Phosphorus Oxynitride Modified Pt/Al₂O₃ Catalyst with High Activity and Coke Resistance over Direct Dehydrogenation of Ethylbenzene

The low activity and rapid coke deposition issues are challenging for the nonmetal and metal catalysts in the direct dehydrogenation (DDH) of ethylbenzene to styrene, respectively. To address these issues, the synergistic effect between nonmetal and metal species was explored in this paper by successively loading Pt species and phosphorus oxynitride (PNO) on Al2O3 support to fabricate PNO/Pt/Al2O3 catalyst. The XPS, TEM, NH3-TPD, and CO2-TPD characterizations revealed an obvious strong interaction between Pt and P, increasing the loading amount of PNO and significantly modifying the electronic properties of the Pt species. The catalytic performance results showed that PNO/Pt/Al2O3 not only exhibited higher catalytic activity with XEB of 56.68% than that of PNO/Al2O3 (39.55%) and Pt/Al2O3 (41.65%) but also displayed better coke resistance than Pt/Al2O3 at high-concentration of ethylbenzene feed. DFT calculations confirmed that the interaction between Pt and PNO led to the obviously reduced energy barriers for α-C–H and β-C–H bond breaking, which therefore enhanced the catalytic activity.