Polymer-assisted Synthesis Of Nanoparticle Cobalt Based Catalysts For Low-temperature Carbon Monoxide Oxidation

Cobalt based catalysts were prepared by a polymer-assisted chemical solution route using ethylenediaminetetraacetic acid (EDTA) and polyethyleneimine (PEI) as binding ligands for the first time. The effect of preparation process, reaction condition, binary and ternary metal component on the catalytic activity were investigated. The physicochemical properties of the catalysts were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron (XPS), Scanning electron microscopy (SEM), Transmission electron microscope (TEM) and H2/CO temperature programmed reduction (H2/CO-TPR). The major conclusions are summarized as follows.(1) Preparation of CO3O4 and binary metal catalysts for CO oxidation. Co3O4 and binary metal catalysts were prepared by a polymer-assisted chemical solution route using EDTA and PEI as binding ligands. The CO catalytic performance was measured using a fixed bed reactor. The optimum conditions for the preparation of Co3O4 were listed as follows:PEI of 2 g, EDTA of 2 g, calcination temperature of 500℃, PEI molecular weight of 10000 and cobalt nitrate molar weight of 6 mmol. CeO2 could facilitate the dispersion of Co3O4, resulting in the Co3O4 with small crystallite size. Moreover, it could increase the content of higher oxidation state cobalt and the specific surface area. Therefore, the Co3O4/CeO2 catalysts exhibit excellent activity toward CO oxidation. The optimal Ce/Co mole ratio was found to be 1, which achieved a 100% oxidation of CO at 30℃ with a CO concentration of 100 ppm.The deactivated catalyst could be regenerated via the heat treatment in the percent of oxygen. The carbon dioxide adsorption on the surface of the catalyst is the main reason for the deactivation of the catalysts, the secondary reason is CO adsorption on the activated oxygen vacancy.(2) Preparation of ternary metal catalysts for CO oxidation based on the polymer-assisted chemical solution route. The effect of third metal Fe, Mg, Cu, Mn and Au on Co-Ce system for the CO oxidation was investigated. Addition of Fe, Mg, Cu and Mn as the third metal component failed to improve the catalytic activity of the catalyst. The catalyst using Au as the third metal component synthesized from one-step method had poor catalytic performance due to the sintered Au and oxidation of Au to Au3+ with high valence.The ternary metal catalyst synthesized from two-step method performed better than the Co3O4/CeO2 catalyst. The catalyst with Au content of 1%could achieve a complete oxidation of CO at 30℃ for 700 mins. In addition, the catalyst with Au content of 3% could convert all CO for 1200 mins, while the catalyst with Au content of 5% could reach a CO conversion of 100% for more than 1400 mins.