RHA-Al, RHA-Ga, RHA-In and RHA-Fe heterogeneous catalysts were prepared by modifying the surface of silica extracted from rice husk ash (RHA) with Al3+, Ga3+, In3+ and Fe3+ ions, respectively. The as-synthesized solid catalysts showed good textural and structural properties as it was confirmed by the physico-chemical techniques such as FT-IR, 29Si MAS NMR, solid-state NMR and ESR for metal nuclei, powder XRD, N2-adsorption, SEM-EDX, TEM and ICP-MS elemental analysis. The heterogeneous catalysts exhibited good activity for the benzylation and tert- butylation of benzene and some substituted...