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Patented cc. 1?, 1946 STATS 2,412,650 PROCESS OF SEPARATING 3-PICOLINE, 4-PICOLINE, AND 2,6-LUTIDINE George Riethof, Mount Lebanon. Pa. No Drawing. Application June 15, 1945, Serial No. 599,766 7 Claims. (Cl. 202-42) 1 2 This invention relates to a separation process; and more particularly it relates to the separation of 3-picoline, é-picoline, and 2,6-luticline from one another. in that the beta picoline can be obtained sub stantlally pure and in a much simpler operation. There is no separation to be carried out before the beta picoline comes over, as the fractional pounds, 3-picoline, 4-picoline, and 2,6-lutidine is distillation of the maximum azeotrope has only to separate the beta picoline from the gamma by the basic coal tar oils in which they commonly occur associated with one another. These basic coal tar oils may be practically fractionated to an operation which in effect is similar to a ?rst cut in a distillation procedure. It is a principal object of this invention to pro One of the principal sources of these three com produce certain cuts composed predominately of 10 vide a process for the separation of B-picoline, a mixture of 3-picoline, é-picoline and 2,6 lutidine. Hence, these materials are generally commercially obtained as a basic oil mixture 4-picoline and 2.6-1utidine from one another and from basic coal tar oils comprised predominately of these compounds. It is a further object to provide a process for boiling about 140-145" C. Since these compounds boil so closely together, it is not commercially 15 resolving 3-picoline, 4-picoline and 2,6-lutidine containing oils into their separate components feasible to fractionate such basic oil mixtures into which can be easily operated with close control their separate components. so as to yield commercially pure products. In my co-pending application, Serial No. It is a still further object to provide a new 535,397, ?led May 12, 1944, now Patent 2,383,016, granted August 21, 1945, I have disclosed that 20 separation process which employs the use or" maximum boiling azeoptropic mixtures. such bases may be separated from each other and Additional objects and the entire applicability recovered by azeotropic distillation utilizing a of the present process will become more apparent maximum boiling azeotrope and the process is from the description of the invention given here carried out by admixing a suitable quantity of is’) in inafter. phenol with the basic oils. The objects are accomplished according to the I have now discovered that formic acid may be process of my invention by admixing the indi employed to recover such bases by a process of cated basic oils with a suitable quantity of formic azeotropic distillation utilizing a maximum boil acid and distilling from this mass the maximum ing point azeotrope. The use of such acid has boiling azeotropes of the basic components of certain advantages over phenol. the oil with the acid and separately collecting the The azeotrope formed with formic acid boils various fractions, between 155° and 165° C. but by using these high The process of this invention is more fully illus temperatures, the formic acid decomposes rapid trated in the following example, in which all ly and therefore is not useable. I have found parts are by weight unless otherwise speci?ed. that formic acid becomes useable if the distilla tion is carried out under a sufficiently reduced Example pressure, e. g., 100 mm. to 200 mm. of mercury to thereby lower the temperature of the maximum azeotrope so far, that none or very little decom A commercial mixture of 300 parts of a basic coal tar oil containing approximately 30% 2,6. lutidine, 35% 3-picoline and 35% 4-picoline is position of formic acid occurs. Moreover, and 41 quite unexpectedly there is obtained a new result. charged into the still pot of a rather high e?~ That is, I ?nd in all other maximum azeotropes ciency fractionating column. To this basic oil is such as those produced with phenol, acetic, pro added 450 parts of formic acid (90% concentra pionic and isobutyric acids, the order of dis tion) , a ratio of acid to basic oil of about 4 to 3. tilling over of the different picolines is ?rst, 2-6 a 1.1 The acid/basic oil mixture is then subjected to lutidine, 2nd, beta picoline and 3rd, gamma pico fractional distillation through the column under line. On the other hand, the formic acid azeo trope distills over in a different order namely, first beta-picoline, 2nd, gamma picoline, and 3rd, 2-6 lutidine. Thus, the lowest boiling maximum azeotrope in the case of the phenol and the all phatic acids becomes the highest boiling azeo a pressure of about 200 mm. of mercury and a temperature of about 110 to 125° C. or a pressure of about 100 mm. of mercury and a temperature of about 98 to 110° C. A forerun of approxi~ mately 100 cc. of the total mixture, mostly of aqueous formic acid, is collected after which the trope by using formic acid. Since the most valu maximum boiling azeotropes of B-plcoline, Isl-pic able component of the basic oils is the beta pico- ‘ oline and 2.6-lutidine distill over and are collect line, this formic acid process has great advantage 55 ed in that order. - 2,412,850 4 3 In order to obtain 3-picoline of even higher purity the ?rst cut or 3-picoline/acid azeotrope is again fractionated through a similar column and a fraction of 80% to 90% is collected. This middle fraction is then treated with an excess of sodium hydroxide solution and the 3-picoline is distilled off. The 2,6-lutidine and the 4-picoline fractions are treated in a similar fashion in order to obtain the substantially pure compounds. The temperature range as given above as Well as the pressure ranges may of course be varied but pressures and temperatures are utilized of an 2. The process-of claim 1 wherein the distillates are acid azeotropes of said bases. 3. The process of claim 1 wherein the distillate fractions boiling in the range between substan tially 98-125° C. under a pressure of about 200 to 100 mm. of mercury are separately collected. 4. The process of claim 1 wherein the distillate fractions boiling in the range between substan tially 98-125” C. under a pressure of about 200 to 10 100 mmv of mercury separately collected and redistilled. 5. The process of claim 1 wherein the distillate fractions boiling in the range between substan order which is effective to prevent decomposition tially 98-125" C. under a pressure of about 200 to of the formic acid and assure that the fractions 15 100 mm. of mercury are separately collected and redistilled and wherein the redistilled fractions will distill over in the manner above described with the beta picoline constituting the ?rst cut. are treated to recover the substantially pure base The ratio of formic acid to basic oils as illus contained therein. 6. The process of separating a mixture con trated in the above example may be varied but preferably more acid by weight is employed than taining at least two of the bases S-picoline, é-plc the weight of the oil and it has been found best oline and 2,6-lutidine which comprises including to employ an amount of the acid effective to form in the mixture formic acid, fractionally distilling an azcotrope with all of the basic oil present, plus the mass, and thereafter recovering from the allowance for some decomposition of formic acid. fractions the substantially pure case contained The composition of the basic oil being treated 25 therein, the fractional distillation being under re may be varied. However, this process is princi duced pressure and at a temperature effective to pally applicable to those basic oils which are com susbtantially prevent decomposition of the formic posed predominately of 3-picoline, 4-picoline and 2,6-lutidine. The ratio by weight of these latter acid, '7. The process of separating a mixture pre materials may be varied relative to one another. 30 dominately containing at least two of the bases Iclaim: l. The process of separating a mixture pre 3-picoline, el-picoline, and 2,6-lutidine which comprises including in the mixture formic acid dominately containing at least two of the bases and fractionally distilling the mass under re— B-picoline, é-picoline, and 2,6-lutidine which duced pressure, the fractions distilling over as comprises including in the mixture formic acid 35 3-picoline, 4-picoline and 2,6-lutidine in the order and fractionaiiy distilling the mass under reduced named. pressure. . GEORGE RIETHOF'.