Title of Invention

A PROCESS FOR THE MANUFACTURE OF AN ALKANESULPHONYL CHLORIDE

Abstract

invention concerns a method for making alkanesulphonyl chloride RCH¿2?-SO¿2?CI by oxidising chlorinolysis of the corresponding mercaptan RCH¿2?-SH, mercaptan and water being introduced in the reaction mixture in the form of a water dispersion in mercaptan. Said process results both in very high quality alkanesulphonyl chloride and commercial grade hydrochloric acid. (FR) Dans le procédé selon l'invention pour la fabrication d'un chlorure d'alcane-sulfonyle RCH¿2?-SO¿2?CI par chlorolyse oxydante du mercaptan RCH¿2?-SH correspondant, le mercaptan et de l'eau sont introuduits dans le mélange réactionnel sous forme d'une dispersion d'eau dans le mercaptan. Ceci permet d'obtenir à la fois un chlorure d'alcanesulfonyle de très bonne qualité et un acide chlorhydrique de qualité commerciale.

Full Text

The present invention relates to a process for the manufacture of an alkanesulphonyl chloride and has more particularly subject-matter their synthesis by oxidative chlorolysis of the corresponding mercaptan in the presence of water according to the overall reaction: RCH2-SH + 2 H20 + 3 Cl2 -> RCH2-SO2CI + 5 HC1 Consultation of the prior art shows that this synthesis of alkanesulphonyl chlorides from mercaptans is carried out, under batchwise or continuous conditions, by bringing chlorine and the mercaptan into contact in a concentrated aqueous hydrochloric acid solution (Patents FR 1 598 279, DE 1 811 768, US 3 626 004, JP 52-020970, US 3 600 136 and US 3 993 692) or in pure water (Patents DE 2 845 918, JP 52-008283, US 3 248 423 and US 4 280 966), the objective being to obtain an alkanesulphonyl chloride with a good yield and the best possible purity, that is to say while avoiding the formation of troublesome byproduct or intermediate compounds. One of the most troublesome among these compounds is 1-chloroalkane-sulphonyl chloride RCHC1-S02C1; alkanesulphinic acid RCH2-SO2H, alkyl alkanethiosulphonate RCH2-SO2-SCH2R and alkanesulphinyl chloride RCH2-S0C1, optionally in combination with their a-chlorinated derivatives, are also encountered. These compounds, for the most part of low stability, are the source of the colouring of alkylsulphonyl chloride over time. In order to avoid the formation of such compounds, it is advantageous to operate with an excess of water. This makes it possible to greatly restrict the formation of 1-chloroalkanesulphonyl chloride and alkanesulphinic acid, alkyl alkanethiosulphonate or alkanesulphinyl chloride is no longer encountered in alkanesulphonyl chloride prepared in this way. The hydrochloric acid produced by the reaction remains predominantly trapped in the water, which has to be introduced in large amounts in order to ensure good selectivity for alkanesulphonyl chloride. This is one of the reasons why the abovementioned Patents FR 1 598 279, DE 1 811 768, US 3 626 004, JP 52-020970, US 3 600 136 and US 3 993 692 recommend introducing the water in the form of a concentrated aqueous hydrochloric acid solution, so as to recover a pure hydrochloric acid gas, the impurities being predominantly trapped in the acidic aqueous phase. However, as explained above, the formation of the a-chlorinated derivative RCHCI-SO2CI, a troublesome impurity for the applications of the chloride RCH2-SO2CI which is very difficult to separate by standard purification techniques, is thus promoted. On analysing the prior art, it emerges that the processes provided do not take into account the quality of the hydrochloric acid coproduced and that there was no interest in its enhancement in value. Recovered after separation by settling of the reaction mixture, it accumulated various by-products, such as sulphuric acid, sulphinic and sulphonic acid, a small amount of alkanesulphonyl chloride, and the like, and it is therefore unsuitable in this state for marketing. In summary: 1) when the water is introduced in the form of a concentrated aqueous hydrochloric acid solution, a gaseous HCl of good quality is recovered but the alkanesulphonyl chloride obtained comprises relatively large amounts of the a-chlorinated derivative RCHCI-SO2CI; 2) when the water is introduced pure, the alkanesulphonyl chloride is of very good quality (very little 1-chloroalkanesulphonyl chloride) but the aqueous phase recovered is contaminated by sulphuric acid and organic compounds and the concentration of the hydrochloric acid obtained does not necessarily correspond to a commercial specification. An aim of the present invention is thus to combine the respective advantages of the processes with pure water and of the processes using a concentrated aqueous hy rochloric acid solution, so as to obtain both an alkanesulphonyl chloride of very good quality and a hydrochloric acid of commercial grade. It has now been found that this aim can be achieved by dispersing water beforehand in the mercaptan and by adding the dispersion thus obtained into the reaction mixture. According to the present invention, there is provided a process for the manufacture of an alkanesulphonyl chloride RCH2-S02C1 which process comprises oxidative chlorolysis of the corresponding mercaptan RCH2-SH, in which the mercaptan and water in the form of dispersion of water in the mercaptan are added into the reaction mixture; the reaction mixture being initially composed of a concentrated aqueous hydrochloric acid solution. The dispersion can be obtained, for example, by mechanical stirring, by a static mixer or by any other means known to a person skilled in the art for obtaining a fine dispersion of water in the organic mercaptan phase. The dispersion can optionally be stabilized by the addition of a small amount (500 to 1000 ppm with respect to the weight of makeup water) of a surfactant, such as, for example, octanesulphonic acid, decanesulphonic acid, dodecanesulpbonic acid or the sodium salt of such an acid. Although the watenmercaptan molar ratio can range from 0.5:1 to 5:1, the amount of water dispersed in the mercaptan is advantageously that which corresponds to the stoichiometry of the reaction mentioned above, i.e. two moles of water per mole of mercaptan. With a watenmercaptan molar ratio equal to 2:1, the content by mass of water in the dispersion will vary, for example, from 28.5% for butyl mercaptan to 17.1% for decyl mercaptan (23.3% for hexyl mercaptan, 19.7% for octyl mercaptan, and the like). In accordance with the process according to the invention, the dispersion of water in the mercaptan is subsequently added into the reaction mixture, which has been rendered as homogeneous as possible and which is composed initially of a concentrated solution of hydrochloric acid in water (33 to 40%) The concentration of alkanesulphonyl chloride in the reaction mixture can range from 0 to 50%; it varies according to the degree of progress of the reaction and the operating method. The process according to the invention can be implemented under batchwise conditions or under continuous conditions. Under batchwise conditions, a hydrochloric acid (36 to 40%) heel is placed beforehand in the reactor and then, with vigorous stirring, the water/mercaptan dispersion and the chlorine are gradually introduced with a chlorine:mercaptan molar ratio preferably equal to 3:1. The gaseous hydrochloric acid produced during the reaction is scrubbed out with water in a column of the type well known to a person skilled in the art and the alkanesulphonyl chloride produced is recovered after settling and separation of the acidic aqueous phase, which can optionally be recycled for another operation. The implementation of the process according to the invention under continuous conditions requires two reactors in series, the reaction being essentially carried out in the first (main reactor) and the second (finishing reactor) being used to remove the nonoxidized intermediates. A turnround of hydrochloric acid (33 to 40% in water) is created, which turnround will condition the residence time in the reactor and the finisher. The reactants are introduced into the main reactor in the same way as under batchwise conditions. Downstream of the main reactor, a gas-liquid separator makes it possible to recover the gaseous hydrochloric acid, subsequently scrubbed out with water in a column provided for this purpose. The finishing reactor, itself also stirred, receives an additional chlorine contribution and its contents subsequently pass into a separator for separating the sulphochloride from the concentrated aqueous hydrochloric acid solution, which is recycled using a The process according to the invention can be applied to the synthesis of alkanesulphonyl chlorides RCH2-SO2CI comprising from 2 to 12 carbon atoms, preferably 4 to 10. The RCH2 radical is preferably a linear alkyl radical but it can also be branched, such as, for example, in the case of isobutyl mercaptan. The following examples, in which the percentages shown are percentages by mass, illustrate the invention without limiting it. The tests were carried out in a device comprising a reactor with a capacity of 10 litres equipped with a jacket connected to a cooling system, with a condenser, with a temperature recorder and with a mechanical stirrer comprising two rotors which can rotate at from 250 to 1 000 revolutions per minute. Gas (chlorine or nitrogen) is fed in by means of a pipe via a sintered glass sparger. The flow rate for the gas is controlled by a mass flowmeter under electronic control. Two metering pumps respectively inject the mercaptan and the makeup water into a static mixer, placed directly in the reaction medium such that the mercaptan/water emulsion does not have the time to separate. The gas exiting from the condenser is introduced into a column for scrubbing out with water the hydrochloric acid produced by the reaction. A rotameter measures the total gas flow rate at the outlet of the reactor and the chlorine content of the gaseous effluent exiting from the reactor is measured using a UV spectrophotometer connected in line. Example 1; Preparation of n-octanesulphonyl chloride under batchwise conditions 5 200 grams (4.41 litres) of a 36% aqueous hydrochloric acid solution were place beforehand in the reactor and, after having brought this solution to 6°C with vigorous stirring, the introduction of the water/n-octyl mercaptan dispersion (molar ratio 2/1) was begun and, at the same time, that of chlorine was begun, so that the chlorine/mercaptan molar ratio is equal to 3/1. To convert 3 000 grams of an n-octyl mercaptan into n-octanesulphonic chloride, 4 362 grams of chlorine (61.5 mol) and 738 grams of water (41 mol) were introduced. The temperature, gradually raised to 20°C/ was maintained at this level by virtue of the cooled jacket. After having introduced, over 5 hours, all the desired amount of n-octyl mercaptan (3 000 g), the feeding of the mercaptan and that of the makeup water were halted but the injection of the chlorine was continued for one hour at only 5% of its initial flow rate, while continuing to stir, in order to bring the :idation of the synthetic intermediates to octane-ilphonyl chloride to completion. 9 974 g of a two-phase mixture, composed of 362 g of crude n-octanesulphonyl chloride, 66 g of ;i dissolved in this chloride and 5 546 g of a 40% ^drochloric acid solution, were recovered in the factor. Settling for one hour made it possible to sparate the two organic and aqueous phases. After stripping the HC1 and the traces of ilorine which it comprises, analysis of the organic lase yielded the following results: - octanesulphonyl chloride: 97% production: 4 231 g) - 1-chlorooctanesulphonyl chloride: 0 .25% - 1-chlorooctanesulphinyl chloride: 0-1% - octyl octanethiosulphonate: 0-1% - water: 0.1% - octanesulphonic acid: 0.2% - octanesulphinic acid: 0.1% - isooctanesulphonyl chloride: 0.3% originates from the isomercaptan present in the tarting reactant) - other heavy products: 1.85% For a total production of 3 739 g of hydrochloric acid, the balance sheet worked out as follows: - 65.44 g dissolved in the crude octane-sulphonyl chloride - 346.7 g trapped in the acidic aqueous phase, which they bring to an assay of 40% - 3 327 g (i.e. 89% of the acid produced) scrubbed out with water to form 33% acid (9 981 g). The acidic aqueous phase (5 546 g) had the following composition: - HC1 assay: 40% - octanesulphonyl chloride: 0.20% - sulphuric acid: 0.26% - octanesulphonic acid: 0.074% - octanesulphinic acid: 0 . 023% and can be recycled for another operation, with an addition of water, if necessary. The scrubbed hydrochloric acid assayed 33% and did not comprise detectable traces of organic compounds. Because of its very low content of sulphuric acid (37 ppm), it was suitable for marketing. Comparative example 2 The preparation was carried out as in Example 1 but without the addition of water and while directly introducing the n-octyl mercaptan into the reaction mixture. To obtain complete conversion of the mercaptan and the reaction intermediates to octanesulphonyl chloride, the overall reaction time changed from six hours to nine hours and thus increased by 50%. The purity of the octanesulphonyl chloride obtained under these conditions was only 92% (production: 4 013 g) and it comprised 4.65% of 1-chlorooctanesulphonyl chloride, 1.3% of octane-sulphinyl chloride and of its chlorinated derivative, 1.2% of octanesulphinic acid and 0.5% of octyl octanethiosulphonate. The purity of the 33% hydrochloric acid recovered in the scrubbing column is equivalent to that in Example 1. Comparative Example 3 The preparation was carried out as in Example 1 but replacing the heel of 36% hydrochloric acid solution with a heel of pure water of the same mass (5 200 g) and introducing the n-octyl mercaptan alone (without water) into the reactor. The total reaction time was the same as that in Example 1. The organic phase recovered assayed 97.5% of octanesulphonyl chloride (i.e. 4 230 g of octanesulphonyl chloride) and comprised only 0.2% of 1-chlorooctanesulphonyl chloride; the synthetic intermediates (octanesulphinyl chloride, octanesulphinic acid, octyl octanethiosulphonate) totalled only 1%. 7 435 g of acidic aqueous phase assaying 40% of hydrochloric acid were recovered, this aqueous phase being contaminated by 2 620 ppm of sulphuric acid, 740 ppm of octanesulphonic acid, 350 ppm of octane-sulphonyl chloride and a not insignificant amount of octanesulphinic acid which could not be quantitatively determined. The pure hydrochloric acid fraction which reached the scrubbing with water only corresponded to 18.7% of the total acid produced, i.e. 700 g, giving 2 100 g of 33% solution with a purity equivalent of that of the acid obtained in Example 1. The aqueous hydrochloric acid phase had a composition similar to [lacuna] the residual aqueous phase in Example 1. It is therefore not possible to have available 81.3% of the hydrochloric acid from the reaction without purifying the latter and thus increasing its cost price. The main results obtained in the preceding examples are summarized in the following table, in which OSC denotes n-octanesulphonyl chloride and ClOSC denotes 1-chlorooctanesulphonyl chloride, for a production of 4 362 g of crude OSC. Examples 4, 5 and 6; Preparation of butane-sulphonyl chloride (BSC), hexanesulphonyl chloride (HSC) and decanesulphonyl chloride (DSC) The preparations were carried out as in Example 1 with premixing of the mercaptan and the water before injecting them into the reaction mixture but replacing the n-octyl mercaptan with the same amount (3 000 grams) of n-butyl mercaptan, of n-hexyl mercaptan or of n-decyl mercaptan respectively. In all cases, the water heel was 5 200 grams. The results obtained are collated in the following table, which shows the production of crude alkanesulphonyl chloride, its purity and its content of cc-chlorinated derivative, and the production of 33% hydrochloric acid of commercial grade. WE CLAIM: 1. A process for the manufacture of an alkanesulphonyl chloride RCH2-S02C1 which process comprises oxidative chlorolysis of the corresponding mercaptan RCH2-SH, in which the mercaptan and water in the form of a dispersion of water in the mercaptan are added into the reaction mixture; the reaction mixture being initially composed of a concentrated aqueous hydrochloric acid solution. 2. The process as claimed in claim 15 in which the amount of water dispersed in the mercaptan is such that the water:mercaptan molar ratio is between 0.5:1 and 5; 1. 3. The process as claimed in claim 2, in which the watenmercaptan molar ratio is equal to 2:1. 4. The process as claimed in any one of claims 1 to 3, in which the reaction mixture is initially composed of a concentrated aqueous hydrochloric acid solution having an HC1 content of 33 to 40%. 5. The process as claimed in any one of claims 1 to 4, in which the chlorine is introduced in a chloxine:mercaptan molar ratio equal to 3:1. 6. The process as claimed in any one of claims 1 to 5, in which the alkyl mercaptan RCH2-SH comprises from 2 to 12 carbon atoms. 7. The process as claimed in claim 6, in which the alkyl mercaptan comprises from 4 to 10 carbon atoms. 8. The process as claimed in claim 6 or 7, in which the RCH2 radical is a linear alkyl radical. 9. The process as claimed in any one of claims 1 to 8, in which the alkanesulphonyl chloride manufactured is n-octanesulphonyl chloride.

Documents:

532-chenp-2003-abstract.pdf

532-chenp-2003-claims duplicate.pdf

532-chenp-2003-claims original.pdf

532-chenp-2003-correspondnece-others.pdf

532-chenp-2003-correspondnece-po.pdf

532-chenp-2003-description(complete) duplicate.pdf

532-chenp-2003-description(complete) original.pdf

532-chenp-2003-form 1.pdf

532-chenp-2003-form 26.pdf

532-chenp-2003-form 3.pdf

532-chenp-2003-form 5.pdf

532-chenp-2003-other documents.pdf

532-chenp-2003-pct.pdf