Chemistry of inorganic compounds – Halogen or compound thereof – Hydrogen halide
Reexamination Certificate
1998-07-30
2001-02-20
Nguyen, Ngoc-Yen (Department: 1754)
Chemistry of inorganic compounds
Halogen or compound thereof
Hydrogen halide
C423S24000R, C423S243010, C423S245100, C562S120000
Reexamination Certificate
active
06190635
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns the field of methanesulphonic acid (referred to hereinbelow as MSA) and relates more particularly to a process for the purification of the hydrochloric acid by-product of the synthesis of MSA.
BACKGROUND OF THE INVENTION
The synthesis of MSA from methyl mercaptan and chlorine according to the reaction:
CH
3
SH+3 Cl
2
+3 H
2
O→CH
3
SO
3
H+6 HCl
produces a large amount of hydrochloric acid by-product. The HCl gas flow separates from the reaction medium, entraining some of the volatile compounds, and this entrainment is proportionately larger when the reaction is carried out at 100° C. By means known per se, the chlorine and the methyl mercaptan are readily eliminated from the hydrochloric acid. The water is not a hindrance since the aim is to recover a 33% solution of HCl in water.
However, during the reaction which leads to methanesulphonic acid, a relatively volatile intermediate is produced, methylsulphonyl chloride CH
3
SO
2
Cl (MSC), which, on working up the gaseous HCl with water, converts into methanesulphonic acid, thereby contaminating the hydrochloric solution and making it unsuitable for a certain number of applications.
The entrainment of MSC is considerable since the contact between the HCl and the MSC takes place at high temperature. The excess MSC is readily removed using the known standard techniques such as, for example washing the hydrochloric effluent with the MSA produced in the reaction and preferably purified. Neverless, appreciable amounts of MSC are entrained by the HCl since the operations do not take place at low temperature, but in the region of room temperature. It is known that depending on the temperature (see Table I), the MSC content of the hydrochloric acid takes increasing values.
TABLE I
Temperature
MSC in HCl gas
MSA in aqueous
(° C.)
(ppm)
33% HCl (ppm)
−5
728
203
0
1245
350
5
1770
495
8
2570
720
12
4610
1290
15
5440
1520
18
7120
1990
21
8830
2470
In a usual process for the synthesis of MSA, the HCl flow is at a temperature in the region of 20° C. It thus contains from 5000 to 9000 ppm of MSC, which lead to a 33% hydrochloric solution containing from 1500 to 2500 ppm of MSA.
BRIEF SUMMARY OF THE INVENTION
The aim of the present invention is to. provide a process which makes it possible to reduce the MSC content in the HCl gas as much as possible, without making it necessary to use extremely low temperatures or highly sophisticated and expensive techniques.
REFERENCES:
patent: 2416467 (1947-02-01), Carney
patent: 3931289 (1976-01-01), Bundy
patent: 4280966 (1981-07-01), Hubenett
patent: 4549993 (1985-10-01), McElligott
patent: 4859373 (1989-08-01), Ollivier
patent: 0 675 106 (1995-10-01), None
patent: 0 675 107 A1 (1995-10-01), None
patent: 740242 (1955-11-01), None
patent: 1 350 328 (1974-04-01), None
Search Report, Dated Apr. 6, 1998.
Clair Rene
Ferrigno Marc
Molines Denise
Ollivier Jean
Elf Atochem S.A.
Nguyen Ngoc-Yen
Smith , Gambrell & Russell, LLP
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