Cellulose as a precursor of catalyst support: new aspects of thermolysis and oxidation - IR, XPS and TGA studies

Microcristalline cellulose was thermally treated in order to obtain a precursor of carbonaceous support. Thermolyses at 450 degrees C were done under different conditions and the effect of some thermal parameters was evaluated in respect with the specific surface of the sample and the yield of solid residue at the end of the carbonization processes. Pretreatments under air or N-2 at 250 degrees C were found to be unable to further increase the char yield but very efficient in order to expand the specific surface area of the sample. The carbonized residues were oxidized in air in a TG oven under different temperature conditions and characterized by DRIFTS and XPS. A weight gain of about 5% attributed to the formation of oxygenated surface groups was observed in the first part of the experiment, and later a gradual loss of weight occurred. Analyses of functional groups by DRIFTS and XPS seem to show the progressive decrease of carboxyles and increase of anhydrides during oxidation. The loss of weight and the increase of the O/C ratio at the end of the process can be explained by the regeneration of new sites of oxidation with consumption of carbon in gasification reactions. (C) 2000 Elsevier Science B.V. All rights reserved.