Search

The catalytic hydrogenation of a carbon–carbon triple bond in acetylene compounds is an important industrial process in which high selectivity toward olefin compounds must be ensured. This work considers the effect of treating palladium catalysts based on hyper-cross-linked polystyrene (HPS) with sodium carbonate on the activity and selectivity in the hydrogenation of 2-methyl-3-butyn-2-ol and phenylacetylene is considered. The effect of such treatment depends on the palladium precursor and the polymer support (HPS non-functionalized or HPS containing tertiary amino groups). Selectivity in the hydrogenation of 2-methyl-3-butyn-2-ol (95% conversion of the substrate) is 98% at ambient hydrogen pressure and 90°C in toluene for 1%-Pd/HPS catalysts treated with Na2CO3 and 99.5% in the hydrogenation of phenylacetylene.

Catalytic hydrogenation of the triple carbon-carbon bond of acetylene compounds is an important industrial process. High selectivity to the olefin compound should be provided in the process. This study considers the effect exerted by sodium carbonate treatment of the palladium catalysts containing super-cross-linked polystyrene (SPS) on their activity and selectivity in the hydrogenation of 2-methyl- 3-butin-2-ol and phenylacetylene. The effect of such treatment was shown to depend on the chosen palladium precursor and the type of polymeric support (non-functionalized SPS or that containing ternary amino groups). At atmospheric pressure of hydrogen and a temperature of 90 °C in a toluene medium, the 1%-Pd/SPS catalysts treated with Na2CO3 provided a 98 % selectivity in the hydrogenation of 2-methyl-3-butin-2-ol (at a 95 % conversion of the substrate), while selectivity in the hydrogenation of phenylacetylene reached 99.5 %.

RuO2 particles stabilized in a polymeric matrix of hypercrosslinked polystyrene of MN100 type (5% Ru/MN100) are characterized by physicochemical methods (low-temperature nitrogen adsorption, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy), and the catalytic activity of these particles is studied in the reaction of selective hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). It is shown that synthesized catalyst 5% Ru/MN100 ensures a GVL yield above 99% under mild reaction conditions (90°C; hydrogen partial pressure, 2 MPa) in an aqueous medium and can compete with commercial catalyst 5% Ru/C.

Hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) is among the most promising reactions for valorization of biomass and manufacturing of fine chemicals and liquid fuels. GVL synthesized from lignocellulose biomass is, potentially, a universal semiproduct for the production of fuel additives and reagents. Development of the effective process for synthesis of GVL is of urgent importance. The catalyst containing RuO 2 particles stabilized in the polymer matrix of hypercrosslinked polystyrene NM100 (5% Ru/MN100) was developed for selective hydrogenation of LA to GVL. The catalyst and the catalytic behavior was characterized using physicochemical techniques (low temperature nitrogen adsorption, TEM, REM, XPS, FTIR). The synthesized 5%-Ru/MN100 catalyst was shown to provide more than 99 % yield of GVL under mild conditions (90 °C, partial hydrogen pressure 2 MPa) in an aqueous medium that makes it competitive with the commercial 5%-Ru/C catalyst.

This work is dedicated to studying the thermal degradation of palladium acetate in commercial MN270 hypercrosslinked polystyrene in the temperature range of 200 to 325°C by means of TGA and XPS. It is shown that palladium acetate distributed in hypercrosslinked polystyrene is destroyed with the formation of palladium metal at lower temperatures than the pure salt powder. It is established that the formation and stabilization of Pd7-Pd10 palladium clusters and their partial aggregation with the formation of palladium nanoparticles occur in the course of destruction. Catalytic testing of the resulting systems in selective triple bond hydrogenation in dimethylethynylcarbinol in a toluene solution at 90°C reveals their considerable superiority in activity and selectivity over commercial Lindlar catalyst: a more than twofold increase in TOF at 97.8% selectivity.

This work is devoted to the investigation of surface characteristics such as contact angle and surface tension of the poly(ethylene oxide)-block-poly(2-vinyl pyridine) (PEO- b -P2VP) block copolymer solutions. The block copolymer was used for the development of micellar and heterogenized selective Pd-containing hydrogenation catalysts. Besides, surface tension of solutions of a reactant (dehydrolinalool) and a product (linalool) were investigated as a function of solvent nature and composition. It was found that varying the solvent polarity allows tuning the access of the reactant to catalytic sites and the removal of the product from the micelle core. The surface tension measurements were in accordance with the results of the catalytic investigation. Among the investigated solvents the iso-propanol plus water mixture (30 vol.% of H 2 O) was found to provide the best catalytic properties, although such a complex solvent revealed higher surface tension than pure iso-propanol. In the case of heterogenized catalyst, a scheme of the block copolymer interaction with the SiO 2 surface was proposed.

Structured polyphenylenes that are used as matrices for immobilization of palladium nanoparticles are synthesized through the cyclocondensation of acetylaromatic compounds followed by structuring at different temperatures and, as a result, different crosslink densities. The relationship between the structure and structuring temperature of the polymers is investigated. It is shown that the sizes of palladium nanoparticles immobilized in polyphenylene matrices depend on the conditions of polymer structuring. The resulting catalytic systems are examined for the selective hydrogenation of triple bonds in acetylene alcohols.

Here, a systematic study of magnetite nanoparticle (NP) formation in the presence of functional polyphenylenepyridyl dendrons and dendrimers of different generations and structures (such as focal groups, periphery and a combination of phenylene and pyridyl moieties) has been reported. For certain dendron/dendrimer concentrations and structures, well-dispersible, multi-core, flower-like crystals are formed which display ferrimagnetic-like behavior. It is noteworthy that the least complex second generation polyphenylenepyridyl dendrons with a carboxyl focal group already allow formation of flower-like crystals. Magnetically recoverable catalysts were obtained via Pd NP formation in the dendron/dendrimer shells of magnetite NP and tested in selective hydrogenation of dimethylethynylcarbinol to dimethylvinylcarbinol. Dependences of catalytic activity and selectivity on the dendron/dendrimer generation and structure, type of Pd species, and Pd NP size have been demonstrated. High selectivity and activity of these catalysts along with easy catalyst recovery and successful repeated use make them promising in catalytic hydrogenation.