Refining of Coal Tar by Hydrogenation in the Presence of Nanoheterogeneous Nickel Sulfide Catalyst
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Refining of Coal Tar by Hydrogenation in the Presence of Nanoheterogeneous Nickel Sulfide Catalyst A. S. Maloletneva, *, Zh. K. Kairbekovb, c, **, and N. T. Smagulovab, c, *** a
Moscow Mining Institute, Moscow Institute of Steel and Alloys, Moscow, Russia bAl-Farabi Kazakh National University, Almaty, Kazakhstan c Research Institute of New Chemical Technologies and Materials, Almaty, Kazakhstan *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] Received February 12, 2020; revised February 12, 2020; accepted April 20, 2020
Abstract—The refining of coal tar by hydrogenation is considered. In this process, nanoheterogeneous Nibased catalysts may expediently be produced in situ from precursors in the reaction medium. The yield of needle coke in complete coal processing with recirculation of the residue at the coking stage is found to be 50–55%. That is 1.5 times the industrial yield in the coking of pitch. Keywords: coal tar, hydrogenation, refining, nanoheterogeneous nickel sulfide catalysts, needle coke DOI: 10.3103/S1068364X20050038
Coal tar, a coking byproduct formed in the pyrolysis of coal at 800–900°C, contains numerous reactive compounds, which undergo condensation after distillation at 350–380°C, with the formation of pitch fractions that do not boil below 380°C. The pitch fractions of tar that boil above 350–380°C are used directly as binder in electrode production or are first oxidized to increase their softening temperature and the yield of pitch coke. The coke obtained from high-temperature pitch is predominantly of isotropic structure and may be used to produce anodes and artificial graphite for the construction industry. However, they are unsuitable for the production of graphitized electrodes and cathode modules in aluminum electrolysis tanks. Those components are produced from anisotropic needle coke [1]. Coal pitch may be divided into four main fractions, in terms of solubility 1. The γ fraction, which is soluble in isooctane, determines the liquidity of the whole system, as well as the viscosity and wettability of pitch. 2. The β fraction, which is insoluble in isooctane but soluble in benzene and toluene, determines the binding and sintering properties of the pitch. 3. The α2 fraction, which is insoluble in toluene but soluble in quinoline, determines the sintering and coking conditions of the pitch, as well as its susceptibility to graphitization. 4. The α1 fraction, which is insoluble in quinoline and unreactive, may be a gas or a liquid. In either case,
it prevents the formation of block structures in graphitization, thereby constraining the formation of anisotropic needle coke in pitch coking. To obtain anisotropic (needle) coke, the coking batch must have a minimal content (no more than 1.0%) of the α1 fraction. Its content in pitch depends on the method of batch preparation [2]. By varying the content of the quinoline-insoluble fraction in the pitch, the properties of pitch coke may be adjusted over a wide range. Likewise, the microstructure of t
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