US2404591A

US2404591A - Preparation of aromatic hydrocarbons from hydrocarbon mixtures

Info

Publication number: US2404591A
Application number: US539006A
Authority: US
Inventors: Ernest A Naragon
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1944-06-06
Filing date: 1944-06-06
Publication date: 1946-07-23
Anticipated expiration: 1963-07-23

Description

July 23, 1946. E. A. NARAGON 2,404,591

PREPARATiON 0F AROIA'I'IC HYDROCARBONS FROIHYDROCARBOK MIXTURES I Filed June 6, 1944 2 sheets-sheet 1 AROMATIC PRODUCT HIGH aouuuq HYDROCARBONS PARAFFI N l3 HCL. RECYCLE AROMATICS IN ENTOR ER EYANARAGON Patented July 23, 1946 UNITED, STATES PATENT mm;

' PREPARATION oF AuoMA'rIo HYDROCAB- BoNs FROM HYDROCARBON MIXTURES Ernest A; Naragon, Beacon, N. Y., assignor to The Texas Company, New

of Delaware Ami fi We ,9, Claims.

This invention relates to the preparation of aromatic hydrocarbons from hydrocarbon mixtures and particularly from naphtha hydrocarbon mixtures.

The invention involves separation of aromatic hydrocarbons, particularly aromatics of higher molecular weight than'toluene; from hydrocarbon mixtures containing them and converting the separated hydrocarbonsinto aromatic hydro-' carbons of improved character for motor fuel manufacture. "In accordance with the invention, aromatic hydrocarbons, such as xylenes or arcmatic concentrates separatedfrom naphtha, are subjected to the action of an aluminum halide catalyst so as to effect reforming or transforming intoaromatics-which have a greater blending value for gasoline. v r r i More specifically, anaromatic hydrocarbon such as ortho Xylene which has a; blending I. M. E. P. (indicated mean effective pressure) value of 0, is isomerized to give a blending value of 320 which is to be compared with a-similar blending value of about244 for iso-octan: Like wise, an aromatic concentrate, boiling within the range of about 212-300" FQ, separated from by droformed naphtha and having a' blending value of about 1'70 may be subjected to the action" of an isomerizing catalyst so' as toproduce a producthaving a blending value of about 231.

An effective catalyst forthis purpose is tained by reacting aluminum chloride with kerosene in the presence of hydrogen chloride at a temperature of about ZOO-250 so' astoproduce a complex having a heat of hydrolysis of around 290-330 small calories pergram of com plex.

the action of such complex catalyst in the presence of hydrogen halide promoter at temperatures ranging from' IOU-300 F. and preferably about 180-220 F. such that the hydrocarbons undergo reforming, in which isomeri zation is one of the principal reactions involved in increasing the blending value of the aromatic hydrocarbons undergoing treatment.

A complex'catalyst of the? foregoing character is effective as a solventifor'extracting aromatic hydrocarbons from mixtures containing them alu-i minum halide-hydrocarbon" complex such as 'ob-i The aromatic hydrocarbonsare subjected to York, N. Y., a corporation:

"1944, Serial No. 539,006

the aromatic from the wash solvent by di'stilla-' tion.

If it is not required to isolate the treated are matics, the washsolvent may have a boiling range withinthat of thetreated aromatics,}

The wash solvent may be a paraflin'hydr 'oca'r-f bon, mixture of parafiins', a""naphthene hydro-'f carbon} mixture of na 'phthenes, or a mixture ofparaffin and naphthene hydrocarbons.

IO. The invention thus contemplates the resulting extract, comprising aromatics dissolved in complex, may'then be exposedto"coriversion conditions so that the dissolvedaromatic hydrocarbons undergo isomerization or "other re--' Thereafter theconverted hydrocarbons may be separated fromforming conversion reaction.

the complex either by'dist llation or by washing with a suitable washjsolvent.

'neously and in v a continuousfmanner an m -a;

described,

tinuously displaced from with or 'without washing carbon such pentane.

a thereaction zone either separate reaction zone to ;efiect convers'ion of dissolved aromatic hydrocarbons.

Figure 3" illustrates a 1 thre e-stage process wherein an aromatic concentrate is obtained in an extract stage, the resulting solutionbf f-aro-j matics incomplex liquid passed" toa; reaction stage and'from there toa'final stfage wherein the aromatic products are washed from thecomplex'fi Referring now to Fig. 1, an aromatic hydrocarbon such as ortho xyleneis conducted from a source hotshownthrough a pipe! andpas'sed through a heater or" heatexchanger 2 wher it is heated to a temperatureof about180 210f Theh eatedstream'is-thenco d cted'through a:

pipe 3 to the lower portion of a verticalreaction tower 4. g

The tower 4 contains-a column of aluminum chloride-hydrocarbon complex-having a vheat of an hydrolysis of about 320'ca1ories. per'gram?of,com-

I 7 employin the aluminum halide-hydrocarborr' -co n'i1:v1exf.- in the dual capacity oi reforming catalyst and ex traction solvent. "Thus, aromatic hydrocarbons maybe extractedfrom afaaphthagmixmre-a u It is contemplated that theextraction and conversion reactions mayIbe carried out"sinuilto} singlereaction tower. th;e other' hand} the extraction and conversion reactions may be-"c'a'rried out in separate zonesaswill be hereinaite'r I the accompanying drawings illus trates a method of o peration wherein aromatic hydrocarbons are continuously subjected to coni tact with the catalyst under conversion condij tions and the resulting aromatic productscon tioniwith complexliquid in anextraction' zone; and the resulting extract solution lpassedtb a plex. Advantageously, the complex liquid column is maintained in a'substantially static condition, without mechanical agitation, and may have a 1 '-height ranging from about to feet.

The feed hydrocarbons are injected intothe bottom of the liquid catalyst columnin dispersed. form and the dispersed hydrocarbons tend to rise through 1 the catalyst column by difference in density.

A The catalyst column is maintained at the fo regoing reaction temperature of about ISO-210 F. 1 efiective for converting ortho xylene into'meta f and para xylenes as well as other valuable aro-' matic hydrocarbons.

A small amount of hydrogen chloride promoter is continuously added" from a" source not shown and introduced through a pipe 1 leading to the;

p pet:

The aromatic hydrocarbons-are thus exposed to the catalyst in the presenceof thepromoter which latter-may amount. to from 0.5 to 5.0% orfrom 4 which is removed through a pipe 22 and a residual fraction comprising high boiling hydrocarbons which is removed through apipe 23; This latter fraction may be recycled through a pipe 24 to the reactor 4. r

A continuous tower operation as illustrated in Figure 1 may be carried out without the wash solvent, since the treated aromatics will rise about 2.'0 -to 3;0%'by weight of the aromatic hydrocarbonundergoing treatment. Make-up-alw minum chloride maybe addedintermittently'or continuously in small amount so asto maintain the catalystliquid-at the: predetennined-level of i activity.- The aluminum chloridemaybe added 3 as'a solution oras aesuspension in a portion of A 1 the aromatic feed stream. 7

carbon, suchasnormal pentana-is continuously recycled through-the system as will bedescribed and enters-the reactorl-4 throu gh a pipe 8 communicatingwith the pipe 3; The pentane is introduced to thereactor-in the proportion of about, 1v to'3-parts :by volume of'pentane -to one volume of aromatic feed hydrocarbon; The pentane 3 strearrn-also-maybe used for introducin make-up-aluminum'chloride.

-;.The aromatic-' hydrocarbons andpentanerise the j through-the catalyst column-and accumulate in, v

the-top of-thereaction-vessel. The paraflinhydrocarbon may undergo'some f conversion but the extent of such conversion islimited-due. togthe inhibiting effect' of the-'arof :matic hydrocarbons present, In other words,-

aromatic hydrocarbons substantially j inhibit isormerization of normal paraffins-under the con-- ditions: prevailing: within the reactor :3.

The effluent hydrocarbon stream containing through a pipe I0 to a, fractionator or'strip'pcrgi l wherein the promoter is stripped from the-hydrocarbons; The= promoter-gas is: removed I lthrough a. pipe l2- and recycled .all orlin part through apipe I3 communicatingwiththe prev lviouslymentioned pipe 3. 7 V I The hydrocarbons from which. thepromoter hasbeen removed are conducted through apipe L ld to a fractionator; l5.wherein apentane-fraction is continuously removed as a distillate frac- ;tion through a pipe [6 andcooler I1; 'Ihepentane fraction so-removedis conducted through a pipe l8 -and may be recycled all or in ,part through the previously mentioned pipe 8. How- ;eVer-in the absence-of the wash solvent, the fracftionator |5'may/ be by-passed by conducting the hydrocarbon stream from the stripper i I through v pipe Hatoithe fractionator 2i. p g I The residual hydrocarbon fraction comprising aromatics is conducted from the fractionator- Hi through a pipe 20, or from the stripper i I through pipe; Ma to a fractionator 2| wherein it maybe separated'into fractions as desired; for example,

'itlmay be separatedzinto a' distillate fraction 6:)- converted 'aromaticsgis: continuously drawn .off

:through the foolumn-tof liquid by difference in density. The complex catalyst is thus maintained saturated with aromatics and even though 7 saturated, retains substantial activity for isomerizing and reforming aromatic feed hydrocarbons.

' The saturated complex contains approximately equal volumes of free aromatics and complex.

,Referring now to Figure 2, 'a naphtha mixture or a mixture of' aromatics and ,paraflins is con". ducted'from a source'not shown through a pipe V i-t is brought and a heat exchanger 3| wherein to a temperature of: about 70-100 The mixturethen flows through apipett-tothe bottomof an extractiontower-33 whereinit' is subjected to countercurrentcontact with a body of aluminum This -complex-may' be; used. complex such asis drawn off' from the subsequent conversionreaction. It is introduced into the top of the tower:v

through a pipe 34.

As' the feed hydrocarbons risethrough the tower 33, aromatic constituents aredissolved-in the complex. The undissolved non-aromati'c hydrocarbons rise-to the topof the tower and are continuously removed therefromthrcugh a pipe 7 35 and cooler 36.:

v undergo conversion;

A stream of paraifinhydrocarbon such'as pen- 7 tane-is likewise introduced continuously to the reactor'AG so as to subject the complex t eontinuous washing and thereby effect displacement of 'theearomatic hydrocarbon product from the complex. I I I The hydrocarbon products are continuously drawn oif from the top of the reactor through a pipe 4|; 1 r

.The pipe il advantageously leadsto afractionating systemsuch as is: illustrated in Figure ii 1;

The fractionating system may comprise astripper for stripping the promoter whichis then recycled through a pipe 'I3. as in Figure 1. Likewise, the parafiin hydrocarbon is separated from' the products and recycled through a pipe8.

Referring to Figure 3, a hydrocarbon mixture containing aromatics is drawn from a zone not shown through a pipe and heat exchanger 5|;

' The heated mixture then passes into the bottom to countercurrentcontact with a body of complex liquid as in the case of extraction tower 33 of Figure 2. i 1 7 Temperature conditions are maintained so as to dissolve the aromatic hydrocarbons and thus chloride-hydrocarbon complexv 7 characterized .by having a heat of hydrolysis of about 290 to 330-calories per gram of complex of an extraction tower 52"wherein it is subjected patingr 'system such as described'in Figure 1-. r

5 extract them from J the non-aromatic Jhydrocan-m bons. The latter are continuously discharged from the top of thetower through a pipe. 53 :and I cooler "54;; II j The resulting solution of aromaticsin: com- 5 plex is drawn ofi fromthe bottom of the tower 52 throughva pipe 55: to a reaction vessel 56. Hydrogen chloride :promoter. may be introduced from: asource not shown througha pipe 51-.

Thereaction vessel 56 is maintained at an ele-i vated temperature adapted :toefiect isomerization of aromatic hydrocarbons. 'The products of V conyersion,iincluding catalyst, are continuously v drawn off through the pipe 51 to awash towerf 58 wherein the mixture of complex catalyst and aromatic, hydrocarbons is subjected: to countercurrenticontact with a body-of paraffin hydro carbons a, such as pentane. Thus; the complex mixture enters the upper portion of the wash tower 58 while the stream of 'normalpentane is continuouslyl introduced :to the to lower portion thereof. through pipe 59;in the proportion of about 1 to 3 volumes per volume-of complexmixture; Thelzwashing is effected. atla temperature of about 1100:1509 so as to continuously displacearomatic" hydrocarbonproducts from the complex catalyst; z 1 a The 2 aromatic. products are continuously, dis; charged through a pipe 60 leading to: a fractioninl ywasheds complex substantially free from aromaticsis drawn :ofi. i through =a5pipe 6I. and recycled all orfin partthrough a pipe fiz' leading i tothert'opxof. thezextractorbl; Soniefof the com plex 'mayxbelrecycled directly. througha bran'ch pipe 6 3.to the ractor5fi'; 13,; A Int order to maintain the activity hr thecomplex catalyst; additional aluminum lialideis added to the system jthrough a pipe 6.4; such addition being-made in somewhat the. samem'annerias has been described in. .connectionwith Figure 1...

vProvision maybemade for recycling recovered promoter and wash solvent also as.:described in Fi ure 1.5. I a 1 l r n. Y Example! A quantity of orth'o' xylene was charged ltd a reaction vessel, together with aluminum chloride; hydrocarbon complex in the proportion" of 2 vol-,5 umes' of complex to '1 volume of hydrocarbon; Hydrogen chloride was added to'the extent of.2% by weight of the total charge; The resulting mixture was maintained at a temperature of 210 Frandunder-pressure'ranging from 43 to '10. pounds-for a periodof about .30 minutes 'I 'he. complex catalyst was -characterized by having a heat of hydrolysis of about 320 calories per gram; The hydrocarbons were separated from the catalyst, and thatportion free froznCeand lower hydrocarbons was found to havethe following composition: y M V I V Percent by volume Hydrocarbons boiling below benZ n6- '7 Benzene; Toluene Meta and para xylenes,and ethyl benzenm--- 3.L Orthp l l fi' -ir-r-r?-' -:-1 8 (39.1112

1o Res d :--t-,--.-

'1 Apparentlyprincipally mesitylene r il A quantity of ethyl benzene was charged to a--reaction vessel,':together with analuminum chloride-hydrocarbon complex in the samepro-" Per cent by volume Apparently all ethylbenzene r 1 Mariam ,Ir l t tam er 'l ff a l the j following volume percent com Meta and p miyhhs; ethyl benzeneconcentrate was mixed,' thcoiilple'x of about the same character andin thef'sarne 5mportions as ExampleII; The reaction was" carried; cut i'n thepresence of a similar amount of pr moter at a temperature of 210 Fkfor 30 niinut'es, the pressure ranging from about 20 to 31pounds f :The liquid productsiafter removal of Cl and lo hydrocarbons were ofthe following composition.

per-cent by Volume" Hydrocarbons boiling below benzene.

a In eachofthe foregoing examples the hydroe.

carbon products were separated from the'comple'x by distillation at reducedpressure; It will be ob.- 7

served that in Example I the orthoxylene was H isomerized to produce a substantial yield of a; fraction comprising meta and para xylenes and ethyl benzene. In addition, thepe fraction ap parently consisted principally of Inesitylen e.

It will be noted in the case of Example III that the ortho xylene content of the concentrate was reduced from 2lxfto 6% with'the formation'fojrfl benzene, toluene, "meta and para xylenes and mesitylene etc. V

In the following example orth xylene was' treated with a complex catalyst under ,substah tially the same conditions as used in Example I At the end of the reaction, the reaction mixture of catalyst and hydrocarbons was subjected to extraction with normal pentane at aternpe'rature or about 70 F. so as to separate the aromatic hydrocarbon from "the complex"catalyst; "The sepa' rated hydrocarbons after removal of C5 andlow'er hydrocarbons had thefollowing' composition z the reaction tower.

.Mention has been made of using aluminum chloride-complex as the catalyst. However, it is contemplated thatother aluminum halide isom- 1 eriz ation catalyst such as aluminum bromide may also be used. H Other hydrogen halide promoters besideshydrogen chloride may be used.

Also other'wash solvents besides normal pentan'e 1 may be employed. Such other solvents ma com-f prise liquified' normally gaseous parafiin. hydro,-. carbons or normally liquid hydrocarbons of highermolecular weight than pentana Organic halides such as CCl and CHCla. maybe used as Wash solvents. I

' Reaction temperatures ,of. about 210 F. have 'beenementioned. in the examples but it ne n templated that other temperatures may be 'em-;

ployed, dependin upon the activity of the'cataly'st, the character of the aromatic hydrocarbons undergoing treatment, andthe extent of conversio'n desired; Thus, temperatures ranging from Iroom temperature up to 300"F.'may be employed,

althoughtemperaturesranging from 180 to about 220F, are preferred. V

The'complex catalyst may havea heat of hydrolysis ranginggfrom .about'2 70 to 350 small calories per' gram of complex, although aheatiof' hydrolysis in the range of about 290 to 330 is preferred. The activity of the catalyst should be such that the eflluent strearn of hydrocarbons will be substantially 'free from aluminumhalide.

A reaction time of minutes has been referred to in the examples, but a reaction time substantially below this maybe used in a continuous flow system in which case the hydrocarbon residence within the reaction tower may be a matter of several minutes.

Complex catalyst will form in situ as a result 7 of 'reactionbetween added aluminum halide and a small proportion of thearomatics undergoing treatment. Therefore, the rate of halide addition is controlled by observing the heat ofhydrolysis l ,of the complex catalyst fromtime to time during continued operation. Provision is made for withdrawal of a small portionof used complex from Advantageously, used complexis withdrawn from an upper portion of the tower while make-up aluminum halide is added to the lower portion. Provision is also made for adequate space in the top of the reaction tower to effect disengagement between thehydrocarbon' phase and the catalyst phase.

Thus, while complex formed by reacting with kerosene has been mentioned at the outset, nevertheless, it is contemplated that the complex employed inthe system during continued operation may consist essentially of that formed by reaction between the halide and aromatics. Sufficient aluminum halide is added to the system to maintain the complex at the desired level ofactivity,

i. e., having a heat of hydrolysis'in the range about 290-330 calories. i

It alsocontemplated that provision ma be made for'effecting the extraction steps of Figs. 1 2 and, 3 in'the' presence'of a small amount of promoter-sufiicient. to pre vent. the complex from.

becoming too vi'scousaz 1 i The term reforming asused herein isfcontemplated as including reactions other than isom.- j erizationsuch ascracking; alkylation, alkyl exchange, etc. These rfeactionsmay occur simultaneously with i'somerization, although isomeriza-l 1 tion is regarded as a principal reaction.

' Obviously many modifications and variations of' the invention as hereinbeforexset forth maybe made without departing from the spirit and scope thereof, and therefore; only such limitationsshould be imposed as arfejindicated in-the ap-' pended claims. Iclaim: x

l; A process for: improving the blendingvalue of an aromatic-rich naphtha by isomerization of aromatic constituents whichjcomprises subjecting a fraction of said naphtha boilingin the range of 'abouti-2l2'to 300';F.'to. contact with: an aluminum halide-hydrocarbon complex isomerizing catalyst having a heat, of hydrolysis int'he range of about 270-to 350 calories, and effecting said contactrfor a short period, of'jtime at aitemper'ature-in the rangeabout 180 to 300 F. in metres-1 ence of a small amount of hydrogen halide such that aromatic hydrocarbons containedi therein undergo isomerizationto a substantialextent:

2. A process for-ppreparing-"aromatic' hydrocarbon'sof improved .blendinglvalue by isomer- 1 ization for the manufactureof motorxfuel which comprises separating from naphtha a fraction rich in xylene and" aromatics 0f 1 higher molecular weight than toluene, subjecting said fraction" to contact 'with :analuminum halidef-hydrocarbo stantial extent.

3. A continuous process for isomerizing aromatic hydrocarbons of higher'molecular weight than toluene which comprises continuously injecting said aromatic hydrocarbons into the lower portion of a vertical columnof aluminum chloride-hydrocarbon complex catalyst, liquid havinga heat of hydrolysis in the range of about 270 to 350 calories, dispersing the injected hydrocarbons upwardly. through the column. in the presence of hydrogen halide at. a temperature in the range of about 180 to 300 Fjsuch that substantial 'isomerization, occurs' and continuously 1 removing from the top of the column a hydrocarbon stream containing. .isomerized aromatic hydrocarbons. r V v v 4. A continuous process for isomerizing aromatic hydrocarbons of higher molecular weight than, toluene which comprises continuously injecting said aromatic hydrocarbons into the lower portion of a vertical column of aluminum chloride-hydrocarbon complex catalyst liquid havinga heat of hydrolysis. in therange of about 270 to 350 calories, dispersing the injected hydrocarbons upwardly through the column in the presence of hydrogen halide at a temperature in the range.

of about 180 to 300 F., simultaneously dispersing upwardly through the column a 'low boiling saturated hydrocarbon so as, tofacilitate displacement of aromatics from the complex catalyst, and continuously removing from the upper portion of the column a hydrocarbon stream containing isomerized aromatic hydrocarbons.

5. A continuous process for isomerizing aromatic hydrocarbons of higher molecular Weight than toluene which comprises extracting naphtha containing said aromatic hydrocarbons with aluminum halide-hydrocarbon complex having a heat of hydrolysis in the range of about 2'70 to 350 calories, forming a solution of aromatics in the complex, subjecting said solution in the presence of hydrogen halide to elevated temperature in the range 180 to 300 F. for a few minutes time such that the complex effects substantial isomerization of aromatic hydrocarbons, washing resulting complex containing dissolved isomerized hydrocarbons with a low molecular weight saturated hydrocarbon so that aromatic hydrocarbons are displaced therefrom and removing the displaced hydrocarbons.

6. A continuous process for isomerizing aromatic hydrocarbons of higher molecular weight than toluene which comprises passing a naphtha fraction rich in said aromatics and containing paraflinic hydrocarbons in countercurrent contact in an extraction zone with a body of aluminum halide-hydrocarbon complex having a heat of hydrolysis in a predetermined range of about 270 to 350 calories, effecting said contact at a temperature such that aromatics are dissolved in said complex in preference to paraffins, discharging undissolved parafiins, passing resulting solution of aromatics in complex to a reaction zone, subjecting it therein to a temperature in the range 180 to 300 F. in the presence of a small amount of hydrogen halide for a period of time ranging from several up to about 30 V 85 amount of hydrogen halide for a short period minutes such that substantial isomerization of said aromatics occurs, passing the so-treated mixture of hydrocarbons and catalyst to a separating zone, subjecting said mixture therein to countercurrent contact with a low boiling saturated hydrocarbon at a temperature in the range of about 100 to 150 F. such that isomerized aromatics are displaced from said mixture, separately discharging displaced hydrocarbons and said low boiling saturated hydrocarbon is normal pentane.

8. A continuous process for isomerizing aromatic hydrocarbons of higher molecular Weight than toluene which comprises extracting naphtha containing said aromatic hydrocarbons with aluminum chloride-hydrocarbon complex having a heat of hydrolysis in the range of about 270 to 350 calories, forming a solution of aromatics 10 in the complex, subjecting said solution in the presence of hydrogen halide to elevated temperature in the range 180 to 300 F. for a few minutes time such that the complex efiects substantial isomerization of aromatic hydrocarbons,

washing resulting complex containing dissolved isomerized hydrocarbons with a low molecular weight saturated hydrocarbon so that aromatic hydrocarbons are displaced therefrom and removing the displaced hydrocarbons.

9. A continuous process for isomerizing aromatic hydrocarbons of higher molecular weight than toluene which comprises passing a naphtha fraction containing aromatic and paraffinic hydrocarbons in countercurrent contact in an ex- 26 traction zone with a body of aluminum chloridehydrocarbon complex having a heat of hydrolysis in a predetermined range of about 270 to 350 calories, effecting said contact at a temperature such that aromatics are dissolved in said com-' plex in preference to parafiins, discharging undissolved paraifins, passing resulting solution of aromatics in complex to a reaction zone, subjecting it therein to a temperature in the range about 180 to 300 F. in the presence of a small of time such that substantial isomerization of said aromatics occurs, passing the so-treated of hydrocarbons and catalyst to a separatingv zone, subjecting said mixture therein to counter- 40 current contact with a low boiling saturated hydrocarbon at a temperature in the range of about to F. such that isomerized aromatics are displaced from said mixture, separately discharging displaced hydrocarbons and complex complex catalyst from the Separating zone, 45 catalyst from the separating zone, recycling discycling discharged catalyst to said extraction zone and supplying make-up aluminum halide to the extraction zone to maintain the complex therein at said predetermined range.

7. The process according to claim 6 in which charged catalyst to said extraction zone and supplying make-up aluminum chloride to the extraction zone to maintain the complex therein at said predetermined range.

ERNEST A. NARAGON.