The activation stage of high-performance cobalt catalysts for Fischer–Tropsch synthesis has been studied, taking into account the transformation of emerging structures and the presence of a percolation heat-conducting network of metallic aluminum. The influence of temperature, process duration, composition of the reducing gas, as well as its volumetric velocity on the degree of reduction and surface area of the active component of the catalyst was studied. These characteristics were determined by low- and high-temperature oxygen titration in a chromatographic-type sorption unit, as well as using temperature-programmed reduction. The possibility of reducing the temperature and concentration of hydrogen in the gas to achieve the required parameters during reduction to obtain a high-performance catalytic system has been experimentally demonstrated. Its performance in Fischer–Tropsch synthesis (CO conversion, liquid hydrocarbon productivity) is comparable or better than that achieved on a catalyst reduced under standard conditions.

A method for leaching Co2Al9 alloy was developed and optimized to produce nonpyrophoric Raney cobalt, which is used as a component of a highly efficient granular Fischer-Tropsch synthesis catalyst. A comparative study of the laboratory-produced Raney cobalt with commercially available analog was done using the methods of low-temperature nitrogen sorption, thermoprogrammed reduction (TPR), thermoprogrammed ammonia desorption, thermal analysis, thermal conductivity, and scanning and transmission electron microscopy. Partial dissolution of cobalt with the formation of Co2+ and Co3+ ions was detected during aluminum leaching. It was found that incomplete purification of commercial Raney cobalt from aluminum hydroxide impurity may lead to overestimation of specific surface area. It was also found that the acidity of the molded catalyst is mainly determined not by Raney cobalt, but by elements of the composite catalyst carrier. For the first time, a linear dependence between the content of structures in a Fischer-Tropsch synthesis catalyst with TPR-AR maxima of 500-800 degrees C and the amount of synthesized liquid hydrocarbons has been established. It is concluded that metal nanoparticles with partial charge transfer (Co delta+) are active centers of selective formation of C5+ hydrocarbons. Obtaining the maximum number of these centers and reaching a high thermal conductivity of the composite with a developed system of transport pores is a criterion for creating an effective cobalt catalyst for low-temperature synthesis of hydrocarbons.

Electrochemical recharging behavior of a binder-free flexible carbon nanotube cloth (CNTC) material in respect to aqueous supercapacitor applications is reported. To provide high enough pseudocapacitance, the surface of CNTC was exposed to wet oxidative functionalization by a KMnO4 treatment in an acidic medium. We report the effect of a KMnO4 to CNT molar ratio on capacitance, electrical resistivity and specific surface area of the CNTC material. The change in the composition of oxygen-containing interfacial functional groups attached to the carbon surface is also investigated by X-ray photoelectron spectroscopy and temperature-programmed desorp-tion methods. For the most oxidized CNTC sample the capacitance of ca. 71 F g-1 (29 mu F cm-2 BET) in 0.5 M H2SO4 (slightly decreasing with a scan rate up to 100 mV s-1) with the retention of ca. 99% during 30,000 recharging cycles as well as specific resistivity of ca. 31 mu ohm m are achieved. Finally, two flexible symmetric supercapacitor prototypes based on a 38% H2SO4 solution and operating at 1.3 or 1.5 V were assembled from the freestanding and graphite foil supported functionalized CNTC electrodes, respectively. For the former device, the volumetric capacitance of ca. 22 F cm-3, power density of ca. 10 kW l- 1 and energy density of ca. 3 Wh l- 1 (per total volume of both electrodes) are demonstrated. The issues of the long-term stability and self-discharge behavior of assembled prototypes are also considered. Reported results allow us to consider the functionalized CNTC ma-terial as a promising electrode material for flexible aqueous supercapacitors.

A cobalt catalyst was manufactured using polyacrylonitrile (PAN)-based carbon fiber as a support. The surface of the fiber was covered with thin layer of alumina before cobalt impregnation. The catalyst was studied by a number of physicochemical methods including low-temperature nitrogen adsorption, TPR, DTG, chromatography, electron microscopy (TEM and SEM) and thermal conductivity measurements. The properties measured were discussed along with data on the activity in Fischer–Tropsch synthesis. It was found that the catalyst after the synthesis becomes significantly different from the starting catalyst, mostly because of the deposition and accumulation of high-molecular products of the Fischer–Tropsch synthesis. At the same time, in the steady-state mode, its catalytic parameters correspond to a high-performance granular catalyst based on graphite, which allows us to use the results obtained as a model for identifying the surface states of a porous catalyst of the new generation gas-to-liquid (GTL) process.

The effect of the dilution of a synthesis gas with nitrogen on the activity, selectivity and productivity of a Fischer–Tropsch reactor with a fixed bed of granular catalyst during synthesis on a pilot plant of a full cycle for the conversion of natural gas into synthetic oil is studied experimentally. Experimental data are presented that were obtained at different contents of nitrogen in the synthesis gas: up to 2, 50, and 70%. Analysis of the experimental data shows that diluting the synthesis gas contributes to an increase in the selectivity to C5+, and a decrease in the selectivity to methane. A drop in the reactor’s productivity observed upon the dilution of synthesis gas can be compensated for by increasing the consumption of synthesis gas. The negative effect of decrease in the pressure of FT synthesis from 2 to 1.5 and 1.0 MPa on the catalytic FT synthesis performed on a twice-diluted synthesis gas at a synthesis gas space velocity of 4000 h–1 is demonstrated.

Высокая потребность в биосенсорах, с помощью которых можно количественно измерять концентрацию глюкозы в крови человека, приводит к поиску новых, недорогих и надёжных решений для удовлетворения растущего спроса.Основным компонентом таких биосенсоров является графитовый электрод, который наносят на подложку с помощью технологии трафаретной печати.Для трафаретной печати обычно используют графитовую пасту.Этовысокодисперсная коллоидная система, которая состоит из термопластичного полимера-диэлектрика, низкокипящего растворителя и электропроводящего компонента.Реология и физические свойства готовой графитовой пасты зависят в значительной мере от состава жидкой фазы, которая содержит раствор полимера и стабилизирующие компоненты

The introduction of exfoliated graphite into pelletized Co-based catalysts affects in the most positive way both catalytic and physico-chemical properties. Unlike other carbons, the exfoliated graphite allows combination of extended surface with high thermal conductivity. An open-ended system of slit-type pores is revealed by X-ray tomography. Electron microscopy shows graphitic platelets forming an all-penetrating heat-conductive frame. Element distribution analysis shows that this catalyst cannot be considered as a cobalt-on-carbon catalyst since the graphitic component carries insignificant amount of cobalt and serves as a heat-conductive frame only. Thermal conductivity of a catalyst with graphite frame is 2 times higher than that of its industrial predecessor with Al metal frame and 30 times higher than that of a catalyst without heat-conductive additive. Testing in exothermal Fischer-Tropsch synthesis shows a favorable influence of the graphitic additive, i.e. such catalyst shows productivity of 455 g/kg/h at GHSV of 3000 h(-1).

A cobalt catalyst supported on titania-doped silicon carbide for the Fischer – Tropsch synthesis was synthesized and comprehensively studied using various physicochemical methods. The dynamics of behavior and deactivation of the catalyst, which showed a stable operation for 1500 hours, was studied in a continuous pilot-plant lifecycle test with periodic variation of flow rate, syngas pressure and process temperature. This catalyst has two types of active sites on which products with different parameters of the Schulz – Flory distribution are formed. Depending on the process mode, the efficient formation of «soft waxes» or products with a higher molecular weight can occur.

A cobalt catalyst supported on titania-doped silicon carbide for the Fischer – Tropsch synthesis was synthesized and comprehensively studied using various physicochemical methods. The dynamics of behavior and deactivation of the catalyst, which showed a stable operation for 1500 hours, was studied in a continuous pilot-plant lifecycle test with periodic variation of flow rate, syngas pressure and process temperature. This catalyst has two types of active sites on which products with different parameters of the Schulz – Flory distribution are formed. Depending on the process mode, the efficient formation of «soft waxes» or products with a higher molecular weight can occur.

A method for producing skeletal cobalt (Raney cobalt) for the use in highly efficient granular Fischer-Tropsch synthesis catalysts with high performance for C5+ liquid hydrocarbons is presented. The proposed method makes it possible to obtain skeletal cobalt in a relatively simple, reproducible method and in a safe, non-pyrophoric form of ultrafine powder. Skeletal cobalt, along with additional additives introduced into the composite, can provide the implementation of the percolation network necessary for heat transfer and the optimized porous structure of the catalyst. The obtained Raney cobalt is characterized by a number of physical and chemical methods with the development of process control parameters for the production of Raney cobalt. It is shown by transmission electron microscopy that the Raney cobalt particles, which look like monoliths in low-resolution micrographs, consist of weakly interconnected nanoparticles. In the production of a porous metal, a partial dissolution of cobalt with the formation of divalent Co2+ due to oxidation by water and further transition to colored Co3+ in the interaction with dissolved air oxygen was found, which was not previously discussed in the literature on the production of Raney metals. The introduction of skeletal cobalt in an amount of up to 3% wt. in the composition of the Fischer-Tropsch synthesis catalyst leads to a significant increase in the performance of the catalyst, up to 410 g/l/h compared to the value of 320-340 g/l/h for the initial catalyst. It is also shown that the intrinsic acidity of reduced cobalt is sufficiently low and the main contribution to the acidity of the catalyst is made by impurity aluminum oxide structures or other elements of the composite catalyst carrier.

The methodology for manufacturing composite catalyst supports comprising 50 wt.% exfoliated graphite by mold pressing was developed.The technique of wetting a relatively hydrophobic powder with liquid to obtain uniform paste for press machine was proposed and tested.The dependencies of the samples density on the compacting pressure were obtained.The structural characterization was done, i.e. specific surface area, porosity, micro-and mesopores volume, pore size distribution were measured.It was found that obtained samples have a specific surface area of about 340 m 2 /g, total pore volume of about 0.28 cm 3 /g at a true density of 2.3-2.5 g/сm 3 , practically regardless of compacting pressure in the range from 16 to 230 MPa.The thermal conductivity coefficients of the sample pressed at 230 MPa were 3.6 and 12.2 W/(m⋅K) along the cylinder axis and perpendicular to it, respectively.This anisotropy is due to specific preferential orientation of the heatconducting component.The composite reveals similar anisotropy in strength.The strength was measured as 39.4 and 87.6 N/granule along the axis of the granule and perpendicular to it, respectively.The results of the paper demonstrate that a contradictive task of combining high specific surface area, strength and thermal conductivity can be realized in one sample, which is important for catalysis applications.

The effect of syngas dilution with nitrogen on the activity, selectivity and capacity of the Fischer–Tropsch reactor with a fixed granulated catalyst bed was studied during the synthesis at the integrated pilot plant for conversion of natural gas to syncrude. Experimental data were obtained at different nitrogen content in syngas: up to 2, 50 and 70 %. The analysis of experimental data shows that the dilution of syngas increases the selectivity to C5+ and decreases the selectivity to methane. The decrease in the reactor capacity observed upon dilution of syngas can be compensated by increasing the syngas flow rate. A decrease in the pressure of the Fischer–Tropsch synthesis from 2 to 1.5 and 1.0 MPa was shown to exert a detrimental effect on the catalytic performance of the process carried out with a twofold dilution of syngas at its hourly space velocity of 4000 h–1.

A cobalt Fischer–Tropsch synthesis catalyst supported on titania-doped silicon carbide is synthesized and comprehensively studied by a number of physicochemical means. The dynamics of the behavior and deactivation of the catalyst was studied after its stable operation for 1500 h during continuous experimental resource testing with a periodic change in the syngas flow rate and pressure and the process temperature. This catalyst has two types of active sites, on which products with different Schulz–Flory distribution parameters form. Depending on the process regime, the effective formation of soft waxes or more high-molecular-weight products is possible.

On the basis of analysis of experimental data on the temperature in a reactor for Fischer–Tropsch synthesis, a method for prediction of loss in thermal stability of such a reactor by extrapolating the reactor temperature in time with the use of the first-order and second-order time derivatives of experimental data on this temperature has been developed. Since, in this case, the calculation of derivatives is an incorrect procedure because of the rapid changes in the reactor temperature and the accidental errors in its measurement, this problem was solved using the Tikhonov stabilizing-functional method. An integro-differential equation of calculating the first-order and second-order time derivatives of experimental temperatures of the reactor, providing a minimum of the stabilizing functional, has been derived. The possibility of predicting the behavior of the temperature in a reactor under the conditions of loss in its thermal stability was demonstrated through the comparison of calculation and experimental data on the reactor temperature. The method proposed can be used for development of an automated system for control over the working conditions of a reactor for Fischer–Tropsch synthesis for prevention of its thermal explosion.

The productivity of Fischer-Tropsch reactors is determined by the efficiency of heat and mass transfer processes inside the catalyst granules. To reduce the diffusion resistance the granules base is made from ceramic highly porous material. The porous structure of the granules causes a discrete arrangement of cobalt metallic microparticles whose size can reach tens of microns. Cobalt particles are the active centres on which the synthesis reactions are realized. The distance between these active centres significantly exceeds their characteristic size and the homogeneous model for heat and mass transfer is incorrect. In our paper a mathematical model of heat and mass transfer processes in a porous spherical granule with localised active centres is proposed. The heat of the exothermic synthesis reaction is removed from the surface of the granule by heat transfer into the synthesis gas stream washing the granule. The components of the synthesis gas enter to the granule surface as a result of mass transfer. On the basis of the mean-field approach the values of the temperature and concentration of the synthesis gas components at the active centres inside the granule were determined. In the reactor tube, where the catalyst granules are placed, there is a critical temperature. The excess of the critical temperature leads to a thermal explosion, i.e. a substantial overheating of the active centres. In this case, the surface of the catalyst granule is superheated slightly. The principal difference between the homogeneous and heterogeneous models in catalytic reactions is discussed. We analysed influence of the temperature inside the reactor tube, size of the granule, and coefficient of thermal conductivity on the thermal stability of the granule. (C) 2018 Elsevier Ltd. All rights reserved.

The Fischer–Tropsch synthesis (FTS), which is important for energy and alternative fuels, is a strongly exothermic and temperature sensitive process. Therefore, the use of a catalyst with low thermal conductivity may lead to rapid deactivation. It means that efficient heat removal by thermally conductive additives is of crucial importance. Efficient mass transfer is also important for the viscous product removal. This work shows that a percolating heat-conductive network (characterized by newly introduced interconnectivity function) in combination with extended pore system provides an unmatched performance of composite catalysts in FTS. The electron microscopy and X-ray tomography support the conclusions.

Composite pelletized catalysts for higher one-pass conversion and productivity in the Fischer–Tropsch process are reported. The introduction of aluminum metal powder as a thermal conductor leads to the formation of a new family of composite pelletized catalysts, very different from reference systems. In particular, these catalysts retain high activity and C5+ selectivity at increasing gas-hour space velocities of up to 5,000 h−1. The productivity of these composite catalysts increases almost fourfold for fivefold GHSV increase. Composite catalysts with different types of active cobalt (conventional, introduced by impregnation, or skeletal) show similar values of one-pass conversion and productivity but give different fractional and group composition of liquid hydrocarbon products. Testing of these highly productive catalysts in reactors with different aspect ratios showed that high productivity and one-pass conversion can be achieved in industrial-size units, where feasible liquid yield of up to 140 barrels per million standard cubic feet (MMSCF) of natural gas can be reached.

The formation of surface cobalt structures was investigated for a number of β-SiC-supported Fischer–Tropsch catalysts.

Based on a complex mathematical model of the Fischer–Tropsch process the high-perfimance cobalt catalyst for synthetic oil production is developed and tested. The catalyst is granular thermally conductive composite material with a well-developed system of transport pores, which provides an effective mass and heat transfer in the granules. The influence of nature of the heat-conducting aluminum- containing additives on the physical properties of the support and catalytic properties of Fischer–Tropsch catalyst is shows. Found that increasing of catalysts granules thermal conductivity is one of the factors that increase the performance of the catalyst. In the presence of developed catalyst the performance for hydrocarbons С5+ achieved 600 g/(kg·h) or 480 g/(l·h) at 0,8 g/cm3 packing density. A pilot plant to obtain up to 20 liters of synthetic oil per day from natural gas using the catalyst is established and put into operation. Catalyst testing in this plant has confirmed receipt in the laboratory performance of granular bed.