Mars van Krevelen Mechanism for the Selective Partial Oxidation of Ethane

Abstract

Abstract Ethylene is the most important olefin in the petrochemical context, since it is the main raw material for the production of many polymers. Traditional production of ethylene via thermal cracking and catalytic dehydrogenation consumes large amounts of energy; hence selective partial oxidation of ethane has been considered as an attractive alternative production path. Recently, development of a promising catalyst for selective partial oxidation of ethane, which consists of multi-metallic mixed oxides of Mo, Te, V, and Nb, has been published. It is also noteworthy that this catalytic system starts to be active at temperatures below 400 °C, substantially lower than the one required by commercial thermal processes, >800 °C. In this work, a kinetic mechanism based on Mars van Krevelen formalism is proposed for the selective partial oxidation of ethane, considering the surface itself as active protagonist of the reaction. RedOx steps on active sites are considered as the controlling ones, and the rest of transformations are considered as pseudo-steady steps. It is noticed that there are side reactions, which produces CO and CO2 as combustion by-products. Additionally, there is competition for reduced sites on the catalytic surface, mainly between oxygen and water molecules, which adsorb strongly on these sites. Adjusted results by the mechanism proposed are in agreement with experimental observations of reaction rates diminishing proportionally to partial pressure of water, caused by competition of reduced sites on catalyst surface.