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Preparation and Operating Conditions for Cobalt Cerium Oxide Catalysts Used in the Conversion of Synthesis Gas into Light Olefins

A.A. Mirzaei^a,*, M. Galavy^a, A. Beigbabaei^a and V. Eslamimanesh^b

^aDepartment of Chemistry, Faculty of Science, University of Sistan and Baluchestan, Zahedan 98135-674, Iran
^bIran Polymer and Petrochemical Institute, P.O. Box 14965/115, Tehran, Iran

Cobalt cerium oxides, prepared using a co-precipitation procedure, were studied as catalysts for the conversion of synthesis gas to light olefins (C₂-C₄). Specifically, we studied the effect of a range of preparation variables, including the molar ratio of the [Co]/[Ce] of the precipitation solution, ageing time and calcination temperature. In addition, the effects of supports and promoters on the catalysts’ activity and selectivity and a range of reaction temperatures using synthesis gas with different H₂/CO molar feed ratios were investigated. The catalyst containing a molar ratio of 80% Co and 20% Ce, aged for 2 h, supported with 15 wt% SiO₂ without any promoter, at an operating temperature of 450 ºC and an H₂/CO feed ratio of 2/1 (GHSV = 4500 h^-1), performed optimally for the conversion of synthesis gas to light olefins. The characterization of both the precursors and the calcined catalysts by powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller specific surface area measurements and thermal analysis methods, including TGA and DSC, show that all the preparation variables influenced the catalyst precursor structure.

Keywords: Co-precipitation, Ageing time, Fischer-Tropsch synthesis, Light olefins, Cobalt cerium catalyst, Characterization