The effects of asphaltenes from two heavy oil residues on the sedimentation stability of residual marine fuels were assessed and compared. As base components of residual marine fuels, the vacuum residue (VacRes) and visbreaking residue (VisRes) were taken. The heptane-insoluble fractions (HI-fractions), including asphaltenes, isolated from vacuum residue and visbreaking residue, were analyzed to determine the elemental composition (XRF) and cluster parameters (XRD). The results of the analysis of the parameters of the asphaltene cluster (HI-fraction) for vacuum residue and visbreaking residue showed that dγ – 6.1 and 5.9 Å, Lc – 26.72 and 20.78 Å, and La – 7.68 and 7.20 Å. The sedimentation stability of residual marine fuel was determined according to the ISO 10307-1-2009 (TSA) method and described using ternary phase diagrams. The ratio of stable compositions to the total number of possible compositions (with a step of 10 wt%) was 65/66 or 98.5% for residual marine fuel comprising a mixture VacRes/ULSD/LCGO (vacuum residue/ultra-low sulphur diesel/light catalytic gas oil). Meanwhile, the ratio of stable compositions to the total number of possible compositions was 38/66 or 57.6% for residual marine fuel comprising a mixture VisRes/ULSD/LCGO (visbreaking residue/ultra-low sulphur diesel/light catalytic gas oil).
A prerequisite for commercial production of rare metals is a continuous effort given to developing knowledge-intensive recovery and refining techniques. Commonly known natural raw materials and conventional processing techniques, which are based on initial acid activation and recovery of minerals, as well as selective recovery of the target component (i.e. by sorption and extraction) cannot always ensure sufficient productivity or cost-effectiveness. This paper considers certain aspects of continued research in this area, which would require novel techniques. Such techniques should be based on new approaches allowing for the use of alternative raw materials to produce valuable rare metals on a cost-effective basis. It is demonstrated that red mud, i.e. waste material generated by bauxite industry and rich in scandium and other rare metals, can serve as such alternative source material. The paper describes the results of a study that looked at finding an optimum carbonization process for red mud that would ensure a consistent and predictable complexing process with regard to certain components. The paper also examines the environment in which soluble carbonate complexes can be stabilized and concentrated in the pregnant solution before the primary scandium-bearing concentrate can be recovered. The authors identified target parameters that determine enhanced filtration properties of carbonized slurry to ensure complete separation of the pregnant solution from the dehydrated (to the residual moisture content of 18%) carbonized residue. The paper highlights some positive factors of the carbonization process which enable a comprehensive utilization of alumina production waste. They include a long-term sequestration of carbon dioxide in the air and modified physical and chemical properties of red muds. This makes carbonized muds more compactable and thus more suitable for transportation and minimizes waste disposal hazards. The experimental research was carried out in conformance with the governmental assignments of the Institute of Solid State Chemistry of the Ural Branch of the Russian Academy of Sciences and Saint-Petersburg Mining University.
This paper presents the results of the study on the development of a methodology for the production of pure amorphous silicon dioxide containing up to 99.8 wt.% of SiO2. As a starting material, a silica gel with a moisture content of up to 55 wt.% and an SiO2/AlF3 ratio of 4 was used. The silica gel was purified using alkaline and acidic solutions in concentrations ranging from 0.1 to 25 wt.%. The analysis of the experimental data allowed to identify the most suitable purification parameters of the starting material. The initial silica gel and the reaction products were studied using the methods of X-ray fluorescence, X-ray phase analysis, electron scanning microscopy, EDS microanalysis, and particle-size analysis. Amorphous silicon dioxide obtained according to the methodology developed by the authors forms agglomerates of spherical silicon dioxide particles up to 1 μm in size. Amorphous silicon dioxide was involved in the preparation of catalyst supports in order to consider the possibility of replacing part of the expensive raw material in the form of aluminum hydroxide. In the work, the characteristics of the addition of this amorphous silicon dioxide and the supports obtained from the traditionally used raw materials were evaluated.
The results of experimental investigations on the coking of decanted heavy gasoil of catalytic cracking with polystyrene in a certain concentration range to obtain petroleum needle coke with the most developed string-base anisotropic structure and a microstructure point of at least 6.2 corresponding to the super-premium grade are presented. Certain regularities have been established to improve the structural quality index of the resulting needle coke from the optimal content of polystyrene in the base raw material, including the extreme dependence of the quality indices of needle coke on the polystyrene content (10 wt %). The decrease in the quality indices of the obtained carbon material is a consequence of uncontrolled changes toward an increase in the system viscosity performance (the viscosity increases 2.7 times). The experimentally obtained coefficient of thermal expansion (CTE) of needle coke-synthesized samples within the temperature range of 40–500 °C showed a reducing trend in CTE depending on the polymer additive proportion in the feedstock; for example, at 300 °C, the CTE decreases to 5.732 × 10–6 °C–1.
The development of a comprehensive approach to preventing the pollution of natural objects is necessary due to the high requirements of environmental legislation for the discharge of industrial wastewater. Adsorbents are used in various industries to extract heavy metals from wastewater. In this study the possibility of using saponite clay as a raw material for the production of sorbent for the extraction of copper ions Cu2+ from industrial wastewater is considered, a recipe and technology of sorbent production are developed, and its chemical composition is established. It has been established that the optimum temperature for heat treatment of the sorbent and corresponds to 550 ºC, since at this temperature saponite extrudates acquire strength (strength 34.1 kg/mm2) and textural properties (specific surface area of pellets 22.803 m2/g), allowing them to be used as sorbents. The kinetics of molecular adsorption was studied using model solutions of copper (II) sulfate. The extraction efficiency of copper (II) ions from the model solutions is 93 %. Extraction efficiency of copper (II) ions from copper plating wastewater reaches 94 %. SEM results confirm the presence of metal on the sorbent surface.
The article presented the results of studies on the production of low-modulus zeolites from two types of technogenic resources containing a sufficient amount of silicon in their composition. The raw materials were nepheline concentrate and silica gel, which are products of the processing of apatite-nepheline ore. Directly before the synthesis of low-modulus zeolites, the morphology, chemical composition, and particle size of the starting materials were analyzed. The optimal parameters for sample preparation and purification of the raw materials used were also selected. The influence of the ratio of components in the reaction mixture on the type of synthesized zeolite and its characteristics were studied. The properties of synthesized zeolites from the proposed type of raw material were compared with the properties of zeolites synthesized today using the popular technology from kaolin clay, which is currently offered as an inexpensive natural raw material.
The article is devoted to the neutralization of the harmful effects of aluminochrome catalyst sludge. Catalyst sludge is a waste product from petrochemical production and poses a serious threat to the environment and humans because of the toxic hexavalent chromium it contains. The emissions of Russian petrochemical enterprises’ alumochrome sludge is 10,000–12,000 tons per year. In this paper, research related to the possibility of reducing the harmful effects of sludge by converting hexavalent chromium to a less dangerous trivalent state is presented. The reduction of hexavalent chromium was carried out with different reagents: Na2SO3, FeSO4, Na2S2O3, and Na2S2O5. Then, a comparative analysis was carried out, and sodium metabisulfite was chosen as the most preferred reagent. The peculiarity of the reducing method was carrying out the reaction in a neutral medium, pH = 7.0. The reduction was carried out in the temperature range of 60–85 °C and under standard conditions. The maximum recovery efficiency of chromium from the catalyst sludge (100%) was achieved at 85 °C and 10 min. This method did not involve the use of concentrated sulfuric acid, as in a number of common techniques, or additional reagents for the precipitation of chromium in the form of hydroxide.
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