Oxidative dehydrogenation of propane on NixMg1-xAl2O4 and NiCr2O4 spinels

The NixMg1-xAl2O4, NiCr2O4, and MgCr2O4 spinels have been synthesized, char acterized with the XRD and XPS methods, and tested in the oxidative dehydro genation of propane. The crystallochemical model of solid surfaces, CMSS, h as been used to calculate the oxygen cation's bond energies in the spinels. For the NiMgAl spinels the activity and selectivity to propene increase wi th the increase in the Ni content. The Ni ions surrounded by oxygen in the spinel structure are proposed as active centers for oxidative dehydrogenati on to propene. The NiCr spinel is more active but less selective than the N iMgAl spinels; the difference in catalytic behavior has been ascribed to di fferent coordination of Ni ions in the two groups of the spinels and to the lower oxygen cation's bond energy in the NiCr spinel. (C) 1999 Academic Pr ess.