Title of Invention

A PROCESS FOR THE PREPARATION OF 2-METHYL-2-PROPENE-1-SULPHONIC ACID, SODIUM SALT

Abstract

The present invention provides a process for the preparation of highly pure 2-Methyl-2-propene-l-sulphonic acid, sodium salt in high yield, with very low iron content, by the reaction of distilled sulfur tri oxide complexed with a Lewis base in a halogenated solvent, the unreacted sulfur tri oxide vapors being removed from the reactor before the mixture is treated with liquefied isobutylene,and neutralization by a base with an iron content within the range of 0-20ppm.

Full Text

The present invention relates to a process for preparation of highly pure 2-Methyl-2-propene-l-sulfoacid, sodium salt. More particularly the present invention relates to a 'process for the preparation of highly pure 2-Methyl-2-propene-l-sulfonic acid, sodium salt in high yield, with very low iron content, by the reaction of distilled sulfur trioxide complexed with a Lewis base in a halogentated solvent, removing the unreacted sulfur trioxide vapors from the reactor before the mixture is treated with liquefied isobutylene, and neutralization by a base iron content within the range of 0 to 20 ppm. 2-Methyl-2-propene-l-sulfonic acid, sodium salt as well as its homologues are used for improving the affinity of the acrylic fibers, towards dyes, in the dyeing process. 2-Methyl-2-propene-l-sylfonic acid, sodium salt and its homologues function as co-monomers during the polymerization process with acrylic monomers. Further, the homopolymers or the co-polymers of 2-Methyl-2-propene-l-sulfonic acid, sodium salt as well as its homologues, are used as extremely superior high molecular electrolytes, brighteners for electroplating, lubricating anti wear and HaS neutralizing additive for water based drilling mud. However, highly pure material is required (with the aim of obtaining the water soluble polymer that is colorless, has high molecular weight and high solubility). The iron content in the product must not exceed 3 ppm. The manufacturing method for 2-Methyl-2-propene-l-sulfonic acid, sodium salt known in the art consists, in general, of preparing a complex of SCh with solvents like dimethylformamide, dimethylacetamide, tetra alkyl urea or dioxane in an inert solvent like ethylene dichloride or methylene chloride or n-methyl pyrrolidone etc., reacting this complex with isobutylene followed by neutralization with aqueous sodium hydroxide etc. Another method of manufacturing 2-Methyl-2-propene-l-sulfonic acid, sodium salt known in the art is based on reaction of sodium sulfite with allyl chloride or methallyl chloride. Various methods of manufacturing 2-Methyl-2-propene-l-sulfonic acid, sodium salt based on the above general methods have been suggested in the prior art. Reference is made to Patents Ger. Offen. 1804135 (dated 30- April-1970) Ger. East 70086 (dated 05-December-1969) and Japan 76 56792 (dated 18-May, 1976) for the manufacture of 2-Methyl-2-propene-l-sulfonic acid, sodium salt which described a process of manufacture, using allyl chloride or methyl chloride and sodium sulfite as reacting components. However, this method unavoidably leads to the formation of large amounts of inorganic salts like sodium chloride, sodium sulfate and sodium sulfite. Therefore, these processes need complex methods of isolation and refinement of the desired product. Similarly, the 1 quantity of effluent needs to be treated before disposal. Hence, the •process may become uneconomical. Reference is also made to the method based on sulfur trioxide-dioxane complex disclosed in J. Am. Chem. Soc. Vol. 63, Page 978, 1941 and subsequent patents Japan 73 34827 (dated 25-05-73), Japan 73 56621 (dated 09-08-73), Japan 76 43715 (dated 14-04-76), and JP 57007145 B4, (dated 09-02-1982). These references disclose improvements over the base method of SOs - dioxane route. Although this route in general improves the yield of the desired 2-Methyl-2-propene-l-sulfonic acid, sodium salt, they also produce comparatively large quantities of side products. Furthermore the complex of SCVdioxane is extremely unstable and has to be maintained under controlled conditions. Therefore this route of manufacture is also not very practicable. A review of the latest developments in sulfonation with complex systems consisting in general of, preparing a complex of SOa with a Lewis base like dimethylformamide or dimethylacetamide, reveal some reports for preparation of 2-Methyl-2-propene-l-sulfonic acid, sodium salt by sulfonation of isobutylene with SOa-Lewis base complex. Reference is made to Patents Ger. Offen. 1804833 (dated 09-07-70), Ger. Offen. 1965002 (dated 01-07-71), Japan Kokai 74 43926 (dated 25-04-74). And Japan JP 63088167 A2, (dated 19-04-1988), in which the method of preparation of 2-Methyl-2-propene-l-sulfonic acid, sodium salt is in general described. In these dislcosures, isobutylene is sulfonated by the above mentioned complex of SOs with dimethylformamide or dimethylacetamide in an inert solvent like ethylene dichloride or methylene chloride etc. followed by neutralization with aqueous sodium hydroxide. Similarly the patent Japan Kokai 75 123625 (dated 29-09-75) also describes a method of isolation of the product from the by product sulfate salts by treating the solution with a lower aliphatic alcohol like methanol and concentration or drying to get the pure product. However, it is observed that during the process of mixing of isobutylene with SCh-Lewis base complex, a black material is generated which contaminates the product later. Furthermore, it is also observed that the formation of the black coloured contaminant was due to the vapor phase sulfonation of isobutylene at uncontrolled rate in the vapor space of the reactor resulting in the formation of tar. The formation of black coloured contaminant occurs even when product the product is isolated using methanol for precipitation. While in this method, the byproduct sulfone compounds or sodium sulfate etc. can be removed to a large extent, still the coloration takes place and the product appears off-while and the product does npt meet the spf' nations on color which should be less than 10 APHA for 5% aqueous solution. Extensive research and analysis on the phenomenon of coloration and black material formation during the reaction show that the cause of coloration in final product was specifically due to iron contained in the 2-Methyl-2-propene-l-sulfonic acid, sodium salt as an impurity. They present invention provides the solution to the above mentioned disadvantages of the past methods. The main object of the present invention is to provide an improved method for the preparation of highly pure 2-Methyl-2-propene-l-sulfonic acid, sodium salt in high yield, with very low iron content. Another object of the present invention is to eliminate the formation of black material during the course of addition of isobutylene in the SOa-Lewis base complex in the preparation of highly pure 2-Methyl-2-propene-l-sulfonic acid, sodium salt. Still another object of the present invention is to reduce the iron content in the final product, thereby improving the color. Another object of the invention is to provide a process for the preparation of highly pure-2-Methyl-2-propene-l-sulfonic acid, sodium salt with very low iron content, which obviates the disadvantages of the past methods. Accordingly the present invention provides a process for the preparation of highly pure 2-Methyl-2-propene-l-sulfonic acid, sodium salt in high yield and with very low iron content comprising reacting distilled sulfur trioxide complexed with a Lewis base, in a halogenated solvent, removing unreacted SCh vapors, treating the mixture with liquefied isobutylene, neutralizing the reaction mixture with a base, separating the layers into a heavy organic and a lighter aqueous layer, separating the impurities from the aqueous layer by precipitation in a non-solvent, removing the solvent to obtain the product. In one embodiment of the invention, the distilled sulfur trioxide is substantially free from iron. In another embodiment of the invention, the Lewis base is selected from dimethylformamide and dimethylacetamide. In another embodiment of the invention the molar ratio of the Lewis base with distilled S03 is in the range of 1.5:1 to 2.5:1, preferably 2:1. In still ar ?r embodiment, the molar ratio of isobutylene to distilled SCb is in the range of 1:1 to n^f preferably 1.15:1 In another embodiment of the invention, the halogenated solvent is selected from ethylene dichloride and methylene chloride. In yet another embodiment of the invention, the molar ratio of halogenated solvent to the distilled SOs is in the range of 5:1 to 9:1 preferably 7:1. In another embodiment of the invention, the base comprises NaOH lye (of 50% by wt concentration). In a further embodiment of the invention the base has a iron content from 0 to 20 ppm. In yet another embodiment of the invention, the non-solvent comprises a lower aliphatic alcohol. In yet another embodiment of the invention, the lower aliphatic alcohol is selected from the group consisting of methanol, ethanol and isopropanol. In yet another embodiment of the invention, the weight ratio of non-solvent to the aqueous layer is in the range of 1:1 to 2:1 preferably 1.4:1 In yet another embodiment of the invention, the iron free distilled SOj is obtained by distillation of commercial grade oleum or flash distillation of SOs - liquid in a glass or glass lined distillation assembly. The present invention provides a process for the preparation of highly pure 2-Methyl-2-propene-l-sulfonic acid, sodium salt in high yield and with very low iron content by reacting distilled sulfur trioxide complexed with a Lewis base, in a halogenated solvent, removing unreacted SCh vapors, treating the mixture with liquefied isobutylene, neutralizing the reaction mixture with a base, separating the layers into a heavy organic and a lighter aqueous layer, separating the impurities from the aqueous layer by precipitation in a non-solvent, removing the solvent to obtain the product. The distilled sulfur trioxide is substantially free from iron and is obtained preferably by distillation of commercial grade oleum or flash distillation of SOa - liquid in a glass or glass lined distillation assembly. The Lewis base is selected from dimethylformamide and dimethylacetamide and the molar ratio of the Lewis base with distilled SO3 is in the range of 1.5:1 to 2.5:1, preferably 2:1. The molar ratio of isobutylene to distilled SQ3 is in the range of 1:1 to 1.3:1, preferably 1.15:1. The halogenated solvent is preferably ethylene dichloride and methylene chloride and is present in me ratio of halogenated solvent to distilled SOs in the range of 5:1 to 9:1 preferably 7:1 • The base used for neutralisation comprises preferably NaOH lye (of 50% by wt concentration) and advantageously has a iron content of not more than 0 to 20 ppm. The non-solvent comprises a lower aliphatic alcohol such as methanol, ethanol, isopropanol and other lower aliphatic alcohols. The weight ratio of non-solvent to the aqueous layer is in the range of 1:1 to 2:1 preferably 1.4:1. A most important feature of the present invention is that, iron free distilled 863 is obtained by conventional distillation of commercial grade oleum or flash distillation of SOa -liquid, in a glass or glass lined distillation assembly. The iron free SOs is stored as distillate or condensate in a suitable container for using in the process. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention. EXAMPLE 1 20 liters of 35% oleum was distilled by conventional glass distillation assembly comprising of a round bottom flask of 10 liter capacity, provided with electrical at bottom, a 25 mm diameter, 2 meter high column packed with pall rings followed by a glass condenser and a glass receiver of 8L capacity. About 10 kg of iron free SOs was collected as distillate in the receiver. In a glass lined jacketed and agaitated reactor of 65L capacity, 50.85 kg Ethylene dichloride and 10.2 kg N, N-dimethylformamide, was charged. The mixture was cooled to 20°C by circulation of chilled brine in the jacket 5.516 kg iron free distilled SCb from the glass receiver was charged slowly into this mixture under agitation. The temperature of the mixture was maintained at 20 to 25°C during addition of iron-free distilled SOs by chilled brine circulation in jacket. After the addition was over, the vapors of unreacted 863 were sucked by applying vacuum to the system. When the vapor space was clear from the white fog, 4.44 kg isobutylene was quickly mixed with the reaction mixture. The temperature of the mixture was further raised to 42°C. It was maintained at about 42°C for one hour. Then the mixture was cooled to 20°C, and transferred to another glass lined reactor of 125 litre capacity. Aqueous sodium hydroxide of 20% (by wt) concentration was prepared in an HDPE container using 50% (by wt) sodium hydroxide lye having 3 ppm iron content. The reaction mixture was neutralized with 13.3 kg aqueous sodium hydroxide 20% (by wt.) to adjust the pH within 7 to 7.5. The temperature of mixture was maintained at 18 to 20°C by circulating chilled brine in jacket of the reactor. The mixture was digested for 1 hour 0.85 kg isobutylene was severed from this mixture by conventional distillation. The mixture was then cooled to room temperature. Then the agitation was topped and the layers were allowed to separate. The mixture was then cooled to room temperature. Then the agitation was stopped and the layers were allowed to separate. The heavier organic layer was separated by conventional method. Then 28 kg Methanol was charged in the reactor and the contents were cooled to 10°C. The slurry was filtered in the centrifuge. The filtrate was subjected to evaporation, concentration and distillation for removal of Methanol, water and traces of ethylene dichloride. The product obtained was further dried in conventional dryer to get 9.6 kg 2-Methyl-2-propene-l-sulfonic acid, sodium salt (94.8% yield on Isobutylene) with 99.8% purity and with 0.43 ppm iron content. The product obtained was very white in appearance and the color measured on APHA scale for 5% solution was 7. EXAMPLE-2 The procedure followed was very similar to that elaborated in example 1 except that 11.94 kg N, N-dimethylacetamide was used instead of N, N-dimethylformamide, The product 2-Methyl-2-Propene-l-sulfonic acid, sodium salt obtained as a result was very white in appearance with 99.7% purity, with 0.6 ppm iron content. The color measured on APHA scale for 5% solution was 9. The main advantages of the present invention are: 1. This method yields the product of very superior quality with very low iron content. 2. By following this method, the side reaction sulfonation of isobutylene in vapor phase can be black coloured by products is reduced. Thus in the methods of this invention, as compared to the usual methods, extremely high quality 2-Methyl-2-Propene-l-sulfonic acid, sodium salt is obtained in high yields and of very high purity with very low iron content. We claim l.A process for the preparation of 2-Methyl-2-propene-l-sulphonic acid, sodium salt in high yield and with very low iron content comprising reacting distilled sulfur tri oxide complexed with dimethyl formamide or dimethylacetamide wherein the molar ratio of Lewis base with distilled SO3 is in the range ofl .5:1 to 2.5:1, in a halogenated solvent such as herein described, wherein the molar ratio of halogenated solvent to the distilled SO3is in the range of 5:1 to 9:1characterized in that removing unreacted SO3 vapors, treating the reaction mixture with liquefied isobutylene wherein the molar ratio of isobutylene to distilled SO3is in the range of 1:1 to 1.3:1 neutralizing the reaction mixture with NaOH lye of 50% by weight concentration, separating the mixture into a heavy organic and a lighter aqueous layer containing 2-Methyl-2-propene-l-sulphonic acid, separating methanol, water and traces of ethylene dichloride from the aqueous layer by precipitation in methanol, ethanol or isopropanol, wherein the weight ratio of non-solvent to the aqueous layer is in the range of 1:1 to2:1 ,removing the solvent to obtain the product. 2. A process as claimed in claim 1 wherein the distilled sulfur trioxide is substantially free from iron. 3. A process as claimed in claim 1-2, wherein the molar ratio of Lewis base with distilled SO3 is preferably 2:1. 4. A process as claimed in claim 1-3, wherein the molar ratio of isobutylene to distilled S03is preferably 1.15:1. 5. A process as claimed in claim 1-4, wherein the molar ratio of halogenated solvent used is selected from ethylene dichloride and methylene chloride. 6. A process as claimed in claim 1-5, wherein the molar ratio of halogenated solvent to the distilled SO3is preferably 7:1. 7. A process as claimed in claim 1-6, wherein the base has a iron content from 0 to 20 ppm. 8. A process as claimed in claim 1-7, wherein the weight ratio of non-solvent to the aqueous layer is preferably 1.4:1. 9. A process as claimed in claim 1-8, wherein the iron free distilled SO3 is obtained by distillation of commercial grade oleum or flash distillation of S03-liquid in a glass or glass lined distillation assembly. 10. A process as claimed in claim 1-9, wherein the unreacted SO3 vapors are removed from the reactor before the SO3-Lewis base adduct is mixed with isobutylene. 1 l.A process for the preparation of highly pure 2-Methyl-2-propene-l-sulphonic acid, sodium salt in high yield and with very low iron content, substantially as herein described with reference to the examples accompanying this specification.

Documents:

408-DEL-2002-Abstract-(26-11-2008).pdf

408-del-2002-abstract.pdf

408-DEL-2002-Claims-(26-11-2008).pdf

408-del-2002-claims.pdf

408-del-2002-correspondence-others.pdf

408-del-2002-correspondence-po.pdf

408-del-2002-description (complete).pdf

408-del-2002-form-1.pdf

408-del-2002-form-18.pdf

408-del-2002-form-2.pdf

408-DEL-2002-Form-3-(26-11-2008).pdf

408-del-2002-form-3.pdf

408-DEL-2002-Petition-137-(26-11-2008).pdf