Improvement of biomass char-CO2 gasification reactivity using microwave irradiation and natural catalyst

• We study microwave-induced gasification of EFB ash-loaded biomass char with CO2.
• Synergistic effect of microwave and catalyst resulted in CO2 conversion of 93%.
• Gasification of pristine char using conventional heating gives CO2 conversion of 58%.
• Ea of 74 and 247 kJ/mol were obtained for microwave and conventional CO2 gasification.

In char-CO2 gasification, the highly endothermic nature of the Boudouard reaction (CO2 (g) + C (s) ↔ 2CO (g)) dictates use of very high temperatures to shift the equilibrium towards CO production. In this study, such high temperature (750–900 °C) was provided by microwave irradiation. A microwave heating system was developed to perform the gasification tests by passing CO2 through a packed bed of oil palm shell (OPS) char. In order to speed up the microwave-induced CO2 gasification, ash of palm empty fruit bunch (EFB) was used as natural catalyst (rich in potassium) and incorporated into the skeleton of the OPS char. The synergistic effect of microwave and catalyst concluded to very encouraging results, where a CO2 conversion of 93% was achieved at 900 °C, within 60 min microwave gasification. In comparison, CO2 conversion in thermal gasification (conventional heating) of pristine OPS char was only 58% under the same operating condition.