L / (g·h) space velocity, and reaction gas composition: 4% CO2 / 72% H2 / 4% N2, no byproduct CH4 is produced in either catalyst, indicating that the molybdenum-based catalyst has good CO selectivity. By comparison, it can be found that the catalyst in Example 1 has better performance and stability, and its initial CO yield is 40.2g CO ·g cat -1 ·h -1 , and there was no obvious deactivation after 70h of reaction. The catalyst in Comparative Example 1 had poor stability and the initial CO yield was 32.1g CO ·g cat -1 ·h -1 After 70 hours of reaction, the CO yield dropped to 29.1 g. CO ·g cat -1 ·h -1 The above experimental results show that the performance of Ir additives doped by high temperature quenching method is better than that by impregnation method.

[0101] (3) The EXAFS images of the Ir element on the catalysts in Example 1 and Comparative Example 1 were analyzed and compared with the standard images of iridium foil and iridium dioxide. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the Ir species in Example 1 is mainly in the form of Ir-Ir, that is, the Ir in the catalyst is mainly distributed in the metallic state, closer to iridium foil. In contrast, the Ir species in Comparative Example 1 is mainly in the form of Ir-O, that is, the Ir in the catalyst is mainly distributed in the oxidized state, closer to iridium dioxide. These results indicate that the Ir species in the two preparation methods exist in different forms, which in turn have different promoting effects on the platinum-based catalyst support, thereby affecting its catalytic performance.

[0102] (4) The activities of the catalysts obtained in Examples 1 to 4 were analyzed respectively. The results are as follows: Figure 4 As shown. Figure 4It can be seen that different metal doping contents have little effect on the activity of the catalyst in RWGS. When the Ir doping amount is 5%, the CO2 conversion rate is 45.3%. When the Ir doping amount is reduced by 100 times to 0.5%, the CO2 conversion rate is 45.2%, and there is no significant change. When the Ir doping amount is reduced by 250 times to 0.02%, the CO2 conversion rate can still reach 40.3%. This shows that the additives doped by the high-temperature quenching method have a higher dispersion, and the modification effect of low-content additives is similar to that of high-content additives, which can significantly reduce the amount of precious metals used. On the other hand, the CO2 conversion rate of the catalyst in Example 4 is 42.2%, and the effect of doping with Pt is similar to that of doping with Ir, which shows that the modification effect of different types of precious metal doping on MoO3 is not much different.

[0103] (5) From Figure 5 It can be seen that different pretreatment temperatures have a significant effect on the performance of the FSP-IrMoO3 catalyst. In Example 1, the pretreatment temperature of the catalyst is 400°C, and the CO2 conversion rate is 45.2%; when the pretreatment temperature is 200°C (Example 5), the CO2 conversion rate drops to 33.0%; and when the pretreatment temperature is 600°C (Example 6), the CO2 conversion rate is 39.3%. This shows that an appropriate pretreatment temperature is very important for the catalytic reaction performance of the catalyst in RWGS. Too low a reduction temperature may lead to incomplete reduction of the catalyst, while too high a reduction temperature may cause sintering and aggregation of active species. However, the catalytic performance of the catalysts after treatment at different reduction temperatures is higher than that of Comparative Example 1, indicating that the preparation method of high-temperature quenching plays a decisive role.

[0104] Experimental results:

[0105] The metal-modified molybdenum-based oxide catalyst prepared by the high-temperature quenching method described in this application has a simple process, a short preparation cycle, and is easy to operate. It eliminates the drying and calcination steps required in traditional catalyst preparation methods such as precipitation and impregnation, thereby reducing preparation costs. The catalyst has excellent catalytic performance for RWGS. Under conditions of 24% CO2 / 72% H2 / N2 and a space velocity of 300 L / (g·h), the FSP-MoO3 catalyst obtained in Example 1 achieved a CO yield of 40.1 g at 600°C. CO ·g cat -1 ·h -1 , while no CH4 byproduct is produced, and there is no significant deactivation within 70 hours of reaction. In summary, this catalyst has high conversion rate, selectivity, and stability in the reverse water gas shift reaction, meeting the requirements of low cost, high activity, and long-term stable operation. It is a promising invention technology in the field of metal-modified molybdenum-based catalysts for CO2 catalytic conversion.

[0106] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A molybdenum oxide catalyst, characterized in that The molybdenum oxide catalyst comprises molybdenum oxide and a metal promoter; The molybdenum oxide is molybdenum trioxide and / or molybdenum dioxide; The metal adjuvant exists in a metallic form.

2. The molybdenum oxide catalyst according to claim 1, characterized in that In the molybdenum oxide catalyst, the mass fraction of molybdenum oxide is 30% to 99.98%; In the molybdenum oxide catalyst, the mass fraction of the metal additive is 0.02% to 5%, preferably 0.02% to 0.5%; Preferably, the metal additive is at least one of Ir, Pt, and Pd.

3. The molybdenum oxide catalyst according to claim 1, characterized in that The molybdenum oxide catalyst also includes a carrier; The carrier is a metal oxide; The metal oxide contains a metal element X; The metal element X is selected from at least one of Zn, Ce, Zr, Mg, Ti, La, Si, and Al.

4. A method for preparing the molybdenum oxide catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises: According to the composition ratio of the molybdenum oxide catalyst, a mixed solution containing a molybdenum precursor and a metal additive precursor is subjected to a high-temperature quenching method to prepare the molybdenum oxide catalyst.

5. The preparation method according to claim 4, characterized in that The molybdenum precursor is selected from at least one of molybdic acid, molybdenum acetylacetonate, molybdenum acetate, and ammonium molybdate; The metal auxiliary agent precursor is selected from at least one of acetylacetonate, acetate, and oxalate containing a metal auxiliary agent element, wherein the metal auxiliary agent element is selected from at least one of Ir, Pt, and Pd.

6. The preparation method according to claim 4, characterized in that The high temperature quenching method comprises: The mixed solution is pumped into a nozzle, the mixed solution is ejected from the nozzle, dispersed into droplets by a dispersion gas, the droplets are introduced into a flame and burned to obtain composite oxide particles, and the composite oxide particles leave the flame zone driven by the dispersion gas to obtain the molybdenum oxide catalyst; Preferably, the pumping speed is 1 to 20 ml / min; Preferably, the combustion gas required for flame combustion is a mixture of methane and oxygen, and the flow rates of methane and oxygen in the mixture are independently 0.1 to 10 L / min.

7. The preparation method according to claim 4, characterized in that The mixed solution also includes a carrier precursor; The carrier precursor is selected from at least one of acetylacetonate, acetate, and oxalate containing a metal element X, wherein the metal element X is selected from at least one of Zn, Ce, Zr, Mg, Ti, La, Si, and Al.

8. Use of the molybdenum oxide catalyst according to any one of claims 1 to 3 in a reverse water gas shift reaction, characterized in that: The applications include: The reaction atmosphere contacts the pretreated molybdenum oxide catalyst and reacts; The reaction atmosphere includes hydrogen and carbon dioxide.

9. The use according to claim 8, characterized in that The atmosphere of the pretreatment is hydrogen, The pretreatment temperature is 200-600°C, preferably 350-450°C; The pretreatment time is 0.5 to 10 hours, preferably 1 to 3 hours.

10. The use according to claim 8, characterized in that In the reaction atmosphere, the volume ratio of hydrogen to carbon dioxide is 1 to 5, preferably 2 to 4; Preferably, the total concentration of hydrogen and carbon dioxide in the reaction atmosphere is 0.1 to 100%; Preferably, the reaction pressure is 0.1 to 5.0 MPa, preferably 0.1 to 0.5 MPa; Preferably, the reaction temperature is 300-700°C, preferably 500-600°C; Preferably, the volume space velocity of the reaction atmosphere is 10 to 1000 L / (g·h).

Images