Iron incorporated heterogeneous catalyst from rice husk ash

Silica supported iron catalyst was prepared from rice husk ash (RHA) via the sol–gel technique using an aqueous solution of iron(III) salt in 3.0 M HNO3. The sample was dried at 110 °C and labeled as RHA-Fe. A sample of RHA-Fe was calcined at 700 °C for 5 h and labeled as RHA-Fe700. X-ray diffraction spectrogram showed that both RHA-Fe and RHA-Fe700 were amorphous. The SEM/EDX results showed that the metal was present as agglomerates and the Fe ions were not homogeneously distributed in RHA-Fe but RHA-Fe700 was shown to be homogeneous. The specific surface areas for RHA-Fe and RHA-Fe700 were determined by BET nitrogen adsorption studies and found to be 87.4 and 55.8 m2 g−1, respectively. Both catalysts showed high activity in the reaction between toluene and benzyl chloride. The mono-substituted benzyltoluene was the major product and both catalysts yielded more than 92% of the product. The GC showed that both the ortho- and para-substituted monoisomers were present in about equal quantities. The minor products consisting of 16 di-substituted isomers were also observed in the GC–MS spectra of both catalytic products. The catalyst was found to be reusable without loss of activity and with no leaching of the metal.

Graphical abstractThe catalyst, RHA-Fe and RHA-Fe700 was prepared from rice husk ash silica. It was used in the benzylation of toluene as shown in the figure. The mono-substituted product was found to be the major yield with more 92%. The mono-substituted product was found to be a mixture of ortho- and para-isomers. These isomers were successfully separated in the GC and the distribution of these isomers was found to be in a 1:1 ratio.Figure optionsDownload full-size imageDownload as PowerPoint slide