Effects of particle size, pretreatment, and catalysis on microwave pyrolysis of corn stover

The effects of particle size, pretreatment (acid pretreatment and steam explosion), and catalysis of aluminum oxide (Al2O3) on heating efficiency, product distribution, and gaseous product composition of corn stover pyrolysis using microwave heating were investigated in this study. Both maximum temperature and heating rate increased with decreasing particle size of corn stover. The heating efficiency was also improved over Al2O3 and by applying both pretreatment methods. Adding 10-mesh Al2O3 increased the gaseous yield but decreased the liquid yield. However, this phenomenon did not exist when 50-mesh Al2O3 was used. This may be attributable to that small catalyst particles are encapsulated by other catalyst and biomass particles to reduce their catalytic activity. Applying acid pretreatment substantially decreased the gaseous yield but increased the liquid yield, whereas the effect of steam explosion was not significant. Approximately half of CO was produced during the first 5 min of experiment, but the yields of H2, CH4, and CO2 produced from microwave pyrolysis of corn stover pretreated by acid were relatively small or even none during this initial period. The reaction kinetics for microwave pyrolysis of corn stover was analyzed by using the first- and second-order reaction models.