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

Abstract

Well dispersed iron catalysts were synthesized in silica (Fe 0.0X SiO 2 ) by a one-step synthesis procedure. These materials were tested in the propylene epoxidation reaction with gaseous O 2 . 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. Insitu FTIR was also used to analyze the interaction between propylene and iron-based catalysts. This is a previous version of the article published in Journal of Catalysis. 2016Catalysis. , 338: 154-167. doi:10.1016Catalysis. /j.jcat.2016 2 Computational calculations considering a single-site iron catalyst incorporated into the silica structure show a possible interaction between O 2 and the incorporated iron atom and the olefin bond and the acidic proton neighboring the iron species which favours the reaction between the two molecules near the iron atom.

A Sustainable Heterogeneous Iron Catalyst Fe/SBA‐15 towards Direct Arylation of Unactivated C(sp3)−H and C(sp2)−H Bonds with Arenes

“…Generally, low nuclearity species reduces at high temperature due to strong interaction with the support, while the reverse is likely for the high nuclearity species. The first reduction peak centered at 410 °C is attributed to two‐dimensional oligomeric FeO x species as there is no evidence for three dimensional Fe 2 O 3 crystallites in DRS‐UV and EPR results . It has been reported in the literature that reduction of single site iron takes place between 600 °C to 700 °C.…”

“…DRS‐UV spectrum of 8 wt %Fe/SBA‐15 (Supporting Information, Figure S5) showed a weak signal at 220 nm and a peak at 250 nm due to oxygen to Fe III charge transfer involving isolated Fe III in octahedral environment . Furthermore, an intense band at 330 nm and a shoulder at 470 nm at higher wavelength can be assigned to Fe III ‐clusters and amorphous FeO x oligomers, respectively, due to increase in the nuclearity of Fe III oxide ,,. The absence of peak beyond 500 nm undoubtedly indicates the absence of bulk iron oxide phase formation in the mesopores during the grafting process …”

Strengths, Weaknesses, Opportunities and Threats: Computational Studies of Mn- and Fe-Catalyzed Epoxidations

“…Despite this, a limited number of sources has explored other routes, such as the formation of an hydroperoxo-Fe(porphyrin) complexes in P45models [55][56][57][58][59], in non-porphyrinic Fe catalysts [60][61][62][63] and also on Mn catalysts [64][65][66][67]. Nevertheless, the activity of such hydroperoxo species towards epoxidation reactions has been questioned by Shaik and co-workers [68], at least in models of cytochrome P450.…”

Mechanism of Propylene Epoxidation via O2 with Co‐Oxidation of Aldehydes by Metalloporphyrins

“…But the result of direct epoxidation of propylene catalyzed by Fe x SiO 2 or Sb 2 O 3 –CuO–NaCl/SiO 2 without other auxiliaries is still unsatisfactory , . Base‐metal complex, like Manganese(III) or Nickel(II) complexes used as catalyst in the olefins epoxidation had been investigated by T. Yamada et al,, it revealed that the co‐reductant aldehyde was necessary and did have a significant influence on the catalytic performance.…”