Supported molybdena catalysts: Characterization of oxidized,reduced, and sulfided MoO3 prepared by an adsorption method |
| |
Authors: | Kohichi Segawa Tomotsune Soeya Du Soung Kim |
| |
Institution: | 1. Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, 102, Chiyoda-ku, Tokyo, Japan 2. Zettlemoyer Center for Surface Studies, Lehigh University, 18015, Bethlehem, Pennsylvania, USA
|
| |
Abstract: | Highly dispersed molybdena-titania catalyst can be prepared by an equilibrium adsorption method. In this method, molybdate
anions adsorb onto the positively charged titania surfaces via electrostatic attraction by controlling the pH of the impregnating
solution and they increase as an inverse function of the pH. 95Mo-NMR and UV spectroscopic studies of impregnating solution show that the polymeric species like Mo7O24
6-ions are adsorbed on titania in the acidic impregnating solution. XRD, Raman, and XPS data of the calcined samples show that
mono-layer coverage of molybdenum oxide over-layer possesses a highly distorted MoO6 group with a molecular geometry resembling the distorted square pyramid.
The catalytic oxidation of methanol over the surface molybdate species on titania possesses higher turnover numbers and higher
selectivities of partial oxidation products than the catalysts supported on alumina, silica, zirconia, or magnesia. Changes
of the surface properties either after reduction and sulfiding treatment over monolayer catalyst on titania have also been
investigated. The NO chemisorption and XPS studies show that two types of active sites appeared after reduction treatment:
one site is active for hydrogenation of 1,3-butadiene and the other site is active for metathesis of propene. A higher degree
coordinative unsaturations of MO is required for hydrogenation than metathesis. After sulfiding treatments of the catalyst,
hydrogenation of 1,3-butadiene also requires triply coordinative unsaturation, and hydrogenolysis of thiophene requires the
ensemble of doubly or triply coordinative unsaturations. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|