US2511936A - Process of producing cycloalka - Google Patents

Description

MORRELL. ET AL.

E. PROCESS 0F PRODUCING CYCLOALKADIENE FROM PETROLEUM OILS Filed Sept. 24., 1946 June 20, 1950 Patented June 20, 1950 PROCESS OF PRODUCINGICYCLOALKA'- DIENE FROM PETROLEUM OILS Charles E. Morrell, Westfield, Harold W. Scheeline, Llewellyn Park, and Carl S. Carlson and Harry J. Heinemam'Jr., Elizabeth, N. J., as-

signors to Standard Oil Development Company, a corporation of Delaware Application September 24, 1946, Serial No. 699,014

i claim. (o1. zet- 666) This invention relates to a practical method y y ,and means for obtaining cycloalkadienes of high .purity from cracked petroleum oils. Prior to the present invention there has been no economically feasible method of procuring cycloy alkadienes from petroleum oils.

It is known 'that limited amounts of cyclopentadiene have beenv commercially available only byprocessing of coal tar oil forerunnings, in which .-cyclopentadiene is present as the monomer.` This cyclopentadiene is recovered from the light ends of the coal tar forerunnin-gs, containing mainly benzene, by the steps of:

(l) Heating the light ends under high pressure without vapor-separation until as much of the monomer as possible is polymerized therein,

(2) Distilling the aromatic light ends from the Ipolymer which remains as a bottoms or residue,

. l (3) Vacuum distilling the cyclopentadiene polymer from the bottoms, and

(4) Cracking the thus purified cyclopentadiene 'polymer distillate in a column packed with iron turnings or similarjmaterial.

The method by which cyclopentadiene is recovered from light ends of coal tar forerunnings iis not practically applicable to cracked petroleum f-distillates which contain very small amounts of cyclopentadiene monomer and in which many .otherhydrocarbons of unstable characteristics are present in much larger quantities.

pentadiene polymer from cracked petroleum prodfucts such as may be-obtained, for instance, from .thermal cracking of gas oils or heavy naphthas. An object-of this invention is-to provide a com- No satisfacstory method has been found for separating cyclomercially feasible process of obtaining cycloalkavidienes,such as, cyclopentadiene and methyl cyclo- .pentadiene,l each in a substantially pure state,

-from cracked petroleum products by collecting inv the bottoms o i1an aromatic naphtha distillate, i polymers of the cycloalkadienes formed in the .cracking and naphtha fractionation operation,

then heat treating and processing the aromatic distillatebottoms in such a vmanner as to evolve ,substantially pure monomer distillates therefrom. Among its objects, this invention is primarily concerned with obtaining C5 to Ca oycloalkadienes from cracked petroleum distillates produced under alkadienes and Vthe cycloalkadienes such as, butadienes, pentadienes, -`c'y'clopentadiene, methyl and The mono-olefins, or'

dimethyl cyclopentadienes, hexadienes, cyclohexadienes, methyl cyclohexadiene, dimethyl cyclohexadienes, and the like.V The aromatics lnclude benzene vand its homologs. The cracked products issuing from the cracking Zone are quenched to a temperature at which thermal polymerization of the non-cyclic unsaturated hydrocarbons is repressed in order to obtain a high yield of the low boiling alkadienes, such as butadiene, pentadienes, and the like.

This invention is also concerned with effecting separation of an aromatic naphtha fraction from the higher boiling Icracked products and separating from the lower boiling unsaturated hydrocarbons a heavy portion of the aromatic naphtha fraction as bottoms inl such a manner as to accumulate,cycloalkadiene polymers in vthis heavy aromatic naphtha Lfractionbefore it is subjected to a heat treatment under proper conditions for converting the cycloalkadiene polymers to monomers without undesired side reactions, and subsequently isolating th monomers,

Conditions favorable for obtaining high yields of unsaturated hydrocarbons and aromatics in cracking volatile petroleumV cracking stocks, such as naphtha cuts, kerosene, or gas oils, are high temperatures of the order of 1000 F. to 1600 F., preferably'l200". to l500 F., Iand lov7 pressures of the order of l to 10 atmospheres. The chargving'stock is preferably diluted with up to 90 mole per cent of steamin the cracking zone in order to restrict carbonzation,

The hot cracked products issuing from the cracking zone are quenched to a temperature at 'which hydrocarbons boiling above the naphtha boiling range are condensed,then the naphtha -and lower boiling hydrocarbons are fractionated. By processing the highly cracked products formed in this manner, the cycloalkadienes show up in v'the final naphtha product both as monomers and polymers. It is found that the amounts of the cycloalkadiene monomers present in the low boil-v 'ing cracked products are so small as to make their products', theV aromatic naphtha together with the lower 'boiling hydrocarbons and steam are `,removed overhead y' from ythe higher boiling cracked products which are quenched to a liquid state. The overhead naphtha vapors and steam are condensed by cooling, but some or all of the normally gaseous hydrocarbons may be allowed to remain in gaseous state. Water condensate is separated from the thus-obtained aromatic naphtha distillate.

After separation of the water condensate, the aromatic naphtha distillate is subjected to a fractional distillation to remove therefrom any remaining condensed C1 to C5 hydrocarbons, and if desired, C6 to Cg hydrocarbons. This fractional distillation is performed without heating the distillate to above the normal boiling points of C's non-aromatic hydrocarbons and may be carried out by passing the distillate into one or a series of topping towers, such as demethanizing, deethanizing, depropanizing, debutanizing, and depentanizing towers, for removal of the lower boiling C1 to C5 hydrocarbons. It is desirable to remove non-aromatic C6 to Ca hydrocarbons from the aromatic naphtha distillate if higher cycloalkadiene homologs of cyclopentadiene are to be recovered. It is not necessary to remove the Cs to C5 aromatics, but those which distill olf with the C5 to Ca non-aromatics can be removed therewith, and in removing the C6 to Ca hydrocarbons, both aromatic and non-aromatic, it is best to use a distillation aid such as steam or vacuum.

The conditions of the fractional distillation treatment are thus controlled so that the ratio of cycloalkadiene polymers retained in the aromatic naphtha bottoms is kept high with respect to their monomers originally present in the cracked product streams. The remaining aromatic naphtha bottoms following sepa-ration of C5 and lower boiling `hydrocarbons boil mainly in the range of 176 F. to 456 F. and following separation of C5 and Cs hydrocarbons, the aromatic naphtha bottoms are higher boiling and contain largely alkyl aromatic homologs of benzene with cycloalkadiene polymers.

Following the separation of the C5 to C8 and lower boiling hydrocarbons from the aromatic naphtha fraction, the resulting heavier aromatic naphtha bottoms is subjected to a heat treatment in which the temperatures employed are in the range of 300-800 F. The heat-treated aromatic naphtha bottoms are entirely or partly in vapor phase or entirely in liquid phase depend ing on the actual temperature and pressure of the heat treatment and the end boiling point of the naphtha.

In general, the end boiling point of the heat treated naphtha bottoms is not above 500 F. and the heat treatment pressure is atmospheric pressure or slightly thereabove, so that a partial or complete vapor phase operation is obtained. The

naphtha bottoms are exposed to the heat treatment for as short a period as is necessary for conversion of the cycloalkadiene polymers to the monomers with minimum cracking or decomposition of other naphtha components to substances which would interfere with separation of the monomers by distillation.

The best results in the vapor phase heat treatment were obtained at temperatures of 600 F. to

`@450 F. for a duration `of 0.15 to 25 seconds. Liquid phase heat treatments require up to 1.0 hours at 300 F.

The cyclopentadiene .monomer liberated by the heat treatment of the .aromatic knapbtha bottoms is taken overhead by distillation from .the .cooled or quenched heat-treated naptha bottoms as .a

C5 distillate cut. The heat treatment is thus controlled to evolve very little of other lower boiling hydrocarbons which would interfere with separation of a high purity cyclopentadiene cut. Any gaseous hydrocarbons formed are readily separated from the quenched heat treated naphtha before liberation of the cyclopentadiene monomer or are separated from the cyclopentadiene monomer distillate taken overhead while repolymerization of the monomer is minimized.

In a manner similar to that described for obtaining the cyclopentadiene monomer, its homologs, such as, methylcyclopentadiene, dimethylcyclopentadiene and cyclohexadiene can also be separated from the cracked petroleum products,

with the modication that the aromatic naphtha distillate is freed of C6 to Cs hydrocarbons as well as the C1 to C5 hydrocarbons prior to the heaty treatment. The methylcyclopentadiene and cyclohexadiene polymers along with cyclopentadiene polymers are collected in the heavy ends of the aromatic naphtha distillate and their monomers are liberated by the heat treatment. rThe monomers can be collected as one or more distillate cuts after which they can be subjected to further distillation, if necessary.

Having outlined the process of the invention in a general manner, further specific details will be explained with reference to the accompanying drawing which schematically illustrates a flow diagram of means and steps in carrying out a preferred embodiment of the invention.

In the ow diagram I represents a high temperatfure steam cracking zone into which a petroleum cracking stock is charged from line 2 and steam or preheated Water is supplied from line 3, the oil charging stock being in the liquid or preheated vapor condition. The cracking zone may be contained in a fired pipe coil or other conventional type of cracking apparatus. Steam or preheated water may be supplied at a. multiplicity of points to the coil. The cracked products leave the cracking zone through line 4 and are promptly quenched by introduction of cool liquid cycle oil introduced by line 5 into line 4. The quenched cracked products are discharged from line 4 into a fractionation zone 6 from which cracking tars are withdrawn by line 'I and liquid cycle oil is withdrawn as a sidestream by line 8. Cooled cracked naphtha vapors together with steam and gases are drawn overhead from the fractionation zone I through line 9 and through cooling condenser I0 into a. separation zone II. Uncondensed gases leave the separation zone through line I2. Water condensate is removed from the bottom of the separation zone through line I3 and naphtha distillate, which may include varying amounts o! condensed C1 to C5 hydrocarbons, is withdrawn through line I4 from the separation zone II to a fractional distillation means I5.

The uncondensed gases withdrawn from the separation zone II through line I2 may be subjected to compression and cooling for liquefaction by means not shown in the drawing and then be combined with the aromatic distillate supplied to the fractionating means I5 for -common fractionation therein.

The fractional distillation means -IE may comprise one or a series of towers, only one being vshown for convenience and simplification. 'I n the fractionatinlg means I5 the naphtha distil'- late is kept at as low a temperature as possible during removal of C; to C5 hydrocarbons `to minimize decomposition of cyclodiolen polymers.

Steam or similar gases may be 'introduced into the fractionating means for lowering the distillation temperatures of the hydrocarbons which are to be stripped from the aromatic distillate. One or more of the C1 to C5 cuts may be jointly or separately removed through the lines I6, I1, I8, I9 and 20 and similarly in certain cases Cs to Cs cuts.

In recovering a C4 cut from the f ractionating means l5 as a separate stream withdrawn, for example, through line I9, this stream will contain large amounts of butenes and butadienes mixed with some C4 paramns. A C5' stream Withdrawn, for example, through line 20 contains pentenes, pentadienes, C5 parains, and a small amount of cyclopentadiene monomer. The thustopped aromatic naphtha distillate is Withdrawn as bottoms from the fractionating means l5 through line 22 to the heat treating zone 23 which is combined with a fractionating means 24.

As previously mentioned, it is not necessary to remove Cs hydrocarbons completely, if only cyclopentadiene is to be obtained from its polymers in the aromatic naphtha bottoms and therefore benzene may remain in the bottoms. If Cs to Ca cycloalkadienes are to be obtained from their polymers in the aromatic naphtha bottoms, then it is desirable to remove from these bottoms Cs to Ca hydrocarbons as Well as the C5 and lighter hydrocarbons and more particularly to remove the Ce to Cs non-aromatics.

The heat treating zone 23 may Ibe in the form of a heated tube or tank. In this heat treating zone the topped aromatic naphtha fraction is heated to 2, temperature in the range of 300800 F. and at these temperatures the polymers of cyclopentadiene and its homologs undergo rapid depolymerization to the monomers. The heattreated aromatic naphthaJ bottoms is discharged from the heat treating zone 23 through line 25 into the fractionating zone 24 preferably with addition of quenching liquid from line 26. This quenching liquid may be cold water, coldl aromatic naphtha, distillate bottoms or similar liquid which will not introduce interfering distillation components.

By quenching, the hot products leaving the heat treating zone are suddenlycooled to below 300 F. They may be thus cooled to below 100 F. to avoid cycloalkadiene repolymerization.

Distillaticn of the heat treatment product following the cooling is carried out in such a way as to minimize polymerization of cycloalkadiene monomers. The distillation preferably follows the quenching immediately. Steam may be introduced into the distillation and fractionation means either directly or as quench uid. Hold up time in the distillation and fractionation is minimized. The temperature of overhead vapors from the fractionation means 24 should preferably not exceed 120 F.

Overhead of cyclopentadiene vapors are withdrawn from fractionating means 24 through line 21 and cooler 28 into receiver 29 for collection of cyclopentadiene monomer cut. A methylcyclopentadiene fraction may be Withdrawn from fractionating means 24 through line 30. Higher boiling homologs may be withdrawn as separate streams from fractionator 24. The remaining high boiling aromatic naphtha freed of polymers of cyclopentadiene and its homologs is withdrawn from the fractionating zone 24 through line 3|.-

les

6 diene present as monomer,`polymer. or both, in the C1 to Cs cuts fractionally distilled from an aromatic cracked naphtha' obtained in steam cracking a gas oil at 12501265 F. and remaining in the aromatic naphtha. bottoms.

TABLE 1 Distribution of eyczopeniadiene in cuis fractionatedv from a cracked aromatic naphtha distillate 0 Cumulative Flnal Temp.. F. Cliireentl Volume Cut Per Cent Weight Per Distilled In stili *eu alii Yields of cyclopentadiene from its dimer in topped aromatic naphtha distillates of steam cracked oils nl i' wi P t' im Cim wi P o i .ea er yc open aer en Treatment qlgggct Cent diene Yield Cyclopenta- Temp., Seconds Liquid Re- Based on diene Loss In F. covery Naphtha Be- Topping fore Topping TABLE 3 Yield of cyclopentadiene from a synthetic mixture of 4.56 wt. per cent dicyclopentadiene in aro- "matic naphtha of 300-400 F. boiling range Heat'lreat- C'Iontact Wfr Wtfligelfent men emp" me Liquid Cyclopenta oF' Seconds Recovery diene TABLE 4 Recovery of cyclopentadiene and alkyl homologs of cyclopentacliene by depolymerization of dmers in cracked distillate topped to remove Cs and lower boiling components Wt; ler Cent Yield From Aromatic Distillata F. Tune Sec Recovery C C10 ents substituted y .e216 Cyclpentadiene 560. 22.9 9e 2.o o. 25

The points of interest shown by the data in the Tables 2, 3 and 4 are summarized as follows:

(a) Cyclopentadine losses resulting from the topping of` the; aromtienaphtha distillate.asem-- (-b 'Recovery oii'monomer. fromtheheat ,treat-H ed dilute solution of polymer in-a aromatic naphtha.I

fraction is good, cf the orderof 90% or` better. (Table 3); Y,

(c) A higher yield of cyclopentadiene is obtained With heat.: treatments. of shorter duration (e) High purity and yields of cycloalkadiene'- products are obtained by the method of topping heat treating the topped naphtha (bottoms) un-y der proper conditions, and fractionating these-- products from the heat treated naphtha bottoms cranes V2, 3 ande).

s The separation of product. Thel cycloalkadienes recovered iny themanner described. are useful. ink chemicalf reactions as. monomers or they may be subsequently converted..

to pure dimers or high polymers by thermal or catalytic polymerization methods. These materials are important iny the manufacture of highly1 unsaturated oils, plastic polymers and resins which may be utilized in surface coatings, ink oils, various drying compositions, synthetic bers; etc. The invention has been described with reference to preferred modifications and adaptations, but it is to be understood that other modifications come within theA scope of the invention as defined in the appended claim,

We claim:

A process of producing and recovering mono meric cyclopentadiene of high purity in cracking a petroleum oil boiling-in theheavy naphtha and gasoil range, whichcomprises-cracking the pe-i troleum oil invaporvphaseata temperature in therange of 1000 F. to,l 1,600.9 F. in the presence of steam under a pressure of 1 to l0 atmospheres, promptly quenching the resulting cracked petroleum products to a temperature at which thermal polymerization of unsaturated hydrocarbons is Other hydrocarbons were hardly de.

the` cyclo'alkadienes `in the, manner. described ishelpiul to the recovery of the. non-,cyclic diol'ens. andv advantageously improves. the stability of the final aromatic naphthay 8 repressed, separating from the quenched cracked@ productsy an aromatic; naphtha. distillate: fractioni containing cyelopentadiene monomerA and cyclo-1 pentadiene dimer distilled with steam, distilling, Crthrough C5 hydrocarbons including the cyclo-A pentadiene monomer from said aromatic naphtha distillate fraction to obtain a residual fraction 0f*l the aromatic naphtha boiling in the. range' of 176 F. to- 450 F. and. containing thecyclopentam diene dimer in. low concentration withy higher boiling aromaticy hydrocarbons, continuously passing. said' aromaticV fraction. in liquid phase',y without vinterinediete separation of the cyclopentadiene dimerl as vapor therefrom,` through a. dlepclymeriza,tionv reaction zone at a, temperature-l of,300. tof600 F. todecompose/the cyclopenta-f dienedimer contained in the liquid phase aro* matic hydrocarbons, continuously withdrawing fromn saidreaction@ zone; an* eiiiuent of the liquid;-

aromatic hydrocarbons from the heat treated aro- The following referencesv are *ofv record` in. the.

ma-tic fraction andr the. cyelopentadienev monomer vapor. formed by depolymerizationof the dimer.. immediately,l cooling the withdrawn cyclopentadienemonomer vapor and fractionatingsaid vapor in a tractional distillation zoner in which the overhead vapors have a. temperature not. exceeding. F. to obtain an overheaddistillate of cyclo,- pentadiene monomer substantially free of other. hydrocarbons. l

CHARLES. E. MORRELL.

HAROLD W. SCHEELINE.

CARLS. CARLSON.

HARRY J.. I-IlElINElVIALN,y JR.v

i REFERENCES CITED le` of this patent:

y UNITED vSTATES PATENTS VBirch et al.:

Jour. Ind. Eng. Chem., vol. 24., 1g-5.0 (1932).

Images