Hydrogen production by sorption-enhanced steam reforming of acetic acid over Ni/CexZr1−xO2-CaO catalysts

Abstract

The production of high purity hydrogen via the sorption-enhanced steam reforming of acetic acid, a model compound of bio-oil, was investigated in this work. A bi-functional catalyst with stable catalytic activity and CO2-capture ability, Ni/CexZr1−xO2-CaO, was prepared by a sol–gel method and characterized in details by BET, XRD, TPR and SEM-EDX analytic techniques. The characterization of these materials showed that the catalysts were mainly composed of Ni, CexZr1−xO2 and CaO. As CaO loading increased, a new species, CaZrO3, with a perovskite structure was formed. The presence of CaZrO3 in the catalysts acted as a barrier to CaO grain growth at high temperatures and thus improved the CO2-capture stability. These catalysts exhibited good CO2 sorption capacity in 15 consecutive carbonation–calcination cycles, even at a high calcination temperature of 900 °C. Particularly, in case of the Ni/CZC-2.5 catalyst, 98% high purity H2 could be obtained during the prebreakthrough stage when the catalysts were tested in the SESR of acetic acid at 550 °C with an S/C ratio of 4. In addition, high hydrogen purity was maintained over 15 cyclic reaction-calcination operations, which was mainly attributed to the uniform distribution of Ni, CaO, CexZr1−xO2 and CaZrO3 in the catalysts. These results indicated the great potential of the SESR technique for hydrogen production from bio-oil.