INTRAZEOLITE NONSTOICHIOMETRIC TUNGSTEN-OXIDES N[WO3-X]-NA56Y(0-LESS-THAN-N-LESS-THAN-OR-EQUAL-TO-32, 0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1)


OZIN G., PROKOPOWICZ R., ÖZKAR S.

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol.114, no.23, pp.8953-8963, 1992 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 114 Issue: 23
  • Publication Date: 1992
  • Doi Number: 10.1021/ja00049a028
  • Title of Journal : JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
  • Page Numbers: pp.8953-8963

Abstract

The photooxidation of alpha-cage encapsulated n[W(CO)6]-Na56Y, where 0 < n less-than-or-equal-to 16 and Na56Y denotes sodium zeolite Y, provides a mild, clean, and quantitative synthetic pathway to molecular dimension tungsten(VI) oxide moieties, encapsulated within the void structure of the zeolite Y host, according to the reaction stoichiometry n[W(CO)6]-Na56Y + 9/2nO2 --> hv n[WO3]-Na56Y + 6nCO2 Following photooxidation, half of the alpha-cage void volume in the Na56Y host is freed so that subsequent precursor (saturation level) impregnations/photooxidations can be carried out in a stepwise fashion, proceeding as n = 16, 24, 28, 30, ..., 32 per unit cell. Thermal vacuum treatment of these materials proceeds in two well-defined steps around 300 and 400-degrees-C to yield encapsulated n[WO3-x]-Na56Y materials having x = 0.5 and 1, respectively. This reduction process is reversible by heating in an O2 atmosphere at 300-degrees-C. The entire redox process can be summarized according to the reaction stoichiometry