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 VOx 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 VOx species. Acidic properties of the support were found to be crucial for the generation of such catalytically active carbon species.