Palladium supported nitrogen-doped carbon material, and preparation method and application thereof

Abstract

The application provides a palladium-loaded nitrogen-doped carbon material and a preparation method and application thereof, and belongs to the technical field of organic synthesis. In the application, imidazole-based polyionic liquid can be highly complexed with metal palladium, so that the metal palladium has good dispersibility, and the nitrogen-containing organic matter and the imidazole-based polyionic liquid have strong action with the metal palladium during calcination, so that the metal palladium is not allowed to agglomerate during the calcination process. Therefore, the dispersibility of the metal palladium is increased by the imidazole-based polyionic liquid and the nitrogen-containing organic matter, so that the active sites can be increased. In addition, the imidazole-based polyionic liquid and the nitrogen-containing compound can fill the space of the polymer generated by the phenol compound and the aldehyde, so that the stability of the structure of the palladium-loaded nitrogen-doped carbon material is increased. In addition, due to the existence of the imidazole-based polyionic liquid and the nitrogen-containing organic matter, rich mesoporous channels can be formed during the calcination process, so that the palladium-loaded nitrogen-doped carbon material is not easy to be blocked.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a palladium-loaded nitrogen-doped carbon material and a preparation method and application thereof. BACKGROUND

[0002] In organic synthesis, catalytic hydrogenation reaction has advantages such as stable product quality and green safety. The catalyst has an important influence on the catalytic hydrogenation reaction. The active component of the hydrogenation catalyst is easy to lose activity (poisoning) due to the action of some foreign components, which is often permanent deactivation. For example, the foreign components and the active component of the catalyst undergo chemical reaction or ion exchange, resulting in changes in the active component. The active component is covered and gradually deactivated, which belongs to non-permanent deactivation. For example, the carbon deposition generated in the reaction process can cover the active component or block the pores of the catalyst, so that the reactants cannot contact the active component.

[0003] The traditional palladium catalyst has high activity, but some raw materials are easy to generate green oil through polymerization on the surface of the catalyst, thereby blocking the pores of the catalyst, resulting in non-permanent deactivation of the catalyst. Therefore, the traditional palladium-based catalyst has the problem of poor stability. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a palladium-loaded nitrogen-doped carbon material and a preparation method and application thereof. The palladium-loaded nitrogen-doped carbon material prepared by the present application has high activity and good stability when used as a catalyst.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] The present application provides a preparation method of a palladium-loaded nitrogen-doped carbon material, comprising the following steps:

[0007] The imidazole-based polyionic liquid, the nitrogen-containing organic matter, the phenolic compound and the aldehyde are subjected to phenolic aldehyde condensation reaction under alkaline conditions to obtain a nitrogen-doped phenolic aldehyde condensate solution;

[0008] The nitrogen-doped phenolic aldehyde condensate solution is diluted, and the pH value of the obtained diluted solution is adjusted to alkaline to obtain a nitrogen-doped phenolic aldehyde condensate alkaline dilution solution;

[0009] The nitrogen-doped phenolic aldehyde condensate alkaline dilution solution is mixed with a palladium salt to perform gelation reaction to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0010] The palladium-loaded nitrogen-doped carbon material precursor is calcined to obtain the palladium-loaded nitrogen-doped carbon material.

[0011] Preferably, the imidazole-based polyionic liquid comprises poly(vinyl dodecylimidazole iodide), poly(vinyl dodecylimidazole bromide), poly(1-hexyl-3-vinylimidazole bromide), poly(1-vinyl-3-ethylimidazole bromide), or poly(1-vinyl-3-ethylimidazole hexafluorophosphate).

[0012] The nitrogen-containing organic compound comprises melamine, aniline, pyrrole, or o-phenanthroline.

[0013] The phenolic compound comprises 2-bromophenol, hydroquinone, 2-chlorophenol, or p-nitrophenol.

[0014] The aldehyde comprises formaldehyde, glutaraldehyde, or succindialdehyde.

[0015] Preferably, the molar ratio of the imidazole-based polyionic liquid to the nitrogen-containing organic compound is 1:(0.5-3); the molar ratio of the imidazole-based polyionic liquid to the phenolic compound is 1:(0.5-3); and the molar ratio of the imidazole-based polyionic liquid to the aldehyde is 1:(1-4).

[0016] Preferably, the temperature of the phenolic condensation reaction is 50-110℃, and the holding time is 0.5-4h; and the pH value of the alkaline condition is 8-10.

[0017] Preferably, the dilution ratio of the nitrogen-doped phenolic condensate solution is 1-5 times; and the pH value of the alkaline dilution solution of the nitrogen-doped phenolic condensate is 8-14.

[0018] Preferably, the palladium salt is palladium chloride, palladium nitrate, or palladium sulfate; and the mass percentage of the palladium salt in the alkaline dilution solution of the nitrogen-doped phenolic condensate is 0-7% and is not 0.

[0019] Preferably, the temperature of the gelation reaction is 50-150℃, and the time is 1-10 days.

[0020] Preferably, the temperature of the calcination is 300-900℃, and the time is 1-10h.

[0021] The present application provides a palladium-loaded nitrogen-doped carbon material prepared by the preparation method described in the above scheme, which comprises a nitrogen-doped carbon material and palladium metal nanoparticles loaded on the nitrogen-doped carbon material; and the nitrogen-doped carbon material has a phenolic condensate organic skeleton structure.

[0022] The present application provides an application of the palladium-loaded nitrogen-doped carbon material described in the above scheme as a catalyst in the catalytic hydrogenation of acetylene to ethylene.

[0023] The application provides a preparation method of a palladium-loaded nitrogen-doped carbon material, comprising the following steps: performing a phenolic aldehyde condensation reaction on an imidazole-based polyionic liquid, a nitrogen-containing organic compound, a phenol compound and an aldehyde under alkaline conditions to obtain a nitrogen-doped phenolic aldehyde condensate solution; diluting the nitrogen-doped phenolic aldehyde condensate solution, adjusting the pH value of the obtained diluent to alkaline to obtain a nitrogen-doped phenolic aldehyde condensate alkaline diluent; mixing the nitrogen-doped phenolic aldehyde condensate alkaline diluent with a palladium salt to perform a gelation reaction to obtain a palladium-loaded nitrogen-doped carbon material precursor; and calcining the palladium-loaded nitrogen-doped carbon material precursor to obtain the palladium-loaded nitrogen-doped carbon material.

[0024] In addition, the imidazole-based polyionic liquid and the nitrogen-containing organic compound are used as a support template in the application, the phenol compound and the aldehyde are polymerized into particles using the imidazole-based polyionic liquid and the nitrogen-containing organic compound as a template (the particles are formed by directly self-assembling the polyionic liquid), and the particles do not need to be filtered and recovered for reuse, which can effectively improve the problem of difficult recovery of the catalyst; the particles are formed by directly self-assembling the polyionic liquid without a support carrier, and the cost can be reduced; and the preparation method provided by the application is simple in operation, the raw materials are easy to obtain, and industrial production can be easily realized. DETAILED DESCRIPTION

[0025] The application provides a preparation method of a palladium-loaded nitrogen-doped carbon material, comprising the following steps:

[0026] performing a phenolic aldehyde condensation reaction on an imidazole-based polyionic liquid, a nitrogen-containing organic compound, a phenol compound and an aldehyde under alkaline conditions to obtain a nitrogen-doped phenolic aldehyde condensate solution;

[0027] diluting the nitrogen-doped phenolic aldehyde condensate solution, adjusting the pH value of the obtained diluent to alkaline to obtain a nitrogen-doped phenolic aldehyde condensate alkaline diluent;

[0028] mixing the nitrogen-doped phenolic aldehyde condensate alkaline diluent with a palladium salt to perform a gelation reaction to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0029] The palladium loaded nitrogen-doped carbon material precursor is calcined to obtain the palladium loaded nitrogen-doped carbon material.

[0030] In the present application, the imidazole-based polyionic liquid, the nitrogen-containing organic compound, the phenolic compound and the aldehyde are subjected to phenolic aldehyde condensation reaction under alkaline conditions to obtain a nitrogen-doped phenolic aldehyde condensate solution.

[0031] In the present application, the imidazole-based polyionic liquid preferably comprises poly(vinyl dodecylimidazole iodide), poly(vinyl dodecylimidazole bromide), poly(1-hexyl-3-vinylimidazole bromide), poly(1-vinyl-3-ethylimidazole bromide) or poly(1-vinyl-3-ethylimidazole hexafluorophosphate), and is further preferably poly(vinyl dodecylimidazole bromide); the nitrogen-containing organic compound preferably comprises melamine, aniline, pyrrole or o-phenanthroline, and is further preferably melamine; the phenolic compound preferably comprises 2-bromophenol, hydroquinone, 2-chlorophenol or p-nitrophenol, and is further preferably 2-bromophenol; and the aldehyde preferably comprises formaldehyde, glutaraldehyde or succindialdehyde, and is further preferably formaldehyde.

[0032] In the present application, the molar ratio of the imidazole-based polyionic liquid to the nitrogen-containing organic compound is preferably 1:(0.5-3), and is further preferably 1:(1-2); the molar ratio of the imidazole-based polyionic liquid to the phenolic compound is preferably 1:(0.5-3), and is further preferably 1:(1-2); and the molar ratio of the imidazole-based polyionic liquid to the aldehyde is preferably 1:(1-4), and is further preferably 1:(1.5-3). In the present application, the imidazole-based polyionic liquid can be highly complexed with the metal palladium, so that the metal palladium has good dispersibility, and the nitrogen-containing organic compound and the imidazole-based polyionic liquid have strong force with the metal palladium during calcination, so that the metal palladium is not aggregated during calcination. Therefore, the present application increases the dispersibility of the metal palladium by the imidazole-based polyionic liquid and the nitrogen-containing organic compound, so as to increase the active sites; in addition, the imidazole-based polyionic liquid and the nitrogen-containing compound can fill the space of the polymer generated by the phenolic compound and the aldehyde, so as to increase the stability of the structure of the palladium loaded nitrogen-doped carbon material, and due to the presence of the imidazole-based polyionic liquid and the nitrogen-containing organic compound, abundant mesoporous channels can be formed during calcination, so that the palladium loaded nitrogen-doped carbon material is not easily blocked. Therefore, the palladium loaded nitrogen-doped carbon material prepared by the present application has high activity and good stability when used as a catalyst.

[0033] In the present application, the pH value of the alkaline condition is preferably 8-10, further preferably 8.5-9.5. The present application preferably uses a sodium hydroxide solution to adjust the pH value; the concentration of the sodium hydroxide solution is preferably 0.5-3 mol / L, further preferably 0.8-2.5 mol / L, and more preferably 1.2-2.2 mol / L. In the present application, the alkaline condition can initiate the reaction to allow the phenolic compound and the aldehyde to undergo a phenolic aldehyde condensation reaction.

[0034] In the present application, the temperature of the phenolic aldehyde condensation reaction is preferably 50-110℃, further preferably 70-90℃, and more preferably 75-85℃; the holding time of the phenolic aldehyde condensation reaction is preferably 0.5-4 h, further preferably 0.5-2 h, and more preferably 1-1.5 h. In the present application, the phenolic aldehyde condensation reaction is preferably carried out by water bath heating under a condensation reflux state. In the present application, the phenolic aldehyde condensation reaction is preferably carried out under stirring; the stirring speed is preferably 800-1000 r / min, further preferably 850-950 r / min, and more preferably 880-930 r / min. In the present application, during the phenolic aldehyde condensation reaction, the phenolic compound and the aldehyde undergo a phenolic aldehyde condensation reaction, and the imidazole-based polyionic liquid and the nitrogen-containing organic matter are also doped on the polymer, respectively.

[0035] After obtaining the nitrogen-doped phenolic aldehyde condensate solution, the present application dilutes the nitrogen-doped phenolic aldehyde condensate solution, adjusts the pH value of the obtained dilution liquid to be alkaline, and obtains a nitrogen-doped phenolic aldehyde condensate alkaline dilution liquid.

[0036] In the present application, the dilution multiple of the nitrogen-doped phenolic aldehyde condensate solution is preferably 1-5 times, further preferably 1.5-4.5 times, and more preferably 2-4 times; the dilution solvent preferably includes anhydrous ethanol. By diluting the nitrogen-doped phenolic aldehyde condensate solution, the present application allows the phenolic aldehyde condensation reaction to proceed slowly, and can obtain a palladium-loaded nitrogen-doped carbon material with regular shape, which is beneficial to improve the catalytic activity and stability of the palladium-loaded nitrogen-doped carbon material.

[0037] In the present application, the pH value of the nitrogen-doped phenolic aldehyde condensate alkaline dilution liquid is preferably 8-14, and further preferably 8-9. The present application preferably uses a sodium hydroxide solution to adjust the pH value of the obtained dilution liquid to be alkaline; the concentration of the sodium hydroxide solution is preferably 1-20 mol / L, further preferably 5-15 mol / L, and more preferably 7-12 mol / L. By adjusting the obtained dilution liquid to be alkaline, the present application can supplement the alkaline environment required for the phenolic aldehyde condensation reaction.

[0038] After obtaining the alkaline dilution of the nitrogen-doped phenolic condensate, the present application mixes the alkaline dilution of the nitrogen-doped phenolic condensate with a palladium salt to perform a gelation reaction, thereby obtaining a palladium-loaded nitrogen-doped carbon material precursor.

[0039] In the present application, the palladium salt is preferably palladium chloride, palladium nitrate or palladium sulfate, and is further preferably palladium sulfate; the mass percentage of the palladium salt in the alkaline dilution of the nitrogen-doped phenolic condensate is preferably 0-7% and is not 0, and is further preferably 0-5% and is not 0, and is more preferably 1-4%. In the present application, the temperature of the gelation reaction is preferably 50-150℃, and is further preferably 70-100℃, and is more preferably 80-90℃; the time of the gelation reaction is preferably 1-10 days, and is further preferably 2-7 days, and is more preferably 3-5 days. The present application preferably performs the gelation reaction in a sealed glass container, and places the sealed glass container in an oven. During the gelation reaction, the phenolic compounds and aldehydes are completely polymerized to form a gel and gradually age.

[0040] After obtaining the palladium-loaded nitrogen-doped carbon material precursor, the present application calcines the palladium-loaded nitrogen-doped carbon material precursor to obtain the palladium-loaded nitrogen-doped carbon material.

[0041] In the present application, the temperature of the calcination is preferably 300-900℃, and is further preferably 400-800℃, and is more preferably 500-700℃; the time of the calcination is preferably 1-10h, and is further preferably 2-8h, and is more preferably 3-6h; and the atmosphere of the calcination is preferably nitrogen, argon or helium, and is further preferably nitrogen.

[0042] In the present application, before calcining the palladium-loaded nitrogen-doped carbon material precursor, it is also preferable to include drying the palladium-loaded nitrogen-doped carbon material precursor. In the present application, the temperature of the drying is preferably 50-150℃, and is further preferably 70-100℃, and is more preferably 80-90℃; and the time of the drying is preferably 1-10h, and is further preferably 2-5h, and is more preferably 2.5-4h. Through calcination, the present application can carbonize the palladium-loaded nitrogen-doped carbon material precursor from an organic form to an inorganic form, thereby becoming a palladium-loaded nitrogen-doped carbon material.

[0043] The present application provides a palladium-loaded nitrogen-doped carbon material prepared by the preparation method described in the above scheme, which comprises a nitrogen-doped carbon material and palladium metal nanoparticles loaded on the nitrogen-doped carbon material; and the nitrogen-doped carbon material has a phenolic condensate organic skeleton structure.

[0044] In the present application, the mass content of carbon in the palladium loaded nitrogen-doped carbon material is preferably 87.5-90.5%, the mass content of palladium metal nanoparticles is preferably 4.5-5.5%, and the mass content of nitrogen is preferably 5-7%.

[0045] The present application provides the palladium loaded nitrogen-doped carbon material as described in the above-mentioned scheme as a catalyst for catalyzing the hydrogenation of acetylene to prepare ethylene.

[0046] In the specific application in the present application, the palladium loaded nitrogen-doped carbon material is preferably used as a catalyst to be loaded in a high-pressure reaction kettle to catalyze the hydrogenation of acetylene to prepare ethylene. In the present application, the conditions for the hydrogenation of acetylene to prepare ethylene include that water is preferably used as a solvent, the reaction temperature is preferably 70°C, the reaction pressure is preferably 0.5 MPa, the reaction atmosphere is preferably hydrogen, and the mass ratio of acetylene to catalyst is preferably 2:1.

[0047] In order to further illustrate the present application, the palladium loaded nitrogen-doped carbon material provided by the present application, the preparation method and application thereof are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0048] Example 1

[0049] The poly(vinyl dodecylimidazole iodide), melamine, 2-bromophenol and formaldehyde (molar ratio of 1:2:1:2) are subjected to a phenolic aldehyde condensation reaction under alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution is added), 60°C water bath heating, and constant stirring and condensation reflux for 1 h to obtain a nitrogen-doped phenolic aldehyde condensate solution;

[0050] The nitrogen-doped phenolic aldehyde condensate solution is diluted with anhydrous ethanol at a dilution ratio of 2.5 times, and the pH value of the obtained diluted solution is adjusted to 8-9 with a 10 mol / L sodium hydroxide solution to obtain a nitrogen-doped phenolic aldehyde condensate alkaline dilution solution;

[0051] Palladium sulfate is weighed and added to the nitrogen-doped phenolic aldehyde condensate alkaline dilution solution, and the mass of the palladium sulfate is 1% of the mass of the nitrogen-doped phenolic aldehyde condensate alkaline dilution solution. The glass container is sealed and placed in a 100°C oven to perform a gelation reaction and an aging reaction for 5 days to obtain a palladium loaded nitrogen-doped carbon material precursor;

[0052] The palladium loaded nitrogen-doped carbon material precursor is dried and then calcined at a temperature of 700°C for 7 h in a nitrogen atmosphere to obtain the palladium loaded nitrogen-doped carbon material.

[0053] Application Example 1

[0054] The palladium loaded nitrogen doped carbon material obtained in Example 1 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 89.4%, and the selectivity was 87.5%.

[0055] Example 2

[0056] The poly(1-vinyl-3-ethylimidazole bromide), aniline, 2-chlorophenol, and polyformaldehyde (molar ratio of 1:1:1.5:2) were subjected to a phenolic aldehyde condensation reaction under the conditions of alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 100℃ water bath heating, and condensation reflux under constant stirring for 1 h, to obtain a nitrogen doped phenolic aldehyde condensate solution.

[0057] The nitrogen doped phenolic aldehyde condensate solution was diluted with anhydrous ethanol, the dilution multiple was 2.5 times, and the pH value of the obtained diluted solution was adjusted to 8-9 with a 10 mol / L sodium hydroxide solution, to obtain a nitrogen doped phenolic aldehyde condensate alkaline dilution solution.

[0058] Palladium sulfate was weighed and added to the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, the mass of the palladium sulfate was 0.5% of the mass of the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, the glass container was sealed, and the gelation reaction and aging reaction were carried out in an oven at 100℃ for 5 days, to obtain a palladium loaded nitrogen doped carbon material precursor.

[0059] The palladium loaded nitrogen doped carbon material precursor was dried, and then calcined at 800℃ for 8 h in a nitrogen atmosphere, to obtain the palladium loaded nitrogen doped carbon material.

[0060] Application Example 2

[0061] The palladium loaded nitrogen doped carbon material obtained in Example 2 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 98.6%, and the selectivity was 98.9%.

[0062] Example 3

[0063] The poly(1-vinyl-3-ethylimidazole bromide), aniline, 2-chlorophenol, and polyformaldehyde (molar ratio of 1:1:1.5:2) were subjected to a phenolic aldehyde condensation reaction under the conditions of alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 100℃ water bath heating, and condensation reflux under constant stirring for 1 h, to obtain a nitrogen doped phenolic aldehyde condensate solution.

[0064] The nitrogen-doped phenolic condensate solution is diluted with anhydrous ethanol, the dilution ratio is 3 times, and the pH value of the obtained diluted solution is adjusted to 8-9 with 10 mol / L sodium hydroxide solution to obtain a nitrogen-doped phenolic condensate alkaline dilution solution;

[0065] Palladium sulfate is weighed and added to the nitrogen-doped phenolic condensate alkaline dilution solution, the mass of the palladium sulfate is 1% of the mass of the nitrogen-doped phenolic condensate alkaline dilution solution, and the glass container is sealed and placed in a 100℃ oven for gelation reaction and aging reaction for 5 days to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0066] The palladium-loaded nitrogen-doped carbon material precursor is dried and calcined at 600℃ for 8h in a nitrogen atmosphere to obtain the palladium-loaded nitrogen-doped carbon material.

[0067] Application Example 3

[0068] The palladium-loaded nitrogen-doped carbon material obtained in Example 3 is used as a catalyst and packed in a high-pressure reaction kettle, water is used as a solvent, acetylene is subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, and acetylene:catalyst mass ratio = 2:1 to obtain ethylene, the conversion rate is 89.3% and the selectivity is 97.2%.

[0069] Example 4

[0070] Poly(1-hexyl-3-vinylimidazole bromide), melamine, 2-chlorophenol and formaldehyde (molar ratio of 1:2:2:1) are subjected to a phenolic condensation reaction under alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution is added), 85℃ water bath heating, constant stirring and condensation reflux for 1h to obtain a nitrogen-doped phenolic condensate solution;

[0071] The nitrogen-doped phenolic condensate solution is diluted with anhydrous ethanol, the dilution ratio is 3 times, and the pH value of the obtained diluted solution is adjusted to 8-9 with 8 mol / L sodium hydroxide solution to obtain a nitrogen-doped phenolic condensate alkaline dilution solution;

[0072] Palladium nitrate is weighed and added to the nitrogen-doped phenolic condensate alkaline dilution solution, the mass of the palladium sulfate is 3% of the mass of the nitrogen-doped phenolic condensate alkaline dilution solution, and the glass container is sealed and placed in a 100℃ oven for gelation reaction and aging reaction for 6 days to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0073] The palladium-loaded nitrogen-doped carbon material precursor is dried and calcined at 700℃ for 8h in a nitrogen atmosphere to obtain the palladium-loaded nitrogen-doped carbon material.

[0074] Application Example 4

[0075] The palladium loaded nitrogen doped carbon material obtained in Example 4 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 84.9%, and the selectivity was 74.6%.

[0076] Example 5

[0077] The poly(1-hexyl-3-vinylimidazole bromide), o-phenanthroline, 2-chlorophenol and glutaraldehyde (molar ratio of 1:1.5:1:2) were subjected to a phenolic aldehyde condensation reaction under the conditions of alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 70℃ water bath heating, and constant stirring and condensation reflux for 1 h, to obtain a nitrogen doped phenolic aldehyde condensate solution;

[0078] The nitrogen doped phenolic aldehyde condensate solution was diluted with anhydrous ethanol, the dilution ratio was 3 times, and the pH value of the obtained diluted solution was adjusted to 8-9 with an 8 mol / L sodium hydroxide solution, to obtain a nitrogen doped phenolic aldehyde condensate alkaline dilution solution;

[0079] Palladium nitrate was weighed and added to the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, the mass of the palladium nitrate was 2% of the mass of the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, the glass container was sealed, and the gelation reaction and aging reaction were carried out in an oven at 100℃ for 5 days, to obtain a palladium loaded nitrogen doped carbon material precursor;

[0080] The palladium loaded nitrogen doped carbon material precursor was dried, and then calcined at 600℃ for 7 h in a nitrogen atmosphere, to obtain the palladium loaded nitrogen doped carbon material.

[0081] Application Example 5

[0082] The palladium loaded nitrogen doped carbon material obtained in Example 5 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 69.2%, and the selectivity was 93.5%.

[0083] Example 6

[0084] The poly(1-vinyl-3-ethylimidazole bromide), pyrrole, 2-chlorophenol and paraformaldehyde (molar ratio of 1:1:1:2) were subjected to a phenolic aldehyde condensation reaction under the conditions of alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 80℃ water bath heating, and constant stirring and condensation reflux for 1 h, to obtain a nitrogen doped phenolic aldehyde condensate solution;

[0085] The nitrogen-doped phenolic condensate solution is diluted with anhydrous ethanol, the dilution ratio is 3 times, the pH value of the obtained diluted solution is adjusted to 8-9 with 10 mol / L sodium hydroxide solution, and a nitrogen-doped phenolic condensate alkaline diluted solution is obtained;

[0086] Palladium sulfate is weighed and added to the nitrogen-doped phenolic condensate alkaline diluted solution, the mass of the palladium sulfate is 0.5% of the mass of the nitrogen-doped phenolic condensate alkaline diluted solution, the glass container is sealed and placed in an oven at 100°C, and the gelation reaction and aging reaction are carried out for 5 days to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0087] The palladium-loaded nitrogen-doped carbon material precursor is dried and calcined at 600°C for 6h in a nitrogen atmosphere to obtain the palladium-loaded nitrogen-doped carbon material.

[0088] Application Example 6

[0089] The palladium-loaded nitrogen-doped carbon material obtained in Example 6 is used as a catalyst and packed in a high-pressure reaction kettle, water is used as a solvent, acetylene is subjected to hydrogenation reaction under the conditions of 70°C, a reaction pressure of 0.5 MPa of hydrogen, and an acetylene:catalyst mass ratio of 2:1, and ethylene is obtained, with a conversion rate of 66.3% and a selectivity of 82.1%.

[0090] Example 7

[0091] Poly(1-vinyl-3-ethylimidazole hexafluorophosphate), pyrrole, p-nitrophenol, and paraformaldehyde (molar ratio of 1:1:1:2) are subjected to a phenolic condensation reaction under alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution is added), in a condensation reflux state with constant stirring under a 90°C water bath, for 1h, to obtain a nitrogen-doped phenolic condensate solution;

[0092] The nitrogen-doped phenolic condensate solution is diluted with anhydrous ethanol, the dilution ratio is 2 times, the pH value of the obtained diluted solution is adjusted to 8-9 with 5 mol / L sodium hydroxide solution, and a nitrogen-doped phenolic condensate alkaline diluted solution is obtained;

[0093] Palladium nitrate is weighed and added to the nitrogen-doped phenolic condensate alkaline diluted solution, the mass of the palladium sulfate is 0.5% of the mass of the nitrogen-doped phenolic condensate alkaline diluted solution, the glass container is sealed and placed in an oven at 100°C, and the gelation reaction and aging reaction are carried out for 2 days to obtain a palladium-loaded nitrogen-doped carbon material precursor;

[0094] The palladium-loaded nitrogen-doped carbon material precursor is dried and calcined at 500°C for 5h in a nitrogen atmosphere to obtain the palladium-loaded nitrogen-doped carbon material.

[0095] Application Example 7

[0096] The palladium loaded nitrogen doped carbon material obtained in Example 7 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 64.7%, and the selectivity was 72.1%.

[0097] Comparative Example 1

[0098] Melamine, 2-bromophenol and formaldehyde (molar ratio of 1:1:2) were subjected to phenolic aldehyde condensation reaction under alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 85℃ water bath heating, and constant stirring and condensation reflux for 1 h to obtain a nitrogen doped phenolic aldehyde condensate solution;

[0099] The nitrogen doped phenolic aldehyde condensate solution was diluted with anhydrous ethanol, the dilution ratio was 2.5 times, and the pH value of the obtained diluted solution was adjusted to 8-9 with 10 mol / L sodium hydroxide solution to obtain a nitrogen doped phenolic aldehyde condensate alkaline dilution solution;

[0100] Palladium sulfate was weighed and added to the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, the mass of the palladium sulfate was 0.5% of the mass of the nitrogen doped phenolic aldehyde condensate alkaline dilution solution, and the glass container was sealed and placed in a 100℃ oven for gelation reaction and aging reaction for 5 days to obtain a palladium loaded nitrogen doped carbon material precursor;

[0101] The palladium loaded nitrogen doped carbon material precursor was dried and calcined at 800℃ for 8 h in a nitrogen atmosphere to obtain the palladium loaded nitrogen doped carbon material.

[0102] Comparative Example 1

[0103] The palladium loaded nitrogen doped carbon material obtained in Comparative Example 1 was packed in a high-pressure reactor as a catalyst, water was used as a solvent, acetylene was subjected to hydrogenation reaction under the conditions of 70℃, 0.5 MPa hydrogen pressure, acetylene: catalyst mass ratio = 2:1, ethylene was obtained, the conversion rate was 53.1%, and the selectivity was 55.6%.

[0104] Comparative Example 2

[0105] The difference from Example 2 is that the nitrogen doped phenolic aldehyde condensate solution is not diluted, and the specific steps are as follows:

[0106] Poly(vinyl dodecylimidazole bromide), melamine, 2-bromophenol and formaldehyde (molar ratio of 1:1:1:2) were subjected to phenolic aldehyde condensation reaction under alkaline conditions (2 mL of 1 mol / L sodium hydroxide solution was added), 85℃ water bath heating, and constant stirring and condensation reflux for 1 h to obtain a nitrogen doped phenolic aldehyde condensate solution;

[0107] The nitrogen-doped phenolic condensate solution is adjusted to pH 8-9 with 10 mol / L sodium hydroxide solution to obtain a nitrogen-doped phenolic condensate alkaline solution;

[0108] Palladium sulfate is weighed and added to the nitrogen-doped phenolic condensate alkaline solution, the mass of the palladium sulfate being 0.5% of the mass of the nitrogen-doped phenolic condensate alkaline solution, and the mixture is sealed in a glass container and placed in an oven at 100°C to perform a gelation reaction and an aging reaction for 5 days, to obtain a palladium-loaded nitrogen-doped carbon material precursor.

[0109] The palladium-loaded nitrogen-doped carbon material precursor is dried and calcined at 800°C for 8h in a nitrogen atmosphere to obtain the palladium-loaded nitrogen-doped carbon material.

[0110] Comparative Example 2

[0111] The palladium-loaded nitrogen-doped carbon material obtained in Comparative Example 2 is packed into a high-pressure reaction kettle as a catalyst, water is used as a solvent, and acetylene is subjected to hydrogenation reaction under the conditions of 70°C, a reaction pressure of 0.5 MPa of hydrogen, and an acetylene-to-catalyst mass ratio of 2:1, to obtain ethylene, with a conversion rate of 88.7% and a selectivity of 85.1%.

[0112] Performance characterization

[0113] Table 1 shows the specific surface area of the palladium-loaded nitrogen-doped carbon material obtained in Examples 1-7 and Comparative Example 1, as well as the conversion rate and selectivity data.

[0114] Table 1 shows the specific surface area of the palladium-loaded nitrogen-doped carbon material obtained in Examples 1-7 and Comparative Example 1, as well as the conversion rate and selectivity data.

[0115] Item Specific surface area (m 3 / g) % Conversion % Selectivity Example 1 431.3 89.4 87.5 Example 2 587.2 98.6 98.9 Example 3 418.3 89.3 97.2 Example 4 323.4 84.9 74.6 Example 5 317.2 69.2 93.5 Example 6 281.3 66.3 82.1 Example 7 259.7 64.7 72.1 Comparative Example 1 245.1 53.1 55.6 Comparative Example 2 358.1 88.7 85.1

[0116] As can be seen from Table 1, the greater the specific surface area, the more active sites the palladium-loaded nitrogen-doped carbon material has as a catalyst, and the higher the reaction activity; without adding imidazole-based polyionic liquid (Comparative Example 1), the reaction activity of the palladium-loaded nitrogen-doped carbon material prepared as a catalyst is low; without diluting the nitrogen-doped phenolic condensate solution with ethanol (Comparative Example 2), the reaction activity of the palladium-loaded nitrogen-doped carbon material prepared as a catalyst is low; dilution with ethanol can make the substances uniformly dispersed, increase the porosity, and make the product skeleton structure more stable, capable of withstanding greater damage and resisting collapse of the morphology, and the reaction activity of the palladium-loaded nitrogen-doped carbon material prepared as a catalyst is high.

[0117] The catalysts of Example 2 and Comparative Example 1 are subjected to stability testing, specifically, the catalyst used in the previous reaction is dried and directly used in the next acetylene hydrogenation reaction, under the same reaction conditions as in each application example. The results are shown in Table 2.

[0118] Table 2 Comparison of conversion and selectivity data for repeated use of the palladium on nitrogen-doped carbon material of Example 2 and Comparative Example 1

[0119]

[0120] As can be seen from Table 2, the palladium on nitrogen-doped carbon material prepared by the present application still has high catalytic activity after repeated use for several times, indicating good stability.

[0121] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for preparing a palladium supported nitrogen-doped carbon material, characterized by, The method comprises the following steps: a phenol-aldehyde condensation reaction is performed on an imidazole-based polyionic liquid, a nitrogen-containing organic compound, a phenolic compound and an aldehyde under alkaline conditions to obtain a nitrogen-doped phenol-aldehyde condensate solution; the nitrogen-containing organic compound comprises melamine, aniline, pyrrole or o-phenanthroline; the nitrogen-doped phenol-aldehyde condensate solution is diluted, and the pH value of the obtained diluted solution is adjusted to alkaline to obtain a nitrogen-doped phenol-aldehyde condensate alkaline diluted solution; the nitrogen-doped phenol-aldehyde condensate alkaline diluted solution is mixed with a palladium salt to perform a gelation reaction to obtain a palladium-loaded nitrogen-doped carbon material precursor; the palladium-loaded nitrogen-doped carbon material precursor is calcined to obtain the palladium-loaded nitrogen-doped carbon material.

2. The production method according to claim 1, characterized by, the imidazole-based polyionic liquid comprises poly(vinyl dodecylimidazole iodide), poly(vinyl dodecylimidazole bromide), poly(1-hexyl-3-vinylimidazole bromide), poly(1-vinyl-3-ethylimidazole bromide) or poly(1-vinyl-3-ethylimidazole hexafluorophosphate); the phenolic compound comprises 2-bromophenol, hydroquinone, 2-chlorophenol or p-nitrophenol; the aldehyde comprises formaldehyde, glutaraldehyde or butanedial.

3. The production method according to claim 1 or 2, characterized by, the molar ratio of the imidazole-based polyionic liquid to the nitrogen-containing organic compound is 1:(0.5-3); the molar ratio of the imidazole-based polyionic liquid to the phenolic compound is 1:(0.5-3); and the molar ratio of the imidazole-based polyionic liquid to the aldehyde is 1:(1-4).

4. The production method according to claim 1, characterized by, the temperature of the phenol-aldehyde condensation reaction is 50-110°C, and the holding time is 0.5-4h; and the pH value of the alkaline condition is 8-10.

5. The method of claim 1, wherein, the dilution multiple of the nitrogen-doped phenol-aldehyde condensate solution is 1-5; and the pH value of the nitrogen-doped phenol-aldehyde condensate alkaline diluted solution is 8-14.

6. The method of claim 1, wherein, the palladium salt is palladium chloride, palladium nitrate or palladium sulfate; and the mass percentage of the palladium salt in the nitrogen-doped phenol-aldehyde condensate alkaline diluted solution is 0-7% and is not 0.

7. The production method according to claim 1 or 6, characterized by, the temperature of the gelation reaction is 50-150°C, and the time is 1-10 days.

8. The method of claim 1, wherein, the temperature of the calcination is 300-900°C, and the time is 1-10h.

9. The palladium supported nitrogen-doped carbon material prepared by the preparation method according to any one of claims 1-8, characterized in that, The palladium-loaded nitrogen-doped carbon material comprises a nitrogen-doped carbon material and palladium metal nanoparticles loaded on the nitrogen-doped carbon material; and the nitrogen-doped carbon material has a phenol-aldehyde condensate organic skeleton structure.

10. Use of the palladium-loaded nitrogen-doped carbon material in claim 9 as a catalyst in catalyzing hydrogenation of acetylene to ethylene.

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