阅读说明：本技术 一种将禾本科植物化学组分分离并将木质素提纯的方法 (Method for separating chemical components of gramineous plants and purifying lignin ) 是由 程金兰 尹崇鑫 翟华敏 于 2019-09-30 设计创作，主要内容包括：本发明提供了一种将禾本科植物化学组分分离并将木质素提纯的方法,所述方法以禾本科植物秸秆为原料,使用酸性增溶剂溶解木质素,经过过滤、洗涤、稀释、静置和离心步骤后,得到纤维素固体产物和木质素沉淀物,沉淀物经过渗析,从而得到纯净的木质素。本发明利用一种方便回收的酸性增溶剂,便可对植物组分进行有效的分离,是一种环境友好的绿色工艺,在低温短时的条件下分离禾本科秸秆化学组分,不需要高温高压的压力容器,可节约生产成本,提高生产效率,降低能源消耗。(The invention provides a method for separating chemical components of gramineous plants and purifying lignin, which comprises the steps of taking gramineous plant straws as raw materials, dissolving the lignin by using an acid solubilizer, filtering, washing, diluting, standing and centrifuging to obtain a cellulose solid product and a lignin precipitate, and dialyzing the precipitate to obtain pure lignin. The invention utilizes the acid solubilizer which is convenient to recycle, can effectively separate the plant components, is an environment-friendly green process, separates the chemical components of the gramineous straws under the conditions of low temperature and short time, does not need a high-temperature high-pressure container, can save the production cost, improves the production efficiency and reduces the energy consumption.)

1. A method for separating chemical components of gramineous plants and purifying lignin, characterized in that: the method comprises the following steps:

(1) Crushing: selecting dried gramineous plant straw, and crushing by using a crusher to prepare gramineous plant straw slag for later use;

(2) Acid hydrolysis: weighing the grass family plant straw slag prepared in the step (1), an acid solubilizer and deionized water, putting the grass family plant straw slag into a porous round-bottom flask, putting the acid solubilizer and the deionized water into a conical flask, uniformly stirring, putting the porous round-bottom flask and the conical flask into a water bath kettle, fixing the porous round-bottom flask and the conical flask by using a test tube rack, heating the porous round-bottom flask and the conical flask in the water bath kettle to a set temperature, adding the acid solubilizer solution in the conical flask into the porous round-bottom flask, continuously stirring, setting the reaction time, and adding deionized water with the weight equal to the total weight of the reaction raw materials into the porous round-bottom flask when the reaction is finished to prepare a fiber suspension for later;

(3) and (3) filtering: filtering the fiber suspension obtained in the step (2), and separating to obtain a solid product containing cellulose and a filtrate dissolved with lignin for later use;

(4) Washing: washing the solid product prepared in the step (3) by using deionized water, and collecting the waste liquid obtained by washing;

(5) diluting: mixing the filtrate obtained in the step (3) and the waste liquid obtained in the step (4) to prepare a mixed solution, and diluting the mixed solution by using deionized water until the concentration of the acid solubilizer is lower than the critical micelle concentration of the acid solubilizer;

(6) Standing: standing the mixed solution obtained in the step (5) until the supernatant of the upper layer is separated from the precipitate of the lower layer;

(7) centrifuging: sucking off the supernatant obtained in the step (6), centrifuging the lower-layer precipitate, and removing excessive water;

(8) And (3) dialysis: transferring the precipitate obtained in the step (7) after centrifugation into a semipermeable membrane bag, and putting the semipermeable membrane bag into deionized water for dialysis;

(9) And (3) drying: and (8) after dialysis is finished, centrifuging the precipitate, removing water, and freeze-drying to obtain pure lignin.

2. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: the gramineae plant in the step (1) is any one of wheat, corn, soybean, rice, barley, sorghum, oat and sugarcane.

3. The method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: in the step (2), the acid solubilizer is p-toluenesulfonic acid, and the mass percentage concentration of the p-toluenesulfonic acid in the total weight of the experiment is 30-60%.

4. The method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: in the step (2), the set temperature is 60-80 ℃, and the reaction time is 15-60 min.

5. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: and (4) filtering in the step (3) by adopting vacuum filtration, wherein the vacuum filtration adopts a Buchner funnel to be sequentially connected with a suction bottle and a vacuum pump.

6. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: the washing described in step (4) uses deionized water to wash the solid product to neutrality.

7. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: the critical micelle concentration in step (5) is 1%.

8. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: and (4) standing the mixed solution in the step (6) for 24 hours.

9. The method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: and (5) putting the mixture into deionized water for dialysis, specifically measuring the conductivity of the deionized water every 12 hours, and replacing the deionized water until the conductivity is less than 0.1.

10. the method for separating chemical components of gramineous plants and purifying lignin according to claim 1, wherein: the centrifugation conditions in the step (7) and the step (9) are that the rotation speed is 8000r/min at 20 ℃, and the centrifugation is 10 min.

Technical Field

The invention relates to the technical field of biomass energy, in particular to a method for separating chemical components of gramineous plant straws and purifying lignin.

Background

excessive consumption of fossil fuels such as petroleum, coal mines, etc. has resulted in continuous deterioration of the ecological environment, and fossil fuels are difficult to regenerate. Lignocellulose is derived from natural renewable plants, and cellulose is polysaccharide which is distributed most widely in nature and has the largest content, accounts for more than 50% of carbon content in the plants, and is renewable organic energy with the most abundant reserves on the earth. The solid fiber component obtained after separation can be further developed and utilized by a component separation mode, such as papermaking, monosaccharide manufacturing, methyl cellulose, cellulose ether, multi-polymer cellulose and the like; the obtained lignin can be made into reinforcing agents, antiscaling agents, binding agents and the like by means of grafting or modification and the like. Therefore, there is an increasing interest in developing lignocellulose to replace fossil fuels and to use the value of the lignocellulose more greatly.

lignocellulose is the most abundant biomass resource in nature, and is mainly composed of cellulose, hemicellulose and lignin. Cellulose is a linear high molecular compound formed by connecting beta-D-glucose units through 1-4-glycosidic bonds. Hemicellulose is a generic term for non-cellulosic high glycans in the cell wall, consisting of two or more sugar groups, usually with a branched structure. The lignin is an aromatic high polymer which is formed by connecting phenylpropane units through ether bonds and carbon-carbon bonds and has a three-dimensional space structure. Together, lignin and hemicellulose form a so-called lignin-hemicellulose complex, which fills the space between the microfibrils of the cell wall and is also present in the intercellular layer.

The gramineous plant straws have short growth period and high yield, and the straws, bean stalks, wheat stalks and the like which are agricultural byproducts are inexhaustible renewable natural resources. The grass plant straw not only has renewability, but also has good biocompatibility and biodegradability. At present, straws, bean stalks, wheat stalks and the like are mostly used for power generation, incineration, ethanol production and the like, have low added value and have certain destructive effect on the environment.

the patent (CN104404803B) discloses a method for separating straw components and utilizing the straw components, which separates hemicellulose by performing steam explosion treatment on the straw, and then performs steam explosion treatment on the residual material after extracting the hemicellulose again to realize the separation of cellulose and lignin. Although the process can effectively avoid the problem of secondary pollution of chemical treatment, the method has high requirement on the accuracy of parameters, the process parameters actually applied to production must be consistent with laboratory equipment to ensure the usability of the parameters, otherwise, the process can only stay in a laboratory stage, and therefore, the method may restrict the realization of industrial application.

The patent (CN104987429B) discloses an extraction method for separating Antrodia camphorata compound components, which takes Antrodia camphorata fruiting body powder or mycelium as a raw material and adopts the technology of combining enzymolysis, supercritical CO ₂ extraction, ion exchange chromatography, membrane separation ultrafiltration and chromatography purification to realize the separation and extraction of the Antrodia camphorata compound components.

the patent (CN105484083B) discloses a process for separating lignocellulose components, which comprises pretreating biomass by irradiation, coupling low-boiling tetrahydrofuran or high-boiling γ -amyl ester reaction, performing primary filtration to obtain cellulose components, recovering tetrahydrofuran from filtrate, or adding saturated NaCl solution to perform phase separation and precipitate lignin, performing secondary filtration to obtain lignin components as residues, and drying the secondary filtrate to obtain hemicellulose components. The irradiation pretreatment adopted by the method has certain radioactivity, has certain potential safety hazard to human bodies, and the used tetrahydrofuran has certain carcinogenic risk to the human bodies, so the method is not a very friendly process method probably to the human health.

The patent (CN106061891B) discloses a process for removing lignin from plants by using mixed acid. The process relates to a system for delignifying plant matter impregnated with a solution of an organic acid selected from acetic acid, formic acid, propionic acid, butyric acid or a mixture of these acids, preferably a mixture of acetic acid and formic acid, containing said plant matter and a hydrogen peroxide composition comprising hydrogen peroxide and at least one phosphorus additive, for the delignification of plant matter impregnated with a solution of an organic acid selected from acetic acid, formic acid, propionic acid, butyric acid or a mixture of these acids, preferably a mixture of acetic acid and formic acid. The method needs more types of mixed acids, uses phosphorus as an additive, easily causes the problem of secondary pollution of chemical reagents, and is probably not an environment-friendly process method.

The patent (CN105861592B) discloses a method for pretreating lignocellulose biomass, which comprises using lignocellulose biomass with a particle size of 0.5-2 mm as a raw material, and using solid alkali as a catalyst to pretreat the lignocellulose biomass in a hydrothermal environment, so as to break a dense structure of lignocellulose, catalyze the stripping degradation of lignin in the lignocellulose, and dissolve and separate hemicellulose. The preparation method of the solid alkali used in the method is complex, the requirement on raw materials is high, the raw materials need to be pretreated to reduce the granularity, and the mode can cause the increase of the production cost.

The patent (CN105854907B) discloses a method for preparing carboxymethyl cellulose with ultralow viscosity by separating straw components, which comprises the steps of hydrolyzing straw hemicellulose by an acid method to obtain fermentable monosaccharide, extracting straw lignin by an organic solvent method to obtain high-activity lignin, refining cellulose by an alkaline oxidation method, and finally carrying out etherification modification on the straw cellulose to prepare carboxymethyl cellulose. The process is divided into four stages, which are complicated, each stage uses chemicals, and the process may cause secondary pollution of the chemicals.

The existing separation technology of the chemical components of the gramineous plants is complex, the requirements on experimental conditions are high, and secondary pollution is easily caused. Therefore, how to achieve separation of plant components with maximum efficiency under optimal conditions is an important research direction for the application range of biomass energy.

disclosure of Invention

the invention mainly aims to provide a method for separating chemical components of gramineous plant straws, which uses an acid solubilizer to efficiently separate chemical components of cell walls of gramineous plant straws, wherein the acid solubilizer can be recycled, has simple operation process, reduces time cost, energy consumption and cost, and can reduce the pollution of chemicals to the environment and the phenomenon of cost increase caused by long reaction time and high reaction temperature.

the invention also aims to provide a method for purifying the lignin prepared by the method, and the method can prepare pure lignin by conventional experimental methods such as dilution, standing, centrifugation, dialysis and the like so as to achieve the aim of efficiently utilizing biomass resources.

A method for separating chemical components of straw of Gramineae plant and purifying lignin comprises the following steps:

(1) Crushing: selecting dried grass family plant straw, and crushing by a crusher to obtain grass family plant straw slag for later use.

(2) acid hydrolysis: weighing the grass family plant straw slag prepared in the step (1), an acid solubilizer and deionized water, putting the grass family plant straw slag into a porous round-bottom flask, putting the acid solubilizer and the deionized water into a conical flask, uniformly stirring, putting the porous round-bottom flask and the conical flask into a water bath kettle, fixing by using a test tube rack, heating to a set temperature in the water bath kettle, adding the acid solubilizer solution in the conical flask into the porous round-bottom flask, continuously stirring, setting the reaction time, and adding deionized water with the weight equal to the total weight of the reaction raw materials into the porous round-bottom flask when the reaction is finished to prepare a fiber suspension for later use.

the acid solubilizer solution and the grass plant straw slag are separately and simultaneously heated to a set temperature and then mixed together, so that the separation effect of the acid solubilizer on plant components at the temperature can be accurately researched. In order to avoid the influence of the rotating speed on the reaction, all reactions are carried out at the same rotating speed.

The addition of deionized water can cause the temperature to drop rapidly, thus the temperature required by the reaction can not be reached, and the method can ensure the accuracy of the reaction time.

(3) And (3) filtering: and (3) filtering the fiber suspension obtained in the step (2), and separating to obtain a solid product containing cellulose and a filtrate dissolved with lignin for later use.

(4) Washing: washing the solid product prepared in the step (3) by deionized water, and collecting the waste liquid obtained by washing.

(5) Diluting: and (4) mixing the filtrate obtained in the step (3) and the waste liquid obtained in the step (4) to prepare a mixed solution, and diluting the mixed solution by using deionized water until the concentration of the acid solubilizer is lower than the critical micelle concentration of the acid solubilizer.

lignin is dissolved in acid and when the acid concentration is low to its critical micelle concentration, lignin precipitates from the acid solution to form a precipitate.

(6) Standing: and (5) standing the mixed solution obtained in the step (5) until the supernatant of the upper layer and the precipitate of the lower layer are separated.

(7) Centrifuging: and (4) sucking off the supernatant obtained in the step (6), centrifuging the lower-layer precipitate, and removing excessive water.

The centrifugation is mainly to separate lignin from water, and the acidic solubilizer and monosaccharide micromolecule substances dissolved in the water are removed simultaneously when the water is removed.

(8) And (3) dialysis: transferring the precipitate obtained in the step (7) after centrifugation into a semipermeable membrane bag, and putting the semipermeable membrane bag into deionized water for dialysis.

The acidic solubilizer and the small monosaccharide molecules attached to the lignin are transferred to the deionized water through the semipermeable membrane, and the large lignin molecules are retained in the semipermeable membrane.

(9) And (3) drying: and (8) after dialysis is finished, centrifuging the precipitate, removing water, and freeze-drying to obtain pure lignin.

and the moisture is removed by centrifuging again, so that the drying time of the lignin at the later stage can be reduced.

Preferably, the gramineous plant in the step (1) is any one of wheat, corn, soybean, rice, barley, sorghum, oat and sugarcane.

preferably, the component of the acidic solubilizer in the step (2) is p-toluenesulfonic acid, and the concentration of the p-toluenesulfonic acid in the total weight of the experiment is 30-60% by mass.

Preferably, the set temperature in the step (2) is 60-80 ℃, and the reaction time is 15-60 min.

Preferably, the filtration in step (3) is vacuum filtration, and the vacuum filtration is performed by connecting a Buchner funnel with a suction bottle and a vacuum pump in sequence.

wherein, buchner funnel connects gradually with suction bottle, vacuum pump, can accelerate filter speed.

preferably, the washing described in step (4) uses deionized water to wash the solid product to neutrality.

The solid product is washed to be neutral, so that the solid product can not be attached with an acid solubilizer, and monosaccharide micromolecule substances on the solid product can be dissolved in water and removed in the washing process, so that a pure solid product can be obtained.

Preferably, the critical micelle concentration in step (5) is 1%.

Preferably, the mixed solution in the step (6) is allowed to stand for 24 hours.

Preferably, the deionized water is put into the step (8) for dialysis, specifically, the conductivity of the deionized water is measured every 12 hours, and the deionized water is replaced until the conductivity is less than 0.1.

the acid solubilizer and the monosaccharide micromolecule substance are dissolved in water to generate electric conductivity, and the dialysis speed and the reaction end point can be effectively known by comparing the electric conductivity of pure water with the electric conductivity of dialyzed water.

preferably, the centrifugation conditions in step (7) and step (9) are 20 ℃, 8000r/min and 10min of centrifugation.

Advantageous effects

1. The method of the invention realizes effective separation of plant components by only using one acid solubilizer which is convenient to recover, is an environment-friendly green process, effectively avoids the defect of large cost investment in the recovery of chemical reagents in the traditional process, and gets rid of the problem of dependence of the component separation process on the combined action of various chemical reagents.

2. The method disclosed by the invention separates the gramineous plant components under the conditions of low temperature and short time, does not need a high-temperature high-pressure container, can save the production cost, improve the production efficiency and reduce the energy consumption, and can effectively avoid safety accidents such as scalding and the like under the low-temperature operation condition.

3. because the chemical components are separated in a low-temperature environment, the degradation degree of cellulose and hemicellulose is low, so that the yield of the obtained solid fiber component is high, the polycondensation degree of the obtained lignin is low, and the original macromolecular structure of the lignin is well reserved.

4. The solid fiber product obtained by the method can better preserve the original form, can be further used for manufacturing paper, provides a novel pulping thought for the pulping and papermaking industry, and can also be used for the biomass energy industry, the solid fiber product is subjected to enzymolysis to form monosaccharide, and then the monosaccharide is fermented to form bioethanol or biomass diesel oil and the like.

the foregoing is only an overview of the technical solutions of the present invention, and in order to more clearly understand the technical solutions of the present invention, the present invention is further described below with reference to the accompanying drawings.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 shows the morphology of a solid product prepared by the present invention under a 40-fold microscope;

FIG. 3 is a graph of the molecular weight distribution of lignin according to the present invention.

Detailed Description

The invention discloses a method for separating chemical components of gramineous plant cell walls and purifying lignin. According to the property that the lignin is soluble in acid and insoluble in water, the filtrate containing the acid solubilizer and the lignin is diluted, and when the concentration of the acid solubilizer is lower than the critical micelle concentration, the lignin is separated from the acid solubilizer to form a precipitate. The obtained lignin can remove acidic solubilizer and monosaccharide micromolecule substances attached to the lignin by simple dialysis, thereby obtaining pure lignin. The solid product can retain better fiber form, and can be used for making paper, hydrolyzing to obtain fermentable monosaccharide, and the like.

In order to understand the present invention, the following examples are given to further illustrate the present invention.

wherein the gramineous plant is any one of wheat, corn, soybean, rice, barley, sorghum, oat and sugarcane, and the specific embodiment adopts rice straw as an example for illustration.

in order to examine the influence of different process conditions on the solid product yield and the lignin removal rate, different examination conditions are set, wherein the examination conditions comprise different concentrations of the acid solubilizer, different reaction temperatures and different reaction times, and the specific examples are as follows: