Preparation method of Pd-based bimetallic catalyst and application of Pd-based bimetallic catalyst in preparation of formic acid by hydrogenation of carbon dioxide

Abstract

The invention discloses a preparation method of a Pd-based bimetallic catalyst and application of the Pd-based bimetallic catalyst in preparation of formic acid through hydrogenation of carbon dioxide, and relates to the technical field of catalysts, a Pd-S5 precursor, a Si-doped alumina carrier and a second metal precursor are dissolved in ultrapure water, and then heating, cooling, suction filtration, washing, drying, roasting and grinding are performed to obtain the catalyst. The method has the advantages of mild conditions in the preparation process, meeting of the requirements of green chemistry, easy operation, realization of reduction of carbon dioxide into formic acid in the presence of alkali, and strong practicality.

Description

Technical Field

[0001] The present application relates to the field of catalyst technology, and in particular to a method for preparing a Pd-based bimetallic catalyst and its application in the hydrogenation of carbon dioxide to formic acid. Background Art

[0002] Against the backdrop of a sharp increase in global carbon dioxide, renewable energy is essential to maintaining world economic growth. Hydrogen has received widespread attention as a clean fuel, but large-scale hydrogen storage and controlled release remain issues.

[0003] Existing theoretical studies have shown that the reaction of producing formic acid by hydrogenation of carbon dioxide and producing hydrogen by dehydrogenation of formic acid can be used as a sustainable hydrogen storage system. Supported heterogeneous hydrogen storage catalysts based on formic acid have the advantages of good recyclability and easy separation, and are considered to be the catalysts with the most promotion prospects, mainly involving Ru-based, Au-based and Pd-based catalysts, among which Pd-based catalysts have attracted much attention due to their unique ability to adsorb and dissociate hydrogen.

[0004] At present, most of the research on Pd-based catalysts for the hydrogenation of carbon dioxide to formic acid is focused on Pd-based single metal catalysts. Although some progress has been made, bimetallic catalysts show higher activity and selectivity than single component catalysts for the catalytic functionalization of carbon dioxide. Since bimetallic nanoparticles contain two metals and their unique interactions, the selection of bimetallic nanoparticles is more flexible compared to single metals, and bimetallic nanoparticles provide important opportunities for maximizing catalytic activity and selectivity.

[0005] From the perspective of reducing costs, introducing a second metal into the catalyst can effectively reduce the amount of precious metal Pd used, which is conducive to the practical and industrial development of the catalyst.

[0006] However, the existing catalysts used for the hydrogenation of carbon dioxide to produce formic acid include perovskite catalysts (CN202110668877.8), PdAgMOF catalysts (CN202311001327.6, the TON value of CO2 catalytic hydrogenation reaction can reach 3000~10000), and PdAuC catalysts (CN202311061206.0; the TON value of CO2 catalytic hydrogenation reaction can reach 2000~7000).

[0007] However, both PdAgMOF catalysts and PdAuC catalysts require the use of Pd in ​​combination with precious metals Ag and Au, which is not effective in reducing catalyst costs. In addition, the existing catalysts do not disclose the concentration of formic acid in the product obtained after catalysis, and cannot accurately reflect the actual effect of using them for the hydrogenation of carbon dioxide to produce formic acid.

[0008] The information disclosed in the background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0009] In response to the above technical problems, the present application provides a method for preparing a Pd-based bimetallic catalyst and its application in the hydrogenation of carbon dioxide to formic acid. The preparation process of the method has mild conditions, meets the requirements of green chemistry, and is easy to operate. At the same time, it can reduce carbon dioxide to formic acid in the presence of an alkali, and has strong practicality.

[0010] The present application provides a method for preparing a Pd-based bimetallic catalyst, comprising: The Pd-S5 precursor, the Si-doped alumina support, and the second metal precursor are dissolved in ultrapure water, and then heated, cooled, filtered, washed, dried, calcined, and ground to obtain a catalyst; The second metal precursor is any one of RuCl3, H2IrCl6, Rh(NO3)3, Bi(NO3)5·5H2O, Ce(NO3)3·6H2O, La(NO3)3·6H2O, Cu(NO3)2·3H2O, and Pt(NO3)2.

[0011] Preferably, the total metal loading of Pd and the second metal in the obtained catalyst is 0.5-3.5 wt %; preferably 1.0 wt %.

[0012] Preferably, the mass ratio of Pd to the second metal is 3:1~1:3; specifically, 3:1, 2:1, 1:1, 1:2, 1:3.

[0013] Preferably, the heating temperature is 60° C. and the heating time is 3 h; the roasting temperature is 250° C. and the roasting time is 3 h.

[0014] Another aspect of the present application also provides a catalyst for preparing formic acid by hydrogenation of carbon dioxide obtained by the above method, which is 1.0wt% Pd x A y / SiAl, wherein A is any one of Bi, Ce, La, Cu, Rh, Ru, Ir, and Pt; x=0.25~0.75; y=0.25~0.75 and x+y=1.

[0015] Preferably, 1.0wt% 0.75 R 0.25 / SiAl, 1.0wt% Pd 0.5 R 0.5 / SiAl, 1.0wt% Pd 0.25 R 0.75 / SiAl, 1.0wt% Pd0.75 Cu 0.25 / SiAl, 1.0wt% Pd 0.66 Cu 0.34 / SiAl, 1.0wt% Pd 0.5 Cu 0.5 / SiAl, 1.0wt%Pd 0.5 Bi 0.5 / SiAl, 1.0wt% Pd 0.5 Ce 0.5 / SiAl, 1.0wt% Pd 0.5 La 0.5 / SiAl, 1.0wt% Pd 0.5 Ru 0.5 / SiAl, 1.0wt% Pd 0.5 Ir 0.5 / SiAl, 1.0wt% Pd 0.5 Pt 0.5 / SiAl.

[0016] Preferably, 1.0wt% Pd 0.25 R 0.75 / SiAl or 1.0wt% Pd 0.5 Cu 0.5 / SiAl.

[0017] Another aspect of the present application also provides a method for preparing formic acid by hydrogenating carbon dioxide, comprising: Any of the above catalysts is used as a catalyst for preparing formic acid by hydrogenating carbon dioxide, and a formic acid-containing product is prepared by reaction in an alkaline environment with hydrogen and carbon dioxide introduced.

[0018] Preferably, the reaction temperature is 80-120°C, the reaction time is 3-24h, and the reaction pressure is 2-6MPa; Preferably, the pressure ratio of hydrogen to carbon dioxide during the reaction is 1:1.

[0019] Preferably, the obtained formic acid-containing product is filtered and then subjected to chromatographic analysis to detect the formic acid content.

[0020] Preferably, the chromatographic column model used in the chromatographic analysis is: AS22 4*250mm+AG22 4*50mm; the suppressor used is AERS 500 4mm suppressor.

[0021] Preferably, the chromatographic analysis injection conditions are: injection volume of 725ul for 30min.

[0022] The beneficial effects of this application include: 1) The present application provides a method for preparing a Pd-based bimetallic catalyst and its application in the hydrogenation of carbon dioxide to formic acid. The second non-precious metal used in the method can be Bi, Ce, La, Cu, Rh, Ru, Ir, which can effectively reduce the cost of the catalyst. The preparation method is simple and easy to operate, the preparation conditions are mild and have wide applicability, which meets the requirements of green chemistry and is more conducive to promotion and application. The metal loading of the catalyst obtained by this method is close to the theoretical loading, indicating that the method can stably load the metal particles on the carrier.

[0023] 2) The preparation method of the Pd-based bimetallic catalyst provided in this application and its application in the hydrogenation of carbon dioxide to formic acid. The Pd-based bimetallic catalytic material obtained by this method can realize the efficient reduction reaction of carbon dioxide in a high-pressure reactor with high selectivity. The concentration of formic acid in the product obtained after catalysis can reach 74.708 mg / L, and the TOF can reach 8.6 h -1 Compared with Pd-based single metal catalysts, the activity is improved, the device is simple, the catalyst can be recycled, the reaction conditions are mild, and the energy consumption and cost are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The 1.0wt% Pd in ​​Example 1 is provided for this application. x R y / XRD diagram of SiAl-supported catalyst; in the figure, x=0.25; y=0.75 in line 1; x=0.5; y=0.5 in line 2; x=0.75; y=0.25 in line 3; the unnumbered lines are SiAl test result lines; Figure 2 The 1.0wt% Pd in ​​Example 1 is provided for this application. x Cu z / XRD diagram of SiAl-supported catalyst; in line 1, x=0.25; z=0.75; in line 2, x=0.66; z=0.34; in line 3, x=0.75; z=0.25; the unnumbered lines are SiAl test result lines; DETAILED DESCRIPTION The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention fall within the protection scope of the present invention.

[0025] Example Unless otherwise specified, the materials and instruments used in the following examples were obtained from commercial channels; the detection methods used were all existing methods unless otherwise specified.

[0026] Example 1 Preparation of Pd-based bimetallic catalyst (1) According to the theoretical loading amount shown in Table 1, weigh the Pd-S5 precursor (tetraamminepalladium nitrate), the second metal precursor and the Si-doped alumina carrier (SiAl), dissolve them in ultrapure water in sequence, and heat and stir at 60°C for 3 h.

[0027] (2) After the solution is cooled to room temperature, the obtained product is filtered, washed and dried.

[0028] (3) The product obtained in step 2 was placed in a muffle furnace at 250°C and calcined for 3 h. The product was taken out and ground to obtain a Pd-based bimetallic catalyst.

[0029] The second metals in Table 1 are Bi, Ce, La, Cu, Rh, Ru, and Ir. The corresponding second metal precursors are RuCl3, H2IrCl6, Rh(NO3)3, Bi(NO3)5·5H2O, Ce(NO3)3·6H2O, La(NO3)3·6H2O, and Cu(NO3)2·3H2O.

[0030] Table 1 According to the method in Example 1 and the composition shown in Table 1, catalyst samples of Examples 1-1 to 8 were prepared, and quantitative determination was performed using an inductively coupled plasma emission spectrometer. The actual loading amounts of the catalyst samples of Examples 1-1 to 8 obtained are shown in the actual loading amount results in Table 1: It can be seen from the table that the actual loading amount is very close to the theoretical loading amount, which proves that the Pd-based bimetallic catalyst preparation method provided by the present invention can stably load metal particles on the carrier and has excellent reproducibility.

[0031] Catalysts numbered as Examples 1-9 to 14 were prepared according to the method in Example 1, and the metal loading was 1.0 wt %. In the catalyst of Example 1-9, Pd:Rh=0.75:0.25; in the catalyst of Example 1-10, Pd:Rh=0.5:0.5; in the catalyst of Example 1-11, Pd:Rh=0.25:0.75; in the catalyst of Example 1-12, Pd:Cu=0.75:0.25; in the catalyst of Example 1-13, Pd:Cu=0.66:0.34; in the catalyst of Example 1-14, Pd:Cu=0.5:0.5.

[0032] Comparative Example 1 The difference from Example 1 is that only one metal is used for loading, and the loaded metals used are Pd, Rh, and Cu respectively; the metal element-containing reagents used in step 1 are Pd-S5 precursor (tetraammine palladium nitrate), Rh(NO3)3, and Cu(NO3)2·3H2O respectively, and the obtained catalysts are numbered as Comparative Examples 1-1 to 3. The metal loading amount in the obtained catalysts is 1.0wt%.

[0033] Example 2 The Pd-based bimetallic catalyst obtained in Example 1 is used to catalyze the hydrogenation of carbon dioxide to produce formic acid The catalyst samples No. 1-9 to No. 14 obtained in Example 1 and the catalyst samples No. 1-1 to No. 3 obtained in Comparative Example 1 were dispersed in a mixed solution of 0.1 mol / L KOH and ethanol, respectively, and placed in a high-pressure reactor. The flow rates of carbon dioxide and hydrogen were adjusted in turn, and the total reaction pressure was controlled to be 4 MPa according to a pressure ratio of hydrogen to carbon dioxide of 1:1. The reaction temperature was set at 100°C, and the reaction was carried out for 3 h under stirring. After the reaction was completed, the reaction was filtered, and the obtained filtrate was subjected to chromatographic analysis under the following conditions to determine the yield of formic acid obtained by each catalyst as shown in Table 2.

[0034] The chromatographic analysis conditions of the filtrate were: AS22 4*250mm+AG22 4*50mm chromatographic columns, AERS 500 4mm suppressor, and injection volume of 725ul for 30min.

[0035] Table 2 The above table reflects the catalytic activity of each catalyst sample. The above catalysts are all prepared under exactly the same steps, and the reaction conditions for catalyzing carbon dioxide to formic acid are also kept consistent. From the data in Table 2, it can be seen that the single metal-loaded Rh / SiAl and Cu / SiAl have almost no catalytic activity, but after introducing them as the second metal component to prepare the Pd-based bimetallic catalyst, the activity of the obtained catalyst is improved to varying degrees compared with 1.0wt% Pd / SiAl after the catalyst is prepared in different proportions, proving that the Pd-based bimetallic catalyst obtained by the preparation method provided by the present invention has a good catalytic effect for the hydrogenation of carbon dioxide to formic acid. In Table 2, TOF is the conversion frequency of formic acid, which is the ratio of the turnover number (TON) to time.

[0036] The reaction conditions for catalyzing the hydrogenation of carbon dioxide to produce formic acid using the obtained catalyst are easy to control, the operation cost is low, and the reaction conditions are mild.

[0037] The catalysts numbered as Example 1-11, Example 1-10, and Example 1-9 were selected and subjected to XRD detection together with the carrier. The detection method was based on the commonly used operation process in the field. The detection sample size was 0.1 g and the results were as follows: Figure 1 As shown in the figure, it can be seen that during the precious metal loading process, the carrier remains intact. In addition, no new characteristic diffraction peaks of Pd and Rh were found in the catalyst after loading PdRh, indicating that the metal is highly dispersed on the carrier and the particle size is small.

[0038] The catalysts numbered as Example 1-12, Example 1-13, and Example 1-14 were selected and subjected to XRD detection together with the carrier. The detection method was in accordance with the commonly used operation process in the field, and the detection sample size was 0.1 g. The results obtained are as follows Figure 2 As shown in the figure, it can be seen that the carrier remains intact during the precious metal loading process. In addition, no new characteristic diffraction peaks of Pd and Cu were found in the catalyst after loading PdCu, which may be because the Pd and Cu loading is low and highly dispersed on the carrier with small particle size.

[0039] Example 3 The difference between the catalyst numbered as Example 1-1 obtained in Example 1 is that the second metal precursor used is Pt(NO3) 2。

[0040] Example 4 The difference between the catalyst numbered as Example 1-1 and the catalyst obtained in Example 1 is that the metal loading is 0.5 wt %, and Pd:Bi=3:1.

[0041] Example 5 The difference between the catalyst numbered as Example 1-1 and the catalyst obtained in Example 1 is that the metal loading is 3.5 wt %, and Pd:Bi=1:3.

[0042] Example 6 The difference between the catalyst obtained in Example 1 and the catalyst numbered as Example 1-1 is that: Pd:Bi=2:1; Example 7 The difference between the catalyst obtained in Example 1 and the catalyst numbered as Example 1-1 is that: Pd:Bi=1:1; Example 8 The difference between the catalyst obtained in Example 1 and the catalyst numbered Example 1-1 is that Pd:Bi=1:2.

[0043] Example 9 The difference between the catalysts numbered in Example 1-9 used in Example 2 is that the reaction pressure is 2 MPa; the reaction temperature is 80° C. and the reaction time is 3 h.

[0044] Example 10 The difference between the catalysts numbered in Example 1-9 used in Example 2 is that the reaction pressure is 6 MPa; the reaction temperature is 120° C., and the reaction time is 3 h.

[0045] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a Pd-based bimetallic catalyst, characterized in that: include: The Pd-S5 precursor, the Si-doped alumina support, and the second metal precursor are dissolved in ultrapure water, and then heated, cooled, filtered, washed, dried, calcined, and ground to obtain a catalyst; The second metal precursor is any one of RuCl3, H2IrCl6, Rh(NO3)3, Bi(NO3)5·5H2O, Ce(NO3)3·6H2O, La(NO3)3·6H2O, Cu(NO3)2·3H2O, and Pt(NO3)2.

2. The method for preparing a Pd-based bimetallic catalyst according to claim 1, characterized in that: The total metal loading of Pd and the second metal in the obtained catalyst is 0.5-3.5 wt %.

3. The method for preparing a Pd-based bimetallic catalyst according to claim 1, characterized in that: The mass ratio of Pd to the second metal is 3:1~1:

3.

4. The method for preparing a Pd-based bimetallic catalyst according to claim 1, characterized in that: The heating temperature is 60°C and the heating time is 3 h; the calcination temperature is 250°C and the calcination time is 3 h.

5. A catalyst for preparing formic acid by hydrogenating carbon dioxide, prepared by the method for preparing a Pd-based bimetallic catalyst as claimed in any one of claims 1 to 4, characterized in that: 1.0wt% Pd x A y / SiAl, wherein A is any one of Bi, Ce, La, Cu, Rh, Ru, Ir, and Pt; x=0.25~0.75; y=0.25~0.75 and x+y=1.

6. The catalyst according to claim 5, characterized in that 1.0wt% 0.75 R 0.25 / SiAl, 1.0wt%Pd 0.5 R 0.5 / SiAl, 1.0wt% Pd 0.25 R 0.75 / SiAl, 1.0wt% Pd 0.75 Cu 0.25 / SiAl, 1.0wt% Pd 0.66 Cu 0.34 / SiAl, 1.0wt% Pd 0.5 Cu 0.5 / SiAl, 1.0wt% Pd 0.5 Bi 0.5 / SiAl, 1.0wt% Pd 0.5 Ce 0.5 / SiAl, 1.0wt%Pd 0.5 La 0.5 / SiAl, 1.0wt% Pd 0.5 Ru 0.5 / SiAl, 1.0wt% Pd 0.5 Ir 0.5 / SiAl, 1.0wt% Pd 0.5 Pt 0.5 / SiAl.

7. The catalyst according to claim 5, characterized in that 1.0wt% Pd 0.25 R 0.75 / SiAl or 1.0wt%Pd 0.5 Cu 0.5 / SiAl.

8. A method for preparing formic acid by hydrogenating carbon dioxide, characterized in that: include: The catalyst according to any one of claims 5 to 7 is used as a catalyst for preparing formic acid by hydrogenation of carbon dioxide, and a formic acid-containing product is prepared by reaction in an alkaline environment in which hydrogen and carbon dioxide are introduced.

9. The method for preparing formic acid by hydrogenating carbon dioxide according to claim 8, characterized in that: The reaction temperature is 80~120°C, the reaction time is 3~24h, and the reaction pressure is 2~6MPa.

10. The method for preparing formic acid by hydrogenating carbon dioxide according to claim 8, characterized in that: During the reaction, the pressure ratio of hydrogen to carbon dioxide is 1:1.

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