Thermally assisted hydrolysis and methylation of milled beech leaf litter

Thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) of milled beech leaf litter was used to investigate the behaviour of polysaccharides, lipids and lignin components in complex organic matrices. THM at 300 degrees C produced a limited fragmentation of lignin derivatives and the relative proportion of fatty acid methyl esters increased with respect to aromatic compounds when compared with THM at 500 degrees C. Polysaccharide pyrolysis products were minor compounds at both temperatures. In addition, three different procedures for TMAH reaction at 300 degrees C were tested. Method A consisted in the application of TMAH solution to the sample, drying with a N-2 flow and immediate insertion in the pyrolyser. In method B the sample plus TMAH was sonicated for 30 min. In method C the sample was maintained with TMAH for 48 h at room temperature. It was shown that a prolonged time of reaction and/or disruption of structures by sonication and more intensive mixing with TMAH increases the yield of evolved products. Therefore, it is proposed that a standardization of the pretreatment procedure with TMAH is needed in order to compare results obtained by different authors. (C) 1999 Elsevier Science B.V. All rights reserved.