JP2007282597A - Method for solubilizing woody biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for solubilizing a woody biomass capable of efficiently separating cellulose, hemicellulose and lignin in the woody biomass and breaking the embedding structure of cellulose in lignin. <P>SOLUTION: A woody biomass 10 is mixed in an aqueous solution containing bicarbonate ion, and immersed 11 for a definite period. The mixture is heated 12 to remove hemicellulose and lignin in the woody biomass and separate cellulose. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for solubilizing woody biomass for extracting cellulose from woody biomass.

  Plant-based biomass that is used as a raw material for ethanol production is roughly divided into sugar-starch biomass and cellulose-based biomass.

  Sugar / starch biomass, which has been generally used as a raw material for ethanol fermentation, is an agricultural product that has been used for food such as sugarcane (sucrose), corn seeds, and sweet potato (starch). About 70% of starch, which is a convertible C6 sugar, is composed of 10% hemicellulose (containing xylose, which is a C5 sugar), and 20%.

  In contrast, cellulosic biomass represented by vegetation is approximately 40-50% cellulose (polymer of glucose that is a C6 sugar), 20-30% hemicellulose, and 25-30% lignin as others. It is configured.

  Cellulosic biomass, yeast (Saccharomyces cerevisiae), which has been generally used in alcoholic fermentation using starch-based biomass as raw material, cannot convert C5 sugar to ethanol, so far, only C6 sugar content has been used as a fermentation raw material.

  In terms of yield, there is no problem in starch-based biomass, but in cellulosic biomass that contains a relatively large amount of C5 sugar, only C6 sugar is converted to ethanol, so the low yield hinders practical application as a fermentation raw material It was. For example, although existing alcohol fermentable yeast cannot use xylose, it has been reported that xylose can be fermented by introducing a gene for a xylose metabolic enzyme, and the fermentation efficiency is improved.

  In addition, cellulosic biomass is a soft biomass (rice husk, rice straw, bagasse, corn and wheat leaves / stems / sheaths, other vegetation; C6 (cellulose) 45%, with relatively low lignin content, C5 (hemicellulose) 30%, lignin 25%) and hard biomass with relatively high lignin content and a strong tissue structure (sawmill waste, forest residue, building waste, etc.); C6 (cellulose) 40%, C5 ( Hemicellulose) 27%, lignin 33%).

  Currently, in the United States, corn leaves, stems, and pods are being used as soft biomass. Compared with soft biomass, hard biomass, generally called woody biomass, has a strong organizational structure. Therefore, it is said that saccharification treatment is not easy and it is difficult to find business and economic efficiency.

  However, it is considered promising to use woody biomass such as thinned wood and non-agricultural products (stems, leaves, rice husks) as biomass resources because of its large amount and non-competitive food supply. It is done.

  These are called lignocellulosic woody biomass, and are mainly composed of cellulose, hemicellulose and lignin as described above.

  Cellulose is a crystalline polymer of a single monosaccharide containing glucose as a constituent component, and hemicellulose is an amorphous high polymer containing various monosaccharides (such as xylose) and six monosaccharides (such as glucose) as constituent components. Is a molecule.

  Lignin is a high molecular compound in which phenolic aromatics are complexly polymerized, and is present in a complex relationship with cellulose and hemicellulose.

  When using these biomass materials, it is necessary to efficiently recover sugar that is a raw material for the fermentation process, such as ethanol, which is a subsequent product.

  An effective pretreatment method is required to enable efficient conversion in this saccharification step (improvement of saccharification rate and saccharification rate).

  In order to efficiently hydrolyze and saccharify lignocellulosic biomass, pretreatment for removing lignin, reducing the crystallinity of cellulose, and increasing the specific surface area of saccharification reaction is required.

  As these pretreatment methods, various methods such as physical, chemical or biological methods have been studied.

  Practical technologies include 1) dilute sulfuric acid method, 2) dilute sulfuric acid + hot water method, and 3) steaming explosion method.

1) Dilute sulfuric acid method Usually, sulfuric acid with a concentration of 0.5 to 1.5% is used as diluted sulfuric acid, and woody biomass is mixed and treated at 165 to 183 ° C for 3 to 12 minutes. The dilute sulfuric acid treatment reduces the crystallinity of cellulose and facilitates saccharification in the next step.

2) Dilute sulfuric acid / hydrothermal method An improvement of the dilute sulfuric acid method, there was a problem that most of the lignin remained in the dilute sulfuric acid method alone, so this problem was solved by hot water washing after solid-liquid separation. Resolve.

  According to this method, since the lignin component is not contained in the cellulose crystal, the yield of the saccharification step is increased. Usually, after treatment with sulfuric acid having a concentration of 0.1% or less, solid-liquid separation at 140 ° C. and washing with hot water at 140 ° C. are also performed.

3) Steaming explosion method The steaming explosion method was devised for the pulping of 1 wood. After the steaming process in which the raw material is steamed for a short time with steam of high temperature and high pressure (200 ° C or higher) in a pressure vessel, It consists of a blasting process in which it is suddenly released to atmospheric pressure and rapidly cooled to 100 ° C. or less by adiabatic expansion.

  In the steaming process, the effect of high-temperature high-pressure water penetrating into the sample under high-pressure conditions and various hydrothermal reactions with the high-temperature high-pressure water are expected. In the blasting process, by the rapid pressure reduction, a crushing effect due to expansion of water vapor that permeates inside and a physical crushing effect due to collision with the wall surface can be obtained, and the sample can be made finer.

JP 2005-117842 A JP 2005-229822 A JP 2005-229821 A JP 2000-185300 A JP 2000-9410 A

  However, each of the above methods requires high temperature and high pressure, and in the case of wood or wood, solubilization with sulfuric acid is necessary, which is extremely expensive in terms of cost and equipment.

  Further, when sulfuric acid is used, it is necessary to neutralize the pH because of the saccharification / fermentation process, which causes environmental problems and secondary waste problems.

  Then, the objective of this invention solves the said subject, and provides the solubilization method of the woody biomass which can fractionate the cellulose, hemicellulose, and lignin contained in woody biomass efficiently, and can destroy the embedding structure by the cellulose lignin. There is.

  In order to achieve the above object, according to the invention of claim 1, wood biomass is mixed in an aqueous solution containing bicarbonate ions, soaked for a certain period of time, and then the mixture is heated to heat hemicellulose and lignin in the wood biomass. A method for solubilizing woody biomass, which is characterized by removing cellulose and removing cellulose.

  Invention of Claim 2 is the solubilization method of the woody biomass of Claim 1 whose bicarbonate ion concentration of the aqueous solution containing bicarbonate ion is 100 mg / L or more.

  The invention according to claim 3 is the method for solubilizing woody biomass according to claim 1 or 2, wherein the heating temperature of the mixture is 50 ° C. or higher and the temperature is maintained for at least 1 hour.

  ADVANTAGE OF THE INVENTION According to this invention, the wood biomass is immersed in the aqueous solution containing a bicarbonate ion, Then, the outstanding effect that wood wood biomass can be solubilized by heating is exhibited.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows an outline of the method for solubilizing woody biomass of the present invention.

First, as woody biomass 10, 100 g of softwood (wood chips such as pine, cedar and hinoki or sawdust (moisture 15.0%)) is added to baking soda (NaHCO ₃ , concentration 1,000 mg / L) for a certain time (1 to 24 hours). ) After immersion 11, heat treatment 12 is performed at 50 ° C. for 24 hours, whereby liquid 13 in which 1.6 g of lignin and 8.2 g of C5 sugar (hemicellulose) are eluted in an aqueous solution containing bicarbonate ions, and cellulose 33 It is fractionated into a solid 14 of .8 g, 26.0 g of lignin and 15.1 g of C5 sugar (hemicellulose).

  Thereafter, the solid 14 is treated with cellulase (enzyme) to obtain 26.1 g of glucose from cellulose. The obtained glucose is used for alcoholic fermentation.

  The lignin remaining in the solid 14 or the liquid 12 from which the cellulose content has been extracted is reduced in molecular weight by the opening of the allyl ether bond, so that it becomes soluble in organic solvents and dilute alkalis and can be easily separated from C5 sugars.

  As described above, the present invention mixes biomass in an aqueous solution containing bicarbonate ions such as baking soda and soaks the woody biomass for a certain period of time (1 to 24 hours), and then heats the mixture (50 to 180 ° C.). ) To remove the hemicellulose and lignin components in the biomass so that the cellulose can be taken out.

  Solubilization is achieved by maintaining the temperature of bicarbonate ion mixed with woody biomass at 100 mg / L or more, preferably 1,000 mg / L or less, and at a heating temperature of 50 to 180 ° C. for at least several minutes to 24 hours. Is to do.

  The solubilization treatment of the present invention efficiently separates components (cellulose, hemicellulose, lignin) contained in wood resources, destroys the embedded structure of cellulose lignin, and increases the saccharification properties of cellulose by enzymes. It is pre-processing to do.

  That is, by immersion in an aqueous bicarbonate ion solution, bicarbonate ions first enter the woody structure. In the subsequent heat treatment, wood chips are treated with warm water and steam at 50 to 180 ° C. for an appropriate time to chemically decompose and destroy hemicellulose and lignin.

  When wood chips are treated as woody biomass, acetyl groups in hemicellulose are liberated, and hemicellulose undergoes partial hydrolysis to become a low molecular weight and become soluble in water.

  Lignin is reduced in molecular weight by cleavage of the allyl ether bond, and a significant portion becomes soluble in organic solvents and dilute alkalis. Cellulose is exposed by the alteration of lignin, and the reactivity of the enzyme increases.

  This process separates hemicellulose and lignin that have been reduced in molecular weight for effective use, and cellulose can be converted into microbial proteins, alcohols, etc. by enzymatic hydrolysis and fermentation. Is possible.

  In addition, when the cow or goat ingests the cellulose in the fiber obtained by the treatment of the present invention, it can be digested, so that the fiber can be used as roughage.

The concentration, immersion time, heating temperature, and heating time of this bicarbonate ion aqueous solution are:
Concentration conditions: sodium bicarbonate 100 to 10,000 mg / L
Immersion conditions: 1 to 24 hours Temperature conditions: 50 to 180 ° C
Heating time: By making it from 15 minutes to 24 hours,
Sugar recovery rate: 20 to 90% or more can be achieved.

  For example, a 66.7% sugar recovery rate can be obtained by immersing wood chips in an aqueous bicarbonate ion solution having a sodium bicarbonate concentration of 10,000 mg / L for 1 hour, followed by heat treatment at 121 ° C for 15 minutes. it can.

  Next, utilization of the obtained cellulose, hemicellulose, and lignin will be described.

Saccharification and fermentation production of cellulose:
By using microorganisms and various enzymes, cellulose can be hydrolyzed into glucose and converted into alcohol, organic acid or protein.

For example, in ethanol fermentation, ethanol and CO ₂ are produced from a monosaccharide having 6 carbons (C6 sugar) according to the following formula.

C ₆ H ₁₂ O ₆ → 2C ₂ H ₅ OH + 2CO ₂
Ethanol production using starch-based resources has already been put into practical use. In reality, 100% conversion is impossible, but industrially, it is converted with a yield of 90%.

Use of hemicellulose:
When the treated woody biomass is extracted with water, xylo-oligosaccharides, which are hydrolysates of xylan, are obtained in a yield of approximately 15 to 20%.

  Since this water extract contains various impurities and colored substances, these are removed with an adsorbent or an ion exchange resin to purify xylo-oligosaccharides. Moreover, when this is reduced and converted into xylo-oligosaccharide alcohol, heat resistance, acid resistance, alkali resistance, etc. are improved, and the usage is expanded.

  Xylooligosaccharides are resistant to digestion and are low calorie foods. There is also a report of selectively growing Bifidobacteria, which is an enteric bacterium having a function of preventing aging. It can be used for confectionery, jams, beverages, boiled rice cakes, sake, etc.

Use of lignin:
After extracting the xylo-oligosaccharide with water and extracting the residual fiber with dilute alkali, lignin is obtained in a yield of approximately 12-20%.

  This lignin can be converted into a fuel, and when it is reformed into a hot-melt material by phenolysis, spun, and carbonized at about 1000 ° C. in a nitrogen stream, the yield is 30-50% and the strength of general-purpose grade Carbon fiber with properties can be obtained. Phenolytic lignin can also be reacted with formaldehyde to form a wood adhesive. Currently, adhesives that are comparable to the performance of commercially available phenolic resin adhesives are being developed.

  Examples will be described below.

  FIG. 2 shows the results of measuring COD values of wood-derived organic substances eluted in the liquid phase when 10 g of wood chips were immersed in 100 ml of sodium bicarbonate solution for 15 hours and then reciprocally shaken at 50 ° C. for 24 hours. Is.

  From FIG. 2, elution (COD; 5,500 mg / L) occurred at a sodium bicarbonate concentration of 100 mg / L or more. The maximum value (COD; 19,000 mg / L) is reached at 10,000 mg / L. In this case, considering the superiority of the cost as compared with the conventional wood treatment technology (sulfuric acid method), 100 to 1,000 mg / L is more preferable.

  FIG. 3 shows the measurement results of the DNA concentration eluted in the liquid phase by the process of FIG.

  Elution with sodium bicarbonate is confirmed at a concentration of 100 mg / L or more. The reason for this is considered to be that DNA is eluted from the destroyed wood cells by the synergistic effect of the physical action on the wood structure by the gasification of carbonate and the alkalinification of the sodium bicarbonate solution by the delignification reaction.

  FIG. 4 shows that when 5.0 g of wood chips are immersed in 50 ml of a sodium bicarbonate solution (concentration of sodium bicarbonate 0, 100, 1000, 10000, 100000 mg / L) for 24 hours and then treated at 121 ° C. for 15 minutes, and at 50 ° C. for 24 hours. It shows the acid-soluble lignin concentration (g / 100 g wood) eluted in the liquid phase when processed.

  In the figure, in the treatment at 50 ° C. for 24 hours (the graph on the right side in the figure), the maximum lignin elution amount (2.4 g / 100 g wood) is obtained at a sodium bicarbonate concentration of 1,000 mg / L. In the fraction treatment (left graph in the figure), the maximum amount of lignin elution (3.8 g / 100 g wood) was obtained at 10,000 mg / L.

  In the treatment at 50 ° C. for 24 hours, the lignin elution amount is 10,000 mg / L, which is lower than that in the case of treatment with a sodium bicarbonate concentration of 1,000 mg / L, and in the treatment at 121 ° C. for 15 minutes, it is 100,000 mg / L. As a result, the lignin elution amount was lower than that when treated with a sodium bicarbonate concentration of 10,000 mg / L. This is considered to be lower because a saturated solution in which sodium bicarbonate is not partially dissolved is obtained.

It is a flowchart which shows the outline of the solubilization process of this invention. In this invention, it is a figure which shows the relationship of the amount of organic substances eluting from a woody biomass to a liquid phase with respect to baking soda density | concentration. In this invention, it is a figure which shows the relationship of the DNA elution amount of woody biomass with respect to baking soda density | concentration. In this invention, it is a figure which shows the relationship between a sodium bicarbonate density | concentration and the lignin elution amount in heat processing time.

Explanation of symbols

10 Woody biomass 11 Immersion for a certain time 12 Heat treatment 13 Liquid 14 Solid

Claims (3)

  After mixing woody biomass in an aqueous solution containing bicarbonate ions and soaking for a certain period of time, this mixture is heated to remove hemicellulose and lignin components in the woody biomass, and the cellulose is taken out. Solubilization method.   The method for solubilizing woody biomass according to claim 1, wherein the concentration of bicarbonate ions in the aqueous solution containing bicarbonate ions is 100 mg / L or more. The method for solubilizing woody biomass according to claim 1 or 2, wherein the heating temperature of the mixture is maintained at 50 ° C or higher for at least 1 hour.

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