Bimetallic Ru-(Cr, Ni, or Cu) and La-(Co or Mn) incorporated MCM-41 molecular sieves as catalysts for oxidation of aromatic hydrocarbons

Bimetallic Ru-(Co, Nr, Cu) and La-(Co or Mn) modified-MCM-41 molecular sieves are prepared by direct synthesis using surfactant templating process and evaluated in liquid phase selective oxidation of styrene and benzene with hydrogen peroxide. The fresh and used bimetallic molecular sieves were characterized by various techniques such as X-ray diffraction (XRD), N-2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and infra-red (IR) spectroscopy. These materials have a typical MCM-41 structure. It is very interesting to note that bimetallic Ru or La-based MCM-41 catalysts have a very high conversion in hydroxylation of benzene to phenol, but a lower activity in oxidation of styrene to benzaldehyde, being contrary to the catalytic behavior of monometallic modified MCM-41 catalysts. It is shown that the activity and selectivity of bimetallic Ru, La-MCM-41 catalysts and the efficiency of H2O2 depend on the presence of the second metal, temperature and conditions of the reactions. The reaction mechanism is proposed on the basis of the observation of different reaction products. (C) 2003 Elsevier B.V. All rights reserved.