Design of a new iron catalyst by mechanochemistry using rice husk as a green silica source

Biomass has become an alternative to replace petroleum derived materials. Several methodologies for its valorization have been investigated to obtain high value products in a more sustainable way. Rice husk (RH) is an agricultural waste that contains up to 20 wt% of silica. Microwave assisted extraction was employed to remove metal ions from rice husk to obtain a highly pure mesoporous silica. Biogenic silica (RH-Silica) was employed as a support to design a new iron oxide catalyst (Fe/RH-Silica) by an efficient mechanochemical process. Synthesized materials were characterized by different techniques including N₂ physisorption, XRD, TEM, SEM and DRIFT. Materials presented excellent properties and a high activity in organic reactions. Fe/RH-Silica catalyst was tested in the selective oxidation of styrene and the alkylation of toluene under microwave irradiation. High conversion and selectivity were achieved for the desire products.