CA2056429A1 - Method for preparing 1,4-diacyloxy-2-butenes - Google Patents

Abstract

METHOD FOR PREPARING 1,4-DIACYLOXY-BUTENES

Abstract of the Disclosure Crude butadiene can be used for making 1,4-diacyloxy-2-butenes by acyloxylation over palladium-containing catalyst by hydrogenating the crude butadiene sufficient to enhance at least one of catalyst activity and catalyst life for acylozylation.

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Description

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~ETHOD FQ~ 1.4-~IACY~OIY ~ I~E5 This invention pertains to processes for the preparation of 1,4-~iacyloxy-2-blltenes from crude butadiene streams.
~ac~g~n~nd to ~he In~en~iQn Heretofore, the reaction of ~utenes and~or ~utadiene with oxygen and carboxylic acid (acyl~ylation~ has been proposed to make, ~mong other compounds, 1,4-~iacyloxy-2-butene (DAOB).
DAOB can be used as an intermediate to, e.g., 1,4-butanediol and tetrahydrouran.
E~emplary of the process~s for makin~ DAO~
include that disclosed in United States Patent No.

3,872,163 (Shimizu, et al.). According to the patent, at least one unsaturated compound selected from the ~roup consisting of butene-l~ eis-butene-2, trans-bute~e-2, 1-acylo~y-2-butene, l-acylo~y-1,3-butadiene and 1,3-butadiene is reacted with a carbo~ylic acid and o~ygen in the presence of ~n effective amount of a catalyst containi~g palladium. The carbogylic acid is a monocarbo~ylic acid of ~he general ormula RCOOH wherein R i8 a hydrocarbon radical of 1 to lB carbons, an~ the ratio of starting-unsaturated compound ~o car~Q~ylic acid is in ~he range of from 10:0.1 ~o 10:100. The ~mount of o~ygen in the gas mi~ture is preferably 2 to 10 percent ~y volume and the reac~ion is carried out ~t temperatures pre~erably in the range of 80 to 200 C ~n~ a pressure of 20 ~tmospheres or less.
Th~ palladium ca~alyst pr~erably contains a promoter which i~ an ~lkall metal salt of o ;;

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carbo~ylic acid. The e~amples show various butenes, mi~tures of butenes, and butadiene as feed reactaDts. E~ample XXIX discloses the use of ~8B-fraction" in the feed. The BB-fraction is said to contain butane, l-butene, 2~butene, isobutene, butadiene and hydro~arbons having more than five carbon atoms at a volu~e ratio of respectively 4, 11, 6, 19, 56 and 4 perc~nt.
Onoda, et al., in United States Patent No.
3,755,423 disclose the preparation of unsaturated glyeol ~iesters by reacting a conjugated diene, a carbo~ylic acid and o~ygen in the presence of a catalyst composed of a misture of palladium and at least one component of antimony, bismuth, selenium or tellurium. This cata}yst is said by Onoda, et ~1., to be improved in their United States Patent No. 3,922,300 in which an activatea carbon support is used and the catalyst has l:~een treated ~y ~equential o~idation and reduction ~teps. In the latter patent, the patentees state that butadiene and isopr~ne ~re the preferred conjugated dienes.
"The eonjugated ~iene need not be in purified form dll1l may contain inert gases, ~uch as nitrogen; or the like, or a ~atur~ted hydrocarbon ~uch as methane, eth~ne, butane ~nd others, N ~Colurnn 2, lines 45 to 4B) The carboxyliG ~id are aiâ to in~lude ~ny aliphatic, alicyclic or ~romatic aei~s with lower aliphatic ~rbo3ylic arids being intiustrially ~esirable, and th2 aci~ is provi~ed in an amount prefera~ly ~ o~e ~0 wei~ht percent of the reaction medium. The o:~cygen i~ provi~led in ~n amount of 1 to 60 mole perc~nt of the fe.ed ~a~e~. The re~ction is .

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preferably conducted at 60O to 180 C at atmospheric or superatmospheric pressure.
Japanese patent B~022592 discusses the preparation of acetic acid esters by reacting butenes with o~ygen and acetic 3cid over palladium and lead-containing catalyst. l-Buten~ i~ said to provide butyl acetate, sec~butyl acetate an~
1,4-diaceto~ybutane.
Tanabe in ~nited Stat.es Patent No.

4,075,413 addresses a prob~em of catalyst deactivation in the preparation of DAOB by the reaction of butadiene, acetic acid and oa:y~en over palladium-containing ~atalyst. Tanabe states that vinylcyclohe~ene can have a deleterious effect on catalyst life and therefore states that the vinylcyclohea~ene conten~ of the ~eed should be 1 to 5000 parts per million by weight of butadi~ne and at least one polymerization inhibitor be present. At colllmn 2, lines 53 ~ ~a-, the patent~e states:
"A small amount of impurities such as carbonyl compounds, acetylenes, etc., are ~ontained in industrial grade butadiene. ~nong such impurities, vinylcyclc~he~sene, if ~ontained in es~cess, may gi~e ri~e to ~ ide rea~tion an~ c~use d~zcessive dleactivation of ~he 8cetogylation reaction caltalyst. "
Inaustrial grade,~utad;ene was not aefinsd by Tanabe. Although there are ~ew general ~pecifications for bu~adîene, industrial grade butudiene i~ conventionally ~nsidere~ to be a xefined bu~adi~ne 6tream ~rom ~hich impurities ~ave been removed. aenerally, industrial srade butadiene ha less than 1000 parts per million by wei~ht D 16,275 . .

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(ppmw) of acetylenes-~and sometimes less than 50 ppmw of acetylene and less than ~5 ppmw carbonyls~.
The majority of the butenes and butanes have also been ~eparated from the butadiene. Vinyl cyclo-hexene is an impurity that is generated upon storage of butadiene and therefore may not be present in significant amounts in a freshly refined butadiene stream.
~ itsubishi Rasei Corporation has implemented a commercial process for making 1,4-butanediol and tetrahydrofuran involving producing 1,4-diacetylo~y-2-butene from 1,3-butadiene by reaction with acetic acid and o~ygen in the presence of palladium-containing catalyst. ~ee, for instance, Tanabe, nNew Route to 14~G and THF,~ ~ , 5eptember, l9Bl, pages 187 to 190, and ~1,4-ButanPdiol/Tetrahydrofuran Production Technology,~ C~m~ , Decem~er 198B, pages 759 to 763.
While 1,4-diacetylo~y-2-butene has been effectively pxoduced on a commercial scale using a r~fi~ed butadiene feed which has a relatively low content of vinylcyclohe~ene, refining these crud~
butadiene streams to obt~in a refined butadiene can be relatively e~pensive. Gen~rally, these r~fining processe~ involve one or more e~tsactive ,_ distillation ~teps and two or more distillation opera~ions.
The ability to e4fectively use crude butadiene ~eedst~eams coul~ offes additional economic a~vant~ges. Cru~e butadiene ~treams, e.g., D-16,275 ,;' .
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2 ~ 9 ~rom thermally cracking ethane, other lower alkanes, naph~has or gas oils to ethylene, contain hutane, various butenes (l-butene, cis-2-butene, trans-Z-butene and isobutene), various acetylenes (e.g., methyl acetylene, dimethylacetylene and vinyl acetylene), carbonyls and heavier hydrocarbons, especially those containing five or more carbon atoms. Processes are thereore sought to effectively use these crude butadiene streams to produce 1,9-diacylo~y-2-butene~
~_o In accordance with this invention, crude butadiene streams which have been subjected to mild :~
hydrogenation to reduce the content of acetylenic components, are reacted (acyloxylated) with carboxylic acid and o~ygen in the presence of an effecti~e amount of palladium-containing catalyst to produce 1,4-diacyloxy-2-butene (DAOB). Preferahly, the total acetylene components in the hydrogena~ed crude butadiene stream are less than about 0.5, most preferably less than about 0.05, weight percent based on the total weight of the crude butadiene stream. O~ten, the mild hydrogenation conditions comprise a t~mperature of about 20C to 70C, a pressure of 6 to 11 atmospheres absolute, the presence of a ~atalytically-effective amount of palladium hydrogenation catalyst and a mole ratio of hydrogen to acetylenic components of about 0.5:1 to S:l or 10:1 or more. By the processes of this invention, crude ~utadiene streams can effectively be used to produce DAOB without undue deactiva~ion of the palladium-contai~ing catalysts.

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2~3 Petailed Di~~s~iQn ~, In the processes of this invention, treated, crude butadiene ~treams are reacted with carbo~ylic acid and o~ygen to produce DAOB. Crude butadieDe streams typically contain:
Typical Amounts, ome~n~n~ h~_E~I~
Methyl acetylene0.01 to 1.5 Isobutane0.01 to 20 n-Butane 1 to 20 I~obutylene0.02 to 40 l-Butene 4 to 25 Trans-2-Butene1 to 10 Cis-2-Butene1 to 10 1,3-But~diene25 to 90 C4 Acetylenes0.1 to 5 Cs's up to ltO
Vinylcyclohexene0.01 to 0.5 Crude butadiene streams may be obtained as a co-product from the thermal pyrolysis of hydrocarbon feedstocks to ethylene. The crude butadiene is typically the ~i~tillation fraction from the ~thylene unit refining train which has predominately four carbons in the hydrocarbon chain, ~nd boils in the range of about -11.6C to about 10.9C at atmospheric pressure. The ~rude butadiene is typîcally recovered as the overhead from the debutanizer tower in the ethylene unit. See for instance, Albright, ~yle F.; Cryneæ, Billy L. and Corcoran, William H., ~
Industrial_Pra~ice, pp. 41, 28~-291 and 402-~06, herein incorporated ~y reference. Alternatively, if the ethylene unit feedstock is predominately ethane, which produces only small quantities of C5 and heavier hydrocarbons, the refining train may be D-16,275 configured such that a rough C3/C5 fractionation is made first, with the C4's recovered later from the lower boiling cut as a t2ils from the depropanizer column.
The composition of the crude butadiene stream can vary gre3tly, depending on the type of hydrocarbon feedstock and cxacking ~everity used in the pyrolysis section in the ethylene unit. In general, higher ~everity produces higher concentrations of 1,3-butadiene an~ C4 ~cetylenes, and results in lower csncentrations of butanes and ~utenes, in the crude butadi~ne ~or a given feedstock. The 1,3-butadiene an~ C~ acetylenes concentr~tions are highest for high severity eth~ne cracking, and lowest ~or n-butane cracking at moderate severity. Isobuty~ene concentrations from ethane or propane cracking are generally low, with higher concentrations from naphtha or gas oil cracking. (~ee, for instance, Schulze, J., and Humann, M., (198~), pp. 19-2~.
~ ecause the crude butadiene i~ recovered from the ~thylene unit as a distillation raction, the ~ncentration of vinylcyclohe~en , which bvils at a much higher temperature (126C at ~tmospheric pressure), is e~tr~mely low i~ the crude ~utadiene ~s it leaves the~olefins UDit. Generally, the-concentr~tion o~ 4-vinylcyclohe~ene in the crude butadiene is le~s than 0.04 weight per~ent a~ the material leaves the ethylene uni~. Howev~r~ because the 1~3-buta~iene can dimerize ~lowly to 4~vinylcyclohe~ene, even at ambi~nt temperQtures, .

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- 8~ 2 9 the concentration of 4-vinylcyclohe~ene may increase to as high as 0.4 weight percent (or more) in the crude butadiene as the material sit~ in storage, or during shipment to a butadiene refining f~cility.
By feeding the erude butadiene from the olefins unit directly to the acylo~ylation process, only minimal amounts of vinylcyclohe~ene have time t~ form. Usually, the amount of vinylcyclohe~ene in the feedstream for reaction with the carboxylic acid is less than 5000, preferably, less than about 2000, parts per million by weight based on the weight of butadiene.
To the e~tent that vinylcyclohe~ene is present in deleterious amounts, it may be removed by distillation or adsorption such as disclosed in United States Patent No. 4,075,413, herein incorporated by reference.
As stated above, the crude butadiene stream contains acetylenic compon~nts. In accordance with this invention, sufficient ~mounts of the ~cetylenic components are hydroyenated to enhance at least one of catalyst activity and catalys~ life. The ~ydrogen~tion is preferably conducted under conditions such th~t relatively little, if any, of the butenes and but~dienes ar~ hydrogenated.
Esemplary of the hydrogenation proc~sses includes De~iderio, et a-~, in United St~tes Patent Nv.
3,898,298; Frevel, et ~1., in Vnited ~tates Patent 3,B97,Sll: and ~ross, et al., in Vnite~ States Patent 3,859,377, all herein incorporate~ by zeference.

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g According to Desiderio, et al., which is practiced commercially, a preferred process or selectively hydro~enating the vinyl ac~tylene and ethyl ~cetylene wi~h relatively low conversion of but~diene uses a catalyst of about 0.05 to 0.
percent palladium supported on alumina under hydrogenation conditions including a temperature within a range of about 20C to about 70C, preferably about 35C. Selectivity is achieved by maintaining the pressure within a ran~e of about 6 to 11 atmospher~s a~solute, e.g., near 7, to achieve mi~ed (liquid and vapor) phase operation. The crude buta~i~ne stream is passed through two reactors in seri~s, with the hydrogen to acetylenes ratio set at ~bout one in the first reactor and not more than about fiYe in the ~econd reactorO In a given e~ample, the fir~t reactor was operated with an inlet temperature of 41C and outlet temperature of 52C, and the ~econd reactor with an inlet temperature of 30C and ~utlet of 60~C. A 93%
conver~ion of vinylacetylene ~nd 78% conv~rsion of ethylacetylene was obtai~d wi~h a 1% net loss of 1,3-butadiene to n-butenes.
Accor~ing to Gross, et al., a preferred process f or ~ele~tively hy~rogenating C9 acetylenes in crude butadien~ uses a ~atalyst of 0.01 to 1.0 weig~t percent pall~ium impregnated to depth of at l~sst 0.012 inch on ~ kiesel~uhr ~upport havin~ ma~ropore~ of greater than 700A , constituting ~t least 75 percent of the total pore volume thereo~. The reaction is carried out in the -:
llquid phase ~t temperatures of 10C to 80C, D-1~,275 ' .
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preferably from 21C to 66C and pressures of about 40 psig to a~out 300 psig, preferably 80 to 200 psig. The weight hourly spaee velocity of the liquid C~ hydroearbons is less than about 50 ~nd preferably within the range of 2 to 35. The hydrogen stream is diluted by at l~ast 50 percent with an inert gas, preferably contains from 4 to about 35 mole percent hydrogen, and is present in a ratio of hydrogen to total C4 hydroearbons of 0.005 to 0.08 mole ratio, pre~erably at about 0.008 to 0.06 mole ratio. At these conditions about 94 to 99.5 percent of the vinylacetylene is converted and 48 to 77 percent of the ethylacetylene is converted, with a net 1,3-butadiene loss as low a~ one percent.
Frevel, et al., which has also been commercialized, disclose a process whieh ~electively reacts the alpha acetylenes from hydrocarbon streams u~ing a finely diYided metal catalyst, consisting of copper plus at least one poly~alent activator metal ~upported on a high surface area gamma alumina containing a de ined amount of Na2O. Suitable activatox metals include silver, platinum, palladium, manganese, nickel, cobalt, chr~mium and molybdenum. The hydrocarbon ~tream, ~uch as crude butadiene, is fed as a vapor over the catalyst at ~emperatures o~ about ~0C to about 250C, preferably 50 to'100C. Pres~ure is stated tô~havç
little effec~ on catalyst perfoxmance.
In one e~mple, the erude butadiene was fed : at 64 gas hourly space ~elocity at 49-59C c~talyst temperature and ambient pressure to ~ive greatex ~han 96 percent conver~ion of acetylenes. ~o da~a were giYen on net lo~es of 1 9 3 bulta~liene.

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Vinylacetylene and other acetylenes from the crude butadiene would be hydrogenated in the liquid phase, according to the proc~sses disclo~ed by Desiderio, et al., or Gross, et al~ Cru~e butadiene is generally a~ailable from the ethylene unit as a liquid. Thereore, by performing the hydrogenation in the liquid phase, the eostly vaporization and reconden~ation of the hydrogenated crude buta~iene can be avoided.
Although acetylene~ can be removed from crude butadiene to low levels according to any ~umber of absorptio~ processes, e.g., ~ee Unitsd S~ates Pa~ent ~os. 3,436,43B; 3,772,15B: 3,798,132;
4,024,028; 4,D38,156; 4,054,613 and 4,076,595, in accordance with this invention the acetylenes are selectively hydro~enated. Thus, the energy an~
capital intensive distillation and refining st~ges required in the absorption processe~ ~re avoided.
Moreover, by this invention, the hydrogenated crude butadiene is proven to be an advantageous feed for acylo~ylation.
Advantageously, the hydrog~nated crude butadiene stre~n~ can be directly used to make DAOB
without ~urther ~reatment. Preferably, the crude buta~iene stream is used within about ~0, preferably within about 30, hours of the cracking ~peration which gener~tes ~he C4 ~tream.
The carbo~ylic acid used in making D~OB may be any suitable aliphatic, alicyclic or ~romatic carboxylic 3Ci~, e.g., of 2 to 18 or more carbon atoms. Pre~era~ly, the ~arbosylic acid i~
monofunctional~ The ~ommercially pr~erred ..

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carbo~ylic acids are acetic acid and propionic acid with acetic acid being most fr~quently desired. The carbo3ylic acid is usually provided in a molar amount of at least about 1:1 prefera~ly about 2:1 to 20:1, to the unsaturated components in the feedstream. The source and amount of o~ygen provided for the reaction may also vary widely.
Often oxygen or air is used as the sour~e o oxygen due to their ready availability. Prefera~ly, the oxygen concentration in the reactor ;s maintained below esplosive limits, and the mole ratio of o~ygen to total unsaturates is about 0~5:1 to 20:1 or more, ~:
and the mole ratio of o~ygen to carboxylic acid is often about 5:1 to 20:1. The o~ygen may be diluted with gases such as nitroyen and carbon ~io~ide.
The palladium-containing catalyst is provided in a catalytically-effective amount. In batch processes, the catalyst is usually present in ~n amount of about 0.001 to 5 weight percent based on the wei~ht of the feed; however, the processes are preferably conducted in a contin.uous mode, and the ~pace velocity ~based on the volume of carbosylic acid and crude butadiene fed to the volume occupi~d by the catalyst) is about 0.5 to 100 or more reciproca~ hours. The ~atalyst may be unsupported or supported on-a fiuitable carrier, e.g., activated ~arbon, ~ilica gel, ~ilica-alumina, molecular si~ves, alumina, clay, ~agnesia, magnesium alumi~ates, ~iatomaceous earth and pumi~e. ~hen supported, th~ ~atalyst ~mprises about 0.1 ~o 40, preferably 2 to 30, wei~ht percent palladium. The cataly~t may contain co-~atalysts such ~s bismuth, :

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_ 13 -selsnium, antimony and tellurium, e.g., in amounts of 0.05 to 25 percent by weight as well as promoters such as halide ions and alkali metal salts of carbosylic acids, especially of the carbo~ylic acid used in the formation of DAOB. United ~tates Patents Nos. 3,755,423; 3,872,163; 3,922,300 and 4,075,413 which disclose catalysts and their:
preparation are herein incorporated by reference.
The reaction is frequently conducted at an elevated temperature, e.g., between about 50 and 200 C, say, 80 and 160 C, and at re~uced, atmospheric or superatmospheric pressure, for ;~
instance, between about 0.1 to 200, more often about 10 ~o 100, atmospheres absolute. The reaction may be conducted with the carbo~ylic acid and crude butadiene in the vapor, liquid or mi~ed vapor and liquid phases. Generally, the pressure ~nd temperature are such khat at least a portion o the carbo~ylic acid and crude butadiene stream iæ
maintained in the l;qui~ phase during the reaction.
When a liquid phase reaction is sought, solvents may be used; however, e~cess carbosylic acid reactant may ~onveniently provide suitable ligu;d phases.
The catalytic reaction may be condueted in any su;table reactor, e.g., fi~ed bed, moving bed, fluidized bed, ebulating bed~ or risin~ bed reactors. Often, fi~ed bed reactors prove to-be adequate. The reactants may be introduced into ~he reactor in ~ny ~uitable manner, e.g., ~s ~eparate or multiple ~treams or as premised ~treams. ~hen at least a por~ion of the carbo~ylic acid and crude butadiene ~tream are in the liquid phase, the D-16,275 .
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-- lg--oxygen-containing gas may be introduced countercurrently or, preferably, cocurrently.
The reaction mi~ture, when a liguid phase is to be present in the reactor, may contain polymerization inhibitor such a~ disclosed in United States Patent No. 4,075,413. E~emplary of polymerization inhibitors are phenols and quinones and derivatives th~reof such as hydroquinone, 2,5-di-t-butylhy~roquinone, 2,5-di-t-amylhydroquinone, t-butylcatechol, di-t-butylphenols, di-t-butyl-p-cresol, 4,4'-~utylidene bis (3-methyl-6-t-butylphenol~, 2,2'-methylene bis ~-methyl-6-t-butylphenol), ~uinone, anthraquinone, elemental sulfur and the like. The amount of polymerization inhibitor used will vary by the type of inhibitor used. In general, when employed, the polymeriz~tion inhibitor is present in an amount o4 between about 2 and 5000 parts per million by weight based on the wei~ht of the total crude ~utadiene ~tream and ~arbo~ylic acid.
Optionally, a p~rtion of the liquid product from the acylo~ylation reactor may be recycled to the feed of the reactor ~o help moderate the e~otherm of the reaction to less than about 30C.
See Unitea States Patent No. ~,235,729, herein incorporated by reference. Alternatively, the heat ~ay be r~moved b~ ~ny other conventional means, ~uch as heat e~change ~ith the xeac~or ~u~es. ~he temperature is preferably kept low to limit the react;on of ~ut~diene to ~inylcycloh~sne.
The unreacted C4 hydrocarbons from the reactor ~ffluent may be ~lashed from th~ rea~tion D-16,275 : .

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produ~ts 9 and be recovered from the gas phase by absorption into aeetic acid as described by Tanabe, et al., in United States Patent No. 4,152,5~5, herein incorporated by reference. Alternatively, the untreated C4's may be recovered by absorption into another suitable solvent, by aistillation, or by other suitable means. The recovered C4's may then be recycled to the reactor. ~ee also, United States Patent No. 4,057~472.
Generally, a portion o~ the unreacted C4 hydrocarbons are purged from the reactor system to remov~ the butanes and other unreactive species.
Because the butenes are l~ss reactive than 1,3-butadiene in the a~ylo~ylation rea~tion, the unreacted C4 hydrocarbons purge typically contains butenes and butanes. In ~act, this unreacted C4 hydrocarbon stream may be similar in composition to the butenes/~utanes co-produ~t ~tream typically recovered from r~fining cru~e butadiene to rubber grade 1,3~butadiene. ln this manner, ~he - 1,3~but~iene frvm the original crude buta~iene can be reacte~ out of the ~tream, eliminating the need to separate the ~ru~e butadiene into refined 1,3 butadiene dnd bu~enes/butanes in 6everal ~eparate e~pensive absorption and di~tillation steps before the acylo~ylation reactors.
~ y ~ay Of e~ample, a crude butadiene feedstream, available as ~ uid co-produc~ fsom an ethylene unit, contains:

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Poun~ ~çr Hour Methylacetylene 170 Isobutane 889 n-~utane 606 : Isobutylene 465 l-Butene 857 -But ene 1150 1,3-Butadiene 6679 C4 Acetylenes 233 .~s 3S6 ~-Vinyl-l-cyclohe~ene 9 and is fed at ~ rate of 11,416 pounds per hour to a hydrogenation reactor. The hydrogenation reactor feed is pumped directly to the first stage hydrogenation reactor as a li~uid at 35C ~nd 150 psig. The reactor is a series of two fi~ed beds, packed with a 0.1% palladium on alpha alumina catalyst, such ~s disclosed in E~ample 1 of Desi~esio, et al., Vnit~d States Patent No.
3,898,298. The two beds contain a total of 900 lbs.
o~ catalyst, giving a WHSV of 12.7 pound fee~/pound cataly~t/hr.
A mi~ture o~ hydrogen and me~hane is ~ed co-currently with the crude butadiene stream ~o ~he bottom of the first ~atalyst bed at a hydrogen to total ~cetylenes ratio o~ l~Oo This is e~ual to 17.8 pounds per hour hydrogen and 7.5 pounds per hour ~ethane. The product from the ~irst ~atalyst bed is ~ed to the bottom of the ~econ~ catalyst bed along with an a~ditional llol pounds per hour hydrogen and 4.6 pounds per hour methaneO The : product ~rom the rea~tors is then flashed to remove the residual 1.4 pounds p~r hour ~ydrogen and 12.1 pounds per hour methane. The hydrog~nated str0am ~ont~in~ ~ppro~mately the ~arne amount of but~nes, D~16,27S
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1,3-butadiene, isobutylene and C5'~ as in the feedstream. The methylacetylene is reduced to 17 pounds per hour and the C4 acetylenes are reduced to about 2.9 pounds per hour. Propylene is present in the amount of 161 pounds per hour, and the l-butene and 2-butene contents are increased to 985 per hour and 127B pounds per hour, respscti~ely.
The ~ydrogenated crude stream is admi~ed with an acetic acid feed stream which contains some unreacted C4~s scrubbed from the flashed vapors from the aceto~yl~tion reactor:
~gun~s P~I H
Water 850 Isobutane 8B0 n-8utane 1405 Iso~utylene 476 l-Butene ~76 2-Butene 460 1,3-Butadiene 1163 C4 Acetylenes llS
4-Vinyl-l-cycloh~ne 0 Acetic ~cid 18$895 Total 191620 Th~ resulting crude butadiene/acetic acid mi~ture is blended with 423,467 pounds per hour of liquid recycle from the reactor, ~hich has the : following composition:

; Water 8868 Nitro~en 5244 ~.
O~ygen 61 Argon 88 Carbon dio~ide 9 P~opylene 172 Isobutane 3503 ; n-Butane 399B

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Isobutylene 1355 2-Butene 1339 1,3-~ut~diene 3309 C4 Acetylenes 0 C5 Hydrocarbons 235 4-Vinyl-l-cyclohe~ene0 Acetic Acid 33914B
Allyl acetate 344 l-Acetyosy-1,3-butadiene 136 Methylallyl acetate14 3-Aceto~y-l-butene 3B2 Crotyl acetate 595 tert-Bu~yl acetate191 3,4-Diaceto~y-l-butene 4417 1,4 Diaceto~y-2-butene 46251 1,4-Diaceto~ybutane16 Other 2751 Total 423~67 - By material balance, the sum o ~he three feed streams to the reactor is:

Water 971B
Nitrogen 52 O~ygen 61 Argon 88 Carbon dio~ide 9 ~ Methylacetylene 17 : Propyl~ne 333 I~obutane 5267 n-Butane 6009 I~obutylene 2296 l-~utene 2432 ' 2-~utene 3046 1,3-9ut~diene 11151 C4 Acetylenes 2.4 Cs Hydrocarbons706 4-Yinyl-l-cyclohe~ene 9 ~etic ~cid ~25030 Allyl ~c~tate ~44 l-Acetyoxy-1,3-butadiene 136 . .
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r ~ , ' '; ' .' , 7 -- 19-- , Methylallyl acetate 14 3-Aceto~y-l-~utene 382 Crotyl acetate 595 tert-~utyl acetate 191 - 3,9-Diaceto~y-l-butene 4417 1,4-Diaceto~y-2-butene 46251 1,4-Diaceto~ybutane 16 Other 2751 Total 626517 This liquid reactor feed stream is introduced into the bottom of the ~ceto~ylation reactor at about 870 psia and 80C. The reactor contains 38000 pounds of palladium-tellurium on activated carbon catalyst, ~uch as disclosed in E~ample 3 in Onoda, et al., U.S. Patent ~o.
3,922,300. Sparged into the bottom of the reactor is a compressed air~nitrogen stream containing:

Water 4G939 o~ygen 787 Argon Carbon dioxide 24 Propylene 23 I~obut~ne 180 n-Butane 197 Isobutylene 67 l-Butene 53 2 ~utene 64 1,3-Buta~iene 163 C5 Hydrocarbons 3 ._ Ac~tic Acid 75 Withdrswn ~rom th~ top of the reactor at 102C i~ the pro~uct ~tream containing:

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Po~nds Pe~ Hour Water 13239 Nitrogen 52183 Oxygen 609 Argon 875 Carbon dioxide 33 Methylacetylene 0 Propylene 2~5 Isobutane 5447 n-Butane 6206 I~obutylene 2103 l-Butene 1662 2-Butene 2031 1,3-Butadiene 5136 Cg Acetylenes 0 Cs Hydrocarbons 355 4-Vinyl-l-cyclohesene 0 Acetic Acid ~06282 Allyl acetate 513 l-Aceto~y-1~3-butadiene 202 Methylallyl acetate 21 3-Aceto~y-l-butene 571 Crotyl acetate 888 tert-~utyl acetate 285 3,~-Diaceto~y-l-butene 65g2 1,4-Diaceto~y-2-butene 6~03~
1,4-Diaceto~ybutane 24 Other 4106 Total 678682 The overhead may be ~epar3ted by distillation ~o provide a ~o~oms stream rich in 1,4-diaceto~y 2-butene which may be, e.g., hydrogenated and hydrolyzed to form 1,4-butanediol and tetrahydro~uran. The overhead from this ~eparation may be treated to recover and recycle acetic a~id and butenes and but2nes.

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E~amvl~s_l to 8 The following e~amples are pro~ided in illustration and are not in limitation of the invention. All parts and percentages are by weight unless otherwise stated. The following ~amples illustrate through the use of ~ynthesized feed streams, that hydrogenated, crude butadiene str~ams can effectively be used in acylo~ylation processes.
A synthetic mi~ture of C4 hydrocarbons is prepared to simulate a crude butadiene str~am that has been hydroyenated as above and has the ~omposition set forth in Table I.

~om~nent M~thylacetyleneless than 500 ppmw n-Butane 14.2 Isobutylene 6.3 l-Buten2 15.3 : 2-Butene 6.7 1,3-Butadiene 57.1 C4 Acetylenesless than 200 ppmw ~ 4-vinylcyclohe~ene0.4 .~ Total lOD.0 The catalyst for the ~ceto~ylation reaction is prepared as follows:
Appro~im~t01y 2400 milliliters o~ 15~ ~y weight nitric a~id aqueous ~olution are ~harged to a qlass ~till. AbOut 150 ~rams o$ 20-40 mesh ~ctivated carbo~ are added o the ~olution ~nd reflu~ed or an hour at appro~imately lODC and atmospheric pressure. The li~uid i~ tben p~ured off, an~ the activated carbon i washe~ with ~ixtilled water. The ~ctivated ~arbon i~ then ~ried :' D 16,275 :., .

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in a vacuum oven o~ernight at about 90C and 250 mmHg absolute pressure.
Palladium nitrate is also dried i~ the oven at 90C and about 250 mmHg absolute pressure ~or about 4 hours. A 600 milliliter solution is then made of 30% by weight nitric acid, 6.749 grams of the palladium (II~ nitrate an~ 1.132 grams tellurium powder, 60 mesh. The 150 grams of the washed, activat~d carbon are then added to the solution, with ~entle stirring for about 5 minutes. The mixture is than drie~ slowly for about 36 hours in the vacuum oven at 250 mmHg absolute pr~ssure and 90C. After the catalyst drying is ~omplete the catalyst is purged for at least 30 minutes with flowing nitro~en.
About 56.35 grams of the ~atalyst are then charged to a 16 inch reactor with a 3/~ inch inner diameter. The top inch and bottom in~h of the reaetor are packed with guartz beads, held in place with quartz wool, so that appro3imately 14 inches of catalyst are present in the heated reactor zone.
The cat~lyst i~ then heated to 150C under 3 liters per minute nitrogen flow for 2 hours~ The catalyst is then reduced by passing 3 liters per minute hydrogen over the b~d at 20~C for 2 hours~ ~ollowed by redu~tion at 300C for another hour. The reactor is then purged with 3 liters per minute nitrogen at 300~ or 30 mi~utes ~nd then left o~ernight ~t 300C under 3 liters per minute ~itrogen ~low ~nd up to 315 ~ubic ~entimeters per minute air. Ini~ially, ~are is taken to ~ontrol ~he air ~low at 50 to 100 cubic centimeter~ per minute æo ~s to keep the .

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~sotherm in the catalyst bed below 400C, and then the air flow rate is gradually increased to the 315 cubic ~entimeter per minute rate.
After o~idation ov~rnight (about 12 hours), the air flow is discontinued, and the nitrogen ~low continued for 30 minutes while cooling to 200C.
The catalyst is then further reduced with 3 liters per minute hydrogen at 200~C for 4 hours, then heated to 400C and reduced for another 4 hours under the ~ame hydrogen flow rate.
After completing the final reduction cycle, the cataly~t is purged with 600 cubic centimeters per minute of nitrogen, while cooling to ambient temperature. The rea~tor is then lçf~ under positive nitrogen pressure until the acylo~ylati~n runs are started.
The synthetic S:~4 hydrocarbon stream is blended with acetic acid in the ratios given in Table IIo The resulting mia~ture is introducsd as a liquid into the bottom of a reactor vessel at the conditions given in Table II.

C4'~ i~ Average Llquid Reactor 02/C4 Cataly6t Ex~mple Feed Te~per~ure W~SV Molar On-Stream (w~ ~ ~5~ B~Q ri~Q
1 5 232 B3.8 0.45 3,~3 144 - lS0 2 5 373 78.L~ ~.96 0.50 ~50 - 156 3 ~2261 86.1 0,55 O.B6 16B - 174 4 2.232 B1.8 ~.07 3.54 180 - 186 2.~08 63.~ 0.46 4.15 186 - 192 6 2.077 59.3 8.25 0.76 198 - 204 7 1.545 80.1 0.46 4.15 204 - 210 B 4.672 7B.5 0.45 4.05 210 - 216 .
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To obtain the 0.45 to 8.96 weight hourly space velocities in the catalyst bed requires the liquid mi~ture to be fed at 25 milliliters per hour to 500 milliliters per hour.
The o~ygen for the reaction is suppli~d in an air ~nd nitrogen misture, suGh that the osygen content is present at 10 mole percent. The ~low rates of air and nitrogen are controlled together, to maintain the desired o~ygen to C4 hydrocarbons molar ratio. In e~amples 1 t~ 8, tbis reguires the air flow rates to ran~e from 21 to 1250 cubic centimeters per minute, and the nitrogen flow rates to range from 22 to 1640 ~ubic centimeters per minute.
The effluent ~rom the reac~or vessel is flashed (decanted) at 0C and 1 tv 5 psig (1.06 to 1.35 atmospheres absolute) to remove a gaseous stIeam for analysis~ The liquid from ~he decanter is also recovered and analyzed.
The results are summarized in Table III.

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- 26 - 2~ 9 As seen in E~amples 1 to 8, the catalyst gave high conversion of 1,3-butadiene and high ~electivity to 1,4-diacetoxy-2-butene, even after as much as 216 hours on line.
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~omDar~ive ~am~le By comparison, when the crude butadiene sample given in Table IV is mi~ed with acetic acid to provide 5.132 ~t. ~ crude butadiene in acetic acid, and reacted with N2/air with about the ratio of moles O2~N2, appro~imately the same 2/
C4 hydrocarbons, at about the same reactor temperature (78C) and pressur~ (90 psig) as in E~amples 1 and 8, the catalyst activity rapidly ~eclined, possibly due to ~he high levels o~ methyl acetylene and vinyl acetylene present in the feed mi~ture. The conversion of 1,3-butadiene dropped from 81~ at 229 hours total catalyst on~stream time and 13 hours with the unhydrotraated crude buta~iene feea to ~1% at 300 hours total ca~alys~ on-s~ream (84 hours with the unhydro~reated crude butadiene feed)~ The results are summarized in Table V.
A~E IV

Ccm~L?~ Wt.
Propylene 0.05 Methylacetylens 2.07 I~obutane 7.62 n-Butane 5.32 I~obutylene 4.05 l~Butene 7.~8 2-Butene 10.07 1,3-But~diene 58.49 C~ Acetylenes l.S0 C5'8 3.27 Vinylcyclohe~ene 0.08 . .

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Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A process for the production of 1,4-diacyloxy-2-butene from crude butadiene containing acetylenic components comprising contacting the crude butadiene with hydrogen under mild hydrogenation conditions to produce an hydrogenated crude butadiene and then contacting the hydrogenated crude butadiene with carboxylic acid and oxygen under acyloxylation conditions in the presence of an effective amount of palladium-containing catalyst to produce

1,4-diacyloxy-2-butene, wherein the hydrogenation is sufficient to enhance at least one of ennanced catalyst activity and catalyst life for acyloxylation.

2. The process of claim 1 wherein the carboxylic acid comprises acetic acid.

3. The process of claim 2 wherein the total acetylene components in the hydrogenated crude butadiene stream are less than about 0.5 weight percent based on the total weight of the crude butadiene stream.

4. The process of claim 3 wherein the total acetylene components in the hydrogenated crude butadiene stream are less than about 0.05 weight percent based on the total weight of the crude butadiene stream.

5. The process of claim 2 wherein heat is removed during the acyloxylation to mitigate the formation of vinylcyclohexene.

6. The process of claim 6 wherein the acyloxylation is at 3 temperature of about 80° to 160°C.

7. The process of claim 6 wherein a portion of the product from the acyloxylation is recycled to the acyloxylation to assist in temperature control.

8. The process of claim 2 wherein the crude butadiene stream is the result of thermal pyrolysis of hydrocarbon and the crude butadiene is subjected to acyloxylation within about 50 hours of the thermal pyrolysis.

9. The process of claim 2 wherein the mild hydrogenation conditions comprise a temperature of about 20°C to 70°C, a pressure of about 6 to 11 atmospheres absolute and a supported palladium hydrogenation catalyst.

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