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C−H Activation of Methane to Formaldehyde on Ce 1− x Zr x O 2 Thin Films: A Step to Bridge the Material Gap
Author(s) -
Dubey Anjani,
Kolekar Sadhu K.,
Gopinath Chinnakonda S.
Publication year - 2016
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201600670
Subject(s) - formaldehyde , methane , thin film , diffusion , chemistry , molecular beam , activation energy , oxygen , materials science , analytical chemistry (journal) , molecule , nanotechnology , organic chemistry , physics , thermodynamics
Abstract Ce 1− x Zr x O 2 (CZ) thin films were prepared by a combination of sol–gel and spin‐coating methods and were evaluated for the C−H activation of methane by using a molecular beam set‐up with the aim to bridge the material gap. The C−H activation of methane begins at 950 K, and a Ce‐rich CZ composition displays a high selectivity (4–12 %) to the partially oxidised product, formaldehyde. A 10–12 % selectivity towards HCHO with 1.6 % methane conversion was observed with methane‐rich CH 4 /O 2 reactant compositions at 1050 K. Short contact times, prevalent under molecular beam conditions, could be a possible reason for HCHO formation. Although combustion products were observed instantly upon shining the mixture of reactants on CZ surfaces, up to 20 s delay was observed before formaldehyde generation, which indicates that the oxygen vacancy migration contributes to the rate‐determining step and the diffusion‐controlled nature of the reaction. A burst in HCHO generation at the point of molecular beam opening, after beam‐closed conditions, suggests that the diffusion of oxygen vacancies to the surface is the reason for HCHO formation. Kinetics results also indicate the necessity of reduction sites for HCHO generation.