Enhanced catalytic performance of Ni/alpha-Al2O3 catalyst modified with CaZrO3 nanoparticles in steam-methane reforming

Abstract

Ni/α-Al2O3 catalysts containing CaZrO3 nanoparticles as a promoter were prepared by sequential impregnation for H2 production from steam-methane reforming. The effects of different loadings of CaZrO3 nanoparticles from 0 to 15 wt% on the catalytic performance of Ni/α-Al2O3 catalysts in steam-methane reforming were studied. The Ni/α-Al2O3 catalysts containing 15 wt% CaZrO3 nanoparticles provided the highest H2 yield due to facilitative steps of enormous steam adsorption-dissociation at the sites of oxygen vacancies on the surface of CaZrO3 nanoparticles. The existence of facilitative steps created additional H+ and OH− enhancing both H2 yield and the gasification of deposited carbon, respectively. The tests of steam-methane reforming at low S/C ratio of 1/3 for 97 h revealed that the catalytic performance of CaZrO3-modified Ni/α-Al2O3 catalysts was higher than that of the unmodified Ni/α-Al2O3 catalyst. Interestingly, at high S/C ratio of 3 excessive steam adsorption at the oxygen vacancies on CaZrO3 nanoparticles resulted in highly competitive adsorption between steam and methane decreasing CH4 dissociation. The results suggested that in the steam-methane reforming, optimum S/C ratios for the CaZrO3-modified Ni/α-Al2O3 catalysts were relatively lower than those for the unmodified Ni/α-Al2O3 catalyst due to excellent steam adsorption-dissociation capability for CaZrO3 nanoparticles.