A. L. Maksimov

Macrocomplexes on the basis of functionalized polyethylene glycols and copolymers of ethylene oxide and propylene oxide: synthesis and catalysis

Water soluble catalysts combining the properties of metal complexes and surfactants on the basis of terminally functionalized polyethylene glycols and block-copolymers of ethylene oxide and propylene oxide with various combinations of ethylene and propylene oxide fragments were investigated. Polymers, functionalized by dipyridyl and acetylacetone were used as ligands for preparation of Fe(III) and Co(II) complexes, which showed a high activity and selectivity in oxidation of cyclohexane and ethylbenzene by both hydrogen peroxide and oxygen. An aqueous phase hydroformylation rhodium catalyst was prepared on the basis of polyethylene glycols functionalized by phosphine groups.

Synthesis of nickel–tungsten sulfide hydrodearomatization catalysts by the decomposition of oil-soluble precursors

Nickel–tungsten sulfide catalysts for the hydrogenation of aromatic hydrocarbons have been prepared by the in situ decomposition of an oil-soluble tungsten hexacarbonyl precursor in a hydrocarbon feedstock using oil-soluble nickel salt nickel(II) 2-ethylhexanoate as a source of nickel. The in situ synthesized Ni–W–S catalyst has been characterized by X-ray photoelectron spectroscopy. The activity of the resulting catalysts has been studied in the hydrogenation of bicyclic aromatic hydrocarbons and dibenzothiophene conversion in a batch reactor at a temperature of 350°C and a hydrogen pressure of 5.0 MPa. It has been shown that the optimum W : Ni molar ratio is 1 : 2. Using the example of the hydrofining of feedstock with high sulfur and aromatics contents, it has been shown that the synthesized catalyst exhibits high activity in the hydrogenation of aromatic hydrocarbons.

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.

Iron and copper complexes with nitrogen-containing ligands as catalysts for cyclohexane oxidation with hydrogen peroxide under mild reaction conditions

Oxidation of cyclohexane (CH) with hydrogen peroxide under mild reaction conditions in the presence of systems containing in situ generated iron complexes with nitrogen-containing ligands (2,2′-bipyridyl and o-phenanthroline) and chlorinated (Cl15) copper phthalocyanine (CuPcCl15) have been studied. It has been shown that in water-acetonitrile blends under optimum conditions, CH is oxidized with the formation of cyclohexanol, cyclohexanone, and acids involving cyclohexane hydroperoxide. High total selectivity for ketone and alcohol is reached in the excess of ligands and the substrate.

Hydrogenation of phenols in ionic liquids on rhodium nanoparticles

A new catalyst system based on rhodium nanoparticles stabilized by polyacrylic acid have been suggested for the hydrogenation of phenols in ionic liquids. It has been shown that high near-quantitative yields of reaction products are achieved in ionic liquids containing a tetraalkylammonium cation. By the TEM and XPS techniques it has been revealed that the use of ionic liquids substantially decreases the particle size and reduces the aggregation of nanoparticles through the inclusion of the ionic liquid cations into the surface layer along with polyacrylic acid.

Oxidative desulfurization of diesel fraction with hydrogen peroxide in the presence of catalysts based on transition metals

The oxidative desulfurization of a straight-run, nonhydrotreated diesel fraction (boiling range 178–342°C) containing benzothiophene, dibenzothiophene, their alkyl-substituted derivatives, and thioxanthene by the action of hydrogen peroxide in the presence of transition metal compounds (Na2MoO4, Na2WO4, NaVO3, WO3, tungstic acid, and heteropoly tungstate/molybdate H3PMo6W6O40) in a biphasic system followed by the extraction of the oxidation products with dimethylformamide has been studied. The oxidation of the hydrocarbon fraction in the presence of heteropoly tungstate/molybdate under biphasic conditions provides for the removal of up to 82% of total sulfur.

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.

Supramolecular catalytic systems in biomimetic oxidation

Oxidation of alkylaromatic hydrocarbons and benzene with hydrogen peroxide was studied under homogeneous and heterophase conditions. The catalytic systems contained the transition metal complex and salt along with the phase-transfer catalysts of different nature (micelle-forming surfactants, compounds containing a substrate in the polymer globule, macromolecules capable of forming host—guest complexes) and cosolvents. This substantially enhanced the yield of the oxidation product and selectivity of the process compared to the classical systems of hydrocarbon oxidation with hydrogen peroxide.

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.

Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons

Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2–5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896–2590 min−1, selectivity 89–98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850–5000 min−1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294–2400 min−1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14–22 min−1, selectivity 7–16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.