Catalytic Route for the Production of Alkanes from Hydropyrolysis of Biomass

In this work, we report a catalytic route to produce liquid alkanes from hydropyrolysis of biomass. This route uses a NiMo-HZSM-5 catalyst in situ and takes place primarily in three steps: (1) nickel promotes the formation of methane, (2) molybdenum oligomerizes the methane into aromatics, and (3) nickel hydrogenates the aromatics into alkanes (primarily cycloalkanes). In support of this route, we investigated the effect of nickel and molybdenum metals, together and independently, doped on HZSM-5 during hydropyrolysis of Arundo donax. Nickel (without hydrogen) promotes gas formation (CO, CO2, and CH4), and hydrogen atmosphere (without nickel) consumes oxygenated volatiles to produce aromatics. At the highest nickel loading (1.5 wt %) in hydrogen, the yield of liquid hydrocarbons dropped from 6.2 to 1.5 C%, while the yield of methane increased from 0.9 to 22.6 wt %. Molybdenum increased the yield of liquid hydrocarbons during catalytic fast hydropyrolysis from 1.5 to 7.9 C% at 400 °C. The oligomerization of methane and hydrogenation of the resulting aromatics in a fixed bed reactor with NiMo-HZSM-5 in a hydrogen atmosphere showed that, at high temperature (400 °C), NiMo-HZSM-5 converted about 68% of the methane into larger paraffins on a carbon basis. Overall, the results of this work suggest a combined effect of nickel and molybdenum metals to produce sustainable liquid hydrocarbons from hydropyrolysis. With molybdenum, the liquid yields reported in this work correspond to an overall production of about 15 gal of alkanes per ton of biomass.