Chemical Yields from Low-Temperature Pyrolysis of CCA-Treated Wood

摘要

Low-temperature pyrolysis offers a feasible option for wood-waste management and the recovery of a variety of useful chemicals. The effect of chromated copper arsenate (CCA) wood preservative on the yield and composition of various pyrolysis products was investigated in the present research. A novel quantitative 31P nuclear magnetic resonance (NMR) spectroscopy methodology has been developed to quantify levoglucosan and levoglucosenone from the pyrolysate of CCA-treated and untreated wood. The CCA treatment of wood had a notable effect on the characteristics of the carbohydrate-derived degradation products of tar. In particular, yields of the important pharmaceutical precursors levoglucosan and levoglucosenone were elevated by 3 and 4.5 times, respectively, when compared with those from untreated wood. Phosphoric acid has proven to be an efficient catalyst to favor levoglucosenone formation. The pyrolysis of CCA-treated wood in the presence of phosphoric acid gave rise to high yields of levoglucosenone, demonstrating the potential for a new pathway in the rational use of CCA-treated wood waste. Pretreatment of wood with metal compounds has demonstrated that K2Cr2O7 and CuSO4 salts promote the formation of levoglucosan. The CrO3 treatment was found to favor the formation of levoglucosenone. A kinetic study of the pyrolysis of CCA-treated wood by thermogravimetric analysis has shown that CCA components have a significant influence on the thermal decomposition behavior of CCA-treated wood and accelerate the weight loss of wood and the oxidation of the char.