Supercritical Methanol Treatment Research Articles

Influence of Proteins on the Lignin Decomposition Behavior of Japanese Cedar (Cryptomeria japonica) Wood by Supercritical Methanol Treatment.

The effect of adding protein on the decomposition behavior of lignin in Japanese cedar under supercritical methanol conditions (270 °C/27 MPa) was studied. The Klason method was used to detect the lignin content in the insoluble residue following to a 30 min treatment. Adding either an animal (bovine serum albumin) or plant (soy) protein enhanced delignification from 50 to 65% of the lignin-based wt %. This result was attributed to enhanced lignin depolymerization owing to inhibited lignin recondensation and/or the suppressed formation of polysaccharide-derived char via reactions between the protein and polysaccharides. Although the solubilization of lignin was promoted and the yield of lignin-derived low-molecular-weight compounds increased, the selectivity of major monomers such as coniferyl alcohol (CA) and γ-methylated CA decreased. The addition of proteins has a substantial impact on the decomposition behavior of cell wall components under supercritical methanol conditions. This information provides insights into the use of protein-rich lignocelluloses.

Topochemistry of the Delignification of Japanese Beech (Fagus crenata) Wood by Supercritical Methanol Treatment.

The topochemistry of Japanese beech (Fagus crenata) wood delignification was evaluated in this study following a supercritical methanol treatment (270 °C, 27 MPa). Ultraviolet microscopic analysis of the insoluble residue revealed that the lignin in the secondary wall was easily decomposed and removed because of the preferential cleavage of ether-type linkages. In contrast, the middle lamella lignin was initially resistant to supercritical methanol but eventually decomposed and was removed. In addition, UV-absorbing secondary products formed selectively inside the parenchyma cells. Results from the supercritical methanol treatment of demineralized beech wood indicated that inorganic substances in the lumen of parenchyma affected the formation of these secondary products, thus leading to an overestimation of the residual lignin. Therefore, the topochemistry of delignification was more precisely evaluated when using demineralized beech wood.

Research on Supercritical Methanol Treatment of Lignite

China has rich lignite reserves which are the proper resources to be liquefied. As its low coalification degree, much hydrogen is wasted. Solvent extraction can save hydrogen and improve its liquefaction performance. The paper studies supercritical methanol treatment of lignite with a device at high temperature and pressure. Experiments mainly focus on the effects of temperature, pressure, catalysts and pretreatment ways on the extraction rate. Results indicate that the extraction rate increases with raising of temperature and pressure below 330 ℃,10 MPa. When temperature exceeds 330 ℃, extraction rate decreases slightly. After swelling pretreatment in methanol for 8 h, the lignite is treated for 60 min at 330 ℃，8.2 MPa with NaOH as catalyst(1%wt). The weight ratio of methanol/ Xilinhaote lignite is 5/1. Under these conditions, the extraction rate can reach 22.88%.

Effect of Supercritical Methanol Treatment on the Surface Property of Activated Carbon and the Activity of Ru/Activated Carbon Catalyst

Activated carbon(AC) was modified by supercritical fluidic methanol in order to obtain materials with different surface properties.Several techniques were used to characterize the activated carbon and Ru/AC catalysts including N2 physisorption,Boehm titration,XPS and temperature-programmed reduction(TPR).The results show that supercritical fluid treatment does not remarkably change the surface structure of activated carbon,but significantly reduce the amount of the surface acidic groups.Thus Ru deposited on them will assemble.These led to a higher dispersion of Ru and enhanced the activity of the catalysts prepared by impregnation of AC supported with RuCl3 solution.The activities of Ru/AC catalysts for hydrogenation of glucose were tested under 4.0 MPa and 120 ℃.The results show that activities of Ru/AC catalysts prepared by supercritical fluid treatment are increased,and the highest reaction rate(in Ru mass unit) for hydrogenation of glucose reaches 118.65 mmol/(min·g),which was 1.96 times higher than that without treatment.

Physical and rheological properties of thermoplasticized crosslinked-polyethylene foam in supercritical methanol

The physical and rheological properties of thermoplasticized irradiation-crosslinked polyethylene foam using supercritical methanol treatment were investigated by GPC, FTIR, DSC, WAXS, DMTA and UDS. The polyethylene foam was selectively decrosslinked into thermoplasticized polyethylene in an appropriate supercritical methanol condition without any undesirable side reactions such as oxidation and disproportionation. The thermoplasticization was promoted with increasing reaction temperature to reach completion above 380 °C. The supercritical reaction condition affected the crystallization behavior, and mechanical and rheological properties of the decrosslinked polyethylene foam, but not its crystallographic structure or crystallinity.

New process for catalyst-free biodiesel production using subcritical acetic acid and supercritical methanol

Abstract The production of glycerol as a by-product is unavoidable in the current conventional biodiesel manufacturing processes. Since biodiesel production is expected to increase in the near future, effective utilization of glycerol will become an issue of interest. In this study, therefore, a process consisting of subcritical acetic acid treatment to convert rapeseed oil to fatty acids and triacetin followed by conversion of the obtained fatty acids to their fatty acid methyl esters in supercritical methanol treatment was investigated. The obtained results clearly revealed that this two-step reaction could proceed effectively at a high reaction rate, and that fatty acid methyl esters and triacetin could be obtained under milder reaction condition than the one-step process utilizing supercritical methyl acetate and supercritical methanol.

Improvement of the oxidation stability of biodiesel as prepared by supercritical methanol method with lignin

AbstractAn antioxidation effect of lignin‐derived products in biodiesel prepared using supercritical methanol (300°C/20 MPa) with molar ratio between rapeseed oil and methanol of 1:42 was studied. It was found that lignin could be decomposed to low molecular compounds that have a free radical‐trapping effect after supercritical methanol treatment. However, longer treatment time decreased the antioxidation effect of the lignin‐derived compounds. Rapeseed biodiesel prepared by supercritical methanol method at 300°C/20 MPa for 20 min with a small amount of added lignin showed an induction period longer than 6 h at 110°C in a Rancimat test. In addition, it was found that lignin had a catalytic effect in biodiesel production using the supercritical methanol method without significantly affecting other fuel properties of the prepared biodiesel. Thus, the study proved that lignin addition provides an inexpensive and technically acceptable way to improve the oxidation stability of biodiesel prepared by the supercritical methanol method with satisfactory fuel properties.

Wood solubilization and depolymerization using supercritical methanol. Part 1: Process optimization and analysis of methanol insoluble components (bio-char)

Abstract Conversion of wood into a methanol soluble liquid (bio-oil) was shown to occur under supercritical methanol treatment (SCM). The particle size of the solid material (bio-char) left after evaporating the solvent from the bio-oil was analyzed. Expectedly, the degradation of the particle size was more pronounced during a severe SCM treatment in comparison to subcritical solubilization conditions. Molecular mass was reduced by 90% under optimal conditions of SCM treatment under which the highest degree of solubilization (degradation) was obtained. The bio-char was also analyzed by pyrolysis GC-MS. The composition of the bio-char after sub- and moderate SCM treatments consisted mainly of carbohydrate derived degradation products, which was mixed with some lignin moieties. At near to optimal SCM treatment conditions, the remaining bio-char was composed mainly of modified cellulose and lignin. The optimization of the liquefaction process was performed by means of the statistical design called “response surface model with a central composite design”.

Oxidation stability of biodiesel fuel as prepared by supercritical methanol

A non-catalytic supercritical methanol method is an attractive process to convert various oils/fats efficiently into biodiesel. To evaluate oxidation stability of biodiesel, biodiesel produced by alkali-catalyzed method was exposed to supercritical methanol at several temperatures for 30min. As a result, it was found that the tocopherol in biodiesel is not stable at a temperature higher than 300°C. After the supercritical methanol treatment, hydroperoxides were greatly reduced for biodiesel with initially high in peroxide value, while the tocopherol slightly decreased in its content. As a result, the biodiesel prepared by the supercritical methanol method was enhanced for oxidation stability when compared with that prepared by alkali-catalyzed method from waste oil. Therefore, supercritical methanol method is useful especially for oils/fats having higher peroxide values.

Two-step preparation for catalyst-free biodiesel fuel production: hydrolysis and methyl esterification.

Biodiesel fuel was prepared by a two-step reaction: hydrolysis and methyl esterification. Hydrolysis was carried out at a subcritical state of water to obtain fatty acids from triglycerides of rapeseed oil, while the methyl esterification of the hydrolyzed products of triglycerides was treated near the supercritical methanol condition to achieve fatty acid methyl esters. Consequently, the two-step preparation was found to convert rapeseed oil to fatty acid methyl esters in considerably shorter reaction time and milder reaction condition than the direct supercritical methanol treatment. The optimum reaction condition in this two-step preparation was 270 degrees C and 20 min for hydrolysis and methyl esterification, respectively. Variables affecting the yields in hydrolysis and methyl esterification are discussed.

Effects of water on biodiesel fuel production by supercritical methanol treatment

In the conventional transesterification of fats/vegetable oils for biodiesel production, free fatty acids and water always produce negative effects, since the presence of free fatty acids and water causes soap formation, consumes catalyst and reduces catalyst effectiveness, all of which result in a low conversion. The objective of this study was, therefore, to investigate the effect of water on the yield of methyl esters in transesterification of triglycerides and methyl esterification of fatty acids as treated by catalyst-free supercritical methanol. The presence of water did not have a significant effect on the yield, as complete conversions were always achieved regardless of the content of water. In fact, the present of water at a certain amount could enhance the methyl esters formation. For the vegetable oil containing water, three types of reaction took place; transesterification and hydrolysis of triglycerides and methyl esterification of fatty acids proceeded simultaneously during the treatment to produce a high yield. These results were compared with those of methyl esters prepared by acid- and alkaline-catalyzed methods. The finding demonstrated that, by a supercritical methanol approach, crude vegetable oil as well as its wastes could be readily used for biodiesel fuel production in a simple preparation.

Reaction behavior of lignin in supercritical methanol as studied with lignin model compounds

The reaction behavior and kinetics of lignin model compounds were studied in supercritical methanol with a batch-type supercritical biomass conversion system. Guaiacol, veratrole, 2,6-dimethoxyphenol, and 1,2,3-trimethoxybenzene were used as model compounds for aromatic rings in lignin. In addition, 5-5, β-1, β-O-4, and α-O-4 types of dimeric lignin model compounds were used as representatives of linkages in lignin. As a result, aromatic rings and 5-5 (biphenyl)-type structures were stable in supercritical methanol, and the β-1 linkage was not cleaved in the β-1-type structure but converted rapidly to stilbene. On the other hand, β-ether and α-ether linkages of β-O-4 and α-O-4 lignin model compounds were cleaved rapidly, and these compounds decomposed to some monomeric compounds. Phenolic compounds were found to be more reactive than nonphenolic compounds. These results indicate that cleavages of ether linkages mainly contribute to the depolymerization of lignin, whereas condensed linkages such as the 5-5 and β-1 types are not cleaved in supercritical methanol. Therefore, it is suggested that the supercritical methanol treatment effectively depolymerizes lignin into the lower-molecular-weight products as a methanol-soluble portion mainly by cleavage of the β-ether structure, which is the dominant linkage in lignin.

Comparison of the decomposition behaviors of hardwood and softwood in supercritical methanol

The chemical conversion of Japanese beech (Fagus crenata Blume) and Japanese cedar (Cryptomeria japonica D. Don) woods in supercritical methanol was studied using the supercritical fluid biomass conversion system with a batch-type reaction vessel. Under conditions of 270°C/27 MPa, beech wood was decomposed and liquefied to a greater extent than cedar wood, and the difference observed was thought to originate mainly from differences in the intrinsic properties of the lignin structures of hardwood and softwood. However, such a difference was not observed at 350°C/43 MPa, and more than 90% of both beech and cedar woods were effectively decomposed and liquefied after 30 min of treatment. This result indicates that the supercritical methanol treatment is expected to be an efficient tool for converting the woody biomass to lower-molecular-weight products, such as liquid fuels and useful chemicals.

3-21.超臨界メタノールを用いた木質系バイオマスからの液体燃料の創製((5)水熱II,Session 3 バイオマス等)

3-21.超臨界メタノールを用いた木質系バイオマスからの液体燃料の創製((5)水熱II,Session 3 バイオマス等)

Chemical conversion of cellulose as treated in supercritical methanol

The chemical conversion of cellulose as treated in supercritical methanol was studied using a batch-type reaction vessel at temperatures from 220 to 450°C and pressures from 14 to 72MPa. Supercritical methanol treatment at 350°C and 43MPa for 7min was sufficient to convert microcrystalline cellulose (avicel) to the methanol-soluble. To study the kinetics of the decomposition of cellulose, the decomposition rate constants were obtained, and rapid increase was observed at about 270°C which was about 30°C higher than the critical temperature of methanol. The main products from cellulose decomposition were methylated cellotriose, methylated cellobiose, methyl α- and β-D-glucosides, levoglucosan and 5-hydroxymethylfurfural. Monomeric compounds such as methyl α- and β-D-glucosides were stable in supercritical methanol, allowing high yields of monomeric products by supercritical methanol treatment. Based on these results, a pathway of cellulose decomposition treated in supercritical methanol was proposed. These findings suggest that the supercritical methanol treatment of various cellulosic materials may be suitable to obtain useful chemicals and liquid fuels without using fossil resources.