Modeling gold/iron oxide interface system

Guczi, L.; Pászti, Zoltán; Frey, Krisztina; Beck, A.; Petö, G.; Daroczy, Cs. S.

doi:10.1007/s11244-006-0049-y

Cited by 25 publications

(19 citation statements)

References 28 publications

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“…Moreover, for a same value of particle surface density, there is no significant variation of the binding energy with the nature of the alumina support. Keeping in mind that all the catalysts have the same particle size, we can exclude a size effect or a final state effect to interpret this result as it is widely reported in the literature [56][57][58][59][60]. A relative variation of the intrinsic electronic properties of the particles is thus proposed leading to a negative shift (decreasing BE) when particle surface density increases.…”

Section: Resultsmentioning

confidence: 61%

Synthesis of highly dispersed palladium alumina supported particles: Influence of the particle surface density on physico-chemical properties

Benkhaled

Morin

Pichon

et al. 2006

Applied Catalysis A: General

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Complexation with nitrite ions in aqueous medium was used to prepare highly dispersed Pd8 particles supported on alumina. It has been possible to obtain catalysts with different Pd loading keeping the particle size lower than 1 nm as shown by HRTEM, chemisorption, or extended X-ray absorption fine structure (EXAFS) characterizations, and as a consequence with different particle surface density. We observed that electronic properties measured by IR(CO) or X-ray photoelectron spectroscopy (XPS) measurements are strongly influenced by this last parameter and that the origin of these variations can be related to the different strengths of the interactions of the palladium precursor with the alumina surface sites as shown by low temperature CO adsorption followed by FTIR spectroscopy. On increasing Pd loading, saturation of unsaturated Lewis surface sites follows their acid strength: the more acidic ones are the first to react as germination sites, followed by the medium and finally the weaker sites. These different interactions may explain the variation of electronic properties of such small reduced particles which appears to be very sensitive to the chemical nature of their initial germination site on the oxide support. On the other hand, no such effects were observed on changing the type of alumina (d or g) support, in agreement with the principle of the synthesis method which tends to limit strong interaction with the support. Comparison with Pd8 particles with the same particle size and particle surface density but prepared with the well known grafting of acetylacetonate precursor shows marked differences in terms of electronic properties followed by CO FTIR. This result illustrates the possibility to prepare highly dispersed Pd particles with different physico-chemical properties. #

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Section: Resultsmentioning

confidence: 61%

Synthesis of highly dispersed palladium alumina supported particles: Influence of the particle surface density on physico-chemical properties

Benkhaled

Morin

Pichon

et al. 2006

Applied Catalysis A: General

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“…It is well established that the catalytic properties may be strongly influenced by the size of metal particles. 32,33 Depending on whether or not the turnover frequency (TOF) is affected by the structure of the particle surface, Boudart coined the terms structure-sensitive or structure-insensitive reactions. 34 There are numerous studies indicating some structure sensitivity of hydrogenation reactions on Pt, Pd, Ni, Rh, Ru, and Au.…”

Section: Resultsmentioning

confidence: 99%

“…[35][36][37][38] Concerning the origin of the particle size effect, various explanations have been forwarded, putting the emphasis on the electronic or the geometric parameters. 33,39 Regarding the electronic properties, the critical size above which the d-band structure appears is about 2 nm. At a lower size, the d-band becomes narrower with the appearance of discrete levels, leading to electron deficiency of small particles, where the small metal particles bind their core electrons more tightly.…”

Section: Resultsmentioning

confidence: 99%

Transition metal-based bimetallic catalysts for the chemoselective hydrogenation of furfuraldehyde

Vetere

Merlo

Ruggera

et al. 2010

J. Braz. Chem. Soc.

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Neste trabalho foi estudada a hidrogenação quimiosseletiva em fase líquida do furfural, empregando-se catalisadores baseados em Pt, Rh e Ni. Sistemas bimetálicos, contendo diferentes quantidades de estanho, foram obtidos por meio de reações de superfície controlada entre um catalisador monometálico e Sn(C 4 H 9 ) 4 . Quando foram utilizados catalisadores monometálicos, os resultados obtidos sugerem uma relação entre as propriedades do metal e da atividade e seletividade. Todos os sistemas permitiram a obtenção do álcool furfurílico com alta seletividade (99, 97 e 76% com catalisadores de Pt, Rh e Ni, respectivamente). A adição de estanho tem efeitos diferentes sobre os três sistemas, tanto em termos de conversão quanto na seletividade. Um resultado interessante foi obtido para os catalisadores baseados em Ni, para os quais a adição de estanho levou a um aumento significativo da seletividade do álcool furfurílico e, dependendo da razão Sn/Ni, também há um aumento na atividade catalítica do sistema.In this work, the liquid-phase chemoselective hydrogenation of furfural was studied, employing Pt, Rh and Ni-based catalysts. Bimetallic systems, containing different amounts of tin, were obtained by means of controlled surface reactions between a monometallic catalyst and Sn(C 4 H 9 ) 4 . The results obtained when monometallic catalysts were employed suggest a relationship between metal properties and the activity and selectivity obtained. All systems allowed obtaining furfuryl alcohol with high selectivity (99, 97 and 76% were achieved with Pt, Rh and Ni catalysts, respectively). The addition of tin has different effects on the three systems, both in terms of conversion and selectivity. An interesting result was obtained for the Ni-based catalysts, for which the addition of tin led to a significant increase in furfuryl alcohol selectivity and, depending on the Sn/Ni ratio, also to an increase in the catalytic activity of the system. Keywords: furfural, furfuryl alcohol, hydrogenation, bimetallic catalysts, PtSn IntroductionThe hydrogenation of furfural is an important reaction in the chemical industry as it is the main way of obtaining furfuryl alcohol.1 This product is widely used in the production of resins, as an intermediate in the manufacture of lysine, vitamin C and lubricants, and to obtain tetrahydrofurfuryl alcohol, among other applications. [2][3][4] Due to the large variety of products that can be obtained from the hydrogenation of furfural, this reaction represents a great challenge from the point of view of its chemoselectivity. As shown in Figure 1, in addition to the products coming from the hydrogenation of the C=O bond and/or the furan ring, there are numerous compounds derived from side reactions (hydrogenolysis of the C=O bond, decarbonylation, hydrogenation and ring opening, condensation reactions, etc.). 3,5 In chemoselective hydrogenation reactions using heterogeneous catalysts, the choice of the active metal is a key factor, since its influence on the resulting activity and/or selectivity is wel...

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“…We are aware of the work by Horva´th et al who post decorated inactive Au/SiO 2 with active TiO 2 patches to create new gold-TiO 2 boundaries, thus increasing the catalytic activity for CO oxidation [53]. Analogously, Guczi et al post deposited active FeO x layers onto Au/ SiO 2 /Si(100) by pulsed laser deposition, and found that the activity of the FeO x /Au/SiO 2 /Si(100) model catalyst was higher than those of Au/SiO 2 /Si(100) and FeO x / SiO 2 /Si(100) because of the creation of gold-FeO x interface [54]. Others and us have post modified Au/ TiO 2 by nitrate [55], sulfate [56], and phosphate [57] to study the anion effects on activity.…”

Section: Stability and Regeneration Of Sio 2 /Au/tiomentioning

confidence: 98%

Rational design of gold catalysts with enhanced thermal stability: post modification of Au/TiO2 by amorphous SiO2 decoration

Zhu

Overbury

et al. 2007

Catal Lett

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Au/TiO 2 is highly active for CO oxidation, but it often suffers from sintering in high-temperature environments. In this work, we report on a novel design of gold catalysts, in which pre-formed Au/TiO 2 catalysts were post decorated by amorphous SiO 2 to suppress the agglomeration of gold particles. Even after being aged in O 2 -He at 700°C, the SiO 2 -decorated Au/TiO 2 was still active for CO oxidation at ambient temperature.

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Modeling gold/iron oxide interface system

Cited by 25 publications

References 28 publications

Synthesis of highly dispersed palladium alumina supported particles: Influence of the particle surface density on physico-chemical properties

Synthesis of highly dispersed palladium alumina supported particles: Influence of the particle surface density on physico-chemical properties

Transition metal-based bimetallic catalysts for the chemoselective hydrogenation of furfuraldehyde

Rational design of gold catalysts with enhanced thermal stability: post modification of Au/TiO2 by amorphous SiO2 decoration

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