Near-Surface Imaging of the Multicomponent Gas Phase above a Silver Catalyst during Partial Oxidation of Methanol

Journal Article · Tue Dec 15 00:00:00 EST 2020 · ACS Catalysis

DOI:https://doi.org/10.1021/acscatal.0c04396· OSTI ID:1772037

Zhou, Bo ^[1]; Huang, Erxiong ^[2]; Almeida, Raybel ^[2]; Gurses, Sadi ^[3]; Ungar, Alexander ^[2]; Zetterberg, Johan  ^[4]; Kulkarni, Ambarish  ^[3]; Kronawitter, Coleman X.  ^[3]; Osborn, David L.  ^[2]; Hansen, Nils  ^[2]; Frank, Jonathan H.  ^[2]

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1. Sandia National Lab. (SNL-CA), Livermore, CA (United States); Southern Univ. of Science and Technology, Shenzhen (China)
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
3. Univ. of California, Davis, CA (United States)
4. Lund Univ. (Sweden)

Fundamental chemistry in heterogeneous catalysis is increasingly explored using operando techniques in order to address the pressure gap between ultrahigh vacuum studies and practical operating pressures. Because most operando experiments focus on the surface and surface-bound species, there is a knowledge gap of the near-surface gas phase and the fundamental information the properties of this region convey about catalytic mechanisms. In this work, we demonstrate in situ visualization and measurement of gas-phase species and temperature distributions in operando catalysis experiments using complementary near-surface optical and mass spectrometry techniques. The partial oxidation of methanol over a silver catalyst demonstrates the value of these diagnostic techniques at 600 Torr (800 mbar) pressure and temperatures from 150 to 410 °C. Planar laser-induced fluorescence provides two-dimensional images of the formaldehyde product distribution that show the development of the boundary layer above the catalyst under different flow conditions. Raman scattering imaging provides measurements of a wide range of major species, such as methanol, oxygen, nitrogen, formaldehyde, and water vapor. 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 the partial oxidation of methanol. The combination of these techniques provides a detailed picture of the coupling between the gas phase and surface in heterogeneous catalysis and enables parametric studies under different operating conditions, which will enhance our ability to constrain microkinetic models of heterogeneous catalysis.

• Research Organization: Sandia National Lab. (SNL-CA), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; USDOE Laboratory Directed Research and Development (LDRD) Program; Swedish Research Council (VR); Swedish Foundation for Strategic Research (SSF); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000; SC0020320; NA0003525
• OSTI ID: 1772037
• Report Number(s): SAND-2021-2784J; 694696
• Journal Information: ACS Catalysis, Vol. 11, Issue 1; ISSN 2155-5435
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
planar laser-induced fluorescence
Raman scattering
molecular beam mass spectrometry
catalytic partial oxidation of methanol
pressure gap