Monatomic loaded lignin carbon-based photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a monatomic loaded lignin carbon-based photocatalyst as well as a preparation method and application thereof. The preparation method of the photocatalyst comprises the following steps: S1, grinding and blending lignin and melamine, then adding the mixture into water, transferring the obtained solution into a hydrothermal reaction container, reacting at 175-195 DEG C for 4-10 hours, and after the reaction is finished, cooling at room temperature, washing and centrifugally separating to obtain a solid mixture; s2, dispersing the solid mixture in an aqueous solution containing metal salt, stirring at room temperature, and drying after the reaction is finished; and S3, putting the dried solid into a container, putting the container into a pyrolysis reactor, heating to 800-1000 DEG C in an argon atmosphere, pyrolyzing for 2-6 hours, and naturally cooling to obtain the monatomic loaded lignin carbon-based photocatalyst. The monatomic loaded lignin carbon-based photocatalyst provided by the invention can efficiently catalyze glucose to synthesize glucaric acid under mild conditions, and the obtained target product is relatively high in yield and easy to separate, and has a very good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical engineering, in particular to a single-atom supported lignin carbon-based photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Bio-based glucaric acid is a kind of binary organic acid, which is rare in nature and can be used to prepare food additives, anticancer treatment adjuvants, polymers, chelating agents and the like, and has a wide range of applications. However, the yield of naturally extracted glucaric acid is extremely low, which cannot meet the market demand. Glucaric acid can be synthesized by photocatalysis of glucose under mild conditions, which has a wide application prospect. However, the yield of glucaric acid synthesized by photocatalysis is usually less than 30%, and the performance of the catalyst needs to be improved. The noble metal used in the catalyst is expensive and difficult to mass-produce. Biomass is widely distributed, has many types, large reserves and low price. Lignin, as the most abundant natural aromatic compound derived from biomass, has high carbon content and rich oxygen-containing functional groups. Preparing lignin into a photocatalytic material can enhance light absorption, promote electron transfer and prevent particle aggregation, which is beneficial to reduce the synthesis cost of glucaric acid and improve the added value and application range of lignin. Therefore, how to develop a new type of lignin carbon-based photocatalyst to improve the efficiency of synthesizing bio-based glucaric acid is of great significance to the industrial application of biomass-based high-added value energy chemicals, and is also a difficult problem that the field has been eager to solve. SUMMARY

[0003] In order to solve the problems of low performance of photocatalyst used in the process of photocatalytic synthesis of glucaric acid and high price of noble metal catalyst system in the prior art, the present application provides a single-atom supported lignin carbon-based photocatalyst and a preparation method and application thereof. The photocatalyst prepared by the present application uses lignin and melamine as raw materials, prepares a mixture through hydrothermal reaction, and then uses metal salt impregnation and high-temperature pyrolysis to prepare a single-atom supported lignin carbon-based photocatalyst. The catalyst has low cost and simple preparation process, and can efficiently catalyze the synthesis of glucaric acid from glucose under mild conditions.

[0004] The first object of the present application is to provide a preparation method of a single-atom supported lignin carbon-based photocatalyst, which comprises the following steps:

[0005] S1, grinding and blending lignin and melamine, then adding the mixture into water, and transferring the obtained solution to a hydrothermal reaction container to react at 175-195℃ for 4-10h, and then cooling at room temperature, washing and centrifuging to obtain a solid mixture;

[0006] S2, dispersing the solid mixture in an aqueous solution containing metal salt, stirring at room temperature, and drying after the reaction is completed;

[0007] S3, the dried solid is put into a container and into a pyrolysis reactor, pyrolysis is carried out at 800-1000 DEG C for 2-6 h under an argon atmosphere, and after natural cooling, a single-atom loaded lignin carbon-based photocatalyst is obtained.

[0008] The photocatalyst is simple in component, inexpensive, and simple in preparation process.

[0009] Preferably, the mass ratio of lignin to melamine in step (1) is 1:1-1:10, the mass concentration of lignin in the solution is 10-40 g / L, and the mass concentration of melamine in the solution is 10-400 g / L.

[0010] Further preferably, the mass ratio of lignin to melamine in step (1) is 1:5, the mass concentration of lignin in the solution is 15-20 g / L, and the mass concentration of melamine in the solution is 150-200 g / L.

[0011] Preferably, the reaction condition in step (1) is 185 DEG C for 8 h.

[0012] Preferably, the mass ratio of the metal salt to lignin in step (2) is 1:1-1:10, and the metal salt is selected from one of manganese chloride, cobalt chloride, ferrous chloride, manganese nitrate, cobalt nitrate, and ferrous nitrate. The concentration of the aqueous solution containing the metal salt is 2 g / L.

[0013] Preferably, the reaction condition in step (3) is a temperature rising rate of 10 DEG C / min, and pyrolysis is carried out at 900 DEG C for 4 h.

[0014] A second object of the present application is to provide a single-atom loaded lignin carbon-based photocatalyst prepared by the preparation method.

[0015] A third object of the present application is to provide an application of the single-atom loaded lignin carbon-based photocatalyst in photocatalytic synthesis of glucaric acid.

[0016] The present application also protects a method for photocatalytic synthesis of glucaric acid, comprising the following steps: adding the single-atom loaded lignin carbon-based photocatalyst into a glucose aqueous solution, adding a hydrogen peroxide solution with a mass concentration of 25%-35%, and after room temperature photoreaction, filtering and separating the catalyst to obtain a glucaric acid aqueous solution, and using HPLC to analyze the yield of glucaric acid.

[0017] Preferably, the concentration of the glucose aqueous solution is 5-30 g / L, the mass ratio of the single-atom loaded lignin carbon-based photocatalyst to glucose is 1:45-1:15, and the volume ratio of the hydrogen peroxide solution to the glucose aqueous solution is 0.001-0.006:1.

[0018] Further preferably, the concentration of the glucose aqueous solution is 20 g / L, the mass ratio of the monatomic supported lignin carbon-based photocatalyst to glucose is 1:25, and the volume ratio of the hydrogen peroxide solution to the glucose aqueous solution is 0.002-0.003:1.

[0019] Preferably, the power of the light irradiation reaction is 0-10 w, and the reaction time is 1-6 h.

[0020] Compared with the prior art, the monatomic supported lignin carbon-based photocatalyst has the advantages of simple components, low cost, simple preparation process, high efficiency in catalyzing glucose to synthesize glucose diacid under mild conditions, high yield of the target product, easy separation, and good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a reaction principle diagram of the monatomic supported lignin carbon-based photocatalyst for catalyzing glucose to synthesize glucose diacid according to the present application;

[0022] Figure 2 is a TEM and HAADF-STEM diagram of the monatomic supported lignin carbon-based photocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in conjunction with examples. These examples are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods not specified in the following examples are usually carried out according to the conventional conditions in the art or according to the suggested conditions of the manufacturers; the raw materials, reagents, etc. used are commercially available raw materials and reagents, unless otherwise specified.

[0024] Example 1

[0025] A preparation method of a monatomic supported lignin carbon-based photocatalyst, comprising the following steps:

[0026] S1, 0.4 g of lignin is ground and blended with 2 g of melamine, and then the mixture is added to 20 mL of water, the solution is transferred to a hydrothermal reaction kettle, and reacted at 185 ℃ for 8 h. After the reaction is completed, the solution is cooled at room temperature, washed, and centrifugally separated to obtain a solid.

[0027] S2, then the solid mixture is dispersed in a 40 mL aqueous solution containing 80 mg of manganese chloride, stirred at room temperature for 2 h, and after the reaction is completed, the solution is dried in a 105 ℃ oven to remove water.

[0028] S3, transfer the dried solid into a crucible and put into a tube furnace, under argon atmosphere, the heating rate is 10 ℃ / min, heat to 900 ℃ for 4 h, and then get the single atom loaded lignin carbon-based photocatalyst after natural cooling. The characterization spectrum of the photocatalyst is shown in Figure 2

[0029] The method for synthesizing glucose diacid by the single atom loaded lignin carbon-based photocatalyst is as follows: 8 mg of the single atom loaded lignin carbon-based photocatalyst is added into 10 mL of glucose aqueous solution with a mass concentration of 20 g / L, then 30% hydrogen peroxide solution is added, the volume ratio of the hydrogen peroxide solution to the glucose aqueous solution is 0.003:1, after 3 h of reaction under room temperature and 10 w light irradiation, the catalyst is separated by filtration, and the glucose diacid aqueous solution is analyzed by HPLC. The glucose conversion rate is 72.6%, and the glucose diacid yield is 38.5%.

[0030] Comparative Example 1

[0031] The same as Example 1, except that no melamine is added in step S1, and only 2.4 g of lignin is added.

[0032] The method for synthesizing glucose diacid by the obtained catalyst is the same as that in Example 1, the glucose conversion rate is 26.1%, and the glucose diacid yield is 10.6%.

[0033] Comparative Example 2

[0034] The same as Example 1, except that no lignin is added in step S1, and 2.4 g of melamine is added.

[0035] The method for synthesizing glucose diacid by the obtained catalyst is the same as that in Example 1, the glucose conversion rate is 55.3%, and the glucose diacid yield is 23.4%.

[0036] Example 2

[0037] The same as Example 1, except that:

[0038] In step S1, the mass ratio of lignin to melamine is 1:1, the mass concentration of lignin in the solution is 20 g / L, and the mass concentration of melamine is 20 g / L, and the reaction is carried out at 175 ℃ for 10 h; in step S2, the metal salt is cobalt chloride, and the mass ratio of cobalt chloride to lignin is 1:5; in step S3, the pyrolysis reaction is carried out at a temperature of 800 ℃ for 6 h.

[0039] ​In the method for photocatalytic synthesis of glucaric acid, the concentration of the aqueous glucose solution is 15 g / L, the mass ratio of the monatomic loaded lignin carbon-based photocatalyst to the glucose is 1:20, the volume ratio of the 30% hydrogen peroxide solution to the aqueous glucose solution is 0.003:1, the power of the light irradiation reaction is 9 w, and the reaction time is 4 h. The glucose conversion rate is 53.4%, and the glucaric acid yield is 22.1%.

[0040] Example 3

[0041] The same as example 1, except that:

[0042] In step S1, the mass ratio of lignin to melamine is 1:2, the mass concentration of lignin in the solution is 30 g / L, and melamine is 40 g / L, and the reaction is carried out at 195℃ for 4 h; in step S2, the metal salt is ferrous chloride, and the mass ratio of ferrous chloride to lignin is 1:10; in step S3, the pyrolysis reaction conditions are: heating to 1000℃ for 2 h.

[0043] In the method for photocatalytic synthesis of glucaric acid, the concentration of the aqueous glucose solution is 30 g / L, the mass ratio of the monatomic loaded lignin carbon-based photocatalyst to the glucose is 1:45, the volume ratio of the 30% hydrogen peroxide solution to the aqueous glucose solution is 0.002:1, the power of the light irradiation reaction is 10 w, and the reaction time is 2 h. The glucose conversion rate is 24.6%, and the glucaric acid yield is 17.2%.

[0044] Example 4

[0045] The same as example 1, except that:

[0046] In step S1, the mass ratio of lignin to melamine is 1:10, the mass concentration of lignin in the solution is 10 g / L, and melamine is 200 g / L, and the reaction is carried out at 195℃ for 6 h; in step S2, the metal salt is manganese nitrate, and the mass ratio of manganese nitrate to lignin is 1:1; in step S3, the pyrolysis reaction conditions are: heating to 1000℃ for 2 h.

[0047] In the method for photocatalytic synthesis of glucaric acid, the concentration of the aqueous glucose solution is 5 g / L, the mass ratio of the monatomic loaded lignin carbon-based photocatalyst to the glucose is 1:15, the volume ratio of the 35% hydrogen peroxide solution to the aqueous glucose solution is 0.001:1, the power of the light irradiation reaction is 10 w, and the reaction time is 5 h. The glucose conversion rate is 63.6%, and the glucaric acid yield is 29.8%.

[0048] Example 5

[0049] The same as example 1, except that:

[0050] The mass ratio of lignin and melamine in step S1 is 1:5, the mass concentration of lignin in the solution is 20 g / L, the mass concentration of melamine is 400 g / L, and the reaction is carried out at 185°C for 6 h; the metal salt in step S2 is cobalt nitrate, and the mass ratio of cobalt nitrate to lignin is 1:1; the pyrolysis reaction in step S3 is carried out at 900°C for 6 h.

[0051] In the method for photocatalytic synthesis of glucaric acid, the concentration of the glucose aqueous solution is 30 g / L, the mass ratio of the monatomic supported lignin carbon-based photocatalyst to glucose is 1:30, the volume ratio of the 25% hydrogen peroxide solution to the glucose aqueous solution is 0.006:1, the power of the light irradiation reaction is 10 W, and the reaction time is 6 h. The glucose conversion rate is 45.8%, and the glucaric acid yield is 20.7%.

[0052] The above examples are only used to help understand the technical solutions of the present application and its core idea. It should be pointed out that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a single-atom supported lignin carbon-based photocatalyst, characterized in that, The method comprises the following steps: S1, grinding and blending lignin with melamine, then adding the mixture into water, transferring the obtained solution into a hydrothermal reaction container, reacting at 175-195 DEG C for 4-10 h, cooling at room temperature after the reaction, washing and centrifugal separation to obtain a solid mixture; S2, dispersing the solid mixture in an aqueous solution containing a metal salt, stirring at room temperature, drying after the reaction; S3, placing the dried solid into a container and into a pyrolysis reactor, pyrolyzing at 800-1000 DEG C under an argon atmosphere for 2-6 h, naturally cooling to obtain a single-atom loaded lignin carbon-based photocatalyst.

2. The production method according to claim 1, characterized by, The mass ratio of lignin to melamine in step (1) is 1:1-1:10, and the mass concentration of lignin in the solution is 10-40 g / L.

3. The production method according to claim 1 or 2, characterized by, The reaction condition in step (1) is 185 DEG C for 8 h.

4. The method of claim 1, wherein, The mass ratio of the metal salt to lignin in step (2) is 1:1-1:10, and the metal salt is selected from one of manganese chloride, cobalt chloride, ferrous chloride, manganese nitrate, cobalt nitrate and ferrous nitrate.

5. The preparation method according to claim 1, characterized in that, The reaction condition in step (3) is a heating rate of 10 DEG C / min, pyrolyzing at 900 DEG C for 4 h.

6. The single-atom loaded lignin carbon-based photocatalyst prepared by the preparation method in claim 1.

7. The application of the single-atom loaded lignin carbon-based photocatalyst in claim 6 in photocatalytic synthesis of glucaric acid.

8. A method of photocatalytic synthesis of glucaric acid, characterized by, The method comprises the following steps: adding the single-atom loaded lignin carbon-based photocatalyst in claim 6 into a glucose aqueous solution, adding a hydrogen peroxide solution with a mass concentration of 25%-35%, and obtaining a glucaric acid aqueous solution after room temperature light irradiation, and analyzing the glucaric acid yield by HPLC.

9. The method of claim 8, wherein, The concentration of the glucose aqueous solution is 5-30 g / L, the mass ratio of the single-atom loaded lignin carbon-based photocatalyst to glucose is 1:45-1:15, and the volume ratio of the hydrogen peroxide solution to the glucose aqueous solution is 0.001-0.006:

1.

10. The method according to claim 8 or 9, characterized in that, The power of the light irradiation reaction is 0-10 w, and the reaction time is 1-6 h.

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