Oxidative dehydrogenation of ethane on rare earth oxides: Effects of chlorine additives in gas and solid phase on the oxidation over cerium oxide

The oxidative dehydrogenation of ethane in the presence and absence of tetrachloromethane (TCM) has been investigated on La2O3,Sm2O3,Pr6O11 and CeO2 at 773 and 973 K. Although the introduction of TCM into the ethane feedstream produced no significant changes with La2O3,Sm2O3 and Pr6O11 at 773 K, the conversion of ethane and the selectivity to ethylene on CeO2 were distinctly enhanced by the addition of the chlorinated additive. At 973 K, with all of the rare earth oxides studied the selectivities to CH4 increased while those to CO2 decreased, the latter particularly significantly, suggesting that the further oxidation of CO and/or CH4 is suppressed by the addition of the chlorinated additive. XPS measurements provide evidence for the introduction of Cl into the surface of CeO2, apparently forming CeOCl which is responsible for the enhancement observed in the reactions catalyzed by CeO2.