US2388081A

US2388081A - Catalytic isomerization of hydrocarbons

Info

Publication number: US2388081A
Application number: US444505A
Authority: US
Inventors: Anthony E Robertson
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1939-08-12
Filing date: 1942-05-26
Publication date: 1945-10-30
Anticipated expiration: 1962-10-30

Description

30, 5- A. E. ROBERTSON I 2,333,081

CATALYTIC ISOMERIZATION OF HYDROCARBONS Original Filed Aug. 12, 1939 2 Sheets-Sheet l CONDENSfiR FRACTIONAT/NG TOWER PRODUCT OUTLET ATALY T srozac:

EQUALIZ LINE 30 GRT'ALYST IIOPPER rncmcrza INLET l r FILTER sws/v-r aA- LYsT rzz :3 FEED IMLET Wamaw Patented Oct. 30, 1945 UZNiTEE D, STATES OFFICE 2,388,081

omrALr rIcJsoMmzAi-rromor' HYDBOCARBQNS Anthony E. Robertson, Roselle, N. 3,, assignorto Standard Oil Development Company, "a corp Tation or Delaware Original application August :12, :Serial -No, 289,867. Dividedand thisanplication May 26,, 1942, Serial'No. 444,505

4 Cla'ims. (Cl. Em -16835) ,mhislapplication'is a diuisionvof Serial -No. 289,- 867,;flledugust 12, @939. l

, Thisinventionrelates to a process for producing branched hydrocarbons from normal or straight, :chain hydrocarbons.

It is known thatrhydnocarbons in :the ,presence of :certain catalysts, .such :as aluminum chloride, aluminumbromide :and "the like, .are ii'somerized toiproduce :hydroca'r-bons .of :difllerent ;physical and chemical properties (from those :originally conconstructithe apparatus 11581111 .in the :process so as'lto he ableto'carryout the process inf'a continuous manner with .a maximum conversion :of Tith'e ieedzstock duto zhighly 11581111 :products. It is a s'im'ther object of dshe :invention .to :isomerize straight chainzparafhnsscontainingmt?least tour carbon DItOmSJSO :asrto produce maximum practical yields :of branched chain hy drocarbonsrwhich find particularly suitable 'uses as :motor cinel-rconstitnents :or,=mcre n-ecently, as reactants in the alkylation reactions :in-vohiing the reaction ofiisoparafllns with olefinstolzpro duce high (octane :number 'tgasoline petroleum mixtures. l i

rlnzordertoaccomplishthe-nbove specifiednib jects as welltas others which'willlbe:readilyapparentzto rthose cskilled fin the art :upon attainmg ta iuller rrunderstandingfofthe invention to bex-more Iully i-heteina'tter :d'escribed, :n'or'mally liquid straightw'chain rparaffins' lcr nonmally :gaseous straight chain :paraflins which have been isub- :lected' tmsufllcientnpressure totmaintain them in theilinuid .hhase, for example, normalibutane," are conducted continuously :into a .still pot or indirectlyintoaistill colunm from whenoe they rea'ch the-still potuwhere they'am contacted with asuitable tsmnerization catalyst, iior example, f the 3181- ides ofucertainxmetals'of group 1III:oT-the=periodic system, :either rwithlor without smallnmountstoi promoters; leach :as water, Ithe :hyiirogen umn :or .in the :still ;pot, was the case'may be, isomericyparafiinielhydrocanbons are formed which in turn :havaa .lower boi ng @oint than the corresponding :straight chain isomers from which theylare iormed.

,-A more complete understanding of the operation of 117116 zpresent invention can be attained :bY reference to athe accompanying diagrammatic views in .sectional elevation :of two embodiments of the :conoept otathe .present invention. Figmass ,1 and .2 will be more fully hereinafter de-- scribed. V l

one embodiment .of the invention, .pnre straight {chain maraffimhydrocarbons :may .beremplayed the lieedetock stor the :process of the reaction. For example, mormal butane, normal pentane, xnormal =hexane,snormal :heptaneand Lthe like,zas;pure compounds may besubjected 'to the isomenizationtreatmentzashereinaiter moreiully described. aHowever -it :isvto .-be:;distinctly .understood that .-.the madness :of :the apresentzinvention equally as welliapplies :to .the 'ztreatment .01". mixtures *of hydlzocarbons :predominantly composed of tstraight chain constituents, ior exfi-mpleifitraightrrnn'naphthas of low :octane number, ipreierably those ,ahaving relatively narrow boiling zrances, may :be zisomerized according to the process inf the (present .invention .to improve their octane number rand 17o "bring about other desirable :changes .in their ;characteristics. Likewise, normally gaseous *panafilni'c mixtures, such as field ibutanes, araffinic mixtures resulting from the aremoval of olefinic constituents of refinery :(14 cuts, athatzis, waste :gases from nct'and cold acid polymerization processes, waste gases oi paraflinicnaturecevolvediromthermal-or catalyticalkylation processes and esimilar sources of mixed gparafiinic :hydrocarbon nature, may be utilized-as suitablezfeedistocks for use inth'e'pres ent process. In sgeneral, the process operates more cefliciently iorthe lower members of the parafiin aseries. i'I-Iowever, the presence of propaneiinithareaotants objectionable since its physical characteristics -are:not changed-by treatmentraccording :to 'Pthe present process and its I pmence. same: :to inhibitcracking to some extent.

employed. "Thus,"whe're normal *heptane' is the" feed stock, a temperature of 100 C. or even as low as 30 C. with an absolute reaction pressure of from two atmospheres to one-third of. an 'at-Z mosphere may be employed with highly 'satis- In general, the isomerization, I

factory results.

of straight chain paraifinic droca bons'in thel presence of halides of the third'group of the periodic system is advantageously performed at room temperature or below. However, the speed of reaction is sacrificed at these low temperatures whereas at higher temperatures appreciable cracking of the feed stock occurswhich undesirable for ultimate high yields of isomeric' hydrocarbons. It is therefore necessary for those skilled-in the art to determine according to their own'needs whether to operate the process at low temperatures and slow conversion rates or at higher-temperatures and quicker conversion rates but accompanied with a high u percentage of cracking-r -In-- general, for best operating conditions, temperatures ofaround 25 C. up to as high as-200 C. may be employed depending, however, upon the type of catalyst -used,=:the"amount of catalyst used, the residence of the feedstock in thereactor (in the present I case, the still pot)- and the throughput of the feedstock in the system. Pressures ranging from a fractionbf one atmosphere up to as high as=20 atmospheres may be-employed, the upper limitin working temperature and pressure beingthe critical temperatures and pressure of thefeed stock being isomerized. J However, pressures even" as high as 50 atmospheres may be -used without seriously affecting the general expediency of the reaction. Thethroughput most advantageous in operating theprocess of the presentinvention-maybe varied over quite wide ranges depending-upon the. correlation of the other reaction conditions andfactorsincident thereto. The capacity and size of .the: apparatus, inparticular, the isomeri- 'zation chambers andstill towers, depends upon the. relative purity of. the product desired, i. -'e.; the. degree of isomerization requiredfthe'catalyst to..hydrocarbon ratio in..the.still.body which, in general, will be maintained between about 0.05

' to. 1.0 and about 1.0 to. 115,prefe'rablyabout 0.5

to- 1.0, said ratios beingiemployed when using the apparatusdisclosed in.either Figure 1 on Figure 2, and the temperaturelat which the isomeriza tionis carried out. As heretofore explained, the temperature is correlatedwitlr the pressure applied to ,the system; Ingeneral, the throughput should be relatively low undermild isomerizing conditions and high under more drastic isomerizing conditions, low at high reflux ratios to make pure product and high at low'reflux ratios to make a mixed product.

Aluminum chlorideeither of commercial grade or chemically, pure may; beused as the catalyst for the reaction. .l-Ioweven; it is contemplated to also use aluminum bromide, both of these catalysts being extremely active as isomerization catalysts. Where possible, freshly. aprepared aluminum bromide should. be *used, and in the case of aluminum chloride, finely dividedalum-L inum chloride materially'increases the rate of reaction, Likewise freshly. prepared aluminumchloride appears to materially. increase the rate? of reaction, all other conditions being equal. The reaction also proceeds at high conversion rates by intimately agitating and lnixing the catalyst and reactants. Any suitable method may be employed, such as, for example, jets, whereby theliquid'feed stock is forced through jets of restricted internal diameter "into the catalyst .-c hamber containing a relatively large amount tr the catalyst. Likewise turbo mixers and other 10'.

types of.'.orifice mixers, centrifuges, mechanical stirre'rs, motor driven if desired, and the like,

may he -employed to accomplish this result. Other I c'ataIystsQsuchaS molybdenum trisulfide, zinc chloride, etc, I maybe employed.

As above mentioned, the quantity of catalyst materiallyfcontrolsthe rate of conversion of the reactant; III general, as large a body of catalyst should'be'maintained in the still pot or reboiler ".of a reflux tower as is consistent with practical and economical operation of the apparatus. {ls will be'- shown -hereinafter, filters are neec'ssary to separate the catalyst;--ei-ther partially spent'or otherwise; from the :reacted' hydrocarbons? The question of capacity of these filters is one of the factors limiting the quantity of i catalyst mam:

tained in th'e isom'eriza'tion zone; a 9

Whenusing aluminum chloride 'as the isomerizationcatalyst, it is desirable to have present measured amounts of a catalyst promoter; 'iIn thepresent 'caseit is desirableto employ asthe catalyst promoter a hydrogen halideor sub stances equivalent "thereto under the reaction conditions. -Any hydrogen halide :may' be em ployed 'although-itis desirable to use, in general; hydrogen chloride or hydrogen brom'i'defi .The' hydrogen halide or-its equivalentmay be present in-relatively small quantities, 'but,' if;desired, larger quantities. may. be' employed. Specifically between about 0.01% and 'a.bout 2.0%: oil-I20 based 'on the fresh feed,:.may" be employed-al though itiis preferred toluse between abou't0.05 a

and about 0.5 With HCl: as a promoter; the amount circulated may be between 0.5 and-50 on the hydrocarbon present inthe system, but-to" obtain good still operation .and lower costs, the quantity: preferredis between 1% 3.110133%. Referringto Fig. 1 of thedrawings, a; suitable feed stock, for example, normal butane ormixtures of normal 'paraffins containing/rnor'mal butane, is introduced through: feed inlet '2. into line.3 which in turn leads into a plurality of lines. 4, 5; Sand-.1 controlled byvalves :8, 9,110 and 1H respectively; The'plurallty of inletsior the fresh Jfeed-stock' into .the fractionatingz-col umn 12 is. provided so as to enablethe operator to introduce thefeed stock throughthatr-inlet which leads to that portion of the refluxiin the tower corresponding approximately to the composition of the feed stock. Thus, for example, a feed stock. composed, essentially of normalrbutane would be; introduced; through ,pipe con trolled by c-valve ll, valves :9. and .10. remain: ing close'd- .On the other hand, a feed s'tock'containing substantial amounts of .isobutane as mm as some normal butane would be. introduced through pipe ,4' controllediby valve ';8;::'valves::9, l0 and. remaining--closed-.::In practical opera-i tion, fractionating column [2 xwould con'tain some 50 or 60 plates where a bubbleatcap:ar v rangement l3 waszemployed. Iti isrto ..be.- .jdis-. tinctly understood, however, .that any:- suitable equipment may, be employed, .such-*Ias,mfor flex-'- I be employedi meant contain exactly-501 plates inthe case ol-tlie bubble cap arrangementzy For each partitulwr 'type pfi reed stock those skilled in the art' may readily dbterminethe size of the tower Where a feed ot normal butane isfi-ihtroduced into tractionating tower l2, the temperature or the t'ower is maintained so as to allow substantially only i'sobutane to be drawn olrrrem theuppermost portion of thetower; In such-arr instance, the normal butane, after absorbing some-of the heat of the reflux, passes into the stili pot- M where it is contacted with an isomerization catalyst. The catalyst is introduced into the system from catalyst storage bin 24 eonnectedto the catalyst hopper 21 by means or conduit 25 controlled by valve-'26, -The catalysthopper-IT is' intermittently emptied and filled with catalyst; The arrangement of the

valves

26 and 29, together with valves33 and 35-, permits the introduction of catalyst at atmospheric pressure asit exists in storage bin 24 into the reactor or still pot M which maybe maintained under considerable superatmospheric pressure, thus the contents of hopper 21' are conducted into reactor I4 through conduit 2'8 and open valve zsyvawe 35 remaining closed and valve 33=openg When the hopper 21 has become exhausted of its supply of catalyst, valve" 24) is closed, valve 33 is closed, valve'ZG is closed andva'lve 35 is openedtoaliowthehopper 21 to return toatniospheric pressure. Valve 35 is then closed; valve26 is' opened andthe hopper is filled? with fresh catalyst from the storage chamber 21 Valve 26 is then closed and the operation repeated as above described." By means of pump [9 and openvalve H the partially reacted hydrocarbon liquid' is withdrawn through pipes i6 and I8 and recycled through a heating unit back to reactor II by closing valves 31-, 39, M and- 41 and opening valve 2!, thereby allowing-a partially isomerized hydrocarbon mixture to flow into heater 22 and from there through line 2 3 into reactor Hi The rate of circulation is adjusted so that there is intimate mixing of the catalyst and liquid hydrocarbon in the still pot. The heater supplies the heat required for distillation as well as maintainingthe mixture at reaction temperature. As the reaction proceeds more nearly toequilibrium, there isa certain amount of heavier products formed; for example Ceparaflins and heavier where normal butane is "employed as the feedstock. Provision is therefore made for withdrawing from reactor H a portlon of the reacted mixture througha suitable filter I5, forexample, a 'rotary' drum knifeedged type filter or, as illustratedin Fig. 1 a

Cuno filter, in either case permitting the aluminum chloride catalyst to be retained the 'isomerization zone without removing anything but liquid from thereactionzone. Provision is made by mean's M: for continuously cleaning the filter. The filtered hydrocarbon liquid is then pumpedthrough line 61 by means of pump 62 into a fractionating tower Ill-provided with any suitable'packing material or bubble cap trays I2 analogous to the contents of tower 123 as illustrated by numeral I3; This-toweris provided with heating coils l3 inthe bottom andcooling coils 1| in the top. I'he heavier productsof the isomerization are withdrawn through line 14 controlled by valve 15. Here again a plurality oi inlets. isp'rovided whereby the filtrate i from reactor I4 I18 conducted .by means ofline fi l t'o'line 631 which leads into; "a plurality "of: lines to jmctionatmg, tower 1,, 4'1heSBL1i'neS -6", #65

and: W being controlled by valves E5, 81 and: 89 respectively; The operator is then able. to introduce the-filtrate into the'fractionating tower at apoint wherein the reflux of the tower correspends most nearlyto the composition of-"the feed stock. In cases where normal butane is used as the feed stock, normal and isobutane together with lighter eflluents; pass overhead through line 'lfi into either lines 1 1 controlled by valve 18" or: lines IS-controlled by valve 80. If valve Wis closed, valve 18' is opened and the overhead efiluent from the tower passesthrough 1 line: 11 backttothe originalfracti'onating column l2 where-it is reprocessed as heretofore described; It may be desirable, however, to permit the overhead efiluent, from fractionating tower 10 to be returnedldirectly': to the reaction medium, especially so in: cases where the overhead ellluent from fractionating tower 10 contains relatively little isobutane. In such a case, valve 18 is closed, valve is opened and the overhead eilluentpasses through line 19 back into line I8 and through pump I29: As heretofore described, the contents of this line arepassed? through a heating zone and allowed to return to the reactor lo v miter somehours "of continuous usage, the catalyst is allowed tov proceed to a point where its ultimate use has; become definitely diminished such a case, the catalyst may be with drawn from the system as a batch operation or thespent catalyst may be withdrawn 'from the system. continuously in small amounts together with fresh. catalyst, catalyst activity being maintaihed; at theldesired level. by withdrawal of catalyst and addition' of fresh catalyst frorn hopper 211 In either case,when it is desired: to remove catalyst from th reaction medium, valve 2| is closed; either entirely or partially, and the'catae lyst slurry isiconducted by means of pipe 38 through valve .39 into a filter: 48 of any suitable design, for example, this filter may be of the ordinary press andframe type, a rotary drum filter with knife-edged plate, a centrifuge, a Curio filter, or any other suitable commercial type of filtering apparatus may be employed. The spent catalyst isdiagrammatically represented as being removed through line 4i controlled by valve 42, although it is realized that for: as natural operation some meansfor specifically removing solids from the filter would necessarily be employed. The filtrate is then conductedby meansof line 43 through openvalve 44, throughiline-dfi into heating zone 22* and from there back to reactor M by means of line 23'. Valve 30 insuch an instance, may remain closed, or if 'open, blower 4-9 mayb employed to recirculate or introduce the gaseous promoter into line 45. Fresh feed inlet 36 is provided with a valve 31 by means of which the feed may be introduced directly into the recycle stream rather than into the fractionating column I2. In

cases where the food contains practically no isoparafli'ns, i-t ma-y' bedesirable to introduce the feed through inlet 3% controlled by valve 31*. However, it is more desirable to introduce the feed'through inlet 2 in cases where the feed stock contains substantial amounts of'the desired prodloss of catalyst promoter dissolved in the prod: uct being removed from the system since it is believed that the promoterfunctions as a -true promoter and is not materially altered jby the process of the invention. However, it maybe desirable at times to vary the quantity of promoter in the reaction system, in which case line 46 controlled by valve 41 may be employed either as an inlet or an outlet as the occasion demands.

The overhead from fractionating tower I2, which consists mainly of isobutane, some small amounts of propane and hydrogen chloride, is conducted by means of line 52 into a condensing unit 53. having cooling coils 54. The condensate is conducted by means of line 55 into a receiving drum 56. From the upper portion ofthis drum the lighter products are withdrawn by means of line 48 and returned to the reaction zone I4 by means of blower 49 through lines 45 and '48 passing through heater 22 and thence through line 23 into reactor I4. Naturally, when adding catalyst through inlet 28 and valve 29 from hopper 21, the pressure is equalized through line 32 and'some-of the light constituents may find their way into reactor I4 by this means.

The condensate collected in receiving drum 56, and which is substantially isobutane in cases where normal butane is used as the feed stock, may be withdrawn from the system by-means of line 50 and valve On the other hand, provision is also made for the withdrawal of isobutane from the system through line 59 controlled by valv 60. In either case, it probably contains small amounts; of lighter hydrocarbons and of hydrogen chloride. A separate and distinct fractionation under the required temperatures and pressures may be employed for obtaining substantially pure isobutane. The condensate from receiving drum 56 may be pumped back to the fractionating column I2 as reflux condensate by means of pump 58, line 51 and open valve 3|. 7

Fig. 2 represents a diagrammatic View in side elevation of another type of apparatus suitable for the carrying out of the present invention. For purposes of illustration, normal butane will be described as the feed stock. Normal butane may be introduced through line I02 by means of, open valve I03 into lines I04 and I05 from which, according to the desire of the operator, the feed is introduced into fractionating column H2 through one or more of lines I06, I 08 and H0 through valves I01, I89 and III respectively. As is the case with Fig. 1, the composition of the feed stock determines the point of introduction of that feed stock into the fractionating column 'IIZ. In the case of substantially pure normal butane, it may be introduced in the system ither-through line I02 or through line I23 controlled by valve I44. In either case, the normal butane emerges from fractionating tower I I2 which may contain bubble cap equipment H3 or packed inert material such as carborundum,

packing rings, jack chain, pumice, etc., through line I41 controlled by valve I48, thereby permitting th liquid effluent from fractionating tower II2 to be returned by means of reflux line I41 to reactor H6 equipped with a, heating coil or other suitable heating means I I I which is provided with mechanical agitating means I I9 and stirrer II 8. Vapors from reactor 6 are permitted to enterthe fractionating column II2 by mean of line II4 controlled by valve H5. The catalyst is conducted into reactor II 6 in substantially the same manner as described in the with the catalyst hopper I24 by means of conduit The catalyst hop- I2I controlled by valve I22; per is connected with reactor H6 by means of conduit I25 controlledby valve. I26. The elllu ent from reactor 6 i pumped through line I33 controlledby valve I82 by means of pump f34. In order to remove the spent or partially spent catalyst from reactor II6, the filter I 36 maybe of any suitableconventional design and may be of. the same type as described for the filterin Fig. 1. Likewise, draw-oil line I31 controlled by valve I38 is analogous to draw-ofi line 4I coritrolled by valve 42 previouslydescribed for Fig.; l. The filtrate is then returned to the reactor I I6 bymeans of line I39.

.When the reaction has proceeded sufllciently, there may be produced heavier compounds than that introduced in the feed stock, for example, the pentanes. At such times, it is preferred to'conduct the filtrate either continuously or intermittently from filter I36 directlyto bubble tower. I59 by closing or partially closing valve II 5 and; opening or partially opening valves I50 and/or I82 in order to separate out the heavier constituents. In such a case, valves I35 andl44 arepartially or completely closed, and pump filtrate to be conducted through line I49 to the bubble tower I59 provided with a pluralitypf fractionating devices diagrammatically represented as element I60 through one or more of lines I53, I55, and I 5'Icontrolled by, valves I54, I56, and I58 respectively. This arrangement corresponds to tower 1 0 controlled by lines 64, and 68 controlled by valves 65, 61 and 69 of Fig. 1 and operates in substantially the same way. As in the case of bubble tower I0 in Fig. 1, bubbletower I59 is provided with cooling coils I62 and heating coils I6I, the heavier material being withdrawn from the tower through pipe I68 controlled by valve I69. conducted. by means of pipe I63 either directly to the feed lines I02 and I04 by means of line I64 controlled by valve .I65, valve I61 being closed, or valve I65 maybe closed and 'valve I61 opened, thereby permitting the overhead eflluent to be conducted by means of line I66 to fractionating tower. II2. This latter procedure is particularly desirable where very little, if any, isomers have been formed or in cases where the heavier products have been allowed to accumulate for considerableperiods of time while'the isomers of the feed have been substantially completely removed asformed. r

It is advantageous, when; expedient, to, withdraw the hydrocarbons from reactor I I6 by means of line I46 sincethis small amountsof catalyst therein and'the'efi'icient lifeof: filter' I 36 is thereby greatly prolonged. When it is desired to introduce the feed stock directly into reactor II6, valves I35'and I44 may be opened, valves I54, I56, and I58 being closed, thereby permitting, the feed stock to enter the system through lines I23 and I39.

The promoter, for-example hydrogen chloride, hydrogen bromide or water in the required amounts, may-:be introduced into the system through line I40 controlled by valve MI, in which .case it is introduced into reactor II6 by means of line I42 and blower. I43. The desired product which may comeoverhead from column I I2 may be withdrawn through line no controlled waive I 5I causes the The overhead from this tower is' efiiuent contains relatively assaoar I or, uuesmd the product present in the sysan mayrbe taken overhead through line IE2 and condensedfincondenser HE containing cooling coils: I The condensate is then allowed to run to the settling: drum- I19 through line I15. The lighter constituents; which are usually in the vapor stateaundert'he conditions prevailing insettI-ingdrum HS, arewithdrawn through line- I-W controlled by: valves I 80- and WI and returned tothereaotor I I 5 by means of line I42 and blower- M31 The condensate may be withdrawn through line H1 and pumped back bymeans of'pu-mp I-T lt and line l l l controlled by valve I45 into the top ofthefractionatingcolumn M2 to serve as reflux condensate." If desired, however, a portion or substantially all al this draw-off from settling drum I16 maybe removed from the system by closing valve F43, opening valve I-32 and permitting the product toflow through line I 3l Various modifications asto the design and size of the equipment maybe made to fit the exigenales of the particular case. It is not intended that the invention should be limited by the type of equipment described, it being suilicient for the successtul' operation of this invention to provide for asemi-continuous or batch operation wherethe-conditions are so maintained that normal paratllns entering the bottom of a still column either in a reboiling equipment or in a still colu-mn provided for the purpose may be isomerized in the presence-of an isomerization catalyst under suitable reaction conditions; thereby simultaneously'removingirom the system as overhead from the fractionating column the desired isomeric hydrocarbons. Any means Within the skill of those working in the art by which this result may be accomplished are entirely suitable and are considered to be within the scope of the invention herein described. Those parts of the apparatus coming in contact with the catalyst and/or promoters preferably should be lined with or constructed of corrosion-resistant materials such as stainless steel, ceramic materials, or other types of corrosion-resistant materials commonly employed in chemical plants for such purposes.

The following examples illustrate the process of the invention, although it is to be distinctly understood that the invention is not limited thereto.

Example 1 500 cc. of normal heptane was charged into the distilling flask of a 5 ft. column packed with carborundum. This column was equivalent to 30 theoretical plates and was equipped for operation under reduced pressure. Aluminum chloride was charged into the distilling flask with the normal heptane. The normal heptane was boiled and refluxed in the column. Products were taken overhead when the temperature at the top of the column was below the boiling point of normal heptane. The aluminum chloride was charged to the extent of by weight of the feed. The reaction temperature automatically remained at about 98 C. The experiment was conducted under atmospheric pressure and there resulted a 33.7% by volume yield of isomeric products which had an octane blending value of about 96. The isomerized product contained .4% by volume of propane, 37% by volume of isobutane, about 21.1% by volume of isopentane, 7.8% of isohexane and 27.5% of isoheptane. The remainder of the isomerized product was made up of normal parafflns of 4 to 6 carbon atoms. The average reactlon-tlme' was. alm'ut 2 hoursv with continuous reflux. w

Example z.

In. a similar run conducted at about. 33 C. in volying, the, use. of 10%. by weight. of aluminum chloride and about. 1% by weight of water. based on the feed; a. reaction timelof about. 8. hours and an absolute reaction pressure of about, 1.45. lbs/ so. in, a 49.4% by volume yield of isomerized products were. obtained, analysis of the produotjshowcd' that it contained about 24.9% by. volume of isobutane with only about .6% by volume of. normal. butane... about 23.5% byvolumeof. isopentanewith no detectable amounts of, normal pentane. present, about 16% by volume. of isohexane with. about 2.4% of normal hexane. and 32.6% by volume. of. isoheptane. The bl n ing value of the. isomerized product, was about. 751:5 in this particular. instance.

' Example: 3;

As exemplary of the continuous operation on normal butane, the still. pot was, maintained at a. temperature of. about 200 lit, the pressureon the still being. about 260. lbs/sq. in. gauge, approxi-. mately 40. lbs/sq. in, of this pressure, being due to HCl being recirculated. through the gasv sy,s tem. A. reflux ratio of about 10. to l was, maintained on. the, top of the. still which was equivalent to about 50 theoretical plates. The butane product, drawn oft overhead. consisted. of about. 35% isobutane, about. 151%. normal butane and contained a trace of propane.

The. normal but ne was tied to. the still in the still pot rather than in the side of the still column and contained a trace of olefins and between about 7 and about 10% isobutane. The aluminum chloride in the still was equivalent to about 25% of the weight of the hydrocarbon in the still pot and had a volume of approximately 10% of the volume of the still pot. Additional alumwhile the run was in progress.

inum chloride equivalent to about 2.0% by weight of the normal butane in the feed was added. Spent catalyst was withdrawn intermittently and was found to be still quite active so that thecatalyst consumption was actually less than the 2.0% by weight on the fresh feed. The spent catalyst withdrawn, which was equivalent to that in the still, was a brown finely divided solid which, when dumped into water, reacted violently.

The hourly rate of addition of normal butane was such that the time of residence in the still was about 2 hours, that is, it was equivalent to about one-half the volume of the hydrocarbon in the still pot and column.

Example 4 In a small laboratory run in a /2 inch diameter column of a height equivalent to about 50 plates, the still pot was charged with a mixture of about gms. normal pentane and about 110 gms. A1013. A small amount of HCl was added slowly Operating the still at atmospheric pressure with a still 'temperature of about 96 F., lsopentane practically pure was produced at the rate of about 4 gins. per hour. No butane or other lower boiling hydrocarbons could be detected in the product although they may have been present in small amounts.

Example 5 In another experiment run according to the conditions specified in Example 1 except that the reaction temperature was about 67 C., the catalyst was activated by the addition of 1% of water which about 34.8%

based on the feed, and the length of catalyst contact was about 6 hours, the pressure being about 5.15 lbs/sq. in. absolute. Isomers were obtained to the extent of about 21% by volume of by volume was isobutane, about 1.3% normal butane, about 23.2% isopentane, about 4.1% normal pentane, about 6.8% isohexane, about 6.3% normal hexane and about 23.3% isoheptane were produced.

The present invention is not intended to be limited to any theory or mechanism of the reaction but only to the following claims in which it is desired to claim all novelty inherent in the invention. The nature and objects of the present invention having been thus fully described and illustrated, what is new and useful and is desired to be secured by Letters Patent is:

l. A continuous process which comprises reacting a refinery C4 cut substantially free of olefins and containing substantial amounts of normal butane in a combination isomerizationfractionation operation under isomerization reaction conditions in the presence of an aluminum halide and a hydrogen halide, directly, simultaneously and continuously removing overhead from the boiling liquid reaction mixture as distillate substantially only products of the reaction boiling below normal butane, removing at least a portion of the undistilled boiling liquid reaction mixturesubstantially free of aluminum halide from the reaction zone, and separately and independently fractionally distilling the said undistilled boiling liquid reaction mixture to obtain at least two fractions, one of which is higher boiling than the normal butane and the other of isomerization which boils'at substantially the boiling point of normal butane, continuously returning to the reaction zone the second-mentiom ed fraction and removing from the isomerization system the first-mentioned fraction.

2. A continuous process which comprises isomerizing normal parafiin containing at least four carbon atoms per molecule in the presence of an isomerization catalyst, under isomerization reaction conditions in a combination isomerizationfractionation operation, directly, simultaneously and continuously removing overhead from the boiling liquid reaction mixture as distillate substantially only products of the reaction boiling below the boiling point of the normal paraflln feed stock, removing at least a portion of the undistilled boiling liquid reaction mixture substantially free of isomerization catalyst-from the reaction zone and separately fractionally distilling the said undistilled boiling liquid reaction mixture to obtain at least two fractions, one of which is higher boiling than the normal paraflin feed stock and at least one other of which boils at substantially the boiling point of the normal paraffn feed stock, continuously returning to the isomerization reaction 'zone the last-mentioned fraction and removing from the isomerization system the first-mentioned fraction.

3. A process as in claim 2 wherein the feed stock comprises essentially normal butane.

4. A process as in claim 2 wherein the feed stock comprises essentially normal pentane.

ANTHONY E. ROBERTSON.

and independently