Silicon microreactors have been coated with mixed-metal Fe-Co Fischer-Tropsch catalysts in alumina sol-gel for conversion of syngas (CO + H 2 ) to higher alkanes. Characterization of the nanocatalysts using scanning electron microscopy, energy-dispersive X-ray, atomic force microscopy, and Brunauer-Emmett-Teller surface area measurements, packaging, and the reaction results from a mass spectrometer at controlled temperatures (200-260 °C) and pressure (1 atm) with varying H 2 :CO ratios from 1:1 to 10:1 are described. The catalyst does not adequately infiltrate the 5-µm channels; it coats nicely the 25-µm channels. The initial results are consistent with a lower conversion of CO (∼32%) in a 5-µm-channel reactor and a higher conversion (∼52%) in a 25-µm-channel reactor. The selectivity to propane (∼80%) is not affected by the width of the microchannels. The activity of the sol-gel-encapsulated catalyst before and after the reactions is estimated from its magnetic properties using a vibrating sample magnetometer.

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.