Maximizing paraffin to olefin ratio employing simulated nitrogen-rich syngas via Fischer-Tropsch process over Co3O4/SiO2 catalysts

Abstract

The optimization of cobalt oxide (Co3O4) loading on silica for the low-temperature Fischer-Tropsch (LTFT) synthesis process employing simulated nitrogen-rich syngas (50 vol%) to produce highly paraffinic biodiesel is studied. Four different amounts of Co3O4 varying from 15 to 36 wt% were loaded on silica in order to examine the catalytic performance of Co/SiO2 catalysts. The supported catalysts were characterized using XRF, nitrogen physisorption, XRD, TPR, DRIFT and SEM fixed with EDS analysis. The performances of the catalysts were examined in a single channel fixed bed reactor employing simulated nitrogen-rich syngas (CO:H2:N2 = 17:33:50 vol%). The reactor was operated at P = 20 bar, T = 237 °C and WHSV = 3.0 Nl/h.gcat. The active site concentration was maximized by (i) utilizing all the available surface area of the sphere's porous support, (ii) using ethanolic impregnation solution to hinder sintering of Co3O4 phases due to presence of ethoxyl groups, and (iii) connecting oxide crystallites to the neighbouring pores by increasing the active metal content. As a result, the production of heavy hydrocarbons per unit of time was maximized with 36 wt% cobalt loading on silica (CO conversion and C5+ selectivity were 87.65 and 81.78 mol%, respectively, and also paraffin: olefin ratio was 98:2).