CN101514349B - Method for preparing fuel ethanol from bamboo fibers - Google Patents

Abstract

The invention discloses a method for preparing fuel ethanol from bamboo fiber. The present invention uses bamboo processing waste (also applicable to other non-wood biomass) as raw material, cuts it off, dries, pulverizes, and passes through an 80-mesh sieve. What passes through the 80-mesh sieve is bamboo fine powder, and what does not pass through is bamboo coarse powder. pink. Bamboo powder is cooked with a mixture of formic acid, acetic acid and water to hydrolyze hemicellulose and remove lignin to obtain cellulose, and the cellulose is hydrolyzed with organic acid to obtain reducing monosaccharides. Bamboo fine powder was directly hydrolyzed with organic acid to produce reducing monosaccharides. The reducing sugar obtained by hydrolyzing the above-mentioned hemicellulose, cellulose and bamboo fine powder is detoxified with excess Ca(OH) ₂ , then the pH value is adjusted back, and fuel ethanol is obtained after fermentation and rectification. This method produces fuel ethanol, which not only ensures the yield of fuel ethanol, but also reduces the energy consumption of hydrolysis, and the organic acid used in hydrolysis can be recycled. , and reduce the cost.

Description

A method for preparing fuel ethanol from bamboo fiber

technical field

The invention relates to a method for preparing fuel ethanol from bamboo fiber, that is, taking bamboo as raw material, hydrolyzing the bamboo fiber with an organic acid to obtain reducing sugar, and then fermenting the obtained reducing sugar to obtain fuel ethanol. Among them, the used organic acid can be recycled.

technical background

With the increase of the world's population and the improvement of the industrialization of various countries, energy and environmental issues have become the focus of global attention. Fossil energy materials such as petroleum, coal and natural gas are gradually depleted. In order to protect the environment and achieve the goal of sustainable human development, the production of high value-added chemical products from renewable resources, especially woody biomass, has become an important development strategy and scientific research in many countries. hotspot areas. Biomass energy is a renewable and clean energy, and the use of biomass as raw material for hydrolysis and fermentation to produce chemical products such as fuel ethanol is attracting increasing attention.

The technology of fermenting crops containing sugar and starch to produce ethanol has become increasingly mature and widely used. However, with the growth of the world population and the shortage of food supply, it is impossible to use food crops as raw materials to prepare fuel ethanol on a large scale. Therefore, it is of great significance to use wood fiber as raw material to produce fuel ethanol through biomass hydrolysis. The three major components of woody biomass are polymers such as cellulose, hemicellulose and lignin, among which cellulose and hemicellulose can be converted into ethanol, and the theoretical yield can be similar to that of grain (more than 400L/t) . In total, cellulose, hemicellulose and lignin are the most extensive renewable biomass resources in the world. Bamboo belongs to Gramineae, with higher cellulose and hemicellulose content, lower lignin content, and less phenolic acid secondary substances. As a kingdom of bamboo, my country is rich in bamboo plant resources. Bamboo forest is widely distributed, grows fast, has a short cutting period, and has high yield. It is an important forest type in my country. Therefore, bamboo can be a high-quality and abundant ideal raw material for the production of fuel ethanol.

Since the 1970s, there has been a wave of research on clean alternative energy around the world. Among them, fuel ethanol derived from biomass energy is characterized by its renewability, non-pollution, no greenhouse effect, and improved explosion-proof performance of automobiles. Recognized as one of the most promising renewable energy sources for industrial applications, it has been extensively studied. The conversion of biomass to ethanol begins with converting the biomass into a fermentable feedstock - reducing sugars. At present, reducing sugars are mainly produced by hydrolyzing fiber materials with inorganic acids (dilute or concentrated) and enzymes.

1. Acid hydrolysis

Acid hydrolysis can be divided into dilute acid hydrolysis and concentrated acid hydrolysis. Dilute acid hydrolysis usually hydrolyzes hemicellulose into five-carbon sugar at a lower temperature, and then adds acid to hydrolyze the residual solid at a higher temperature to obtain the hydrolyzed product glucose. . The conversion rate of dilute acid hydrolyzed sugar is only 50%, and there are more depolymerized products that will prevent yeast from fermenting to produce ethanol. Concentrated sulfuric acid hydrolyzes about 90% of cellulose and hemicellulose into fermentable sugars, but the acid in the hydrolysis is difficult to recover, and a large amount of gypsum is produced after neutralization with lime, and its value is very low.

2. Enzymatic hydrolysis

Enzymatic hydrolysis is a biochemical reaction. The biomass material is pretreated and placed in a hydrolysis reactor, and cellulase is added. Cellulase is catalyzed to hydrolyze cellulose into fermentable monosaccharides. The hydrolysis process has mild reaction conditions and does not generate toxic degradation products. However, due to the high cost of cellulase production, long hydrolysis time, and the yield largely depends on the effect of pretreatment, pretreatment requires large equipment and high operating costs.

Contents of the invention

The object of the present invention is to provide a kind of method that uses bamboo as raw material to prepare fuel ethanol, namely prepare reducing sugar with organic acid hydrolysis bamboo fine powder (or organic acid treated bamboo meal), then ferment hydrolyzate, obtain fuel ethanol.

Conception of the present invention

Biomass hydrolysis is the process of degrading hemicellulose and cellulose into pentoses and glucose. However, under high temperature conditions, pentose and glucose are unstable and will be further degraded into by-products such as furfural and hydroxymethylfurfural, which will have adverse effects on subsequent microbial fermentation. Therefore, the hydrolysis process should minimize the production of by-products while increasing the sugar concentration.

Compared with cellulose, the hydrolysis of hemicellulose is relatively easy to carry out. When the temperature is 100-105°C, add a certain concentration of organic acid for cooking, the lignin surrounding the cellulose can be dissolved, and the hemicellulose is degraded into pentose sugar, and the pentose sugar and lignin are dissolved in the organic acid solution at the same time. Dilute with water, filter out the lignin precipitate, and concentrate the filtrate to obtain a xylose concentrate. The solid residue cellulose separated after cooking is hydrolyzed with organic acid and catalyst at room temperature, and the organic acid is distilled to obtain reducing sugar. Considering factors such as fermentation cost and equipment, the reducing sugars obtained by the hydrolysis of pentose and subsequent cellulose were fermented into fuel ethanol with Candida shohata and Saccharomyces cerevisiae. The recovered lignin can be used to produce other high value-added chemicals or burn as fuel.

The present invention contemplates using organic acids formic acid and acetic acid when cooking bamboo meal, using formic acid when hydrolyzing bamboo fine powder and cellulose prepared from bamboo meal, and using hydrochloric acid as a catalyst.

Technical solutions

1. The present invention takes the bamboo leftovers (also applicable to other non-wood biomass) as raw material, which is cut off, dried, pulverized, and crossed through an 80-mesh sieve. What passes through the 80-mesh sieve is bamboo fine powder, and what does not pass through the 80-mesh sieve is bamboo coarse powder.

2. Put the bamboo powder into the cooker, cook it at 100-105° C. for 2 hours with a mixture of formic acid, acetic acid and water (10/70/20 ratio) (10:1 liquid-solid ratio). Hemicellulose is hydrolyzed into xylose and dissolved in acid solution, lignin is also dissolved in acid solution, the acid solution is diluted with water and lignin is precipitated, and the cooking liquid is concentrated to obtain pentose concentrate, and the obtained solid residue is cellulose component.

The solid residue cellulose obtained above was hydrolyzed with 85% formic acid plus 4% hydrochloric acid at 60° C. for 6 hours, and the formic acid was distilled and recovered under reduced pressure to obtain reducing sugar.

3. Add bamboo fine powder into the hydrolysis reactor, add 85% formic acid and 4% hydrochloric acid at a liquid-solid ratio of 25:1 and hydrolyze at 60° C. for 6 hours, recover formic acid and hydrochloric acid to obtain reducing sugar.

4. Mix the reducing sugars obtained above, and after detoxification treatment, use Saccharomyces cerevisiae and Candida shohata to ferment at 30° C. for 48 hours.

Description of drawings

Figure 1 Schematic diagram of the process for preparing fuel ethanol from bamboo fiber

Specific implementation method

Below by example the present invention will be further described, but do not affect protection scope of the present invention:

Example 1

The moso bamboo leftovers are cut off, dried and crushed. Pass 80 mesh sieves, those that pass through the 80 mesh sieves are bamboo fine powders, those that fail to pass are bamboo coarse powders. Take by weighing 400 grams of bamboo meal and add in the cooking reactor, add the mixed solution of formic acid/acetic acid/water (10/70/20) with liquid-solid ratio 10:1, cook at 105 DEG C for 2h, filter to get 50.2% filter residue (main component cellulose); the filtrate was diluted with water and precipitated out, and 16% lignin was obtained by filtration; the filtrate was concentrated and tested to contain 20% pentosan.

Example 2

Add the cellulose obtained in Example 1 into a hydrolysis reactor, add 85% formic acid and 4% hydrochloric acid at a liquid-solid ratio of 25:1, and hydrolyze it at 60° C. for 6 hours. After the formic acid is recovered by distillation under reduced pressure, 55% reducing sugar can be obtained.

Example 3

Take by weighing 400 grams of bamboo fine powder prepared in Example 1 and add it to the hydrolysis reactor, add 85% formic acid and 4% hydrochloric acid with a liquid-solid ratio of 25:1 and hydrolyze it for 6 hours at 60° C., after formic acid and hydrochloric acid are recovered by distillation under reduced pressure , to obtain 72.7% reducing sugars.

Example 4

The hydrolyzed reducing sugar solution obtained in Examples 1, 2, and 3 was adjusted to pH 9-10 with Ca(OH) ₂ (overliming with excess alkali), and then adjusted back to pH 5.5 with H ₂ SO ₄ . 150ml of the hydrolyzed sugar solution after the detoxification treatment and 50mL of the Saccharomyces cerevisiae strain concentrate after the proliferation and cultivation were mixed and fermented. After 48 hours of fermentation, the fermentation broth was unloaded, and 50mL of the strains in the reactor were retained as the inoculum. Continuously add 400 mL of hydrolyzate within 72 hours. The fermentation temperature was 30° C., and the ethanol yield was 0.40 g/g.

The yeast strains used in the fermentation broth are Saccharomyces cerevisiae Meyen et Hansen 2157 and Candida shehatae.

The acclimatization method of used bacterial classification is as follows:

Medium (g/L): peptone 3, yeast extract 2.5, MgSO ₄ 0.25, KH ₂ PO ₄ 2.5, CaCl ₂ 0.25, glucose 15.00, pH 5.0-5.5. The medium was sterilized at 121°C for 20 minutes.

Enrichment culture of strains: Inoculate the preserved strains in 100 mL of liquid medium, activate at 30°C, 80 rpm for 24 hours. Then replace with fresh medium, proliferate under the same conditions for 48h.

Claims (3)

1. one kind is the method that the hydrolysis of raw material organic acid prepares alcohol fuel with the bamboo wood, it is characterized in that, comprises the steps:

A, be starting material, it blocked, dry, pulverize, cross 80 mesh sieves with the mao bamboon tankage, through 80 mesh sieves be the bamboo fine powder, mistake 80 mesh sieves is the bamboo meal;

B, boiling bamboo meal, are removed lignin at hydrolyzed hemicellulose, isolate Mierocrystalline cellulose: with the bamboo meal with formic acid/acetic acid/water mixed solution in 100-105 ℃ of boiling 2h; Remaining residue is a Mierocrystalline cellulose after the boiling, adds entry in the filtrating lignin deposition is leached, and hydrolysis of hemicellulose is that pentose is dissolved in the acid solution, after evaporation concentration, obtains the pentose liquid concentrator;

C, organic acid hydrolysis de-fibering element: the formic acid with 85% adds hydrochloric acid and makes catalyzer, the Mierocrystalline cellulose of hydrolysing step b preparation, and liquid-solid ratio 25: 1, at 60 ℃ of hydrolysis 6h, underpressure distillation Separation and Recovery formic acid obtains the reductibility liquid glucose;

D, organic acid hydrolysis bamboo fine powder: the bamboo fine powder is added hydrochloric acid with 85% formic acid make catalyzer, liquid-solid ratio 25: 1, at 60 ℃ of hydrolysis 6h, underpressure distillation Separation and Recovery formic acid obtains the reductibility liquid glucose;

E, with step b, c, d hydrolysis gained liquid glucose detoxification secondary fermentation.

According to claim 1 said a kind of be the method that the hydrolysis of raw material organic acid prepares alcohol fuel with the bamboo wood, it is characterized in that among the said step e, the detoxification process is with excessive Ca (OH) ₂Adjust pH is used H again to 9-10 ₂SO ₄Recall to pH5.5.

According to claim 2 said a kind of be the method that the hydrolysis of raw material organic acid prepares alcohol fuel with the bamboo wood, it is characterized in that, after the step e adjust pH; With liquid glucose 150ml after the detoxification treatment and the yeast saccharomyces cerevisiae bacterial classification liquid concentrator 50mL mixed fermentation behind the multiplication culture;, after 48 hours fermented liquid is drawn off 30 ℃ of fermentations, the bacterial classification in the reactor drum is kept 50mL as inoculum; Liquid glucose 400mL in 72 hours after the continuous adding detoxification treatment; Obtain tunning, carry out rectifying, collect ethanol wherein.

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