Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Patent
1998-05-12
1999-11-23
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
210660, 210638, C07C31506
Patent
active
059903562
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for the purification of dimethyl sulphoxide (DMSO) and to the DMSO thus purified.
BACKGROUND OF THE INVENTION
The DMSO currently available on the market is a product which is already of good purity. Its commercial specifications are generally:
purity: .gtoreq.99.7% by chromatography
acidity:.ltoreq.0.04 mg KOH/g by potentiometry
crystallization
point: .gtoreq.18.2.degree. C.
visual
appearance: clear
water content: .ltoreq.0.15% by weight relative to the total weight
colour (APHA): .ltoreq.10
Patent application FR 2,014,385 describes a process for the preparation of purified DMSO. This process uses a cationic ion exchanger which can be regenerated by a treatment with acids. On the other hand, the DMSO treated with this ion exchanger has a very high water content. Furthermore, the examples indicate the use of a strongly basic resin of the Amberlite IR-A 400 or Merck III type for dimethyl sulphide/DMSO/10% sulphuric acid ternary mixtures, which possibly leads to the neutralization of the acidity but also the introduction of the counterion of the basic resin into the mixture thus treated. Indeed, in this process the purification appears to be afforded essentially by fractional distillation of an aqueous DMSO solution treated beforehand with one or more ion exchangers.
Analyses of traces of metals have now been carried out on several samples (1 to 6) of commercial DMSO, from different sources. These analyses are reported in Table I.
The sodium, iron, potassium, calcium, chromium, copper, nickel and zinc concentrations were measured by ICP (plasma-torch atomic emission spectrometry, Perkin Elmer machine, Optima 3000 model) and are expressed in ppb (1 ppb=1 part by weight per billion=1 .mu.g per kg).
The list of metal elements featured in Table I is not exhaustive as regards the metal elements present in these samples.
TABLE 1 ______________________________________
Metal cations
Sample Na Fe K Ca Cr Cu Ni Zn
______________________________________
1 40 13 60 20 2 10 8 10
2 39 60 3 13 13 <2 18 3
3 30 40 3 20 12 <2 15 3
4 30 40 3 14 13 <2 15 3
5 30 <1 20 25 <2 <2 <3 <3
6 70 90 65 55 15 2 25 60
Detection
2 1 3 2 2 2 3 3
limit
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For certain applications such as, for example, in electronics or in pharmacy, the DMSOs analysed above contain too many metal impurities. In general, a DMSO containing less than 10 ppb of each alkali metal and alkaline-earth metal contaminant would be necessary for most of the uses in the two abovementioned technical fields.
DESCRIPTION OF THE INVENTION
The aim of the present invention is to find a process for the purification of commercial DMSO which is already of good purity but which is, however, of insufficient purity for certain applications.
This aim is achieved by a process for the purification of dimethyl sulphoxide (DMSO) in order to decrease the content of cations other than H.sup.+ therein, characterized in that it includes the following steps:
1) a DMSO in the liquid state and with a low water content is selected, 2) this DMSO is placed in contact with a solid consisting of an ion exchange resin of sulphonic type having its active groups in sulphonic acid (SO.sub.3 H) form, 3) the liquid consisting of the purified DMSO with very low contents of cations other than H.sup.+ is then separated from the solid by any suitable known means, in particular filtration, percolation or centrifugation.
Advantageously, the DMSO selected in step 1) has a water content of less than or equal to 0.15% by weight relative to the total weight.
Ion exchange by the use of resins is a very widely used technique for aqueous media and makes it possible in particular to obtain deionised water. The exchange of anions in liquid DMSO medium with a low water content has already been performed by Alan M. Phipps, Anal. Chem. 40(12) pp. 1769-1773, 1968, for the purpose of measuring the amounts of anions bound to the resin under experimental conditions appr
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patent: 5300628 (1994-04-01), Honda
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"Anion Exchange in Dimethyl Sulfoxide" Alan M. Phipps, Anal. Chem. 40(12):1769-1773 (1968).
"La purification du dimethylsulfoxide" Chaudron et al., Chimie Analytique 53(5):310-314 (1971).
International Search Report dated Feb. 4, 1997.
Bazin Isabelle
Commarieu Annie
Elf Acquitaine Production
Geist Gary
Vollano Jean F
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