Activity and stability performance of multifunctional catalyst (Ni/CaO and Ni/Ca12Al14O33CaO) for bio-hydrogen production from sorption enhanced biogas steam reforming

•Modification of CaO by adding Ni2+ and Al3+ for improved CO2 capture.•Bio-hydrogen production by sorption enhanced biogas steam reforming.•Ni/Ca12Al14O33CaO as multifunctional catalyst.•Best synthesis sequence by simultaneous adding of Ni2+ and Al3+ on CaO.•Multiple cycle operations are tested for both CO2 capture and H2 production.

Modified sorbents (NiOCaO and Ca12Al14O33CaO) were synthesized by hydration followed by wet mixing (HW) and tested in terms of their CO2 sorption/desorption performance over multiple cycles. The results indicated the sorption capacities for Ni–CaO-HW and Al–CaO-HW decreased by only 3.8% and 6.4%, respectively, over 10 cycles. Various sequences of Ni2+ loading onto modified CaO were investigated. The results indicated Ni–Al–CaO-HW to be the best performing exhibiting a pre-breakthrough time 30 min longer than the other samples. However, the H2 purity and CH4 conversion did not differ significantly amongst the various sorbents (approx. 94% purity H2 and approx. 90% CH4 conversion pre-breakthrough). The stability of the Ni–Al–CaO-HW was also investigated and the results indicated that the pre-breakthrough CH4 conversion could be maintained at steady values for five cycles. However, the post-breakthrough CH4 conversion decreases slightly over five cycles. A plausible explanation is that the formation of CaCO3 results in the blockage of pores and active sites, which is supported by XPS results.