Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 1, pp. 89−97.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.I. Andreikov, I.S. Amosova, Yu.A. Dikovinkina, O.V. Krasnikova, M.G. Pervova, 2012, published in Zhurnal Prikladnoi Khimii,
2012, Vol. 85, No. 1, pp. 93−102.
AND INDUSTRIAL ORGANIC CHEMISTRY
Pyrolysis of Polystyrene in Coal Tar and Ethylene Tar Pitches
E. I. Andreikov, I. S. Amosova, Yu. A. Dikovinkina,
O. V. Krasnikova, and M. G. Pervova
Postovskii Institute of Organic Synthesis, Ural Branch,
Russian Academy of Sciences, Yekaterinburg, Russia
Received January 25, 2011
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 .
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 .
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 .
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 [3–9]. 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 [9–11]. 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 low-
molecular-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  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 . Studies involving heat treatment
of coal tar pitch with PS were primarily aimed at
preparing modiﬁ ed asphalt and carbon materials [15–
18]. Carbonization of pitch with 10% PS was studied by
Brzozowska et al. [15–17], 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 . Pyrolysis
of medium-temperature coal tar pitch at 410–450°C was
suggested in a patent  for preparing high-temperature
modiﬁ ed pitches. Finqueneisel et al.  examined the
effect of PS additions to coal tar on the yield of distillate
fractions and on the properties of the distillation residue,
coal tar pitch. The pitch yield increased, and 10% of the
added PS remained in the pitch; a new peak at 460°C,