Nano size H beta zeolite as an effective support for Ni and Ni-Cu for COx free hydrogen production by catalytic decomposition of methane

摘要

Mono and bimetallic catalysts of Ni and Cu on H beta 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 H beta zeolite particles (nano-H beta), the Ni and Cu were only present in the form of a Ni-Cu alloy, whereas when commercial H beta zeolite (H beta) was used; segregated Cu degrees and Ni degrees species were also observed. Addition of Cu was found to dramatically improve the H-2 yield by the formation of surface Ni-Cu alloys. The particle size of the H beta zeolite has a pronounced effect on the Ni and Ni-Cu dispersion, and consequently on the methane decomposition activity. The surface area of Ni-Cu on the nano-H beta surface was estimated by a combination of H-2 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 H-2 formation. Consistent with this finding, Ni-Cuano-H beta was the most active of the catalysts tested. The physicochemical characteristics of the commercial and nano-H beta supported Ni and/or Ni-Cu catalysts are rationalized by TEM, H-2-TPR, XPS and Raman spectroscopy in conjunction with H-2 production rates. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.