Acidity, cumene conversion and thiophene hydrodesulfurization over alumina and surface modified aluminas Original Research Article

The acidic and catalytic properties of alumina as well as fluoride- and sodium-modified alumina were characterized by FT-IR spectroscopy of adsorbed pyridine and t-butylcyanide (TBC), and by cumene and thiophene decomposition. Experimental evidence demonstrated that Al2O3 contains a high number of Lewis acid sites. A higher number of these sites of higher strength as well as Brönsted acid sites were detected for Al2O3single bondF−. In the case of Al2O3single bondNa+, the concentration of Lewis acid sites was lower compared to Al2O3 and also the acid strength was weaker. The Al2O3single bondF− sample showed high activity in cumene dealkylation whereas Al2O3single bondNa+ was most active in cumene dehydrogenation. The most active catalyst for thiophene hydrodesulfurization was Al2O3single bondNa+ while Al2O3single bondF− was a little less active and lost its original activity rapidly. It was suggested that in the first step a thiophene molecule is chemisorbed vertically through a sulfur atom on Lewis acid sites localized on the alumina surface.