Determination of the Acidity of Montmorillonite Pillared with Aluminum by IR Using Pyridine Adsorption

Abstract
Spectroscopic studies of chemisorbed pyridine indicate that Na-montmorillonite which has been degassed at 200°C contains only Lewis acid sites. The reaction of Na-homoionic montmorillonite with Al polyoxycations generates pillared montmorillonite which is thermally stable up to 500°C. The pillaring process seems to enhance Lewis acid sites and generate Brönsted acid sites. Above 300°C pyridine is adsorbed mainly on Lewis centers.