Synthesis of Pd/SiO2, Ag/SiO2, and Cu/SiO2 cogelled xerogel catalysts: study of metal dispersion and catalytic activity

Lambert, Stéphanie D.; Cellier, Caroline; Grange, Paul; Pirard, Jean‐Paul; Heinrichs, Benoı̂t

doi:10.1016/j.jcat.2003.07.014

Cited by 96 publications

(99 citation statements)

References 31 publications

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“…Furthermore, the sol-gel method permits metal-supported catalysts synthesis in one step that means that the dispersion of metal precursors takes place during the support synthesis by sol-gel. Other than the convenience of saving a step, one step sol-gel method may also introduce unique metal-oxide interactions [13] or oxide-oxide interactions [14] that are inaccessible with other preparative methods.…”

Section: Introductionmentioning

confidence: 99%

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Kim

Heinrichs

Colomer

et al. 2007

Applied Catalysis A: General

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The production of carbon nanotubes by the chemical catalytic vapour deposition, CCVD, process was examined over iron, cobalt, and a mixture of iron and cobalt supported on alumina catalysts synthesized by a one step sol-gel process. The catalysts were synthesized from several metal precursors, iron nitrate, cobalt and iron acetylacetonate, and cobalt acetate. Ethylene was used as the carbon source.The Co/Al 2 O 3 catalysts showed better activity and selectivity in carbon nanotubes synthesis than Fe/Al 2 O 3 and Fe-Co/Al 2 O 3 catalysts. The carbon deposit was found by TEM analysis to be rich in carbon nanotubes in the case of Co/Al 2 O 3 but to be very poor in the case of the Fe-Co/ Al 2 O 3 catalysts. The catalysts were characterized by TEM, XRD, and nitrogen adsorption. It was shown that iron and cobalt are in oxide form. Metal-support interactions and metal oxide particle size are influenced by the nature of the precursor and this nature is an important factor for the activity and selectivity of the catalysts. Moreover, a correlation has been found between the metal oxide particle sizes, the diameter of the carbon nanotubes, and the catalytic activity. #

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Section: Introductionmentioning

confidence: 99%

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Kim

Heinrichs

Colomer

et al. 2007

Applied Catalysis A: General

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“…[19] To determine the TOF value, the number of surface sites for Au/C was estimated from the TEM-determined metal particle size, for Pd/C, Pt/C, Ir/C, Rh/C, and Ru/C the number of surface sites was measured by CO adsorption at 298 K, and for Ag/C the number of surface sites was determined by O 2 adsorption at 423 K as is established elsewhere. [22] The metal dispersion (the number of surface metal atoms normalized by the total number of metal atoms) is 0.12 for Au/ C, 0.39 for Pt/C, 0.23 for Pd/C, 0.13 for Ir/C, 0.18 for Rh/C, 0.55 for Ru/C, and 0.09 for Ag/C.…”

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confidence: 99%

Preferential Oxidation of CO in H₂ by Aqueous Polyoxometalates over Metal Catalysts

et al. 2005

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Production of H 2 for fuel cells is usually accomplished by a multistep process, which starts with catalytic reforming of hydrocarbons [1] or oxygenated hydrocarbons over metal catalysts [2,3] to produce a mixture of H 2 , CO, and CO 2 . These reformate gases are subsequently treated by several steps, such as water-gas shift (WGS) (CO + H 2 O!CO 2 + H 2 ) [4,5] and preferential oxidation of CO in the H 2 -rich gas stream (PROX; CO + 1/2 O 2 !CO 2 ), [6,7] for applications involving proton-exchange membrane (PEM) fuel cells, this oxidation of CO is necessary owing to the strong poisoning effects of CO on Pt-based anodes.[8] While these methods for removing CO from H 2 gas stream are well established, they suffer from several limitations. For example, the WGS reaction is slow at the low temperatures (e.g., 500 K) required to achieve favorable thermodynamics for this reaction, [9] and PROX requires the injection of O 2 (or air) into the H 2 gas stream and consumes a fraction of the H 2 as well. Moreover, these processes for CO conversion often involve the use of platinum or platinum-alloy catalysts, which are expensive and compete with fuel-cell electrodes for the limited supply of this precious metal, compared with the abundant holdings of gold in the world.[10]Recently, we reported the discovery of a room-temperature process for production of electrical energy using a fuel cell containing a carbon anode and operating with an aqueous solution of a polyoxometalate (POM) compound that had been reduced with pure CO over gold-nanotube catalysts. [11] This process for the oxidation and utilization of CO involves the reaction of CO and liquid water with a reducible POM, such as [H 3 PMo 12 O 40 ], which serves as an oxidizing agent for reaction of CO with liquid water and as an energy-storage agent for electrons; the process takes advantage of the high catalytic activities of gold for CO oxidation, [12][13][14] especially in the presence of liquid water, as shown experimentally using gold-nanotube membrane catalysts [15] and as predicted by density functional theory calculations. [16,17] A representative

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“…The reaction rates (r) were calculated from chromatographic measurements of C 2 H 6 , C 2 H 5 Cl and C 2 H 4 concentrations in the reactor effluent and from the differential reactor equation that can be written as follows [13,19]:…”

Section: Catalytic Testsmentioning

confidence: 99%

“…This synthesis method consists in co-gelation of tetraethylorthosilicate TEOS with additives with functional groups of the form (RO) 3 Si-X-A, in which A is a functional organic group able to form a chelate with a metal cation and X is an inert hydrolytically stable spacer, which links A to the hydrolysable group (RO) 3 Si-. These additives enable to introduce the metal directly during the synthesis of the catalytic support rather than dispersing the active component on a previously synthesised support [7][8][9][10][11][12][13][14]. The co-condensation of TEOS with such molecules results in materials in which the catalytic metal is anchored to the SiO 2 matrix.…”

Section: Introductionmentioning

confidence: 99%

Pd–Ag/SiO2 xerogel catalyst forming by impregnation on alumina foams

Alié

Ferauche

Léonard

et al. 2006

Chemical Engineering Journal

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A Pd-Ag/SiO 2 xerogel catalyst prepared in one step by sol-gel process has been entrapped in cylindrical porous alumina foams of three different pore sizes in order to shape the catalyst under the appropriate form with suitable mechanical resistance to be used in an industrial fixed bed reactor. After drying, calcination and reduction, the Pd-Ag/SiO 2 xerogel catalyst pellets are immobilized inside the open porosity of the alumina foam. The localization of the xerogel catalyst in the alumina foams has been studied by X-ray tomography. The threedimensional porous structure was reconstructed from the consecutive cross-sections obtained by this technique. This method shows that the Pd-Ag/SiO 2 xerogel catalyst is uniformly dispersed inside the porosity of the alumina foams. Activity and selectivity of Pd-Ag/SiO 2 xerogel catalyst reference or catalyst entrapped in alumina foams have been studied for selective hydrodechlorination of 1,2-dichloroethane into ethylene. The specific reaction rate obtained with catalyst entrapped in alumina foams is smaller than the one obtained from corresponding catalyst powders. The catalytic activity decrease observed for Pd-Ag/SiO 2 xerogel catalyst entrapped in porous alumina foams most probably arises from diffusional limitations inside the porous texture of the alumina foams.

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Synthesis of Pd/SiO2, Ag/SiO2, and Cu/SiO2 cogelled xerogel catalysts: study of metal dispersion and catalytic activity

Cited by 96 publications

References 31 publications

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Preferential Oxidation of CO in H₂ by Aqueous Polyoxometalates over Metal Catalysts

Pd–Ag/SiO2 xerogel catalyst forming by impregnation on alumina foams

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Synthesis of Pd/SiO2, Ag/SiO2, and Cu/SiO2 cogelled xerogel catalysts: study of metal dispersion and catalytic activity

Cited by 96 publications

References 31 publications

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Carbon nanotubes synthesis by the ethylene chemical catalytic vapour deposition (CCVD) process on Fe, Co, and Fe–Co/Al2O3 sol–gel catalysts

Preferential Oxidation of CO in H2 by Aqueous Polyoxometalates over Metal Catalysts

Pd–Ag/SiO2 xerogel catalyst forming by impregnation on alumina foams

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Preferential Oxidation of CO in H₂ by Aqueous Polyoxometalates over Metal Catalysts