US2314040A - Process for converting hydrocarbons - Google Patents

Description

March 16, 1943. F.l E. FREY PROCESS FOR CONVERTING HYDRQGARBNS original Fild oct. e, 19,32

I Patented Mar. 16, 1943 Frederick E. Frey, Bartlesville, Okla., assignor to Phillips Petroleum Company, Bartlesville, Okla., a corporation o! Delaware Original application October 6, 1932, Serial No. 636,555. Divided and this application March 30,

1936, Serial No.- 71,763

15 Claims.

'I'his invention relates to an improved process for converting volatile aliphatic hydrocarbons, especially natural gas and/or the gases produced by the cracking and distilling of petroleum, or by the destructive distillation of bituminous materials such as coal, into valuable normally liquid hydrocarbons by thermal treatment. The pres- Serial No. 636,555, filed October 6, 1932, which is now U. S. Patent 2,038,834.

As stated in my parent application, it has been proposed to convert such gases into aromatic oils by heating them to elevated temperatures, 1250- '1750 F. for a sufficient time to effect a substantial conversion into aromatic oils. The conversion takes place at atmospheric or higher pressure with the formation of aromatic oils, and, owing to the drastic cracking conditions required, the gaseous hydrocarbons are for the most part destroyed with the exception of methanewhich is produced in the cracking, and which in itself can be converted into oils by cracking at excessively high temperatures only. Consequently, lit-- tle material suitable for retreatment is obtained. f It has also been proposed to convert gaseous hydrocarbons into normally liquid hydrocarbonsr by heating to a reaction temperature under'high pressure, above 500 pounds per square inch. In'

this way gaseous oleflnes have been shown to polymerize to liquid hydrocarbons in good yield.

The conversion of the more refractory gaseousv paraiiins into normally liquid products has also been proposed. 'While gases produced by oil cracking processes contain both paraiiins and olefines, natural gases contain only the paraiiins. At a temperature of preferably 950-1100 F. and pressure of preferably 2000 to 3500 pounds per square inch, butane may be converted in a single cracking operation into normally liquid hydrocarbons mostly aliphatic and alicyclic in natureto the extent of v8-16 -per cent. I have found that propane at such pressures requires a highertemperalture, while ethane is inferior to propane.- In fact, the presence of propane and ethane, I have found, is usually undesirable in admixture with butanes or gaseous oleiines to be converted under such high pressures into liquid hydrocarbons,in asmuch as they detract from the eiciency of the conversion unit. In the treatment of the lower boiling paraiiins under heat and heavy pressure to produce an optimum conversion int'o aliphatic and alicyclic hydrocarbons of higher boiling point, I have found that when the time of reac-` tion is the minimum necessary to produce avirtually maximum yield of volatile oils, there sur- A ent application is a division of my application,

vives a great part of the paratn treated unaltered, and some of the unchange parains may be advantageously separated from the products and returned to the cracking operation. Methane, l

ethane, ethylene, propane, and propylene, I have found to be formed in considerable amounts, in such high pressure thermal treatment, that is, in quantities compara-ble to the oils formed and exceeding 5 per cent of the hydrocarbon treated,

and these lower parailins are not as suitable Ifor retreatment as the butanes.` A part `of the propane and ethane, however, may be returned with the butane chiefly for the sake of the yield of oils obtainable from the accompanying propylene or ethylene, but a considerable part of the hydrocarbons boiling below butane and butene must be continually discharged from the system. Consequently, in operating to otain the best economy,

a quantity of gas containing propane, ethane,

propylene, ethylene, methane and hydrogen is obtained as a by-product.

The conversion of hydrocarbon gases into aromatic oils previously described may be accomplished at moderate pressures, say below 500 pounds per square inch, and is applicable to all simple paraiiins and oleiines, all of which give a substantial yield, of 7 per cent or more, of aromatic oils with the exception of methane which requires prohibitive conversion temperatures.

'The present invention deals with a novel method of obtaining liquid products from normally gaseous hydrocarbons, and in accordance with the invention I propose to scrub olene-con- 1 taining gases with liquid butane and thereby concentrate the olefine content thereof. Subsequently the concentrated olene gases are converted at elevated temperatures to obtain a yield of liquid products.

With the foregoing object outlined and with other objects in view, the invention consists in the novel features hereinafter described in detail in connection with the accompanying drawing; which shows an elevation of an apparatus suit-v .able for the practice of my invention.

A charging stock consisting predominantly of lbutane but which may contain gaseous olenes `and limited amounts of lower paraflins is delivered by pumps I, 2 and 3 continuously under a pressure between 500 pounds .and 5000 pounds per square inch through a heating tube 4 positioned within a furnace housing 5 wherein the hydrocarbons are maintained at a conversion temperature preferably between 750 and 1200 F., for a time sufficient to eiect the conversion of a substantial portion of the charging stock into normally liquid hydrocarbons, together with quantities of paraiiins and olefines lower than butane and butene. -The thermally treated hydrocarbons are discharged into a primary condenser 6 maintained under substantially the same pressure as the coil 4, Where the temperature is reduced by direct or indirect cooling means to eiect condensation of some gasoline and heavier liquid hydrocarbons. The liquid is separated in separator 'I from vapors, and the vapors are discharged. into a secondary cooler condenser 8 anda separator -9. A further extraction of heat takes place in condenser 8 and the greater part of the uncracked butane, together with the remainder of the normally liquid hydrocarbons are condensed. Vapors discharged from 9 enter an absorber or rectifier IIJ, still under such high pressure, and therein undergo further condensation and come into contact with an absorption liquid which, under the conditions 'existing in the absorber, absorbs ethane, ethylene, and higher hydrocarbons, leaving in the unabsorbed gas the greater part of the methane and any gases of lower boiling point, which gases are discharged from the absorber through a pipe I a that leads to the lower portion of a heat exchanger II of the plate and tube type. After passing through the tubes of the heat' exchanger, these gases are discharged through a pipe I Ia and some of the same may be expanded through an expansion valve IIb and a conduit IIc back into the heat exchanger II. Due to the expansion of this portion of the gases, a very low temperature will be maintained in the heat exchanger and this'will result in the condensation of a portion of the gases entering the heat exchanger from the pipe IDa. Such condensate is returned to the top of the absorber or rectifier through a pipe Ib. Gas which has been expanded through the heat exchanger` may be vented from the system through the pipe IId.

If desired, some of this high pressure gas may be alsoutilized as a cooling agent for other purposes. For example, some of the gas from pipe IIa may be fed-through a manually controlled valve Ile, pipes Ilf and Ilg and an expansion valve Ilh to any suitable point in the system where a refrigerating eiect is desired.

Should it be desired to crack this gas which is high in methane, some of it may be fed from the pipe Ilj through pipesIIi and IIk into a low pressure cracking unit I4.

Ifpreferred, some of the gas which is high in methane may be vented from the system through the line I3 by passing the same through a valved pipe I3a which connects pipes IIf and I3.

portion of the system, liquefied hydrocarbon gas, preferably butane, may be used as an absorption or reiiux medium in I0. This medium extracts the valuable hydrocarbonsmore eifectively at a reduced temperature. Accordingly, butane from a pipe I3b is mixed with the cold condensate from the heat exchanger II before said condensate enters the absorber or rectifier.

The liquid separated in I0 contains the absorption medium, the butane and butene not previously condensed, and the greater part of the propane, propylene, ethane and ethylene formed by the high pressure conversion operation. 'Ihis liquid is discharged by pipe I through a pressure regulator I5a into a. rectier. and condenser I6 and II in which the butane and butene mixed By reason of the high pressure existing in a with al controlled limited proportion of propane and lighter hydrocarbons are separated under a pressure of about 500 pounds per square inch, and returned bypump 3 through pipe I8 to be retreated in the high pressure conversion coil 4. Hydrocarbons lighter than butane, in gaseous and liquid condition, pass respectively from condenser I'I, through pipes I'Ib and I'Ic to an exhausting or rectifying column I9 in which lighter hydrocarbons, chiefly methane may be separated under a pressure of about 500 pounds per square inch and discharged through pipe 20, leaving the system at I3. The liquefied hydrocarbons discharged at 22 are chiefly ethane and ethylene, propane and propylene, and are led through a pressure reducing valve 22a to the low pressure cracking unit I4 for conversion into aromatic oils under a pressure between atmospheric and 500 pounds per square inch, but preferably about pounds per square inch. If the quantity of methane is not large, it need not be separated and discarded, and by opening Valve 23, all the vapors from I'Imay pass directly to the cracking unit I4.

'I'he normally liquid hydrocarbons formed in the high pressure conversion coil 4 which condense, together with the butane, in 8 and 9, are fractionated in a rectier 24 having a still 25; the butane and lighter hydrocarbons being delivered by pump 26 through pipes 26a and I5 into the rectifier I6 wherein butane and butene are separated and passed through Ia, 3 and Ib, ultimately into pipe I8 to return to the high pressure conversion coil, while lighter vapors may be allowed to pass through a pressure regulator 3I and into the cracking unit I4. The normally liquid hydrocarbons are fractionated in the rectier 21 together with the condensate from 1, which enters through pipe 29, and the vapors from the rectier 21 are condensed in a condenser 21a and such condensate becomes the motor fuel distillate which is collected in a receiver 30. A less volatile residue is discharged from the still 28.

A conventional reflux condenser 2lb is positioned between the rectier 21 and condenser 21a.

Normally liquid hydrocarbons, as for example, the higher boiling fractions of natural gasoline, of low anti-knock value, may be introduced, preferably mixed with other charging stock, to the high pressure conversion coil 4 at 32 to undergo conversion into liquid hydrocarbons of higheranti-knock value, Which are recovered at 30. Or such material, as well as gases of high olene content, may be charged into an intermediate point of the high pressure conversionl zone at a point 33 nearer the exit to avoid excessive reaction in case a refractory charging stock requiring a high temperature, such as butane, is at the same time undergoing treatment and entering from pipe I8.

The gaseous hydrocarbons lighter than butane, produced by the pressure conversion operation and separated as described, are passed into a common conduit 35 into which also may be led other hydrocarbon gases of limited methane content, which may be available at a moderate pressure. These gases pass into the low pressure cracking unit I4 in lwhich they are heated' to a temperature of 12501750 F., for a time suicient to produce a substantial yield of aromatic oils. 'I'he reaction products are discharged from I4 through a conduit I4a into a primary cooler 36 in which by either direct or indirect cooling means. the temperature is reduced and tar scpv roleA in eiiectin: separations of hydrocarbon`r v grated: thence into` an extraction plant `Ii in constituents in connection yith both the which the remainder oithehoilmowhicharelare-f' toria# ly aromatic, Renovated-pand@ f mique/L. operationsrmdfmantn oi lighter oleiinic hydrocarbonsmay be' 5 l Both thclhiihnreuure andfioy A and returned to either conversionffxone Il. The gases discharged from the syst??? l e,- to their high 'hydrogeli,carlfion-g'l tio, Aare par ocularly mutable :or memo-annuo d f] j dro: Since methane ,is thej only gaseouefhydrocar bon unsuitable forgconyersion' intolaromatico all 'available hydrocarbon gases ,'enceptf th e containing vexcessive amounts: jot A' be treated in Vthe low preaskurecracking, to produce aromatic oils; includingl 'j'gaaesjp dominating in butane and. butche.` .Whicmfwhil suitable for conversion in higheryields" intdioil `by high nressurewnfverslm; be! aeilab in excessive qimntlties or under, flo as to unntthem for conversionin'rthe. sure unit I. For ,the l high ypressure;,convenio operatiom hydrocarbons highrthan'lfpropa are most" suitable, )butyl whenfpropylene x ethylene arel,p11eaent` in .vsubstantialjconcentrya-Q, um 1n numerose; they' areswfbleifr versionfin ,the "high pressure 'unil'.g 11\7`i1`ei;he1` lnot a high cohcentratiori oi butanegaccomp them. The operatingy condition'sgiving' suits depends fori'V the?. composition of.' x stock. The ,conversion-loibutanea oleiines insmail amounts niay'ffbesnonducted at .1000-5000`v0und8 Per Square #ich Present. d aso-120m F..`;the higher tempertureewithin.. mee bem the more 'emilie an propane arev present in 'substantial Lower temperatures-Me Plerlll When-Pe' 111.84 f olene @nient Mwmpaniesthafvmfnn.; tem-f .t ventures s levas 'ISGF-end-.Pressuresa vw, 40 u 500 wundszvefdueremoh Ethylene suits when-oleiines predomina v PPOPBM.

charged from me symmmrouspios; @ed

n@v mehr!! V4one or two etaiee. As.

example of comme@ baie; ht

, ,lntheharslns stock. A partlcmarlyngulablevchargmggtocmsf,, Pmi-viel?? the morev eaelly--fliqueedvssesfproducedylinx:a' Buien?! crackin: Petroleum. whichesfvredominaterlnf B lines butanes and boiseries.l Buchgaaea ,maygbe con@`VV` verd i0 the ,extent 01,50%,1andeven muret, into normally fliqindhydrocarbons.;z` while butanes sive a somewhat -,lower yield,e,-,even y,with ,fthe ereater extent ,of-recyclingfyvhichtheyirequire: 50

Glassesk various yfsources.;,s\1l:iect:;l.o vt-he above limitations. `may1,be;treated',Arr tirent-,high pressure 'and theflow pressure conversion Loper tions while retaining the advantagesroithendve combination oi this inven'tionar-` Byf-fgthe use'fo extraction :by means Dof 4-oii :absorptionga fllowe by distillationpconcentrates oii suitable: gases. may obviously be obtained in liquid formeandgs under high pressurefmithoutxthefusefsoncostly direct compression;.-z;;andzfin1someicasesijdirect b compressionpwith orLwithouti;.theiusefiotfwliqul pump forpiurthereincreasingthe ressuresa beproitablygemployedw;

Inconiunctionwithfanat gaso erf-extra tion plant or-1 f a-freilnernadditionalgueconomie can' be eiectedu1fhepmductsf Loi: thevpr sure conversion-,operationficonductedoinflcon can be 2019i heat exchanaegi'elation withloils and sasefy 01, lower,temperaturertherebyeifeot ina hetfeqriomie ando-#hermanasfoiith fm mw ePf--f9rnied`-tfa1hishe ,i

" ambe Lfait.,

i Mmmm-.im aten Y, it h mite e magneet.. incliner ,w L,

4 Y :,sreos'o mented when gases containing olednes -are availto C4 hydrocarbons along -with methane while q able i'or treatment. under an elevated super-atmospheric pressure with It wm be noted that the combination is nexibge in that the relative proportions of productsfrom sthe high pressure and low pressure process can be varied within certain limits, and thereby render the combination process capable of operation under the most advantageous conditions. In other words, the yield of benzol from the low pressure cracking unit il could be increased at the expense of adecrease in yield of liquid productsfrom the high pressure conversion zone 4. This mode of operation could be followed when the market price of benzol was considerably higher than the market price of high octane motor fuel.

While I have disclosed preferred ways of practicing the process, it will be understood by those skilled in the art that changes in procedure may be resorted to without departing from the spirit. of the invention, as set forth in the claims.

What I claim and desire to secure by Letters Patent is:

l. In a' process of the character described, scrubbing hydrocarbon gases including oleilnic gas while under superatmospheric pressure with a liquid menstruum composed principally of hydrocarbons of three and four cl|.rbon atoms per molecule and thereby concmtrating the oleiinic gases. releasing the pressureonundisaolvedgasestopermittheundissolvedgases to expand and abmrb heat, utiliz insthecoldthuscreatedtocool themenstruum before contacting the menstruum with tbe ilrstf mentioned hydrocarbon gases, discharging the expanded undissolved gases from the process, separating-said concentrated oleiinic gases from the menstrmun, and Subsequently converting the last-mentioned concentrated oleiinic gases at elevated temperatures and thereby obtaining liquid products.

2. In a process of the character described. scrubbing hydrocarbon gases including oleiinic gases while under superatmospheric pressure withv a liquid menstruum composed principally oi hydrocarbons ofthreeand four carbon atoms per molecule and thereby concentrating the oleiinic gases, releasing the pressure on lmdissolved gases Vtoperrnlttheedgasestocxpandand absorb nece, ntmnng the continus created to'cool the menstruum before contacting the menstruum with the mst-mentioned hydrocarbon gases. disharaing the expanded undissolved gases from c the process. separating said concentrated olennic gases from the menstruum. and subsequently con-` verting the'last-mentioned concentrated oleiinic gaaeaatelevated temperatures between 1250 P.

-9. A process for the production of normally and 1750 l'. nets.

3. In a procesador the conversion otnormally saaeomhydrocaoonaintonoxmallylilluidhydroscrubbing-1l containing Aamil'thereby obtaining liquid prodcarbone, butane. bntene. propane. propylene. ethane. ethyll a liquid menstrumncomposed principally of hy` drocarbons heavier than C: hydrocarbons to separate C: and heavier hydrocarbons from undissolved lighter gases, releasing the pressure on said undissolved lighter gases to permit the undissolved gases to expand and absorb heat'. utilizing` the cold thus created to cool the menstruum bei'orecontacting the menstruum with the ilrst mentioned gaseous mixture. discharging the ex- Apanded undissolved gases from the process, separating the absorbed gases from the menstruum.

' and subsequently converting the last mentioned gases at elevated temperatures and thereby producing liquid hydrocarbons.

5. I'he process'of claim 4' wherein the liquid menstruum comprises principally butane.

8. A process for the conversion of normallyv gaseous hydrocarbons, which comprises scrubbing predominantly hydrocarbon gases including olenic gases and gases'lower boiling than Cs hydro carbons while under an elevated superatmospheric pressure with a liquid menstruum composed principally of butane to concentrate the Voleilnic gasesfreleasing the pressure on undissolved gases to expand them and absorb heat. utilizing the cold thus created to cool the menstruum before contacting the menstruum with the first mentioned gases. discharging the ex-` panded undisaolved gases from the process. separating said concentrated oleiinic gases from the menstruum, and subsequently converting the last before contacting the menstruum withenamethaneandlnrdrogemwithaliqulximenfV struumcompoaedprincipaliyofhydrocarbonsol three andfourcarbmatomsper Y therebyscparatingthebutanes; butenes. propane.

4.1n the procesa-for the conversionof-normally gaseom hydrocarbons. the stepgwhich coin.-

-prinsscrubbing-a gaseous (bis mentioned concentrated oleiinic gases at elevated temperatures and thereby producing liquid hydro- 7. A process for the conversion of normally gaseous hydrocarbons. which comprises scrubbing 'predominantly hydrocarbon gases including oleiinic gases and gases lowerI boiling than C: hydrocarbons while under an elevated superatmospheric pressure with a liquid menstruum comprising substantially entirely normally gaseous hydrocarbons, mainly butane to concentrate. the

oliefinic gases, releasing the pressure on undissolvedgases to expandzthemand absorb'heat, utilizingth'ecoldthuacreatedtocoolthemem.

the iirst-mentloned gases, discharging` the e'xpanded undissolved gases from the process, and subjecting a hydrocarbon mixture comprising said concentrated oleiinic gases to conversion to proi duce hydrocarbon liquids.'

8.'.l'heprocess-ofclaim7wherein thelaid hydrocarbon `mixture converted also comprises atleastapartofthebutaneofsaidiiquidmem liquid hydrocarbons in the motor fuel boiling range from lowerboiling hydrocarbons. which commises scrubbing predominantly hydrocarbon gasesl including olefinic gases and gases lower boiling than Cs hydrocarbons while under an velevated superatmospheric pressure with a liquid menstruum comprising substantially entirely normally gaseous hydrocarbons, mainly butane to concentratel the oleiinic gases, releasing the presasiatico I 2.1;

Iliquid menstruum to a conversion under a pressure in excess of 500 pounds per square inch at a temperature and for a period of time to produce' hydrocarbons, which comprises subjecting the first-mentioned hydrocarbons to conversion in a heating zone at temperatures of 750 to 1200 F.

and pressure of 500 to 5000 pounds per squareinch, separating the'etliuent from said heating zone into a gasoline and heavier fraction and a lighter fraction, scrubbing said lighter fraction with a liquidmenstruum composed principally of butane, eliminating undissolved gases fro'm the system, separating absorbed C2 and Cs hydrocarbons from the menstruum and converting said C2 and C3 hydrocarbons at temperatures betweenl250 and l750 F. and under a pressure between atmospheric and 500 pounds per square inch for a suilcient period of time to produce a substantial yield of aromatic oils and subsequently recovering said aromatic oils.

11. In a process for obtaining liquid products from dilute olefinic gases, the steps of concentratingsaid dilute olefinic gases by scrubbing with a liquid butane menstruum, eliminating undissolved gases from the system, and subjecting concentrated olefinic gases together with at least a part of the butane of said liquid menstruum to a conversion under a pressure in excess of 500 pounds per square inch at a temperature and for a period of time to produce liquid hydrocarbons in the motor fuelboiling range. i

12. In a process for obtaining liquid products from dilute oleflnic gases, the steps oi concentrating said dilute oleflnic gases by scrubbing with a liquid butane menstruum, eliminating undissolved gases from the system, separating absorbed C2 and. C3 hydrocarbons from the menstruumand converting said Cz and Cs hydrocarbons at temperatures between 1250 and 1750 F.

and under a pressure less than 500 pounds per fuel boiling range, and subsequently recovering said liquid hydrocarbons.

13. In a process for obtaining liquid products 'from gaseous hydrocarbons, the steps which comprise scrubbing' gases predominantly hydrocarbon and including olenic gases and gases lower boiling than C2 hydrocarbons while under an elevated superatmospheric pressure with a liquid menstruum composed principally of butane to concentrate the v'olefinic gases, discharging undissolved gases comprising gases lower boiling than Cz hydrocarbons from the process, and subjecting a hydrocarbon mixture comprising said concentrated olenic gases together with at least a part of the butane ofsaid liquid menstruum to a. conversion under a pressure in excess of 500 pounds per square inch at a temperature and for a period of time to produce liquid hydrocarbons in the motor fuel boiling range, and subsequently recovering'liquid hydrocarbons in the motor fuel boiling range so produced.

14. A process for separating normally gaseous hydrocarbon mixtures which comprises subjecting the mixture to reux fractionation, subjecting the separated overhead gaseous light fractional product of the fractionation to cooling and partial condensation under a substantial superatmospheric pressure, separating the condensate from the uncondensed gas, releasing the pressure on such uncondensed gas to further cool it, utilizing such cooled uncondensed gas as a cooling medium a fractionating zone, therein separating said mixture into an overhead vaporous fraction and carbon mixture comprising heavier concentrated olenic gases together with at least a part of the butane of said liquid menstruum to a conversion under a pressure in excess of 500 pounds per square inch at a temperature and for a period of time to produce liquid hydrocarbons in the motor a liquid residue, withdrawing said vaporous and said residual fractions from said zone, iiowing said vaporous fraction while under a substantial -superatmospheric pressure in indirect heat ex` change relation with a cold expanded hydrocar-4 bon gas to partially condense said overhead fraction, separating the vaporous portion thereof from the liquid portion, returning said liquid portion to said fractionating zone as reux, reducing the pressure on said vvaporous portion to expand and cool the same, and utilizing the thus cooled vapors as the cold expanded hydrocarbon gas in the heat exchange step Specified. V v FREDERICK E. FREY.

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