A Ca-modified Ni/CeO2·Al2O3 bifunctional catalyst for two-stage steam reforming of biomass pyrolysis oil for hydrogen production

Abstract

Steam reforming of bio-oil is a promising technology for the industrial-scale conversion of biomass into hydrogen energy, in which the catalyst plays the crucial role. This study proposes a Ni-Ca-Al-Ce-O catalyst, prepared by CaO loading onto Ni/CeO₂·Al₂O₃, and tested in the two-stage adsorption-enhanced reforming of biomass pyrolysis oil for hydrogen production. The effects of carrier type and Ni loading on the physicochemical properties of the Ca modified Ni-based reforming catalyst and its reforming performance were investigated, and its reusability was tested finally. The results revealed that more Ni metal active sites are available on CeO₂·Al₂O₃ compared to biochar as carrier. However, side reactions such as ketonization were significantly promoted due to the metal oxides in red mud (RM), resulting in a large amount of methane as a by-product over the Ni/RM catalyst. When Ca additive introduced on the well selected Ni/CeO₂·Al₂O₃, the selectivity of hydrogen in the reforming gas was enhanced. Meanwhile, more spinel NiAl₂O₄ was formed due to the interaction between NiO and Al₂O₃, which enhanced the stability and activity of the Ni-Ca-Al-Ce-O catalyst. With a Ca/Al ratio of 1:1, Ni was more uniformly dispersed, and the yield and selectivity of hydrogen reached 73.35 % and 76.90 %. In the reusability tests, the yield of hydrogen remained above 60 % after six runs, which was superior to that of similar reforming catalysts, suggesting that the proposed Ni-Ca-Al-Ce-O catalyst is reliable in terms of reusability.