JP2011056406A - Catalyst for hydrolysis of cellulose and method of hydrolysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel catalyst which does not require energy costs for recovery for chemical hydrolysis of cellulose without heavy loading to the environment, and to provide a method of hydrolysis of cellulose under a substantially normal pressure by using the catalyst. <P>SOLUTION: The hydrolysis of cellulose can be carried out under a substantially normal pressure without heavy loading to the environment by hydrolysis of cellulose in a medium comprising water and a polyhydric alcohol kept under normal pressure and at 90-150°C in the presence of the catalyst of hydrolysis of cellulose using a non-crosslinking-type polymer acid having a sulfonic acid group for a repeating unit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a catalyst for cellulose hydrolysis and a method for hydrolysis of cellulose using the catalyst.

  Cellulose, which occupies the main part of plant biomass, is a chain polymer compound in which β-glucose is bonded in many numbers via 1,4 glucoside bonds, and its high crystallinity contributes to the physical and chemical stability of plant fiber cells. It contributes greatly. However, its physical and chemical stability, at the same time, prevented the use of cellulosic biomass as a starting material for various chemical substances, and so far, cellulosic biomass has not been fully utilized.

  One of the most effective methods of using cellulose as a starting material for various chemical substances is to convert cellulose into oligosaccharides and even monosaccharide glucose by cleaving the glycosidic bonds of cellulose by hydrolysis. . Conventionally, this method includes (1) an enzymatic saccharification method and (2) an acid hydrolysis method. Recently, (3) a method using pressurized hot water, and a method using supercritical water or subcritical water. ,and so on.

  The enzymatic saccharification method of (1) above is a method of saccharifying cellulose using cellulase, which is a method that does not use chemicals and has a low environmental impact. However, because cellulose is crystalline, starch is saccharified. There is a problem that it takes a long time.

  In the acid hydrolysis method (2), sulfuric acid is generally used. Concentrated sulfuric acid acts as a solvent or swelling agent for cellulose, and contributes to breaking up the strong crystal structure of cellulose and increasing the hydrolysis rate. Moreover, dilute sulfuric acid works as a hydrolysis catalyst. Recently, in consideration of the economics of this method, methods for performing hydrolysis in stages have been proposed (Patent Documents 1 and 2). However, this method has a problem that a great energy cost is required to recover sulfuric acid after hydrolysis, and the remaining sulfuric acid generates a by-product called gypsum, which has a large environmental load.

  Water does not function as a swelling agent or solvent for cellulose at normal pressure of 100 ° C. or lower, but functions to swell or dissolve cellulose at high temperature and pressure. Utilizing this is the method (Patent Documents 3 and 4) using the pressurized hot water and catalyst of (3) above, and supercritical water (above 374 ° C. or more, 22.1 MPa or more) or subcritical water, or This is a method for hydrolyzing cellulose using pressurized hot water without using a catalyst (Patent Documents 5 and 6). These have little impact on the environment because they use almost no chemicals with water as a medium, but have problems in terms of energy costs and continuation of processes because they are reactions at high temperature and pressure.

Special table 11-506934 (announced June 22, 1999) JP2007-202560 (released on August 16, 2007) JP 2006-129735 (Released on May 25, 2006) JP2008-297229 (Released on December 11, 2008) JP 2005-206468 (Released on August 4, 2005) JP-A-10-327900 (Released on December 15, 1998)

  An object of the present invention is to chemically hydrolyze cellulose without imposing a significant burden on the environment. For this reason, a novel catalyst that does not incur energy costs for recovery, and the catalyst are substantially used. The object is to provide a method for hydrolyzing cellulose under normal pressure.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies on the hydrolysis reaction of cellulose.As a result, a non-crosslinked polymer acid is used as a hydrolysis catalyst for cellulose, and in the presence of the catalyst, It has been found that if cellulose is hydrolyzed in a medium composed of water and a polyhydric alcohol, the cellulose can be hydrolyzed substantially under normal pressure without much environmental load.

  When sulfuric acid, phosphoric acid or the like is used as a hydrolysis catalyst for cellulose, a method of concentrating by evaporating water is used for the recovery. However, this requires a great energy cost. The non-crosslinked polymer acid catalyst used in the present invention can be recovered by a precipitation separation method using the solubility of the catalyst polymer instead of the evaporation concentration method. Although the non-crosslinked polymer acid according to the present invention is water-soluble, it is insoluble in organic solvents such as ethanol and methanol. Therefore, if this property is used, the polymer acid that is a catalyst can be easily recovered by precipitation. Can do. Thus, in the present invention, it is not necessary to spend a great amount of energy on the recovery of the catalyst.

  Since the hydrolysis reaction rate of cellulose increases as the temperature increases, the higher the temperature, the higher the temperature. However, when a normal pressure reactor is used with water as a medium, the upper limit is 100 ° C. of the boiling point of water. If cellulose is hydrolyzed in a medium comprising water and a polyhydric alcohol of the present invention, it can be maintained at 120 to 130 ° C. under normal pressure, so that the reaction rate can be increased even in a normal pressure reactor. Become.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

  The non-crosslinked polymer acid according to the present invention is (1) non-crosslinked, that is, a polymer having a linear or branched structure, and (2) having an H-type sulfonic acid group in the repeating unit. (3) It is a cellulose hydrolysis catalyst that satisfies the three conditions of containing a repeating unit having no other sulfonic acid group if necessary.

  As is clear from the definition of (1) above, the cellulose hydrolysis catalyst according to the present invention does not include a crosslinked cation exchange resin having a sulfone group. When cellulose is dispersed in a medium containing water as a main component and hydrolyzed, the catalyst must be not completely dissolved or substantially dissolved in the medium, and contact between the cellulose and the catalyst becomes insufficient. Insufficient catalytic action. This is why the cation exchange resin, which is a crosslinked polymer acid, is excluded from the scope of this patent.

  The linear polymer can be obtained by a usual polymerization method, for example, a radical polymerization method of a monomer containing a vinyl group. Since the monomer is water-soluble, a linear polymer acid can be easily obtained by aqueous solution polymerization using a water-soluble polymerization initiator. The branched polymer can be obtained by various graft polymerization methods.

  The repeating unit (2) having a sulfonic acid group can be introduced by polymerization of a sulfonic acid-containing vinyl monomer such as styrene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid. Since these sulfonic acid group-containing vinyl monomers are usually polymerized in the form of a sodium salt, after polymerization, sodium ions must be replaced with hydrogen ions to convert them into H-type sulfonic acid groups.

  The repeating unit (3) having no sulfonic acid group includes non-dissociative monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, vinyl acetate and methyl acrylate, or acrylic acid and methacrylic acid. Or the like can be introduced by copolymerizing a sulfonic acid group-containing vinyl monomer.

  The type and amount of the non-dissociable or weakly dissociable monomer copolymerized with the sulfonic acid group-containing vinyl monomer is an important factor for enhancing the catalytic action of the resulting polymer acid. In the medium containing water as a main component, cellulose is dispersed only in the form of fine particles and not dissolved in the medium. Instead, the polymer acid catalyst must be dissolved in the form of molecules in the medium and coordinated with the fine cellulose particles. However, in order for the polymer acid to easily coordinate to the cellulose fine particles, it is necessary to make the polymer acid difficult to dissolve in the medium. Because of this delicate adjustment, the type and amount of non-dissociable or weakly dissociable monomers are important factors.

  The hydrolysis of cellulose according to the present invention is carried out in a medium comprising water and a polyhydric alcohol in which cellulose is maintained at 90 to 150 ° C. using a non-crosslinked polymer acid having an H-type sulfonic acid group as a catalyst as a catalyst. It is characterized by being performed in By conducting hydrolysis in a medium comprising water and a polyhydric alcohol, the hydrolysis can be carried out substantially under normal pressure.

  As the polyhydric alcohol, ethylene glycol, diethylene glycol, glycerin, sorbitol and the like are used. The boiling point of the medium changes depending on the ratio of water and polyhydric alcohol. If the amount of water is small, the boiling point becomes high and approaches the boiling point of the polyhydric alcohol alone, and the hydrolysis reaction rate increases, but a minimum amount of water is necessary for the hydrolysis. On the contrary, if there is much water, a boiling point will fall near 100 degreeC and a hydrolysis reaction rate will become slow.

  The cellulose content in the medium is not particularly limited, but is preferably 1 to 10% by weight based on the medium. If it exceeds 10%, the system becomes viscous and it becomes difficult to uniformly disperse cellulose, and if it is 1% or less, the production efficiency is deteriorated. The hydrogen ion concentration in the medium acting as a catalyst for the hydrolysis reaction is preferably 0.01 mol / L or more, preferably 0.1 mol / L or more, and kept as high as possible.

  Cellulose fine particles are dispersed in a medium composed of water and a polyhydric alcohol, and the polymer acid catalyst according to the present invention is added to a container equipped with a reflux condenser to heat the entire container. Although various methods can be taken, heating by microwave irradiation is extremely effective from the viewpoint of energy saving.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to this.

  As an experimental device, a household microwave oven modified so that a flask equipped with a reflux condenser and a thermocouple thermometer can be attached is used. As the polymer acid catalyst, a redox polymerization catalyst of potassium persulfate-sodium hydrogen sulfite is used, and a 25% aqueous solution of p-sodium styrenesulfonate or sodium p-styrenesulfonate / hydroxyethyl methacrylate 80/20 at 80 ° C. The mixture is heated for 60 minutes to conduct polymerization, and the polymer aqueous solution is poured into ethanol to precipitate the polymer, and further redissolved in 6 mol / L hydrochloric acid to change the sulfonic acid group to H type, and then excess hydrochloric acid is removed. Remove to create a polymeric acid catalyst. The H-type p-styrenesulfonic acid homopolymer (PSS) and the p-styrenesulfonic acid / hydroxyethyl methacrylate 80/20 copolymer (PSS / HEMA) thus obtained are used in Example 1. When the acid content of the polymer was measured by a neutralization titration method, it was found that 1.3 mmol and 1.0 mmol / L of strong acid type acidic groups were contained per 1 g, respectively. Further, it was confirmed from the infrared absorption spectrum that the acidic group was sulfonic acid.

0.10 g of cellulose microcrystals (manufactured by Merck & Co., Inc.), 5.0 mL of glycerin and the above polymer acid catalyst are placed in a flask with an internal volume of 30 mL, and water is added to make the total volume 12 mL. The amount of the polymer acid catalyst added was such that the hydrogen ion concentration in the reaction system was 1.0 mol / L. This flask was attached to the above-mentioned modified microwave oven and reacted by microwave irradiation at 115 to 130 ° C. The temperature control was manually turned on and off. Table 1 shows the hydrolysis rate of cellulose after 1.5 hours and 3.0 hours. However, the hydrolysis rate (%) is a value representing the proportion of the glucose residue constituting the used cellulose that has undergone hydrolysis.
The hydrolysis rate of cellulose was determined from the quantitative result of the reducing end in the hydrolyzate by the dinitrosalicylic acid method (DNS method).

  The cellulose was hydrolyzed in the same manner as in Example 1 except that sulfuric acid was used as the hydrolysis catalyst. The results are shown in Table 1.

  Using the p-styrenesulfonic acid homopolymer (PSS) used in Example 1 as a catalyst and sulfuric acid as a comparative catalyst, cellulose was hydrolyzed to determine the hydrolysis rate and hydrolysis rate. The hydrolysis reaction conditions are summarized in Table 2, and the results are summarized in Table 3.

However, water / glycerin ratio = 1/0 (98 ° C.), 1/1 (115 ° C.), 1/2 (130 ° C.)

When comparing the values of hydrolysis rate (% / h) representing the hydrolysis rate per hour, Example 2 shows a hydrolysis rate several times higher than that of Comparative Example 2 under substantially the same conditions. Comparative Example 3 shows the result of changing the temperature by further increasing the acid concentration with a sulfuric acid catalyst. From this, it is clear that the hydrolysis of cellulose is greatly affected by temperature and acid concentration. Even in the case of polymer acid catalyst, if hydrolysis is carried out under higher acid concentration, a higher hydrolysis rate is expected. The

  As described above, the polymer acid catalyst according to the present invention has a function comparable to that of sulfuric acid conventionally known as a cellulose hydrolysis catalyst, and is also an evaporative concentration method for recovering the catalyst from the reaction product. Instead, a precipitation separation method that utilizes the fact that the polymer acid is insoluble in an organic solvent such as ethanol can be employed, so that a significant reduction in the recovery energy cost can be expected. This is the reason why the present invention can provide a process for cellulose hydrolysis with a low environmental impact.

Claims (10)

  A cellulose hydrolysis catalyst comprising a non-crosslinked polymer acid having an H-type sulfonic acid group in a repeating unit.   The cellulose hydrolysis catalyst according to claim 1, wherein the non-crosslinked polymer acid is a homopolymer or copolymer of a vinyl monomer having a sulfonic acid group.   The cellulose hydrolysis catalyst according to claim 2, wherein the copolymer is a copolymer of a vinyl monomer having a sulfonic acid group and a non-dissociable or weakly dissociable vinyl monomer.   The cellulose hydrolysis catalyst according to claim 2 or 3, wherein the sulfonic acid group is substantially H-type.   5. The cellulose hydrolysis catalyst according to claim 1, wherein the catalyst is uniformly dissolved or dispersed in a medium comprising water and a polyhydric alcohol.   Cellulose characterized in that cellulose is hydrolyzed in a medium composed of water and a polyhydric alcohol maintained at 90 to 150 ° C. using a non-crosslinked polymer acid having an H-type sulfonic acid group as a catalyst as a catalyst. Hydrolysis method.   The method for hydrolyzing cellulose according to claim 6, wherein the catalyst is the cellulose hydrolysis catalyst according to claims 2 to 5.   The method for hydrolyzing cellulose according to claim 6 or 7, wherein the polyhydric alcohol is a dihydric or higher aliphatic alcohol.   9. The method for hydrolyzing cellulose according to claim 6, wherein the hydrolysis is carried out substantially under normal pressure.   10. The method for hydrolyzing cellulose according to claim 6, wherein the hydrolysis is performed under microwave irradiation.