Effect of N_2O-mediated calcination on nickel species and the catalytic activity of nickel catalysts supported on γ-Al_2O_3 in the steam reforming of glycerol

摘要

The steam reforming of glycerol over supported nickel catalysts is a promising and cost-effective method for producing hydrogen. The activity of nickel catalysts supported on γ-Al_2O_3 is low, primarily due to the formation of inactive nickel species during high temperature calcination in air. In order to address this problem, a Ni/γ-Al_2O_3 catalyst was prepared by calcination at 700 ℃ in a nitrous oxide (N_2O) environment. The N_2O calcined catalyst showed an enhanced activity for the steam reforming of glycerol. A variety of characterization techniques (XRD, TPR, XPS and H_2 Chemisorption) confirmed that the high temperature N_2O calcination resulted in a significant decrease in the levels of nickel aluminate. The N_2O calcination also led to an enhancement in the amount of NiO as well as nickel ions present on the surface of the catalyst. Interestingly, compared to an air calcined catalyst, the N_2O calcined catalyst contained larger nickel particles after reduction but the N_2O calcined catalyst had a much larger nickel surface area and dispersion, which resulted in higher glycerol conversion and hydrogen yield.