One step-synthesis of highly dispersed iron species into silica for propylene epoxidation with dioxygen

• Hierarchical ferrosilicates were synthesized by a simple one-pot method.
• The degree of speciation of iron in the framework changes with iron loading.
• Ferrosilicate catalysts are active in propylene epoxidation with dioxygen as oxidant.
• Our experimental results have been complemented using DFT calculations.

Well dispersed iron catalysts were synthesized in silica (Fe0.0XSiO2) by a one-step synthesis procedure. These materials were tested in the propylene epoxidation reaction with gaseous O2. The influence of the iron metal loading on the iron incorporation and distribution in the support (both influenced by the synthetic procedure) were thoroughly studied (conversion, generation and selectivity). Electron Microscopy and UltraViolet–Visible (UV–VIS), Raman and Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy techniques were used to analyze the iron distribution in the catalysts and to probe its incorporation into the silica framework. In situ FTIR was also used to analyze the interaction between propylene and iron-based catalysts. Computational calculations considering a single-site iron catalyst incorporated into the silica structure show a possible interaction between O2 and the incorporated iron atom and the olefin bond and the acidic proton neighboring the iron species which favor the reaction between the two molecules near the iron atom.

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