Hydrotreatment of corn stover bio-oil using noble metal catalysts

• Corn stover bio-oil was hydrotreated using Ru and Pd at 100 bar and 200 or 300°C.
• Ruthenium performed better at 300°C and was more effective than palladium.
• The product obtained at 300°C had the lowest oxygen content and total acid number.
• The major reactions involved conversion of ketones to alcohols.

Hydrotreatment of corn stover bio-oil and its distilled fraction was performed using noble metal catalysts such as ruthenium and palladium on carbon support at 125 bar, 4 hour reaction time and 200 °C or 300 °C in a batch catalytic reactor. Results showed that ruthenium performed better at higher temperature (300 °C) and was more effective than palladium, giving about 25–26% deoxygenation. Higher yields (54–67 wt.%), higher H/C molar ratios (1.46–1.48) and lower O/C molar ratios (0.065–0.08) were obtained for the products from Ru-catalyzed processes at 300 °C. Analysis of the chemical composition of the products indicated that the major reactions involved hydrogenation of ketones to alcohols. Carbon dioxide, methane, ethylene and propane, were detected in the gas phase, indicating significant activity for this catalyst as compared to palladium. The hydrotreated product from the heavy distillate with ruthenium as catalyst at 300 °C had the lowest oxygen content (7.0 wt.%) and exhibited better product properties: lower moisture (2.6%), TAN (5.3 mg KOH/g sample), and the highest heating value (40.2 MJ/kg), making it a potential feedstock for co-processing with crude oils in existing refineries.