To remove sulfur-containing compounds (SCC) from the diesel fraction 200–360 °C extraction systems have been created based on coordinating organic solvents—dimethylformamide and dimethylsulfoxide, metal chlorides (CoCl2, CuCl2, CdCl2, MnCl2 and CrCl3), and metal trifluoroacetates (Co(TFA)2, Cu(TFA)2 and Mn(TFA)2). Using PMR spectroscopy the coordination of metal chloride and metal trifluoroacetate on the oxygen atom in the carbonyl group of DMF was shown to redistribute electron density in the solvent molecule and to enhance properties of the acceptor center localized on the nitrogen atom. The removal of sulfur-containing compounds from the diesel fraction proceeded under mild conditions—at the temperature of 25 °C and atmospheric pressure. The degree of SCC removal from the diesel fraction in 30 minutes extraction was more than 90%. The interaction of organic solvents with metal salts and sulfur-containing compounds of the diesel fraction was considered within the framework of the concept of “hard and soft acids and bases” (HSAB). The most complete SCC extraction was carried out with DMF-Mn(TFA)2, MnCl2 and CrCl3 systems, that was probably connected with the implementation of the ‘hard base–hard acid’ system.
The paper studies oxidative desulphurization of oils with an initial sulphur content of 1.98 wt% by hydrogen peroxide on a carbon-black (CB) catalyst coated by a combination of cobalt and nickel. The results demonstrate the effects of temperature and duration of the process, amount of the catalyst and the nature of the selected extractant on the removal efficiency of oxidized sulphur compounds. The extractant was represented by a solution of dimethylformamide (DMF) with water (10 vol%). The maximum removal degree of sulphur exceeded 70% and was achieved in 90 minutes with an amount of the catalyst of 1.0–1.3 wt.% and a temperature of 50 °C.
Carbon materials are widely used in catalysis as a support for active catalyst components due to their chemical inertness and developed surface. The most common carbon carriers are represented by activated carbons, carbon black and various carbon-carbon composites. In petrochemistry, carbon materials are also employed as catalysts to oxidize sulfur compounds contained in heavy fractions of oil being refined. In this regard, the present paper discusses the issues of metal-carbon composite material manufacturing. Technical carbon, or carbon black (CB), was used as a carbon support, the surface of which was modified with nickel and cobalt. The resulting composite material, Ni-Co-CB, has a high specific surface area comparable to that of the pristine carbon material, thereby favoring its catalytic activity. The high catalytic activity of the composite material developed was observed during oxidative desulfurization of heavy oil feedstock. Hence, the degree of sulfur removal for fuel oil was found to be 82.7 %, whereas for oil it reached 70.7 %.
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