Influence of solvent on upgrading of phenolic compounds in pyrolysis bio-oil

Solvents play a pivotal role in many chemical reactions as well as in upgrading of pyrolysis bio-oil. Herein we report a systematic study of the effects of solvents such as water, methanol, ethanol, propanol, butanol, acetone, ethyl acetate, tetrahydrofuran and hexane on hydrogenation of a lignin-derived component of pyrolysis bio-oil, phenol, over activated carbon supported palladium catalysts. The solvents were classified into four groups so as to better understand the effect of them. For hydrogen bond donor–hydrogen bond acceptor (HBD–HBA) solvents and hydrogen bond acceptor (HBA) solvents, the conversion of phenol decreased with increasing polarity/polarizability π*. Phenol was converted completely in hexane or water at 250 °C. However, in methanol or ethanol, it was converted partially. Synergistic action of multiple factors had an effect on the hydrogenation of phenol. To convert phenol better, water and hexane as solvents were excellent in upgrading of pyrolysis bio-oil.