Unravelling the Origins of the Synergy Effect between ZrO2 and CrOx in Supported CrZrOx for Propene Formation in Non-oxidative Propane Dehydrogenation

In this work, steady-state tests of propane dehydrogenation, density functional theory calculations, operando UV-vis spectroscopy, ex situ and in situ EPR spectroscopy, IR spectroscopy and temperature-programmed techniques were combined to provide fundamentals for tuning activity and on-stream stability of low-loaded catalysts with supported CrZrOx species. Two neighboring Zrcus (cus=coordinatively unsaturated) sites were concluded to be mainly responsible for propane dehydrogenation to propene. They are formed upon reductive catalyst treatment and their concentration depends on the strength of interaction between CrOx, ZrO2 and support and on the size of ZrO2 crystallites in CrZrOx. SiO2 weakly interacting with CrOx was found to be more preferable support than Al2O3- or TiO2-based supports. CrOx species promotes formation of Zrcus sites and improves their intrinsic activity for the desired reaction. CrOx also contributes to coke formation as concluded from operando UV-vis analysis. Cr20Zr80/SiO2 possessi...