US2422672A

US2422672A - Selective demethylation of trimethylpentanes to form triptane

Info

Publication number: US2422672A
Application number: US504456A
Authority: US
Inventors: Haensel Vladimir; Vladimir N Ipatieff
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1943-09-30
Filing date: 1943-09-30
Publication date: 1947-06-24
Anticipated expiration: 1964-06-24

Description

June 24, 1947- v. HAENsEl. ETAL 2,422,672

`SELECTIVE DEMETHYLATION OF TRIMETHYLPENTANES TO FORM TRIPTANE 2 Sheets-Sheet 1 Filed Sept. 30, 1943 A y"June 24, 1947. v. HAENsEL ETAL SELECTIVE DEMETHYL-ATION OF TRIMETHYLPENTANES TO FORM TRIPTANE 2 sheets-sheet "2 Filed Sept. 30, 1943 Patented June 24, 1947 T osFicl-z' SELECTIVE DEMETHYLATION F TRI- METHYLPENTANES T0 FORM TRIPTANE Vladimir Hunsel and Vladimir N. rpauen. mverside, Ill., assignors to Universal Oil Company, Chicago, Ill

Wan

Products a' corporation o! Dela- Application September 30, 1943, Serial No. 504,456

3 Claims. (Cl. 26o-683.6) j

This invention relates to the conversion of hydrocarbons and more particularly to the conversion oian aliphatic hydrocarbon containing at least six carbon atoms to the molecule into an aliphatic hydrocarbon having at least one carbon atom less tothe molecule.

We have shown that aliphatic hydrocarbons, and preferably paraiiinic hydrocarbons having a 'branched chain structure, may be subjected to selective demethylation in the presence of hydrogen and a hydrogenating catalyst at a temperature of from about 350 to about 700 F. and preferably of from about 400 to about 650'1". under a pressure of substantially atmospheric to 1500 pounds per square inch, or more. Suitable catalysts comprise the metals of the iron group and their oxides including iron, nickel and cobalt, and the noble metals, platinum and palladium, used as such or supported by carriers. Under some conditions of operation, selective demethylation may also be 'effected in the vpresence of an oxide or sulde of chromium, molybdenum, tungsten and vanadium. A highly selective catalyst contains approximately 66 per cent by weight of total nickel, 30 per cent of diatomaceous earth and 4 per cent of oxygen, the latter being present with nickel as nickel oxide.

The present invention is characterized by one or more of thev following features, either singly or in combination.

(1) Selective demethylation of a branched chain aliphatic hydrocarbon in the manner heretofore set forth, separating a fraction containing methane from the products of said demethylation, subjecting said methane fraction to conversion into hydrogen, and supplying the resultant hydrogen to 4the demethylation process.

(2) Purifying the hydrogen being supplied to the demethylation process to remove any moisture which may 'be present therein'. The presence of moisture has been found to be detrimental to the catalyst employed in the demethylation process and its substantial removal is essential for eiilcient operation of the demethylation process.

(3)` Close control of the temperature in the reaction zone of the selective demethylation process since experiments have shown that the temperature employed is critical and, in accordance with the present invention, the control of` temperature is eii'ected by means of a circulating heat exchange medium.

(4) Maintaining a temperature differential between the inlet and outlet of the demethylation reactor.

(5) Close fractionation of the charging stock to the process to separate a selected fraction for treatment in the selective demethylation process in order to obtain improved results therein.

(6) Close fractionation of the products from the demethylation process, `with recycle of particular fractions in order to obtain increased yields of the desired product.

(7) Separation of a hydrogen-containing fraction and a methane-containing fraction from the demethylation products by ashing ina plurality of zones maintained at successively decreased pressures.

The present invention is applicable to the treatment of aliphatic hydrocarbons and particularly branched chain paraiiinic hydrocarbons containing at least six carbon atoms per molecule. It is also applicable to the treatment of naphthenic hydrocarbons containing alkyl side chains, p

although the results obtained are not necessarily equivalent. The invention is particularly applicable to the production of triptane which is otherwise known as 2,2,3-trimethy1butane.

In a. broad aspect the present invention relates to a. process for converting an aliphatic hydrocarbon into an aliphatic hydrocarbon containing at least one carbon atom less to the molecule, which comprises subjecting the nrst mentioned aliphatic hydrocarbon to selective demethylation in the presence of hydrogen and a hydrogenating catalyst under conditions to produce an aliphatic hydrocarbon having at least one carbon atom less to the molecule, separating from the demethylation products a methane-containing fraction, subjecting the latter fraction to conversion to produce hydrogen'therefrom, and supplying at least a portion of the resultant hydrogen to the demethylation reaction.

In one specific embodiment the present invention relates Ito a process for producing triptane which comprises heating a fraction containing 2,2,3-trimethylpentane, simultaneously heating a hydrogen fraction substantially free of moisture, commingling the heated streams and introducing the same at a temperature of from about 400 to about 650 F. into a reaction zone, maintaining the temperature in the reaction zone within a relatively narrow range by means of indirect contact with a circulating heat exchange medium, flashing the demethylation .products to separate a hydrogen-containing fraction, further ashing the remaining products to separate a methanecontaining fraction, subjecting .the methaneing said hydrogen and commingling the same with said fraction containing 2,2,3-trimethylpentane as aforesaid.

The invention will be further explained in connection with the attached diagrammatic flow drawing comprising Figures 1 and lA which illustrate several specific embodiments of the invention. In the interest of simplicity, the description of the drawing will be limited to a process for the treatment of an isooctane fraction for the production of triptane. It is understood, however, that the broad scope of the invention is not so limited, but that it is applicable, with suitable modifications, to the treatment of other hydrocarbons. In general, the preferred charging stocks are those containing at least ve carbon atoms to the molecule and having a quaternary carbon atom, and particularly those having a triptyl group. By quaternary carbon atom it is meant a carbon atom which isA combined chemically with four other carbon atoms, neopentane being the simplest example of a hydrocarbon containing a quaternary carbon atom. By triptyl group it is meant a hydrocarbon containing adjacent quaternary and tertiary carbon atoms; that is, one carbon atom is combined chemically with four other carbon atoms and one of said four carbon atoms is tertiary in that it is bound l to the quaternary carbon atom, to two other carbon atoms and to only one hydrogen atom.

The charging stock to the process of the present invention may suitably comprise an isooctane fraction produced by the polymerization of normal and isobutylenes in the presence of suitable catalysts and particularly sulfuric acid, the latter polymerization being effected ata temperature within the range of from about 150 to about 200 F., followed by hydrogenation of the polymerization products. The hydrogenated products may be subjected to fractionation or other treatment to separate an isooctane fraction having an initial boiling point of about 194 F. and containing 22,4-, 2,2,3-2,3,4, and 2,3,3-trimethylpentanes along with higher boiling compounds.

The isooctane fraction charging stock, at a suitable temperature and pressure, is introduced to the process through line I containing valve 2 and is directed into fractionator 3. Fractionator 3 may comprise any suitable zone for effecting the separation of the products introduced thereto into the desired fractions and may suitably comprise a fractionating column containing bubble trays, baille plates, side-to-side pans or other contact means. Fractionator 3 is preferably heated at the bottom by means of closed coil 4 or other suitable means and is cooled at the top in any suitable manner such as by recycling a portion of the condensed overhead fraction as will be hereinafter described.

As applied to the particular isooctane fraction as heretofore set forth, zone 3 will be operated to separate an overhead fraction having an initial boiling point of about'l94 F. and an end boiling point of about 239 F. from higher boiling bottoms fraction. The higher boiling bottoms fraction is withdrawn from the lower portion of zone 3 through line 5 containing valve 6 to storage or elsewhere as desired. The overhead fraction, which now comprises a mixture of the various trimethylpentanes, is Withdrawn from the upper portion of zone 3 through line 1 containing valve 8 and is passed through condenser 9 and rundown line I containing valve Il into receiver I2, having conventional gas release line I3 containing valve I4. The condensate in receiver I2 is withdrawn therefrom through line I5 containing valve I6 to pump I1, by means of which a regulatedportion thereof is recycled by way of line I8 containing valve I9 to the upper portion ol fractionator 3 to serve as a cooling and refluxing medium therein, while the remaining portion of the condensate from yreceiver I2 is directed through line 20, valve 2 I, heat exchanger or other suitable heating means 2l to fractionator 22.

Fractionator 22 may be similar to heretofore described fractionator 3 and contains closed coil 23 or other suitable heating means in the lower portion thereof. This fractionator will function to separate an overhead fraction comprising hydrocarbons boiling below about 226 F from higher boiling trimethylpentanes. The light fraction withdrawn as an overhead product from fractionator 22 will comprise principally 2,2,4- trimethylpentane and 2,3-dimethylpentane, the latter being produced in the process as will be hereinafter set forth. This fraction is directed through line 24 containing valve 25 into and through condenser 26, rundown line 21 and valve 28 into receiver 29, having conventional gas release line 30 containing valve 3l. The condensate in receiver 29 may be withdrawn therefrom through line 32 and valve 33 to pump 34, by means of which a iegulated portion thereof may be recycled by way of line 35 and valve 36 t0 the `:pper portion of fractionator 22 to serve as a cooling and refluxing medium therein, while the remaining portion of the condensate from receiver 29 may be withdrawn from the process through line 31 and valve 38 to storage or elsewhere as desired.

The bottoms product in fractionator 22 will comprise principally 2,2,3, 2,3,4, and 2,3,3-trimethylpentanes and may be withdrawn therefrom through line 39`,and valve 40 to pump 4I by means of which it may be supplied to furnace 42 having heating coil 43 disposed therein. In passing through coil 43, the hydrocarbons are heated to the desired temperature which, as heretofore set forth, will be within the range of 350 to '700 F. and preferably within the range of 400 to 650 F., at a superatrnospheric pressure which will be correlated with the temperature in order to obtain the desired demethylation. It has been found that when higher pressures are employed, generally higher operating temperatures are required. In one specific operation of the present process, the hydrocarbons are heated in coil -43 to a temperature of about 500 F. at a superatmospheric pressure of about 510 pounds per square inch.

The heated products are withdrawn from coil 43 through line 44 and may be supplied through valve 45 to mixing chamber 46. In chamber 46, hydrocarbons are admixed with separately heated hydrogen, the latter being introduced'to the process through line 41 containing valve 48 and supplied to heating coil 49 disposed in furnace 50. The hydrogen is heated to the desired temperature and then supplied through line '5I and valve 52 into mixing chamber 46. Mixing chamber 46 may comprise any suitable apparatus and may or may not contain a bed of packing. The function of the mixing chamber is to obtain intimate mixing of the hydrocarbons and hydrogen and also to separate out any unvaporized material. The unvaporized material may comprise, for example, lubricating oil fractions which are carried over with the hydrogen from the compressors. The unvaporzed material may be withdrawn from chamber 4S through line 53 containing valve 54.

It is understood, when desired, that the hydrogen and hydrocarbons' may be heated in admixture in one heating zone and that mixing chamber .46 may be omitted. Even in case separate heaters are provided for the hydrocarbons and hydrogen, mixing chamber 46 may be omitted and the heated hydrocarbons may be directed from line 44 through line 55 containing valve 56, while the heated hydrogen may be directed through line 51 containing valve 58. The heated hydrogen and hydrocarbons may then be directed, either through line 59 and valve 60 from mixing chamber 46 or through by-pass lines 55and 51, into reactor 6|, which may comprise any suitable apparatus and which contains a suitable hydrogenating catalyst as heretofore set forth.

One of the important features of the demethylation process is that the temperature within the reaction zone must be maintained within a criti- .cal narrow range. When the temperature in this zone becomes too high, there is excessive demethylation of the hydrocarbons and, on the other hand, if the temperature is too low, selective demethylation does not occur to any substantial extent. As heretofore set-forth, the exact temperature will depend upon the pressure. One particularly suitable method of maintaining close control of the temperature is by means of a reactor, as illustrated, containing tubes in which the catalyst is disposed, and provision for circulating a heat exchange medium in the annular space surrounding the tubes. Reactor 6| is therefore preferably of this form, although it is understood that other suitable types of reaction zones may be employed.

' In order to maintain close control of the reaction temperature, drum 62 may be filled with any suitable heat exchange medium, such as Dowtherm, tetralin or the like, which circulates in a thermo-Siphon system through line 63,v line 64 and valve 65 into the space surrounding the tubes in reactor 6| and is returned by way of line 66 to drum 62. The vaporous material from drum 92 passes through line 61, valve 68 and line 69 into and through condensery 10 containing suitable cooling means such as closed coil 1|. The condensate from the'condenser passes through rundown line 12 back'into drum 62. Drum 62 and accordingly the space surrounding the catalystcontaining tubes in reactor 6| will be operated at the desired pressure in order to maintain the heat exchange medium in the space surrounding the catalyst-containing tubes as a boiling liquid.'A

This may be any suitable superatmospheric pressure or, in certain cases, may even comprise subatmospheric pressure, depending upon the particular heat exchange medium employed. .Vacuum operation may be accomplished by means of vacuum .iet 13 havingline 14 and valve 15 for the introduction of steam or other suitable gas and outlet line 16, and being in communication with condenser 10 by means oi line 69 and valve 11. Even when superatmospheric pressure is employed in drum 62, vacuum jet 13 and its appurtenances may be employed at the start of operation or intermittently during operation, if desired, to remove incondensable gases from the system. These incondensable gases interfere with the pressure on the heat exchange medium and therefore must be vented as required.

The demethylation reaction is -highly exothermic and usually will liberate enough heat to maintain the heat exchange medium at the desired temperature. However, in case additional heat is required and also in order to start up the unit, all or a portion of the heat exchange medium may be directed from line 63 through is heated to the desired temperature, and the heated material may be directedvthrough line 82 containing valve 83 into the surrounding space in reactor 6|. An extension of line 63 containing valve 94 is provided either for the introduction of heat exchange medium to, or the withdrawal of the heat exchange medium from the process.

Since the temperature of the demethylation reaction is so closely related to the pressure, in another embodiment of the -invention a temperature differential of from about 10 to about 20 F. may be maintained between the inlet and outlet sections of reactor 6|. As the hydrogen is consumed in the lower portion of the reaction zone, there occurs a decrease in available hydrogen and accordingly a. reduction in pressure in the upper portion of the reaction zone. One particularly suitable means of accomplishing the temperature differential in reactor 6| is by maintaining a pressure diierential between the upper and lower sections of the space surrounding the catalyst-containing tubes, since the temperature of the liquid therein is dependent upon the pressure. This difference in pressure may be obtained by maintaining a level of liquid in drum 62, as illustrated diagrammaticaliy by line 85, and accordingly in the surrounding space in reactor 6|, as indicated by line the liquid levels being approximately the same height as the level of catalyst in the tubes of reactor 6|. The pressures at the lower portion of the surrounding space and drum will thereby be higher due to the fluid headrof the liquids therein.

Although upow. of hydrocarbons and hydrogen is illustrated in reactor 6|, it is understood that downlow may be used. Thevproducts from reactor V6| may be withdrawn therefrom through line 86 containing valve 81 into and through condenser 88, line 89 and valve 90, and may be supplied to flash zone 9|. Line 55' containing valve 56 is provided in order to by-pass the reactor and supply the heated hydrocarbons directly into line 86. This by-pass will be used primarily in case excessive temperatures develop in reactor 6|. A sumcient reduction in the temperature in the reaction zone may be accomplished solely by means of by-passing the reactor in this manner. When desired, hydrogen from line 41 or line 96 may be supplied through valve 5|' and line 5| and the unheated hydrogen passed through

lines

51 and 59 into reactor 6| in order to effect all or a part of the desired cooling.

Flash zone 9| may comprise the first of a series of flash zones being operated at successively decreasing pressures, as illustrated by flash zones 9| and 92. It is understood, however, that one -or three or more, and preferably three, of such head fraction will be released which will be high in hydrogen content. This overhead fraction may then be directed through line v93 and valve 94 to compressor, pump or the like 95, by means of which the hydrogen may be supplied through line 96 and valve 91 into line 41'for treatment in the manner as heretofore set forth. Y

The unvaporized bottoms from flash zone 9| which will contain substantial proportions of methane, may be withdrawn therefrom through line 98 and reduced in pressure as it passes through valve 99 and introduced into flash zone 92. Assuming that three flash zones are employed, the pressure reduction may be from about 200 pounds in the firstnash zone to about 70 pounds in the second flash zone and down to about 25 pounds in the third flash zone. It is understood that the present invention is not limited to these particular pressures and any suitable series of pressure reductons may be employed. A level of unvaporized liquid is likewise preferably maintained in flash zone 92 but, in this case, the liberated overhead fraction will be rich in methane and may be withdrawn from Zone 92 through line and valve |0| and then may be passed through line |02, wherefrom a portion may be removed from the process through line |03 but, in accordance with the preferred embodiment of the present invention, at least a portion thereof is directed through line |04 and valve '|05 for further treatment in the manner to be hereinafter described in detail. In case only oneflash zone is employed or for other reasons, all or a portion of the overhead fraction from flash zone 9| may be directed through line |02 and valve |05 for removal from the process or treatment in the manner to be hereinafter described in detail.

Any other suitable means of separating a methane fraction may also be employed within the scope of the present invention and this may comprise, for example:

(1) Absorblng the methane .in a liquid stream and subsequently stripping the methane therefrom.

(2) Absorbing the methane on a suitable solid adsorbent, such as activated carbon or the like, and then subsequently stripping the methane therefrom.

It is understood, however, that these various alternative means are not necessarily equivalent in their efficiency in separating the methane from tbe other products. The unvaporized material in ash zone 92 may be withdrawn from the lower portion thereof through line |01 and valve |08 to pump |09, by means of which it may be directed through line ||0 and valve into fractionator I2. Fractionator ||2 may be similar to the heretofore described fractionators, having reboiler I3 or other suitable heating means in the lower portion thereof, and will function to separate an overhead fraction having an end boiling point of about 158 F. from higher boiling material. The overhead fraction, which will comprise principally pentane, 2,2 and 2,3-dimethylbutane, may be withdrawn froml the upper portion of fractionator ||2 through line ||4, valve ||5, condenser IIB, rundown line `and valve ||8 into receiver ||9, having conventional gas release line |2| containing valve |20. The condensate in receiver ||9 may be withdrawn therefrom through line |22 and valve |23 to pump |24, by means of which a regulated portion thereof may be recycled by Way n( line |25 and valve |26 to the upper portion of fractionator ||2 to serve as a cooling and refluxing medium therein, while the remaining portion of the condensate from receiver ||9 may be withdrawn from the process by way of line |21 andv valve |28 to storage or elsewhere as desired.

The bottoms product may be withdrawn from fractionator ll2'through line |29 and valve |30 te pump |3| by means of which it may be directed through line |32 and valve |33 to fractionator |34, which may be similar to the heretofore described drawn from the lower portion of fractionator |34 through line |36 and may be withdrawn from the process through line |31 but, in a preferred embodiment of the invention, at least a portion of this stream is directed through line |33 and valve |39 to pump |40 by means of which it is directed through line |4| and valve |42 into line 20 to be supplied into fractionator 22 for separation and further treatment within the process in the manner heretofore set forth. Thus, the 2,3-dirnethylpentane will be recovered in the overhead fraction from fractionator 22, while the trimethylpentanes will be supplied in the bottoms fraction to demethylation treatment.

In accordance with a preferred embodiment of the present invention, the methane fraction being supplied through line |04 may be subjected to suitable treatment for conversion thereof into hydrogen. vOne suitable process comprises the so-called water-gas reaction in which the methane fraction is treated with water in the form of steam at elevated temperatures in the presence of suitable catalysts to form hydrogen. This Aprocess is well known and no novelty is claimed the particular catalyst and other conditions of4 operation and in some cases it may be as low as 600 F. while in other cases may be as high as 1800 F. It is understood that the present invention is not limited to any particular catalyst or temperature employed in this step of the process since the only requirement, insofar as the combination aspect of the present invention is concerned, is that at least a portion of the methane be converted into hydrogen. In this process, carbon dioxide and some carbon monoxide is usually produced and it is preferred to utilize a suitable solvent or other means for separating the carbon oxides from the hydrogen in order to leave a substantially pure hydrogen product.

Another method of converting the methane into hydrogen within the scope of the present invention is by cracking the methane either in the presence or absence of suitable catalysts. In this method of operation the temperature employed is usually within the range of from about 1200 to about 1800 F. When employed, any suitable catalyst may be used and here again a large variety of catalysts have been proposed for effecting the decomposition of methane into hydrogen.

-Referring again to the drawing, the methane fraction being supplied through line |04 may be directed into heating coil |58 disposed infurnace |59. In case the water-gas reaction is employed,

steam may be introduced through line |60 and valve 6| to commingle with the methane fraction in line |04 and then directed into heating coil |58. If the methane conversion step comprises the cracking of the methane, line |50 may be omitted or it may be utilized for the introduction of addi- .tional methane from an extraneous source or for any other desired purpose. The heated products from coil |58 may be directed through line |62 and valve |63 into reactor |64. The catalyst, when employed, may be disposed within reactor |64 and the heated hydrocarbons suitably contacted therein. Either up or downflow may be employed, as desired. The exact form of reactor |64 will depend upon the particular process being employed. The products from reactor |64 may be directed through line |65 and valve |66 to separator and purifier |61. 'I'he design of zone |61 will depend upon the particular process utilized for converting the methane into hydrogen. For example, in case this process comprises the water-gas reaction, zone I 61 preferably consists of one or more. fractionating zones in which the products are treated with a suitable solvent or other means in,

The hydrogen separated in zone |61 may be withdrawn therefrom through line |12 and may be directed through line |12' and valve |13 into line 41 to be supplied to the demethylation step of the process in the manner heretofore set forth. Usually the hydrogen recovered from zone |61 will be saturated with moisture at the temperature conditions at which it is recovered. As heretofore stated, moisture is detrimental to the demethylation catalyst and, in the preferred embodiment of the present invention, the hydrogen fraction is directed from line |12 through line |14 and valve |15 into dryer |16. It is also within the preferred embodiment of the invention that, when the hydrogen introduced to the process from an extraneous source contains moisture, the hydrogen be introduced to the process through line |11 and valve |18, instead of through line 41 and valve 48 as heretofore set forth. Dryer |16 may comprise any suitable apparatus and contain any suitable absorbent material, such as alumina or the like, in order to reduce the water content of the hydrogen fraction to as low as practicably possible and preferably to completely remove thewater. Either upiiow or downilow may be employed in dryer 16, as desired, and the dried hydrogen fraction may then be directed through line` |18 and valve |80 into lines |12, |12' and 41 to be supplied to the demethylation step of the process as heretofore set forth.

It is a particular feature of the combination aspects of the present invention that at least sufficient hydrogen will be produced in the methane conversion step of the process to meet the requirements of the demethylation reaction. When the methane conversion step comprises a vorder to separate the hydrogen Afrom other io water-gas reaction, three molecules of hydrogen are theoretically obtainable from one molecule of methane and one molecule of steam, or four molecules of hydrogen are theoretically obtainable from one molecule of methane` and two molecules of steam, depending upon whether carbon monoxide or carbon dioxide is formed. Likewise, in the cracking of methane, two molecules of hydrogen are theoretically possible from one molecule of methane. Since the methane conversion step will convert at least 50% and usually a much higher proportion of the methane into hydrogen, it is readily seen that suilcient hydrogen to meet vthe requirements of the demethylation process will be available, thus providing a unitary process. Any excess hydrogen may be withdrawn from the system through an extension of line |12 and valve |13'.

'I'he following example is introduced to further illustrate the novelty and utility of the present invention but not with the intention of undul limiting the same.

The charging stock to the process may comprise 65.4 moles per day (equivalent to 1257 gallons per day) of an isooctane fraction as heretofore described and is supplied at a temperature of F. to fractionator 3 whichmay be operated with a top temperature of 215 F. and a bottom temperature of 245 F. A bottoms fraction comprising 13 moles per day (equivalent to '251 gallons per day) of higher boiling bottoms is withdrawn and recovered, while an overhead fraction comprising 52.4 moles per day (equivalent to 1006 gallons per day) issupplied to fractionator 22 which may be operated with a top temperature of 211 F. and a bottom temperature of 230 F. An overhead fraction comprising 34.7 moles per day (equivalent to 662 gallons per day) and comprising principally 2,2,4-trimethylpentane is recovered from fractionator 22. The bottoms product from fractionator 22 comprises 30.4 moles per day (equivalent to 573 gallons per day). A hydrogen fraction containing 91.2 moles per day of hydrogen and 9.1'moles per day of methane, to make a total of 100.3 moles per day of gas, is heated to a temperature of about 500 F. at a pressure of about 500 pounds per square inch. 'Ihe bottoms fraction from fractionator 22 is likewise heated to a temperature of 500 F. at a pressure of about 500 pounds and the heated products are supplied to reactor 6| containing a hydrogenating catalyst comprising 66 per cent by weight of total nickel, 30 per cent of diatomaceous earth and 4 per cent of oxygen as nickel oxide.

Reactor 6| may comprise an insulated reaction i chamber having catalysts containing tubes disposed therein and communicating with drum 62 containing Dowtherm. 'I'he Dowtherm is maintained at a pressure of 12 pounds absolute at the top and 14 pounds absolute at the bottom, and

the circulation rate is controlled so that the temperature of the heat. exchange medium in the lower portion of the space surrounding the tubes in reactor 6| is about 490 F. and the temperature in the upper portion of this space is about 480 F.

'I'he demethylation products are Withdrawn from reactor 6| at a temperature of about 495 F., cooled in condenser 88 to a temperature of 90 F., and then supplied to flash zone 9| at a, pressure of about 200 pounds per square inch. A fraction rich in hydrogen is withdrawn from the upper portion of zone 8| and is recycled to the demethylation process, while the liquid products are flashed in a second flash zone at a pressure 11 of about 70 pounds and then flashed in a third flash zone at a pressure of about 25 pounds per square inch. The overhead products from the second and third ash zones are supplied to treatment in the methane conversion step of the process.

The bottoms product from the last flash zone is supplied to fractionator |I2 which may be operated with a top temperature of 130 F. and a bottom temperature of 185 F. An overhead product comprising principally 2,2- and 2,3-dimethylbutane is separated and recovered as one of the nai products of the process. The bottoms product from fractionator I l2 is supplied to fractionator |34 which may be operated with a top temperature of 185 F. and a bottom temperature of 200 F. An overhead fraction comprising triptane is separated and recovered as a ilnal product of the process, while the bottoms product from fractionator |34 may be recycled to fractionator 22 for further separation and treatment within the process.

In a process such as h'ereinbefore described, there may be produced, based upon an isoqctane fraction charge of 1257 gallons per day, the following products:

Gallons per day Higher boiling isooctane bottoms 251 2,2,4-trimethylpentane and 2,3-dimethylpeni-,ane frartinn y 2 80 2,2 and 2,3-dimethylbutane fraction 77 Triptane fraction 193 The triptane fraction will be of high purity and will be particularly suitable for blending in aviation gasoline or may be used for any other desired purpose.

The previously separated methane fractions are reacted with steam in the presence of a nickelcatalyst promoted with alumina at a temperature of about 1300 F. to produce carbon monoxide and hydrogen. The products may then be reacted with additional steam at about 900 F. in the presence of an iron oxide catalyst promoted with chromium oxide to form carbon` dioxide and hydrogen. The carbon dioxide may be separated from the hydrogen by absorption in a solvent comprising ethanol amine, and the hydrogen may then be supplied to the demethylation process in the manner hereinbefore described.

We claim as our invention:

1. A process for the production of triptane from anisooctane fractioneomprisingl 2,2,4-,2,2,3-,2,3,4- and 2,3,3-trimethylpentanes and higher boiling compounds, which comprises ractionating said isooctane fraction to separate higherv boiling compounds from the trimethylpentanes, further fractionating the trimethylpentanes to separate 2,2,4- trimethylpentane from a fraction comprising the other trimethylpentanes, heating the last mentioned fraction to a selective demethylation temperature, simultaneously heating a hydrogen fraction to substantially the same temperature, commingling the heated fractions and contacting the same with a nickel catalyst at a temperature of the orderof 500 F. and at a. superatmospheric pressure of the order of 500 pounds per square inch, hashing and reducing the pressure of the products of said demethylation to a pressure of the order of 200 pounds per square inch to separate a hydrogen fraction, recycling the hydrogen fraction to said demethylation, further reducing the pressure of said products to apresvsure of the order of v pounds per square inch to separate a methane fraction, fractionating the remaining products to separate an overhead fraction containing 2,2- and 2,3-dimethylbutanes from higher boiling products, further fractionating the higher boiling products to separate a triptane fraction from higher boiling trimethylpentanes.

2. The process of claim 1 further characterized in that at least a portion of the last mentioned higher boiling trimethylpentanes is recycled to further selective demethylation treatment.

3. The process of claim 1 further characterized in that the amount of hydrogen is of the order of 3 moles of h'ydrogen per mole of said other trimethylpentanes.

VLADIMIR HAENSEL. VLADIMIR N. IPATIEFF.

REFERENCES CITED The following references are of record in the 4ille of this patent:

UNITED STATES PATENTS Number Name Date 1,004,632 Day Oct. 3, 1911 1,365,849 Ramage Jan. 18, 1921 1,878,580 Gray Sept. 20, 1932 2,209,346 y McCausland July 30, 1940 2,270,303 Ipatiei Jan. 20, 1942 2,181,690 Deanesly et al. Nov. 28, 1939 2,184,930 Ruys et al Dec. 26, 1939 2,214,463 Ipatieff et al Sept. 10, 1940 OTHER REFERENCES Nat. Pat. News, June 15, 1938, R-291, IRP-292, Rf-294, and R-296. (Pat. Oi. Lib.)