Nano size Hβ zeolite as an effective support for Ni and Ni[sbnd]Cu for COx free hydrogen production by catalytic decomposition of methane

Abstract

Mono and bimetallic catalysts of Ni and Cu on Hβ zeolite supports were tested for the COx free hydrogen production by decomposition of methane. The effect of Cu addition and the support particle size were investigated. XRD analysis of the reduced samples demonstrated that for catalysts based on nano-sized Hβ zeolite particles (nano-Hβ), the Ni and Cu were only present in the form of a NiCu alloy, whereas when commercial Hβ zeolite (Hβ) was used; segregated Cu0 and Ni0 species were also observed. Addition of Cu was found to dramatically improve the H2 yield by the formation of surface NiCu alloys. The particle size of the Hβ zeolite has a pronounced effect on the Ni and NiCu dispersion, and consequently on the methane decomposition activity. The surface area of NiCu on the nano-Hβsurface was estimated by a combination of H2 pulse chemisorption and N2O titration methods. The Cu species in close proximity to Ni sites inhibited carbon deposition at the Ni sites, resulting in higher rates of H2 formation. Consistent with this finding, NiCu/nano-Hβ was the most active of the catalysts tested. The physicochemical characteristics of the commercial and nano-Hβ supported Ni and/or NiCu catalysts are rationalized by TEM, H2-TPR, XPS and Raman spectroscopy in conjunction with H2 production rates.