A Mesoporous SiO₂/γ-Fe₂O₃/KI Heterogeneous Magnetic Catalyst for the Green Synthesis of Biodiesel

Abstract

A magnetic catalyst (sample MCat) consisting of KI supported on a mixture of silica and maghemite (γ-Fe 2 O 3 ) was prepared and used in the transesterification reaction for the synthesis of biodiesel. The energy dispersive X-ray spectrum of the catalyst showed signals due to Si, Fe, K, and I. Powder X-ray diffraction data revealed the amorphous nature of the SiO 2 and the duly impregnation of the support with KI. 57Fe Mössbauer spectroscopy and magnetization measurements confirmed the ferrimagnetic iron oxide in the catalyst to be maghemite. N 2 adsorption-desorption data indicated that the silica is mesoporous with a specific area of 352 m 2 g -1 , enabling the impregnation of 40 and 11 wt.% of KI and maghemite, respectively, according to the chemical composition obtained by the X-ray fluorescence measurements. The MCat was found to be efficient in the transesterification reaction in the macaúba and soybean oils. The MCat was easily removed from the reaction medium, with a hand magnet, and efficiently reused for more four consecutive reaction cycles. The good catalytic activity along with its magnetic behavior, high chemical stability and recyclability make the MCat a suitable material for the green synthesis of biodiesel.