On the Chemistry of Iron Oxide Supported on γ-Alumina and Silica Catalysts

Abstract

Catalysts of iron oxide on γ-alumina and silica which were prepared by an incipient wetness impregnation technique have been investigated in an effort to understand how the surface chemical properties are influenced by the nature of the supports. Surprisingly, this is the first study to compare in depth the influence of the supports on physicochemical parameters such as acidity, site nuclearity, and reducibility. In this study, surface characterisation techniques including N 2 physisorption at −196 °C, ammonia temperature-programmed desorption, inductively coupled plasma optical emission spectrometry, temperature-programmed reduction with hydrogen, CO-chemisorption, scanning electron microscopy, transmission electron microscopy, and NO adsorption by in situ Fourier transform infrared spectroscopy have been performed to understand the different surface reactions occurring over the two different supports. The aim of this study is to ascertain the primary differences between these two catalysts using several catalyst characterization techniques and correlate their chemical and structural differences to their catalytic activity in the conversion of 2-chlorophenol. The results disclose a higher density of acid sites, a smaller particle size of iron oxide, stabilization of Fe(II) aluminate after reduction on the alumina surface, and finally, the formation of isolated iron cations on the surface of alumina which are notably absent on the silica-supported catalyst.

Eco-friendly removal of hexavalent chromium from aqueous solution using natural clay mineral: activation and modification effects

“…Previous studies [41][42][43] have motioned the importance of the oxides of SiO 2 , Al 2 O 3 and Fe 2 O 3 particles in improving the tendency of adsorption. These oxides have reactive groups that interact with the adsorbate and thus increase the adsorption capacity [41].…”

Regeneración de convertidores catalíticos usados a partir de desechos de vehículos a gasolina

“…La señal de TPR a la temperatura de 322 ºC corresponde a la reducción de Fe2O3 → Fe3O4. A la temperatura de 499 ºC se tiene la reducción de Fe3O4→ FeO y, por último, la señal a la temperatura de 628 ºC corresponde a la reducción de FeO + H2 → Feº + H2O [16], [17]. Por otra parte, se ha demostrado que el hierro con el fosfato forma especies de FePO4 y se reduce a Fe2P2O7 a una temperatura similar [18].…”

Magnetic Nanoparticles based on Natural Silica as a Methyl Ester Forming Acid Catalyst

“…The 0.0212 mmol/g difference in the acidity of the MSNP/SO 4 2before and after was significantly low, hence the acidity is relatively constant and the MSNP/SO 4 2catalyst could be reused. The acid site on the MSNP/SO 4 2catalyst resulted from sulfuric and also from silica and iron [15].…”