Thermal chlorination of methyltrichlorosilane

Article abstract of DOI:10.1023/A:1012753203518

The procedure for thermal chlorination of methyltrichlorosilane to chloromethyltrichlorosilane in a circulation flow system was developed. The yield of ClCH₂SiCl₃ was studied as influenced by the reaction temperature and the reactant ratio.

Full text of DOI:10.1023/A:1012753203518

Russian Journal of Applied Chemistry, Vol. 74, No. 5, 2001, pp. 800 803. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 5,
001, pp. 778 780.
Original Russian Text Copyright
2
2001 by Voronkov, Stankevich, Kukharev, Abzaeva.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Thermal Chlorination of Methyltrichlorosilane
M. G. Voronkov, V. K. Stankevich, B. F. Kukharev, and K. A. Abzaeva
Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received October 12, 1999; in final form, February 2000
Abstract The procedure for thermal chlorination of methyltrichlorosilane to chloromethyltrichlorosilane
in a circulation flow system was developed. The yield of ClCH SiCl was studied as influenced by the
2
3
reaction temperature and the reactant ratio.
Chloromethyltrichlorosilane, ClCH SiCl (CMTS),
is a valuable reagent for preparing carbofunctional
organosilicon monomers and polymers (surface-modi-
of gaseous reactants [10]. The industrial process of
dark chlorination of MTS in the presence of asobis-
(isobutyronitrile) is performed in a distillation column
2
3
fying and cross-linking agents, adhesion promoters, under inversion conditions (the temperature in the
immobilized catalysts, etc. [1 6]) and is used in syn-
thesis of sorbents, ion exchangers, and bioprotecting
coatings. This compound is also a precursor of widely
used biostimulant, 1-(chloromethyl)silatrane (Mival)
reaction zone and in the still is 64 and 110 C, re-
spectively) [12]. The CMTS yield based on the spent
MeSiCl is 75%. In this case the steady-state inver-
3
sion conditions in the upper part of the column and
the working temperature in the reaction zone are dif-
ficult to maintain, and large amount of the expensive
[
7, 8]. Chloromethyltrichlorosilane is usually prepared
by free-radical chlorination of methyltrichlorosilane
MTS) with gaseous chlorine:
initiator and large excess of MeSiCl are required. In
(
3
addition, Cl CHSiCl and Cl CSiCl are formed in
2
3
3
3
considerable amounts, i.e., the selectivity of the proc-
ess is low.
Cl2 + CH SiCl
ClCH SiCl + HCl.
2 3
3
3
The reaction is performed either in the vapor phase
on exposure to UV [9, 10] or visible [11] radiation or
in a solution in the dark in the presence of azobis-
Another procedure for preparing CMTS is based on
photochemical chlorination of MeSiCl with sulfuryl
3
chloride [13, 14]:
(
isobutyronitrile) as the initiator [9, 10]. It should be
h
noted that, since chlorination of mono- and dichloro-
methyltrichlorosilanes (ClCH SiCl and Cl CHSiCl )
SO Cl + CH SiCl
SO + ClCH SiCl + HCl.
2 2 3
2
2
3
3
2
3
2
3
This reaction is catalyzed by yttrium chloride, lan-
thanum chloride, and manganese chloride [14].
Although this procedure does not require complex
equipment, it is more expensive as compared to the
chlorination with gaseous chlorine.
is considerably faster than that of the initial MTS, the
monochloro derivative is prepared at its continuous
removal form the reaction mixture or at a large excess
of MTS. The first procedure is based on photochemi-
cal chlorination of MeSiCl vapor with gaseous chlor-
3
ine on exposure to UV [9, 10] or visible light [9].
We developed a new procedure for preparing
CMTS by chlorination of MeSiCl with gaseous chlor-
ine at 300 400 C in a circulation system.
Large-scale photochemical chlorination of MTS is
complicated by the lack of industrial reactors contain-
ing parts made form optical quartz and by the need for
intermittent removal of the polymeric film absorbing
UV Vis radiation from the surface of the transparent
window or from the built-in light sources. It is dif-
ficult to construct powerful photochemical reactors
since the light intensity decreases proportionally to the
square of the distance form the light source. In some
cases the photochemical reaction can be accompanied
by spontaneous combustion or explosion of a mixture
3
This reaction occurs by the radical mechanism
similar to that of thermal chlorination of alkanes [15].
The chain propagation involves formation of Cl and
CH SiCl radicals:
2
3
300 400 C
Cl2
2Cl ,
Cl + CH SiCl3
CH SiCl3 + HCl,
3
2
Cl2 + CH SiCl3
ClCH SiCl3 + Cl .
2
2
1
070-4272/01/7405-0800$25.00 2001 MAIK Nauka/Interperiodica

THERMAL CHLORINATION OF METHYLTRICHLOROSILANE
801
Yield of ClCH SiCl as influenced by the conditions of thermal chlorination of MeSiCl .
2
3
3
Treactor
,
Feed rate
Flow rate
MeSiCl : Cl ,
3
2
,
h
CMTS yield, %
,* %
1
1
C
of MeSiCl , g h
of Cl , l h
mol : mol
3
2
350
300
350
400
450
500
300
250
829.4
222.7
576.0
783.3
852.5
844.8
238.1
162.8
1.18
1.27
2.42
2.63
1.66
3.18
1.20
0.22
105 : 1
26 : 1
36 : 1
45 : 1
77 : 1
40 : 1
30 : 1
111 : 1
12
12
6
6
12
6
82.2(42)**
72.3(35)
51.1
48.4
49.5
53.2
60.3
56.3
49.0
9
77.7(38.5)
76.3(40.6)
66.7(40.2)
62.5(35.2)
77.0(37.8)
85.9(7.7)
12
20
*
is the MTS conversion.
*
* Yield of CMTS based on reacted and initial (in parentheses) MTS.
It is known that the rate constants and activation
(2) and a condenser with a dosing apparatus and then
energies of radical-chain consecutive chlorination with an electrically heated flow reactor. The reactor is
reactions yielding mono-, di-, and trichloro derivatives
are almost the same [15]. Hence, for CMTS to be
selectively formed, large excess of MTS with respect
to chlorine should be used and CMTS being formed
should be removed from the reaction mixture.
connected with two condensers (straight-run 6 and re-
flux 7). The condensate formed in the first condenser
goes in the accumulator with a siphon and then back
in the flask. Gaseous HCl and unchanged Cl pass
2
to the absorbers through the reflux condenser. The
reactor is a quartz tube 12.5 mm in diameter and
The chlorination was performed at MeSiCl : Cl2
3
250 mm long, packed with quartz chips.
1
00 : 1 (see table). At 350 C the selectivity of the
process (the CMTS yield based on consumed MTS)
was higher than 82% and the MTS conversion in 12 h
was 51%. With a larger MTS excess, the output of
CMTS is lower. At MeSiCl : Cl = 25 : 1 49.5% of
An MTS vapor formed in the flask passes through
the packed column, is condensed in the condenser,
and is fed into the dosing apparatus form which it is
fed with a controlled rate to the reactor heated to
3
2
MTS is converted within 6 h; however the selectivity
decreases to 77%. Thus, taking into account the out-
put of the reactor and the process selectivity, the
MeSiCl : Cl molar ratio can be varied from 25 : 1 to
3
2
1
00 : 1 depending on the technical and economical
requirements.
The temperature influence on the MTS chlorination
is similar to that of alkane chlorination. With increas-
ing temperature the reaction is accelerated, and its
selectivity decreases. In addition, at 500 C the reactor
nozzle is strongly clogged with coke.
At the same time the process occurs even at 250 C.
However, in this case, despite high selectivity (the
CMTS yield based on consumed MTS is 86%), a 9%
conversion of MTS is reached only in 20 h.
Thus, as seen from the table, the best reaction tem-
perature is 350 400 C.
EXPERIMENTAL
Scheme of the unit for gas-phase thermal chlorination of
methyltrichlorosilane: (1) 0.5-l flask, (2) packed column,
Methyltrichlorosilane was chlorinated on a circula-
tion unit (see figure). The unit consists of a 0.5-l
heated flask (1), connected through a packed column
(
3, 6, 7) condensers, (4) dosing pump, (5) reactor, (8) con-
densate accumulator, (9) thermometer, (10) tubular furnace,
and (11) electric heater.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 5 2001

8
02
VORONKOV et al.
3
00 400 C. Chlorine is fed simultaneously form a
3% OV-17 on Inerton Super (0.160 0.200 mm).
The column was heated form 40 to 180 C at a rate of
4 deg min .
cylinder. The flow rate of chlorine is measured with a
rheometer. The flask temperature in the first and final
steps of the process is 65 and 105 C, respectively.
The temperature of the column head is about 65 C.
The MeSiCl : Cl molar ratio at the outlet of the
1
1
The H NMR spectra were recorded at 25 C on a
Tesla 480 C spectrometer operating at 80 MHz, with
TMS as the internal reference. The spectra of
ClCH SiCl and Cl CHSiCl contain only one singlet
3
2
reactor was maintained constant.
2
3
2
3
An example of the CMTS synthesis is presented
below. Methyltrichlorosilane (149.5 g, 1 mol) is placed
in the still of the packed column and is heated to boil.
When the temperature of the top of the column reaches
at 3.24 and 5.44 ppm, respectively. The chemical
shifts agree with the published data [14].
The 35Cl NQR spectrum of ClCH SiCl recorded
2
3
on an IS-3 spectrometer contains the following sig-
6
5 C, MTS condensate formed in the condenser is fed
77
nals,
SiCl ) (cf. [16]).
, MHz : 36.77 (ClCH ); 19.555, 19.470
1
2
into the dosing apparatus and then with a 830 g h
(
1
3
(
5.55 mol h ) flow rate into the reactor heated to
3
50 C. Simultaneously gaseous chlorine is fed with
1
1
a 1.18 l h (0.0526 mol h ) flow rate into the
reactor. The MeSiCl : Cl molar ratio is 105 : 1. The
CONCLUSION
Thermal chlorination of methyltrichlorosilane with
elemental chlorine in the gas phase at 300 400 C
yields chloromethylchlorosilane in a 63 82% yield
based on reacted MeSiCl3.
3
2
process lasts for 12 h. In this period 14.2 l (0.63 mol)
of chlorine is passed through the system. Fractiona-
tion of the bottoms on a 20-TP column yields the ini-
tial MTS (73.1, 0.49 mol) with bp 65 66 C (720 mm
Hg) and CMTS (77.3 g, 0.42 mol) with bp 117 119 C
720 mm Hg), n2 = 1.4530, d4 = 1.4420, and a
0
20
(
D
REFERENCES
9
[
9.7% purity determined by GLC {published data
14]: bp 118 120 C (760 mm Hg), n2 = 1.4530}.
0
1. Sobolevskii, M.V., Muzovskaya, O.A., and Popele-
va, G.S., Svoistva i oblasti primeneniya kremniiorga-
nicheskikh produktov (Properties and Fields of Ap-
plication of Organosilicon Compounds), Sobolev-
skii, M.V., Ed., Moscow: Khimiya, 1975.
D
Found (%): C 6.56, H 1.03, Cl 77.00, Si 15.07,
6
.25,
1.12,
76.91,
15.14.
CH Cl Si.
2
4
Calculated (%): C 6.53, H 1.10, Cl 77.10, Si 15.27.
2. Motsarev, G.F., Sobolevskii, M.V., and Rozen-
berg, V.R., Karbofunktsional’nye organosilany i
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and Siloxanes), Moscow: Khimiya, 1990.
The CMTS yield based on the initial MeSiCl and
3
spent MTS is 82.2 and 42%, respectively. The MTS
conversion is 51.1%.
3. Edwin, P., Pludeman Silane Coupling Agents, New
York: Plenum, 1982.
The weight of the remaining bottoms is 10.2 g.
As determined by GLC, the bottoms contain 31%
Cl CHSiCl and 69% Cl CSiCl . Cl CHSiCl (2.6 g,
4
. Makarskaya, V.M., Pashchenko, A.A., and Kru-
pa, A.A., Povyshenie kachestva stekloplastikov s po-
moshch’yu appretov (Improvement of Fiber Glass
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2
3
3
3
2
3
0
.012 mol) was isolated by fractionation of the bot-
toms; bp 141 142 C (720 mm Hg), 99.3% purity
1
976.
determined by GLC, n2 = 1.4715, d4 = 1.5503
0
20
D
5
6
7
. Voronkov, M.G., Vlasova, N.N., and Pozhida-
ev, Yu.N., Zh. Prikl. Khim., 1996, vol. 69, no. 5,
pp. 705 718.
20
{
published data [14]: bp 144 C (760 mm Hg), n
=
D
1
.4715}.
. Voronkov, M.G., Chernov, N.F., and Baigozhin, A.,
Zh. Prikl. Khim., 1996, vol. 69, no. 10, pp. 1594
Found (%): C 5.40, H 0.41, Cl 81.27, Si 12.32,
.44, 0.53, 81.21, 13.05.
5
1
601.
CH Cl Si.
2
5
. Voronkov, M.G., Silatrany (Silatranes), Novosibirsk:
Calculated (%): C 5.50, H 0.46, Cl 81.18. Si 12.86.
Nauka, 1978.
The purity of the chlorine-containing products was
determined by GLC on an LKhM-80 chromatograph
equipped with a catharometer. Helium was the carrier
gas. A 3000 3 mm steel column was packed with
8. Voronkov, M.G., Top. Curr. Chem., 1970, vol. 84,
pp. 77 135.
9. Motsarev, G.F., Andrianov, K.A., and Zetkin, V.I.,
Usp. Khim., 1971, vol. 40, no. 6, pp. 980 1013.
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803
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1
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1
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1
1
1
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 5 2001