阅读说明：本技术 一种腐殖质基磺化碳固体酸及其制备方法和应用 (Humic substance-based sulfonated carbon solid acid and preparation method and application thereof ) 是由 杨金帆 张宏宇 敖志锋 张素风 于 2019-09-19 设计创作，主要内容包括：本发明提供一种腐殖质基磺化碳固体酸及其制备方法和应用,包括以下步骤：(1)腐殖质的制备：将木质纤维素和稀硫酸溶液混合,置于密闭反应容器中,加热搅拌反应,反应结束后过滤分离出固体残渣,洗涤干燥,得到腐殖质；(2)水热法炭化磺化：将腐殖质与有机磺化剂加入水中,置于密闭反应容器中进行水热反应,水热反应结束后过滤分离出产物,洗涤至滤液呈中性,干燥后得到腐殖质基磺化碳固体酸。本发明方法成功回收碳资源,制备的固体酸可作为固体酸催化剂循环使用于制备生物柴油,原料成本更加低廉,来源更加广泛,更环保。(The invention provides a humic substance-based sulfonated carbon solid acid and a preparation method and application thereof, and the preparation method comprises the following steps: (1) preparation of humus: mixing lignocellulose and dilute sulfuric acid solution, placing the mixture in a closed reaction container, heating and stirring the mixture for reaction, filtering and separating solid residues after the reaction is finished, and washing and drying the solid residues to obtain humus; (2) carbonizing and sulfonating by a hydrothermal method: adding humus and an organic sulfonating agent into water, placing the mixture into a closed reaction container for hydrothermal reaction, filtering and separating a product after the hydrothermal reaction is finished, washing the product until filtrate is neutral, and drying the product to obtain the humus-based sulfonated carbon solid acid. The method successfully recovers carbon resources, the prepared solid acid can be used as a solid acid catalyst to be recycled for preparing the biodiesel, and the raw material cost is lower, the source is wider and the method is more environment-friendly.)

1. A preparation method of humus-based sulfonated carbon solid acid is characterized by comprising the following steps: the method comprises the following steps:

(1) Preparation of humus: mixing lignocellulose and dilute sulfuric acid solution, placing the mixture in a closed reaction container, heating and stirring the mixture for reaction, filtering and separating solid residues after the reaction is finished, and washing and drying the solid residues to obtain humus;

(2) carbonizing and sulfonating by a hydrothermal method: adding humus and an organic sulfonating agent into water, placing the mixture into a closed reaction container for hydrothermal reaction, filtering and separating a product after the hydrothermal reaction is finished, washing the product until filtrate is neutral, and drying the product to obtain the humus-based sulfonated carbon solid acid.

2. the method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (1), the lignocellulose is straw or corncob.

3. The method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (1), the concentration of the dilute sulfuric acid solution is 0.01-0.1 mol/L, and the feed-liquid ratio of the lignocellulose to the dilute sulfuric acid solution is 50-200 g/L.

4. The method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (1), the heating temperature is 80-150 ℃, and the heating and stirring time is 4-10 hours.

5. The method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (2), the organic sulfonating agent is p-toluenesulfonic acid, sulfamic acid or chlorosulfonic acid.

6. the method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (2), the feed-liquid ratio of the humus to the water is 1 g: (10-30) mL, wherein the mass ratio of humus to organic sulfonating agent is 1: (1-5).

7. The method of preparing a humus-based sulfonated carbon solid acid according to claim 1, wherein: in the step (2), the hydrothermal reaction temperature is 150-200 ℃, and the hydrothermal reaction time is 10-24 h.

8. A humic substance-based sulfonated carbon solid acid produced by the production method according to any one of claims 1 to 7.

9. use of the humus-based sulfonated carbon solid acid of claim 8 as a solid acid catalyst in the preparation of biodiesel.

10. The use of humic substance based sulfonated carbon solid acid as a solid acid catalyst in the preparation of biodiesel according to claim 9, wherein: mixing humic substance-based sulfonated carbon solid acid, fatty acid and methanol, heating and stirring for esterification reaction to obtain fatty acid methyl ester; wherein the molar ratio of the fatty acid to the methanol is 1 (10-20), the dosage of the humic base sulfonated carbon solid acid is 5-20% of the mass of the fatty acid, and the fatty acid is oleic acid, palmitic acid or stearic acid; the esterification temperature is 60-100 ℃, and the esterification time is 5-10 h.

Technical Field

The invention relates to the technical field of preparation of carbon-based solid acid catalysts, in particular to sulfonated carbon solid acid synthesized by using a byproduct humic substance of carbohydrate acidolysis as a raw material, and a preparation method and application thereof.

Background

At present, the energy crisis is continuously deepened, and the environmental awareness of people is continuously strengthened. Development of environmentally friendly, renewable energy and chemicals is being focused on by more and more people, and lignocellulose is one of the most abundant biomass resources. Lignocellulose can be converted by acid catalysis to yield many useful platform chemicals such as sugars, furans, and the like. This process is divided into three phases: lignocellulose is firstly hydrolyzed into cellulose and hemicellulose by acid catalysis, and the cellulose and the hemicellulose are continuously hydrolyzed into monosaccharide. Further dehydration of the sugars results in the formation of 5-hydroxymethylfurfural, levulinic acid, furfural and the like. A solid by-product, humus, is also produced during this process. The humus is a carbonaceous polymer with carbon content of about 60%, has a furan ring structure and rich oxygen-containing functional groups, and the yield of the humus is influenced by various factors such as raw materials, catalysts, reaction media, process parameters and the like. For example, dehydration reaction occurs in aqueous phase conditions, and the carbon equilibrium yield of humus is as high as 50% or more. If the lignocellulose is dehydrated and decomposed in the organic solvent, the yield of the humus is reduced to 25 to 45 percent. Therefore, in view of the overall economy and environmental protection of the biomass conversion process, it is necessary to upgrade the humus produced in large quantities in the biomass refining process.

At present, the humus waste is mainly used for directly burning to produce heat, and the added value is low. Recently, researchers have succeeded in developing some high-added-value utilization methods. For example, hydrogen and synthesis gas are produced by gasification from humus (Hoang et al, Green Chemistry,2015,17: 959-972); humic substances are impregnated on paper or wood after being compounded with furfuryl alcohol resin to improve the strength of the material (a. mija et al, Construction and Building Materials,2017,139: 594-601). However, the application of the solid byproduct of acid hydrolysis lignocellulose as a solid acid catalyst precursor for preparing a solid acid catalyst for catalysis has not been reported.

The biodiesel is a long-chain fatty acid alkyl ester substance generated by ester exchange reaction of animal and vegetable oil and short-chain alcohol. In order to avoid food competition with people, the non-edible oil is usually used for replacing rapeseed oil/soybean oil to prepare biodiesel in China, but the non-edible oil has high fatty acid content, the non-edible oil with high acid value needs to be pre-esterified, and an acid catalyst is usually adopted. Acidic catalysts include homogeneous liquid acids and solid acid catalysts. Homogeneous liquid acids (such as sulfuric acid) have the disadvantages of difficult recovery, corrosion of equipment, complex post-treatment and the like.

The carbon-based solid acid is a novel green catalyst appearing in recent years, and the preparation process comprises the steps of carrying out high-temperature pyrolysis on various carbohydrates (such as glucose, starch, microcrystalline cellulose and the like) in an inert atmosphere to obtain a carbon material, and then sulfonating the carbon material by concentrated sulfuric acid to obtain the carbon-based solid acid catalyst. The preparation of this catalyst has the following disadvantages: (1) the high-temperature pyrolysis process has high energy consumption, (2) the sulfonation process uses concentrated sulfuric acid, which is not environment-friendly, and (3) the raw materials such as glucose, microcrystalline cellulose and the like have high cost, which is not beneficial to large-scale production. Therefore, the need for cheap and efficient solid acid catalysts to catalyze fatty acid esterification reaction is needed.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides the humic base sulfonated carbon solid acid and the preparation method and application thereof, the cost is low, the environment is protected, and the additional value of lignocellulose acid hydrolysis solid waste is improved.

the invention is realized by the following technical scheme:

A preparation method of humic substance-based sulfonated carbon solid acid comprises the following steps:

(1) Preparation of humus: mixing lignocellulose and dilute sulfuric acid solution, placing the mixture in a closed reaction container, heating and stirring the mixture for reaction, filtering and separating solid residues after the reaction is finished, and washing and drying the solid residues to obtain humus;

(2) Carbonizing and sulfonating by a hydrothermal method: adding humus and an organic sulfonating agent into water, placing the mixture into a closed reaction container for hydrothermal reaction, filtering and separating a product after the hydrothermal reaction is finished, washing the product until filtrate is neutral, and drying the product to obtain the humus-based sulfonated carbon solid acid.

Preferably: in the step (1), the lignocellulose is straw or corncob.

Preferably: in the step (1), the concentration of the dilute sulfuric acid solution is 0.01-0.1 mol/L, and the feed-liquid ratio of the lignocellulose to the dilute sulfuric acid solution is 50-200 g/L.

Preferably: in the step (1), the heating temperature is 80-150 ℃, and the heating and stirring time is 4-10 hours.

Preferably: in the step (2), the organic sulfonating agent is p-toluenesulfonic acid, sulfamic acid or chlorosulfonic acid.

Preferably: in the step (2), the feed-liquid ratio of the humus to the water is 1 g: (10-30) mL, wherein the mass ratio of humus to organic sulfonating agent is 1: (1-5).

Preferably: in the step (2), the hydrothermal reaction temperature is 150-200 ℃, and the hydrothermal reaction time is 10-24 h.

The humic substance-based sulfonated carbon solid acid prepared by the preparation method.

The application of the humic substance-based sulfonated carbon solid acid as a solid acid catalyst in preparation of biodiesel is provided.

Preferably: mixing humic substance-based sulfonated carbon solid acid, fatty acid and methanol, heating and stirring for esterification reaction to obtain fatty acid methyl ester; wherein the molar ratio of the fatty acid to the methanol is 1 (10-20), the dosage of the humic base sulfonated carbon solid acid is 5-20% of the mass of the fatty acid, and the fatty acid is oleic acid, palmitic acid or stearic acid; the esterification temperature is 60-100 ℃, and the esterification time is 5-10 h.

Compared with the prior art, the invention has the following beneficial technical effects:

The method takes the humus byproduct generated in the lignocellulose hydrolysis process as a raw material, and prepares the carbon-based solid acid in one step under mild hydrothermal conditions. The method successfully recovers carbon resources, the prepared solid acid can be used as a solid acid catalyst to be recycled for preparing the biodiesel, the process is green and environment-friendly, the problem of recycling of the humus solid waste in the biomass refining process is solved, and the additional value of the solid waste generated in the biomass refining process is improved. In another aspect, the present invention utilizes the sulfonation mechanism Ar-H + P-SO₃H→Ar-SO₃H + P-H (Ar represents an aromatic ring in the humus structure, P-SO)₃H represents an organic sulfonating agent) to prepareThe preparation method is simple to operate, the preparation conditions are mild, and compared with the traditional pyrolysis method, the hydrothermal method shortens the process flow, avoids high-temperature links, and is economical and feasible; compared with the carbon-based solid acid prepared from pure carbohydrate, the carbon-based solid acid prepared from the humus serving as the raw material has the advantages of lower raw material cost, wider source and more environmental protection.

The humic substance-based sulfonated carbon prepared by the invention has a large number of sulfonic acid group active sites, and can be used as a green solid acid catalyst to catalyze fatty acids to prepare biodiesel. Taking oleic acid as an example, the reaction process is as follows: CH (CH)₃(CH₂)₇CH＝CH(CH₂)₇COOH+CH₂OH→CH₃(CH₂)₇CH＝CH(CH₂)₇COOCH₂. The catalyst has ideal activity in fatty acid esterification reaction, and the yield of fatty acid methyl ester can reach 80-98%.

Drawings

FIG. 1(a) shows a humic acid-based solid acid catalyst prepared from straw in the present invention, and FIG. 1(b) shows a humic acid-based solid acid catalyst prepared from corncob.

FIG. 2(a) is a scanning electron microscope image of humus prepared from straw according to the present invention, and FIG. 2(b) is a scanning electron microscope image of humus-based solid acid prepared from straw.

FIG. 3 is an infrared spectrum of humus and humus-based solid acids prepared from straw according to the present invention.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The invention aims to solve the problem of recycling of humus solid waste in the biomass refining process and solve the problems of high cost and environmental pollution in the preparation process of the solid acid catalyst. The invention takes humus as a raw material, synthesizes a carbon-based solid acid catalyst by a one-step hydrothermal method, and is successfully used for catalyzing and synthesizing fatty acid and preparing biodiesel through methanol esterification reaction. The literature at home and abroad is searched, and no report that the humus-based solid acid catalyst is prepared by a hydrothermal method and is used for synthesizing biodiesel is found.

A preparation method of a humus-based sulfonated carbon solid acid catalyst comprises the following steps:

(1) Preparation of humus: mixing lignocellulose and 0.01-0.1 mol/L dilute sulfuric acid solution, and placing the mixture in a closed reaction kettle, wherein the material-liquid ratio of the lignocellulose to the dilute sulfuric acid solution is 50-200 g/L. Heating to 80-150 ℃, and mechanically stirring for 4-10 h. And cooling the reaction kettle after the reaction is finished, filtering and separating black solid residues (shown in figure 1), fully washing with deionized water, drying, and grinding to less than 50 meshes to obtain the humus. The lignocellulose is straw or corncob.

(2) Carbonizing and sulfonating by a hydrothermal method: mixing the humus obtained in the step (1) with an organic sulfonating agent according to the proportion of 1 g: (1-5) g of humic substance and deionized water are mixed in the deionized water, and the ratio of the humic substance to the deionized water is 1 g: 10-30 mL. And transferring the mixture into a closed hydrothermal reaction kettle, heating to 150-200 ℃, and carrying out hydrothermal reaction for 10-24 h. After the reaction is finished, cooling, filtering and separating the product, and repeatedly washing the product by using boiling water until the filtrate is neutral. And drying in vacuum to obtain the humus-based sulfonated carbon solid acid catalyst. The organic sulfonating agent is p-toluenesulfonic acid, sulfamic acid or chlorosulfonic acid.

The application of the humic substance-based sulfonated carbon catalyst in the synthesis of biodiesel takes humic substance-based sulfonated carbon solid acid as a catalyst to catalyze the alcoholysis reaction of fatty acid and methanol to prepare fatty acid methyl ester: the method comprises the following steps: mixing a humus-based sulfonated carbon solid acid catalyst with fatty acid and methanol, adding the mixture into a round-bottom flask, and then carrying out esterification reaction at the esterification temperature of 60-100 ℃ for 5-10 h to obtain fatty acid methyl ester. Wherein the molar ratio of the fatty acid to the methanol is 1 (10-20), the dosage of the catalyst is 5-20% of the mass of the fatty acid, and the fatty acid is oleic acid, palmitic acid or stearic acid.

The present invention will be described in further detail with reference to examples.