The surface chemistry of supported chromium oxide on lanthanum carbonate has been studied by TPD, FTIR, XPS, and electrophoretic measurement techniques. The active center for the oxidative dehydrogenation of isobutane to isobutylene was identified as a chromate species bound to the surface of lanthanum carbonate. This species was formed as a result of interaction between chromium oxide and lanthanum carbonate surface through CO2 elimination. FTIR and XPS experiments have confirmed a complete reversibility of active sites during reduction-oxidation.