阅读说明：本技术 一种提升阔叶木制浆预水解液中低聚木糖纯化效率的方法 (Method for improving purification efficiency of xylooligosaccharide in hardwood pulping prehydrolysis liquid ) 是由 陈嘉川 贾志欣 张凯 杨桂花 吉兴香 于 2019-11-13 设计创作，主要内容包括：本发明涉及一种提升阔叶木制浆预水解液中低聚木糖纯化效率的方法,具体步骤为：将阔叶木水热法得到的预水解液进行浓缩；将浓缩后的水解液利用氢氧化钙进行吸附处理；氢氧化钙处理后的水解液利用活性炭进行吸附处理；利用活性炭进行吸附处理后的水解液利用木聚糖酶进行水解制备得到低聚木糖。本发明的方法,提高了乙酸和糠醛的回收率,提高了对生物酶的水解作用具有抑制作用的物质的去除率,得到的低聚木糖纯化液的浓度提高。(The invention relates to a method for improving the purification efficiency of xylooligosaccharide in a hardwood pulping prehydrolysis liquid, which comprises the following specific steps: concentrating prehydrolysis liquid obtained by a broadleaf wood hydrothermal method; performing adsorption treatment on the concentrated hydrolysate by using calcium hydroxide; performing adsorption treatment on the hydrolysate after the calcium hydroxide treatment by using active carbon; hydrolyzing the hydrolysate subjected to adsorption treatment by using active carbon by using xylanase to prepare xylo-oligosaccharide. The method of the invention improves the recovery rate of acetic acid and furfural, improves the removal rate of substances which have inhibition effect on the hydrolysis of biological enzyme, and improves the concentration of the obtained xylo-oligosaccharide purified solution.)

1. A method for improving the purification efficiency of xylooligosaccharide in a hardwood pulping prehydrolysis liquid is characterized by comprising the following steps: the method comprises the following specific steps:

concentrating prehydrolysis liquid obtained by a broadleaf wood hydrothermal method;

performing adsorption treatment on the concentrated hydrolysate by using calcium hydroxide;

performing adsorption treatment on the hydrolysate after the calcium hydroxide treatment by using active carbon;

hydrolyzing the hydrolysate subjected to adsorption treatment by using active carbon by using xylanase to prepare xylo-oligosaccharide.

2. The method for improving the purification efficiency of xylooligosaccharide in the prehydrolysis liquid of hardwood pulping according to claim 1, characterized in that: the method for concentrating the prehydrolysis liquid comprises the steps of heating and concentrating in vacuum, wherein the heating temperature is 45-75 ℃; preferably 45 deg.C, 50 deg.C, 55 deg.C, 60 deg.C, 70 deg.C or 75 deg.C.

3. The method for improving the purification efficiency of xylooligosaccharide in the prehydrolysis liquid of hardwood pulping according to claim 1, characterized in that: the volume ratio before and after concentration is 1.5-5.5; preferably 1.5, 1.7, 2.0, 3.0, 4, 4.5, 5.0, 5.5.

4. The method for improving the purification efficiency of xylooligosaccharide in the prehydrolysis liquid of hardwood pulping according to claim 1, characterized in that: the addition amount of the calcium hydroxide is 0.4-2.8 wt% of the mass of the hydrolysate;

or, the calcium hydroxide is subjected to adsorption reaction at room temperature, the magnetic stirring rotating speed is 400-500rpm, and the reaction time is 50-70 min.

5. The method for improving the purification efficiency of xylooligosaccharide in the prehydrolysis liquid of hardwood pulping according to claim 1, characterized in that: the dosage of the active carbon is 0.6-4.8 wt% of the mass of the hydrolysate;

or, the active carbon is used for carrying out the reaction at room temperature, the reaction time is 5-15min, and the rotating speed of the magnetic stirrer is 250-350 rpm.

6. The method of claim 1 for improving oligomerization in hardwood pulping prehydrolysis liquidA method for purifying xylose with efficiency, characterized by: the specific conditions of the enzymolysis treatment are as follows: 50-55 ℃, pH: 5-6, total dosage: 1-4 U.mL^-1The hydrolysate is reacted for 6-8 h.

7. The method for improving the purification efficiency of xylooligosaccharide in the prehydrolysis liquid of hardwood pulping according to claim 1, characterized in that: the broadleaf wood is poplar, acacia wood or fast-growing poplar.

8. The method for improving the purification efficiency of the xylo-oligosaccharide in the hardwood pulping prehydrolysis liquid as claimed in any one of claims 1 to 7.

9. The xylose oligosaccharide finished product obtained by separating and purifying the xylose oligosaccharide purified liquid of claim 8.

10. The method for improving the purification efficiency of xylooligosaccharide in hardwood pulping prehydrolysis liquid as claimed in any one of claims 1 to 7 or the use of xylooligosaccharide finished product as claimed in claim 9 in the preparation of medical health-care medicine or food additive.

Technical Field

The invention belongs to the technical field of biomass refining and biology, and particularly relates to a method for improving the purification efficiency of xylooligosaccharide in a hardwood pulping prehydrolysis liquid.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

In the process of preparing dissolving pulp, after broad-leaved wood chips are pretreated by a hydrothermal method, the obtained hydrolysate contains xylan (with polymerization degree of 2-25) and xylose, a small amount of glucose, arabinose and lignin, and substances such as formic acid, acetic acid, furfural and 5-hydroxymethylfurfural generated by saccharide degradation. In the traditional production process, the hemicellulose (the main component monomer is xylose) and black liquor are combusted and converted into heat for recovery, but the calorific value of the hemicellulose is 13.61 MJ.kg^-1The heat value of lignin is only 27 MJ.kg^-11/2, causing waste of resources. Based on the development of a biomass refining technology, the hydrolysate is purified and then xylan components are extracted and utilized to be converted into a xylo-oligosaccharide product with high added value, and the method has great significance for improving enterprise benefits and utilizing biomass in the hydrolysate in a high value.

In the process of preparing xylo-oligosaccharide by degrading xylan in pulping prehydrolysis liquid, the commonly used methods comprise an acidolysis method, a biological enzyme method and the like. Among them, the biological enzyme method has characteristics of mildness, greenness and high efficiency, and is attracting much attention. However, lignin, furfural, 5-hydroxymethylfurfural, acetic acid, and the like, present in the pulping prehydrolysis liquid may inhibit the hydrolysis of biological enzymes. Therefore, to improve the enzymolysis efficiency, the prehydrolysis liquid needs to be purified before the enzymolysis of the pulping prehydrolysis liquid, so as to reduce the inhibition effect.

Currently, the commonly used methods for purifying the hydrolysate include membrane filtration, solvent extraction, ion exchange, adsorption, and the like. The absorption method mainly uses calcium hydroxide and activated carbon which are relatively cheap, and the hydrolysate can be detoxified by using the calcium hydroxide and the activated carbon, so that organic acid, lignin and degradation products thereof are removed by a common purification method. However, the desorption efficiency in the recovery process of the adsorbents such as the activated carbon is low, the using amount is large, and the cost is high.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for improving the purification efficiency of xylooligosaccharide in hardwood pulping prehydrolysis liquid. The invention provides a purification method combining hydrolysate concentration, calcium hydroxide treatment and active carbon adsorption for saving the consumption of purification chemicals, reducing the loss of saccharides and improving the purification efficiency of prehydrolysis liquid, which is used for the purification process of prehydrolysis liquid for wood chip pulping and lays a foundation for the subsequent biological enzyme treatment and the production of high-quality xylo-oligosaccharide.

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

a method for improving the purification efficiency of xylooligosaccharide in hardwood pulping prehydrolysis liquid comprises the following specific steps:

concentrating prehydrolysis liquid obtained by a broadleaf wood hydrothermal method;

performing adsorption treatment on the concentrated hydrolysate by using calcium hydroxide;

performing adsorption treatment on the hydrolysate after the calcium hydroxide treatment by using active carbon;

hydrolyzing the hydrolysate subjected to adsorption treatment by using active carbon by using xylanase to prepare xylo-oligosaccharide.

The purification method comprises the steps of concentrating the prehydrolysis liquid, sequentially and respectively adsorbing by calcium hydroxide and active carbon, recovering furfural and acetic acid, and treating xylan in the hydrolysis liquid by xylanase to obtain xylo-oligosaccharide purified liquid.

According to the method, by means of concentration and adsorption, the concentration of substances in the hydrolysate is improved by utilizing the concentration process, wherein the double electric layers on the surfaces of the lignin colloidal particles are compressed due to the increase of the concentration of the electrolyte, so that the stable system of the colloidal particles is damaged, and lignin molecules are polymerized and settled; secondly, the hydrolysate after concentration is adsorbed by using calcium hydroxide and active carbon, and the polymerized and settled lignin is easy to be adsorbed, thereby further improving the purification efficiency. The purification means of the invention separates and adsorbs more lignin, furfural, acetic acid and other substances in the prehydrolysis liquid as much as possible, reduces the dosage of the adsorbent, and then leaves more xylan, so that the amount of the finally obtained xylo-oligosaccharide is more. The loss of xylan is small.

The concentration process can change the property of the hydrolysate and promote the polymerization and self-precipitation of lignin, thereby improving the adsorption efficiency of calcium hydroxide and active carbon. Part of acetic acid and more than 95 percent of furfural can be separated in the concentration process, and the method is a feasible way for realizing component separation and high-value utilization.

In some embodiments, the prehydrolysis liquid is concentrated by vacuum heating at 45-75 ℃; for example, it may be 45 ℃, 50 ℃, 55 ℃, 60 ℃, 70 ℃ or 75 ℃. In some embodiments, the volume ratio before and after concentration is 1.5 to 5.5; for example, it may be 1.5, 1.7, 2.0, 3.0, 4, 4.5, 5.0, 5.5. The volume ratio of the concentrated solution to the concentrated solution is 2.0 to 4.0.

When the concentration multiple is 2.0, more than 95 percent of furfural can be separated. While the lignin has already undergone polymerization settling. When the concentration multiple is continuously increased, the furfural removal rate reaches 100% at most, and the lignin sedimentation phenomenon is more obvious at the moment. And the promotion effect of the concentration times on the adsorption and purification process is more obvious.

However, when the concentration multiple is greater than 5.0, the viscosity of the hydrolysate is increased due to the increase of the concentration of various substances in the concentrated hydrolysate, and even the lignin precipitates, lumps and adheres to the surface of the equipment, so that the operation and maintenance requirements of the equipment can be improved.

In summary, the patent selects the concentration factor to be 2.0 and 4.0.

In some embodiments, the amount of calcium hydroxide added is 0.4-2.8 wt% of the mass of the hydrolysate. In some embodiments, the calcium hydroxide is subjected to the adsorption reaction at room temperature, the magnetic stirring speed is 400-. In the invention, calcium hydroxide is used for adsorption, and then activated carbon is used for adsorption, so that degradation products such as lignin, organic acid and the like in the hydrolysate are removed. The influence of the addition of the calcium hydroxide is that the removal rate of lignin, organic acid, furfural and other degradation products can be improved along with the increase of the dosage, and when the dosage reaches a certain dosage, the adsorption effect on the lignin is not increased any more.

In some embodiments, the amount of the activated carbon is 0.6-4.8 wt% of the mass of the hydrolysate. In some embodiments, the activated carbon is adsorbed at room temperature for 5-15min, and the rotation speed of the magnetic stirrer is 250-350 rpm. The influence of the addition of the activated carbon is that along with the increase of the dosage, the removal rate of lignin in the hydrolysate can be obviously improved, and meanwhile, xylo-oligosaccharide is adsorbed, so that the proper dosage needs to be selected.

In some embodiments, the specific conditions of the enzymatic treatment are temperature: 50-55 ℃, pH: 5-6, total dosage: 1-4 U.mL^-1The hydrolysate is reacted for 6-8 h. The enzyme dosage is relatively low, and the reaction time is relatively prolonged in order to ensure the yield of xylooligosaccharide.

In some embodiments, the hardwood is poplar, maple, birch, acacia, or fast-growing poplar.

The xylo-oligosaccharide purified liquid prepared by the method for improving the purification efficiency of the hardwood pulping prehydrolysis liquid.

And (3) separating and purifying the xylo-oligosaccharide purified solution to obtain a xylo-oligosaccharide finished product.

The method for improving the purification efficiency of the hardwood pulping prehydrolysis liquid or the application of the xylo-oligosaccharide finished product in preparing medical health-care medicines or food additives.

The invention has the beneficial effects that:

according to the method, the hardwood pulping prehydrolysis liquid is used as a raw material, in the process of preparing the xylo-oligosaccharide, through multiple stages of reasonable purification and enzymolysis steps, a concentration-assisted calcium hydroxide and active carbon synergistic purification and enzyme treatment means is adopted, the lignin removal rate in the hydrolysis liquid is high, the carbohydrate loss is small, the using amount of an adsorbent is effectively reduced, the adsorption efficiency is improved, meanwhile, furfural and part of acetic acid in the hydrolysis liquid can be recovered, the yield of a target product xylo-oligosaccharide in the hydrolysis liquid is greatly improved, and the method for utilizing the carbohydrate in the hydrolysis liquid at a high value is provided. Compared with the traditional acid method for preparing xylan, the method disclosed by the invention is simple, has fewer byproducts, is green and energy-saving, is beneficial to environmental protection, and can generate good social benefit, economic benefit and ecological benefit, so that the method has good practical application value and industrial prospect.

The invention changes the properties of the hydrolysate through the concentration process, thereby improving the delignification efficiency of the calcium hydroxide and the active carbon. Namely: under the condition of the same dosage of calcium hydroxide and activated carbon, more lignin is removed, thereby achieving the purposes of reducing the cost of the medicine and improving the efficiency. The method of the invention improves the efficiency, reduces the consumption, reduces the cost and saves the recovery cost.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As mentioned above, during the prehydrolysis process before pulping, the prehydrolysis liquid mainly contains hemicellulose (mainly containing saccharides such as xylan), lignin and other degradation products. The sugar in the process can not be efficiently utilized, the additional value is low, and the waste of resources and the loss of economic benefits of enterprises are caused. And depolymerizing xylan in the hydrolysate to obtain the xylo-oligosaccharide component with higher added value. The xylo-oligosaccharide content in the hydrolysate is low, and simultaneously, impurities such as lignin and the like have an inhibiting effect on enzymes and the like, so that great difficulty is brought to the preparation of the xylo-oligosaccharide. The invention improves the removal rate of lignin and other impurities. The yield of the xylo-oligosaccharide is improved.