US2414651A - Process for the treatment of hydrocarbons - Google Patents

Description

Jan. 2l, 1947. J. w. LATCHUM, JR 2,414,551

PROCESS FOR THE TREATMENT OF HYDROCARBONS Filed Nov. so, 1944 2 Sheets-Sheet 1 III IIJ 55 Patented Jan. 21, 1947 PROCESS John W. Latchum,

FOR THE TREATMENT F HYDROCARBONS Jr., Bartlesville, Okla., assign` or to Phillips Petroleum Company, a corporation of Delaware Application November 30, 1944, Serial No. 565,929

(ci. 26o-666) 9 Claims. l

This invention relates to a process for the treatment of hydrocarbons and more particularly to a process of treating certain hydrocarbon streams of the type known in theart as aromatic oils" to recover valuable components therefrom. Still more particularly it relates to a process of treating aromatic oils to recover therefrom separate fractions (1) monocyclic aromatic hydrocarbons especially benzene and/or toluene, (2) aliphatic conjugated pentadienes, namely, piperylene and/or isoprene and (3) dicyclopentadiene.

Aromatic oils are commonly produced in thermal pyrolysis of the lighter hydrocarbons especially the low-molecular weight paraillns, although they are also obtained in the production of manufactured gas. In some cases aromatic oils are present in naturally occurring oils or are produced as 'by-products in various refinery operations. For the most part, however, they are produced by high-temperature operations. See

^ for example, Chapter 5 of Ellis, Chemistry of Petroleum Derivatives, volumes 1 and 2, entitled Production of aromatic hydrocarbons bypyrolysis of petroleum hydrocarbons." Cracking processes in particular yield mixtures containing benzene, toluene, piperylene, isoprene and cyclopentadiene; see Ellis, loc. cit. vol. 2, page 144.

Petroleum hydrocarbon conversion processes, especially those involving cracking or high temperature Dyrolysis yield aromatic oils of the type employed as raw material in the present invention'. For example, the pyrolysls of ethane and/or propane at atmospheric pressure at a temperature of from 1450 to 1600 degrees F. for a period of time of from 2 to 0.1 seconds, yields a' mixture containing butadiene, isoprene, piperylene, cyclopentadiene, and monocyclic aromatics such as benzene and toluene. See U. S. Patents to F. E. Frey, Nos. 2,376,425 and 2,376,426.

Aromatic oils to which the present invention may be applied are obtained as by-products in the pyrolytic treatment of propane to produce ethylene. For example, the copending application of Carl J. Maki, Ser. No. 510,172, led November 13, 1943, discloses this method of producing ethylene. The gaseous eiluent from the cracking of propane at 1400 F. and 6 to 8 pounds pressure in accordance with said application is cooled and compressed to drop out heavy hydrocarbons which contain aromatic oils. Upon depropanizing or debutanzing the resulting gaseous stream there is obtained a kettle product which is an aromatic oil. Any of these aromatic oils may be used as feed in the practice of the present invention. The kettle product referred to is preferably treated in the manner disclosed in the c opending application of K H. Hachmuth, Ser. No. 454,312, filed August 10, 1942, for the vremoval of C4 hydrocarbons including butadiene whereupon `feed to the present invention.

Aromatic oils are also produced as luy-products in processes for the production of aliphatic con- Jugated dioleilns from the corresponding oleflns `or paraflins, especially butadiene from normal butene or normal butane. For example, in the two-stage dehydrogenation of normal butane to butadienein accordance with the process described in U. S. patent to K. H. Hachmuch, No. 2,386,310, aromatic oils are produced in the compression systemsoperating on the efliuents from the first and second stages. Another fraction of aromatic oils is obtained in the final or butene-Z column in which butene-2j recycle is separated overhead from a kettle fraction of aromatic oils. The copending application of K. H. Hachmuth, Ser. No. 534,599, filed May 8, 1944, discloses an improved method of removing the butene--2 from this aromatic oil kettle fraction whereby polymerization thereof is prevented.

It appears that those pyrolytic or thermal hydrocarbon conversion processes which yield one member of the group consisting of monocyclic aromatics (such as benzene), cyclopentadiene, and aliphatic conjugated pentadienes also yield appreciable quantities of-the other members of this group as accompanying products. See, in addition to chapter 5 of Ellis, above cited, chapter 4 on production of unsaturated hydrocarbons especially the section on diolefins, chapter 3 on cracking processes and their products and chapter 2 on thermal decompositionof hydrocarbons. A survey of sources of cyclopentadiene and accompanying hydrocarbons will 'be found in the article of Wilson and Wells, entitled The chemistry and utilization of cyclopentadiene," appearing in Chemical Reviews, `vol. 34, February, 1944, pages 1 to 50, especially pages 2 to 4. It is evident that the formation of any one of these three classes of hydrocarbons by high temperature hydrocarbon conversion processes and the like is closely linked up with the formationof the others in a manner but imperfectly understood at present. For these reasons, aro-matic oils containing these three types of material recovered by my process are quite commonly available, so that ample supplies of feed for thefprocess of the present invention are assured. As a matter of fact aromatic oils are often considered to be objectionable by-products of processes making other materials such as dehydrogenation, cracking, pyrolysis, etc., and have often been discarded as of little or no value. Disposal of these aromatic oil streams has been a source of expense. My invention not only eliminates the problem of disposal but provides a simple and commercially feasible method of recovering highly valuable organic chemicals.

The principal object of the present invention is to provide an improvedmethod of recovering L valuable components of aromatic oils.

Another object is to provide a commercially feasible method of recovering separate fractions l of monocyclic aromatic hydrocarbons, cyclopentadimer, dicyclopentadiene, from an aromatic oil containing cyclopentadiene in the form of the monomer or the dimeror both. Another object is'to provide such a process wherein there is simultaneously recovered a monocyclic aromatic fraction and an aliphatic pentadiene fraction. Another object is to provide a process of the foregoing type which is simple and economical, requires a minimum of relatively simple equipment, and is easy to operate. Numerousother objects will hereinafter appear or become apparent to those skilled in the art from the following illustrative description of the best mode known-to me of carrying out my invention.

In the accompanying drawings: Fig. 1 portrays diagrammatically one arrangement of equipment which has been found very satisfactory in carrying out the present invention. Fig. 2 is a graphical presentation of the initial concentration of cyclopentadiene vs. final concentration of dimer showing influence of time. temperature and initial concentration of monomer upon nal concentration of dimer.

My invention is a method of recovering cyclopentadiene in the form of dicyclopentadlene from an aromatic oil mixture containing cyclopentadiene in the form of the monomer (as will hereinafter appear, if the feed contains cyclopentadiene in the form of the dimer the feed is rst treated to convert most or substantially all of the dimer to monomer) in admixturewith aromatic hydrocarbon and aliphatic conjugated pentadiene which comprises fractionally distilling said mixture under such conditions that substantially all of said cyclopentadiene monomer and aliphatic conjugated pentadiene are taken overhead while substantially all of said aromatic hydrocarbon is taken olf in the kettle product, subjecting said overhead to an elevated temperature for a period of time such as to dimerize a major proportion, and preferably substantially all, of the cyclopentadiene without substantially polymerizing the other unsaturated hydrocarbon content thereof, and fractionally distilling the resulting mixture under such conditions that substantially all of the dicyclopentadiene content thereof is taken voff in the kettle product. Preferably the condii tions in the latter distillation are such that substantially no dedimerization of dicyclopentadiene in the column takes place. y

Referring now to Fig. 1 of the accompanying drawings:

In accordance with the present invention the aromatic oil containing cyclopentadiene in the form of monomer or dimer or both, aromatic hydrocarbons such as benzene and toluene, and aliphatic conjugated pentadiene such as piperylene and isoprene is employed as the feed entering via line I. If dicyclopentadiene is present, the feed unit 2 to an elevated temperature for a period of `time such that all of the dicyclopentadiene in the mixture is converted to the monomer. lFor example, it may be heated to 350 F. for 6 hours.

'The depolymerization step is preferably conducted with the feed in the vapor phase.- Vapor phase 4 depolymerization results in conversion of any polymers heavier than the dimer present in the vfeed to the monomer also. The depolymerization effluent is condensed in condenser 3A to form the fractionator feed. Other methods of converting the dimer to the monomer will be obvious to those skilled in the art. The depolymerization step is omitted where the feed contains no dimer.

The resulting dimer-free feed flowing via line 3 or. where all of the cyclopentadiene content of the original feed is in the form of monomer. the original feed flowing via line 4, passes via line 5 into fractionating column 6 where it is fractionally distilled under such conditions that all of the cyclopentadiene, piperylene, isoprene and any lighter material pass overhead while all of the benezene, toluene and any heavier material are withdrawn as kettle product. It has been found preferable to maintain bottom time and temperature conditions such that substantially no dimer leaves in the bottom product and to employ steam stripping in combination with the continuous fractional distillation. Raw steam is injected via line 1 directly into the bottom of the column 6 to aid in the fractionation. A Water layer is withdrawn from the upper portion of the column via line 8, for example, by means of atrapout tray of known type (not shown), and is cooled and pumped into the top of the column via line 9 as the sole reflux. By the use of steam stripping a sharp separation is obtained, all of the piperylene and lighter going overhead via line I0 and the heavier-than-piperylene material going out the base of the column via line 8A, this being the benzene and toluene concentrate. While use of the dephlegmator with a Water reux in the manner described above and shown in the drawings is most highly preferred, it may in some cases be dispensed with, column 6 being reuxed in the conventional manner; however, operation in such manner involves the sacrifice of the many advantages accruing from the refluxing with water. In some instances column Ii may be refluxed with the water layer obtained upon condensation of the overhead.

The overheadproduct is cooled in unit II and passed to accumulator I2 from which a water layer may separate and be drawn off vialine I3. The emulsion of water and hydrocarbons obtained by condensing the overhead from column 6 is often very slow-breaking so that if sole reliance is placed upon gravity to effect the separation of water in vessel I2, several hours must elapse. However, failure to separate the water is not particularly harmful in the later steps of the process the principal disadvantage being the added load on subsequent units of the equipment.

The overhead product is next passed to dimerizing unit I4 in which it is reheated to convert the monomeric cyclopentadiene to the dimer under suitable conditions of time and temperature known to the art. The conversion may be carried out by heating for the proper period of ,time whereupon the mixture may be quenched in any suitable manner. 'I'his conversion may be vaccomplished without significantly polymerizing the other unsaturated hydrocarbons in the mixture.

The dimerized product is cooled and fed via line I5 to fractionation column IB where it is fractionated at relatively low temperatures with the bottom temperature being preferably not over 212 F. so that little if any of the dimer will be converted to monomer. In column I6 the piperylene and lighter go overhead and are removed via line I8 while the dimer is taken of! as kettle product via boiling between piperylene and line I 9. Care must be taken to keep the temperature above 94 F. until it is in the shipping container so as to prevent formation of the solid phase. During the fractionation steam or other inert gas is injected as a stripping medium into the bottom of column I6.

The piperylene and lighter fraction withdrawn via line I8 may be treated in any manner as by refractionation to secure a piperylene kettle product, the overhead being discarded or refractionated to yield isoprene. The benzene-toluene concentrate withdrawn via line 8 is refractionated to give raw toluene and raw benzene and the residue is discarded. The raw products are purified to the grade desired by means well-known to the art.

Operating conditions for column 6 may be as follows: pressure ranging from atmospheric to 10 pounds gauge, conveniently 5 pounds; bottom temperature 150 to 170 F., conveniently 160 F. at 5 lbs. gauge; top temperature 100 to 120 F., conveniently 115 F. at 5 lbs. gauge.

Operating conditions for column I6 may be as follows: pressure ranging from atmospheric to 10 pounds gauge, conveniently 5 pounds; bottom temperature ranging from 170 to 212 F., conveniently 212 F. at 5 lbs. gauge; top temperature of 120 to 130 F., conveniently 125 F. at 5 lbs. gauge. Fractionator I6 functions somewhat like a. stripper since its principal function is that of i' removing piperylene and lighter from the dimer of cyclopentadiene. It is preferred that the bottoms product in column I6 not be reboile'd in order to avoid dedimerization. The stripping action of the steam or other inert gas introduced via line I'I aids markedly in the separation in column I 6 and in keeping the bottom temperature in column I 6 at a suitable low level so that dedimer ization of dicyclopentadiene is prevented.

In some cases it may be found desirable to introduce into the feed entering column I6, or at some other point in column I6, a paraiiin hydrocarbon having` a boiling point below dicyclopentadiene (338 F.) and preferably at least 100 degrees F. therebelow, such as certain octanes, heptanes, hexanes, etc. The parains are em,- ployed because of their inertness. Such a paraffin should preferably boil substantially above piperylene (109112 F.), i. e., be a hexane or heavier in which case it appears in the bottom product, keeping the bottom temperature down, allowing reboiling of the bottom product at a ternperature well below the point at which dedimerization of dicyclopentadieneoccurs.

Such a parailin, dicyclopentadiene, has the further advantage that it is a solvent or suspension medium for dicyclopentadiene, preventing solidification thereof or tendency to solidify. Such a paraffin may be introduced via line I'I. If desired such a paraiiin may be introduced in the original feed in line I in which case it must in practice be hexane in order to insure its going overhead in column 6 and its presence in column I6 tadiene and above piperylene.

If desired there may be present in the feed to column I6 or there may be employed as the stripping agent fed in via line I1 a parafn boiling below piperylene such as a pentane, a butane, propane, ethane, etc. Such a lower paraffin appears in the overhead of column I6 and aids greatly in the stripping of the dicyclopentadiene in column I6 and in the maintenance of a low temperature in this column. It is desirable that the fractionation and stripping in the column Hexanes are preferred because they boil well below dicyclopentake place very rapidly in order to avoid a. long residence time of the dicyclopentadiene in col'- umn I 6.

The pressure on the system at any point depends on the temperature. Preferably the`column B and I6 are run at slightly above atmospheric pressure. Depolymerization unit 2 is operated at substantially similar pressures in order to avoid the necessity for high pressure pumps or reducers or for high pressure differentials, namely, the pressure of the feed, e. g., in dedimerizing unit 2, will be somewhat above that in column 0 in order to force the material through the column.

Conditions for operation of dimerizer I4 may be determined readily by those skilled in the art. Fig. 2 portrays graphically the inter-relation between initial concentration of cyclopentadiene, final concentration of dimer thereof, and time at one temperature, namely 300 F. Similar graphs may be plotted for any temperature level such as 200, and 250 F. To use the chart. the initial concentration of monomer is fixed. Then, 'knowing either final concentration oi' dimer or time, the other mined. The slanting lines represent the percentage of dimer in the treated product.

Dimerizer I 4 is preferably operated under 1iq uid phase conditions. The material in dimerizer I4 is ordinarily maintained under sufflciently elevated pressure to maintain it in liquid phase. 'I'he pressure will depend upon its composition and upon the dimerizing temperature used. In general it will be of the order of several hundred pounds per square inch gauge. For example, at 300 F. it may be about 400 pounds per square inch gauge. Vapor phase operation may be used but is less desirable.

The conditions of depolymerizationin unit 2 may readily be determined for any given feed by those skilled in the art in the light of present-day knowledge of the dedimerization of dicyclopentadiene. This reaction is preferably carried out in vapor phase.

.Following are specific examples of the practice of my invention.

ExAmLr: I

A feed stream having the following composition was fed to a unit essentially as shown in the drawings via line I. The feed was a low stage accumulator or scrubber oil obtained as a by-product in the cracking of ethane and propane to Analysis of feed-line 1 Liquid Component vulume Pcntadiene 2-methylbutene-l Isoprene. Pentene-2.-

Residue...

This feed was passed via lines l and to fractionating column B'at the rate of 2000 gallons per 24-hour day. Column 6 was of the eonven tional type having thirty (30) bubble trays and was provided with the usual steam reboiler, and with a, water separating tray in the upper section. Steam was fed into the bottom of column 6 by means of line i at the rate of 300 pounds per day. Column 6 was operated at a pressure of 5 pounds per square inch gauge and with a kettle temperature of 160 F. and a top temperature of 115 F. The kettle product withdrawn via line 8 had the following analysis:

Analysiskettle product-line 8A The overhead vapors in line I0 were condensed in cooler ll and accumulated in vessel i2. The condensate had the following analysis on a waterfree basis:

Exner.: 1I

Afeed having the following analysis was fed into the system via line I:

This material was the aromatic oil obtained as a heavy product in the recovery of butadiene from the gaseous eiiiuent from the compression system applied to the cracking eiliuent from which, the feed of Example I was derived.

The feed was passed through dedimerizing unit 2 Where it was heated at 21.3 pounds gauge to 425.F. for 15 minutes which effected dedimerization of substantially all the dimer of cyclopentadiene. The resulting stream was passed by lines 3 and 5 at the rate of 2000 gallons per 24- hour day into column 6 operated as in Example I. The kettle product of column 6 had the following analysis:

Analysis-overhead productline 10 so Kettle product-.line 8 Liquid Liquid Component volume Component volume per cent per cent Pentadiene- 31-0s 35 59. 2-methylbutene-l 9- 23 Unsaturates in benzene 9. Isoprene. 4 27 Intermediate to dicyclopentadiene 21. Pentene 4* 60 Residue..- 0. 2-methyibutene-2 4. 52 Cyclopentadiene 24. Piperylen 22.00 o The overhead product of column analyzed as The overhead condensate was then fed into dimerizer I4 where it was heated to a temperature of 300 F. for 30 minutes under pressure sufficient to maintain liquid phase thereby converting 96 per cent of monomeric cyclopentadiene to the dimer. The resulting mixture was then passed via line i5 to column I6 which was operated at a pressure of 5 pounds per square inch gauge and with a bottom temperature of 212 F. and a top temperature of 125 F. Steam was fed in via line i1 at the rate of 200 pounds per day. The kettle product had the following analysis:

Analysis-kettle productline 19 follows on a water-free basis:

Overhead product-line 10 Liquid volume per cent Component Cr-Cl gyciopentadiene 57 Liquid operated a-s in Example I. The overhead product component volumet had the following analysis:

T0911 De Overhead product-line 18 r(.liycloplentadiene (as dimer) 903g Li id ene u .pery 60 Component voaime percent The overhead product from column I6 had C the following analysis on a water-free basis: Csenmienn 9%?. Analysis-overhead product-line 18 65 Bamm" f 65 Li um The kettle product of column 16 analyzed as Component voime follows per mnt Kettle product-linen? Pentadiem 39.50 Li 'Ia-methylbutene-l 7o Component voixgi S0 rene. Pesten-2 5 93 per cent 2-methylbutene-2 5. B3 C plage-Miami 1.00 :n IR 0.5 Piperylene 30. 34 Dicyclopentadlene 99. 5

From the foregoing it will be seen that the present invention provides a highly improved method of recovering aromatics, aliphatic conjugated pentadiene, and cyclopentadiene from aromatic oil containing the same. The process of the present invention presents numerous advantages among which are the small equipment requirements, the simplicity of the operation and its ease of control, the effectiveness of the recovery of three valuable hydrocarbons from materials which have heretofore been wasted, and the fact that the cyclopentadiene is recovered as the dimer which is convenient for shipping and 10 the cyclopentadiene and aliphatic conjugated pentadiene are taken overhead and substantially all of said monocyclic aromatic hydrocarbon is taken ofi in the kettle product, injecting liquid water into the top of said column as the sole reflux, withdrawing a water layer from a lower handling since it is a non-volatile liquid or solid at ambient temperatures. Another advantage is that the three product streams are very little contaminated with material belonging in other streams, so that purification of the product streams is much simplified. Another advantage is that dicyclopentadiene of excellent purity is obtained as a product. Another` advantage is that the injection of steam into the columns in which the 'fractional distillations are conducted suppresses polymerization of unsaturates including cyclopentadiene and aliphatic conjugated pentadiene. Numerous other advantages will be apparent to those skilled in the art.

I claim:

1 The-process of recovering cyclopentadiene in the form of dicyclopentadiene from an aromatic oil mixture containing dicyclopentadiene in admixture with monccyclic aromatic hydrocarbon and aliphatic conjugated pentadiene which comprises heating said mixture to an elevatedtemperature and for a period of time such that substantially all of said dicyclopentadiene is converted to the monomer, passing the resulting substantially dicyclopentadiene-free mixture to a fractionation column and there distilling same under such condition that substantially all of the cyclopentadiene and aliphatic conjugated pentadiene are taken overhead and substantially all of said monocyclic aromatic hydrocarbon is taken oif in the kettle product, injecting steamdirectly into the bottom of said column, withdrawing a water layer from said column at a point near but above the feed entry to said column, cooling the water layer so withdrawn and injecting it into the top of said column as the sole reflux, condensing said overhead, subjecting the resulting condensate to an elevated temperature for a period of time suchas to dimerize substantially all of the cyclopentadiene Without substantially polymerizing the other unsaturated hydrocarbon content thereof, passing the resulting mixture to a second fractionation column and there distilling same under such conditions that substantially all of the aliphatic conjugated pentadiene 'content thereof and lighter are taken overhead While sub- ,santially all of the dicyclopentadiene content thereof is taken olf in substantially pure form as the kettle product and that substantially no Vcledimerization of dicyclopentadiene takes place.

2. The process of recovering cyclopentadiene in the form ofdicyclopentadiene from an aromatic oil mixture containing dicyclopentadienein admixture with monocyclic aromatic hydrocarbon and aliphatic conjugated pentadiene Which comprises heating said mixture lto an elevated .temperature and for a period of time such that substantially all of said dicyclopentadiene is converted to the monomer, passing the resulting substantially dicyclopentadiene-free.mixture to a fractionation coltimn and there distilling same under such conditions that substantially all of point in said column, said lower point being near but above the point of feed entry to said column, condensing said overhead, subjecting the resulting condensate to an elevated temperature for a period of time such as to dimerize substantially all of the cyclopentadiene without substantially polymerizing the other unsaturated hydrocarbon content thereof, passing the resulting mixture to a second fractionation column and there distilling same under such conditions that substantially all of the aliphatic conjugated pentadiene content thereof and lighter are taken overhead while substantially all of the dicyclopentadiene content thereof is taken off in substantially pure form as the kettle product and that substantially no dedimerization of dicyclopentadiene takes place.

The process of claim 1 wherein said dedimerization is carried out with the aromatic oil mixture in the vapor phase.

4. The process of claim 1 wherein said firstnamed column is operated at a. pressure ranging from atmospheric to 10 pounds gauge, with a bottom"temperature ranging from 150 to 170 F. and a top temperature ranging from to 120 F., and said second column is operated at a pressure ranging from atmospheric to 10 pounds gauge, with a bottom temperature ranging from 170 to 212 F. and a top temperature ranging from 120 to 130 F.

5. The process of claim 1 wherein said first; named column is operated at a pressure of approximately 5 pounds gauge, with a bottom temperature of approximately 160 F. and a top temperature of approximately v F. and said second column is operated at a pressure of approximately 5 pounds gauge, with a bottom temperature of approximately 212 F. and a top temperature of approximately 125 F.

f ated Without reboiling of its bottoms product, and

an inert gaseous stripping medium is injected directly into the bottom of said second column.

7. The process of claim 1 wherein said firstnamedcolumn is operated at a pressure ranging from atmospheric to 10 pounds gauge, with a bottom temperature ranging from 150 to 170 F. and a top temperature ranging from 100 to F., said second column is operated at a pressure ranging from atmospheric to 10 pounds gauge, with a bottom temperature ranging from 170 to 212 F. and a top temperature ranging from 120 to 130 F., said second column is operated without reboiling of its bottoms product, and steamas a stripping medium is injected directly into the bottom of said second column.

8. The process of claim 1 wherein said firstnamed column is operated at a pressure ranging from atmospheric to 10 pounds gauge, with a bottom temperature ranging from to 170 F. and a top temperature ranging from 100 to 120 F.,

said second column is operated at a.. pressure low piperylene as a stripping medium is injected ranging from atmospheric to 10 pounds gauge, directly into the bottom of said second column.4

with a, bottom temperature ranging from 170 to 9. The process of claim 1 wherein hexane is 212 F. and a. top temperature ranging from 120 present in substantial amount in said second to 130 F.. said second column is operated with- 6 column and appears in the kettle product in ad out reboiling of its bottoms product, and a. mixture with said dicyciopentadiene.

parafn hydrocarbon having a boiling point be- JOHN W. LATCHUM, JR.

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