Oct. 14, 1952 W. M. SMITH 2,614,070 HEAT TREATING AND DISTILLATION OF OXO Filed Nov. 16, 1949

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Patented Oct. 14, 1952 2,614,070 UNITED STATES PATENT OFFICE 2,614,070 HEATREATING AND DASALLATION OF OXO ALCOHOLS Warren M. Smith, Baton Rouge, La., assignor to Standard Oil Development Company, a corpo ration of Delaware Application November 16, 1949, Seria No. 2,628 5 Claims. (C. 202-5) 1. 2 This invention relates to improvements for the a large number of different types of reactions purification of crude alcohols, by a distillation take place to form a variety of products. The procedure. More specifically the invention re chief primary reaction products as Outlined lates to an improved distillation method for puri above are . These aldehydes themselves fying higher boiling Oxo alcohols which contain 5 can undergo further reactions to yield other prod inpurities of the type tending to undergo de ucts. For instance, the aldehydes condense: With composition at the normal boiling point of the each other to yield aldols. At least a part of Oxo undergoing purification by distilla the aldols undergo dehydration to yield alpha-, tion. beta-unsaturated aldehydes. Some ketones are In practicing this invention, the crude Oxo 0 also formed under the reagtion conditions. A alcohols containing the impurities are subjected part of the aldehydes formed in the reaction Zone to a thermal treatment at elevated pressure for is hydrogenated to alcohols and the alcohols so a sufficient period of time to decompose and/or formed react with aldehydes and ketones present convert the higher boiling impurity compounds to give mixtures of acetals, hemi-acetals, and present in the crude OXO alcohols to Some other 5 ketals. These compounds can undergo further. materials, generally easily volatilizable materials, reactions, including dehydration, to give ethers, which are removed from the OXO alcohol prod particularly those of the unsaturated types. The ucts by distillation. The heat treatment is car alcohols can esterify the acids present to give ried out in One Zone and the materials Yinore esters. of a part of the olefin volatile than the alcohol are removed from this 20 starting feed stock, as well as some deoxygena Zone as overhead while the bottoms product con tion of oxygenated intermediates, gives. Some hy taining substantially all the Oxo alcohol is dis drocarbons in the final Oxo product mixture. In charged to a second distillation Zone Operating addition, other more complex and less known re-- preferably at a lower pressure and slightly lower actions also occur between the various inter 25 mediates and products obtained thereby yielding temperature, from which zone the Oxo alcohol, a mixture of higher boiling impurities and con relatively free of both more volatile and higher taminants of the oxygenated type. - boiling impurities is taken off as overhead In the hydrogenation stage, the rinixtures of product, acids, Saturated and unsaturated aldehydes, A number of alcohols which are of great Com alcohols, ethers, products, mercial importance are prepared by Synthetic 30 glycols, acetals, ketals and esters are hydro processes and especially by the so-called OXO re genated in the presence of a suitable hydro action. The term "Oxo reaction' is a term used genating catalyst to yield more saturated prod to describe the preparation of oxygenated organic lucts containing a higher percentage of alcohols compounds by the reaction of and non-Olefinic compounds. The product from and hydrogen with olefinic hydrocarbons in the 35 the hydrogenation stage is essentially alcoholic presence of a carbonylation catalyst. The in nature, with various impurities. Some of . method is used particularly for the manufacture these inpurities, especially the unsaturated of various primary alcohols, Specifically Octyl ethers, acetals, ketals, aldols and esters are quite alcohols, by operations involving interaction of unstable toward heat. For instance, in general, carbon monoxide, hydrogen, a hydrocarbon mix 40 the aldols, acetals, heini-acetals and ketals have ture containing substantial amounts of heptenes, a great tendency to undergo degradative decom and a cobalt carbonylation catalyst to form octyl position reactions whenever the alcohol is sub aldehydes, and subsequent reduction of these jected to a simple atmospheric distillation. In octyl aldehydes by catalytic hydrogenation to a many cases, thermally unstable esters are present mixture relatively high in Octyl alcohols. 45 and undergo both thermal and hydrolytic decom Primary alcohols of this general type are of positions under distillation conditions. great economic importance and interest because To be more Specific, if a crude fraction of iso of their use as intermediates in the manufacture Octyl alcohol as produced by the oxonation of of piasticizers of di-ester type. Those considered Ci olefins, followed by hydrogenation, is distilled to be particularly valuable are the di-esters of 50 either in a batch or continuous manner and cuts phthalic and maleic acids. The Oxo reaction and removed according to increasing boiling point, subsequent hydrogenation have been found to then the following fractions can be isolated: comprise a highly economical and valuable 1. A fraction containing unconverted olefin hy method for manufacturing octyl alcohols from drocarbons, Saturated hydrocarbons, and unhy. cheap and readily available hydrocarbon ma 55 drogenated aldehydes. terials.In the Oxo or carbonylation stage of the process 2. A fraction containing principally iso-octyl 2,614,070 3 4. alcohol contaminated with decomposition prod additional and excessive purification prior to their ucts of aldols, hemi-acetals, acetals, ketals, esters, use aS plasticizers. ethers, and the like. It can thus be seen that it is highly desirable 3. A fraction containing higher boiling mate to have the alcohol products Such as those ob rials including esters and unsaturates of low vola tained in the Oxo reaction, as free of aldehydes, tility, higher alcohols, decomposition products of acetals, and other chemically reactive and ther acetals and undecomposed acetals, ethers, and mally unstable Substances as possible, particu ketals. larly if they are to be used later for the produc A mechanism which fits the facts in a general tion of plasticizer materials. fashion may beformulated in which it is assumed O This same type of problem of unstable impuri that decomposition reactions of various thermally ties also exists in connection with other alcohols and hydrolytically unstable materials proceed to made by the OXO reaction, particularly for alco an appreciable extent at the normal distillation hols of the range of C4 to C15 or higher. For ex temperature of the alcohol being purified, in this ample, the C9 alcohols, prepared by the reaction particular case, the iso-octyl alcohol. The de of C8 olefins such as diisobutylene with carbon composition reactions occurring produce Water, monoxide and hydrogen may be purified in the especially by aldol dehydration, and this water Same manner as that described herein for the probably contributes further to decomposition re purification of the C8 OXO alcohols. actions by its hydrolytic action, especially on such This novel distillation process can be used for inpurities as esters, ketals, acetals and unSat 20 purification of alcohols containing thermally un urated ethers. The more Wolatile of the deCOm Stable high boiling impurities obtained from any position products, including various Saturated and Source, and is especially applicable to treatment unsaturated aldehydes, Water, and alcohols (in Of alcohols having from 4 to 15 carbon atoms. It cluding both iso-octyl and other alcohols of lower finds particular application in purification of al boiling point), go overhead with the alcohol prod Cohols obtained by the so-called Oxo reaction uct and contaminate the latter since all these mentioned above and especially to alcohols of the products frequently boil within the same range. C8 and C9 class, although the process can also be Any aldehydes, which are usually quite volatile, applied advantageously for other alcohols con are distilled over With the alcohol fraction in this taining similar types of thermally unstable im manner and Subsequently combine very readily 30 purities, particularly alcohols obtained by hydro with the distilled alcohol product, reforming ac genation of carbonyl compounds. etals and henni-acetals, which are likewise subject A typical Ca Crude Oxo alcohol mixture such as to a second and Similar decomposition process can be employed as starting feed in this improved When a redistillation of the alcohol fraction is purification process has the following composi attempted for further purification. Aldehydes tion: and other low boiling decomposition products are objectionable because they lower over-all product Weight per cent purity, and, due to instability, cause difficulties in Alcohol as C8------65.0 the use of the alcohol especially When it is used as as C8------1.8 an esterification reactant. 40 Acetal as C24------3.7 It can readily be seen that it is difficult, if not Fister as Co------3.0 impossible, to remove completely these acetals, Unsaturates as C7------6.3 aldehydes, and other interfering impurities from Acid as C8------0. alcohols produced by Such methods as the Oxo Water ------2.0 reaction using straight distillation and using suc 45 Saturates and unknowns.------18.1 Cessive steps for removing fractions of increasing The high-boiling impurities including the ace boiling points. The presence of free aldehydes or tals, hemi-acetals, esters and ethers, which ordi potentially free aldehydes such as acetals or narily occur in the OXO alcohols cannot with hemi-acetals in any kind of commercial alcohol Stand continued heating at elevated tempera product is objectionable for a number of reasons. 50 tures without undergoing serious and extensive Aldehydic compounds are relatively unstable to decomposition to give volatile products causing Ward air, elevated temperatures, and other vari contamination of the final alcohol product. ously encountered conditions to which ordinary In the first Stage, there is carried out a heat chemicals are exposed when stored. As a result, treating of the crude Oxo alcohol mixture in inpurities such as color bodies are produced upon 55 cluding any acetals, hemi-acetals, and other storage, especially under varying temperature thermally unstable compounds followed by a va conditions. Any aldehydes present in the alcohol porization and 1removal of the materials more react readily with a part of the alcohol, thereby Volatile than the alcohol. This heating treat reducing the amount of total alcohol present and ment may be done in any type of conventional the amount which would be readily available for 30 still column or it may even be done in a kind of other chemical reactions. Perhaps the most im heat Soaking drum, thereafter passing the mix portant commercial use for these higher molecu ture to a still for removal of volatiles as over lar weight alcohols, such as the C8 iso-octyl alco head. One critical factor in this first stage heat hols produced by the Oxo reaction, is in esterifi ing and distillation is that the bottoms tempera cation reactions to form compounds of the di 65 ture must be maintained sufficiently high to ester type for use as plasticizers in resin and cause a Substantially complete decomposition of plastic compositions. Those of the phthalate and the heat-unstable impurities, thereby releasing at adipate type are widely manufactured. Although least a najor portion of the combined alcohol as an alcohol product of a synthetic source appears Well as volatile decomposition products. The to be perfectly colorless, it frequently contains 70 bottons should always be above the normal boil Small amounts of impurities which form colored ing point of the alcohol, and generally consid bodies during the Subsequent esterification reac erably above it. For Ca alcohol, the amount of tion. These colored materials are difficult to re material taken overhead comparative to the move from the resulting high-boiling ester prod amount of bottoms allowed to remain in the still lucts and result in inferior esters which require 75 Will depend on the degree of decomposition of

2,614,070 5 6. acetals and other unstable compounds obtainable. a slight excess of the Oxo alcohol for a time. Suf at the bottons temperature employed as well as ficient to permit substantially" complete. esteris on the precise composition of the impurities in fication of the anhydride. The excess alcohol is the alcohol since some types of impurities may removed and the color of the ester determined be decomposed to a somewhat greater extent by 5 and expressed in terms of a HaZen ester color the heat treatment, and others may be extremely . number, on the Pt-Co Scale, a high number in resistant to thermal attack. The Overhead vapor dicating a darkened, low quality ester product, temperature of the first distillation stage should This standard test for ester color is Widely used not be high enough to permit too great an in the literature and in the trade. It is described amount of alcohol passing overhead in the vola O in A. S. T. M. D 268-46. tiles, thus it should not be in excess of the boil Other modifications within the spirit of the in: ing-range of the particular alcohol product be wention will also be suggested to one skilled in ing purified. The residence time for the alcohol distillation techniques. In any case, regardless and impurities in this heat treating zone. will of the exact manner in which the alcohol prod depend on temperatures and pressures. The tem 15 uct is removed from the small quantity of residual perature, and residence times are roughly quali high boilers, it is highly desirable to maintain. tatively interchangeable. For the is0-0ctyl al as low a bottons temperature in the second va cohols the bottoms temperatures during the heat porization step as possible and preferably not to treating should be at least 600 F. and preferably allow a temperature appreciably higher than the are maintained at Somewhat Over this minimum. 20 boiling range of the alcohol itself. AS' One, alter-. This high temperature is maintained by the use nate method of operation, the first stage operas. of a pressure in the first thermal heating stage. tion Inay be carried out at atmospheric pressure, The bottoms temperature necessary in the first alld the Second stage conducted at Subatmos stage for substantial cracking of the unstable pheric pressures with temperatures adjusted ac high boiling impurities will depend to a more or cordingly, It is also considered to be within the . less extent on the exact nature of the alcohol Scope of this invention to subject the alcohol to being purified but will frequently be in excess of the thermal treatment in a soaking, drum and the boiling point of the alcohol. transfer the heat treated products afterward to In the second stage of operation, the bottoms a distillation Zone for removal of volatiles. from the first stage containing the alcohol and In the accompanying, drawing there is shown any high boiling impurities is passed to a Second diagrammatically a form of distillation equip vaporization or distillation zone. ment and its accessory apparatus in which a pre The temperatures in this column are substan ferred modification of the invention may be car tially lower than those of the first distillation ried out. zone. Conveniently, the column is. Operated at EXAMPLE atmospheric pressure or at subatmospheric pres-- This example will be described with reference sure. The desired alcohol product is removed to Figure 1. A mixture of crude octyl alcohols, overhead from this column. This overhead prepared by catalytic reaction of carbon monox product will be substantially pure OXO alcohol ide and hydrogen, with C7 olefins with a com free of volatile degradation products as Well as 40 position such as that shown above, is passed by high boiling, color forming impurities. line into a preheater 2 and is passed through High boiling, undecomposed impurities are ob-. control valve 3a and subsequently into an inter tained as bottoms from the Second stage distilla mediate point of tower A, this tower having 30 tion ZOne. plates. The crude alcohol preheated feed is pref Since, in general, for efficient operation, it erably introduced at a location about plate 15 would seen desirable to recover ultimately the of tower 4. Tower 4 is maintained under about. combined alcohol remaining in the bottoms from 50 p.s. i. g. pressure and the liquid bottoms are the alcohol recovery tower, these bottoms may be heated to temperatures of at least 600 F. The recycled to the first distillation stage for further material in the column is heated by employing decomposition. The process may generally be 50 reboiler 3 as follows: the bottoms are withdrawn, operated with good results within the range of from Still 4 through pipe f2 and passed by line, conditions in Table I below: 2 in part into a heater 3 and thence returned to the stabilizer tower 4. The remainder of the Table I bottoms removed in line f2 is discharged into 55. about plate 6 of a second distillation zone, a 12 Tower (1) Tower (2). plate-fractionating tower 8 via lines 5 and 7 carrying a pressure reducing valve 6. A partial Bigns or Pot Tempera- 530° to 750° F -...-450° to 550°F, condenser may be used in line 5, if desired. The Towerlife------'m Pressure------r mV, re. 20 to 209 fifsq. in. atmos. to 5- #fsq. in. reflux ratio in stabilizer tower 4 is preferably gauge. gauge. 60 about 12:1. The heat which must be furnished Residence Time------% to 10 hours.---- 4to.5 hours. by the reboiler 3 must be of an amount to equal the heat lost overhead plus heat lost by radiation The degree of purification accomplished by from the column. There is removed overhead this process can readily be evaluated in any num by line 5 from stabilizer tower 4 a stream of light ber of ways. One of the simplest is by observa 65 tion of the number of degrees of spread in boil volatile products, both materials existing in the ing range of the alcohol product obtained. As is OXO alcohol originally and more degraded vola the general rule in chemical practice, the nar tile byproducts produced by cracking and decom rower boiling range is an indication that a purer position of the higher molecular weight impuri product has been obtained. Color stability tests, 70 ties undergoing thermal treatment in the tower. particularly those involving esterification, can This overhead stream contains aldehydes, hy also be used to give an indication of any color pro drocarbons, and a small amount of C8 alcohol. ducing impurities present. It is passed to a condenser 6 wherein it is liqui Generally, the esterification tests are carried fied, and from condenser 6 by lines 7 and 8 apart out by refluxing together phthalic anhydride and 75 of the liquid is returned as reflux to tower 4 and 2,614,070 7 8. a part is removed by lines 9 and through pres stage distillation is about 600 F. under a pres Sure control valve 0 to release the pressure to sure of about 50 lbs. per sq. in. From this stage, atmospheric in line before sending the Over water, hydrocarbon and volatile decomposition head product to storage. products from the high boiling are taken off as Stabilizer tower s is maintained at a pressure vapors. In the Second stage the alcohol product of around 50 p.s. i. g., such that the temperature is distilled at Somewhat lower temperature at Of the liquid bottomS is at a temperature of at about 450–550 F. and under about atmospheric least 600 F. and the temperature at each plate preSSure, whence the alcohol is taken off as over up the column is kept at a level at least 100 Fahr head, condeinsed and collected as a relatively pure enheit degrees above that which normally obtain O product. at atmospheric pressure. The average residence What is claimed is: time of material in tower 4 is about 1 hour. 1. An improved continuous distillation process In tower 8, the refiux ratio is about 1.5:1 and for the purification of a mixture of crude water both the temperature and pressure are somewhat immiscible C4 to C15 alcohols containing high lower than in tower 4. In this tower the bottoms boiling thermally unstable impurities including are at a pressure of 0-2 p.s. i. g. and the tempera acetals, esters, hemi-acetals, and ethers, and ob ture is maintained around 450–550 F. not being tained by the catalytic reaction of olefins with permitted to rise above 550 F., the cracking tem Carbon monoxide and hydrogen and subsequent perature of the bottoms. The high boiling bot hydrogenation of the aldehydes resulting there toms product is Withdrawn through line 24 and from, which comprises introducing said mixture passed in part through reboiler 29 and thence re of Crude alcohols into an initial distillation stage turned to tower 8 by return line 39. The re maintained at Superatmospheric pressure and at maining portion of the bottoms is rejected from temperatures Substantially above the normal boil the system through lines 25, cooler 26 and line ing point of the alcohol, heat treating therein the 2. A part of the bottoms may be recycled, if 2 5 mixture of crude alcohols in the liquid phase for desired, by line 3 f to the feed inlet of tower 4. a period of time sufficient to decompose thermally In this column the temperature is somewhat a Substantial portion of the high boiling impuri lower than in the column 4 and is maintained ties into more volatile products, removing by sufficiently low to avoid bottoms cracking and Vaporization the impurities more volatile than 4. resulting contamination by volatile decomposi t the alcohol, passing the alcohol and the residual tion products. The purified C8 OXO alcohol is impurities less volatile than the alcohol to a recovered from column 8 through line 9 as over Second distillation stage maintained at atmos head, Condensed in a condenser 20 and a part pheric pressure, separating as overhead an alco returned through lines 2 and 22 to tower f3 as hol rich vapor stream, and removing as a liquid reflux. The remaining portion of the purified 3 3 bottoms product the residual undecomposed in overhead alcohol is collected from line 25a as purities boiling higher than the alcohol. C8 Oxo alcohol product and sent to storage. Op 2. A process such as that described in claim 1 erating in this manner about 54 volume per cent in which the alcohols in Crude alcohol mixture of alcohol based on the feed to stabilizer tower 4 being purified contains from eight to nine carbon is recovered. About 27 volume per cent of the atoms. feed is obtained as overhead from tower 4 and 3. A process Such as that described in claim 1 about 19 volume per cent is obtained as bottoms in which the mixture of crude alcohols is ob product from tower 8. tained by catalytic reaction of a CI olefin stream By Operating in such a manner as to subject With carbon monoxide and hydrogen followed by the crude alcohol entering tower 4 to a tempera hydrogenation of the Ce aldehydes obtained ture of about 600 F. prior to distillation for a therefron. time of about 1 hour, an alcohol product was 4. An improved continuous distillation process recovered, and tested by a study of the ester for the purification of a mixture of crude water Hazen color of the phthalate ester, prepared by immiscible C8 iso-octyl alcohol obtained by the refluxing the Oxo alcohol for one hour with 50 catalytic reaction of a CT olefin stream with phthalic anhydride. The results, compared with carbon monoxide and Subsequent hydrogenation those from untreated alcohol are shown in of the Ca aldehydes obtained therefrom, and con Table II. taining high boiling, thermally unstable impuri Table II ties including acetals, esters, hemi-acetals and 55 ethers, which comprises introducing the mixture of crude iso-octyl alcohols into an initial distilla Alcohol (HazenE.Ester ColorPt-Co tion Zone, maintained at pressures of from 20 to Scale) 200 lbs. per Sq. in. and at a temperature of from 530 F. to 750°F, heat treating therein the mix Untreated.------500 ture of crude alcohols in the liquid phase for Heat Treated.------200 a period of time Sufficient to effect substantial decomposition, of the thermally unstable, high To summarize, the invention relates to dis boiling impurities to more volatile components, tilling an impure OXO alcohol containing high removing overhead a vapor stream of impurities boiling impurities Such as acetals, hemi-acetals, 65 more volatile than the alcohol, removing the esters, and ethers which tend to undergo decom alcohol and residual impurities less volatile than position when exposed to high temperatures. In the alcohol as liquid from the lower part of the general, the Oxo alcohol is subjected to at least distillation Zone, introducing said liquid contain one distillation operating at Sufficiently high ing the alcohol into a second distillation zone pressure in the first stage to maintain the alcohol 70 maintained at atmospheric pressure, removing in liquid phase and for a Sufficient period of time as overhead a Substantially pure alcohol vapor to decompose a major portion of the impurities stream, and removing as a liquid bottoms product to more volatile decomposition products. Hence the residual impurities less volatile than the the distillation is a time, temperature, pressure alcohol. operation, A Suitable temperature in the first 75 5. A process as described in claim 4 in which

2,614,070 10 the initial distillation zone is maintained at a REFERENCES CITED pressure of 50 lbs. per sq. in. and the temperature The following references are of record in the is at least 600 F. and the pressure in the second file of this patent: distillation Zone is maintained at 0 to 2 lbs. per UNITED STATES PATENTS 5 Sq. in and the temperature in the second distilla Number Name Date tion. ZOne is continuously maintained below 2,151,46. Britton et al. ----- Mar. 21, 1939 550° E. WARREN. M. SMITH. 2,417,886 Redcay ------Mar. 25, 1947