Zr-Doped TiO_2–<i>x</i> Nano-Oxide with Coordinatively Unsaturated Ti(Zr)–O Acid–Base Pairs for Efficient Propane Dehydrogenation

Recently, some traditional oxide supports, such as nano TiO2 and ZrO2 with high surface energy, have been found to be partially reduced to generate oxygen vacancies and coordinatively unsaturated metal (Mcu) cations as efficient active sites for nonoxidative propane dehydrogenation (PDH). However, the primary challenge in their industrial applications is rapid deactivation because of coke, over-reduction, and aggregation under the reaction conditions of high temperature and reducible atmosphere. Herein, we reported that cost-effective and environmentally friendly Zr-doped TiO2 (TixZr1) prepared by a simple coprecipitation method can be used as a highly efficient and stable catalyst for PDH. Ti3Zr1 exhibited the C3H6 formation rate [r(C3H6)] of 0.6 mmol g–1 min–1 at 550 °C, which was 17 times that of pure TiO2, and a deactivation constant (Kd) 2.8 times lower than that of commercial TiO2. Moderate Zr doping promotes the generation of surface active lattice oxygen, which can be reduced at a relatively low temperature to form oxygen vacancies and Ti(Zr)cu–O acid–base pairs as the active sites for PDH, and their number is in line with r(C3H6) of TixZr1 catalysts. With the increase of the Zr doping amount, the bulk crystal phase of TixZr gradually transforms from Zr-doped anatase TiO2 to TiZrO4 via Ti2ZrO6 with enhanced thermostability, which can inhibit over-reduction and aggregation of the nano-oxide.