US2295808A - Treatment of hydrocarbons - Google Patents

Description

Patented Sept. 15,1942? TREATMENT or nYDRoCARBoNs Raymond E. Schaacl, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application September 13, 1940, Serial No. 356,594

'l'his invention relates to the treatment of hydrocarbon fractions of low antiknock value such as straight-run gasolines. and naphthas produced from parainic and naphthenic crudes or from any other source for the purpose of producing therefrom substantially saturated motor fuel of relatively high antiknock value.

In a more specic sense the invention 1s concerned with a process` for converting essentially parailinic and naphthenic hydrocarbons into a gaseous product rich in isobutane, an intermediate product containing branched chain pentanes and hexanes, and a higher boiling liquid product which may be dehydrogenated to normally liquod olefinic hydrocarbons utilizable for alkylating said gaseous product rich in lsobutane to form a substantially saturated alkylate of improved antiknock value. Said substantially saturated alkylate maybe increased further in antiknock value by a moderate addition of lead tetraethyl.

The formation of isobutane and of other isoparaiiins or more highly branched chain paraln hydrocarbons from less branched chain liquid parains and from naphthenic` hydrocarbons is desirable because of the generally higher antiknock value of the isomeric parailn hydrocarbons so formed. Furthermore, the branched chain paraftlns, both gaseous and liquid, are generally more reactive than the corresponding normal hydrocarbons and consequently these may be utilized in the production of other branched chain parailins by so-called alkylation reactions in the presence of suitable catalysts.

In one specic embodiment the present invention comprises a process for converting a substantially saturated liquid hydrocarbon fraction of relatively low antiknock value into a substantially saturated motorfuel of improved antiknock' valueA which comprises treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen chloride to produce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction; catalytically dehydrogenating said higher boiling hydrocarbon fraction to form a substantial yield of normally liquid olelins; and subjecting said isobutane and said normally liquid oleflns to catalytic alkylation to form a substantially saturated alkylate comprising essentially hydrocarbons of motor fuel boiling range and high antiknock value.

'I'he substantially saturated hydrocarbons preferred as charging stock for the process of this invention and comprising essentially parailins and naphthenes are normally liquids with relatively low antiknock values. Such substantially saturated hydrocarbons are recovered in considerable quantities in the oil refining industry by distillation of parafilnic, naphthenic, and mixed base crudes. Further, paraflins occur in substantial amountsin other gasolines and in the higher' boiling constituents of natural gas commonly v known as casing head gasoline, in certain hydrocarbon materials produced synthetically, and in gasolinesproduced in relatively high yields by the cracking of relatively heavy petroleum fractions. In the case of cracked gasolines produced from paraflinic and naphthenic oils, the

relative proportions of isoparailins, normal part mate limits of and 500 F. In'the absence of an added hydrogen-containing ga`s, isomerization and destructive hydrogenation vreactions are accompanied by the formation of undesirable products, rapid sludge formationon the aluminum chloride catalyst, and an early decrease in catalytic activity. y

It appears that anhydrous aluminum chloride as generally obtainable contains Ma small but necessary percentage of hydrogenchloride and/ or of oxygen compounds, such as hydroxy-aluminum dichloride, or other oxygen derivatives formed by the reaction of pure aluminum chloride with relatively minor proportions of water or of other oxygen compounds. Further, it has been found advisable to add small but denite quantities o! hydrogen chloride to the hydrocarbon fraction being contacted with the aluminum chloride-con- .taining catalyst in order to prevent fouling of the catalyst and a consequent diminution in its hydrocarbon converting activity.

According to the process of the present invention, it has been found that substantially anhydrous aluminum chloride may be subjected to I contact with a hydrocarbon fraction comprising essentially paramns and naphthenes at an ele-` vated temperature and under a hydrogen pressure inthe presence of hydrogen chloride to convertinto isoparaflins a substantial proportion of the fraction charged and to produce simultaneously a substantial yield of isobutane. The use of superatmospheric hydrogen pressure is of con- 'siderable importance in eiecting hydrocarbon i desiredI products, but also results in a substantial conversion of the catalyst into a sludge-like material with relatively low catalytic activity.

Continuous destructive hydrogenation of naphtha may be eiected by passing the naphtha through a reactor'where it may be subjected to contact with hydrogen, hydrogen chloride, and aluminumv chloride or a` mixture of aluminum chloride with a member selected from the group of so-called Friedel-Craftsv catalysts consisting of `ferric chloride, zinc chloride, zirconium chloride,7 and boron uoride. Or, the destructive hydrogenating catalyst may consist of a so-called Friedel-Crafts catalyst selected fromthe group consisting of ferric chloride, Yzinc chloride, zirconium chloride, and boron fluoride.

To the hydrocarbon fraction being treated it is preferable to add an amount of hydrogen chloride usually Within the llimits of O.5-10% by weight of said hydrocarbon fraction,`since continuous operation may otherwise remove small but desirable amounts of hydrogenchloride often present as impurity in substantially anhydrous aluminumchloride available commercially. Because ofthe shorter time of contact of the hydrocarbon fraction with the catalyst in such continuous conversions, the operating temperature y used isy generally higher than that required to effect a similar change in batch operations. After lsuch treatment which may be. in liquid, vapor, or mixedphase, depending upon the hydrocarbon treated and the'temperatureand pres- A sure conditionsv employed,` the hydrocarbon material may be removed from the catalyst and Vfractionally distilled to separate selected fractions of conversion products while unconverted or incompletely converted fractions comprising essentially `those boiling abovehexane may be subjected to` dehydrogenation to form olenic hydrocarbons utilizable in alkylatingv isobutane formed in the destructive hydrogenation step of :fthe process as hereinabove set forth.

l Destructive hydrogenation products boiling above butanes may `hexane mixture and-a higher'boiling'substantially saturated fraction containing heptanes and higher l boiling lparaiiins. heptanes and higher subjected to contact with a dehydrogenating cat- Lalyst preferably in thefpresencae-o'i` from about per centof water vapor at be separated into a pentane- Said fraction containing boiling parafns may be 0.1 `to about 10 mole a temperature between about `800 and l200 F. 'under a. pressure-'of present Yin the fraction'Y so" aromatic hydrocarbons. It a hydrogen-containing gas from ,substantially atmospheric to approximately :150,.poundsl per square :inch to vform a product containing a substantial .proportion of normally liquid olens.

- thenic hydrocarbons ,subjected to dehydrogenation may be 'converted simultaneously into iis preferable to have -piesent inthe mixture -being contacted with the .dehydrogenating catalyst whichfrnay comprise a composite of a substantially inert carrier selected from the group consisting of alumina, magnesia, silica, thoria, titania, zirconia, and zinc oxide, and a relatively smaller proportion of an oxide of an element selected from the members of the left-hand columns of groups V and VI of the periodic table consisting of vanadium, columbium, tantalum, chromium, molybdenum, tungsten, and uranium.

The carriers or supports above referred to have relatively low catalytic activity while the oxides of the elements mentioned, which may be used singly or as mixtures, are of relatively high catalytic activity and furnish by far the greater proportion of observed catalytic effects. The oxides cf these several elements vary in any given reactioncomprised within the scope of the invention, this variation may be greater in the case of different types of dehydrogenation reactions.

The isobutane obtained by destructive hydrogenation of the naphtha or other hydrocarbon I fraction charged may be alkylated by the normally. liquid olefins formed in the dehydrogenating stage of the process. This alkylation may be carried out in the presence of a suitable catalyst such as sulfuric acid, hydrogen fluoride, aluminum chloride with hydrogen chloride, and boron fluoride with hydrogen uoride at some temperature between about *-15 and 210 F. under suicient pressure to maintain in liquid phase a substantial proportion of the isobutane present. In general from approximately 4 to about 20 molecular proportions of isobutane or other isoparaim should be present in the reaction zone for each molecular proportion of olen introduced thereto tol avoid polymerization reactions.

Alkylation of isobutane-by a normally liquid c-len formed` as hereinabove set forth may be carried out also in the presence of a phosphoric acid-containing catalyst conveniently employed in the form of a solid mixture or granular precalcined composite with a generally siliceous adsorbent such as diatomaceous earth. Such a preferred composite alkylating catalyst is the socalled solid phosphoric acid catalyst found useful also in polymerization reactions and described in U. S. Patent No. 1,993,513 and others. In the presence of this phosphoric acid-containing material, isobutane and otherisoparains may be alkylated vby oleiins at a temperature within the approximate limits of 600 and 900 F.

under a pressure between about 1000 and about 3000 pounds per square inch to form a product containingxa substantially saturated alkylate of relatively high antiknock value.

These diierent alkylating catalysts, which may be usedalternatively, are not necessarily equivalent in their, action, and the conditions of temperature,vpressure, and time employed for any -given alkylation are determined byrthe catalyst,

thecompositionof the reaction mixture, and by other factors. l

For the purpose of illustrating the combination of `steps characteristic of the presentk invention, the attached drawing shows diagrammatically a typical processiiow for treating paraflnic and/or `naphthenic hydrocarbon fractions to produce Vsubstantial yields of isobutane, a mixture'ofl branched chain pentanes and hexanes,l and a higher boiling fraction which may -be catalytically dehydrogenated to oleflns utilizable in alkylating' said isobutane to form 'a substantia ly saturated alkylate of high antiknock value.'I

Referring to the drawing, a naplitha fraction 'of relatively low antiknck value A:comprising essentially paraillns and naphthenes substantially free from olefins and/or aromatics may be introlimits of 300 `and 2500 pounds per square inch. Destructive hydrogenation zone z maycontain mixing devices of suitable design for effecting con- 100 and 500 F. and preferably under a superatmospheric pressure within the. approximate tact between the hydrocarbons and the aluminum'I chloride-containing catalyst consisting of aluminum, chloride sludge formed in the process recycled through lines I and 8 and fresh aluminum chloride introduced through line 3 to destructive hydrogenation 4zone 2 or alternatively through line 4 to line I, already mentioned.

The products of destructive hydrogenation may be Withdrawn from zone 2 through line 5 to separation zone 6 which may comprise settling, stripping, and fractional distlling equipment of adequate design for separating a used aluminum chloride-containing sludge, a gas containing hydrogen and hydrogen chloride, an isobutane fraction, a mixture comprising essentially'branched 1 chain pentanes and hexanes, and a higher boiling `fraction of relatively low yantilmock value. From lseparation zone 6 the used catalyst sludge may be directed through line 1 to storage, reactivation,

or other treatment, or, if desired, a portion of the used aluminum chloride-containing sludge may be recycled from line 1 through line 8 to line I, already mentioned, through which a mixture of fresh naphtha and a gas containing hydrogen and hydrogen chloride is being conducted to destructive hydrcgenation.

Said gas containing hydrogen and hydrogen chloride separated from the destructive hydrogenation products may be directed from separation zone 6 through line 9 in which it may be commingled with fresh hydrogen chlorideadmitted from an outside source through line l0 and thence introduced to line I, already mentioned, through which naphthav is charged to de-4 spectively, as hereinafter setforth.

'Unconvertedlfnaphtha .and products boiling higher than hexanes which may be referred to. as Cv and higher hydrocarbons may a be conducted -from separation zone 6 through line I5,

Vtherein commingled by way of line 2| with hydrogen and light gases formed in the process as hereinafter set forth, and thence admitted to dehydrogenation zone 'I6 Whichmay comprise a reactor. or group of reactors containing a suitable dehydrogenating catalyst as aforementioned and maintained at a temperature betweenvabout 800 and about 1200 F. under a pressure of from substantially atmospheric to approximately 150 pounds perfsquare-inch. Under these conditions normally liquid parailinic hydrocarbons present may be dehydrogenated to the corresponding normally liquid volei'lns while naphthenic hydrocar- .bons may fundergo conversion to aromatic hydrocarbons.

If desired, propane being discharged through line I3 may be directed through alternative line II to corn-mingle with the mixture being subjected `to dehydrogenation in zone I6. The total product may be discharged from dehydrogenation zone I6 through line I8 to separation zone I9 which may comprise absorbing and stripping equipment of'adequate design for separating a mixture of hydrogen and light gases, such as methane,ethane, etc., from higher boiling and generally normally liquid hydrocarbons contain-l ing olenns formed by dehydrogenation in zone I6. as hereinabove set forth. Said mixture of hydrogen and light gases may be directed from separation zone I9l through line 20,to line 9, already mentioned, through which hydrogen, hydrogenchloride, and light gases are being recycled to further use in destructive hydrogenation zone 2. A portion of said mixture of hydrogen and light gases being directed through line 20 may be conducted. therefrom through line 2l to commingle with said unconverted naphtha and products boiling higher than hexanes being conducted to dehydrogenation zone I6.

` Said hydrocarbons containing olens separated in separation zone I9 from a mixture of hydrogen and light gases may be directed through line 22 and therein commingled with isobutane,

or another isoparailin, being conducted from separation zone 6 through line I4, already mentioned. The resulting commingled mixture maybe directed from line 22 to alkylation zone 23 which may comprise a suitable reactor provided with adequate agitating, cooling, and/or heating `devices for maintaining the uniform temperature preferable for alkylation in the presence of a catalyst I and 210 F. Means not shown may be provided for adding fresh catalyst and for removing used catalyst during the-course o f the aforementioned alkylation reactions, Also alkylation of isobutane by normally liquid olefins may be effected in the presence of a prealcinedv composite of an acid of` phosphorus and a generally siliceous adsorbent in a reactor or plurality of reactors containing the granular catalytic material and operated at 'a temperature between about 600 and 900 F. under a pressure within the approximate limits of 1000 and 3000 pounds per square inch.

Normally liquid products formed by such a1- kylation and admixed with unconverted isobutane and with normally liquid hydrocarbons boiling above hexane which were not dehydrogenated in zone I 6 may be discharged from ,alkylation zone 23 through line 24 to separation zone 25 which mayA comprise fractional distilling equipment of adequate design for separating a substantially saturated and alkylate-containing motor fuel from unconvertedisobutane and lighter gasessuch as propane which may be present when this gaseous hydrocarbon is admixed with the liquid hydrocarbons being subjectedto dehydrogenation as hereinabove set forth. Said unconverted isobutane may be recycled from separation zone 25 through lines 26V and 22 to further alkylating treatment. 'Ilhe motor fuel fraction containing of the invention:

urated hydrocarbons not dehydrogenated in zone I6 and presentin said motor fuel may be separated from thealk'ylation product in separatingv zone'25 and thence yrecycled by means notv shown to further dehydrogenation treatment in Zone i6 in' order to provide sucient normally liquid olefor alkylating substantially al1 offthe iso-v butane derivedfrom the 'primary destructivel hydrogenati'on step of the process. f y' Y The following specific example is presented. as

illustrative off the process as it maybe conclueted, using ai process iloW'as hereinabove described, al-

though this 'illustrative material should. not`V be miscoristr'ued to limit the'y generally broad scope A substantially normal 'paraffin hydrocarbon vention and particularly its commercial value are evident from the preceding specification `and limited numerical material presented although I claim as my invention:

. 1. A process for converting asubstaritiall'y7 satrated hydrocarbon fraction of motorfuel boiling range and relatively low antiknock value into a .substantially 'saturated motor fuel of improved antiknock value [which comprises treating said hydrocarbon fraction, with aluminum chloride, hydrogen, andhydrogen chloride to produce sub-- stantial yields'offisobutana a fraction containing .branchedilchainh.pentanes and hexanes.. and `a higher boilinghydrocarbon fraction; catalytically dehydrogenating',saidlhigher boiling hydrocarbon fraction ".toform a dehydrogenation product containing a substantial. proportion of normally` liquid. olefins; andsubjecting said isobutane and "said dehydrogenationproduct to catalytic alkylafraction containing 2% by volume of hexane, 10%

'.heptane, 13`% octa`ne', 25%nonane,` 20% decane, undecane, and 10% by volume of. higher boilinghydrocarbons may be heatedat 165" F. in

the presence of hydrogen undera pressure of l 1600 pounds per square inch'iand in the presence of 10% by weight of aluminum chloride and 1.2% by Weight of hydrogen chloride, The products of this treatment may consist of 25.8%by weight of isobutane; 24.5% of a pentane fraction ywith 85.5 octane number and approximately 90% isopentane'content; 9.7% of a hexane fraction with 80 octane number; 27.2% of a fraction with 5.5 octane number comprising essentially heptanes and higher boiling products; 4.2% of non-condensible gases; 4.9% of hydrocarbonaceous residue; and 3.3% loss.

The fraction comprising essentiallyheptanes and higher-boiling hydrocarbons may-be vaporized and commingled with 'approximately 4 mole per cent of water vapor and the commingled mixture then subjected at 1020 F. under substantially atmospheric pressure to Contact with a composite comprising essentially 8% by weight vof chromium sesquioxide and 92% by Weight of activated alumina to form a product containing substantial proportions of normally liquid olens.

Isobutane derived from destructive hydrogenaltion of the parafnic fraction charged may be'alkylated by said normally liquid olefins in the presence of sulfuric acid of 95% concentration at 45 F. under a pressure of200 poundsl per s quare inchl to form a substantially saturated alkylate admixedwithheptane and higher boiling hydrocarbonsremaining-unconverted after the original treatmentV with the chromium sesquioxide-alumina catalyst. Av sufiicient proportion*v ofv said heptane -and higher boiling hydrocarbons maybe separated from said motor fuel by 'fractional distillation and thenA recycled tofurtherrdehydrotionftoform a' substantially saturated alkylate comprising essentially hydrocarbons of motor fuel boiling range and high antiknock value.

2. A process for convertinga substantially sat- *urated hydrocarbon fraction of motor fuel boiling range and relatively low antiknock value into a substantially saturated motor fuel of improved antiknock value which comprises treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen chloride at a temperature between about 100 and about 500 F. under a pressure within the approximate limits of 300 and`2500 pounds per square inch to produce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher bolling hydrocarbon fraction; catalytically dehydrogenating said Vhigher boiling hydrocarbon fraction to form a dehydrogenation product containing a substantial proportion of normally liquid olens; and subjecting said isobutane and said dehydrogenation product to catalytic alkylation to form a substantially saturated alkylate comprising ,essentially hydrocarbons of motor fuel boiling range and high antiknock value.

3. A process for converting a substantially sat'- urated hydrocarbon fraction of motor fuel boiling range and relatively low antiknock value into a substantially saturated motor fuel of improved antiknock value which comprises `treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen chloride to produce substantial yields of isobutane, a fraction 'containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction; subwith a dehydrogenating catalyst at a temperature between about 800 and about l200 F; under genation to produce oleiins necessary for alkylating substantiallyall of the isobutane produced in theprimary destructive hydrogenation step.

Thus by combining destructive hydrogenation, t dehydrogenation, and alkylation it is possible to obtain approximately 34% by weight of ja pentane-hexanefraction of approximately 84 octane number, 45 `by weight of a substantially saturated alkylate of gasoline boiling range and 90 octane'numloer,y and 10% by Weight of a higher boiling residue from anaphtha fraction of relatively low antiknock value.

The character of the process of the present ina pressure offrom substantially atmospheric to approximately 1 50 pounds per square inch to form a; dehydrogenation product containing a substantial proportion of normally liquid olefns;

and subjecting said isobutane and said dehydrogenation product to `catalytic alkylation to form a substantially saturated alkylate comprising essentially hydrocarbons of motor fuel boiling range and high antiknock value..

4. Aypioces's for converting a substantially saturated hydrocarbon fraction of motor fuel boiling range and relatively low antiknook value into a substantially saturated motor fuel of improved antiknock value which comprises treating said hydrocarbon fraction with aluminum chloride,

hydrogen, `and hydrogen chloride at a temperature between about and about 500 F. un-

`der a pressure within the approximatev limits of 300 and 2500 pounds per square inch to produce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction;

vsubjecting said higher boiling fraction-,in the presence of from about 0.1 to about mole per cent of water vapor to contact with a dehydrogenating catalyst comprising essentially a major proportion of a substantially inert carrier and a relatively smaller proportion of an oxide of an element selected from the members of the left-hand column of group V of the periodic table consisting of'vanadium, columbium, and tantalum to form a dehydrogenation product containing a substantial proportion of normally liquid olens; and subjecting said isobutane and said dehydrogenation product to catalytic alkylation to form a substantially saturated alkylate comprising essentially hydrocarbons o1' motor fuel boiling range and highantiknock value.

5. A process for converting a substantially saturated hydrocarbon fraction of lmotor fuel boiling range and relatively low antiknock valueinto a substantially saturated motor fuel of improved antiknock value which .comprises treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen ychloride at a temperature between about 100 and about 5009 F. under a pressure within the approximate limits of 300 and 2500 pounds per square inch to pro- -duce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction; subjecting said higher` boiling fraction in y the presence of from about 0.1 to about 10 moleI percent of water vapor to contact with a dehydrogenating catalyst comprising essentially a major proportion of a substantially inert carrier and a. relatively smaller proportion-of an oxide of an element selected from thev members of the left-hand column of group VI of the periodic table consisting of chromium, molybdenum, tungsten, and uranium to form a dehy-l drogenaton product containing a substantial proportion of normally liquid olens; and subjecting said isobutane and said dehydrogenation product to catalytic alkylation to form a substantially saturated alkylate comprising essentially hydrocarbons of motor fuel boiling range and high antiknock value.

6. A process for converting a substantially saturated hydrocarbon fraction of motor fuel boiling range and relatively low antiknock value into a substantially saturated motor fuel of improved antiknock value which comprises treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen chloride at a tem- Derature between about and about 500 F. under a pressure within the approximate limits of 300 and 2500 poundsper square inch to produce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction; subjecting 4said higher boiling fraction in the presence of between about 0.1 and 10 mole per cent of water vapor and a hydrogen-containing gas derived from the process to contact with a dehydrogenating catalyst comprising essentially a major proportion of a substantially inert carrier and a relatively smaller proportion of an oxide of an element selected from the members of the left-hand column of group VI of the periodic table consisting of chromium, molybdenum, tungsten, and uranium to form a dehydrogenation product containing a substantial1 proportion of normally liquid olens; and subjecting said isobutane and saiddehydrogenation product to catalytic alkylation to form a substantially saturated alkylate comprising essentially hydrocarbons of motor fuel boiling range proved antiknock value which comprises contin.

uously treating said hydrocarbon fraction with aluminum chloride, hydrogen, and hydrogen chloride to produce substantial yields of isobutane, a fraction containing branched chain pentanes and hexanes, and a higher boiling hydrocarbon fraction; simultaneously catalytically dehydrogenating saidv higher boiling hydrocarbon fraction to form a dehydrogenation product containing a substantial proportion of normally liquid olens; and continuously subjecting said isobutane and said dehydrogenation product to catalytic alkylation to-form a substantially satu rated alkylate comprising essentially hydrocarbons of motor fuel boiling range and high antiknock value. f

8. A process for producing anti-knock motor fuel from substantially saturated hydrocarbon oil, which comprises subjecting the oil to catalytic destructive hydrogenation such as to produce a substantial quantity of isobutane, separating from the resultant products an isobutane fraction and a fraction higher boiling than hexane, subjecting the last-named fraction'to catalytic dehydrogenation to form normally liquid olens, commingling the latter with said isobutane fraction, subjectingthe resultant mixture to catalytic alkylation to react olefins with isobutane and recovering the resultant alkylate.

RAYMOND E. SCHAAD.

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