US2056979A - Process for polymerizing unsaturated hydrocarbons - Google Patents

Description

Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE PROCESS FOR POLYMEIZING UNSATU- RATED HYDROCARBONS ration of Ohio Application November zo, 1999, serial No. 496.912

9 Claims.

This invention relates to an improved process of producing gasoline-like hydrocarbons from unsaturated hydrocarbons, and has for its primary object the provision of a process for treating unsaturated hydrocarbons developed by cracking and -other similar operations, whereby to render such hydrocarbons efiicient for use as motor fuels, to reduce the amount of xed gas developed by such operations and totreat the gasoline-like distillates' to remove therefrom compounds of an objectionable nature when such -distillates are intended for use as motor fuels.

In the cracking of high boiling oils in the )vapor phase, it is customary to employ relatively high temperatures during 4the conversion or cracking operation. Such high temperatures result in the formation of very substantial quantities of gas in proportion to the total amount of oil charged to the cracking operation. In a prior application filed by Cary R. Wagner, Serial No. 283,145, filed June 5, 1928, a process is set forth wherein such gas is passed at elevated temperatures and pressures through a heated zone and therein maintained under conditions promoting the polymerization of the gas into compounds possessing higher molecular weights and which fall within the range of gasoline.

In addition, vapor phase cracked distillates contain certain undesirable compounds which, upon standing, produce gums or resinous deposits tending to discolor the distillates and to render them objectionable for use in internal combustion engines as a fuel. led by the applicant, Rudolph C. Osterstrom, Serial No. 447,532, filed April 26, 1930, of which this application is a continuation-impart., a process has been set forth for removing suchf deposits from vapor phase cracked distillates3 by passing the latter through a heated reaction zone maintained under superatmospheric pressures and high temperatures whereby to polymerize the objectionable compounds which produce the aforesaid resinous deposits. In accordance with the present invention, a process is provided wherein polymerization reactions on the part of the gas and the motor fuel distillate take place in a single treating system to the end of reducing the equipment costs and to obtain other highly desirable operating economies.

In the accompanying drawing, which forms a part of this specification, the single gure illustrates diagrammaticallyv apparatus used in carrying out the present invention.

Referring more particularly to the drawing, th numeral I designates a pipe line through which In the co-pending application is passed a vapor phase cracked petroleum distillate in an untreated condition and containing a large percentage of certain highly reactive unsaturated hyrdocarbons which require removal before the distillate is rendered suitable for com- 5 mercial distribution and use. The pipe line AI enters a working tank 2 in which is also contained 'hydrocarbon gas of the type producedby, for example, vapor phase cracking operations. This gas may enter the tank 2 either through the 10 pipe line I or by any other desired method of introduction. As is Well known, refinery gas of this character, also, contains a large percentage of unsaturated hydrocarbons.

Leading from the bottom of the tank 2 is a pipe 15 line 3 by which the gasoline distillate is conducted to the suction side of pump 4. The discharge side ofthe pump 4 is connected with a pipe line-5 which leads to a heating coil 6 disposed in a suitable furnace 1. The furnace' is 20 provided with burner means, indicated at 8, by which adequate heat is developed within the furnace to raise the temperature of the hydrocarbons passing through the coil to a polymerization temperature which may vary between .substan- 25 tially 300 F. to 750 F. The pump 4 operates preferably to maintain the distillate during its flow through the coil 6 under superatmospheric pressures varying between 500 to 1200 pounds per square inch in order that the gasoline distillate, 30 undergoing treatment, will be maintained substantially in the liquid phase, although vaporization of the distillate under treatment may be provided for in the coil 6 under-certain circumstances by the use oi lower pressures. 35

The gas withdrawn from the top of the tank 2 passes by way ofa pipe line 9 to a compressor I0 and from the compressor I0 to an accumulator Il. In this acciunulator the 'gas is maintained under a pressure of approximately pounds 40 per square inch. Within this accumulator there takes place a separation of low boiling liquid oils from the gases, and these oils are withdrawn from the bottom of the accumulator, together with gases dissolved therein, by way of la valve con- 45 trolled pipe line I2, which leads to a pump I3 and from the discharge side of this pump to the pipe line 5.

Leaving the top of the accumulator II is a valve pipe line I4 which extends to a compressor -50 I5 wherein the pressure on the gas is increased to approximate the pressure which obtains in the 1 line 5, and a pipe line I6 connects the discharge side of the compressor I5 with the pipe line 5 immediately ahead of the coil 6.

that both the gasoline distillate and the gas will pass as a mixed stream through the polymerization zone formed by the coil 6. The coil is preferably Iformed from ordinary mild steel sections of pipe of desired llength and may or may not contain a catalyst, such as aluminum chloride,

' nickel chloride or other metallic halids. In the preferred form of my invention I have found it unnecessary to employ a catalyst in the coil 6 although, of course, such a catalyst as those of the type described may be used if desired; .The unsaturated gases introduced into the coil preferably contain propylene, butylene and, in certain instances, ethylene. Gases such as propylene and butylene, show a marked tendency to polymerize lunder the conditions of elevated temperature and pressure present in the coil 6. The polymerization of these gases results inthe formation of additive compounds of higher molecular weights, which, upon subsequent cooling or condensation, possess the boiling range of motor fuel.

While the gases are being polymerized in the single coil 6 likewise polymerization of certain undesired compounds present in the distillate removed from the bottom of tank 2 takes place. The vapor phase cracked distillate possesses, when untreated, certain highly -r'eactiv'e unsaturated compounds which, in time, produce particularly upon exposure `to air undesired gums and color producing bodies. By acceleratingthe rate of polymerization of these undesirable coml pounds in vapor phase cracked distillate, the same may be separated from the distillate at the` time the motor fuel is being manufactured so that the latter will remain stable, in so far as l content and color are concerned. I have found that by passing a vapor phase cracked distillate through a polymerizing zone such as the coil 6 under conditions of elevated temperatures and y pressure, that the polymerization of thesegumformed and color-producing bodies can be secured, and therefore I make use of the coil 6 for this purpose, whereby the single coil serves the double function of polymerizing both the gas and the undesired compound in the distillate.

The treated hydrocarbons are discharged from the'coil B by way of a pipe -line I1, and enter a lvessel I8 in which is contained a bed of fullers earth or other equivalent materials. Preferably, pressure is maintained on the -distillate to maintain the latter in the liquid phase while passing through the'fullers earth bedin vessel I8. 'I'he fullers earth may be said to act either as a catalyst or adsorbent'in effecting further polymerization of the --selected hydrocarbons. The treated oils are passed from the vessel I8 by way of a pipe line to a stabilizing column 2| and the line 20 may` be provided with a pressure reducing valve 22 by whichseparation of the heavy polymerized compounds from the lighter and desired products is permitted to take place in' said co1- umn. The heavy polymerized compounds collect in the bottom lof column 2| and may be removed by means of the valve controlled outlet 23, whereas the desired lighter hydrocarbons, by reason of the temperatures which prevail in column 2 I, assume a vaporous form, especially in view of the reduced pressures, and pass overhead-from the column through an outlet line 24 together 'with By this method oi' operation it will beobserved rator 26 and passed to a stabilizer r2II insurey the removal of all xed gas from the distillate.l

, finished commercial motor fuel.

In view of the foregoing, it will be.. seen that the present invention provides a ,method for treating l'ow boiling crackedjoils, obtained especially from vapor. phase cracking' plants, to remove from such oils undesired gum-forming and color-forming compounds. At the same time refinery gas, which is developed in relatively large quantities by the` operation of high temperature \or vapor phase cracking units, is subjected to a polymerizing operation whereby a large proportion lof the gas is converted into higher boiling products having the characteristics of an antiknock gasoline. Both of 'these operations, which I now consider to Vbe the result of polymerization, take place in a single treating system which includes a heating unit, instead of taking place in separate systems as was heretofore done. This improved combined treating system results in decreasing equipment and operating costs and provides generally for increasing the yields of the vdesired motor fuel endproduct of vapor phase cracking systems.

While I do notidesire to be limitedby the following explanation of reactions which take place in my process, yet it is my opinion that one explanation for the favorable results obtained is "as follows: In the presence of normally liquid hydrocarbons, such as the low boiling distillate undergoing gum removal treatment, I am able'to maintain ethylene, propylene and butylene in solution in the liquid state whereas they normally-would exist in a gaseous condition. As a result ofthis change of state, the molecules of these unsaturated gases are brought closer together and'caused to collide with each other more frequently and thereby increasing the tendency thereof to polymerize.

While I have described the invention as being especially applicable for use inl connection -withvapor phase cracking systems, nevertheless I do,not limit myself to such systems or operations but reserve the right to employthe invention in any capacity where it may be used to advantage. v

What is claimed is:

1'. The method of polymerizing unsaturated` hydrocarbons, which consistsA in passing a mixture composed of unsaturated hydrocarbon gases and a cracked low boiling oil containing unsaturated compounds through a heated reaction zone, heating the mixture during its passage through said zone to a temperature varying between 300 Frto '700 F., while said mixture is maintained under superatmospheric pressure,

then passing said mixture, following its removal from said heated reaction zone .through a stationary body of fullers earth, and then separating the undesired polymerized compounds from the desired .low boiling oils and remaining fixed gas.V

2. The method of polymerizing unsaturated hydrocarbons, which consists ifn passing a stream of such hydrocarbons consisting of a mixture of cracked low boiling oils containing unsaturated compounds and unsaturated hydrocarbon gases through an externally heated reaction zone, heating the mixture during its passage through said `reaction zone while under superatmospheric pressure to a polymerizing temperature wherein no substantial cracking of the hydrocarbons com prising. the mixture takes place, then passing the mixture from the reaction zone through Va bed of fullers earth and finally reducing the pressure on the mixture to permit of the separation heated reaction zone, maintaining the mixture during its passage through said zone under superatmospheric pressure, heating the mixture during its passage Athrough said zone to a temperature suiiiciently high'to effect therein polymerization of said undesirable compounds and unsaturated constituents of said gas -while avoiding any substantial cracking of the hydrocarbons comprising the mixture, discharging the mixture from the reaction zone under reduced pressures into an expansion chamber, and removing from one portion of said chamber high boiling polymerized compounds and from another portion of said chamber the desired treated compounds.

4. In the treatment of unsaturated hydrocarbons obtained from vapor phase cracking operations, the steps which comprise continuously passing a mixture composed ofl cracked low boiling oils containing unsaturated hydrocarbons and an unsaturated hydrocarbon gas through an elongated externally heated reaction zone, maintaining the mixture during its passage through said zone under superatmospheric pressure, heating the mixture during its passage through said zone to a temperature varying between 300 F. to 750 F., while avoiding any substantial cracking 'of the hydrocarbons comprising the mixture, reducing the pressure on the 4mixture following its release from said reaction zone and separating "from the mixture undesirable polymerized compounds.

5. In the treatment of unsaturatedhydrocarbons obtained from vapor phase cracking operations, which consists in continuously passing a mixture composed of unsaturated hydrocarbon gases and cracked low boiling oils containing unsaturated compounds through a tube still,f\heating the mixture during its passage througlsaid still to a temperature varying between 300 F. to 750 F., maintaining the mixture during its passage through said still under superatmospheric pressures sulficiently high to maintain the low boiling oils in the liquid phase, removing the mixture from said still and, without reducing the pressure thereon, passing said mixture through a bed df fullers earth, and then passing the mixture under reduced pressures into an expansion chamber, whereby to separate undesirable polymerized compoundsfrom the treated mixture.

6. The method of polymerizing unsaturated hydrocarbons obtained from vapor phase cracking operations, which consists in passing a mixture composedof cracked low boiling oils containing unsaturated compounds and unsaturated hydrocarbon gases through a tube still, heating 'the mixture during ,its-passage through said still to reaction producing temperatures varying between 300 F. to '750 F., maintainingthe mixture while in said still under superatmospheric pressures, then bringing the mixture following its passing discharge from said still into contact with a catalyst capable of promoting polymerizing reactions, and iinally passing the mixture into a separating zone under reduced pressure to effect the removal ofthe undesired polymerized compounds therefrom.

7. The method of treating unsaturated hydrocarbons, which consists in producing a mixture t of a low boiling vapor phase cracked distillate containing undesired unsaturated hydrocarbons of a gum-forming and color-imparting character and an unsaturated hydrocarbon gas obtained from a vapor phase cracking operation, passing said mixture of liquid and gas through an elongated. heating zone of restricted cross sectional larea while said mixture is maintained under a pressure varyingbetween A500 and 1200 pounds per square inch and wherein the mixture is heated to a temperature varying between 300 F.

and '750 F., maintaining the mixture in said heating zone for a sufilcient period of time to secure desired polymerizing reactions, then without substantial reduction in pressure removing the heated mixture from the 'heating zone and same through a treating zone, bringing said mixture during its passage through said treating zone into contact with a finely divided solid adsorbent during uninterrupted passage ofv the mixture through said treating zone, reducing the pressure on the mixture following its discharge from. the treating zone and i'ractionating said mixture in a fractionating zone, removing from one portion of said fractionating zone liquid hydrocarbons having a boiling range higher than the cracked distillate originally charged to the heating zone, removing from another portion of said tractionating zone as a vaporous overhead-product vapors composed oi desired low boiling oils substantially free from objectionable gum-forming and color-imparting bodiesand iixed gas condensing the combined vaporous and gaseous fractions, and separating the condensate from the fixed gas.

8. The method of treating low boiling hydrocarbons produced by vapor phase cracking of high boiling oils into low boiling oils, which eiect polymerization of the undesired compounds present in the cracked distillate and certain of the gaseous hydrocarbons into liquid hydrocarbons, then passing lsaid flow stream under revduced pressure into a fractionating zone, removing from one portion of said fractionating zone the undesired compounds contained in said distillate in the form of a reflux condensate having an average boiling range higher than that ,of said distillate forming the ow stream, separately removing from another portion of said zone a vaporous overhead fraction composed of hydrocarbons of gasoline boiling range and iixed gas, condensing the last-named fraction and separating the condensate from theflxed gas.

9. The method of treating unsaturated hydrocarbons obtained from vapor-phase crackingroperations, which comprisescontinuously passing a mixture composed of normally gaseous unsaturated hydrocarbons and cracked low-boiling oils containing unsaturated compounds undesired in the -ilnal product through a tube still under superatmospheric pressure, heating the mixture during its passage through. said still to a reaction li:em 1:erature of from 300 to 750 F. to effect la. polymerization oi' normally gaseous hydrocarbons to normally liquid' hydrocarbons lying within a motor-fuel boiling-point range and a polmerization of said undesired unsaturatedcompounds to polymers lying above the motor-fuel boilingpoint range, while avoiding any substantial crack- V ing of hydrocarbons comprising the mixture, subeiect a separation of relatively high-boiling un` desired polymerized compounds from the treated lo RUDOLPH C. QSI'I'ERS'I'ROM.

Images