Characterization and catalytic performance of hydrotalcite-derived Ni-Cu alloy nanoparticles catalysts for steam reforming of 1-methylnaphthalene

Supported Ni-Cu alloy nanoparticles prepared from Ni-Cu-Mg-Al hydrotalcite-like compounds (HTlcs) with Cu/Ni = 0.25 have been shown to be an active catalyst for the steam reforming of tar derived from the biomass pyrolysis. In the present work, Ni-Cu alloy catalysts with wider compositions of Cu/Ni were characterized and their performances were evaluated in the steam reforming of 1-methylnaphthalene (1-MN), which has lower reactivity than the biomass tar, in order to make the effect of Cu/Ni much clearer. The characterizations with XRD, STEM-EDX, H2 chemisorption, and FIIR of CO adsorption suggest that the obtained Ni-Cu alloy nanoparticles had uniform composition in the range of Cu/Ni = 0.1–1; the particle size was decreased with the increase of Cu/Ni ratio (ca. 5–7 nm), and Cu tended to be enriched on the particle surface. The HTlcs-derived Ni-Cu alloy catalysts showed a volcano-type dependence of activity on the alloy composition; the highest reforming activity and lower yields of byproducts including benzene, naphthalene, and coke were obtained at Cu/Ni = 0.25. The kinetic study indicates that 1-MN was strongly adsorbed on both the Ni and Ni-Cu catalysts; in contrast, the adsorption of steam was promoted by the alloying of Ni with Cu even in the presence of strongly adsorbed 1-MN. The property of stronger adsorption of steam can be connected to higher reforming activity and lower coke deposition through the dissociative adsorption of steam to supply more adsorbed oxygen species, which enhance the gasification of carbonaceous species.