ROLE OF THE STRUCTURAL AND ELECTRONIC-PROPERTIES OF CR-1-XFEXVO4 (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1) SOLID-SOLUTIONS ON THEIR CATALYTIC ACTIVITY

A series of solid solutions having the general formula Cr(1-x)Fe(x)VO4 (0 less-than-or-equal-to x less-than-or-equal-to 1) was prepared. X-ray analysis revealed that the structure of the solid solutions formed at 0 < x < 1 represents a compromise between the distorted cation environments in FeVO4 and the regularity of the CrVO4 structure. The catalytic activity data of the vapour-phase decomposition of 2-propanol over this series was obtained in the temperature range 200-350-degrees-C. The results were discussed on the basis of the coordination and electronic state of the active sites exposed in the surface planes, which seem to be greatly influenced by the Cr3+/Fe3+ ratio. According to the ligand field stabilization energy considerations, it was suggested that coordinatively unsaturated Cr3+ ions represent the active sites responsible for the higher dehydration activity of the catalysts. Electrical conductivity measurements proved that the lowering in activity runs parallel to the decreasing of the energy barrier which the bulk electrons are required to overcome. A possible decomposition mechanism was proposed.