Olga A. Kirichenko

Pd-Fe nanoparticles stabilized by chitosan derivatives for perchloroethene dechlorination.

A series of chitosan-stabilized Pd-NZVI (nano-zero-valent-iron) catalysts for dechlorination with variation in their composition and in the nature of the polymer has been prepared. The synthesis procedures and palladium and chitosan contents were optimized. It was demonstrated by the XPS method that Fe and Pd in Fe-Pd/chitosan samples exist in the metallic state. The positive shift of the binding energy as compared with the bulk metal shows that the iron metal in the surface layers exists as very small nanoparticles. The prepared materials were characterized also by the XAS method. The presence of O and N atoms in the first coordination shell of the central Fe atom in the Fe-Pd/chitosan samples certifies the binding of the Fe metal particles with the chitosan surface via OH and NH(2) groups. The samples are characterized by the high stability of the nanoparticles as compared to unstabilized Pd-NZVI. The materials were tested to evaluate their catalytic activity in the perchloroethene (PCE) dechlorination reaction. Some samples of chitosan-stabilized Pd-NZVI revealed a good performance in PCE degradation as compared to unstabilized Pd-NZVI.

The influence of the dispersion of metals on the activity of Pt/C and Pd/C catalysts in the dehydrogenation of perhydroterphenyl

The activity of Pt/C and Pd/C catalysts in the dehydrogenation of perhydroterphenyl was studied at conversions lower than 30% depending on the dispersion of platinum and palladium metals, which was estimated by two independent methods (adsorption of CO and X-ray diffraction).

Novel Fe-Pd/SiO2 catalytic materials for degradation of chlorinated organic compounds in water

Abstract Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 or Pd acetate as reaction precursors. According to temperature programmed reduction (TPR) studies, Pd introduction decreased the reduction temperature of the supported Fen+ species and nearly complete reduction with H2 was observed at 400 °C. The successful surface loading with Pd was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Characterization of the samples by X-ray diffraction (XRD) and X-ray absorption near-edge structure + extended X-ray absorption fine structure (XANES + EXAFS) verified the presence of highly dispersed Pd0, Pdx Fe1–x and Fe0 phases. Reduction of the supported precursors in hydrogen resulted in materials that were highly active in perchloroethene (PCE) degradation and 2-chlorobiphenyl (2-ClBP) dechlorination. It was found that highly dispersed amorphous Fe-Pd bimetallic nanoparticles on silica support showed superior catalytic activity against PCE dechlorination in comparison to the free-standing Fe-Pd nanoparticles. For the samples with the same Fe content, the conversion of chlorinated organics as well as the stability increased with the Pd loading, e.g., the most effective degradation of PCEs and 2-ClBP was achieved at a Pd loading of 2.3–3.2 wt. %.

Application of silica-supported Fe–Cu nanoparticles in the selective hydrogenation of p-dinitrobenzene to p-phenylenediamine

Supported bimetallic Fe–Cu/SiO2 materials are synthesized, and their catalytic activity in hydrogenation of dinitrobenzene to phenylenediamine at 145–180°С and 1.3 MPa hydrogen pressure is studied for the first time. The best results (89% selectivity toward p-phenylenediamine at complete conversion of p-dinitrobenzene) are obtained for the sample synthesized via co-deposition with subsequent calcination at 300°С. The sample contains 7% iron and 3% copper. The formation of separate phases of metal oxides (for the catalysts prepared by impregnation) and mixed bimetallic oxide phases (in case of co-deposition procedure) in calcined samples is revealed via thermoprogrammed reduction with hydrogen.

Influence of the thermal treatment conditions and composition of bimetallic catalysts Fe—Pd/SiO2 on the catalytic properties in phenylacetylene hydrogenation

The supported bimetallic Fe—Pd/SiO2 catalysts with the different Fe (0.025—8 mass.%) and Pd (0.05—3.2 mass.%) loadings were synthesized by the incipient wetness impregnation of support. The samples were heat-treated under different conditions (calcination in air at 240—350 °C or reduction in an H2 flow at 400 °C). The X-ray phase analysis revealed the formation of Pd0, α-Fe2O3 and Fe3O4 phases after calcination of the samples at 240—260 °C. The reduction of the calcined Fe—Pd samples in an H2 flow at 400 °C enables the formation of Fe0 nanoparticles of size 17—20 nm. The synthesized catalytic systems were studied in the selective hydrogenation of phenylacetylene at room temperature and atmospheric pressure in a solvent (ethanol, propanol). The catalytic properties of the Fe—Pd catalysts depend on the nature of solvent, catalyst composition, and thermal treatment conditions. The application of the Fe—Pd bimetallic catalysts with a low Pd loading of 0.05—0.1 mass.% made it possible to reach the high activity and selectivity to styrene (91%) at the complete conversion of phenylacetylene.

Nickel catalysis for hydrogenation of p-dinitrobenzene to p-phenylenediamine

The activity of supported nickel catalysts (5–20% Ni) in the hydrogenation of p-dinitrobenzene to p-phenylenediamine was investigated. The catalysts were obtained by ureainduced precipitation. Activated carbon, alumina, titania, and silica gel were evaluated as supports. The most active catalysts, 5%Ni/TiO2 and 20%Ni/SiO2, provided 50–54% yields of p-phenylenediamine at complete dinitrobenzene conversion.

Silica-supported copper nanoparticles as efficient catalysts for the liquid-phase selective hydrogenation of p-dinitrobenzene by molecular hydrogen

Monometallic and bimetallic copper-containing catalysts supported on silica gel KSKG were synthesized. The bimetallic Cu—Zn catalysts were most active and selective in the hydro-genation of p-dinitrobenzene (DNB) to p-phenylenediamine (PDA) (99% at 100% conversion of DNB). The highest activity and 99% selectivity to PDA at 100% DNB conversion were demonstrated by the monometallic catalysts with a Cu content of 9%. Unlike hydrogenation on the conventional catalysts, molecular H2 is the hydrogenating agent in the presence of the copper-containing catalysts under relatively mild conditions (110–140 °C, 1.3 MPa).

Microwave-activated carbon dioxide reforming of propane over Ni/TiO2 catalysts

The use of microwave activation in Ni/TiO2-catalyzed carbon dioxide reforming of propane increases the catalytic activity and significantly reduces the coke formation in comparison with conventional thermal heating. During microwave activated reaction, C2—C3 olefins were formed, apart from CO and H2, and the selectivity to olefins reached 6%. It was suggested that exposure to microwave radiation may induce local high-temperature heating of catalytically active phases and catalyst sites, which is not inherent in conventional heating. According to X-ray absorption spectroscopy (XAS = XANES + EXAFS), unlike conventional thermal heating in a hydrogen flow, on exposure to microwave radiation, the Ni2+ cations are partly reduced to Ni0.