Abstract
Our recent work has reported that higher propylene selectivity and improved stability can be achieved by combining redox-active VOx and basic In2O3 for CO2-assisted oxidative dehydrogenation of propane (CO2-ODHP). In the present work, we continued to explore the stability and regenerability of V/In catalysts. In particular, our interest lies in identifying the effect of mono- and polyvanadate on catalytic performance and regenerability. A V/In catalyst with an increased proportion of monovanadate was prepared using the Schlenk line under moisture-free conditions (V/In–S), while the fully polymerized vanadate catalyst was prepared through a regular impregnation (V/In) for comparison. The Schlenk-line-prepared catalyst, namely, V/In–S, not only exhibits a 17–30% enhanced propylene yield at high temperatures (500–540 °C) over V/In but also presents improved stability and regenerability with nearly 88% activity recovered after regeneration in O2. Detailed characterizations have been performed to reveal the catalyst structure–performance relationship, including chemisorption (NH3/CO2-temperature-programmed desorption, NH3/CO2-TPD), H2-temperature-programmed reduction (H2-TPR), and spectroscopic studies [Raman spectroscopy, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS), and high-sensitivity low-energy ion scattering (HS-LEIS)]. Characterization results demonstrate that compared with polyvanadates, monovanadates lead to strengthened interaction with In2O3 and a more stabilized V/In surface and subsurface, as well as improved redox properties of VOx. These advantages give rise to the observed enhancement in activity, stability, and regenerability. These findings advance the understanding of the relationship between the activity/stability and the molecular structure of surface oxide species (vanadia) and the interplay between acid–base interactions and redox properties of mixed metal-oxide catalysts for efficient CO2-ODHP.
