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Patented Apr. 7, ‘1942' 2,279,194 ‘

UNITED STATES PATENT OFFICE‘

' ' v' 2.21am _ ~ ‘

Edmund Field, Wilmington, m1, mum»- to E. '1. du Pont de Nemours & Company, 11,. Del, a corporation of Delaware - No Drawing. Application August 22, 1940, Serial No. 353,674 ' 5 (Cl. 202-42) This inventionrelates to a method for separat Although the proportions of methyl ing substances which either boil closely together ‘ added to the -containing mixture, or form binaries such that separation cannot be and speci?cally the proportions of methyl acetate " achieved by simple fractional distillation. More to the mixture of cyclohexane and , may particularly, this invention relates to the sepa vary over a considerable range, I have found that ration of cyclohexane from and is a modi the greatest e?ciency of operation may be ob ?cation of U. S. Patent 2,212,810, which relates tained by adding the quantity of methyl acetate to the same separation. ‘ ' to a cyciohexane-containing mixture which cor it is an object of this invention to provide a responds approximately with the proportions of ‘method for separating closely-boiling substances 10 methyl acetate and cyclohexane in t_he binary or substances which form where sepa which is formed between these two substances. ration by fractional distillation is difficult or im Thus, by the addition of 77.7% by weight of methyl practical. It is a. further object of this invention acetate to a cyclohexane-containing mixture to provide a method for separating cyclohexane there will result a cyclohexane-methyl acetate from benzene. It is an additional object of this 15 binary containing 77.7% by weight methyl acetate invention to increase the e?lciency of separation and 22.3% by weight cyclohexane. When acetone of cyclohexane from benzene by altering the ra is so utilized as a separating medium, such as de tio of acetone to cyclohexane in the distillate, scribed in U. S. Patent 2,212,810,,the quantity of from that of the acetone-cyclohexane . methyl acetate necessary for the formation of a - Other objects and advantages of the invention will 20 cyclohexane-acetone-methyl acetate ternary aze be apparent from the following speci?cation. otrope is considerably smaller. Thus, the addi ! have found, as described in U. 8. Patent tion of 18.0% by weight methyl acetate to a cy 2,212,810, that cyclohexane can be removed from clohexane-acetone mixture on distillation gives a mixture containing cyclohexane and substances a product containing 31.9% by weight cyclohex of similar boiling point, such as benzene (B. P. 25 ane, 50.1% acetone and 18.0% methyl acetate. 80.1" C.) (which cannot be distilled ordinarily The distillation occurs at 51.7-53.0. ' ' from cyclohexane, B. P. 80.8’ C.) by adding The general technique described inlU. S. Pat acetone to the mixture and distilling. As de ent 2,212,810 may be followed in the operation of scribed in the ‘patent previously referred to,‘I ' the present invention, the prime diiference ‘be have found that acetone forms a binary azeotrope 30 tween the present invention and that described with cyclohexane (67.3% acetone by weight) in U. S. Patent 2,212,810 being in the use of which boils at a lower temperature (53.1" C.)' methyl acetate in place of or together with the than either acetone or any benzene-'cyclohexane acetone of my prior application. Thus, when mixture and a weight ratio of acetone‘ to cycle treating cyclohexane-benzene mixtures for re of at least 2.0:1.0 is preferable when sep 35 covery of benzene or cyclohexane, or both, each arating thesev substances by distilling under a in the pure form, methyl acetate may be 'added to pressure of one atmosphere. the cyclohexane-benzene mixture to which ace According to the present invention cyclohexane tone has previously been added or to which ace- _ can be removed ‘from a mixture containing cy tone may be simultaneously added and the mix clohexane and substances of a similar boiling 40 ture thereafter distilled. Preferably, at least 2 point by adding methyl acetate to the mixture parts by. weight of methyl acetate are employed and distilling. Methyl acetate and cyclohexane per part of cyclohexane'. ' form a binary containing 77.7% methyl acetate In the preferred operation of this invention, and 22.3% clclohexane, the binary boiling at methyl acetate is utilized together with acetone 553° C. As an added and preferred feature of 45 in the removal of cyclohexane from benzene or the present invention, cyclohexane is removed conversely in the removal of benzene from cy from a mixture containing cyclohexane and sub clohexane because of the smaller quantities of stances of a similar boiling point by adding. methyl acetate necessary when used in conjunc methyl acetate and acetone to the mixture and tion with acetone. distilling. The addition of acetone and ‘methyl 50 The process of this invention preferably in acetate to the cyclohexane-containing mixture volves -washing of the azeotrope formed permits a more emcient separation than when between methyl acetate‘ and cyclohexane, if acetone alone is utilized in the process such as methyl acetate is utilized alone for cyclohexane described in U. 8. Patent; 2,212,810 which ‘relates removal and the process, is carried out by con to the-separation of cyclohexane from benzene. 55 ducting the binary to the bottom of the ba?le 2 ' r 2,270,194 _' " " - tower down which water is flowing. The com . cyclohexane-acetone-methyl acetate ternary is, tercurrent ?ow of the methyl acetate and water - then separated into ‘its constituents by counter-_ affects solution of the methyl acetate in water currentwater extraction such as previously out;v and release of the cyclohexane which rises to the , lined and the acetone-methyl acetate binary is‘ ' top of the tower and is‘ removed by decantation. ,6 recovered from the water by simple dis The methyl acetate dissolved in the water may tillation; . be recovered for further use by distillation from Following the removal of cyclohexane, the re- ‘ 1 its mixture with water. The cyclohexane may be sidual mixture of acetone, isopropanol, and ben obtained chemically pure by removing the traces zene is tapped to remove acetone and the un of residual water by distillation or by the use 10 converted benzene and isopropanol are returned of common drying agents. . - to the unit for reprocessing. ' When the mixture of methyl acetate and ace While I have illustrated my invention by cer tone are utilized according to the preferred em taln applications, I do not limit my claims to ' bodiments of this invention, the same water-wash such speci?c'cases, for there are many possible treatment of the ternary azeotrope formed be-_ 15 problems of separation‘where their solutions may tween methyl acetate, acetone and cyclohexane is ' be employed as a basic principle the recovery of carried out as has been described in connection cyclohexane from mixtures by means of its azeo- _ with the removal of methyl acetate from cyclo trope with methyl acetate or its ternary with hexane by water-washing. The same effect is ob methyl acetate and acetone. ’ served, namely; the cyclohexane rises to the top 20 1 claim: ‘ of the tower and is removed by. decantation, 1. ‘A method for the ‘removal of cyclohexane whereas the methyl acetate and acetone are dis from admixture with benzene which comprises solved in the water and removed by distillation treating a cyclohexane-benzene-containing mix as an- azeotrope which may be recycled or sepa- _ ture wtih methyl acetate and distilling off the re rated for further usein cyclohexane separation. 25 sultant cyclohexane-methyl-acetate-containing ' The process as above described may be applied azeotrope. _ to anymixture of compounds containing cyclo '2. A method for the-removal of cyclohexane -hexane, provided the boiling temperatures of the from admixture with acetone and benzene which additional constituents or any azveotrope mixture comprises treating the cyclohexane-containing between .suchcon'stituents or between such con- 30 mixture with methyl acetate and the stituents and methyl acetate or acetone or both resultant cyclohexane-methyl acetate-ternary are su?iciently remote from the boiling temper azeotrope. . atures of the cyclohexane-methyl acetate binary ’ _3. A method for the‘ removal of cyclohexane. or the cyclohexane-methyl acetate-acetone ter from admixture with benzene which‘ comprises nary. In certain cases involving constituents, as treating the .cyclohexane-containing . mixture part of whichare water soluble, water extraction with methyl acetate and distilling off the result ‘may be substituted for distillation. None .Of' - ant cyclohexane-methyl acetate-containing azeo these primary treatments are necessary, however, trope and thereafter removing the cyclohexane in the following illustrative case, the technique by treating the resultant distillate with water. 'of which I have successfully employed in con- 40 4. A method for the removal of cyclohexane junction with a process and ‘the simultaneous from admixture with acetone andbenzene which manufacture of acetone and cyclohexane by ex comprises treating the cyclohexanekoontaining change of between isopropanol and mixture with methyl acetate and distilling oi! the benzene as described in copending application of. resultant cyclohexane-methyl acetate-acetone E.,P.~Bartlett, 8. N. 265,932. " I‘ 4, ternary azeotrope andthereafter removing the ~ vis a process of this type involves equilibrium, ‘’ cyclohexane by treating the resultant distillate the product is a mixture of isopropanol, acetone, with water. ' ' benzene and cyclohexane. Such a mixture con 5. A method for the removal of cyclohexane tains constituents for forming at least three dif- ' from admixture‘with benzene which comprises ferent azeotropic mixtures. Benzene-isopropanol treating the cyclohexane-containing] mixture ’(boiling point 71.9“ C), cyclohexane-isopropanol with methyl acetate in the proportions of at least (l3. P.'d8.6° C.) , both of which are revealed in the 2.0 parts‘of methyl acetate per part of cyclohex- ' literature, and acetone-cyclohexane (B. P. 53.1° ane and thereafter distilling oi! theresultant C). From such- a mixture cyclohexane may be cyclohexane-methyl acetate-containinz_ areo removed quantitatively in the form of a ternary '_ trope. azeotrope_with acetone and methyl acetate. ~ A 6° . 'EDMUND FIELD.