Highly selective oxidation of aromatic hydrocarbons (Styrene, Benzene and Toluene) with H2O2 over Ni, Ni-Cr and Ni-Ru modified MCM-41 catalysts

Abstract

Ni, Cr, Ru ions incorporated mono- and bimetallic MCM-41 catalysts were investigated in the selective oxidation of styrene, benzene and toluene to benzaldehyde, phenol and cresol, respectively, with diluted hydrogen peroxide between 293–343K. Two kinds of catalysts, dried as-synthesized samples without elimination of surfactants and calcined samples where surfactants were removed, have been tested. The fresh catalysts and used ones in the oxidation reaction after several cycles were intensively characterised by XRD, N 2 adsorption-desorption, SEM, TEM, FTIR and TGA. Under the same reaction conditions, Ni-Cr-MCM-41 catalyst is much more active compared with Ni and Ni-Ru-MCM-41 catalysts in oxidation of styrene. However, all these three catalysts showed relatively low activity in the oxidation of benzene. It is shown that the activity and selectivity of Ni-MCM-41 catalysts and the efficiency of H 2 O 2 depend on the presence of the second metal, amount of nickel, calcination conditions of the catalyst, temperature and time of reaction and utilization of acetonitrile as solvent. It reveals that only dried samples containing surfactants give a much higher activity in oxidation of styrene and toluene than calcined catalysts. A benefit effect of surfactant in the phase transfer of H 2 O 2 has been evidenced. Active species leaching is also studied.