Hydrodechlorination of chlorobenzene in the presence of Ni/Al2O3 prepared by laser electrodispersion and from a colloidal dispersion

The low-percentage Ni/Al₂O₃ catalysts with active metal contents of 0.0002–0.1 wt % were prepared using the laser electrodispersion (LED) method and by means of supporting from a colloidal dispersion (CD). Their composition and physicochemical properties were determined by atomic absorption spectrometry, transmission electron microscopy (TEM), and XPS. With the use of TEM, it was found that average size of nickel particles in the LED catalysts was smaller than that in the CD catalysts. According to XPS data, the supporting of a metal onto a substrate by the LED method makes it possible to obtain samples containing Ni metal with a low active metal content (0.03 wt %). They exhibited a high initial activity in the hydrodechlorination reaction of chlorobenzene in a vapor phase, which was performed in a flow system at temperatures of 100–350°C. The CD catalysts were active in this reaction only at temperatures of 300–350°C. Reductive treatment led to the deactivation of LED catalysts and increased the activity and stability of samples prepared by supporting from a CD. The possible reasons for the observed changes are considered.     

Gas-Phase Hydrodechlorination of Chlorobenzene over Alumina-Supported Nickel Catalysts: Effect of Support Structure and Modification with Heteropoly Acid HSiW

Kinetics and Catalysis - The physicochemical and catalytic properties of 6%Ni/Al2O3 catalysts in the gas-phase hydrodechlorination of chlorobenzene (CB) are studied. The catalysts are synthesized...     

Reactivity of Tyrosyl–Proline toward Benzoylation in Aqueous 1,4-Dioxane

Russian Journal of Organic Chemistry - The kinetics of the reaction of L-tyrosyl-L-proline (Tyr–Pro) with di- and trinitrophenyl benzoates in aqueous 1,4-dioxane (40 wt % of water) were...     

New antireflection coatings on silicate glass, deposited from a silicon dioxide sol containing a nonionogenic surfactant and an oligoether based on ethylene oxide

Transparent nanoporous thin films with low refractive index (1.23–1.25) were produced on glass substrates by application of a formulation based on a silicon dioxide sol into which two organic compounds, an oligoether based on ethylene oxide and a nonionogenic surfactant, are introduced. It is shown that the antireflection capacity of the nanoporous coating can be substantially raised at comparatively low concentrations of silicon dioxide and organic additives in the sol by making higher the rate at which the formulation is applied to the substrate.     

The hydrodechlorination of chlorobenzene in the vapor phase in the presence of metal-carbon nanocomposites based on nickel,palladium, and iron

Metal-carbon nanocomposites based on nickel, palladium, and iron and bimetallic palladium-nickel-carbon nanocomposites were for the first time used as catalysts of hydrodechlorination of chlorobenzene in the vapor phase in the atmosphere of hydrogen. Nickel and Pd-Ni nanoparticles completely coated by a carbon layer not only were stable to oxidation and agglomeration but also exhibited considerable activity in hydrodechlorination of chlorobenzene at temperatures much lower than those at which dechlorination on carbon carriers occurred. The dependence of catalytic properties (activity, selectivity, and stability) on temperature and nanocomposite composition was studied. Depending on the nature of the metal, the composition of bimetallic particles and temperature the selectivity could be changed, and the reaction could be directed toward the formation of benzene or cyclohexane. Carbon coating was stable under reaction conditions at least up to 350°C and did not hinder hydrodechlorination. Substrate adsorption likely occurred on the outside carbon surface of composite particles. The activity and structure of Ni@C composite remained almost unchanged after triple cycling over the temperature range from 50 to 350°C in a flow system.     

Interaction of amorphous and crystalline nickel nanoparticles with hydrogen

Nickel nanoparticles were deposited on the surface of highly oriented pyrolytical graphite by laser electrodispersion and precipitation from a solution of reverse micelles. The particles were studied using scanning tunneling microscopy and spectroscopy as well as Auger spectroscopy. The elemental composition of the nanoparticles and specific features of the electronic structure of their surface were determined. Adsorption of molecular hydrogen was also studied.     

ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> binary oxides as promising supports for palladium catalysts of hydrodechlorination

Deposited palladium catalysts of the hydrodechlorination of 1,3,5-trichlorobenzene were studied. Pure zirconium and aluminum oxides and ZrO₂-Al₂O₃ mixtures with 1, 5, and 10 mol % Al₂O₃ prepared by coprecipitation were used as supports. Palladium was deposited by the precipitation of its hydroxide on supports. Catalysts on binary supports (ZrO₂ + 1% Al₂O₃ and ZrO₂ + 5% Al₂O₃) exhibited higher activity and stability in hydrodechlorination compared with catalysts on pure supports. The suggestion was made that the high activity and stability of these systems in hydrodechlorination was related to the formation of binary oxide in the interaction of ZrO₂ with palladium oxide at the stage of annealing of the catalyst precursor. Binary oxide, which was a center of the activation of the C-Cl bond, was simultaneously a source of active hydrogen. The presence of various palladium states in catalysts was substantiated by the temperature programmed reduction method.     

Preparation of Poly(methyl methacrylate) Nanoparticles 15–50 nm in Diameter from Submicrometer-Sized Latex Particles

Russian Journal of Applied Chemistry - A procedure was developed for preparing poly(methyl methacrylate) nanoparticles of 15–50 nm size from coarser (200–300 nm) polymer latex particles...     

Catalytic properties of Ce<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zr<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> prepared using a template in the oxidation of CO

The catalytic activity in CO oxidation of Ce _x Zr_1–x O₂ double oxides prepared using pine sawdust and cetyltrimethylammonium bromide (CTAB) as templates is compared. It is found by means of SEM and the low-temperature adsorption of N₂ that biomorphic oxides reproduce the macropore structure of the template. It is shown via XRD and Raman spectroscopy that all samples contained mixed ceria-zirconia oxide. The double oxides form a cubic phase with a lattice of the fluorite type at a ratio of Ce: Zr = 4, regardless of the nature of the template; when Ce: Zr = 1, the biomorphic mixed oxide forms a tetragonal phase. According to Raman spectroscopy and XRD it was shown that the distortion of the oxygen sublattice is higher in biomorphic samples. Energy dispersive analysis shows that Ca impurities were present in the biomorphic samples, introducing additional distortions in the lattice of double oxide and leading to the formation of anionic vacancies. It is found that when Ce: Zr = 4, the conversion of CO on biomorphic oxide in the range of 100–350°C is higher than that observed for Ce _x Zr_1–x O₂ (CTAB); reducing the Ce: Zr ratio in the biomorphic sample to 1 results in a marked decrease in CO conversion at 100–200°C. It is concluded that these differences are due to changes in the mobility of the lattice oxygen.