Silica gel slurry for preparing porous material, and preparation method and application of porous carbon nitride

Abstract

The invention provides silica gel slurry for preparing a porous material and a preparation method and application of porous carbon nitride, porous carbon nitride is prepared with the assistance of silica gel slurry, and the preparation process mainly comprises the steps that vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil and the like are mixed to prepare the silica gel slurry, then a carbon nitride precursor and the silica gel slurry are fully mixed, and the porous material is prepared. And sintering at high temperature to obtain the porous carbon nitride material. The preparation method is simple and efficient, the problem of low chemical activity caused by insufficient specific surface area of the carbon nitride material is solved, and the development of a porous material preparation technology is promoted. The porous carbon nitride material prepared by the invention has a high specific surface area and a rich pore structure, and can be effectively used for photocatalytic CO2 reduction reaction.

Description

TECHNICAL FIELD

[0001] The application provides a silica sol slurry for preparing a porous material, a porous carbon nitride preparation method and application, and belongs to the fields of material preparation and catalysis. BACKGROUND

[0002] As an organic semiconductor material, porous carbon nitride has shown great application potential in the fields of catalysis, adsorption separation, energy storage and the like due to its unique physical and chemical properties. It is widely concerned in the fields of materials and catalysis because of its rich raw material sources, simple synthesis, stable performance and easy control. As a star material of photocatalytic technology, carbon nitride can prepare value-added chemicals such as methanol and carbon monoxide by photocatalytic reaction of carbon dioxide, and the reaction efficiency is restricted by factors such as specific surface area and pore structure of the catalytic material. These restriction conditions affecting the catalytic efficiency are closely related to the preparation method of the material.

[0003] Traditional porous carbon nitride material preparation methods mainly include template method, thermal polymerization method and the like. However, these methods have problems such as complex preparation process, high raw material cost, environmental pollution and the like, and the prepared carbon nitride has limited pore volume and it is difficult to further improve the specific surface area. In order to overcome these shortcomings, a simple and efficient method for preparing porous carbon nitride material assisted by silica sol slurry is introduced in this paper. The prepared porous carbon nitride material has high specific surface area, excellent controllability of pore structure and good chemical stability, and its application in photocatalytic reaction shows that the porous carbon nitride material prepared by the method has advantages. SUMMARY

[0004] The application provides a silica sol slurry for assisting in preparing a porous material, which comprises the following components in parts by mass: vinyl silicone oil 0.5-95 parts, viscosity 100-700000 cps, vinyl content 0.01-10%; hydroxyl silicone oil 0.1-50 parts, viscosity 10-5000 cps, hydroxyl content 0.5%-10%; hydrogen-containing silicone oil 0.1-50 parts, viscosity 10-5000 cps, active hydrogen mass fraction 0.1-2%; inhibitor 0.1-50 ppm of slurry concentration, platinum gold catalyst 0.1-50 ppm of slurry concentration.

[0005] Further, the inhibitor is selected from one or more of 3-methyl-1-butyne-3-ol, 1-ethynylcyclohexanol, 3-phenyl-1-butyne-3-ol, 3-propyl-1-butyne-3-ol or 3-octyl-1-butyne-3-ol; Further, the platinum coordination compound is selected from one or more of an alcohol solution of chloroplatinic acid, tetrahydrofuran coordinated platinum, or divinyltetramethylsiloxane coordinated platinum.

[0006] The silica sol slurry for assisting in the preparation of the porous material is used for preparing the porous carbon nitride.

[0007] The application also provides a method for assisting in the preparation of the porous carbon nitride material by using the silica sol slurry, comprising the following steps: S1, preparing the silica sol slurry: uniformly mixing vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor, and a platinum catalyst to obtain the silica sol slurry; S2, blending: uniformly mixing the carbon nitride precursor and the silica sol slurry to obtain a blend; S3, firing: firing the blend obtained in S2 at a high temperature in an inert gas atmosphere to obtain a fired product, and then performing post-processing to obtain the porous carbon nitride material.

[0008] Further, the raw materials of the silica sol slurry are mixed in the following proportions by mass fraction: vinyl silicone oil 0.5-98 parts, viscosity 100-700000 cps, vinyl content 0.01-10%; hydroxyl silicone oil 0.1-50 parts, viscosity 10-5000 cps, hydroxyl content 0.5%-10%; hydrogen-containing silicone oil 0.1-50 parts, viscosity 10-5000 cps, active hydrogen mass fraction 0.1-2%; the inhibitor accounts for 0.1-50 ppm of the slurry concentration, the platinum catalyst accounts for 0.1-50 ppm of the slurry concentration.

[0009] Further, the carbon nitride precursor includes at least one of melamine, cyanamide, thiourea, or guanidine carbonate.

[0010] Further, the carbon nitride precursor accounts for 5%-95% of the mass of the blend.

[0011] Further, the carbon nitride precursor accounts for 30%-90% of the mass of the blend.

[0012] Further, the high-temperature firing temperature is 500-650℃, and the high-temperature firing time is 1-3h.

[0013] Further, the post-processing includes, after the fired product is cooled, sequentially performing grinding, hydrofluoric acid washing, chloroform washing, water washing, and drying; and the hydrofluoric acid concentration is 3%-7%.

[0014] The porous carbon nitride is prepared by utilizing the addition polymerization reaction and dehydrogenation reaction of silica gel polymers during temperature rising, uniformly dispersing carbon nitride precursors into the new polymer network structure formed by silica gel, and continuing to raise the temperature to make the polymer decompose and the carbon nitride precursors gradually form the porous carbon nitride material.

[0015] The present application has the following beneficial effects: 1. The present application utilizes silica gel as a porous material template to prepare porous carbon nitride. Unlike the traditional template method, the silica gel slurry mainly exists in liquid form at room temperature and has a certain viscosity, and the carbon nitride precursors can be uniformly distributed in the slurry to form a blend. Before the temperature is raised to 300 DEG C, the hydrogen-containing silicone oil in the silica gel slurry reacts with the vinyl silicone oil to form a polymerized dense crosslinked network through silicon hydrogen addition reaction, and at the same time, the dehydrogenation reaction with the hydroxyl silicone oil produces gas to promote the formation of a porous structure. In this process, the slurry begins to change from a liquid state to a solid porous template. At this time, the carbon nitride precursors can be uniformly distributed in the porous network material formed by the polymerization reaction of silica gel. When the temperature exceeds 300 DEG C, the silica gel polymer begins to decompose, and the carbon nitride material begins to form, and finally the porous carbon nitride material with high specific surface area and rich pore structure is obtained.

[0016] 2. The present application can realize precise control of the pore structure of the porous carbon nitride material by changing the composition and adding amount of the silica gel slurry. The prepared porous carbon nitride material has rich pore structure, high specific surface area and structure controllability, and can effectively solve the problem that the catalytic efficiency is difficult to improve due to the limited pore structure and low specific surface area of the existing porous carbon nitride material. In addition, this method ingeniously utilizes the phase change of the silica gel slurry to form a polymer template through the chemical reaction of the polymer precursor, and can uniformly distribute the precursors of the target material in the polymer template. Further heating makes the template decompose, and the porous carbon nitride is formed. This preparation strategy is simple and efficient, enriches the material preparation means, and can promote the further development of material preparation technology. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The electron microscope photo of the porous carbon nitride material prepared in Example 2.

[0018] Figure 2 The XRD graph of the porous carbon nitride material prepared in Example 1 (CN1) and Example 2 (CN2). DETAILED DESCRIPTION

[0019] The embodiments of the present application will be described in detail below with reference to the examples, which are only used to illustrate the present application and should not be regarded as limiting the scope of the present application.

[0020] In the examples and comparative examples of the present application, the silicone oil involved in the silica gel slurry is a commercially available product of Hubei Xingrui Silicon Material Co., Ltd., and other reagents are purchased from National Pharmaceutical Reagent.

[0021] The specific surface area (S BET ), average pore size (Dave) and total pore volume (V tota ) of the materials in the examples and comparative examples of the present application were tested by low-temperature nitrogen adsorption method, and the materials were vacuum degassed at 300℃ for 6h before testing.

[0022] Example 1 A method for preparing a porous carbon nitride material assisted by a silica gel slurry, comprising the following steps: (1) Preparing a silica gel slurry: the following materials are fully mixed and stirred according to the mass fraction to obtain a silica gel slurry: 90 parts of vinyl silicone oil with a viscosity of 50,000 and a vinyl content of 0.08%; 5 parts of hydroxyl silicone oil with a viscosity of 2,000 and a hydroxyl content of 3%; 5 parts of hydrogen-containing silicone oil with a viscosity of 1,000 and a hydroxyl content of 0.8%; The inhibitor is selected to be 1-ethynylcyclohexanol, which accounts for 10 ppm of the slurry concentration; The platinum catalyst is selected to be platinum coordinated with divinyltetramethylsiloxane, and the amount added accounts for 5 ppm of the slurry concentration.

[0023] (2) Blending: melamine is selected as the carbon nitride precursor, and the melamine powder and the silica gel slurry are fully mixed and uniformly stirred at room temperature to obtain a blend; wherein the melamine accounts for 60% of the mass of the blend; (3) Firing: the blend obtained in step (2) is placed in a tubular furnace with inert gas, and is fired at 550℃ for 2 hours, and then naturally cooled. After that, the obtained fired material is ground, and the ground powder is washed with a 5% hydrofluoric acid solution for three times, washed with chloroform, washed with water and dried to obtain a porous carbon nitride material.

[0024] Example 2 The difference from Example 1 is that the mass fraction of vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil is changed from 90, 5, 5 parts to 95, 3, 2 parts, and the rest is the same as Example 1.

[0025] Example 3 The difference from Example 1 is that the mass fraction of vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil is changed from 90, 5, 5 parts to 98, 1, 1 parts, and the rest is the same as Example 1.

[0026] Example 4 The difference from Example 1 is that 90 parts of vinyl silicone oil with a viscosity of 50,000 and a vinyl content of 0.08% is replaced by 90 parts of vinyl silicone oil with a viscosity of 300,000 and a vinyl content of 1.5%, and the rest is the same as Example 1.

[0027] Example 5 Different from example 1, the hydroxyl silicone oil and hydrogen-containing silicone oil are changed from 5, 5 parts to 4, 1 part, and the rest is the same as example 1.

[0028] Example 6 Different from example 1, the melamine accounts for 30% of the mass of the blend, and the rest is the same as example 1.

[0029] Example 7 Different from example 1, the melamine accounts for 90% of the mass of the blend, and the rest is the same as example 1.

[0030] Example 8 Different from example 1, the firing conditions are different, specifically: the blend is placed in a tube furnace with inert gas, and the temperature is kept at 600°C for 1 hour.

[0031] Comparative example 1 Different from example 1, no silica slurry is added, and the rest is the same as example 1.

[0032] Comparative example 2 Different from example 1, no melamine is added, and the rest is the same as example 1, and no carbon nitride product is obtained.

[0033] The porous materials obtained in the above examples and comparative examples are tested for specific surface area (S BET ), average pore size (Dave) and total pore volume (V tota l). The test results are shown in Table 1.

[0034] Table 1

[0035] Application example The carbon nitride materials prepared in example 2 and comparative example 1 are compared in terms of photocatalytic carbon dioxide reduction reaction performance.

[0036] Photocatalytic carbon dioxide reduction reaction: 2g of porous carbon nitride is added to a photoreactor with gas inlet and outlet, pure CO2 and water vapor are introduced into the reactor, and a xenon lamp is used for light irradiation for 5 hours, while the gas chromatograph (Agilent, column type WH-5B) is connected to the gas outlet to detect the concentration of reaction products (in ppm). In order to clearly reflect the advantages of the materials prepared in this application, only the content of the main reduction products CO and CH3OH is used to reflect the efficiency of the catalytic reaction, and other trace products are not shown, and the results are shown in Table 2.

[0037] Table 2

[0038] It can be seen from the test data that the porous material preparation method described in the application is simple and has strong applicability, and the pore performance of the porous material can be adjusted by changing the composition of the silica sol slurry. Compared with the carbon nitride prepared by the conventional method, the porous carbon nitride material prepared by the method has high specific surface area, abundant pore volume, and high activity for use in photocatalytic reactions.

Claims

1. A silica sol slurry for assisting in the preparation of a porous material, characterized by, The following components are included by mass fraction: Vinyl silicone oil 0.5-95 parts, viscosity 100-700000 cps, vinyl content 0.01-10%; Hydroxyl silicone oil 0.1-50 parts, viscosity 10-5000 cps, hydroxyl content 0.5%-10%; Hydrogen-containing silicone oil 0.1-50 parts, viscosity 10-5000 cps, active hydrogen mass fraction 0.1-2%; Inhibitor 0.1-50 ppm of slurry concentration, Platinum gold catalyst 0.1-50 ppm of slurry concentration.

2. The silica sol slurry for assisting the preparation of a porous material according to claim 1, wherein The inhibitor is selected from one or more of 3-methyl-1-butyne-3-ol, 1-ethynylcyclohexanol, 3-phenyl-1-butyne-3-ol, 3-propyl-1-butyne-3-ol, or 3-octyl-1-butyne-3-ol; The platinum gold coordination compound is selected from one or more of an alcohol solution of chloroplatinic acid, platinum coordinated with tetrahydrofuran, or platinum coordinated with divinyltetramethylsiloxane.

3. Use of a silica sol slurry for assisting the preparation of a porous material according to claim 1 or 2, characterized in that, A porous carbon nitride is prepared.

4. A method for the assisted preparation of a porous carbon nitride material from a silica sol, characterized in that, The following steps are included: S1, preparing a silica gel slurry: uniformly mixing vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor, and a platinum gold catalyst to obtain a silica gel slurry; S2, blending: uniformly mixing a carbon nitride precursor and the silica gel slurry to obtain a blend; S3, firing: firing the blend obtained in S2 at a high temperature in an inert gas atmosphere to obtain a fired product, and then performing post-processing to obtain a porous carbon nitride material.

5. The method for preparing porous C3N4 material assisted by silica sol according to claim 4, characterized in that, The raw materials of the silica gel slurry are mixed in the following proportions by mass fraction: Vinyl silicone oil 0.5-98 parts, viscosity 100-700000 cps, vinyl content 0.01-10%; Hydroxyl silicone oil 0.1-50 parts, viscosity 10-5000 cps, hydroxyl content 0.5%-10%; Hydrogen-containing silicone oil 0.1-50 parts, viscosity 10-5000 cps, active hydrogen mass fraction 0.1-2%; Inhibitor 0.1-50 ppm of slurry concentration, Platinum gold catalyst 0.1-50 ppm of slurry concentration.

6. The method according to claim 4, wherein the silica sol is used as a pore- forming agent. The carbon nitride precursor includes at least one of melamine, cyanamide, thiourea, or guanidine carbonate.

7. The method according to claim 4, wherein the silica sol is used as a pore- forming agent. The carbon nitride precursor accounts for 5%-95% of the mass of the blend, preferably 30%-90%.

8. The method according to claim 4, wherein the silica sol is used as an auxiliary agent for the preparation of the porous C3N4 material. The high-temperature firing temperature is 500-650°C, and the high-temperature firing time is 1-3h.

9. The method according to claim 4, wherein the silica sol is used as an auxiliary agent for the preparation of the porous C3N4 material. The post-processing includes, after the fired product cools, sequentially performing grinding, hydrofluoric acid washing, chloroform washing, water washing, and drying; the hydrofluoric acid concentration is 3%-7%.

10. The porous carbon nitride material prepared by the method of any one of claims 4-9, for use in a photocatalytic carbon dioxide reduction reaction.

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