Catalytic hydrotreatment of fast pyrolysis oil: Model studies on reaction pathways for the carbohydrate fraction

Fast pyrolysis oil can be upgraded by a catalytic hydrotreatment (250-400° C, 100-200 bar) using heterogeneous catalysts such as Ru/C to hydrocarbon-like products that can serve as liquid transportation fuels. Insight into the complex reaction pathways of the various component fractions during hydro treatment is desirable to reduce the formation of by-products such as char and gaseous components. This paper deals with the catalytic hydro treatment of representative model components for the carbohydrate fraction (viz., D-glucose and D-cellobiose) present in concentrations of 20-40% in fast pyrolysis oils. The hydrotreatment was conducted at a temperature of 250°C and 100 bar hydrogen using Ru and Pd on carbon catalysts in water. Two parallel reaction pathways are then observed, a thermal noncatalyzed pathway leading to insoluble humins (char) and a hydrogenation pathway leading to smaller polyols and gaseous hydrocarbons such as methane and ethane. The implications of these findings for the catalytic hydrotreatment of fast pyrolysis oil are discussed.