To achieve the predicted energy characteristics of the Li–O2 battery (LOB), which are expected to be the highest among known metal-air systems, it is necessary to ensure its long-term cycling at high depth of discharge and high current density. However, in such conditions, the deposition of non-conductive lithium peroxide (Li2O2), a product of LOB discharge, is accelerated on the positive electrode, resulting in the blockage of electronic transport. In this work, using a rotating ring disk electrode (RRDE) in the potentiodynamic regime, the possibility of using CNTs in the active layer (AL) of the positive electrode for long-term LOB discharge in Li+ electrolytes based on DMSO and TEGDME is shown. The direct formation of Li2O2 in the pores of the AL electrode ensures the preservation of a surface fraction that is free of lithium peroxide and accessible for electron transport. The effect of the porous structure is most evident in the DMSO-based electrolyte, which facilitates the formation of Li2O2 on a smooth electrode through the diffusion of the superoxide anion (O2–•) to the solution and its subsequent disproportionation. When oxygen is reduced on the CNTs in the given electrolyte, the formed O2–• is converted to Li2O2 directly in the pores of the AL due to diffusion limitations.

It has been shown that solketal can be synthesized from glycerol and acetone irradiation in the presence of montmorillonite (MM) modified with an aqueous solution of 0.25 mol/L of HCl (0.25M HCl/MM). The reaction has been studied in a methanol solution at an acetone/glycerol molar ratio of 2.45–7.53, a catalyst concentration of 1.2–2.8 wt

The possibility of obtaining sorbitol from potato starch via one-pot hydrolysis-hydrogenation is demonstrated using bifunctional catalysts 0.3–3 wt

In order to establish the main factors that make it possible to regulate the activity and selectivity of the solketal synthesis process from glycerol and acetone, the acidic and catalytic properties of mordenite (MOR, SiO2 /Al2O3 = 29.2) and faujasite (FAU, SiO2 /Al2O3 = 14.9, 97 and 810) were studied. The reaction was investigated at 25 and 50°C, at acetone/glycerol molar ratio of 2.5. In the presence of zeolites, solketal is the main product with a selectivity of 88.1–94.7 %. It has been shown that the main factors determining the conversion of glycerol and the yield of solketal are the availability of reagents to active sites, the number and strength of acid sites, as well as their resistance to the poisoning effect of water molecules formed during the reaction.

In this study, the one-pot synthesis of glycidol from glycerol (Gly) and dimethyl carbonate (DMC) was demon-strated in the presence of novel composite materials based on the microporous layered titanosilicate AM-4 (Aveiro-Manchester material number 4) and a zeolitic imidazolate framework ZIF-8. It was found that the re-action rate and selectivity towards glycidol depended on the ZIF-8 content in composite. Maximum 74.4% yield of glycidol with 92.5% conversion of glycerol was observed in the presence of 0.5%ZIF-8/AM-4 at DMC/Gly-molar ratio of 2, catalyst/glycerol weight ratio of 7.9 wt.% and temperature of 100 degrees C for 8 h. The catalytic properties of developed ZIF-8/AM-4 composite correlated with (1) ZIF-8 particle size, (2) the decreasing basic sites strength, and (3) the increasing microporosity of materials.

The electrochemical characteristics of carbon nanotubes subjected to various types of modification, to increase their activity and stability, in the oxygen reduction reaction in alkaline electrolyte are determined by cyclic voltammetry on a rotating disk and rotating ring-disk electrodes. The measurements were performed on the carbon nanotubes after their functionalization, doping with nitrogen, and subsequent modification with platinum in an amount of up to 20 wt %. The resulting dispersed material in the form of an extremely thin layer was applied to a disk electrode, and the effect of carbon nanotubes’ pretreatment on their efficiency in the oxygen reduction reaction in alkaline electrolyte is studied. The activity is shown to be higher, and the degree of degradation, lower, as the selectivity in the oxygen reduction to water increased. When oxygen was reduced through the intermediate formation of hydrogen peroxide, the degradation of the system under study increased. According to the rotating ring-disk electrode data, the greatest contribution of the reaction with the intermediate Н2О2 formation is observed on the carbon nanotubes after their functionalization, whereas the doping with nitrogen increased the activity and the contribution of the four-electron reaction; the value of n is 3.2. After the modification with platinum, the oxygen reduction reaction proceeds predominantly with the breaking of the O–O-bond and the reduction of oxygen to water. The influence of the support on the platinum-modified nanotubes’ characteristics displays itself in the potential range below 0.70 V, where the electroreduction of oxygen on the platinum-free surface proceeds with the transfer of two electrons and contributes to the overall process. The less hydrogen peroxide formed during the oxygen reduction reaction, the less is the degradation of the catalyst. Further increase in the activity of the carbon nanotubes is required; to this purpose, the number of certain types of nitrogen-containing surface groups facilitating the contribution of the four-electron reaction path of the oxygen reduction reaction must be elevated.

The effect of acid activation with 0.125–0.5 M Н 2 SO 4 , HCl, and HNO 3 on the physicochemical properties and catalytic performance of natural clay (the Mukhartalinskii deposit) containing 95% montmorillonite (MM) was investigated in the synthesis of solketal [(2,2-dimethyl 1,3-dioxolan-4-yl)methanol] from glycerol and acetone. The reaction rate and selectivity toward solketal are shown to depend on the type and concentration of acid. Both the yield of solketal and the reaction rate rose with increasing acid concentration, which correlates with the increase in the number of Brønsted acid sites. The efficiency of the system was found to diminish in the order MM/HCl > MM/HNO 3 > MM/H 2 SO 4 as the surface acidity decreased.

Two types of catalysts anchored on the surface of pre-dehydroxylated Nafen alumina nanofibers: (1) bis(imino)pyridyl complex of Fe(II) and (2) titanium-magnesium catalyst obtained by sequential treatment of Nafen with an organomagnesium compound and TiCl4 were synthesized. The formation of the catalytic systems on the Nafen surface was studied by diffuse reflectance infrared Fourier transform spectro-scopy. It was shown that organomagnesium compound interacts with terminal OH groups of Nafen to form surface =Al-O–Mg-C4H9 groups. TiCl4 interacts with the indicated groups to produce titanium-magnesium catalyst. The bis(imino)pyridyl complex of Fe(II) is anchored on the Nafen surface due to the interaction with strong Lewis acid sites residing on the NF surface. The synthesized catalysts are highly active toward ethylene polymerization. Polyethylene/Nafen composites with different molecular weights were obtained by varying the polymerization conditions, i.e. reaction temperature and hydrogen introduction. Scanning electron microscopy and transition electron microscopy were used to investigate the polymer formation on the surface of Nafen nanofibers and the morphology of the composite particles obtained in situ using the anchored catalysts of different composition.

Zeolitic imidazolate frameworks (ZIFs) possess unique structural, textural, and physico-chemical properties and, therefore, they are promising materials for the synthesis of catalysts. The presence of acidic and basic sites in the structure of ZIFs and the possibility of controlling their number and accessibility offer various ways of using ZIFs in acid-base catalysis. Domestic and foreign works devoted to the study of the catalytic properties of ZIFs in reactions of the acid-base type and published within the recent 15 years are reviewed. Special attention is given to the effect of the crystal size of ZIFs on their catalytic properties in such reactions as condensation, cyclization, and esterification. The advantages and drawbacks of ZIFs as catalysts and the main questions that arise during practical use are considered.

The effect of acid activation using 0.125–0.5 mol/l Н2SO4, HCl and HNO3 on the physicochemical and catalytic properties of natural clay (95 % montmorillonite, Mukhartalinsk deposit) was investigated. The rate and selectivity of the solketal (2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane) synthesis from glycerol and acetone were shown to depend on the concentration and type of the acid. The reaction rate and the yield of solketal increase with increasing concentration of the acid, which is consistent with the growth in the amount of Broensted sites. As the surface acidity increases, the efficiency of the system increases in the series MM/HCl > MM/HNO3 > MM/H2SO4.

A series of Zn- and Co containing zeolitic-imidazolate frameworks (ZIFs), such as ZIF-8(Zn)/ZIF-67(Co), MAF-5(Zn)/MAF-5(Co), and MAF-6(Zn)/MAF-6(Co), were investigated as catalysts for the synthesis of propylene carbonate (PC) from propylene oxide (PO) and CO2. The effect of the chemical composition, textural, structural and physicochemical properties on their activity was investigated. It was found that the activity of Zn-containing materials was higher in comparison with Co-based materials. Moreover, the yield of a PC was decreased with increasing Co content in structure of mixed Zn,Co-ZIFs (ZIF-8/ZIF-67) that was related to the accessibility of active centers to reagents and the strength of their interaction with CO2 and propylene oxide. The catalytic performance of Zn-ZIFs was found to improve with increasing the size of pore aperture due to the guest molecule facile diffusion and accessibility of the active site for reagent. In general, based on the results of the present work, the Zn-ZIFs could be considered as promising catalysts for cycloaddition of CO2 to epoxides and thereby opens new paths for further research.

It was shown that sorbite can be obtained from potato starch by its single-step hydrolysis-reduction in the presence of bifunctional catalysts 0.3–3 wt.%Ru/Cs3HSiW12O40 (Ru/Cs-HPA). Most efficient was the catalyst containing 1 wt.%Ru; this is related to the optimal concentration ratio of Broensted and Lewis acid sites on the support surface and a high specific surface area. The reaction kinetics in the presence of 1%Ru/Сs-HPA was studied and the apparent activation energy of the starch hydrolysis-reduction to sorbite (80±8 kJ/mol) was determined. The experimental and literature data were used to propose a kinetic model of the process, which describes quite adequately the hydrolysisreduction of starch. In the presence of the catalyst with the optimal composition (1%Ru/Cs-HPA) at the optimal temperature (150 °С), the yield of sorbite achieved 88 mol.% (99 wt.%) for 3 hours of the reaction.

Aldol condensation of formaldehyde with dihydroxyacetone (DHA) in an aqueous medium (pH 7.54–8.71) was studied at 65–80 °C in the presence of zeolite-like zinc imidazolate frameworks based on 2-methylimidazole (ZIF-8) and 2-ethylimidazole (MAF-5 and MAF-6). Selectivity of the process was shown to depend on the pH of the reaction solution, which is controlled by the amount of catalyst in the reaction mixture, and on the reaction temperature. The reaction carried out at pH 8.36 and 80 °C leads to a high yield of С6-sugars. Erythrulose is formed with a high yield (39–60 %) at a temperature of 65 °C and pH 7.54-8.71. It was found that the yield of erythrulose in the presence of the catalytic systems under consideration depends on the pore radius and increases in the series MAF-6 > MAF-5 > ZIF-8. Advantages of the studied systems in comparison with the homogeneous and heterogeneous phosphate systems proposed in the literature were revealed.

The hydrolysis-reduction of hemicellulose arabinogalactan to arabitol and galactitol polyalcohols, which are widely used in the food and pharmaceutical industries, was studied. It was shown that the process could be performed with the bifunctional catalyst containing highly dispersed ruthenium deposited on the cesium salt of silicon-tungsten heteropolyacid, Ru/Cs3HSiW12O40. The catalysts with different content of ruthenium (0.3, 0.6 and 1 wt.%) were synthesized for the study. The catalysts and their Cs3HSiW12O40 support were examined by various physicochemical methods (low-temperature nitrogen adsorption, IR spectroscopy, XRD, and TEM). The effect of temperature, substrate/catalyst ratio and ruthenium content in the catalyst on the yields of target products was elucidated. The highest yields of target products were achieved at the metal content of 0.6 wt.% and equal weights of the loaded catalyst and substrate (the 1:1 ratio). At a temperature of 200 °C, arabitol and galactitol can be produced with the yields up to 12 and 48 % for 2 h of the reaction in the presence of catalyst with the composition 0.6%Ru/Cs3HSiW12O40.

The hydrolysis-reduction of hemicellulose arabinogalactan to arabitol and galactitol polyalcohols, which are widely used in the food and pharmaceutical industries, was studied. It was shown that the process could be performed with the bifunctional catalyst containing highly dispersed ruthenium deposited on the cesium salt of silicon-tungsten heteropolyacid, Ru/Cs3HSiW12O40. The catalysts with different content of ruthenium (0.3, 0.6 and 1 wt.%) were synthesized for the study. The catalysts and their Cs3HSiW12O40 support were examined by various physicochemical methods (low-temperature nitrogen adsorption, IR spectroscopy, XRD, and TEM). The effect of temperature, substrate/catalyst ratio and ruthenium content in the catalyst on the yields of target products was elucidated. The highest yields of target products were achieved at the metal content of 0.6 wt.% and equal weights of the loaded catalyst and substrate (the 1:1 ratio). At a temperature of 200 °C, arabitol and galactitol can be produced with the yields up to 12 and 48 % for 2 h of the reaction in the presence of catalyst with the composition 0.6%Ru/Cs3HSiW12O40.

The effect of carbon nanotube (CNT) surface modification by oxygen– and nitrogen–containing groups on the activity of Pt–containing catalysts supported on these CNT (Pt/CNT and PtCo/CNT) studied in the oxygen reaction in aprotic electrolyte containing lithiumсations. It is shown, that modification of the CNT surface by oxygen– and nitrogen–containing groups enhances the polarization capacity of the material that characterizes the value of the electrochemically active surface area and lowers the overpotential of the oxygen reduction reaction (ORR). Synthesis of platinum or its alloy (PtCo) on modified CNT allowed establishing the relationship between the activity of these catalysts in the oxygen reaction in aprotic electrolyte and the synthesis conditions and CNT pretreatment. The catalytic effect of modification by platinum consists in a decrease in the ORR overpotential with formation of Li2O2 and its further anodic decomposition and in an increase in the reversibility degree. It is shown that the sites on which Pt nanoparticles are fixed on the CNT surface are oxygen–containing groups. The most probable result of synthesis of PtCo alloy on CNT is the binding of cobalt to nitrogen in nitrogen–containing groups and then to platinum (N–Co–Pt).

In the present work, we demonstrated synthesis of Al-SiO(2)and magnetically recoverable Al-SiO2/Fe(3)O(4)systems via grafting of triethylaluminum on SiO(2)and SiO2-coated magnetic Fe(3)O(4)nanoparticles, respectively. These materials were characterized by various techniques including elemental and N-2-adsorption/desorption analyses, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) using CO and pyridine as probe molecules. Amount of grafted Al on the support was found to affect the textural, acid-base properties and catalytic behavior in the isomerization of alpha-pinene oxide (PO) to campholenic aldehyde (CA). Maximal activity and selectivity towards CA was observed in the presence of sample with 12 wt% of alumina. It was demonstrated that 12%Al-SiO2/Fe(3)O(4)can be used as catalyst for at least four successive cycles without loss of activity.

The necessity of the studying of carbonaceous materials differing in their surface area and structure is called for by the fact that these materials are used until now in the designing of positive electrodes for lithium-oxygen current sources. Under the model conditions, the effect of some factors on the effectiveness of oxygen reduction reaction at the positive electrode is studied. Among them are: properties of the dimethylsulfoxide- and acetonitrile-based electrolytes, the carbonaceous material (ХС 72, Super P, and carbon nanotubes) structure and its relevant transport processes depending on the electrode active layer mass (thickness) and the polarization current density, which determines the oxygen reaction effectiveness at the carbonaceous material. The electrochemically active surface area is shown to increase with the specific surface area, which is determined by the carbonaceous material porous structure, its mass at the electrode, the solvent properties, and the reaction rate. The active layer thickness and current density must be chosen for each carbonaceous material individually, depending upon its structure. At that, the active layer entire surface must be electrochemically accessible; it must make possible the lithium peroxide formation and subsequent decomposition. In the dimethylsulfoxide-based electrolyte (high donor number), the oxygen reduction reaction is highly reversible; the lithium peroxide formation here occurs via disproportionation in the solution bulk and results in the formation of Li 2 O 2 particles with disordered (in all probability, toroidal) structure. This facilitates the back reaction (Li 2 O 2 anodic decomposition), in good agreement with literature data [1]. In acetonitrile-based electrolyte (low donor number), the oxygen reduction reaction occurs in adsorbed state, producing LiО 2 that disproportionates at the electrode surface forming a lithium peroxide insulating film whose oxidation needs high overvoltage. On the strength of all the parameters, carbon nanotubes are most effective in the oxygen reduction reaction in the dimethylsulfoxide-based electrolyte, because the carbon nanotubes have large volume of mesopores for the reactant transport, high electrochemically active surface area for the Li 2 O 2 accumulation, and thus provide high characteristics per electrode.

Catalytic liquid-phase hydrogenation of furfural to commercially important furfuryl alcohol was studied in the presence of Ru-containing catalysts based on Sibunit and zeo-type materials, such as nickel phosphate molecular sieves (VSB-5 and Fe-VSB-5) and zirconium-containing metal–organic frameworks (UiO-66(Zr)-R, R = H and NH2), at 30 and 50°C and 5–25 atm of hydrogen. The yield of furfuryl alcohol was found to depend on the nature of the support and increases in the following order: Ru/UiO-66(Zr)-NH2 < Ru/UiO-66(Zr) < Ru/Fe-VSB-5 < Ru/VSB-5. The effect of hydrogen pressure and temperature on the selectivity toward furfuryl alcohol was investigated.