Bio-oil hydrotreating using nickel phosphides supported on carbon-covered alumina

Fast pyrolysis oil is an attractive second-generation bio-fuel. However, due to its high oxygen content, upgrading technologies are necessary to improve the properties of bio-oil. The objective of this work is to evaluate the performance of nickel phosphides supported on carbon-covered alumina (CCA) in hydrotreating of a commercial bio-oil. The effect of two different phosphides phases was investigated. The results showed that the stoichiometry of the nickel phosphide can be controlled by the weight ratio of sucrose/Al2O3 used in the synthesis. Two distinct catalysts can be produced: Ni12P5/CCA-0.7 (weight ratio of 0.7) and the Ni2P/CC-1.4 (weight ratio of 1.4). The performances of these catalysts were compared with a commercial Ru/C. Catalytic evaluation was carried out at 250 degrees C and 75 bar in a batch reactor and the effect of two-step HDO (150-250 degrees C) was also investigated. The use of two-step HDO produced bio-oils with higher H/C ratios, indicating a higher occurrence of hydrogenation mechanisms. In addition, more thermally stable bio-oils were generated due to the significant reduction of compounds such as ketones, acid acetic and furfural. Nickel phosphides supported on CCA formulations presented similar performance to commercial Ru/C catalyst in terms of, degree deoxygenation (DOD) and O/C bio-oils ratios.