Effect of the acidity of a zeolite and its modification with cerium and zirconium on the activity and thermal stability of Pd/beta in the reaction of deep toluene oxidation

Acidities of beta zeolites with various moduli and the catalytic activities of Pd/beta in the reaction of deep toluene oxidation were compared.     

Determination of arsenic in surface waters of the Ob river basin

A simple voltammetric procedure for determining arsenic is conidered. It was tested in natural water and in substances suspended in river ecosystems of the Ob river basin. The results of analysis using the voltammetric procedure were verified by atomic absorption spectrometry after atomizing arsenic hydride in a fused-silica cell and by statistical methods employing standard criteria. Specific features of the electrochemical determination of arsenic and its spatial distribution in the Upper and Central Ob and in the Novosibirsk water storage basin were considered.     

The Influence of the Specific Surface Area of the Carbon Support on the Activity of Ruthenium Catalysts for the Ammonia-Decomposition Reaction

A method for fractionation of the starting carbon composite Sibunit by density was used to obtain three samples of Sibunit with different values of the specific surface area: Sib10 at 439 m²/g, Sib13 at 389 m²/g, and Sib17 at 256 m²/g. Investigation of Sibunits using both methods, that is, X-ray diffraction analysis and combination (Raman) scattering spectroscopy, did not reveal significant differences (the parameters of the crystal lattice and the I_D/I_G ratio). The fractionated supports were used to obtain Ru-containing catalysts for ammonia decomposition reaction (0.1 MPa, 400°C). The dependence of the specific catalytic activity calculated per 1 m² of the support specific surface a for catalysts of the same composition (4.0% Ru and 13.6% Cs) has an extreme form. The authors connect this with two factors: the blocking support pores contain an active component and a change in features of ruthenium interactions with the promoter (Cs) of the catalyst.     

Pd/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the selective liquid-phase hydrogenation of acetylene to ethylene

The structure of Ga₂O₃–Al₂O₃ supports and Pd/Ga₂O₃–Al₂O₃ catalysts and the performance of these catalysts in liquid-phase acetylene hydrogenation have been investigated. The deposition of Ga(NO₃)₃ onto Al₂O₃ by impregnation followed by calcination of the impregnated support at 600°C yields γ-Ga₂O₃–Al₂O₃ solid solutions containing up to 50 wt % Ga₂O₃. X-ray diffraction characterization of model palladium catalysts and their temperature-programmed reduction with hydrogen have demonstrated that, while palladium in Pd/Ga₂O₃ is in the form of a Pd₂Ga alloy, in the Pd/γ-Ga₂O₃–Al₂O₃ catalyst there is no direct interaction between PdО and Ga₂O₃ particles and palladium is in the monometallic state. The introduction of 10–20 wt % gallium oxide into Al₂O₃ lowers the activity of the supported palladium catalyst relative to that of the initial Pd/Al₂O₃ but increases the ethylene yield by enhancing the ethylene formation selectivity.     

Group preconcentration of ions from acid aqueous solutions with a low-melting extractant

A possibility of the analytical application of a low-melting extractant, antipyrinium acetylsalicylate, to the extraction of a number of ions from acid aqueous solutions is studied. The distribution of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, Sn, Ti, V, and Zn ions between the aqueous solution and an organic extractant is studied by atomic emission spectrometry. The efficiency of ion extraction from acid solutions with a low-melting flux of antipyrinium acetylsalicylate is calculated. It is shown that single extraction with an extractant flux ensures the efficient extraction of Fe, Mo, Sn, and Ti from the water phase of the analyzed solution to the flux. The introduction of chloride ions into the analyzed acid aqueous solution significantly increases the efficiency of the group preconcentration of ions by the ion-exchange mechanism.     

Synthesis and study of Ru–Ba–Cs/Sibunit ternary catalysts for ammonia synthesis

Ru–Ba–Cs/Sibunit ternary catalysts were synthesized. Their activity in ammonia synthesis and the thermal stability of the support in a reducing atmosphere at elevated temperature depend on the molar ratio of the promoters. The results of studies using physical methods suggest that cesium predominantly interacts with the support, acting as an electronic promoter, whereas barium is a structural promoter. The synergistic action of the promoters at increased barium content of the catalyst was revealed. The highest activity in ammonia synthesis, 34.5 mL_NH3 g_cat ^–1 h^–1, was reached for the 4% Ru–10.8% Ba–2.6% Cs/Sibunit catalyst.     

Pyrolysis of Methane on Resistive MgO/SiC Catalyst

Dynamics of methane pyrolysis on the MgO/SiC catalyst was examined at different temperatures of the resistive catalyst. The conversion of methane on the MgO/SiC catalyst at 1200°C passes through a minimum (29%) by 60th minute, with the selectivity with respect to acetylene steadily increasing during the whole experiment. The scanning microscopy with EDAX analysis demonstrated that the full carbonization of the MgO/ SiC sample at 1200°C also occurs after 60 min of the experiment. It was found that a carbon coating of layered structure is formed on the catalyst surface in the course of the experiment, with C₂ hydrocarbons still present among the pyrolysis products. It was shown that carbon deposits formed on the surface of the MgO/SiC catalyst are catalytically active in the process of acetylene formation.     

Liquid-Phase Hydrogenation of Acetylene to Ethylene in a Flow on Pd/Al2O3 and Pd-Ga/Al2O3 Catalysts in the Presence of CO

Catalytic properties of Pd/Al₂O₃ and Pd-Ga/Al₂O₃ in selective liquid-phase hydrogenation of acetylene in a flow under pressure and the effect exerted on them by introduction of CO into the feed were studied. The presence of CO in the reaction mixture ensures the reaction with the predominant formation of ethylene. Introduction of gallium into the catalyst formulation prevents the catalyst deactivation. Simultaneous action of these factors allows reaching high yield of the target product in combination with long operation life of the catalyst.

     

Study of the Influence Exerted by Zinc Additive on the Structure and Catalytic Properties of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Liquid-Phase Hydrogenation of Acetylene

Effect of the phase composition of aluminum oxide [γ- and (δ + θ) phase] and introduction of zinc additives on the catalytic properties of 0.5% Pd/Al₂O₃ systems in the reaction of liquid-phase hydrogenation of acetylene into ethylene under an elevated pressure in a flow-through mode was studied. An increase in the activity of the Pd catalyst upon modification with zinc is only observed in the case of a system supported by the mixed phase of (δ + θ) aluminum oxide. XAFS spectroscopy was used to find that the increase in the activity and selectivity with respect to ethylene (in the presence of carbon monoxide) on the (0.5% Pd–0.62% Zn)/(δ + θ)-Al2O3 catalyst is correlated with the formation of the PdZn intermetallic compound.