Structure and Size of Bimetallic Palladium-Platinum Clusters in an Hydrotreatment

Bazin, Dominique; Denis, Guillaume; Pichon, C.; Uzio, Denis; López, Susana T.

doi:10.2516/ogst:2005057

Cited by 38 publications

(45 citation statements)

References 49 publications

(75 reference statements)

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“…One series was prepared using chloride-containing precursors, the other-metal acetylacetonates. The use of the latter precursors was shown to result in the preparation of well mixed Pd-Pt catalysts, supported on alumina (Micheaud et al 1998;Bazin et al 2005), silica (Renouprez et al 2000) and magnesia (Dossi et al 2003). Easy formation of well-defined mixed acetyloacetonates precursors depositing on a support followed by calcination and reduction results in the preparation of Pd-Pt nanoparticles of homogeneous composition, so this preparation method would be considered as a sort of recommendation.…”

Section: Introductionmentioning

confidence: 99%

n-Hexane conversion on γ-alumina supported palladium–platinum catalysts

et al. 2019

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Two series of Pd-Pt/Al 2 O 3 catalysts, characterized by high metal dispersions were prepared and investigated in the reaction of n-hexane conversion at the temperature < 300 °C. Incipient wetness co-impregnation of γ-alumina with the solutions of Pd(acac) 2 and Pt(acac) 2 led to relatively good Pd-Pt alloying. However, a similar catalyst preparation using solutions of PdCl 2 and H 2 PtCl 6 resulted in unsatisfactory homogenization; furthermore, significant amounts of chlorine were retained in the catalysts. The Pd-Pt alloy homogeneity has a significant effect on the relations of catalytic activities and product selectivities with Pd-Pt alloy composition. The relationship between the catalytic activity of chlorine-free Pd-Pt/Al 2 O 3 catalysts and bulk Pd-Pt composition matches the accepted relation between the surface composition and bulk composition of Pd-Pt, reflecting a high surface enrichment in palladium. In contrast, for the chloride series of Pd-Pt/Al 2 O 3 , variations of the turnover frequency are directly correlated with the bulk composition, indicating that unalloyed, more active, Pt particles decide about the catalytic behavior. Pd/Al 2 O 3 shows better than Pt/Al 2 O 3 selectivity for isomerization, especially after reduction at higher temperatures, ≥ 500 °C. On alloying with Pt, for the Cl-free series the isomerization selectivity was very high for nearly all bimetallic catalysts and showed a synergistic effect for 20 at.% Pt. In contrast, for the Cl-containing series, the isomerization selectivity was proportional to the palladium content. The effect of reduction temperature on the isomerization propensity of Cl-containing Pd-Pt/Al 2 O 3 catalysts was rather small, suggesting that possible variations in support acidity associated with chloride presence do not have large catalytic consequences, confirming the metal-only catalytic action in alkane isomerization carried out at the temperatures below 300 °C. Keywords Pd-Pt/Al 2 O 3 • n-Hexane hydroconversion • Selectivity for isomerization • Effect of alloying • Effect of reduction temperature This article belongs to S.I. ISSHAC10, but it reach the press at the time the special issue was published.

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Section: Introductionmentioning

confidence: 99%

n-Hexane conversion on γ-alumina supported palladium–platinum catalysts

et al. 2019

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“…It has been shown in the literature that if a homogeneous system of A-B bimetallic NPs follows the relationship of N A-A + N A-B > N B-A + N B-B , then the core of the cluster is composed of N atoms of A (N A ) and the surface is made of N atoms of B (N B ); the total coordination number (N A-A + N A-B ) for the "A" atom is greater than that for the "B" atom (N B-A + N B-B ), and this hypothesis is based on the absence of monometallic clusters. [46][47][48] Hence, the observed parameter relationship, that www.chemeurj.org is, AEN Pt-i > AEN Ru-i supports the Pt-rich core -Ru-rich shell structure for all the PtRu/C NPs investigated here. Even though the structures of the as-reduced and heat-treated PtRu/C catalysts appear to be similar, the structural parameters P observed , R observed , J Pt , and J Ru show small but significant changes from the as-reduced to heat-treated conditions, which needs a detailed explanation.…”

Section: Resultsmentioning

confidence: 99%

Heat‐Induced Alterations in the Surface Population of Metal Sites in Bimetallic Nanoparticles

Hwang

Sarma

Wang

et al. 2007

Chemistry A European J

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The ability to alter the surface population of metal sites in bimetallic nanoparticles (NPs) is of great interest in the context of heterogeneous catalysis. Here, we report findings of surface alterations of Pt and Ru metallic sites in bimetallic carbon-supported (PtRu/C) NPs that were induced by employing a controlled thermal-treatment strategy. The thermal-treatment procedure was designed in such a way that the particle size of the initial NPs was not altered and only the surface population of Pt and Ru was changed, thus allowing us to deduce structural information independent of particle-size effects. X-ray absorption spectroscopy (XAS) was utilized to deduce the structural parameters that can provide information on atomic distribution and/or extent of alloying as well as the surface population of Pt and Ru in PtRu/C NPs. The PtRu/C catalyst sample was obtained from Johnson Matthey, and first the as-received catalyst was reduced in 2 % H2 and 98 % Ar gas mixture at 300 degrees C for 4 h (PtRu/C as-reduced). Later this sample was subjected to thermal treatment in either oxygen (PtRu/C-O2-300) or hydrogen (PtRu/C-H2-350). The XAS results reveal that when the as-reduced PtRu/C catalyst was exposed to the O2 thermal-treatment strategy, a considerable amount of Ru was moved to the catalyst surface. In contrast, the H2 thermal-treatment strategy led to a higher population of Pt on the PtRu/C surface. Characterization of the heat-treated PtRu/C samples by X-ray diffraction and transmission electron microscopy reveals that there is no significant change in the particle size of thermally treated samples when compared to the as-received PtRu/C sample. The electrochemical properties of the as-reduced and heat-treated PtRu/C catalyst samples were confirmed by cyclic voltammetry, CO-adsorption stripping voltammetry, and linear sweep voltammetry. Both XAS and electrochemical investigations concluded that the PtRu/C-H2-350 sample exhibits significant enhancement in reactivity toward methanol oxidation as a result of the increased surface population of the Pt when compared to the PtRu/C-O2-300 and PtRu/C as-reduced samples.

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“…Both the pore volume and the pore size of the zeolite are smaller than the alumina sample. The presence of Pt partially reduces the sites, responsible for coking [19] for their masking with the metal particles Pt; hence, the activity of the catalyst persists over a long period.…”

Section: Preparation Of Zeolite Usymentioning

confidence: 99%

Catalytic Activity of a Bifunctional Catalyst for Hydrotreatment of Jatropha curcas L. Seed Oil

García-Dávila

Ocaranza‐Sánchez

Sánchez

et al. 2018

Journal of Spectroscopy

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The hydrotreating process of vegetable oils (HPVO) involves the transformation of vegetable oil triglycerides into straight chain alkanes, which are carried out by deoxygenation reactions, generating multiple hydrocarbon compounds, cuts similar to heavy vacuum oil. The HPVO is applied to Jatropha curcas oil on USY zeolite supported with gamma alumina and platinum deposition on the catalytic as hydrogenation component. The acid of additional activity of the supports allows the development of catalytic routes that the intervention of catalytic centers of different nature reaches the desired product. The products of the hydrotreating reaction with Jatropha curcas seed oil triglycerides were identified by Fourier transform infrared spectroscopy and by mass spectroscopy to identify and analyze the generated intermediate and final hydrocarbon compounds.

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Structure and Size of Bimetallic Palladium-Platinum Clusters in an Hydrotreatment

Cited by 38 publications

References 49 publications

n-Hexane conversion on γ-alumina supported palladium–platinum catalysts

n-Hexane conversion on γ-alumina supported palladium–platinum catalysts

Heat‐Induced Alterations in the Surface Population of Metal Sites in Bimetallic Nanoparticles

Catalytic Activity of a Bifunctional Catalyst for Hydrotreatment of Jatropha curcas L. Seed Oil

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