US2733280A - Recovery of cyclo and methylcyclo - Google Patents

Description

CE.F FIPJEHQ RECOVERY OF CYCLO AND METHYLCYCLOPENTAQIENE Jan. 31, 1956 BY LIQUID VAPOR PHASE CRACKING Filed Sept. 25. 1952 N. T Q H96 f w Il' HHHMJ .11. .E m. QL. I7|la |||-w lull. I Il- Ill m ATI AI m Q Ill A l l 98N N am Glen pHdmner Inventor Bv www Cltforne United States Patent Ciice 2,733,280 Patented Jan. 31,. 195-6 zjssnsof RECOVERY. oF CYCLo A.ND METHYLCYCLO- PENTADIENE BY LIQUID VAPOR PHASE CRACKING' Application September 25, 1952, Serial No. 311,457 4 Claims. (Cl. 260-666) This invention relates to a process for separately dedimerizing the high-purity vdimers of cyclopentadiene and methylcyclopentadiene from petroleum ,streams containing a complex mixture of cyclo-alkadiene dimers and codimers.

Highly cracked petroleum. fractions, as is well known in the art, contain a variety of cyclodiene compoundsfor example, the monomers of C5 and Cs cyclopentadienes, their higherlomologs, also, they dimersfcodimers, higher polymers of these homologous cyclodienes, and interpol-ymers with other dioletins. The dimer and codimer forms are stable at ordinary atmospheric temperatures, but on being heated to elevated temperatures of the order of 140 C. and higher they start to undergo cracking or depolymerization. The monomeric forms are unstable even at ordinary temperatures and undergo rapid polymerization in the range of 252120 C.

A typical steam cracking operation, which. is not part of this invention but is given for background and illustrative purposes only, thus comprises cracking petroleum hydrocarbons boiling in the range of I2l37l C. inthev vapor phase at 538 C. to 871 C. for a shortperiod of 1 to 5 seconds, preferably in the presence of 50 to 90 mole per cent steam based on thehydrocarbon feed and under a pressure of l `to atm. The naphtha distillate distilled from the cracked petroleum will be of approximately Ci-Cis range and will contain C5 and Cs cyclopentadienes in various forms, monomers, dimers, and codimers, together largely with unsaturated aliphatic hydrocarbons and aromatic hydrocarbons within this range.

The naph-tha distillate is treated by distillation, etc., to remove the lower and higher boiling fractions by means known in the art (e. g., see U. S. Patent No.v

This leaves fractions of crude, cracked petroleum naphtha boiling in the approximate range of C5 (15 C.) to 140 C. and higher, which areV then thermally soaked for 4 to 8 hours at temperatures from about 90"-110d C. This converts any cyclopentadiene and methylcyclopentadiene monomers in the naphtha to dimer and codimer forms. The soaked material is -then steam or vacuum stripped to remove V(J5-C9 components, leaving-as residue a concentrate-containing from 55 Yto 82 weight per cent, usually 60-75 weight per cent, of cyclopentadiene plus methylcyclopentadiene present as dimers andV codimers and boiling in. the range of about 150-220 C., 85% or more boilingin the range of about 170%220" C. lt is this concentrate that preferably represents the feed stock for the present invention. The process is applicable to feed stocks containing as little. as weight per cent. cyclopentadiene and methylcyclopentadiene as dimers and codimers or as high as 93% on the same. basis..

In the past many sequences of operations were attempted in order to recover these cyclodiene fractions economically, but all were dependent on a preliminary step of dedimerizing the cyclopentadiene and methylcyclope'ntadiene dimers and codimers. vapor phase or liquid phase dedimerization. has been uti- Thus conventional 2l lized in order to recover Ythe cyclic diolefirr. monomer from the dimers. Vapor phase dedimerizationi at high; temperatures, however, results in extensive undesirable. coking. Liquid phase dedmerization results in lower conversion and recovery of cyclic monomers.

v This invention' provides an improved method for dedimerizirfg and recovering `high` purity cycl'opentadiene and methylcyclopentadiene in separate fractions, it desired, from cracked petroleum streams containing them. The method .comprises dedirnerizing.the` cyclopentadiene and methylcyclopentadienef dimers and'. codimers mattie vapor phase while simultaneously passing', the vapors countercurrentto a superheatedl oil ina tower such .as a bubble. capl type tower. Eihcient dedimerization results with a minimum of fouling from coking. The: Ca-Csvcyclic diene monomers and acyclictdiene dimers. are taken overhead to aftower whereby these vapors. are instantly cooledfrom 200-230 C. to 70-80 C. Ilre first distillation tower isoperated torecover cyclopcntazdiene overhead. under conditions tol provide a-minimtnn. contact time for the .cyclopentadiene monomer'at ternperatures l00 C. Methylcyclopentadiene and heavier materials are fed to a second tower wherethe.,

methyl'cyclopent'adiene is recovered as the overhead product.

This invention`V will be better understoodv by reference to kthe W' diagram shown in the drawing.

In reference tov theatta'chedV drawing, stream I, any thermallystable' organic iinid (high boiling hydrocarbon 371+) 'maybeused This'uid is then supereheated in furnacezto approximately 371"C. Leaving the furnace by stream 3, 5, and 6 to tower 4. The use of multiple hot `injection points to the tower aids in controlling the desi-red ,cracking,gtemp.eraturewithin the cracking zone. The cracking VzoneA tower 4- may have `1.0-.to v30 plates, `de

pending on the required cyclo or methyleycliopenhadiene.v

cracking time. This cracking time may be .varied from 1 to 30 seconds, this being a function 'of the number'of plates in tower 4. Laboratory data on vapor phasecrackingat l400"'-430 C. show the dimers of cyclo and methylcyclopenta'diene are all converted to theirrespective monomers'in' 5 sec'ondscontact time. Stream V7 is the thermal stable fluid (oil) being removed from the bottom of tower4 to be recycled'back to the' tower after p'reheating in furnace 2. Stream 8 contains the cracked monomers of cyclo and methylcyclopentadiene, some acyclic diolens (isoprene, piperylene, ancth'exadienes), uncracked dimers of acyclic dioleiins andsome-entrained thermally stable oil. The overhead vapor temperature` of'tower-fis maintained at 220-230 C. (end poi-nt ot' the original dimer feed stream214'). To prevent the entrainment of the thermally stable oil with the vapors (streamS) it is necessary to introduce the hot oil a' few platesbelow the top of tower 4. Stream 8 has the following composition:

Stream 8 is then fed to'tower. 9 having l0 vto Vl5 plates.

The cracked vapors are instantly quenched to a tempera'- tures of 70 to 80 C. by the liquid. reux of methylcyclopentadiene of the seventhor eighth-.trayfrom th'e'top'.-

of column 9.

Stream 10 (approximately`- 37 weightiper-centbasedon feed stream 24) is. the cyclopentadiene plus"'-sonie==f acyclic C51-.Ciell-.SLA .Part of this stream Viscondense'lby condenser II and returned as liquid reflux to the tower. A minimum reux is maintained to insure the separation of the C5 diene monomers (overhead vapor temperature of 45 C.). Stream 10 should have the following composition:

The major portion of the C5 acyclic dienes may be stripped from the dimerized monomers, thus giving an increase in cyclopentadiene from 91% to 97%.

Tower 9 bottoms temperature is maintained at 170- 180 C. by removing stream 12 and preheating in heat exchanger 13, returning the liquid to the bottom of the tower. For recovery purposes this heat requirement could best be supplied by an external heating medium so the tower bottoms (methylcyclopentadiene and uncracked dimers) will have a minimum hold-up time before stream 25 is fed to tower 17 for recovery of the methylcyclopentadiene. Stream 25 has the following Stream 18 (approximately 33 volume per cent based on feed stream 24) is partially 19, so a minimum reflux may be returned to the top tray to maintain an overhead vapor temperature of 75 C. Composition of stream 18 is as follows:

Component: Weight per cent Cyclopentadiene l Methylcyclopentadiene 90 C5 acyclic dienes 8 C1 cyclic dienes 1 Stream 20 is the tower 17 bottoms having the following composition:

Component: Weight per cent C7 cyclic dienes 26.5 Cyclo and methylcyclo dimer 15.0 C5 and C6 acyclic diene dimers 58.5

Part of this stream is heated by exchanger 21 and returned to the bottom of tower 17 to furnish heat for the distillation (bottoms temperature of l50-160 C.). Stream 22 may be a means of purging C7 cyclic dienes and C5 and Cs acyclic dimers from the system. Stream 23 is a recycle stream of the above materials returned to the cracking tower `4 since this stream contains some dimerized C5 and Cs cyclic dimers formed during the distillation steps.

Feed stream 24 and any recycle streams 23 or 14 are preheated in furnace to a temperature of approximately 177 C. The partially vaporized feed line 16 is fed to the first or second tray from the bottom of the cracking tower 4. Minimum contact time in the furnace 15 is desired, since coking may occur if cracking is allowed to occur in this part of the equipment.

Any entrained cracking oil (streams 1) carried overhead with stream 8 is removed from the system by purge stream 22.

Presented below are further details of this invention.

The feed stock for the process of this invention as detailed above is a cracked petroleum fraction containing preferably from about 55 to 82 weight per cent of cyclopentadiene and methylcyclopentadiene (as dimers or codimers) boiling in the range of l50-220 C. with or more boiling in the range of 170-220 C. Further details on the components and typical actual feed composition are presented directly below:

l Present :is dimers and codmers.

The cil utilized to countercurrently Contact dedirnerizetl monomers is heated to a temperature of 300* 500 C. and is fed to the cracking tower at multiple points such that all zones of the tower are operated at a temperature 350 C. and a sufficient liquid level of oil is carried on each tray. The quantity of hot oil circulated may be varied depending on the concentration of cyclo dienes to be cracked in the dimer feed (circulation rate covering l0 to 100 parts oil to 1 part dimer feed). The oils utilized are thermally stable organic preferbaly hydrocarbon saturates, i. e., parafn or naphthenic oils having an initial boiling point of 371 C. atmospheric, so that the oils are in the liquid phase in tower 4.

Aromatic and oxygenated compounds of similar characteristics may also be employed.

An analysis of a typical hydrocarbon oil is as follows:

COMPOSITION OF BAROSA 56 OIL ASTM Engler Distillaton (10 mm.)

The improved method of this invention is illustrated by the following examples.

held at approximately 340 C. by circulating hot oil to dimer feed at a ratio of /1 respectively. Additional heat required to maintain this temperature was applied electrically since the hot oil was fed as a liquid to the top of the column only. The cracked vapors of cyclodienes and uncracked acylic dimers left the cracking column at temperature of 230 C. and were fed to a distillation column having 20 plates. This tower was operated at 1 to l reflux ratio to maintain an overhead temperature of 43 C., a feed plate (fifth from bottom) temperature of 70-80 C., and a bottoms temperature of 170 C. Analysis of the fractionating tower overhead cyclopentadiene product and the methylcyclopentadene and heavier materials as a bottoms product are as follows:

lAnalysis obtained by ultraviolet procedure after the sample has been dimerized.

The overhead product may be increased in purity by stripping 2 to 3 weight per cent C5 acyclic dienes from the dimerized fraction. The negative answer obtained for cyclopentadiene on the fractionator bottoms indicates a minimum dimerization was occurring within the tower under conditions employed. Some may be present in the bottoms stream since the ultraviolet procedure is not as accurate when applied to such a mixture high in methylcyclopentadiene and other impurities.

It will be further understood that the foregoing examples have been given merely for purposes of illustration, but that other modications of the present invention are possible without departing from the scope of the appended claims.

What is claimed is:

l. In a process for separating and recovering cyclopentadiene and methyl cyclopentadiene from their dimers and codimers in a cracked petroleum concentrate by vapor phase cracking of the dimers and codimers in said concentrate, the improvement which comprises passing said dimers and codimers in the vapor phase up through the cracking reaction zone in a fractionating column; simultaneously passing countercurrent to said vapors a thermally stable organic oil which boils above an initial boiling point of 371 C. under atmospheric pressure down through said reaction zone by introducing said oil at an upper part in said column; preheating said thermally stable oil to a temperature in the range of 300 to 500 C. before it is passed into the upper part of the fractionating column; taking oil a low boiling vapor fraction containing cyclopentadiene and methyl cyclopentadiene monomers with their dimers and codimers at overhead vapor temperatures of 200 to 230 C. from an upper part of the fractionating column above the point where said thermally stable liquid oil is introduced for further fractionation and recovery of monomers from the overhead product, and withdrawing the thermally stable liquid oil from a bottom part of the fractionating column.

2. In a process for separating and recovering cyclopentadiene and methyl cyclopentadiene monomers from their dimers and codimers in a cracked petroleum concentrate by vapor phase dedimerization, the improvement which comprises passing said concentrate into a bottom part of a fractionating column, passing a thermally stable hydrocarbon oil boiling above 371 C. preheated to 300 to 500 C. into an upper part of said fractionating column =so that said oil passes simultaneously countercurrent to vapors of said dimers and codimers in a cracking zone within said fractionat'ing column, withdrawing overhead from said fractionating column cracked monomers of cyclopentadiene and methyl cyclopentadiene with uncracked dimers at a temperature of 220 to 230 C. and withdrawing from a bottom part of said fractionating column the thermally stable hydrocarbon oil.

3. The process as defined in claim 2 wherein said thermally stable hydrocarbon oil is introduced onto plates below top plates in the fractionating column, and wherein Lsaid cracked petroleum concentrate of the dimers and codimers is introduced onto a lower plate above bottom plates in the column.

4. The process as defined in claim 3, wherein the cracked petroleum concentrate is introduced preheated to about 177 C. as a partially vaporized feed and wherein the thermally stable hydrocarbon oil withdrawn from the bottom of the column is heated to 300 to 500 C. and recycled onto plates at an upper part of said column.

References Cited in the file of this patent UNITED STATES PATENTS 2,387,993 Hepp Oct. 30, 1945 2,447,149 Wicr Aug. 17, 1948 2,453,044 Stat NOV. 2, 1948

Claims (1)

1. IN A PROCESS FOR SEPARATING AND RECOVERING CYCLOPENTAMIENE AND METHYL CYCLOPENTADIENE FROM THEIR DIMERS AND CODIMERS IN A CRACKED PETROLEUM CONCENTRATE BY VAPOR PHASE CRACKING OF THE DIMERS AND CODIMERS IN SAID CONCENTRATE, THE IMPROVEMENT WHICH COMPRISES PASSING SAID DIMERS AND CODIMERS IN THE VAPOR PHASE UP THROUGH THE CRACKING REACTION ZONE IN A FRACTIONATING COLUMN; SIMULTANEOUSLY PASSING CONTERCURRENT TO SAID VAPORS A THERMALLY STABLE ORGANIC OIL EHICH BOILS ABOVE AN INITIAL BOILING POINT OF 371* C. UNDER ATMOSPHERIC PRESSURE DOWN THROUGH SAID REACTION ZONE BY INTRODUCING SAID OIL AT AN UPPER PART IN SAID COLUMN, PRETREATING SAID THERMALLY STABLE OIL TO A TEMPERATURE IN THE RANGE OF 300* TO 500* C. BEFORE IT IS PASSED INTO THE UPPER PART OF THE FRACTIONATING COLUMN; TAKING OFF A LOW BOILING VAPOR FRACTION CONTAINING CYCLOPENTADIENE AND METHYL CYCLOPENTADIENE MONOMERS WITH THEIR DIMERS AND CODIMERS AT OVERHEAD VAPOR TEMPERATURES OF 200* TO 230* C. FROM AN UPPER PART OF THE FRACTIONATING COLUMN ABOVE THE POINT WHERE SAID THERMALLY STABLE LIQUID OIL IS INTRODUCED FOR FUTHER FRACTIONATION AND RECOVERY OF MONOMERS FROM THE OVERHEAD PRODUCT, AND WITHDRAWING THE THERMALLY STABLE LIQUID OIL FROM A BOTTOM PART OF THE FRACTIONATING COLUMN.

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