US2301391A - Process for converting normally gaseous hydrocarbons into motor fuel - Google Patents

Description

F. E. FREY Nov. 10, 1942.

PROCESS FOR ONVERTING NORMALLY GASEOUS HYDROCARBONS INTO MOTOR FUEL Filed March 24. 1936 Patented Nov. 10, 1942 PROCESS Fort coNvERTING HYDRooARBoNs INT Mo'roR GASEOUS FUEL N ORMALLY Frederick E. Frey, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application March 24, 1936, Serial No.y 'i0,656

(Cl. 19d-10) 6 Claims. 'Ihis invention relates to the conversion of normally gaseous hydrocarbons into motor fuel, this invention relates to the range with decreased production of polymeric products of higher boiling point.

Normally gaseous parans or olens are converted into normally liquid hydrocarbons of the type of gasoline by the application of pressure and heat at a temperature level suicient to effect reaction whereby the polymerization of oleiin hydrocarbons into hydrocarbons of high molecular weight is effected, and also the conversion of paran hydrocarbons provided the temperature level is sufliciently high to effect their decomposition into olens which subsequently polymerize. The polymerization. reaction in the initial stages eifects the formation of volatile normally liquid hydrocarbons, but as reaction proceeds hydrocarbons of increasingly higher weight are built up, part of which are relatively heavy and have a boiling range above that of gasoline when the reaction is sufficiently protracted to elect theconversion inal hydrocarbon into polymeric products. In comparison with gasoline, the heavier hydrocarbon polymers are of comparatively little value and the production of a maximum yield of the more volatile products and the minimum amount of the heavier products is accordingly desirable.

of a large fraction of the origgasoline hydrocarbons and at the same time produce heavier polymers of markedly dilerent characteristi-cs which are largely aliphatic. Such a heavier polymer will decompose largely into gasoline and lighter hydrocarbons at a pyrolysis temperature, and can be returned to the reaction zone wherein partial decomposition into gasoline and lighter hydrocarbons will take place. At the same time the formation of additional amounts of aromatic heavy products takes place by union with lighter unsaturated hydrocarbons present to 'produce an increased amount of heavy aromatic Because of the mild reaction temperpartial pressure of lower unsaturated hydrocarbons the undesirable latter reaction takes place to a considerable degree.

The object of this invention is to provide a novel method for effecting more elicient conversion of heavier polymers from the last mentioned type of polymerizing operation, into hydrocarbons boiling within the gasoline range by subjecting them in a second reaction step, and in the presence of gaseous hydrocarbons undergoing thermal conversion, to conditions of higher temperat-ure and lower pressure whereby a maximum proproducts.

duction of gasoline hydrocarbons 1s obtained with It has been proposed to reduce the quantity of heavier polymers formed in such an operation by returning the heavier polymers to the reaction zone wherein a cracking or depolymerizing is effected, and more or less of the heavier polymers are converted into products boiling within the gasoline range. When such a thermal treatment is applied to gaseous hydrocarbons which are largely parainic, elevated temperature and reaction time suicient to eiect splitting reactions matic in character. When such hydrocarbons are returned to the reaction zone a limited amount of gasoline is produced from the aliphatic structures present. At the same time aromatic and unsaturated hydrocarbons, comparatively resistant to decomposition by heat, unite with lighter hydrocarbon molecules to produce heavy products of essentially aromatic structure. I have found further, however, that the conversion of gases of high olen content, if conducted at sufciently high pressure, can be effected at comparatively low reaction temperatures to a lessened formation of additional heavy aromatic polymers.

The process will be understood from the following description: Hydrocarbons suitable for the process are those ratus for effecting the present process for converting normally gaseous hydrocarbons into motor fuel.

The conversion stock which may `consist of normally gaseous hydrocarbons of predominantly three and four carbon atoms per molecule, and which may have .been derived from cracking still gases is drawn through a conduit or pipe I0 by is forced into a reaction zone at a temperature preferably below 1000" F. I2 may be heated inany desired manner in the furnace I3, and polymeric products are formed in the coil I2 as the result of such temperature and of the conversion stock. The thermally treated hydrocarbons pass from the .coil

produce I2`through pipe I4 to a series of fractionators which are diagrammatically illustrated by the fractionator I5 and wherein there is separated a fraction composed of normally gaseous hydrocarbons, a fraction which is essentially gasoline, a heavy fraction composed of hydrocarbons of higher boiling point than gasoline, and a fourth fraction of relatively small volume which consists of heavy tar of a still higher molecular weight.

The rst mentioned fraction consisting of normally gaseous hydrocarbons surviving thermal treatment in the reaction coil or zone I2 and depleted of the more readily converted components passes through conduit IIS to a second reaction zone or heated coil I1, which is contained in a suitable furnace I8, and wherein more drastic conditions of thermal treatment are maintained than in reaction coil or zone I2 and wherein there may exist a higher `pressure by virtue of pump I9. If it is not desired to maintain a high pressure in reaction zone or coils I1 the hydrocarbon materials flowing thereinto may be bypassed from pipe I6 through pipe 20 controlled by the valve 2|. The temperature in reaction coil I1 is usually 1,000 F. or higher and the pressure 3,000 pounds or lower.

The second or gasoline fraction from the fractionator I5 is discharged from the system through pipe 22.

The third fraction above mentioned separated in fractionator I5 namely the polymers heavier than gasoline, flow therefrom through pipe 23 and are introduced wholly or in part into the reaction coil I1 by way of pipe 24 controlled by the valve 25 and which makes connection with lpipe I6, or this third fraction consisting of polymers heavier than gasoline may be caused to flow from pipe 23 through pipe 2B, controlled by the valve 21, and enter the reaction lcoil I1 at an intermediate point thereof within the furnace I8 as illustrated in the drawing. This latter mode of introducing the third fraction consisting of polymers heavier than gasoline is resorted to when a shorter reaction period produces better results, or is otherwise desired.

The fourth fraction consisting of the heaviest products from the reaction coil I2 need not be removed from the system in some cases, but may be introduced through pipe 28 to the pipe 23 by flowing it through pipe 29 controlled by the valve 30 and thence to the reaction coil I1 by way of pipe I6, or it may be withdrawn from the system by the pipe 3I controlled by the valve 32.

In reaction coil I1 a conversion of the charge into normally liquid hydrocarbons takes place, the major part being contributed by the incoming gaseous hydrocarbons and a smaller part by the decomposition of the heavier hydrocarbons introduced. The thermally treated material passes from the reaction coil I1 by way of pipe 33 to a series of fractionators which are also diagrammatically illustrated by the fractionator 34 wherein light gaseous hydrocarbons are separated from the mixture and may be discarded through the pipe 35. In fractionator 34 gasoline and heavier hydrocarbons are separated and discharged through pipe 36, and the normally gaseous hydrocarbons suitable for retreatment are separated from the mixture and may be returned through pipe 31 to pipe I6 for retreatment in the reaction coil I1.

Suitable fractions consisting of the more reactive gaseous hydrocarbons, and preferably high in olefin content, may be returned from the fractionator 34 through pipe 38 by means of the pump 45 and introduced into pipe I0 whereby they are caused to enter the reaction coil I2 along with the other gaseous hydrocarbons being treated in this process.

An additional fraction, consisting of the more reactive gaseous hydrocarbons and preferably high in olefin content, may be withdrawn from the series of fractionators illustrated diagrammatically by the fractionator I5, through pipe 39 controlled by the valve 40 and passed through pipe 4I by means of pump 42 to feed the same into pipe III along with the charge therein.

In some instances it may be desirable to withdraw a portion of the material flowing through pipe I6, namely the first fraction, and introduce it into pipe I0 along with the charge therein, and when this is desired valve 43 in pipe 44 is opened thus allowing a part of the material in -pipe I6 to flow through pipes 44 and 4I and into pipe I0.

Gaseous hydrocarbons may also be introduced from an outside source to the reaction coils I1, and to effect this pipe 45 is provided which connects with pipe I6 leading to the coil I1.

Hydrocarbons most suitable for conversion in the rst thermal treatment effected in coil I2 contain preferably over 20 per cent olefins and may be gases derived from oil cracking or from hydrocar-bon gas pyrolysis. The conversion conditions required to effect conversion of gaseous olens by heat and pressure are well known and will be in the neighborhood of '150 to 1,000 F. at pressures of 500 to 3,000 pounds per square inch and higher, the higher pressures being desirable when olefin content is not high with a reaction in the range .5 to 3 minutes, the time being dependent upon the temperature and pressure level employed. A conversion into polymeric products equivalent to 40 per cent or more of the olefin present is usually desirable for economic conversion and the polymeric products will contain from l5 to 35 per cent of hydrocarbons boiling above the gasoline range, which usually embraces temperatures up to about 400 F. With the thermal treatment conducted under substantially the conditions described the gasoline will contain only a minor proportion of aromatics. The second conversion step conducted in reaction coil I1 will normally be conducted under more drastic conditions such that gaseous paraffin hydrocarbons, ethane, propane and butane, will be substantially decomposed while concurrent polymerization of Vthe gaseous oleiins takes place and requires, for

the eflicient conversion of the heavier polymer introduced, a higher temperature and in any case a more drastic time-temperature condition than does the rst reaction step of coil I2. In this operation temperatures of about 1,000 to 1,40()o F. are required and operating pressures of from 3,000 pounds per square inch more or less to about 200 pounds per square inch, the lower temperatures within the range being used with the higher pressures. Operation under the conditions described leads to the formation of heavier polymers accompanying the gasoline produced which are of high specific gravity and mostly aromatic.

For treatment in this process gaseous hydrocarbons varying in composition over a wide range may be used. All gaseous hydrocarbons are convertible except methane which is substantially inert under these conditions. Conversion under mild conditions, in coil I2 (step l) requires that 20 per cent or more of olens be present and preferably 35 per cent or more. Lower olefin contents are converted more satisfactorily if butanes, which are the only parailin hydrocarbons reacting extensively under mild conditions, are presentto-the extent ofl 40 per cent or more. By the expression .gaseous hydrocarbons containing a substantial proportion of" reactive components is meant hydrocarbons ofthe composition above defined.

- I claim as my invention: Y

LA'process for converting a normally gaseous hydrocarbon mixturecontaining both unsaturated and saturated components into normally liquid hydrocarbons ofthe motorfuel boiling range, which comprises thermally-treating such a mixture under a pressure greater than 500 pounds per square inch atA a temperature between 750 and 1,0007 F. in a iirst reaction zone and producing normally liquid hydrocarbons, separating from the eliluents of said first reaction Zone a first fraction consisting of normally gaseous hydrocarbons, a second fraction consisting of normally liquid hydrocarbons boiling in the motor fuel range and a third fraction boiling above the motor fuel range, and thermally treating said rst fraction in admixture with said third fraction and in the absence of hydrocarbon oils from an extraneous source in a second reaction zone under a pressure between 200 and 3,000 pounds per square inch at a temperature between 1,000 and 1,400 F. and such that aromatic hydrocarbons are produced in said second reaction zone.

2. In a process for converting a mixture of normally gaseous hydrocarbons containing a substantial proportion of reactive components into normally liquid hydrocarbons suitable for motor fuel, the steps which comprise thermally treating a mixture of gaseous hydrocarbons containing a substantial proportion of reactive components under a pressure between 500 and 3,000 pounds per square inch and within the temperature range of 750 to 1,000 F. to produce normally liquid hydrocarbons, separating from the resultant mixture a first fraction consisting of normally gaseous hydrocarbons and a second fraction consisting of normally liquid hydrocarbons boiling in the gasoline range and a third fraction consisting of hydrocarbons boiling above the gasoline range, thermally treating said iirst fraction in admixture with said third fraction and in the adsence of hydrocarbon oils from an extraneous source under a pressure between 200 and 3,000 pounds per square inchv within the temperature range of 1,000 to 1,400" F. and such that aromatic hydrocarbons are produced in said second reaction zone, separating from said thermally treated fractions said normally liquid hydrocarbons and removing them from the process, and also separating a mixture of gaseous hydrocarbons containing a substantial proportion of reactive components and admixing the same as a part of the rst mentioned mixture of gaseous hydrocarbons containing a substantial proportion of reactive components.

3. A process for converting a normally gaseous hydrocarbon mixture containing a substantial proportion of reactive components into normally liquid hydrocarbons of the boiling range of gasoline, which comprises passing such a hydrocarbon mixture while under a pressure between 500 and 3,000 pounds per square inch and at a temperature of 750 to 1000 F. through a first reaction zone wherein normally liquid hydrocarbons are formed, separating from the thermally treated hydrocarbon mixture a first fraction consisting of normally gaseous hydrocarbons, a second fraction consisting of normally liquid hydrocarbons in the gasoline boiling range and removing it from the process, 4and a third fraction containing hydrocarbons boiling above the gasoline boiling range, passing said iirst fraction together with said third fraction and in the absence of hydrocarbon oils from an extraneous source to a second reaction zone wherein the last mentioned fractions are mingled and subjected to a conversion temperature of 1000 to 1400 F. while under a pressure greater than 200 pounds per square inch and less than that in said iirst conversion zone and such that aromatic hydrocarbons are produced in said second reaction zone, whereby an optimum conversion to gasoline boiling range hydrocarbons takes place, and then separating from the hydrocarbons thermally treated in the second reaction zone the normally liquid hydrocarbons produced therein.

4. A process for converting normally gaseous hydrocarbons into normally liquid hydrocarbons in the gasoline boiling range which comprises treating a normally gaseous hydrocarbon mixture substantially free of methane and containing at least 20 per cent of olefin hydrocarbons under a pressure between 500 and 3000 pounds per square inch in a rst reaction zone maintained at a temperature between 750 to 1000 F. whereby normally liquid hydrocarbons are produced, separating from the eiliuents of said rst reaction zone a iirst fraction consisting of normally gaseous hydrocarbons, a second fraction consisting of normally liquid hydrocarbons boiling in the gasoline boiling range and removing it from the process, and a third fraction consisting of normally liquid hydrocarbons boiling above the gasoline boiling range, treating said Iirst fraction and said third fraction in the absence of hydrocarbon oils from an extraneous source under a pressure lower than that in said first reaction zone and between 200 and 3000 pounds per square inch in a second reaction zone maintained at a temperature between 1000 and 1400 F. and such that aromatic hydrocarbons are produced in said second reaction zone whereby anoptimum yield of normally liquid hydrocarbons in the gasoline boiling range is produced, and separating from the eiiiuents of said second reaction zone the gasoline boiling range hydrocarbons so produced.

5. A process for converting normally gaseous hydrocarbons into a maximum quantity of normally liquid hydrocarbons in the gasoline boiling range which comprises treating a normally gaseous hydrocarbon mixture substantially free of methane and containing at least 40 per cent of butanes and at least 20 per cent of olefin hydrocarbons under a pressure between 500 and 3000 pounds per square inch in a iirst reaction zone maintained at a temperature between 750 and 1000 F. whereby normally liquid hydrocarbons are produced, separating from the eliuents of said first reaction zone a first fraction consisting of normally gaseous hydrocarbons, a second fraction consisting of normally liquid hydrocarbons boiling in the gasoline boiling range and removing it from the process, and a third fraction consisting of normally liquid hydrocarbons boiling above the gasoline boiling range, treating said lrst fraction and said third fraction in the absence of hydrocarbon oils from an extraneous source under a pressure lower than that in said iirst reaction zone and between 200 and 3000 pounds per square inch in a second reaction zone maintained at a temperature between 1000 and 1400 F. and such that aromatic hydrocarbons are produced in said second reaction zone whereby an optimum yield of normally liquid hydrocarbons in the gasoline boiling range is produced, and separating from the effluents of said second reaction zone the gasoline boiling range hydrocarbons so produced.

6. A process for converting a normally gasecus hydrocarbon mixture containing both saturated and unsaturated hydrocarbons into normally liquid hydrocarbons of the gasoline. boiling range, which comprises subjecting said mixture in a first Zone to conditions of temperature and pressure suflioient to convert a substantial proportion of the unsaturated hydrocarbons to normally liquid products, separating from the eiiuent of said zone a normally gaseous fraction, a fraction boiling Within the gasoline range and a fraction boiling above the gasoline range, subjecting the rst and lastA mentioned fraction in the absence of hydrocarbon oils from an eX- traneous source in a second zone to a higher temperature than said first zone and elevated pressure, said temperature and pressure being so regulated that a substantial proportion of aromatic products boiling Within the gasoline range are produced, and separating the normally liquid hydrocarbons from the effluent of said second zone.

FREDERICK E. FREY.

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