Fundamental studies of hydrogen interaction with supported metal and bimetallic catalysts

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1993
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Bhatia, Sandeep
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Terry S. King
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

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The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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Abstract

An in situ [superscript]1H nuclear magnetic resonance (NMR) technique has been employed to study the interaction of hydrogen with silica supported metal and bimetallic catalysts. This technique was applied in the temperature range of 300 to 473 K and at pressures of 10[superscript]-5 to 760 Torr. On ruthenium and rhodium catalysts two distinct adsorbed resonances were detected. We have labelled these resonances as [alpha] and [beta]. The [beta] resonance is associated with a more weakly adsorbed species and was observable only at pressures greater than 100 Torr. Both these resonances represent adsorbed hydrogen interacting with the metal. The delocalized nature of [beta] hydrogen makes it difficult to associate it with any particular adsorption site. The population of [beta] hydrogen was found to be a strong function of the concentration of surface defects. Studies of hydrogen interaction with silica supported Ru-Group Ib bimetallic catalysts revealed several interesting facts. Addition of silver to Ru was found to greatly diminish the relative amount of the [beta] resonance. Since silver preferentially populates edge, corner and other defect-like sites, the weakly bound species associated with the [beta] resonance was correlated with low coordinated metal atoms. The total hydrogen population on the catalyst remained approximately the same with the addition of copper because dissociated hydrogen on ruthenium atoms can spillover to copper. We postulate that the difference in catalytic behavior of Ru, Ru-Cu and Ru-Ag is due to the surface segregation induced structure sensitivity of the weakly bound hydrogen. On silica supported platinum catalyst, no [beta] hydrogen was detected. The availability of the [beta] hydrogen, a weakly adsorbed species associated with the [beta] resonance, on ruthenium and rhodium may open reaction pathways that would not be available on platinum catalysts. Several hydrocarbon reactions involving hydrogen show great sensitivity to hydrogen pressure and the catalyst metal. We postulate that some of these previously well noted hydrogen effects are the manifestation of the availability (or unavailability) of different hydrogen states with variations in pressure.

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Fri Jan 01 00:00:00 UTC 1993