Understanding the pyrolysis of CCA-treated wood: Part I. Effect of metal ions

The influence of several inorganic compounds (K2Cr2O7, CrO3 and CuSO4) on the pyrolysis of southern pine wood has been investigated. The wood powder was pre-treated with various inorganic compound solutions prior to the pyrolysis and the distribution and yields of the pyrolysis products were obtained by gas chromatography and quantitative 31P nuclear magnetic resonance (NMR) analyses. Our experiments showed that K2Cr2O7 and CuSO4 salts promoted the formation of levoglucosan (LG). In particular, the former providing higher LG yields up to 26.7%. The CrO3 treatment induced the production of low tar and high char yields, with a very low yield of LG and high yield of levoglucosenone (LGO). The underlying reasoning behind these findings may be due to an acidic catalysis mechanism, which promotes cellulose depolymerization and dehydration processes. Due to acid-catalyzed lignin condensation reactions, the yield of lignin degradation products from the pyrolysis of pre-treated wood was found to dramatically decrease in comparison to untreated wood.