METAL NANOPARTICLES



Over the last decade, our group has been interested in the use metal nanoparticles (NPs) as novel catalysts that can be considered at the interface of classical homogeneous and heterogeneous catalysts. With the aim of designing new selective nanocatalysts, we have been working on the stabilization of these nanostructures using modular phosphorus ligands to search for structure-reactivity relationships. Recently, our group has also been involved in a study on metal nanoparticles as catalysts in the aqueous Fischer-Tropsch synthesis for the production of clean synthetic fuels.


LIGAND STABILIZED TRANSITION METAL NANOPARTICLES


As in homogeneous catalysis, the ligand structure was shown to influence the size and shape of the nanoparticles. The design of specific ligands for NP stabilization is therefore of interest.
For instance, as the presence of a long alkyl chain in the stabilizing agent was shown to lead to the formation of smaller metallic nanoparticles, we synthesized a series of chiral backbones/ligands presenting such features.


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HYDROGENATION PROCESSES

Ligand effect in the Rh-NP catalysed partial hydrogenation of substituted arenes

Catalysis Science and Technology, 2013, 3, 2828- 2833

J. Llop Castelbou, A. Gual, E. Mercadé, C. Claver and C. Godard

 

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The hydrogenation of substituted arenes such as styrene, xylenes and methylanisoles was investigated using soluble Rh-NPs as catalysts, and results showed relevant differences in activity and selectivity depending on the properties of the NP-stabilising P-ligand used.

 

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For instance, large differences in activity and selectivity were observed for Rh1 and Rh2, stabilised by triphenylphosphine I and triphenylphosphite II, respectively.
The presence of the P-ligand was shown to be critical: the THF/MeOH-stabilised Rh5 was inactive in the hydrogenation of xylenes, although hydrogenation of both the aromatic ring and the vinylic group of styrene were observed. In the case of disubstituted arene substrates, selectivities for the corresponding cyclohexene derivatives of up to 39% were achieved at ca. 40% conversion. The effect of parameters such as temperature and pressure was also examined. In the hydrogenation of styrene, very high selectivities for ethylbenzene were achieved with TOF values up to ca. 23500 h-1. All these results show that the catalytic performance of small Rh-NPs can be modulated by the appropriate choice of stabilising agent.

 

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Ru,Rh,Ir/hydrogenation of disubstituted arenes

We recently reported the use of chiral diphosphites as efficient stabilizers for Ru, Rh and Ir nanoparticles for use in the hydrogenation of ortho- and meta-methylanisole.



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Hydrogenation of ortho- and meta-methylanisole



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Synthesis of chiral diphosphite ligands used for the stabilization of M-NPs





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TEM images and size distributions of the Ru, Rh and Ir-NPs synthesized in this study

 


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Results obtained: arene hydrogenation using Ru, Rh and Ir-NPs stabilized by ligand 13

 

 

FISCHER-TROPSCH SYNTHESIS

Water soluble colloids

Our group is currently working on the use of metal nanoparticles in the Fischer-Tropsch Synthesis, focusing on NP size-product distribution correlations. This project is financed by Gaz & Energies Nouvelles, Total S.A.
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Topics in Catalysis 2013, 56, 1208-1219

Novel Polymer Stabilized Water soluble Ru-Nanoparticles as aqueous colloidal Fisher-Tropsch catalysts

Aitor Gual • Jorge A. Delgado • Cyril Godard • Sergio Castillón • Daniel Curulla-Ferre ́ • Carmen Claver

 

In 2013 our group reported the application of lignin polymers as stabilizers for the synthesis of Ru nanoparticles. The obtained NPs were tested in Fischer-Tropsch synthesis.

Structure of lignins research

 

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C-C BOND FORMATION REACTIONS


Pd/asymmetric allylic alkylation (disphophite stabilizers)

In 2004, our group reported in collaboration with the group of Prof. Chaudret (J. Am. Chem. Soc. 2004, 126, 1592) a study on Pd-nanoparticles stabilized by chiral diphosphite ligands derived from carbohydrates. This study showed that asymmetric Pd-catalyzed allylic alkylation reactions could be performed using chiral NPs as catalysts.

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Asymmetric Pd-catalyzed allylic alkylation using chiral Pd-NPs as catalysts

 

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