Method for preparing straw ethanol with assistance of ionic liquid
阅读说明：本技术 一种离子液体辅助制备秸秆乙醇的方法 (Method for preparing straw ethanol with assistance of ionic liquid ) 是由 刘弋潞 周子凡 王春燕 梁秋志 于 2019-10-30 设计创作，主要内容包括：本发明公开了一种离子液体辅助制备秸秆乙醇的方法,所述方法包括以下步骤：步骤S1.预处理：将秸秆粉碎过筛,得秸秆粉,然后进行化学预处理；步骤S2.离子液体处理：取预处理后的秸秆粉,加入离子液体,混匀后于135～150℃加热4～6h,冷却,过滤,并用去离子水清洗,滤渣干燥,得离子液体处理后的秸秆粉；步骤S3.水解及发酵：将步骤S2处理后的秸秆粉先用去离子水润湿,然后加入含纤维素酶的缓冲溶液,再加入甜酒曲,35℃水浴恒温发酵2天,过滤并用去离子水清洗5～6次,收集滤液,并蒸馏,得秸秆乙醇。本发明提供的离子液体辅助制备秸秆乙醇的方法,能提高预处理的效果,提高乙醇的得率和转化,并且步骤简单,适合工业化生产。(The invention discloses a method for preparing straw ethanol by ionic liquid assistance, which comprises the following steps: step S1, pretreatment: crushing and sieving the straws to obtain straw powder, and then carrying out chemical pretreatment; s2, ionic liquid treatment: adding ionic liquid into the pretreated straw powder, uniformly mixing, heating at 135-150 ℃ for 4-6 h, cooling, filtering, washing with deionized water, and drying filter residues to obtain ionic liquid-treated straw powder; s3, hydrolysis and fermentation: wetting the straw powder treated in the step S2 with deionized water, adding a buffer solution containing cellulase, adding sweet distiller' S yeast, fermenting for 2 days in a water bath at constant temperature of 35 ℃, filtering, washing with deionized water for 5-6 times, collecting filtrate, and distilling to obtain the straw ethanol. The method for preparing the straw ethanol by the ionic liquid assistance can improve the pretreatment effect and the yield and the conversion of the ethanol, has simple steps, and is suitable for industrial production.)
1. The method for preparing straw ethanol by ionic liquid assistance is characterized by comprising the following steps:
step S1, pretreatment: crushing and sieving the straws to obtain straw powder, and then carrying out chemical pretreatment;
s2, ionic liquid treatment: adding ionic liquid into the pretreated straw powder, uniformly mixing, heating at 135-150 ℃ for 4-6 h, cooling, filtering, washing with deionized water, and drying filter residues to obtain ionic liquid-treated straw powder;
s3, hydrolysis and fermentation: wetting the straw powder treated in the step S2 with deionized water, adding a buffer solution containing cellulase, adding sweet distiller' S yeast, fermenting for 2 days in a water bath at constant temperature of 35 ℃, filtering, washing with deionized water for 5-6 times, collecting filtrate, and distilling to obtain the straw ethanol.
2. The method for preparing straw ethanol with the assistance of the ionic liquid as claimed in claim 1, wherein the ionic liquid is an alcohol amine ionic liquid comprising one of triethanolamine lactic acid, triethanolamine acetic acid and triethanolamine formic acid.
3. The method for preparing straw ethanol with the assistance of the ionic liquid as claimed in claim 1, wherein in the step S2, the addition amount of the ionic liquid is 20-40 mL/g of straw powder.
4. The ionic liquid assisted method for preparing straw ethanol as claimed in claim 1, wherein in the step S1, the chemical pretreatment comprises one of acid treatment, alkali treatment and wet oxidation treatment.
5. The ionic liquid assisted method for preparing straw ethanol as claimed in claim 4, wherein the wet oxidation treatment comprises the following steps: taking straw powder and deionized water according to the solid-liquid ratio of 6: 100, stirring and mixing, and then placing the mixture in Na containing 2g/L2CO3Treating the solution in a high-pressure steam kettle at 150 ℃ and 0.165MPa for 30-50 minutes, cooling to room temperature, and performing suction filtration and drying to obtain a wet oxygen treatment product.
6. The ionic liquid assisted method for preparing straw ethanol as claimed in claim 4, wherein the acid treatment comprises the steps of: mixing straw powder with 1% of H2SO4The solution is mixed according to the solid-liquid ratio of 1g to 30mL, and zeolite bath is carried outAnd (3) performing medium ultrasonic treatment for 20-30 min, adjusting the pH value to be neutral by using a 1% NaOH solution, filtering, washing with water, performing suction filtration and drying to obtain an acid treatment product.
7. The ionic liquid assisted method for preparing straw ethanol as claimed in claim 1, wherein in the step S3, the buffer solution is citric acid-trisodium citrate buffer solution, and the pH value of the buffer solution is 4.8.
8. The ionic liquid assisted preparation method of straw ethanol as claimed in claim 1, wherein in the step S3, the concentration of cellulase in the buffer solution is 0.01 g/L.
9. The ionic liquid assisted straw ethanol preparation method of claim 1, wherein in the step S3, the sweet wine yeast is added in an amount of 10% by weight of the straw powder.
Technical Field
The invention relates to the technical field of ethanol production, and particularly relates to a method for preparing straw ethanol by ionic liquid assistance.
Background
Ethanol is a high-efficiency, clean, safe and renewable fuel, is also an important chemical raw material, and has wide application. The traditional ethanol production method takes starchiness as raw materials, has high cost and occupies grain resources. At present, agricultural and forestry waste crops with high wood fiber content are used as raw materials to produce ethanol, so that the pollution of the agricultural and forestry waste crops to the environment can be relieved, and the dependence of fuel production on grains can be reduced. The agricultural and forestry waste crop raw materials in China are very rich, comprise crop straws, forestry fiber waste materials and industrial fiber waste residues, are wide in source and huge in quantity, the total amount is up to 20 hundred million tons, and the quantity of the light crop straws is more than 7 hundred million tons. Therefore, the development of corresponding technology for producing ethanol by hydrolyzing and fermenting the agricultural and forestry waste crops with high wood fiber content has great significance for sustainable development of economy and society in China.
The main components of the agricultural wastes, grass and other straw wastes comprise cellulose, hemicellulose, lignin and the like, and the cellulose and the hemicellulose can be converted into ethanol through hydrolytic fermentation. In the prior art, the process for converting straw into ethanol is also called a cellulose fuel ethanol process, and mainly comprises the following steps: the method comprises the following process steps of raw material pretreatment, cellulose and hemicellulose hydrolysis saccharification, fermentation of pentose and hexose, distillation dehydration and the like, wherein the pretreatment and hydrolysis are key steps influencing conversion of lignocellulose into ethanol. The existing pretreatment methods comprise a physical method, a chemical method and a biological method, and lignin in the pretreatment methods is removed to improve the subsequent hydrolysis efficiency. The chemical method treatment is a commonly used method at present, and acid addition, addition and subtraction or wet oxidation is usually adopted, but the prior pretreatment methods all have the problem of incomplete lignin removal, which causes low subsequent hydrolysis efficiency. In addition, the hydrolysis method in the prior art usually adopts acid hydrolysis and enzyme hydrolysis, the acid hydrolysis has the defects of producing organic acid, phenols and aldehyde compounds with the inhibiting effect on fermentation, and the enzyme hydrolysis has the defects of low enzyme activity and high cost.
It is seen that improvements and enhancements to the prior art are needed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for preparing straw ethanol by using ionic liquid in an auxiliary manner, and aims to overcome the defects of poor pretreatment and hydrolysis effects, long time and low ethanol conversion rate in the production process of straw ethanol in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing straw ethanol by ionic liquid assistance, wherein the method comprises the following steps:
step S1, pretreatment: crushing and sieving the straws to obtain straw powder, and then carrying out chemical pretreatment;
s2, ionic liquid treatment: adding ionic liquid into the pretreated straw powder, uniformly mixing, heating at 135-150 ℃ for 4-6 h, cooling, filtering, washing with deionized water, and drying filter residues to obtain ionic liquid-treated straw powder;
s3, hydrolysis and fermentation: wetting the straw powder treated in the step S2 with deionized water, adding a buffer solution containing cellulase, adding sweet distiller' S yeast, fermenting for 2 days in a water bath at constant temperature of 35 ℃, filtering, washing with deionized water for 5-6 times, collecting filtrate, and distilling to obtain the straw ethanol.
In the method for preparing straw ethanol with the assistance of the ionic liquid, the ionic liquid is alcohol amine ionic liquid and comprises one of triethanolamine lactic acid, triethanolamine acetic acid and triethanolamine formic acid.
In the method for preparing straw ethanol with the assistance of the ionic liquid, in the step S2, the addition amount of the ionic liquid is 20-40 mL/g of straw powder.
In the method for preparing straw ethanol with the assistance of the ionic liquid, in the step S1, the chemical method includes one of acid treatment, alkali treatment and wet oxidation treatment.
In the method for preparing straw ethanol with the assistance of the ionic liquid, the wet oxidation treatment comprises the following steps: taking straw powder and deionized water according to the solid-liquid ratio of 6: 100, stirring and mixing, and then placing the mixture in Na containing 2g/L2CO3Treating the solution in a high-pressure steam kettle at 150 ℃ and 0.165MPa for 30-50 minutes, cooling to room temperature, and performing suction filtration and drying to obtain a wet oxygen treatment product.
In the method for preparing straw ethanol by the aid of ionic liquid, the acid treatment comprises the following steps: mixing straw powder with 1% of H2SO4Mixing the solutions according to a solid-to-liquid ratio of 1 g: 30mL, performing ultrasonic treatment in a zeolite bath for 20-30 min, and adding 1% NaOHAdjusting pH value of the solution to be neutral, filtering, washing with water, filtering, and drying to obtain the acid-treated product.
In the method for preparing straw ethanol with the assistance of the ionic liquid, in the step S3, the buffer solution is a citric acid-trisodium citrate buffer solution, and the pH value of the buffer solution is 4.8.
In the method for preparing straw ethanol with the assistance of the ionic liquid, in the step S3, the concentration of cellulase in the buffer solution is 0.01 g/L.
In the method for preparing straw ethanol with the assistance of the ionic liquid, in the step S3, the addition amount of the sweet distiller' S yeast is 10% of the weight of the straw powder.
Has the advantages that:
the invention provides a method for preparing straw ethanol by ionic liquid assistance, which adopts ionic liquid assistance pretreatment to comprehensively and thoroughly remove lignin, and simultaneously adopts a mode of synchronously carrying out enzymolysis and fermentation, thereby shortening the reaction time and improving the conversion efficiency. Compared with the prior art, the method has the following beneficial effects:
(1) the ionic liquid is used for assisting in pretreatment, and is an alcohol amine ionic liquid, so that the crystal structure of cellulose can be further destroyed, the effective contact between cellulase and cellulose biomass is improved, the enzyme hydrolysis rate and the sugar yield are improved, and the yield and the conversion rate of cellulosic ethanol are improved. The alcohol amine ionic liquid has the characteristics of no toxicity, no harm, good stability, easy synthesis and recovery, wide raw material source and low price, and can greatly improve the industrial possibility of the production of the cellulosic ethanol.
(2) The ultrasonic treatment is adopted for reaction in the acid treatment and alkali treatment processes, so that half of the time can be shortened, and the pretreatment efficiency is improved.
(3) The mode of synchronously carrying out enzymolysis and fermentation is adopted, on one hand, the inhibition effect of enzymolysis products on enzyme can be reduced, the activity of the enzyme is improved, on the other hand, the using amount of the enzyme can be reduced, the cost is reduced, and moreover, the reaction time can be shortened and the fermentation yield can be improved because the enzymolysis and the fermentation are carried out simultaneously.
Detailed Description
The invention provides a method for preparing straw ethanol by ionic liquid assistance, and in order to make the purpose, technical scheme and effect of the invention clearer and clearer, the invention is further described in detail by the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a method for preparing straw ethanol by ionic liquid assistance, which mainly aims at crop straws with high wood fiber content, including crop straws of corn, wheat, rice and the like, and particularly aims at the corn straws, and specifically comprises the following steps:
step S1, pretreatment: crushing the straws, sieving the crushed straws with a 40-mesh sieve to obtain straw powder, and then carrying out pretreatment by a chemical method. The chemical pretreatment comprises one of acid treatment, alkali treatment and wet oxidation treatment, wherein the acid treatment and the alkali treatment both adopt an ultrasonic mode for reaction;
s2, ionic liquid treatment: adding ionic liquid into the pretreated straw powder, uniformly mixing, heating at 135-150 ℃ for 4-6 h, cooling, filtering, washing with deionized water, and drying filter residues to obtain ionic liquid-treated straw powder;
s3, hydrolysis and fermentation: wetting the straw powder treated in the step S2 with deionized water, adding a buffer solution containing cellulase, adding sweet distiller' S yeast, fermenting for 2 days in a water bath at constant temperature of 35 ℃, filtering, washing with deionized water for 5-6 times, collecting filtrate, and distilling to obtain the straw ethanol.
According to the method, the straws can be prepared into the ethanol, the method adopts ultrasonic treatment in the pretreatment process, so that the pretreatment time is greatly shortened, and an ionic liquid treatment link is added after the pretreatment step, so that the removal rate of lignin in the straws is improved, and the hydrolysis efficiency is further improved; in addition, the method adopts a mode of synchronously performing hydrolysis and fermentation steps, so that the inhibition effect of an enzymolysis product on enzyme can be reduced, the activity of the enzyme is improved, the using amount of the enzyme can be reduced, the cost is reduced, and the reaction time can be shortened and the fermentation yield can be improved by simultaneously performing enzymolysis and fermentation. The method is simple and easy to implement, does not need special equipment, and is low in cost and short in time consumption.
In the above preparation method, in the step S1, the chemical pretreatment includes one of acid treatment, alkali treatment and wet oxidation treatment. Because lignocellulose mainly comprises cellulose, hemicellulose and lignin, the cellulose and the hemicellulose are combined by hydrogen bonds, and the hemicellulose and the lignin are combined by hydrogen bonds and chemical bonds. The presence of lignin results in a very compact cellulose structure, making biodegradation of cellulose difficult to perform, thus requiring pretreatment to remove some or all of the lignin. The acid treatment, the alkali treatment and the wet oxidation treatment are chemical treatment methods, can break the combination of lignin, cellulose and hemicellulose and remove the lignin, and has the characteristics of simple operation, low requirement on equipment and easy realization.
Specifically, the acid treatment of the present invention comprises the steps of: mixing the pulverized and sieved straw powder with 1% of H2SO4Adding 30mL of 1% H into 1g of straw powder2SO4Mixing the solid-liquid ratio, performing ultrasonic treatment in a boiling water bath for 20-30 min, adjusting the pH value of the mixed solution to be neutral by using a 1% NaOH solution, filtering, washing filter residues with deionized water, and drying to obtain an acid treatment product.
In the pretreatment method, the step of the alkali treatment is close to the step of the acid treatment, and the method specifically comprises the following steps: mixing the crushed and sieved straw powder with 1% NaOH solution according to the solid-to-liquid ratio of 1g of straw powder to 30mL of NaOH solution, carrying out ultrasonic treatment in a boiling water bath for 20-30 min, and then adding 1% H2SO4Adjusting the pH value of the mixed solution to be neutral, filtering, washing filter residue with deionized water, and drying to obtain an alkali treatment product.
The acid treatment method and the alkali treatment method replace the prior boiling water bath reaction for 1 hour through the ultrasonic reaction, greatly shorten the time and improve the pretreatment efficiency. It should be noted that, in the acid treatment and alkali treatment processes, the concentrations and the ratios of the acid and the alkali need to be controlled, and when the concentrations are too high or the solid-to-liquid ratio is too high, excessive degradation is easily caused, and small molecular by-products such as acetaldehyde, furfural, acetic acid and the like are generated, which may inhibit the subsequent fermentation. In the invention, the solid-to-liquid ratio of the straw powder to the acid or the alkali is controlled to be 1g/30ml, and when the concentration of the acid or the alkali is controlled to be 1%, the pretreatment effect is better, and the byproducts are less.
Preferably, in the above pretreatment method, the wet oxidation treatment has the best treatment effect. The wet oxidation treatment specifically comprises the steps of: taking straw powder and deionized water according to the solid-liquid ratio of 6 g: 100mL, stirring and mixing, and then placing the mixture in a reactor containing Na with the concentration of 2g/L2CO3Treating the solution in a high-pressure steam kettle at 150 deg.C under 0.165MPa for 30min, cooling to room temperature, vacuum filtering, and drying to obtain wet oxygen treated product of straw powder. Note that 2g/L of Na was wet-oxidized2CO3The solution can be used repeatedly, and only Na needs to be supplemented in time2CO3The concentration was adjusted to 2 g/L.
The straw powder after the pretreatment step can destroy the crystalline structures of cellulose, hemicellulose and lignin, so that the raw material structure is loose, and the subsequent enzymolysis efficiency is improved.
In the above preparation method, the ionic liquid in step S2 is an alcohol amine ionic liquid, and includes one of triethanolamine lactic acid, triethanolamine acetic acid, and triethanolamine formic acid. The alcamines ionic liquid can improve the pretreatment effect, further destroy the crystal structure of cellulose, improve the effective contact between cellulase and cellulose biomass, and improve the enzyme hydrolysis rate and the sugar yield, thereby improving the yield and the conversion rate of ethanol. The three ionic liquids can greatly improve the yield and the conversion rate of the ethanol, and particularly, the triethanolamine lactic acid ionic liquid has better effect.
The alcohol amine ionic liquid has the characteristics of no toxicity, no harm and good stability, and has wide raw material source, easy synthesis and low price.
In the preparation method, in the step S2, the addition amount of the ionic liquid is 20-40 mL per 1g of straw powder. The more the ionic liquid is added, the more the complex structure between cellulose-hemicellulose-lignin is changed, but when the ionic liquid is added too much, part of cellulose is easily dissolved in the ionic liquid, and the yield of ethanol is reduced. In the specific implementation process, when the addition amount of the ionic liquid is 20-40 mL/g of straw powder, the method has a good treatment effect. The ionic liquid obtained by filtering in step S2 can be recycled after purification treatment.
In the preparation method, the step S3 is performed by synchronously performing enzymolysis and fermentation, wherein the buffer solution is a citric acid-trisodium citrate buffer solution, the pH value of the buffer solution is 4.8, the concentration of cellulase in the buffer solution is 0.01g/L, and the addition amount of the sweet distiller' S yeast is 10% of the weight of the straw powder. In the preparation method, the pH value of the solution directly influences the activity of the cellulase, the buffer solution can provide conditions suitable for enzymolysis of the cellulase, and the activity of the cellulase is highest when the pH value is 4.8. The addition amount of the cellulase and the sweet wine yeast affects the enzymolysis speed and the ethanol yield, because the enzymolysis and the fermentation are carried out synchronously, the enzymolysis speed directly affects the fermentation efficiency, if the enzymolysis is too fast, a large amount of monosaccharide is accumulated to breed bacteria, so the acid rising amplitude in the fermentation process is large, and the ethanol conversion rate is affected; and when the enzymolysis speed is low, the saccharification rate is low, so that the monosaccharide is too little, and the lack of a carbon source is easy to occur to influence the growth of the yeast. When the concentration of the cellulase is controlled to be 0.01g/L and the addition amount of the sweet distiller's yeast is 10 percent of the weight of the straw powder, the enzymolysis speed and the fermentation speed are better.
The following examples are given for further illustration.