Comparative study on carbon dioxide-cofed catalytic pyrolysis of grass and woody biomass.

This study investigated the mechanistic functions of CO2 on the pyrolysis of two different biomasses to elucidate the effect of CO2 on syngas formations during pyrolysis. To this end, CO2-assisted pyrolysis of cellulosic biomass (barnyard grass, Echinochloa) and lignin-rich woody biomass (retinispora, Chamaecyparis obtusa) were compared. The confirmed mechanistic effectiveness of CO2 on pyrolysis of biomass was gas phase reactions between CO2 and volatile matters from biomass pyrolysis. Lignin-rich biomass had more CO2 susceptibility, resulting in more enhanced CO formation via the gas phase reactions. To expedite the slow reaction rate of the gas phase reactions during biomass pyrolysis, earth-abundant catalysts (Co/SiO2 and Ni/SiO2) were employed for pyrolysis of two biomass substrates. With Co and Ni catalysts, the syngas formations were 2 and 3 times higher comparing to the pyrolysis of without catalyst. The cumulative formations of syngas from lignin-rich biomass was nearly doubled than that from cellulosic biomass.