Ultra-pure hydrogen from chemical looping preferential oxidation of CO over a Cu–O–Ce based dual function material

Abstract

Hydrogen from hydrocarbon reforming contains small amounts of CO, necessitating further purification for its use in fuel cell applications. In this work, a novel chemical looping preferential oxidation (CL-PROX) process is proposed for efficient hydrogen purification. Enabled by a Cu–O–Ce based dual function material (DFM), the process uniquely combines both catalytic CO preferential oxidation and in-situ immobilization. This results in near-complete CO conversion and < 20 ppm COx concentration with hydrogen recovery of 97 % in the purification step. Experimental characterizations indicate that CO is converted into formate and carbonate on the DFM, which can easily decompose to CO2 during the regeneration step. The interaction between copper and ceria species increased the reducibility of the DFM, as well as the CO activation and immobilization. Facile and reversible transformations between Cu2+/Ce4+ and Cu+/Ce3+ were observed throughout the reduction and re-oxidation stages. This work suggests an intensification strategy for selective hydrogen purification, and provides insights into the redox chemistry of Cu–O–Ce DFMs.