Preparation of high-activity Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction

Abstract

The invention belongs to the technical field of catalysis, and particularly relates to preparation of a high-activity Cu / ZnO / SiO2 catalyst and a reverse water gas shift reaction. Aiming at the problems of low reaction activity of low-temperature RWGS, low selectivity of a target product CO and the like in the existing Cu / ZnO-based catalyst, the invention prepares a novel Cu / ZnO / SiO2 catalyst which is used for promoting the reaction activity of medium-low-temperature reverse water gas shift. According to the invention, the polyhydroxy high-molecular compound is adopted to replace a part of small-molecular solvent, the novel Cu / ZnO / SiO2 catalyst with a silicon source, copper and zinc highly dispersed in mesoporous SiO2 is obtained by utilizing the polyhydroxy characteristic and low degree of freedom of the polyhydroxy high-molecular compound, and when the novel Cu / ZnO / SiO2 catalyst is used for a medium-low temperature reverse water gas shift reaction, the reaction activity can be effectively improved to 58%, and the reaction time can be shortened to 30-50 minutes. Meanwhile, the selectivity of the target product CO is 99% or above. The method has the advantages of low catalyst cost, high reaction efficiency, simple process operation and the like, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic technology and specifically relates to a highly active Cu / ZnO / SiO 2 Catalyst preparation and reverse water-gas shift reaction. Background Art

[0002] The mining and utilization of carbon-containing resources such as oil, coal, and natural gas will inevitably produce CO. 2 .CO 2 The emission of CO has caused serious environmental and ecological problems, such as ocean acidification and extreme climate change. 2 Green and efficient catalytic conversion into carbon-containing chemicals is not only conducive to achieving my country's dual carbon goals, but also conducive to the recycling of carbon resources. 2 It can be converted into C1 platform molecules such as CO and methanol through hydrogenation reaction. Among them, CO has a unique position in the future chemical and energy industries. CO can be converted into liquid fuels such as gasoline and diesel through FT synthesis reaction. These hydrocarbon molecules can be prepared into basic chemical raw materials such as branched hydrocarbons, low-carbon olefins, aromatics and oxygen-containing chemicals through dehydrogenation and isomerization reactions. Therefore, CO 2 The technology of producing CO by hydrogenation (i.e. reverse water gas shift reaction, RWGS reaction) has broad application prospects. Copper-based catalysts have the advantages of low price, high reaction activity and few by-products, and are currently the most commonly used catalysts for RWGS reaction. It is a reversible, endothermic reaction. High temperature (500-800℃) is conducive to promoting the reaction to generate CO and promoting CO 2 Conversion rate. However, when copper reacts at high temperatures, it is very easy to aggregate and sinter, resulting in catalyst deactivation. In order to avoid this problem, researchers often apply copper-based catalysts to medium and low temperature (180-400°C) RWGS reaction processes. However, when reacting at medium and low temperatures, the activity of the catalyst is often low, often around 5%-15%. Therefore, designing a new copper-based catalyst system and significantly improving the RWGS reaction activity of copper-based catalysts under medium and low temperature conditions is one of the key technical challenges of the RWGS reaction process.

[0003] At present, the commonly used strategies include: (1) introducing metal or metal oxide promoters into the copper-based catalyst system to promote CO 2 (2) Prepare a catalyst with a large specific surface area and abundant pores, increase the dispersion of active metals, generate more active sites, and promote the reaction. For this purpose, patent CN 201811539419.9 discloses a ternary Cu / MgO / Al 2 O 3Preparation method of catalyst and its application in RWGS reaction. The catalyst is prepared by hydrothermal synthesis, has strong alkalinity, and can better adsorb acidic CO 2 When it is used in RWGS reaction at 300℃, CO 2 The conversion rate is close to 20%, and the CO selectivity is close to 100%. Patent CN 201710678000.0 discloses a mesoporous Cu-CeO 2 Catalyst and preparation method thereof. The main raw materials used are copper nitrate, cerium nitrate, glycine, neutral silica sol and NaOH. Neutral silica sol is used as a hard template to construct the mesoporous structure of the catalyst, and CeO 2 The carrier has excellent oxygen storage capacity to promote CO 2 When the catalyst is used in RWGS reaction, CO 2 The conversion rate reached 31.8%. However, during the preparation of the catalyst, an inorganic strong base NaOH is required to remove the neutral silica sol, which not only complicates the preparation process, but also easily produces alkaline wastewater, which is not conducive to environmental protection. Compared with the hard template, the soft template can be removed during the high-temperature roasting process, which is conducive to the simplification of the catalyst preparation process. For this reason, patent 201610954936.7 discloses a Cu / CeO 2 Catalyst and preparation method thereof. 2-Methylimidazole is used as a soft template to construct a copper-cerium catalyst with rich pore structure, large specific surface area and high dispersion, so as to promote the activity of medium and low temperature RWGS reaction. When this series of catalysts react at 400°C, CO 2 The conversion rate is in the range of 6.9%-20.1%. However, 2-methylimidazole is toxic and expensive, and its use is not only disadvantageous for actual production operation, but also increases production costs.

[0004] Compared with Cu / CeO 2 Based on the catalyst system, the Cu / ZnO based system is low in price and is also an industrial catalyst for CO hydrogenation to methanol. It effectively improves the RWGS reaction activity under low temperature conditions, which is not only beneficial to CO 2 The promotion and application of hydrogenation to CO technology is also conducive to coupling CO 2 Technologies such as hydrogenation to CO and CO hydrogenation to methanol can achieve CO 2To this end, patent CN 201310120254.2 discloses a method for preparing a Cu / ZnO / M catalyst for RWGS reaction. Where M is one or more combinations of transition metals, alkali metals, alkaline earth metals or rare earth metals. The patent first uses a coprecipitation method to obtain a Cu / ZnO precursor, and then uses an equal volume impregnation method to introduce the M component into the Cu / ZnO precursor to obtain the final catalyst. When reacting at 280°C, the CO 2 The conversion rate reached 19.1%, but in addition to CO, mixed alcohols and other oxygen-containing compounds were also generated on the catalyst. The generation of these by-products reduced the selectivity of the target product CO (76.9%). In summary, when performing RWGS reactions under medium and low temperature conditions, in order to improve the reaction activity of copper-based catalysts, it is often necessary to contain CeO in the copper-based catalyst. 2 For Cu / ZnO-based catalysts, the selectivity of the target product CO is not high, and the low-temperature reaction activity is not ideal. Summary of the invention

[0005] Aiming at the problems of low low-temperature RWGS reaction activity and low selectivity of target product CO in current Cu / ZnO-based catalysts, the present invention provides a novel Cu / ZnO / SiO catalyst. 2 Catalyst, a method for significantly promoting the activity of medium and low temperature RWGS reaction and effectively improving the selectivity of product CO.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A highly active Cu / ZnO / SiO 2 The preparation of the catalyst and the reverse water-gas shift reaction include the following steps:

[0008] Step 1, preparation of catalyst: fully mix silicon source, copper salt, zinc salt, solvent and polyhydroxy polymer compound, dry and calcine to obtain Cu / ZnO / SiO 2 catalyst;

[0009] Step 2, reverse water gas shift reaction: Cu / ZnO / SiO 2 The catalyst is subjected to a reduction treatment and then to a reverse water-gas shift reaction.

[0010] The copper-based system is one of the most commonly used catalysts for the RWGS reaction, with the advantages of low price and high selectivity for the target product CO. The RWGS reaction is a reversible, endothermic reaction. High temperature conditions are conducive to the reaction in the direction of generating CO, obtaining higher reaction activity and CO yield. However, when reacting at high temperatures, copper-based catalysts are often prone to aggregation and sintering of copper active sites, leading to catalyst deactivation. In order to avoid this problem, the RWGS reaction of copper-based catalysts is often carried out under medium and low temperature conditions (180-400°C). Although medium and low temperature conditions improve the stability of copper-based catalysts, they are not conducive to the reaction activity of copper-based catalysts. Limited by the equilibrium of the RWGS reaction, the reaction activity of copper-based catalysts is often low, often around 5%-15%. Therefore, the development of new copper-based catalysts to significantly improve their RWGS reaction activity under medium and low temperature conditions is one of the key technical challenges in the RWGS reaction process. Compared with Cu / CeO 2 Based on the catalytic system, the Cu / ZnO based catalytic system is cheaper and is also an industrial catalyst for the production of methanol from syngas. It effectively improves the reaction activity of low-temperature RWGS, which is not only beneficial to CO 2 The promotion and application of hydrogenation to CO technology will also be beneficial to CO 2 The CO production reaction and the CO production methanol reaction are coupled to achieve the CO 2 Purpose of preparing methanol.

[0011] Considering that the RWGS reaction is a reversible reaction In order to improve the activity of the reaction, it is necessary not only that the Cu / ZnO-based catalyst has a high adsorption and activation capacity of the reactant CO 2 Molecule and H 2 In addition, the catalyst must be able to rapidly desorb the product CO. In order to achieve the above goals, zinc oxide and copper are highly dispersed in the form of nanoparticles on SiO 2 In the three-dimensional structure of Cu / ZnO / SiO 2 First, there are often a large number of coordination unsaturated sites (edges, corners, edges, defects, etc.) on the surface of zinc oxide and copper nanoparticles, which have strong adsorption and activation of CO 2 and H 2 The ability of the molecules is conducive to promoting the RWGS reaction. Secondly, the SiO2 around the ZnO and Cu nanoparticles 2 The carrier has a large specific surface area, well-developed pores, and abundant hydroxyl groups, all of which are conducive to the enrichment and adsorption of CO 2 molecules, which is beneficial to increase the surface CO of the catalyst 2 Finally, the generated CO in Cu / ZnO / SiO 2 The adsorption is weak and it is easy to desorb in the form of gas at the reaction temperature, thereby promoting the RWGS reaction.

[0012] In order to achieve the above goals, in the preparation of Cu / ZnO / SiO 2 In the process of preparing the catalyst, a large amount of polyhydroxy polymer compounds are used to replace part of the small molecule solvent system (such as water, etc.), and the adsorption performance of polyhydroxyl groups on copper ions, zinc ions and silicon sources is utilized to adsorb the three around them and fully mix them, so as to form a system in which copper ions, zinc ions and silicon sources are evenly dispersed. In the drying process of removing the solvent, compared with small molecule solvents, polyhydroxy polymer compounds have large sizes and low degrees of freedom, so they will not deform or migrate significantly. In this way, the copper ions, zinc ions and silicon sources adsorbed thereon can still maintain a highly dispersed state, and will not agglomerate or reduce dispersion as the small molecules of the solvent leave. In addition, in the drying process, as the solvent is removed, SiO 2 The primary structure of the carrier is basically formed, which further improves the stability of the system and is conducive to the formation of copper and zinc highly dispersed in SiO 2 The structure of the carrier. During the calcination stage, the polyhydroxy polymer compound is converted into CO 2 and H 2 O molecules are removed, which is conducive to the formation of SiO 2 The mesoporous structure and abundant surface defects of the carrier, the former is conducive to increasing the specific surface area of ​​the carrier, while the latter is conducive to the formation of surface hydroxyl groups.

[0013] Cu / ZnO / Al 2 O 3 The catalyst needs to be reduced before the reaction. The purpose of the reduction treatment is to reduce the copper oxide of the catalyst to active metallic copper, making it reactive.

[0014] Furthermore, in step 1, the silicon source is any one of sodium silicate, tetraethyl orthosilicate, tetramethyl orthosilicate, and silica sol, or a combination of several of them.

[0015] In the solvent system, sodium silicate, tetraethyl orthosilicate, tetramethyl orthosilicate, and silica sol can form Si-O-Si bonds through hydrolysis and polymerization, and these Si-O-Si bonds can then form a three-dimensional network structure, which is conducive to the formation of mesopores and SiO 2 The specific surface area is increased. The SiO 2 It promotes the high dispersion of copper oxide and zinc oxide nanoparticles.

[0016] Furthermore, in step 1, the copper salt is any one or a combination of copper nitrate, copper acetate, and copper chloride, and the zinc salt is any one or a combination of zinc nitrate, zinc acetate, and zinc chloride.

[0017] Metal nitrates, acetates and chlorides are the most commonly used metal salts for preparing Cu / ZnO-based catalysts. They have the following advantages: (1) The above metal salts have high solubility in solvents such as water, which facilitates the preparation of metal salt solutions of different concentrations; (2) When the above metal salts are dissolved in water or other solutions, they generally exhibit varying degrees of acidity, which can promote the hydrolysis and polycondensation of silicon sources; (3) After the above metal salts are dissolved, their metal cations generate electrostatic attraction with the hydroxyl oxygen atoms (with partial negative charge) of the polyhydroxy polymer compound, which is conducive to the adsorption and dispersion of metal ions on the polyhydroxy polymer compound.

[0018] Furthermore, the solvent in step 1 is any one or a combination of water, methanol, ethanol, propanol, and isopropanol.

[0019] Solvents such as water, methanol, ethanol, propanol, and isopropanol have good solubility for silicon sources, metal salts, polyhydroxy polymer compounds, etc., which is conducive to the full mixing of the three and achieving a highly dispersed state among each other; in addition, the boiling points of solvents such as water, methanol, ethanol, propanol, and isopropanol are not high and can be easily removed by evaporation under dry conditions.

[0020] Furthermore, the polyhydroxy polymer compound in step 1 is any one or a combination of polyvinyl alcohol, soluble starch, corn starch, potato starch, and potato starch.

[0021] The above-mentioned polyhydroxy polymer compounds all contain abundant hydroxyl groups and have strong ability to adsorb silicon sources, copper ions and zinc ions. They can replace some solvent molecules, adsorb silicon sources, copper ions and zinc ions, and make silicon sources, copper ions and zinc ions highly dispersed in polyhydroxy polymer compounds. During the drying process, polyhydroxy polymer compounds can stabilize these silicon sources, copper ions and zinc ions, significantly inhibit their migration and agglomeration during the solvent removal process, and maintain their highly dispersed state in the system.

[0022] Furthermore, the masses of the silicon source, copper salt, and zinc salt in step 1 are respectively SiO 2 , CuO, and ZnO, the mass of the polyhydroxy polymer compound is 10-30 times the total mass of the silicon source, copper salt, and zinc salt.

[0023] If the amount of polyhydroxy polymer compound added is small, it cannot form a good competitive adsorption relationship with small molecule solvents such as water, which affects its adsorption and stabilization effect on silicon source, copper ions and zinc ions. If the amount of polyhydroxy polymer compound added is too much, it will not have more positive effects in promoting the adsorption of silicon source, copper and zinc ions, but will increase the cost of raw materials and process.

[0024] Furthermore, in step 1, the silicon source, copper salt, zinc salt and solvent are calculated according to the molar number of Si atoms, the molar number of Cu atoms, the molar number of Zn atoms and the volume of the solvent, respectively, and the ratio of the silicon source, copper salt, zinc salt and solvent is in the range of 1 mol: 0.005-3 mol: 0.005-3 mol: 100-5000 mL.

[0025] Metal ions compete with silicon sources for adsorption on polyhydroxy polymer compounds. When the molar ratio of metal to silicon is too high, too many metal ions will "squeeze out" part of the silicon source and adsorb around the polyhydroxy polymer compound. The "squeezed out" silicon source loses the protection of the polyhydroxy polymer compound and tends to agglomerate with each other to form a compact structure with a low specific surface area and underdeveloped pores. In addition, when the amount of metal added is too high, a large number of metal oxide particles will be formed, which are easy to cause SiO 2 The collapse of the structure, the blockage of the pores and the loss of specific surface area. When the molar ratio of metal to silicon is too low, too much silicon source will be adsorbed around the polyhydroxy polymer compound, which is not conducive to the adsorption of metal ions and the uniform dispersion of metal ions and silicon source. In addition, when the amount of metal added is too low, the metal oxide particles formed are too small and are easily embedded in SiO 2 In the three-dimensional structure, it is difficult for the reactant molecules to contact these metal particles, which is not conducive to the reaction. When the volume of added solvent is too small, it is not conducive to the uniform dispersion of metal salts, silicon sources and polyhydroxy polymer compounds; when the volume of added solvent is too large, due to the small size of solvent molecules and strong mobility (polyhydroxy polymer compounds are large in size and poor in mobility), metal ions and silicon sources tend to be adsorbed on solvent molecules. In the process of removing solvents such as drying and roasting, metal ions and silicon sources are prone to agglomeration.

[0026] Furthermore, the drying conditions in step 1 are: temperature of 60-150° C. and time of 0.5-20.0 h.

[0027] If the drying temperature is low, the solvent is difficult to completely remove from the mixture system or the time consumed for solvent removal is too long. The former is not conducive to the preparation of the catalyst, and the latter increases the cost of the process. If the drying temperature is high, the hydroxyl groups of the polyhydroxy polymer compound may undergo a dehydration reaction, which on the one hand leads to a decrease in its ability to adsorb metal ions and silicon sources, resulting in different degrees of agglomeration of metal ions and silicon sources. On the other hand, the water produced by the dehydration reaction easily adsorbs metal ions and silicon sources, causing them to separate from the polyhydroxy polymer compound and move in the system, causing them to become unstable. If the drying time is short, the solvent cannot be completely evaporated and removed. If the drying time is long, energy consumption and process costs will increase.

[0028] Furthermore, the calcination conditions in step 1 are: temperature of 300-650° C., air atmosphere, and time of 2-12 h.

[0029] When calcined in air, the oxygen in the air is conducive to the gradual oxidation of the polyhydroxy polymer compound, which is eventually removed from the system in the form of gas. The generation of gas is also conducive to the formation of pores. If the calcination temperature is too low or the time is too short, the polyhydroxy polymer compound is not easy to be completely oxidized, but remains in the catalyst in the form of carbon deposits, blocking some of the catalyst's pores and covering some of the catalyst's metal active particles. If the calcination temperature is too high or the time is too long, it is easy to cause SiO 2 The collapse of the structure and the aggregation and sintering of metal oxides increase the process energy consumption and process cost.

[0030] Furthermore, the reduction and reverse water-gas shift reaction in step 2 are both carried out on a fixed bed reaction evaluation device.

[0031] Cu / ZnO / SiO 2 The catalyst is solid and needs to be reduced with gas. 2 and CO 2 is gas, and the products are CO and H 2 O are gas and liquid, and the byproducts are methanol and CH 4 The entire reaction involves three phases: gas-liquid-solid. The fixed bed reaction evaluation device can ensure that the reducing gas and the reaction gas are fully in contact and react with the solid catalyst, promote the full reduction of the catalyst, and improve the reaction efficiency of the catalyst. At the same time, the cold trap component in the reaction device can facilitate the separation and collection of gas-liquid reaction products.

[0032] Furthermore, the reduction conditions in step 2 are: pure H 2 , H 2 The volume content is 2.5-30% H 2 / N 2 Mixed gas or H 2 The volume content is 2.5-30% H 2 / Ar mixed gas, temperature 180~400℃, pressure 0.1~0.5MPa, space velocity 1.0~20.0NL·g cat -1 ·h -1 , until no water is detected in the tail gas; the conditions for the reverse water gas shift reaction are: a volume ratio of 1:1 to 5:1 H 2 / CO 2 , temperature 180~350℃, pressure 0.1~5.5MPa, space velocity 0.5~20.0NL·g cat -1 ·h -1 .

[0033] Using pure H2 Or contain H 2 The mixed gas of components can convert Cu / ZnO / SiO 2 The copper oxide and zinc oxide in the catalyst are fully reduced to reactive metallic copper and low-valent zinc oxide species. If the reduction temperature is too low, it is not conducive to the full reduction of the copper oxide and zinc oxide in the catalyst, resulting in the catalyst showing lower activity; if the reduction temperature is too high, due to the instability of copper, the obtained metallic copper is very easy to migrate, aggregate and sinter at high temperature, causing the catalyst to deactivate. If the reduction pressure is too high, it is not conducive to the operation of the process. If the reduction pressure is low (<1atm, normal pressure), the entire device also requires vacuum equipment, which increases the process cost. If the reduction space velocity is too low, the water generated during the reduction process is not easy to diffuse, which easily leads to the aggregation, sintering and loss of copper. If the reduction space velocity is too high, the amount of reducing gas used increases, increasing the process cost.

[0034] For RWGS reactions CO 2 and H 2 The theoretical molar ratio (volume ratio) of the reaction gas H is 1:1. 2 / CO 2 The volume ratio should be close to the theoretical value. Too low is not conducive to CO 2 The conversion rate is too high, resulting in low overall reaction efficiency; too high a conversion rate leads to H 2 The utilization rate is low. If the reaction temperature is too low, the catalyst activity is low; if the reaction temperature is too high, the metallic copper in the catalyst is prone to aggregation and sintering, resulting in a decrease in catalyst activity. If the reaction pressure is too high, it is not conducive to the operation of the process; if the pressure is too low, the catalyst activity is low. If the reaction space velocity is too low, the space-time yield of the target product methanol is not high; if the reaction space velocity is too high, the gas consumption increases, increasing the process cost.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Combine the catalyst preparation method and reaction process conditions to effectively improve the activity of medium and low temperature RWGS reaction, CO 2 The conversion rate can be increased to 60%, while the by-product CH 3 OH and CH 4 Selectivity, so that the selectivity of the target product CO reaches more than 99 mol%.

[0037] (2) Polyhydroxy polymer compounds are used to replace part of small molecule solvents such as water, and the adsorption and complexing ability of the hydroxyl groups on metal ions and silicon sources is utilized to achieve full mixing and high dispersion of metal and silicon sources; in addition, the low degree of freedom and non-migratory characteristics of the polymer compounds are utilized to stabilize the metal and silicon during the solvent removal process (such as drying), inhibit the agglomeration of the metal and silicon, and prepare new Cu / ZnO / SiO 2Catalyst. The catalyst is low-cost and has the characteristics of large specific surface area, rich pore size and high metal dispersion.

[0038] (3) The reaction process of the present invention is simple to operate, the reaction temperature is mild, and it has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Catalyst N 2 - Adsorption-desorption curves: (a) Cu / ZnO / SiO of Example 1 2 -1 catalyst, (b) Cu / ZnO / SiO of Example 2 2 -2 catalyst, (c) Cu / ZnO / SiO of Example 3 2 -3 catalyst, (d) Cu / ZnO / SiO of Example 4 2 -4 catalyst;

[0040] Figure 2 XRD spectra of catalysts: (a) Cu / ZnO / SiO of Example 1 2 -1 catalyst, (b) Cu / ZnO / SiO of Example 2 2 -2 catalyst, (c) Cu / ZnO / SiO of Example 3 2 -3 catalyst, (d) Cu / ZnO / SiO of Example 4 2 -4 catalyst;

[0041] Figure 3 HRTEM images of the catalysts: (a-b) Cu / ZnO / SiO of Example 1 2 -1 catalyst, (cd) Cu / ZnO / SiO of Example 2 2 -2 catalyst. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0043] Example 1

[0044] 0.1 mol of tetraethyl orthosilicate (SiO 2 The mass of the mixture is 6.01 g), 0.15 mol of copper nitrate (trihydrate) (the mass of CuO is 11.93 g), 0.15 mol of zinc nitrate (hexahydrate) (the mass of ZnO is 12.21 g), 250 mL of deionized water, 80 mL of ethanol, and 603.0 g of potato starch (the mass of SiO 2The resulting mixture was dried at 120 °C for 3 h and calcined at 600 °C in air for 8 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO 2 -1.

[0045] Cu / ZnO / SiO 2 -1 N 2 -Physisorption-desorption curves are shown in Figure 1 (a), the texture properties are shown in Appendix 1, and its specific surface area is 501.6m 2 / g, with an average pore size of 2.5nm, which is a typical mesoporous material. Cu / ZnO / SiO 2 -1 X-ray diffraction (XRD) pattern is shown in Figure 2 (a), SiO 2 It is a typical amorphous structure; except for SiO 2 Diffraction peaks of CuO and ZnO were not observed, indicating that CuO and ZnO were dispersed in the system as nanoparticles, and the particle sizes of both were below the XRD detection limit (XRD detection limit: solid particle size ≤ 5nm). 2 -1 high magnification transmission electron microscopy (HRTEM) image is shown in Figure 3 (a)-3(b), SiO 2 It has an amorphous structure with worm-like mesoporous channels. The average particle sizes of CuO and ZnO nanoparticles are 4.9nm and 4.5nm, respectively.

[0046] Cu / ZnO / SiO 2 -1 Catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 10% H 2 / N 2 Mixed gas (H 2 The volume content is 10%), 400℃, 0.1MPa and 8.0NL·g cat -1 ·h -1 Reduction under the conditions for 14h.

[0047] The Cu / ZnO / SiO 2 -1 catalyst for the reverse water-gas shift reaction under the following reaction conditions: H 2 / CO 2 =3:1 (volume ratio), 280°C, 0.1MPa, 10.0NL·g cat -1 ·h -1The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 40.4%, the CO selectivity was 99.2 mol%, and the selectivities of by-products methanol and methane were 0.5 mol% and 0.3 mol%, respectively.

[0048] Example 2

[0049] 0.1 mol of tetraethyl orthosilicate (SiO 2 The mass of the mixture was 6.01 g), 0.3 mol of anhydrous copper chloride (the mass of CuO was 23.86 g), 0.1 mol of anhydrous zinc acetate (the mass of ZnO was 8.14 g), 200 mL of deionized water, 300 mL of methanol, and 570.2 g of potato starch (the mass of SiO 2 The mixture was dried at 110 °C for 6 h and calcined at 450 °C in air for 10 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO 2 -2.

[0050] Cu / ZnO / SiO 2 -2 N 2 -Physisorption-desorption curves are shown in Figure 1 (b), the texture properties are shown in Appendix 1, and its specific surface area is 468.7m 2 / g, with an average pore size of 2.6nm, which is a typical mesoporous material. Cu / ZnO / SiO 2 -2 X-ray diffraction (XRD) pattern is shown in Figure 2 (b), SiO 2 It is a typical amorphous structure; except for SiO 2 Diffraction peaks of CuO and ZnO were not observed, indicating that CuO and ZnO were dispersed in the system as nanoparticles, and the particle sizes of both were below the XRD detection limit (XRD detection limit: solid particle size ≤ 5nm). 2 -2 high magnification transmission electron microscopy (HRTEM) image is shown in Figure 3 (c)-3(d), SiO 2 It has an amorphous structure with worm-like mesoporous channels. The average particle sizes of CuO and ZnO nanoparticles are 4.2nm and 3.8nm, respectively.

[0051] Cu / ZnO / SiO 2-2 Catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 5% H 2 / Ar mixed gas (H 2 Volume content is 5%), 280℃, 0.15MPa and 4.0NL·g cat -1 ·h -1 Reduction under the conditions for 4h.

[0052] The Cu / ZnO / SiO 2 -2 catalyst performance in the reverse water gas shift reaction under the following reaction conditions: H 2 / CO 2 =4:1 (volume ratio), 250°C, 3.0MPa, 8.0NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 38.3%, the CO selectivity was 99.6 mol%, and the selectivities of by-products methanol and methane were 0.3 mol% and 0.1 mol%, respectively.

[0053] Example 3

[0054] 0.1 mol of tetramethyl orthosilicate (SiO 2 The mass of CuO is 6.01 g), 0.1 mol of anhydrous copper acetate (the mass of CuO is 7.95 g), 0.3 mol of zinc chloride (the mass of ZnO is 24.42 g), 100 mL of deionized water, 200 mL of propanol and 383.9 g of soluble starch (the mass of SiO 2 The mixture was dried at 60 °C for 20 h and calcined at 500 °C in air for 12 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO 2 -3.

[0055] Cu / ZnO / SiO 2 -3 N 2 -Physisorption-desorption curves are shown in Figure 1 (c), the texture properties are shown in Appendix 1, and its specific surface area is 408.5m 2 / g, with an average pore size of 3.0nm, which is a typical mesoporous material. Cu / ZnO / SiO 2 -3 X-ray diffraction (XRD) pattern is shown in Figure 2 (c), SiO 2It is a typical amorphous structure; except for SiO 2 No diffraction peaks of CuO and ZnO were observed, indicating that CuO and ZnO were dispersed in the system in the form of nanoparticles, and the particle sizes of both were below the XRD detection limit (XRD detection limit: solid particle size ≤ 5 nm).

[0056] Cu / ZnO / SiO 2 -3 Catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 20% H 2 / N 2 Mixed gas (H 2 Volume content is 20%), 300℃, 0.1MPa and 6.0NL·g cat -1 ·h -1 Reduction under the conditions for 14h.

[0057] The Cu / ZnO / SiO 2 -3 catalyst performance in the reverse water gas shift reaction under the following reaction conditions: H 2 / CO 2 =5:1 (volume ratio), 300℃, 5.5MPa, 3.0NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 58.5%, the CO selectivity was 99.1 mol%, and the selectivities of by-products methanol and methane were 0.6 mol% and 0.3 mol%, respectively.

[0058] Example 4

[0059] 0.1 mol of sodium silicate (SiO 2 The mass of the mixture was 6.01 g), 0.1 mol of copper nitrate (trihydrate) (the mass of CuO was 7.95 g), 0.08 mol of zinc nitrate (hexahydrate) (the mass of ZnO was 6.51 g), 355 mL of deionized water, 35 mL of isopropanol, and 204.8 g of corn starch (the mass of SiO 2 The mixture was ground in a ball mill until uniformly mixed. The uniform mixture was dried at 150 °C for 0.5 h and calcined at 590 °C in air for 6 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO 2 -4.

[0060] Cu / ZnO / SiO2 -4 N 2 -Physisorption-desorption curves are shown in Figure 1 (d), the texture properties are shown in Appendix 1, and its specific surface area is 249.1m 2 / g, with an average pore size of 3.9nm, which is a typical mesoporous material. Cu / ZnO / SiO 2 -4 X-ray diffraction (XRD) pattern is shown in Figure 2 (d), SiO 2 It is a typical amorphous structure; except for SiO 2 No diffraction peaks of CuO and ZnO were observed, indicating that CuO and ZnO were dispersed in the system in the form of nanoparticles, and the particle sizes of both were below the XRD detection limit (XRD detection limit: solid particle size ≤ 5 nm).

[0061] Cu / ZnO / SiO 2 -4 catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated under H 2 , 240℃, 0.1MPa and 10.0NL·g cat -1 ·h -1 Reduction under the conditions for 10 h.

[0062] The Cu / ZnO / SiO 2 -4 catalyst for the reverse water gas shift reaction under the following reaction conditions: H 2 / CO 2 =2:1 (volume ratio), 230°C, 2.0MPa, 4.0NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 30.6%, the CO selectivity was 99.6 mol%, and the selectivities of by-products methanol and methane were 0.3 mol% and 0.1 mol%, respectively.

[0063] Example 5

[0064] 24.04 g of acidic silica sol (0.1 mol SiO 2 , SiO 2The mass of the mixture was 6.01 g), 0.1 mol of copper nitrate (trihydrate) (the mass of CuO was 7.95 g), 0.12 mol of anhydrous zinc acetate (the mass of ZnO was 9.77 g), 50 mL of deionized water, 50 mL of isopropanol, and 237.3 g of potato starch (the mass of SiO 2 The mixture was dried at 100 °C for 8 h and calcined at 650 °C in air for 2 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO. 2 -5.

[0065] Cu / ZnO / SiO 2 -5 catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 30% H 2 / N 2 Mixed gas (H 2 The volume content is 30%), 260℃, 0.2MPa and 12.0NL·g cat -1 ·h -1 The reduction was carried out for 6 h.

[0066] The Cu / ZnO / SiO 2 The performance of the reverse water gas shift reaction of the catalyst of -5 was studied under the following reaction conditions: H 2 / CO 2 =1:1 (volume ratio), 180°C, 4.0MPa, 2.0NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 19.3%, the CO selectivity was 99.9 mol%, and the selectivity of by-product methanol was 0.1 mol%.

[0067] Example 6

[0068] 0.1 mol of tetramethyl orthosilicate (SiO 2 The mass of the mixture was 6.01 g), 0.015 mol of copper chloride monohydrate (the mass of CuO was 1.19 g), 0.0005 mol of zinc acetate (dihydrate) (the mass of ZnO was 0.04 g), 500 mL of deionized water, and 217.3 g of polyvinyl alcohol (the mass of SiO 2The mixture was dried at 80 °C for 14 h and calcined at 300 °C in air for 12 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO. 2 -6.

[0069] Cu / ZnO / SiO 2 -6 catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 2.5% H 2 / N 2 Mixed gas (H 2 The volume content is 2.5%), 180℃, 0.5MPa and 1.0NL·g cat -1 ·h -1 Reduction under the conditions for 24h.

[0070] The Cu / ZnO / SiO 2 -3 catalyst performance in the reverse water gas shift reaction under the following reaction conditions: H 2 / CO 2 =3.5:1 (volume ratio), 350°C, 0.5MPa, 20.0NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 30.7%, the CO selectivity was 99.0 mol%, and the selectivities of by-products methanol and methane were 0.5 mol% and 0.5 mol%, respectively.

[0071] Example 7

[0072] 0.05 mol of tetramethyl orthosilicate and 0.05 mol of tetraethyl orthosilicate (SiO 2 The mass of the mixture was 6.01 g), 0.0005 mol of copper nitrate (trihydrate) (the mass of CuO was 0.04 g), 0.08 mol of zinc chloride (the mass of ZnO was 6.51 g), 8 mL of deionized water, 2 mL of ethanol, 62.8 g of polyvinyl alcohol, and 62.8 g of potato starch (the total mass of polyvinyl alcohol and potato starch was SiO 2 The mixture was dried at 120 °C for 6 h and calcined at 550 °C in air for 4 h to obtain the final catalyst, which was labeled as Cu / ZnO / SiO 2 -7.

[0073] Cu / ZnO / SiO 2 -7 catalyst online reduction, specifically: 0.5g catalyst particles (20-40 mesh) were mixed with quartz sand of the same mesh, loaded into the fixed bed reactor reaction tube, and heated at 2.5% H 2 / Ar mixed gas (H 2 The volume content is 2.5%), 380℃, 0.1MPa and 20.0NL·g cat -1 ·h -1 Reduction under the conditions for 4h.

[0074] The Cu / ZnO / SiO 2 The performance of the reverse water-gas shift reaction of the catalyst of -7 was studied under the following reaction conditions: H 2 / CO 2 =2:1 (volume ratio), 220°C, 1.0MPa, 0.5NL·g cat -1 ·h -1 The fixed bed reaction evaluation results show that the catalysts all reach a steady state after 24 hours of reaction. The steady state reaction results are shown in Appendix 2. 2 The conversion rate was 20.1%, the CO selectivity was 99.7 mol%, and the selectivity of by-product methanol was 0.3 mol%.

[0075] Table 1 Catalysts and surface properties of various examples

[0076]

[0077] a : TEOS stands for tetraethyl orthosilicate, TMOS stands for methyl orthosilicate; b :m OH :m SiO2+MOx It is a polyhydroxy polymer compound and (SiO 2 +CuO+ZnO) mass ratio; c : Specific surface area of ​​the catalyst after calcination; d : The average particle size of the metal oxide particles obtained by XRD, wherein ND represents the XRD diffraction peak of the metal oxide not detected; e : Average particle size of metal oxide particles obtained by HRTEM.

[0078] Table 2 Fixed bed evaluation conditions and reaction results of the catalysts in each example

[0079]

[0080] The above description is only for better explaining the embodiments of the present invention, and is not intended to limit the present invention. Any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. Preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction, characterized in that: The following steps are involved: Step 1, preparation of catalyst: fully mixing silicon source, copper salt, zinc salt, solvent and polyhydroxy polymer compound, drying and calcining to obtain Cu / ZnO / SiO2 catalyst; Step 2, reverse water-gas shift reaction: the Cu / ZnO / SiO2 catalyst is subjected to a reduction treatment and then subjected to a reverse water-gas shift reaction.

2. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: In step 1, the silicon source is any one of sodium silicate, tetraethyl orthosilicate, tetramethyl orthosilicate, and silica sol, or a combination of several of them.

3. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: In step 1, the copper salt is any one or a combination of copper nitrate, copper acetate and copper chloride, and the zinc salt is any one or a combination of zinc nitrate, zinc acetate and zinc chloride.

4. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: The solvent in step 1 is any one of water, methanol, ethanol, propanol, and isopropanol, or a combination of several of them.

5. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: In step 1, the polyhydroxy polymer compound is any one of polyvinyl alcohol, soluble starch, corn starch, potato starch, and potato starch, or a combination of several thereof.

6. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: In the step 1, the masses of the silicon source, copper salt and zinc salt are calculated as SiO2, CuO and ZnO respectively, and the mass of the polyhydroxy polymer compound is 10-30 times the total mass of the silicon source, copper salt and zinc salt.

7. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: In the step 1, the silicon source, copper salt, zinc salt and solvent are calculated according to the molar number of Si atoms, the molar number of Cu atoms, the molar number of Zn atoms and the volume of the solvent, respectively, and the ratio of the silicon source, copper salt, zinc salt and solvent is in the range of 1 mol: 0.005-3 mol: 0.005-3 mol: 100-5000 mL.

8. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: The drying conditions in step 1 are: temperature of 60-150° C., time of 0.5-20.0 h; the calcination conditions are: temperature of 300-650° C., air atmosphere, time of 2-12 h.

9. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: The reduction and reverse water-gas shift reaction in step 2 are both carried out on a fixed bed reaction evaluation device.

10. The preparation of a highly active Cu / ZnO / SiO2 catalyst and reverse water gas shift reaction according to claim 1, characterized in that: The reduction conditions in step 2 are: pure H2, H2 / N2 mixed gas with H2 volume content of 2.5-30%, or H2 / Ar mixed gas with H2 volume content of 2.5-30%, temperature of 180-400°C, pressure of 0.1-0.5MPa, space velocity of 1.0-20.0NL·g cat -1 ·h -1 , until no water is detected in the tail gas; the conditions for the reverse water gas shift reaction are: H2 / CO2 with a volume ratio of 1:1 to 5:1, a temperature of 180 to 350°C, a pressure of 0.1 to 5.5 MPa, and a space velocity of 0.5 to 20.0 NL·g cat -1 ·h -1 .

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