Hydrogen production from catalytic gasification of switchgrass biocrude in supercritical water

Biomass can be liquefied to produce biocrude for ease of transportation and processing. Biocrude contains oxygenated hydrocarbons of varying molecular structure and molecular weights, including lignin derived products, sugars and their decomposition products. In this work several catalysts were screened for hydrogen production by gasification of switchgrass biocrude in supercritical water at 600 °C and 250 bar. Nickel, cobalt, and ruthenium catalysts were prepared and tested on titania, zirconia, and magnesium aluminum spinel supports. Magnesium aluminum spinel was seen to be an inappropriate support as reactors quickly plugged. Ni/ZrO2 gave 0.98 mol H2/mol C, the highest hydrogen yield of all tested catalysts; however, over time, increase in pressure drop lead to reactor plugging with all zirconia supported catalysts. Titania supported catalysts gave lower conversions, however they did not plug during the course of the study. Charring of all catalysts was seen to occur at the entrance of the reactor as the biocrude was heated. All support materials suffered significant surface area loss due to sintering.