MXPA98003782A - Dimetilsulfoxide purification procedure (dm - Google Patents

Abstract

The present invention relates to purifying a dimethylsulfoxide (DMSO), it is put in contact with a plurality of cation exchange resins, wherein at least one is a sulphonic type resin in the form -SO3NH or -SO3NH4, which may be the another or the others of the chelating type. As-absorbed dimethylsulfoxide has an amount of iron cations of less than 1 ppm and an amount of sodium cations of less than 2 p.

Description

DIMETILSULFOXIDE PURIFICATION PROCEDURE (DMSO) The present invention relates to a process for the purification of dimethylsulfoxide (DMSO) and of the dimethylsulfoxide thus purified. The dimethyl sulfoxide currently available in the market is a product that already has a good purity. Its commercial specifications are generally: purity = 99.7% by chromatography acidity = 0.04 mg KOH / g by potentiometry point of crystallization = 18.1 ° C visual aspect = clear percentage in water s? .15% color (APHA) = IO Patent FR 2 014 385 describes a process for the preparation of purified dimethylsulfoxide using an ion exchanger. In the two examples of this patent, a strongly basic resin of the Amberlite IR-A 400 or Merck III type is used to treat the ternary dimethylsulfide / dimethyl sulfoxide / 10% sulfuric acid mixtures. In fact, in this known process, the purification appears to be essentially provided by a fractional distillation of an aqueous solution of dimethylsulfoxide previously treated by an anion exchanger. Trace metal analyzes have now been carried out on many samples of commercial dimethyl sulfoxide, from different sources. These analyzes are reported in Table 1. The concentrations of sodium, iron, potassium, calcium, chromium, copper, nickel and zinc were measured by ICP atomic emission spectrometry-plasma torch, Perkin Elmer apparatus, Optima 3000 model) and They are expressed in ppm (1 ppm = 1 part by weight per thousand = 1 μg per kg). The list of metallic elements listed in table 1 is not exhaustive as regards the metallic elements present in these samples.

TABLE 1 For certain applications, such as in electronics or pharmacy, the dimethylsulphoxides discussed above contain many metallic impurities. In general, a dimethylsulfoxide containing less than 10 ppm of each metallic, alkaline and earthy alkaline contaminant would be necessary for most uses in the two technical domains previously cited. The object of the present invention is to find a process for the purification of commercial dimethylsulphoxide which is already of good purity, but the latter being, however, insufficient for some applications. The exchange of ions using resins is a technique widely used for aqueous media and allows especially obtaining deionized water. The exchange of anions in liquid dimethyl sulfoxide medium with little water content has already been carried out by Alan M. Phipps. Anal. Chem. 40 (12) pp. 1769-1773, 1968, in order to measure the amounts of anions fixed on the resin under the experimental conditions that approach the thermodynamic equilibrium. The object of the invention is now a process for purifying dimethylsulfoxide to reduce the content of metal, alkali and alkaline earth cations, characterized in that it consists essentially in putting the dimethylsulfoxide to be purified in contact with at least two cation exchange resins wherein at least one is one resin of sulfonic type, the other (or the others) can be of chelant type. Conveniently, it is dimethyl sulfoxide with a small amount of water, this amount preferably being less than or equal to 0.15 percent by weight relative to the total weight. In accordance with the present invention, any Mn + cation (n is from 1 to 4) is retained and exchanged for the H + protons or the NH4 + cations emitted from the resins employed under the acid form or under the ammonium form. A very efficient purification of the almost anhydrous dimethylsulfoxide can be obtained by the joint use of a chelating resin having, for example, the aminophosphonic or iminodiacetic groupings, effective for exchanging the iron and the multiply charged metals (Mn +, n = 2, 3 and 4) and a sulphonic type resin, effective for exchanging sodium and monocharged ions. Preferably, the cationic resins used are based on a polystyrene-divinylbenzene copolymer. Indeed, these resins have a skeleton resistant to chemical attacks and, in particular, do not dissolve in dimethyl sulfoxide. When contacting the dimethylsulfoxide to be purified with the resins takes place at a temperature ranging from 18.45 ° C (melting point of dimethylsulfoxide) to 120 ° C (limit temperature of thermal stability of the resins). This temperature is conveniently comprised between 19 and 80 ° C, preferably between 20 and 50 ° C. The dimethylsulfoxide to be purified can be contacted with a mixture of different resins or successively with each of the different resins. The operation can be carried out in batch (batch) or continuously in conditions and equipment well known to those skilled in the art. The separation of the purified dimethylsulfoxide from the resins can be done by any suitable known means, especially by filtration, percolation or centrifugation. In order to define the quality of the dimethylsulfoxide capable of being obtained by the process according to the invention, iron and sodium were retained as tracers and indicators of the general content of metal, alkaline and alkaline-earth cations. This purified dimethylsulfoxide is characterized in that it comprises an iron cation content less than or equal to 1 ppm and a sodium cation content less than or equal to 2 ppm, respective detection limits of the method of analysis by plasma atomic emission spectrometry. The invention will be better understood with the help of the following experimental part which describes an embodiment of the present invention.

Experimental part I. Method of analysis To analyze the traces of metals in the dimethylsulfoxide, I 'ICP (atomic emission spectrometry-plasma torch) was used: the sample is introduced in a plasma torch, the different elements present are excited and they emit the photons whose energy is characteristic of the element, because it is defined by the electronic structure of the element considered. A Perkin Elmer device (Optima 3000 DV model) was routinely used. II. Methodology: Principle: the metallic traces are in the form Mn +. By passing dimethylsulfoxide on two cation exchange resins, themselves under the H + form, the Mn + ions in solution are replaced by n.H +. III. Test: Principle: in order to simplify the analyzes, sodium and iron were chosen as tracers representative of the set of metallic impurities contained in dimethylsulfoxide. Sodium is characteristic of atmospheric and accidental pollution (soot, environment) and iron is characteristic of the contamination that may come from the process (stainless steel unit). The dimethyl sulfoxide contaminated with 1000 ppm of iron and 1000 ppm of sodium is contacted successively with two cation exchange resins, under the H + form (2 grams of each resin for 100 grams of dimethylsulfoxide) at 25 ° C. After a first cation exchange with a chelating resin, the dimethylsulfoxide is separated from the solid by filtration on a polyethylene frit with a porosity of 70 m, after which it is contacted with a sulphonic type resin. The samples of dimethyl sulfoxide were taken in the course of time during each of the stages to follow the evolutions of the iron and sodium concentrations. As the sulphonic type resin, the Amberlyst® 35 resin marketed by Rohm & Haas, and as a chelating resin, the S940 aminophosphonic resin of the Société Purolite. These resins were pretreated to obtain the H + form in the following manner: through 90 milliliters of resin, 540 milliliters of 5 percent HCl are passed at a constant rate and so that the operation lasts 30 to 45 minutes . After rinsing with the demineralised water until the neutrality of the outgoing water, the resin is dried to be suspended in methanol and under vacuum in the rotary evaporator (90 ° C, 2000 Pa) until constant weight is observed . Table 2 gathers the amounts of iron and sodium according to the times for the first and the second exchange.

TABLE 2

Claims (6)

1. NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered as a novelty and, therefore, the content of the following is claimed as property.
2. CLAIMS 1. Process for the purification of dimethylsulfoxide (DMSO) to reduce the amount of metal cations, alkaline and alkaline-earth, characterized in that it consists essentially of putting the dimethylsulfoxide to be purified in contact with at least two cation exchange resins where at least one it is a sulphonic type resin, the other (or others) being of the chelating type, these resins are used in the form of acid or ammonium. 2. Method according to claim 1, characterized in that a dimethylsulfoxide with a low water content is treated, this content preferably being less than or equal to 0.15 weight percent with respect to the total weight.
3. 3. Method according to claim 1 or 2, characterized in that each resin is based on a polystyrene-divinylbenzene copolymer.
4. 4. Method according to claim 1, characterized in that the contact of the dimethyl sulfoxide to be purified with the ion exchange resins takes place at a temperature of 19 to 80 ° C.
5. 5. Method according to claim 4, characterized in that the temperature is between 20 and 50 ° C.
6. 6. Dimethylsulfoxide capable of being obtained following the process of one of claims 5, characterized in that it comprises an iron cation content less than or equal to 1 ppm and a sodium cation content less than or equal to 2 ppm, respective limits of detection of the analysis method by atomic emission spectrometry - plasma torch.