For high-quality biodiesel fuel production from oils/fats, the catalyst-free two-step supercritical methanol process has been developed in a previous work, which consists of hydrolysis of triglycerides to fatty acids in subcritical water and subsequent methyl esterification of fatty acids to their methyl esters in supercritical methanol. In this paper, therefore, kinetics in hydrolysis and subsequent methyl esterification was studied to elucidate reaction mechanism. As a result, fatty acid was found to act as acid catalyst, and simple mathematical models were proposed in which regression curves can fit well with experimental results. Fatty acid was, thus, concluded to play an important role in the two-step supercritical methanol process.

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The chemical conversion of Japanese beech (Fagus crenata Blume) and Japanese cedar (Cryptomeria japonica D. Don) woods in supercritical methanol was studied by using the supercritical fluid biomass conversion system with a batch-type reaction vessel. As a result, at a condition of 270 o C-27MPa, beech wood was decomposed and liquefied to a greater extent than cedar wood, and the difference observed was considered to be mainly originated from intrinsic properties in lignin structure between hardwood and softwood. However, at 350 o C-43MPa, such a difference was not observed and over 90% of both beech and cedar woods were effectively decomposed and liquefied after 30 min treatment. This result indicates that the supercritical methanol treatment is expected as an efficient tool to convert the woody biomass into the lower molecular products such as liquid fuels and useful chemicals.

The liquefaction of Japanese beech (Fagus crenata Blume) was studied with various straight-chain alcohols in subcritical or supercritical state using a batch-type reaction vessel to obtain liquid fuel from lignocellulosics. Under the reaction condition of 270 o C, beech wood was liquefied to some extent in any alcohol with about 50~65% of insoluble residue left after the treatment for 30 min. Under the condition of 350 o C, however, more than 90% of wood was decomposed and liquefied in any alcohol. Alcohol with the longer alkyl chain could have lignocellulosics liquefied in the shorter reaction time. Since many kinds of alcohols such as methanol and ethanol can be produced from biomass, the 100% biomass-based liquid fuel can be prepared by supercritical alcohol technology when using such bioalcohols.