JP2007301468A - Woody waste material decomposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve such problems that, in a biological decomposition or a chemical decomposition by acid and alkali employed as a woody waste material decomposition method, treating speed or treatment of waste liquid after decomposition causes problems, and decomposition by supercritical water or subcritical water causes problems of separation of decomposition products or waste water treatment. <P>SOLUTION: Contact of pulverized powder of woody waste materials with carbon dioxide containing lower alcohol in a supercritical state or subcritical state, decomposes recalcitrant lignin, cellulose and hemicellulose. After treatment, carbon dioxide can be vaporized and separated by returning to a normal temperature and a normal pressure. Lower alcohol and decomposition products are separated by vaporization, distilling or filtration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a treatment of wood waste, and more specifically, a method for decomposing a wood waste, comprising contacting a ground powder of waste wood with carbon dioxide containing a lower alcohol in a supercritical state or a subcritical state. It is about.

  Energy development other than fossil fuels, such as biomass energy and solar energy, has been rapidly progressing toward the maintenance of the global environment and the realization of a sustainable society in contrast to the conventional development that has used fossil fuels such as oil and coal. It has been broken.

  Also, from the viewpoint of protecting the global environment, there are many problems with waste, such as a shortage of waste disposal sites and reuse / recycling of waste.

  Under such circumstances, there is a strong demand for the development of technology for recycling wood-based waste materials generated from bark, thinned wood, pruned branches, building waste materials, and the like. In addition to the above-mentioned building waste materials, wood-based waste materials, such as palm coconut shell waste, waste leaves, and waste trunks that are cultivated in Southeast Asia, are generated in large quantities. It is rare.

  As a decomposition treatment method of woody waste materials, biological decomposition by fungi and chemical decomposition by acid, alkali, etc. have been studied a lot. Recently, various treatments by high-temperature high-pressure water have been studied.

Particularly recently, many decomposition methods using supercritical fluids have been proposed. For example, Patent Document 1 discloses high-speed saccharification of wood with supercritical water or subcritical water, Patent Document 2 discloses a method of decomposing plant-derived waste with supercritical water or subcritical water, and Patent Document 3 discloses lignocellulose or Methods for treating cellulose, nitrogen-containing polysaccharides and proteins with supercritical alcohols and subcritical alcohols have been proposed.
JP 2001-205070 A JP 2005-81332 A JP 2005-206468 A

  As described above, from the viewpoint of energy problems and environmental problems, many methods for decomposing wood waste materials are being studied. However, biological decomposition is slow and the processing speed is slow and the amount of efficient processing and processing on an industrial scale. There is a problem. In addition, in chemical decomposition with acid / alkali, processes such as separation of acidic and alkaline liquids after decomposition, liquid management, and secondary treatment of liquids are indispensable. It may also cause the following environmental problems.

The decomposition process using a supercritical fluid can be performed in a short time, and when water is used, it is promising from the viewpoint of liquid safety. However, in the case of treatment with water, a step of separating the decomposed product and water after treatment is essential, and in some cases, waste water treatment after separating useful components is necessary. When processing with an alcohol system such as a supercritical alcohol, the reaction is generally slower than with a supercritical water system, but it can still be processed industrially sufficiently, and the separation of the decomposed product and alcohol after processing is compared to that of an aqueous system. And easy. Furthermore, since alcohol becomes a supercritical state at a lower temperature and lower pressure than water, it can be considered more useful because it can reduce the cost of the decomposition treatment apparatus, the running cost, and the processing energy. However, even when decomposing with alcohol alone, it is necessary to treat waste alcohol.

  In view of the disadvantages of the conventional methods as described above, an object of the present invention is to provide a method for easily decomposing wood-based waste materials at low cost.

  The present invention includes a step of pulverizing a wood-based waste material, and a step of bringing the pulverized powder into contact with carbon dioxide containing a lower alcohol in a supercritical state or a subcritical state. The method solves such a conventional problem.

  Note that the average particle size of the pulverized powder is preferably 1 mm or less in order to improve the decomposition efficiency.

  The lower alcohol is preferably at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol, and isopropanol.

  As described above, the present invention is a main component of a wood-based waste material by contacting the ground powder of the wood-based waste material with carbon dioxide containing a lower alcohol in a supercritical state or a subcritical state. Cellulose, hemicellulose, lignin and the like can be decomposed and processed, and the decomposition product can be reused as a new raw material.

  In the present invention, the amount of alcohol used can be greatly reduced as compared with the case of treating with only a supercritical or subcritical lower alcohol, and separation from the decomposed product becomes easy. Moreover, since carbon dioxide is also in a supercritical state, it can be efficiently decomposed with alcohol without inhibiting the penetration of the alcohol into the waste material.

  Furthermore, since the processing method of the present invention requires little processing such as waste liquid, processing energy and processing cost can be reduced.

  The wood-based waste materials used in the present invention can be decomposed by any wood waste material, and wood-based waste materials generated from thinned wood, bark, and pruned branches of cedar and birch, as well as from such construction waste materials are also decomposed. it can. In addition, any tree may be used, such as palm coconut shell waste, waste leaves, and stems, which are widely cultivated in Southeast Asia.

  The main components of such wood-based waste materials are cellulose, hemicellulose, and lignin. In the present invention, by changing the decomposition treatment conditions such as temperature, pressure, treatment time, etc., which components are decomposed to what extent. Can be adjusted.

  However, the wood-based waste material provided for the present invention needs to be pulverized before the decomposition treatment. The pulverized particle size is desirably as fine as possible, and preferably 1 mm or less. If the pulverized particle size is large, the decomposition takes a long time and may not be sufficiently decomposed. For pulverization, the water content of the wood-based waste material should be as small as possible, preferably 50% or less. Therefore, depending on the type of waste material, it may be better to perform a drying process in advance.

  For the pulverization treatment, a general pulverization apparatus such as a crusher, a cutter mill, a disk mill, or the like can be used in combination.

The lower alcohol used in the present invention is preferably at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol, and isopropanol. These alcohols may be one kind or a mixture of two or more kinds.

  The addition amount of the lower alcohol of the present invention is determined by the type and amount of the wood-based waste material to be treated. If the amount is too small, the decomposition of the waste material becomes insufficient, and if it is too much, the treatment process and time of the liquid after the decomposition treatment are large. Therefore, it is necessary to select an appropriate amount.

  The treatment temperature and pressure are preferably at or above the temperature and pressure at which the lower alcohol becomes subcritical or supercritical. The critical temperature of methanol is 512.6 K, the critical pressure is 8.09 MPa, the critical temperature of ethanol is 516.2 K, the critical pressure is 6.30 MPa, the critical temperature of n-propanol is 536.7 K, and the critical pressure is 5. 10 MPa, the critical temperature of isopropanol is 508.3 K, and the critical pressure is 4.70 MPa.

  In the treatment method of the present invention, the subcritical or supercritical lower alcohol is added to the supercritical carbon dioxide to decompose the wood-based waste material and to separate, recover, and treat the waste liquid after the decomposition treatment. It can be done easily.

  In the treatment method of the present invention, for example, first, the woody waste material to be decomposed is pulverized by a pulverizer or the like. Next, the pulverized powder and lower alcohol are put in a pressure vessel, and a little vacuum is drawn with a vacuum pump, and liquefied carbon dioxide is sealed in a state where the air inside is removed. Next, the pressure vessel is heated to adjust the lower alcohol to a subcritical or supercritical state, and a treatment is performed for several minutes to several hours. Through this treatment, cellulose, hemicellulose, and lignin in the woody waste powder are decomposed into their low molecular compounds, monomers, oligomers, and the like. Thereafter, the carbon dioxide is volatilized and separated by opening the pressure vessel back to room temperature and normal pressure. Further, the decomposition product and the lower alcohol are separated by volatilizing the lower alcohol or by a distillation operation. In particular, when the decomposition product is a solid component that does not dissolve in the lower alcohol, it can be easily separated by filtration or the like. Hereinafter, the present invention will be described in more detail with reference to specific examples.

  In this example, cedar wood cut out in a plate shape of 200 × 300 × 50 mm was used as the woody waste material.

  This cedar was coarsely pulverized to about several millimeters by a cutter mill VM-22 manufactured by Sugano Sangyo with a screen of φ10 mm. Next, the coarsely pulverized product was further pulverized by a fine pulverizer DD-2-3.7 manufactured by Hadano Sangyo. The screen used was Φ0.35 mm. As a result, a fine powder having an average particle size of about 0.15 mm was obtained.

  10 g of this fine powder was placed in a heat-resistant / pressure-resistant vessel, about 5 ml of methanol was added, and vacuuming was performed for about 20 seconds with a vacuum pump. Next, this heat-resistant / pressure-resistant vessel was cooled with ice water, and about 50 g of liquefied carbon dioxide was injected therein. The heat-resistant / pressure-resistant container was placed in a tin bath, heated to 350 ° C., and treated at about 23 MPa for 10 minutes. Moreover, the sample processed for 30 minutes and 1 hour on the same conditions was also created.

  Thereafter, the heat-resistant / pressure-resistant container was transferred to a water bath and cooled to room temperature, and then carbon dioxide was gradually released. After the pressure of the heat and pressure resistant container returned to normal pressure, the lid of the heat and pressure resistant container was opened.

When treated for 10 minutes, a slight residue and a dark brown liquid remained, but when treated for 30 minutes or more, almost no solid matter disappeared and only a dark brown liquid was obtained. The slight residue was filtered through filter paper to separate the liquid and solid. These liquids were analyzed by high performance liquid chromatography. The liquid treated for 10 minutes includes coniferyl alcohol and p-coumaryl alcohol, which are considered to be derived from lignin, and glucose, fructose, cellobiose, erythrose, and methylated derivatives of sugar, which are considered to be derived from cellulose and hemicellulose. It was.

  It was found that the liquid treated for 30 minutes or more contained more acetic acid than the decomposition product.

  From this result, it was found that by treating for 10 minutes under the above conditions, a useful decomposition product could be further decomposed and acetic acid could be obtained by treating for 30 minutes or more.

  Thus, the decomposition product obtained by changing decomposition conditions can be adjusted, and the target product for reuse can be adjusted.

  In this example, a palm palm waste trunk cut into a plate shape of 170 × 320 × 40 mm was used as the wood-based waste material. Since this waste trunk contained about 70% of moisture, the moisture was reduced to about 20% with a dryer.

  Next, when pulverized by the same pulverization method as in Example 1, fine powder having an average particle size of about 0.3 mm was obtained.

  This fine powder was treated for 10 minutes under the same conditions as in Example 1. As a result, a very small amount of residue and a dark brown liquid remained. Examples of the liquid include coniferyl alcohol and p-coumaryl alcohol which are considered to be derived from lignin as in Example 1, and glucose, fructose, cellobiose and sugar methylated derivatives which are considered to be derived from cellulose and hemicellulose. It was included.

  In this example, cedar wood crushed by the same method as in Example 1 was used as the woody waste material.

  The treatment was carried out for 10 minutes under the same conditions as in Example 1 except that methanol was used as the lower alcohol and the treatment temperature was changed to 200 ° C., 250 ° C., and 300 ° C. The pressure at that time was about 17 MPa, 20 MPa, and 22 MPa at each temperature.

  As a result, at 200 ° C., the pulverized powder was hardly changed, and a yellow liquid was obtained. About 250% of the residue and a dark brown liquid were obtained at 250 ° C., and a slight residue and a dark brown liquid almost the same as in Example 1 were obtained at 300 ° C. These residues were separated by filter paper, and the liquid was analyzed in the same manner as in Example 1.

  The liquid treated at 200 ° C. was mainly methanol, and contained a small amount of oil and a small amount of coniferyl alcohol, p-coumaryl alcohol, monosaccharides, and sugar methylated derivatives. The liquid treated at 250 ° C. contained many low-molecular components and oligomers of lignin and cellulose constituent molecules, and also contained coniferyl alcohol, p-coumaryl alcohol, glucose, cellobiose, and methylated derivatives of sugar. The liquid treated at 300 ° C. contained a lot of coniferyl alcohol, p-coumaryl alcohol, sugar methylated derivatives and the like as in Example 1.

  From this result, in order to promote decomposition, it is considered better to raise the temperature to the supercritical state of the lower alcohol.

  In this example, cedar wood crushed by the same method as in Example 1 was used as the woody waste material.

  The treatment was performed for 10 minutes under the same conditions as in Example 1 using isopropanol as the lower alcohol. The pressure at that time was about 21 MPa.

  As a result, a slight residue and a dark brown liquid were obtained, and the residue was separated by filter paper. The liquid contained coniferyl alcohol, p-coumaryl alcohol, glucose, fructose, cellobiose, erythrose, and methylated derivatives of sugar as in Example 1.

  In the above examples, while being treated, it was allowed to stand, but it is not limited to this method. For example, the liquid may be promoted by stirring or applying ultrasonic waves. Of course it doesn't matter.

As described above, according to the present invention, it is possible to easily decompose a wood-based waste material that has a great influence on the environment, and to easily recover a product after the decomposition. Furthermore, since the waste liquid after the treatment can be easily treated, the apparatus can be greatly simplified and industrially effective as compared with the conventional method using supercritical water or subcritical water.

Claims (3)

A method for decomposing a wood-based waste material, comprising: a step of pulverizing a wood-based waste material; and a step of bringing the pulverized powder into contact with carbon dioxide containing a lower alcohol in a supercritical state or a subcritical state. The method for decomposing a wood-based waste material according to claim 1, wherein an average particle size of the pulverized powder is 1 mm or less. The method for decomposing a wooden waste material according to claim 1 or 2, wherein the lower alcohol is at least one alcohol selected from the group consisting of methanol, ethanol, n-propanol, and isopropanol.