Hydrogenation of rice stalk in situ in supercritical ethanol-water co-solvent via catalytic ethanol steam reforming

Liquefaction of biomass by an in situ hydrogenation process has received increasing attention to upgrade bio-oil. This study aims to examine the hydrogenation of rice stalk using ethanol-water co-solvent in an autoclave with hydrogen generated in situ mainly from ethanol steam reforming (ESR) reactions. ESR occurred at a mild temperature of 320 degrees C over Ni-Mo-S/Al2O3 catalyst with H-2 being the major gaseous product, and the H-2 yield increased significantly with elevated temperature. A higher energy recovery of 0.79 was obtained at 320 degrees C with NiMoS/Al2O3. Methoxy-substituted phenols were reduced due to the hydrogenolysis reactions, and the total content of phenols was decreased by as high as 37% at 340 degrees C. TG analysis indicated that higher temperature promoted the formation of low-boiling point compounds in the bio-oil, especially in the presence of Ni-Mo-S/Al2O3. This work demonstrated the feasibility of in situ hydrogenation of rice stalk in supercritical ethanol-water co-solvent.