Sol immobilization technique: a delicate balance between activity, selectivity and stability of gold catalysts

Villa, Alberto; Wang, Di; Veith, Gabriel M.; Vindigni, Floriana; Prati, Laura

doi:10.1039/c3cy00260h

Cited by 115 publications

(127 citation statements)

References 25 publications

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“…Post-synthesis treatments were also applied to remove the residual PVA. Lower activity of Au/TiO 2 catalysts in the presence of PVA resulting from the formation of core-shell structures was reported by Villa et al [42]. Indeed, as described in their work, the maximum catalytic activity was reached for the catalysts calcined at 250-350 • C. A higher temperature permits to remove more PVA from the catalyst surface.…”

Section: Supported Au-based Catalystsmentioning

confidence: 63%

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

et al. 2017

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Abstract:The oxidation of bio-based molecules in general, and of carbohydrates and furanics in particular, is a highly attractive process. The catalytic conversion of renewable compounds is of high importance. Acids and other chemical intermediates issued from oxidation processes have many applications related, especially, to food and detergents, as well as to pharmaceutics, cosmetics, and the chemical industry. Until now, the oxidation of sugars, furfural, or 5-hydroxymethylfurfural has been mainly conducted through biochemical processes or with strong inorganic oxidants. The use of these processes very often presents many disadvantages, especially regarding products separation and selectivity control. Generally, the oxidation is performed in batch conditions using an appropriate catalyst and a basic aqueous solution (pH 7-9), while bubbling oxygen or air through the slurry. However, there is a renewed interest in working in base-free conditions to avoid the production of salts. Actually, this gives direct access to different acids or diacids without laborious product purification steps. This review focuses on processes applying gold-based catalysts, and on the catalytic properties of these systems in the base-free oxidation of important compounds: C5-C6 sugars, furfural, and 5-hydroxymethylfurfural. A better understanding of the chemical and physical properties of the catalysts and of the operating conditions applied in the oxidation reactions is essential. For this reason, in this review we put emphasis on these most impacting factors.

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Section: Supported Au-based Catalystsmentioning

confidence: 63%

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

et al. 2017

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“…By using a similar procedure and by monitoring the protecting agent removal by IR spectroscopy, Villa et al [65] demonstrated that the relative amount of residual protecting agent represents a key factor in determining the catalytic performances of Au/TiO 2 catalysts. Indeed, washing with water at 298 K yields just a partial removal of the capping agent (PVA), as confirmed by IR spectra and HRTEM images ( Figure 5).…”

Section: Shielding Effect and Selective Blockingmentioning

confidence: 99%

“…Recently, a drop in the activity due to the PVA shielding effect has been reported for supported gold catalyst in glycerol oxidation [65].…”

Section: Shielding Effect and Selective Blockingmentioning

confidence: 99%

“…Analogously, diphenyl sulphide ligands on Pd/TiO 2 surface generate an appropriate ensemble which accommodates alkynes, but prevents the adsorption of alkenes, thus promoting the selective hydrogenation of acetylene to ethylene [81]. Residual PVA on TiO 2 -supported Au NPs results in a porous-like structure in which the OH groups of PVA interact with the analogous groups of glycerol [65]. The adsorption of the reactant is therefore directed on the active site leading to a modification of the selectivity of in glycerol oxidation.…”

Section: Steric Effects and Surface Crowdingmentioning

confidence: 99%

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Untangling the Role of the Capping Agent in Nanocatalysis: Recent Advances and Perspectives

et al. 2016

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Capping agents (organic ligands, polymers, surfactants, etc.) are a basic component in the synthesis of metal nanoparticles with controlled size and well-defined shape. However, their influence on the performances of nanoparticle-based catalysts is multifaceted and controversial. Indeed, capping agent can act as a "poison", limiting the accessibility of active sites, as well as a "promoter", producing improved yields and unpredicted selectivity control. These effects can be ascribed to the creation of a metal-ligand interphase, whose unique properties are responsible for the catalytic behavior. Therefore, understanding the structure of this interphase is of prime interest for the optimization of tailored nanocatalyst design. This review provides an overview of the interfacial key features affecting the catalytic performances and details a selection of related literature examples. Furthermore, we highlight critical points necessary for the design of highly selective and active catalysts with surface and interphase control.

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“…In the case of liquid phase reaction, the density of SA must be controlled, and the presence of SA can even play a positive role in activity, selectivity and stability; for instance PVA-stabilized Au on SiO 2 showed a positive influence on the activity of glycerol oxidation and selectivity [52]. The removal of SA is a critical step because particles may sinter, and stabilizer residues may poison the catalyst [53].…”

Section: Reduction-deposition (Deposition Of Preformed Metal Nanopartmentioning

confidence: 99%

Chemical Preparation of Supported Bimetallic Catalysts. Gold-Based Bimetallic, a Case Study

Louis

2016

Catalysts

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This review focuses on the chemical methods used to prepare supported bimetallic heterogeneous catalysts, i.e., bimetallic nanoparticles deposited on a support. The review is limited to the preparation of gold-based bimetallic catalysts and moreover to bimetallic nanoparticles supported on powder inorganic supports, i.e., on the surface or in the porosity, and not on model supports such as single crystals.

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Sol immobilization technique: a delicate balance between activity, selectivity and stability of gold catalysts

Cited by 115 publications

References 25 publications

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

Untangling the Role of the Capping Agent in Nanocatalysis: Recent Advances and Perspectives

Chemical Preparation of Supported Bimetallic Catalysts. Gold-Based Bimetallic, a Case Study

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