Abstract:
The purpose of the process of the present invention is to remove excess sulfuric acid from a mixture of paraffin-sulfonic acids free or substantially free, from paraffins. 
     In order to remove said sulfuric acid, according to the process of the present invention, the paraffin-sulfonic acid mixture is mixed with one or more halogenated solvent(s), possibly in mixture with sulfuric acid to form a two phase mixture consisting of an organic phase containing paraffin-sulfonic acids dissolved therein and an aqueous phase substantially containing sulfuric acid. The organic phase is then treated with sulfuric acid and the organic phase and aqueous phase are then separated and the organic phase is submitted to evaporation, for the removal of the halogenated solvent(s), and with the concentrated paraffin-sulfonic acids being obtained.

Description:
This is a continuation of co-pending application Ser. No. 07/136,559, filed on 12/22/87, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a process for the separation of sulfuric acid (H 2  SO 4 ) from aqueous mixtures of paraffin-sulfonic acids. 
     SUMMARY OF THE INVENTION 
     The present invention is a process for removing sulfuric acid (H 2  SO 4 ) from a paraffin-sulfonic solution. The process comprises (a) admixing with the paraffin sulfonic solution at least one halogenated solvent selected from the group consisting of methane, ethane, and ethylene halogenated derivatives of the following formulas: ##STR1## wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6 , each independently, is halogen or hydrogen, with at least one of R 1 , R 2 , R 3 , R 4  is halogen, at a temperature of from 10° of an to 80° C., thereby forming a two-phase mixture consisting of an organic phase containing paraffin-sulfonic acids dissolved therein and an aqueous phase substantially containing sulfuric acid; 
     (b) separating the organic phase from the aqueous phase; 
     (c) optionally admixing the organic phase with sulfuric acid, thereby forming a two phase mixture consisting of an organic phase containing paraffin-sulfonic acids dissolved therein and an aqueous phase substantially containing sulfuric acid, separating the organic phase from the aqueous phase, and 
     (d) removing the halogenated solvents from the separated organic phase. 
     The object of the present invention is to provide a process to remove excess H 2  SO 4  from a refined mixture of paraffin-sulfonic acids free or substantially free, from paraffins. 
     The residual mixtures from which H 2  SO 4  must be separated according to the present invention are those which derive from the sulfoxidation of (C 12  -C 18 )-n-paraffin with sulfur dioxide (SO 2 ) and oxygen (O 2 ) in the presence of water (H 2  O) and ultra-violet light, at a temperature between 25° to 50° C. These residual mixtures undergo one of the following extraction treatments after the removal of n-paraffins (which separate spontaneously) and excess SO 2 . 
     a) The residual mixture is dehydrated until the residual mixture becomes cloudy (due to the formation of a two phase system). The cloudy mixture or the supernatant phase of the two phase system is then extracted with CO 2  under supercritical conditions to separate the non-sulfoxidated paraffins from the dehydrated residual mixture at a temperature between 32° to 80° C., a pressure between 75 to 350 bars, and with a CO 2  to paraffin-sulfonic acids weight ratio of 1/1 to 50/1 so as to obtain a refined mixture. 
     b) H 2  SO 4  is added to the residual mixture until at least the residual mixture becomes cloudy (due to the formation of a two-phase system). The cloudy mixture or the supernatant phase of the two phase system is then extracted with CO 2  under supercritical conditions, to separate the residual paraffins from the residual mixture at a temperature between 32° to 80° C., a pressure between 75 to 350 bars, and with a CO 2  to paraffin-sulfonic acids weight ratio of 1/1 to 50/1 so as to obtain a refined mixture. 
     c) An aliphatic alcohol containing a number of carbon atoms up to about 4, preferably isopropanol, is added to the residual mixture until a two phase system is formed. The two phase system is then extracted with CO 2  under supercritical conditions to separate the residual paraffins from the mixture at a temperature between 32° to 80° C., a pressure between 75 to 350 bars and with a CO 2  to paraffin-sulfonic acids weight ratio of from 1/1 to 50/1 so as to obtain a refined mixture. 
     The refined mixture of paraffin-sulfonic acids free, or substantially free, from paraffins, obtained by means of the above treatments still contains, besides the paraffin-sulfonic acids, a considerable amount of H 2  SO 4 . 
     The composition of the refined mixtures of paraffin-sulfonic acids obtained by the above methods, i.e., (a) to (c), are the following: 
     1) (C 12  -C 18 )-Paraffin-sulfonic acids: from 3 to 83% by weight; 
     2) H 2  O: from 79 to 8.5% by weight; 
     3) H 2  SO 4 , from 18 to 8.5% by weight and 
     4) (C 12  -C 18 )-Paraffins: less than 1% by weight, relative to the weight of (C 12  -C 18 ) paraffin-sulfonic acids 
     The starting mixture, even if it is obtained in the above three ways, i.e., (a) to (c), can be obtained in other ways too, so that the present invention should not be considered as being limited to the way in which the starting mixture with the above reported composition is obtained. The process of the invention can be applied to any mixtures, in whatever way they are obtained, having the above compositions. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The process is carried out at a temperature between 10° to 80° C., preferably between 20° to 50° . The refined mixture of paraffin-sulfonic acids is mixed with one or more of the above halogenated solvents. 
     In the two phase mixture, which is formed, the aqueous phase constitutes H 2  SO 4  and H 2  O and the residual refined phase contains paraffin-sulfonic acids dissolved therein. The residual refined phase is separated from the aqueous phase. Optionally it is mixed with H 2  SO 4  ranging from an aqueous H 2  SO 4  having a minimum concentration of 70% by weight of H 2  SO 4  to concentrated H 2  SO 4 , or oleum, or even SO 3 , at a temperature between 10° C. to 80° C., preferably between 20° C. to 50° C., in such a way that a second phase is formed. The second phase, which constitutes H 2  SO 4  and H 2  O, is then separated from the residual refined phase. The halogenated solvent is separated from the residual refined phase. In particular, the separation is carried out by distillation at a temperature below 100° C., preferably lower than 60° C., and more preferably at least partially under vacuum. 
     Among the halogenated solvents preferred are methylene chloride, chloroform, carbon tetrachloride and dichloroethane. The amount of halogenated solvent(s) added depends on the type of solvent used and the composition of the refined mixture of paraffin-sulfonic acids. The amount used should make it possible to separate the largest amount of H 2  SO 4  possible. 
     The amount of H 2  SO 4  optionally added can be, in the case of 96% concentrated H 2  SO 4 , up to 200% by weight, preferably from 50% to 150% by weight, relative to the weight of the paraffin-sulfonic acids contained in the refined mixture. 
     A practical embodiment of the process of the present invention is to mix the halogenated solvent(s) and H 2  SO 4  simultaneously with the refined mixture of paraffin-sulfonic acids in a single processing step. 
     If any residual H 2  SO 4  is present before the application of the process according to the present invention, can be removed by being converted into an insoluble product by means of the addition of carbonates, hydroxides or oxides of alkaline-earth metals, particularly, by calcium carbonate, calcium hydroxide or calcium oxide. 
     Some examples are now given for the purpose of better illustrating the invention. It is understood that the invention is not to be limited to or by the Examples. 
     EXAMPLE 1 
     The upper-phase of a raw mixture (from which Decantable n-paraffins and SO 2  have been removed) of paraffin-sulfonic acids obtained by sulfoxidation of (C 12  -C 18 ) n-paraffins, and having the following composition: 
     Paraffin-sulfonic acids: 24.74% by weight 
     (C 12  -C 18 )-n-paraffins: 26.46% by weight 
     H 2  O: 40.94% by weight 
     H 2  SO 4  : 7.86% by weight 
     was extracted with CO 2  under supercritical conditions, so as to separate the residual paraffins after the addition of 20% by weight of H 2  SO 4  at 96% by weight, referred to the weight of said raw mixture. 
     The upper phase of the raw mixture was extracted with CO 2  under the following conditions: 
     CO 2  /paraffinsulfonic acid ratio: 15.5 
     Extraction pressure: 150 bar 
     Extraction temperature: 45° C. 
     Extraction time: 1 hour 
     Analysis of the upper phase of the paraffin-sulfonic acids after extraction showed the following composition: 
     Paraffinsulfonic acids: 59.95% by weight 
     (C 12  -C 18 )-n-paraffins: 0.22% by weight 
     H 2  O: 28.73% by weight 
     H 2  SO 4  : 11.11% by weight 
     Then 20.47 g of the upper phase after extraction was mixed with 30.69 g of CH 2  Cl 2  (methylchloride) in a tightly sealed glass separator funnel. 
     The separator funnel was thoroughly shaken for a few minutes, and two phases were allowed to separate. After 3 hours of standing at 22° C., the two separated phases were taken away from each other, and analyzed. The lower phase was constituted of: 
     H 2  O: 55.44% by weight 
     H 2  SO 4  : 44.02% by weight 
     CH 2  Cl 2  : traces 
     In the upper phase, all charged paraffin-sulfonic acids were present, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins, and CH 2  Cl 2 . In particular, the content of H 2  SO 4 , as referred to the present paraffin-sulfonic acids, decreased from 18.5% by weight (before the treatment with CH 2  Cl 2 ) to 8.36% by weight. Also the H 2  O content, still referred to paraffin-sulfonic acids, decreased from 47.9% by weight to 31.7% by weight. 
     Aliquots of the upper phase, obtained by means of the treatment with CH 2  Cl 2 , had the composition of: 
     Paraffin-sulfonic acids: 25.92% by weight 
     (C 12  -C 18 )-n-paraffins: 0.094% by weight 
     H 2  O: 8.21% by weight 
     H 2  SO 4  : 2.168% by weight 
     CH 2  Cl 2  : the balance to 100 
     were extracted, inside a separator funnel, with different amounts of H 2  SO 4  at 96% by weight to form a lower phase at 22° C. The lower phase was constituted by H 2  SO 4  and H 2  O and separated from the upper phase. 
     The values obtained for each phase are reported in Table 1. 
     
                                           TABLE 1__________________________________________________________________________          Added          H.sub.2 SO.sub.4 /               H.sub.2 SO.sub.4 /                                                   H.sub.2 O/paraffin                                                   -          paraffin-               Analysis of the upper phase                             Analysis of the lower                                           paraffin-                                                   sulphonic ac-          sulphonic               Paraffin-     Paraffin-     sulphonic                                                   ids ratio in    CH.sub.2 Cl.sub.2     Added          acids %               sulphonic                     H.sub.2 O,                         H.sub.2 SO.sub.4,                             sulphonic                                   H.sub.2 O,                                       H.sub.2 SO.sub.4,                                           ratio in                                                   the upperTest    Phase H.sub.2 SO.sub.4          ratio, by               acids, %                     % by                         % by                             acids, %                                   % by                                       % by                                           upper phase,                                                   phase,No. Charge, g     at 96%, g          weight               by weight                     weight                         weight                             by weight                                   weight                                       weight                                           % by weight                                                   % by__________________________________________________________________________                                                   weight1.1 10.2143     1.0944          41.33               28.64 2.74                         1.364                             0     35.28                                       63.64                                           4.76    9.571.2 10.3137     1.5468          57.87               28.51 1.94                         1.268                             0     30.37                                       68.69                                           4.45    6.801.3 10.6545     2.0810          75.3 29.91 1.46                         1.292                             0     27.50                                       71.08                                           4.14    4.88__________________________________________________________________________ 
    
     EXAMPLE 2 
     217.8 g of the upper phase mixture of paraffin-sulfonic acids after extraction as in Example 1, was mixed with 652.9 g of CH 2  Cl 2  in a tightly sealed separator funnel. The separator funnel was thoroughly shaken and two phases were allowed to separate. After standing 24 hours at 22° C., the two separated phases were taken away from each other, and analyzed. 
     The lower phase was constituted by: 
     H 2  O: 50.73% by weight 
     H 2  SO 4  : 44.03% by weight 
     CH 2  Cl 2  : small amount 
     In the upper phase, all charged paraffin-sulfonic acids were present, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins and CH 2  Cl 2 . In particular, the content of H 2  SO 4 , referred to the present paraffin-sulfonic acids, decreased from 18.5% by weight (before the treatment with CH 2  Cl 2 ) to 7.49% by weight. Also the H 2  O content, still referred to the present paraffin-sulfonic acids, decreased from 47.9% by weight to 30.0% by weight. 
     Aliquots of the upper phase, obtained by means of the treatment with CH 2  Cl 2 , had the composition of: 
     Paraffin-sulfonic acids: 16.535% by weight 
     (C 12  -C 18 )-n-paraffins: 0.060% by weight 
     H 2  O: 4.96% by weight 
     H 2  SO 4  : 1.238% by weight 
     CH 2  Cl 2  : the balance to 100 
     were extracted inside a separator funnel, with different amounts of H 2  SO 4  at 96% by weight at 22° C., to form a second phase or lower phase. The lower phase was constituted by H 2  SO 4  and H 2  O and separated from the upper phase. The values obtained for each phase are reported in Table 2. 
     
                                           TABLE 2__________________________________________________________________________          Added          H.sub.2 SO.sub.4 /               H.sub.2 SO.sub.4 /                                                   H.sub.2 O/paraffin                                                   -          paraffin-               Analysis of the upper phase                             Analysis of the lower                                           paraffin-                                                   sulphonic ac-          sulphonic               Paraffin-     Paraffin-     sulphonic                                                   ids ratio in    CH.sub.2 Cl.sub.2     Added          acids %               sulphonic                     H.sub.2 O,                         H.sub.2 SO.sub.4,                             sulphonic                                   H.sub.2 O,                                       H.sub.2 SO.sub.4,                                           ratio in                                                   the upperTest    Phase H.sub.2 SO.sub.4          ratio, by               acids, %                     % by                         % by                             acids, %                                   % by                                       % by                                           upper phase,                                                   phase,No. Charge, g     at 96%, g          weight               by weight                     weight                         weight                             by weight                                   weight                                       weight                                           % by weight                                                   % by__________________________________________________________________________                                                   weight2.1 23.8090     3.5494          90.2 16.60 0.499                         0.496                             0     24.41                                       72.84                                           2.99    3.012.2 24.1925     5.9650          149.1               16.49 0.176                         0.594                             0     19.42                                       79.73                                           3.60    1.072.3 24.1608     8.3762          209.7               16.52 0.118                         0.914                             0     15.55                                       83.12                                           5.53    0.714.1 17.7698     1.2404          45.15               16.28 1.306                         0.586                             0     33.43                                       65.66                                           3.60    8.024.2 19.0743     2.0422          69.25               16.46 0.801                         0.511                             0     28.06                                        71.515                                           3.10    4.874.3 17.9379     2.5976          93.67               16.40 0.498                         0.502                             0     25.02                                       74.18                                           3.06    3.04__________________________________________________________________________ 
    
     EXAMPLE 3 
     22.45 g of the upper phase mixture of paraffin-sulfonic acids after extraction as in Example 1, was mixed with 224.35 g of CH 2  Cl 2  in a tightly sealed separator funnel. The separator funnel was thoroughly shaken and two phases were allowed to separate. After standing 24 hours at 22° C., the two separated phases were taken away from each other, and analyzed. 
     The lower phase was constituted by: 
     H 2  O: 53.51% by weight 
     H 2  SO 4  : 42.48% by weight 
     CH 2  Cl 2  : minor amounts 
     In the upper phase, all charged paraffin-sulfonic acids were present, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins and CH 2  Cl 2 . In particular, the content of H 2  SO 4 , referred to the present paraffin-sulfonic acids, decreased from 18.5% by weight (before the treatment with CH 2  Cl 2 ) to 6.36% by weight. Also the H 2  O content, still referred to the present paraffin-sulfonic acids, has decreased from 47.9% by weight to 33.0% by weight. 
     Aliquots of the upper phase, obtained by means of the treatment with CH 2  Cl 2 , had the composition of: 
     Paraffin-sulfonic acids: 5.584% by weight 
     (C 12  -C 18 )-n-paraffins: 0.020% by weight 
     H 2  O: 1.840% by weight 
     H 2  SO 4  : 0.355% by weight 
     CH 2  Cl 2  : the balance to 100 
     were extracted, inside a separator funnel, with different amounts of H 2  SO 4  at 96% by weight at 22° C., to form a second phase or lower phase. The lower phase was constituted by H 2  SO 4  and H 2  O and separated from the upper phase. The obtained values of each phase are reported in Table 3. 
     
                                           TABLE 3__________________________________________________________________________          Added          H.sub.2 SO.sub.4 /               H.sub.2 SO.sub.4 /                                                   H.sub.2 O/paraffin                                                   -          paraffin-               Analysis of the upper phase                             Analysis of the lower                                           paraffin-                                                   sulphonic ac-          sulphonic               Paraffin-     Paraffin-     sulphonic                                                   ids ratio in    CH.sub.2 Cl.sub.2     Added          acids %               sulphonic                     H.sub.2 O,                         H.sub.2 SO.sub.4,                             sulphonic                                   H.sub.2 O,                                       H.sub.2 SO.sub.4,                                           ratio in                                                   the upperTest    Phase H.sub.2 SO.sub.4          ratio, by               acids, %                     % by                         % by                             acids, %                                   % by                                       % by                                           upper phase,                                                   phase,No. Charge, g     at 96%, g          weight               by weight                     weight                         weight                             by weight                                   weight                                       weight                                           % by weight                                                   % by__________________________________________________________________________                                                   weight3.1 38.6158     1.9658          91.2 5.809 0.139                         0.091                             0     25.14                                       71.30                                           1.57    2.393.2 38.1813     3.7011          173.6               5.806  0.0317                         0.123                             0     17.84                                       79.05                                           2.12    0.553.3 38.2163     1.3300          62.32               5.720 0.260                         0.106                             0     29.15                                       68.00                                           1.85    4.553.4 38.0728     0.7079          33.30               5.640 0.491                         0.152                             0     36.63                                       61.26                                           2.70    8.713.5 27.9606     1.9132          122.6               5.804 0.080                         0.142                             0     21.35                                       76.47                                           2.45    1.38__________________________________________________________________________ 
    
     EXAMPLE 4 
     16.1 g of the upper phase mixture of paraffin-sulfonic acids after extraction as in Example 1, was mixed with 48.6 g of CH 2  Cl 2  in a tightly sealed separator funnel. The separator funnel was thoroughly shaken and placed inside an oven maintained at the controlled temperature of 40° C. After 30 minutes, the separator funnel was thoroughly shaken once more inside the oven. Two phases were allowed to separate. After standing 16 hours at 40° C., the lower phase was removed, with the separator funnel being kept inside the oven. The funnel containing the upper phase was removed from the oven, and was cooled to room temperature. The two phases were analyzed. 
     The lower phase was constituted by: 
     H 2  O: 53.47% by weight 
     H 2  SO 4  : 42.90% by weight 
     CH 2  Cl 2  : minor amounts 
     In the upper phase, all charged paraffin-sulfonic acids were present, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins and CH 2  Cl 2 . In particular, the content of H 2  SO 4 , referred to the present paraffin-sulfonic acids, decreased from 18.55% by weight (before the treatment with CH 2  Cl 2 ) to 5.58% by weight. Also the H 2  O content, still referred to the present paraffin-sulfonic acids, decreased from 47.9% by weight to 27.22% by weight. 
     Aliquots of the upper phase, obtained by means of the treatment with CH 2  Cl 2 , had the composition of: 
     Paraffin-sulfonic acids: 15.98% by weight 
     (C 12  -C 18 )-n-paraffins: 0.058% by weight 
     H 2  O: 4.35% by weight 
     H 2  SO 4  : 0.892% by weight 
     CH 2  Cl 2  : the balance to 100 
     were extracted, inside a tightly sealed separator funnel that can withstand moderate pressure, with different amounts of H 2  SO 4  at 96% by weight, by operating at 40° C. inside an oven, to form a second phase or lower phase. 
     After the phases separated, at 40° C., the lower phase was removed, inside the oven. The lower phase was constituted by H 2  SO 4  and H 2  O. 
     The separator was then removed from the oven, and was cooled to room temperature. The two phases were then analyzed. The values obtained for each phase are reported in Table 4. 
     
                                           TABLE 4__________________________________________________________________________          Added          H.sub.2 SO.sub.4 /               H.sub.2 SO.sub.4 /                                                   H.sub.2 O/paraffin                                                   -          paraffin-               Analysis of the upper phase                             Analysis of the lower                                           paraffin-                                                   sulphonic ac-          sulphonic               Paraffin-     Paraffin-     sulphonic                                                   ids ratio in    CH.sub.2 Cl.sub.2     Added          acids %               sulphonic                     H.sub.2 O,                         H.sub.2 SO.sub.4,                             sulphonic                                   H.sub.2 O,                                       H.sub.2 SO.sub.4,                                           ratio in                                                   the upperTest    Phase H.sub.2 SO.sub.4          ratio, by               acids, %                     % by                         % by                             acids, %                                   % by                                       % by                                           upper phase,                                                   phase,No. Charge, g     at 96%, g          weight               by weight                     weight                         weight                             by weight                                   weight                                       weight                                           % by weight                                                   % by__________________________________________________________________________                                                   weight6.1 11.4404     1.0814          59.2 17.005                     0.860                         0.497                             0     29.71                                       69.57                                           2.92    5.066.2 12.7039     2.0280          99.9 17.090                     0.355                         0.447                             0     24.60                                       75.7                                           2.62    2.086.3 10.9668     2.2819          130.2               16.890                     0.243                         0.570                             0     21.32                                       78.88                                           3.37    1.44__________________________________________________________________________ 
    
     EXAMPLE 5 
     23.0 g of the upper phase mixture of paraffin-sulfonic acids after extraction as in Example 1, were mixed with 142.6 g of CH 2  Cl 2  in a tightly sealed separator funnel that can withstand moderate pressure. The separator funnel was thoroughly shaken. The separator funnel was then placed inside an oven maintained at the controlled temperature of 40° C. After 1 hour, the separator funnel was thoroughly shaken once more inside the oven. The phases were allowed to separate. After standing 26 hours at 40° C., the lower phase was removed from the interior of the oven. The funnel containing the upper phase was removed from the oven, and was allowed to cool down to room temperature. The two phases were analyzed. 
     The lower phase (4.4391 g) was constituted of: 
     H 2  O: 56.66% by weight 
     H 2  SO 4  : 43.08% by weight 
     CH 2  Cl 2  : minor amounts 
     In the upper phase (160.8172 g), all of the charged paraffin-sulfonic acids were present, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins, and CH 2  Cl 2 . In particular, the content of H 2  SO 4 , referred to the present paraffin-sulfonic acids, decreased from 18.5% by weight (before the treatment with CH 2  Cl 2 ) to 4.84% by weight. Also the H 2  O content, still referred to the present paraffin-sulfonic acids, decreased from 47.9% by weight to 28.11% by weight. 
     11.5 g of H 2  SO 4  at 96% by weight was charged into a separator funnel resistant to moderate pressures, with 148.1 g of the upper phase. The separator funnel was thoroughly shaken, and placed inside an oven maintained at the controlled temperature of 40° C. After 1 hour, the separator funnel was thoroughly shaken once more and then left standing for 4 hours at 40° C. The lower phase (15.2294 g) was removed inside the oven. The separator containing the upper phase (143.9 g) was removed from the oven, and allowed to cool down to room temperature. The two phases were then analyzed. 
     The lower phase was constituted of: 
     H 2  O: 25.5% by weight 
     H 2  SO 4  : 73.6% by weight 
     CH 2  Cl 2  : the balance to 100% 
     The lower phase did not contain paraffin-sulfonic acids. 
     The upper phase had the following composition: 
     Paraffin-sulfonic acids: 9.07% by weight 
     (C 12  -C 18 )-n-paraffins: 0.033% by weight 
     H 2  O: 0.230% by weight 
     H 2  SO 4  : 0.198% by weight 
     CH 2  Cl 2  : the balance to 100 
     The H 2  SO 4  /paraffin-sulfonic acids ratio was 2.18% and the H 2  O/paraffin-sulfonic acids ratio was 2.54%. 134 g of the upper phase was fed, in continuous mode, to a rotary evaporator operating under a slight vacuum (120-130 mm Hg ), and with the temperature of the heating bath being between 50° to 55° C. When all of the product had been fed, and approximately the total amount of CH 2  Cl 2  has evaporated, the vacuum was increased up to 700 mm Hg . The whole process step lasted about 1 hour. 
     The residual product remaining inside the kettle of the rotary evaporator after all the CH 2  Cl 2  had evaporated, was a thin liquid essentially constituted by paraffin-sulfonic acids, with 1.585% by weight of H 2  O, 2.182% by weight of H 2  SO 4  and 0.360% by weight of (C 12  -C 18 )-n-paraffins. 
     The distribution of monosulfonic, disulfonic and trisulfonic acids found in the concentrated residual product resulted to be the same as found in the raw mixture of paraffin-sulfonic acids downstream from the sulfoxidation reactor. 
     EXAMPLE 6 
     By operating at 22° C., and using the same mixture of paraffin-sulfonic acids as used in Example 1, tests of purification of the paraffin-sulfonic acids from H 2  SO 4  using different solvents, were carried out. 
     The results obtained are shown in Table 5. It can be observed how only the halogenated solvents supply interesting results. 
     
                                           TABLE 5__________________________________________________________________________            Grams of                 Separated                       Separated                             Ratio, by weight,                                       Ratio, by weight,            paraffin-                 organic                       aqueous                             of H.sub.2 SO.sub.4 /paraffin-                                       of H.sub.2 O/paraffin-Test   Type of  Grams of            sulphonic                 phase,                       phase,                             sulphonic acids in                                       sulphonic acids inNo.   solvent  solvent            mixture                 g     g     organic phase, %                                       organic phase,                                                REMARKS__________________________________________________________________________1  CHCl.sub.3       3.4815            3.2700                 6.0640                       0.5247                             4.12      32.22  CCl.sub.4       2.5884            3.4649                 5.7156                       0.3264                             7.79      38.33  CH.sub.2 Cl--CH.sub.2 Cl       3.0531            3.4600                 5.1625                       0.4214                             10.2      35.4     Also present in the                                                intermediate phase                                                of                                                CH.sub.2 Cl--CH.sub.2                                                 Cl4  CCl.sub.2 =CH.sub.2       2.6188            3.4609                 5.6313                       0.4488                             10.99     33.75  (C.sub.2 H.sub.5).sub.2 O       1.7001            3.3640                 4.9189                       0.0810                             16.26     40.66  CH.sub.3 COOC.sub.2 H.sub.5       2.3794            3.4308                              Single phase7  Petroleum ether,       1.9217            3.3102                              Single phase   40-70° C.__________________________________________________________________________ 
    
     EXAMPLE 7 
     7.4428 g of the upper phase mixture of paraffin-sulfonic acids after extraction as in Example 1, was mixed with 14.7382 g of CHCl 3  in a tightly sealed test tube. The test tube was thoroughly shaken, left standing at 23° C. for 6.5 hours, and then centrifuged to favor the phase separation of the two phases that have formed. The two phases were taken away from each other and were analyzed. 
     The lower phase (1.3330 g) was essentially constituted by H 2  O (57.5% by weight) and H 2  SO 4  (42.46% by weight). 
     The upper phase (20.7284 g), was constituted of all the charged paraffin-sulfonic acids, together with minor amounts of H 2  O, H 2  SO 4 , n-paraffins, and CHCl 3 . In particular, the content of H 2  SO 4 , referred to the present paraffin-sulfonic acids, decreased from 18.5% by weight (before the treatment with CHCl 3 ) to 5.74% by weight. The H 2  O content, still referred to the present paraffin-sulfonic acids, decreased from 47.9% by weight to 29.35% by weight. 
     To 10.5305 g of the beforehand separated upper phase, 2.0448 g of H 2  SO 4  at 96% by weight was charged. The test tube was thoroughly shaken, and was left standing at 23° C. After 7 hours, two phases formed and were taken away from each other and analyzed. 
     The lower phase contained H 2  O (25.08% by weight), H 2  SO 4  (73.44% by weight), together with a small amount of CHCl 3 , and did not contain paraffin-sulfonic acids. 
     The upper phase had the following composition: 
     Paraffin-sulfonic acids: 22.75% by weight 
     (C 12  -C 18 )-n-paraffins: 0.082% by weight 
     H 2  O: 0.80% by weight 
     H 2  SO 4  : 0.686% by weight 
     CH 2  Cl 2  : the balance to 100 
     The H 2  SO 4  /paraffin-sulfonic acids ratio was 3.02% and the water/paraffin-sulfonic acids ratio resulted to be 3.52%.