Combustion synthesized materials as catalysts for liquid-phase oxidation

With combustion synthesis it is possible to achieve catalytic active binary oxides of chromium, iron, cobalt, nickel and copper within a few seconds. The catalytic activity of combustion synthesized oxides was compared with commercially available spinel oxides and materials obtained by thermal nitrate decomposition in the selective liquid-phase oxidation of benzyl alcohol to benzaldehyde with a stoichiometric amount of tert-butyl hydroperoxide as the oxidant. The combustion synthesized materials revealed both higher reactivity and higher stability compared to those oxides available from high temperature ceramic processes or thermal nitrate decomposition. Crystallite sizes, microstrains, and phase compositions have been analyzed by X-ray powder diffractometry as important parameters for the catalytic activity. By applying combustion synthesis, it is possible to obtain several different low density oxides with smaller crystallites and higher values for microstrains compared to other methods of preparation. Thus, providing an explanation for the improved catalytic performance of those materials. (C) 2011 Elsevier B.V. All rights reserved.