Special Article on Chemistry and Technology for Recycling Inorganic and Organic Materials Direct Liquefaction of Woody Biomass

Abstract

Wood powder suspended in an aqueous solution of alkali or alkaline earth salt was directly liquefied without a reducing agent such as 112 and/or CO. Heavy oils were obtained in 4550% yields under the following conditions: pressure, 110 atm; temperature, 300 °C;
holding time, 0-30 min; catalyst l oading, 5 wt%. The heating values were about 25 MJ/kg. Carbonate and hydrogencarbonate of sodium, potassium and calcium showed marked catalytic effects. Various kinds of wood and bark were used as a feedstock. In case of wood, heavy oil yields were 50%, irrespective of the indivisual species. In case of bark, however, heavy oil yields were as low as 20-27%. To improve the yields, steam explosion was applied to bark and as a result heavy oil yields increased to 33%.
Heavy oils obtained from wood in the above-mentioned manner were very viscous. Organic solvents such as propyl and butyl alcohols were added to the reaction system to reduce the viscosity of heavy oils. As a result, heavy oils with low viscosity were obtained in 50%yields. It was clarified that the additional alcohol functions not as a hydrogen donor but as a stabilizer of unstable breakdown products of wood. Because the additional alcohol was not consumed duririg the reactions, extended batch reactions in which water/2-propanol mixture was used repeatedly were examined. As a result, heavy oils were obtained in the yields of about 35% till the fourth run in five sequential runs.