A copper-based catalyst, its preparation method and use
The preparation of copper-based catalysts by hydrogen reduction combined with photoreduction solved the problems of low catalyst activity and easy sintering, and achieved efficient conversion of carbon dioxide into carbon monoxide, exhibiting excellent catalytic activity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-04
- Publication Date
- 2026-07-07
AI Technical Summary
Existing copper-based reverse water-gas shift catalysts suffer from low catalytic activity and are prone to sintering, making it difficult to achieve efficient conversion of carbon dioxide into carbon monoxide.
A copper-based catalyst was prepared by a combination of hydrogen reduction and photoreduction. Highly dispersed copper nanoparticles were loaded onto a nano-titanium dioxide support, and a xenon lamp light source was used to promote the dispersion of copper active centers and inhibit aggregation.
It improves the catalytic activity and high-temperature stability of the catalyst, significantly enhances the selectivity of carbon monoxide, and reduces the formation of by-products, showing promising prospects for industrial applications.
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Figure CN119588352B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst preparation technology for reverse water-gas shift reaction, and particularly to a copper-based catalyst, its preparation method, and its application. Background Technology
[0002] The rapid increase in carbon dioxide emissions has exacerbated the greenhouse effect's impact on global ecosystems, drawing global attention. Therefore, reducing atmospheric carbon dioxide concentration through resource utilization is imperative to address global environmental issues. The reverse water-gas shift (RWGS) reaction, which catalytically converts carbon dioxide into more valuable carbon monoxide, is one of the most valuable pathways for carbon dioxide resource utilization. In modern chemical industries, carbon monoxide and hydrogen can be further synthesized through the Fischer-Tropsch reaction to produce important, high-value-added chemical products such as olefins, alcohols, and formaldehyde.
[0003] Currently, catalysts for reverse water-gas shift reactions (RWGS) mainly include noble metal-based catalysts and non-noble metal-based catalysts. Noble metal-based catalysts, primarily Pt, Au, Rh, and Pd, exhibit high catalytic activity, but their high cost makes industrial application difficult. Therefore, the development of highly active non-noble metal catalyst systems has received extensive research. Copper-based catalysts, due to their low cost and high carbon monoxide selectivity, have attracted particular attention as alternatives to noble metal catalysts in RWGS reactions. However, copper-based catalysts still suffer from low catalytic activity and susceptibility to sintering. Chinese patent CN 107497439A uses the silica sol method to prepare a copper-cerium catalyst with a mesoporous structure, resulting in good thermal stability and carbon monoxide selectivity; however, the catalyst activity needs further improvement. Chinese patent CN103230799A discloses a Cu-Zn-based catalyst for RWGS, exhibiting high reactivity at low temperatures, but with low carbon monoxide selectivity and the presence of other oxygen-containing compounds in the products.
[0004] In conclusion, developing copper-based reverse water-gas shift catalysts that combine high activity and good stability remains both challenging and of practical significance. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a catalyst for reverse water-gas shift reaction and its preparation method. The catalyst prepared by this invention exhibits highly dispersed copper active sites, resulting in high carbon dioxide conversion and high carbon monoxide selectivity in the reverse water-gas shift reaction.
[0006] One of the objectives of this invention is to provide a method for preparing a copper-based catalyst.
[0007] The second objective of this invention is to provide a copper-based catalyst prepared by this method.
[0008] A third objective of this invention is to provide an application of this copper-based catalyst.
[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:
[0010] In a first aspect, the present invention provides a method for preparing a copper-based catalyst, comprising the following steps:
[0011] S1. Place nano-titanium dioxide in a tube furnace and perform high-temperature treatment under a hydrogen atmosphere;
[0012] S2. Dissolve the high-temperature treated nano-titanium dioxide in an aqueous methanol solution and stir until homogeneous under nitrogen purging to obtain a nano-titanium dioxide solution.
[0013] S3. Turn on the xenon lamp light source to expose the nano-titanium dioxide solution to the xenon lamp light.
[0014] S4. Inject the copper salt aqueous solution into the nano titanium dioxide solution and continue stirring under the irradiation of a xenon lamp to obtain a mixed solution. Based on the mass of the nano titanium dioxide, the copper ion content is 2wt%-8wt%.
[0015] S5. Wash and dry the obtained mixed solution to obtain a copper-based catalyst.
[0016] The copper-based catalyst prepared by the present invention via hydrogen reduction combined with photoreduction has highly dispersed copper metal as its active center.
[0017] Step S1:
[0018] In step S1, the nano-titanium dioxide is commercially available nano-titanium dioxide, preferably with an average particle size of 20nm to 30nm and a rutile phase structure.
[0019] In some embodiments, in step S1, the hydrogen flow rate is 20 mL / min to 60 mL / min, the high-temperature treatment temperature is 200℃ to 500℃, the heating rate is 2 to 5℃ / min, and the treatment time is 1h to 5h.
[0020] Step S2:
[0021] In some embodiments, in step S2, the volume of the methanol aqueous solution is 50 mL to 200 mL for every 500 mg of nano titanium dioxide, and the volume percentage of methanol in the methanol aqueous solution is 5% to 50%.
[0022] In some embodiments, in step S2, the flow rate of nitrogen is 20 mL / min to 60 mL / min, the stirring speed is 300 r / min to 1000 r / min, and the stirring time is 0.5 h to 3 h.
[0023] Step S3:
[0024] In some implementations, in step S3, the power of the xenon lamp light source is 100W to 800W, and the irradiation time is 0.1h to 2h.
[0025] Step S4:
[0026] In some embodiments, in step S4, the copper salt is one or more of copper nitrate hexahydrate, copper sulfate pentahydrate, and copper chloride;
[0027] In some embodiments, in step S4, for every 500 mg of nano-titanium dioxide, the volume of the copper salt aqueous solution is 1 mL to 5 mL, and the concentration is 0.1 to 1 mol / L.
[0028] In some embodiments, the stirring time in step S4 is 0.1h to 2h.
[0029] Step S5:
[0030] In some embodiments, in step S5, centrifugal washing is performed with ethanol and water respectively, and the number of centrifugal washings is 1 to 5 times with ethanol and water respectively.
[0031] In some embodiments, in step S3, the drying process involves placing the item in a vacuum drying oven and drying it overnight at a temperature of 50–80°C.
[0032] Secondly, the present invention provides a copper-based catalyst prepared by the above preparation method. The copper-based catalyst includes a nano-TiO2 support and highly dispersed copper nanoparticles supported on the nano-TiO2 support. The size of the copper nanoparticles is 3 nm to 5 nm.
[0033] Based on the mass of the TiO2 support, the copper loading is 2wt%-8wt%.
[0034] In some embodiments, the average particle size of nano-titanium dioxide is 20 nm to 30 nm, and the phase is a rutile phase structure.
[0035] Thirdly, the present invention provides an application of the above-mentioned copper-based catalyst in the reverse water-gas shift reaction.
[0036] Preferably, the reaction is carried out in a fixed-bed reactor;
[0037] The catalyst is tableted, pulverized, and then sieved into 20-40 mesh particles and packed into a fixed-bed reactor.
[0038] The reaction conditions are as follows: reaction temperature is 400-500℃, reaction pressure is 0.1-0.5MPa, total space velocity of raw material gas is 3000-8000mL / g / h, and the gas used is a mixture of CO2 and H2, wherein the volume ratio of CO2 to H2 is 1:1-1:4.
[0039] Preferably, the copper-based catalyst is subjected to hydrogen pre-reduction treatment before use. The reduction conditions are: hydrogen space velocity of 3000 mL / g / h to 10000 mL / g / h, reduction temperature of 200℃ to 400℃, and reduction time of 0.5h to 5h.
[0040] Technical effects:
[0041] (1) The preparation method of the present invention is simple to operate and has low cost;
[0042] (2) The preparation method of the present invention adopts high-temperature hydrogen reduction combined with photoreduction treatment, which introduces abundant surface defects and oxygen vacancies to the surface of the support. Then, copper metal is photodeposited. Under the strong interaction between abundant surface defects and metal support, the copper active center is anchored to the surface of the support, while inhibiting the aggregation of copper active centers. This achieves high dispersion of copper active centers, thereby improving the catalytic activity and high-temperature stability of the catalyst.
[0043] (3) The catalyst prepared by this invention exhibits excellent catalytic activity in the reverse water gas reaction test, significantly inhibits the generation of byproducts methane and methanol, improves the selectivity of carbon monoxide, and has high industrial application prospects.
[0044] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description
[0045] Figure 1 This is a high-resolution transmission electron microscope image of the catalyst prepared in Example 2.
[0046] Figure 2 The results show the performance test results of the catalysts prepared in the examples and comparative examples. Detailed Implementation
[0047] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.
[0048] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.
[0049] Example 1
[0050] (1) Place 500 mg of nano titanium dioxide (P25) in a tube furnace, introduce high-purity hydrogen gas at a rate of 30 mL / min, heat to 400 °C at a rate of 2 °C / min, and maintain for 3 h.
[0051] (2) Dissolve the treated titanium dioxide in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then maintain a stirring speed of 500 r / min for 2 h.
[0052] (3) Turn on the xenon lamp light source so that the solution is irradiated by the xenon lamp for 0.5 hours, wherein the power of the xenon lamp light source is 300W;
[0053] (4) Dissolve 46.3 mg of copper nitrate hexahydrate in 1 mL of deionized water, then inject it into the above solution, and continue stirring for 1 h under xenon lamp irradiation, wherein the loading of copper relative to the nano titanium dioxide carrier is 2 wt%.
[0054] (5) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0055] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0056] Example 2
[0057] (1) Place 500 mg of nano titanium dioxide (P25) in a tube furnace, introduce high-purity hydrogen gas at a rate of 30 mL / min, heat to 400 °C at a rate of 2 °C / min, and maintain for 3 h.
[0058] (2) Dissolve the treated titanium dioxide in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then maintain a stirring speed of 500 r / min for 2 h.
[0059] (3) Turn on the xenon lamp light source so that the solution is irradiated by the xenon lamp for 0.5 hours, wherein the power of the xenon lamp light source is 300W;
[0060] (4) Dissolve 92.6 mg of copper nitrate hexahydrate in 1 mL of deionized water, then inject it into the above solution, and continue stirring for 1 h under xenon lamp irradiation, wherein the copper loading is 4 wt%.
[0061] (5) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0062] Its transmission electron microscope image is as follows Figure 1 As shown, from Figure 1 It can be seen that the copper in the catalyst has a high degree of dispersion, with a size of about 3nm to 5nm.
[0063] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0064] Example 3
[0065] (1) Place 500 mg of nano titanium dioxide (P25) in a tube furnace, introduce high-purity hydrogen gas at a rate of 30 mL / min, heat to 400 °C at a rate of 2 °C / min, and maintain for 3 h.
[0066] (2) Dissolve the treated titanium dioxide in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then maintain a stirring speed of 500 r / min for 2 h.
[0067] (3) Turn on the xenon lamp light source so that the solution is irradiated by the xenon lamp for 0.5 hours, wherein the power of the xenon lamp light source is 300W;
[0068] (4) Dissolve 138.9 mg of copper nitrate hexahydrate in 1 mL of deionized water, then inject it into the above solution, and continue stirring for 1 h under xenon lamp irradiation, wherein the copper loading is 6 wt%.
[0069] (5) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0070] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0071] Example 4
[0072] (1) Place 500 mg of nano titanium dioxide (P25) in a tube furnace, introduce high-purity hydrogen gas at a rate of 30 mL / min, heat to 400 °C at a rate of 2 °C / min, and maintain for 3 h.
[0073] (2) Dissolve the treated titanium dioxide in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then maintain a stirring speed of 500 r / min for 2 h.
[0074] (3) Turn on the xenon lamp light source so that the solution is irradiated by the xenon lamp for 10 minutes, wherein the power of the xenon lamp light source is 300W.
[0075] (4) Dissolve 92.6 mg of copper nitrate hexahydrate in 1 mL of deionized water, then inject it into the above solution, and continue stirring for 1 h under xenon lamp irradiation, wherein the copper loading is 4 wt%.
[0076] (5) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0077] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0078] Comparative Example 1: Pretreatment without Xenon Lamp Irradiation
[0079] (1) Place 500 mg of nano titanium dioxide (P25) in a tube furnace, introduce high-purity hydrogen gas at a rate of 30 mL / min, heat to 400 °C at a rate of 2 °C / min, and maintain for 3 h.
[0080] (2) Dissolve the treated titanium dioxide in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then maintain a stirring speed of 500 r / min for 2 h.
[0081] (3) Turn on the xenon lamp source, dissolve 92.6 mg of copper nitrate hexahydrate in 1 mL of deionized water, and then inject it into the above solution. Under the irradiation of the xenon lamp, continue stirring for 1 h. The power of the xenon lamp source is 300 W and the copper loading is 4 wt%.
[0082] (4) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0083] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0084] Comparative Example 2: Hydrogen-free reduction pretreatment
[0085] (1) Dissolve 500 mg of nano titanium dioxide (P25) in 100 mL of 20% methanol aqueous solution, purge with nitrogen gas at 30 mL / min to remove air, and then keep stirring at 500 r / min for 2 h.
[0086] (2) Turn on the xenon lamp source so that the solution is irradiated by the xenon lamp for 0.5 hours, wherein the power of the xenon lamp source is 300W; dissolve 92.6mg of copper nitrate hexahydrate in 1mL of deionized water, and then inject it into the above solution. Under the irradiation of the xenon lamp, continue stirring for 1 hour, wherein the copper loading is 4wt%.
[0087] (3) After washing the solution three times by centrifugation with ethanol and water respectively, place it in a vacuum drying oven and dry it overnight at 60°C. Collect the catalyst for testing and use.
[0088] The catalyst was tableted, pulverized, and sieved into 20-40 mesh particles, which were then packed into a fixed-bed reactor. Before reaction testing, the catalyst underwent hydrogen pre-reduction treatment under the following conditions: hydrogen space velocity (HHSV) 6000 mL / g / h, reduction temperature 300℃, and reduction time 2 h. After the temperature cooled to room temperature, the reaction gas was introduced. The reaction conditions were: reaction temperature 480℃, reaction pressure 0.1 MPa, total space velocity (THV) of the feed gas 4000 mL / g / h, and a carbon dioxide to hydrogen volume ratio of 1:2 in the feed gas. The catalytic performance test results are shown below. Figure 2 .
[0089] The calculation process for CO2 conversion rate and selectivity of each component is as follows:
[0090]
[0091] Among them, [CO2] inlet and [CO2] outlet These represent the molar concentrations of CO2 in the raw gas and the exhaust gas, respectively.
[0092]
[0093] Among them, [CO] and [C] i H x ] represent the molar concentrations of CO and hydrocarbons, respectively.
[0094] from Figure 2 As can be seen, compared with the examples, the catalyst prepared by hydrogen reduction combined with photoreduction treatment of the support exhibits higher catalytic activity and carbon monoxide selectivity. This indicates that the preparation method of the present invention can effectively improve the dispersion of copper active sites, inhibit agglomeration, and thus significantly enhance the activation ability of the catalyst for carbon dioxide, and avoid excessive hydrogenation of the generated carbon monoxide. Therefore, at a reaction temperature of 480°C, the carbon monoxide selectivity is as high as 95%.
[0095] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.
Claims
1. A method for preparing a copper-based catalyst, characterized in that, Includes the following steps: S1. Place nano-titanium dioxide in a tube furnace and perform high-temperature treatment under a hydrogen atmosphere; in step S1, the hydrogen flow rate is 20 mL / min to 60 mL / min, the high-temperature treatment temperature is 200℃ to 500℃, the heating rate is 2 to 5℃ / min, and the treatment time is 1h to 5h. S2. Dissolve the high-temperature treated nano-titanium dioxide in an aqueous methanol solution and stir until homogeneous under nitrogen purging to obtain a nano-titanium dioxide solution. S3. Turn on the xenon lamp light source to expose the nano-titanium dioxide solution to the xenon lamp light; in step S3, the power of the xenon lamp light source is 100W to 800W, and the irradiation time is 0.1h to 2h. S4. Inject the copper salt aqueous solution into the nano titanium dioxide solution and continue stirring under the irradiation of a xenon lamp to obtain a mixed solution. Based on the mass of the nano titanium dioxide, the copper ion content is 2wt%-8wt%. S5. Wash and dry the obtained mixed solution to obtain a copper-based catalyst.
2. The preparation method according to claim 1, characterized in that, In step S2, for every 500 mg of nano-titanium dioxide, the volume of the methanol aqueous solution is 50 mL to 200 mL, and the volume percentage of methanol in the methanol aqueous solution is 5% to 50%.
3. The preparation method according to claim 1, characterized in that, In step S2, the flow rate of nitrogen is 20 mL / min to 60 mL / min, the stirring speed is 300 r / min to 1000 r / min, and the stirring time is 0.5 h to 3 h.
4. The preparation method according to claim 1, characterized in that, In step S4, the copper salt is one or more of copper nitrate hexahydrate, copper sulfate pentahydrate, and copper chloride; In step S4, for every 500 mg of nano titanium dioxide, the volume of the copper salt aqueous solution is 1 mL to 5 mL, and the concentration is 0.1 to 1 mol / L.
5. The preparation method according to claim 1, characterized in that, In step S4, the stirring time is 0.1h to 2h.
6. A copper-based catalyst, characterized in that, The copper-based catalyst is prepared by the preparation method according to any one of claims 1-5, comprising a nano-TiO2 support and highly dispersed copper nanoparticles supported on the nano-TiO2 support; the size of the copper nanoparticles is 3nm to 5nm; and the copper loading is 2wt% to 8wt% based on the mass of the TiO2 support.
7. The application of the copper-based catalyst according to claim 6 in the reverse water-gas shift reaction.
8. The application according to claim 7, characterized in that, The reaction is carried out in a fixed-bed reactor; the reaction conditions are: reaction temperature of 400-500℃, reaction pressure of 0.1-0.5MPa, total space velocity of feed gas of 3000-8000mL / g / h, and the gas used is a mixture of CO2 and H2, wherein the volume ratio of CO2 to H2 is 1:1-1:
4.
9. The application according to claim 8, characterized in that, The copper-based catalyst is subjected to hydrogen pre-reduction treatment before use. The reduction conditions are: hydrogen space velocity of 3000 mL / g / h to 10000 mL / g / h, reduction temperature of 200℃ to 400℃, and reduction time of 0.5h to 5h.