Study of the catalytic dehydrochlorination of 1,2-dichloropropane

Article abstract of DOI:10.1134/S1070427211090138

Catalytic dehydrochlorination of 1,2-dichloropropane in the presence of γ-Al₂O₃, CaX, and haydite was studied. A relationship between the catalytic activity and acidity of the catalysts under study was revealed.

Full text of DOI:10.1134/S1070427211090138

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 9, pp. 1532−1540. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © Dzh.Yu. Nadzhafov, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 9, pp. 1482−1490.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Study of the Catalytic Dehydrochlorination
of 1,2-Dichloropropane
Dzh. Yu. Nadzhafov
Azerbaijani State Oil Academy, Baku, Azerbaijan
Received June 8, 2010
Abstract—Catalytic dehydrochlorination of 1,2-dichloropropane in the presence of γ-Al O , CaX, and haydite
2
3
was studied. A relationship between the catalytic activity and acidity of the catalysts under study was revealed.
DOI: 10.1134/S1070427211090138
Development of new high-efficiency techniques for
oxide in optimal conditions for each catalyst, were
production of C H hydrocarbons will make it possible
reported. It was found that γ-Al O , CaX zeolite, and
3
4
2
3
to master manufacture of a wide variety of organic
compounds widely used in pulp-and-paper and medical
industries, in production of vitamins and mixed fodder,
and in chemical industry for manufacture of polymeric
materials, including synthetic caoutchoucs, oil additives,
and antioxidant agents [1–3].
haydite are the most selective and active catalysts for
dehydrochlorination of 1,2-dichloropropane [7].
This communication report results of a comparative
study of the gas-phase dehydrochlorination of
1
,2-dichloropropane and intermediate reaction products
in the presence of γ-Al O , CaX zeolite, and haydite and
2
3
However, industrial production based on allene and
methyl acetylene has not found wide application, which
is primarily due to the lack of economically feasible
industrial methods for obtaining C H hydrocarbons.The
of the effect of water vapor on process parameters.
EXPERIMENTAL
3
4
existing techniques for production of allene and methyl
acetylene have such inherent disadvantages as low yield
and selectivity with respect to target products, multistage
technology and high process temperature [4, 5]. For
As starting raw materials served 1,2-dichloropropane
(94–98% purity) isolated by rectification from
organochlorine waste formed in synthesis of allyl
chloride and propylene chlorohydrin.
example, the only way to obtain C H hydrocarbons at
3
4
The process of catalytic dehydrochlorination of
present is by pyrolysis of hydrocarbon raw materials.
However, their content in the pyrolysis gas does not
exceed 0.2–2.0%, which hinders their isolation. In
1
,2-dichloropropane and the fundamental aspects of
the course of the reactions involved in a conventional
flow-through installation with a 10-cm integral reactor
were studied. The flow-through installation comprised
3
addition, the thus obtained C H hydrocarbons contain
3
4
approximately equal amounts of allene and methyl
acetylene, which requires special conditions for their
separation.
(
Fig. 1) an integral reactor having the form of a quartz
glass tube with a total length exceeding by 15–20 cm the
furnace length. To make lower the temperature gradient
and gradients of the concentrations of the starting raw
materials and reaction products, the ratio between
the reactor and catalyst grain diameters was 12–30.
The reactor tube was equipped with inlet for delivery
of gases and liquid reagents and was connected by
In [6], data on the activity exhibited in the reaction of
dehydrochlorination of 1,2-dichloropropane (DCP) by
a number of catalysts, such as industrial aluminosilicate
cracking catalyst AS-37, magnesium oxide, sodium
and calcium forms of type-X zeolites, and aluminum
1
532

STUDY OF THE CATALYTIC DEHYDROCHLORINATION OF 1,2-DICHLOROPROPANE
1533
a ground joint to a cooled receiver for a liquid catalyst.
The temperature in the reaction zone was measured
with a chromel–alumel thermocouple connected to a dc
potentiometer. The thermocouple was preliminarily
calibrated (with its cold junctions placed within
a test tube in a Dewar vessel with ice). The catalytic
reactor was heated with a tubular electric furnace with
a temperature control system. The tube was charged
with 5 ml of a catalyst placed in the reactor between two
layers of quartz sand (particle size 3 mm). The end of the
thermocouple pocket was in the middle of the catalyst
bed. The reactor was carefully inserted into the furnace
so that the catalyst bed was situated at that place of the
furnace in which the temperature gradient is zero and
then fixed in this position. The reactor was connected to
the system for delivery of raw materials and removal of
reaction products.
temperatures in the range 300–500°C under atmospheric
pressure. The starting raw materials and reaction
products were analyzed by GLC. Gaseous reaction
products were analyzed on a chromatograph with a heat-
conductivity detector on a 6-m-long compound column:
4 m, with fixed TEGNM liquid phase supported in an
amount of 20 wt % by INZ-600 Inza brick; and 2 m,
with 3.0 wt % Vaseline oil on a tripoli powder from
the Zikeevo open pit. The products were preliminarily
neutralized and dried over activated aluminum oxide.
Aluminum oxide sieved with 0.25–0.5-mm mesh was
prepared by calcination at 750°C for 7 h and subsequent
cooling in a desiccator to room temperature. Liquid
reaction products were analyzed in the isothermal mode
at 120°C an detector current of 110 mAon a 3-m column
packed with tricresyl phosphate (18%) supported by
N-AW Chromaton.
Liquid raw materials were delivered through an
evaporator with an electromechanical syringe batching
unit. The system for collection of liquid products
comprised a trap and Dewar and Marriott vessels. The
volume of gases being formed was determined from the
volume of brine displaced from the Marriott vessel.
Products of the thermocatalytic conversion of
1,2-dichloropropane are a complex mixture of various
organic (organochlorine) compounds, which are
separated upon cooling to –10 to 0°C into two phases,
liquid and gaseous.
The gas phase contains methane, ethylene,
propane, propylene, allene, methyl acetylene, and
Theexperimentswereperformedinthevaporphaseat
1
0
1
7
Fig. 1. Schematic of the flow-through catalytic installation. (1) Quartz reactor, (2) syringe batching unit for delivery of liquid products, (3)
thermocouple pocket, (4) cooled ampule-receiver for liquid catalyzate, (5) rheometer, (6) electric furnace, (7) laboratory autotransformer
or controlling potentiometer, (8) measuring thermocouple, (9) cylinder for supply of gases, (10) evaporator, (11) autotransformer, (12)
foam meter of the gas flow rate, (13) liquid chromatograph, (14) gas chromatograph, (15) recording device, (16) dc potentiometer, (17)
columns for drying and purification of gases, (18) Dewar vessel, and (19) Marriott vessel.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

1534
NADZHAFOV
Table 1. Effect of temperature on the dehydrochlorination
of 1,2-dichloropropane in the presence of γ-Al O and CaX.
Contact duration 7.4 s, raw material delivery rate 6.2 g h
C4 hydrocarbons. The liquid phase concentrates
unconverted raw materials, chloropene isomers,
and trace amounts of macromolecular products. In
discussion of the experimental data, changes occurring
in the composition of the gaseous and liquid phases will
be considered.
2
3
–
1
Content, wt %, at indicated
temperature, °C
Reaction products
3
00
400
500
As follows from the data in Tables 1 and 2, the
conversion of 1,2-dichloropropane and the redistribution
of the reaction products in the liquid and gaseous phases
depend on the nature of a catalyst.
γ-Al O
2
3
Composition (wt %):
gas phase
4.2
78.5
10.3
1.9
8.9
73.0
14.2
2.8
10.1
66.7
16.9
4.3
The process on the γ-Al2O3 catalyst yields
hydrocarbon gases in which about 80% are C2–
C4 hydrocarbons (Table 1). In the thermocatalytic
conversion of 1,2-dichloropropane at 30°C, the main
products in the gas phase are ethylene, propylene, and
the allene–methyl acetylene fraction whose contents
are 20.1, 50.2, and 23.1%, respectively. As the process
temperature is raised from 300 to 500°C, the amounts
of ethylene and propylene decrease to 15.9 and 48.8%.
The maximum content of allene and methyl acetylene in
the gas phase, 34.1 mol %, is reached at a temperature
of 400°C. In the temperature range under study, the
process performed at 400°C yields the smallest amount
of the liquid phase. On raising the process temperature
to 500°C, the conversion of the starting raw material
increases from 35.3 to 54%.
liquid phase
hydrogen chloride
densification products
loss
5.1
1.1
2.0
Composition of the gas
phase (mol %):
methane
0.2
20.1
0.7
0.2
26.8
0.9
0.2
15.9
0.6
ethylene
propane
propylene
50.2
3.4
34.1
5.6
48.8
4.9
allene
methyl acetylene
ΣС4
19.7
5.7
28.5
3.9
25.3
4.3
Experimental data on the temperature dependence of
the dehydrochlorination of DCP in the presence of CaX
are listed in Table 1. It can be seen that the conversion of
therawmaterialandthevolumeoftheresultinggasphase
grow with increasing temperature. The temperature
dependences of the conversion of DCP and of the
concentration of the reaction products formed in steam
conversion of DCP on CaX and γ-Al O catalysts were
CaX
Composition (wt %):
gas phase
12.2
51.3
23.5
8.5
20.3
41.0
25.6
9.7
21.3
35.0
31.4
11.2
1.1
liquid phase
hydrogen chloride
densification products
loss
2
3
found to be different. It should be noted that the process
performed on CaX is characterized, in contrast to that on
γ-Al O , by a comparatively high content of allene on
4.5
3.4
2
3
Composition of the gas
phase (mol %):
methane
the background of a lower content of methyl acetylene.
The maximum yield of the allene–methyl acetylene
fraction (41.1%) was reached in a process performed at
0.2
10.4
1.0
0.4
7.1
0.2
8.0
4
00°C. The fact that allene is predominantly formed in
ethylene
the presence of CaX suggests that the reaction of allene
isomerization into methyl acetylene does not occur, i.e.,
differences in the nature of active centers in the CaX and
γ-Al2O3 catalytic systems are manifested.
propane
1.2
1.3
propylene
57.0
25.5
4.2
48.8
35.9
5.2
53.9
30.0
5.5
allene
Table 2 presents experimental data on how the
process temperature affects parameters of the reaction
of DCP dehydrochlorination on haydite. The data
methyl acetylene
ΣС4
1.7
1.4
1.1
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

STUDY OF THE CATALYTIC DEHYDROCHLORINATION OF 1,2-DICHLOROPROPANE
1535
Table 2. Effect of temperature on the dehydrochlorination of
are indicative of an extremal dependence of the yield
of, and selectivity for allene and methyl acetylene on
the process temperature. At 400°C, haydite shows the
lowest activity and the conversion of raw materials does
not exceed 35%. As the process temperature is raised
to 450°C, the temperature dependence of the product
yield somewhat changes, which leads to an increase in
the yield of allene and methyl acetylene, with their total
yield reaching the maximum value of 79%.
1
,2-dichloropropane on haydite. Contact duration 10.5 s, raw
–
1
material delivery rate 6.2 g h
Content, wt %, at indicated
temperature, °C
Reaction products
4
00
450
500
Composition (wt %):
gas phase
26.0
59.3
13.2
1.0
30.9
49.1
18.3
1.3
33.5
44.5
20.1
1.4
Raising the process temperature to 500°C results in
that the yield of allene and methyl acetylene decreases
on the background of a rise in the formation of ethylene,
propylene, densification products, and hydrogen
chloride. As a consequence, their relative amounts
change in favor of destruction products. The fact that
the ratio between allene and methyl acetylene in the gas
phase is 7 : 1 indicates that no isomerization of allene
into methyl acetylene occurs in the presence of haydite.
liquid phase
hydrogen chloride
densification products
loss
0.5
0.4
0.5
Composition of the gas
phase (mol %):
methane
8.5
24.5
–
5.5
14.0
–
4.8
27.5
–
ethylene
The results obtained give reason to believe that
dehydrochlorination of DCP on the catalytic systems
under consideration occurs by various pathways, with
acid centers of varied nature involved. For example,
mostly methyl acetylene is formed in the presence of
aluminum oxide, and allene, on CaX and haydite. As
follows from the data in Tables 1 and 2, the total yield
of the allene–methyl acetylene fraction per the delivered
raw material also differs from that per aluminum oxide.
The yield of the target fraction in the presence of haydite
substantially exceeds the amount of allene and methyl
acetylene formed on CaX and aluminum oxide. Here, as
also in the case of CaX, predominant formation of allene
is observed (Table 2). On the basis of the experimental
data obtained in conversion of 1,2-dichloropropane to
give methyl acetylene, the catalysts under study can be
arranged in order γ-Al O > CaX > haydite.
propane
propylene
1.4
57.7
7.9
–
1.5
69.2
9.8
–
1.8
57.2
8.7
–
allene
methyl acetylene
ΣС4
and 2-chloropropene in the catalyzate are very close
on all the catalysts. A different situation was observed
for 3-chloropropene: it is hardly formed on γ-Al O ,
2
3
whereas on CaX and haydite, its content is 2.2 and 3.9%,
respectively. Under the same conditions, the lowest
yield of 2-propane was observed on γ-Al O (1.28%)
2
3
and reached values of 4 and 6.8% on, respectively, CaX
and haydite.
These, to a certain extent ambiguous, results
demonstrate that the reaction mechanism is rather
intricate. To elucidate the mechanism by which
hydrocarbons are formed from DCP on γ-Al O ,
2
3
For the reaction of 1,2-dichloropropane dehydro-
chlorination accompanied by the formation of allene,
the sequence is different: haydite > CaX > γ-Al O .
2
3
2
3
and also on CaX zeolite and haydite, the conversion
of intermediate dehydrochlorination products was
studied: 2-chloropropane (1), 1-chloropropene-1 (2),
2-chloropropene-1 (3), and 3-chloropropene-1 (4)
(Table 3).
The diagram in Fig. 2 presents the qualitative-
quantitativehydrocarboncompositionoftheliquidphase,
obtained in dehydrochlorination of 1,2-dichloropropane
on γ-Al O , CaX, and haydite. The comparative results
2
3
make it possible to arrange the catalysts under study in
order of decreasing quantitative yield of the liquid phase
The dehydrochlorination of the intermediate
products
(1-chloropropene-1,
2-chloropropene-1,
as γ-Al O > CaX > haydite.
2
3
and 3-chloropropene-1) on γ-Al O is accompanied
2
3
Acomparatively high content of 1,2-dichloropropane
was observed when the process was performed on
γ-Al O , and the lowest, on CaX. The contents of 1-
by unequal amounts of C H hydrocarbons in the gas
phase. The yield of methyl acetylene is the highest in
conversion of 2-chloropropene-1. The main product in
3 4
2
3
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

1536
NADZHAFOV
A, %
formation in dehydrochlorination of the intermediate
products (1-chloropropene-1, 2-chloropropene-1,
-chloropropane, and 3-chloropropene-1) and the
starting 1,2-dichloropropane on γ-Al O , CaX, and
2
2
3
haydite confirms the rather good consistency of the
process mechanism (Table 4). The largest allene : methyl
acetylene ratio is characteristic of dehydrochlorination
of 1,2-dichloropropane and 2-chloropropene on CaX and
haydite (6.90 and 7.30, and 7.70 and 8.19, respectively),
whereasonaluminumoxide,thisparameterissubstantially
smaller and does not exceed 0.2, with the total content
of the allene–methyl acetylene in the presence of this
catalyst also being the lowest. In addition, irrespective
of a raw material under study, the dehydrochlorination
reaction in the presence of aluminum oxide mainly
yields methyl acetylene and an insignificant amount of
allene, which is, probably, a consequence of the allene–
methyl acetylene isomerization at the catalyst surface.
From the results of a thermodynamic calculation [7,
Fig. 2. Content of hydrocarbons in the liquid phase formed
in dehydrochlorination of 1,2-dichloropropane on catalysts
of varied nature under reaction cycle conditions. T = 400°C,
–1
contact duration 10.5 s, raw material delivery rate 6.2 g h . (A)
8
] of the isobaric-isothermal potential of the reaction
Yield of products, conversion. (1) 1,2-Dichloropropane, (2)
1
-chloropropene, (3) 2-chloropropene, (4) 2-chloropropane,
of structural isomerization of methyl acetylene into
allene and of allene into methyl acetylene, depending
on temperature, follows that the formation of methyl
acetylene from allene must be spontaneous, whereas
the rearrangement of methyl acetylene into allene has
thermodynamic limitations. Thus, the experimental
results obtained when performing dehydrochlorination
of 1,2-dichloropropane and its chlorine-containing
hydrocarbons in the presence of γ-Al2O3 are in good
agreement with the theoretical predictions.
(
3 3
5) 3-chloropropene, and (6) C H6 oligomers + C H4
oligomers.
the liquid phase in conversion of 2-chloropropane is
-chloropropene-1; however, its yield is substantially
lower than that in conversion of 1,2-dichloropropane
Fig. 2). The yield of the allene–methyl acetylene
fraction in conversion of the intermediate chlorine-
containing hydrocarbons on aluminum oxide is lower
than that in conversion of 1,2-dichloropropane.
2
(
On the whole, the transformation of 1,2-dichloro-
propane and 2-chloropropene is characterized by the
same type of conversion of raw materials and similar
qualitative compositions of the reaction products for
CaX and haydite. In the case of aluminum oxide, the
composition is different and the process occurs under
the active of surface active centers of a different nature
[9].
In dehydrochlorination of 2-chloropropanein the
presence of CaX, as also in that of 1,2-dichloropropane,
-chloropropene-1 is formed in the highest yield.
The experimental data on dehydrochlorination of the
intermediate products on CaX indicate that the yield of
allene is the highest in conversion of 2-chloropropane;
thatofmethylacetylene,inthecaseof1-chloropropene-1;
predominant formation of propylene and ethylene in the
gas phase is characteristic of 3-chloropropene-1.
2
In numerous heterogeneous catalytic reactions,
e.g., in synthesis of hydrocarbons, the water molecule
is regarded as a reactant or a reaction product. An
insignificant amount of water can strongly affect the
reactionselectivityas, e.g., inthecatalytichydrogenation
of benzene over metallic ruthenium. The effect of water
vapor on parameters of the dehydrochlorination of
1,2-dichloropropane was studied by its introduction into
the reaction zone.
A similar set of experiments was also performed in
the presence of haydite. Their results demonstrate that
-chloropropene-1 is the main source of allene formation
on CaX and haydite, and 1-chloropropene-1, that of
methyl acetylene. In contrast to the rest of the catalysts,
allene is mostly formed from 2-chloropropane on
γ-Al O , and methyl acetylene, from 2-chloropropene.
2
2
3
The dependence of allene and methyl acetylene
The formation of the allene–methyl acetylene
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

STUDY OF THE CATALYTIC DEHYDROCHLORINATION OF 1,2-DICHLOROPROPANE
1537
Table 3. Comparative reactivities in thermocatalytic conversion of chlorine-containing C3 compounds
Content, wt %, in the presence of indicated catalysts
Reaction products
1
2
3
4
1
2
3
4
1
2
3
4
γ-Al O
СаХ
haydite
2
3
Composition (wt %):
gas phase
43.6
38.3
12.3
1.6
29.1
40.7
11.1
14.0
5.1
38.6 20.2 52.8 36.0 43.2 19.4 53.4
31.9 52.8 30.4 31.3 23.5 46.4 35.3
44.4
30.1
2.0
48.0 40.00
liquid phase
26.6
1.0
39.6
0.7
hydrogen chloride
densification products
loss
12.2 11.1
14.5 12.8
11.5 19.9 20.0 19.1 10.0
0.3 10.7 11.0
11.4
3.7
0.2
1.1
23.4
0.1
24.2
0.2
19.6
0.1
1.1
2.4
3.1
5.0
2.1
2.3
Composition of the gas
phase (mol %):
methane
0.6
24.8
2.0
0.5
25.3
2.8
0.6
0.2
0.4
6.6
1.0
0.4
7.2
1.2
0.5
0.4
4.6
9.0
2.0
5.4
6.9
8.5
19.6
1.5
ethylene
24.5 37.2
1.5 0.8
6.9 12.5
1.4 0.5
22.1
20.7
propane
propylene
53.7
4.3
38.9
3.6
38.4 35.4 35.5 37.7 38.6 53.4 71.4
1.3
14.8
56.4
–
1.6
63.1
7.7
–
1.1
allene
3.5
2.3 43.4
5.9 43.9 17.8
5.7 13.4
7.0
6.0
–
56.1
13.2
–
methyl acetylene
ΣС4
11.6
3.0
24.3
4.6
26.9 16.2 11.3 43.4
4.6
7.9
1.8
4.2
3.0
2.0
Composition of the liquid
phase (mol %):
1
1
2
2
3
,2-dichloropropane
-chloropropene
-chloropropene
-chloropropane
-chloropropene
3.4
4.4
–
45.2
54.6
–
–
–
–
2.6 50.2
–
–
–
–
–
38.7
57.5
–
–
42.2
3.7 49.7 37.1 13.9
3.4
9.1
49.0
43.3
–
12.5
15.4
–
12.6
77.5
0.8
57.4 36.3
8.8
–
0.1
–
62.6 32.9
–
1.5 79.6
–
3.5 78.6
0.2
–
0.4 62.2
–
–
–
0.3 49.7
–
5.2
2.4
0.1
–
70.8
0.5
0.8
C H oligomers
0.6
–
–
–
–
–
–
–
–
–
1.5
7.4
1.9
1.9
3
4
C H oligomers
0.7
–
–
3
6
fraction may be due to presence of both basic and
acid centers: however, the substantially higher content
of methyl acetylene, compared with allene, results
from the action of the stronger acid centers [10]. It is
known that adsorption of water vapor on the surface
C H hydrocarbons on aluminum oxide is higher in the
3 4
presence of water, compared with that without water,
which is, probably, due to appearance of additional
Table 4. Allene : methyl acetylene ratio in the reaction of
catalytic dehydrochlorination
–
1
of γ-Al O in amounts of up to 8 mmol g results in
2
3
a strong increase in the concentration of basic centers
and acid centers are transformed to become weaker. If
it is assumed that acid-base active centers of moderate
strength are involved in the dehydrochlorination of
Allene : methyl acetylene
Composition of raw
materials
γ-Al O
СаХ
haydite
2
3
1
1
2
2
,2-Dichloropropane
-Chloropropene
-Chloropropene
-Chloropropane
0.17
0.15
0.13
0.37
0.14
6.90
0.14
7.70
3.80
1.33
7.30
0.26
8.19
3.58
1.99
chlorine-containing C hydrocarbons, then performing
3
the reaction in the presence of water vapor must lead to
a higher yield of dehydrochlorination products. The data
in Table 5 demonstrate that, as expected, the yield of
products in dehydrochlorination of chlorine-containing
3-Chloropropene
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

1538
NADZHAFOV
Table 5. Catalytic conversion of 1,2-dichloropropane in the
centers. It is known that the acidity of catalysts can be
determined by such methods as ion exchange, indicator
technique, method of adsorption of volatile amines, and
IR spectroscopy [11–14]. It was shown in the present
study that the nature of acid centers on the surface can
be determined under conditions close to real operation
conditions of a catalyst (in situ). This technique consisted
in the following: isomerization of butene-1 was
performed on the surface of the starting catalyst sample,
with analysis of the isomer composition of butenes-2; in
the steady mode of the reaction of dehydrochlorination
of 1,2-dichloropropane in the presence of water vapor,
butene-1 was delivered into the reaction zone and
changes in the concentration of the isomers, allene, and
methyl acetylene in the reaction products were analyzed;
as the reaction of dehydrochlorination was complete,
isomerization of butene-1 was again performed on the
catalyst surface. The uniqueness of this method is in
that, being nonstationary, it enables studies under steady
process conditions when the rates of all the reaction
stages and the state of the catalyst remain invariable.
presence of water vapor. Contact duration 7.4, water vapor :
–
1
DCP molar ratio = 1 : 1, raw material delivery rate 6.2 g h
Content, wt %
Reaction products
γ-Al O
СаХ
haydite
2
3
Composition (wt %):
gas phase
10.8
75.0
11.6
1.7
22.3
45.1
23.0
8.7
28.2
53.7
14.0
3.5
liquid phase
hydrogen chloride
densification products
loss
0.9
0.9
0.6
Composition of the gas
phase (mol %):
methane
0.1
23.7
0.4
0.3
4.0
7.8
22.1
–
ethylene
propane
0.7
propylene
29.3
3.6
50.1
37.7
5.5
2.1
59.6
8.4
–
allene
methyl acetylene
ΣС4
31.9
8.0
Butene-1 was isomerized on CaX, haydite, and
1.7
γ-Al O in the flow-through mode at a temperature of
2
3
Composition of the
liquid phase (mol %):
3
50°C, atmospheric pressure, and volumetric flow rate
–1
of butene-1 equal to 120 h . Butene-1 was produced
by dehydration of n-butanol on aluminum oxide treated
with 0.05 wt % KOH, which favored poisoning of strong
acid centers and made it possible to obtain a product
containing 94–95% butene-1.
1
1
2
2
3
,2-dichloropropane
-chloropropene
-chloropropene
-chloropropane
-chloropropene
43.9
11.3
34.9
9.2
0.1
0.6
–
51.2
8.8
54.2
8.2
21.7
9.6
6.3
–
26.4
9.7
Figure 3 presents data on properties of various acid
centers of the catalysts, as determined by performing
isomerization of butene-1 on their surface. The high
yield of the cis-isomer on aluminum oxide is probably
due to the large amount of Lewis acid centers and the
possibility of co-existence of aluminum cations in
different coordinations (CN = 6, 5, 4) predetermines
their sufficiently high strength. It should be noted here
that the formation of the trans-isomer, which mostly
occurs on Brønsted acid centers, is not so intense
because its yield is nearly two times lower than that of
the cis-isomer.
3.5
C H oligomers
0.2
3
4
C H oligomers
0.2
–
3
6
basic centers on the catalyst surface and to weakening
of the strength of the acid centers.
Introduction of water vapor into the reaction
zone in dehydrochlorination of 1,2-dichloropropane
in the presence of CaX and haydite hardly causes
a redistribution of the reaction products.
An important specific feature of the catalysts under
study is the simultaneous presence on their surface of
Brønsted and Lewis acid centers, with no possibility
of varying properties of centers of one type without
changing those of the other type. Therefore, a study was
performed in order to determine the nature and strength
of all types of centers and acid-base interaction of starting
reagents, reaction products, and water vapor with these
The results of a study of the isomerization of butene-1
on CaX suggest that there are surface acid centers with
nearly equal strengths. The higher yields of trans-
butene-2, compared with those on aluminum oxide, can
be attributed to structural bridge OH groups situated on
the outer surface and on defects in zeolite crystals.
The Brønsted centers of haydite are also sufficiently
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

STUDY OF THE CATALYTIC DEHYDROCHLORINATION OF 1,2-DICHLOROPROPANE
1539
c, %
A, %
Haydite
cis/trans
Fig. 3. Dependence of the isomer yield c on the catalyst
nature. (1) cis/trans-butene-2 ratio, (2) cis-butene-2, and (3)
trans-butene-2.
Fig. 4. Dependence of the yield A of products formed in joint
dehydrochlorination of 1,2-dichloropropane and isomerization
of butene-2 on the isomer ratio. (1) Methyl acetylene and (2)
allene.
strong, with the strength of the centers substantially
exceeding that for previously studied catalysts. The
high Brønsted acidity is possibly a consequence of the
formation of Al–O–Si and Fe–O–Si bridges in which
SiOH enhances the overall acidity of iron–aluminum–
silicon fragments on the periphery.
allene and methyl acetylene on γ-Al O , CaX, and
2
3
haydite can be suggested. An analysis of possible
correlations between the catalytic activity and the
acidity of the catalysts demonstrated that allene is
mostly formed on Lewis acid centers, whereas methyl
acetylene is formed on Brønsted acid centers. The
use of isomerization of butene-1 made it possible to
reveal a number of fundamental distinctions between
the acid centers on the surface of the catalysts under
study. Performing the process in the presence of water
hardly affects the redistribution of the reaction products.
Possessing stronger Brønsted acid centers, haydite is the
most active among other catalysts (CaX and aluminum
oxide) for dehydrochlorination of 1,2-dichloropropane
to give allene and methyl acetylene.
Figure4presentsdataontheyieldofalleneandmethyl
acetylene in dehydrochlorination of 1,2-dichloropropane
in the presence of water and in joint isomerization of
butene-1. Analysis of the target and isomeric reaction
products reveals the following behavior: the small ratio
between cis and trans isomers on CaX and haydite is
characterized by a high yield of allene and low yield
of methyl acetylene, whereas a large ratio between the
isomers (in the case of aluminum oxide), by low yield of
allene and more than four times higher yield of methyl
acetylene. The so large ratio between the components
of the allene–methyl acetylene fraction in the case of
aluminum oxide assumes that structural isomerization
occurs in the presence of Lewis acid centers. At the same
time, introduction of water vapor into the reaction zone
leads to dissociated adsorption of water molecules and
to an increase in the strength of Brønsted acid centers,
with partial blocking of Lewis acid centers, which
causes, in the end, an overall decrease in the yield of the
allene–methyl acetylene fraction.
CONCLUSIONS
(1) The conversion of 1,2-dichloropropane and the
formation selectivity of allene and methyl acetylene
are affected both by the nature of a catalyst and by the
temperature, partial pressure, and contact duration.
(
2) Among the heterogeneous catalysts (γ-Al O ,
2 3
CaX, and haydite) used to obtain allene and methyl
acetylene, haydite is the most promising because of the
high rate of elimination of 1,2-dichloropropane, ready
availability, and process selectivity. The optimal process
conditions are found.
Thus, a possible mechanism of the reaction of
dehydrochlorination of 1,2-dichloropropane to give
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 9 2011

1540
NADZHAFOV
Institute), Moscow: 1996, pp. 3–12.
(3) The haydite catalyst remains unchanged in
regeneration, is stable during no less than 20 min, and
provides a 70.9% conversion of raw materials at a 22%
yield of target products.
6. Nadzhafov, Dzh.Yu., Guseinova, E.A., andAdzhamov, K.
Yu., AMEA, Zh. Khim. Probl., 2009, no. 3, pp. 544–547.
7. Nadzhafov, Dzh.Yu. and Guseinova, E.A., AMEA,
Azərbaycan Kimya Jurnali, 2009, no. 4, pp. 38–43.
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