Search Results (7)

Coal has been widely used as a reducing agent for metallurgical-grade silicon (MG-Si). As a crucial raw material, the coal selection process represents one of the most critical steps in MG-Si production. However, due to the inherent complexity of coal, there is currently a lack of efficient and accurate methods for screening highly reactive coal in industrial production. This deficiency leads to significant carbon loss and excessive CO₂ emissions, ultimately reducing the overall efficiency of industrial processes. To address this challenge, this study selected three types of bituminous coal with different performance characteristics from an MG-Si production plant for investigation. The aliphatic structures of the three coals were 69.85, 43.87, and 37.44%, respectively. The carbon-to-hydrogen ratio (C/H) of the coals exhibited an increasing trend with temperatures over the range of 0–1600 °C. The C/H of the No. 3 coal was the highest at different temperatures, with the highest degree of dehydrocyclization. The degree of ordering also increased with temperature for all three coals. The higher proportion of aliphatic structures in the No. 1 coal led to a long-range disordered microcrystalline structure. The No. 2 and No. 3 coals had higher percentages of aromatic structures and showed short-range ordered spikes. This study systematically investigated the correlation between stacking height (Lc), crystallite diameter (La), and C/H ratio. These results showed that C/H was positively correlated with the degree of ordering, and the correlation coefficient (R²) for La reached 0.87. Additionally, CO₂ reactivity tests revealed a significant negative correlation between reactivity and both degree of ordering and C/H. These findings provided insights into the efficient utilization of coal for MG-Si production. Full article

The structural features and thermophysical and transport properties of dense nonporous membranes of the casting type from (co)polyamide-imides synthesized by the polycondensation of the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5′-methylene-bis (2-aminophenol) (DADHyDPhM) and 4,4′-methylenebis(benzeneamine) (DADPhM), taken in molar ratios of 7:3, 1:1, and 3:7, have been studied. The effect of hydroxyl-containing modifying fragments of dihydroxy diphenylmethane introduced in various amounts into the main polymer chain on the pervaporation properties of the formed films is discussed. It has been shown that the presence of the residual solvent N-methyl-2-pyrrolidone in the films not only has a plasticizing effect on the characteristics of film membranes but also promotes the preferential transmembrane transport of polar liquids, primarily methanol (permeation rate over 2 kg for a copolymer with a ratio of DADHyDPhM:DADPhM = 7:3). The removal of the residual solvent from the polymer film, both thermally (heating to 200 °C) and by displacement with another solvent as a result of sequential pervaporation, led to a significant decrease in the rate of transfer of polar liquids and a decrease in the selectivity of the membrane. However, the dehydrocyclization reaction resulted in more brittle films with low permeability to penetrants of different polarities. The results of our comprehensive study made it possible to assume the decisive influence of structural changes in membranes occurring in connection with the competitive formation of intra- and intermolecular hydrogen bonds. Full article

Mixed oxides of ZnO and Cr₂O₃ with varied mole ratios were synthesized, characterized, and evaluated for the dehydrocyclization of crude glycerol for the production of 2-methylpyrazine (2-MP). The Zn-Cr-O composition was optimized using the bulk and surface properties of the catalysts rationalized by BET-SA, XRD, XPS, H₂-TPR, O₂ pulse chemisorption, and Raman spectroscopic techniques to achieve a high rate of 2-MP. Full article

Heavy oil and natural bitumen resources in carbonate formations are huge and considered as the promising alternative energy resource to the conventional crude oils. However, the production of such resources is challenging due to the low permeability, high viscosity and significant content of resins and asphaltenes in the composition of heavy oil and natural bitumen. The combination of thermal, chemical and gas enhanced oil recoveries can be a promising method to unlock and upgrade heavy oil and natural bitumen in carbonate reservoirs. In this paper, we propose a novel in-situ liquid-phase oxidation of light hydrocarbons for a revolutionary thermo-gas-chemical enhanced oil recovery method, which can be applied in carbonate heavy oil reservoir formations. It is assumed that the oxidation process is carried out in a downhole well reactor, the products of which are a high temperature mixture of organic carboxylic acids and organic solvents. Here, we present the results of laboratory investigations of liquid-phase oxidation of n-hexane as a model compound imitating associated petroleum gases in the presence of Fe, Cr and Ni catalysts, which were introduced in the form of oil-soluble catalyst precursors. It was revealed that the oxidation process yields hydro peroxides, organic carboxylic acids (acetic, propionic and valeric acids), alcohols and ethers. The products of the oxidation process were justified by the results of FT-IR and GC-MS analysis methods. According to the results, Cr-based catalyst leads to the increase of CH₃-groups in the products. The oxidation process in the presence of nickel-based catalyst is compared with a control sample. The naphthalene was detected in the oxidation products of all experiments, the formation of which is explained by polymerization of benzene rings. In its turn, benzene is obtained due to dehydrocyclization of n-hexane on the surface of nanoparticles. However, iron-based catalyst showed the best catalytic performance in low-temperature oxidation of n-hexane in autocatalysis mode as the yield of acetic acid prevailed 52%. The given approach provides prolonged thermal and acid treatment of carbonate formations, where the evolved CO₂ gas will further assist in increasing the mobility of crude oil. Moreover, the produced alcohols, ethers and other hydrocarbons play the role of solvents, which dissolves polar and non-polar components of crude oil. Full article

The on-surface C–H bond activation and coupling reaction is a powerful approach to constructing fine-tuned surface nanostructures. It is quite challenging to control its regioselectivity due to the inertness of the C–H bond involved. With scanning tunneling microscopy/spectroscopy and theoretical calculations, the C–H activation and sequential intramolecular dehydrocyclization of meso-tetra(p-methoxyphenyl)porphyrinatocobalt(II) was explored on Au(111), showing that the methoxy groups in the molecule could kinetically mediate the selectivity of the intramolecular reaction over its intermolecular coupling counterpart. The experimental results demonstrate that the introduced protecting group could help augment the selectivity of such on-surface reaction, which can be applied to the precise fabrication of functional surface nanostructures. Full article

Several fused imidazolopyrimidines were synthesized starting from 6-amino-1-methyl-2-thiouracil (1) followed by nitrosation, reduction and condensation with different aromatic aldehydes to give Schiff’s base. The dehydrocyclization of Schiff’s bases using iodine/DMF gave Compounds 5a–g. The methylation of 5a–g using a simple alkylating agent as dimethyl sulfate ((CH₃)₂SO₄) gave either monoalkylated imidazolopyrimidine 6a–g at room temperature or dialkylated derivatives 7a–g on heating 6a–g with ((CH₃)₂SO₄). On the other hand, treatment of 1 with different aromatic aldehydes in absolute ethanol in the presence of conc. hydrochloric acid at room temperature and/or reflux with acetic acid afforded bis-5,5́-diuracylmethylene 8a–e, which cyclized on heating with a mixture of acetic acid/HCl (1:1) to give 9a–e. Compounds 9a–e can be obtained directly by refluxing of Compound 1 with a mixture of acetic acid/HCl. The synthesized new compounds were screened for antimicrobial activity, and the MIC was measured. Full article

A series of novel benzimidazole derivatives 3-10 were synthesized. Benzimidazolyl-substituted acrylonitriles 3 and 4 underwent a photochemical dehydrocyclization reaction to give the corresponding mono- and dicyano-substituted benzimidazo[1,2-a] quinolines 5 and 6. Pinner reaction of these compounds did not give the expected mono- and diamidines, but rather only compounds 7-10, with amido groups at 6-position were isolated. A mechanism for the reaction is proposed. Acyclic compounds 3 and 4, as well as cyclic benzimidazo[1,2-a]quinolines 5-8, exhibit interesting spectroscopic properties and are potential biologically active compounds. Full article