Liquefaction of lignin extracted from aspen wood resulted in a 78% yield of bio-crude oil. The direct conversion of five types of lignin was studied, including Kraft pine lignin provided by MeadWestvaco Corp, Kraft pine lignin obtained from Sigma-Aldrich, organosolv lignin extracted from oat hull, the residues of mixed southern hardwoods, and switchgrass after hydrolysis. The major compounds from lignin liquefaction were identified by GC-MS. A kinetic model was proposed to describe hydrothermal treatment of Kraft pine lignin, and compared with another model from literature. The kinetic parameters of the presented model were estimated, including the reaction constants, the pre-exponential factor and the activation energy of the Arrhenius equations. The presented model was well in agreement with the experiments. This is an abstract of a paper presented at the 2007 AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).