US2370810A - Process for segregating valuable hydrocarbon constituents - Google Patents

Description

March 6,

c. E ,MORRELL ErAl.

POCESS 4FOR SEGREGATING VALUABLE HYDROCARBON CONSTITUNTS Filed Aug. 21, 1942 :Patented Mar# 6,11945 A .UNITED "s'rATlszs PATENT OFFICE i r'nocnss ron sEGnEGA'r'ING vALUABLa i mmaocmaon coNsTrrUnNTs Charles Morrell, Roselle, and Miller W. Swaney, Linden, N. J., assignors to Standard i! Development f Delaware P Company, a corporation of Application August 21, 1942, serial No..455,s7c 1o claims. l(ci. 26o-677) The `presentinvention relates to the art ofthe segregation of certain unsaturated hydrocarbons from mixtures with other hydrocarbons of closely similar boiling points, and more speciilcally to the separation and purification of tertiary oleflns from their mixtures `withvnorinal or secondary y olens or from saturated hydrocarbons.

The process will be understood from the following description and drawing. The drawing is asemi-diagrammatic view in sectional elevation showing the ilow of the various materials employed in the process.

Tertiary olens, such as isobutylene and iso. amylenefoccur together with many other oleflns, ,both normal and secondary, as well as saturated the above mentioned process by which increased yieldsmay be obtained.

Referring to the drawing, numeral E denotes. a line through which the hydrocarbon feed is introduced. For purposes of illustration, a refinery .Ca cut from cracking' operations will be taken but it will be understood that a Cs cut or other hydrocarbons.' in cracked 'hydrocarbon oil frac;v

. tions, and it-has been for some time desirable to develop acheap, effective method for segregating the tertiary oleilns from other constituents in narrow boiling cuts. In the lower molecular weight ranges, forexample, in'the so-called C; and Cs cuts, which comprise those hydrocarbons having 4 and 5 carbon atoms respectively inthe molecule, separation can be accomplished by distillation but due to the close boiling points, this is a very diilicult and expensive operation. Better results have been obtained by chemical means; for example, isobutylene has been selecoriginal feed s'tcck, but boiling below the boiling* point of the phenolic material used, is also sup` mixture of hydrocarbons including tertiary olens might be taken equally well for purposes of illustration. The cut is preferably a rather narrow boiling fraction, such as can be readily producedA in ordinary reiinery equipment without great .difculty. The feed stock is preferably fed in liquid phase and sufficient pressure is imposed to maintain it throughout the absorption step.

In addition to the feed stock, a second" liquid hydro-carbon of a higher boiling point than the plied by the pipe 2. The nature of this hydrof.

carbon,which is termed the added hydrocarbon l 5 will be more speciilcally disclosed later. A suittively extracted from normal butenes and butanes by solution in 65% to 75% sulfuric acid.' Acids of this strength absorb the tertiary olefin without substantially aecting the normal olefins or parafllns, and the iso-olefin can be recovered from the acid liquor by dilution Iand distillation.

' Another method of accomplishing the same result employsfa mixture of phenols, cresols and the like along with" a minor amount of mineral alkylation acid by 'means of which the reactive tertiary oleflns are caused to unite with the phenolic material to .form an alkylated phenol.

. The unailectedhydrocarbons may be distilled oilI from this product and the residue, which' consists of the alkylated phenol, is then heated to effect the dealkyl'ation so that the .tertiary olen is'then collected and the phenol returned.

This method is not entirely satisfactory because of the fact that the yield is not as high as able, absorption medium, which for the present will be described as a, phenolic material, is added through a pipe 3 and the mixture of thes three materials is passed through an absorption zone t by way of a common leader pipe da. An alkylating catalyst supplied by pipe 4b isfsmall in amount. and it is preferably also added to the leader. This mixture of ingredients now passes' through `the absorption zone 4 in liquid phase. Any particula'i desigm for the absorption zone may be employed in which all of the ingredients are mixed thoroughly and given soient time for reaction. As shown in the drawing, the reaction zone is' merely a pipe tted with baies-b and a jacket 6a through which a coolingmedium may -be circulated, since there is considerable heatevolved in the alkylation step. The conditions are such that only the tertiary olefins are caused to alkylate .the phenolic material, the other olens passing' through substantially unaected. The reaction product is discharged through a heating coil Gf and into a distillation column l which is provided with a reuxing coil 8 and a reboiling` coil 8 at its lower end; In this fractionating zone,

the -'uncombined hydrocarbons, namely the butanes and the normal butenes, are distilledy overhead through a pipe l0, condensed in acondenser l2 and collected inthe drum I3 through which they may be withdrawn as a liquid, by pipe I 4, From the base oi' the tower 1,. the residue containing the alkylated phenolic material and the added hydrocarbon along with a small amount of" .alkylation catalyst passes by pipe IB through a heat exchanger II and a second heating coil l1 y "and thence into aA stripping tower In Thistower is similar to tower 'I containing the reuxing coil i and reboiling coil 2l. It will be understood that vin this tower, the temperature is raised to a sufficient point to cause the dealkylation of the alkylated phenol and the distillation overhead not only of the tertiary olenns but also of the added hydrocarbon. The vaporized substances removed by a pipe 2| and discharged into a secondary tower 22 which is similar to thoseshown above and is devised to make a close fractionation between the tertiary olefin and the higher boiling added hydrocarbon. The tertiary olen is taken overhead by a pipe 23, is condensed in 24 and collected in 25. It is withdrawn as a liquid by a pipe 28. The added hydrocarbon is withdrawn from the base of tower 22 by a pipe 21 and is passed by a pump 28a for recirculation. It ispreferably joined by the'stripped phenolic mate- 20 rial from tower il which is added by pipe and the mixture formed by the materials .owing through pipes 21and 28 then passes'through the` heat exchanger il; through a cooler. and by a pipe 30 back to the leader 4a and the absorber 5. A\I'h\xs it will be seen that the phenolic material, the added hydrocarbon andthe alkylation cata.-

lyst are continually circulated through a, closed system and used over and over again to treat fresh quantities of the C; cut which is,continually added and resolved into components consisting on the one hand ofthe. tertiary oleilns and on the other of a mixture of oleflns and saturated C4V begun with simple phenol after a while`the absorption medium is largely mono-tert-butyi phenolwhich has proved to be a very satisfactory modo o1 operation. If dealkylation conditions maintained are'sumciently drastic, however. all tert-butyl groups can be remov butyl phenol converted back to henol. The materials Vduring absorption are maintained, as indie cated above, preferably in the liquid phase at .temperatures between about 60 and 100 C., and

\ a complete absorption of the tert-oleiin. canbe.

accomplished in from 201:0 120 minutes, depend- V ins on the amount of tert-olefin in the feed.v stock, theratio of absorption agent to the feed l stock and other ponditions. It is found desirable' to provide about 33 to 1.0 mois of phenolic mate- -rial for each mol of iso-olen to be absorbed although even higher ratiornjxay be used. The v alkylation d ealkylation catalyst is .preferably a mineral acid, suchfas concentrated sulfuric or .concentrated phosphoric acid,` but bther acid re'- :acting catalysts such as potassium acidpho'sphatemay alsobe used, as well as benzene or phenol-sulfonic acids or some of their salts. The

amount of the alhlation'catalyst is small indeed. 70

ate or for example from 0.1 t6 `i0 mol per cent' thereof based on thejphenol or equivalent material employed, and with otherwise` good conditions about one `mol'per cent ofthe catalyst is quite effective in quickly effecting theaikylationof the'phenolic j andere 25 plete. The amount of the added 55 drocarbon.

material without causing any substantial polymerization of the tertiary oledn.

An important feature'of the process is the presence of the so-called added hydrocarbon which,

5 asstated above, should be a relatively stable material boiling conveniently above the boiling range of the feed stock and below the 4phenolic material so that it may be on the one hand readily separated Vfrom the unabsorbed constituents of lothe feed stock by the first distillation step and 15 material to employ but other materials may be used as well, for example hexane, di-isobutylene and other equivalent materials.A The added hydrocarbon is preferably added at the inlet' of the 'absorber 4 so that it may be. present during the absorption. When so used it tends to slow down the alkylation reaction, making the control easier, a and tends to prevent excess polymerization of the C4 olens. It mayfhowever, be added to the reaction mixture iust after the absorption is comhydrocarbon can be varied over quite a range. say from 10 to 100%, by volume, based on the amount of phef nolic material, but from i0 to 60% is generally quite satisfactory. o After' the absorption is complete, the first step is the distillation of the normal oleflns and the saturated hydrocarbons contained in the feed stock. This distillation is `carried out preferably under pressure so that the products may be collected in liquid phase without the use of refrigeration and with the C4 cut this distillation may be accomplished under super-atmospheric pressure. say 40 to 60 pounds gauge. The'head temperature `of the stillwill be about 43 C. and the 40 bottom temperature about 82 C. .In any case,

the bottom temperature of this first distillation should not be above about 100" C., ,in order to prevent a partial dealkylation and loss of the tertiary olefin. 'I'he residue from the first disl 45 tillation consists of the phenol-tertiary oleiln alkylate, the acid catalyst and the added hydrocarbon and this mixture, which forms 'a single phase, is passed into thesecond distillation column or 4the regenerator. Thisdistillation column to lsnkewise preferably held under pressure and and the monothe temperature is raised sufficiently high'to not only cause the dealkylation of thephenol but also to distill olf not only the tertiary olefin but likewise causethe distillation of the addedhy- The actual temperature therefore depends on the boiling` point of the added hydro carbon, the extent of alkylation ofthe phenol andbther conditions. `With pentane and using a` pressure of say to "I0 pounds gauge, the

.o maximum temperature will be about 250 C. .4

When working at lower pressures, below 50 l. pounds. lower temperatures. in therange of to 200 Cfare adequate. In cases where the phenol is combined with 2 to 3 molecules of olel c5 iin in the absorption step. regeneration temperatures as low as 100 to.110' C.' sumce at pressuresA regeneration step.

The third Fdistillation step is also preferably accomplishedunder pressure vso aste permit the 7e tertiary olefin to be eollectedin liquid phase at tower 22 are returned or recycled for furtherV reaction. As indicated before, the phenolic niaterial which also contains the alkylation catalyst is returned to the inlet of the reactor 4. The" added yhydrocarbonis also preferably returned to the same point but may be returned to the inlet of the heating coil 6, if desired.

As a specific example of the operation of the process, a mixture of meta and para cresols and a C4 cut containing 18-l`9% isobutylene was continuously fed into and through a steel reaction drum at 85 to 90 C. Pressure sufficient to mainconsisted of 5 mols cresol to 1 more ofisobutylene and about .2 mol per cent of cresol sulphonlc acid based on the cresols was included in the feed.

As the reaction mixture emerged from the chamber it was continuously admixed with oneff tain the reactants in liquid vphase was provided and the reactor was of size to give a time of125 throughput of about 1 hour. The mixture i'ed half of its value of mixed pentanes and this mixture sent to a distillation towerwhich was under 3 atmospheres pressure (abs.) and distillationof the C4 hydrocarbon was effected using a 1' maximum temperature 'of 95 to 100 C. Practically no decomposition of the alkyl phenol was noted during this distillation. v

The debutanized mixture was now distilled in a regeneration tower with a maximum temperature of 200 C. and under atmospheric pressure. From the top of the tower 'a mixture of pentane and regenerated isobutylene was recov ered while the regenerated cresol and catalyst were drawnvoff of the tower from the bottom and reused for further absorption of isobutene. .The regenerated isobutene and the pentanes were separated'by distillation and the pentane reused as before. A careful balance showed that 93.7%`v of the isobutene fed tothe system was recovered and the product contained 97.2% isobutene.

The present invention is not to be limited to the 'segregation of any particular tertiary olefinA nor to the use of any particular phenolic material nor to any particular alkylation catalyst or -added hydrocarbon, but only to the following claims in which it isdesiredto claim ali novelty 'inherent in the invention.

We claim:

1. An improved process for recovering tertiary olefin from tertiary alkylated phenolic material, which comprises heating the alkylated material in order to produce thetertiary olefin and produce'a Adealkylatecl material in the presence of an added hydrocarbon having a boiling temperature be,- tween thatA of the olefin recovered and the dealkyl- .ated phenolic material, whereby the tertiary olefin and the added hydrocarbon are distilled from the ence of an acidic dealkylation catalyst, wherebythe tertiary oleiin and the added hydrocarbon are distilled. from the dealkylated material, and sep-v arating the tertiary olefin and the added hydrocarbon by fractional distillation. f

3. Process according to claim 2 in which the added hydrocarbon is employed in an amount. of-

10 to 100% of the volume of the phenolic absorbent.

4. An improved process for recovering tertiary oleflns from hydrocarbon mixtures of similar boiling range containing tertiary olef'lns which comprises admixing with the hydrocarbon feed a phenolic material and, a minor amount of an alkylation'.catalyst, whereby the tertiaryolefin alkylates the said phenol, distilling ofi the unalkylated hydrocarbons contained, in the feed stock ata temperature below that at which de*- alkylation takes place, and while in the presence of an added hydrocarbon boiling between the tertiary olefin and the phenolic material, lregeneratingpthe tertiary olefin by heating the tertiary alkylated phenol to a dealkylating temperature and distilling the tertiary olefin and the'added hydrocarbon from the regeneratedphenolic materia-l, then separating theregenerated tertiary olen from the added hydrocarbon by fractional distillation and returning the phenol and the hy drocarbon for reuse.

5. Process according to claim: 4 in 'which the added hydrocarbon is a saturated hydrocarbon and it is present during, the alkylation step.

- 6. Process according to claim 4 in which the added-hydrocarbon is asaturated hydrocarbon and itis added to the alkylation product.

7. An improved process for recovering isobutylthe presence of an addedhydrocarbon having a y absorbent 4to'iorm an alkylated phenolic product,

dealkylated phenolic materiahand thereafter sep arating the tertiary olen andthe added hydro'- carbon by fractional distillation.

boiling point between that of the C4 hydrocarbons and the phenolic absorbent, whereby the isobutylene is chemically combined with the phenolic distilling the uncombined C4 hydrocarbons origginally in the feed at atemperature below that at 8Process according to claim 7A in which the phenolic solvent is mono-tertiary butyl phenol.

9. An improved lprocess for recovering tertiary amylenesv from their mixtures with other C5 hydrocarbons which comprises'agitating the Ca hydrocarbons in the liquid phasewith a phenolic absorbent,v and asmall amount of an alkylation catalyst while in the presence of an added hydrocarbcn' having a boiling point between that of the C5 hydrocarbcnt and the phenolic absorbent. .whereby the tertiary olefins arevchemically combined with the' phenolic absorbent to form an 4 alkylation prodiict, distllllng the uncombined Cs hydrocarbons originally in the feed at a texperature below that at which dealkylation takes place, heating the alkylated phenolic absorbent while the alkylation catalyst to a temperature between about 100 and 250 C., whereby the phenolic substance is dealkylated producing tertiary amylenes and a dealkylated phenolic absorbent, removing the regenerated tertiary amylenes and the added l0 still in the presence of the added hydrocarbon and' 5 asma-10 CHARLES E. MORRELL mma w. swarm.

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