Abstract: The mixed sawdust was liquefied by glycerin and methanol as mixed solvents using a 1 L stainless steel high-pressure autovalve. This reaction was carried out at critical/supercritical effect of methanol in high temperature and pressure. The influence of reaction conditions such as reaction time, reaction temperature, catalyst types and dosage on liquefaction reactions was investigated. The results showed that the optimal liquefaction conditions of the mixed sawdust is methanol 30 g, glycerin 10 g, oxalic acid 0.25 g, mix sawdust 6 g(0.28-0.90 mm), at 290℃ with reaction time 40 min. Under this reaction conditions, the conversion of sawdust is up to 92.79%. Various analysis methods such as Gas chromatography-mass spectrometer(GC-MS), fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography(GPC) were used to analyze the composition and molecular structure of the liquefaction oil. Moisture, acid value, viscosity and other properties of the liquefied product were also studied. The analytical results showed that the liquefaction oil is complex compounds, which mainly contains oxygen derivatives such as alcohol, ether, ester and hydroxybenzene, etc. The liquefaction oil consists of low molecular weight components, i.e., which is below 2 300.

Key words: mix solvents, critical or supercritical effects, sawdust, liquefaction