Impact of Mineralizing Agents on Aluminum Distribution and Acidity of ZSM‐5 Zeolites
Shadi Al‐Nahari, Eddy Dib, Claudia Cammarano, Etienne Saint‐Germes, Dominique Massiot, Vincent Sarou‐Kanian, Bruno Alonso
Abstract
Abstract Intensive research on improving the catalytic properties of zeolites is focused on modulating their acidity and the distribution of associated Al sites. Herein, by studying a series of ZSM‐5 zeolites over a broad range of Al content, we demonstrate how the nature of the mineralizing agent (F − or OH − ) used in hydrothermal syntheses directly impacts Al sites distribution. The proportions of Al sites, probed by 27 Al NMR, depend on the Si/Al ratio for F − , but remain identical for OH − (from Si/Al=30 to 760). This leads to contrasting variations in weak and strong acidities. Such opposite effect of mineralizers is explained by the spatial location of negative charges and the resulting balance between short‐ and long‐range electrostatic interactions. This understanding paves the way for additional and simple opportunities to control zeolites’ acidity.