Патент USA US2403742код для вставки
July 9, 1946- , > I. L. ,MURRAY ET AL 2,403,742 ‘PROCESS FOR MAKING‘ BUTADIENE Filed Sept. 9, 1943 g0 g1 HYDROGEN A T y ' I 4/ ‘. © 18 45 - 1' 40 46 57 T '36 L T2 \ Q» , ' ‘"6 ~9 ? 1 ‘55 BUT DIENE a A -+ 85 <55 27 45+ 49 \80 ‘ T T m E Q Q 5‘: 2' E E< 5/ ‘ 52 ~- Fri-152m. INVENTORS I lRVlN L. MURRAY 75 55f’/ ——-l , 1% g6 / _> ’ 1* ' 1 y $6145 2'1 QFAISFH JR BY ATTORNEY ,_ _. Patented July 9, 1946 2,403,742 " f ui-mlrso-"srA'r-ss PATENT ‘OFFICE » PROCESS FOR ~MAKING ,BUTADIENE Irvin L. .Murray, “Charleston, and Jay L. Marsh, South Charleston, W. Va., and Silas vP. Smith, JL, ‘Louisville, Ky, assignors to Carbide and Carbon Chemicals Corporation, a corporation ‘of New York‘ - I > Application-September 9, 1943, Serial No. 501,611 ~ 8' Claims.‘ (omen-cs1) ’ , . 1 . - This invention relates to a process for making butadiene from ethanol. According to this condensed. Any permanent gases produced'in . the reaction, .or present in ‘the reaction products, also, ‘contain the vapors of vthis condensate, invention, ‘ butadiene is formed from ethanol in twosteps, one step being namely,‘ acetaldehyde, ethanol, Water and by the conversionof ethanol to acetaldehydein ,a products. . The valuable constituents may be re separate reaction, and the other step beingthe covered fromjthese gases by compressing .the separateconversibn to butadiene of a mixture - of theacetaldehyde formedin' the ?rst stepivand , gases andscrubbing them with water. In the second step of the process, ethanol and 'acetaldehyde, preferably in 'the'm‘olar' ratio of ethanol. Both reactions are carried outginthe vapor‘phase, Although; some savingsin the total about 3vto 1, are reacted 'inithe' vapor .state in the heat required vto operate both. steps, of the'process may'be obtained by introducingthe-gaseous re action products-from the i acetaldehyde converter directly into» the butadiene converter, greater ad vantages. in economyw-and ease of operation are obtained bythe process of thisinvention. ‘ In‘ this invention,‘ the products from both the; acetalder hyde and the butadiene converters arezseparated from permanent gasesproduced- in, the reactions, the butadiene is separated from any unreacted ethanol and acetaldehyde, and thevpmaterials re presence of suitablej_.catalystsf to form butadiene. A preferred catalystis described in .W. J. Tons saint and ‘J. 'I'.v , Dunn application Serial‘v No. ‘$60,120, ?led September 29, 1942. Other catalysts 1:5. for ‘this reaction are, reported ‘in the vliterature. ‘Theie?luentvaporszand gases. from the buta‘die'ne converter,_containing butadiene, ethanol, acet— aldehyde, diethyl'ether, ethylene, propylene and saturated hydrocarbon gases, and other by-p'ro'ds maining from these separations, containing », eth -, anol, acetaldehyde and by-products areintro duced to a common distillation system.. This dis tillation system removes the by-products pro duced‘in both‘ reactions and supplies ethanol to the acetaldehyde' converten; andv ethanol and acetalde'hydeto the *butadiene converters,’ Thus, the‘ entire process is Operated-i113 cyclicand con tinuous; manner. EthanoLequivalent to, that con- ‘ nets are. passed throughfa condenser. Most of the vapors are condensed in this operation, but , alargeffraction of the butadiene ‘is notlique?ed and suchjfract'ion is presentin the gases. leaving the condenser. ,‘The butadiene' may be recovered from. such gases by compressing the gases and scrubbingthem'lwith a solvent, such as ethanol. Howeveneconomyin operation maybe obtained by employing. as the scrubbing liquid a material which ‘is to be'subjected to distillation 'inany event as described in the copending application, sumed in the process, is. supplied to the system,. v‘fProcess'_ for \ making butadiene,” ~ Serial No. preferably'as reflux'in a distillation column in 501,610, of I, L.,,Murray, J. L. Marsh and ‘S. P. which ethanol vaporsare beingremoved. How :Smi‘th,;Jr. Such‘ a material ‘is the condensate of ever, make-up ethanol may be supplied in "any ethanoland acetaldehyde from the acetaldehyde other convenient manner. ,For instancait'may ':* reaction. Alternatively, the make-up ethanol re beadded ; as scrubbing liquid to separate buta quired in the process-may be employed as scrub diene ‘from. other gases of lower boiling point. The process of" this invention has theadvantae'e .Asubsequentscruhbing tower may be provided that,“ by providing ‘appropriate storage " facilities ‘tore'cover thevapors of the scrubbing: liquid: from thelgasesleavingthe butadiene scrubbing tower. for the crude productsof eachreaction; each re action may be conducted independently. IA, fur-7 Watefisasuitabl'e scrubbing liquid for use in this ther ' advantageis that'iboth reaction systems’ uti lize ‘the same distillation system‘ for the recovery The ?rst condensate from the butadiene‘ reac hing. liquid. second tower.‘ ‘ofhnconverted materials, which provides econ , _ ' ' ' ' ' ' _ . ' tion andlthe liquid. e?lux from the scrubbing'tower may in "the equipmentrequ-ired to operate the (-1 win whichibutadieneis removed from other gases are mixed ‘and treatedto recover’ the butadiene. process.v ‘ Inthe ?rst stepgof . .r the ' process, ' ethanol vapors This. may be accomplished by a distillation proc are passed to‘a reaction; zone, and a part of such ess, in which butad-iene is removed as a head vapors'convertedxto acetaldehyde by any of the product along with some acetaldehyde. _ The ‘known methods. These, methods include dehy- : I drogenation of the ethanolto acetaldehyde in the presence of dehydrogenation catalysts, or the ‘catalytic oxidation ofrethanol, toacetaldehyde-by molecular oxygen; ' The‘products from .thisireac- ‘ vtion ‘containing ac'etaldehydeandyethanolqare 55; acetaldehyde may be removed by scrubbing the ,butadiene vaporswith Water, and the l'butadiene maybe puri?ed‘, if necessary, by known methods. > The condensatesstill residuesand liquid scrub ‘ber products from the previousv operations which contain all the effluent materials" ofboth reaction 2,403,742’ 4 3 systems with the exception of butadiene, hydro carbon impurities associated with the butadiene, and the permanent gases, are subjected to a series of distillations. The streams remaining after the separation of butadiene and other gases contain ethanol, acetaldehyde, water, and by-products, such as diethyl ether, which is formed in the bu tadiene reaction, and miscellaneous by-Products . verter need not be operated at undesirably high ' pressures in order to compensate for the pressure drop through both converters. If such high pres sures were maintained, the yield of acetaldehyde by the dehydrogenation of ethanol would be de creased. The alternative to this, in which com pressors are provided between the acetaldehyde . converter and the butadiene converter, would greatly increase the cost of the installation and ethy1 acetate, acetic acid and butyraldehyde. 10 would make operation of the process more com plex. The distillation system removes suf?cient of the In addition, they passage of the 'by-products by-products to prevent their accumulation in the from the acetaldehyde reaction, including hydro cyclic system, and recovers ethanol and acetalde- -. gen, through the butadiene converter might tend hyde for passage to the acetaldehyde and buta to injure the butadiene catalyst, reduce the yield diene reaction systems. One method by which of butadiene, or form other lay-products trouble of the acetaldehyde-forming reaction, such as this may be accomplished is to provide a series of stills adapted to remove the components in the order of their volatility. The ?rst column in such a series removes acetaldehyde from the feed for some to remove. ' ' Suitable apparatus and operating conditions for practicing the process described above will now be described with reference to the attached passage to the butadiene converter. The acet 20 drawing but the invention isnot restricted to aldehyde distills as its azeotropic mixture with these specific embodiments. All proportions diethyl ether, boiling at about 57° C. at 40 p. sci. speci?ed are by weight. , _ ‘ gauge pressure and containing approximately Ethanol vapors alOng with about 10% water 75% acetaldehyde and 25% diethyl ether. Rela tively large amounts of diethyl ether thus accu mulate in the cyclic system and are recirculated through the butadiene converter. This tends to prevent the formation of additional amounts of diethyl ether in the reaction. , The residue from this distillation passes to an other continuous column where the lay-products are removed as a heads product containing a mix ‘ture of binary and ternarygazeotropes involving vapor are introduced to a converter ID of the shell-and-tube type, through a pipe I I, after pass ing through a heat exchanger 12., The converter contains a copper catalyst‘ at a temperature of about 280° C. and part of the ethanol is dehydro genated to acetaldehyde in passing over this cat alyst. The converter may be heated by circu lating a high-boiling organic liquid through heat ing elements in the converter. ~The vapors leave the bottom of the converterthrough a' pipe l3, acetaldehyde, water, diethyl ether, ethyl acetate, pass through the ‘heat exchanger l2 used to pre butyraldehyde and otherimpurities. A batch still 35 heat the feed, and pass through a pipe I4 to a may be provided for the periodic recovery from condenser |5,‘in which most of the vapors are the by-prcducts of the materials employed in the condensed. process. . ' v The uncondensed vapors, the gases and the The residue from the by-products removal still, condensate pass through a pipe I E to a separating consisting largelyv of ethanol and water, passes to 40 ' tank IT, in which’ the condensate collects at the an alcohol still operated under pressure, which bottom. The uncondensed vapors and gases con generates an azeotropic mixture of ethanol and taining acetaldehyde, ethanol, water and hydro‘ ‘water for feeding both reaction systems. The gen pass from the top of the tank through a pipe water removed as a residue is customarily used 7 l8 to a compressor [9, where they are compressed for heating purposesv before being discarded. to a pressure of about 55 p.‘ s. i. The compressed Thus, it may be employed for heating the feed to vapors and gases pass through a condenser 20, the still in which acetaldehyde is removed and from which they are introduced through a pipe ‘the feed to the still in which butadiene is re 2| to the base of a scrubbing tower 22. ‘Here, moved. the water-soluble vapors are dissolved'and re Various methods of removing by-products, -moved from the hydrogen by means of scrubbing other than as indicated, may also be practiced,‘ water, and the liquid effluent flows through pipe as by withdrawing by-products from plates in the 23 to the recovery distillation system. butadiene, acetaldehyde, by-products, and eth The chemical reaction producing butadiene is iuti’ol column, in which such by-produ'cts accumu conducted concurrently with that producing ac a e. etaldehyde In this second chemical reaction, a Other arrangements of the distillation series mixture of ethanol and acetaldehyde vapors, may be carried out in which the materials to :be preferably in the molar ratio‘ ‘of about 3 to 1, is separated are divided into two or more fractions, passed through a heat exchanger 24 through a and such fractions treated to isolatethe compo 60 pipe 25 to a converter 26. The converter con nents, rather than the successive removal of each tains a catalyst of an appropriate type at a tem component in the order of its volatility, as de perature oi 300° to 350° C. Part of the ethanol scribed above. and acetaldehyde are converted to butadiene in The process of this invention represents an in the converter, and the e?iuent vapors pass tegrated process for making butadiene from eth through a pipe 21 to the heat exchanger 24 which anol, in which the acetaldehyde formed by de preheats the reactants. The vapors leave the hydrogenationof ethanol is not passed directly heat exchanger through a pipe 28, and pass to into the butadiene converter, but, instead, is ?rst a condenser 29, where more than half of’ both the passed to a recovery distillation system which butadiene and the acetaldehyde, and almost all produces acetaldehyde, largely freed from impuri the ethanol, are condensed. The vapors and ties formed in both reactions, for passage to the condensate pass through pipe 9 to a settling tank butadiene converter, and recovers unreacted eth 30, where the condensate is drawn o?'through anol. This process possesses the advantage over pipes 3| and 32 to distillation column 5| to re a process in which the products from the acetal cover the butadiene. The vapors from the set dehyde converter are fed directly into the buta diene converter, in that the acetaldehyde con ul s tling tank 30'contain acetaldehyde, butadiene in 5. 6 anamount or about 20%‘,diethy1 ether... ethanol. proximately 1.0%. acetaldehyde. 5%‘ .diethylether, and mono-ole?nes and saturated hydrocarbon gaseseimtheaamount' or. about 1.0 %,. and. they pass 55% ~ethanol,.l5.% Water, 10% butadiene and‘a5% of.‘ other hydrocarbons and. impurities is passed through‘ pump 41 and is'introduced. through pipe through a pipe-.33 toacompressor‘ 34 where they are .compressedito about 55p: s. i-.. The-compressed vapors» and gasespass. through a pipe'S‘SY-toa‘condenser'36, where they are cooled. to; a temperature; of. about; 238-“ C. Part of the vapors:condensev under theseconditions and the condensate and unicon-denscdv vapors and. gases, 10 are introduced under pressure through pipe 31 to the-base ofascrubbing tower 38, having about ‘ 4n. ‘trays- The?rst. condensate from the acetalde hy'sleaproducing; reaction: is: withdrawn from. ‘tank l‘lrxthrousha pipe-3.9 and-pumped by a. pump-4.11. through ‘a pipe: ill]; to the top :of; tower 3:8,. This condensate ‘may-contain‘ about. 8 parts. of. acet'g Miv under .apressureof 55 to 70 p. s. i. to ahea-t exchanger 4.9, where. it is; heated to about 1-109 0. by-meansrof' a suitable. heating ?uid. The feed passes througha .pipe: ‘50- to a distillation column 5|. at about thefthirtiethtray' thereof. This col umnmay' be ofthe. ordinary bubble-cap type with coppertrays; A ?fty-?ve’ traycolumn possesses sui?cient trays for the: separation desired with adequate»allowan'ceior plate. ef?ciency. The col umnisxheated .lby‘ steam, preferably by means -of:.a ealandria through which thecontents of the kettle circulate. - .7 ‘When: the: column‘: .operates under a pressure oi’v aldehyde-,Twparts of‘ ethanol, 13 parts of" water about 6.5 p.. s. i., the- overhead; :vaporfdistills at and .2. parts-of acetic acid... This mixture of about 472°C. :and contains approximately 5.0% ethanol and acetaldehyde is a strong solvent for 20 acetaldehyda; 90% butadiene and. 5.0% butenes butadiene even in the presence of a small amount of: watenand 'it'is; capable-of: scrubbing completely ‘and butane. A smallamount of water may also be. present in the overhead‘ vapor. Part of the therbutadiene from the ascending vapors'w-hen . overhead‘ ‘vapor’ which is removed through pipe employed‘ in. amounts about equal to, or even 52 is condensed‘in a. condenser 53, the condensate somewhat lessithanythat. of the'vapors and con 25 being pumped through. a pipe? 54- as re?ux: to: the densatetentering the baserof the scrubbing. tower at~._-the temperature and‘ pressure specified. - The liquid e?iuent. from the base. of thetower contains column. The reflux ratio. employed’ inv the: opera tion ofythe column’ may be varied from about 4:1 ‘to 20:1. ' substantially all the'butadiene. originally present ‘The residue. is removed from the kettle '55 in-the entering-gases and: it is-withdrawn through 30 through a pipe 56 audit contains acetal'clehyde, pipe 3.2v to distillationcolumni'l for recovery of di'ethyl ether,. ethanol, water andimpurities. It the butadiene. . . is tube noted1 that thescolumn operates with both 'li'hegasesv leaving. the top of tower 3.8 are .ap an: enriching. and. exhausting section, and that proximately saturated. with. the. components of the residue is denuded: of. buta'diene. The residue the. scrubbing liquid,- principally, acetaldehyde passes tothe :recoverydistillation' system through andethanoLand it .iseconomicalto recover these materials. ‘To-effecttherecovery of the acetalde hydeandethanol, the. gases are. passed through a pipe-.42 to a .second scrubbing tower .43, where they are subjected to the washing action of. a pipe'2'3. . condensed. and returned- as: re?ux passes through a valve ‘5''!’ ‘and through pipe '58, and enters a scrubber 59 through a pressure reducing valve 60. The scrubber maybe a forty-tray'column which operates at .a pressure. of 35 pounds per square inch'ata-temperatureof 35° C... and it is designed to remove ‘the acetaldehyde. from the butadiene down ?owing, stream. of water. The liquid. e?iux from the tower passes through pipe 44 to pipe 273, and. thence tothe recovery distillation system. The gases. from this scrubbing tower, containing mono-ole?nes, such .as ethylene and propylene, saturated .hydrocarbon gases, ‘and some carbon vapor by dissolving the acetalde-hyde- in water. dioxide. and carbon monoxide are. discharged from I the system. 'The process‘ just described is the subject to the copending application Serial No. I 0f the overhead ‘vapor, the part which is: not Butacliene is. agasv at this ‘temperature and pres sureandit' does not. appreciably condense, where asy’at thesamelt‘ime, acetaldehyde is'readily ab sorbed in water. ‘.Thewater, introduced at the 501,610 of I. L. Murray, J. 'L. Marsh and S. P. 50 top of the vcolwnns?ows .downward and selectively Smith, Jr., entitled “Process for making buta dissolves the acetaldehyde from the ascending diene." , . . ‘ ' vapors. The'vapors-irom the top of'thIe vcolumn However,_ it is not essential to practice the mayicontain ab out 951%" butadiene. and~ 5% butenes .and' butane. The bntadiene may be separated the bene?ts of the present invention. The con 65 from‘ the butenes' and they butane by known densate from the tank l1 may be withdrawn .method's,;which are nota :part of. the present in through by-pass pipe 45 to pipe 23, and be carried vention. directly to the distillation system. The scrubbing V’I'he aqueous scrubbing liquid from the bottom ‘liquid employed in column 3.8 may then comprise fof'the scrubbing tower contains a. small amount part or‘ all'oi the make-up ethanol required‘ in the ofacetaldehyde; and it passes through a pipe 6| process, which maybe introduced‘ through pipe to: the‘ recovery distillation system. 46, from ethanol storage tank 41. This make-up ‘The scrubber residues from scrubbers 22, 43, ethanol passes to the column for the recovery of and“, and the residue from column 5| are com butadiene and eventually to the recovery disti1la~ iming‘l'ed: in pipe .23- to ‘form a composition con tion system ‘without additional equipment being taining approximately‘ 1.5% acetaldehyde, 5.%-di provided. However, the heat economy secured ethyl.‘ ether, 40% ethanol, and 35% Water and ‘by feeding the make-up ethanol as part of the 5% vIcy-products. This mixture is introduced re?ux required in the operation of the ethanol ‘through- a- preheaters?zibymeans of‘pipe 63 to ' a still would be lost. Alternatively, ‘a separate cycle distillation column 61. This column may operate for scrubbing such butadiene-containing ‘gases 70 at'a pressure-of about 40 p. s. i. gauge'and at a may be provided in which the solvent employed head temperature-"of about 5'7” to 58°C. It is as scrubbing liquid isseparately distilled‘ to strip heated ‘by steam‘, preferably by circulating the ‘process of that application‘in order to secure 0d‘ the ‘butadiene; and residue cooled and. re used in thescrubbingoperation. > y r A- composite feed from'pipe 32 containing ap contentsv of‘ the kettle‘ through an external in ' clined ca-landria. Amixture. of the. azeotrope of 75 acetail'dehyde ‘and .diethyl ether, together with 2,403,742. 7 azeotropes of acetaldehyde and other and employed by products, the composition being about ‘75% acet aldehyde, 20% diethyl ether, and 5% by-products, changer 62; as ~ heating ?uid in heat ver: ' v t ‘ . ' =1 The addition of make-up ethanol as part of the re?ux-required‘ in the column used for distilla tion of the alcohol provides a saving in the heat otherwise required to operatethe still, as de scribed in I. L. Murray Patent No. 2,249,847. Obviously, however, the make-up ethanol may be is withdrawn as vapor through pipe 65, and passes as one of the reactants to the butadiene converter 26. Suf?cient overhead Vapor to con stitute a re?ux ratio of about 3 to 1 is withdrawn through proportioning valve 66 through a pipe 61 added in other ways to the cyclic process, as pre to- a condenser 68, where it is condensed and re turned as re?ux to the column 64 through pipe 69. 10 viously pointed out. Modifications of the inven tion other than as speci?cally described‘, may be a The residues from column 64, containing prin made without departing from the principle of cipally ethanol and water, the remainder being the invention. The essential features of the in diethyl ether, acetaldehyde and other by-products vention consist of a cyclic two-step process 'for pass through a pipe 16 to distillation column ‘H, the production of butadiene from ethanol, them-' 15 after passing through a pressure reducing valve tegration of an acetaldehyde-producing reaction 12. This column may operate at a pressure of with a butadiene producing reaction, and the 20 p. s. i. gauge and a head temperature of 65°‘ to provision of a common distillation system for re-‘ 75° C. It generates an overhead vapor containing covering the‘ unconverted products of the two aldehyde, methyl ethyl ketone, and other im 20 reactions. We claim:; I x ' purities. This overhead vapor all passes through 1. A cyclic process for making butadiene which pipe ‘I3 to condenser 14, where about 116 of the comprises introducing ethanol vapors to a reac condensate is withdrawn through pipe 15 to tion zone, converting a part of such ethanol va storage. These by-products may be distilled from time to time to recover their valuable com 25 pors to acetaldehyde’ and separating an acetale dehyde-ethanol condensate from the remainder ponents. The remainder of the condensate passes of the reaction products; concurrently introduc through pipe 16 to column 1| as re?ux. The ing ethanol and acetaldehyde vapors to a sepa column is heated by steam, preferably by circu acetaldehyde, diethyl ether, ethyl acetate, butyr lating the contents of the kettle through an ex ternal inclined calandria. rate reaction zone, converting a part of the temperature is su?iciently high, about 120° C., ethanol and acetaldehyde to butadiene and sepa rating‘the butadiene from unconverted ethanol and acetaldehyde; distilling acetaldehyde from a mixture containing such unconverted acetalde hyde and said condensate and passing it to the to volatilize all the acetaldehyde from the base of butadiene-producing reaction zone; distilling eth the column. anol from a mixture of the remainder of said con densate and such unconvertedethanol and re 30 In‘ the operation of the acetaldehyde still 64, there is a tendency for by-products to accumulate in the upper third of the column, when the base Such icy-products eventually pass fromv the top of the column and reduce the con centration of acetaldehyde below the desired turning said recovered ethanol to at least one of value. This may be prevented by withdrawing the reactionzones; and introducing additional .40 about 2 to 5% of the total down-?ow from the ethanol to at least one reaction zone. _ column 64, through pipe 11, either in the liquid 2. A cylic process for making butadiene which or vapor phase, and introducing it in the upper comprises introducing ethanol vapors to a reac third of the by-products distillation column ‘H. The approximate composition of the side stream thus withdrawn may be acetaldehyde, 40%, di tion zone, converting a part of such vapors to acetaldehyde and separating an acetaldehyde ethanol condensate from .the remainder of the ethyl ether, 45%, and .by-products, 15%. This process is more fully described in application Serial No. 526,792, ?led March 16, 1944, by M. E. Hitchcock and J. A. Field, which is assigned to the same assignee as the present application. The residue from column ‘H , containing mostly ethanol and‘water, along with some by-products, ‘is pumped through pipe 18 to distillation column 19 in which ethanol is separated from the water. This column may operate at a pressure of 50 r p. s. i. gauge and a head temperature of 118° C. It generates an azeotropic mixture of 85% ethanol, 10% water and 5% by-products, which is withdrawn through pipe 80 as reactant material for the acetaldehyde and butadiene converters. The feed to the butadiene converter is withdrawn through pipe 85. About twice as much vapor as is withdrawn through pipe 80 is withdrawn through pipe BI and condensed in condenser 82. The condensate passes to a re?ux storage tank 83 .to which is added an amount of ethanol equiva lent to that consumed in the process. This mix ture is pumped through pipe 84 as re?ux for the column 19. The column is heated by steam, preferably by the direct introduction of steam into the kettle. The aqueous waste is withdrawn from the kettle through a line 84, and before being discarded, it is used as a heating ?uid in the various preheaters shown in the system, for instance, it may be withdrawn through pipe 86 r reaction products; concurrently introducing ethé anol and acetaldehyde vapors to a separate reac tion zone, converting a part of the ethanol and acetaldehyde in the vapor phase to butadiene and separating the butadienefrom unconverted eth anol and acetaldehyde; distilling acetaldehyde vapors ‘from a‘mixturecontaining suchuncon verted acetaldehyde andv said condensate and passing such vapors to the butadiene-producing reaction zone; distilling ethanol vapors from a mixture containing. such unconverted ethanol and the remainder of said condensate, after expulsion of acetaldehyde, and returning such ethanol va pors to both reaction zones; and introducing make-up ethanol as a reactant to at least one reaction zone. 3. A cyclic process for making butadiene which comprises introducing ethanol vapors to a reac tion zone, converting a part of such vapors to ‘acetaldehyde and separating, an acetaldehyde ethanol condensate from the remainder of the reaction products; concurrently introducing eth anol and acetaldehyde vapors to a separate re action zone, coverting a part of the ethanol and acetaldehyde in the vapor phase to butadiene and separating the butadiene from unconverted ethanol and acetaldehyde; combining such un converted ethanol and acetaldehyde with said condensate to form a mixture containingv acetal ' 2,403,742 , 9 , ~ . dehyde and ethanol; distilling acetaldehyde va phasev reactions, distilling acetaldehyde vapors pors from said'mixture and passing such vapors from said mixture and introducing them to the to the butadiene-producing reaction zone; , dis butadiene-producing reaction zone; distilling at tilling ethanol vapors from the residue remain least part of the by-products from the residue ing from this distillation and returning such eth anol vapors to, at least one of the reaction zones, from the acetaldehyde distillation; distilling eth anol vapors from the residue. of vthe lay-products distillation and returning such recovered ethanol to both of said vapor phase reactions, and intro ducing make-up ‘ethanol as re?ux in said third and introducing make-up ethanol as a' reactant to at least one reaction zone. 7 4. Acyclic process for making butadiene which comprises introducing ethanol vapors to a reac 10 tion zone, converting a part of such ethanol to ‘distillation. ‘ '7. A cyclic process for making butadiene, which acetaldehyde and separating an acetaldehyde comprises introducing ethanol‘ vapors to a, reac tion zone, converting a part of such ethanol to ethanol condensate from the remainder of the reaction products; concurrently introducing eth acetaldehyde and separating an acetaldehyde anol and acetaldehyde vapors to a separate re action zone, converting ethanol and acetaldehyde to butadiene and by-products and separating 15 ethanol condensate from the remainder of the reaction products; converting a, part of ethanol and acetaldehyde vapors to butadiene and other hydrocarbon gases in a separate reaction zone, butadiene from the by-products formed and un converted ethanol and acetaldehyde; separating vat least part of such by-products from uncon verted acetaldehyde and ethanol; distilling acet condensing the reaction products, and separating 20 a gaseous hydrocarbon mixture containing buta diene from unconverted acetaldehyde and etha aldehyde vapors from a mixture containing such nol; bringing such hydrocarbon gases in intimate contact with a scrubbing liquid containing etha unconverted acetaldehyde and, said condensate and introducing them to the butadiene-producing nol as the principal constituent to liquefy and reaction Zone; distilling ethanol vapors from a mixture containing such unconverted ethanol and the remainder of .said condensate, after expulsion of acetaldehyde, and returning such recovered dissolve butadiene therein; distilling butadiene from such scrubbing liquid and. recovering a scrubbing liquid residue; distilling acetalde hyde vapors from a mixture containing such un ethanol to at least one reaction zone; and intro converted acetaldehyde and said condensate, and ducing make-up ethanol to at least one reaction 30 passing such vapors to the butadiene reaction zone. zone; distilling ethanol vapors from a mixture 5. A cyclic process for making butadiene which containing said scrubbing liquid residue, said un comp-rises introducing ethanol vapors to a reac converted ethanol, and the remainder of said tion zone, converting a part of such ethanol to acetaldehyde and separating an acetaldehyde ethanol condensate from the remainder of the condensate, after expulsion of acetaldehyde, and 35 returning such ethanol vapors to both reaction zones; and introducing make-up ethanol to at reaction products; concurrently introducing eth least one reaction zone. anol and acetaldehyde vapors to a separate re action zone, converting ethanol and acetaldehyde to butadiene and separating butadiene from un converted ethanol and acetaldehyde; combining .8. A cyclic ‘process for making butadiene, which comprises introducing ethanol vapors to a reac 40 tion zone, converting a part of such ethanol to acetaldehyde and separating an acetaldehyde ethanol condensate from the remainder of the reaction products; converting a part of ethanol such unconverted ethanol and acetaldehyde with said condensate to form, a mixture containing acetaldehyde, ethanol‘and by-products of the two vapor phase reactions, distilling acetaldehyde vapors from said mixture and introducing them to the butadiene-producing reaction zone; dis tilling at least part of the Icy-products from the residue from the acetaldehyde distillation; dis tilling ethanol vapors from the residue of the by 50 products distillation and returning such recovered ethanol to at least one of said reaction zones; and introducing make-up ethanol to at least one re action zone. and acetaldehyde vapors to butadiene and other hydrocarbon gases in a separate reaction zone, condensing the reaction products, and separating a, gaseous hydrocarbon mixture containing buta diene from unconverted acetaldehyde and eth anol; bringing such hydrocarbon gases in inti mate contact with a scrubbing liquid containing ethanol as the principal constituent to liquefy and vdissolve butadiene therein; distilling butadiene from such scrubbing liquid and recovering a ' scrubbing liquid residue; distilling acetaldehyde 6. A cyclic process for making butadiene which 55 vaporsfrom a mixture containing such uncon verted acetaldehyde and‘said condensate, and passing such vapors to the butadiene‘ reaction comprises introducing ethanol vapors to a reac tion zone, dehydrogenating a vpart of such etha . nol to acetaldehyde and separating an acetalde— hyde-ethanol condensate from the hydrogen gas ~ ‘zone; distilling ethanol vapors from a mixture containing vsaid scrubbing liquid residue, said un produced; concurrently introducing ethanol and converted ethanol, and the remainder of said con acetaldehyde vapors to a separate reaction zone, 60 densate, after expulsion of acetaldehyde, and re converting ethanolv and acetaldehyde to butadiene and separating butadiene from unconverted eth anol and acetaldehyde, combining such uncon verted ethanol and acetaldehyde with said con densate to form a mixture containing acetalde hyde, ethanol and by-productsof the two vapor turning such ethanol vapors to both reaction zones; and introducing make-up ethanol as said scrubbing liquid. 65 ' ' IRVIN L. MURRAY. JAY L. MARSH. SILAS P. SMITH, JR.