Influence of Synthesis Conditions on the Physicochemical Properties and Catalytic Activity of Fe/Cr-Pillared Bentonites

Abstract

The synthesis of Fe/Cr-pillared bentonites starting from a 2% clay suspension and also from dry clay using ultrasound treatment for both the aging and the intercalation steps of the pillaring solution considerably reduces the time and the amount of water required compared with the conventional synthesis method. The catalysts were characterized using scanning electron microscopy with an energy dispersive system (SEM-EDS), powder X-ray diffraction (XRD), N2and CO2-adsorption/desorption, electron paramagnetic resonance (EPR), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis and the catalytic activity of selected samples was evaluated for the phenol oxidation reaction. The results of XRD analysis showed that delaminated Fe/Cr-pillared bentonite with d001value 68 Å was observed after intercalation a direct mixture of the pillaring solution and dry clay. The adsorption-desorption isotherm analysis showed that the samples synthesized with the proposed methodology in intercalation stage have similar textural properties and these properties do not change remarkably with synthesis conditions. In addition, the characterisation studies showed that the physicochemical properties of samples synthesized by ultrasound were comparable to those of sample synthesized by conventional method in this study. The sample synthesized by conventional method show 50% phenol conversion. This value was higher than those of samples synthesized by the ultrasound.