Influence of Biochar on the Steam Reforming of Biomass Volatiles: Effects of Activation Temperature and Atmosphere

This study aims to investigate the effects of biochar activation temperature and atmosphere on the steam reforming of biomass volatiles. The biochar produced from biomass pyrolysis was activated under an atmosphere of 100% N2, 100% CO2, or 5% O2/95% N2, with an activation temperature of 500, 600, 700, or 800 °C, respectively. The volatile reforming in the presence and absence of biochar and the self-gasification of biochars were conducted on a two-stage fixed-bed reaction system. Compared with N2 and CO2 activation, the biochar undergoing 5% O2/95% N2 activation (O2 activation) at 800 °C showed a porous structure but relatively lower self-gasification reactivity. A positive interaction between volatiles and biochar was also obtained for the biochar activated under O2 atmosphere as more active sites might be formed during the O2 activation. Furthermore, the O2 activation under lower temperature was found to be better for both the biochar gasification reactivity and the volatile reforming with biochar. A strongest positive interaction between volatiles and biochar was achieved at an activation temperature of 600 °C. The physical pore structure of biochar was not deemed the direct factor for the char reactivity, as all the biochars already had a high Brunauer–Emmett–Teller surface area of ∼300 m2/g or more. It is believed that the chemical structure of biochar, especially the O-containing functional groups, played an important role in the volatile reforming in the presence of biochar.