ELECTROCHEMICAL METHOXYLATION OF STYRENE WITH GAS-LIFT IN CONTINUOUS MODE 1319
ing alternating anode and cathode plates was placed
inside the electrolyzer. Two platinum plates of size
1
5
80 mm were used as anode, and three stainless
steel plates of the same size, as cathode. The inter-
electrode spacing of 3 mm was ensured by fluoro-
plastic spacers placed at electrode edges. The instal-
lation is shown schematically in the figure. The as-
cending pipe of the gas-lift system had inner diam-
eter of 6 mm and height of 1650 mm. The capacity of
the whole system was 420 ml. The current density
was calculated on the assumption of the uniform
distribution of current over the entire surface of the
cathodes.
A 20.8-g portion of styrene (0.2 mol), 1.4 g
0.02 mol) of KF, and 397 ml of methanol was placed
(
in the system, so that it was filled to the level shown
in the figure. The electrolysis was carried out at a cur-
rent density of 0.1 A cm (current strength 4.8 A),
Electrolyzer with gas-lift system. (1) Electrolyzer, (2) glass
tube, (3) condenser, (4) separator, (5) system filling level,
(6) dosing pump, and (7) discharge cock.
2
with 8 F of electricity passed per 1 mol of styrene I
and no fresh electrolyte added. The voltage across the
electrolyzer was 10 V.
tinuous mode (Table 2). Also, the possibility was ver-
ified of conversion of the intermediate electrolysis
product 1,2-dimethoxyethylbenzene, in an electro-
lyzer of continuous type with gas-lift. In this case,
one more product of the reaction of electrochemical
methoxylation of styrene 1,1,2-trimethoxyethylben-
After the electrolysis was complete, methanol was
evaporated under a water-jet pump vacuum at a tem-
perature of 40 C, still bottoms were extracted with hex-
ane (20 3), and the solvent was evaporated from the
extract. The still bottoms were weighed and analyzed
by liquid-gas chromatography on an LKhM-8MD chro-
matograph (detector catharometer, carrier-gas helium,
column length 1.5 m, column diameter 3 mm, sup-
port Chromaton-N-AW, immobile phase PEG-4000,
Table 1. Electrooxidation of styrene in methanol in batch
mode in electrolyzers with (A) mechanical stirring and
(
B) gas-lift
Composition of electrolysis
products, %
Quantity of
electricity,
F mol 1
1
flow rate 4 ml s , sensitivity 1 : 3, column tempera-
ture 130 C, evaporator temperature 250 C).
(
I)
(II)
(III)
(IV)
BA
For comparison, experiments were performed in an
electrolyzer with magnetic stirrer, with design close
to that described in [1 5].
Electrolyzer (A)*
1
2
3
4
5
6
7
8
20
12
73.2
76.5
87.5
74.2
67.7
59.5
54.7
39
4.4
7.4
7.9
16.8
20.9
29.1
33.6
42.8
1.9
2.3
2.6
7
8.4
8.5
8.7
13
1
2
2
2
3
3
3
5
Table 1 presents data on the accumulation of elec-
trolysis products both in an electrolyzer with gas-lift
and in that with mechanical stirring. It can be seen
that the yield of benzaldehyde dimethylacetal III is
nearly 14% higher in the electrolyzer with a gas-lift
system, compared with that equipped with mechanical
stirrer.
Electrolyzer (B)
1
2
3
4
5
6
7
8
25
18.3
9.7
65.5
68.9
70.7
71
6.9
1.6
3.2
5.5
6
6.5
8
1
2
3
3
3
4
4
4
7.6
11.1
20
Further experiments were carried out in order to
verify the possibility of performing the process in the
continuous mode. A certain amount of electrolyte so-
lution was removed from the electrolyzer every hour
and a fresh portion of the same volume was added.
Two sets of experiments were carried out with fresh
66.7
56
45.3
30
29.8
32
41.8
57
8.9
9
1
electrolyte supplied at a rate of 25 ml h .
*
Electrolysis conditions: 10.4 g (0.06 mol) styrene, 0.7 g
(0.01 mol) KF, and 185 ml methanol; T = 60 C; BA, benz-
aldehyde.
The yield of the reaction products was found not
to change substantially on passing from batch to con-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 8 2001