A Review of Preparation Methods for Supported Metal Catalysts

Mehrabadi, Bahareh Alsadat Tavakoli; Eskandari, Sonia; Khan, Umema; White, Rosemary E.; Regalbuto, John R.

doi:10.1016/bs.acat.2017.10.001

Cited by 150 publications

(108 citation statements)

References 46 publications

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“…Knowledge of the nanoscale processes involved in such syntheses is incomplete, limiting thus our ability to control the catalyst structure [4]. Despite the massive body of work on catalyst synthesis and a large variety of preparation methods, this lack of fundamental knowledge results in catalyst preparation often being considered more of an art rather than a science [30]. Furthermore, stability of catalysts in liquid phase reactions, in particular for biomass conversion [31,32], is highly important, but still poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Assessment of oxide nanoparticle stability in liquid phase transmission electron microscopy

2019

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Studying liquid phase nanoscale dynamic processes of oxide nanoparticles is of considerable interest to a wide variety of fields. Recently developed liquid phase transmission electron microscopy (LP-TEM) is a promising technique, but destabilization of oxides by solid-liquidelectron interactions remains an important challenge. In this work we present a methodology to assess LP-TEM oxide stability in an aqueous phase, by subjecting several oxides of technological importance to a controlled electron dose in water. We show a correlation based on the Gibbs free energy of oxide hydration that can be used to assess the stability of oxides and demonstrate the existence of several remarkably stable oxides, with no observable structural changes after one hour of electron beam irradiation in LP-TEM. Rationalizing such destabilization phenomena combined with the identification of stable oxides allows for designing LP-TEM experiments free from adverse beam effects and thus investigations of numerous relevant nanoscale processes in water.

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Section: Introductionmentioning

confidence: 99%

Assessment of oxide nanoparticle stability in liquid phase transmission electron microscopy

2019

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“…The negatively charged [Au(OH) 4 ] À species are unlikely to deposit on either TiO 2 or SiO 2 surface via the strong electrostatic mechanism. [19] Therefore, Au precursor is believed to be randomly deposited on the TS-1 surface without a preferential adsorption site.…”

Section: Resultsmentioning

confidence: 99%

Gold Catalysts Synthesized Using a Modified Incipient Wetness Impregnation Method for Propylene Epoxidation

et al. 2020

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Propylene epoxidation in the presence of oxygen and hydrogen were measured for a series of Au/TS-1 catalysts prepared by a modified incipient wetness impregnation (mIWI) method. This method enables precise control of the Au : Ti ratio in the Au/TS-1 catalysts. The optimized Au/TS-1 catalyst exhibited 12 % propylene conversion, 87 % PO selectivity, and 25 % hydrogen efficiency. The particle size of gold nanoparticles prepared by the modified IWI was between 2 and 3 nm, as demonstrated by XRD patterns, STEM images, and X-ray absorption spectroscopy at the Au L 3 edge. XPS spectra showed that the surface species on the catalysts were similar. UV-Vis spectra suggested that in the modified IWI method, the chlorine ligands in Au(Cl) 4 À were replaced by hydroxyl groups, which contributes to form small gold nanoparticles. Kinetic studies showed that the active sites of Au(mIWI)/TS-1 are similar to the Au(DP)/TS-1 prepared by deposition precipitation.

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“…Accomplishing the synthesis of stable QSMNPs on dielectric nanospheres can benet from the positive knowledge in the vast literature that reported the use of the impregnation method for the synthesis of metal/oxide composite nanoparticles. [82][83][84] It is worth pointing out that the crystalline type (e.g., terraces, edges, corners, steps, kinks, twin boundaries, and vacancies) and oxidation state of surface metal atoms of QSMNPs may vary under the reaction conditions to inuence their catalytic activity. 85,86 The inuence can be either positive or negative toward the promotion of catalytic activity, which adds one more dimension of complexity of designing/synthesizing stable and efficient QSMNP photocatalysts.…”

Section: Remarks and Perspectivesmentioning

confidence: 99%