Acid-catalysed benzene hydroconversion using various zeolites: Brönsted acidity, hydrogenation and side-reactions Original Research Article

Several zeolites (cubic and hexagonal faujasites, steamed or not) are tested as acid catalysts. The strength and number of Brönsted acid sites are determined from FTIR studies of adsorbed probe molecules (CO, pyridine). Direct benzene hydrogenation leading to cyclohexane is observed only at low temperature (500 K) with the less acid zeolites (H0=−8.5). Side-reactions grow progressively with the acid strength of the catalyst and, in some cases, with increasing reaction temperature (in other cases, a drastic deactivation is observed). Coke is generated by the more acid hydroxyl groups (H0=−12). The occurrence of the various steps of the scheme describing the benzene hydroconversion process depends on the strength of Brönsted acid sites and reaction temperature.