Search results for " Supported Catalyst"

Computational Investigation of Palladium Supported Boron Nitride Nanotube Catalysts

2015

A QM/MM investigation is reported dealing with the nucleation and growth of small palladium clusters, up to Pd8 , on the outer surface of a suitable model of boron nitride nanotube (BNNT). It is shown that the BNNT could have a template effect on the cluster growth, which is due to the interplay between Pd-N and Pd-Pd interactions as well as to the matching of the B3N3 ring and the Pd(111) face arrangement. The values for the clusters adsorption energies reveal a relatively strong physisorption, which suggests that in particular conditions the BNNTs could be used as supports for the preparation of shape-controlled metal cluster

A supercritical-fluid method for growing carbon nanotubes

2007

Large‐scale generation of multiwalled carbon nanotubes (MCNTs) is efficiently achieved through a supercritical fluid technique employing carbon dioxide as the carbon source. Nanotubes with diameters ranging from 10 to 20 nm and lengths of several tens of micrometers are synthesized (see figure). The supercritical‐fluid‐grown nanotubes also exhibit field‐emission characteristics similar to MCNTs grown by chemical‐vapor deposition.

Recyclable Chiral Imidazolidinone Catalyst for α-Alkylation of Aldehydes

2014

Carbons from second generation biomass as sustainable supports for catalytic systems

2018

Abstract In this study activated carbons were produced from the wood of three different wood species (pine, birch, spruce). The resulting activated carbons were characterized in bulk for ash content, carbon content (elemental analyses), specific surface area, and pore size distribution, and at the surface by measuring the autogenerated pH and studying their structure by XPS. All the samples presented high surface areas and appeared to be mesoporous materials (mesopores >80%). The carbons were then used as support for AuPt nanoparticles and tested in the liquid phase oxidation of glycerol (GLY) and in the hydrogenation of levulinic acid (LA), two important chemicals from cellulose-based biom…

GREEN CONDITIONS FOR THE SUZUKI REACTIONS BY USING MICROWAVE IRRADIATION AND MODIFIED HALLOYSITE/Pd CATALYST

2014

Halloysite nanotube (HNT) is an emerging biocompatible material with appealing perspective for technological applications, such as in catalysis1 and in pharmaceutical research.2 Halloysite is a double-layered aluminosilicate mineral that has a predominantly hollow tubular structure. The functionalization of HNTs is a good strategy to introduce an organic moiety onto the external surface and, therefore, to obtain innovative catalyst supports.3 We have modified the external surface of halloysite nanotube with octylimidazolium moieties (HNT-IL) by microwave irradiation in solvent-free conditions and we have have employed this material as support catalyst of Pd nanoparticles. The new HNT/Pd cat…

SYNTHESIS AND EVALUATION OF CATALYTIC ACTIVITY IN WATER AND MICROWAVE IRRADIATION OF A NEW SUPPORT BASED ON HNT TRIAZOLIUM SALTS

2014

In the last years SILLP (supported ionic liquid-like phase)-based materials prepared by covalent attachment have been synthesized [1]. Recently, we have synthesized a palladium-based catalytic system using halloysite nanotubes modified with octylimidazolium moieties and we have tested it in the Suzuki cross-coupling reaction under traditional heating, microwave irradiation and a very small amount of Pd catalyst [2,3]. It is known that support based on triazole motif showed superior activity to the analogous imidazole molecules [4] so, we have focused our attention to develop a new SILLP system with triazolium moiety. Herein we report the synthesis of an original Pd-dicationic triazolium sup…

Cross-Linked Imidazolium Salts as Scavengers for Palladium.

2014

Five imidazolium-based materials have been synthesised and used for the first time as palladium scavengers. Radical reactions of suitable bis-vinylimidazolium salts led to a series of insoluble materials through homo-polymerisation, immobilisation with a 3-mercaptopropyl-modified silica gel or co-polymerisation with ethylene glycol dimethylacrylate. These materials were screened as palladium scavengers with a set of palladium(0) and palladium(II) compounds in different solvents and at different starting amounts of palladium. In many cases, residual amounts of palladium were lower than 5 ppm, as requested for the manufacture of active pharmaceutical ingredients and fine chemicals. The applic…

Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides

2015

Nickel(II) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and…