Preparation method of carbon-supported co-mo2c heterojunction catalyst and application of the catalyst in catalyzing conversion of furfural

Abstract

The application discloses a preparation method of a carbon-loaded Co-Mo2C heterojunction catalyst and application of the carbon-loaded Co-Mo2C heterojunction catalyst in catalyzing conversion of furfural. The carbon-loaded Co-Mo2C heterojunction catalyst is obtained by calcining a protein-metal ion precursor under an inert atmosphere through strong alkali modification. The preparation strategy disclosed by the application can control formation of different phases of molybdenum carbide. The strong alkali in the precursor can induce formation of a Mo2C phase, and the precursor without alkali can form a MoC phase. The carbon-loaded Co-Mo2C heterojunction catalyst has the characteristics of a large specific surface area and good hydrogen dissociation capacity, and can specifically adsorb furfural and intermediates, so that efficient conversion of furfural can be realized. The application has the advantages of cheap raw materials, a simple preparation method, low production cost, good cycle performance, and mild catalytic conditions, and is easy to popularize and use.

Description

Technical Field

[0001] This invention relates to the field of materials preparation, and in particular to a method for preparing carbon-supported Co-Mo2C heterojunction catalysts and their application in catalyzing furfural conversion. Background Technology

[0002] Furfural is a hemicellulose obtained by hydrolyzing xylose. More than 1600 chemicals can be synthesized directly or indirectly from furfural, with products used in resins, daily chemicals, pharmaceuticals, and many other fields. In particular, furfuryl alcohol, 2-methylfuran, and furans have extremely wide applications. Developing efficient catalysts for the conversion of furfural into specific products has always been a research hotspot.

[0003] Currently, the commonly used methods for furfural conversion mainly include gas-phase hydrogenation and liquid-phase hydrogenation. Industrially, gas-phase hydrogenation is more commonly used, and the reaction is generally carried out at temperatures above 200℃ and pressures above 3MPa. Furthermore, the catalyst metal is easily lost, causing environmental pollution. In contrast, liquid-phase hydrogenation offers milder reaction conditions, easier separation of the product from the catalyst, and reduces the use of catalysts with significant heavy metal pollution. Based on these advantages, liquid-phase hydrogenation of furfural has become the mainstream research direction.

[0004] In furfural conversion systems, numerous publications and patents have reported on noble metal (platinum, palladium, ruthenium) catalysts. While noble metal catalysts exhibit high hydrogenation activity, they are costly and their selectivity is difficult to control. Non-noble metal (cobalt, copper, nickel) catalysts have industrial potential due to their low cost and availability, but they suffer from low activity, demanding reaction conditions, and difficulty in controlling selectivity. Therefore, the development and preparation of high-performance non-noble metal catalysts has become an urgent problem to be solved. Lee et al. used a carbon-based catalyst derived from ZIF-67 for furfural conversion (Journal of Catalysis 2020, 392:302-312). Although the activity was significantly improved, the selectivity for the target product furan was very low (23.6%), and the catalyst preparation cost was high. Chinese patent document CN114367289A discloses a method for preparing a copper-based bimetallic alloy catalyst, including 1. preparation of SiO2 electrodeposition solution, 2. preparation of copper-cobalt bimetallic alloy electrodeposition solution, and 3. preparation of copper-cobalt bimetallic alloy catalyst. Although this catalyst has achieved high reactivity, its preparation process is complex and its development cost is high.

[0005] In summary, from the perspective of green and sustainable chemistry, there is an urgent need to develop a high-efficiency, low-cost non-precious metal catalyst for the conversion of furfural. Summary of the Invention

[0006] To address the technical problems of low activity, harsh reaction conditions, and difficulty in controlling selectivity of non-precious metals in furfural conversion systems, as well as the high cost and difficulty in controlling selectivity of precious metal preparation, this invention provides a method for preparing a carbon-supported Co-Mo2C heterojunction catalyst. The resulting catalyst, when used to catalyze furfural conversion, can significantly improve the conversion rate and selectivity, and is low in cost, highly efficient, and green and sustainable.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a carbon-supported Co-Mo2C heterojunction catalyst includes the following steps:

[0009] (1) Dissolve molybdenum salt or a mixture of cobalt salt and molybdenum salt in deionized water to obtain a metal salt solution;

[0010] (2) Add the metal salt solution obtained in step (1) to the protein solution to obtain a mixture;

[0011] (3) Add a strong alkali solution to the mixture obtained in step (2), dry it, and obtain a mixed powder precursor. The strong alkali can induce the formation of the Mo2C phase at high temperature. If there is no alkali in the precursor, the MoC phase will be formed at high temperature.

[0012] (4) The mixed powder precursor obtained in step (3) is placed in an inert atmosphere for calcination, then naturally cooled and washed with water to obtain a carbon-supported Co-Mo2C heterojunction catalyst.

[0013] Therefore, this invention utilizes a strong base to modify a protein-metal ion precursor, and obtains a carbon-supported Co-Mo2C heterojunction catalyst by calcination under an inert atmosphere. The resulting carbon-supported Co-Mo2C heterojunction catalyst has the characteristics of large specific surface area and good hydrogen dissociation ability.

[0014] Preferably, in step (1), the cobalt salt is one or more of cobalt nitrate, cobalt chloride, cobalt acetate, or cobalt sulfate; and the molybdenum salt is one or more of sodium molybdate, ammonium molybdate, or potassium molybdate.

[0015] Preferably, in the mixture of molybdenum salt and cobalt salt, the mass ratio of molybdenum salt to cobalt salt is 0.1 to 10:1.

[0016] Preferably, in step (2), the protein solution is one or more of egg white, bovine serum albumin solution or silk protein solution.

[0017] Preferably, in step (3), the strong alkali solution is a sodium hydroxide solution and / or a potassium hydroxide solution, and the concentration of the strong alkali solution is 80-120 mg·mL. -1 More preferably 100 mg·mL -1 .

[0018] Preferably, in step (4), the inert gas is nitrogen or / and argon, the calcination temperature is 600-1000℃, and the calcination time is 1-5h, more preferably 2-4h.

[0019] The application of the above-mentioned carbon-supported Co-Mo2C heterojunction catalyst in the catalytic conversion of furfural.

[0020] Preferably, furfural and a carbon-supported Co-Mo2C heterojunction catalyst are used to catalyze the furfural conversion reaction under reaction solvent and hydrogen gas conditions.

[0021] Preferably, the reaction solvent is one or more of isopropanol, methanol, or ethanol, more preferably isopropanol.

[0022] Preferably, the mass ratio of catalyst to furfural is 1:1 to 100.

[0023] Preferably, the reaction temperature is 140–200°C, more preferably 180–200°C; the reaction time is 3–24 h, more preferably 15–20 h; the hydrogen pressure is 1–4 MPa, more preferably 2–3 MPa; and the stirring speed is 500–700 rpm, preferably 600 rpm.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention utilizes a strong base to modify a protein-metal ion precursor, and obtains a carbon-supported Co-Mo2C heterojunction catalyst by calcination under an inert atmosphere. The resulting carbon-supported Co-Mo2C heterojunction catalyst exhibits a large specific surface area and good hydrogen dissociation capability. Compared with existing technologies, this invention has the following advantages:

[0026] 1. The prepared carbon-supported Co-Mo2C heterojunction catalyst can directly use molecular hydrogen to catalyze the conversion reaction of furfural, and has high reaction activity;

[0027] 2. The prepared carbon-supported Co-Mo2C heterojunction catalyst can specifically adsorb furfural and its intermediates, thus achieving efficient conversion of furfural;

[0028] 3. The non-precious metal catalyst of the present invention has inexpensive raw materials, simple preparation method, low production cost and good recycling performance. Attached Figure Description

[0029] Figure 1 These are scanning electron microscope (SEM) images of Co-Mo2C / CN(a) in Example 1 and Co-MoC / CN(b) in Example 2;

[0030] Figure 2 This is a transmission electron microscope image of Co-Mo2C / CN in Example 1;

[0031] Figure 3 This is a transmission electron microscope image of Co-MoC / CN from Example 2;

[0032] Figure 4 These are the XRD patterns of Co-Mo2C / CN in Example 1 and Co-MoC / CN in Example 2;

[0033] Figure 5 These are the product distribution diagrams of Co-Mo2C / CN(a) in Example 1 and Co-MoC / CN(b) in Example 2 over time.

[0034] Figure 6 This is a graph showing the recycling performance of Co-Mo2C / CN in Example 5;

[0035] Figure 7 This is a gas chromatography chromatogram of the reaction products from Example 1. Detailed Implementation

[0036] The method provided by the present invention will be further described in conjunction with the following embodiments, but the present invention is not limited thereto.

[0037] Example 1

[0038] A method for preparing a carbon-supported Co-Mo2C heterojunction catalyst and its application in catalyzing furfural conversion includes the following steps:

[0039] (1) Place 0.291g of cobalt nitrate, 0.242g of sodium molybdate, and 5mL of deionized water in a 100mL beaker and dissolve to obtain a metal salt solution;

[0040] (2) Place 10g of egg white in a 100mL beaker and stir at room temperature for 5 minutes;

[0041] (3) Add the metal salt solution obtained in step (1) to the egg white obtained in step (2) within 30 minutes, and continue stirring for 5 minutes to obtain a mixture;

[0042] (4) Place 0.4g of sodium hydroxide and 4mL of deionized water in a 100mL beaker and dissolve to obtain a sodium hydroxide solution;

[0043] (5) Quickly drop the sodium hydroxide solution obtained in step (4) into the mixture obtained in step (3) to obtain a black colloid;

[0044] (6) Place the black colloid obtained above into a 60°C oven and dry it overnight;

[0045] (7) Place the dried powder in a porcelain boat and, under nitrogen protection, heat it at 3°C·min. -1The temperature was rapidly increased to 800℃ and held for 2 hours, then allowed to cool naturally.

[0046] (8) The calcined powder was washed with a large amount of water until neutral, and then dried in an oven at 100°C overnight to obtain a carbon-supported Co-Mo2C heterojunction catalyst, labeled as Co-Mo2C / CN;

[0047] (9) In a high-pressure reactor with a 25 mL liner, add 0.1 g of furfural, add 6 mL of isopropanol as solvent, and then add 40 mg of the catalyst prepared in step (8).

[0048] (10) After sealing the reactor, close the outlet valve and introduce hydrogen gas to start heating.

[0049] (11) When the temperature inside the reactor reaches the reaction temperature of 180°C, open the main valve and the inlet valve of the hydrogen cylinder to increase the hydrogen pressure to the reaction pressure of 2MPa, and record the reaction start time.

[0050] (12) After 5 hours, the reaction ends. Close the main valve of the hydrogen cylinder and cool the reactor to room temperature.

[0051] Gas chromatography analysis of the reaction solution showed that the conversion rate of furfural was 100% and the selectivity of furan was 63.03%.

[0052] Figure 1 (a) is a scanning electron microscope image of Co-Mo2C / CN in Example 1; Figure 2 This is a transmission electron microscope image of Co-Mo2C / CN in Example 1; Figure 4 This is the XRD pattern of Co-Mo2C / CN in Example 1; Figure 5 (a) is a time-dependent reaction product distribution diagram of Co-Mo2C / CN in Example 1; Figure 7 This is a gas chromatography chromatogram of the reaction products from Example 1.

[0053] Example 2

[0054] Everything else is the same as in Example 1, except that:

[0055] In step (4), sodium hydroxide is not added; that is, only 4 mL of deionized water is placed in a 100 mL beaker to obtain a pure aqueous solution.

[0056] Step (5) is to quickly drop the pure aqueous solution obtained in step (4) into the mixture obtained in step (3) to obtain a yellow mixture.

[0057] Step (6) is to place the yellow mixture obtained above into a 60°C oven and dry it overnight;

[0058] The product obtained in step (8) is a carbon-supported Co-MoC catalyst, labeled as Co-MoC / CN.

[0059] Gas chromatography analysis of the reaction solution showed that the conversion rate of furfural was 97.19% and the selectivity of furan was 4.74%.

[0060] Figure 1 (b) is a scanning electron microscope image of Co-MoC / CN in Example 2; Figure 3 This is a transmission electron microscope image of Co-MoC / CN from Example 2; Figure 4 This is the XRD pattern of Co-MoC / CN in Example 2; Figure 5 (b) is a time-dependent distribution diagram of the reaction products of Co-MoC / CN in Example 2.

[0061] Example 3

[0062] Everything else is the same as in Example 1, except that:

[0063] Step (12): Change the reaction time to 15h.

[0064] Gas chromatography analysis of the reaction solution showed that the conversion rate of furfural was 100% and the selectivity of furan was 72.21%.

[0065] Example 4

[0066] Everything else is the same as in Example 1, except that:

[0067] Step (1) is as follows: Place 0g of cobalt nitrate, 0.242g of sodium molybdate, and 5mL of deionized water in a 100mL beaker and dissolve them to obtain a metal salt solution;

[0068] The product obtained in step (8) is a carbon-supported Mo2C catalyst, labeled as Mo2C / CN.

[0069] Gas chromatography analysis of the reaction solution showed that the conversion rate of furfural was 46.61% and the selectivity of furan was 39.52%.

[0070] Example 5

[0071] The Co-Mo2C / CN catalyst obtained in Example 1 was used to conduct a cyclic experiment on the Co-Mo2C / CN in the furfural conversion reaction. 40 mg of catalyst, 0.1 g of furfural, and 6 mL of isopropanol were placed in a high-pressure reactor for reaction at 180 °C for 5 h and a hydrogen pressure of 2 MPa.

[0072] Gas chromatography analysis of the reaction mixture showed a furfural conversion rate of 100% and a furan selectivity of 63.03%. The catalyst in the reaction mixture was centrifuged and dried before the next experiment. After four furfural conversion experiments, the furfural conversion rate and furan selectivity remained stable. Figure 6 As shown.

[0073] This indicates that the catalyst in Example 1 did not lose activity during the reaction. Therefore, the non-precious metal catalyst in Example 1 has high stability and is expected to replace precious metal catalysts in the furfural conversion reaction.

Claims

1. A method for preparing a carbon-supported Co-Mo2C heterojunction catalyst, characterized in that, Includes the following steps: (1) Dissolve a mixture of cobalt salt and molybdenum salt in deionized water, wherein the mass ratio of molybdenum salt to cobalt salt is 0.1 to 10:1, wherein the cobalt salt is one or more of cobalt nitrate, cobalt chloride, cobalt acetate or cobalt sulfate; wherein the molybdenum salt is one or more of sodium molybdate, ammonium molybdate or potassium molybdate, to obtain a metal salt solution; (2) Add the metal salt solution obtained in step (1) to the protein solution, wherein the protein solution is one or more of egg white, bovine serum albumin solution or silk protein solution, to obtain a mixture; (3) Add a strong alkali solution dropwise to the mixture obtained in step (2), wherein the strong alkali solution is a sodium hydroxide solution and / or a potassium hydroxide solution, and the concentration of the strong alkali solution is 80-120 mg·mL. -1 The strong alkaline solution induces the formation of the Mo2C phase, which is then dried to obtain a mixed powder precursor. (4) The mixed powder precursor obtained in step (3) is placed in an inert atmosphere for calcination, then naturally cooled and washed with water to obtain a carbon-supported Co-Mo2C heterojunction catalyst.

2. The method for preparing the carbon-supported Co-Mo2C heterojunction catalyst according to claim 1, characterized in that, In step (3), the strong alkali solution is a sodium hydroxide solution and / or a potassium hydroxide solution, and the concentration of the strong alkali solution is 80-120 mg·mL. -1 .

3. The method for preparing the carbon-supported Co-Mo2C heterojunction catalyst according to claim 1, characterized in that, In step (4), the inert gas is nitrogen or / and argon, the calcination temperature is 600~1000℃, and the calcination time is 1~5 h.

4. The application of the carbon-supported Co-Mo2C heterojunction catalyst obtained by the preparation method according to any one of claims 1 to 3 in the catalytic conversion of furfural.

5. The application according to claim 4, characterized in that, Furfural and carbon-supported Co-Mo2C heterojunction catalysts were used to catalyze the conversion of furfural in a reaction solvent and under hydrogen gas conditions.

6. The application according to claim 5, characterized in that, The reaction solvent is one or more of isopropanol, methanol or ethanol; the mass ratio of catalyst to furfural is 1:1 to 100.

7. The application according to claim 5, characterized in that, The reaction temperature is 140~200℃; the reaction time is 3~24h; the hydrogen pressure is 1~4 MPa; and the stirring speed is 500-700 rpm.

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