Natalia I. Kosova

Activity and Deactivation of ZSM–5 Catalysts in the Dimethyl Ether Synthesis from CO and H2 and Methanol Dehydration

The increasing demand for producing dimethyl ether from synthesis gas explains the renewed interest in studying the activity and stability of catalysts. In the present work, resource catalytic testing of ZSM-5 zeolites was carried out in the one-step synthesis of dimethyl ether from synthesis gas for 120 hours. Formation of condensation products was observed on zeolite surface after catalytic tests which leads to lower catalytic activity of samples. Condensation products were investigated by thermal analysis in an oxidizing atmosphere. Textural characteristics of zeolites before and after reaction were investigated. It was shown that methanol significantly contribute to formation of condensation products on the catalyst surface in the process of dimethyl ether production.

The preparation of the Ti-Al alloys based on intermetallic phases

This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

Synthesis of dimethyl ether from CO and H2

Thermodynamic conditions for synthesizing dimethyl ether from synthesis gas are determined. The optimum conditions of the process are as follow: T ∼ 300°C at p = 3 MPa for two catalysts loaded into the reactor: methanol synthesis catalyst (Katalco-58) and catalyst of methanol dehydration to dimethyl ether (γ-Al2O3). The changes that occur with the catalysts during this process are demonstrated by electron scanning microscopy.

Surface layer composition of titania produced by various methods. The change of layer state under illumination

The comparative analysis of experimental data over titanium dioxide powders prepared by various ways under ambient air is carried out. The results over TiO2 prepared by high-temperature heating of anatase, produced by burning of titanium micro particles and grinding of rutile crystal are used for that comparison. Water and carbon dioxide were the main products released from the surface of the titania powders. It was found that under UV irradiation absorbed by titania, in absent oxygen, water effectively reacts with lattice oxygen of titanium dioxide.

Influence of the Catalyst Preparation on Properties of Chromium-Magnesium Catalysts for Freon 125 Synthesis

The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested.

Surface acid-base Characteristics and their Contribution to Aggregative Stability of Nanoparticles

Toxicant properties of nanoparticles are influenced by their dispersiveness, catalytic activity, aggregation and dissolution properties, which are determined by acid-base properties of the surface. This paper provides the experimental results of the research of surface acid-base characteristics for pH = 2.0...9.0, and takes into account their contribution to aggregative activity of Zn and ZnO nanoparticles in suspensions with pH = 4.0, 6.0, and 8.0. The maximum value of adsorption capacity can be expected in acid medium for Zn nanoparticles, and in base medium for ZnO nanoparticles. This study showed that when the value of pH is different from 6, suspension aggregative stability was strengthened or weakened for Zn and ZnO nanoparticles, respectively. The conclusion concerning the contribution of nanoparticles adsorption activity which is changed by surface acid-base characteristics to aggregative stability of particles of different compounds has been made.

Complex Catalysts for Direct Synthesis of Dimethyl Ether from Synthesis Gas. Part I: Study of the Catalytic Properties

The results of the development of combined process for production of dimethyl ether (CuO/ZnO/Al2O3) and methanol dehydration (γ-Al2O3, zeolite (ZSM-5 type) with a silicate modulus (М) 20, 30, 60, 80, 100, and 200) are presented. The experiments on the influence of the catalysts loading and catalytic conditions were carried out (Р=3 MPa, Н2/СО=2, Т=553 К). It was established that the use of ZSM-5 zeolite catalysts with silicate modulus of 30 allows obtaining the yield of dimethyl ether up to 39%. It was stated that catalytic systems were stable during 180 h.

Bimetallic Ni-Mo Nitride as the Carbon Dioxide Hydrogenation Catalyst

The possibility of bimetallic Ni-Mo nitrides usage as the catalysts in carbon dioxide hydrogenation reaction was examined in this work. Powders were synthesized through thermo-programmed reduction of precursor, which was produced by evaporation of the metal-containing solution. Specimens were investigated by x-ray diffraction, thermogravimetry, low-temperature nitrogen adsorption and scanning electron microscopy. It is shown that final powders provide CO2 conversion of 29 % for contact time of 0.26 s.

The character of interactions of CO, H2, and CH3OH with the surface of γ-Al2O3 and Cu-Zn oxide catalyst

The thermal desorption of CO, H2, and CH3OH from the surface of Katalco-58 industrial catalyst for the synthesis of methanol and γ-Al2O3 was studied. Weak interaction of the gases with the surface of samples was observed over the temperature range 75–400°C. The desorption of the gases obeyed the second-order Wigner-Polyani equation. The desorption energies of the gases were calculated. The mechanism of dimethyl ether synthesis was studied.