Hydroxylation of Benzene over V-HMS Catalysts with the Addition of Fe as the Second Metal Component

Second metals (Fe, Al, Cu, Ni, Co, Mo, Cr) were incorporated into V-HMS catalyst by impregnation to enhance the catalytic activity for the hydroxylation of benzene with hydrogen peroxide as the oxidant. Among the studied second metals, Fe was found to be effective in improving the catalytic performance. Therefore, we synthesized a series of Fe(x)V(x)-HMS catalysts containing different amounts of Fe and V by the co-synthesis method. The catalysts were characterized by powder X-ray diffraction (XRD), N(2), physisorption, transmission electron microscopy (TEM), NH(3) temperature-programmed desorption (NH(3)-TPD), and H(2) temperature-programmed reduction (H(2)-TPR). The characterization results show that the mesoporous structure of HMS is maintained and the addition of Fe creates new acid sites and a stronger redox ability. Catalytic tests show that vanadium species are the active species and that the iron species promote the reaction. Under optimal reaction conditions, the Fe(0.04)V(0.06)-HMS catalyst gives the best catalytic performance with a highest phenol yield of 18.1% by comparison with 13.1% over the Fe-free catalyst Fe(0.00)V(0.06)-HMS. We propose a possible mechanism involving the Fe and V species for the hydroxylation of benzene with H(2)O(2) as the oxidant.