Thermochemical conversion of biomass to fuels and chemicals: a review of catalysts, catalyst stability, and reaction mechanisms

Woody biomass can be converted into a synthesis gas, a mixture of H2, CO, and CO2, by gasification. Removal of refractory tars, produced during biomass gasification, requires highly active catalysts that can be applied in-situ during gasification or in secondary catalytic tar cracking reactors. Subsequently, the water-gas-shift (WGS) reaction adjusts the H2 to CO ratio, prior to the synthesis of the desired products (CH4 as renewable natural gas or RNG, alcohols, hydrocarbons, and olefins). Catalysts play a pivotal role in all processing steps, with recent advances in catalyst development discussed herein with an emphasis on catalyst stability, reaction mechanisms, and structure-activity relationships. The economic viability of biomass conversion to fuels and chemicals is also reviewed and shown to be dependent on end-product, location, and government incentives.