On the Production of Hydrogen from Bio-Oil: A Representative Study Using Propylene Glycol

Abstract

In a bio-refinery focused on fast pyrolysis, hydrogen (H2) producible from reforming of the aqueous fraction of bio-oil with steam can be utilized for upgrading pyrolytic lignin into fuels by hydrotreatment. In this work, propylene glycol (PG) was chosen as a typical compound symbolizing higher polyols in the bio-oil aqueous fraction. Catalytic processing of PG into H2 at low temperature (T = 500°C) was investigated using several commercial catalysts such as Ni/Al2O3, Ru/Al2O3, Ru/C, Pt/C, and Pd/C in a laboratory-scale fixed-bed reactor. The efficiencies of the catalysts were presented as selectivity to CO, CO2, CH4 and H2, and PG conversion into gaseous phase. Wide ranges of temperature (300–500°C), W/FO (18.6–92.9 g h/mol), and S/C ratio (5.6–12.7 mol/mol) were examined using Ni/Al2O3. At T = 500°C, H2 selectivity (73.7%) and PG conversion (66.2%) were maximized using ratios of catalyst mass to molar flow rate of PG (W/FO) = 18.6 g h/mol and steam to carbon (S/C) = 12.7 (10 wt% PG solution). It was found that Ni/Al2O3 demonstrates stable operation for at least 6 h of time-on-stream. Finally, a plausible reaction pathway for PG reforming was proposed.