Modulation of surface chemistry by boron modification to achieve a superior VOX/Al2O3 catalyst in propane dehydrogenation

Abstract

The VOX/Al2O3 is known as an active catalyst in the propane dehydrogenation, however, with poor stability due to the severe coking problem. In this study, the VOX/Al2O3 catalyst was modified by boric acid, and the catalyst exhibited significantly improved stability and less coke deposition than the unmodified counterpart. The experimental results and theoretical modeling (DFT) suggested that the boron decreased the polymerization degree of VOX species, generated a high proportion of isolated vanadium species that reduced the initial activity but enhanced the stability of VOX/Al2O3 catalyst. Boron interacted with Al and V forming B-O-Al and B-O-V bonds, which significantly reduced the amounts of both Brønsted and Lewis acid sites, alleviating the coke deposition rate on the catalyst surface. The boron on VOX/Al2O3 promoted the desorption of propylene that inhibited further cracking and its polymerization, thus improving the propylene selectivity and catalyst stability.