Ethane Oxidative Dehydrogenation over ternary and binary mixtures of alkaline and alkaline earth chlorides supported on zeolites

International audienceEthane Oxidative Dehydrogenation (ODH) into ethylene was successfully catalyzed by binary RbCl/MgCl2 and ternary NaCl/KCl/MgCl2 mixtures (with the eutectic composition) supported over lanthanum exchanged Na–Y zeolite. At 500 °C, both catalysts exhibited 100% selectivity towards ethylene at 40 and 20% ethane conversion for the binary and ternary mixtures, respectively. According to nitrogen physisorption results, the ternary mixture supported over Ultra stable zeolite led to inefficient catalyst due to the diffusion of melt throughout the zeolite cavities, while the use of MgO–like support should be avoided on the basis of XRD results. For binary mixtures, the size of the alkaline atom influences the melt mobility and therefore the catalytic activity. In this context, large sized atoms, like cesium, and small atoms, like sodium should be avoided. In fact, CsCl/MgCl2 binary mixture exhibited higher eutectic temperature (491 °C) and the corresponding catalyst is low in activity, while NaCl/MgCl2 does not behave like a binary mixture in the presence of zeolite on the basis of thermal analysis results. The presence of rare earths cations, namely bare La3+ (unreduced by hydrogen in TPR) obtained from lanthanum chloride, and Tb4O7 (reduced under hydrogen at 433 °C) issued from terbium nitrate, improved the catalytic activity