Surface Impregnation Combustion Method to Prepare Nanostructured Metallic Catalysts without Further Reduction: As-Burnt Co/SiO2 Catalysts for Fischer–Tropsch Synthesis

Abstract

A series of the as-burnt supported metallic catalysts (Co/SiO2) were prepared by a novel surface impregnation combustion method using cobalt nitrates (noted as M) and citric acid (noted as CA), and burnt in the argon atmosphere. H2 and CH4 which were derived from the decomposition of the CA, acted as the reducing agents for synthesizing metallic Co from Co2+ in the chelated compounds. The X-ray diffraction (XRD) patterns revealed that all the as-burnt catalysts with different M/CA molar ratios were converted into Co and CoO species supported on SiO2 (Q-50). The as-burnt catalyst C1.5, with M/CA = 1/1.5, was almost fully converted to metallic Co species and amorphous carbon supported on SiO2. With increase of the content of CA in the initial precursors, the reduction degree of the as-burnt catalysts which was measured by temperature-programmed reduction (TPR) and the dispersion of metallic cobalt increased gradually. The as-burnt catalysts were used directly in slurry-phase Fischer-Tropsch synthesis (FTS) ...