US2474924A - Alkylation method - Google Patents

Description

- july c. w. WATSON Erm- ALKYLATION METHOD 2 sheets-shew 1 Filed June 2l, 1945 2 Sheets-Sheet 2 C. W. WATSON EVAL. ALKYLATIO METHOD ,Judy 59 R949.

Filed June 21, '1945 XEN ORS Caf-'Faro C (/Pm/V.

,0 my L LE.

i N (2m/af aff ATTOR EY Patented July 5, 1949 ALKYLATION METHOD Claude W. Watson, Eastchester, 'Clifford C. Burton, New York, and Loren P. Scovllle, Yonkers, N. Y., assignors to The Texas Company, New York, N. Y.,a corporation of Delaware Application'June 21, 41945, Serial No. 600,686

2 Claims.

This invention relates to the catalytic alkylation of a hydrocarbon or other organic compound having a replaceable hydrogen atom with a suitable alkylating agent, such as an olefin, for the production of gasoline hydrocarbons of high antiknock value suitable for aviation gasoline and motor fuel, or for the production of valuable alkylated organic products for other purposes. 'I'he invention is particularly applicable to the alkylation of a low-boiling isoparailin, such as isobutane, with an olefin or other alklylating agent for the production of aviation gasoline of improved quality.

One of the principal objects of the invention is to provide an improved catalytic alkylation process capable of producing a superior alkylate containing higher proportions of highly branched parail'in hydrocarbons which give superior leaded octane ratings by both the AFD-1C and AFD-3C test methods, and smaller proportions of less highly branched hydrocarbons which have inferior octane ratings.

Another object of the invention is to carry out the alkylation reaction and separate the resulting alkylate from the catalyst with exceptionally short overall contact time, to thereby obtain an increased yield of primary `alkylation products of improved quality and to prevent secondary or degradation reactions from altering the composition of the primary alkylate so obtained.

A further object of the invention is to carry out the alkylation reaction with'extremely short ormicrocontact times, with unusually high catalyst to hydrocarbon ratios and with a set olen or other alkylating agent space rate while still maintaining desired capacity.

An additional object of theinvention is to proy vide an improved form of alkylation apparatus for carrying out the foregoing methods, and which is adaptable for catalytic alkylation generally.

Still another object of the invention is to provide improved alkylation apparatus of the tube and header heat exchanger type equipped for multipoint olen or other alkylating agent injection, coupled with intensive agitation immediately adjacent the points of olen addition, and with efllcient refrigeration in the tube sections intermediate points 'of olefin addition, and Which is capable of giving high capacity with the desired short contact time.

Other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying drawing and appended claims.

Catalytic isoparaflln-olefin alkylation with (Cl. 26o-683.4)

2 strong H2S04 and with HF has gone into wide commercial use for the production of aviation gasoline and motor fuel. In these commercial processes, contact times of the order of 20-60 minutes in the reaction zone, coupled with a substantial time of the order of 30-120 minutes for gravity settling, are conventional. A vcatalyst to hydrocarbon volume ratio in the reaction zone ofl around 1:1 and an loleiin space rate averaging about 0.3 v./v./hr. are customarily used.- These processes give a typical alkylate from isobutanebutylene alkylation in which the octane (Ca) fraction contains mainly 2,2,4- and 2,3,4-trimethylpentanes together with an appreciable proportion of dimethylhexanes, the latter resulting in an rappreciable lowering of both the clear and leaded octane values. While the 2,2,4- and 2,3,4-trimethylpentanes have fairly high clear octane values, the leaded octane values by the AFD-1C and AFD-3C test methods are not uniformly high. Thus, 2,2,4-trimethylpentane has a high 1C Value but only a moderately good 3C value; and the 2,3,4-trimethylpentane has lower 1C and moderately high 3C values.

From tests on pure hydrocarbon compounds, it is known that certain highly branched paratlin hydrocarbons will give a combination of high 1C and 3C values. In the octane iCa) fraction, both 2,2,3- and 2,3,3-trimethylpentanes have this desirable properly, with the former being somewhat superior to the latter. Among the heptanes, 2,2,3-trimethylbutane or -triptane is outstanding. Likewise, among the nonanes, 2,2,3,3tetrameth ylpentane is superior. While the desirable knock `ratings of these pure hydrocarbons have been kylation have. been unsuccessful.

In accordance with the present invention, a radically new method involving the use of a completely diierent type of alkylation apparatus is employed to greatly reduce the overall contact time in the reaction and settling zones to less than five minutes and preferably less than 2-3 minutes. For example, the alkylation reaction or contact time ln the reaction zone may be limited to a micro contact time, which expression is herein used to designate a fraction of a minute. Further, the reaction products discharged from the alkylation reaction zone are immediately subjected to positive separating action, as opposed to merely gravity separation, as by passing through a centrifuge, whereby the settling time -nlay also be limited to not vmore than several minutes and preferably less than a minute. It

is to be understood that "contact time, as the expression is used herein, means the volume of hydrocarbon in the reactor divided by the volume of hydrocarbon charged per hour: thus, for a given velocity of once-through ow through the reactor. the contact time varies inversely with the acid to hydrocarbon volume ratio in the reaction zone.

Further, the alkylation reaction is carried out under conditions which are markedly distinguished from the prior practice in this art, and involve an optimum correlation of olefin feed distribution and mixing in a flowing stream of the isoparafiin and catalyst providing high isoparafiin concentration at the immediate points of olefin introduction, with high catalyst to hydrocarbon volume ratio, controlled olefin space rate in accordance with the mixing efficiency'and the temperature, and refrigerative chilling of the reaction mix immediately adjacent the points of olen addition. This is accomplished by passing the reactants or hydrocarobns in once-through flow through a pipereactor of the refrigerated jacketed coil type or heat exchanger type, introducing the olefin by multipoint addition at a large number of points spaced throughout the length of the reaction zone, subjecting the flowing stream of reaction mix to intensive mixing or mechanical agitation immediately adjacent each point of olen addition, controlling the oleiin space rate so that the olefin is fed into the reaction mix in a quantity per unit of time less than that which results in undesired reactions such as hydropolymerization, this rate being a function of the mixing efiiciency and the temperature, and refrigeratively chilling the owing stream of reaction mix intermediate the spaced points of olefin addition. Further. as permitted by the improved mixing eiliciency of the present invention, it is preferred to provide a catalyst to hydrocarbon volume ratio in the reaction zone considerably in excess of that previously used, so that the reaction mix contains about 'l5-95% catalyst by volume.

By a combination of the above-described conditions of the alkylation reaction with the overall short contact time of reaction and separation, a novel type of alkylate may be produced which is materially enriched in highly branched paramn hydrocarbons which ailord the desired high 1C and 3C ratings. It is postulated that the 2,2,3- trimethylpentane is a primary product of the alkylation of isobutane with butylene-1 and butylene `2;` while 2,2,4 trimethylpentane is a primary alkylation product of isobutylene. Thus. it is theoretically possible to obtain nearly 100% of 2,2,3-trimethylpentane from anormal butylene charge stock substantially free from isobutylene; and to obtain about 70% 2,2,3-trimethylpentane-to 30% 2,2,4-trimethylpentane from a total C4 plant gas fraction. Moreover, it is postulated that prolonged contact of such primary alkylation products with H2804 under alkyl- 'ating conditions degrades those products, particularly the 2,2,3-trimethylpentane, into less desirable hydrocarbons. The extremely short overall contact time of the present invention inhibits such secondary or degradation reactions. It is further believed thatthe eii'ective control of the alkylation reaction conditions as set Aforth-above increases the selectivity of the reaction for the desired primary alkylation products. and materially reduces-the yield of less highly branched parains, such as dimethylparamns.

Conventional alkylation with long contact time of the order of 20 minutes or more is capable of producing an alkylate containing as high as about 90% trimethylpentanes under optimum conditions with low olefin space rate and very high isoparamn concentration in the reaction mix. Due to the method of olefin feed distribution previously used, and the comparatively lower mixing efficiencies of conventional alkylation reactors, the long time of contact was required to produce this quality of alkylate. However, this long time of contact apparently permitted initially formed primary alkylation products to isomerize or undergo degradation reactions, with the result that the alkylate obtained consisted mainly of the 2,2,4- and 2,3,4-trimethylpentanes and only small amounts of the more desirable 2.2.3- and 2,3,3-trimethylpentanes. In accordance with the method of the present invention, the greatly improved olefin feed distribution at a controlled temperature, coupled with effective agitation at the immediate zones of olefin introduction providing improved mixing efficiency, enable the alkylation reaction to be completed in a much shorter time, and prompt removal of the primary alkylation products from the acid inhibits the above-mentioned secondary degrading reactions.

The rate of activation of the olefin for reaction with the isoparafiin, possible through the formation of an intermediate complex, is a function of the temperature, increasing rapidly rise in temperature. For example, butylene-2 will alkylate very slowly, if at all, at 0 F. with H2804 catalyst; but in the range of (i5-60 F., the rate of activation of this olefin increases many fold. Immediately at the time of activation of the olen, it is necessary that isoparaffln be brought into contact with the activated olefin to produce the desired alkylate; otherwise, the activated olefin will undergo hydropolymerization or other undesired reactions with the acid and with itself. By distributing the olen feed by multipoint addition, the likelihood of these undesired reactions taking place, with a given isoparailin concentration y so thatthe isoparafliin lrenewal at the immediate zones of activation and reaction will be at least as fast as the oleiin activation.

The actual olefin space rate may therefore vary widely within the range of about 0.050.5 v./v./hr. or somewhat higher, depending upon the reaction conditions. With a lower temperature where the rate of activation of the olefin is limiting, or with a lower mixing eiiiciency where the rate of renewal of the isoparaflin at the'immediate zone of formation of activated olefin -is limiting, a lower olen space rate within the above range is employed. At somewhat higher temperatures, and with improved mixing eificienoy, higher olefin space rates may be employed. While the temperature should thus be high enough to secure lthe desired rate of olefin activation for the particular olefin and catalyst employed, substantially higher temperatures are objectionable because the rate of olen activation then increases rapidly beyond the mixing eillciencies attainable, and

Valso because undesired oxidation reactions then The selectionl of the olen space rate in accordance with the foregoing principles is best made by cut and try runs in accordance with the results attained; thus, for a given temperature and a given reactor, the olen space rate is set somewhat below the point at which further increase results in evidence of hydropolymerization with appreciable reduction in catalyst life.

In the case where sulfuric acid is employed as the alkylation catalyst, the control of the olen space rate is further correlated with the water content of the sulfuric acid in the reaction zone. Thus, lowering the water content of the sulfuric acid in the reaction zone has a similar effect to increasing the temperature in that the rate of activation of the olen is increased; and, conversely, raising the water content of the system acid decreases the rate of activation of the olen. It is preferred to operate in accordance with the present method with a water content of the system acid in the reaction Zone less than 2% by weight, and better still less than 1% by weight,

to secure the required high rate of olefin activa.

tion at temperatures low enough to avoid oxidation and other acid degrading reactions.

Novel alkylation apparatus has been devised to carry out the foregoing method. It is to be understood, however, that this apparatus is adaptable to catalytic alkylation generally and is not restricted to the short contact time or other improvements described above relating more particularly to isoparaiiin-olen alkylation. This apparatus comprises a continuous pipe reactor equipped with a multiplicity of olefin feed jets at spaced points along the length of the pipe reactor, coupled with mixing devices or rnechanical agitators immediately adjacent each point of olen addition, and a refrigerating jacket for the pipe reactor intermediate points of olen addition. In its preferred embodiment, the pipe reactor is of thev tube and header heat exchanger type having a tube bundle equipped with opposed alkylation unit containing four series-connected reactors of the tube and header heat exchanger type. with a centrifugal separator;

Fig. 2 is a vertical sectional view through one of the tube and :header heat exchanger reactors of Fig. l, the section being taken on the plane of the line 2-2 0f F18. 3; I

Fig. 3 is a vertical sectional view taken on the plane of the line 3-3 of Fig. 2;

Fig. 4 is a vertical sectional view taken on the plane of the line 4--4 of Fig. 2;

Fig. 5 is an end elevational view looking toward the right handend of Fig. 2;

Fig. 6 is an end elevational view looking toward the left hand end of Fig. 2;

Fig. 7 is a partial vertical sectional view ,on an enlarged scale, illustrating the agitator shaft mounting and olefin jet connection; and l Fig. 8 is a partial vertical sectional view on an enlarged scale of a modified construction of multipoint olen jet arrangement for each header compartment.

For purposes of description, the invention-is more particularly described in connection with the alkylation of isobutane with a suitable olefin, such as C4, Ca, C5 or mixtures thereof, for the production of aviation alkylate. It will be understood that the invention is not so limited, and that baied heads providing return bend compartments at opposite ends of the tubes, and forming a multi-pass ow path constituting the reaction zone. The olen jets with associated mechanical agitators are mounted in the header compartments, and the intermediate tube bundle is equipped with the refrigerating jacket. The desired capacity of the apparatus is obtained by providing a large number of tubes per pass, whereby the flowing stream of reaction mix is sub-divided into a large number of l parallel streams, each of small crosssection,in the tube section, and these streams are recombined as they emerge into each header compartment. A plurality of these pipe reactors or tube and header reactors are connected for series ow to provide the desired contact time and aiord a large number of agitated points of olefin addition; and the reaction products discharging from the last reactor in series are led directly to a centrifuge where the rapid separation of catalyst from hydrocarbons takes place.

Referring to the drawing, which discloses preferred embodiments of alkylation apparatus constructed in accordance with the present invention,

Fig. 1 is a diagrammatic elevational view of an the apparatus can be employed for catalytic alkylation generally, as more particularly described hereinafter.

Referring to Fig. duced through line II) by pump I i; and the olefin feed is introduced through line I2 by pump I3. It will be understood that the isobutane includes fresh feed isobutane and also recycle isobutane separated from previously formed alkylate and returned to the system. It also will be understood that a portion of the recycle isobutane may be mixed with the olen feed in line I2 to adjust the isobutane: oleiin molar ratio to about 1:1 or somewhat higher.

The isobutane from line 10 meets a stream of recycle catalyst, such as strong HzSOi, passed through line I4 by recycle pmnp I5. The acid and isobutane in liquid phase then flow through a baiiled mixer I6, and thence pass by pipe I'I into the inlet of the tube andheader heat exchanger reactor indicated by the numeral 20.

The construction of this reactor is more particularly illustrated in Figs. 2-7 inclusive. As shown, a cylindrical shell 2I enclosed by end plates 22 and 23 forms a refrigerant chamber 24 surrounding a tube bundle consisting of a large number of tubes 25 of small cross-section. The end plates 22 and 23 are drilled as indicated at 2B and 21 respectively to receive the opposite ends of the tubes 25 with a snug fit. Bolted at 28 to the end plate 23 is a cylindrical channel member or insert 29.\ Bolted in turn to the outer end of the channel member 29 by bolts 30 is a header plate 3|. The channel member 29 is provided with ballles 32 of a length to abut in sealing relation against end plate 23 and header plate 3I, when the parts are properly assembled.

The construction of the bailies 32 carried by the channel member 29 is more particularly shown in Fig. 3. A central vertical bale extends completely across the interior of the channel member. f

1, the isobutane feed is intro-r avec . 7 inlet compartment into which feed line I1 (indicated in-1dotted lines in Fig. 3) discharges. A portion of the tubes 25 communicate with said compartment I 'and lead the liquid mix fed to that compartment through the refrigerating chamber' 24 to the'opposite end of the reactor.

The left hand end of the reactor (Fig. 2) is likewise provided with a channel member 34 bolted at 85 to end plate 22; and a header plateft is bolted at 31 to the outer end of the channel member 34. Channel member 34 is in turn provided with four horizontal bailles 38. as shown' more particularly in Fig. 4. The baliies 38 all are of a length adapted to sealingly engage the outer face of end plate 22 and the inner face of header plate 36 when the parts are assembled. Consequently, the left hand end (Fig. 2) of the reactor is divided into ve compartments.

Flow through the reactor is as "follows: The mixture of isobutane and acid introduced by'inlet I1 into compartment i at the right hand end of the reactor passes by tubes 25 tothe portion of the lowermost compartment at the left hand end of the reactor which is indicated by the numeral Il in Fig. 4. An approximately equal number of tubes 25 in turn communicate with the right hand side (Fig. 4) of said lowermost compartment, which is indicated by the numeral 2. The mixture then returns through said tubes to the lower part of the right hand compartment (Fig. 3) indicated by the numeral 2. Said compartment in turn communicates with another set of approximately equal number of tubes, as indicated by the numeral 3, through which the mixture returns to the left hand end of the reactor (Fig. 2) and to the right hand side of the next higher compartment.

indicated by 3'l (Fig. 4). It will thus 'be evident that the numerals I|0 (Fig. 3) and the numerals |-|ii'- (Fig. 4) indicate ten passes through the reactor, the flow being from l to I', 2' to 2, 3 to 3', 4 to 4, and so on for a total of ten passes until the reaction mix eventually reaches the discharge lcompartment I0 (Fig. 3), from where it is discharged by line 40.

Propane or other suitable refrigerant is supplied in liquid phase under pressure froma suit-V able storage reservoir by line 42, and then by branch line 44 to reactor 20. Branch line 44 discharges into' the interior chamber 24 containing the tube bundle, so that substantially the entire length of the tubes 25 between the headers is effectively refrigerated. The expanded propane or other refrigerant discharges from chamber 24 by line 45 communicating with aline 48 which leads back to a suitable suction trap and thence to the compressors of the refrigerating unit in conventional manner.

The olefin feed supplied from line I2 by pump I3 passes through line 48 to manifolds 49 and 50 at the left and right hand ends respectively of the reactor (Fig. 1). Manifold 49 in turn supplies ive branch lines 52 which extend through the header plate 36 and terminate in nozzles or jets 53 near the center (Fig. 4) of the header compartments. An olefin dispersion jet is thus provided for each of the live compartments at the left hand end of the reactor. Likewise, the manifold 50 (Fig. 5) at the right hand end of the reactor is provided with ve branch lines 55 which extend through header plate 3l and terminate near the center of each of the compartments at this end, with the exception of the discharge compartment I0. This construction is more particu- Alarly illustrated in Fig. 7, wherein the branch pipe 55 passesl througha drilled opening 58 in header plate 8|. A sealing plate 51 which may be welded or otherwise secured, fastens the pipe in place and seals the same against leakage. The inner end of pipe 55 within the header compartment is bent downwardly as indicated at 58 and terminates in nozzle 59 at a position somewhat nearer the header plate 3i than to the end plate 28. It is thus seen that the olefin feed is dispersedat ten points which are spaced rather uniformly along the path of flow of the reaction mix through the reactor.

Each of the header compartments containing an olefin jet is also equipped with a mechanical agitator to'subject the reaction mix to intensive agitation immediately adjacent each point of olen entry. As shown, header plate Il provides bearings for a series of ve shafts 88 (Figs. 2 and .5) Each of said shafts carries on the exterior of the header plate a. sprocket wheel 89. The ilve sprocket wheels are interconnected by sprocket chain 10, which is, tightened by the usual idler sprocket 1l mounted on idler shaft 12. The lowermost sprocket shaft 88 extends outwardly beyond the sprocket wheel 69, and this extension carries a bevel gear 13 meshing with bevel gear 14 on driving shaft 15 of motor 18.

As shown more particularly in Fig. 7, header plate 3| carries a bearing' sleeve 11 within which shaft 68 is rotatively mounted. The shaft extends inwardly within the header compartment to about midway between header plate 8l and end plate 2 3. Mounted on the inner extremity of the shaft are suitable agitating blades ll which are adapted to violently churn or agitate the reaction mix in each compartment. On'the exterior of header plate II, the shaft passes through a suitable stuffing box having an outer casing 80 within which is compressed packing 8| by the sliding plunger 82 actuated by screws 83.

'I'he left hand header of the reactor is likewise equipped with ve shafts 85 (Figs. 2 and 6) carrying within its compartment agitating blades 86 associated with an olefin Jet 53 similar to the arrangement in Fig. 7. In this case. however, the shafts are in vertical alignment so that the agitators 85 are positioned centrally of the header compartments (Fig. 4). Each shaft 85 passes through a suitable stuffing box 88 to the exterior and has mounted thereon a gear 89. As shown, the five gears 89 are interconnected in line, so that rotation of the bottom shaft 85 through the bevel gear 90 meshing with .bevel gear 9| on shaft 92 of driving motor 83 drives all the agitators 86.

In the specific embodiment shown, the reactor comprises a tube and header having ten passes, with 22 tubes per pass, and ten points of olefin entry in the header compartments or zones of intense mechanical agitation. The flowing stream entering the-rst compartment I receives dispersed olen in the immediate zone of agitation provided by agitator 18. Then the stream is divided into a large number of small parallel streams owing through the tubes 25 where it is subjected to eflicient refrlgerative cooling to immediately remove the heat of reaction. Upon emerging into header compartment I-2', where the small streams are recombined, a further charge of olen is dispersed into the recombined streams in the immediate zone of agitation provided by agitator 85. The reaction mix is then alternately subdivided into the small parallel streams and recombined in the header compartments'where further charges of olefin are introduced while the mixture is subjected Vto mechanical agitation. While ten passes are shown in the reactor, it will be understood that any convenient number can be provided. Moreover. desired capacity of the reactor is obtained by the number of tubes per pass, and the volume of the header compartments, which of course can be varied substantially from that shown. The tubes 25 are ordinarily constructed of about i" to 2" in diameter, with a 3A" tube being preferred, to provide adequate heat exchange 4surface. As shown, the reactor is of the short tube exchanger type, wherein the tubes are generally about 3-4 feet or somewhat more in length. The short length permits the tubes to be carried in rigid heads, thereby providing an economical construction. However, the use of longer tubes with a floating header to provide for expansion and contraction is included within the scope of the present invention.

The volume of each header compartment may be roughly equivalent to the total volume of the tubes in a single pass, although this can be varied. In fact, the time of contact in a given reactor of this type can readily be varied by altering the width of the channel members 29 and tt, with corresponding alteration in the length of the bafiies 32 and 38, to thereby increase or decrease the size of the header compartments. It is preferred to provide the reactor with blownup heads, which signifies compartments of increased size over those ordinarily provided in a conventional heat exchanger. This affords additional room for mounting of the agitators and the olefin jets and also affords control of the time of contact or flow through the reactor.

It will be appreciated that the present reactor does not depend upon turbulent flow to provide agitation. In fact, for economy in power consumption, it is ordinarily preferred to operate the reactor with an emulsion velocity below the ranger of turbulent flow. For this purpose, an emulsion velocity through the 3A inch tubes of less than about five feet per second is employed, such as an emulsion velocity of about two-four feet per second which is within the range of viscous flow. Moreover, positive mechanical agitation in the header compartments appears to` give more effective results, possibly due to the more eiiicient action oi the agitator blades in resaturating the acid with isobutane. postulated that the alkylation reaction takes place between the isobutane in solution in the acid and the activated olefin. Consequently, the effective dispersion of the olen by jetting from a small-sized nozzle or orifice of the order of 11g-1A; inch in diameter, and preferably about 1A; inch, with an effective pressure drop of aboutl 5-50 pounds per square inch and preferably about 25-35 pounds per square inch, coupled with the renewal of the surface at the interface and the It is..

While in the specic fonn shown in Figs. 2-7,

the olefin feed pipe 56 for each compartment terminates in a single jet 59, it will be understood that the pipe 56 can be provided with a plurality of branches extending to different locations throughout said compartment, such as a so-called Christmas tree construction, with each branch provided with an olefin feed jet. In this manner, the olefin may be dispersed by multipoint addition throughout the volume vof each compartment, in addition to the multipoint addition at spaced points or compartments along the pathbf flow through the alkylation apparatus as previously described.

In Fig. 8 there is disclosed a modification of this general ytype adapted for multipoint addition adjacent each compartment of the tube and header heat exchanger reactor, Similar elements to those previously described in Figs. 2-7 are indicated by similar primed reference numerals.

Thus, the end plate at the right hand end of the i iinto the end of a tube 25! discharging into that compartment, the direction of flow through said tubes being indicated by the arrows H1. It is thus apparent that the branch pipes H6 extend into thev ends of the one set of tubes which discharge into that compartment, but not into the other set of tubes which receive liquid flowing out of that compartment. Each pipe H6 terminates in a suitable mixing nozzle H8 discharging counter to the direction of flow through the tube. Preferably, the nozzles H8 are constructed to disperse the olefin feed in the form of conical jets l I9, so that the olefin is substantially evenly distributed throughout the crosssection ofthe tube 25. In the preferred construction, as many branch pipes I I6 having dispersing nozzles I I8 are provided for each compartment as there are tubes discharging into that compartment.v However, it will be obvious that only certain ofthe tubes 25' feeding into any compartment need be provided with olefin dispersing jets, since the small streams are immediately discharged into and combined within the compartment where further mixing takes place.

Due to the effective mixing and agitating action of the Jets H8 introduced with substantial pressure drop counter to the iow of reaction mix Y through the small diameter tubes, it is possible resaturation of the acid with isobutane followto dispense with the mechanical agitators in the header compartments, particularly where some i'orm of orifice or baille mixing action is provided in each compartment, However, it is preferred to also provide a mechanical agitator indicated at 18' with its shaft 68 within each compartment. The agitator is preferably mounted centrally and between the inlet and outlet tubes in the manner-previously described.

As shown more particularly in Fig. 1, the reaction mix discharging by line 40 from reactor 2|)` is immediately passed to the inlet of a second reactor 9|) which may be identical in construction with reactor 20. Two additional reactors 9| and 92, also of the same construction, are connected for series flow by the lines 93 and 94. Oleiln feed to the reactors 90, 9| and 92 is supplied by the valve-controlled branch lines 95, 96 and 91 respectively. which supply manifolds at opposite ends of each reactor as previously described.` This provides a total of forty-points of oleiln addition vin once-through ow through the reaction zone. Propane refrigeration for reactors 90, 9|

and 92 is furnished by the valve-controlled 10 branch lines 98, 99 and |00 respectively, with the. expanded refrigerant being discharged to the return line 46 by lines |0I, |02 and |03 respectively. While four tube and header heat exchanger reactors are thus shown connected in series, it will be understood that any desired number can be employed to provide the required contact time and number of points of olefin injection. Moreover, itis obvious that a single reactor with sufElcient passes can be employed for this purpose, al-

though it is generally more economical to construct the individual reactors of a uniform smaller size and connect a number in series as shown.

While a reactor of the tube and header heat exchanger type is preferred, it is to be understood that any suitable pipe reactor ofthe heat exchange type, such as a concentric pipe reactor with enlarged return bends to provide for the mounting of the mechanical agitators and olen injectors, can be employed. Moreover, while me' 30 pure hydrocarbons or other alkylating agents, it is of course to be understood that various renchanical stirrers or agitating blades located at the immediatezones of ol'eiin vintroduction are preferred.- it'is to be understood that other forms of intensive mixing at-vsaid zones of olefin feed,

suchas'the use of mixing nozzles and orifice 35 Aplates in the-header compartments or return bends with substantial pressure drop, the use of fins, pins or other protuberances within the pipe coil to give a shearing eil'ect on a flowing `emulsion stream etc., are not excluded from the scope of 40 the presentinvention.

The reaction products discharging from the last reactor 92 pass by line |05 to centrifuge |06, where the acid is immediately separated and discharged by line |01 to acid storage tank |00. The hydro- 45 carbon phase, removed from the center zone of the centrifuge, discharges byline |09 'and passes to conventional neutralizing and fractionating equipment. Acid from storage tank |08 is withdrawn by line |10. A minor .proportion of the 5o acid may be discharged to recovery by valve-controlled line and the balance passed by valvecontrolled line H2 together with makeup acid from line H3 to the recycle pump 5 which re-v turns the recycle acid to the alkylation unit.

acid titratable acidity in the reaction zone of about 85 to 96%.,that is, about 89-96% for C4 and about 85-92% for C5, with makeup acid of about 98-100% strength. a temperature of about 20-100" F. and preferably about 35-60" F., and

sumcient pressure to maintain the hydrocarbon reactants in the liquid phase. Moreover. while the short contact time and higher acid-to-hydrocarbon ratio are preferred to obtain the superior quality ofalkylate. it will of course be obvious that the reactor of the present invention can be employed under conventional conditions with contact times of about 20-30 minutes or more and acid-to-hydrocarbon ratios of as low asv about 0.8: 1 up to the high ratio specified above. Mores paraiiln concentration in the hydrocarbon phase of the reacted mix to be reduced to about iii-50% with substantial economy, higher isoparailln concentrations of around Btl-70% and higher by volume can of course be employed.

The present invention is applicable to the a1- kylation of any low-boiling isoparailln with any normally gaseous or normally liquid oleiin. Thus, the isoparailin may be isobutane, isopentane or isohexane. The olefin may be ethylene. propylene, butylenes, pentylenes, hexylenes, other higher boiling monomeric oleflns or certain selected fractions of cracked naphthas, olefin polymers such as di-isobutylene, tri-isobutylene, cross polymers of isobutylene and normal butylenes, and various mixed or non-selective polymers. In place of oleiins as the alkylating agent, various alkyl esters, such as the sulfates, chlorides, fluorides, etc., may be used. Moreover, various aliphatic alcohols and ethers, such as tertiary butyl alcohol, isopropyl alcohol, butyl ether. etc. may be employed as the alkylating agent, particularly wth catalysts which have tolerance for water liberated in the reaction. The expression alkylating agent is used herein throughout the description and claims to denote any of the above ycompounds which react with an isoparailln or other organic compound having a replaceable hydrogen atom in this alkylation reaction to produce alkylated hydrocarbons. In place of the ery fractions, ,such as a C4, Cra-C4, CQ-Cs, C5, etc. may be employed.

'I'he present invention is applicable to the use of any of the well-known alkylation catalysts, such as sulfuric acid, hydroiluoric acid, aluminum chloride-hydrocarbon complex, BF3.nH2O, chlorsulfonic acid, iiuorsulfonic acid and the like. 'I'he various Aconditions for the reactions employing these catalysts are well known; and conventional conditions coupled with the features of the present invention as set forth above may be used.

While the reactor of the present invention is particularly suitable for use in the short or micro v contact time, alkylation of isobutane with Ca,

C4, or Cs-lmono-olens or their corresponding esy ters to produce a superior quality of isoparaiiln alkylate as described above, it is tobe understood that the reactor is applicable to the alkylation of any organic compound having a readily replaceable hydrogen atom with a suitable a1- klyating agent. For example, the method and apparatus described herein can be employed for the alkylation of a normal paraiiin with an olefin or other alkyla'ting agent, employing a catalyst effective for this normal parainn alkylation, such as HF-BFs, aluminum chloride with hydrogen,

chloride, and the like. Likewise, the invention is applicable to the alkylation of aromatica and hydroxyaromatics, such as benzene, toluene, xylene, phenol, cresol, etc., with an alkylating agent such as an olefin, an alcohol, an alkyl halide, etc. The expression organic compound having a replaceable hydrogen atom is used for convenience throughout the description and claims to designate the various materials described above which can be alkylated with the mentioned alkylating agents in the presence of suitable alkylation catalysts as described.

The following example of the present invention is listed for purposes of illustration. 'I'he alkylation reaction system comprises four reactors of the tube and header heat exchanger type conover, while the present invention enables the isonected in series, with the reaction products from Y theylast reactor discharging to a centrifuge in the manner disclosed in Fig. 1. Each reactor is of the short tube type having inch diameter tubes four feet in length. A total of 864 tubes are included in the tube bundle which is mounted within a casing 36 inches in diameter. The headers are constructed to provide ten tube passes with roughly about 86 tubes per pass. Utilizing a flow velocity through the reactor system oi' 3.36 feet per second with a pressure drop of 90 pounds per square inch, a contact time for flow through the reactor system of about 15 seconds is provided with normal size heat exchanger heads; The above figures apply to a 500 barrel per day a1- kylation unit. Utilizing 40 oleiin injection points equipped with mechanical agitation, as illustrated in Figs. 1-7, with an emulsion temperature of 50 F., a propane temperature of about 32 F.

is required to remove the heat of reaction and the sensible heat, as well as the mechanical heat at this extremely short or micro contact time. As propane temperatures considerably below this can be economically provided, it is apparent that the contact time can be still further reduced, or the olefin space rate increased above the 0.05 v./v./hr. for which the unit was designed. By

equipping each of the four series-connected reactors with blown-up heads, alfording twice the volume in the header at each end of the reactor over the standard size, a total contact time in the reactor of approximately one minute results. The overall contact time in the reaction and separating zones in the former case is slightly more than one minute; while the overall contact time with the blown-up heads is slightly less than two minutes.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departingfrom the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. The method in the alkylation of an alkylatable organic compound having a replaceable hydrogen atom with an alkylatingl agent in the presence of a liquid alkylation catalyst, which comprises introducing a mixture of said alkylatable organic compound in liquid phase and the liquid alkylation catalyst in a flowing stream to the inlet of a combined reaction and chilling zone, dividing the flowing stream into a substantial number of parallel streams, each of small cross-section and having a velocity within the range of viscous flow but below the range of turbulent ow, recombining the said parallel streams while maintaining the continuous flow thereof, reversing the direction of flow of the recombined stream, repeating the division into small parallel streams vand the recombination thereof with reversal of direction of ow a substantial number of times during once-through continuous flow through the combined reaction and chilling zone, introducing alkylating agent by multipoint addition into the reaction mix at the spaced regions of recombination of the small parallel streams by at least ten feed jets, each having a diameter of not more than Mi", subjecting the reaction mix to mechanical agitation at each spaced region of recombination and immediately adjacent each point of alkylating agent addition, and refrigeratively chilling the parallel small streams between the spaced points of alkylating agent addition.

2. The method according to claim 1, wherein the organic compound is a low-boiling isoparafiin, the alkylating agentis an olefin, the alkylation catalyst is a mineral acid, the flowing stream comprises about -95% by volume of the acid catalyst, the olefin is added at a space rate of less than about 0.5 v./v./hr., each of said parallel streams has a diameter not greater than 2" and the contact time for ilow through the combined reaction and chilling zone is less than two minutes. l

CLAUDE W. WATSON. CLIFFORD C. BURTON. LOREN P. SCOV'JLLE.

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

UNITED STATES PATENTS OTHER REFERENCES Badger et al., Elements of Chemical Engineering (page 166), 2d ed.. McGraw-Hill, 1936.

Walker et al., Principles of Chemical4 Engineering (page 316), 3d ed., McGraw-Hill, 1937.

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