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

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.We thank the MINECO, Generalitat Valenciana and FEDER (Projects CTQ2012-31762, CTQ2015-66080-R and PROMETEOII/2014/010) for financial support. A.B.M. and J.G.A. thank the Spanish Ministry of Economy and Competitiveness (MINECO) for their fellowships (RyC 2009-03913 and BES-2013-063678, respectively)