US2165526A - Conversion of hydrocarbons - Google Patents

Description

July l1, 1939. H. ATWELL n 2,165,526

'CONVERSIONA oF HYD'RocARBoNs Filed Aug.v 29, 1936 Patented July 11, 1939 .UNITED STATES PATENT oDFFi-cs 2,165,526 CONVERSION OF HYDBOCARBONS Harold V. Atwell, White Plains, N. Y., assignor to.Process Management Company, Inc., New York, N. Y., a corporation of Delaware Application August 29, 1936, Serial' No. 98,558

. 11`Claims.

My invention relates in general to the converg sion of normally gaseous hydrocarbons and more particularly to a process for producing normally liquid hydrocarbons suitable for use as motor fuel with the utilizatin of normally unreactive products'of the process, together with similar products from an outside source, to obtain an increase in the volumetric yield above that heretofore accomplished.

It is generally recognized that methane and, to a somewhat less extent, ethane cannot be converted to give commercially attractive yields of oleilns for polymerization to gasoline. Some gases however, such as naturalgas and residue gas v 15 from low temperature oil cracking, contain large 3,] Still another object of my invention is to provide a process wherein normally gaseous parafnic hydrocarbons are separately converted tonormally liquid hydrocarbons and-normally gaseous olefmic hydrocarbons, oleilnic hydrocarbons 35 therefrom being polymerized to normally liquid hydrocarbons with the unreactive gases from one or more of the stages being oxidized and the oxidized products therefrom reacted with hydrocarbons undergoing conversion.

Other objects of my invention will appear in th following detailed description.

For a better understanding of my invention, reference is now made to the accompanying drawing in which the single ilgure is a diagrammatic 4: elevational view of apparatus suitable iorcarryfA ing out my invention.

Referring' to the single figure, I have illustrated my invention as involving three' jcoordinated operations:

First, the conversion of hydrocarbon gases to olens and liquid products with the aid of oxygenated hydrocarbons .as promoters;

Second, the conversion of a special fraction of residue gas from this operation to oxygenated 55 products; and

An object of my invention is to provide a (Cl. ISB-) Third, the conversion of normally liquid, but relatively low boiling hydrocarbons to higher boiling hydrocarbons mainly in the motor fuel range, with the aid of o xygenated promoters. A

'I'he rst mentioned operation is illustrated in two forms. One alternative is single stage thermal polymerization, illustrated by converter #I `and its associated fractionating equipment, .wherein mainly parainic gas is converted'in a single stage with recycling to liquid hydrocarbons in the motor -fuel boilingrange. The second alternative is a two-stage operation,` illustrated by gas cracking unit 2 and olefin polymerizing unit 3, wherein parafnic gas is rst` cracked to gaseous olellns for polymerization in a separate zone `to `liquid hydrocarbons. A more detailed description of the operationof these units is given below.

A lgaseous mixture consisting mainly of parafilnic hydrocarbons in the boiling range of propane and butanei is supplied to converter i, which may bea. conventional type of tube heater, through charging line 2 under' pressure maintained by charging pump 3. In converter I this gas is subjected to a temperature in therange of 1000 to 1100 F., or higher, under a pressure of 500 to 2500 lbs. for a sufcient length of time to accomplish simultaneous cracking of the parafnic hydrocarbons and polymerization and other v conversion of the resulting oleilns to yield normally liquid hydrocarbons in the motor fuel boiling range. The products of this conversion leave converter I through transfer line and are cooled by indirect heat exchange in cooler 5, optionally assisted bythe direct admixture of quenching fluid through valved line The suitably cooled .products are discharged into fractionator l from 4thexbottom of which material' heavier than the desired motor fuel product iswithdrawn through valved line 8. Vapors pass from the top offractionator 1 through line 9 into fractionator i0 from the bottom of which is withdrawn through valved line I I a heavy naphtha in the upper part of the y boiling range of the desiredjmotor fuel product. `Vapors from the top of fractionator i0 pass through line I2l to fractionator I3 from the bottom of which isv withdrawn through valved line' It a liquid which may be termed light naphtha, extending over the lower part of the boiling range of the desired motor fuel product. Fromthetop of efractionator I3 normallyA gaseous hydrocar bons, mainly lower boiling than those desired in the motor. fuel product, pass through line I5 to fractionator I6 from the bottom of which is withdrawn through valve'd line I1 a mixture of olenic and parafnic hydrocarbons corresponding in boiling range to the fresh gaseous charging stock supplied through line 2. These normally gaseous hydrocarbons are recycled by means of pump I8 through line I9 to the inlet of conversion unit .I for further treatment.

From the top of fractionator I6 a gaseous mixture consisting mainly of hydrogen, methane, ethylene, and eth'ane is withdrawn through line 20. If it is desired to recover a portion of the ethylene content of this gas for further polymerization to liquid products, the gas is forced by pump 2| through line 22 and valved line 23 into scrubber 24, wherein it is contacted with a suit-l able selective absorbent supplied through valved line 25. A liqueed low boiling hydrocarbon, such as butane, may be used as the selective absorbent.

in this operation. Such a hydrocarbon absorbent, enriched with dissolved ethylene, is withdrawn from the bottom of scrubber 24 through line 26, and 'is forced by pump 21 through line 28 either through line 29 to recycle line I9 for .further conversion in unit #L orthrough valved line 30 to charging line 55 for further conversion inA polymerizing unit 3.

Gases from which a considerable proportion of their initial ethylene content has been removed pass from the top of scrubber 24 through 1ine,3I to secondary scrubber 32, wherein they are contacted with a heavier absorbent such as gas oil introduced through line 33 for lthe recovery of such light absorbent as may have been vaporized in scrubber 24. Enriched heavy absorbent is withdrawn from the bottom of scrubber 32 through valved line 34. and is pumped by pump 3 5 through line 36 and either through valvedline 31 to transferline 4 of converter I or through valved line 60 to transfer line 51 of polymerizer 3. This disposition of the enriched heavy absorbent provides a convenient means of recovering the low boiling hydrocarbons therefrom -and introducing them into appropriate gas conversion zones for the formation. of higher boiling hydrocarbons. However, if desired, this enriched oil may be diverted, as through; valved line 38, for stripping in separate apparatus of conventional design (not shown) with return of the absorbent oil and the recovered light hydrocarbons to appropriate parts of the gas conversion system.

Gas from the top of scrubber 32, consisting mainly of hydrogen, methane, and ethane is passed through line 80 to line 39 for oxidation in a manner to be described later, or may be diverted in part or in whole from the system through line 8| Other selective absorbent or adsorbent systems may be used for recovering olefins from-the gas" supplied through line 23 and involving the use of either special liquid scrubbing media such as triethanol amine, or solid adsorbents such as cuprous chloride. The recovery of ethylene in systems of this character would be accomplished in a conventional manner, and the ethylene returned to either of' the gas conversion zones, as illustrated in connection with absorption in liquid butane. Optionally, fractionator operated at such a temperature that most of the ethylene is condensed with ethane and withdrawn-through line I1 with the highen boiling normally gaseous hydrocarbons for, recycling to conversion unit I. In this case, the gas passing through vapor line will consist predominantly of hydrogen and methane and may be diverted from line' 22 through line 39 for oxidation in a manner to be described later. If desired, a part or all of this gas may be diverted from the system entirely through valved line-19.

A later.

As another feature of my process a mainly parafiinic gas having in general a lower molecular Weight than the gas charged to converter I, and

consisting predominantly 4of ethane and propane, is supplied by pump 40 through charging line 4I to the gas cracking unit 2, which may also be a conventional form of tube heater, wherein it is heated to a temperature of 1200 to 1600 F. for a period of time generally less than vone second to convert the gaseous parafns extensively to gaseous oleilns. This cracking is preferably conducted under a low or moderate pressure ranging from atmospheric to perhaps 500 lbs. Under these conditions a'limited amount of aromatic hydrocarbons of the nature of benzol and toluol may -be formed. The hot products leaving gas cracking unit 2 through transfer line 42 are cooled by heat exchanger 43, optionally with the assistance of quenching oil injected into the transfer line through line 4'4. The suitably lcooled Iproducts are discharged into fractionator 45 from the bottom of which liquid hydrocarbons suitable for use as motor fuel, and heavier liquid hydrocar- ,bons if any, are withdrawn through valved line liquid products and lighter gases which are not as suitable for such conversion. The hydrocarbon gases-suitable for polymerization are withdrawn from the bottom of fractionator 48 through valvedline 49 and consist mainly of a mixture of parans and oleflns in the general boiling range of propane, propylene, butanes, and butylenes. A gaseous mixture consisting mainly of hydrogen, methane, ethylene, and ethane passes from the top of fractionator 48 through lines 50, 5I, and 23 to scrubber 24 described above. From this mixture a fraction rich in ethylene is recovered` as previously described and is returned through line 30 to polymerizer 3 or through line 29 to polymerizer I.

Fractionator i8 may be operated at a lower temperature if desired so that ethylene and ethane from the top of the tower through line 50 will consist predominantly'of hydrogen and methane, and may be passed through lines 5l, 52, and 39 directly to the oxidizing stage to be described A part or all of the gas from' the top of tower 48 may be diverted from the system through valved line` 53 if desired.

The oleflnic hydrocarbons Withdrawn from the bottom of fractionator 48.through,line 49 are `forced by pump 54 through charging line 55 to sure, such as '500 lbs. or higher, and to discharge the products therefrom through by-pass line 56 directly to the polymerizin'g unit 3. I In this case Vonly sufficient quench oil will be introduced through line 44 to cool the products from gascrac unit 2 to the desired temperature of 800129 1 00 F. for polymerization in unit 3, which through valved line 6|.

will be operated at a pressure only slightly below that prevailing at the outlet of gas cracking unit 2. The products from polymerizing unit 3 pass through transfer line 51 and cooler 58 to fractionator 59. Optionally the cooling of these products is-accomplished in part by the introduction `of the previously described cooling oil through line 6 0, or suitable cooling uid from any other source through line 18. From the bottom of fractionator 59 liquid hydrocarbons heavier than those desired in motor fuel are withdrawn Vapors pass from the top of fractionator 59 through line 62 to fractionator 63 from the bottom of which a liquid comprising the higher boiling constituents of the desired motor fuel product is withdrawn through valved linel 64. Vapors pass from the top of fractionator 63 through line 65 to fractionator 66 from the bottom of which hydrocarbons corresponding to the lower part of the boiling range of the'desired motor fuel product are withdrawn through valved line 61, and are transferred by pump 68 to line ||0 for further treatment to be described later. Hydrocarbons lighter than those desired iri the motor fuel product and consisting mainly vof normally gaseous paraflinic hydrocarbons pass from the top of fractionator 66 through lines 14 and 15 to the charging line 23 for theethylene recovery system previously described. However, under some conditions extensive polymerization of ethylene will occur in polymerizer 3 so that the gas escaping from thetop of fractionator 10 will consist mainly of hydrogen, methane, and ethane, with little or no ethylene,

and therefore will be passed through lines 14 and 16 direct to charging line 39 for the oxidizing system which will be described later. If desired, a part or all of the gas from the top of fractionator 10 may be diverted from the system entirely through valved line 11. Y

Gas from la variety of sources previously described and' consisting mainly of hydrogen, methane, and ethane is subjected to controlled oxida-A tion in one or two stages as its composition may indicate. Ifthe'gas contains a considerable proportion of hydrogen it is first passed through hydrogen oxidizing unit 82 containing a'suitable catalyst for promoting the selective oxidation of' hydrogen. v Relatively pure oxygen or an oxygencontaining gas is supplied to the hydrogen oxidizing unit through line 83. This oxidation/'is carried out at a relatively lowfpressure and at a tem- .perature of VabouiiB'o F., preferably in contact'with a -cataly'st such aslcopper shot or copper oxide. Any suitable known conditions may be used for eifecting this hydrogen oxidation, such forexample as described in Patent No. 1,869,681".` The products of oxidation and unconverted gases from hydrogen oxidizing unit 82 pass through transfer line 84 and are cooled by heat exchanger 85 to a temperature suitable for compression by pump 86-l Pump 86 may be also supplied with gases having a relatively low hydrogen content whichY would not require selectiveoxidation of hydrogen and hence have been diverted from the previouslydescribed sources through lines 81, 88,

- through line 92 to the hydrocarbon oxidizing unit 93. A suitable proportion of oxygen or oxygen-containing gas is supplied also under high pressure through line 94. A suitable gaseous catalyst, such` as oxides of nitrogen, mayalso be introduced through line 94. In oxidizing zone 93 the mixture is subjected to a temperature of 500 to 1000 F., preferably under a pressure of 500 to 3000 lbs. with or without solid catalysts, such as metallic oxides, in order to accomplish conversion of the hydrocarbons to partial oxidation products, such as methyl alcohol, ethyl alcohol, formaldehyde, acetaldehyde, acetone, etc. Any suitable known conditions may be used for effecting this oxidation, such'for example as described in Patent No. 2,042,134. The products `from hydrocarbon oxidizing zone 93 pass through transfer line 95 and cooler 96 to fractionato'r 91 wherein the liquid products of oxidation are condensed and withdrawn through line 98 and the unconverted gases and other gaseous products are withdrawn through line 99.

`The oxidation products withdrawn through line 98, optionally combined with similar oxidation products from other sources, are used in a variety of ways, as will be described hereafter.V The distribution' of these products is accomplished by pump and branch lines |0|, |02, |03, and |00.'

Through line |0| mixed oxidation products optionally combined with similar oxidation products introduced from an extraneous source through line are introduced into the charging stock for olen polymerizing unit 3 for the purpose of accelerating the polymerization of gaseous olens therein.V Similarly, any desired proportion of the oxidation products may be supplied through line |03 to the charging line 4| for gas cracking unit 2 supplemented by similar oxidation products introduced .from an extraneous source through line |06 to promote the cracking of parainic gas to olens, and to permit the operation of gas cracking unit 2 at a lower temperature or with .a shorter time of contact than would otherwise be required. Another portion of these oxidation products may be passed through line |04 to charging line 2 for gas polymerization Y unit optionally supplemented with additional alcohols, aldehydes, etc., introduced through` line |06' to accelerate the conversion of gaseoushydrocarbons in unit effectively by reaction with the lighter compoents of gasoline collected from.other parts of the gas conversion system as described above. Specically, all or part of the light naphtha made by gas conversion unit instead ofbeing withdrawn from the system through line |4 is diverted through line `|01 by pump |00 for reaction with oxidation products in converter |09 also of conventional design. Likewisevall or part of the light naphthamade in olen polymerizing unit 3 instead of being diverted from the system through line 61 is forced by pump 68 through line ||0 to converter |09. Additional lightA naphtha of similar characteristics 'to that obtained from these two sources may-be introduced `from an 'outside source through line |||."y In converter |09 the light naphtha from these various sources is caused to react with mixed oxidation products supplied.

pyrolysis alone would be extremely difficult.

through line |02 by means of pump H2, optionally supplemented by other similar .oxidation products introduced from an extraneous source through line ||3.

In converter |09 the light naphtha is reacted with the oxidation products under a pressure of 500 to .1500 lbs. and at a temperature of 500 to 1000 F. In addition to promoting the polymerization of certainunsaturated components of the light naphtha the oin'dation products also enter into reaction with the naphtha to give newI hydrocarbons of higher molecular weight and high anti-knock value. In this way the low molecular weight gaseous hydrocarbons which constituted the charging stock for the oxidation reaction are incorporated in the final motor fuel product whereas their conversion to liquids by The products from converter |09 pass out through transfer line ||4 and cooler ||5 to fractionator ||6 from the bottom of 'which hydrocarbons heavier than the desired motor fuel product are withdrawn by pump and recycled through line 8 to the charging line for converter |09. A part or all of the bottoms from fractionator IIE may be diverted from the system if desired through valved liri'e |22. From the topof fractionator |6 vapors pass through line I9 to fractionator |20 from the bottomof which a condensate having the boiling rangeof the desired motor fuel product or blending stock therefor is withdrawn through valved line |2|. .Hydrocarbons and other gases lighter than the desired nal condensate escape from the top of fractionator |20 through line |23 and may -be diverted in whole or in part from the 'system through line |20 `or may be passed through line |l25 by means i ess for eifectively converting hydrocarbon gases( and utilizing the xed or dicultly convertible gas resul-ting therefrom to form oxidation products for subjection to conversion conditions with the hydrocarbon gases and liquid products therefrom with the consequent increase in volumetric yield.

It is to be understood that the fractionating equipment for the converters 2, 3, and |08 may be maintained at a lower pressure than that obtaining in the converters and 'desirably a progressively lower pressure is maintained in successive fractionators. Moreover, the number of fractionators shown vmay bei greatly reduced by providing towers with suitable trap-out trays or the like. Any desired form of cooling, such as reuxing, refrigeration, and others, may be used for each of the fractionating towers.

Obviously, many modifications of my inventon may be ms'ade without departing from .the spirit thereof and it is to be understood that my invention is not limited in scope except as appearing in the appened claims.

I claim: 4 1. In the conversion of normally gaseous hydrocarhons to hydrocarbons of different molecular weight, wherein said normally gaseous hydronaphtha fraction, a heavy naphtha fraction and normally gaseous hydrocarbons, separating a fraction predominating in methane from said normally gaseous hydrocarbons, subjecting said fraction to an oxidizing reaction to form oxygenated compounds, utilizing oxygenated' compounds thus obtained for admixture with the normally gaseous hydrocarbons undergoing conversion and separate reaction with at least a part normally gaseous hydrocarbons, subjecting said fraction to an oxidizing reaction to form oxygenated compounds, utilizing oxygenated compounds thus obtained for admixture with the normally gaseous hydrocarbons undergoing conversion, separately subjecting said light naphtha fraction to temperature sufcient to effect conversion thereof andadmixing oxygenated compounds obtained in the process with the light naphtha fraction undergoing conversion.

3. A process for producing normally liquid hydrocarbonssuitable for motor fuel which comprises subjecting a' stream 'ofxnormally gaseous paraiinic hydrocarbons to elevated conditions of temperature and pressure to eect a conversion of constituents thereof to normally liquid products,. subjecting another stream of normally gaseous hydrocarbons containing olenic constituents to elevated'conditions of temperature and pressure to effect conversion of constituents thereof to normally liquid products, fractionating the products from each conversion operation to separate motor fuel and normally gaseous hydroi inthe motor fuel separated fro'rn the products of conversion is separated into a heavy fraction and a light fraction and the light fraction reacted with oxygenated compounds formed in the process.

6. A process in accordance with claim 3 wherein the motor fuel separatedfrom the productsv of conversion`is separated into a heavy fraction and a light fraction, subjecting the light fraction .to conversion conditions of temperature and pressure and admixing oxygenated compounds formed in the process with the light fraction undergoing conversion.

'7.` A process in accordance with claim 34 wherein the fraction predominating in methane and ethane is treated to remove hydrogen therefrom prior to the oxidizing thereof.

8. A process in accordance with claim 3 wherein the stream of normally gaseous hydrocarbons containing olenlc constituents is formed by subjecting paraiilnic hydrocarbons to a temperature of about 1200-1600 F. and oxygenated compounds are admixed therewith while being subjected to said temperature.

9. In the conversion of normally gaseous hydrocarbons wherein said gases are subjected to elevated conditions of temperature and pressure to form normally liquid hydrocarbons within the motor fuel boiling range which are separated from remaining normally gaseous hydrocarbons, the improvement which comprises fractionating the thus separated gases to recover therefrom hydrocarbons predominating in C3 and C4 constituents and a lighter fraction containing Cz hydrocarbons and methane, selectively treating said lighter fraction to: remove ethylene therefrom, subjecting some of the remaining constituents of said lighter fraction to an oxidizing reaction to form oxygenated compounds, and admixing oxygenated compounds thus obtained with the normally gaseous hydrocarbons undergoing conversion. v

10. A process in accordance with claim 9 wherein the hydrocarbons predominating in C3 and C4 constituents and the ethylene selectively separated from the lighter fraction are recycled to the gas conversion operation for conversion into normally liquid hydrocarbons; 1

11. A process for producing normally liquid hydrocarbons suitable for motor fuel which comprises subjecting a stream of normally gaseous parafnic hydrocarbons to elevated conditions of temperature and pressure to effect -a conversion of constituents thereof, subjecting another stream of normally gaseous hydrocarbons containing olenic constituents to elevated conditions of temperature and pressure to eiect conversion of constituents thereof to normally liquid products, fractionating the products from each'conversion operation to separate motorv fuel and normally gaseous hydrocarbons, separating. a fraction pre-.- dominating in methane from said normally gaseous hydrocarbons, subjecting said last mentioned fraction to an oxidizing reaction to form oxygenated compounds and admixing oxygenated compounds thus obtained with at least` one of said streams of normally gaseous hydrocarbons Y undergoing conversion.

HAROLD v.' A'rwnu..

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