Liquefaction of Kraft Lignin: 1. Primary Reactions under Mild Thermolysis Conditions

Primary reactions of kraft lignin liquefaction were studied under mild batch reaction conditions. Experiments using tetralin äs reaction solvent were made both neat and in the presence of a heterogeneous hydrotreating catalyst (CoMo). Thermolysis at 345°C gave only a relatively low yield of gaseous and liquid products. The maximum yield, 20.3 wt-% (dry basis), for ether soluble phenols and acids was attained when a tetralin/m-cresol mixture was used äs a solvent. The main reaction under mild thermolysis conditions is the demethylation of the methoxyl group leading to the formation of methane, and also char through condensation. The high yields of char indicate the inability of both the gas phase hydrogen and the hydrogen from the donor solvent to prevent condensation reactions. Experiments with the hydrotreating catalyst gave a higher yield of both gaseous products and char than neat thermolysis indicating an enhanced reaction of the kraft lignin. The yield of liquid products remained, however, on a low level.