Liquid Fuel Production from Woody Biomass by Direct Liquefaction.

Abstract

Taking into consideration creation of alternative energy and environmental preservation, we have attempted to produce a liquid fuel by direct liquefaction of woody biomass, which is the only renewable organic resource, and which fixes carbon dioxide in the atmosphere. Wood was made to react in an aqueous solution of potassium carbonate under pressurized atmosphere of nitrogen without using reducing gases such as hydrogen and/or carbon monoxide. Heavy oil-like liquid products, having heating values of 25-30MJ/kg, were obtained at yields of 45-50%, under the following optimum reaction conditions: Temperature: 300°C, Initial pressure: 20-40atm, Holding time: 0-30min Potassium carbonate loading: 2-5wt%. Carbonate and hydrogencarbonate of potassium, sodium and calcium showed strong catalytic effects. Species of the wood did not significantly effect the liquid product yield.The liquid product obtained by this method was viscous, which caused troubles in handling. In order to improve this property, some organic solvents, such as 1-, 2-propanol, 1-butyl alcohol, were added to the reaction system. As a result, liquid products with low viscosity were obtained at yield in the range of 50-70%, at 275°C. It was found that the added alcohol did not function as a hydrogen donor but as a stabilizer of unstable products from wood, and that it was not consumed during liquefaction. Since this indicated the possibility of recycling the added alcohol, experiments were conducted in which a water/2-propanol mixture was used repeatedly as a solvent. As a result, it was found that liquid product yields were almost the same, even when recycled solvents were used.This liquefaction method can be applied not only to woody biomass but also to various organic wastes such as sewage sludge.