Metal nanoparticles have attracted much attention over the last decade owing to their unique properties as compared to their bulk metal equivalents, including a large surface-to-volume ratio and tunable shapes. To control the properties of nanoparticles with particular respect to shape, size and dispersity is imperative, as these will determine the activity in the desired application. Supported metal nanoparticles are widely employed in catalysis. Recent advances in controlling the shape and size of nanoparticles have opened the possibility to optimise the particle geometry for enhanced catalytic activity, providing the optimum size and surface properties for specific applications. This Review describes the state of the art with respect to the preparation and use of supported metal nanoparticles in catalysis. The main groups of such nanoparticles (noble and transition metal nanoparticles) are highlighted and future prospects are discussed.

Sustainable Preparation of Supported Metal Nanoparticles and Their Applications in Catalysis

Organic reactions catalyzed over solid acids

Catalytic dehydration of methanol to dimethyl ether (dme) over solid-acid catalysts

Direct hydrocyclization of biomass-derived levulinic acid to 2-methyltetrahydrofuran over nanocomposite copper/silica catalysts.

The effect of micro and nano particle sizes of H-ZSM-5 on the selectivity of MTP reaction

Conversion of alcohols (α-methylated series) on AlPO4 catalysts

N-Alkylation of Aniline with Methanol over CrPO4and CrPO4–AlPO4(5–50 wt% AlPO4) Catalysts

Amorphous AlPO 4 Al 2 O 3 (5–25 wt% Al 2 O 3 , APAl-A) systems were selective catalysts for the N -alkylation of aniline with methanol. The methylation reaction (that was carried out in a continuous down-flow reactor operating at atmospheric pressure, 523 K and aniline feed rates over 3 × 10 −6 mol s −1 ) is a pseudo-first order process with respect to aniline concentration, taking place through consecutive formation of N -methyl and N,N -methylanilines. Also, there is always more N -methylaniline (NMA) than N,N -dimethylaniline (NNDMA). Increasing reaction temperature enhances the selectivity of NNDMA. AlPO 4 and Al 2 O 3 are slightly active, but AlPO 4 Al 2 O 3 catalysts exhibit significantly higher activity (an order of magnitude more active) and, besides, there is a slight increase in activity on increasing Al 2 O 3 loading up to 15 wt%, thereby showing that APAl-A catalysts are suitable for selective obtaining N -alkylation products. The effect of surface acidity on aniline alkylation activity is discussed. Strong acid sites are not required for the N -methylation of aniline, whereas, weak to moderate acid sites seem to be responsible for this reaction. Furthermore, there is no catalyst deactivation by coke deposition, whereas, the addition of pyridine or 2,6-dimethylpyridine deactivate the catalyst.

N-Alkylation of aniline with methanol over AlPO4Al2O3 catalysts

The role of Cu in Sepiolite-supported bimetallic NiCu catalysts has been evaluated through the results obtained in a kinetic study on the influence of temperature in the consecutive hydrogenation of ethyl linolate to ethyl oleate and ethyl stearate, respectively. Liquid-phase hydrogenation reactions (individual and consecutive) were carried out under hydrogen pressure of 0.41 MPa in a temperature range between 305 and 337 K. Thus, the relative reactivities of linoleic and oleic ethyl esters, R L,O , as well as the corresponding relative adsorption constants, K L,O , were obtained at all temperatures studied. According to the results, in both of the Sepiolite supported catalysts studied, selectivity values steadily increased with temperature in the interval studied. Besides, R L,O and K L,O exhibited an Arrhenius type law with temperature that enabled us to obtain several kinetic parameters affecting the selectivity of the consecutive hydrogenation process and closely related to the electronic density of supported nickel which is modified by NiCu alloying.

Influence of NiCu alloying on Sepiolite-supported nickel catalysts in the liquid-phase selective hydrogenation of fatty acid ethyl esters

Different synthetic AlPO4 systems are effective yet mild acid catalysts for the heterogeneous cycloaddition reaction of cyclopentadiene with (-)-menthyl acrylate. The reaction proceeds selectively under mild conditions and in a relatively short reaction time with an almost total conversion, a high endo/exo ratio, and a reasonable asymmetric induction. When the reactions are carried out without solvent, some correlations are obtained between the number of acid sites, titrated with pyridine, and reaction yields, endo/exo and diastereofacial selectivities. The positive influence of surface area of catalysts is also determined. However, the lack of good correlations between reaction results and surface properties of the catalysts indicates the influence of some other factors.

A. Garcia

Papers

Conversion of alcohols (α-methylated series) on AlPO4 catalysts

N-Alkylation of Aniline with Methanol over CrPO4and CrPO4–AlPO4(5–50 wt% AlPO4) Catalysts

N-Alkylation of aniline with methanol over AlPO4Al2O3 catalysts

Influence of NiCu alloying on Sepiolite-supported nickel catalysts in the liquid-phase selective hydrogenation of fatty acid ethyl esters

AlPO4catalyzed Diels-Alder reaction of cyclopentadiene with (-)-menthyl acrylate. Influence of catalyst surface properties