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PRODUCTION OF AROMATIC HYDROCARBONS BY PYROLYSIS OF PULVERIZED SHALE
V. G. KASHIRSKII
V. S. PETELINA
Saratov State Technical University
Saratov. Russia
Aromatic hydrocarbons of benzene series are produced on coal carbonization, but they are
also obtained by pyrolysis or catalytical processing of naphtha and kerosene-gas-oil fractions
of petroleum. Research is under way to use heavy petroleum residues, power-generating coals and
other organic raw materials for this purpose.
In this work the possibility to obtain aromatic hydrocarbons by pyrolysis of pulverized shale
from different deposits of the U.S.S.R. was studied.
Pyrolysis of pulverized shale was studied at a laboratory-scale unit described in [1], a tube
reactor from heat-resistant steel (clear diameter 12 mm, length 3.5 m) being its main element.
In all experiments powdered shale (250–0 µm) was directed into reactor in the flow of
superheated vapour at the of dust feed rate 12–15 g/min and flow rate of superheated vapour
350–500 g per 1 kg of dust. The temperature of reactor wall was kept 1000 °C by the use of
sectional electric heating, dwell time of shale particles in the reactor did not exceed
0.4–0.5 s, the temperature of gas and dust flow after reactor measured by means of a
thermocouple in the flow centre ranged from 820 to 860 °C. Using pulverized shale enabled to
realize high-speed heating up of all particles up to the pyrolysis temperature. Coke dust,
gaseous components and liquid condensed products, mostly monoaromatic compounds were yielded as
a result of deep thermal decompo-sition of shale organic matter.
The pyrolysis products were directed from reactor into the condensation system where coke dust, aqueous condensate and, on
columns with activated coal, casing-head petrol were separated. After each experiment the
latter was distilled with steam and the sample was collected for analysis.
Table 1. Characteristics of shale pyrolysis petrol
|
Shale
deposit
|
Petrol yield, %
|
d420,
g/cm3
|
nD20
|
Stotal
|
Iodine
number
|
|
On dry
shale basis
|
On equivalent
organic mass basis
|
|
Gdov
|
3.10
|
8.27
|
0.8788
|
1.4999
|
–
|
–
|
|
Kenderlyk
|
4.52
|
8.35
|
0.8811
|
1.5010
|
1.16
|
13.9
|
|
Aijuvinsk
|
2.23
|
5.31
|
0.8973
|
1.5049
|
8.54
|
18.6
|
|
Ozinsk
|
1.82
|
4.12
|
0.9091
|
1.5087
|
8.8
|
17.1
|
|
Kashpir
|
1.65
|
5.68
|
0.9048
|
1.5068
|
8.15
|
9.14
|
|
Savelyev
|
2.20
|
4.76
|
0.9002
|
1.5055
|
9.2
|
13.2
|
|
Obschchii
Syrt
|
2.25
|
4.32
|
0.9140
|
1.5079
|
10.6
|
8.3
|
The yield and main constants of casing-head petrol obtained by pyrolysis of oil shales of
different deposits are presented in Table 1.
All samples of shale pyrolysis petrol undergo total sulfurization that indicates the absence
of paraffinic and naphthenic hydrocarbons in their composition. Data in Table 1 and the results
of sulfuration show that pyrolysis petrol represents a highly-aromatized product into which
composition in case of processing sulfur-rich shales also organic sulfur compounds are
transferred. The content of unsaturated compounds is low.
A common property characterizing all pyrolysis petrol samples is their narrow boiling range.
As one can see in Table 2, the most part of pyrolysis petrol distils off at a temperature
close to benzene boiling point.
Table 2. Fractional composition of pyrolysis petrol
|
Shale
deposit
|
Initial boiling
point, °C
|
Distils off below the temperature, %
|
End point of
distillation,
°C
|
|
70 °C
|
80 °C
|
90 °C
|
100 °C
|
110 °C
|
|
Gdov
|
72
|
–
|
50
|
88
|
–
|
–
|
92
|
|
Kenderlyk
|
48
|
5
|
23
|
83
|
89
|
92
|
130
|
|
Aijuvinsk
|
57
|
2
|
12
|
75
|
90
|
95
|
125
|
|
Ozinsk
|
36
|
3
|
23
|
76
|
87
|
93
|
120
|
|
Kashpir
|
46
|
4
|
26
|
80
|
93
|
96
|
118
|
|
Obschchii
Syrt
|
38
|
6
|
23
|
78
|
85
|
91
|
120
|
In all cases distillation yields a dark-colored viscous distillation residue consisting of
the crystals of mononucleous aromatic compounds and polymerization products of unsaturated
compounds.
Table 3 presents the results of distillation of the neutral part of high-sulfur pyrolysis
petrol on a rectification column with resolving power 20 theoretical plates.
Table 3. Rectification of high-sulfur pyrolysis petrol
|
Boiling range
of fraction, °C
|
Yield, % on
neutral petrol
|
d420, g/cm3
|
nD20
|
Stotal
|
Iodine
number
|
|
38–60
|
5.4
|
1.2394
|
1.6202
|
82.00
|
6.8
|
|
60–79.3
|
72.8
|
0.8836
|
1.5025
|
1.39
|
1.7
|
|
79.3–83
|
13.4
|
0.9948
|
1.5190
|
28.60
|
3.7
|
|
83–106.5
|
3.5
|
0.9909
|
1.5158
|
22.00
|
8.0
|
|
Residue
|
3.4
|
0.9399
|
1.5080
|
–
|
–
|
|
Losses
|
1.5
|
–
|
–
|
–
|
–
|
Data in Table 3 show that the low-boiling head fraction consists mainly of carbon bisulfide.
The benzene fraction, distilled off at 79.3 °C, is the main product in our experiments. It is
necessary to note that on rectification of high-sulfur pyrolysis petrol the benzene fraction
always is distinguished by a reduced sulfur content that makes the following purification of
benzene from sulfur compounds much easier. Sulfur compounds accumulate in higher boiling
fractions and are represented, presumably, mainly by thiophene and its simple derivatives.
In particular, the fraction distilled at 79.3–83 °C contains 28.6 % sulfur and represents a
thiophenoaromatic concentrate that may be used for separation of thiophene and its derivatives.
The other products of pulverized shale pyrolysis are also of practical value. So, the gas of
pyrolysis with calorific value 3000–3500 cal/m3 is obtained in an amount of 400–600 l per
kilogram shale processed. This gas may be used in organic synthesis industry or for household
and industrial consumers. Dust-like coke may be used as a power-generating fuel at power plants.
Comparison of our data on the yield of monocyclic hydrocarbons (benzene derivatives) with those
published about the pyrolysis of petroleum products [2, 3] proves oil shales to be a prospective
enough raw material for production of aromatic hydrocarbons as well as some valuable organic
sulfur compounds.
A special attention should be paid to pyrolysis of Gdov and Kenderlyk oil shales. Their
pyrolysis in dust-like state yields more aromatic hydrocarbons (on organic matter basis) than
pyrolysis of petrochemicals (in raw petroleum basis). Experiments have demonstrated the need to
develop industrial units for pyrolysis of oil shales in the dust-like state.
REFERENCES
- Kashirsky V. G., Petelina V. S. Proceedings of higher educational institutions //
Chemistry and chemical engineering. 1959. Vol. 2, No. 3. P. 443–448.
- Obryatchikov S. N. Technology of petroleum, Part II. Gostoptehizdat, 1952.
- Butkov N. A. Aromatization of petrolic hydrocarbons. Gostoptehizdat, 1947.
Translated by Ph.D. H. Luik from Proc. Acad. Sci. of the U.S.S.R. Division of Technical
Sciences. Metallurgy and fuel. 1959. No. 6. P. 170-172 [in Russian].
We thank Estonian Science Foundation for the financial support under Grant No. 2702.
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