CBE Seminar (Zoom): Near-Surface Imaging of Multicomponent Gas Phase above a Catalyst Surface During Methanol Oxidation

Non-UCI people: Please use this registration link: https://forms.gle/FaCQx8YhGSPkEBvq5 

Abstract: In catalysis science, operando experiments are essential to generate fundamental knowledge for practical catalysis conditions. We have built an optically accessible catalytic flow reactor for operando measurements using in situ optical probes, and ex situ mass spectrometry probes that enable detection of free radicals and reactive intermediates. We have applied these diagnostics to partial oxidation of methanol (CH3OH) catalyzed by polycrystalline Ag and methanol conversion over Pd-based catalysts in collaboration with researchers at UC Davis. We demonstrate gas-phase measurements of major and minor species above the Ag catalyst using 1-D Raman scattering, laser-induced fluorescence (LIF) imaging of formaldehyde (CH2O), and universal species mapping with molecular beam mass spectrometry. Imaging of CH2O shows growth of a steady boundary layer as the flow of CH3OH and O2 in N2 progresses over the Ag surface. As CH3OH is oxidized, the resulting CH2O diffuses into the boundary layer. LIF imaging reveals variations in product distributions and provides a measure of catalytic activity as a function of reactant mixture, catalyst temperature and localized deactivation. Raman scattering measurements provide maps of temperature and composition. Mass spectrometry detects species sampled by a quartz nozzle with a 50mm orifice diameter. Near-surface molecular beam mass spectrometry enables simultaneous detection of all species using a gas sampling probe. Detection of gas-phase free radicals, such as CH3 and CH3O, and of minor products, such as acetaldehyde, dimethyl ether, and methyl formate provides insights into catalytic mechanisms of methanol oxidation. In particular, we detected methoxymethanol (CH3OCH2OH) over Pd-based catalysts, which is a rarely observed and reactive C2 oxygenate that has been proposed to be a critical intermediate in methyl formate production. The combination of these optical and mass spectrometry techniques provides a detailed picture of the coupling between the gas phase and surface in heterogeneous catalysis.

Bio: Jonathan Frank is the principal investigator for the Combustion Research Facility’s Advanced Imaging Laboratory, which includes research funded by the U.S. Department of Energy Basic Energy Sciences and Fusion Energy Sciences Programs. His research focuses on the development and application of laser-based imaging diagnostics for fundamental studies of chemically reacting systems in combustion, catalysis and plasma science. Frank has also worked as a visiting scholar at the University of Cambridge, pursuing experimental research in combustion and optical diagnostics for microscopy. He received his Ph.D. in mechanical engineering from Yale University and has been a staff member at Sandia for over 20 years. In 2020, he was elected as a fellow of the Combustion Institute.

Host: Professor Erdem Sasmaz