Microreactors for Syngas Conversion to Higher Alkanes: Effect of Ruthenium on Silica-Supported Iron−Cobalt Nanocatalysts

Abstract

The effect of ruthenium (Ru, 0.4 wt %) as a promoter on silica-supported iron and cobalt nanocatalysts (∼3 wt % each) for syngas (H2 and CO) conversion to higher alkanes was studied in a silicon microreactor. Fe−Co/SiO2 catalysts with and without Ru were synthesized by a sol−gel methods. The high specific surface area (325 m2/g) from BET analysis can be attributed to the porous structure of silica supported by its SEM images. The FE-STEM image indicated that the catalyst particle size is <10 nm. The magnetic studies of Co catalysts using a vibrating sample magnetometer suggest that Ru does not influence the reduction of cobalt oxide to cobalt, the active form of Co catalysts in silica. The highest conversion of CO (∼78%) was observed with a Ru−Fe−Co/SiO2 catalyst at 220 °C, 1 atm, total flow rate of 0.4 sccm, and H2/CO ratio of 3:1 in microreactors containing 25 μm channels. The addition of Ru to the Fe−Co/SiO2 catalyst increased CO conversion by 16% but lowered selectivity to propane by 10%. The catalysts remained active after 25 h of reaction, although the magnetic properties indicated that ∼85% of metal nanoparticles formed non-ferromagnetic species.