High purity hydrogen production from sorption enhanced chemical looping glycerol reforming: Application of NiO-based oxygen transfer materials and potassium promoted Li2ZrO3 as CO2 sorbent

Abstract

Ni based oxygen transfer materials (OTMs) and Li2ZrO3 based sorbent have been synthesized for their potential use in a sorption enhanced chemical looping steam reforming (SE-CLSR) process. Ni based OTMs were firstly tested under chemical looping steam reforming (CLSR) process and the gaseous products with temperature variety during this process were measured and analyzed. Experimental results indicated that both of the OTMs exhibited good activities and stability during multiple glycerol reduction-air oxidation cycles towards H2 production. The desired maximum hydrogen selectivities of 87.9% and 84.7% were obtained for NiO/NiAl2O4 and NiO/ZrO2 for steam to carbon ratio of 3 at 550°C. The fuel feed step of reduction process could be divided into two periods with the OTMs possessing a dual function of oxygen carrier and catalyst. The decrease of conversions and selectivity for both OTMs was mainly due to the coke deposition, which reduced the catalytic effect in the reforming reaction as well as the oxygen transfer effect in the reduction reaction. Sorption enhanced chemical looping steam reforming (SE-CLSR) process for H2 production with in-situ CO2 removal was carried out with OTM/sorbent ratio of 1 and multi-cyclic reaction/regeneration processes under 550°C/850°C with a steam/carbon ratio of 3 was also achieved. H2 purity were both enhanced by the two OTMs and sorbent in SE-CLSR. Therefore, it is possible to utilize oxygen from NiO and steam to oxidize glycerol, while enhancing the water-gas-shift reaction by capturing CO2 at the same time.