Anna Zolotukhina

Pd Nanoparticles in Dendrimers Immobilized on Silica–Polyamine Composites as Catalysts for Selective Hydrogenation

New heterogeneous hydrogenation catalysts, based on Pd nanoparticles and polypropyleneimine (PPI) dendrimers of the third generation that have been covalently grafted to a silica surface modified with polyallylamine (PAA) have been synthesized. The final products were characterized by TEM, XPS, and solid-state NMR spectroscopy. The synthesized materials are effective catalysts for selective hydrogenation of dienes to monoenes and phenyl acetylene to styrene at very high substrate/Pd ratios with turnover rates higher than related Pd nanoparticle catalysts. The synthesized catalysts can be reused without any loss of activity in the case of styrene and isoprene.

Nanocatalysts based on dendrimers

Nanostructured regular materials based on dendrimers bound by covalent or coordination bonds between surface functional groups were synthesized. Bimetallic Cu(II) and Pd(II) metal complexes with nitrile-based dendrimers demonstrated high activity in Wacker oxidation of terminal alkenes along with good selectivity for methylketone formation. New heterogeneous catalysts based on Pd nanoparticles and cross-linked polypropylene imine (PPI) and polyamidoamine (PAMAM) dendrimers were prepared and examined for selective hydrogenation of unsaturated compounds.

Ruthenium Nanoparticles Stabilized in Cross‐Linked Dendrimer Matrices: Hydrogenation of Phenols in Aqueous Media

Novel catalysts consisting of ruthenium nanoparticles encapsulated in cross‐linked matrices based on the poly(propylene imine) dendrimers of the 1st and 3rd generations have been synthesized with a narrow particle size distribution (3.8 and 1.0 nm, respectively). The resulting materials showed high activity for the hydrogenation of phenols in aqueous media (specific catalytic activity reached turnover frequencies of 2975 h−1 with respect to hydrogen uptake). It has been shown that the use of water as a solvent leads to a 1.5 to 50‐fold increase in the reaction rate depending upon the nature of the substrate. It has been established that unlike the traditional heterogeneous catalysts based on ruthenium, during the hydrogenation of dihydroxybenzenes, the hydrogenation rate decreases in the order: resorcinol>hydroquinone≫catechol. The maximum specific activity for resorcinol was a turnover frequency of 243150 h−1 with respect to hydrogen uptake. The catalyst based on the dendrimer of the 3rd generation containing finer particles has significantly inferior activity to the catalyst based on the dendrimer of the 1st generation by virtue of steric factors, as well as the need for prereduction of the ruthenium oxide contained on the surface. These catalysts showed resistance to metal leaching and may be reused several times without loss of activity.

Design of dendrimer-based nanostructured catalyst systems and their catalytic activity in hydrogenation: Synthesis of ruthenium nanoparticles immobilized in dendrimer networks

A new method has been proposed for immobilization of 3-nm ruthenium nanoparticles on special supports synthesized for this purpose, polymer networks based on poly(propylene imine) dendrimers. It has been shown that the structure of the support has a substantial effect on the size of particles and their catalytic activity in the hydrogenation reactions of unsaturated and aromatic compounds. The catalysts can be reused without loss of activity.

Palladium nanoparticles on dendrimer-containing supports as catalysts for hydrogenation of unsaturated hydrocarbons

A new method has been proposed for encapsulation of palladium nanoparticles with a size of up to 2.5 nm in the matrix of special supports, the polymer networks based on poly(propylene imine) dendrimers, synthesized for this purpose. It has been shown that the particle size distribution of the materials obtained and their catalytic activity in the hydrogenation reactions of unsaturated compounds substantially depend on the specific features of the support structure. A high activity (TOF up to 15000 h−1) has been observed in the hydrogenation of styrene. The catalysts can be repeatedly used without loss of activity.

Hydrogenation catalysts based on metal nanoparticles stabilized by organic ligands

The review analyses principal approaches to the synthesis of hydrogenation catalysts based on noble metal nanoparticles stabilized by different organic ligands, such as alcohols, amines, phosphines, ionic liquids, linear polymers, and dendrimers. A possibility of application of new materials, the so-called “breathing” metal-organic frameworks, as matrices for the development of heterogeneous catalysts was considered.

Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions

Nanoheterogeneous catalysts based on ruthenium nanoparticles dispersed in crosslinked dendrimer matrixes with a size of polymer particles of 100–500 nm show high activity in the hydrogenation of aromatic compounds under two-phase conditions. The addition of water to the reaction medium exerts a strong promoting effect on the activity of the catalysts: The turnover frequency increases by a factor of 3–90 depending on the substrate. When bimetallic (PdRu) nanoparticles are incorporated into the catalyst composition, the rate of benzene hydrogenation increases while the rate of transformation of substituted benzenes decreases.

Thermo-responsive Ruthenium Dendrimer-based Catalysts for Hydrogenation of the Aromatic Compounds and Phenols

In this work thermo-responsive ruthenium catalysts, based on the poly(propylene imine) dendrimers cross-linked with the poly(ethylene glycol) diglycidyl ether, have been prepared for the first time. The materials obtained were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy, and tested in the phenol and benzene hydrogenation. Conditions for the metal impregnation into the polymeric matrix were demonstrated to have a great influence both on physical chemical properties of the synthesized catalysts (metal loading, mean particles size, surface structure etc.), and, as a consequence, on their hydrogenation activity and thermo-responsive properties.

Hybrid catalysts based on platinum and palladium nanoparticles for the hydrogenation of terpenes under slurry conditions

Catalysts based on platinum and palladium nanoparticles immobilized in mesoporous phenolformaldehyde polymers modified with sulfo groups have been used for the hydrogenation of a number of terpenes, such as (S)-(–)-limonene, α-terpinene, γ-terpinene, and terpinolene. It has been found that Pd-containing catalysts exhibit higher activity in the exhaustive hydrogenation of terpenes, whereas Pt-containing catalysts have high selectivity for p-menthene.

Nanoparticles Formed onto/into Halloysite Clay Tubules: Architectural Synthesis and Applications

Nanoparticles, being objects with high surface area are prone to agglomeration. Immobilization onto solid supports is a promising method to increase their stability and it allows for scalable industrial applications, such as metal nanoparticles adsorbed to mesoporous ceramic carriers. Tubular nanoclay - halloysite - can be an efficient solid support, enabling the fast and practical architectural (inside / outside) synthesis of stable metal nanoparticles. The obtained halloysite-nanoparticle composites can be employed as advanced catalysts, ion-conducting membrane modifiers, inorganic pigments, and optical markers for biomedical studies. Here, we discuss the possibilities to synthesize halloysite decorated with metal, metal chalcogenide, and carbon nanoparticles, and to use these materials in various fields, especially in catalysis and petroleum refinery.