Thermal degradation of lignocellulosic materials treated with several acids

A lignocellulosic material (sawdust) was treated with several acids (AlCl3, H3PO4, H2SO4 and HCl) under different experimental conditions. The pyrolysis behaviour of the reaction products was studied by thermogravimetric analysis (TG/DTG) in nitrogen and oxygen media and the results were assessed as a function of the chemical nature of the acids. Under nitrogen, all the acid treatments led to an increase in the carbon yield, which was due to the consolidation of the cellular structure of the parent sawdust, especially in the case of AlCl3 and H2SO4. In contrast, the oxygen reactivity of the reaction products is dependent on the protic characteristics of the acid. In order to find out more about the effects of the treatments on the composition of the sawdust, the four reaction products were pyrolyzed to 350 and 450 °C and the resultant gases, liquids and chars were studied. An analysis of the liquids by 1H NMR revealed significant differences in the chemical natures of the samples.