Influence of regeneration conditions on the activity of the catalyst for oxidative chlorination of ethylene

Article abstract of DOI:10.1007/s11167-005-0455-0

The possibility of thermochemical regeneration of an industrial batch of a spent and partially deactivated catalyst to improve its activity and selectivity in oxidative chlorination of ethylene to give 1,2-dichloroethane was studied.

Full text of DOI:10.1007/s11167-005-0455-0

Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1088 1092. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
2005, pp. 1110 1113.
Original Russian Text Copyright
2005 by Kurta, Mykytyn, Khaber.
CATALYSIS
Influence of Regeneration Conditions on the Activity
of the Catalyst for Oxidative Chlorination of Ethylene
S. A. Kurta, I. M. Mykytyn, and M. V. Khaber
Stefanik Precarpathian National University, Kalush, Ivano-Frankovsk oblast, Ukraine
Received October 13, 2004; in final form, March 2005
Abstract The possibility of thermochemical regeneration of an industrial batch of a spent and partially
deactivated catalyst to improve its activity and selectivity in oxidative chlorination of ethylene to give
1,2-dichloroethane was studied.
In the existing process for manufacture of vinyl
chloride by a balanced scheme, 1,2-dichloroethane
1,2-C H Cl is produced by direct and oxidative
EXPERIMENTAL
The study was performed on the newly created
experimental laboratory installation that operates on
real process gases (taken from the stage of ethylene
oxychlorination at a shop of Lukor Private Company,
Kalush) and adequately models the industrial process.
2
4
2
chlorination of ethylene. The oxidative chlorination
process uses as a catalyst CuCl supported by -Al O
2 3
2
[1]. The reaction requires a slight excess of C H and
2
4
occurs in accordance with the overall equation [2]
After two years of operation, the characteristics of
the catalyst changed, which led to a decrease in its
activity in oxychlorination. Therefore, our goal was to
study the possibility of regenerating the oxychlorina-
tion catalyst and to analyze methods of such a regen-
eration under the conditions maximally similar to
those used in the industry.
C2H4 + 2HCl + 0.5O2 C2H4Cl2 + H2O + Q. (1)
The main reaction is accompanied by side reac-
tions: complete and incomplete combustion of C H
2
4
to give CO and CO [3]:
2
C2H4 + 3O2
C2H4 + 2O2
2CO2 + 2H2O,
2CO + 2H2O.
(2)
(3)
Experiments on catalyst regeneration were per-
formed in two ways: by thermal treatment of the cata-
lyst in a fluidized bed in oxygen-rich gas mixture or
in air and by washing the catalyst in dichloroethane.
In addition, the physicomechanical properties of cata-
lyst samples before and after regeneration were
studied.
Other possible side reactions yield CCl , chloral,
4
trichloroethane, trichloroethylene, etc. (a total of up to
2% relative to 1,2-C H Cl obtained) [4].
2
4
2
In the course of the process, redox reactions may
occur on the catalyst surface [5]:
The regeneration was performed in two modes: in
air with heating to 180, 210, and 250 C and at in-
creased oxygen content (20, 30, and 40 vol %) and
nitrogen content of 80, 70, and 60 vol %, respectively.
Simultaneously, analyses for the content of copper(I,
II, total) chloride and iron(III) in the catalyst were
C2H4 + 2CuCl2
C2H4Cl2 + 2CuCl,
2CuCl2 + H2O.
(4)
(5)
2CuCl + 0.5O2 + 2HCl
The appearance of iron in the catalyst can be ac-
counted for by the following reactions between the
reactor walls and the catalyst:
made, with the bulk weight m , specific surface area
b
S , and pore volume V in the catalyst determined
sp
before and after regeneration. The data obtained are
listed in the table.
Fe + CuCl2
FeCl2 + Cu,
(6)
(7)
In addition, the table lists data on washing of the
catalyst to remove iron(III) chloride by extraction into
dichloroethane and describes changes in the physico-
mechanical properties of the catalyst.
4FeCl2 + O2 + 4HCl
4FeCl3 + 2H2O,
2FeCl3 + 3H2O
Fe2O3 + 6HCl.
(8)
1070-4272/05/7807-1088 2005 Pleiades Publishing, Inc.

INFLUENCE OF REGENERATION CONDITIONS ON THE ACTIVITY OF THE CATALYST
1089
Physicomechanical properties of the catalyst for oxychlorination of ethylene before and after its regeneration in the air
and oxygen-rich gas mixture. Regeneration duration 8 h
Cu(I, II) content Fe(III) content
1
1
3
Catalyst
V, cm3 g
Ssp, m2 g
mb, g cm
Color
wt %
Fresh
4.2
4.15
0.12
0.30
0.36
0.26
140.0
74.5
1.02
1.31
Green
Brown
Without regeneration
After regeneration:
180 C
4.10
4.51
4.585
0.30
0.301
0.30
0.26
0.276
0.286
78.5
85.0
99.0
1.29
1.28
1.27
Dark green
Green
Lettuce-green
210 C
250 C
Extraction in dichloroethane:
80 C
60 C (agitation)
After regeneration with
O2/N2, vol %:
210 C 30/70
4.75
4.58
0.254
0.255
0.276
0.269
101.2
100.0
1.12
1.12
Dark green
Green
4.18
4.76
4.77
0.31
0.275
0.26
0.27
0.28
0.32
100.5
105.0
108.0
1.27
1.26
1.25
210 C, 40/60
250 C, 40/60
Light green
Green
As the concentration of oxygen in the regenerating
gas increases, the bulk weight of the catalyst decreases
from 1.3 to 1.27 1.25 g l , which is due to partial
removal of by-products formed in the oxychlorination.
This may be confirmed by a simultaneous increase
in the pore volume in the catalyst, with this depen-
dence being more pronounced at 250 C.
C H : HCl : O = 1.07 : 2 : 0.7, flow rate of the cir-
2 4 2
1
culation gas (60% CO ) 72 80 l h , temperature of
2
1
the quenching column 87 100 C, pressure in the sys-
tem 7 12 kPa, total flow rate of exhaust gases 76
1
86 l h , and experiment duration 1 h. Additionally,
the circulation gas was analyzed for the content of
CO, CO , C H , and O in the course of an experi-
2
2
4
2
ment. After the experiment, the weight of the di-
chloroethane formed was determined, its purity and
the content of microimpurities were analyzed chroma-
tographically, and the content of unchanged HCl was
measured. After that, the conversion in terms of hy-
drogen chloride and C H and the yield of dichloro-
ethane in percent relative to the theoretical value
before and after regeneration in air and in oxygen-rich
gas mixture were calculated.
Gradually raising the temperature from 180 to
250 C in regeneration leads to a considerable increase
in the pore volume from 0.25 to 0.3 0.33 cm g ,
and this dependence is stronger at increased concen-
trations of oxygen, compared with the regeneration
in air.
3
1
2
4
As seen from the table, the content of Fe(III) in the
catalyst remains, on the whole, unchanged when the
temperature is raised in air and decreases from 0.3 to
0.26 wt % in the case of regeneration in the oxygen-
rich gas mixture. The best results, as regards the
decrease in the amount of Fe(III), were obtained in
extraction washing of the catalyst in boiling dichloro-
ethane. In this case, the content of Fe(III) in the cata-
lyst decreased to 0.25 wt %. Apparently, dichloro-
Figure 1 (curves 1, 2) shows that the conversion
of hydrogen chloride remains unchanged ( 98.5%)
upon regeneration of the catalyst in air and O . At
2
the same time, the conversion of C H upon regenera-
2
4
tion (curves 3, 4) grows from 89 to 94 95% as the
content of O in the regenerating gas increases from
2
20 to 40%, with this trend being particularly pro-
nounced at 250 C.
ethane can dissolve FeCl [1], which makes it pos-
3
sible to use this method to partly diminish the amount
of Fe(III) formed on the oxychlorination catalyst and
poisoning it.
Figure 2 shows how the combustion of C H on
2
4
the catalyst subjected to regeneration depends on the
content of O in the regenerating gas at 210 and
250 C.
2
After regeneration for 8 h at a prescribed tem-
perature, the activity and selectivity of the regen-
erated catalyst in oxidative chlorination of C H
After regeneration of the catalyst, the combustion
of C H in synthesis of 1,2-dichloroethane (Fig. 2)
2
4
was studied in the standard operation mode: 225 C,
2
4
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005

1090
KHCl, KC2H4, %
KURTA et al.
, %
Before
regeneration
Before regeneration
cO2, vol %
cO2, vol %
Fig. 1. Conversion of (1, 2) HCl (K ) and (3, 4) C H
HCl
2
4
(K
on a regenerated catalyst vs. the content of oxygen,
, in the regenerating gas. Temperature, C: (1, 3) 210
Fig. 2. Combustion of C H on a regenerated catalyst vs.
C H )
2
4
2
4
c
the content of oxygen, c , in the regenerating gas. Tem-
O
O
2
2
and (2, 4) 250.
perature, C: (1) 250 and (2) 210.
(a)
(b)
c, %
c, %
Before
regeneration
Before
regeneration
T, C
cO2, vol %
Fig. 3. Purity c of dichloroethane obtained on a regenerated catalyst vs. (a) content of oxygen, c , in the regenerating gas and
O
2
(b) temperature T of the catalyst regeneration. (a) Temperature, C: (1) 210 and (2) 250. (b) Medium: (1) air and (2) 40 vol %
oxygen; the same for Fig. 4.
decreases from 5 to 2.5 3% in proportion to an in-
Figures 3a and 3b show how the purity of dichloro-
ethane in synthesis of 1,2-dichloroethane depends on
crease in the content of O in the regenerating gas.
2
The same trend is observed on raising the regeneration
temperature from 180 to 210 and 250 C.
the content of O in the regenerating gas and on the
2
temperature of catalyst regeneration. It can be seen
that the purity of dichloroethane grows from 98.6%
before regeneration to 99.5% after regeneration as
KHCl, %
the temperature is raised or the content of O in the
2
regenerating gas is made higher. In this case, the
tendency toward an increase in the purity of dichloro-
ethane is more pronounced when the regeneration is
performed in an oxygen-rich gas mixture (Figs. 3a,
3b; curves 2).
Figure 4 shows how the conversion of HCl in the
catalytic synthesis of 1,2-dichloroethane depends on
the temperature of the catalyst regeneration in air and
in an oxygen-rich gas mixture (Fig. 4, curves 1, 2).
It can be seen that the conversion of HCl decreases
Before regeneration
T, C
Fig. 4. Conversion of HCl, K , on a regenerated catalyst
vs. the temperature T of catalyst regeneration.
HCl
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 78 No. 7 2005

INFLUENCE OF REGENERATION CONDITIONS ON THE ACTIVITY OF THE CATALYST
1091
Figure 5 shows how the efficiency of C H conver-
2
4
E, %
, %
sion (curves 1, 2) and C H combustion (curves 3, 4)
2
4
in synthesis of 1,2-dichloroethane on a regenerated
catalyst depend on the temperature of catalyst regen-
eration in air and an oxygen-rich gas mixture. It can
be seen that the efficiency of C H conversion into
2
4
dichloroethane grows from 92.5 to 93 94% as the re-
generation temperature increases from 180 to 250 C
in the oxygen-rich has mixture (Fig. 5, curve 2).
Simultaneously, the combustion of C H decreases
2
4
from 5% before regeneration to 2 2.5% after regen-
eration as the temperature of catalyst regeneration is
increased to 250 C.
Additionally, we calculated the yield of dichloro-
ethane in synthesis of 1,2-dichloroethane (relative to
the theoretical value) and its dependence on the tem-
perature of catalyst regeneration (Fig. 6, curves 1, 2).
These data are compared with the dependence of the
ethylene conversion in synthesis of 1,2-dichloroethane
on the temperature of the catalyst regeneration (Fig. 5,
curves 1, 2) in the air and oxygen-rich gas mixtures.
Figure 5 shows that the C H conversion and yield
Before
T, C
regeneration
Fig. 5. (1, 2) Efficiency E of C H conversion and
2
4
(3, 4) C H combustion on a regenerated catalyst vs. the
2
4
temperature T of catalyst regeneration. Medium: (1, 3) air
and (2, 4) oxygen-rich gas mixture; the same for Fig. 6.
KC2H4, %
w, %
2
4
of dichloroethane relative to the theoretical value tend
to increase on a regenerated catalyst as the tempera-
ture of catalyst regeneration is raised. In this case,
the C H conversion increases by 5 7% upon regen-
2
4
eration, the yield of dichloroethane also grows by
5 7%. This confirms once more the fact that the cata-
lyst activity in C H conversion into dichloroethane
2
4
increases after regeneration. The yield of by-products,
trichloroethane, trichloroethylene, and others, does not
increase in the case of a partly regenerated catalyst,
and the combustion of C H is suppressed.
2
4
T, C
Before
regeneration
CONCLUSIONS
Fig. 6. (1, 2) Yield w of dichloroethane (relative to the
theoretical value) and (3, 4) C H conversion K on
2
4
C H
2 4
(1) A partly deactivated catalyst for C H oxy-
2
4
a regenerated catalyst vs. the temperature T of catalyst
chlorination can be regenerated. The regeneration in
regeneration.
an oxygen-rich gas mixture (30 40 vol % O ) is more
2
effective than that in air (20 vol % O ) under the same
2
from 98.5 to 97.5 98%. This decrease is more pro-
nounced in the case of regeneration in air, compared
with that in the oxygen-rich gas mixture.
treatment conditions (180 210 250 C, 8 h).
(2) The regeneration improved the physicomech-
anical properties of the catalyst, namely, increased the
pore volume and the specific surface area (by 10
20%) and decreased the bulk weight, and thus en-
hanced the activity and selectivity of a regenerated
catalyst in oxychlorination of ethylene into 1,2-di-
chloroethane.
The increase in the conversion of C H and de-
2
4
crease in its combustion after regeneration is under-
standable, because they are associated with partial
restoration of the structure and activity of the catalyst
after its thermochemical treatment in an O atmos-
2
phere, which is due to oxidation of the catalyst surface
and removal of tar and carbon black therefrom. This
is, in turn, confirmed by the improvement of the
physicomechanical properties of the catalyst, namely,
by an increase in the specific surface area and pore
volume and decrease in the bulk weight (see table).
REFERENCES
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4. Promyshlennye khlororganicheskie produkty: Spra-
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Book), Oshin, L.A., Ed., Moscow: Khimiya, 1978.
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