Patented Mar. 2, 1954 2,671,052

' UNITED STATES PATENT OFFICE

Christi, Tex., assignors to. Celanese Corpora tion of America, New York,_ N. Y., a corporation of Delaware N 0 Drawing. ApplicationNovember 13, 1951, Serial No. 256,123 4 Claims. (Cl. 202-395‘) ‘ V 1 This invention relates to the separation. of or ganic compounds. and relates more particularly 50 to 75% by weight, an excellent separation may to an improved process for the separation of be achieved‘ with the methylv acetate remaining methyl acetate from a m‘xture of organic com behind in the aqueous-bottom product beingv so pounds. small as to be undetectable by chemical analy An object of this invention is the provision of SIS. an efficient process for the separation of methyl Reflux ratios of ‘from 5 to I up to about l0‘to 1 acetate from a mixture of organic compounds may be employed‘. Preferably, the water con containing methyl acetate and including pro centration is maintained at 67% by weight in the pionaldehyde, acetone, methanol and other al liquid phase on the upper trays of the column cohols. ~ 10 with a re?ux ratio of‘ 6‘t'o- 1 being employed‘. Other objects of this invention will appear In order’ further to illustrate the novel process from the following detailed description. of our invention but without being limited‘ there In many industrial operations or processes, to the following example is given: mixtures of organic compounds are formed. Example Normally, these mixtures, for obvious economic reasons, are not discarded but are subjected to 2 parts by weight per minute of a crude mix some subsequent treatment in order that the ture containing 50% by weight of methyl acetate, mixtures may be separated into the various 5% by weight of propionaldehyde, 33% by weight components present. One such mixture is ob of acetone, 10% by weight of methanol and other tained as a crude fraction during the treat 20 alcohols, and 2 o by weight of water is fed to a ment of the product of the liquid phase oxi 50-tray distilling column at the 20th tray from dation of aliphatic hydrocarbons, such as n the top and 10 parts by weight per minute of butane or isobutane, for example. This crude Water are introduced into the column at about the fraction comprises a mixture of methyl ace 5th tray from the top. The concentration of tate, propionaldehyde, acetone, methanol and 25 on the upper trays is other alcohols. The separation of the methyl about 67% by weight. The re?ux is maintained acetate from this mixture by an ordinary at a rate of 5 parts by weight per minute and straight distillation is not feasible because of methyl acetate is taken off overhead at a rate of the several azeotropes formed and other meth 1 part by weight per minute. A small amount of ods are required if the desired separation is 30 acetone comes over with the methyl acetate un to be effected in ‘an efficient and economical der these conditions. The distillate contains 91 % manner. by weight of methyl acetate and 6% by weight of We have now found that methyl acetate may acetone. During a continuous operation of 8 be separated satisfactorily from such a mixture hours, it is found that about 99% of the methyl of organic compounds comprising essentially pro 35 acetate introduced into the system with the pionaldehyde, acetone, methanol and other alco crude aqueous feed is recovered in the overhead hols, by subjecting the mixture to an extractive product. The aqueous mixture separated from distillation employing water as the extracting the base of the column may be subjected to sep agent. The methyl acetate is found to distill arate distillation in order to remove the acetone, over and is obtained as the overhead product 40 propionaldehyde and other organics while the remainder of the organic compounds is contained therein. recovered from the column in which the distilla It is to be understood that the foregoing de tion is carried out as an aqueous bottom product. tailed description is given merely by way of illus In order to carry out the novel distillation proc tration and that many variations may be made ess of our invention, the crude mixture of organic 45 therein without departing from the spirit of our compounds is charged to a fractionating column invention. provided with suitable bubble cap trays or pack Having described our invention, what we desire ing to insure satisfactory vapor-liquid contact to secure by Letters Patent is: ‘and water is fed into the column above the point 50 1. Process for the separation of methyl acetate or above the tray at which the feed containing from a mixture of organic compounds contain~ the methyl acetate is introduced. By introducing ing methyl acetate, propionaldehyde, acetone, water in the column at a rate sufficient to main methanol and other alcohols, which comprises tain the concentration of water in the liquid subjecting said mixture of organic compounds phase on the upper column trays at from about to an extractive distillation employing Water as 55 the extractant and taking methyl acetate off as 2,671,052 4 anol and other alcohols, which comprises sub the overhead product, the residual aqueous mix jecting said mixture of organic compounds to an ture containing substantially all or the propion extractive distillation employing water as the aldehyde of said mixture of organic compounds. extractant, maintaining the concentration of 2. Process for the separation of methyl acetate water in the liquid phase at about 67% by weight from a mixture of organic compounds containing and the re?ux ratio at about 5 to 1, and taking methyl acetate, propionaldehyde, acetone, meth methyl acetate o? as the overhead product, the anol and other alcohols, which comprises sub residual aqueous mixture containing substantially jecting said mixture or organic compounds to all of the propionaldehyde of said mixture of an extractive distillation employing water as the 10 organic compounds. extractant, maintaining the concentration of ROBERT L, MITCHELL. water at from about 50 to ‘75% by weight in the JAMES W. WALKER. liquid phase and taking methyl acetate off as the overhead product, the residual aqueous mix References Cited in the ?le of this patent ture containing substantially all of the propion aldehyde of said mixture of organic compounds. 15 I UNITED STATES PATENTS 3. Process for the separation of methyl acetate Number Name Date i'rom a mixture of organic compounds containing 1,929,901 Ricard et a1. ______Oct. 10, 1933 methyl acetate, propionaldehyde, acetone, meth 2,290,636 Deanesly ______July 21, 1942 2,514,967 Pierotti ______July 11, 1950 anol and other alcohols, which comprises sub 20 ,jecting said mixture of organic compounds to an 2,551,625 Morrell et al ______May 8, 1951 extractive distillation employing water as the OTHER REFERENCES extractant, maintaining the concentration of “Handbook of Chemistry and Physics,” Twen water at from about 50 to ‘75% by weight in the ty-eighth Edition, published 1944 by Chemical liquid phase and the re?ux ratio at 5 to 10 to 1, 25 and taking methyl acetate off as the overhead Rubber Publishing Company, 2310 Superior Ave "product, the residual aqueous mixture contain nue, Cleveland, Ohio, pages 556, 557, 972. ,ing substantially all of the propionaldehyde oi Maurice Lecat, “Tables Azeotropiques,” Second Edition, vol. 1, published 1949 by the author, 29 said mixture of organic compounds. Rue Auguste Danse, Brussels, Belgium, pages 4. Process for the separation of methyl acetate 30 vfromv a mixture of organic compounds containing xi, xii, 156, 214, 352. _methyl acetate, propionaldehyde, acetone, meth