Confined Iron Nanoparticles on Mesoporous Ordered Silica for Fischer–Tropsch Synthesis

Abstract

Iron oxide particles were deposited in an ordered mesoporous material (SBA-15) with the aim of studying its behavior in the catalytic hydrogenation of CO (Fischer–Tropsch Synthesis). Bulk iron oxide, and iron supported on porous silica with different textural properties (Aerosil®-200) were used for comparison. The characterization of the materials showed that in the Fe@SBA-15 material, iron nanoparticles were confined inside the mesopores of the SBA-15 support (pore diameter ~ 8 nm), and Fe@Aerosil®-200 material also presented iron oxide nanoparticles highly dispersed on the material. In situ Synchrotron radiation XRD studies were performed in order to study the evolution of iron phases in the Fe@SBA-15 and the bulk iron oxide under hydrogen and hydrogen/carbon monoxide conditions. DFT calculations were performed on bare Fe(100) and a Fe16 cluster in CO activation and CxHy hydrogenation. Catalytic microactivity tests, performed at conversions of ~ 6–8%, showed important differences in the selectivity of the materials. Higher selectivity to methane and light hydrocarbons were observed in the supported catalysts (Fe@SBA-15 and Fe@Aerosil®-200) than in bulk Fe catalyst. Moreover, the supported catalysts showed selectivity to ethylene (Fe@SBA-15) and propylene (Fe@Aerosil®-200), products that were not observed in the bulk iron catalyst. On the other hand, bulk iron showed a major selectivity to higher hydrocarbons (C5–C9) and oxygenates.