NOV- 29, 1949 c. s. cARLsoN ETAL 2,489,619 ‘ RECOVERY OF NORMAL PROPYL __./'FRQM OXYGENATED COHPOUNDS ' Filed Aug. 23, 1948

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Carl 6. Carlson ~ T2411 6.32.051: tson. {inventors Carter E.‘ orLer I bg M Clbborneg Patented Nov. 29, 1949 2,489,619

UNITED STATES ‘PATENT ' OFFICE

RECOVERY OF NORMAL PROPYL ALCOHOL ' FROM OXYGENATED COMPOUNDS Carl S. Carlson, Elizabeth, N. J ., Nat C. Robertson,. Corpus Christi, Tex., and Carter E. Porter, Cranlord, N. J., assignors to Standard Oil De velopment Company, a corporation of Delaware Application August 23, 1948, Serial No. 45,724 11 Claims. (Cl. 202-42) - 1 ‘This invention relates to the puri?cation of n Bolling propyl alcohol, and particularly, to the puri?ca Boiling P omt- (H10 tion of an aqueous n-propyl alcohol fraction Ccmpound Poirétédry), Azeotropmy which is contaminated with other close-boiling l ' 0 C. oxygenated compounds, such as other , 5 ' Ethyl Alcohol ______._ 78. 3 78. 1 esters, aldehydes and ketones. ______82. 4 80. 2 The drawing shows diagrammatically a train n-propyl Alcohol. _ _ 97. 2 87. 7 Ethyl Propionatc ______99. 1 81. 2 of apparatus for carrying out my process. Sec Butyl Alcohol. 99. 5 87. 7 Numerous processes are known in which an propyl Acetate 101. 6 82. 4 10 t amyl Alcoh ._ 102. 4 87. 2 aqueous solution of a mixture of oxygenated com Isobutyl Alcohol 108. 1 89. 8 pounds are produced. Typical of these processes sec-Butyl acetate . _ _ _ _ . _ _ _ __ 112. 0 y 87. Isobutyl Acetate- ___ 117. 2 ‘ 87. 4 are the well-known Fischer ‘synthesis, wherein . n-butyl Alcoh _ . _ 118. 92. 3 hydrocarbons and oxygenated compounds are Ethyl Butyrate__-__ 121. 6 87. 9 produced by the reaction between oxides of car Paraldehyde ______124 90. 4 bon and in the presence of catalyst; 15 the numerous processes employed for the oxida It will be seen from the above range of boiling tion and partial oxidation of petroleum hydro points that the separation of an aqueous mixture carbons, particularly the lower aliphatic hydro of the above materials or any number'of them by carbons; and the so-called “0x0” process, where fractional distillation, would be a very di??cult in ole?ns are reacted with carbon monoxide and 20 procedure, demanding highly e?icient fraction hydrogen in the presence of a catalyst. ation. The presence of water during fractional A typical mixture consisting substantially of distillation is conducive to the formation of the n-propyl alcohol, which is to -be puri?ed accord binary aqueous azeotropes which boil so closely ing to the terms of this invention, has the follow that separation is practically impossible on an 25 economic basis. ing composition. ‘ This invention provides a means whereby'n propyl alcohol can be substantially freed from Component Amount other close-boiling components by distillation, by Wt. Percent the creation of other azeotropes in the system 2-6 Aldehydes ______. . 30 which make the separation'easier as a result of Esters . _ _ . . _ _ . _ . _ _ _ _ _ . _ _ _ _ . ______. __ 0. 2-3 the increase in boiling point spread between the Water ______28~29 Alcohols (principally n-propyl) _ . _ _ _ 62-69. 8 azeotropes so produced and the azeotrope of n Ketones . ______. _ _ _ _ _ . ______. _ _ _ Trace propyl alcohol; According to the terms of this invention an The alcohols involved included ‘on an alcohol 35 aqueous “n-propyl cut” is puri?ed by an azeo basis, analyzed as follows: tropic distillation process wherein the harmful Volume per cent close-boiling impurities are removed overhead by an aliphatic ether entrainer. The aliphatic ether n-Propanol ______90 employed according to the terms ofthis inventionv i-Propanol ______6 40 is one boiling between 55° C. and 110° C., but pref Sec. BuOI-I ______2 erably an aliphatic ether boiling in the range ______2 of 55° C. to '70 C. i-BuOH ______Trace The following ethers are suitable: The above analysis is typical of the so-called “n Boiling point ‘’ C. propyl cut” obtained from the water-soluble neu 45 tral products of the Fischer synthesis. Such a Diisopropyl ether ______67.5 out has a boiling range of 783° C. to 124° C., on Ethyl propyl ether ______64 an anhydrous basis, and a boiling range of 78.1° Chloro ethyl methyl ether ______59.5 C. to 92.3" C., on a wet basis. Tertiary butyl ethyl ether ______69 The following compounds are included among 50 Allyl ethyl ether ____'______67.6 those found in the “n-propyl cu.” The com Isobutyl methyl ether (at 741 mm) ______59 pounds are listed with their boiling points and Butyl methyl ether ______70 the boiling points of their aqueous azeotropes: Etc. 2,489,619 . 3 In the distillation puri?cation process employ is an ether boiling in the range of 70° C. to 110° 6., ing an ether boiling between 55° C. and 70° C., the provided one uses such ethers in controlled n-propyl alcohol does not azeotrope with the amounts so as to remove from the “n-propyl alco aliphatic ether nor with the aliphatic ether and hol cut” only those contaminants other than water; hence, its e?ective boiling point remains 5 n-propyl alcohol, or in amounts such that only a the same, thus permitting its separation from the very limited amount of n-propyl alcohol is re other impurities whose boiling points are e?ec moved with the ether. tively lowered due to the formation of azeotropes, In batch operation, however, the advantage is thus allowing the separation to occur. In car unique in that employing entrainers within the rying out the invention, suiiicient ether is added 10 narrow boiling range of 55° C. to 70° C. none of to the crude aqueous n-propyl alcohol mixture to the n-propyl alcohol whatever is lost overhead cause its dehydration and its puri?cation due to during removal of the impurities. ' the formation of azeotropes between the con Examples of the higher boiling ethers which taminants and the aliphatic ether employed. may be employed are: This invention is particularly applicable to the 15 Boiling point °C. recovery of n-propyl alcohol from an aqueous Amyl methyl ether ______88. 5 mixture comprising n-propyl alcohol, ethyl al Butyl methyl ether ______.._ 90-93 cohol, isopropyl alcohol, paraldehyde, and esters, Allyl ether ______94. 3 such as ethyl propionate, n-propyl acetate, iso Propyl ether ______.._ 91 butyl acetate, ethyl butyrate and secondary butyl 20 Ethyl isobutyl ether ______80 acetate. When such a mixture is subjected to Dichloromethyl ether ______105 fractional distillation in the presence of at least Etc. one aliphatic ether boiling in the range of 55° C. Although all of the ethers boiling in the range of to 110° C., and preferably, 55° C. to 70° C., an overhead distillate is produced containing sub 55° C. to 110° C. are operable under the conditions 25 stated, the unsaturated ethers are not preferred stantially all the ethyl alcohol, all of the isopropyl due to their tendency to undergo polymerization. alcohol, paraldehyde (in the form of acetalde Likewise, the chloroethers are not preferred due hyde produced by depolymerization) and all the to their tendencies to undergo hydrolysis during esters. The bottoms resulting from such an azeo tropic distillation consist substantially of n \distillation. The saturated ethers, among those propyl alcohol. 30 mentioned, are the preferred species according to When substantial amounts of the butyl alcohols the terms of this invention. are present, such as secondary butyl alcohol, The invention will be illustrated by the'puri? n-butyl alcohol, and isobutyl alcohol, and tertiary cation of a “n-propyl cut” from which secondary , the “n-propyl cut” is ?rst subjected butyl alcohol, isobutyl alcohol and tertiary amyl to a water extractive distillation whereby sec 35 alcohol have been removed, such as by a water ondary butyl alcohol, isobutyl alcohol, tertiary extractive distillation process previously de amyl alcohol and some isopropyl alcohol are dis scribed. The crude n-propyl alcohol feed will tilled overhead. Such a normal propanol cut con then consist of a mixture of ethyl, isopropyl, taining substantial amounts of the butyl alcohols 40 n-butyl and n-propyl alcohols, paraldehyde, and and tertiary amyl alcohol, has the following typi esters, such as ethyl propionate, n-propyl acetate, cal analysis: secondary butyl acetate, isobutyl acetate and ethyl butyrate. The crude aqueous “n-propyl Weight per cent alcohol cut” of the above composition is led to Water ______. _ _ __ _ 30 n-Propanol 59 fractional distillation zone 2 through line I. An Iso-propanol _ ‘ 4 45 ether of the type described, such as diisopropyl ether, is added to the tower via line 3. Alter n-Butanol ______. 1 natively, the ether entrainer could be added to Sec-butanol _._.. 3 the crude alcohol out prior to introduction of the Iso-butanol ______2 same into the fractionation zone. Su?icient heat Esters, carbonyls, t-amyl alcohol ______.. 1 50 is supplied to the fractionation zone, such as by In the water extractive distillation of such an a reboiler later described, so that an overhead n-propanol cut, more than 80 mol per cent water, distillate is obtained comprising re preferably above 84 mol per cent water is em sulting from depolymerization of the paralde ployed in the aqueous internal reflux.‘ The hyde, all of the esters, and all of the alcohols with aqueous bottoms obtained from the extractive 55 the exception of n-propyl alcohol and n-butyl distillation column which contain some n-butyl alcohol. These impurities present in the distillate alcohol is then concentrated by normal fractiona will 'beeither inthe form of their water azeo tion to remove as much water as possible, that is, tropes, of their binary azeotropes with diisopropyl to bring the water content thereof as close to the ether, or as their ternary azeotropes with water azeotropic water composition as is economically 60 and diisopropyl ether. The distillate vapors are possible. The n-propyl alcohol fraction thus freed removed from the fractionation zone via line 4, of secondary butyl alcohol, isobutyl alcohol, ter condensed in condenser 5 and led via line '6 to a tiary amyl alcohol and some of the isopropyl alco settling zone ‘I. In the settling zone the con hol is then ready to be fed to the azeotropic dis densed distillate separates into an upper ether tillation column wherein the action of the ether 65 layer and a lower water layer. The condenser is azeotrope-former completes the dehydration and thoroughly mixed before settling. The upper the removal of all the impurities from the n-pro ether layer is re?uxed, in whole or in part, via pyl alcohol except n-butyl alcohol which can then line 8 to fractionation zone 2. Excess ether may be removed by ordinary fractional distillation. be removed from the system via line ll. Esters When an ether boiling in the range of 55° C. 70 present in the distillate are more soluble in other to 70° C. is employed, no n-propyl alcohol what than in water but when present in low concen soever is lost in the form of an azeotrope with the trations in the feed, they will be continuously re ether. However, in a continuous distillation proc moved from the distillate by water. However, the ess, one may employ an ether which is capable of ether layer may be distilled or water-washed for forming an azeotrope with n-propyl alcohol, that 75 further removal of water-soluble impurities there 2,489,619 6 from before it is re?uxed to the fractionation zone therefrom. About 4 per cent of ethanol and iso via line 8 and/or line 3. The lower water layer is propanol were found in the distillate which cor responds to approximately the ethanol and iso led via line 9 to a second fractionation zone l0 ' wherein the water layer is fractionated for more propanol composition of the original feed.v No complete removal of water therefrom. In the ethanol or isopropanol could be found in the bot fractionation zone 10 the esters, alcohols and toms from the azeotropic distillation zone. acetaldehyde are recovered overhead via line H These bottoms analyzed as follows: in concentrations at least equal to their water Wt. per cent azeotropes. Excess water is removed from the n-Propanol ____ -_.______'______1 97.5 10 system via line 82. Bottoms consisting substan Acid (as acetic) ______0.1 tially of anhydrous n-propyl alcohol and n-butyl Ester (as ethyl acetate) ______0.4 alcohol are removed from fractionation zone 2 via Aldehyde, (as butyraldehyde) ______0.7 line l3. A portion of the bottoms being removed Ketone (MEK) ______' ______-_ 0.0

from tower 2 via line 13 may be withdrawn via line Water ______.- ______1.7 ’ it into reboiler 15 for heating by indirect or direct 15 heat exchange with a heating medium, such as 1 (97.5 to 99.5 wt. per cent). live steam. This portion of liquid bottoms, heated Although the invention has been described as and partially vaporized in reboiler i5, is recycled pertaining to the puri?cation and dehydration of via line 16 to the lower part of zone 2 to supply an aqueous crude normal propyl alcohol resulting the necessary heat for the distillation thereto. 20 from the hydrocarbon synthesis operation, it is The n-butyl'~ alcohol is readilyremoved from the equally applicable to the preparation and dehy n-prop'yl alcohol by- rerunning of the anhydrous dration of crude normal propyl alcohol contam~ bottoms from the tower 2. inated by- close-boiling oxygenated impurities ‘re 'Paraldehyde, aj unique impurity, has been found gardless of its source. Fortexample, the inven in the “n-propyl- cut" from the Fischer synthesis 25 tion is particularly applicable to the crude product in amounts as high as 5 or 6 weight per n-propyl alcohol produced by the reaction be cent. It has been found that when especially tween and carbon monoxide and subse— large concentrations of paraldehyde, such as quent hydrogenation of'the product in the so these, are present in-the crudepropyl cut, it is called “0x0” process. advantageous to maintain a pH of 3 ‘or slightly 30 Having described the invention in a manner less in the fractionation zone during the distilla such that it may be practiced by those skilled in tion to make the decomposition of paraldehyde the art, what is claimed is: to the very volatile acetaldehyde more rapid and l. A process for dehydrating and purifying an complete. To this endjsma'llconcentrations of a aqueous n-propyl alcohol contaminated with substantially non-volatile mineral acid may be ethyl alcohol, isopropyl alcohol and non-alcoholic added to the distillation zone 'or to the feed there oxygenated aliphatic compounds whose binary to either initially or periodically. ‘ aqueous azeotropes boil in the range of 78.1” An analysis of the dehydrated n-propyl alcohol C. to 90.4" C., which comprises distilling the con bottoms obtained from the above distillationis-as taminated aqueous n-propyl alcohol in a distilla follows: . tion zone in the presence of an aliphatic ether Wt. per cent boiling in the range of 55° C. to 110° C., collecting n-Propyl alcohol (including small amounts a distillate comprising water, ethyl alcohol, iso of n-butyl alcohol) ______~_'-___'___ 97.3 propyl alcohol, non-alcoholic oxygenated ali Water ______' ______1.6 phatic compounds and the aliphatic ether, and Aldehyde __-______-.______- ______0.7 45 recovering substantially pure anhydrous n-propyl Esters-1---. ______, ______,__ 0.4 alcohol as a distillation residue. The original composition of the feed was: 2. A process for dehydrating and purifying an aqueous n-propyl alcohol contaminated with ' Wt. per ‘cent ethyl alcohol, isopropyl alcohol and non-alcoholic n-Propyl alcohol (including ethyl, isopropyl 50 oxygenated aliphatic compounds whose binary and n-butyl alcohols) ______64.4 aqueous azeotropes boil in the range of 78.1° Water ______28.9 C. to 90.4“ C., which comprises distilling the con Esters ______1.3 taminated aqueous n-propyl alcohol in a distilla Aldehyde ______5.4 tion zone in the presence of an aliphatic ether Example 55 boiling in the range of 55° C. to 70° C., collecting a distillate comprising water, ethyl alcohol, iso Two and a half liters of an “n-propyl alcohol propyl alcohol, non-alcoholic oxygenated ali cu ” which analyzed as follows: phatic compounds and the aliphatic ether, and Wt. per cent recovering substantially pure anhydrous n-propyl n-Propyl alcohol ______63.5 alcohol as a distillation residue. Ethyl alcohol ______0.9 3. A process according to claim 2 in which the Isopropanol ______0.4 aliphatic ether is diisopropyl ether. Acid .(as acetic) ______0.01 4. A process according to claim 2 in which the Ester (as ethyl acetate) ______1.2 ether is tertiary butyl ethyl ether. Aldehyde (as butyraldehyde) ______4.3 65 5. A process for dehydrating and purifying an Ketone (as MEK), ______0.04 aqueous n-propyl alcohol contaminated with ethyl Water ______29.7 alcohol, isopropyl alcohol and non-alcoholic oxy genated aliphatic compounds whose binary aque 100.05 ous azeotropes boil in the range of 78.1° C. to 70 90.4" C., which comprises distilling the contam was fed to a distillation zone with 1500 cc. of di inated. aqueous n-propyl alcohol in a distillation isopropyl ether. The mixture was distilled at a zone in the presence of an aliphatic ether boiling temperature between 600° C. and 615° C., over a in the range of 70° C..to 110° C., collecting a dis period of approximately 40 hours. During the tiilate comprising water, ethyl alcohol, isopropyl azeotropic distillation, the aqueous distillate alcohol, non-alcoholic oxygenated aliphatic com was collected and topped to recover alcohols 8 pounds and the aliphatic ether, and recovering cohol contaminatedv with n-butyl alcohol as a dis substantially pure‘ anhydrous n-propyl alcohol as tillation residue and fractionating the distillation a distillation residue. residue to separate the n-propyl alcohol from the 6. A method according to claim 5 in which the n-butyl alcohol. ‘ aliphatic ether is added in amounts only to form 11. A process according to claim 10 in which azeotropes with the water, ethyl alcohol, iso the aliphatic ether is diisopropyl ether. propyl alcohol and the non-alcoholic oxygenated 12. A processaccording to claim 10 in which compounds. the aliphatic ether is tertiary butyl ethyl ether. 7. ‘A process for dehydrating and purifying an 13. A process for dehydrating and purifying an ‘ aqueous n-propyl alcohol contaminated with ethyl l0 aqueous n-propyl alcohol contaminated with ethyl alcohol, isopropyl alcohol, n-butyl alcohol and alcohol, isopropyl alcohol, n-butyl alcohol and non-alcoholic oxygenated aliphatic compounds non-alcoholic oxygenated aliphatic compounds whose binary aqueous azeotropes boil in the range whose binary aqueous azeotropes boil in the range of 78.1“ C. to 923° C., which comprises distilling of 78.1° C. to 923° C., which comprises distilling the contaminated aqueous n-propyl alcohol in a 15 the contaminated aqueous n-propyl alcohol in a distillation zone in the presence of an aliphatic distillation zone in the presence of an aliphatic ether boiling in‘ the range of 55° C. to 110° C., col ether boiling in the range of 70° C. to 110° C., lecting a distillate comprising water, the aliphatic collecting a distillate comprising water, the all ether, ethyl alcohol, isopropyl alcohol and the phatic ether, ethyl alcohol, isopropyl alcohol and non-alcoholic oxygenated aliphatic compounds, 20 the non-alcoholic oxygenated aliphatic com recovering substantially anhydrous n-propyl al pounds, recovering substantially anhydrous n cohol contaminated with n-butyl alcohol as a dis propyl alcohol contaminated with n-butyl alcohol tillation residue. ' a as a distillation residue and fractionating the dis 8. A process for dehydrating and purifying an tillation residue to separate the n-propyl alcohol aqueous n-propyl alcohol contaminated with ethyl 25 from the n-butyl alcohol. alcohol, isopropyl alcohol, n-butyl alcohol and 14. A method according to claim 13 in which non-alcoholic oxygenated aliphatic compounds the aliphatic ether is added in amounts only to whose binary aqueous azeotropes boil in the range form azeotropes with the water, ethyl alcohol, of 78.1” C. to 92.3", C., which comprises distilling isopropyl alcohol and the non-alcoholic oxy the contaminated aqueous n-propyl alcohol in a genated aliphatic compounds. distillation zone in the presence of an aliphatic 15. A process for dehydrating and purifying an ether boiling in the range of 55° C. to 70° C., 001 aqueous 'n-propyl alcohol contaminated with lecting a distillate comprising water, the aliphatic ' ethyl alcohol, isopropyl alcohol and non-alcoholic ether, ethyl alcohol, ‘isopropyl alcohol and the oxygenated aliphatic compounds whose binary non-alcoholic oxygenated aliphatic compounds, 35 aqueous azeotropes boil in the range of 78.l° C. to recovering substantially anhydrous n-propyl al 90.4° C., which comprises distilling the contami cohol contaminated with n-butyl alcohol as a nated aqueous n-propyl alcohol in a distillation distillation residue. zone in the presence of an aliphatic ether boiling 9. A process for dehydrating and purifying an in the range of 55° C. to 70° C., collecting a dis aqueous n-propyl alcohol contaminated with 40 tillate comprising water, the aliphatic ether, ethyl ethyl alcohol, isopropyl alcohol, n-butyl alcohol , alcohol, isopropyl alcohol and the non-alcoholic and non-alcoholic oxygenated aliphatic ‘com oxygenated aliphatic compounds, condensing the pounds whose binary aqueous azeotropes boil in distillate whereby an ether-rich phase and a the range of 781° C. to 923° C., which comprises water-rich phase are formed, returning the ether distilling the contaminated aqueous n-propyl al 45 rich phase to the distillation zone, and recovering cohol in a distillation zone in the presence of an substantially pure anhydrous n-propyl alcohol as aliphatic ether boiling in the range of 55° C. to a distillation residue. ' -' . 110° C., collecting a distillate comprising water, 16. A process according to claim 15 in which the aliphatic ether, ethyl alcohol, isopropyl alcohol the aliphatic ether is diisopropyl ether. and the non-alcoholic oxygenated aliphatic com 50 17. A process according to claim 15 in which pounds, recovering substantially anhydrous n the aliphatic ether is tertiary butyl ethyl ether. _ propyl alcohol contaminated with n-butyl alcohol . CARL S. CARLSON. as a distillation residue and fractionating the NAT C. ROBERTSON. distillation residue to separate the n-propyl al CARTER E. PORTER. cohol from the n-butyl alcohol. 55 10. A process for dehydrating and purifying an REFERENCES CITED aqueous n-propyl alcohol contaminated with The following references are of record in the ethyl alcohol, isopropyl alcohol, n-butyl alcohol ?le of this patent: and non-alcoholic oxygenated aliphatic com pounds whose binary aqueous azeotropes boil in 60 UNITED STATES PATENTS the range of 78.1” C. to 92.3" C., which comprises Number Name Date distilling the contaminated aqueous n-propyl in a 1,422,583 Lebo ______July 11, 1922 distillation zone in the presence of an aliphatic 1,568,349 ste?ens ______Jan. 5, 1926 ether boiling in the range of 55° C. to 70° C., col 65 1,831,425 Ricard ______Nov. 10, 1931 lecting a distillate comprising water, the aliphatic 1,862,706 Ricard et a1 ______June 14, 1932 ether, ethyl alcohol, isopropyl alcohol and the non-alcoholic oxygenated aliphatic compounds, 2,140,694 Evans ______Dec. 20, 1938 recovering substantially anhydrous n-propyl al 2,392,534 Von Keussler ______Jan. 8, 1946