Inhibition of dibenzothiophene hydrodesulfurization by di-aza heterocycles

The hydrodesulfurization of dibenzothiophene over a sulfided CoMo/Al₂O₃ catalyst can be severely inhibited by 1,10-phenanthroline. The catalysts hydrogenation activity is totally suppressed and cannot be fully recovered upon stripping of adsorbed nitrogen species. The bulk of the hydrogenolysis activity is suppressed but can be completely recovered upon stripping. Implications of these observations are discussed, including the possibility of a chelating-enhanced adsorption mechanism.