The dynamics of the silicon sorption on the NiMo/Al₂O₃ guard-bed catalyst containing ~2.0 wt % Ni and ~6.0 wt % Mo during hydrotreating of diesel was studied. The catalyst bed was divided into five equal sections separated by perforated metal partitions permeable to the feed. Four series of experiments were performed; their time was varied in the range 48–200 h, and the temperature was 340°C. A diesel fraction containing ~1.0 wt % sulfur, 130 ppm nitrogen, and 200 ppm silicon introduced in the form of decamethylcyclopentasiloxane was used as the feed. The specific surface area of all the spent samples was 170–190 m²/g, the pore volume was 0.35– 0.43 cm³/g, and the average pore diameter was 8–9 nm. The sorption on a catalyst grain 2.5 mm in diameter is diffusion-controlled. The effective mass transfer coefficient and the catalyst capacity under the experimental conditions (5 wt %) were estimated using the equation describing the sorption process.

Introduction. Titanium carbide and diboride are characterized by high values of hardness, chemical inertness and for this reason are widely used in modern technology. This paper provides information on the synthesis of titanium carbide and diboride by carbothermal and carbide-boron methods, respectively, on the use of titanium carbide as an abrasive and in the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, as well as titanium diboride in the production of cutting tools and ceramics based on boron carbide The aim of this work is to study the processes of synthesis of highly dispersed powders of titanium carbide and diboride, which are promising for the manufacture of cutting tools, wear-resistant coatings, abrasives and ceramics. Research methods. Titanium oxide TiO2, nanofibrous carbon (NFC), and highly dispersed boron carbide were used as reagents for the synthesis of titanium carbide and diboride. Experiments to obtain titanium carbide were carried out in a resistance furnace, and titanium diboride in an induction furnace. X-ray studies of the phase composition of titanium carbide and diboride samples were carried out on an ARL X-TRA diffractometer (Thermo Electron SA). The determination of the content of titanium and impurities in the samples of titanium carbide and diboride was carried out by the X-ray spectral fluorescence method on an ARL-Advant'x analyzer. The total carbon content in the titanium carbide samples was determined on an S-144 device from LECO. The content of boron and other elements for titanium diboride samples was determined by inductively coupled plasma atomic emission spectrometry (ICP AES) on an IRIS Advantage spectrometer (Thermo Jarrell Ash Corporation). The surface morphology and particle sizes of the samples were studied using a Carl Zeiss Sigma scanning electron microscope (Carl Zeiss). The determination of the particle/aggregate size distribution was performed on a MicroSizer 201 laser analyzer (BA Instruments). Results. The paper proposes technological processes for obtaining highly dispersed powders of titanium carbide and diboride. The optimum synthesis temperature for titanium carbide is 2,000…2,100 oC, and for titanium diboride 1,600…1,700 oC. The content of the basic substance is at the level of 97.5…98.0 wt. %. Discussion. A possible mechanism for the formation of titanium carbide and diboride is proposed, which consists in the transfer of vapors of titanium oxides to the surface of solid carbon (synthesis of titanium carbide) and vapors of boron and titanium oxides to the surface of solid carbon (synthesis of titanium diboride). Due to the high purity and dispersion values, the resulting titanium carbide powder can be used as an abrasive material and for the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, and titanium diboride powder can be used for the preparation of cutting tools and ceramics based on boron carbide.

The regeneration of the coked catalyst of gas-phase perchloroethylene hydrofluorination to pentafluoroethane (Freon 125) has been investigated at 370–420°C and atmospheric pressure. The parameters of the mathematical model (rate constant and activation energy) for coke combustion have been determined from the experimental data obtained in a laboratory reactor and from thermoanalytical data. The data obtained have provided a basis for optimization of catalyst regeneration in an industrial reactor.

Sr-La₂O₃ material was prepared by incipient wetness impregnation of La₂O₃ with an ammonia solution of strontium nitrate. The material was characterized using XRD and BET techniques. The influence of temperature (450–630°C) and contact time (0.02–0.06 s) on the kinetics of oxidative coupling of methane (OCM) was studied in an isothermal reactor. A schematic of the OCM process over the Sr-La₂O₃ catalyst was suggested. The experimental results obtained in the range of very low conversions (0.25–8.5%) led to conclude about concurrent formation of primary OCM products which are ethane (C₂H₆) and carbon oxides (CO, CO₂).

The influence of the tetrachloroethylene (TCE) hydrofluorination reaction conditions (temperature and residence time) on the activity of the Cr-Mg catalyst and pentafluoroethane selectivity has been experimentally studied. It has been established that the process proceeds via a complex parallel-consecutive mechanism that includes, along with hydrogen fluoride (HF) molecule addition at the double bond and consecutive substitution of fluorine for chlorine, the disproportionation reaction resulting in the formation of by-products. A kinetic model of the process has been proposed and its parameters, such as rate constants and activation energies, have been determined. The model allows predicting the composition of the target and intermediate products and by-products in wide ranges of residence times and reaction temperatures (300–400°C).