Consecutive coproduction of H and syngas from waste polyolefins derived pyrolysis gas via chemical looping cracking-gasification.

Upcycling waste plastics into H and syngas offers a sustainable strategy for mitigating their accumulation and addressing the global issue of plastic pollution. The deposition of coke during thermocatalytic reforming processes poses a significant challenge for efficient conversion. Here we report the consecutive coproduction of high-concentration H (up to 80.5 vol%) and hydrocarbon-free syngas with tunable H/CO ratios of 1.1-4.8 via a stepwise chemical looping cracking-gasification (CLCG) process over equimolar NiFeAl catalyst. Optimal gas yields of 0.26 mol g and 0.52 mol g per redox cycle for H and syngas are obtained from the cracking and gasification reaction stages, respectively. The CLCG process is investigated at a reaction temperature range of 700-900 °C which significantly impacts the H/syngas coproduction due to the promoted catalyst reduction and segregation of Ni and Fe phases. Furthermore, quantitative analysis of the metal distribution in the reduced NiFeAl catalysts by energy-dispersive X-ray spectroscopy reveals that the reaction temperature is essential in tuning the catalyst structure and performance. This work demonstrates the viable coproduction of separate H and syngas streams via the CLCG process which is promising for the circular management of waste plastics.