US2583413A - Preparation of alcohols - Google Patents

Description

Patented Jan. 22, 1952 PREPARATION OF ALCOHOLS Paul H. Carnell, Bartlesville, kla., asslgnor to Phillips Petroleum Company, a corporation of Delaware Application September 30, 1946, Serial No. 700,277

the hydrating medium. In a typical embodiment it relates to an improved method of hydrating a mixture of ethylene, propylene and butylene to the corresponding aliphatic alcohols with aqueous hydrofluoric acid as the hydrating agent.

The copending patent application of Frederick r E. Frey entitled Hydration oi Olefins," Serial No; 521,833, filed February 10, 1944, now Patent 7 Claims. (01. 260-6 41) 2 individual cuts. Another object is to provide a process wherein concentration of the aqueous hy- No. 2,484,702, discloses the hydration-of olefins with aqueous HF. These olefins may be in admixture with other hydrocarbons which are inert, particularly parafilns. p

The copending application of Frederick E. Frey, Serial No. 559,115, filed October 1'7 1944, now Patent No. 2,457,882, which is a continuation in-part of the application just mentioned, disclosed and claims the hydration of olefins to the corresponding alcohols in the presence of an inorganic fluoride promoter such as a metal fluoride, hydrofluoboric acid, boron trifluoride, etc.

It has heretofore been deemed necessary to treat mixed aliphatic olefin streams to segregate therefrom individual streams containing olefin having a single number of carbon atoms per molecule and to individually hydrate the olefin content of the resulting streams in separate and distinct steps; For example, in the case of a mixture of ethylene, propylene and butylene, it is thought essential to separate this, as by tractionation, into an ethylene stream, a propylene stream and a butylene stream and to hydrate these to ethyl alcohol, propyl alcohol and butyl alcohol or alcohols in three hydration steps maintained entirely distinct from one another. In some situations it has been the practice of the art to segregate an ethylene-containing stream from such a mixed olefin stream by removing the Ca and higher content by compression or oil. absorption or by absorption in acid.

Preliminary separation procedures such as are referred to in the preceding paragraph are compllcated and expensive and in some cases do not result in conversion of all of the olefin content of the original mixed stream to the correspondv ing alcohols.

The principal object of the present invention is to provide an improved process for the preparation of aliphatic alcohols from mixed aliphatic olefin streams byhydration with aqueous hydrofiuoric acid. Another object is to provide such a process which eliminates the necessity of preliminary separation of such mixed olefin streams into drofiuoric acid is automatically accomplished by the hydration reactions. Another object is to provide a process of the foregoing type, the individual steps of which are correlated in a novel and highly advantageous manner to give a simple and unitary process requiring a minimum of equipment and control. Another object is to provide a method of the foregoing type which gives a maximum yield of alcohols from such mixed olefin streams. Many other objects will appear from the following description of the present invention.

The accompanying drawing illustrates in simplified form how the process of the present invention operates tor a mixed olefin stream of ethylene, propylene and the butenes. I

My invention is based on the discovery that reaction conditions required to produce a maximum yield of alcohol from olefins, such as ethyl-' ene, propylene, and the butenes, by HF-catalyzed hydration, become progressively more seyere as the molecular weight of the olefin decreases. In other words, the. production of ethanol from ethylene requires more drastic reaction conditions, i. e. acid concentration, temperature, and pressure, than the production of butanols from butenes. If a given concentration of acid, for example, 40 per cent HF, is contacted with a stream of mixed olefins, for example, ethylene, propylene and the butenes at asufiiciently high temperature to hydrate the low molecular weight olefin in the stream, i. e., ethylene, the higher molecular weight olefins, i. e., propylene and the butenes, either polymerize to relatively undesirable by-products, or form alkyl fluorides or ethers, and the overall alcohol yield is reduced.

According to this invention, mixed aliphatic olefin streams are hydrated to the corresponding aliphatic saturated monohydric alcohols by treating the olefin mixture, in successive steps, with aqueous HF, such aqueous HF being more concentrated in each successive step. The increase in acid concentration is produced by removal of water from the aqueous HF when alcohol is formed. The acid is further concentrated when the alcohol is distilled from the HF-water-alcohol mixture as an alcohol-water azeotrope. According to a further feature of this invention, the temperature and pressure are increased with acid concentration in each successive hydration step. By hydrating a mixture of olefins in this manner, the maximum alcohol yield is obtained from the olefin mixture with a minimum production of undesirable by-products. The alcohol formed in each step is distilled oil and any alkyl fluoride is recycled, along with unreacted olefin, for conversion to alcohol. Since the aqueous acid to be used in each hydration step is gradually concentrated by alcohol formation and by the removal of alcohol as an alcohol-waterazeotrope, the concentration of acid desired in each hydration step is obtained by'the controlled addition of olefin.

With a mixed olefin stream consisting of eth ylene, propylene, and the butenes, the process operates essentially as follows: The mixed olefin stream is contacted initially with to per cent HF at temperatures from about 60 to 90 C. at superatmospheric pressure. Under these conditions, the major portion of the butenes is hydrated to butanols. The propylene and ethylene are contacted in the next step with 20 to per cent HF at 90 to 120 C. and super-atmospheric pressure to effect hydration of the propylene. The remaining olefin, ethylene, is contacted in a third reactor with 30 to per cent HF, preferably about 40 per cent, at about 180 to 280 C. at superatmospheric pressure to' produce ethanol.

The process may be operated by passing the acid from the first hydration step, concentrated -somewhat by alcohol formation and removal, to the second hydration step, where the acid is again concentrated by alcohol formation and removal,

and subsequently to the third hydration step where'the acid is further concentrated by alcohol formation. The relatively concentrated acid from the last hydration step-is then diluted and recycled to the first hydration step.

The process, as described, is not necessarily limited to the hydration of mixtures of ethylene, propylene, and the butenes, but may be applied to olefin mixtures containing higher molecular weight olefins. The process may also be used for the concentration of a particular" olefin or oleflns in a mixed olefin stream.

' The amount of HF used in each hydration step is not critical, but, in general, is in excess of the olefin to be hydrated. With a constant olefin quantity, the excess of HF increases with decreasing olefin molecular weight. The mol ratio of HF to olefinmay vary from about 1.5 for oleflns such as the butenes, to 20, for low molecular weight olefins. such as ethylene. One of the marked advantages of the present invention is that the ratio of HF to olefin automatically increases in each successive step by reason of the removal of the next higher olefin content in each preceding step. To produce the maximum alcohol yield, each particular olefin mixture will require somewhat diflerent reaction conditions, contact time, etc., in each hydration step, depending upon the type and quantity of oleflns present in the mixture. For example, with a mixture of olefins. consisting of butenes, propylene, and ethylene, that is deficient in one or more of the olefins. for example, butenes, it may be necessary to add a small amount of HF to the nextreactor, e. g., that used to hydrate propylene, to raise the acid concentration to the desired value.

In the drawing, reactor I contains 10 to 20 per cent aqueous HF. 'A mixed olefin stream consisting of ethylene, propylene and butenes, passes to reactor I via line 2 and is contacted at temperatures ranging from to C. with the aqueous HF to form butanols. From reactor I. aqueous HF somewhat concentrated by alcohol formation in reactor I, unreacted butenes. butyl fluorides, ethylene and propylene are passed to fractionator 3 via line 4. Ethylene and propyl- 4 ene from fractionator 3 are passed via line I to second stage reactor I. Butyl fluorides, when present. and unreacted butenes from fractionator 3 are withdrawn and recycled to reactor .I via line I. Butanols from fractionator 3 are withdrawn as the aqueous azeotropes via line and the hydrofluoric acid is thus further concentrated. From the kettle of fractionator 3, aqueous HF, which has been concentrated to 20 to 30 I per cent by butanol formation and removal is passed via line 9 to reactor 6. The ethylene and propylene are contacted in reactor 6 with the 20 to 30 per cent HF at temperatures ranging from 90 to C. to hydrate propylene. From reactor 6, the reaction mixture consisting essentially of aqueous HF somewhat concentrated by alcohol formation, unreacted propylene, isopropyl fluoride, propanol and ethylene is passed vialine ID to fractionator II. ator II is passed via line I2 to third stage reactor I3. Isopropyl fluoride and unreacted propylene from fractionator II are recycled via line I4 to reactor 8. Isopropyl alcohol from fractionator II is withdrawn via line It as an alcohol-water azeotrope and the hydrofluoric acid is thus further concentrated. From the kettle of fractionator I I, aqueous HF, concentrated to 30 to 40 per cent by isopropyl alcohol formation and removal is passed via line It to reactor I3. Ethylene is contacted in reactor II with 30 to 40 per cent HF attemperatures ranging from to 280 C.

From reactor I3 the reaction eiliuent consisting essentially of aqueous H'F somewhat concentrated by ethanol formation, unreacted ethylene, ethyl fluoride and ethanol is passed via line II to fractionator II. Water is added to fractionator it via line I! to dilute the acid to 10 to 20 per cent for recycling to reactor I via line." and to aid in stripping out the'ethanol as an alcohol-water azeotrope. Ordinarily the water is introduced into the portion of column I8 which is below the point of feed entry via line H. The ethanolwater azeotrope is removed via line 2|. The ethyl fluoride and unreacted ethylene from fractionator I are recycled to reactor 13 via line 22.

Aqueous HF for starting or as make-up may be introduced to the system via line 23.

If desired, concentrated HF, from an outside source (not shown) may be passed into reactor I and/or reactor I3, through means not shown, in

order to obtain additional acid concentration. In many cases, however, particularlyv when the feed stream contains substantial proportions of olefin may be vented from each stage and this hydration zone.

3. II and It may include provision for recovery Ethylene from i'ractionpropane and ethane which fractions may be bled from the system.

The process of my invention may be applied to mixed olefin streams containing a plurality of aliphatic olefins having two or more carbcnatoml semen 1 i To determine the effect of agiven concentration of aqueous H! on olefins of different molec- 'ular weight, three batch runs were made in which ethylene. propylene. and isobutylene were per molecule. The olefins may range as high ascontacted with 40 per cent HF.

Ron I Run 2 Run s Ole Eth lone Acid concentration, It per cent... 40 ii l wbutybnig 6t?" I it 4% m u... 4 sun ,inrna 1.1 so &3 Reaction temperature, 227-281 90-106 23-29 ......a "rust s ":2 Lleoholyield,'wi.peroen was: a so #1 Polymer, grams, approx 2 0 may comprise any or all of the butenes, namely 1-butene, 2-butene or isobutylene. Likewise where Cs olefin is present it may be any one or any combination of two or more of the pentenes.

It will be understood. however that my invention is directed to the treatment of mixtures of olefins having differing numbers of carbon atoms per molecule and is not intended primarily for the treatment of olefin mixtures wherein the olefin content consists of olefins having identical numbers of carbon atoms per molecule.

It will be seen that the process of the present invention offers many advantages over a process wherein the mixed olefin feed is treated, byfractionation and/or solvent extraction, to concentrate each of the olefins and each olefin conce'ntrate is then separately passed to the proper hydration step, which is operated under the conditions herein specified.

EXALIPLES The procedure for investigating the HF-catalysed hydration of olefins was as follows:

A mixture of aqueous HF and the olefin being studied was charged to a Monel bomb at reduced temperature. The reactor was closed and attached to a mechanical rocker for vigorous shaking. The temperature was increased, and readings of the temperature and the pressure were made every minutes. From the data thus obtained, the temperature at which the pressure reversed its trend of increasing with increasing temperature was determined; this temperature was considered to be approximately that at which hydration began. The reaction time and the temperature subsequent to this point, until the pressure decreased to a relatively constant value, are given in the following tabulation. The reaction mixture was cooled and. in some instances, gas was removed for analysis. The acid was removed with sodium hydroxide, and the resulting mixture was examined.

fins.

Example I! To determine the eflect of varying concentrations of B1" on isohutyiene hydration, three batch runs were made in which isobutylene was contacted with 10.20 andeopercentnr.

An analysis of the gas'from run 4 revealed no alkyl fluoride. The amount of polymer formed in these runs increased with increasing acid concentration. These data show that HP of 10 to 20 per cent concentration is preferred for isobutylene hydration.

' trample III To show the effect of increased acid concentration on alcohol yield, and on alkyl fluoride and polymer formation. two batch runs were made in which propylene was contacted with 50 and 70 per cent H1".

Run 7 Run 8 Acid concentration, wt. per cent 50 70 Acid, Ira 130 182 Olefin, ms.-. 44.9 44.6 Moi re 0, HF:C|H. 8.1 8. 6 Reaction temperature, 0., approx.. 71-76 22-28 Reaction promre, p. s. 1., approx. 370 85 Reaction time, minutes, approx 80 Com ition oi efiluent was, mol'per cent:

4i. 74 39. 38 Propylene 20. 84 3. l8 Isopropyl fluoride 37. 42 57. 44 Propanol yield. wt. per cent of theoretical 44 29 decreases the alcohol yield. a

7 Example IV To determine the eflect of EB concentration on alcohol yield in ethylene hydration, five batch runs were made in which ethylene was which has a higher catalytic concentration in each successive step, said concentration being effective for the hydration of only the olefin containing the most carbon atoms per molecule present in each step, efi'ecting the increase in contacted with HF of different c n r i acid concentration in successive steps by removal Run 9 Run 10 Run 11 Run 12 Run 18 Acid conwniration, wt. per 1 t 35 40 50 60 70 182 10 130 156 182 16.8 19.1 11.0 27.7 40.8 15.1 7.6 9.2 7.9 6.8 Reaction temperature, 0.,

approx 210-228 227-231 185-191 148-148 lib-H8 Reaction pressure, p. s. 1., approx 810 635 736 836 Reaction time, minutes, ap-

prox 35 60 70 11) no Ethanol yield, weight per cent of theoretiml 32 89 88 29 8 These data show ,that the maximum ethanol yield is obtained with approximately 40 per cent HF.

Example V To determine the effect of acid concentration on ethanol recovery, by distillation from an HF- ethanol-water mixture, three synthetic mixtures of ethyl alcohol, water, and HF were made up and fractionated in a copper column at an overhead temperature of about 78 C., the boiling In run 16, an alcohol-HF-water azetrope, which boiled at about 103 0., was formed. These data show that acid concentrations below that of the constant-boiling I-lF-water mixture (about 38 per cent HF) are preferred for maximum alcohol recovery from an HF-ethanol-water mixture by fractionation.

From the foregoing description, many advantages of the process of the present invention will be apparent to those skilled in the art. A major advantage is that mixtures of aliphatic olefins having difierent numbers of carbon atoms per molecule are converted to excellent yields of the corresponding aliphatic saturated monohydric alcohols in a simple, economical and unitary process. Another advantage is that the hydrofluoric acid is automatically concentrated to the proper level for each succeeding hydration stage of the process. Another advantage is that the ratio of HF to olefin automatically increases to the proper extent from the first to the final stage of the process as a result of the removal of olefin from the feed as the feed progresses through the several sequential stages. Another advantage is that the process of my invention eliminates expensive preliminary segregation of the olefin feed into cuts having the same number of carbon atoms per molecule and separate treatment of the resulting cuts to hydrate the olefin content.

I claim:

1. The process of converting a mixture of aliphatic olefins having different numbers of carbon atoms per molecule to the corresponding alcohols which comprises selectively hydrating said olefins by treating the olefin mixture in successive steps with aqueous hydrofluoric acid of the alcohol from the eiiluent 0! a preceding step and passing the resulting more concentrated residual acid to a succeeding step, and thereby eflecting successive hydration of the oleflns in order or decreasing molecular weight, introducing water continuously while removing the alcohol corresponding to the olefin having'the fewest carbon atoms per molecule whereby an alcohol-water azeotrope is formed and separation of that alcohol from. said aqueous hydrofluoric acid isaided and said aqueous hydrofiuoric acid is diluted to the strength necessary to hydrate the olefln having the most carbon atoms per molecule, and recycling said dilute aqueous hydrofluoric acid to said first successive hydration step.

2. The process of converting a mixture of aliphatic olefins having different numbers of carbon atoms per molecule to the corresponding alcohols which comprises contacting said mixture or olefins with aqueous hydrofluoric acid, oi a catalytic concentration and at a temperature and pressure eilective for the selective hydration of the olefin having the most carbon atoms per molecule to the corresponding alcohol, recovering from the resulting reaction mixture alcohols.

thus produced, olefins having fewer carbon atoms per molecule than the thus hydrated olefin and aqueous hydrofluoric acid of a higher concentration than the first-named aqueous hydrofluoric acid and suitable for the catalytic hydration 01' an olefin 01' fewer carbon atoms than the thus hydrated olefin, contacting olefins and aqueous hydrofluoric acid thus recovered at a temperature and pressure effective for the selective hydration of the olefin having the next greatest number of carbon atoms per molecule to the corresponding alcohol, recovering alcohols thus produced in these successive steps, introducing water continuously while removing the alcohol corresponding to the olefin having the fewest carbon atoms per molecule whereby an alcohol-water azeotrope is formed and separation of that alcohol from said aqueous hydrofluoric acid is aided and said aqueous hydrofluoric acid is diluted to the strength necessary to hydrate the oleflns having the most carbon atoms per molecule, and recycling said dilute aqueous hydrofluoric acid to saidfirst successive hydration step.

3. The process of converting the olefin content of a hydrocarbon stream containing at least two aliphatic olefins having diflering numbers of carbon atoms per molecule to the corresponding aliphatic alcohols which comprises contacting said stream in a first hydration step with aqueous asaaua hydrofluoric acid, of a catalytic concentration and at a temperature and pressure effective for the selective hydration of the olefin having the most carbon atoms per molecule while the olefins of fewer carbon atoms per molecule are substantially unaffected, separating from the resulting reaction mixture 1) fluorides of the olefln having the most carbon atoms per molecule and unreacted olefin having the most carbon atoms per molecule, (2) alcohols thus formed, (3) unreacted olefins of fewer carbon atoms per molecule than the thus-hydrated olefin and (4) aqueous hydrofluoric acid of aconcentration higher than the concentration of the first-named aqueous hydrofluoric acid and suitable for the catalytic hydration of the olefin having the most carbon atoms per molecule in fraction (3), recycling fraction 1) to the flrst hydration step. contacting fractions (3) and (4) in a second hydration step at a temperature and pressure effective for the selective hydration of the olefin having the most carbon atoms per molecule in the second hydration step while oleflns having fewer carbon atoms per molecule remain substantially unaflected, recovering alcohols produced in said second hydration step, introducing water continuously while removing the alcohol corresponding to the olefin having the fewest carbon atoms per molecule whereby an alcoholwater azeotrope is formed and separation of that alcohol from said aqueous hydrofluoric acid is aided and said aqueous hydrofluoric acid is diluted to the strength necessary to hydrate the olefin having the most carbon atoms per molecule, and recycling said dilute aqueous hydrofluoric acid to said first successive hydration step.

4. The process of converting the olefin content of a mixed stream containing ethylene, propylene and butane to the corresponding aliphatic alcohols which comprises contacting said mixed stream in a first hydration step with to per cent aqueous hydrofluoric acid at a temperature oi from 60 to 90 C. and under superatmos-- pheric pressure and thereby effecting selective conversion of said butene to butanol while said propylene and ethylene are substantially unaffected, separating butanol, a mixture of un reacted propylene and ethylene, and 20 to per cent aqueous hydrofluoric acid from the resulting reaction mixture, contacting said mixture of propylene and ethylene and said 20 to 30 per cent aqueous hydrofluoric acid in a second hydration step at a temperature of from 90 to 120 C. and under superatmospheric pressure and thereby -efl'ecting selective conversion of said propylene to propanol while said ethylene is substantially unaffected, separating propanol, unreacted ethylene, and 30 to per cent aqueous hydrofluoric acid from the resulting reaction mixture, contacting said ethylene and 30 to 50 per cent aqueous hydrofluoric acid in a third hydration step at a temperature offrom 180 to 280 C. and under superatmospheric pressure to convert ethylene to ethanol, separating ethanol from the resulting acid, introducing water continuously' while removing said ethanol whereby an ethanol-water azeotrope is formed and separation of ethanol from said aqueous hydrofluoric acid is aided and said aqueous hydrofluoric acid is diluted to 10 to 20 per cent strength, and recycling said dilute aqueous hydrofluoric acid to said first hydration step.

5. The process of claim 1 wherein said acid is further concentrated between stages by distilling the alcohol from the hydrofluoric acid-wateralcohol mixture eflluent from a preceding step in the form of an alcohol-water azeotrope.

6. The process of claim 1 wherein said oleflns are butene, propylene and ethylene.

7. The process of converting the olefin content of a hydrocarbon stream containing ethylene, propylene and butenes to the corresponding aliphatic alcohols which comprises contacting said stream in a first hydration step with 10 to 20 per cent aqueous hydrofluoric acid at a temperature of from to C. and under superatmospheric pressure and thereby effecting selective conversion of said butenes to butanols while said propylene and ethylene are substantially unaifected, fractionating the resulting reaction mixture to separately recover fractions of (1) butyl fluorides and unreacted butenes (2) butanols (3) propylene and ethylene and (4) aqueous hydrofluoric acid of 20 to 30 per cent strength, recycling fraction (1) to the first hydration step. passing fractions (3) and (4) to a second hydration step in which the propylene and ethylene are contacted under more severe conditions with 20 to 30 per cent aqueous hydrofluoric acid at a temperature of from 90 to C. and under superatmospheric' pressure, and thereby effecting selective conversion of said propylene to propanol while said ethylene is substantially unaffected, fractionating the resulting reaction mixture to separately recover fractions of (1) propyl fluoride and unreacted propylene (2) propanol (3) ethylone and (4) aqueous hydrofluoric acid of 30 to 40 per cent strength, recycling fraction (1) to the second hydration step, passing fractions (3) and (4) to a third hydration step in which the ethyl one is contacted under still more severe conditions with 30 to 40 per cent aqueous hydrofluoric acid at a temperature of from to 280 C. and under superatmospheric pressure and thereby effecting conversion of said ethylene to ethanol, fractionating the resulting reaction mixture to separately recover fractions of (1) ethyl fluoride and ethylene (2) ethanol-water azeotrope (3) aqueous hydrofluoric acid, introducing water continuously to the fractionation zone wherein ethanol is separated overhead from said aqueous hydrofluoric acid to dilute said aqueous hydrofluoric acid to 10 to 20 per cent strength and to aid in stripping out the ethanol as an ethanol-water aaeotrope, recycling fraction (1) to the third hydration step. and recycling fraction 3) to the first hydration step.

PAUL H. CARNELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,438,123 McElroy Dec. 5, 1922 2,014,740 Larson Sept. 17, 1935 2,070,258 Coleman et a1. -c Feb. 9, 1937 2,093,426 Dreyfus Sept. 21, 1937 2,112,793 Stanley et al. Mar. 29, 1938 2,135,455 Loder Nov. 1, 1938 2,141,275 Lewis Dec. 2'1, 1938 2,431,685 Cade Dec. 2, 1047

Claims (1)

1. THE PROCESS OF CONVERTING A MIXTURE OF ALIPHATIC OLEFINS HAVING DIFFERENT NUMBERS OF CARBON ATOMS PER MOLECULE TO THE CORRESPONDING ALCOHOLS WHICH COMPRISES SELECTIVELY HYDRATING SAID OLEFINS BY TREATING THE OLEFIN MIXTURE IN SUCCESSIVE STEPS WITH AQUEOUS HYDROFLUORIC ACID WHICH HAS A HIGHER CATALYST CONCENTRATION IN EACH SUCCESSIVE STEP, SAID CONCENTRATION BEING EFFECTIVE FOR THE HYDRATION OF ONLY THE OLEFIN CONTAINING THE MOST CARBON ATOMS PER MOLECULE PRESENT IN EACH STEP, EFFECTIVING THE INCREASE IN ACID CONCENTRATION IN SUCCESSIVE STEPS BY REMOVAL OF THE ALCOHOL FROM THE EFFLUENT OF A PRECEDING STEP AND PASSING THE RESULTING MORE CONCENTRATED RESIDUAL ACID TO A SUCCEEDING STEP, AND THEREBY EFFECTING SUCCESSIVE HYDRATION OF THE OLEFINS IN ORDER OF DECREASING MOLECULAR WEIGHT,INTRODUCING WATER CONTINUOUSLY WHILE REMOVING THE ALCOHOL CORRESPONDING TO THE OLEFIN HAVING THE

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