A Pd-Cu bimetallic supported In2O3-TiO2 catalyst, a preparation method and application thereof

Abstract

The application provides a Pd-Cu bimetallic supported In2O3-TiO2 catalyst and a preparation method and application thereof, and belongs to the technical field of CO2 hydrogenation to prepare methanol. The catalyst comprises a composite carrier and Pd nanoparticles and Cu nanoparticles supported on the surface of the composite carrier. Pd and Cu are combined to form bimetallic sites in the application, the advantages of the bimetallic sites can be fully exerted, and the reaction activity of CO2 hydrogenation to prepare methanol can be significantly improved through the electronic effect and geometric effect between the metals. The Pd-Cu / In2O3-TiO2 catalyst provided by the application has the advantages of high conversion rate and high catalytic activity in the reaction of carbon dioxide hydrogenation to prepare methanol; wherein, in the process of carbon dioxide hydrogenation, the Pd-Cu / In2O3-TiO2 catalyst can obtain a one-way CO2 conversion rate of 23.5% and a methanol yield of 15.83% at 250 DEG C.

Description

Technical Field

[0001] This invention belongs to the technical field of CO2 hydrogenation to methanol production, specifically relating to a Pd-Cu bimetallic supported In2O3-TiO2 catalyst, its preparation method, and its application. Background Technology

[0002] Methanol, as a basic organic chemical raw material and a potential clean liquid fuel, occupies an important position in the energy and chemical industries. Currently, using green hydrogen produced from renewable energy sources to convert greenhouse gas carbon dioxide (CO2) into methanol through catalytic hydrogenation is not only an effective way to achieve carbon recycling, but also an important means to alleviate the energy crisis.

[0003] Among the numerous catalyst systems for CO2 hydrogenation to methanol, Cu-ZnO-Al2O3 catalysts have been widely studied and applied due to their low cost and good activity. However, these traditional Cu-based catalysts exhibit significant stability issues under industrial application conditions. This is because: firstly, the medium to high temperatures (200~300℃) required for the catalytic reaction... o In the C) environment, Cu nanoparticles are prone to migration, aggregation, and sintering, leading to a sharp decrease in the active specific surface area. Secondly, water generated during the reaction or unreacted CO2 promotes the oxidation or loss of the active component, copper, further exacerbating catalyst deactivation. This instability severely restricts the long-term operation and industrial lifespan of Cu-ZnO-Al2O3 catalysts. To overcome the aforementioned defects of Cu-based catalysts, such as easy sintering and deactivation, researchers have made numerous improvement attempts, mainly including the following strategies: First, adding structural or electronic additives: By adding oxide additives containing Zr, Si, Mn, and Mg to the catalyst, attempts are made to stabilize copper particles using geometric isolation effects or electronic effects. For example, the addition of ZrO2 can form a Cu-ZrO2 interface, which can inhibit copper migration to some extent. However, this type of method can only alleviate sintering to a limited extent and may introduce new side reactions or reduce the intrinsic activity of the catalyst; long-term stability still cannot meet industrial requirements. Second, develop novel heat-resistant supports: explore the use of novel materials such as carbon nanotubes, graphene, and metal-organic frameworks (MOFs) to replace traditional Al2O3 or SiO2 supports. However, these supports generally have poor thermal and mechanical stability under CO2 hydrogenation reaction conditions, or their interaction with active components is too strong, leading to a decrease in activity. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst, its preparation method, and its application. This catalyst has advantages such as high single-pass conversion and good catalytic activity in the CO₂ hydrogenation to methanol reaction.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst, comprising a composite support and Pd nanoparticles and Cu nanoparticles supported on the surface of the composite support. The composite support is In₂O₃-TiO₂.

[0007] Preferably, the molar ratio of Pd nanoparticles to Cu nanoparticles is 1:(3~7).

[0008] More preferably, the molar ratio of the Pd nanoparticles to the Cu nanoparticles is 1:(4~5).

[0009] Preferably, the loading of the Pd nanoparticles is 1~5 wt%, based on 100% of the mass of the composite carrier.

[0010] Preferably, the loading of Cu nanoparticles is 5~20 wt%, based on the mass of the composite carrier as 100%.

[0011] Preferably, the Pd nanoparticles and Cu nanoparticles have a size of 3~6 nm.

[0012] Preferably, the mass ratio of In2O3 to TiO2 is (8~12):1.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned Pd-Cu bimetallic supported In2O3-TiO2 catalyst, comprising the following steps:

[0014] Palladium precursor, copper precursor, composite support and water were mixed at pH 9-10. After reaction, the mixture was separated, dried and ground to obtain a solid powder. The solid powder was calcined to obtain a Pd-Cu bimetallic supported In2O3-TiO2 catalyst.

[0015] Preferably, the palladium precursor is selected from any one or more of palladium nitrate, palladium chloride, or palladium acetate.

[0016] Preferably, the copper precursor is selected from any one or more of copper nitrate, copper chloride, or copper acetate.

[0017] Preferably, the pH is adjusted to 9-10 using ammonia.

[0018] Preferably, the reaction is carried out under stirring conditions for 1 to 10 hours.

[0019] Preferably, the drying temperature is 50~80℃ and the time is 6~24 h.

[0020] Preferably, the calcination heating rate is 1~5 °C / min, the calcination temperature is 300~500 °C, and the calcination time is 1~6 h.

[0021] Thirdly, the present invention provides an application of the above-mentioned Pd-Cu bimetallic supported In2O3-TiO2 catalyst in the reaction of CO2 hydrogenation to methanol.

[0022] Preferably, the temperature of the CO2 hydrogenation reaction to prepare methanol is 200-300℃, the pressure is 3-5 MPa, and the space velocity is 400-1200 mL·g. -1 ·h -1 .

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst. This catalyst constructs Pd-Cu bimetallic active sites and achieves high dispersion and synergistic effect of the bimetallic sites by selecting a suitable In₂O₃-TiO₂ composite support. Pd possesses excellent H₂ dissociation ability, enabling efficient activation of hydrogen gas; Cu exhibits high selectivity for methanol production. This invention combines Pd and Cu to form bimetallic sites, fully leveraging their respective advantages and significantly enhancing the reactivity of CO₂ hydrogenation to methanol through electronic and geometric effects between the metals.

[0025] Tests have shown that the Pd-Cu bimetallic supported In2O3-TiO2 catalyst provided by this invention has advantages such as high conversion rate and high catalytic activity in the CO2 hydrogenation reaction to methanol. Specifically, in the CO2 hydrogenation process, the catalyst can achieve a single-pass CO2 conversion rate of 23.5% and a methanol yield of 15.83% at 250℃. Attached Figure Description

[0026] Figure 1 The image shows a TEM image of the Pd1Cu5 / In2O3-TiO2 catalyst in Example 1.

[0027] Figure 2 The graph shows the performance test results of the Pd1Cu5 / In2O3-TiO2 catalyst in Example 1.

[0028] Figure 3 This is a TEM image of the Pd1Cu3 / In2O3-TiO2 catalyst in Example 2;

[0029] Figure 4 The graph shows the performance test results of the Pd1Cu3 / In2O3-TiO2 catalyst in Example 2.

[0030] Figure 5 The image shows a TEM image of the Pd1Cu7 / In2O3-TiO2 catalyst in Example 3.

[0031] Figure 6 The graph shows the performance test results of the Pd1Cu7 / In2O3-TiO2 catalyst in Example 3.

[0032] Figure 7 This is a TEM image of the Pd1Cu5 / In2O3-TiO2 catalyst in Example 4;

[0033] Figure 8 The graph shows the performance test results of the Pd1Cu5 / In2O3-TiO2 catalyst in Example 4.

[0034] Figure 9 TEM image of the Pd / In2O3-TiO2 catalyst in Comparative Example 1;

[0035] Figure 10 Performance test results curves of the Pd / In2O3-TiO2 catalyst in Comparative Example 1;

[0036] Figure 11 This is a TEM image of the Cu / In2O3-TiO2 catalyst in Comparative Example 2;

[0037] Figure 12 The graph shows the performance test results of the Cu / In2O3-TiO2 catalyst in Comparative Example 2.

[0038] Figure 13 TEM image of the Pd1Cu5 / In2O3-SiO2 catalyst in Comparative Example 3;

[0039] Figure 14 The graph shows the performance test results of the Pd1Cu5 / In2O3-SiO2 catalyst in Comparative Example 3.

[0040] Figure 15 The graph shows the stability test performance of the Pd1Cu5 / In2O3-TiO2 catalyst in Example 1. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] To overcome the limitations of traditional Cu-based catalysts, this invention utilizes Pd and Cu, which have high efficiency in dissociating H2, to construct a bimetallic catalyst and exert a synergistic effect. At the same time, it utilizes the advantages of efficient Pd sites and efficient Cu sites to develop a Pd-Cu bimetallic supported In2O3-TiO2 catalyst that can efficiently utilize the active sites of Pd and Cu, which has important scientific significance and industrial application value.

[0043] Specifically, the technical solution of the present invention will be described from the following aspects.

[0044] In a first aspect, the present invention provides a Pd-Cu bimetallic supported In2O3-TiO2 catalyst, comprising a composite support and Pd nanoparticles and Cu nanoparticles supported on the surface of the composite support.

[0045] In this invention, the composite support is preferably In2O3-TiO2, which has a stronger CO2 adsorption and activation ability than other supports (such as SiO2) and can effectively stabilize Pd-Cu nanoparticles.

[0046] In some embodiments of the present invention, the mass ratio of In2O3 to TiO2 in the composite carrier is (8~12):1, such as 8:1, 9:1, 10:1, 11:1 or 12:1, preferably 10:1.

[0047] In some embodiments of the present invention, the molar ratio of Pd nanoparticles to Cu nanoparticles is 1:(3~7), such as 1:3, 1:4, 1:5, 1:6 or 1:7, preferably 1:5.

[0048] In some embodiments of the present invention, the loading of Pd nanoparticles is 1-5 wt% based on 100% of the mass of the composite carrier, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%, etc.; the loading of Cu nanoparticles is 5-20 wt% based on 100% of the mass of the composite carrier, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, etc.

[0049] TEM characterization showed that the Pd nanoparticles and Cu nanoparticles were uniformly dispersed on the surface of the In2O3-TiO2 support, with particle sizes mainly concentrated in the range of 3 to 6 nm, such as 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, or 6 nm.

[0050] Secondly, the present invention also provides a method for preparing the above-mentioned Pd-Cu bimetallic supported In2O3-TiO2 catalyst, comprising the following steps:

[0051] Palladium precursor, copper precursor, composite support and water were mixed at pH 9-10. After reaction, the mixture was separated, dried and ground to obtain a solid powder. The solid powder was calcined to obtain a Pd-Cu bimetallic supported In2O3-TiO2 catalyst.

[0052] In this invention, the palladium precursor is selected from any one or more of palladium nitrate, palladium chloride, or palladium acetate; the copper precursor is selected from any one or more of copper nitrate, copper chloride, or copper acetate.

[0053] In some embodiments of the present invention, the pH of 9-10 is preferably adjusted by ammonia, because ammonia, as a weak base, can gently adjust the pH, and its ammonium ions can react with Pd. 2+ Cu 2+ The formation of stable complex ions effectively slows down the rapid hydrolysis and precipitation of metal ions under alkaline conditions, promoting uniform dispersion of the metal precursor on the carrier surface. Simultaneously, the ammonium salt can completely decompose into gas and escape during subsequent calcination, without introducing impurities. In the experimental stage, the applicant also used alkaline substances such as sodium hydroxide and sodium carbonate to adjust the pH, but found that when using sodium hydroxide and sodium carbonate, sodium ions easily remained in the catalyst, severely affecting catalytic performance, and the metal hydroxide precipitation was too rapid, easily leading to metal particle agglomeration. Therefore, this invention preferably uses ammonia to adjust the pH to 9-10.

[0054] The purpose of adjusting the pH to 9-10 is to impart an appropriate amount of negative charge to the surface of the In2O3-TiO2 composite support, while simultaneously allowing the metal ions to carry a positive charge, thereby achieving uniform anchoring of the metal ions on the support surface through electrostatic attraction.

[0055] In some embodiments of the present invention, the reaction is preferably carried out under stirring conditions, and the stirring time is 1-10 h, preferably 3-8 h, more preferably 4-5 h. The drying temperature is 50-80°C, preferably 60-70°C; the drying time is 6-24 h, preferably 12-20 h.

[0056] In some embodiments of the present invention, the calcination is preferably carried out in an oxygen-containing atmosphere, and the heating rate of the calcination is 1~5 °C / min, such as 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, or 5 °C / min; the calcination temperature is 300~500 °C, such as 300 °C, 320 °C, 350 °C, 380 °C, 400 °C, 420 °C, 450 °C, 480 °C, or 500 °C; the calcination time is 1~6 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, or 6 h.

[0057] In some specific embodiments of the present invention, the preparation method of the Pd-Cu bimetallic supported In2O3-TiO2 catalyst includes the following steps:

[0058] The palladium precursor solution and the In2O3-TiO2 composite support were uniformly dispersed in water to obtain the first mixed solution; the copper precursor solution was dispersed in water, and the pH was adjusted to 9-10 with ammonia to obtain the second mixed solution.

[0059] After adding the first mixed solution to the second mixed solution, stir, centrifuge, dry and grind;

[0060] The obtained solid powder was calcined in an oxygen-containing atmosphere at a certain temperature to obtain a Pd-Cu bimetallic supported In2O3-TiO2 catalyst.

[0061] In the above implementation scheme, the palladium precursor solution is selected from palladium nitrate solution, the copper precursor solution is selected from copper nitrate trihydrate solution, and the ratio of palladium nitrate to copper nitrate trihydrate is (0.2~0.4) mmol:(0.6~3) mmol, such as 0.2 mmol:0.6 mmol, 0.2 mmol:1.0 mmol, or 0.2 mmol:1.4 mmol, etc.

[0062] This preparation method utilizes the principle of electrostatic adsorption. By adjusting the pH value of the solution with ammonia, the surface of the composite carrier and the metal precursor are respectively charged with opposite charges, thereby achieving the directional and uniform adsorption of metal ions on the carrier surface through electrostatic attraction. The preparation method provided by this invention is simple and convenient, requires no expensive instruments or equipment, and is conducive to large-scale or industrialized production.

[0063] Thirdly, the present invention provides an application of the above-mentioned Pd-Cu bimetallic supported In2O3-TiO2 catalyst in the reaction of CO2 hydrogenation to methanol.

[0064] Specifically, the CO2 hydrogenation to methanol reaction is carried out in a fixed-bed reactor at a pressure of 30–50 bar and a temperature of 200–300 °C, preferably 250 °C. The catalyst is loaded into a fixed-bed reactor with an inner diameter of 9 mm. Subsequently, a reaction gas at 50 bar (72 vol% H2, 24 vol% CO2, and 4 vol% Ar, with Ar as an internal standard) is used as the feed gas at a rate of 400–1200 mL·g. -1 ·h -1 Preferred concentration: 600-800 mL / g -1 ·h -1 The space velocity is introduced into the fixed-bed reactor.

[0065] Tests have shown that the Pd-Cu bimetallic supported In2O3-TiO2 catalyst provided by this invention has advantages such as high conversion rate and high catalytic activity in the CO2 hydrogenation reaction to methanol. Specifically, in the CO2 hydrogenation process, the catalyst can achieve a single-pass CO2 conversion rate of 23.5% and a methanol yield of 15.83% at 250℃.

[0066] To further illustrate the present invention, the following embodiments provide a detailed description. Unless otherwise specified, all experimental materials used in the following embodiments of the present invention are commercially available products.

[0067] This invention utilizes two gas chromatographs for online detection of products and reactants. H2, CO, CO2, CH4, and Ar are analyzed using a carbon molecular sieve column (TDX-1) with a thermal conductivity detector (TCD); CH4 and CH3OH are analyzed using a PLOT-Q column with a flame ionization detector (FID), with CH4 serving as a reference bridge between the TCD and FID. Assuming the amount of Ar remains constant after the reaction, the CO2 conversion is calculated using the internal standard method.

[0068] CO2 conversion rate is calculated based on carbon atoms, using the following formula:

[0069] CO2 conversion rate = (CO2 conversion rate) 2 inlet -CO 2 outlet ) / CO 2 inlet ×100%;

[0070] Among them, CO 2 inlet and CO 2 outlet These are the number of moles of CO2 at the inlet and outlet, respectively.

[0071] Example 1

[0072] The Pd1Cu5 / In2O3-TiO2 catalyst was prepared by the following method:

[0073] First, 0.9 g of titanium dioxide and 0.1 g of indium oxide were physically mixed and ground uniformly to obtain a composite support. A palladium nitrate aqueous solution and 1.0 g of the composite support were dispersed in 50 mL of water to obtain a first mixed solution; a copper nitrate solution was dispersed in 50 mL of water, and the pH of the second solution was adjusted to 9-10 with ammonia to obtain a second solution; wherein the molar ratio of palladium nitrate to copper nitrate was 1:5. The first solution was added to the second solution, and the mixture was stirred for 5 h. After centrifugation, the solid was heated to 60 °C in an oven at a heating rate of 10 °C / min and dried for 12 h. The resulting product was ground and heated to 350 °C in an oxygen-containing atmosphere at a heating rate of 2 °C / min and held for 3 h. After natural cooling to room temperature, the product Pd1Cu5 / In2O3-TiO2 catalyst was obtained. A TEM image of this catalyst is shown below. Figure 1 As shown, it can be observed that Pd and Cu metal nanoparticles are dispersed on the surface of the In2O3-TiO2 support, with particle sizes mainly concentrated in the range of 3~6 nm.

[0074] The carbon dioxide hydrogenation performance of the prepared Pd1Cu5 / In2O3-TiO2 catalyst was tested:

[0075] 1.0 g of the prepared Pd1Cu5 / In2O3-TiO2 catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 2 After 5 hours of reaction, the carbon dioxide conversion rate reached 23.5%, while the methanol yield reached 15.83%, demonstrating excellent catalytic activity.

[0076] Example 2

[0077] The difference from Example 1 is that the molar ratio of palladium nitrate to copper nitrate is 1:3, while the remaining parameters and steps are the same as in Example 1. The TEM image of the prepared Pd1Cu3 / In2O3-TiO2 catalyst is shown below. Figure 3 As shown, it can be observed that the metal nanoparticles are dispersed on the surface of the In2O3-TiO2 support, and the particle size is mainly concentrated at about 6 nm.

[0078] The carbon dioxide hydrogenation performance of the prepared Pd1Cu3 / In2O3-TiO2 catalyst was tested:

[0079] 1.0 g of the prepared Pd1Cu3 / In2O3-TiO2 catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 4 After 5 hours of reaction, the carbon dioxide conversion rate reached 13.77%, and the methanol yield reached 9.53%. Compared with Example 1, both the CO2 conversion rate and the methanol yield decreased significantly.

[0080] Example 3

[0081] The difference from Example 1 is that the molar ratio of palladium nitrate to copper nitrate is 1:7, while the remaining parameters and steps are consistent with Example 1. The TEM image of the prepared Pd1Cu7 / In2O3-TiO2 catalyst is shown below. Figure 5 As shown, it can be observed that the metal particles still maintain good dispersibility, and the particle size is comparable to that of Example 1.

[0082] The carbon dioxide hydrogenation performance of the prepared Pd1Cu7 / In2O3-TiO2 catalyst was tested:

[0083] 1.0 g of the prepared Pd1Cu7 / In2O3-TiO2 catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 6 After 5 hours of reaction, the carbon dioxide conversion rate reached 13.59%, while the methanol yield was 9.43%. It is evident that the results of this example are similar to those of Example 2, but compared to Example 1, both the CO2 conversion rate and methanol yield decreased significantly.

[0084] Example 4

[0085] The difference from Example 1 is that sodium carbonate was used as the alkaline substance for adjusting the pH; all other parameters and steps remained the same as in Example 1. A TEM image of the prepared Pd1Cu5 / In2O3-TiO2 catalyst is shown below. Figure 7As shown, it can be observed that the metal particles still maintain good dispersibility, and the particle size is comparable to that of Example 1.

[0086] The carbon dioxide hydrogenation performance of the prepared Pd1Cu5 / In2O3-TiO2 catalyst was tested:

[0087] 1.0 g of the prepared Pd1Cu5 / In2O3-TiO2 catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 8 After 5 hours of reaction, the carbon dioxide conversion rate reached 3.97%, while the methanol yield was 2.38%. It is evident that the results of this example differ significantly from those of Example 1, with both CO2 conversion rate and methanol yield decreasing markedly.

[0088] Comparative Example 1

[0089] The preparation method for palladium-based catalysts without copper modification is as follows:

[0090] First, 0.9 g of titanium dioxide and 0.1 g of indium oxide were physically mixed and ground uniformly to obtain a composite support. 1.0 g of the composite support was dispersed in 50 mL of water, and the pH was adjusted to 9-10 with ammonia. Then, a palladium precursor solution was added, and the mixture was stirred for five hours. After centrifugation, the solid was heated to 60°C in an oven at a heating rate of 10 °C / min and dried for 12 h. The resulting product was then ground and heated to 350°C in an oxygen-containing atmosphere at a heating rate of 2 °C / min. o The mixture was kept at C for 3 h, and after natural cooling to room temperature, the Pd / In₂O₃-TiO₂ catalyst was obtained. A TEM image of the prepared Pd / In₂O₃-TiO₂ catalyst is shown below. Figure 9 As shown, it can be observed that the Pd metal particles are uniformly dispersed, and the particle size of the Pd metal particles is approximately 5 nm.

[0091] 1.0 g of the prepared Pd / In₂O₃-TiO₂ catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 10 After 5 hours of reaction, the carbon dioxide conversion rate reached 20.84%, but the methanol yield was only 3.00%. This indicates that the addition of Cu metal is important for methanol production.

[0092] Comparative Example 2

[0093] The preparation method for copper-based catalysts without palladium modification is as follows:

[0094] First, 0.9 g of titanium dioxide and 0.1 g of indium oxide were physically mixed and ground uniformly to obtain a composite support. 1.0 g of the composite support was dispersed in 50 mL of water, and the pH was adjusted to 9-10 with ammonia. Then, a copper precursor solution was added, and the mixture was stirred for five hours. After centrifugation, the solid was heated to 60°C in an oven at a heating rate of 10 °C / min and dried for 12 h. The resulting product was then ground and heated to 350°C in an oxygen-containing atmosphere at a heating rate of 2 °C / min. o The mixture was kept at C for 3 h, and after natural cooling to room temperature, the Cu / In₂O₃-TiO₂ catalyst was obtained. A TEM image of the prepared Cu / In₂O₃-TiO₂ catalyst is shown below. Figure 11 As shown, it can be observed that metallic Cu is mainly distributed in block form on the In2O3-TiO2 support, exhibiting a certain degree of agglomeration.

[0095] The prepared 1.0 g Cu / In₂O₃-TiO₂ catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 12 After 5 hours of reaction, the carbon dioxide conversion rate reached 10.47%, while the methanol yield was 2.73%. This indicates that the activation ability of a single Cu site for H2 is insufficient, resulting in a decrease in CO2 conversion rate.

[0096] Comparative Example 3

[0097] The Pd1Cu5 / In2O3-SiO2 catalyst was prepared by the following method:

[0098] First, 0.9 g of silica and 0.1 g of indium oxide were physically mixed and ground uniformly to obtain a composite support. 1.0 g of the composite support was dispersed in 50 mL of water, and the pH was adjusted to 9-10 with ammonia. Then, a palladium precursor solution was added, and the mixture was stirred for five hours. After centrifugation, the solid was heated to 60°C in an oven at a heating rate of 10 °C / min and dried for 12 h. The resulting product was then ground and heated to 350°C in an oxygen-containing atmosphere at a heating rate of 2 °C / min. o The mixture was kept at C for 3 h, and after natural cooling to room temperature, the Pd1Cu5 / In2O3-SiO2 catalyst was obtained. A TEM image of the prepared Pd1Cu5 / In2O3-SiO2 catalyst is shown below. Figure 13 As shown, it can be observed that the metal particles are evenly dispersed.

[0099] 1.0 g of the prepared Pd1Cu5 / In2O3-SiO2 catalyst was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 14 After 5 hours of reaction, the carbon dioxide conversion rate was 2.92% and the methanol yield was 2.38%. This indicates that the TiO2 support is important for improving the conversion rate.

[0100] Furthermore, the present invention conducts stability tests on the catalyst obtained in Example 1, and the specific test methods are as follows:

[0101] 1.0 g of the Pd1Cu5 / In2O3-TiO2 catalyst obtained in Example 1 was loaded into a fixed bed, and a mixture of carbon dioxide and hydrogen was introduced. The mixture contained 4% argon gas by volume as an internal standard for calculating conversion and selectivity. The volume ratio of carbon dioxide to hydrogen in the mixture was 1:3. The reaction was carried out at 250 °C, 50 bar, and 600 mL·g. -1 ·h -1 The reaction was carried out continuously under the specified reaction conditions. The reaction tail gas passed through a fully insulated needle valve and heating pipes before entering a gas chromatograph for online analysis. Results are shown below. Figure 15 After 100 h of reaction, the carbon dioxide conversion rate reached 22.6%, and the methanol yield reached 15.10%, demonstrating excellent catalytic activity.

[0102] Test results are as follows Figure 15As shown, the results indicate that the catalyst did not show a significant decrease in CO2 conversion or methanol selectivity within a 100-hour reaction time.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst, characterized in that, Includes a composite carrier and Pd nanoparticles and Cu nanoparticles loaded on the surface of the composite carrier. The composite carrier is In2O3-TiO2; The molar ratio of Pd nanoparticles to Cu nanoparticles is 1:(3~7).

2. The Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst according to claim 1, characterized in that, The molar ratio of Pd nanoparticles to Cu nanoparticles is 1:(4~5).

3. The Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst according to claim 1 or 2, characterized in that, The loading of Pd nanoparticles is 1-5 wt%, based on the mass of the composite carrier being 100%. With the composite carrier as 100% by mass, the loading of Cu nanoparticles is 5~20 wt%.

4. The Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst according to any one of claims 1 to 3, characterized in that, The Pd and Cu nanoparticles have a size of 3-6 nm.

5. The Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst according to any one of claims 1 to 4, characterized in that, The mass ratio of In2O3 to TiO2 is (8~12):

1.

6. A method for preparing a Pd-Cu bimetallic supported In₂O₃-TiO₂ catalyst as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Palladium precursor, copper precursor, composite support and water were mixed at pH 9-10. After reaction, the mixture was separated, dried and ground to obtain a solid powder. The solid powder was calcined to obtain a Pd-Cu bimetallic supported In2O3-TiO2 catalyst.

7. The preparation method according to claim 6, characterized in that, The palladium precursor is selected from any one or more of palladium nitrate, palladium chloride, or palladium acetate. The copper precursor is selected from any one or more of copper nitrate, copper chloride, or copper acetate.

8. The preparation method according to claim 6 or 7, characterized in that, The pH is adjusted to 9-10 using ammonia. The reaction is carried out under stirring conditions for 1 to 10 hours. The drying temperature is 50~80℃, and the time is 6~24 h; The calcination heating rate is 1~5 ℃ / min, the calcination temperature is 300~500℃, and the calcination time is 1~6 h.

9. The application of the Pd-Cu bimetallic supported In2O3-TiO2 catalyst according to any one of claims 1 to 5 or the Pd-Cu bimetallic supported In2O3-TiO2 catalyst prepared by the preparation method according to any one of claims 6 to 8 in the reaction of CO2 hydrogenation to methanol.

10. The application according to claim 9, characterized in that, The CO2 hydrogenation reaction to prepare methanol is carried out at a temperature of 200-300℃, a pressure of 3-5 MPa, and a space velocity of 400-1200 mL·g. -1 ·h -1 .

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