ED-XAS Data Reveal In-situ Time-Resolved Adsorbate Coverage on Supported Molybdenum Oxide Catalysts during Propane Dehydrogenation

摘要

Energy-Dispersive X-ray Absorption Spectroscopy (ED-XAS) data combined with UV/Vis, Raman, and mass spectrometry data on alumina- and silica-supported molybdenum oxide catalysts under propane dehydrogenation conditions have been previously reported. A novel μ adsorbate isolation technique was applied here to the time-resolved (0.1 min) Mo K-edge ED-XAS data by taking the difference of absorption, μ, at t>1 against the initial time, t=0. Further, full multiple scattering calculations using the FEFF 8.0 code are performed to interpret the μ signatures. The resulting difference spectra and interpretation provide real time propane coverage and O depletion at the MoOn surface. The propane coverage is seen to correlate with the propene and/or coke production, with the maximum coke formation occurring when the propane coverage is the largest. Combined, these data give unprecedented insight into the complicated dynamics for propane dehydrogenation.