Improving the hydrothermal stability and hydrogen selectivity of Ni-Cu based catalysts for the aqueous-phase reforming of methanol

Abstract

Non-precious metal catalysts suitable for hydrogen production via aqueous phase reforming (APR) of methanol show important technical and commercial value in the development of distributed, small/micro-scale on-site hydrogen production systems. They still face the challenges of reduced activity and stability due to sintering and oxidation of active metal nanoparticles, change of the surface state and collapse of the pore structure of used supports under hydrothermal conditions. To solve these problems, a series of ZnO/Ni-xCu/Al2O3 (x = 0, 2, 4, 6, 8, 10) catalysts were prepared by a simple impregnation method in this work. The addition of Cu improved the reducibility of NiO, and promoted the formation of smaller and more dispersed metal particles on the surface of Al2O3, facilitating hydrogen production and hindering methane formation. Among them, the highest average hydrogen production rate (362.1 μmol‧min−1‧gcat−1) and the highest hydrogen selectivity (99%) were reached using ZnO/Ni-8Cu/Al2O3 catalyst, which were 1.6 times and 20.7% higher than those obtained on the mono-metallic ZnO/Ni/Al2O3 catalyst, respectively. On the other hand, the modification of Ni-8Cu/Al2O3 with ZnO prevented effectively the reaction of surface water with Al2O3 and inhibited the formation of boehmite phase, leading to dramatical improvement of its stability during APR of methanol with a prolonged lifetime (72 h) by 6 times. This new developed ZnO/Ni-xCu/Al2O3 catalysts offer great potential for the development of commercial catalysts to produce hydrogen from APR of methanol.