Catalytic oxidation of vinyl chloride over Co–Ce composite oxides derived from ZIF-67 template: Effect of cerium incorporation

Abstract

Transition metal oxides are regarded as an economical and efficient catalytic alternate for catalytic oxidation of volatile organic compounds (VOCs) emissions. The morphological decoration and the incorporation of extrinsic metals were demonstrated to be effective strategies for achieving noticeable catalytic improvement. In this work, a novel Co–Ce composite oxides catalyst was obtained by the pyrolysis of ZIF-67 template with the impregnation of certain cerium cations (denoted as ZIF-CoCe). Compared with the reference Co–Ce composite oxides by the sol-gel (denoted as SG-CoCe) and physical mixing (denoted as MIX-CoCe) methods, ZIF-CoCe delivers significantly higher catalytic activity for vinyl chloride oxidation, which are demonstrated to be closely related with its superior redox capacity, more abundance of surface active Co3+ sites and adsorbed active oxygen species from oxygen vacancies. In addition, the unique cage-like morphological feature of the Co-based catalysts derived from ZIF-67 template plays a crucial function in kinetically facilitating the mass transfer of catalytic reaction and promoting the catalytic VC oxidation activity. With regard to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) analysis, enol and carboxylic acid species are identified to be the key organic intermediates during catalytic vinyl chloride oxidation.