Catalytic hydrothermal liquefaction of corn stover pellets for production of biofuels

Z. Fickbohm, B. Maddipudi, K. Huynh, G. Bauer, R. Shende
South Dakota Mines,
United States

Keywords: corn stover, pellets, hydrothermal, BTMO, HBO


Pelletized biomass offers many advantages to traditional powdered biomass. It provides several benefits in terms of shipping and handling, and storage. However, this type of biomass has not yet fully investigated for catalytic thermochemical processing. Hydrothermal liquefaction (HTL) is an effective thermochemical process used to convert biomass into fuels and value-added products such as heavy biooil (HBO), hydrochar, and aqueous biocrude that typically contains important oxygenated hydrocarbons. Binary transition metal oxides (BTMOs) have shown to improve both the conversion and quality of HTL derived HBO. However, BTMO catalytic materials have not been explored so far for the pelletized biomass. In this study, HTL of pelletized corn stover was investigated at 225-300 oC in the presence of BTMO catalyst to generate a renewable biofuel. The catalyst was prepared by the sol-gel method wherein the transition metal salt precursors were dispersed in a solvent and propylene oxide was added to achieve the gel formation. The gel was dried, aged and calcined at 600 oC to obtain BTMO catalyst. HTL processing was performed in a stainless steel 316 PARR reactor using 10 wt.% biomass loading in water. After HTL process, HBO was extracted from the hydrochar using acetone and characterized using gas-chromatography mass spectrometry (GC-MS) and elemental analysis to determine the quality of the HBO. The HBO was compared to the HBO derived from powdered corn stover and uncatalyzed HTL to determine the effects of both pelletization and BTMO catalyst on the yield and quality of HBO. Uncatalyzed corn stover pellet reactions achieved higher HBO yields as compared to powdered corn stover yields around, showing the possibility of another advantage to the pelletization of biomass for thermochemical processing.