Hydrocarbons via catalytic hydrogen treatment of a wood pyrolytic oil

Abstract

Pyrolysis exhibits promise as a process for the conversion of biomass residues into chemical and fuel feedstocks. The oil product derived from this process, namely pyrolytic oil, is a complex mixture of many components including phenolics, anhydrosugars and polynuclear aromatics, and is believed to have good potential as a liquid fuel. However, due primarily to its high oxygen content and high viscosity, the oil can currently only be used as a boiler fuel. An upgrading process would be necessary to convert pyrolytic oil into a fuel suitable for use in internal combustion engines. This study reports progress in the application of catalytic hydrotreating and hydrocracking procedures to the pyrolytic oil to improve volatility, decrease oxygen content and generally to produce liquid hydrocarbon mixtures. Results of a screening program using twelve catalysts are reported, leading to the identification of 0.5% Platinum or Palladium catalysts as catalysts with some desired specificities for hydrotreating. Further studies suggested that 5% Pt and Pd catalysts in the presence of decalin solvent promotes more hydrogenolysis of C-O bonds and further reduction of large molecules. Analyses showed that the raw oil was upgraded to a low viscosity, low oxygen content light liquid mixture of hydrocarbons with increased heating value. The process was further improved in the use of one component of the hydrocarbon product as a solvent, and indicates that the process can be independent of petroleum-based solvents. The conversion rate of pyrolytic oil into liquid hydrocarbons by this process is above 50%, weight basis, and approximately 85-90%, energy basis. The product contains 40% light hydrocarbons in the gasoline range, a 50% middle fraction distributed in the diesel range and some 10% heavier ends. A total of more than 120 compounds, generally hydrocarbons, were identified by GC-MS analysis. Preliminary investigations into some physical properties of these hydrocarbons such as viscosity, heating value, carbonaceous residue, specific gravity, etc. were also conducted.