COMPLEX METAL HALIDE OXIDES (2) - LAYERED COMPLEX METAL CHLORIDE OXIDES HAVING THE X1X2 STRUCTURE AS CATALYSTS FOR THE OXIDATIVE DEHYDROGENATION OF ETHANE

SrBi3O4Cl3 with the X1X2 structure, in which metal-oxygen sheets were separated by single chlorine layers and double chlorine layers alterna tely, has been prepared and tested as a catalyst for the oxidative deh ydrogenation of ethane. SrBi3O4Cl3 crystallized in space-group I4/mmm with lattice parameters of a=3.9370(1), c=27.0177(7) Angstrom. The str ucture was refined by a Rietveld analysis, which showed that between t wo Bi(1) and Bi(2) sites, the former being of Bi in the metal-oxygen s heet faced the single chlorine sheet and the later faced the double ch lorine sheet, strontium ions occupied the Bi(2) site only, and did not occupy the Bi(1) site. The SrBi3O4Cl3 catalyst showed a good catalyti c performance for the oxidative dehydrogenation of ethane. Particularl y, a high selectivity to ethene of more than 90% was obtained. Based u pon an investigation of the potential role of chlorine during the cour ce of the reaction, it was apparently shown that a role of surface chl orine species was important, rather than gas-phase chlorine, for the r eaction. It is considered that the high selectivity to ethene can be a ttributed to the fact that the chlorine radical mechanism operates on the catalysts, and that the surface chlorine blocks the formation of a ctive-oxygen species to prevent destructive oxidation reactions.