Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous alkaline earth metal-promoted nickel-alumina xerogel catalysts

Abstract

A series of mesoporous alkaline earth metal-promoted nickel-alumina xerogel (M/NA, M=Mg, Ca, Sr, and Ba) catalysts were prepared by a single-step epoxide-driven sol–gel method and a subsequent incipient wetness impregnation method. They were applied to the hydrogen production by steam reforming of liquefied natural gas (LNG). For reference, a nickel-alumina xerogel catalyst without promoter (NA) was prepared by a single-step epoxide-driven sol–gel method. The catalysts were characterized by N2 adsorption–desorption, ICP-AES, XRD, TPR, H2-chemisorption, TEM, and CHNS analyses. Surface area and pore volume of M/NA catalysts were smaller than those of NA catalyst due to blockage of mesopores by promoters during the impregnation step. Both NA and M/NA catalysts exhibited X-ray diffraction patterns corresponding to nickel aluminate phase. In the TPR measurements, it was revealed that all the catalysts retained surface nickel aluminate phase, regardless of the identity of alkaline earth metal. Nickel surface area of reduced catalysts decreased in the order of Mg/NA>Sr/NA>Ca/NA>NA>Ba/NA. In the hydrogen production by steam reforming of LNG, the catalytic performance of NA and M/NA catalysts was well correlated with the nickel surface area of the catalysts; LNG conversion and hydrogen yield increased with increasing nickel surface area. Among the catalysts tested, Mg/NA catalyst with the highest nickel surface area showed the best catalytic performance. The amount of carbon deposition on the used M/NA catalysts was less than that on the used NA catalyst.