Biomass & Bioenergy, Vol.106, 63-73, 2017
Reactivity of platform molecules in pyrolysis oil and in water during hydrotreatment over nickel and ruthenium catalysts
Hydrodeoxygenation (HDO) of fast pyrolysis oils for fuel and chemical production was investigated in a batch autoclave at 340 degrees C (8.0 MPa H-2 at room temperature) over nickel-based catalysts and Ru/C. The deoxygenation degree was similar over all catalysts, but different H/C ratios were observed in the upgraded oils, in line with the corresponding H-2 consumption. The highest values were found for Ru/C followed by NiCu/Al2O3. The composition of the upgraded oils produced over Ni-catalysts showed high ketone content, while the upgraded oil over Ru/C contained hydrocarbons and alcohols. Phenolic compounds exhibited low conversion over all catalysts. Subsequently the influence of the reaction medium (bio-oil or water) on the activity and selectivity of the catalyst was probed using phenol and D-glucose as model compounds representative for the cellulose and lignin fraction, respectively. Their reactivity in the bio-oil was tracked using isotopically-labelled phenol-d(6) and D-glucose-C-13(6). Phenol was HDO resistant, while D-glucose formed a complex product mixture recovered in the upgraded oil. In aqueous solution, phenol was converted mainly to methane over Ru/C and cyclohexane over NiCu/Al2O3, whereas both catalysts promoted hydrocracking of D-glucose to methane. Comprehensive analysis of the spent catalysts showed that inorganic deposits and further components in the bio-oil lead to different reactivity in the two media. (C) 2017 The Authors. Published by Elsevier Ltd.