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  • Title: Hydrogenation of the alpha,beta-unsaturated aldehydes acrolein, crotonaldehyde, and prenal over Pt single crystals: a kinetic and sum-frequency generation vibrational spectroscopy study.
    Author: Kliewer CJ, Bieri M, Somorjai GA.
    Journal: J Am Chem Soc; 2009 Jul 29; 131(29):9958-66. PubMed ID: 19580314.
    Abstract:
    Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three alpha,beta-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr of aldehyde, 100 Torr of hydrogen) in the temperature range of 295-415 K. SFG-VS data showed that acrolein has mixed adsorption species of eta(2)-di-sigma(CC)-trans, eta(2)-di-sigma(CC)-cis as well as highly coordinated eta(3) or eta(4) species. Crotonaldehyde adsorbed to Pt(111) as eta(2) surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the eta(2) adsorption species and became more highly coordinated as the temperature was raised to 415 K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation "cracking" product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotyl alcohol.
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