Alkane conversion and topological segregation in PtM/Al2O3 catalysts

Coq, Bernard; Chaqroune, A.; Figuéras, F.; Nciri, B

doi:10.1016/0926-860x(92)85007-x

Cited by 35 publications

(7 citation statements)

References 40 publications

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“…The interpretation we have made of the low wavenumber features in the infrared spectra from the systems, where there is no formation of PtGe alloys, necessarily assumes that the interfacial sites are all Pt. The intensity of these features in the Pt(acac) 2 /GeBu 4 /H I SiO 2 derived system within this interpretation would support this notion and be in line with previous work that has suggested that in these alloy systems Ge shows no preferential occupation of defect or interfacial sites (in contrast to Sn, which shows a marked preference for the occupation of these sites in the analogous PtSn alloys). , …”

Section: Discussionsupporting

confidence: 90%

“…The intensity of these features in the Pt(acac) 2 /GeBu 4 /H I SiO 2 derived system within this interpretation would support this notion and be in line with previous work that has suggested that in these alloy systems Ge shows no preferential occupation of defect or interfacial sites (in contrast to Sn, which shows a marked preference for the occupation of these sites in the analogous PtSn alloys). 23,34 The diminished adsorption of CO at either on top or interfacial sites is not readily explained by site occupancy arguments, as there are no priori reasons why this should vary between the three systems. However, if we refer back to the results of the EXAFS analysis for these three reduced systems, we note that they show an increasing level of low Z coordination being retained in the Ge K-edge XAFS in the order Pt(acac) 2 /GeBu 4 / H I SiO 2 < Pt(acac) 2 /GePh 4 /H I SiO 2 < Pt(acac) 2 /GeBu 3 H/H I SiO 2 .…”

Section: Discussionmentioning

confidence: 99%

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A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

et al. 2001

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Five synthetic approaches to the incorporation of germanium into materials based upon Pt(acac) 2 supported on H I SiO 2 have been assessed by using Pt L III -and Ge K-edge extended X-ray adsorption fine structure (EXAFS), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed CO. After reduction in 10% H 2 /N 2 (T > 673 K), two of these methods (utilizing GeBu 4 (Bu ) C 4 H 9 ) and GePh 4 (Ph ) C 6 H 5 )) appear to result in the uniform formation of PtGe alloy particles though their capacities for CO chemisorption are markedly different. The successful formation of uniformly alloyed PtGe particles is determined by a competition between processes resulting in the formation of stable GeO x species, and those that result in intimate contact between the Ge precursor and evolving Pt particles. The latter processes are promoted by mobile precursors that interact with the support via physical interactions alone. However, the final character of the catalyst is also determined by the character of the ligands present in the Ge precursor; increasingly stable and aromatic ligands result in increased carbon retention and subsequent loss of adsorptive capacity. Further, it is found that the use of a mesoporous SiO 2 support results in new CO adsorptions in DRIFTS that may not be ascribed to the formation of conventional Chini type Pt-carbonyl complexes or CO adsorption upon typical Pt particles. The origin of new absorptions is discussed in terms of the formation of Pt or PtGe particles with a morphology that has been directed by the internal structure of the mesoporous support.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

et al. 2001

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“…This effect is especially pronounced when tin is added using methods of surface organometallic chemistry. [46][47][48] XANES studies conducted on NiSn catalysts similar to those studied here have shown a decrease in the intensity of the white line at the Ni K edge for samples containing tin, as compared to monometallic systems. 49 This is an indication of an increase in the electron density of Ni due to the presence of Sn alloyed with it or in its immediate vicinity.…”

Section: Resultsmentioning

confidence: 94%

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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“…Here we are in the presence of dilution effect of Pt ensembles. This reduction of large Pt atoms ensembles caused by Sn 0 explains the diminution of deep hydrogenolysis in n-heptane conversion according to an ensemble effect [32,33]. The decrease in hydrogenolysis is observed to a lower extent on the PS/A-SI catalyst, since in this preparation tin would be deposited mainly on the support.…”

Section: Discussionmentioning

confidence: 99%

Effect of lanthanum on the catalytic properties of PtSn/γ-Al2O3 bimetallic catalysts prepared by successive impregnation and controlled surface reaction

Angel

Bonilla

Peña

et al. 2003

Journal of Catalysis

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Bimetallic PtSn/γ -Al 2 O 3 -La 2 O 3 catalysts were prepared by two comparative methods, successive impregnation (SI) and controlled surface reaction (CSR). FTIR-pyridine adsorption revealed a decrease in support acidity as a function of lanthanum content. Oxidized Pt 2+ was identified by CO-FTIR chemisorption and by XPS spectra on catalysts prepared by SI. When the CSR preparation method was used, reduced Pt 0 was observed and oxidized Pt 2+ was not detected. As the lanthanum content increased a diminution in cyclohexane dehydrogenation and n-heptane conversion was observed. Low hydrogenolysis and high selectivity to C 7 -olefins were obtained in both preparations. It is proposed that lanthanum in SI catalysts stabilizes the platinum in an oxidation state, Pt 2+ , and diminishes the support acidity. In CSR preparations the lanthanum effect is limited to inhibit the support acidity and hence to the bifunctional reactions occurring during the n-heptane conversion.

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Alkane conversion and topological segregation in PtM/Al2O3 catalysts

Cited by 35 publications

References 40 publications

A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

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

Effect of lanthanum on the catalytic properties of PtSn/γ-Al2O3 bimetallic catalysts prepared by successive impregnation and controlled surface reaction

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Alkane conversion and topological segregation in PtM/Al2O3 catalysts

Cited by 35 publications

References 40 publications

A Comparative Study of Methodologies for the Incorporation of Ge into HISiO2-Supported, Pt(Acac)2-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

A Comparative Study of Methodologies for the Incorporation of Ge into HISiO2-Supported, Pt(Acac)2-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

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

Effect of lanthanum on the catalytic properties of PtSn/γ-Al2O3 bimetallic catalysts prepared by successive impregnation and controlled surface reaction

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A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption

A Comparative Study of Methodologies for the Incorporation of Ge into H_ISiO₂-Supported, Pt(Acac)₂-Derived, Pt−Ge Catalysts and the Effect of Internal Oxide Structure on Particle Morphology and CO Adsorption