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The review discusses the results of recent studies in the promising field of integrated processing of lignocellulosic biomass – the reductive catalytic fractionation (RCF). The effect of catalysts, cocatalysts, solvents, hydrogen sources and features of lignocellulosic feedstock on the selectivity of monomeric products formation from lignin is considered. RCF processes are performed mostly with the heterogeneous catalysts, which allow implementing the reductive depolymerization of lignin to obtain low-molecular compounds and preserve carbohydrate components of biomass. Among the studied catalysts based on platinum group metals and transition metals, the highest activity is observed for the catalysts containing Pd, Pt, Ru and Ni. Features of the metal also affect the composition of the resulting products. Thus, ruthenium catalysts make it possible to obtain 4-propylguaiacol as the main product, while Ni and Pd – 4-propanolguaiacol. Mo-containing catalysts, owing to their lower hydrogenating activity, can be used to obtain monolignols or their etherified derivatives with the preservation of carbohydrate components of lignocellulosic biomass. However, most efficient in RCF processes are the bifunctional catalysts, which have both the acidic and metallic active sites. Acidic sites promote the cleavage of the ether β-O-4 bonds, whereas metallic sites – the reduction of the formed intermediate compounds. An important aspect of choosing the appropriate catalysts for RCF process is the possibility of their repeated application. The use of a ferromagnetic catalyst or a catalyst basket allows separating the catalyst from the products.

The optimization of the process of β-sitosterol extraction from the original and activated with two different methods (drum mill, explosive autohydrolysis) pine bark was carried out. The effect of the duration of the extraction process and the concentration of NaOH in the saponification solution on the yield of β-sitosterol was explored. The concentration of NaOH in the saponification solution appeared to have the highest effect on the β-sitosterol yields from activated pine bark. Mechanical activation of pine bark significantly increased the yield of β-sitosterol and reduced the duration of the isolation process. The highest yield of β-sitosterol was achieved with the use of pine bark activated by explosive autohydrolysis. According to the proposed mathematical model, the maximum predicted value of the β-sitosterol yield from this sample is 0.078 (wt%). This could be achieved using the process duration 10.3 hours and a 0.5 N solution of NaOH. This yield is close to the content of β-sitosterol in the original pine bark

Water oxidation is the bottleneck of the water splitting process. A novel highly efficient and stable for many cycles heterogeneous Cu-contained catalysts supported on MFI-type zeolite (1% Cu-ZSM-5) for water oxidation were prepared. Oxo/hydroxo complexes of copper (II) were stabilized in the zeolite channels via polycondensation. The analysis of the electron states of copper in the Cu-containing zeolite-based catalysts using EPR and UV–vis DR techniques revealed that the catalytic efficiency of Cu(II) state in zeolite grew up in the series: [Cu(NH3)4]2+

This work contains an analysis of the total content of petroleum products (hydrocarbons) in samples and columns of bottom sediments (BS) of the Noril’skaya–Pyasino group of water objects contaminated as a result of a diesel fuel spill from the CHPP-3 reservoir at AO NTEC near Norilsk. Two methods—fluorimetry and gas chromatography—have been used for analysis. Gas chromatography is also used to obtain the distribution of n-alkanes in extracts from BS and study the contribution of hydrocarbons (HCs) of diesel fuel and of slightly mature organic matter from modern sediments in the total content of HCs. The HC composition of diesel fuel and of chloroform extracts from BS is determined. It is shown that the pollution of BS in Lake Pyasino with HCs is insignificant when compared with their background content, and the maximal pollution is revealed for BS in the Ambarnaya River.

γ-Valerolactone (GVL) is a valuable chemical compound known as a platform molecule. It is considered as an intermediate product for the synthesis of chemical compounds with high added value, components of motor fuels, and biopolymers. GVL is well established as an environmentally safe solvent, fuel additive, flavoring, and nutritional supplement. This review summarizes the latest advances in the development of catalytic ways of GVL synthesis from levulinic acid (LA), alkyl levulinates (ALs), and carbohydrates and plant polymers. Special attention is given to heterogeneous catalysts based on metals and metal oxides, which are more promising for practical application. Proposed mechanisms of the processes are considered in detail, and the prospect of using hydrogen-donor solvents in the processes of GVL production is discussed. Catalysts demonstrating the best catalytic properties are compared from the viewpoint of their productivity, an important parameter for industrial catalysis.

γ-Valerolactone (GVL), which is a valuable chemical compound and a platform molecule, is considered as an intermediate product for the synthesis of chemical compounds with high added value, components of motor fuels and biopolymers. GVL is successfully used as an environmentally friendly solvent, fuel additive, fragrance and food additive. This review summarizes recent advances in the development of catalytic methods for the production of GVL from levulinic acid (LA), alkyl levulinates (AL), carbohydrates and vegetable polymers. Particular attention is paid to heterogeneous catalysts based on metals and metal oxides, which are more promising for practical application. The proposed mechanisms of processes are considered in detail, and prospects of using hydrogen-donor solvents in the production of GVL are discussed. Catalysts with the best catalytic performance were compared in terms of their productivity, which is an important parameter for industrial catalysis.

Nanostructured 1 and 3% catalysts containing ruthenium nanoparticles supported on the initial and oxidized at different temperatures graphite-like carbon material Sibunit-4 prepared. A features of this support are mesoporous texture, hydrothermal stability and the presence of surface oxygen-containing functional groups responsible for the distribution of Ru nanoparticles and the catalyst acidic properties. The catalysts characterized using methods TEM, XPS, N2 adsorption, pHpzc and tested in the hydrogenation of levulinic acid to γ-valerolactone. It was found that the reaction rate and GVL selectivity are influenced by solvent choice, fractional composition, and acidic properties of the support. The obtained catalysts provide high activity in the reaction of direct hydrogenation of levulinic acid to γ-valerolactone (GVL yield 98 mol.%, At 160°С, 1.2 MPa H2) and high productivity (15.9 gGVL/gCat.). Obtained catalyst can be reused several times without noticeable loss of activity

A method for production a new fertilizer was proposed. This method is based on the impregnation of a substrate from pine bark with a water solution of ammonium nitrate, and containing 20.0 wt. % nitrogen. The physicochemical properties of a pine bark substrate and prepared fertilizers were studied. A field experiment was conducted on growing wheat of the variety “Krasnoyarskaya 12”. The yield of wheat when fertilized with pine bark was applied to the soil increased by 2.9 centners/ha compared to blank experiment without fertilizer. The use of this fertilizer results in an increase in the quality (higher nutritional value) of the grains in comparison blank experiments with ammonium nitrate and without fertilizer

The kinetic parameters of the pyrolysis of Siberian fir bark were estimated by thermogravimetric analysis. The thermochemical conversion of the bark biomass was performed at heating rates of 5, 10, and 20 deg/min in an inert (argon) medium. The results of thermogravimetric and differential thermogravimetric analyses were studied by model-fitting (Arrhenius and Coats–Redfern) and model-free (Friedman and Ozawa–Flynn–Wall) kinetic methods. The most reliable values of the activation energy were obtained by the model-free Ozawa–Flynn–Wall and Friedman methods (159 and 156 kJ/mol, respectively). It was shown that using these kinetic models enables one to determine more accurate temperature ranges of decomposition of biomass components under pyrolysis conditions.

Lignin is a large-scale waste product of hydrolysis and the pulp-and-paper industries. The problem of lignin utilization is addressed by developing techniques for the comprehensive processing of wood biomass that are based on preliminary catalytic fractionation into its key components, which are subsequently used for obtaining target products. Hemicelluloses of larch wood are known to undergo effective depolymerization (~95 wt %) in ethanol at 250°C. Using hydrogen in combination with a catalyst enables us to increase the lignin conversion to 61 wt %, with 47 wt % of the cellulose left in the solid residue. The highest lignin conversion (67 wt %) is achieved using formic acid, but there is undesirable cellulose depolymerization (conversion, 66 wt %) under these conditions. The main monomer products of the catalytic conversion of lignin are 4-propenylguaiacol and 4-propylguaiacol. The content of 4-propenylguaiacol among the liquid products obtained using ethanol and formic acid as reducing agents can be as high as 36 and 33 rel %, respectively. The content of 4-propylguaiacol among the liquid products obtained using hydrogen grows to 33 rel % when a catalyst is used. This work describes the first study of the catalytic fractionation of larch wood in supercritical ethanol in the presence of the bifunctional 3%Ru/C catalyst containing acidic groups. The aim is to identify the effect of the catalyst and the nature of the hydrogen donor (ethanol, H2, or formic acid) on the yield and composition of the product.

It is shown that the reaction of the hydrolysis–hydrogenolysis of cellulose to alcohols can be catalyzed by the binary system Ca(OH)2–composite material based on tungsten carbides W2C/WC, obtained by combining mechanochemical activation and self-propagating high-temperature synthesis with an exothermic mixture of tungsten oxide, metallic magnesium, and technical carbon. It is demonstrated that the amounts of tungsten carbides (W2C, WC) and the ratio between them can be controlled by introducing inert additives (metallic tungsten or calcium carbonate) to the exothermic mixture. The order of introducing reagents to the exothermic mixture and their activation is found to affect the textural properties of the materials. Self-propagating high-temperature synthesis is shown to be superior to mechanochemical activation. The catalytic properties of these materials are studied in the hydrolysis–hydrogenolysis of cellulose. It is determined that the phase composition of the composite materials affects the yields of ethylene glycol and 1,2-polyethylene glycol and their ratio. The maximum total yield of the glycols (25–31%) is obtained using a sample with a high W2C content.

The effect pine bark activation by explosive autohydrolysis and mechanical treatment in a ball mill on the yield and properties of resinous and pectin substances and β-sitosterol was studied. Pine bark physicochemical properties after its activation by a batch of methods were studied. It was shown that the activation of pine bark by explosive autohydrolysis result in the highest increase in the yield of extractive substances. The conditions providing the highest yield of target products from the activated pine bark were determined: for resinous substances and β-sitosterol – the use of 0.5 n alkali solution; for pectin substances – the use of hydrochloric acid

In this paper we continue working on our theory of electrical double layers resulting exclusively from dissociation of a solid electrolyte, which we previously proposed as a medium for catalytic interaction between solid cellulose and solid acid catalysts of hydrolysis. Two theoretical unidimensional models of the inner grain volume are considered: an infinitely long cylindrical pore, and a gel electrolyte near a grain outer surface. Despite the model simplicity, the predictions for the cylindrical pore case are in semi-quantitative agreement with literature data on electroosmotic experiments, adequately explaining high proton selectivity of sulfonic membranes, and decline of such selectivity at high background acid concentration. The gel model predicts less concentrated diffuse layer in comparison to electrolytes with impenetrable skeleton (e. g., sulfonated carbons). This suggests limited suitability of gel electrolytes as catalysts if a substrate cannot diffuse into the gel bulk and the reaction is thereby spatially limited to the near-surface region, for example if a substrate is solid like aforementioned cellulose.

The impact of the preparation techniques of niobium oxide and two-component systems based on niobium and zirconium oxides on the catalytic properties was studied in the one-pot hydrolysisdehydration of cellulose into glucose and 5-hydroxymethylfurfural. Cellulose transformation was performed in an autoclave at 180 °С under argon atmosphere. The most promising methods for the preparation of solid catalysts were found to be microwave heating and mechanical activation. Glucose and 5-hydroxymethylfurfural can be produced with total yield equal to 20-21 % in the presence of catalysts prepared using these techniques

The regularities of thermocatalytic transformation of pine ethanol lignin in supercritical ethanol in the presence of catalysts NiCu/SiO₂ and NiCuMo/SiO2 in the temperature range 250–400 °C were established. The composition and structure of ethanol lignin, liquid and solid products of its conversion were studied by methods of elemental analysis and gel-permeating chromatography (GPC). The composition of gaseous products – by method of gas chromatography. At the process temperature of 250 °C the catalysts do not have a significant effect on conversion of ethanol lignin. The maximal yield of liquid products (83.5 wt. %) was obtained at temperature 300 °C in the presence of catalyst NiCuMo/SiO₂ containing 8.8 wt. % of molybdenum. At temperature 350 °C NiCu/SiO₂ and NiCuMo/SiO2 catalysts contribute to the almost complete conversion of ethanol lignin into liquid and gaseous products, and the yield of solid products does not exceed 1 wt. %. In liquid products of catalytic conversion there is a decrease in the atomic ratio of O/C and the increase of H/C atomic ratio as compared to initial ethanol lignin due to catalytic intensification of reactions of deoxygenation and hydrogenation of lignin and products of its depolymerization. According to GPC data on the curves of molecular mass distribution (MMD) of liquid products of thermocatalytic conversion of ethanol lignin at 300 °C there are peaks with highs at 160 and 380 Da, probably related to guiacyle monomers and dimmers, respectively. From the comparison of MMD of liquid products obtained by ethanol lignin depolymerization at 300 °C over catalysts NiCu/SiO₂ and NiCuMo/SiO₂ it follows, that the introduction of molybdenum in the catalyst promotes the formation of monomeric guaiacyl products

The possibility of using aspen bark modified with zinc and iron chlorides for preparing highly porous materials with specific properties was examined. The effect of the treatment temperature and modifiers on the structural and electrochemical parameters of the carbon-containing product was revealed. Carbonization of aspen bark modified with ZnCl2 yielded a material with the specific surface area of up to 1350 m2 g–1, containing a crystalline zinc oxide phase. The material obtained using a mixture of aspen bark with FеCl3 had the specific surface area of up to 300 m2 g–1 and contained magnetite and maghemite. Modification of the bark with zinc and iron chlorides simultaneously yielded a highly porous product with ferromagnetic properties. The apparent capacitance of the samples carbonized at 800°С was found to be 150–400 F g–1. The possibility of using these materials in electrochemical devices was suggested.

Lignin is a bulky waste of the hydrolysis and paper-pulp industry. To solve the problem of its utilization, approaches to deep processing of wood biomass are being developed; they are based on a preliminary catalytic fractionation of wood biomass into main components, which are processed into target products. For the first time, the reductive catalytic fractionation of larch was studied in a supercritical ethanol medium in the presence of 3%Ru/С bifunctional catalyst containing acid groups. The goal of the study was to reveal the effect of the catalyst and features of a hydrogen donor (ethanol, H2, formic acid) on the yields and composition of the products. It was shown that wood hemicelluloses efficiently (ca. 95 wt.%) depolymerize to ethanol at 250 °С. The use of hydrogen in the presence of the catalyst makes it possible to increase the conversion of lignin to 61 wt.% with retaining 47 wt.% cellulose in a solid residue. The maximum conversion of lignin equal to 67 wt.% was obtained in the presence of formic acid; however, the indicated conditions lead to undesirable depolymerization of cellulose (the conversion of 66 wt.%). The main monomeric products of lignin conversion on the catalyst are propenylguaiacol and propylguaiacol. In the liquid products obtained with ethanol and formic acid as the reductants, the content of propenylguaiacol reaches 36 and 33 rel.%, respectively. In the products obtained with hydrogen, the content of propylguaiacol increases to 33 rel.% in the presence of the catalyst.

Cu(Fe)-containing zeolites are promising catalysts for biomimetic functionalization of light hydrocarbons. Catalysts with various copper states have been elaborated and studied in the peroxide oxidation of methane to methanol and formic acid. ICP-AES, UV–vis DR, EPR, NH3-TPD, H2-TPR, and N2 adsorption techniques were used for the characterization of the Cu(II) states, the textural, acidic and redox properties of the catalysts. The prepared zeolites contained the following Cu species: (1) isolated Cu2+ ions, (2) square planar binuclear oxo/hydroxo complexes ([Cu2(OH)2]2+) in the zeolite channels, (3) CuO- and/or Cu(OH)2-like clusters and nanoparticles on the zeolite external surface. UV–vis DR spectroscopy also was used for studying the ability of different Cu-ZSM-5 to form Cu peroxocomplexes with H2O2. Three types of peroxocomplexes were detected. These were terminal Cu–OOH originated from the isolated Cu2+ ions, binuclear Cu(II) with a terminal OOH group and the binuclear Cu(II) with a bridging OO-group formed from the Cu-species with extra lattice oxygen. 1H and 13C NMR analysis revealed the formation of methylhydroperoxide, formaldehyde, and CO2 as side products during peroxide oxidation of methane. Two pathways of methane oxidation with hydrogen peroxide involving both binuclear Cu-species with extra-lattice oxygen and isolated Fe-sites and/or oligomer oxo-clusters of Fe(III) ions were supposed.

Solid bifunctional catalysts based on cesium salts of V-containing heteropoly acids (CsHPA: Cs3.5H0.5PW11VO40, Cs4.5H0.5SiW11VO40, Cs3.5H0.5PMo11VO40) and Cs2.5H0.5PMo12O40 were used for studying one-pot hydrolysis–oxidation of potato starch to formic acid at 413–443 K and 2 MPa air mixture. It was shown that the optimum process temperature that prevents formic acid from destruction is 423 K. The studies were focused on the influence of the composition of heteropoly anions on the yield and selectivity of formic acid. Using W–V–P(Si) CsHPA results in the product overoxidation compared to Mo–V-containing CsHPA. The activity of Cs–PMo was significantly lower compared to Cs–PMoV. This may indicate that vanadium plays an important role in the oxidation process. The most promising catalyst was Cs3.5H0.5PMo11VO40 which provided the maximum yield of formic acid equal to 51%. Cs3.5H0.5PMo11VO40 was tested during nine cycles of starch hydrolysis–oxidation to demonstrate its high stability and efficiency.

The effect of bifunctional catalyst Pt/ZrO₂ on the yield and composition of products of abies wood and ethanol lignin hydrogenation in supercritical ethanol at temperature of 250 °C was established. In the process of abies wood hydrogenation, the catalyst Pt/ZrO₂ increases the degree of conversion of wood from 52.0 to 65.7 wt.%, the yield of liquid products from 31.0 to 38.1 wt.%,.%, and also increases the content of monomeric compounds in the liquid products. In the presence of catalyst, the cellulose content in the solid product of wood catalytic hydrogenation reaches to 77.1 wt.%, and the content of lignin and hemicelluloses decreases to 21.2 wt.% and 1.7 wt.%, respectively. In the process of ethanol lignin hydrogenation the catalyst Pt/ZrO₂ increases the degree of lignin conversion from 86.0 to 99.4 wt.%, the yield of liquid products from 75.0 to 90.0 wt.%, and also reduces the yield of solid residue from 14.0 to 0.6 wt.% and the yield of gases from 4.7 to 3.3 wt.%. Thus, the polysaccharides of wood biomass complicate the reductive depolymerization of native lignin in comparison with the depolymerization of isolated ethanol lignin. The use of the catalyst Pt/ZrO₂ makes it possible to fractionate the abies wood in supercritical ethanol at 250 °C on solid product with a high content of cellulose, as well as liquid and gaseous products from lignin and hemicelluloses

Double activation catalysis was experimentally observed in hydrolysis of cellobiose catalyzed simultaneously with phthalic and hydrochloric acids, confirming earlier theoretical prediction known from literature. Both acids can catalyze the reaction individually, and contribution of the double-activation pathway to the total reaction rate declines as temperature increases. In fact, above a certain temperature, the hydrolysis rate in presence of both acids becomes lower than the sum of the rates for the two acids acting individually. A kinetic model is proposed to explain this transition between double-activated catalysis and inhibition. The trend of declining contribution of cooperative catalytic pathway with rising temperature is theorized to be generally applicable for any reaction with a pathway involving simultaneous action of two catalysts when either of them can individually catalyze the reaction.

The one-pot hydrolysis-dehydration of activated microcrystalline cellulose was studied in pure hydrothermal water at 453 K over ZrO2 catalysts produced by thermodegradation, microwave treatment, mechanical activation, and sol–gel methods and spent without any co-catalyst. ZrO2 prepared by microwave treatment was more active compared to ones derived by other methods. The catalyst calcination temperature also impacted reactivity. The cellulose conversion increased simultaneously with acidity and SBET, which in turn were set by the preparation method and calcination temperature. Phase composition did not affect the activity. Yields of glucose and 5-HMF reaching 18 and 15%, respectively, were over the most promising ZrO2 prepared by microwave treatment at 593 K. To our knowledge, this ZrO2 sample provided the highest activity in terms of TOF values (15.1 mmol g−1 h−1) compared to the pure ZrO2 systems reported elsewhere. High stability of ZrO2 derived by microwave irradiation was shown in five reaction runs.

Thermal conversion of flax shives was studied in sub- and supercritical ethanol medium at 225 and 250 °C in the presence of the bifunctional catalyst 3% Ru/C. The use of 3% Ru/C catalyst in the process of thermal conversion of flax shives in supercritical ethanol was found to increase the conversion of the shives by 27% and the yield of liquid products by 10%. The use of 3% Ru/C catalyst in sub- and supercritical ethanol led to the destruction of both lignin and cellulose. The degree of delignification in the non-catalytic thermal conversion increased upon transition from subcritical (225 °C) to supercritical (250 °C) conditions. Main monomeric products of the thermal conversion process were guaiacylpropene or guaiacylpropane depending on the process temperature. In the presence of Ru/C catalyst, the molecular weight distribution was shifted towards an increase in the content of monomeric compounds in the liquid products.

In the presence of acidic catalysts based on the Sibunit-4 material the effects of mechanical activation and a lignin impurities on both the reactivity of cellulose and yields of products (monosaccharides and furfurals) being achieved during the hydrolysis of the polysaccharide isolated by hydrotropic cooking of miscanthus, wheat straw, and fruit shells of oats were studied. Activation was shown to significantly increase the reactivity of all substrates and the yields of the target products. Impurities of lignin led to decreasing product yields

In a de novo physicochemical modeling, the synthesis of biologically important sugars and other chiral compounds without any chemical initiators is demonstrated for the first time by photolysis of a concentrated formaldehyde solution and subsequent condensation of the product; chiral condensed phase detected; the splitting of enantiomers in terms of chirality sign at the moment of condensation is determined; hierarchical (three-level) helical structure of the optically active anisometric phase (strings) is detected, in which the strings of a larger diameter consists of helically plaited strings of a smaller diameter; it was found that the direction of twisting of the strings when they are helically plaited from the strings of the previous hierarchical level is determined by their supramolecular chirality (the sign of an excess of the left or right helical supramolecular submicroscopic structures); it was shown that structure formation in systems similar to prebiological may occur through the mechanism of supercoiling already in an aqueous solution of sugars with molecular weights μ of ~102 Da, that is, much earlier than linear chiral macromolecules are formed. The results are obtained under conditions that correspond to modern ideas about the form and vector of prebiological evolution, and therefore may be of fundamental importance for molecular biology.

The effect of a bifunctional catalyst containing nano-dispersed ruthenium particles on an oxidized carbon support “Sibunit” on the yield and composition of products in the processes of hydrogenation of abies wood and abies ethanol-lignin in a supercritical ethanol medium at 250° C was studied. The presence of Ru/C catalyst resulted in a raise the ethanol-lignin conversion from 85 to 98 wt.%, the yield of liquid product from 75 to 85 wt.%, the yield of gases – by 1.5 times, but the yield of solid products dropped from 14 to 2.8 wt.%. Ruthenium catalyst increased the conversion of abies wood by 12.5 wt.%, but did not affect the yield of liquid products. The yield of the solid residue in the presence of the catalyst was reduced by 12.5 wt.%, and the yield of gases rose by 2.5 times. Simultaneously, the ruthenium catalyst promoted the process of hydrodeoxygenation of liquid products, diminution their average molecular mass from 1174 g/mol to 827 g/mol and the formation of monomeric and dimeric compounds with a molecular mass 193 and 426 g/mol, respectively. The solid residue of catalytic hydrogenation contained 70.1 wt.% of cellulose. Thus, the application of Ru/C catalyst in the process of hydrogenation of abies wood allowed the reductive fractionation of wood biomass into a solid cellulose product, liquid and gaseous products from lignin and hemicelluloses.

A novel highly efficient and stable for many cycles catalyst (1% Со-ZSM-5(17)) for water oxidation was developed using the method of polycondensation for stabilization of oxo/hydroxo complexes of cobalt (II, III) and nanosize Co3O4 in zeolite channels. In a weak-alkaline medium (pH 8.0, 9.2, 10.0) in the presence of a one-electron oxidant (Ru(bpy)33+), the catalyst provided the yield of oxygen as high as 56, 73 и 78% of the stoichiometric quantity, respectively. Catalysts based on ZSM-5 zeolite exhibited higher catalytic activity as compared to the catalysts based on the MOR, BEA, Y. Inspection of the electron states of cobalt in the Co-containing zeolite-based catalysts using TPR-H2 and UV–Vis DR techniques revealed that α-Co(OH)2-like polynuclear clusters and hydrocomplexes stabilized in the zeolite channels were most active to catalytic oxidation of water, while their transformation to Co3O4-like clusters/nanoparticles and Co2+ oxocomplexes, respectively, during thermal treatment led to some decrease in the catalyst efficiency. Coarsening of Co3O4-like clusters/nanoparticles caused the further decrease in the system efficiency. The minimal activity was observed with the catalysts containing predominantly isolated Co2 +Oh ions. The result obtained indicates a kind of at least polynuclear structure of the catalytically active center ConOx, where n > 2.