Evidence of surface active sites on NaY zeolite by a model reaction

Abstract

Owing to the development of a new test reaction, namely the isomerization of 1-dodecene, it becomes possible to characterize the activity of cationic zeolites under conditions close to those of industrial adsorption and separation processes (temperature around 150–200 °C and liquid phase). Indeed, 1-dodecene is highly active and still in a liquid state at 150 °C. Furthermore, by comparing the reactivity of NaY before and after treatments applied to reduce its activity ((i) passivation of the external surface by deposition of TetraEthylOrthoSiloxane (TEOS) and (ii) washing the zeolite with a basic or neutral solution), we are able to propose a nature and localization for the residual active sites of this zeolite. Indeed, the evolution of the NaY activity in their function indicates that the active sites are located both at the external and internal surfaces of NaY and that two types of sites can be described: OH groups and structure defects.