Home – Home – Jornals – Chemistry for Sustainable Development 2014 number 6

The effect of the nature of modifying agent and chemical composition on the phase state, texture characteristics and acid properties of Р₂O₅–Al₂O₃, МоO₃–Al₂O₃, and WO₃–Al₂O₃ systems was studied. Supported platinum catalysts based on these systems were tested in hydroisomerization of a model mixture of heptane and benzene in a flow set-up at reaction temperature of 300–350 °C, pressure 1.5 MPa, mass rate of raw material input 3.0 h^–1, molar ratio of Н₂/raw material equal to 5. A Pt/WO₃–Al₂O₃ sample with WO₃ 25.9 mass % was chosen as a promising catalyst of hydroisomerization.

It is demonstrated on the basis of thermodynamic calculations that the synthesis of propylene from ethylene with intermediate formation of n- butenes under equilibrium conditions is most probable within temperature range 450–550 °C with propylene yield up to 50 mass %. In the case of the kinetic control of ethylene dimerization into butene–1, the achievement of propylene yield at a level of 60 mass % is theoretically possible at low temperatures (40–60 °C) and ethylene conversion degree about 80 %. For the NiO–Re₂O₇/B₂O₃–Al₂O₃ catalyst, a kinetic model of the process was constructed. The model provides adequate description of process parameters within temperature range 40–120 °C with ethylene converison degree up to 30 % and propylene yield up to 25 mass %.

The problem of the high concentration of n–propylbenzene as undesirable component of the product mixture formed during liquid-phase alkylation of benzene with propylene ios investigated. Monitoring of alkylation set-up (Omskiy Kauchuk JSC) was carried out; technological parameters affecting the concentration of n–propylbenzene were revealed. A mathematical model of alkylation was worked out. A computer-based modeling system Alkylation involving this model was developed in Borland Delphi 7; it allows calculating the composition of product flows under variations of the most importnat technolgoical parameters of reactor operation (temperature, molar ratio of benzene to propylene, volume rate of raw material input).

The structure and properties of nanodispersed globular carbon (NDGC) after thermooxidative treatment with water vapour were studied. The properties and structural changes in non-conducting NDGC of P 145 and P 234 grades were studied in comparison with conducting grades P 267–E, Printex XE–2b and Ketjen EC. A complex interconnection between electric resistance of the material and the parameters of X–ray structural analysis and Raman spectroscopy was revealed.

The effect of the technological parameters of thermal treatment (carbonization, carbon restoration and activation) of molded extruded carbon on the texture and strength characteristics of final carbon sorbents for medical purposes was studied. Temperature-time parameters of carbon restoration and activation processes providing the formation of molded carbon sorbent shaped as cylinders with the external diameter of 8–10 mm, internal chanel 3–4 mm and the length of 45–60 mm were determined; the specific surface of the sorbent is S_BET = 220–320 m²/g, crushing strength Р > 20 kgf/cm².

Using modern methods and approaches of surface science, the model supported catalysis Au/AlO_x and Ag/HOPG were studied in the reactions of NO decomposition and ethylene oxidation, respectively. It is assumed that a combination of X–ray photoelectron miscoscopy and scanning tunneling microscopy turns out to be very informative in establishing the reasons of the catalytic action of model catalysts and can be used in the studies aimed at improvement of the catalytic properties of real catalysts.

Low-temperautre hydrogen generation from solid-phase compositions based on amminborane (NH₃BH₃) and TiO₂ under external heating to 80 °C depending on the physicochemical properties of titanium dioxide, its content in the composition and the amount of adsorbed water was studied. It was established that the maximal yield and rate of hydrogen formation are achieved for the system prepared on the basis of fine titanium dioxide witht eh participation of adsorbed water. It is assumed that an increase in the efficiency of hydrogen obtaining from the composition in comparison with initial hydride is due to a conjugation of the exothermal process of amminborane hydrolysis with its dehydrogenation (thermolysis).

Adsorption properties of gold nanoparticles deposited on pyrolytic graphite were studied. It was established that water molecules are formed as a result of serial adsorption of hydrogen and oxygen on the surface of nanoparticles. The energies of bonding between chemisorbed hydrogen and gold were determined.

Deactivation of tungsten-containing zeolite at different stages of nonoxidative conversion of methane into aromaic hydrocabrons was studied. The factors causing a decrease in the activity of the catalyst were revealed. The distribution and state of the active components in the catalytic system were studied. The nature of carbon deposits formed during the reaction on the catalyst under investigation was studied, and the amount of the deoposits was determined.

Acid properties and catalytic activity of high-silica zeolites of ZSM–5 type modified with platinum and gallium were studied in the process of joint conversion of butane and hexane. It was demonstrated that the introduction of modifying metals (Ga, Pt) at the stage of hydrothermal synthesis changes the acid and catalytic properties of initial zeolite. The highest efficiency in the process of aromatization of alkanes under study is exhibited by Ga–НZSM–5. With all samples (Н–ZSM–5, Ga–НZSM–5, Pt–НZSM–5), the effect of the joint transformation of butane and hexane was not discovered.

Results of the studies dealing with the development of application carbon sorbents for medical purposes are presented. The directions of the synthesis of carbon application materials are outlined, the methods of carbon surface modification are described. Physicochemical and medical–biological studied of the resulting sorbents were carried out.

Acid centres of bifunctional catalysts Rh/SO₄/ZrO₂, Rh/WO_x/ZrO₂ and Rh/Cs_хH_3–хРW₁₂O₄₀ were studied by means of IR spectroscopy of adsorbed pyridine. The effect of type, concentration and strength of acid centres on the activity and selectivity of catalysts in halogen-free carbonylation of dimethyl ether was established. It was demonstrated that the most efficient catalysts are those with the high concentration of strong Brøensted acid centres Rh/Cs_хH_3–хРW₁₂O₄₀ (1.5 ≤ x ≤ 2).