Characterization of Pd–Au/SiO2 Catalysts by X-ray Diffraction, Temperature-Programmed Hydride Decomposition, and Catalytic Probes

Bonarowska, Magdalena; Pielaszek, J.; Juszczyk, W.; Karpiński, Zbigniew

doi:10.1006/jcat.2000.2989

Cited by 104 publications

(70 citation statements)

References 31 publications

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“…[4] Most reports on bimetallic Pd catalysts refer to systems prepared by means of a co-impregnation of the metal salts on solid supports using an incipient wetness technique followed by calcination. [25][26][27][28][29] However, by using the usual preparation procedures some metal sintering and segregation of the surface is evident. [28,30,31] Reduction at high temperature in molecular dihydrogen and interaction of these metals with the support favor this process.…”

Section: Introductionmentioning

confidence: 97%

Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Pârvulescu

Endruschat

et al. 2006

Chemistry A European J

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Colloids embedded in a silica sol-gel matrix were prepared by using fully alloyed Pd-Au colloids, and pure Pd and Au colloids stabilized with tetraalkylammonium bromide following a modified sol-gel procedure with tetrahydrofuran (THF) as the solvent. Tetraethoxysilicate (TEOS) was used as the precursor for the silica support. The molar composition of the sol was TEOS/THF/H2O/HCl = 1:3.5:4:0.05 for the bimetallic Pd-Au and TEOS/THF/H2O/HCl = 1:4.5:4:0.02 for Pd and Au monometallic systems. After refluxing, the colloid was added as a 4.5 wt % solution in THF for Pd-Au, 10.2 wt % solution in THF for Pd and 8.4 wt % solution in THF for Au at room temperature. The gelation was carried out with vigorous stirring (4 days) under an Ar atmosphere. Following these procedures, bimetallic Pd-Au-SiO2 catalysts with 0.6 and 1 wt % metal, and monometallic Pd- and Au-SiO2 catalysts with 1 wt % metal were prepared. These materials were further treated following four different routes: 1) by simple drying, 2) in which the dried catalysts were calcined in air at 723 K and then reduced at the same temperature, 3) in which they were directly reduced in hydrogen at 723 K, and 4) in which the surfactant was extracted using an ethanol-heptane azeotropic mixture. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption measurements, solid-state 1H, 13C, 29Si-CP/MAS-NMR spectroscopy, powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and 197Au Mössbauer spectroscopy. The physical characterization by a combination of these techniques has shown that the size and the structural characteristics of the Pd-Au colloid precursor are preserved when embedded in an SiO2 matrix. Catalytic tests were carried out in selective hydrogenation of 3-hexyn-1-ol, cinnamaldehyde, and styrene. These data showed evidence that alloying Pd with Au in bimetallic colloids leads to enhanced activity and most importantly to improved selectivity. Also, the combination of the two metals resulted in catalysts that were very stable against poisoning, as was evidenced for the hydrogenation of styrene in the presence of thiophene.

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Section: Introductionmentioning

confidence: 97%

Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Pârvulescu

Endruschat

et al. 2006

Chemistry A European J

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“…Based on the literature data and our earlier experience concerning the formation and decomposition of β-PdH phase [15,[18][19][20][21][22][23][24], the position, shape (width, distortion), and intensity of a TPHD peak depend on different variables, among which Pd dispersion, type of support, and modifying additives play a dominant role. The introduction of gold to the palladium lattice brings about a more-or-less serious decrease in hydrogen dissolution (i.e., a lower H/Pd ratio in respective hydride phase).…”

Section: Resultsmentioning

confidence: 99%

“…The differences between the position, shape (width, distortion), and intensity of a TPHD peak for two palladium catalysts could be explained by different Pd dispersion in both samples. Based on the literature data concerning the distinct relationship between the palladium dispersion and the stability of a hydride phase [8,15], it seems possible that the TPHD maximum shift toward higher temperatures for the Pd-Imp-MW catalyst results from presence of [ 1.6 times bigger palladium nanoparticles in Pd-Imp-MW than in the case of the palladium catalyst reduced by conventional method ( Table 2). …”

Section: Resultsmentioning

confidence: 99%

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Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

Bonarowska

Zieliński

Matus

et al. 2018

Reac Kinet Mech Cat

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This work investigates the influence of activation by microwave irradiation on the catalytic properties of Pd-Au/C Sibunit catalysts in the hydrodechlorination of CCl 4 . Pd and Pd-Au samples were thoroughly characterized by CO chemisorption, X-ray diffraction, TPHD and STEM, and used in gas phase hydrodechlorination of tetrachloromethane. The studies showed that homogenous Pd-Au alloys are formed more efficiently if short-time microwave activation is applied instead of conventional activation by H 2 reduction at 380°C. These catalysts show higher activity, stability and higher selectivity towards the desired products (C1-C5 hydrocarbons) than the catalysts activated by conventional reduction in 10%H 2 /Ar flow.

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“…They can be used as such as homogeneous catalysts, or as heterogeneous catalysts if they are first deposited onto asupport and then activated to produce supported nanoparticles. In the latter area, the use of Au-Pd mixed metal clusters as precursors for mixed-metal nanoparticles is of particular interest because of the number of catalysed reactions by this alloy [6][7][8][9]. Nevertheless, only fifteen Au-Pd clusters were fully characterized, what is relatively poor compared to the Au-Pt analogues [10].…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of nonacarbonylhexakis(triphenylphosphane)- nonapalladiumgold hexafluoridophosphate, [Pd9Au(CO)9(PPh3)6](PF6)

Willocq¹,

Hermans²,

Devillers³

et al. 2008

Zeitschrift Für Kristallographie - New Crystal Structures

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C 129 H 114 AuF 6 O 12 P 7 Pd 9 ,trigonal, R3 (no. 148), a =22.520(4) Å, c =39.433(7) Å, V =17319 Å 3 , Z =6, R gt(F) =0.047, wRref(F 2 ) =0.129, T =120 K. Source of materialSuitable crystals for X-ray diffraction analysis were obtained from the crude product resulting of the reaction of [Pd 3(CO)3(P-tBu 3)3]with [Au(PPh3)Cl] in presence of TlPF6.The crystals were grown by slow diffusion of diethylether in aCH 2 Cl 2 solution under carbon monoxide atmosphere at 4°C. Experimental detailsThe data were not corrected for absorption, but the data collection mode with high redundancy, partially takes the absorption phenomena into account (62 images, DF =2°, 29272 reflections measured for 7791 independent reflections). The PF 6 anion is disordered with aP-F bond on 3 axis. The solvent molecule is also disordered, the ring atoms were refined isotropically and constraints on bond lengths were applied. All the Hatoms were calculated with AFIX and included in the refinement with acommon isotropic temperature factor (U iso =0.065 Å 2 ). The Hatoms of the solvent molecules were not localized. DiscussionMolecular clusters are fascinating compounds of nanometrical size, comprising several metal atoms (from three to afew hundreds) surrounded by aligand shell, with potential applications in the nano field [1] and also in catalysis [2][3][4][5]. They can be used as such as homogeneous catalysts, or as heterogeneous catalysts if they are first deposited onto asupport and then activated to produce supported nanoparticles. In the latter area, the use of Au-Pd mixed metal clusters as precursors for mixed-metal nanoparticles is of particular interest because of the number of catalysed reactions by this alloy [6][7][8][9]. Nevertheless, only fifteen Au-Pd clusters were fully characterized, what is relatively poor compared to the Au-Pt analogues [10]. Thus, succeeding in obtaining the X-ray structure of such entities remains achallenge. In our attempts to synthesize Au-Pd clusters from homonuclear palladium clusters, the compound [Pd9Au(CO)9(PPh3)6](PF6)was obtained in very low yield. The synthesis of this cluster was based on the known preparation of [Pd14Au2(CO)9(PMe3)11](PF6)2 obtained by reacting [Pd8(CO)8(PMe3)7]w ith [Au(PCy 3 )Cl] in the presence of TlPF6 [11]. The cluster [Pd 9 Au(CO) 9 (PPh 3 ) 6 ](PF 6 )c rystallizes with three molecules of tetrahydrofuran by molecule of cluster (this solvent was used in the work-up of the reaction to obtain the crude product before crystallization). The structure of the metallic core of this cluster can be viewed as an octahedron of palladium atoms in which each bond of one triangular face is bridged by an additional Pd atom, the same face being also capped by the gold atom. Six terminally bounded PPh3 are observed with six bridging (m 2 )and three capping (m3)CO. The Pd-Au distance is 2.8369(7) Å.Due to the position of the gold atom, the Pd-Pd distances of the capped triangular face aree longated compared to the other Pd-Pdbonds of the octahedron (3.0917(9) Å vs. 2.750 Å (average)). ...

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Characterization of Pd–Au/SiO2 Catalysts by X-ray Diffraction, Temperature-Programmed Hydride Decomposition, and Catalytic Probes

Cited by 104 publications

References 31 publications

Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

Crystal structure of nonacarbonylhexakis(triphenylphosphane)- nonapalladiumgold hexafluoridophosphate, [Pd9Au(CO)9(PPh3)6](PF6)

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Characterization of Pd–Au/SiO2 Catalysts by X-ray Diffraction, Temperature-Programmed Hydride Decomposition, and Catalytic Probes

Cited by 104 publications

References 31 publications

Characterization and Catalytic‐Hydrogenation Behavior of SiO2‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Characterization and Catalytic‐Hydrogenation Behavior of SiO2‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

Crystal structure of nonacarbonylhexakis(triphenylphosphane)- nonapalladiumgold hexafluoridophosphate, [Pd9Au(CO)9(PPh3)6](PF6)

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Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids

Characterization and Catalytic‐Hydrogenation Behavior of SiO₂‐Embedded Nanoscopic Pd, Au, and Pd–Au Alloy Colloids