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Patented Mar. 2, 1937 2,072,806 ’ _' UNITED STATES PATENT ‘OFFICE 2,072,806 PROCESS FOR THE SEPARATION O15‘v PRI MARY FROM SECONDARY ALCOHOLS Dennistoun Wood, Jr., Palo Alto, Calif., assignor to E. I. du Pont de Nemours & Company, Wil mington, Del., a corporation of Delaware No Drawing. ApplicationJanuary 6, 1933, Serial No. 650,508 4 Claims. This invention relates to a process for the separation of primary from secondary alcohols contained in a mixture thereof and particularly to the separation of such alcohols contained in a 5 mixture of oxygenated organic compounds ob tained by the catalytic hydrogenation of carbon oxides under pressure. The orthodox method for separating primary from secondary alcohols involves, generally, 10 heating the mixture of alcohols in a benzene so lution with phthalic anhydride. The primary al cohols react with phthalic anhydride to form the esters more readily than do the secondary alco hols and usually the half-ester is produced. The ' ' (0]. 260—1576) thermal treatment, the anhydride and the pri mary alcohol. Other objects and advantages will‘ hereinafter appear. . I have found that ‘primary alcohols can be separated from secondary alcohols by treating a 5 mixture of them with phthalic anhydride in ac cord with the present invention without the many di?iculties inherent in the above method of separation. Furthermore, I have found that in lieu of using phthalic anhydride a number of 10 other anhydrides may be employed for eiiect ing the separation providing these anhydrides from esters with the primary alcohols which have boiling points greater than the boiling points of 15' resulting benzene solution is then cooled to crys ' the mixture of alcohols being treated and furtallize out the phthalic anhydride which has not ther providing they can be reconverted upon reacted, and is subsequently treated with just thermal decomposition into the anhydride. Generally speaking, my process may be car enough alkali to change the monophthalate of the primary alcohol to an alkali monoalkyl ried out in the following manner, for the separa 20 phthalate. By means of this alkali treatment tion of a mixture of alcohols containing both the alkali monoalkyl phthalate containing the 'the primary and secondary alcohols. The mix primary alcohols separate in the lower layer ture is heated with the anhydride until solution is complete and the resulting solution is then're from the benzene containing the unreacted sec ondary alcohols which collect in the upper lay ?uxed at a temperature somewhat ,below the 25 er. The layers are separated and washed-the boiling point, until all of the alcohols present, alkali layer with benzene and the benzene layer which will react with the anhydride, have react with water. A fair degree of separation of the ed. The temperature is then raised, whereupon the unreacted alcohols will distill over leaving alcohols may be obtained The separated alka line portion is then further treated with excess behind the half-ester formed between the pri 30 alkali to give the di-alkali phthalate, and the mary alcohols and the anhydride. In order not to decompose the half-ester the temperature of primary alcohols, which are released by this re this preliminary distillation should be as low action, may then be removed by steam distilla tion. The secondary alcohols are separated by as possible, and it is, therefore, of advantage to distillation from the benzene layer. By this conduct it under a fairly high vacuum,—say, from 1 to 50 mm. of mercury. The remaining 35 treatment, of course, there remains as a by product the di-alkali salt of phthalic acid which half-ester is further heated usually under pres cannot again be used in the process until it has sure, whereupon it \will be decomposed, the pri been reconverted to the anhydride. mary alcohols distilling over leaving behind'as a residue the anhydride. An object of the present invention is to pro 40 vide a process for the separation of primary When effecting the separation of primary from from secondary alcohols having many outstand secondary‘ alcohols present in a mixture of oxy genated organic compounds obtained by the ing advantages over the orthodox method de scribed above. A further object of the invention catalytic hydrogenation of carbon oxides under is to provide such a process for the separation pressure, (these compounds may be made ac 45 of the primary from the secondary alcohols cording to any of the known processes therefor, found in the mixture of oxygenated organic com e. g. those described in U. S. Patents Nos. 1,820, pounds obtained by the catalytic hydrogenation 417 and 1,844,857), or other mixtures contain ing primary and secondary alcohols, there may of; carbon oxides under pressure. A still fur thér object of the invention is to provide a proc be present in these mixtures a number of un known organic substances which are separated 50 ess for the separation of primary from second ary alcohols by the aid of an anhydride which with the primary or secondary alcohols portions. forms an ester with the primary alcohols having Hereinafter, therefore, when referring to the sub a boiling point higher than the ‘boiling point of stances separated by my process from such mix the unreacted secondary alcohols present and tures, in order to include all of those contained 55 which can be readily decomposed to give, by in the portion removed by esteri?cation from the 15 20 25 30 v35 40 45 50 55 > 2 aoveicoa ' _- > I. ' v ‘ \ portion left unesteri?ed, the portions will be -ment, to e?ect a separation of the alcohols from designated as the esteri?ed and unesterified por a fresh mixture thereof. , tions respectively, the former including the pri In order to increase the “rapidity of v the es- " mary and reactive ‘alcohols, the-latter the sec teri?cation stage suitable catalysts may be pre ondary and nonereactive alcohols. " sent, such, for example, as sodium‘ or lead oxide, When separating the primary from the sec ondary alcohols, or ester-forming from non-‘ester forming compounds present in a mixture of oxy although their presence is by no means essential to the operation of the’ process. The temperature used for eifecting the es genated organic ‘compounds obtained by the teri?cation as well as that used to distill over the 10 catalytic hydrogenation of carbon oxides under unes'teri?ed compounds and ?nally that employed pressure, I prefer generally to use phthalic an for decomposing ‘the anhydride will, ' of course hydride, although for the separation’of' the al be determined by the mixture of compounds be cohols present in this mixture, as well as for the ing separated as well as the anhydride being, separation of similar alcohols from any other’ utilized to e?’ect the separation. ‘Ordinarily it 15 mixture containing them, the anhydrides of the has been found advantageous to use a fairly 15 following acids may be employed: adipic, suc high vacuum when e?’ecting by distillation the cinic, sebacic, tartaric, trimesic, hexahydro separation of the unesteri?ed from the esteri?ed phthalic, tetrahydrophthalic; and in many in compounds,_ and when decomposing the half-es stances the anhydride of thehmonobasic acids ter of'thev anhydride, pressure is often of ad may be used, such, for example, as propionic, vantage to facilitate rapid and thorough decom 20 butyric, isobutyric, etc. ' position. \ I will now give an example to illustrate more‘ speci?cally one method by which my process From a consideration of the above specification it will be realized that any process for the sep may be carried out, but it will be understood that aration of primary from secondary alcohols or 25 I shall not be restricted by the details therein the esteri?able from the non-esteri?able por 25 given except as they, may be limited in the» ap tions of a mixture of oxygenated organic com pended claims. 7 pounds will come within the scope of this inven ' EmampZe.—-96,300 cubic centimeters of the tion, if such a separation is e?'ected by the proc oxygenated organic compounds, obtained by the catalytic hydrogenation of carbon oxides'under ess hereinbefore described. pressure, boiling between approximately 133~147° ' 1. In a process for the separation of easily esteri?able'portions from the more di?icultly es teri?able portions of a mixture of oxygenated 0., and which contain approximately 54% pri mary and 40% secondary alcohols including such alcohols as 2,4-dimethyl pentanol-3, 3-methy1 35 pentanol-2, 2-methyl pentanol-l, etc., the re I claim: Y . . 30 organic compounds obtained by the catalytic hy drogenation of carbon oxides under elevated tem 35 maining 6% comprising ketones and other com perature and pressure the steps which comprise pounds, were mixed with 190 lbs. of ?aked - esterifying the easily esterifiable portion of the phthalic anhydride. The mixture was heated mixture of compounds with an organic dibasic to e?ect solution of the anhydride in the mix acid anhydride which forms'therewith an ester, 40 ture of compounds and then re?uxed at a tem the boiling point of which is higher than the boil perature of approximately 100° C. and one at mosphere of pressure in order to convert the pri mary alcohols present into the half-ester of ing point of the unesteri?ed portion of the mix- ' phthalic acid. After approximately 12 hours, the by thermal decomposition splitting up the ester, thereby reforming the anhydride and the ester 45 esteri?cation was considered to be complete and the temperature of the mixture was then raised and the pressure lowered to approximately 5 cm. of mercury and between the temperatures of 110-140° ‘C. 75,200 0. c. distilled over, constitut ing approximately all of the unesteri?ed com pounds present in the mixture of compounds and containing substantially all of the secondary alcohols. The temperature of the mixture was further raised and between 140_-160° 0., which ture of compounds, separating by distillation the resulting ester from the unesteri?ed portion and ifled portion. 1 - 2. In a processfor the separation of easily esteri?ableportion’from the more di?icultly ester i?able portion of a mixture of oxygenated or ganic compounds obtained by the catalytic hy drogenation of carbon oxides under elevated temperature and pressure, the steps which com prise esterifying the easily esteri?able portion of the mixture of compounds with phthalic anhy 55 may be designated as the transition stage, the dride, separating by distillation the resulting last of the unesteri?ed compounds distilled over along with some of the products resulting from the decomposition of the .phthalic ester. The pressure was then vraised to-approximately one atmosphere and from 160° C. up 25,000 0. c. of phthalate from the more di?lcultly esteri?able the phthalate decomposed releasing primary al cohols and esteri?ed compounds which distilled ' over, leaving as a residue phthalic anhydride. The primary and secondary alcohols obtained in 65 accord with this process can then be separated by fractional distillation or by other suitable methods into the individual alcohols. The advantages derived from utilizing my process are apparent when it is realized that all of the laborious extraction and washing opera tions present in the former orthodox method have been eliminated, and, furthermore, the anhydride obtained upon the thermal decomposition ,of the 75 half-ester is ready for use, without further treat portion and’ by thermal decompositionreforming the esteri?ed portion from the reconverted phthalic anhydride. ' 3. In a process for the ‘separation of the pri mary alcohols from the secondary alcohols pres ent in a mixture of-oxygenated organic com pounds obtained by the catalytic hydrogenation of carbon oxides under elevated temperature and ' pressure, the steps which comprise esterifying the primary alcohols of the mixture of compounds with an organic dibasic acid anhydride which forms therewith an ester, the boiling point of which is higher than the boiling point of the sec ondary alcohols present in the mixture of com pounds, .separating by distillation the resulting ester from the secondary alcohols and by thermal decomposition splitting up the ester, thereby re forming the dibasic acid anhydride and the pri mary alcohols. 1 50 2,072,806 4. In a process for the separation of the primary alcohol portion from the secondary alcohol por tion of _a mixture of oxygenated organic com pounds boiling between 133 and ‘147° C., and ob tained by the catalytic hydrogenation of carbon oxides under elevated temperature and pressure, the steps which comprise reacting 96.3 liters of the- oxygenated organic compound with approxi mately 190 pounds of ?ake phthalic anhydride,‘ 10 heating the resulting mixture to 100° C., and re 3 ?uxing for approximately 12 hours, distilling the resulting product under a vacuum oi.’ approxi mately 5 centimeters of mercury and at a tem perature of from 110 to 140° ‘0., to remove the secondary alcohols and the unesteri?ed products, raising the pressure to approximately 1 atmos phere and the temperature to from approximately 160° 0., up and distilling of! the primary alcohols by decomposition of the phthalates. DENNISTOUN WOOD, JR.