Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 6

The recycling process of carbon fibres was investigated using thermal solvolysis of polymer composites in the medium of coal tar pitch in the 320–400 °С temperature range. The effect of thermal treatment therein on properties of carbon fibres isolated via the recycling was investigated. The paper presents research data by scanning electron microscopy and mechanical tests of isolated carbon fibres compared to the initial ones used for composite synthesis.

An opportunity to use Zh, D, and KS coal of the Kuznetsk Basin referred to bituminous coals as raw materials to produce activated carbon was investigated. Formulas of coal/pitch systems were developed using coal-tar pitch as a binder. The optimum coal tar content (5 mass %) in the system was determined. New activated carbons based on coal/pitch systems were produced; parameters of their microporous structure, adsorptive properties, and strength performance were examined.

The paper presents research results on the pore structure and the reactivity of semicoke derived from LF, LFG, G, F, and C coal by low-temperature pyrolysis at 600 °C in the Fisher vessel. It is certified that the development of pore structure upon semi coking depends on the nature of the initial raw materials because when the degree of metamorphism is increased, the specific surface area of semicoke derived therefrom is reduced. As demonstrated by comparative analysis, semicoke derived using coal of a higher degree of metamorphism is characterised by reduced reactivity towards oxygen. The correlation between the temperature of the beginning of mass loss (T₁) and that of maximum mass loss rate (T_max) of oxidative breakdown for the investigated samples of semicoke vs its specific surface area was found. It is stated that T₁ and Tmax indicators are reduced when the specific surface area of semicoke increases.

The paper investigated petrographic characteristics of seam commercial samples of gas coal collected in various Kuznetsk Basin mines. Reflectogram analysis identified petrographic peculiarities that determined coal cokeability during high-temperature coking. According to the results of the additional assessment made for coal physicochemical properties, significant gas coal reserves might be used as valuable raw materials for the coke-chemical industry.

Physicochemical properties of coal dust sampled from the fine filter of the mine degassing plant of the Kuznetsk coal basin were explored. The coal dust sample was thoroughly characterised by scanning electron microscopy and atomic emission spectroscopy; technical analysis was also carried out and granulometric composition was determined. Relationships were found between changing the chemical composition of mineral components of the mineral portion of coal dust and coal particle size relying on the data acquired.

Lately, side products of oil processing and coal liquefaction, i.e., asphaltenes, have been extensively investigated. The data regarding the macromolecular structure and morphological characteristics of asphaltene aggregates were mainly acquired in the area of petrochemical technologies. It is known that the concentration of asphaltenes in solution and the presence of additives of various chemical nature have an effect on the structure of asphaltene associates. The data about the formation of planar asphaltene associates and condensed graphite-like structures are of particular interest. In connection with the optimizing of conditions for anodic mass graphitization, coal tar pitch asphaltenes (β-fraction) were investigated. Coal tars with high contents of β-fraction proved themselves in the best way as efficient binders upon thermal treatment of the anodic mass. The present work investigated structural characteristics of macromolecules of medium-temperature coal tar pitch (CTP) using a set of physicochemical methods. The method of selectively soluble groups was used to isolate β-fraction asphaltenes; toluene and hexane were utilised as selective solvents. In order to form asphaltene films, a 0.01 % solution of asphaltenes in toluene was selected. It was demonstrated that structural fragments of CTP asphaltene molecules contained mainly condensed compounds with a number of rings of 3–7. These species contained C11 alkyl substituents and larger the content of which could not be practically determined. Therefore the structure of CTP asphaltene molecules could be described by the Speight model. The coke residue of CTP asphaltenes is characterised by the presence of crystallites from naphthenoaromatic layers. These structures are comprised of subunits of 7–8 layers, with a size of 20–25 Å, graphite-like; an interlayer distance of 3.42 Å.

Preparation methods of nanostructured composites based on various carbon materials filled with chromium oxides and hydroxides were developed via reduction of potassium dichromate with hydrazine. Materials with different parameters of the porous structure and specific surface, such as microporous Kem10 and mesoporous Carb3, and also carbon nanotubes (non-ozonised CNT-1 and ozonised CNT-2), were used as carbon matrixes. As demonstrated by research on asymmetrical cells of a supercapacitor with working electrodes based on the resulting nanocomposites via a set of electrochemical methods (cyclic voltammetry, chronopotentiometry, and impedansometry), surface decoration of matrixes with chromium oxides and hydroxides leads to an increase in capacitance and a decrease in the inner resistance of supercapacitor cells.

The paper presents the research results of structural-morphological and electrochemical properties of an electrode material for supercapacitors. The material is a porous carbon matrix with embedded mixed cobalt-nickel oxide nanoparticles. A nanostructured composite was produced by thermal decomposition of mixed nickel-cobalt hydroxides on the surface of carbon nanofibres. The composition and dispersion characteristics of the resulting oxide nanoparticles were determined through X-ray structural analysis and small-angle scattering. As demonstrated by the research on electrochemical properties of the synthesized electrode materials through cyclic voltammetry, the electric capacitance of the latter increased proportionally to an increase in the content of nickel cobaltate in the composite. Electrode materials based on nanostructured carbon-nickel cobaltate composite ensured a significant increase in electric capacitance compared to that of the initial carbon matrix.

The paper considers properties of nanostructured composites for supercapacitors electrodes. The materials are based on multi-walled carbon nanotubes obtained by pyrolysis of the propane-butane mixture (CNT-1) and additionally aged in argon atmosphere (CNT-2). The resulting CNT are filled with cobalt and nickel hydroxides nanoparticles deposited on the surface and in channels composing nanotube fibres. The composites were explored through transmission electron microscopy, X-ray diffractometry, X-ray Fluorescence Element Analysis, and Small-Angle X-ray Scattering. Electrochemical properties of the resulting nanocomposites were examined. As shown, both introducing cobalt-nickel hydroxide into the carbon matrix and functionalizing its surface by ozonation facilitates an increase in the electrical capacity of composite electrodes. This is driven by the pseudocapacitance of nickel-cobalt hydroxides generated as a consequence of reversible redox processes with the involvement of oxyhydroxide phases formed upon cell charge-discharge.

The paper presents the results of a voltammetric study of electrodeposition and electrooxidation of nanostructured systems based on iron and platinum with glassy carbon electrodes in various electrolytes. The capabilities of anodic and cyclic voltammetry in the characterization of nanometallic deposits were shown. The conditions for electrochemical synthesis and voltammetric studies of nanostructured electrolytic iron-platinum systems were established.

One of the possible variants of rational processing highly paraffinic gas condensate residues (HPGCR) with the maximum yield of low-sulphur medium-distillate fractions, i.e. hydrocracking in a fixed catalyst bed, was considered. Experiments were carried using a flow through plant. Home-made catalysts, such as KNT-442МNi (hydrorefining catalyst) and KNT-442NiY (hydrocracking catalyst) manufactured at the LLC Ishimbayskiy SKhZK, were used. Process temperature that ensures the maximum yield of diesel fraction was pre-selected. Considering the unique composition of HPGCR, the hydrocracking of initial raw materials, and also 350+ °С and 350–500 °С fractions, was investigated without their pre-preparation. As demonstrated by analysis of diesel fractions of hydrocracking products (180–350 °C), various variants of raw materials, regardless of their fractional composition and recirculation of residues, their key parameters meet the requirements for the commercial diesel fuel of environmental K-5 class. At the same time, regardless of the quality of initial raw materials, the products from variants with the recirculation of residues have somewhat improved characteristics. As demonstrated by analysis results for gasoline fractions (IBP – 180 °C), products have similar characteristics, regardless of the composition of initial raw materials and the residue recirculation mode. These fractions do not require preliminary hydroforming and may be directed to isomerisation and reforming plants. Among the variants considered, the hydrocracking of the initial HPGCR ensuring the maximum yield of diesel fraction and not requiring the preliminary fractionation of initial raw materials and the secondary processing of the primary distillate fractions and the residue is preferable.

This review exposes the issue of the relationship between exposure to dust particles from coal and coal processing industries with the risk of developing cardiovascular diseases (CVD). Typical features of exposure to dust particles of this type involves: 1) high levels and the chronic type of dust pollution, 2) a small aerodynamic diameter (AD) of dust particles (below 10 µm) that facilitates their inhalation and entry into teethridge, 3) their trend towards aggregating to clusters with an AD between 2.5 µm and 10 µm that set in the upper respiratory tract, and 4) specific chemical composition (carbon, silicon dioxide, alumina, sulphates, carbonates, nitrates, and volatile organic matter). In spite of the generally proven relationship of exposure to all fractions of dust particles with elevated morbidity and mortality caused by CVD, the proportion of cases triggered by dust particles regardless of respiratory system diseases that are characterised by comorbidity with CVD remains unclear. Furthermore, there is an obvious shortage of environmental epidemiology research with monitoring the particles with an aerodynamic diameter of less than 0.1 µm, exposure to which could most likely explain the relationship between dust pollution and CVD (the particles with so small AD are able to penetrate to the systemic circulation). At last, the majority of multicentre epidemiological investigations that substantiate relationships between dust particles and developing CVD have been performed in developed countries. Carrying out such research in developing countries, considering their geographical, climatic, and socioeconomic peculiarities, and also characteristics of the implementation of coal mining and processing, would facilitate the research on population interlinks of exposure to dust particles with other CVD risk factors and mechanisms of their pathogenic action. The ultimate objective of such research is to make the personified programme of CVD preventive care considering exposure level and duration to dust particles and co-occurring risk factors.

Carbon black emissions together with diesel engine exhaust cause great harm to the environment. In order to efficiently remove carbon black, catalytically coated particulate filters are used. Kinetic parameters (activation energy and pre-exponential factor) of oxidation of carbon black with O₂ and NO_x were examined in thermoprogrammed and isothermal modes on an example of PtPd/MnO_x-Al₂O₃ catalyst. As shown, reproducible kinetic data may be acquired in the isothermal mode assuming the process is carried out in the kinetically controlled region. This information is important to compare oxidizing properties of catalysts in order to improve compositions of catalytic coatings for particulate filters.

Analysis of environmental issues linked to the thermal treatment of ammunition was carried out. An opportunity to purify ventilation emissions from thermal treatment furnace using a sorbent and deep oxidation catalyst was explored. The activity of a series of complete oxidation catalysts based on transition metal oxides, and also platinum and palladium was investigated. It was determined that Pt-Pd/5 % CeO₂-Al₂O₃ catalyst displayed the highest activity. A technology was suggested and a plant to dispose of ventilation emissions from the thermal utilization of sub-standard ammunition (cartridges, casings, and small arms primers) was developed. The technology includes removal of vapours of mercury, lead, nitrogen oxides, and other inorganic impurities from the gases on a sorbent and CO oxidation over a solid catalyst.

Adsorbents and catalysts based on carbon materials used to remove hydrogen sulphide from gases are reviewed. Alongside with traditional carbon-based materials, much attention is paid to using carbon nanotubes and nanofibres to prepare catalysts for selective oxidation of hydrogen sulphide to sulphur. The efficiency of purification from hydrogen sulphide using catalysts based thereon is much higher, and nitrogen doping of materials substantially improves characteristics of this process. The paper describes three base technologies for hydrogen sulphide removal. They are developed at the Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences and are based on the use of the fluidized bed of the catalyst for selective oxidation of hydrogen sulphide and catalysts-sorbents in the fixed bed. The technologies were as follows: 1) treatment of acid gases from amine purification of associated petroleum gas; 2) purifying gases from blowing off sour crude oil, and 3) utilizing oxidation of hydrogen sulphide directly as a component of associated petroleum gas. Efficient carbon catalysts and sorbents are suggested to be used for the second-stage treatment of tail gas from facilities made according to base technologies.

The effect of techniques for introducing Pd into γ-Al₂O₃ from palladium chloride solutions on physicochemical and catalytic properties of PdO(Pd)/Al₂O₃ catalysts was examined. A series of catalysts were investigated by SEM, XPA, BET, XPS, and H2-TPR. As shown, the use of various methods for introducing Pd into alumina granules enables control of active component distribution along the Al₂O₃ granule section. The localization of Pd in a catalyst grain determines the nature of the reduction in H2-TPR and activity in the reaction of deep oxidation of methane, which is connected with a varying degree of the interaction of the active component with the support. The active component is demonstrated to be formed on the granule surface mainly as PdO when using the adsorption-deposition method followed by calcination at a temperature of 1000 °C ensuring high reactivity in the methane oxidation reaction.

The paper presents data for structural-group and component compositions of bitumoid fractions derived upon sequential extraction of brown coal of the Tyulgan deposit with the following solvents: ethanol, n-heptane, and alcohol-benzene. As demonstrated by FT-IR, ¹³C CPMAS NMR, and GC-MS, the resulting bitumen is a multicomponent mixture of compounds mainly consisting of alkanes, fatty alcohols, unsaturated hydrocarbons, aromatic compounds found in trace amounts, carboxylic acids, and phenols. Bioactive compounds, such as Lignoceic alcohol, Ceryl alcohol, Behenic alcohol, Ferruginol, β-Amyrin, and Heneicosane, were detected therein.

A new gas-phase process of halogen-free carbonylation of dimethyl ether (DME) into methyl acetate is a promising environmental preparation method of methyl acetate. Bifunctional catalysts with a high concentration of strong Bronsted acid sites, i.e. rhodium-promoted acid cesium salts of phosphotungstic heteropoly acid with the formula Rh/CsxH₃ – xPW₁₂O₄₀ (1.5 ≤ x ≤ 2), show the highest activity and selectivity in the carbonylation reaction of DME. Their use in a reducing medium, where there are significant transformations of the catalyst surface area until changing the phase composition, is a distinctive feature of these catalysts. In order to control the activity and selectivity of catalysts in the DME carbonylation reaction, the research on the formation of the active surface of the catalyst was carried out under reaction conditions. The formation of different rhodium carbonyls, such as Rh(CO)+2 and Rh6(CO)16, was detected by FT IR spectroscopy of adsorbed CO on the surface of the in situ reduced Rh/Cs₂HPW₁₂O₄₀ catalyst after filling with CO. The formation of metal particles was identified in case of changing activation conditions. The dependence was found between reduction conditions, the composition of the in situ catalyst surface area with selectivity for methyl acetate. The presence of rhodium metal particles causes C–O bond cleavage in the DME molecule and significantly reduces selectivity for methyl acetate, from 95 to 50 %. Catalysts, on the surface of which there are only rhodium carbonyls under reaction conditions upon a complete lack of trace rhodium metal, showed the highest activity and selectivity for methyl acetate. The acquired results may form the basis for developing a highly active and stable catalyst for an environmentally safe process of halogen-free DME carbonylation.