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Ethanol dehydrogenation by gold catalysts: The effect of the gold particle size and the presence of oxygen

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A range of silica-supported gold nanoparticle catalysts have been synthesized on various silica supports.
The particle size was varied between 1.7 and 15 nm by varying the support (ordered mesoporous silicas,
silicas with and without aluminium impurities) and the gold loading procedure. A strong influence of the
gold particle size on the non-oxidative dehydrogenation of ethanol is noted: gold nanoparticles of about
6 nm show a much higher activity than smaller or larger particles. This optimal catalytic activity is
attributed to the existence of surface steps with a suitable geometry for the removal of b-H atoms from
adsorbed ethoxide. Such stepped sites are expected to be present with maximum density for intermediate
particle size. In the presence of oxygen, the rate fordehydrogenationismuchhigher because of the presence
of an adsorbed oxygen species, but the selectivity becomes lower as combustion starts to contribute. The
intrinsic activity is constant up to about 7 nm and then increases for larger particles. The larger gold
nanoparticles may contain strongly adsorbed oxygen adatoms, which are much scarcer on smaller gold
particles. Infrared spectroscopy shows that, already at room temperature, adsorbed ethoxide reacts with
molecular oxygen, whereas C–H bond cleavage to produce acetaldehyde requires at least a temperature of
75 oC. The reaction rate is first order with respect to ethanol in both cases.

Keywords: Gold, Particle size effect, Ethanol, Dehydrogenation, Oxidation

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Informasi Detail

Judul Seri

Applied Catalysis A: General

No. Panggil

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Penerbit

London : Elsevier B.V.., 2009

Deskripsi Fisik

Applied Catalysis A: General 361 (2009) 49–56

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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