Preparation method and application of Cu-SiAl catalyst for synthesis of methanol / dimethyl ether from CO2

Abstract

This invention discloses a Cu-Si matrix for the synthesis of methanol / dimethyl ether from CO2. x Al 1‑x The catalyst preparation method and application are described. This catalyst can precisely control the selectivity of methanol and dimethyl ether. The catalyst is prepared from silica sol, aluminum isopropoxide, and copper nitrate trihydrate as raw materials. The precursor solution is uniformly mixed with a hexadecyltrimethylammonium chloride solution, followed by aging, evaporation, drying, and low-temperature calcination to produce a Cu-Si catalyst with defined active sites. x Al 1‑x Cluster catalyst, Cu nanoclusters encapsulated by Si with a defined composition x Al 1‑x Enclosed, but due to Si x Al 1‑x The different Si ratios and placement methods restrict the size and electronic states of Cu nanoclusters. As can be seen from the TEM images, the size of Cu nanoclusters increases with increasing Si content, thus forming Cu-Si nanoclusters with different active sites and different Cu electronic states. x Al 1‑x catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the preparation of metal supported catalysts, mainly used in the field of heterogeneous catalytic hydroconversion, and specifically relates to a Cu-Si catalyst containing a well-defined active site x Al 1-x Preparation of catalyst and regulation of carbon dioxide hydrogenation reaction product distribution. BACKGROUND

[0002] With the continuous progress and development of society, global climate problems caused by the greenhouse effect are becoming increasingly prominent, posing a serious threat to human survival and development. Therefore, solving the problem of carbon emissions has become an important issue for various countries.

[0003] Although the CCS technology based on carbon dioxide capture and storage can capture and store a large amount of carbon dioxide, the CCUS technology for carbon dioxide reuse is more economically valuable and sustainable, and is globally recognized as the most effective carbon reduction and carbon negative technology. Converting excessive carbon dioxide emissions into high-value chemicals and energy fuels not only effectively alleviates the greenhouse effect, but also fully utilizes the potential of carbon dioxide in the field of economic value. In particular, the catalytic hydrogenation of CO2 to CH3OH has great potential in business. Methanol is a major raw material for industrial synthesis, and its downstream products are abundant and have high utilization value, such as dimethyl ether, formaldehyde, MTBE, etc. In addition, the methanol industry has become one of the important pillars of the national economy. Not only is it a basic industry, but it has also developed into a key area of the national economy.

[0004] Cu / ZnO / Al2O3 is a commercial methanol catalyst invented by ICI in the 1970s, which has been widely concerned. The study of its active sites continues, and a series of Cu-based catalysts have been developed using various supports, including oxide supports with oxygen vacancies such as ZnO, ZrO2, CeO2, and TiO2, as well as SiO2, Al2O3, Zn-Zr, Ce-Zr, perovskite, and other supports. The choice of different supports will affect the reaction path, activity, and selectivity of the catalyst surface, thus affecting the selectivity and yield of methanol. Although copper-based catalysts have been widely studied and applied due to their low activation temperature, the balance advantage of methanol generation, and the ability to operate at low pressure, their low methanol selectivity and poor stability limit their widespread application in industry. There are two main reasons for this: first, there is a competing reaction (RWGS) with an endothermic effect. Carbon dioxide hydrogenation to produce methanol is an exothermic reaction, which is beneficial to the generation of methanol under low temperature conditions according to Le Chatelier's principle; however, from a kinetic perspective, carbon monoxide is more easily activated than carbon dioxide at low temperatures, so increasing the temperature will inevitably increase the selectivity of carbon monoxide. Second, a high metal loading will usually cause copper species to form large particles, which are prone to sintering under the influence of the reaction atmosphere and water, thus inducing the aggregation and enlargement of active center copper particles, leading to a sharp decrease in effective active sites and a significant reduction in catalyst stability. Therefore, the development of a copper-based catalyst with high selectivity and stability is of great significance for the further development of the carbon dioxide hydrogenation to methanol process.

[0005] Thi Thanh Nguyet Vu (Ind. Eng. Chem. Res. 2022, 61, 41, 15085-15102) et al. developed a series of different CuZn / UGSO catalysts by conventional and modified deposition-co-precipitation methods. For CO2 hydrogenation to methanol, it was found that the presence of basic sites was beneficial to the selectivity of methanol. Under the conditions of 20 bar reaction pressure, reaction temperature 513 K, H2 / CO2 = 3, GHSV = 5000 mL·gcat –1 ·h –1 Under the conditions of 20 bar reaction pressure, reaction temperature 513 K, H2 / CO2 = 3, GHSV = 5000 mL·gcat

[0006] Peng Gao (Journal of Catalysis, 2013, 298, 51-60) et al. investigated the effect of Zr on the performance of Cu / Zn / Al / Zr catalysts based on hydrotalcite-like precursors in the preparation of methanol from CO2 hydrogenation. The results showed that the appropriate addition of Zr was beneficial to the generation of methanol and could improve the catalytic performance. In the presence of Zr4+ :(Al 3+ +Zr 4+ ) atomic ratio of 0.3, temperature of 543 K, pressure of 5.0 MPa, H2 / CO2 ratio of 3, and space velocity of 4000 h -1 Under the conditions of a CO2 conversion rate of 26.6% and a methanol selectivity of 56.9%.

[0007] Huibo Zhao (Nature Catalysis volume 5, pages 818-831 (2022)) et al. found that single-atom Cu-Zr catalysts and Cu1–O3 units only facilitate methanol synthesis around 180 °C, and Cu1–O3 units were observed on the catalyst surface during the catalytic process, which accelerated the hydrogenation of CO2. Under the conditions of a reaction pressure of 1 MPa, a reaction temperature of 453 K, a H2 / CO2 ratio of 3, and a gas flow rate of 10 ml / min, the CO2 conversion rate reached 20%, and the methanol selectivity was 100%.

[0008] Xiaofeng Yan (Chemical Industry Progress, 2020, 39(10):4032-4040) et al. successfully prepared a series of Cu-ZnO-ZrO2 catalysts using the sol-gel method. By adjusting the amount of citric acid, they realized the coordination mode of Cu 2+ , Zn 2+ , and Zr 4+ with carboxylic acid, ensuring that the grain sizes of the active components CuO, ZnO, and ZrO2 in the catalyst match each other. Under the conditions of a citric acid molar amount of 1.5, a reaction temperature of 523 K, a reaction pressure of 3.0 MPa, a H2 / CO2 ratio of 3, and a gas flow rate of 100 mL / min, they observed a CO2 conversion rate of 27.64% and a methanol selectivity of 31.76%.

[0009] Fujimoto (Catalysis Communications, 2014, 54, 50-54) et al. studied the effects of different rare earth elements (La, Ce, Nd, and Pr) on the Cu / Zn / Zr (CZZ) catalyst for the synthesis of CH3OH from CO2 hydrogenation. The experimental results showed that the CO2 conversion rate was related to different metal additives. When a small amount of Ce was introduced, the CO2 conversion rate was higher than 20% and the methanol selectivity remained at 50% under the conditions of T = 483 K, P = 3 MPa, H2 / CO2 = 3, and W / F = 10 g cat ·h / moL.

[0010] Erwin Lam (Chinese Journal of Catalysis, 2019, 40, 11, 1741-1748) et al. investigated the performance of mixed oxide-based catalyst Cu / ZrO2 / SiO2 in the process of CO2 selective hydrogenation to methanol. They found that Zr(IV) Lewis acid surface sites played a key role in promoting methanol selectivity. At a temperature of 503 K, a pressure of 2.3 MPa, a H2:N2 ratio of 1:3:1, and a gas flow rate of 50 mL / min, they observed a CO2 conversion of 20% and a methanol selectivity of 78%. 2: H2:N2 ratio of 1:3:1, and a gas flow rate of 50 mL / min, they observed a CO2 conversion of 20% and a methanol selectivity of 78%.

[0011] Xianquan Li (Chinese Journal of Catalysis, June 2023, Pages 91-101) et al. studied the preparation of Cu-MFI for ethanol dehydrogenation using post-acid treatment methods and found that highly dispersed Cu δ+ species on (1<δ<2) MFI supports were important active sites for ethanol dehydrogenation and played a role as Lewis acid catalysts in promoting ethanol activation and dehydrogenation. At 5% Cu-MFI-deCu, T = 523 K, space velocity 0.64 h -1 -1, acetaldehyde selectivity was 95%, and ethanol conversion was about 87%.

[0012] The above studies show that Cu-based catalysts obtained by conventional synthesis methods generally have the disadvantages of high reaction temperature and low product yield. SUMMARY

[0013] The present invention aims to provide a preparation method for Cu-Si x Al 1-x catalysts containing well-defined active sites and adjustable product distribution, which can be used in low-temperature CO2 hydrogenation to methanol and other derivatives. By adjusting the interaction between Cu species and Si x Al 1-x Al, the reaction temperature is reduced, the methanol selectivity and catalyst stability are improved, and a practical solution for determining catalyst active sites is provided.

[0014] By adjusting the ratio of Si and Al in Cu-Si x Al 1-x catalysts, the size and electronic state of Cu can be accurately controlled. Since the interaction between Cu and SiO2 is weak, and the interaction with unsaturated Al2O3 is strong, by adjusting the ratio of Si x Al 1-xThe regulation of Cu is realized, and it is found that the catalyst changes dynamically during the reaction, and the Cu interacts with different Si x Al 1-x with different Si x Al 1-x The catalyst exhibits different affinities for active intermediates (for example: HCOO*, CO*, H3CO*…), and through different stable intermediates, the controllable coupling of the intermediates is realized, and finally the controllable regulation of the distribution of CO2 hydrogenation products (methanol and dimethyl ether) is realized. At the same time, by deconstructing the O-Al / O-Si bond on Cu and amorphous Al2O3, amorphous SiO2 and amorphous Si x Al 1-x Metal oxides, the different interaction degrees of different active sites, and the adsorption strength of active intermediates on different active sites are revealed, and a large number of surface active sites are formed on the catalyst, which improves the conversion of active intermediates and significantly improves the CO2 conversion rate. On the optimized Cu-Si x Al 1-x Catalyst, the restriction of different bonds to Cu makes the catalyst have higher CO2 hydrogenation activity and stability at low temperature.

[0015] The present application provides a Cu-Si x Al 1-x Catalyst containing a clearly defined active site, the Cu-Si x Al 1-x Catalyst, Cu is the main active component, Si x Al 1-x is the carrier; wherein the loading amount of Cu is 1-10wt% based on the total mass of the catalyst, Si x Al 1-x The value range of x is 0.85-0.99.

[0016] The present application provides a preparation method of a Cu-Si x Al 1-x Catalyst containing a clearly defined active site, comprising the following steps:

[0017] (1) Dissolve aluminum isopropyl alcohol in 100mL anhydrous ethanol, stir vigorously at 50℃, and add 10mL nitric acid to make the solid completely dissolved, then add a certain amount of silica sol, and continue to stir for half an hour to make the solution fully mixed.

[0018] (2) Take a certain amount of copper nitrate trihydrate and 2g of cetyltrimethylammonium chloride, dissolve in 100mL of anhydrous ethanol, and also stir at 50°C until completely dissolved. Under stirring conditions, add the Cu solution to the Si-Al solution obtained in step (1), and continue to stir at 50°C for 6 hours.

[0019] (3) Then, the mixed solution is placed in an oven at 80-120°C, and the liquid is slowly evaporated. After 48h of evaporation, a foam-like solid is obtained. The obtained solid is ground and placed in a muffle furnace, and heated to 400°C at a heating rate of 1°C / min in an air atmosphere, and calcined for 4 hours. After further grinding, a blue Cu-Si x Al 1-x catalyst powder is finally obtained.

[0020] The catalyst of the present application is applied as follows:

[0021] The Cu-Si x Al 1-x catalyst sample is pretreated by blowing H2 at a gas flow rate of 20-50mL / min, a treatment pressure of 1-2bar, a treatment time of 5-20h, and a treatment temperature of 200-300°C. The pretreated sample is reacted by blowing a mixed gas with a H2 / CO2 molar ratio of 3 / 1 at a reaction pressure of 3-5MPa, a reaction temperature of 160-230°C, and a reaction gas flow rate of 10-50mL / min.

[0022] The beneficial effects of the present application are as follows:

[0023] (1) The catalyst surface contains reasonably constructed Cu nanoclusters, and the active sites are accurately constructed. By capturing and reasoning the active intermediates of the well-defined active sites, the reaction context of the CO2 catalytic reaction can be accurately constructed.

[0024] (2) The product distribution can be regulated according to the needs.

[0025] (3) The catalyst has excellent stability and methanol / dimethyl ether activity.

[0026] (4) The preparation method is simple, low-cost, safe, and highly reproducible, and is suitable for industrial applications. The active metal copper species in the obtained catalyst exists in different nanocluster sizes, and the different interactions between Cu 2+ ions and different components make the Cu and Si x Al 1-x between them in the catalyst precursor have a clear definition, which makes the catalyst form a catalyst with a well-defined active site after calcination. The Cu-Six Al 1-x The catalyst contains a defined active site, which can regulate the selectivity of methanol / dimethyl ether prepared by CO2 hydrogenation at low temperature. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The transmission electron micrograph, high-magnification transmission electron micrograph and corresponding element mapping diagram of the fresh catalyst;

[0028] Figure 2 The transmission electron micrograph, high-magnification transmission electron micrograph and corresponding element mapping diagram of the catalyst after different uses.

[0029] By Figure 1 And Figure 2 It is found by comparison that a large number of Cu-Si 0.92 Al 0.08 Single-atom catalyst, Cu-Si 0.88 Al 0.12 Single-atom catalyst, etc. The active site is defined (the loading of Cu is 1%). DETAILED DESCRIPTION

[0030] A catalyst preparation method with a defined active site and adjustable selectivity of methanol and dimethyl ether, the main active components of which are Cu, Si and Al, the method being a modified evaporation-induced self-assembly method, the specific innovation being that the coupling between the metal precursor and the polymer self-assembly method makes the dispersion of each element in the solution uniform, the positioning between Si and Al and the interaction with Cu are regulated by changing the content of Si-Al in the catalyst, and after calcination, different coordination " -Al-O-Cu-O-Si- " three-dimensional spatial structures are formed, which makes the methanol / dimethyl ether active site be able to be reconstructed by adjusting the content of the active components.

[0031] The Cu-Si x Al 1-x The electronic state of Cu in the catalyst will be adjusted by Si x Al 1-x with a defined configuration, and at the same time, the -Al-O-Cu-O-Si- units formed on the catalyst have different stabilities for active intermediates (such as HCOO*, CO*, H3CO*……). With the change of the Si content on the catalyst from 0% to 100%, the coordination of Si species on the catalyst surface gradually increases, and the Cu-Si x Al 1-xThe valence state of Cu on the catalyst surface first increases and then decreases, and the Cu cluster on the catalyst gradually becomes larger; the methanol decreases first and then increases with the change of the Si content on the catalyst surface, and the selectivity of dimethyl ether first increases and then decreases. The reasons for the changes of different active sites and different product distributions are mainly the different interaction degrees of Cu and amorphous Si x Al 1-x .

[0032] The Cu-Si x Al 1-x catalyst has excellent catalytic performance for the low-temperature carbon dioxide hydrogenation to methanol, and specifically, under the condition of low temperature (220℃) and 5Mpa pressure, the Cu-Si 0.66 Al 0.34 catalyst has a dimethyl ether selectivity of 83%, and the carbon dioxide conversion rate is 8%, while the Cu-Si 0.94 Al 0.06 catalyst has a methanol selectivity of 94%, and the carbon dioxide conversion rate is 10%, and it is worth mentioning that the Cu-Si 0.92 Al 0.08 has a methanol selectivity of 86.3%.

[0033] In order to make the content of the application more convenient to understand, the technical solutions of the application will be further described in combination with specific embodiments, but the application is not limited thereto.

[0034] Example 1

[0035] 0.398g aluminum isopropoxide is dissolved in 100mL anhydrous ethanol, stirred vigorously at 50℃, and 10mL 65wt% nitric acid is added to completely dissolve the solid, and then 18.513g silica sol is added, and the solution is fully mixed by continuing to stir for half an hour; 0.200g of copper nitrate trihydrate and 2g of cetyltrimethylammonium chloride are dissolved in 100mL anhydrous ethanol, and are also stirred vigorously at 50℃ until completely dissolved, and the Cu solution is added to the Si-Al solution under stirring, and continues to be stirred at 50℃ for 6 hours; then, the mixed solution is placed in an 80℃ oven, and the liquid is slowly evaporated, and after 48h of evaporation, a foamy solid is obtained, which is ground and placed in a muffle furnace, and heated to 400℃ at a heating rate of 1℃ / min in an air atmosphere, and calcined for 4 hours to obtain a Cu-Si 0.99 Al 0.01 with a Cu loading of 1%, Al: 1%, and Si: 99%. Finally, it is granulated into 40-60 mesh and ready for use.

[0036] The catalyst evaluation was carried out on a single-channel high-pressure fixed-bed catalyst evaluation device. After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250°C under normal pressure. After the pretreatment, the Cu-Si 0.99 Al 0.01 The pretreatment was completed, and the catalyst reaction stage was entered. The reaction gas was switched to CO2 / H2 with a molar ratio of 1 / 3, the reaction pressure was 3.5 MPa, the reaction temperature was 180°C, and the reaction gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 2.48%, the CH3OH selectivity was 83.3%, the dimethyl ether selectivity was 10.4%, the CO selectivity was 6.3%, the CH3OH yield was 2.07%, and the dimethyl ether yield was 0.26%.

[0037] Example 2

[0038] 1.990 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol, stirred vigorously at 50°C, and 10 mL of 65wt% nitric acid was added to completely dissolve the solid, followed by the addition of 17.757 g of silica sol, and the solution was stirred for half an hour to fully mix. Separately, 0.200 g of copper nitrate trihydrate and 2 g of cetyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol, and stirred vigorously at 50°C until completely dissolved. The Cu solution was added to the Si-Al solution under stirring conditions, and the stirring was continued at 50°C for 6 hours. Then, the mixed solution was placed in an 80°C oven to slowly evaporate the liquid. After 48 hours of evaporation, a foam-like solid was obtained. The obtained solid was ground and placed in a muffle furnace, and heated to 400°C at a heating rate of 1°C / min under an air atmosphere, and calcined for 4 hours to obtain a Cu-Si 0.95 Al 0.05 Finally, it was granulated into 40-60 mesh and ready for use.

[0039] The catalyst evaluation was carried out on a single-channel high-pressure fixed-bed catalyst evaluation device. After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250°C under normal pressure. After the pretreatment, the Cu-Si 0.95 Al 0.05The catalyst was evaluated under the conditions of a CO2 / H2 molar ratio of 1 / 3, a reaction pressure of 3.5 MPa, a reaction temperature of 180°C, and a reaction gas flow rate of 15 mL / min. Under these conditions, the CO2 conversion rate was 2.41%, the CH3OH selectivity was 84.1%, the dimethyl ether selectivity was 11.3%, the CO selectivity was 4.6%, the CH3OH yield was 1.69%, and the dimethyl ether yield was 0.23%.

[0040] Example 3

[0041] The Cu solution was added to the Si-Al solution under stirring at 50°C, and stirring was continued for 6 hours at 50°C. Subsequently, the mixed solution was left to stand in an oven at 80°C, and the liquid was slowly evaporated. After 48 hours of evaporation, a foam-like solid was obtained. The solid was ground and placed in a muffle furnace, and was heated to 400°C at a rate of 1°C / min in an air atmosphere, and was calcined for 4 hours. A Cu-Si 0.92 Al 0.08 Finally, it was granulated to 40-60 mesh and was ready for use.

[0042] The catalyst was evaluated on a single-channel high-pressure fixed-bed catalyst evaluation device. After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250°C at normal pressure. The Cu-Si 0.92 Al 0.08 The catalyst was evaluated under the conditions of a CO2 / H2 molar ratio of 1 / 3, a reaction pressure of 3.5 MPa, a reaction temperature of 180°C, and a reaction gas flow rate of 15 mL / min. Under these conditions, the CO2 conversion rate was 2.30%, the CH3OH selectivity was 86.3%, the dimethyl ether selectivity was 11.8%, the CO selectivity was 1.9%, the CH3OH yield was 1.98%, and the dimethyl ether yield was 0.27%. This was the catalyst with the highest methanol selectivity and the best effect, and x=0.92.

[0043] Example 4

[0044] Cu-Si catalyst with Cu loading of 1%; Al: 12%; Si: 88% was prepared as follows: 4.776 g of aluminum isopropoxide was dissolved in 100 mL of absolute ethanol under vigorous stirring at 50 °C, and 10 mL of 65 wt% nitric acid was added to completely dissolve the solid, followed by the addition of 14.924 g of silica sol, and the solution was mixed thoroughly under stirring for half an hour; 0.200 g of copper nitrate trihydrate and 2 g of cetyltrimethylammonium chloride were dissolved in 100 mL of absolute ethanol under vigorous stirring at 50 °C until completely dissolved, and the Cu solution was added to the Si-Al solution under stirring, and the mixture was stirred at 50 °C for 6 hours; then, the mixed solution was left to slowly evaporate in an oven at 80 °C, and after 48 h of evaporation, a foam-like solid was obtained, which was ground and then calcined in a muffle furnace under air atmosphere at a heating rate of 1 °C / min to 400 °C for 4 hours to obtain the Cu-Si catalyst with Cu loading of 1%; Al: 12%; Si: 88%. 0.88 Al 0.12 Finally, it was granulated into 40-60 mesh for use.

[0045] The catalyst evaluation was carried out on a single-channel high-pressure fixed-bed catalytic evaluation device. Pretreatment stage: after the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250 °C at normal pressure. Cu-Si 0.88 Al 0.12 was pretreated for 5 h. After the pretreatment, the catalytic reaction stage was entered, and the reaction gas was switched to CO2 / H2 with a molar ratio of 1 / 3, the reaction pressure was 3.5 MPa, the reaction temperature was 180 °C, and the reaction gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 2.48%, there was no CH3OH selectivity, the dimethyl ether selectivity was 98.1%, the carbon monoxide selectivity was 1.9%, the dimethyl ether yield was 2.44%, which was the highest dimethyl ether selectivity and the most optimal catalyst, x=0.88.

[0046] Example 5

[0047] 5.970 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 13.730 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 0.200 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. This solid was ground and placed in a muffle furnace, heated to 400 °C at a rate of 1 °C / min in air, and calcined for 4 hours to obtain Cu-Si with a Cu loading of 1%; Al of 15%; and Si of 85%. 0.85 Al 0.15 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0048] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.85 Al 0.15 Purging for 5 hours. After pretreatment, the catalytic reaction stage began. The gas was switched to a CO2 / H2 molar ratio of 1 / 3, and the catalyst performance was evaluated under the following conditions: reaction pressure 3.5 MPa, reaction temperature 180℃, and reaction gas flow rate 15 mL / min. Under these conditions, the CO2 conversion rate was 2.36%, there was no CH3OH selectivity, the dimethyl ether selectivity was 93.2%, the carbon monoxide selectivity was 6.8%, and the dimethyl ether yield was 2.20%.

[0049] Example 6

[0050] 1.990 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 17.757 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 1.000 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. This solid was ground and placed in a muffle furnace, heated to 400 °C at a rate of 1 °C / min in air, and calcined for 4 hours to obtain Cu-Si with a Cu loading of 5%, Al of 5%, and Si of 95%. 0.95 Al 0.05 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0051] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 ml / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.95 Al 0.05 Purging for 5 hours. After pretreatment, the catalytic reaction stage begins. The gas is switched to a CO2 / H2 molar ratio of 1 / 3, and the catalyst performance is evaluated under the following conditions: reaction pressure 3.5 MPa, reaction temperature 180 °C, and reaction gas flow rate 15 mL / min. Under these conditions, the CO2 conversion rate is 4.43%, the CH3OH selectivity is 83.9%, the dimethyl ether selectivity is 11.8%, the CO selectivity is 4.3%, the CH3OH yield is 3.72%, and the dimethyl ether yield is 0.52%.

[0052] Example 7

[0053] Cu-Si catalyst with Cu loading of 5%; Al: 8%; Si: 92% was prepared as follows: 3.184 g of aluminum isopropoxide was dissolved in 100 mL of absolute ethanol, stirred vigorously at 50°C, and 10 mL of 65 wt% nitric acid was added to completely dissolve the solid, followed by 16.813 g of silica sol, and the solution was mixed thoroughly by stirring for half an hour; 1.000 g of copper nitrate trihydrate and 2 g of cetyltrimethylammonium chloride were dissolved in 100 mL of absolute ethanol, and stirred vigorously at 50°C until completely dissolved; the Cu solution was added to the Si-Al solution under stirring, and the mixture was stirred at 50°C for 6 hours; then, the mixed solution was left to slowly evaporate in an oven at 80°C, and after 48 hours of evaporation, a foam-like solid was obtained; the solid was ground and placed in a muffle furnace, and heated to 400°C at a rate of 1°C / min in an air atmosphere, and calcined for 4 hours to obtain a Cu-Si catalyst with Cu loading of 5%; Al: 8%; Si: 92% 0.92 Al 0.08 Finally, it was granulated into 40-60 mesh and ready for use.

[0054] The catalyst evaluation was carried out on a single-channel high-pressure fixed-bed catalytic evaluation device. Pretreatment stage: after the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250°C at normal pressure. Cu-Si 0.92 Al 0.08 was pretreated for 5 hours. After the pretreatment was completed, the catalyst reaction stage was entered, and the gas was switched to a reaction gas with a CO2 / H2 molar ratio of 1 / 3, and the reaction pressure was 3.5 MPa, the reaction temperature was 180°C, and the reaction gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 4.52%, the CH3OH selectivity was 86.5%, the dimethyl ether selectivity was 12.1%, and the CO selectivity was 1.4%. The CH3OH yield was 3.91%, and the dimethyl ether yield was 0.55%. This was the catalyst with the highest methanol selectivity and the best effect, and x=0.92.

[0055] Example 8

[0056] 4.776 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 14.924 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 1.000 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. The obtained solid was ground and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 400 °C at a rate of 1 °C / min, and calcined for 4 hours to obtain Cu-Si with a Cu loading of 5%, Al of 12%, and Si of 88%. 0.88 Al 0.12 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0057] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.88 Al 0.12 Purging for 5 hours. After pretreatment, the catalytic reaction stage began. The gas was switched to a CO2 / H2 molar ratio of 1 / 3, and the reaction pressure was 3.5 MPa, the reaction temperature was 180℃, and the gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 4.58%, there was no CH3OH selectivity, the dimethyl ether selectivity was 98.2%, the carbon monoxide selectivity was 1.8%, and the dimethyl ether yield was 4.50%. This was the catalyst with the highest dimethyl ether selectivity and the best performance, x=0.88.

[0058] Example 9

[0059] 5.970 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 13.730 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 1.000 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. The obtained solid was ground and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 400 °C at a rate of 1 °C / min, and calcined for 4 hours to obtain Cu-Si with a content of 5% Cu loading, 15% Al, and 85% Si. 0.85 Al 0.15 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0060] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.85 Al 0.15 Purging for 5 hours. After pretreatment, the catalytic reaction stage began. The gas was switched to a CO2 / H2 molar ratio of 1 / 3, and the catalyst performance was evaluated under the following conditions: reaction pressure 3.5 MPa, reaction temperature 180 °C, and reaction gas flow rate 15 mL / min. Under these conditions, the CO2 conversion rate was 4.36%, there was no CH3OH selectivity, the dimethyl ether selectivity was 92.8%, the carbon monoxide selectivity was 7.2%, and the dimethyl ether yield was 4.05%.

[0061] Example 10

[0062] Cu-Si catalyst with Cu loading of 10%; Al: 8%; Si: 92% was prepared as follows: 3.184 g of aluminum isopropoxide was dissolved in 100 mL of absolute ethanol, stirred vigorously at 50°C, and 10 mL of 65 wt% nitric acid was added to completely dissolve the solid, followed by 16.813 g of silica sol, and the solution was mixed thoroughly by stirring for half an hour; 2.000 g of copper nitrate trihydrate and 2 g of cetyltrimethylammonium chloride were dissolved in 100 mL of absolute ethanol, and stirred vigorously at 50°C until completely dissolved; the Cu solution was added to the Si-Al solution under stirring, and the mixture was stirred at 50°C for 6 hours; then, the mixed solution was left to slowly evaporate in an oven at 80°C, and after 48 hours of evaporation, a foam-like solid was obtained; the solid was ground and placed in a muffle furnace, and heated to 400°C at a rate of 1°C / min in an air atmosphere, and calcined for 4 hours to obtain a Cu-Si catalyst with Cu loading of 10%; Al: 8%; Si: 92% 0.92 Al 0.08 Finally, it was granulated into 40-60 mesh and ready for use.

[0063] The catalyst evaluation was carried out on a single-channel high-pressure fixed-bed catalytic evaluation device. Pretreatment stage: after the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250°C at normal pressure. Cu-Si 0.92 Al 0.08 was pretreated for 5 hours. After the pretreatment was completed, the catalyst reaction stage was entered, and the reaction gas was switched to CO2 / H2 with a molar ratio of 1 / 3, the reaction pressure was 3.5 MPa, the reaction temperature was 180°C, and the reaction gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 6.72%, the CH3OH selectivity was 86.1%, the dimethyl ether selectivity was 12.2%, and the CO selectivity was 1.7%. The CH3OH yield was 5.79%, and the dimethyl ether yield was 0.82%. This was the catalyst with the highest methanol selectivity and the best effect, and x=0.92.

[0064] Example 11

[0065] 4.776 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 14.924 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 2.000 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. The obtained solid was ground and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 400 °C at a rate of 1 °C / min, and calcined for 4 hours to obtain Cu-Si with a Cu loading of 10%, Al of 12%, and Si of 88%. 0.88 Al 0.12 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0066] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.88 Al 0.12 Purging for 5 hours. After pretreatment, the catalytic reaction stage began. The gas was switched to a CO2 / H2 molar ratio of 1 / 3, and the reaction pressure was 3.5 MPa, the reaction temperature was 180℃, and the gas flow rate was 15 mL / min. Under these conditions, the CO2 conversion rate was 6.69%, there was no CH3OH selectivity, the dimethyl ether selectivity was 97.9%, the carbon monoxide selectivity was 2.1%, and the dimethyl ether yield was 6.55%. This was the catalyst with the highest dimethyl ether selectivity and the best performance, x=0.88.

[0067] Example 12

[0068] 5.970 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C. 10 mL of 65 wt% nitric acid was added to completely dissolve the solid. Then, 13.730 g of silica sol was added, and stirring continued for half an hour to ensure thorough mixing. Separately, 2.000 g of copper nitrate trihydrate and 2 g of hexadecyltrimethylammonium chloride were dissolved in 100 mL of anhydrous ethanol and stirred vigorously at 50 °C until completely dissolved. Under stirring, the Cu solution was added to the Si-Al solution, and stirring continued at 50 °C for 6 hours. The mixed solution was then placed in an 80 °C oven to allow slow evaporation. After 48 hours of evaporation, a foamy solid was obtained. The obtained solid was ground and placed in a muffle furnace. Under air atmosphere, the temperature was increased to 400 °C at a rate of 1 °C / min, and calcined for 4 hours to obtain Cu-Si with a content of 10% Cu loading, 15% Al, and 85% Si. 0.85 Al 0.15 Finally, it is granulated to 40-60 mesh and set aside for later use.

[0069] Catalyst evaluation was conducted on a single-channel high-pressure fixed-bed catalytic evaluation apparatus. Pretreatment stage: After the catalyst was loaded, hydrogen (99.99%, 40 mL / min) was used as the pretreatment gas, and the pretreatment temperature was 250℃ at atmospheric pressure for Cu-Si catalysts. 0.85 Al 0.15 Purging for 5 hours. After pretreatment, the catalytic reaction stage began. The gas was switched to a CO2 / H2 molar ratio of 1 / 3, and the catalyst performance was evaluated under the following conditions: reaction pressure 3.5 MPa, reaction temperature 180 °C, and reaction gas flow rate 15 mL / min. Under these conditions, the CO2 conversion rate was 6.46%, there was no CH3OH selectivity, the dimethyl ether selectivity was 91.9%, the carbon monoxide selectivity was 8.1%, and the dimethyl ether yield was 5.94%.

[0070] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A Cu-Si alloy for CO2 synthesis of methanol / dimethyl ether x Al 1-x Catalyst, characterized in that, The Cu-Si x Al 1-x Cu is the main active component in the catalyst, and Si x Al 1-x The catalyst is used as a support; wherein, based on the total mass of the catalyst, the loading of Cu is 1-10 wt%, and Si... x Al 1-x The value of x in the equation ranges from 0.85 to 0.

99. The Cu-Si x Al 1-x The method for preparing the catalyst includes the following steps: (1) Dissolve aluminum isopropoxide in 100 mL of anhydrous ethanol, stir vigorously at 50 °C, and add 10 mL of nitric acid to completely dissolve the solid. Then add a certain amount of silica sol and continue stirring for half an hour to fully mix the solution. (2) Take a certain amount of copper nitrate trihydrate and 2g of hexadecyltrimethylammonium chloride, dissolve them in 100mL of anhydrous ethanol, and stir vigorously at 50℃ until completely dissolved. Under stirring conditions, add the Cu solution to the Si-Al solution obtained in step (1) and continue stirring at 50℃ for 6 hours. (3) Subsequently, the mixed solution was placed in an oven at 80-120℃ to allow the liquid to evaporate slowly. After evaporation for 48 hours, a foamy solid was obtained. The obtained solid was ground and placed in a muffle furnace. Under an air atmosphere, the temperature was increased to 400℃ at a heating rate of 1℃ / min and calcined for 4 hours. After further grinding, blue Cu-Si was finally obtained. x Al 1-x Catalyst powder.

2. The Cu-Si according to claim 1 x Al 1-x Application of catalysts in the hydrogenation of carbon dioxide to methanol / dimethyl ether.

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