Dual-function materials for hydrogen production integrated with carbon dioxide capture and in situ conversion into syngas

Abstract

Sorption-enhanced reforming (SER) is a promising technology to produce high-purity H2 and efficient CO2 capture. However, the further application of the captured CO2 is still limited. In this work, we evaluated the sorption-enhanced steam/autothermal reforming (SESR / SEATR) of bioethanol for H2 production and the conversion of the captured CO2 into syngas via reverse water-gas shift reaction (rWGS). The bimetallic NiM/Al-CaO-based catalysts (M = Co or Cu), were synthesized by the sol-gel method and characterized by different techniques. The Ni/Al- CaO and NiCo/Al-CaO catalysts showed similar capture capacities after 20 carbonation/regeneration cycles, 0.28 and 0.22 g CO2/g CaO, respectively, while the NiCu/Al- CaO catalyst had the poorest capture capacity, 0.18 g CO2/g CaO. This poorest capture capacity may be related to the formation of the Ca2CuO3 phase, which being a denser phase led to a reduction in the specific surface area of the material and a larger CaO crystallite size, decreasing the adsorption of CO2. These properties also significantly impacted the SESR process, since the NiCu/Al-CaO performed poorly with a H2 mole fraction on a dry and inert-free basis (𝑦̅ 𝐻2) of ~ 87%. During SESR, the Ni and NiCo catalysts presented 𝑦̅ 𝐻2 > 93%, and during SEATR 𝑦̅ 𝐻2 > 95% with a pre-breakthrough period of 14 min after 10 cycles in both processes. The NiCo/Al-CaO catalyst showed better performance in CO2 conversion and CO selectivity of 87 and 97%, respectively, during rWGS after 10 SEATR cycles. Furthermore, coke deposition in SER was lower when compared to conventional processes, and O2 injection during SEATR further contributed to coke reduction.