CN103435817B - A method for directly extracting lignin in the process of preparing low-molecular-weight mixed ethers from corn bran - Google Patents

Abstract

The invention discloses a method for directly extracting lignin in the process of using corn bran to prepare low-molecular-weight mixed ether and belongs to the field of lignin extraction by using the corn bran or wheat bran. The method comprises the steps of: using the corn bran to prepare the low-molecular-weight mixed ether, and simultaneously hydrolyzing the lignin from the corn bran structure by alkalization, hydrolysis and oxidization, wherein the hydrolyzed lignin is dissolved in alcohol as medium; distilling organic alcohol solution after centrifugal separation of the low-molecular-weight mixed ether, recovering a part of organic alcohol, distilling the reminding part, adjusting PH of the solution by using an acid regulating agent, filtering and recovering the lignin, washing the lignin to be neutral, and drying to obtain the finished product, that is water-insoluble lignin powder; drying and grinding to obtain the medicine-grade or food-grade low-molecular-weight corn-bran mixed ether. The method disclosed by the invention has the advantages that the extraction cost of the lignin is greatly reduced, and simultaneously the quality of the low-molecular-weight corn-bran mixed ether is improved.

Description

A method for directly extracting lignin in the process of preparing low-molecular-weight mixed ethers from corn bran

technical field

The invention belongs to the field of extracting lignin from corn bran or wheat bran, in particular to a method for directly extracting lignin in the process of preparing low-molecular-weight mixed ethers from corn bran.

Background technique

Extracting high-purity arabinoxylan from corn bran or wheat bran or preparing high-quality mixed ethers requires extracting lignin first. At present, in the process of extracting arabinoxylan from corn bran and wheat bran, there are many methods for extracting lignin lignin, such as: chlorous acid extraction method, high-boiling point alcohol high-temperature and high-pressure extraction hair, etc., all adopt special technology to extract lignin first , these methods use a large amount of water or high-boiling point alcohol, which is very difficult when recovering lignin and high-boiling point alcohol, consumes a lot of energy, and greatly increases the extraction cost.

Corn bran is currently only used for low-grade feed. It is a global research topic to convert corn bran into high-addition products, whether it is extracting arabinoxylan or processing polymer compounds that replace chemicals, such as the preparation of mixed ethers. All need to extract lignin first, the present invention is to directly extract and separate lignin in the process of preparing low-molecular-weight mixed ether through corn bran, so that the extraction process of lignin is more simplified, less waste liquid is produced, and the low-molecular-weight corn bran is improved. Based on the quality of corn bran mixed ether, without increasing the production cost of mixed ether, water-insoluble lignin is extracted, which further improves the economic benefits of corn bran deep processing, and transforms corn bran and wheat bran into high value-added products A new approach is found, and the invention has great significance for promoting the corn planting industry and the corn deep processing industry. The U.S. Department of Energy, the U.S. Corn Growers Association, and U.S. ADM Corporation jointly develop the work of transforming corn bran into high value-added products, and regard this project as an energy reserve project for key development. The lignin extracted from corn bran and processed low-molecular mixed ether products can replace derivative products such as wood, refined cotton, starch, etc. The mixed ether series products and lignin products converted from corn bran can replace petrochemicals in large quantities: Polyvinyl alcohol, dispersible rubber powder, chemical adhesives, etc., are equivalent to reducing the amount of oil extraction. my country is the second largest country in the world in terms of corn production. In 2009, the output reached 160 million tons. It is imminent to upgrade the corn processing industry, transform and increase the value-added products of corn, and protect the corn processing industry from being invaded by the technology of developed countries.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for directly extracting lignin in the process of preparing low-molecular-weight mixed ethers from corn bran, which solves the problem that the current method uses a large amount of water or high-boiling point alcohol, and the recovery of lignin and recovery of high It is very difficult to boil alcohol, consumes a lot of energy, and greatly increases the problem of extraction costs.

In order to solve the problems of the technologies described above, the technical solution of the present invention is:

A method for directly extracting lignin in the process of preparing low-molecular mixed ethers from corn bran is characterized in that it comprises the following steps:

1) Select an organic alcohol solvent and alkalize it with an inorganic base to obtain an organic alcohol-alkali solution, add corn bran powder to the organic alcohol-alkali solution, add an oxidant, perform alkalization, hydrolysis, and oxidation to make lignin from the corn bran The skin is separated, the alkalization and oxidation temperature is 0-120°C, and the reaction time is 0.5-4 hours;

2) Control the temperature at 0-35°C, add an etherification agent, then raise the temperature to 65-95°C, etherify for 1-8 hours, and generate mixed ether; lignin is dissolved in the ethanol solution medium.

3) Centrifuge the mixed ether: wash the mixed ether multiple times with 50-80% ethanol solution to wash off all the lignin in the mixed ether; combine the ethanol solution washed several times, and recycle the ethanol by distillation;

4) Adjust the remaining part of the solution in the distillation kettle in 3) to PH=3-8 with an acid regulator, stir and acidify for 20-120 minutes, filter, and recover lignin;

5) Wash lignin with water to PH=6-8, dry, and pulverize into a finished water-insoluble lignin powder; vacuum deethanolize the washed mixed ether, dry and pulverize to obtain pharmaceutical or edible grade low-molecular corn bran mixed ether .

Preferably, the organic alcohol solvent in the step 1) is methanol, ethanol, propanol, isopropanol, C4-C6 alcohol and isomeric alcohols thereof, propylene glycol, glycerol.

Preferably, the inorganic base in the step 1) is: sodium hydroxide, potassium hydroxide, sodium carbonate.

Preferably, the oxidant in the step 1) is hydrogen peroxide, sodium chlorite, sodium hypochlorite.

Preferably, the etherifying agent in the step 2) is chloroacetic acid, sodium chloroacetate, ethylene oxide, propylene oxide, butylene oxide, methyl chloride, ethyl chloride, chloroethanol, 3-chloro-2-hydroxy Propyl trialkyl ammonium chloride, 2,3-epoxypropyl trialkyl ammonium chloride, wherein the alkyl group in 3-chloro-2 hydroxypropyl trialkyl ammonium chloride is C1-C12, 2, The alkyl group in the 3-epoxypropyltrialkylammonium chloride is C1-C12.

Preferably, the acid regulator is hydrochloric acid, hydrogen chloride gas, sulfuric acid, phosphoric acid, formic acid, acetic acid, glycolic acid, propionic acid.

Preferably, the mass ratio of the corn bran powder to the organic alcohol-alkali solution is 1:1-20;

The mass ratio of corn bran to water in the reaction system is 1:0.1-3, wherein the water comes from organic alcohol and lye or additional water is required by the process);

The mass ratio of corn bran and oxidant is 1: 0.005-1, wherein, hydrogen peroxide concentration is calculated by 30%, sodium hypochlorite concentration is calculated by 12%, and chlorous acid is calculated by 90%;

The mass ratio of corn bran to etherification agent is 1: 0.20-3.0;

The mass ratio of corn bran to inorganic alkali is 1:0.12-2.0.

The above method can also be used for direct extraction of lignin in the process of preparing low-molecular mixed ethers from wheat bran, brewer's grains, rice husks, peanut shells, wheat straw, reeds and wood.

Adopting the above-mentioned technical scheme, the beneficial effects of the present invention are: for the purpose of fully utilizing corn bran and wheat bran, when using corn bran to prepare low-molecular corn bran mixed ether, lignin is directly extracted and separated, greatly reducing The cost of extracting lignin, while improving the quality of low-molecular corn bran mixed ether, so that the prepared low-molecular corn bran mixed ether can meet the use standards of pharmaceutical excipients and food additives, and can partially replace refined cotton, starch, wood pulp Cellulose ethers and starch ethers for fiber production. The extracted lignin belongs to water-insoluble lignin, which can be used in industries such as rubber additives, construction, oil-based coatings, self-leveling base materials, intermediates, etc., and has high use value.

Detailed ways

Below in conjunction with embodiment the present invention is further described.

Embodiment 1, the method for extracting lignin when preparing low-molecular carboxymethyl mixed ether with corn bran:

In a 50L reaction kettle, add 25L of 92% ethanol, add 3.5kg of sodium hydroxide under stirring, heat to 70°C to alkalize for 30 minutes, cool to 35°C, add 5kg of corn bran, alkalize for 0.5 hours, then add 30% Hydrogen peroxide 0.5kg, oxidize for 30 minutes, heat up to 72°C for 30 minutes, start cooling, cool to 25°C in 30 minutes, vacuum to -0.05Mpa, 10 minutes. Add 7.85kg of 50% chloroacetic acid ethanol solution, start to heat up, rise to 55°C in 30 minutes, react for 30 minutes, rise to 78°C in 15 minutes, react for 2 hours. Cool to 45°C, centrifuge to separate low molecular weight corn bran carboxymethyl mixed ether, and dissolve lignin in ethanol filtrate. Wash the mixed ether with 25 L of 75% ethanol aqueous solution, and repeat the washing twice. Combine the filtrate and the secondary washing liquid, distill and recover ethanol for recycling; steam until the concentration of ethanol at the bottom of the kettle is 10-25%, cool the residue at the bottom of the kettle to 35-55°C, add 35% hydrochloric acid to adjust the pH of the distillation residue to 3-6 , acidified for 30 minutes, centrifuged to separate lignin, washed lignin with warm water until neutral, dried and crushed into 300-350g finished non-water-soluble lignin powder. The washed corn bran mixed ether was deethanolized in vacuum, dried and pulverized to obtain 6.5 kg of low molecular weight corn bran carboxymethyl mixed ether.

Use NDJ-1 viscometer to measure the viscosity of 2% aqueous solution of corn bran mixed ether at 25°C to 2-3mpa.s.

The lignin extracted in this example is very ideal for self-leveling floor coverings, paint-based coatings, anti-seepage and crack-resistant concrete, thermal insulation mortar bases, shotcrete, and gypsum products. Low-molecular-weight corn bran carboxymethyl mixed ether is very effective in replacing dispersible rubber powder with thermal insulation mortar, and reduces the cost of use. At the same time, low-molecular products can be used in food additives, pharmaceutical accessories, oil drilling, paper making, construction glue and other industries.

Embodiment 2, the method for extracting lignin when preparing low-molecular hydroxypropyl carboxymethyl mixed ether with corn bran:

Replace the 92% ethanol in Example 1 with 92% isopropanol. After vacuuming, add 1.8 kg of propylene oxide, stir and react at room temperature for 20 minutes, heat up to 45-55° C., react for 2 hours, and cool to 25 ℃, add 7.2kg of 50% isopropanol solution of chloroacetic acid, all the other reaction conditions are identical with example 1. Obtain 300-350kg of finished product non-water-soluble lignin; 6.8kg of finished product of hydroxypropyl carboxymethyl mixed ether; use NDJ-1 viscometer to measure the viscosity of 2% aqueous solution of corn bran mixed ether at 25°C to 3-7mpa.s.

Embodiment 3, the method for extracting lignin when preparing low-molecular hydroxyethyl carboxymethyl mixed ether with corn bran:

Propylene oxide is changed into oxirane in embodiment 2, and other conditions are identical. Obtain 300-350 kg of finished product water-insoluble lignin; 6.3 kg of finished product of hydroxyethyl carboxymethyl mixed ether; use NDJ-1 viscometer to measure the viscosity of 2% aqueous solution of corn bran hydroxyethyl carboxymethyl mixed ether at 25° C. -5mpa.s.

Embodiment 4, the method for extracting lignin when preparing low-molecular hydroxypropyl mixed ether with corn bran:

In a 50L reactor, add 25L of 92% isopropanol, add 1.8kg of sodium hydroxide while stirring, heat to 70°C to alkalize for 30 minutes, cool to 35°C, add 5kg of corn bran, alkalize for 0.5 hours, then add 0.5kg of 30% hydrogen peroxide, oxidize for 30 minutes, heat up to 72°C for 30 minutes, start cooling, cool to 25°C in 30 minutes, vacuumize to -0.06mpa, vacuumize for 7 minutes, repeat three times. Add 3.5kg of propylene oxide, stir at room temperature for 25 minutes, start to raise the temperature, rise to 45°C in 30 minutes, react at 45°C for 2.5 hours, then raise the temperature to 55°C for 2 hours. Cool to 25-45°C, use glacial acetic acid to neutralize pH=7.0-8.5; centrifuge to separate low-molecular-weight corn bran hydroxypropyl mixed ether, and dissolve lignin in ethanol filtrate. Wash the low-molecular-weight mixed ether with 25 L of 70% isopropanol aqueous solution, and repeat the washing twice. Combine the filtrate and the secondary washing liquid, distill and recover the isopropanol for recycling; steam until the concentration of isopropanol at the bottom of the still is 10-20%, cool the residue at the bottom of the still to 35-55°C, add 35% hydrochloric acid to adjust the pH of the distillation residue =3-6, acidify for 30 minutes, centrifuge to separate the lignin, wash the lignin with warm water until neutral, dry and pulverize it into 300-350g finished water-insoluble lignin powder. The washed corn bran hydroxypropyl mixed ether was deisopropanolized in vacuum, dried and pulverized to obtain 6.2 kg of low molecular weight corn bran hydroxypropyl mixed ether.

Embodiment 5, the method for extracting lignin when preparing low-molecular-weight hydroxyethyl mixed ether with corn bran:

The propylene oxide in Example 4 was replaced with ethylene oxide, and the rest of the conditions were identical to obtain 300-350 g of finished product water-insoluble lignin powder. The washed corn bran hydroxypropyl mixed ether was deisopropanolized in vacuum, dried and pulverized to obtain 6.0 kg of low molecular weight corn bran hydroxyethyl mixed ether.

As the present invention is not limited to the above-mentioned specific implementation manners, various transformations made by those skilled in the art starting from the above-mentioned ideas without creative work all fall within the protection scope of the present invention.

Claims (8)

1. a method for directly extracting lignin in the low-molecular mixed ether process with corn bran preparation, is characterized in that, comprises the following steps: 1) Select an organic alcohol solvent and alkalize it with an inorganic base to obtain an organic alcohol-alkali solution, add corn bran powder to the organic alcohol-alkali solution, add an oxidizing agent, and perform alkalization, hydrolysis, and oxidation. The alkalization and oxidation The temperature is 0-120°C, and the reaction time is 0.5-4 hours; 2) Control the temperature at 0-35°C, add etherifying agent, then raise the temperature to 65-95°C, etherify for 1-8 hours, and generate mixed ether; 3) Centrifuge the mixed ether: wash the mixed ether with 50-80% ethanol solution several times, combine the ethanol solution washed several times, and recycle the ethanol by distillation; 4) Adjust the remaining part of the solution in the distillation pot in 3) to pH = 3-8 with an acid regulator, stir and acidify for 20-120 minutes, filter, and recover lignin; 5) Washing lignin with water to pH=6-8, drying, and pulverizing into finished water-insoluble lignin powder; vacuum deethanolizing the washed mixed ether, drying and pulverizing to obtain pharmaceutical or edible grade low-molecular corn bran mixed ether . 2. method according to claim 1, it is characterized in that, in described step 1), organic alcohol solvent is methyl alcohol, ethanol, propanol, isopropanol, C4-C6 alcohol and isomerized alcohol thereof, propylene glycol, glycerine alcohol. 3. The method according to claim 1, characterized in that, in the step 1), the inorganic base is: sodium hydroxide, potassium hydroxide, sodium carbonate. 4. method according to claim 1, is characterized in that, in described step 1), oxygenant is hydrogen peroxide, sodium chlorite, sodium hypochlorite. 5. method according to claim 1, it is characterized in that, described step 2) in etherifying agent is chloroacetic acid, sodium chloroacetate, oxyethane, propylene oxide, butylene oxide, methyl chloride, chlorine Ethane, chloroethanol, 3-chloro-2 hydroxypropyltrialkylammonium chloride, 2,3-epoxypropyltrialkylammonium chloride, of which 3-chloro-2 hydroxypropyltrialkylammonium chloride The alkyl group in ammonium is C1-C12, and the alkyl group in 2,3-epoxypropyltrialkylammonium chloride is C1-C12. 6. The method according to claim 1, characterized in that, the acid regulator is hydrochloric acid, hydrogen chloride gas, sulfuric acid, phosphoric acid, formic acid, acetic acid, glycolic acid, propionic acid. 7. The method according to claim 1, characterized in that, the mass ratio of the corn bran powder to the organic alcohol-alkali solution is 1: 1-20; The mass ratio of corn bran to water in the reaction system is 1:0.1-3, wherein the water comes from organic alcohol and lye or additional water is required by the process; The mass ratio of corn bran and oxidant is 1: 0.005-1, wherein, hydrogen peroxide concentration is calculated by 30%, sodium hypochlorite concentration is calculated by 12%, and chlorous acid is calculated by 90%; The mass ratio of corn bran to etherification agent is 1: 0.20-3.0; The mass ratio of corn bran to inorganic base is 1:0.12-2.0. 8. according to the method described in claim 1-7 arbitrary claim, it is characterized in that, described method can also be used for wheat bran, brewer's grains, rice husk, peanut shell, wheat straw, reed, timber to prepare low molecular weight mixed ether Lignin is extracted directly in the process.