CN111346673A

CN111346673A - Preparation method and application of high-acid-density solid acid catalyst

Info

Publication number: CN111346673A
Application number: CN202010196691.2A
Authority: CN
Inventors: 胡勋; 邵月文; 李庆银
Original assignee: University of Jinan
Current assignee: University of Jinan
Priority date: 2020-03-19
Filing date: 2020-03-19
Publication date: 2020-06-30

Abstract

The invention provides a preparation method and application of a high-acid-density solid acid catalyst. The solid acid catalyst improves the stability of the sulfonic acid type solid acid catalyst by changing the way of introducing sulfonic acid groups into aromatic rings. Sulfonic acid groups are introduced on the surface of the catalyst through electrophilic substitution reaction, and weak acid sites such as carboxyl and the like are introduced on the surface of the catalyst through hydrolysis and oxidation, so that the catalyst has weak acid and strong acid centers. The catalyst improves the acid density of the catalyst by changing the combination mode of sulfonic acid groups and a carrier, and effectively introduces sulfonate with high loading into the surface of the catalyst mainly by adopting different sulfonic acid groups and a feasible connecting medium. The catalyst obtained by the invention shows extremely high catalytic activity in the reaction of preparing levulinate through biomass conversion.

Description

Preparation method and application of high-acid-density solid acid catalyst

Technical Field

The invention relates to a preparation method and application of a high-acid-density solid acid catalyst.

Background

The biomass resource is an important component of a renewable energy system, has the characteristics of being renewable and widely distributed, and plays an important role in an energy supply chain. The good utilization of biomass resources has very important significance for the sustainable development of the economic society. The biomass conversion and utilization modes comprise direct combustion, biochemical conversion, chemical conversion and the like. In order to meet the requirement of industrial production, the chemical conversion process has the characteristics of high reaction rate and the like, and is easier to realize industrial continuous production.

In bio-oil produced by biomass pyrolysis, anhydroglucose and the like are one of the main components, which can be used to produce fine chemicals such as levulinic acid and the like by acid-catalyzed conversion. In addition, hydrolysis of biomass can depolymerize cellulose and hemicellulose in the biomass into monosaccharides such as glucose and xylose, respectively. Glucose and xylose are further converted into furfural, 5-hydroxyfurfural, and the like. 5-hydroxyfurfural can be converted to levulinic acid esters by acid catalysis. Furfural itself is a fine chemical, and can also be converted into furfuryl alcohol by partial hydrogenation, and furfuryl alcohol is then converted into levulinic acid or levulinate ester by acid catalysis. Since the levulinic acid ester has wide industrial application, the market potential of the levulinic acid ester is huge. Most of the steps from biomass to levulinate ester products involve the presence of an acid catalyst. Designing a highly efficient catalyst is key to achieving selective conversion of biomass to levulinate.

Liquid acids such as hydrochloric acid and sulfuric acid are highly effective catalysts for biomass hydrolysis, but these liquid acids as catalysts have several problems: (1) the catalyst has high corrosivity and is easy to corrode a reaction vessel; (2) the cost for separating liquid acid and products is high; (3) the treatment problem of waste acid. Therefore, the development of efficient solid acid catalysts is a hot spot in biomass conversion research. However, there are also other problems with the use of solid acids in biomass hydrolysis: (a) solid acid is difficult to fully contact with solid biomass particles, so that the catalytic efficiency of the solid acid is reduced; (b) sulfonic groups of the sulfonic acid type solid acid are easy to be removed from a benzene ring through hydrolysis at a higher reaction temperature, so that product pollution and catalyst inactivation are caused; (c) the existing commercial solid acid has low density, and the low-temperature catalytic efficiency is influenced. It is necessary to optimize and construct the active center of the solid acid in a targeted manner, and the main problems existing in the use of the existing solid acid, particularly the sulfonic acid type solid acid, are solved.

Solid acid catalysts are an important consideration in designing and optimizing the hydrolysis of biomass to produce levulinate esters. This is because the solid acid catalyst affects depolymerization of cellulose and hemicellulose in biomass, hydrolytic conversion of polysaccharides to monosaccharides, dehydration of monosaccharides, conversion of furfural and 5-hydroxyfurfural to levulinic acid esters, and the like. The acid density of the solid acid catalyst affects the number of catalytic sites on the surface of the catalyst and the catalytic efficiency, and the stability of sulfonic acid groups on the surface of the solid acid catalyst (sulfonic acid type) determines the stability, the repeatable practicability and the use cost of the catalyst. Aiming at the problems of low surface acid density and poor high-temperature stability of sulfonic acid groups of the sulfonic acid type solid acid catalyst, the active center on the surface of the catalyst is optimized and constructed, and the novel solid acid catalyst is designed and developed, so that the selective conversion of biomass to fine chemicals such as levulinate is realized, the process efficiency of converting the biomass to levulinate is improved, and the use cost of the catalyst in the reaction process is reduced.

Disclosure of Invention

In order to solve the problems of low surface acid density and poor high-temperature stability of sulfonic acid groups of the sulfonic acid type solid acid catalyst, the invention aims to provide a preparation method of the high-acid-density solid acid catalyst, and the high-acid-density solid acid catalyst is applied to conversion of biomass into levulinate. The catalyst with high acid density is prepared by adopting a bridging medium method, has high stability and high acid density, and can effectively promote biomass conversion to prepare high-selectivity levulinate.

The purpose of the invention is realized by the following technical scheme:

a preparation method and application of a lignosulfonic acid catalyst are disclosed, which comprise the following steps:

(1) selecting a carbon-containing raw material as a catalyst carrier, uniformly mixing a certain amount of glucose and sodium methallyl sulfonate solution with the carbon-containing raw material at room temperature, and stirring and soaking for a certain time.

(2) And transferring the stirred mixture to an oven at 60-130 ℃ for drying treatment for 10-30 h.

(3) The dried samples were bridged at 200-600 ℃.

(4) And (3) further carrying out ion exchange on the sample in an acid solution at 25-100 ℃, and then drying the exchanged sample in an oven at 60-130 ℃ to finally obtain the solid acid catalyst with high stability and high acid density.

Preferably, in the step (1), the aromatic ring-containing carbonaceous raw material is used as a carrier.

Preferably, in step (1), glucose is used as the bridging medium.

Preferably, in the step (1), sodium methallyl sulfonate is used as a precursor of the sulfonic acid group.

Preferably, in the step (2), the sample is dried in an oven at 60-130 ℃ for 10-30 h.

Preferably, in step (3), the sample is bridged at 200-600 ℃.

Preferably, in the step (4), the dried sample is ion-exchanged in an acid solution at 25 to 100 ℃.

The preparation method and the prepared target product have the following advantages and beneficial effects:

the solid acid catalyst developed by the invention has high stability and high acid density. The catalyst is applied to biomass (comprising cellulose and hemicellulose) to prepare the levulinate, and the catalyst shows optimized catalytic performance.

Drawings

Fig. 1 is an abstract drawing.

FIG. 2 is a schematic diagram of the preparation of the solid acid catalyst in example 1.

FIG. 3 is a plot of surface acid density as a function of time under hydrothermal conditions for Amberlyst 70 and a solid acid prepared from sodium methallyl sulfonate as a precursor in example 2.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without making creative efforts based on the embodiments of the present invention, shall fall within the protection scope of the present invention.

Example 1

Selecting a carbon-containing material as a carrier, respectively preparing 0.01mol/L solution from glucose and sodium methallyl sulfonate, fully mixing 2g of the carbon-containing material with the solution, stirring and soaking at room temperature for 24 hours, and then transferring the mixture into an oven at 100 ℃ for drying for 12 hours. And (3) carrying out bridging reaction on the dried sample at 260 ℃, carrying out ion exchange on the obtained sample and a hydrochloric acid solution at 80 ℃ for 4h, and then drying in an oven at 100 ℃ for 12h to obtain a corresponding solid acid catalyst sample. The specific preparation process is shown in figure 2.

Example 2

The solid acid catalyst prepared by taking sodium methallyl sulfonate as a precursor and the commercialized solid acid catalyst Amberlyst 70 are subjected to stability study, the two catalysts are respectively placed at 210 ℃ for hydrothermal treatment in different time periods, and the change of the acid amount of the two catalysts is observed. The solid acid catalyst prepared by the present invention showed better thermal stability compared to Amberlyst 70 after hydrothermal treatment at 210 ℃ for 150min, as shown in fig. 3.

Example 3

Selecting 0.25g of cellulose as a reaction substrate, adding 20mL of ethanol as a reaction solvent, wherein the dosage of the catalyst is 0.5 wt%, and the reaction temperature is 200 ℃. The yield of the ethyl levulinate prepared by the conversion of the biomass in the embodiment of the invention is 26%.

Claims

1. A preparation method and application of a high-acid-density solid acid catalyst are disclosed, which comprises the following steps:

(1) the high acid density catalyst is prepared by a bridging medium method, and the preparation process of the catalyst is mainly divided into three steps of impregnation, bridging and ion exchange.

(2) Selecting a carbon-based material as a carrier, fully mixing the carbon-based material with a sulfonic acid group precursor and a bridging medium, and impregnating at room temperature.

(3) And carrying out bridging reaction on the impregnated sample, thereby realizing that the bridging medium effectively connects the sulfonic acid group precursor and the carrier.

(4) And finally obtaining the solid acid catalyst with high acid density by adopting an ion exchange mode for the prepared sample.

2. The method for producing a solid acid catalyst according to claim 1, characterized in that:

the carbon-based material selected in the step (1) is used as a carrier.

3. The method for producing a solid acid catalyst according to claim 1, characterized in that:

the sulfonic acid group precursor selected in the step (1) comprises sodium methallyl sulfonate or other sulfonates.

4. The solid acid catalyst of claim 1, wherein: the heat-resisting temperature can reach 240 ℃, and the acid site removal rate is less than 4.5 percent when the catalyst is stable for 250 hours under hydrothermal conditions (not less than 240 ℃).

5. The solid acid catalyst of claim 1, wherein: the surface acid density will be>9.5mmol g^-1。

6. The solid acid catalyst of claim 1, which finds application primarily in the conversion of biomass to levulinate esters.