Dynamics of Propane in Silica Mesopores Formed upon Propylene Hydrogenation over Pt Nanoparticles by Time-Resolved FT-IR Spectroscopy

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• 作者：Walter Wasylenko ; Heinz Frei
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：July 12, 2007
• 年：2007
• 卷：111
• 期：27
• 页码：9884 - 9890
• 全文大小：273K
• 年卷期：v.111,no.27(July 12, 2007)
• ISSN：1932-7455

文摘

Propylene hydrogenation over Pt nanoparticles supported on mesoporous silica type SBA-15 was monitoredby time-resolved FT-IR spectroscopy at 23 ms resolution using short propylene gas pulses joining a continuousflow of hydrogen (in nitrogen, 1 atm total pressure). Experiments were conducted in the temperature rangeof 323-413 K. Propane was formed within 100 ms or faster depending on reaction temperature. The frequencyand temporal behavior of a transient band observed at 1457 cm^-1 are consistent with a surface propylintermediate and its hydrogenation to propane. The CH stretching region revealed distinct bands for propanemolecules emerging inside the nanoscale channels of the silica support. Spectral analysis gave the distributionof the propane product between the support and surrounding gas phase as a function of time. Kinetic analysisshowed that the escape of propane molecules from the channels occurred within hundreds of milliseconds(3.1 ± 0.4 s^-1 at 383 K). A steady-state distribution of propane between the gas phase and mesoporoussupport was established as the product is swept from the catalyst zone by the continuous flow of hydrogencoreactant. This is the first direct spectroscopic observation of emerging products of heterogeneous catalysison nanoporous supports under reaction conditions.