Improvement of the thermal stability of lignocellulosic materials by treatment with sulphuric acid and potassium hydroxide

In this study, a lignocellulosic feedstock obtained from Scandinavian pine wood was thermally treated in the presence of sulphuric acid or potassium hydroxide in order to improve its thermal stability. The thermal decomposition of the reaction products was monitored by thermogravimetric analysis and the microstructure of the chars obtained at 900°C was analysed by optical microscopy. The results show that sulphuric acid and potassium hydroxide transform the lignocellulosic feedstock via different mechanisms of reaction. Sulphuric acid reacts without the incorporation of sulphur, while potassium hydroxide is incorporated into the lignocellulosic feedstock. In both cases, the resultant reaction products are more thermally stable and yield higher residues at 1000°C than the parent feedstock in thermobalance. Observation by optical microscopy of the chars obtained at 900°C evidences that sulphuric acid preserves the honeycomb structure of the parent feedstock, while potassium hydroxide yields a reaction product that passes through a fused stage during carbonization. © 2004 Elsevier B.V. All rights reserved.