Catalytic gasification of wet municipal solid waste with HfO2 promoted Ni-CaO catalyst for H2-rich syngas production

Abstract

Catalytic gasification, coupled with in-situ CO2 capture over Ni-CaO catalyst, is considered to be an effective approach for H2-rich and tar-free syngas production. However, the poor stability of Ni-CaO based catalyst raises a question regarding its large scale application. In this study, HfO2 was used as a stabilizer and promoter for the Ni-CaO catalyst system. The stability of catalyst was evaluated through cyclic carbonation-calcination test with a thermogravimetric analyzer. The results showed that HfO2 incorporated catalysts performed better stability towards cyclic CO2 capture. The effect of different HfO2 additions in catalyst, catalyst to municipal solid waste (C/MSW) ratio, gasification temperature, and moisture content (MC) of MSW was investigated on syngas composition, H2 yield, dry gas yield (DGY) and product distribution (syngas, tar and char). The results indicated that H2 yield was improved from 212 mL/g (without catalyst) to 442 mL/g with Ni-CaO (NC) catalyst and further improved with the application of HfO2 promoted catalysts (Ni-CaO-HfO2). The catalyst with 20% HfO2 (NCH-20) exhibited maximum H2 yield of 597 mL/g. Moreover, a significant reduction in tar content from 8.79 wt% (without catalyst), 3.19 wt% (with Ni-CaO) to 2.81 wt% (with NCH-20) was also recorded with HfO2 promoted catalysts.