Ionic liquids as recycling solvents for the synthesis of magnetic nanoparticles

This work describes an easy synthesis (one pot) of MFe(2)O(4) (M = Co, Fe, Mn, and Ni) magnetic nanoparticles MNPs by the thermal decomposition of Fe(Acac)(3)/M(Acac)(2) by using BMI center dot NTf(2) (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) or BMI center dot PF(6) (1-n-butyl-3-methylimidazolium hexafluorophosphate) ionic liquids (ILs) as recycling solvents and oleylamine as the reducing and surface modifier agent. The effects of reaction temperature and reaction time on the features of the magnetic nanomaterials (size and magnetic properties) were investigated. The growth of the MNPs is easily controlled in the IL by adjusting the reaction temperature and time, as inferred from Fe(3)O(4) MNPs obtained at 150 degrees C, 200 degrees C and 250 degrees C with mean diameters of 8, 10 and 15 nm, respectively. However, the thermal decomposition of Fe(Acac)(3) performed in a conventional high boiling point solvent (diphenyl ether, bp 259 degrees C), under a similar Fe to oleylamine molar ratio used in the IL synthesis, does not follow the same growth mechanism and rendered only smaller NPs of 5 nm mean diameter. All MNPs are covered by at least one monolayer of oleylamine making them readily dispersible in non-polar solvents. Besides the influence on the nanoparticles growth, which is important for the preparation of highly crystalline MNPs, the IL was easily recycled and has been used in at least 20 successive syntheses.

On the catalytic hydrogenation of polycyclic aromatic hydrocarbons into less toxic compounds by a facile recoverable catalyst

Here we present the catalytic hydrogenation of polycyclic aromatic hydrocarbons (PAHs) to less toxic mixtures of saturated and partial unsaturated polycyclic hydrocarbons under mild reaction conditions using a magnetically recoverable rhodium catalyst and molecular hydrogen as the exclusive H source. The catalyst is easily recovered after each reaction by placing a permanent magnet on the reactor wall and it can be reused in successive runs without any significant loss of catalytic activity. As an example, anthracene was totally converted into the saturated polycyclic hydrocarbon form (ca. 60%) and the partially hydrogenated form, 1,2,3,4,5,6,7,8-octahydroanthracene (ca. 40%). The catalyst operates in a broad range of temperature and H(2) pressure in both organic and aqueous/organic solutions of anthracene and it also exhibits significant activity at low substrate concentrations (20 ppm). This can be an efficient recycling process for hydrogenation of PAHs present in contaminated fluid waste streams. (C) 2009 Elsevier B.V. All rights reserved.

Preparation of recoverable Ru catalysts for liquid-phase oxidation and hydrogenation reactions

We here report the synthesis, characterization and catalytic performance of new supported Ru(III) and Ru(0) catalysts. In contrast to most supported catalysts, these new developed catalysts for oxidation and hydrogenation reactions were prepared using nearly the same synthetic strategy, and are easily recovered by magnetic separation from liquid phase reactions. The catalysts were found to be active in both forms, Ru(III) and Ru(0), for selective oxidation of alcohols and hydrogenation of olefins, respectively. The catalysts operate under mild conditions to activate molecular oxygen or molecular hydrogen to perform clean conversion of selected substrates. Aryl and alkyl alcohols were converted to aldehydes under mild conditions, with negligible metal leaching. If the metal is properly reduced, Ru(0) nanoparticles immobilized on the magnetic support surface are obtained, and the catalyst becomes active for hydrogenation reactions. (c) 2009 Elsevier B.V. All rights reserved.

Ligand-Assisted Preparation of Palladium Supported Nanoparticles: a Step toward Size Control

Supported nanoparticles (SNPs) with narrow size distribution were prepared by H(2) reduction of Pd(2+) previously bound, to ligand-modified silica surfaces. Interestingly, the size of the Pd SNPs was tuned by the ligand grafted on the support surface. Amino- and ethylenediamino-functionalized supports formed Pd(0) SNPs of ca. 6 and 1 nm, respectively. The catalytic properties of both Pd(0) SNPs were investigated.