Composition Tuning of Ru-Based Phosphide for Enhanced Propane Selective Dehydrogenation
Rui Ma, Tian-Xing Yang, Junxian Gao, Jiajing Kou, Johnny Zhu Chen, Yufei He, Jeffrey T. Miller, Dianqing Li
Abstract
In this work, we report a robust Ru phosphide (RuP) catalyst, which exhibits high propylene selectivity for propane dehydrogenation, whereas monometallic Ru nanoparticles (NPs) result in cracking. X-ray photoelectron spectroscopy, synchrotron X-ray absorption spectroscopy, transmission CO-IR of the reduced catalyst, and high-angle annular dark-field scanning transmission electron microscopy are used to identify the surface structure of NPs with different P/Ru atomic ratios, changing from Ru to Ru2P to RuP with increasing P loading. In addition to improving the olefin selectivity, increasing the P/Ru ratio leads to higher turnover rates and lowers the deactivation rate. P is thought to act as a structural promoter to reduce the Ru ensemble size, decreasing the hydrogenolysis rate. In addition, increasing the P/Ru ratio leads to a decrease in the energy of the Ru valence orbitals, which are suggested to weaken metal-adsorbate bond energies and reactant surface coverages.