Home – Home – Jornals – Chemistry for Sustainable Development 2017 number 6

Up to 1 billion nm³ of hydrogen sulphide-containing associated petroleum gas (APG) is annually flared in Russia, which leads to the release into the atmosphere to 60 thousand t of H₂S, SO₂, SO₃, carbon black, carbon monoxide, and to 3 million t of carbon dioxide and most importantly, to loss of hundreds of millions of cubic meters of hydrocarbon raw materials. The development of environmentally safe, efficient, and compact technologies to solve this problem is a pressing issue. The paper carries out brief analysis of existing technical solutions and the description and the main trial results for technologies of the Boreskov Institute of Catalysis SB RAS.

The present review is devoted to the study of the process for low-temperature pyrolysis of coal. The effect of genetic and technical factors (heating rate, microwave radiation effects, and catalyst) on the yield and composition of coal thermal decomposition products was assessed. As demonstrated by literature data analysis, low-temperature pyrolysis of coal contributes to an increase in the yield of semi-coke, tar, and gas in inert, reducing, and oxidizing media, respectively. The use of microwave radiation or low temperatures during coal pyrolysis leads to an increase in the yield of liquid products, and of catalysts - tar and light hydrocarbon fractions, correspondingly.

Reduction of freshly precipitated mixed hydroxides with hydrazine in strongly alkaline medium yielded nanostructured (5-20 nm crystallites) powders of the Fe-Co-Ni system in the entire region of compositions. They had different magnetic characteristics and were promising for the use as magnetic materials. The correlation between magnetic properties and phase composition, and also crystallite (species) sizes was explored. The reached values of saturation magnetization of samples in the region of an iron rich solid solution exceeded parameters of the known literature analogues. It was also found that dependencies, such as lattice parameter and composition for face-centered and cubic body-centered cubic phases of solid solutions were described by the flat surface equation.

The properties of nanostructured composites based on porous carbon matrices filled with products of thermolysis of cobalt azide particles pre-synthesized in pores of matrices are considered. Porous carbon materials of the types "Carbonisation 3" and "Kemerite 8" were used as matrices. The investigations were performed by X-ray diffraction, X-ray fluorescence analysis and small-angle X-ray scattering. According to X-ray diffractometry data, the Co (N3) 2 decomposition products in the explosive mode on the "Carbonisate 3" matrix are metallic cobalt and CoO, and on the "Kemerite 8" matrix the main product of thermal decomposition is the spinel Co3O4. The study of matrices and composites based on "Carbonizate 3" by the MCPD method has shown that the sizes of the three detectable groups of inhomogeneities observed on carbon matrices during the preparation of the composite range from 1-3, 6-18, and 160-300 nm. The electrochemical properties of the obtained nanocomposite material were studied. It is shown that the introduction of cobalt oxide into the carbon matrix leads to an increase in resistance and an increase in the electrical capacity of the composite electrodes. The increase in capacity is due to the pseudo-capacity of cobalt oxides due to reversible oxidation-reduction processes involving the oxide-hydroxide phases of cobalt, which are formed during the charge-discharge of the cell.

The paper studied adsorption characteristics of carbon sorbents produced from naturally oxidised coal of Barzas deposit. Synthesis of sorbents was carried out by the chemical activation method using potassium or sodium hydroxide and carbonization at 800 °С. The effect of alkaline nature and the amount of the introduced alkali at the impregnation stage on characteristics of the resulting sorbents was studied. Adsorption characteristics were explored on an example of benzene, phenol, and iodine. Benzene adsorption under the studied conditions linearly depends on the total pore volume in the sorbent. It was demonstrated that sorbents produced from the naturally oxidised Barzas coal activated by potassium hydroxide had the developed porous structure and high adsorption characteristics. To produce sorbents with high characteristics from the naturally oxidised Barzas coal with potassium hydroxide activation it was sufficient to use a coal/KOH mass ratio of 1 : 0.5.

Regularities of electrodeposition and electrooxidation of nanostructured mono- and bimetallic systems based on nickel and cadmium were examined in sulphate and ammonia buffer electrolytes when using the inert glassy carbon substrate for deposition. Nano metallic precipitateswith complex phase composition were formed, as shown by means of anodic voltammetry. Their electrooxidation was accompanied by generating a series of peaks in voltammetric curves. Conditions of electrochemical synthesis of nanostructured electrolytic systems based on nickel and cadmium were determined.

The paper presents the results on synthesis of natural gas hydrates in a medium of water-in-oil emulsions in a high-pressure cell. Hydrates are generated in emulsions via a stepwise mechanism, as established. Its origin is driven by diffusion parameters of natural gas. Hydrate growth from natural gas dissolved in oil occurs in emulsion medium accompanied by concentrating methane, as demonstrated by the study of the composition of the resulting hydrates. Whereas hydrate composition does not depend on a ratio of oil and aqueous components of the emulsion. Hydrate content in emulsions is directly dependent on the amount of water in an emulsion composition and decreases with increasing the water fraction, as demonstrated.

The development of alternative power engineering requires the development of highly effective systems for energy storage and transformation. The paper presents a new approach to the solution of a task of preparation of nanostructured composite electrodes for supercapacitors based on highly porous carbon matrixes. The way consists in thermal (slow or explosive) decomposition of nanocrystals of high-energy compounds pre-generated in matrix pores. A method for preparation of С/CoN₆ composite with a given phase ratio is developed within carried out research. Thermal decomposition of CoN₆ proceeds in explosive or non-explosive modes depending on composite composition and heating mode, as shown. According to X-ray diffractometry, decomposition product in non-explosive mode is Co₂O₃, while in explosive mode - nanoscale cobalt oxide (CoO). The sizes of inhomogeneities formed on the carbon matrix during composite preparation are 7-10 nm, as demonstrated by the study of С/CoN₆ composite using the small angle X-ray scattering (SAXS) technique. Electrochemical properties of the resulting nanocomposite material are studied. The introduction of cobalt oxide into carbon matrix leads to an increase in the resistance and electric capacitance of composite electrodes, as illustrated. Capacitance increase is due to the pseudo-capacitance of cobalt oxides because of reversed redox processes with the involvement of oxide hydroxide phases of cobalt generated during cell charge/discharge.

With a view to optimizing conditions for preparation of promising high magnetic nanomaterials, the dimensional peculiarities of which find the increasing use, the work explored mixed iron, cobalt, and nickel hydroxides, i.e. intermediate products of synthesis by the method of reduction of precursors that refer to this class of nanostructured Fe-Co-Ni powders using methods of X-ray diffraction and mass spectrometry. Precipitation of hydroxides was carried out under conditions of preparation of a polymetallic but with a lack of a reducing agent, both in coprecipitation mode and separately. As established by crystal lattice parameters, iron in coprecipitated mixed hydroxides is largely oxidized to Fe³⁺, which is probably due to their nanoscale dimensionality determined using XPA.The composition of the resulting oxide-hydroxide phases (OHP) canbe expressed by a formula of w Fe(OH)₂ · x Co(OH)₂ · y Ni(OH)₂ · z FeOOH that crystallochemically corresponds to a structural type of brucite. When mixing suspensions of separately precipitated oxides, there occurs recrystallization in two phases, such as macrocrystalline, rich with iron, and superfine, with its lower amount and oxidized to a lesser degree. In addition to OHP, a spinel phase in fine dispersion is generated. Liberation of significant amounts of CO₂ at elevated temperatures points to the presence of carbonates in samples. Since they are not detected by means of X-rays, one may assume that the carbonate anion is embedded into oxygen layers of the structure of brucite of OHP.

The qualititative and quantitative composition of hydrocarbons generated during thermal and hydrolytic decomposition of sapropelites from the Kushmurun and Maoyoming deposits in Kazakhstan and China, respectively, was identified. Thermal and hydrolytic decomposition of sapropelites organic mass in an aqueous alkaline medium at 400 °С by approximately 40-60% was related to the generation of neutral and acid heteroatomic compounds and only by 5-10% - to paraffin-naphthene-aromatic, mainly, normal С₁₂-С₂₇ and С₁₂-С₃₁ alkanes, С₁₃-С₂₃ and С₁₄-С₂₇ alkenes, and also aromatic and naphthene-aromatic components, as discovered. It was noted that unlike anhydrous pyrolysis results, thermal hydrolysis products contained more monounsaturated olefins with different double bond positions. Proceeding from the composition of biomarker hydrocarbons, it was concluded that they were associated with the lithogenetic maturity of sapropelite organic mass. In addition, the sea origin of the initial biomass of lipid structural elements was suggested.

With the common purpose of developing functional and cost-effective new electrode materials, including those for supercapacitors, a preparation method was elaborated and electrocapacitive properties of nanostructured composites based on a mesoporous carbon material filled with manganese oxides were examined. Carbon material used as a matrix of nanocomposites was produced by carbonization of naturally oxidised coal at 800 °С. Composites were obtained by reduction of potassium permanganate solutions with carbon matrix at 20-25 °С without the introduction of additional reducing substances. The content of Mn _x O _y in composites was varied from 1 to 5 mass %. Manganese oxides in nanocomposites were in the X-ray amorphous state, as demonstrated by powder X-ray diffraction technique. Nafion® ion exchange membrane was used as a separator, a 6 M KOH solution - as an electrolyte during studying electrochemical properties using Parstat 4000, potentiostat/galvanostat. The electric capacity of nanocomposite electrodes is higher than that of matrix-based electrode material, as demonstrated by methods of cyclic voltammetry in potential windows a) from -1.5 to 1.5 V; b) from -1 to +1 V; c) from 0.1 to 0.8 V), galvanostatic charge-discharge and electrochemical impedance spectroscopy. Internal resistance and total impedance of asymmetric cells with nanocomposite electrodes was less than appropriate values for the symmetric cell with electrodes based on matrix. The optimum content of manganese in composites was 3 %, as established. Herewith, the reached capacity for Mn _x O _y /C nanocomposite hybrid electrode material in a potential window from 0.1 to 0.8 V was 404 F/g when using a 6 M KОН aqueous solution as the electrolyte.

The paper presents the results of a study into the effect of molecular mass on structure, properties, and behaviour of ultra high molecular mass polyethylene under thermal action. Diversity in physical and thermal properties is due to the difference in polymer structure, as demonstrated.

The paper considers structural characteristics of a promising mesoporous material to develop Kemerit ionistors. Location model of carbon layers is proposed. According to it, three-dimensional ordered nanocrystalline domains are a random overlay of strongly peaked graphene planes. Modelling of the resulting structures is carried out by the molecular dynamics method. The findings qualitatively coincide with the XPA and Raman spectroscopy data.

The paper carries out a comparative study of the chemical composition of chlorinated alumina produced by chlorination of low-temperature modifications of alumina with carbon tetrachloride and its morphological, structural and acid properties. It is demonstrated that residual moisture has a significant impact on listed properties of chlorinated alumina due to chemism of the reaction between carbon tetrachloride, liberated water vapours, and acid sites of alumina.