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Patented Sept. 25, 1945 ' ‘UNITED STATES PATENT orrlieE-i PROCESS FOR THE PRODUCTION OF ’ DIOLEFINS Kenneth A. Wright, 0akland, CaliL, assignor to Shell Development Company, San Francisco, Calih, a corporation of Delaware ‘ ~ :4 ~ No Drawing. Application January 14, 1944, Serial No. 518,257 14 Claims. (Cl. 260-680) above about 580° C. in the presencaof anexcess‘o‘f “ ,1 This invention relates to an improved process steam with an alkalized' iron oxidecatalyst. I for the production of diole?ns by catalytic de preferred alkali is an alkaline compound ‘of potas' hydrogenation characterized by the use of spe sium. In catalysts for dehydrogenation‘at.‘high,‘, cial catalysts and special high temperature con temperatures in the presence of‘ steam‘anauraam ' ditions affording exceptionally high conversion metal promoter or its equivalent isRe'ssenti'aI sincejifj and production capacity with excellent yield. in its absence the catalyst loses itsinit'ial ,activit _ I, Primary objects of the invention are to provide an improved process for the production of diole ?ns, and particularly butadiene, by'catalytic de in a few minutes of use. 1., _ ' ' It has now been found that the prornqtinge fects of the various alkali metaliproiiioters" ‘inv hydrogenation wherein (1) exceptionally high 10 ‘catalysts of this type, when usedun rlthjes'e“ conversions per passmay be realized, (2) sub conditions, are by no means equival nt‘, 'that stantially improved yields of butadiene may be unexpected, different and greatly impfmveqrr ui‘ obtained", (3) the production capacity of a given are obtained if the catalyst is ‘promoted, v.Wit ’ catalytic reactor is exceptionally high, (4) the de rubidium. Thus, by the simple substitution,‘ hydrogenation is carried out in the presence of 15 rubidium for potassium the conversion per passjis , a large excess of steam and the use of vacuum or approximately doubled; contrary‘ to ‘expectation, P: ; ?xed diluent gases is avoided, and (5) the dehy the selectivity is increased and the active life'orj drogenation may be carried out with inexpensive the catalyst is increased. Thus, the production}; catalysts which retain their activity over longer of a given diole?n in a given reactor, in a givenj periods of time before requiring replacement. 20 time is greatly increased, the produc'iiop jperlvj; The importance of diole?ns, particularly but-a pound of reactant is increased, and the‘produc}; ,_ diene, and the desirability of having improved methods for their production are well recognized. tion nitude of the perimportance ofpound the improvement of catalyst of the problem isrealized, increased. andthethe ' In present]; mag-f View Considerable attention has been given in the past to the production of these valuable materials by 25 invention is considered “to be an importantxad catalytic dehydrogenation processes. Catalytic , vancement in theart. - dehydrogenation to produce diole?ns differs from The process of the invention, since it requires“ most other dehydrogenation processes in requir ' the use of very large amounts of steamand-t‘em- ‘ ing a low partial pressure of reactantsin the re peratures in the order of 600° C. or, above,i_s_‘ap- j ,, action zone. Thus, it is necessary either to carry 80 out the dehydrogenation under a. substantial vac plicable tions vantageously areinrequired. such applied casesThus, for where thethe production these'drasticccndi prqcesscan ofstyreneff be ad; uum or to employ large quantities of a diluent. - Operation under a vacuum is very costly. The use from ethyl benzene and for theiproductiow f _‘; of inert diluents to decrease the partial pressure is, however, particularly from cyclopentanei", advantageousl'fogth The pros, ‘s“ "j of the reactants usually makes the efficient sepa 35 cyclopentadiene ration and recovery of the diolefln from the prod production of dioleflns, and especially’conjug'ated if. uct very difficult and is a serious disadvantage. Steam is an ideal diluent but, unfortunately, many of the most active dehydrogenation catalysts are dioleflns, from such mono-ole?ns‘as"ar'e‘ca ablef", of being vaporized and heated :with ste‘arri' ,to' ‘“‘ poisoned by water vapors and steam cannotbe .40 temperatures of at least 600° C. witho ' employed as a diluent with them. Also, most of the catalysts are not su?lciently selective in their action and if steam is used as a diluent they cata tial Thus, quaternary decomposition they process carbonand is atomsv particularly‘; contain in aatileast‘, straight advantag ' lyze the oxidation of the reactant by the steam, for piperylene, the production isoprene, of such and the diole?ris héxadienes. as butadi , thus giving low yields. ‘ Also, the known catalysts 45 ole?n to be dehydrogenated maybe] a‘, singl‘eg'hyéi , lose their effectiveness in a relatively short pe drocarbon or, if desired, a mixtur'eiof ble?ns may j riod, particularly when steam is employed, and be dehydrogenated to produce a mixture 'jof ,diole'f ‘ must be frequently replaced. fins. Also,‘ in some cases a single ,diole?n'mayjbc. , In order to produce dioleiins by catalytic de hydrogenation using steam as a diluent it is nec essary that temperatures above about 580° C. be used and that the catalyst be properly promoted with an alkali metal or its equivalent. Thus, as produced from a mixture of isomeric ole?ns. ‘For 50 example, butadiene may be produced froni' either H butene-l or butene-2 or a mixture‘ ofjthe "two?; and isoprene may be produced from: methylfethyl if ethylene, trimethyl ethylene, or isopropyl'ethyl shown-in appending application Serial No. 520,534, ene or a mixture of these ole?ns. ‘ filed January 31, 1944, diole?ns may be produced 55, In order to facilitate the recovery of the diole- ' by catalytic dehydrogenation at temperatures 2 2,885,484 ?n and unconverted mono-ole?n from the product and for various other practical reasons, itsis usu ally desirable that the feed consist essentially of the desired ole?n or mixture of olefins. This is, however, not essential and excellent results may be obtained using ole?n fractions containing ap preciable amounts of relatively inert. materials. Thus, for example, in the production- of butadiene ing the preparation in the'iorm of various ru bidium. compounds such. for instance, as the ni trate, sulfate, carbonate, hydroxide, oxide and the like. Very suitable and inexpensive rubidium salts are the rubidium alums. These various compounds; are preferably converted at least in part to rubidium oxide during the preparation and/or use of. the catalyst. Halides, when pres a so-called. butane-lbutylene fraction containing substantial amounts of butane maybe used‘. Un 10 ent in the catalyst, appear to exert a detrimen tal' effect. Since traces oi’ residual halide anions - der the. preferred conditions of operation the par are di?lcult to remove from the catalyst, halide a?in hydrocarbons are substantially unaffected salts‘~ are. not recommended in the catalyst prepa~ and. therefore act as inertv diluents; ration. The rubidium may be used alone as the The catalysts which are applicable at high promoter or it may be used‘ in conjunction with temperatures‘ in the presence of large amounts of one or more other alkali metal promoters such, . steam and which are employed in .the process of in particular, as potassium and/or caesium. the- invention comprise as the primary active Thus, the rubidium promoter may be advanta component a d'ehydrogenating oxide of a transi geously substituted in part "by a potassium pro tion metal‘ of the ?rst transition series 01 the ele ments (1.. e. V, Cr, Mn, Fe, Co. and Ni), Of 20 moter. Very suitable mixtures of salts contain ing potassium and caesium‘ as well as rubidium these, iron oxide is particularly effective and suit may be obtained from the working up of certain able, and nickel‘ oxide is the least effective. These minerals such as certain lepidolites, certain car active dehydrogenating. metal oxides may be pres nallites, and. certain porphyries containing ru - ent singly,.in combination, or in combination with minor amounts of known stabilizing and/or pro 25 bidium. A very suitable material‘ may be pre pared, for example, from, the crude mixture of moting substances such as oxides‘ of copper, zinc salts of rubidium, caesiu'm‘and potassium ob and silver, These metal‘ oxides as well as their tained from the mother liquors in the produc combinations are referred to. hereinafter as the tion of potassium salts. I dehydrogenating metal oxide component of relati‘vely high- activity. The catalyst may consist 80 The amount of rubidium. required to produce the desired promoting client is between about ofv the dehydrogenating metal oxide of relatively 0.8% and 5% by weight of; the relatively active high activity and the‘ rubidium promoter, or it dehydrogenating metal oxide or mixture of metal may contain minor or major amounts of a car oxides in the catalyst. This corresponds to. be rier,,support, diluent or extender of relatively low tween about 0.9% and 5.5% by weight of rubid catalytic activity. Thus, the dehydrogenating 35 ium oxide. Thus, if the catalyst contains 50% metal oxide of relatively high activity may be. by weight 0! a relatively inert. diluent such as employed in combination with a dimcultly reduc alumina, magnesia. or the like, the concentration of rubidium in the total catalyst is between about zirconium or the like- These components may 40 0.4% and 2.5%. If'the rubidium is used in con junction with potassium, the concentration may be in the form of intimate mixtures, for, instance, be decreased to about one-half these amounts. mixed gels. In other cases the dehydrogenating , The rubidium promoter may be incorporated metal oxide of relatively high catalytic activity into the catalyst at any suitable stage in the cat may be- incorporated in. relatively minor amounts in the surface of a major amount of a relatively 45 alyst preparation. In catalysts which are pelleted or formed into pieces by extrudation or other inactive support or‘ carrier such as gelsror mix means, the rubidium is preferably incorporated tures of gels o1 silica, alumina, chromi'a, zirconia, prior to such forming operation since catalysts etc.,, activated carbon, magnesia, diatomaceous of somewhat higher activity and longer life are earth, ki‘eselguhr, bauxite, and the like. Also, ible oxide of relatively low catalytic activity such, for instance, as an oxide of aluminum, silicon, . these various materials of relatively low activity 50 may be combined in mass with the relatively more active dehydrogenating metalv oxide to serve as diluents or extenders. Preferred catalysts, thus obtained. a » In order to maintain the proper state of oxi dation of thedehydrogenatliig metal oxide and to - maintain the,catalytic activity, the process of however, consist largely of the dehydrogenating metal oxide of relatively high activity. Thus, a the invention. is can'ied out‘in the presence of a 55 large. excess of steam. Thus, the mo] ratio 01' preferred group of catalysts contain at‘ least 50% steamv to hydrocarbon fed 'to the reaction zone by weight and- preferably about 70% to 95% of. is at least 2:1 and generally between about ‘7:1 iron oxide. and 3011. The preparation- of the catalysts with respect In order; to obtain the desired results in the to the preparation of‘ the d'ehydrogenating metal‘ 60 presence, or a large excess of steam, the dehydro oxides and/or the combining oIv the. dehydrogen genation is carried out at ‘relatively high tem ating metal oxides with such diluent, extender, peratures. Thus, the dehydrogenation is car supporting or stabilizing materials may be eifect ried out at a temperature at. least as high as 580° ed in. any of the conventional manners. Thus, the C. and generally between about 600°C. and 700° catalysts may be prepared in they wet way by pre 65 C, Somewhat higher temperatures may be em cipitation methods or by slurry methods, or they ployed but are usually unnecessary. ‘A preferred may be prepared by thermal decomposition of method of operation affording high conversion suitable salts, or they may be prepared by the efficiencies consists of adjusting the temperature conventional» impregnation methods. initially to limit the conversion. to, say, 35% or The active dehydrogenating metal oxide or 70 40% and then increasing the temperature as the mixture of oxides, or mixture comprising one or more diluent or carrier materials, is promoted with the incorporation of a relatively small amount 01' a compound of rubidium._ The rubid process continues to maintain this conversion. Thus, the process may be initiated with a fresh catalyst at a temperature oi, say, 590° C. and the temperature gradually increase; to, say, 670° C. ium may be incorporated into the catalyst dur 75 during the life 01' the catalyst. By this method 3 2,885,“! The steam and hydrocarbon were passed through the bed 0! catalyst for periods of 90 to 105 min conversioniei'?ciencies in,the order of 70% to- 0 90 %‘-may usually be maintained. The" dehydrogenation may be carried out un der ‘any-"pressurei'at which the steam and react utes and thecatalvst was steamed tor about 15 minutes under the same conditions between each‘ process period. The following results were ob ant exist in‘the're'action zone in the vapor state. Thus, ‘either-‘vacuum or pressure may be used. tainedi' i > An important ‘advantage of the process, however, I is that excellent results may be obtained at at mosplieric pressure; ~ ' Cycle ‘ In ‘viewio't‘the"exceptional activity of the de Butylene -> ' reacted Butylene ' Conversion ' cg?agsggo eiliclency 10 scribed rubidiumépr’omoted catalysts when used Percent underil‘the' described ‘conditions, the process of 1 ......................... .. - ~ , 72 74 the invention; allows excellent conversion to be obtained? ‘quite selectively over a‘ considerable Percent ‘ lPercent ‘ 43.4 40.9 i vs ‘ soc 60.5 t4 range‘ of space'velo'cities. Suitable space veloci 15 _ A catalyst prepared in the. same manner using ties are; for example, between about 300 and 3000, the same materials except that 4.4% or ‘potas volumes‘of' gaseous reactant (N. T. P.) per vol sium nitrate wasused instead of 5.8% of. rubid ume- of ‘catalyst per hour. Aicontact time afford i'um carbonate, when used at a space velocity ing the optimum results depends‘ upon the partic of only 1000 (other conditions the same), gave ular material being dehydrogenated and the par 20 ticular“ conditions chosen within the above given the following results: ranges and may best be determined for any given case by trial starting with a very-short contact Cycle time .andigraduallyiincreasing the contact time . . _ _ ' Butylene Butylene ‘ reacted Maggie)? Conversion e?iciency ; until‘the desireddegree of conversion is obtained. ' The-1 .contact time "in. the dehydrogenation of butylenesf'and ‘butadienes by way of example is preferably in the order of’, 0.02 to 0.5 second. Percent“ 2 ......................... ._ . 'Pcrcen't " ' Patent 73.5 ‘, "r, 34.3 4 ......................... .. The catalystjmayxbe usedv in any of the con-v > 35.1 ' , 7‘ ’ 46.5 52 It will beobserved that by operating according to‘, ven'tional ‘forms such. ‘as pills, spheres, saddles, 30 the process of the invention approximately 6%» ‘ greater conversion to butadiene was obtained at ,- ._ size adapted-tor the reaction system to be used. - extrud-atcs' ‘oréirregular fragments ‘of a shape and If desired, thelp'rocess may be carried out‘in a so-called dust catalyst, ?uidized catalyst or mov twice the space velocity. ing bed system.) Excellent results may, however, to about 230 % of the normal. - Y conversion and production capacity afforded, the l ' present process has other important advantages. actant vapors and-preheated steam through agre- ~ . The. prior-known catalysts containing potassium - ’ 40 become deactivated during use at a relatively fast~ ~ rate. Thus, prior-known catalysts are=presently material. The ‘unconverted material may be sep version considered to butadiene to be goodunder if theytheabove, sustain a conditions 20% con; 3 , arated from ‘the product in conventional man ners. and recycled.v . ~ Tl > Aside from the unexpectedlylarge increase ‘in : be obtained. bysimply ‘ passing the preheated re action chamber-?lled with the catalyst and main tained ati1the. desired ‘temperature and pressure. The steam in the product may beoeondensed and separated from the ‘converted and, unconverted ‘This corresponds-to: increasing the production capacity of the reactor. 7 except at a gaseous hourly space..-velocity of 500 - ‘ - for 300 process hours. It has been determined‘ a‘ that one of the causes of, this deactivation is due , In ma'nyjcases it is most advantageous to carry 4.5 out the; dehydrogenation in'an intermittent man to loss of potassium from the catalyst-byvolatiliz ation. The rubidium in the catalysts used in the ‘process of the present invention is relatively non ner, that; is, a to: carry vout the dehydrogenation in relatively short periods of, for'instance, 1 to 8 hours with intermittent regeneration in the known manner. In such cases the regeneration 50 volatile as compared to potassium and is volatil- _ ized from'the‘catalyst at a much slower rate. This cause of decline in the activity of the cata may be e?ectedby‘ simply treating the catalyst with steam in the absence of the'reactantforpa . short‘period at the reaction temperature.’ Cer - lyst is ‘therefore substantiallyeliminated. Any; ~ small amount of rubidium volatilized in the proct tain of the catalysts, when employed under the described ‘conditions, do not require‘ such periodic 55 ess of the invention may be recovered and re-, . ~ used. Also, rubidium may be recovered from the _ regeneration and when these catalysts are em ployed the dehydrogenation mayxbe advanta- ‘ 1 spent catalyst bysimple leaching treatment and ~ geously carried‘ out in a substantially continuous mannerr." 1.: . . >. Example A catalyst was prepared asnfollowsrBaker’s c- P. ie'rric oxide‘ was slurried ,‘with 5.8% by reused in preparing fresh catalyst. Thus, al though rubidium saltsare relatively costly, the , 60 catalyst costs in the operation of the process of . the invention are not expected‘ to be increased appreciably and may, in fact, be lower.. I claim as my invention: _ . . .. _ y weight of rubidium carbonate in aqueous solu-,_ 7 l. The process for- the productlonof butadiene tion. ‘The, slurry was evaporated to dryness while i 65 which comprises contacting a normal butylene in thepresence of at least 2,mols of steam per mol stirring. Thefmass was heated at 700° C. for 1 ‘ of mono-ole?n at a temperature above '580". C. hourlandithen broken up into_‘8-20 mesh par ticles. '‘ - . > at a gaseous hourly space velocity between about ’ ' This catalyst wasused for the dehydrogenation , 300 and 3000 with a catalyst comprising a de of a butylenelfraction consisting of butene-l and \70 hydrogenating oxide of iron promoted with ru butene-2 ‘under’. ‘the following conditions: Temperaturmh“ ‘___;__'___'.. ____ .._‘»..._° C-.. 630 Pressure_.“‘___.-...;_' 1 atm, at exit of'catalyst bed Gaseous hourly space velocity_--__¢; _____ __ 2000 Mol ratio, steam to butylene _____ _; _____ .. 14:1 bidium in an amount equivalent to 0.9% and 5.5% by weight calculated as the oxidebased on the dehydrogenating metal oxide of the catalyst. 2. The process for the production of .butadiene which comprises contacting a normal butylene in . 4 a,ses,4e4 the presence of at least 2 mols oi steam per mol of mono-ole?n at a temperature above 580‘ C. at a gaseous hourly space velocity between about 300 and 3000 with a. catalyst comprising iron ox ide and magnesia promoted with rubidium in an amount equivalent to 0.9% and 5.5% by weight calculated as the oxide based on the dehydrogen vating metal oxide of the catalyst. ' 3. The process for the production of butadiene which comprises contacting a normal butylene in the presence of at least 2 mols of steam per mol of mono-ole?n at a temperature above 580° C. adjusted to give a conversion to diole?n between 35% and 40% at a gaseous hourly space velocity between about 300 and 3000 with a catalyst com prising a dehydrogenating oxide of a metal of _ series promoted with a mixture or alkali metal ' oxides comprising potassium oxide, rubidium ox ide and caesium oxide in an, amount equivalent to 0.9% and 5.5% by weight. calculated as the oxide based on the dehydrogenating metal oxide 01' the catalyst, and separating the diole?n from the reaction mixture. i _ . p 9. A process for the production of a diole?n - which comprises contacting a mono-ole?n hav ing at least 4 and not more than 5 non-quater nary carbon atoms in a straight'chain in the presence of at least 2 ‘mols of steam per mol of mono-ole?n at a. temperature above 580°C. ad iusted to give a conversion to diole?n between 35% and 40% at a gaseous hourly space velocity between about 300 and 3000 with a catalyst com the ?rst transition series promoted with rubidium _ prising a dehydrogenating oxide of a' metal 01’ in an amount equivalent to 0.9% and 5.5% by the ?rst transition series promoted with rubidi weight calculated as the oxide based on the dehy um in an amount equivalent to 0.9% and 5.5% drogenating metal oxide of the catalyst. by weight calculated as the oxide based on the 4. The process for the production of butadi 20 dehydrogenating metal oxide of the catalyst, and ene which comprises contacting a normal butyl separating the diole?n from the reaction mixture. ‘ ene in the presence of at least 2 mols of steam 10. A process for the production 0! a diole?n per mol of mono-ole?n at a temperature above which comprises contacting a mono-ole?n hav 580° C. at a gaseous hourly space velocity between ing at least 4 and not more than 5 non-quater about 300 and 3000 with a catalyst comprising 25 nary carbon atoms in a straight'chain ‘in the a dehydrogenating oxide of a metal of the ?rst presence 01' at least 2 mols of steam per mol of transition series promoted with a mixture of mono-ole?n at a temperature. above 580° C. at a alkali metal oxides comprising potassium oxide, gaseous hourly space velocity between about 300 rubidium oxide and caesium oxide in an amount 30 and 3000 with a catalyst comprising iron oxide equivalent to 0.9% and 5.5% by weight calcu and magnesia promoted with rubidium in an lated as the oxide based on the dehydrogenating amount equivalent to 0.9% and 5.5% by weight metal ‘oxide of the catalyst. calculated as the oxide based on the dehydro 5. The process for the production of butadi genating metal oxide of the catalyst, and sepa ene which comprises contacting a normal butyl 35 rating the diole?n from the'reaction mixture. ene in the presence of at least 2 mols oi! steam 11. A process for the production of a diole?n per mol of mono-olefin at a temperature above which comprises contacting a mono-ole?n hav 580° C. at a gaseous hourly space velocity between ing at least 4 and not more than 5 non-quater I about 300 and 3000 with a catalyst comprising a nary carbon atoms in a straight chain in the dehydrogenating oxide of a metal of the ?rst transition series promoted with rubidium and potassium in an amount equivalent to 0.9% and 5.5% by weight calculated as the oxide based on the dehydrogenatin'g metal oxide of the catalyst. 6. The process for the production of butadi 45 ene which comprises contacting a normal butyl presence of at least 2 mols of‘ steam per mol oi’ mono-olefin at a temperature above 580° C. at a gaseous hourly space velocity "between about 300 and 3000 with a catalyst comprising an oxide or iron promoted with rubidium in an amount equiv alent to 0.9% and 5.5% by weight calculated as the oxide based on the dehydrogenating metal oxide or the catalyst, and separating the diole?n ene. in the presence of between about '1 and 14 mols of steam per mol of mono-ole?n at a tem from the reaction mixture. ‘ > ' perature above 580° C. at a gaseous hourly space 12. A process-for the production of a diole?n velocity between about 300 and 3000 with a cata. 60 which comprises contacting a mono-ole?n hav lyst comprising a dehydrogenating oxide of a ing at least 4 and not more than 5 non-quater-~ metal of the first transition series promoted with nary carbon atoms in a straight chain in the rubidium in an amount equivalent to 0.9% and presence of at least 2 mols of steam per mol of 5.5% by weight calculated as the oxide based on mono-ole?n at a temperature above 580“ C, and the dehydrogenating metal oxide of the catalyst. 65 at a gaseous hourly space velocity between about 7. The process for the production of butadiene 300 and 3000 with a catalyst comprising a dehy which comprises contacting a normal butylene in drogenating oxide oi’ as metal of the ?rst transi the presence or at least 2 mols of steam per mol tion series promoted with rubidium and potas of mono-ole?n at a temperature above 580° C. at sium in an amount equivalent to 0.9% and 5.5% a gaseous hourly space velocity between about 00 by weight calculated as the oxide based on the 300 and 3000 with a catalyst comprising a dehy dehydrogenating metal oxide of the catalyst, and - drogenating oxide of a-metal of the ?rst transi tion ‘series promoted with rubidium in an amount equivalent to 0.9% and 5.5% by weight calcu separating the diole?n from the reaction mix ture. 13. A process for the production of a diole?n lated as the oxide based on the dehydrogenating 65 which comprises contacting a mono-olefin hav metal oxide of the catlayst. ing at least 4 and not more than 5 non-quater 8. A process for the production of a diole?n nary carbon atoms in a straight chain in the ' which comprises contacting a mono-ole?n hav presence of between about '7 and l4‘mols of steam ing at least 4 and not more than 5 non-quater per mol of mono-olefin at a temperature above nary carbon atoms in a straight chain in the 70 580° C. and at a gaseous hourly space velocity presence of at least 2 mols of steam per mol of between about 300 and 3000 with a catalyst com mono-ole?n at a temperature above 580° C. at a prising a dehydrogenating oxide of a metal of gaseous hourly space velocity between about 300 the ?rst transition series promoted with rubidi~ and 3000 with a catalyst comprising a dehydro um in an amount equivalent to 0.9% and 5.5% genating oxide of a metal of the ?rst transition by weight calculated as the oxide based on the 5 aaemae space velocity between about 300 and 3000 with a catalyst comprising a dehydrogenating oxide 01 a metal of the ?rst transition series promoted ture. ‘ with rubidium in an amount equivalent to 0.9% 14. A process for the production of a diole?n which comprises contacting a mono-ole?n hav Cl and 5.5 %- by weight calculated as the oxide based on the dehydrogenating metal oxide of the cat ing at least 4 non-quaternary carbon atoms in alyst, and separating the dioleiin from the reac a straight chain in the presence of at least 2 dehydrogenatinz metal oxide of the catalyst, and separating-the diole?n from the reaction mix mole oi steam per moi of mono-ole?n at a tem perature above 580° C. and at a :aaeous hourly tion mixture. \ ‘ KENNETH A. WRIGHT.