Effect of alumina–titania supports on the activity of Pd, Pt and bimetallic Pd–Pt catalysts for hydrorefining applications

A series of Pd, Pt and bimetallic Pd:Pt (4:1) based catalysts were supported on various alumina–titania mixed oxides. Their catalytic properties were probed on the thiophene hydrodesulphurisation (HDS). The supports were synthesised by the sol–gel method to obtain bulk mixed oxides. The Pd catalysts were tested in reduced and sulphided state, where the sulphided catalysts showed higher activity. While sulphided Pd increased its activity with titania content in the support, sulphided Pt proved to be more active when supported on the mixed oxide with the lowest titania concentration. The bimetallic catalysts presented the highest activity when supported on equimolar alumina–titania. A dependence of the deactivation rates with titania concentration in the mixed-oxide supports was detected for Pd and Pd–Pt bimetallic catalysts. On the other hand, almost no effect of the support composition on the Pt/alumina–titania deactivation rates was observed. The bimetallic catalyst activity and deactivation rates resemble closely those of the Pd monometallic catalysts suggesting a stronger influence of Pd on the performance of the bimetallic systems.