Complex metal halide oxides (3). Structural characteristics and catalytic performance of lanthanum-substituted X1X2 type complex bismuth chloride oxides

The replacement of bismuth ions with lanthanum ions in the cation-oxygen sh eets of layered Bi3SrCl3O4 catalyst promoted the activity for the oxidative dehydrogenation of ethane prominently. The structure of Bi3-nLanSrCl3O4 re mained in the X1X2 structure by the replacement until the lanthanum ion con tent (n) was in excess of 0.75, and the value of a of the sub-unit cell and the value of c representing thickness of the layer structure were changed reversely. The Rietveld analysis of the Bi2.25La0.75SrCl3O4 catalyst reveal ed that the thickness of the double chlorine sheet decreased when the coord ination number of lanthanum ion facing the double chlorine sheet increased from 8 to 9, suggesting that the interaction between the metal-oxide sheet and the chlorine sheet became stronger. This is supported by a reduced bind ing energy of chlorine in Bi2.25La0.75SrCl3O4 observed by XPS analysis. The activation of structural chlorine into a radical form is promoted by the r eplacement with lanthanum ion, which turns out to cause an increase of the oxidation activity of ethane.