Hydrogen production by steam reforming of simulated liquefied natural gas (LNG) over nickel catalyst supported on mesoporous phosphorus-modified alumina xerogel

A series of nickel catalysts supported on mesoporous phosphorus-modified alumina xerogel (Ni/XPA, X = P/Al molar ratio) were prepared by an epoxide-driven sol―gel method and a subsequent incipient impregnation method, and they were applied to the hydrogen production by steam reforming of simulated liquefied natural gas (LNG). All the calcined phosphorus-modified alumina xerogel supports (XPA, X = P/Al molar ratio) retained a mesoporous structure with amorphous crystalline phase. The amount of penta-coordinated aluminum species increased with increasing X (P/Al molar ratio) of XPA supports. Although the calcined Ni/XPA catalysts retained both nickel oxide phase and nickel aluminate phase, relative distribution of nickel species of the catalysts was different depending on X (P/Al molar ratio). Among the catalysts, Ni/0.05PA catalyst showed the highest binding energy of nickel species. Crystallite size of metallic nickel increased with increasing X (P/Al molar ratio) in the reduced Ni/XPA catalysts. However, Ni/0.05PA catalyst showed the largest amount of strong hydrogen-binding sites and exhibited the largest amount of adsorbed methane in the H2-TPD and CH4-TPD measurements, respectively. Catalytic performance in the steam reforming of LNG over Ni/XPA catalysts showed a volcano-shaped trend with respect to X (P/Al molar ratio). This result was well correlated with the amount of adsorbed methane calculated from CH4-TPD measurements. Among the catalysts tested, Ni/0.05PA catalyst with the highest affinity toward methane showed the best catalytic performance in hydrogen production by steam reforming of LNG.