Ethylene adsorption on HNaZSM-5: Kinetic study

A process of adsorption of ethylene on partially decationated HNaZSM-5 at ambient temperature was studied. It was found that a dependence of the rate of surface oligomer formation upon time or ethylene coverage exhibited a pronounced maximum. A simple kinetic model to describe experimental data was proposed. The model is based on the assumptions that i) the limiting step of reaction is the step of activation of ethylene; ii) the kinetic constant of oligomer chain growth does not depend upon length of hydrocarbon chain and iii) the course of reaction is limited by the void volume of zeolite framework. Based on the values of the kinetic constants obtained it is assumed that the specific activity of the zeolites in the reaction of the chain prolongation does not depend upon the decationation degree whereas the activity in the reaction of chain initiation (ethylene activation) decreases with increase of sodium content.