Platinum Nanoparticle Catalysts

In Situ Study of Reaction Intermediates Using SFG Vibrational Spectroscopy

Abstract Image† Chemical Sciences and Material Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

‡ Department of Chemistry, University of California, Berkeley, California 94720, United States

§ Department of Mechanical Engineering, University of California, Berkeley, California 94720, United States

J. Phys. Chem. C, 2013, 117 (4), pp 1809–1817

DOI: 10.1021/jp311772p

Section:

Abstract

The product selectivity during 1, 3-butadiene hydrogenation on monodisperse, colloidally synthesized, Pt nanoparticles was studied under reaction conditions with kinetic measurements and in situ sum frequency generation (SFG) vibrational spectroscopy. SFG was performed with the capping ligands intact in order to maintain nanoparticle size by reduced sintering. Four products are formed at 75 °C: 1-butene, cis-2-butene, trans-2-butene, and n-butane. Ensembles of Pt nanoparticles with average diameters of 0.9 and 1.8 nm exhibit a 30% and 20% increase in the full hydrogenation products, respectively, as compared to Pt nanoparticles with average diameters of 4.6 and 6.7 nm. Methyl and methylene vibrational stretches of reaction intermediates observed under working conditions using SFG were used to correlate the stable reaction intermediates with the product distribution. Kinetic and SFG results correlate with previous DFT predictions for two parallel reaction pathways of 1, 3-butadiene hydrogenation.Cover Image at internal or terminal carbons leading to the formation of 1-buten-4-yl radical (metallocycle) and 2-buten-1-yl radical intermediates, respectively. Small (0.9 and 1.8 nm) nanoparticles exhibited vibrational resonances originating from both intermediates, while the large (4.6 and 6.7 nm) particles exhibited vibrational resonances originating predominately from the 2-buten-1-yl radical. This suggests each reaction pathway competes for partial and full hydrogenation and the nanoparticle size affects the kinetic preference for the two pathways. The reaction pathway through the metallocycle intermediate on the small nanoparticles is likely due to the presence of low-coordinated sites.

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by PositiveOption

Because I believe
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But Science does not they say there two ways to get a efficient design?
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2

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by PositiveOption

One who loves God will see what they believe and the ones who trust science will believe what they see
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That means I see that, because the cell's nanotechnology and complexity on multiple levels is unmatched by all the engineers on the earth combined, it is a paradox if it comes from a natural cause
But Science does not see it that way they say there two ways to get a efficient design?

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by bionecr

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