Dehydration of ethanol over zeolites, silica alumina and alumina: Lewis acidity, Brønsted acidity and confinement effects

Abstract

Ethanol dehydration was investigated over commercial H-FER, H-MFI, H-MOR, H-BEA, H-Y and H-USY zeolite samples, and alumina and silica alumina for comparison. The catalysts were characterized using FT-IR spectroscopy of the surface OH groups and of adsorbed CO and pyridine. UV–vis, Raman and TG-DTA were applied to characterize coke, formed more on H-MOR and H-BEA. H-zeolites are definitely more active than silica alumina and alumina on catalyst weight base. The H-MOR sample is the most active but the H-MFI samples with Si/Al2 ratios 280 and 50 show higher reaction rates per Al ion, H-FER and faujasites show highest ethylene yield (99.9% at 573K). At lower temperature and higher space velocities, diethyl ether is formed with high yield (>70% at 453–473K on H-BEA and H-MFI (50)). Overconversion of ethylene mainly to aromatics is observed on H-MFI (50). The different behaviour of protonic zeolites can predominantly be explained by confinement effects on the different zeolite cavities.