In comparison with air calcined 12%Co/silica and 0.5%Pt-12%Co/silica catalysts, uncalcined catalysts - containing cobalt nitrate - and especially those that incorporated reduction promoters (Re, Pt, Ru, and Ag) outperformed their calcined counterparts both in terms of CO conversion on a per gram catalyst basis, and in terms of selectivity. For example direct reduction of uncalcined 0.477%Re-12%Co/silica exhibited conversions that were 3.7 times that of reduced air-calcined 12%Co/silica, and 1.64 times higher than reduced air-calcined 0.5%Pt-12%Co/silica. Temperature programmed reduction (TPR) and TPR-XANES experiments indicate that interactions between CoO, produced from direct reduction of cobalt nitrate, and silica support were stronger in comparison to those between CoO, produced from reduction of air calcined Co3O4 particles, and silica. TPR-EXAFS results confirmed that direct reduction of cobalt nitrate resulted in Co particles with significantly lower Co-Co metal coordination numbers as compared to Co metal particles formed from reduction of Co3O4 particles on air calcined catalysts. These smaller Co metal particles were formed from smaller CoO particles, formed during reduction, which exhibited stronger surface interactions with the silica support. At the same space velocity of 6, methane selectivity was just 6.8% for hydrogen-activated 0.477%Re-12%Co/silica and 8.0% and 0.5%Pt-12Co/silica uncalcined catalysts, while higher values of 11.1% and 9.6% were observed for hydrogen-activated air calcined 12%Co/silica and 0.5%Pt-12%Co/silica catalysts.

Fischer-Tropsch synthesis: Improved conversion and selectivity with Co/silica by foregoing calcination and utilizing reduction promoters

255th National Meeting (2018)

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