E. D. Finashina

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.

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. %.

Effect of the conditions of preparing mixed oxide catalyst of Mo-V-Te-Nb-O composition on its activity in the oxidative dehydrogenation of ethane

It is shown that catalytic activity of mixed oxide catalyst of Mo-V-Te-Nb-O composition in oxidative dehydrogenation (OD) of ethane is determined to a substantial degree by the Nb-to-(C2O4)2− ratio in niobium-containing precursors. A pH value of 2.8 to 3.0 for a mixture is optimal when conducting the hydrothermal synthesis of a mixed oxide catalyst; this is achieved by using oxaloniobic acid as a niobium-containing precursor. It is determined that substituting antimony for tellurium results in a loss of catalyst activity during the OD of ethane. The optimum Te content in a catalyst is 0.17 mol %.

Carboxylation of phenylacetylene by carbon dioxide on heterogeneous Ag-containing catalysts

A possibility of using heterogeneous catalysts with a low silver content for the direct carb-oxylation of phenylacetylene by carbon dioxide was demonstrated. A comparative study of the efficiency of the heterogeneous Ag-containing catalysts on different oxide supports (F-γ-Al2O3, γ-Al2O3, TiO2, SiO2) revealed that phenylpropiolic acid in the highest yield (62.1%) was achieved on the 0.5% Ag/F-Al2O3 catalysts.

Hydrogenation of α-oxophosphonates with molecular hydrogen catalyzed by palladium on carbon carrier as synthesis procedure for α-hydroxyphosphonates

Hydrogenation with molecular hydrogen of substituted benzoylphosphonic acids ethyl esters provides a convenient preparation method for diethyl [hydroxy(aryl)methyl]phosphonates. Both the palladium on activated carbon and the palladium immobilized in a chitosan matrix applied on a carbon carrier sibunit can be employed as catalysts.

Preparation, characterization, and catalytic testing of different Me-chitosan complexes for triglycerides transesterification

A number of homogeneous and heterogenized chitosan complexes with different metals (Zn, Co, Ca, Ni, Sn, Pb) were synthesized and tested as catalysts in the reaction of transesterification of tributyrin simulating the process of biodiesel production from renewable natural feedstock (triglycerides, vegetable oils). It is found that chitosan complexes are effective catalysts for transformation of tributyrin into the corresponding esters. The comparative analysis of Me–chitosan (homogeneous), Me–chitosan (heterogeneous) and Me–chitosan/SiO2 catalysts testify that the efficiency of three-component egg-shell systems is close to that of homogeneous catalysts.

Intramolecular hydroamination of 2-(2-phenylethynyl)aniline catalyzed by gold nanoparticles

The possibility of using heterogeneous catalysts with a low content of gold in the intramolecular hydroamination of 2-(2-phenylethynyl)aniline was shown. The catalysts with size of gold particles lower than 3 nm exhibit catalytic activity. The study of efficiency of the heterogeneous Au-containing catalysts on different supports (MCM-41, γ-Al2O3(F), NH4+-Beta, Diasorbamine-60, APTES-MCM-41, and SH-PMO) revealed that the maximum yields of 2-phenylindole were achieved with gold supported on mesoporous silicate materials. A high degree of dispersion of gold in these catalysts is explained by the presence of amino or thiol anchor groups in the support composition. It was found by diffuse reflectance infrared Fourier transform spectroscopy and XPS and XRD methods that gold in these catalysts exists on the support surfaces as small metal particles and due to their size dimensions they show a decreased electron density, i.e., they are electron-deficient Auδ+ nanoparticles.

Three-component Au—Chitosan—SiO2 systems as heterogeneous catalysts for intramolecular cyclization of 2-(2-phenylethynyl)aniline

A series of three-component heterogeneous catalysts Au—Ch—SiO2 with Ch for chitosan was prepared. The size of gold nanoparticles immobilized on the chitosan matrix depends on the method of sample preparation. The particles with the size <3 nm are formed when the preliminary prepared homogeneous Au—Ch complex is supported on SiO2. The catalysts were tested in the intramolecular cyclization reaction of 2-(2-phenylethynyl)aniline to for 2-phenylindole. The maximum conversion of 2-(2-phenylethynyl)aniline (25% within 35 h) was obtained on the Au(0.4%)—Ch(2.9%)/SiO2 catalyst.

Oxidative dehydrogenation of C 2 –C 4 alkanes into alkenes: Conventional catalytic systems and microwave catalysis

Catalytic systems for the nonoxidative or oxidative dehydrogenation of C2–C4 alkanes into the respective alkenes are considered. Scanty data concerning microwave activation of these processes and the potential and advantages of microwave versus conventional technologies are analyzed.

Membrane catalytic systems for C2-C4 alkane conversion

Catalytic processes for the nonoxidative and oxidative dehydrogenation of C2-C4 alkanes, including systems with traditional catalysts and processes conducted with the use of membrane catalysis, are considered in this review. Among the latter, systems with oxidative alkane dehydrogenation have a significant advantage. Both porous membranes and solid electrolytes with oxygen ion permeability can be used in reactors.