Methanation reaction on ruthenium thin films: a mechanistic investigation. [PhD. thesis]

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The kinetics of the methanation reaction were measured on thin ruthenium films in the temperature range 548 to 623K. The pressures of the reactant gases were varied over the ranges 1.5 to 1500 ..mu..m for CO and 300 to 75000 ..mu..m for H/sub 2/ to yield kinetic orders for each gas. The CO kinetic order varied from +1 at low pressures to -2 at high pressures. As the H/sub 2/ pressure was increased its kinetic order varied from +2 to -1. Both of these order plots had unusually sharp maxima. The reaction is zero order in both CH/sub 4/ and ... continued below

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Pages: 186

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Slaughter, M.D. July 1, 1979.

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The kinetics of the methanation reaction were measured on thin ruthenium films in the temperature range 548 to 623K. The pressures of the reactant gases were varied over the ranges 1.5 to 1500 ..mu..m for CO and 300 to 75000 ..mu..m for H/sub 2/ to yield kinetic orders for each gas. The CO kinetic order varied from +1 at low pressures to -2 at high pressures. As the H/sub 2/ pressure was increased its kinetic order varied from +2 to -1. Both of these order plots had unusually sharp maxima. The reaction is zero order in both CH/sub 4/ and H/sub 2/O. The apparent activation energy was dependent upon temperature with a value of 21.9 kcal/mole at 573K. Auger spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) indicated that the surface was always covered with carbon. This carbon could be divided into two types based upon its reactivity toward hydrogen. Type-1 was very reactive to 3.5 torr hydrogen doses at 573K and was completely removed in less than 300 seconds. Type-2 was less reactive and required about 48 hours under the same conditions for removal. No oxygen was ever detected on the surface after methanation. Low energy electron diffraction (LEED) and XPS indicated respectively, that neither graphite nor bulk carbide was associated with the used catalyst. The deposition of up to 0.75 monolayer of carbon enhanced the rate of methanation. More carbon caused a drop in the initial rate. Methanol could be hydrogenated to methane at about the same rate as carbon monoxide. A mechanism was developed which quantitatively fits the kinetic data and qualitatively predicts all of the other observations. This mechanism involves adsorbed hydrogen interacting with non-dissociated carbon monoxide. The rate limiting step involves the interaction of Ru--H and Ru--CH/sub 3/ to form methane. A methylene carbonyl hydride is believed to act as a reversible poison at high H/sub 2/:CO ratios.

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Pages: 186

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Dep. NTIS, PC A09/MF A01.

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  • Other Information: Thesis

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  • Report No.: IS-T-871
  • Grant Number: W-7405-ENG-82
  • DOI: 10.2172/6042605 | External Link
  • Office of Scientific & Technical Information Report Number: 6042605
  • Archival Resource Key: ark:/67531/metadc1095366

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  • July 1, 1979

Added to The UNT Digital Library

  • Feb. 18, 2018, 3:59 p.m.

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  • April 17, 2018, 2:23 p.m.

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Slaughter, M.D. Methanation reaction on ruthenium thin films: a mechanistic investigation. [PhD. thesis], report, July 1, 1979; Iowa. (digital.library.unt.edu/ark:/67531/metadc1095366/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.