HOMOGENEOUS PYROLYSIS OF 1,4-DIMETHOXYNAPHTHALENE
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(in calculations, it was assumed to be equal to the con-
tribution of the ring cleavage).
starts at 700 C. The major liquid products are asphal-
tenes and hydrocarbons. The major gaseous product
is CO.
In the case of naphthalene and -naphthol, the ac-
tivation energy of methane formation is higher by
(2) The hydrocarbon fraction consists of naphtha-
lene, methyl- and dimethylnaphthalenes, phenanth-
rene, fluoranthene, pyrene, and chrysene. The molec-
ular weight of asphaltenes varies within 250 326, and
that of neutral oxygen-containing compounds, within
175 236. The main functional groups are quinoid,
alkoxy, and oxygen-containing heterocyclic groups.
1
almost a factor of 5 (Ea 239.67 and 256.85 kJ mol ,
respectively), which reflects the fact that, for these
compounds, the only pathway of methane formation is
energy-consuming cleavage of the aromatic ring.
Ethene is formed with a still lower activation ener-
1
gy (Ea 27.65 kJ mol ); the reaction order is 1.5.
This is facilitated by the presence of C2 radical frag-
.
.
(3) The kinetic parameters of overall decomposi-
tion of 1,4-dimethylnaphthalene and formation of
particular gaseous products were calculated; the mech-
anisms of formation of these products were suggested.
ments (e.g., CH=CH) in the stage of initiation of ring
cleavage with the formation of CO. The C2 radical
fragments recombine with hydrogen present in the
reaction zone to give ethene:
.
.
REFERENCES
CH=CH + H2(2H)
CH2=CH2
Such radical recombination reactions have zero
activation energy, which is consistent with the low
activation energy of the overall process of ethene
accumulation in the pyrolysis zone. The very low
preexponential term, equal to 2.36, supports the pre-
1. Platonov, V.V., Ivleva, L.N., and Prokof’ev, E.E.,
Khim. Tverd. Topl., 1980, no. 2, pp. 138 147.
2. Platonov, V.V., Ivleva, L.N., Klyavina, O.A., and
Prokof’ev, E.E., Khim. Tverd. Topl., 1982, no. 5,
pp. 88 99.
sumed formation of ethene from radical fragments like
.
.
3. Platonov, V.V., Klyavina, O.A., Ivleva, L.N., and
Prokof’ev, E.E., Khim. Tverd. Topl., 1982, no. 2,
pp. 138 144.
CH=CH or by recombination of methyl radicals,
followed by dehydrogenation, since the probability of
radical recombination under conditions of dilution
with an inert gas (1 : 25 by volume, neglecting addi-
tional dilution with gaseous and vaporous pyrolysis
products) is very low. As a result, the concentration
of ethene is low in most cases, although, in principle,
it could be high.
4. Platonov, V.V., Ivleva, L.N., Klyavina, O.A., and
Prokof’ev, E.E., Khim. Tverd. Topl., 1981, no. 5,
pp. 84 94.
5. Platonov, V.V., Klyavina, O.A., Prokof’ev, E.E., and
Ivleva, L.N., Khim. Tverd. Topl., 1981, no. 6,
pp. 96 103.
Hydrogen can be formed by a number of path-
ways, including condensation of the initial 1,4-DMN
molecules and radical fragments from degradation
processes. The hydrogen formation is satisfactorily
described by a kinetic equation of order 1.5, with
6. Platonov, V.V., Ivleva, L.N., and Klyavina, O.A.,
Khim. Tverd. Topl., 1984, no. 5, pp. 105 114.
7. Platonov, V.V., Proskuryakov, V.A., Ryl’tsova, S.V.,
and Popova, Yu.N., Zh. Prikl. Khim., 2001, vol. 74,
no. 6, pp. 1024 1028.
1
Ea = 79.19 kJ mol (Table 4). For 1,4-dimethylnaph-
8. Platonov, V.V., Proskuryakov, V.A., Ryl’tsova, S.V.,
and Popova, Yu.N., Zh. Prikl. Khim., 2001, vol. 74,
no. 6, pp. 1018 1023.
thalene, this value is higher by almost a factor of 2
1
(159.22 kJ mol ), and for -naphthol [7] and naphtha-
1
lene [19] it is still higher (269.84 and 349.87 kJ mol ,
respectively), which is indicative of the large contri-
bution of molecular condensation reactions for these
compounds.
9. Platonov, V.V., Proskuryakov, V.A., Rozental’, D.A.,
et al., Zh. Prikl. Khim., 2001, vol. 74, no. 5,
pp. 858 862.
10. Magaril, R.Z., Mekhanizm i kinetika gomogennykh ter-
micheskikh prevrashchenii uglevodorodov (Mechan-
ism and Kinetics of Homogeneous Thermal Transfor-
mations of Hydrocarbons), Moscow: Khimiya, 1970.
The activation energy of hydrogen formation from
anisole, 98.88 kJ mol [8], proved to be the closest
to that of hydrogen formation from 1,4-DMN.
1
11. Hund, C.D. and Macon, A.R., J. Am. Chem. Soc.,
CONCLUSIONS
1962, vol. 84, no. 23, p. 1524.
(1) The thermal stability of 1,4-dimethoxynaphtha-
lene is relatively low; its noticeable decomposition
12. Hund, C.D., The Pyrolysis of Carbon Compounds:
Am. Chem. Soc. Monograph, New York, 1929.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 12 2002