Abstract:
1,1,1-Trichloroethane cannot be completely separated from methanol, ethanol, n-propanol, isopropanol, 2-butanol or t-butanol by conventional distillation or rectification because of the minimum boiling azeotropes. 1,1,1-Trichloroethane can be readily separated from these alcohols by extractive distillation. A typical effective agent is dimethylsulfoxide.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method for separating 1,1,1-trichloroethane from the lower alcohols using certain organic the agent in extractive distillation. 
     DESCRIPTION OF PRIOR ART 
     Extractive distillation is the method of separating close boiling compounds from each other by carrying out the distillation in a multiplate rectification column in the presence of an added liquid or liquid mixture, said liquid(s) having a boiling point higher than the compounds being separated. The extractive agent is introduced near the top of the column and flows downward until it reaches the stillpot or reboiler. Its presence on each plate of the rectification column alters the relative volatility of the close boiling compounds in a direction to make the separation on each plate greater and thus require either fewer plates to effect the same separation or make possible a greater degree of separation with the same number of plates. The extractive agent should boil higher than any of the close boiling liquids being separated and not form minimum azeotropes with them. Usually the extractive agent is introduced a few plates from the top of the column to insure that none of the extractive agent is carried over with the lowest boiling component. This usually requires that the extractive agent boil about twenty Celcius degress or more higher that the lowest boiling component. 
     At the bottom of a continuous column, the less volatile components of the close boiling mixtures and the extractive agent are continuously removed from the column. The usual methods of separation of these two components are the use of another rectification column, cooling and phase separation, or solvent extraction. 
     1,1,1-Trichloroethane, B. P.=74° C. forms minimum boiling azeotropes with the lower alcohols. With methanol, the azeotrope boils at 61° C. and contains 20% 1,1,1-trichloroethane; with ethanol, the azeotrope boils at 63° C. and contains 75% 1,1,1-trichloroethane; with isopropanol, the azeotrope boils at 65° C. and contains 80% 1,1,1-trichloroethane; with n-propanol the azeotrope boils at 69.5° C. and contains 85% 1,1,1-trichloroethane; with 2-butanol the azeotrope boils at 70.5° C. and contains 90% 1,1,1-trichloroethane; with t-butanol the azeotrope boils at 66° C. and contains 80% 1,1,1-trichloroethane. Extractive distillation would be an attractive method of effecting the separation of 1,1,1-trichloroethane from these alcohols if agents can be found that (1) will enhance the relative volatility between 1,1,1-trichloroethane and these alcohols and (2) are easy to recover, that is, form no azeotrope 1,1,1-trichloroethane or the alcohols and boil sufficiently above 1,1,1-trichloroethane and these alcohols to make separation by rectification possible with only a few theoretical plates. 
     Extractive distillation typically requires the addition of an equal amount to twice as much extractive agent as the 1,1,1-trichloroethane-alcohol on each plate of the rectification column. The extractive agent should be heated to about the same temperature as the plate into which it is introduced. Thus extractive distillation imposes an additional heat requirement on the column as well as somewhat larger plates. However this is less than the increase occasioned by the additional agents required in azeotropic distillation. Another consideration in the selection of the extractive distillation agent is its recovery from the bottoms product. The usual method is by rectification in another column. In order to keep the cost of this operation to a minimum, an appreciable boiling point difference between the compound being separated and the extractive agent is desirable. We recommend twenty Celcius degrees or more difference. It is also desirable that the extractive agent be miscible with overhead products otherwise it will form a two phase azeotrope with them and some other method of separation will have to be employed. 
     
                       TABLE 1______________________________________Effect of Relative Volatility on the Separation of1,1,1-Trichloroethane From Alcohols at 99% PurityRelative  Theoretical            Actual Plates                        Actual PlatesVolatility  Plates    75% Efficiency                        75% Eff., Min. Reflux______________________________________1.2    50        67          871.5    23        31          402.0    13        17          223.0     9        12          16______________________________________ 
    
     The advantage of employing an effective extractive distillation agent is shown in Table 1. 1,1,1-trichloroethane forms minimum boiling azeotropes with the lower alcohols which possess a relative volatility of 1.0 and cannot be separated by rectification. If extractive distillation is employed with an agent yielding a relative volatility of 2.0, a rectification column of only 22 actual plates will be required 
     OBJECTIVE OF THE INVENTION 
     The objects of this invention are to provide a process or method of extractive distillation that will enhance the relative volatility of 1,1,1-trichloroethane to methanol, ethanol, n-propanol, isopropanol, 2-butanol and t-butanol in their separation in a rectification column. It is a further object of this invention to identify organic compounds that are stable, can be separated from 1,1,1-trichloroethane or the alcohols by rectification with relatively few plates and can be recycled to the extractive distillation column with little decomposition 
     SUMMARY OF THE INVENTION 
     The objects of this invention are provided by a process for the separation of 1,1,1-trichloroethane from methanol, ethanol, n-propanol, isopropanol, 2-butanol or t-butanol which entails the use of certain compounds as the agent in extractive distillation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I have discovered that certain organic compounds will effectively increase the relative volatility between 1,1,1-trichloroethane and methanol, ethanol, n-propanol, isopropanol, 2-butanol or t-butanol by rectification when employed as the agent in extractive distillation. Table 2 lists the compounds that I have found to be effective extractive distillation agents to recover 1,1,1-trichloroethane from methanol. The data in Tables 2, 4, 5,7,8,10, 11, 13, 15 and 16 was obtained in a vapor-liquid equilibrium still. In every case , the starting mixture was the 1,1,1,-trichloroethane - alcohol azeotrope. The relative volatilities are listed for each of the agents. 
     The compounds which are effective extractive distillation agents to remove 1,1,1-trichloroethane from methanol are dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide, acetophenone, 1-methyl-2-pyrrolidone,.ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol hexyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, diethylene glycol hexyl ether, dipropylene glycol methyl ether, propylene glycol isobutyl ether, tripropylene glycol methyl ether, propoxypropanol, butoxypropanol, propylene carbonate, isophorone, diethylene glycol diethyl ether, ethylene carbonate, isoamyl alcohol, 2-ethyl butanol, 4-methyl -2-pentanol, heptyl alcohol, isooctyl alcohol, diisobutyl carbinol, isodecyl alcohol, n-decanol, 2-octanol, benzyl alcohol, tetrahydrofurfuryl alcohol, methyl isoamyl ketone, diisobutyl ketone, 2-heptanone, isobutyl heptyl ketone, 3-heptanone, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol phenyl ether, 2,4-pentanedione, methyl benzoate, methyl salicylate, adiponitrile, amyl acetate, 4-methyl pentyl acetate-2, hexyl acetate, 2-ethyl hexyl acetate, benzyl acetate, isobornyl acetate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, 1-methoxy-2-propanol acetate, dipropylene glycol methyl ether acetate, isobutyl isobutyrate, 1-methoxy-2-acetoxy propanol, ethyl isovalerate, isobutyl butyrate, ethyl n-valerate, n-hexyl formate, ethyl acetoacetate, diethyl maleate, nitrobenzene, nitroethane, 1-nitropropane and 2-nitropropane. 
     
                       TABLE 2______________________________________Effective Agents For Separating1,1,1-Trichloroethane From Methanol                   RelativeCompounds               Volatility______________________________________Dimethylsulfoxide       2.6Sulfolane               2.9Dimethylformamide       2.8Dimethylacetamide       2.5Acetophenone            2.31-Methyl-2-pyrrolidinone                   2.7Ethylene glycol methyl ether                   4.0Ethylene glycol ethyl ether                   4.0Ethylene glycol butyl ether                   3.2Ethylene glycol phenyl ether                   3.1Ethylene glycol hexyl ether                   3.1Diethylene glycol methyl ether                   3.3Diethylene glycol ethyl ether                   2.9Diethylene glycol butyl ether                   2.1Propylene glycol methyl ether                   3.1Diethylene glycol hexyl ether                   4.2Dipropylene glycol methyl ether                   4.3Propylene glycol isobutyl ether                   2.5Tripropylene glycol methyl ether                   3.2Propoxypropanol         3.0Butoxypropanol          2.7Propylene carbonate     2.6Isophorone              2.4Diethylene glycol diethyl ether                   2.7Ethylene carbonate      3.3Isoamyl alcohol         2.22-Ethyl butanol         1.44-Methyl-2-pentanol     4.2Heptyl alcohol          3.6Isooctyl alcohol        2.5Diisobutyl carbinol     2.4Isodecyl alcohol        2.3n-Decanol               2.52-Octanol               2.8Benzyl alcohol          3.0Tetrahydro furfuryl alcohol                   3.3Methyl isoamyl ketone   2.3Diisobutyl ketone       2.72-Heptanone             3.2Isobutyl heptyl ketone  4.43-Heptanone             1.5Propylene glycol methyl ether acetate                   2.3Dipropylene glycol methyl ether acetate                   2.2Propylene glycol phenyl ether                   3.12,4-Pentanedione        2.7Methyl benzoate         2.2Methyl salicylate       2.4Adiponitrile            1.9Amyl acetate            2.14-Methyl pentyl acetate-2                   2.9Hexyl acetate           1.92-Ethyl hexyl acetate   2.0Benzyl acetate          2.5Isobornyl acetate       2.5Ethylene glycol ethyl ether acetate                   2.5Ethylene glycol butyl ether acetate                   2.1Diethylene glycol ethyl ether acetate                   2.81-Methoxy-2-propanol acetate                   1.7Dipropylene glycol methyl ether acetate                   3.61-Methoxy-2-acetoxy propanol                   2.3Isobutyl isobutyrate    1.9Ethyl isovalerate       2.7Isobutyl butyrate       4.0Ethyl n-valerate        2.7n-Hexyl formate         1.7Ethyl acetoacetate      2.8Diethyl maleate         2.6Nitrobenzene            2.5Nitroethane             2.82-Nitropropane          2.01-Nitropropane          2.1______________________________________ 
    
     
                       TABLE 3______________________________________Data From Run Made In Rectification Column            Time   Weight %                           Weight %                                   RelativeAgent   Column   hrs.   CH.sub.3 CCl.sub.3                           Methanol                                   Volatility______________________________________Dimethyl-   Over-    1      90.2     9.8    2.13sulfoxide   head   Bottoms          3.5    96.5   Over-    1.5    90.2     9.8    2.6   head   Bottoms          0.8    99.2______________________________________ 
    
     One of the agents, dimethylsulfoxide, whose relative volatlity had been determined in the vapor-liquid equilibruim still, was then evaluated in a glass perforated plate column and the results listed in Table 3. Dimethylsulfoxide gave a relative volatility of 2.6 after 1.5 hours of operation. 
     Table 4 lists the compounds found to be effective extractive distillatio agents to recover 1,1,1-trichloroethane from ethanol. The effective agents are n-propyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, n-butyl acetate, n-amyl acetate, isobornyl acetate, 4-methyl-pentyl acetate-2, ethylene glycol ethyl ether acetate, ethyl phenyl acetate, benzyl acetate, ethyl acetoacetate, ethylene glycol diacetate, isobutyl butyrate, isobutyl isobutyrate, ethyl valerate, ethyl butyrate, ethyl isovalerate, methyl benzoate, ethyl benzoate, methyl salicylate, ethyl 3-ethoxy propionate, diethyl maleate, hexyl formate, isophorone, 4-methyl-2-pentanone, 2-heptanone, methyl isobutyl ketone, methyl isoamyl ketone, 2,6-dimethyl-4-heptanone, diisobutyl ketone, 2-octanone, isobutyl heptyl ketone, 2-undecanone, 3,3-dimethyl-2-butanone, 1-methyl-2-pyrrolidinone, dimethylsulfoxide, dimethylformamide, dimethylacetamide, sulfolane, acetophenone, adiponitrile, isooctyl alcohol, isobutanol, 2-butanol, 1-butanol, 1-pentanol, t-amyl alcohol, 4-methyl-2-pentanol, tetrahydrofurfuryl alcohol, diacetone alcohol, 1-methoxy-2-propanol, 3-methyl-1-butanol, ethylene carbonate, propylene carbonate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol hexyl ether, propylene glycol methyl ether, propoxypropanol, butoxypropanol, diethylene glycol methyl ether, diethylene glycol ethyl ether, dipropylene glycol methyl ether, ethylene glycol butyl ether acetate, ethylene glycol isobutyl ether, diethylene glycol diethyl ether and anisole. 
     Table 5 lists the compounds that were found to be ineffective agents for separating 1,1,1-trichloroerhane from ethanol. 
     One of the agents, dimethylsulfoxide, whose relative volatlity had been determined in the vapor-liquid equilibrium still, was then evaluated in the glass perforated plate rectification column and the results listed in Table 6. Dimethylsulfoxide gave a relative volatility of 2.6 after 1.5 hours of operation. 
     
                       TABLE 4______________________________________Effective Agents For Separating1,1,1-Trichloroethane From Ethanol                 RelativeCompounds             Volatility______________________________________Isopropyl acetate     1.6Isobutyl acetate      1.3Isoamyl acetate        1.25Isobutyl butyrate      1.25Isobutyl isobutyrate  3.3Ethyl valerate        1.6n-Butyl acetate        3.5*n-Amyl acetate         1.85*4-Methyl pentyl acetate-2                  1.45*Ethylene glycol ethyl ether acetate                  1.5*Isobornyl acetate      1.6*Ethyl phenyl acetate   1.5*Ethyl butyrate         1.2*Ethyl isovalerate     1.4Benzyl acetate        1.2n-Propyl acetate       1.85Ethyl aceto acetate   1.7Methyl benzoate        1.45Ethyl benzoate         1.55Methyl salicylate      1.55Ethyl 3-ethoxy propionate                 1.6Diethyl maleate       1.8Hexyl formate         1.4Ethylene glycol diacetate                 1.7Isophorone             1.554-Methyl-2-pentanone  1.62-Heptanone           1.3Methyl isobutyl ketone                  1.85Methyl isoamyl ketone 2.02,6-Dimethyl-4-heptanone                  1.65Diisobutyl ketone     1.72-Octanone             1.45Isobutyl heptyl ketone                 1.43,3-Dimethyl-2-butanone                  1.652-Undecanone          1.41-Methyl-2-pyrrolidinone                 2.5Dimethylsulfoxide     2.6Dimethylformamide     2.0Dimethylacetamide     2.1Sulfolane             2.2Acetophenone           1.35Adiponitrile          2.0Isooctyl alcohol      2.1Isobutanol             1.352-Butanol             2.01-Butanol             3.51-Pentanol            3.0t-Amyl alcohol        1.54-Methyl-2-pentanol   2.1Tetrahydro furfuryl alcohol                 2.3Diacetone alcohol     2.71-Methoxy-2-propanol  2.93-Methyl-1-butanol    2.9Ethylene carbonate    3.2Propylene carbonate   2.2Ethylene glycol methyl ether                  1.95Ethylene glycol ethyl ether                 2.5Ethylene glycol hexyl ether                 1.8Propylene glycol methyl ether                 2.0Propoxypropanol       2.0Butoxypropanol         1.95Diethylene glycol methyl ether                 3.3Diethylene glycol ethyl ether                 1.2Dipropylene glycol methyl ether                  1.85Ethylene glycol butyl ether acetate                 1.2Ethylene glycol isobutyl ether                 1.8Diethylene glycol diethyl ether                  1.2*Anisole                1.25*______________________________________ *Brings out Ethanol as Overhead 
    
     
                       TABLE 5______________________________________Ineffective Agents, Ethanol From 1,1,1-Trichloroethane______________________________________Hexyl acetate   1-Methoxy-2-propanol acetateEthyl propionate           3-Heptanone5-Methyl-2-hexanone           Ethylene glycol butyl ether______________________________________ 
    
     
                       TABLE 6______________________________________Data From Run Made In Rectification Column            Weight %  Weight %                              Time RelativeAgent   Column   CH.sub.3 CCl.sub.3                      Ethanol hrs. Volatility______________________________________Dimethyl-   Over-    97.3       2.7    1    2.1sulfoxide   head   Bottoms  13.6      86.4Dimethyl-   Over-     99.43     0.57   1.5  2.6sulfoxide   head   Bottoms  14.7      85.3______________________________________ 
    
     
                       TABLE 7______________________________________Effective Agents From Separating1,1,1-Trichloroethane From n-Propanol                   RelativeCompounds               Volatility______________________________________Dimethylsulfoxide       2.3Sulfolane               3.0Dimethylformamide       2.8Dimethylacetamide       2.81-Methyl-2-pyrrolidinone                   3.05-Methyl-2-hexanone     1.33-Heptanone              1.254-Methyl-2-pentanone    1.4Adiponitrile            2.22-Octanone               1.252,4-Pentanedione        1.63,3-Dimethyl-2-butanone 1.4Methyl isobutyl ketone  1.5Isobutyl heptyl ketone   1.25Ethylene glycol methyl ether                   4.4Ethylene glycol ethyl ether                   3.6Ethylene glycol butyl ether                   2.0Ethylene glycol hexyl ether                   1.9Ethylene glycol phenyl ether                   2.5Diethylene glycol methyl ether                   2.7Diethylene glycol butyl ether                   2.8Diethylene glycol hexyl ether                   2.0Propylene glycol methyl ether                   4.2Dipropylene glycol methyl ether                   2.5Propylene glycol isobutyl ether                   1.9Tripropylene glycol methyl ether                   2.2Propoxypropanol         5.0Butoxypropanol          3.0Diethylene glycol diethyl ether                   1.6Ethylene glycol diacetate                   1.7Propylene carbonate     2.0Isophorone              1.8n-Butanol               3.9Isoamyl alcohol         3.6Isobutanol              2.2Hexyl alcohol           2.5Diisobutyl carbinol     1.9Methyl benzoate          1.25Methyl salicylate       1.3Nitroethane             1.92-Nitropropane          1.41-Nitropropane          1.3Nitrobenzene            1.4Acetophenone            1.7Methoxyacetoxypropane   1.4Dipropylene glycol methyl ether acetate                   1.7Propylene glycol phenyl ether                   3.4Isobutyl butyrate       1.3Benzyl benzoate         1.6______________________________________ 
    
     
                       TABLE 8______________________________________Ineffective Agents, n-Propanol From 1,1,1-Trichloroethane______________________________________Amyl acetate     n-Butyl acetateEthyl valerate   3-HexanoneDiethylene glycol ethyl ether            Dipropylene glycol methyl etherEthyl butyrate   Ethyl isovaleraten-Hexyl formate  Ethyl benzoate______________________________________ 
    
     
                       TABLE 9______________________________________Data From Run Made In Rectification Column            Time   Weight %                           Weight %                                   RelativeAgent   Column   hrs.   CH.sub.3 CCl.sub.3                           n-Propanol                                   Volatlity______________________________________Dimethyl-   Over-    1      99.5    0.5     2.17sulfoxide   head   Bottoms         40      60Dimethyl-   Over     1.5    99.7    0.3     2.33sulfoxide   head   Bottoms         41.3    58.7______________________________________ 
    
     Table 7 lists the compounds found to be effective extractive distillation agents to recover 1,1,1-trichloroethane from n-propanol. The effective agents are dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide, 1-methyl-2-pyrrolidinone, 5-methyl-2-hexanone, 3-heptanone, 4-methyl-2-pentanone, adiponitrile 2-octanone, 2,4-pentanedione, 3,3-dimethyl-2-butanone, methyl isobutyl ketone, isobutyl heptyl ketone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol hexyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol isobutyl ether, tripropylene glycol emthyl ether, propoxypropanol, butoxypropanol, diethylene glycol diethyyl ether, ethylene glycol diacetate, propylene carbonate, isophorone, n-butanol, isoamyl alcohol, isobutanol, hexyl alcohol, diisobutyl carbinol, methyl benzoate, methyl salicylate, nitroethane, 1-nitropropane, 2-nitropropane, nitrobenzene, acetophenone, methoxyacetoxypropane, dipropylene glycol methyl ether acetate, propylene glycol phenyl ether, isobutyl butyrate, and benzyl benzoate. 
     Table 8 lists the compounds that were found to be ineffective agents for separating 1,1,1,-trichloroethane from n-propanol. 
     One of the agents, dimethylsulfoxide, whose relative volatility had been determined in the vapor-liquid equilibrium still, was then evaluated in the glass perforated plate rectification column and the results listed in Table 9. Dimethylsulfoxide gave a relative volatility of 2.33 after 1.15 hours of operation. 
     The compounds which are effective extractive distillation agents to remove 1,1,1-trichloroethane from isopropanol are dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide, adiponitrile, amyl acetate, 2-methyl butyl acetate, hexyl acetate, 2-ethyl hexyl acetate, benzyl acetate, ethylene glycol butyl ether acetate, phenyl acetate, 1-methoxy-2-propanol acetate, isobutyl acetate, ethyl n-valerate, ethyl isovalerate, ethyl butyrate, isobutyl butyrate, isobutyl isobutyrate, methyl benzoate, methyl salicylate, butoxypropanol, 1-methyl-2-pyrrolidinone, anisole, propylene glycol methyl ether, nitroethane and propylene glycol phenyl ether and are listed in Table 10. 
     Table 11 lists the compounds that were found to be ineffective agents for separating 1,1,1-trichloroethane from isopropanol. One of the agents, dimethylsulfoxide, whose relative volatility had been determined in the vapor-liquid equilibrium still, was then evaluated in the glass perforated plate rectification column and the results listed in Table 12. Dimethylsulfoxide gave a relative volatility of 2.2 after 1.5 hours of operation. 
     The compounds which are effective extractive distillation agents to remove 1,1,1-trichloroethane from 2-butanol are dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide, acetophenone, 1-methyl-2-pyrrolidinone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, ethylene glycol hexyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol hexyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol isobutyl ether, tripropylene glycol methyl ether, propoxypropanol, butoxypropanol, propylene carbonate, ethylene carbonate, isophorone, diethylene glycol diethyl ether, isoamyl alcohol, 2-ethyl butanol, 4-methyl-2-pentanol, heptyl alcohol, isooctyl alcohol, diisobutyl carbinol, isodecyl alcohol, n-decanol, 2-octanol, benzyl alcohol, tetrahydrofurfuryl alcohol, methyl isoamyl ketone, diisobutyl ketone, 2-heptanone, isobutyl heptyl ketone, 3-heptanone, 2,4-pentanedione, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol phenyl ether, methyl benzoate, salicylate, adiponitrile, amyl acetate, 4-methyl pentyl acetate-2, hexyl acetate, 2-ethyl hexyl acetate, benzyl acetate, isobornyl acetate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, 1-methoxy-2-propanol acetate, dipropylene glycol methyl ether acetate, 1-methoxy-2-acetoxy propane, isobutyl butyrate, isobutyl isobutyrate, ethyl n-valerate, ethyl isovalerate, n-hexyl formate, ethyl acetoacetate, diethyl maleate, nitrobenzene, nitroethane, 1-nitropropane and 2-nitropropane and are listed in Table 13. 
     
                       TABLE 10______________________________________Effective Agents For Separating1,1,1-Trichloroethane From Isopropanol                  RelativeCompounds              Volatility______________________________________Dimethylsufoxide       2.5Sulfolane              1.4Dimethylformamide      1.55Dimethylacetamide      1.75Adiponitrile           1.25Ethyl isovalerate      1.6*Ethyl butyrate         1.3*Isobutyl butyrate      1.25*Isobutyl acetate       1.35*2-Methyl butyl acetate 1.35*Amyl acetate           1.4*Hexyl acetate          1.35*2-Ethyl hexyl acetate  1.3*Benzyl acetate         1.55*Ethylene glycol butyl ether acetate                  1.3*Phenyl acetate         1.25*Isobutyl isobutyrate   1.3*Methyl benzoate        1.4Methyl salicylate      1.45*1-Methyl-2-pyrrolidinone                  1.75Butoxypropanol         1.3Ethyl n-valerate       1.35*Anisole                1.55*Propylene glycol methyl ether                  2.3Nitroethane            1.31-Methoxy-2-propanol acetate                  1.7Propylene glycol phenyl ether                  1.6______________________________________ *Brings Isopropanol out as Overhead 
    
     
                       TABLE 11______________________________________Ineffecitive Agents, Isopropanol From 1,1,1-Trichlorethane______________________________________n-Butyl acetate        n-Propyl acetateIsopropyl acetate        Ethylene glycol ethyl ether acetateIsobornyl acetate        Diethylene glycol ethyl ether acetateEthyl acetoacetate        1-Methoxy-2-propanol acetaten-Hexyl formate        Diethyl maleate3-Ethoxypropionate        Ethylene glycol diacetateNitromethane 2-Nitropropane1-Nitropropane        MethoxyacetoxypropaneIsobutyl butyrate        Dipropylene glycol methyl ether acetateEthyl butyrate______________________________________ 
    
     
                       TABLE 12______________________________________Data From Run Made In Rectification Column                           Weight %            Time   Weight %                           Iso-    RelativeAgent   Column   hrs.   CH.sub.3 CCl.sub.3                           propanol                                   Volatility______________________________________Dimethyl-   Over-    1      99.6     0.4    2.5sulfoxide   head   Bottoms         27.8    72.2Dimethyl-   Over-    1.5    98.8     1.2    2.2sulfoxide   head   Bottoms         23.2    76.8______________________________________ 
    
     
                       TABLE 13______________________________________Effective Agents For Separating1,1,1-Trichloroethane From 2-Butanol                   RelativeCompounds               Volatility______________________________________Dimethylsulfoxde        2.2Sulfolane               2.7Dimethylformamide       2.8Dimethylacetamide       2.5Acetophenone            3.01-Methyl-2-pyrrolidinone                   3.6Ethylene glycol methyl ether                   4.5Ethylene glycol ethyl ether                   3.1Ethylene glycol butyl ether                   2.8Ethylene glycol phenyl ether                   2.0Ethylene glycol hexyl ether                   2.9Diethylene glycol methyl ether                   3.0Diethylene glycol ethyl ether                   2.8Diethylene glycol butyl ether                   2.7Diethylene glycol hexyl ether                   2.3Propylene glycol methyl ether                   3.9Dipropylene glycol methyl ether                   2.3Propylene glycol isobutyl ether                   2.4Tripropylene glycol methyl ether                   2.3Propoxypropanol         2.7Butoxypropanol          2.4Propylene carbonate     2.4Isophorone              2.0Diethylene glycol diethyl ether                   1.6Ethylene carbonate      2.8Isoamyl alcohol         1.62-Ethyl butanol         3.34-Methyl-2-pentanol     3.2Heptyl alcohol          3.1Isooctyl alcohol        2.4Diisobutyl carbinol     2.2Isodecyl alcohol        2.4n-Decanol               2.32-Octanol               2.6Benzyl alcohol          3.5Tetrahydrofurfuryl alcohol                   3.2Methyl isoamyl ketone   1.6Diisobutyl ketone       1.52-Heptanone             1.4Isobutyl heptyl ketone  1.53-Heptanone             1.6Propylene glycol methyl ether acetate                   1.8Dipropylene glycol methyl ether acetate                   1.8Propylene glycol phenyl ether                   2.42,4-Pentanedione        1.8Methyl benzoate         1.6Methyl salicylate       1.3Adiponitrile            2.7Amyl acetate            1.54-Methyl pentyl acetate-2                   1.7Hexyl acetate           1.62-Ethyl hexyl acetate   1.6Benzyl acetate          1.7Isobornyl acetate       1.7Ethylene glycol ethyl ether acetate                   1.9Ethylene glycol butyl ether acetate                   1.8Diethylene glycol ethyl ether acetate                   2.11-Methoxy-2-propanol acetate                   4.3Dipropylene glycol methyl ether acetate                   1.81-Methoxy-2-acetoxy propane                   2.0Isobutyl butyrate       1.5Isobutyl isobutyrate    1.5Ethyl n-valerate        1.5Ethyl isovalerate       1.6n-Hexyl formate         1.5Ethyl aceoacetate       1.8Diethyl maleate         1.9Nitrobenzene            1.6Nitroethane             2.02-Nitropropane          1.61-Nitropropane          1.6______________________________________ 
    
     
                       TABLE 14______________________________________Data From Run Made In Rectification Column            Time   Weight %                           Weight %                                   RelativeAgent   Column   hrs    CH.sub.3 Cl.sub.3                           2-Butanol                                   Volatility______________________________________Dimethyl-   Over-    1      99.6     0.4    2.1sulfoxide   head   Bottoms         53.1    46.9Dimethyl-   Over-    1.5    99.7     0.3    2.15sulfoxide   head   Bottoms         55.1    44.9______________________________________ 
    
     
                       TABLE 15______________________________________Effective Agents For Separating1,1,1-Trichloroethane From t-Butanol                RelativeCompounds            Volatility______________________________________Dimethylsulfoxide    1.7Sulfolane            1.4Dimethylformamide    1.9Dimethylacetamide    1.9Adiponitrile         1.4Ethylene glycol methyl ether                3.1Ethylene glycol ethyl ether                2.2Ethylene glycol butyl ether                1.7Ethyene glycol phenyl ether                1.3Diethylene glycol methyl ether                2.2Diethylene glycol ethyl ether                1.4Diethylene glycol butyl ether                1.5Diethylene glycol hexyl ether                1.5Propylene glycol methyl ether                1.7Dipropylene glycol methyl ether                1.5Propylene glycol isobutyl ether                1.4Tripropylene glycol methyl ether                1.4Propoxypropanol      3.3Butoxypropanol       1.4Ethylene glycol diacetate                1.3Propylene carbonate  1.5Isophorone           1.4n-Butanol            2.7Isoamyl alcohol      3.0Isobutanol           1.2Ethylene carbonate   1.3Hexyl alcohol         1.2*Methyl salicylate     1.3*______________________________________ *Brings out tButanol as Overhead 
    
     
                       TABLE 16______________________________________Ineffective Agents, t-Butanol From 1,1,1-Trichloroethane______________________________________Amyl acetate     n-Butyl acetateEthyl valerate   5-Methyl-2-hexanone3-Heptanone      4-Methyl-2-pentanone2-Octanone       2,4-PentanedioneMethyl isobutyl ketone            3,3-Dimethyl2-butanoneIsobutyl heptyl ketone            3-EthoxypropionateAnisole          Diethylene glycol diethyl etherMethyl benzoate______________________________________ 
    
     One of the agents, dimethylsulfoxide, whose relative volatility had been determined in the vapor-liquid equilibrium still, was then evaluated in the glass perforated plate rectification column and the results listed in Table 14. Dimethylsulfoxide gave a relative volatility of 2.15 after 1.5 hours of operation. 
     The compounds which are effective extractive distillation agents to remove 1,1,1-trichloroethane from t-butanol are listed in Table 15 and are dimethylsulfoxide, dimethylformamide, dimethylacetamide, adiponitrile, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol hexyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol isobutyl ether, tripropylene glycol methyl ether, propoxypropanol, butoxypropanol, ethylene glycol diacetate, propylene carbonate, isophorone, n-butanol, isoamyl alcohol, isobutanol, ethylene carbonate, alcohol and methyl salicylate. 
     Table 16 lists the compounds that were found to be ineffective agents for separating 1,1,1-trichloroethane from t-butanol. 
     One of the agents, dimethylsulfoxide, whose relative volatility had been determined in the vapor-liquid equilibrium still, was then evaluated in the glass perforated rectification column and the results listed in Table 17. Dimethylsulfoxide gave a relative volatility of 1.68 after 1.5 hours of operation. 
     
                       TABLE 17______________________________________Data From Run Made In Rectification Column             Weight   Weight             %        %      Time RelativeAgent   Column    CH.sub.3 CCl.sub.3                      t-Butanol                             hrs. Volatility______________________________________Dimethyl-   Overhead  97.1     2.9    1    1.68sulfoxide   Bottoms   43.4     56.6Dimethyl-   Overhead  95.7     4.3    1.5  1.68sulfoxide   Bottoms   33.5     66.5______________________________________ 
    
     THE USEFULNESS OF THE INVENTION 
     The usefulness or utility of this invention can be demonstrated by referring to the data presented in Tables 2 to 17. All of the successful agents show that 1,1,1-trichloroethane can be separated from methanol, ethanol, n-propanol, isopropanol,2-butanol and t-butanol by means of extractive distillation in a rectification column and that the ease of separation as measured by relative volatility is considerable. 
     WORKING EXAMPLES 
     Example 1 
     Seventy grams of the 1,1,1-trichloroethane-methanol azeotrope and 30 grams of dimethylsulfoxide were charged to a vapor-liquid equilibrium still and refluxed for eight hours. Analysis indicated a vapor composition of 24.2% 1,1,1-trichloroethane, 75.8% methanol; a liquid composition of 11% 1,1,1-trichloroethane, 89% methanol which is a relative volatility of 2.6. 
     Example 2 
     A solution comprising 250 grams of the 1,1,1-trichloroethane-methanol azeotrope was placed in the stillpot of a 7.3 theoretical plate glass perforated plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the top of the column was 65° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane-methanol in the stillpot was adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collected and analysed by gas chromatography. The overhead analysis was 90.2% 1,1,1-trichloroethane, 9.8% methanol and the bottoms analysis was 0.8% 1,1,1-trichloroethane, 99.2% methanol. This gives an average relative volatility of 2.6 for each theoretical plate. This data is in Table 3. 
     Example 3 
     A solution comprising 250 grams of the 1,1,1-trichloroethane ethanol azeotrope was placed in the stillpot of the 7.3 theoretical plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the top of the column was 70° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane ethanol in the stillpot was adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collected and analysed. The overhead analysis was 99.43% 1,1,1-trichloroethane, 0.57% ethanol and the bottoms analysis was 14.7% 1,1,1-trichloroethane, 85.3% ethanol. This gives an average relative volatility of 2.6 for each theoretical plate. This data is presented in Table 6. 
     Example 4 
     A solution comprising 250 grams of the 1,1,1-trichloroethane-n-propanol azeotrope was placed in the stillpot of the 7.3 theoretical plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the top of the column was 75° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane -n-propane in the stillpot was adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collected and analysed. The overhead analysis was 99.7% 1,1,1-trichloroethane, 0.3% n-propanol and the bottoms analysis was 41.3% 1,1,1-trichloroethane, 58.7% n-propanol. This gives an average relative volatility of 2.33 for each theoretical plate. This data is presented in Table 9. 
     Example 5 
     A solution comprising 250 grams of the 1,1,1-trichloroethane-isopropanol azeotrope was placed in the stillpot of the 7.3 theoretical plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the top of the column was 73° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane-isopropanol in the stillpot was adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collected and analysed. The overhead analysis was 98.8% 1,1,1-trichloroethanel 2% isopropanol and the bottoms analysis was23.3% 1,1,1-trichloroethane,76.8% isopropanol. This gives an average relative volatility of 2.2 for each theoretical plate. This data is presented in Table 12. 
     Example 6 
     A solution comprising 250 grams of the 1,1,1-trichloroethane-2-butanol azeotrope was placed in the stillpot of the 7.3 theoretical plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the column was 83° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane-2-butanol in the stillpot as adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collcted and analysed. The overhead analysis was 99.7% 1,1,1-trichloroetahne, 0.3% 2-butanol and the bottoms analysis was 55.1% 1,1,1-trichloroethane, 44.9% 2-butanol. This gives an average relative volatility of 2.15 for each theoretical plate. This data is presented in Table 14. 
     Example 7 
     A solution comprising 250 grams of the 1,1,1-trichloroethane-t-butanol azeotrope was placed in the stillpot of the 7.3 theoretical plate rectification column. When refluxing began, an extractive agent comprising dimethylsulfoxide was pumped into the column at a rate of 15 ml/min. The temperature of the extractive agent as it entered the top of the column was 80° C. After establishing the feed rate of the extractive agent, the heat input to the 1,1,1-trichloroethane-t-butanol in the stillpot was adjusted to give a total reflux rate of 40 ml/min. After 1.5 hours operation, overhead and bottoms samples were collected and analysed. The overhead analysis was 95.7% 1,1,1-trichloroethane, 4.3% t-butanol and the bottoms analysis was 33.5% 1,1,1-trichloroethane, 66.5% t-butanol. This gives an average relative volatility of 1.68 for each theoretical plate. This data is presented in Table 17.