Catalyst for preparing methanol through carbon dioxide hydrogenation, and preparation method and application thereof

Abstract

The invention relates to a catalyst for preparing methanol through carbon dioxide hydrogenation and a preparation method and application thereof. The catalyst for preparing methanol through hydrogenation of carbon dioxide provided by the invention comprises a lanthanum oxycarbonate carrier and metal palladium loaded on the carrier. The catalyst provided by the invention has relatively high catalytic activity for preparing methanol through carbon dioxide hydrogenation at low temperature.

Description

Technical Field

[0001] This application belongs to the field of catalytic technology, and particularly relates to a catalyst for hydrogenating carbon dioxide to methanol, a preparation method thereof, and an application thereof. Background Art

[0002] The extensive use of fossil fuels (coal, oil, and natural gas) has led to a large amount of CO2 emissions, causing serious environmental problems such as global warming and seawater acidification. Therefore, reducing CO2 emissions and developing an effective CO2 capture and utilization system have become the primary goals for solving environmental problems. George A. Olah, the Nobel laureate in chemistry, proposed the concept of "methanol economy" in response to the global energy crisis, believing that hydrogenation of CO2 is one of the most promising renewable routes for methanol production. Converting CO2 and green H2 into methanol (CO2 + 3H2 → CH3OH + H2O) is an effective way to convert CO2 and store hydrogen, and at the same time, an important basic chemical - methanol is obtained while solving environmental problems.

[0003] Currently, the research on catalysts for hydrogenating carbon dioxide to methanol mainly focuses on non-noble metal (Cu)-based catalysts, noble metal (Pd) catalysts, and double metal oxide catalysts. Noble metal Pd-based catalysts have unique properties in the field of hydrogenating carbon dioxide to methanol. First, noble metal Pd-based catalysts have the characteristics of high efficiency at low temperature and good anti-poisoning performance. Pd nanoparticles have a significant ability to dissociate and activate H2 (H2 → 2H*), especially at low temperatures (<200 °C), and their performance is superior to that of Cu-based catalysts, which can accelerate the kinetics of carbon dioxide hydrogenation. At the same time, Pd has a moderate adsorption capacity for intermediate products such as CO and is not easily deactivated due to CO poisoning. Second, noble metal Pd-based catalysts have a stable structure and the characteristics of anti-sintering and oxidation resistance. Pd nanoparticles have strong anti-sintering ability in a reducing atmosphere (maintaining a high degree of dispersion at high temperatures), and the tendency of Pd to oxidize is relatively low. Finally, noble metal Pd can have a synergistic effect with multifunctional supports. For example, when combined with reducible oxides (such as CeO2, TiO2), Pd can induce surface oxygen vacancies (O V ) on the support, promoting the adsorption and activation of CO2 (CO2 → CO2-). However, the methanol selectivity of Pd-based catalysts is low. The Pd surface is prone to promoting the deep hydrogenation of CO2 to form methane (CH4) or carbon monoxide (CO), rather than methanol (CH3OH), and the methanol selectivity needs to be improved by carrier additives or nanostructure regulation. At the same time, Pd-based catalysts are significantly dependent on the support. For example, when combined with a reducible support (such as ZrO2), although it can enhance the Pd-support interaction (SMSI), it may overly inhibit the dissociation of H2.

[0004] In the catalyst provided by the present application, metallic palladium is supported on a lanthanum oxycarbonate carrier in the form of ultra-small nanoclusters. When the size of the Pd clusters approaches the Fermi wavelength (about 1 nm), its electronic energy levels change from a continuous state to a discrete state, resulting in a shift in the position of the d-band center, thereby changing the adsorption strength of reactant molecules (such as H2, CO2). For example, Pd 30 The d-band center of the clusters is 0.3 eV higher than that of bulk Pd, enhancing the adsorption and activation ability of CO2. In the hydrogenation of CO2 to methanol, by precisely controlling the cluster size, side reactions (such as the formation of methane and CO) can be inhibited, and the selectivity and space-time yield of methanol can be improved. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present application provides a catalyst for the hydrogenation of carbon dioxide to methanol, its preparation method and application.

[0006] In a first aspect, the present application provides a catalyst for the hydrogenation of carbon dioxide to methanol, which comprises a lanthanum oxycarbonate (La2O2CO3) carrier and metallic palladium supported on the carrier.

[0007] In some embodiments, metallic palladium is supported on the carrier in the form of ultra-small nanoclusters.

[0008] In some embodiments, based on the mass of the catalyst, the loading amount of metallic palladium is 0.5%-12%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 5.7%, 6%, 6.3%, 6.5%, 6.7%, 7%, 7.3%, 7.5%, 7.7%, 8%, 8.3%, 8.5%, 9%, 9.5%, 10%, 11% or any value therebetween. In some embodiments, the loading amount of metallic palladium is 1%-10%. In some embodiments, the loading amount of metallic palladium is 2%-8%.

[0009] In some embodiments, the diameter of the ultra-small nanoclusters is less than or equal to 2 nm, for example, 0.5 nm, 1 nm, 1.3 nm, 1.5 nm or 1.7 nm.

[0010] In some embodiments, the lanthanum oxycarbonate carrier is selected from a nanorod-shaped lanthanum oxycarbonate carrier. Compared with other morphologies, the nanorod-shaped lanthanum oxycarbonate carrier can provide abundant oxygen vacancies, which is beneficial to the adsorption and activation of CO2.

[0011] In some embodiments, the length of the nanorods is less than or equal to 50 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or any value therebetween. In some embodiments, the length of the nanorods is 30 nm-40 nm.

[0012] In some embodiments, the diameter of the nanorods is 5 nm - 15 nm, such as 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, or any value therebetween. In some embodiments, the diameter of the nanorods is 5 nm - 12 nm. In some embodiments, the diameter of the nanorods is 8 nm - 10 nm.

[0013] In a second aspect, the present application provides a method for preparing a catalyst for hydrogenating carbon dioxide to methanol, which comprises the following steps:

[0014] S1: Mix a first mixed solution containing a lanthanum source with an alkali solution to obtain a mixture containing lanthanum hydroxide;

[0015] S2: Subject the mixture of step S1 to a hydrothermal reaction, and perform a first calcination on the hydrothermal reaction product to obtain a lanthanum oxycarbonate support;

[0016] S3: Mix a second mixed solution containing the lanthanum oxycarbonate support in step S2 with a third mixed solution containing a palladium source to obtain a fourth mixed solution;

[0017] S4: Subject the fourth mixed solution to a precipitation reaction, and perform a second calcination and reduction on the precipitation reaction product to obtain the catalyst.

[0018] The present application synthesizes a catalyst (Pd / La₂O₂CO₃) for hydrogenating carbon dioxide to methanol by a two-step method. The preparation method is simple and the experimental period is short. Moreover, the prepared catalyst has a high methanol yield.

[0019] In some embodiments, based on the mass of palladium, the mass of the palladium source is 0.5% - 15% of the mass of the lanthanum oxycarbonate support, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 5.7%, 6%, 6.3%, 6.5%, 6.7%, 7%, 7.3%, 7.5%, 7.7%, 8%, 8.3%, 8.5%, 8.7%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 13%, 14%, or any value therebetween. In some embodiments, the mass of the palladium source is 2% - 12% of the mass of the lanthanum oxycarbonate support. In some embodiments, the mass of the palladium source is 6% - 10% of the mass of the lanthanum oxycarbonate support.

[0020] In some embodiments, in step S1, the first mixed solution containing a lanthanum source is selected from an aqueous solution of a lanthanum source.

[0021] In some embodiments, in step S1, the lanthanum source is selected from one or more of lanthanum nitrate, lanthanum chloride, lanthanum sulfate, and lanthanum acetate.

[0022] In some embodiments, in step S1, the alkaline solution is selected from one or more of potassium hydroxide solution, sodium hydroxide solution, ammonia water, and urea solution.

[0023] In some embodiments, in step S2, the temperature of the hydrothermal reaction is 150°C - 250°C, such as 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, or 240°C. In some embodiments, the temperature of the hydrothermal reaction is 180°C - 200°C.

[0024] In some embodiments, in step S2, the time of the hydrothermal reaction is 5h - 30h, such as 8h, 10h, 12h, 15h, 18h, 20h, 24h, or 28h. In some embodiments, the time of the hydrothermal reaction is 10h - 20h.

[0025] In some embodiments, in step S2, the temperature of the first calcination is 400°C - 700°C, such as 450°C, 500°C, 550°C, 600°C, or 650°C. In some embodiments, the temperature of the first calcination is 500°C - 600°C.

[0026] In some embodiments, in step S2, after the hydrothermal reaction product is washed and dried, the first calcination is carried out.

[0027] In some embodiments, in step S3, the second mixed solution is selected from an aqueous solution containing a lanthanum oxycarbonate carrier.

[0028] In some embodiments, in step S3, the third mixed solution containing a palladium source is selected from an aqueous solution of a palladium source.

[0029] In some embodiments, in step S3, the palladium source is selected from one or more of palladium nitrate, palladium chloride, palladium acetate, and sodium tetrachloropalladate.

[0030] In some embodiments, in step S4, an alkaline source is used to adjust the pH of the fourth mixed solution to 8 - 9 to cause a precipitation reaction in the fourth mixed solution. In some embodiments, the alkaline solution is selected from potassium hydroxide solution and / or sodium hydroxide solution.

[0031] In some embodiments, in step S4, the temperature of the second calcination is 350°C - 600°C, such as 400°C, 450°C, 500°C, or 550°C. In some embodiments, the temperature of the second calcination is 400°C - 500°C.

[0032] In some embodiments, in step S4, after the precipitation reaction product is washed and dried, the second calcination is carried out.

[0033] In some embodiments, in step S4, the reduction temperature is 250°C - 350°C, for example, 270°C, 300°C or 330°C.

[0034] In some embodiments, in step S4, the reduction is carried out in a hydrogen atmosphere.

[0035] In some embodiments, the preparation method comprises the following specific steps:

[0036] (1) Preparation of La2O2CO3:

[0037] Dissolve lanthanum nitrate hexahydrate (La(NO3)3·6H2O, 0.9855 g) in 40 mL of deionized water and stir magnetically for 10 min. Subsequently, drop the freshly prepared KOH solution (KOH, 10%, 20 mL) into the beaker with a pipette until the mixture turns milky white to form La(OH)3. Stir the mixture for 2 h, then transfer the solution to a 100 ml hydrothermal autoclave and hydrothermal react at 180°C for 12 h. Filter the hydrothermally treated solution by suction and wash it with deionized water until neutral, then dry it overnight at 80°C. Calcinate the dried solid at 550°C for 2 h (while passing air) to form rod-shaped La2O2CO3.

[0038] (2) Preparation of Pd / La2O2CO3:

[0039] Disperse rod-shaped La2O2CO3 (0.5 g) in 120 mL of deionized water and sonicate for 30 min. Add a quantified amount of Pd(NO3)2·2H2O to the above solution and stir magnetically for 2 h. Then drop the freshly prepared NaOH solution (0.1 M) into the mixed solution. When the pH of the solution is 8 - 9, precipitate for 2 h at room temperature. Filter the precipitated solution by suction and wash it with deionized water until neutral, then dry it overnight at 110°C. Calcinate the dried solid at 450°C for 4 h (while passing air) to obtain the Pd / La2O2CO3 catalyst.

[0040] In a third aspect, the present application provides the use of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the hydrogenation of carbon dioxide to methanol.

[0041] In a fourth aspect, the present application provides a method for hydrogenating carbon dioxide to methanol, which comprises reacting carbon dioxide and hydrogen in the presence of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect.

[0042] In some embodiments, the temperature of the reaction is 200°C - 350°C, for example, 220°C, 240°C, 260°C, 280°C, 300°C, 320°C or 340°C. In some embodiments, the temperature of the reaction is 280°C - 300°C.

[0043] In some embodiments, the pressure of the reaction is 2 MPa - 5 MPa, for example, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa or 4.5 MPa. In some embodiments, the pressure of the reaction is 2.5 MPa - 3.5 MPa.

[0044] In some embodiments, the space velocity of the reaction is 8000 mL g cat -1 h -1 -36000 mL g cat -1 h -1 For example, 10000 mL g cat -1 h -1 、15000 mL g cat -1 h -1 、20000 mL g cat -1 h -1 、25000 mL g cat -1 h -1 、30000 mL g cat -1 h -1 or 35000 mL g cat -1 h -1 。In some embodiments, the space velocity of the reaction is 18000 mL g cat -1 h -1 -30000 mL g cat - 1 h -1 。

[0045] Compared with the prior art, the beneficial effects of the present application are as follows:

[0046] 1. In the synthesized Pd / La₂O₂CO₃ catalyst, Pd is loaded on La₂O₂CO₃ in the form of nanoclusters.

[0047] 2. The preparation method of the Pd / La₂O₂CO₃ catalyst in the present application is simple, the experimental period is short, and the methanol yield is high. The space-time yield of methanol can reach 0.36 g CH3OH g cat -1 h -1 。

[0048] 3. The synthesized Pd / La2O2CO3 catalyst can effectively catalyze the conversion of CO2. The experimental results show that at 290 °C, the CO2 conversion rate reaches 15.7%. Description of the Drawings

[0049] Figure 1 XRD spectra of the samples prepared in Comparative Example 1 and Examples 1-4.

[0050] Figure 2 Transmission electron microscope images, high-resolution transmission electron microscope images, high-angle annular dark-field scanning transmission electron microscope images, and elemental distribution maps of the sample 8wt% Pd / La2O2CO3 prepared in Example 3.

[0051] Figure 3 High-angle annular dark-field scanning transmission electron microscope image of the sample 8wt% Pd / La2O2CO3 prepared in Example 3.

[0052] Figure 4 Performance test results of the samples prepared in Comparative Example 1 and Examples 1-4, where Fig. (a) is the methanol selectivity, Fig. (b) is the CO2 conversion rate, and Fig. (c) is the space-time yield of methanol. Detailed Description of the Invention

[0053] To make the objectives, technical solutions, and advantages of this application clearer, the following further elaborates on this application in combination with examples and drawings. The specific examples described herein are only used to explain this application and do not constitute any limitation to this application. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of this disclosure. Such structures and technologies are also described in many publications.

[0054] The following further illustrates this application through specific examples.

[0055] Unless otherwise specified, the reagents used in the following examples and comparative examples are obtained through commercial channels.

[0056] Unless otherwise specified, the pressures mentioned in the following examples and comparative examples are gauge pressures.

[0057] Comparative Example 1

[0058] Lanthanum nitrate hexahydrate (La(NO3)3·6H2O, 0.9855 g) was dissolved in 40 mL of deionized water. After magnetic stirring for 10 min, the newly prepared KOH solution (KOH, 10%, 20 mL) was added dropwise into the beaker through a pipette until the mixture turned milky white to form La(OH)3. The mixture was stirred for 2 h, and then the solution was transferred to a 100 mL hydrothermal autoclave and hydrothermally treated at 180 °C for 12 h. The hydrothermally treated solution was filtered by suction and washed with deionized water until neutral, and then dried overnight at 80 °C. The dried solid was calcined at 550 °C for 2 h (while passing air) to form rod-shaped La2O2CO3. The obtained sample was denoted as 0 wt% Pd / La2O2CO3 (0 wt% Pd / LOC).

[0059] Example 1

[0060] (1) Preparation of rod-shaped La2O2CO3

[0061] Lanthanum nitrate hexahydrate (La(NO3)3·6H2O, 0.9855 g) was dissolved in 40 mL of deionized water. After magnetic stirring for 10 min, the newly prepared KOH solution (KOH, 10%, 20 mL) was added dropwise into the beaker through a pipette until the mixture turned milky white to form La(OH)3. The mixture was stirred for 2 h, and then the solution was transferred to a 100 mL hydrothermal autoclave and hydrothermally treated at 180 °C for 12 h. The hydrothermally treated solution was filtered by suction and washed with deionized water until neutral, and then dried overnight at 80 °C. The dried solid was calcined at 550 °C for 2 h (while passing air) to form rod-shaped La2O2CO3.

[0062] (2) Preparation of 2 wt% Pd / La2O2CO3 catalyst

[0063] The rod-shaped La2O2CO3 (0.5 g) prepared in step (1) was dissolved in 120 mL of deionized water and sonicated for 30 min. 0.025 g of Pd(NO3)2·2H2O was added to the above solution and stirred magnetically for 2 h. Subsequently, the newly prepared NaOH solution (0.1 M) was added dropwise to the mixed solution. When the pH of the solution was 8 - 9, it was precipitated for 2 h at room temperature. The precipitated solution was filtered by suction and washed with deionized water until neutral, and then dried overnight at 110 °C. The dried solid was calcined at 450 °C for 4 h (while passing air), and then reduced at 300 °C for 1 h under a hydrogen atmosphere. The obtained sample was denoted as 2 wt% Pd / La2O2CO3 (2 wt% Pd / LOC).

[0064] Example 2

[0065] The difference from Example 1 was only that the mass of Pd(NO3)2·2H2O added in step (2) was 0.05 g, and the obtained sample was denoted as 4 wt% Pd / La2O2CO3 (4 wt% Pd / LOC).

[0066] Example 3

[0067] The difference from Example 1 is only that the mass of Pd(NO3)2·2H2O added in step (2) is 0.1002 g, and the obtained sample is denoted as 8 wt% Pd / La2O2CO3 (8 wt% Pd / LOC).

[0068] Example 4

[0069] The difference from Example 1 is only that the mass of Pd(NO3)2·2H2O added in step (2) is 0.1502 g, and the obtained sample is denoted as 12 wt% Pd / La2O2CO3 (12 wt% Pd / LOC).

[0070] Structure Characterization

[0071] Figure 1 Shows the XRD patterns of the samples 0 wt% Pd / La2O2CO3, 2 wt% Pd / La2O2CO3, 4 wt% Pd / La2O2CO3, 8 wt% Pd / La2O2CO3, 12 wt% Pd / La2O2CO3 prepared in Comparative Example 1 and Examples 1-4. Diffraction peaks of hexagonal La2O2CO3 appear on the XRD patterns of 0 wt% Pd / La2O2CO3, 2 wt% Pd / La2O2CO3, 4 wt% Pd / La2O2CO3, 8 wt% Pd / La2O2CO3, 12 wt% Pd / La2O2CO3, indicating that the hexagonal La2O2CO3 support was successfully synthesized and the Pd loading did not change the crystal form of the hexagonal La2O2CO3 support.

[0072] Figure 2 Gives the transmission electron microscope image, high-resolution transmission electron microscope image, high-angle annular dark-field scanning transmission electron microscope image and element distribution map of the sample 8 wt% Pd / La2O2CO3 prepared in Example 3. From Figure 2 (a) Clear microtopography can be seen in the transmission electron microscope image. The 8 wt% Pd / La2O2CO3 sample maintains a nanorod-like structure. The length of the nanorods is less than 50 nm, about 20 - 50 nm, and the diameter is 5 - 12 nm; From Figure 2 (b) Lattice fringes of La2O2CO3 can be seen in the high-resolution transmission image, where the characteristic lattice distance is 0.35 nm, matching the (100) crystal plane of hexagonal La2O2CO3; Figure 2 (c) The high-angle annular dark-field scanning transmission electron microscope image and the corresponding element distribution map show that Pd elements are uniformly dispersed on the surface of the support La2O2CO3.

[0073] The spherical aberration corrected transmission electron microscope was further used to study the existence form of Pd atoms in the sample 8wt% Pd / La2O2CO3 prepared in Example 3, as Figure 3 shown. It was observed by atomic-level high-angle annular dark-field scanning transmission electron microscopy that Pd atoms were loaded on the surface of La2O2CO3 in the form of clusters smaller than 2 nm ([ Figure 3 bright spots in).

[0074] The actual loading amounts (ICP data) of Pd in the samples obtained in Comparative Example 1 and Examples 1-4 are shown in Table 1

[0075] Table 1

[0076] Sample Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Pd (wt%) 0％ 1.54％ 2.78％ 6.62％ 8.47％

[0077] Thermal catalytic effect test

[0078] The thermal catalytic performance of the Pd / La2O2CO3 catalysts prepared in Comparative Example 1 and Examples 1-4 was tested. The test method is as follows:

[0079] The performance test of CO2 hydrogenation to prepare CH3OH was carried out in a Ward fixed-bed flow microreactor, and the product distribution was detected by Fuli9790Ⅱ online gas chromatography.

[0080] The above catalysts were pressed, granulated, and screened to obtain catalyst particles of 40-65 mesh (230-400 μm). 0.3 g of the catalyst was mixed evenly with quartz of the same particle size (0.7 g) and filled into the isothermal zone of the quartz tube (i.d. = 6 mm) of the fixed-bed reactor for catalytic performance testing. H2 and CO2 were used as raw material gases, and Ar was used as the balance gas. The reaction conditions were: P = 3 MPa, T = 240-320 °C, V(H2) / V(CO2) / V(Ar) = 72 / 24 / 4, and the space velocity was 24000 mL g cat -1 h -1 . The catalyst was pretreated at 300 °C under atmospheric pressure of H2 (40 ml min –1 ) for 1 h, and then cooled to the reaction temperature to start pressurization. The ratio of reaction gases was regulated by a mass flowmeter, and the system pressure was regulated to 3 MPa by a back pressure valve.

[0081] The main products after the reaction are CH3OH, CH4, and CO. Among them, CO, Ar, and unreacted CO2 are separated, quantitatively and qualitatively analyzed through a thermal conductivity detector (TCD) packed column (Lanzhou Donglilong Information Technology Co., Ltd., TDX-01, 2m×3mm); methanol, methane, and alkanes are analyzed in a capillary chromatographic column (Agilent HP-Plot Q, 30m×0.53mm×40μm) of a hydrogen flame ionization detector (FID). Methane (CH4) serves as the quantitative analysis bridge for both FID and TCD. The temperature between the reactor and the gas pipeline is maintained at 130°C to prevent product condensation.

[0082] Under each reaction temperature condition, at least five stable data points of catalytic data are collected and averaged to calculate the conversion rate of CO2 and the selectivity of the products during the catalytic process. The carbon balance is 100±3%, and at each temperature point, the reaction time is maintained for at least 3 hours, and the last 5 sets of stable gas-phase data of the products are taken.

[0083] The test results of the samples prepared in Comparative Example 1 and Examples 1-4 are as Figure 4 shown. Figure 4 (a) The results show that the methanol selectivity of the 8wt% Pd / La2O2CO3 sample reaches the best. Figure 4 (b) The results show that after loading Pd, the CO2 conversion rate is greatly improved, and the CO2 conversion rate of the 8wt% Pd / La2O2CO3 sample is greater than 15% at 290°C. Figure 4 (c) The results show that the space-time yield of methanol of the 8wt% Pd / La2O2CO3 sample reaches 0.36g CH3OH g cat -1 h -1 .

[0084] The results of methanol selectivity, CO2 conversion rate, and space-time yield of methanol in the thermal catalytic effect test of the samples prepared in Comparative Example 1 and Examples 1-4 at 290°C are shown in Table 2.

[0085] Table 2

[0086] Sample <![CDATA[CO2 conversion rate]]> Methanol Selectivity Methanol Space-Time Yield Comparative Example 1 0％ 0％ 0 Example 1 10.38％ 24.98％ <![CDATA[0.21g CH3OH g cat -1 h -1 > Example 2 13.31％ 27.34％ <![CDATA[0.30g CH3OH g cat -1 h -1 > Example 3 15.76％ 27.61％ <![CDATA[0.36g CH3OH g cat -1 h -1 > Example 4 14.72％ 22.60％ <![CDATA[0.27g CH3OH g cat -1 h -1 >

[0087] The above results show that the Pd / La2O2CO3 catalyst provided by this application has high catalytic activity for the hydrogenation of CO2 to methanol at low temperatures.

[0088] The preferred embodiments of the present application have been described in detail above. However, the present application is not limited thereto. Within the scope of the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A catalyst for preparing methanol by hydrogenating carbon dioxide, comprising a lanthanum oxycarbonate carrier and metal palladium supported on the carrier.

2. The catalyst according to claim 1, characterized in that Based on the mass of the catalyst, the loading amount of metal palladium is 0.5%-12%, preferably 1%-10%, more preferably 2%-8%; and / or The metal palladium is loaded on the carrier in the form of ultra-small nanoclusters. Preferably, the diameter of the nanoclusters is less than or equal to 2 nm.

3. The catalyst according to claim 1 or 2, characterized in that The lanthanum oxycarbonate carrier is selected from a nanorod-shaped lanthanum oxycarbonate carrier, Preferably, the length of the nanorod is less than or equal to 50 nm, preferably 30 nm-40 nm, and the diameter of the nanorod is 5 nm-15 nm, preferably 8 nm-10 nm.

4. A method for preparing a catalyst for hydrogenating carbon dioxide to methanol, comprising the following steps: S1: mixing a first mixed solution containing a lanthanum source with an alkaline solution to obtain a mixture containing lanthanum hydroxide; S2: subjecting the mixture of step S1 to a hydrothermal reaction, and subjecting the hydrothermal reaction product to a first calcination to obtain a lanthanum oxycarbonate carrier; S3: mixing the second mixed solution containing the lanthanum oxycarbonate carrier in step S2 with the third mixed solution containing the palladium source to obtain a fourth mixed solution; S4: subjecting the fourth mixed solution to a precipitation reaction, and subjecting the precipitation reaction product to a second calcination and reduction to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that: Calculated by the mass of palladium, the mass of the palladium source is 0.5%-15% of the mass of the lanthanum oxycarbonate carrier, preferably 2%-12%, and more preferably 6%-10%.

6. The preparation method according to claim 4 or 5, characterized in that: In step S1, the first mixed solution containing the lanthanum source is selected from an aqueous solution of the lanthanum source; and / or The lanthanum source is selected from one or more of lanthanum nitrate, lanthanum chloride, lanthanum sulfate and lanthanum acetate; and / or The alkali solution is selected from one or more of potassium hydroxide solution, sodium hydroxide solution, ammonia water and urea solution.

7. The preparation method according to any one of claims 4 to 6, characterized in that: In step S2, the temperature of the hydrothermal reaction is 150°C-250°C, preferably 180°C-200°C; and / or The hydrothermal reaction time is 5h-30h, preferably 10h-20h; and / or The temperature of the first calcination is 400°C-700°C, preferably 500°C-600°C; and / or The hydrothermal reaction product is washed and dried and then calcined for the first time.

8. The preparation method according to any one of claims 4 to 7, characterized in that: In step S3, the second mixed solution is selected from an aqueous solution containing a lanthanum oxycarbonate carrier; and / or The third mixed solution containing the palladium source is selected from an aqueous solution of a palladium source; and / or The palladium source is selected from one or more of palladium nitrate, palladium chloride, palladium acetate and sodium tetrachloropalladate; and / or In step S4, an alkali source is used to adjust the pH of the fourth mixed solution to 8-9, so that the fourth mixed solution undergoes a precipitation reaction. Preferably, the alkali solution is selected from potassium hydroxide solution and / or sodium hydroxide solution; and / or The temperature of the second calcination is 350°C-600°C, preferably 400°C-500°C; and / or The precipitation reaction product is washed and dried, and then calcined for a second time; and / or The reduction temperature is 250°C-350°C.

9. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8 in the hydrogenation of carbon dioxide to methanol.

10. A method for preparing methanol by hydrogenating carbon dioxide, comprising reacting carbon dioxide and hydrogen in the presence of a catalyst as claimed in any one of claims 1 to 3 or a catalyst prepared by the preparation method as claimed in any one of claims 4 to 8, Preferably, the reaction temperature is 200°C-350°C, preferably 280°C-300°C; Preferably, the reaction pressure is 2MPa-5MPa, preferably 2.5MPa-3.5MPa; Preferably, the reaction space velocity is 8000 mL g cat -1 h -1 -36000mL g cat -1 h -1 , preferably 18000mL g cat -1 h -1 -30000mL g cat -1 h -1 .

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