A comparative kinetic study on the pyrolysis of three different wood species

The catalytic effect of pH-neutral inorganic salts on the pyrolysis temperature and on the product distribution was studied by fractionated pyrolysis followed by GC/MS and GC/FID and by thermogravimetric analysis (TGA) of cold-water-washed hornbeam wood. Sodium and potassium chloride have a remarkable effect on the pyrolysis temperature and on the product distribution, whereas calcium chloride only changes the low temperature degradation of hornbeam wood and the product distribution is nearly unchanged compared with water-washed hornbeam. wood. All studied potassium salts (KCl, KHCO3, and K2SO4) decrease the amount of levoglucosan the order of magnitude being dependent on the anion: chloride has a more pronounced effect than sulphate, and sulphate a more pronounced effect than bicarbonate. The thermal degradation of three different wood species (hornbeam, walnut and scots pine) was investigated by analysis of thermogravimetric/mass spectrometric pyrolysis. Commonly used model substances for the main components of wood, like xylan, pure cellulose or filter pulp, were found to be unreliable for the evaluation of formal kinetic parameters that are able to describe the pyrolysis of wood. A method for the individual evaluation of formal kinetic parameters for the main components of wood was used, that uses specific ion fragments from lignin degradation products to study the lignin degradation. Coniferous lignin is thermally more stable than deciduous lignin, and the latter produces smaller char yields. The differences in wood species mainly result in different degradation rates for the lignin and for the early stages of the hemicellulose degradation. (C) 2003 Elsevier Science B.V. All rights reserved.