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Extraction of Cellulose ether from Plant Raw Materials

Views: 2     Author: Site Editor     Publish Time: 2022-09-27      Origin: Site

Extraction of Cellulose ether from Plant Raw Materials


1.Introduction

Cellulose ether is the most abundant and widely distributed high-molecular polysaccharide in nature. Among them, the content of cellulose ether in cotton

The amount is close to 100%, and it has always been the main source of cellulose. However, due to the increase in cotton prices in recent years, the domestic price has reached 2

About 10,000 yuan / ton; and as a strategic reserve material, the state's control is also constantly strengthened. In view of this, this study uses

Waste plant material, from which cellulose with higher purity is extracted, which adds new avenues for cellulose sources, while in

To a certain extent, it solves the problem of reuse of waste plant raw materials and environmental pollution.

In this chapter, through the determination of the components of five plant raw materials (wheat straw, rice straw, rice husk, bagasse and pine sawdust), the selected

Wheat straw, bagasse and pine sawdust were used to extract cellulose; and the single factor experiment was used to optimize the extraction process of cellulose.

At the same time, the relative purity and yield of cellulose extracted from the three raw materials under the optimal process conditions were determined.

2.2 Experimental part

Test materials Test materials and drugs

Raw materials and drugs Specifications Manufacturer (origin)

rice straw

rice husk

straw

pine sawdust

bagasse

anhydrous ethanol

Hydrogen peroxide (30%)

Nitric acid

sulfuric acid

potassium permanganate

sodium hydroxide

Acetic acid

methyl red indicator

Sodium Silicate

Xinyang, Henan

Zhejiang Jinhua

Xinyang, Henan

Zhejiang Jinhua

Guangxi Guigang

Hangzhou Gaojing Fine Chemical Co., Ltd.

Hangzhou Gaojing Fine Chemical Co., Ltd.

Hangzhou Gaojing Fine Chemical Co., Ltd.

Zhejiang Sanying Chemical Reagent Co., Ltd.

Shanghai Sanying Chemical Reagent Co., Ltd.

Tianjin Comeo Chemical Reagent Co., Ltd.

Hangzhou Chemical Reagent Co., Ltd.

Tianjin Bodi Chemical Co., Ltd.

Huipu Chemical Instrument Co., Ltd.

Determination method of plant raw material components

Moisture determination

Accurately weigh 4-5g (accurate to 0.0001g) of the sample, put it in a clean 50mL conical flask that has been baked to constant weight, and place it in a

In an oven, bake at (105±3) ℃ to constant weight [1].

moisture

In the formula, G1: the mass of the sample before drying, g;

G2: The mass of the sample after drying, g.

During the determination, the determination of two samples should be carried out at the same time, and then the arithmetic mean of the two determinations should be taken as the final determination result.

fruit. The value is accurate to 0.01, and the error of the calculation of the two averages should not exceed 0.2%.

Ash Determination

Accurately weigh 3-4g (accurate to 0.0001g) of the sample, put it in a pre-fired and constant weight porcelain crucible, and place it in a high temperature furnace

, burn at (675±25) ℃ until there is no black carbon in the residue, and the weight is constant.

Ash

where G: ash mass, g;

Instrument Model Manufacturer

High-speed multifunctional pulverizer

Collector type constant temperature heating magnetic stirrer

Program-controlled box-type electric furnace

Vacuum drying oven

Electronic balance

Circulating water type multi-purpose vacuum pump

Fourier Transform Infrared Spectrometer

X-ray diffractometer

UV/Vis Spectrophotometer

Shanghai Bingdu Electric Co., Ltd.

Hangzhou Huichuang Instrument Equipment Co., Ltd.

Shanghai Jinghong Experimental Equipment Co., Ltd.

Shanghai Jinghong Experimental Equipment Co., Ltd.

METTLER TOLEDO Instruments (Shanghai) Co., Ltd.

Hangzhou David Science and Education Instrument Co., Ltd.

American Thermo Fisher Co., Ltd.

American Thermoelectric Switzerland ARL Company

Varian Corporation of America

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G1: sample mass, g;

W: sample moisture, %.

During the determination, the determination of two samples should be carried out at the same time, and then the arithmetic mean of the two determinations should be taken as the final determination result.

fruit. The value is accurate to 0.01, and the error of the two determination results should not exceed 0.05%.

Determination of nitrocellulose content

(1) Configuration of nitroethanol mixture (currently used)

A mixture of 20% nitric acid and 80% ethanol. Take 400 mL of 95% ethanol with a rinsed graduated cylinder in a dry and clean

In a 500mL beaker, use another rinsed graduated cylinder to take 100mL of nitric acid (relative density 1.42), slowly add it to ethanol,

Stir continuously throughout the process until the addition is complete, and continue to stir for 5 min. After the mixture is cooled, it is stored in a brown reagent bottle

Alternate [1]. (2) Determination

Accurately weigh 1g (accurate to 0.0001g) of the sample into a 100mL dry and clean conical flask, and then add 25mL

The mixed solution of nitric acid and ethanol was slowly stirred and refluxed in a boiling water bath for 1 h, the residual liquid was removed, and 25 mL of nitric acid ethanol was added to the mixed solution.

Mix the liquid, continue to stir and reflux for 1 h, and repeat until the fibers turn white. Finally, wash the residue with 10 mL of nitric acid-ethanol mixed solution, at the same time wash it with hot water until it is neutral (methyl red reagent is not acidic), and then wash it with absolute ethanol for two times.

Second, bake at (105±3) ℃ to constant weight.

Fiber content = ( ) 1 2

100%

In the formula, G: the mass of the glass filter, g;

G1: The mass of the glass filter containing the residue after drying, g;

G2: mass of air-dried sample, g;

W: sample moisture, %.

Determination of lignin content

The 72% sulfuric acid method was used to roughly determine the content of lignin in the raw material pine sawdust [1].

Determination of hemicellulose content

The hemicellulose content is calculated by the subtraction method, and the formula is: hemicellulose content = total amount of wood chips - moisture - ash - wood

Quality content - cellulose content.

Extraction Method

The experiment took pine sawdust as an example to discuss the influence of various factors on the relative content of lignin.

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Pine Sawdust Pretreatment (Physical Treatment)

The air-dried sawdust was pulverized with a high-speed multi-function pulverizer for 3 minutes, passed through an 80-mesh sieve, and placed in a wide mouth with a ground glass plug.

bottle for test analysis.

Alkali treatment of pine sawdust

Accurately weigh 3g of pretreated wood chips into a 250mL conical flask, add a certain mass fraction of alkali prepared

After stirring evenly, after two hours of treatment at a certain temperature, add a certain mass fraction of lye and boil for a certain period of time.

In the meantime, fully washed with hot distilled water, suction filtered until the filtrate was neutral, and the residue was dried at (105±3) ℃ to constant weight.

Acid treatment of pine sawdust

Accurately weigh 3g of pine sawdust after two alkali treatments into a 250mL conical flask, add it in a certain volume ratio

A mixture of good nitric acid and acetic acid was refluxed at 100 °C for 30 min under stirring conditions, and heated with distilled water and 90%

Fully washed with ethanol (volume fraction), suction filtered until the filtrate was neutral, and then washed twice with absolute ethanol, and the residue was in

(105±3) ℃ bake to constant weight [2].

Bleaching of pine sawdust

Accurately weigh 3g of acid-treated pine sawdust into a 250mL beaker, and use hydrogen peroxide with a solid-liquid ratio of 1:20 (g/mL).

Bleaching in water at 100°C for 1 hour, the bleaching prescription is: hydrogen peroxide 5%, sodium silicate 10%, JFC 3% (all by volume).

ratio v/v), adjust the pH to 10.5-11.0. After bleaching, the parts were washed and filtered, and the residue was dried at (105±3) ℃ to constant weight.

Test Characterization Methods

Test of relative content of lignin

(1) Determination of Kappa value

The Kappa number is determined by ultraviolet absorption spectroscopy, the principle is based on the specific concentration of potassium permanganate solution in the sample.

The change of its absorbance before and after adding, the change of the concentration of potassium permanganate solution was measured, and then the lignin in the sample was determined.

quantity. Due to the complex composition of organic matter in plant raw materials and the strong oxidizing property of potassium permanganate, the reaction is difficult to be accurate.

Determine the amount, so the measured result is not the absolute true content of lignin, but a relative amount. Proceed as follows:

① Prepare 0.02mol/L potassium permanganate aqueous solution and 2mol/L sulfuric acid solution, and mix them in a volume ratio of 1:8,

Configure the mixed solution; add 12 mg of the sample to a certain volume of the mixed solution and stir for 10 min. ②Filter to remove the unreacted biomass residue, and test the filtrate by ultraviolet absorption spectrum.

③ Compare the spectrum of the sample test with the spectrum of the blank mixed solution, and calculate the kappa value of the sample according to formula 2-(4).

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Where K represents the Kappa value of the sample; a represents the volume of the mixed solution added; w represents the specific mass of the sample added. The value of absorbance is expressed by the integrated value of the absorption peak of potassium permanganate solution at 450nm-600nm. Ae is after reaction

The absorbance of the filtrate, A0 is the absorbance of the blank mixed solution.

(2) Relative content of lignin

Relative lignin content

where:

: Kappa value of raw material;

: Kappa number of the product.

Relative purity of cellulose

The relative purity of cellulose was indirectly characterized by the relative content of lignin.

Relative purity of cellulose = 100% - relative content of lignin.

FTIR test

Infrared spectroscopic analysis was carried out with potassium bromide tablet method to analyze the changes of groups before and after the reaction. Put about 2 mg of pine to be tested

A lignocellulose sample was mixed with 200 mg of potassium bromide, thoroughly ground, tableted, and the FTIR spectrum was determined. The test resolution is 4cm-1,

The number of scans is 32.

XRD test

X'TRA-055 X-ray diffractometer (X'TRA-055) produced by Thermoelectric Switzerland ARL Company at room temperature was used to measure the reaction before and after the reaction.

Crystalline characteristics of the particles, analysis of changes in crystallinity. The powder method was used for sample preparation, and the instrument used Cu kα target, Ni filter,

The preset current is 30mA, the voltage is 40kV, and the measurement range is 2θ=10°~40°.

results and analysis

Determination of various components of plant raw materials

Using the method described in the method for the determination of plant material components, pine sawdust, wheat straw, rice straw, rice husk and

The basic components of five common plant raw materials in bagasse were determined, and the determination results are shown in Figure 2.1.

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The composition of the five plant raw materials as a percentage of the total mass

It can be seen that among the five common plant raw materials, pine sawdust, wheat straw, rice straw, rice husk and bagasse,

Lignin, cellulose and hemicellulose are all its main components, and their content accounts for more than 75% of the total, or even higher. That

The moisture content of the five raw materials is about 6%-8%; the ash content is quite different, and the wheat straw, wood chips and bagasse are all at 9%.

The content of wood chips is the least, only 0.55%, and the rice husk and rice straw are higher, about 15%; the lignin content is not much different,

About 16%-30%, of which rice straw, rice husk and wheat straw are all about 25%; the cellulose content of rice straw, rice husk and wheat straw

The content of cellulose in wood chips and bagasse is relatively low, at 38.55%, respectively.

and 28.7%; the hemicellulose content of bagasse is the highest, reaching 43.99%, and the hemicellulose content of wheat straw and wood chips is about 20%.

The cellulose content of rice straw and rice husk is about 10%.

Among the five plant raw materials, the highest lignin content is pine sawdust, reaching 30.35%; the highest cellulose content

It is wheat straw, reaching 43.28%; bagasse has the highest hemicellulose content, reaching 43.99%. Therefore, in this experiment, the

In the process of extracting cellulose, representative pine sawdust, wheat straw and bagasse are selected as raw materials to extract cellulose.

Optimization of Cellulose Extraction Process

From the analysis in the determination of each component of plant raw materials, it can be seen that the selected raw materials for cellulose extraction in this paper are pine sawdust,

Wheat straw and bagasse. Taking pine sawdust as an example, the process of two-step alkali treatment, one-step acid treatment, and then bleaching treatment is adopted.

to extract cellulose and optimize various factors in the process of cellulose extraction. The following is the process of extracting cellulose from pine sawdust

, the analysis of various factors.

moisture ash lignin cellulose hemicellulose

rice straw

rice husk

straw

pine sawdust

bagasse

content/%

The first step to determine the level of each factor of alkali treatment

The first step of alkali treatment is mainly to remove hemicellulose in wood chips, so according to the removal rate of hemicellulose, that is, in the residual liquid

The percentage of the amount of hemicellulose to the amount of hemicellulose in the wood chip raw material is used to determine the optimal reaction conditions. The first step is to fix the alkali treatment.

The time was two hours, and the solid-liquid ratio was 1g:15mL. The effects of alkali dosage and activation temperature on hemicellulose removal were discussed.

(1) The effect of NaOH concentration on the removal rate of hemicellulose

NaOH mass fraction/%

Analysis of Influence of NaOH Concentration on Hemicellulose Removal Rate

, the alkali concentration has a great influence on the removal effect of hemicellulose.

The contact area between the vitamins increases, and the removal effect increases significantly. When the alkali concentration is 6%, the removal of hemicellulose can reach 55%.

Above, as the alkali concentration continues to rise, the reaction between the alkali and hemicellulose gradually tends to be saturated, although the removal effect will be strengthened,

But the improvement is not obvious.