The synthesis of highly porous ceramic materials for catalytic converters based on coarse-dispersed αAl2O3 was carried out using a combination of compaction and thermochemical synthesis methods with the participation of active ultrafine binders. Using XRD and SEM methods, it was established that the morphology of the synthesized material includes the simultaneous presence of large pores between the filler particles (the dominant αAl2O3 phase) and submicron pores in the transboundary areas that appeared during the processes of liquid-phase sintering and gas evolution. A significant amount of indialite Mg2Al4Si5O18 and spinel MgAl2O4, formed as a result of thermochemical synthesis on the surfaces and in the gaps between coarse particles, was revealed. Pores dominate (according to the volume of mercury intrusion) in the size range from 20 to 60 µm (about 73%), as well as from 0.4 to 2 µm (about 6 %). The average pore size is about 9 µm, the equivalent hydraulic diameter of the pore channels is about 3 µm. Highly porous materials with these characteristics of the pore space can be effectively used after modification as catalytic converters for the dehydrogenation of alkylaromatic hydrocarbons with a large molecular size (about 400 nm) with a long mean free path of about 3 – 4 μm.

This article discusses the application of computational methods using density functional theory (DFT) to construct models of the nitrogen impurity center in octacalcium phosphate (OCP). The performed DFT calculations are compared with the electron paramagnetic resonance spectra (g-factor and the hyperfine interaction constant A). It is shown that in the apatite layer of OCP, a NO_3^2- center is formed, while in the hydrated layer, a NO_2^2- center is the most probable one.

A series of tubular porous ceramic converters modified with mono- and bimetallic catalytic systems based on rhenium and tungsten were prepared by a combination of self-propagating high-temperature synthesis and the sol–gel method. These converters were tested in dehydrogenation of ethylbenzene to styrene. Among the tested samples, a monometallic tungsten-containing converter exhibited the optimal properties as it achieved the highest target product production performance. Within the temperature range of 550–600°C, this converter provided a yield of styrene up to about 15 wt % and styrene productivity up to about 22 g h –1 dm –3 , with the carbonization of the sample not exceeding 5 wt % over about 6 h of reaction.

It was shown that the method for the incorporation of a catalytic tungsten component into a porous ceramic converter has a major effect on the activity and selectivity of cumene-to-AMS dehydrogenation. Specifically, the activity of a surface-modified tungsten-containing converter exceeded by more than 2.5 orders of magnitude the activity of a converter with tungsten incorporated by thermochemical sintering of the initial blend. It was further found that the performance of hydrocarbon dehydrogenation in converter channels nearly doubles that of the process occurring over a granular catalyst with an equivalent composition. It was also demonstrated that the process performance can be enhanced by removing extra-pure hydrogen from the reaction system through a palladium-containing membrane. Cumene dehydrogenation in catalytic converters was identified as a zero-order reaction.

Measurements are reported of the increase in catalytic CO oxidation rate on gold nanocoatings obtained by applying a positive or negative electrical voltage of variable magnitude to a coating. In experiments on an initial mixture of 1.8

Экспериментально определено увеличение скорости каталитического окисления СО на покрытиях из наночастиц золота при подаче на них электрического напряжения различной полярности и величины от внешнего источника. В условиях эксперимента при 430 °С, атмосферном давлении, начальном составе смеси 1.8% СО + 10.2% О 2 + Ar и начальном размере частиц покрытия 0.2–3 нм последовательное увеличение подаваемого положительного напряжения U вначале приводит к росту скорости окисления СО на 28% при U = +10 В, плавно снижающемуся до 20% при U = +30 В. Подача отрицательного напряжения менее эффективна: вначале скорость окисления растет на 12% при U = –10 В, а затем снижается до 7% при U = –30 В. Выполнены квантовохимические расчеты теплот ассоциации СО и О 2 с простейшим электронейтральным или электрически заряженным кластером золота Au 3 , а также теплот реакций Au 3 CO + O → Au 3 CO 2 и Au 3 CO 2 → Au 3 + CO 2 для различных зарядов Au 3 -содержащих комплексов. По результатам расчетов предложено объяснение увеличения скорости каталитического окисления СО на покрытиях из наночастиц золота, электрически заряженных с помощью внешнего источника напряжения.

A porous, catalytically active converter was synthesized based on coarse SiC. For the synthesis of the converter, ultrafine additives of the eutectic composition MgO and SiC were introduced into the original SiC powder. The resulting mixture was pressed at the maximum pressure from 75 to 125 MPa, followed by sintering in the range from 1200 to 1450°C. The open porosity of the converters was ~40%, the size of the pores ranged from 4 to 6 μm. At 600°C, ethylbenzene conversion was ~73%, styrene yield ~9%, selectivity of styrene ~12.3%. The degree of carbonization of the catalyst after 2.5 h did not exceed ~0.003 wt.%, which is an ultra-low indicator that radically increases the life of a catalytic converter without the need for regeneration or replacement.

A porous ceramic catalytic converter was synthesized on the basis of a coarse α-Al2O3 powder filler using ultrafine strengthening binders of the MgO + SiC + SiO2 composition and catalytically active Re2O7 and WO3 components (up to 4 wt %). Double-sided compression of the starting mixture under a pressure from 70 to 90 MPa followed by sintering of the samples at temperatures from 1200 to 1400°C was applied. The synthesized ceramic catalytic converters possessed an open porosity of about 40% and a pore size of 0.5 to 1.5 μm. The styrene selectivity of about 30% and the productivity up to 30 g h–1 dm–3 in the temperature range from 600 to 700°С were experimentally achieved. The degree of catalyst carbonization within the experimental time (6 h) did not exceed 0.31 wt %. The scientific principles of a one-step technology for the synthesis of a porous ceramic with simultaneous imparting of catalytic properties thereto were developed. The obtained ceramic catalytic converters of the [Re,W]/α-Al2O3 composition can produce styrene with a high efficiency in a wide temperature range.

The possibility of increasing the catalytic activity of a coating of gold nanoparticles during the oxidation of carbon monoxide (CO) by applying a positive electric voltage to the coating is experimentally established for the first time. Applying voltage U = +10 V to the coating increases the rate of CO oxidation by 28% at 430°C and atmospheric pressure for the initial mixture of 1.8% CO + 10.2% O2 + Ar.

This article presents the results of the development of membrane-catalytic methods for obtaining purified hydrogen of various degrees of purity required for feeding high-, medium-, and low-temperature fuel cells. In order to conduct this, porous ceramic catalytic converters were obtained using self-propagating high-temperature synthesis. These converters are suitable for high-speed processes for producing synthesis gas with different carbon monoxide content (0.08–0.1 vol. %), which can be used to feed fuel cells of various types. Using a hybrid catalytic membrane reactor, in which the stage of catalytic conversion of organic substrates was combined with the stage of selective extraction of ultrapure hydrogen (content of H2 was not less than 99.9999 vol. %) from the reaction zone, combined carbon dioxide and steam reforming of organic substrates of various origins were carried out. The result of the work was the creation of a prototype of a small-sized electric generator plant in which a catalytic membrane reactor was combined with a solid-oxide fuel cell.

The possibility of increasing the catalytic activity of a coating of palladium nanoparticles during CO oxidation by applying a positive electric voltage to it is experimentally established. Applying U = +10 V on a coating leads to an increase in the rate of CO oxidation by 14% at 330°С, atmospheric pressure, and with the initial composition of the mixture of 1.8% CO + 10.2% О 2 + Ar.

This paper presents the results of a study on the particularities of the process of dehydrogenation of ethylbenzene to styrene over an original [Re,W]/gamma-Al2O3 (K, Ce)/alpha-Al2O3 porous ceramic catalytic converter, obtained by self-propagating high-temperature synthesis and the sol-gel method. It was found that, over this converter, the output of styrene, with a similar to 100 % selectivity to liquid products, is similar to 23 times higher than that over the same conventional bulk of industrial catalysts. Further, after 6 h of reaction, the degree of carbonization of the converter does not exceed 5 wt.%.

The increase in the rate of catalytic oxidation of CO on palladium nanosized coatings is measured when electric voltages of different polarities and magnitudes are applied to the coatings from an external source. Under the experimental conditions at 330°С, atmospheric pressure, and the initial composition of the mixture of 1.8% CO + 10.2% О2 + an Ar application of a positive voltage of +10 or +30 V to the coating leads to the CO oxidation rate increasing by 14 or 42%, respectively. Applying a negative voltage of –10 or –30 V results in less acceleration of oxidation by 4 or 12%. It is shown that the effect of the voltage supply does not depend on the particle size in the coating and increases linearly with increasing voltage. The quantum-chemical calculations of the heat of the association of CO and O2 with the simplest neutral or electrically charged palladium Pd2 clusters are calculated. It is found that the creation on Pd2 of a positive charge leads to a decrease in the difference between the heat of association of CO and O2 by 16.7 kcal/mol, while the creation on Pd2 of a negative charge leads to a smaller effect: a decrease in the specified difference by 10.6 kcal/mol. Based on the results of the calculations, an explanation is proposed for the increase in the rate of catalytic oxidation of CO on palladium electrically charged using an external voltage source is proposed.

Self-propagating high temperature synthesis (SHS) was used to obtain porous cermet membranes based on a mixture of aluminum oxide, silicon carbide, and magnesium oxide powders. The obtained membranes are catalytically active. The surfaces of the open pores in them were modified by rhenium-tungsten active components using the alkoxy method. The highest selectivity in terms of propane (about 60%) is achieved at temperature 600°C. In addition, the optimal conditions for implementing the propane dehydrogenation process is temperature 650°C at which the quite high selectivity for the most important monomers remains with a relatively small contribution of accessory processes.

The features of cumene dehydrogenation to α-methylstyrene on unique porous ceramic catalytic converters having the composition [Re,W]/γ-Al2O3(K,Ce)/α-Al2O3 and [Fe,Cr]/γ-Al2O3(K,Ce)/α-Al2O3, obtained using self-propagating high-temperature synthesis and the sol–gel method, have been studied. It has been established that at an optimum temperature of 625°C, the rhenium–tungsten-containing system has approximately 1.5 times higher catalytic activity than the iron–chromium system. On the Re–W-containing catalytic converter at the optimum temperature, the cumene conversion is ~71 mol %, the α-methylstyrene yield is ~77 mol % of theoretical, and the α-methylstyrene content in the products is ~35 mol %, with productivity for the desired product being ~7.4 g/(h gact.comp.). The degree of catalyst coking for 6 h of the experiment did not exceed 5 wt %.