US2222055A - Production of motor fuels - Google Patents

Description

Nov. 19, 1940. J. T. WARD PRODUCTION 0F MOTOR FUELS Filed Nov. 50, 1936 Patented Nov. 19, 1940 PATENT OFFICE PRODUCTION oF Moron. FUELS John T. Ward, New York, N. Y., assignor to Process Management Company, Inc., New York, N. Y., a corporation of Delaware Application November 3l), 1936, Serial No. 113.415

l Claim.

`This invention relates to the production of normally liquid hydrocarbons, and more particularly, to the conversion of normally gaseous hydrocarbons to normally liquid hydrocarbons.

It is an object of the present invention to'provide a method of treating a stream of normally gaseous hydrocarbons from an oil cracking operation or from any other suitable source, such as by the cracking of gaseous parains to gaseous oleflns, which ordinarilyconsists of hydrogen,

methane, and olenic and paraftlnicCz, Cs, and C4 hydrocarbons, to convert the stream to normally liquid hydrocarbons, fixed gases, e. g. hydrogen and methane, and gaseous hydrocar- 10 bons intermediate the liquid hydrocarbons and fixed gases.

The terms normally gaseous and normally liquid are used herein to describe hydrocarbons which are gaseous and liquid, respectively, at atmospheric conditions of temperature and pressure.

In the present invention a stream of gases of the type described is treated to separate therefrom iixed gases and a fraction containing substantially all the Ca hydrocarbons (e. g. ethane and ethylene) of the stream. Ethylene is separated from the fraction, for example, by means of a preferential solvent by liquefaction and rectiilcation or by an adsorbent, and returned to the stream at a. point subsequent to the separation of xed gases and C2 hydrocarbons. The stream, thus enriched in olens, is then subjected to a polymerizing treatment, either thermal or catalytic, to convert at least a portion thereof to normally liquid hydrocarbons.

The remainder of the fraction from which ethylene is separated, consisting essentially of the morerefractory ethane is subjected to a pyrolytic cracking treatment to produce therein at least a portion of olefins. The cracked products may be added to the stream of gases for subjection to polymerization at a point preceding the separation of xed gases and C: hydroa carbons, with or without the preliminary removal of xed gases. Or the cracked products may have the fixed gases removed therefrom and be returned to the stream at' a point subsequent to the removal of xed gases and C2 hydro- 50 carbons and before the polymerizing treatment. The products of the polymerizing treatment may have removed therefrom normally liquid hydrocarbons, formed by polymerization, and the remainder may be returned to the stream 'at a 55 point preceding the separation of C: hydrocarstream is compressed by means of compressor 3 i bons, with or without the preliminary removal of xed gases. y

The accompanying drawing constitutes a diagrammatic plan of apparatus capable of operation embodying the invention but it is to be 5 understood that it is illustrative only, the invention not being limited thereby. V

Referring to the drawing for more detailed description, the feed, which consists ordinarily of normally gaseous hydrocarbons from an oil lo cracking operation or any other'suitable source and contains hydrogen, methane, and olenic and parafnic C2, Ca, and C4 hydrocarbons, is introduced into the system through feed line I. The

and cooler 4 to liquefy the C3 and C4 hydrocarbons prior to entering chamber 2, which may be a fractionator of suitable design. This is accomplished, for example, by maintaining a pressure of 300 pounds per square inch and a tem- 20 perature of -60 F. in the top of chamber 2. Suitable cooling and reboiling means may be provided in the top and bottom, respectively, of chamber 2 to facilitate separation. The uncondensed gases, consisting of hydrogen, methane, and substantially all the ethylene and ethane of the stream. paSS overhead through line 5 and are further cooled and compressed, by means of cooler 6 and compressor l, to liquefy ethylene and ethane and permit the separation of xed 30 gases in separating chamber 8 which may be a suitable fractlonator. -A pressure of 500 pounds may be maintained with a temperature in the top of fractlonator 8 of 10'to 20 F. The.

viixed gases, e. g.-methane and hydrogen pass off through line 9. They may be further cooled by expansion, for example, by assisting in the workl of compressing gases in line 5, and used tomaintain proper temperature conditions in fractionator 8 by' indirect heat exchange. Any other suit- 40 able cooling means may also be used for this purpose. Suitable reboiling means may be provided in the bottom of fractlonator 8 to assist'in separation. The C2 hydrocarbons may be expanded somewhat by means of valve I0 through line II and cooler I2 to assist in cooling for liquefaction the gases passing through line 5. For example, the expansion may be from 500 pounds in chamber 8 to 300 pounds in line II and cooler I2. 50

From line II the C2 hydrocarbons are introduced into" absorber chamber I3 wherein the ethylene of the mixture is selectively absorbed by a suitable selective solvent such as acetone, acetaldehyde, or liquid acetylene. The remain- 2 ing part of the fraction, consisting essentially of ethane, passes off overhead through line I4.

The mixture of solvent and ethylene is withdrawn from absorber I3 by means of line I5 and l expanded into stripping chamber I6 by means of valve I1. In chamber I6 the pressure is adjusted to permit the dissipation of ethylene from the solvent which is then returned through line I8 and pump I9 to chamber I3 for re-use. evolved ethylene passes oil overhead through line 20 and may be further treated for recovery of any entrained absorbent in suitable apparatus not shown.

From chamber 2 the liqueiiedCa and C4 hydrocarbons are withdrawn to pass through line 24 and various heat exchangers to the junction of lines 20 and 24 where they are combined with previously separated ethylene and passed through line 25 by compressor 1I to polymerizing heater 26 wherein they are heated to a temperature of '150-l200 F. at a pressure of 400 to 3000 pounds per square inch. After being heated under polymerizing conditions to effect conversion into liquids the products are passed through line 21 to cooler 28 wherein they are sharply cooled to prevent over-polymerization by heat exchange with the cool ethane', etc., gases passing from chamber I 3 through line I4 or by quenching with suitable hydrocarbons. The polymerized products continue through line 21 and are further cooled in cooler 29 by heat exchange with the C3 and C4 gases passing from chamber 2 in line 24. The cooled products of polymerization may be further cooled, if necessary, by means of cooler 3| and are passed to fractionator 32 wherein they are subjected to conditions of temperature and pressure to cause condensation of normally liquid hydrocarbons and fractionation of the stream into a gaseous fraction consisting essentially of normally gaseous hydrocarbons and a liquid fraction consisting essentially of normally liquid hydrocarbons. This may be accomplished by concurrent stripping, scrubbing,v

and absorption operations for which suitable-refiuxing and reboiling means may be provided. Fractionation may be maintained at a pressure of about 50 pounds per square inch and with a temperature of -100 F. in the top.

By means of fractionator 32 the normally liquid hydrocarbons formed by polymerization are separated. from lower boiling hydrocarbons and are withdrawn through line 39. The normally liquid hydrocarbons thus obtained may be fractionated to'separate a satisfactory motor fuel of good quality, leaving a heavier fraction which may be suitably utilized, for example, as charging material in an oil cracking operation or for quenching the polymerized products.

The normally gaseous hydrocarbons separated in fractionator 32 pass through line 4I and are added to the stream passing to chamber 2 through line I. These gases may be preliminarily cooled by heat exchange, in cooler 31, with materials passing through line 24 or cooled or liquefied gases from other parts of the system.

The ethane fraction passing from chamber I3 through line I4 is preliminarily heated by heat exchange with the products of polymerization in cooler, or heat exchanger, 28. The fraction then proceeds through compressor 30 and line 42 to cracking heater 43 wherein it is subjected to a cracking treatment at a temperature of 1250 F.1750 F. and at a pressure of 0'500 pounds per square inch to convert at least a portion thereof to olefins.

The

'I'he products of the cracking operation pass from heater 43 through line 44 and are cooled quickly, for example, by heat exchange, in heat exchanger 45, with the C3 and C4 hydrocarbons passing through line 24 from chamber 2. I f

desired, a portion of the C3 and C4 hydrocarbons may be added to the products of cracking through line 46 to quench the hot gases and prevent over-cracking. Contact with the hot gases also will serve to polymerize at least a portion of the C3 and C4 hydrocarbons used for quenching, which polymerization will be checked by the subsequent cooling of the combined gases in cooler 45, to prevent over-polymerization.

All or a portion of the gases cooled in cooler 45 may be combined, through line 41, with the gas feed to the system passing through line I, or all or a portion thereof may be passed through line 48 to separator 49 which may be a fractionator. The gases are suitably cooled, for example, to a temperature of 10 to 20 F. by cooler 5I to liquefy C2 to C4 hydrocarbons in separator 49 and permit removal overhead of fixed gases through line 52. A pressure of about 500 pounds per square inch is maintained in fractionator 49 by lsuitable means. The condensed C2, Ca and C4 hydrocarbons collect in the bottom of separator 49 and are withdrawn through line 51. Suitable cooling and reboiling means may be provided in the top and bottom, respectively, of chamber 4 9 to 4facilitate separation. The hydrocarbons condensed in separator 49 are passed through line '51 and cooler 58 to eiect a preliminary cooling of the incoming gases in line 48.

From line 51 gases pass through line 60 and are combined with the ethylene passing through line 20. The low temperature of the combined gases may be utilized, for example, by passing them in heat exchange in heat exchanger 6I, With the incoming gas feed in line I. By this means the gas feed is cooled prior to compression and the mixed gases in line 20 are warmed as a preliminary to polymerization.

The fixed gases passing from fractionator 49 l.-

through line 52 may be separately recovered and utilized, or they may be introduced into chamber 2, e. g., byline 63, to recover any entrained higher boiling hydrocarbons. By this means all the fixed gases pass from the system through line 9 "l from chamber 8.

The high pressure of the fixed gases may be utilized to assist in compression and pumping by expanding them from 500 pounds per square inch pressure to 300 pounds per square inch pres- -liquids and gases therein. Absorber I3 may be similarly provided to facilitate contact of the gases and absorbent.

The temperature and pressure required in absorber chamber I3 and expansion chamber I6 will depend upon the solvent employed. If it is desired to use an adsorbent instead of a solvent it is necessary to provide parallel contact towers,

topermit alternate saturation and revivication of the adsorbent, e. g., cuprous chloride.

Other methods of separating ethane and ethylene,

such as fractional distillation, may be used.

In the detailed description the polymerization step is described as pyrolytic but it is to be understood that the advantages of the invention may be realized equally well in connection with any suitable method of polymerization.

Similarly the treatment of ethane to produce ethylene and higher hydrocarbons is described as a cracking operation. However, the invention is not limited thereby, and any method of treat.

ment to produce the same results, such as catalytic dehydrogenation by means of a chromic oxide gel as the catalyst, may be used.

The invention provides a complete, etllcient method `of converting a large proportion of the normally gaseous hydrocarbons, resulting from an oil cracking operation, to normally liquid hydrocarbons. The removal of Cz hydrocarbons from the gaseous stream and the separation and return of ethylene to the stream provides a s tream of gases rich in olens and especially subject to eicient polymerization by reason'of the absence of ethane therefrom. 'I'he concurrent cracking of the .ethane fraction provides an eicient method of disposal of this gas to produce a cracked gas containing a large proportion of ethylene and higher hydrocarbons, readily subject to polymerization.

It is to be understood that the embodiment of th e invention described herewith is toA be taken as a preferred example and that many changes and modifications may be made without departing from the scope of the invention.

I claim:

The method of treating a hydrocarbon gas comprising ethane, ethylene and normally gaseous olenic and parafflnic hydrocarbons higher boiling than ethane to produce normally liquid hydrocarbons therefrom which comprises separating from said gas ethylene and normally gaseous hydrocarbons higher boiling than ethane, subjecting said separated ethylene. and higher boiling hydrocarbons in admixture separately from remaining constitutents of said hydrocarbon gas to elevated conditions of temperature and pressure to eifect thermal conversion thereof to normally liquid hydrocarbons, separating ethane from said mst-mentioned hydrocarbon gas, heating said separated ethane in a zone sepa--`

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