No abstract

No abstract

No abstract

Pyrolysis of polystyrene in the medium of coal tar pitch and of pitch prepared from ethylene production tar was performed in the temperature range 360-420°C at atmospheric pressure.Polystyrene (PS) is one of the most widely used polymers, and utilization of waste PS requires the development of cost-saving and safe technologies [1]. Pyrolysis of polymeric wastes is an effi cient method of their reprocessing. The pyrolysis products are raw materials for the production of fuels or chemicals [2]. In PS pyrolysis, the yield of low-molecular-weight mononuclear aromatic compounds exceeds 95%. Therefore, this process is actively studied as a method for recirculation of the waste polymer [3].The yields and composition of PS pyrolysis products depend on the temperature, presence of catalysts and solvents, type and design of the reactor, and other process conditions [3][4][5][6][7][8][9]. Performing the polymer pyrolysis in solvents allows the conditions of mass and heat transfer in the reaction medium to be improved (otherwise these conditions are unfavorable because of high viscosity of polymer melts) and the process temperature to be decreased [9][10][11]. The solvent can also affect the PS pyrolysis, entering into chemical reactions with the initial polymer or its degradation products.Murakata et al. [9,12] examined the effect of various solvents on the thermal degradation of PS in an autoclave and showed that solvents with high hydrogen donating ability decrease the PS conversion. The major lowmolecular-weight products of PS pyrolysis under these conditions are saturated compounds (ethylbenzene > toluene > styrene). The results are attributed to the hydrogen transfer from solvents to PS degradation products and from PS to solvent radicals. With the aim to increase the styrene yield, Karaduman [13] studied the PS pyrolysis in an autoclave at 350-450°C in phenol, quinone, naphthalene, and diphenylamine. The highest yield of styrene (74%) was attained in naphthalene; in diphenylamine, the styrene yield was lower than when the process was performed without solvent. The amount of the solid pyrolysis residue in the solvents was lower than without solvent.Coal tar pitch can be used as high-boiling solvent for polymers [14]. Studies involving heat treatment of coal tar pitch with PS were primarily aimed at preparing modifi ed asphalt and carbon materials [15][16][17][18]. Carbonization of pitch with 10% PS was studied by Brzozowska et al. [15][16][17], who showed that addition of PS accelerates the formation of the mesophase, affects its structure, and increases the carbonizate yield. Slow heating to 430°C of the toluene-soluble fraction of coal tar pitch with the addition of PS, followed by keeping at high temperature, increases the amount of alkyl groups in the pitch and affects the yield and structural characteristics of the soluble mesophase [18]. Pyrolysis of medium-temperature coal tar pitch at 410-450°C was suggested in a patent [19] for preparing high-temperature modifi ed pitches. Finqueneisel et al. [20] examined the...

No abstract