Effect of support on selectivity and on-stream stability of surface VOx species in non-oxidative propane dehydrogenation

Abstract

Al₂O₃, SiO₂(MCM-41), and Al₂O₃–SiO₂ (Siral®) with a SiO₂ content varying from 1 to 70 wt.% were used to prepare supported catalysts with a V loading below one monolayer. Their activity, selectivity and on-stream stability were tested in non-oxidative propane dehydrogenation (DH) at 550 °C. The highest space–time yield of propene was only 25% lower than that over industrially relevant Pt–Sn/Al₂O₃ under the same reaction conditions. All catalysts deactivated with time on stream, but restored their initial performance after oxidative regeneration as proven in a sequence of 10 DH/regeneration cycles lasting in total over 60 h. The deactivation was related to propene-derived carbon deposits covering active VO_x sites. However, depending on the catalyst, such deposits formed on bare support sites can also participate in propane dehydrogenation. Their DH activity is, however, significantly lower compared to VO_x species. Acidic properties of the support were found to be crucial for the generation of such catalytically active carbon species.