Effects of Sn Promoter on the Ordered Mesoporous Co3O4-Al2O3 Mixed Metal Oxide for Fischer–Tropsch Synthesis Reaction

Abstract

The highly ordered mesoporous Co3O4-Al2O3 bimetal oxide, prepared by a nano-casting method, was modified with Sn promoter (denoted as Sn/m-CoAlOx) to enhance selectivity to liquid-hydrocarbons as well as to suppress CO2 formation formed by a water gas-shift (WGS) reaction activity during CO hydrogenation to hydrocarbons (Fischer–Tropsch Synthesis (FTS) reaction). Based on the surface properties of the Sn/m-CoAlOx in the range of 0.25–0.65 wt%Sn, the Sn promoter generally decreased CO conversion and increased C5+ selectivity through its non-selective blockages of the active metallic cobalt sites, which were responsible for more difficult reducibility of cobalt nanoparticles with an increase of Sn content as well. In addition to those contributions of Sn promoter, the decreased CO2 and CH4 selectivity was clearly observed on the optimal Sn(2)/m-CoAlOx with only small decrease of CO conversion with 79.1% from 81.5% for the reference m-CoAlOx. Those phenomena were mainly attributed to the suppressed WGS reaction activity as well as the decreased hydrogenation activity to form CH4 due to the suppressed H2 adsorption capacity on the less reduced surface Co sites on the Sn(2)/m-CoAlOx.