阅读说明：本技术 一种木质纤维素原料的预处理方法 (Pretreatment method of lignocellulose raw material ) 是由 戴红旗 周雪莲 高欢力 卞辉洋 王瑞彬 杨益琴 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种木质纤维素原料的的预处理方法,属于生物质分离与转化技术领域。该方法为以对甲基苯磺酸为氢键供体,以氯化胆碱为氢键受体,添加乙醇合成新型低共熔溶剂,在温和条件下对木质纤维素原料进行预处理。采用该方法能够降解木质纤维素原料中70％以上的木质素和40％～90％的半纤维素,将纤维素酶水解得率提高至100％,同时低温条件下分离得到的木质素组分可进一步高值化利用,这种新型DES体系可回收再利用,是一种绿色高效的预处理方法,应用推广价值高。(The invention discloses a pretreatment method of a lignocellulose raw material, belonging to the technical field of biomass separation and conversion. The method comprises the steps of taking p-toluenesulfonic acid as a hydrogen bond donor, taking choline chloride as a hydrogen bond acceptor, adding ethanol to synthesize a novel eutectic solvent, and pretreating a lignocellulose raw material under mild conditions. The method can degrade more than 70% of lignin and 40% -90% of hemicellulose in the lignocellulose raw material, the hydrolysis yield of the cellulase is improved to 100%, meanwhile, the lignin component obtained by separation under the low-temperature condition can be further utilized in a high-value mode, and the novel DES system can be recycled and reused, is a green and efficient pretreatment method, and has high application and popularization values.)

1. A pretreatment method of a lignocellulose raw material is characterized in that p-toluenesulfonic acid is used as a hydrogen bond donor, choline chloride is used as a hydrogen bond acceptor, ethanol is added to synthesize a novel eutectic solvent, and the lignocellulose raw material is pretreated under mild conditions.

2. The pretreatment method for the lignocellulose raw material as recited in claim 1, wherein the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1: 0.5-1: 3, and the addition amount of ethanol is 1-50 wt% of the solvent system of p-toluenesulfonic acid and choline chloride.

3. The method of pretreating a lignocellulosic feedstock according to claim 1, wherein the moles of hydrogen bond acceptor and hydrogen bond donor are 1:1, and the amount of ethanol added is 30 wt% of the solvent system of p-toluenesulfonic acid and choline chloride.

4. The method for pretreating a lignocellulosic feedstock according to claim 1, wherein the synthesis temperature of the novel eutectic solvent is 50-100 ℃.

5. The method for pretreating a lignocellulosic feedstock according to claim 1, wherein the synthesis temperature of the novel eutectic solvent is 60 to 100 ℃.

6. The method for pretreating a lignocellulosic feedstock according to claim 1, wherein the temperature for pretreating the lignocellulosic feedstock is 60 to 120 ℃ and the reaction time is 5 to 60 min; the mass ratio of the lignocellulose raw material to the novel eutectic solvent is 1: 20-1: 5.

7. The method of claim 1, wherein the lignocellulosic feedstock is pretreated at a temperature of 100 ℃ for a reaction time of 30 min; the mass ratio of the lignocellulose raw material to the novel eutectic solvent is 1: 10.

8. The method for pretreating a lignocellulosic feedstock according to claim 1, wherein the lignocellulosic feedstock is any one of hardwood, agricultural and forestry processing residues, or gramineous plants.

Technical Field

The invention belongs to the technical field of biomass separation and conversion, and particularly relates to a pretreatment method of a lignocellulose raw material.

Background

The heterogeneity of the physicochemical properties of the components of the wood fiber cell wall and the complexity of the cell wall structure lead the wood fiber cell wall to have a natural anti-degradation barrier, and the natural anti-degradation barrier of the biomass is reduced by adopting a proper pretreatment method, so that the method has important significance for the subsequent enzymatic hydrolysis, transformation, utilization and fermentation of wood fiber raw materials. An effective pretreatment method aims at removing lignin and hemicellulose, reducing the crystallinity of cellulose and increasing the porosity of materials. Heretofore, various pretreatment methods have been used for treating lignocellulosic raw materials, mainly including alkali pretreatment, acid pretreatment, ionic liquid pretreatment, steam explosion pretreatment, ammonia fiber explosion pretreatment, biological pretreatment, and the like. The traditional pretreatment mostly adopts acid pretreatment or alkali pretreatment, but has the obvious defects of equipment corrosion, high wastewater treatment cost, difficult chemical reagent recovery and the like. Therefore, the search for a solvent system which has the advantages of green and renewable raw materials, simple and cheap synthesis, mild pretreatment process, high efficiency, easy operation and recyclability is the development direction for developing the pretreatment method.

In recent years, eutectic solvents (DES) have been widely studied and used as a new generation of green solvents due to their excellent properties of both ionic liquids and organic solvents. DES is usually a two-component or three-component eutectic mixture composed of Hydrogen bond acceptor (HBA, such as quaternary ammonium salt for short) and Hydrogen bond donor (HBD, such as amide, polyol and carboxylic acid for short) in a certain stoichiometric ratio, and its freezing point is significantly lower than that of each component, and has the advantages of low cost, easy synthesis, biocompatibility and cyclic utilization, etc. The DES system has excellent properties in dissolving, modifying and converting lignocellulosic feedstocks, and is therefore a very valuable pretreatment system in a number of pretreatment processes.

Disclosure of Invention

Aiming at the problems in the prior art, the technical problem to be solved by the invention is to provide a pretreatment method of a lignocellulose raw material, which is beneficial to realizing high-value utilization of all components of the lignocellulose raw material while improving the conversion efficiency of cellulose sugar.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a pretreatment method of a lignocellulose raw material is characterized in that p-methyl benzenesulfonic acid is used as a hydrogen bond donor, choline chloride is used as a hydrogen bond acceptor, ethanol is added to synthesize a novel eutectic solvent, and the lignocellulose raw material is pretreated under mild conditions.

According to the pretreatment method of the lignocellulose raw material, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1: 0.5-1: 3, and the addition amount of ethanol is 1-50 wt% of a p-toluenesulfonic acid and choline chloride solvent system.

According to the pretreatment method of the lignocellulose raw material, the mol ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1, and the addition amount of ethanol is 30 wt% of a p-toluenesulfonic acid and choline chloride solvent system.

According to the pretreatment method of the lignocellulose raw material, the synthesis temperature of the novel eutectic solvent is 50-100 ℃.

According to the pretreatment method of the lignocellulose raw material, the synthesis temperature of the novel eutectic solvent is 60-100 ℃.

According to the pretreatment method of the lignocellulose raw material, the pretreatment temperature of the lignocellulose raw material is 60-120 ℃, and the reaction time is 5-60 min; the mass ratio of the lignocellulose raw material to the novel eutectic solvent is 1: 20-1: 5.

According to the pretreatment method of the lignocellulose raw material, the pretreatment temperature of the lignocellulose raw material is 100 ℃, and the reaction time is 30 min; the mass ratio of the lignocellulose raw material to the novel eutectic solvent is 1: 10.

The pretreatment method of the lignocellulose raw material is characterized in that the lignocellulose raw material is any one of broad-leaved wood, agriculture and forestry processing residues or gramineae plants.

Has the advantages that: compared with the prior art, the invention has the advantages that:

the pretreatment method can degrade and convert more than 70% of lignin and 40-90% of hemicellulose in the lignocellulose raw material, the hydrolysis yield of the cellulase is improved to 100%, meanwhile, the molecular weight of the lignin obtained by separation under the low-temperature condition is greatly reduced, the high-value utilization can be further realized, the novel DES system can be recycled, and the method is a green and efficient pretreatment method and has high application and popularization values.

Drawings

FIG. 1 is a graph of the effect of pretreatment of a lignocellulosic feedstock;

FIG. 2 is a graph showing the effect of lignin feedstock treatment with different ethanol recovery times;

FIG. 3 is a graph showing the results of the study in example 2.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with examples are described in detail below.

Example 1

A method of pretreating a lignocellulosic feedstock comprising the steps of:

(1) heating choline chloride and p-toluenesulfonic acid to clear and transparent liquid at 80 ℃, and respectively adding 10 wt% and 30 wt% of absolute ethyl alcohol into the system to obtain a novel DES system, wherein the molar ratio of the choline chloride to the p-toluenesulfonic acid is 1: 2;

(2) mixing the poplar processing residues with DES according to the mass ratio of 1:10, reacting for 30min at 100 ℃, separating to obtain a pretreatment material and a pretreatment liquid containing lignin after the pretreatment is finished, and cleaning the pretreatment material with distilled water until the washing liquid is neutral.

The research result is shown in figure 1, the content of the lignin of DES pretreated materials without ethanol is not reduced or increased, the removal rate of xylan reaches 95.5%, and the recovery rate of cellulose is 86.3%. The enzyme hydrolysis yield of cellulose 72h was only 1.2% with the addition of 15FPIU/g substrate of cellulase at 5% substrate concentration. As the amount of ethanol added increased from 10% to 30%, the removal rates for xylan were 25.9% and 41.7%, and the removal rates for lignin were 38.7% and 69.2%. The enzyme hydrolysis yield of the cellulose for 72h is increased from 1.7% to 76.6% by adding 15FPIU/g substrate of cellulase according to the substrate concentration of 5%. The novel DES pretreatment with ethanol can efficiently depolymerize the lignocellulose structure of the poplar processing residues, thereby greatly improving the sugar conversion efficiency of the cellulose.

Adding distilled water with 4 times volume of the pre-treated liquid obtained by separation, performing centrifugal separation to obtain a lignin component, distilling a liquid phase to respectively obtain ethanol, water and a DES organic phase, adding 30% of recovered ethanol into a DES organic phase system, pre-treating poplar processing residues under the same conditions, and recovering for 4 times in total, wherein the results are shown in figure 2. The removal rate of xylan and lignin is kept above 40% and 70%, the enzyme hydrolysis yield is reduced, and various xylan degradation products exist in the recovered DES organic phase, so that the pretreatment efficiency of a DES system is influenced, and the cellulose conversion efficiency of substrate fiber is further inhibited.

The particle size and molecular weight of the lignin obtained by separation under different pretreatment conditions (T100T30 and T100T30E30) were analyzed, and the results are shown in Table 1. The addition of ethanol reduces the condensation polymerization of lignin, and the formation of nano lignin is beneficial to the further utilization of lignin.

Wherein, the removal rate of xylan/lignin is 1- (pretreatment material xylan/lignin content)% recovery mass m of pretreatment material₁) V (raw material xylan/lignin content% raw material mass m₂) (ii) a Cellulose recovery ═ mass m (pretreated material cellulose%. pretreated material recovery mass m)₁) V (% of cellulose content of raw Material) by mass m₂)。

TABLE 1 Lignin particle size and molecular weight

	Particle size (nm)	Number average molecular weight Mn	Weight average molecular weight Mw
				T100t30	5004	1686	4975
T10030E30	688.8	1706	3539

Example 2

A method of pretreating a lignocellulosic feedstock comprising the steps of:

(1) heating choline chloride and p-toluenesulfonic acid to clear and transparent liquid at 80 ℃, and respectively adding 15 wt% of absolute ethyl alcohol and water to obtain a DES system, wherein the molar ratio of the choline chloride to the p-toluenesulfonic acid is 1: 1;

(2) mixing the miscanthus sinensis raw material and a DES system according to the mass ratio of 1:10, reacting for 30min at 100 ℃, separating to obtain a pretreatment material and a pretreatment liquid containing lignin after the pretreatment is finished, and cleaning the pretreatment material with distilled water until the washing liquid is neutral.

The results of the study are shown in fig. 3, where the removal rate of lignin of DES pretreated material with added water was negative 13.3%, the removal rate of xylan reached 93.1%, and the recovery rate of cellulose was 82.1%. The cellulose yield after 72h of enzymatic hydrolysis was only 12.6% with the addition of 15FPIU/g substrate of cellulase at 5% substrate concentration.

When ethanol was added, the xylan removal rate was 90.9% and the lignin removal rate was 72.2%. The cellulose yield of 72h enzyme hydrolysis reaches 100% by adding 15FPIU/g substrate of cellulase according to 5% substrate concentration. The novel DES pretreatment with ethanol can efficiently depolymerize the compact cell wall structure of the miscanthus raw material, thereby greatly improving the sugar conversion efficiency of the cellulose.