US2368063A - Reaction of hydrocarbons - Google Patents

Description

Jan. 23, E945. 1 P. ELLIOTT REACTION OF HYDROCARBONS Filed May ll, 1940 Patented Jan. 23, 1945 REACTION OF HYDROCARBONS Laverne P. Elliott, Berkeley, Calii'., assignor to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application May 11,1940, Serial No. 334,603

(Cl. 26o-683.4)

3 Claims.

This invention relates to an improved process for the production ofhydrocarbon motor fuels of high antiknock value from low boiling parains and olens, and more particularly to a process wherein isoparaiiins' of less than six carbon atoms per molecule and/or normal paraliins of less than six but more than two carbon atoms per molecule are reacted with olens of less thanVK six carbon atoms per molecule by means of anlalkylation catalyst and under conditions specifically regulated tol convert a maximum quantity of the reactants into motor fuel of high volatility.

It has previously been disclosed that sobutane and/or isopentane may be caused to react with the knormally gaseous olens, such as propylene or any of the three butenes, by means of a liquid acid catalyst, such Vas sulfuric acid. It has also been disclosed that this reaction and the analogous reaction of normal parafns with oleflns may be effected by means of aluminum chloride. While the products of these reactions as disclosed correspond in substantial part to the union of one molecule of the paraiiin with one molecule of the olefin, they nevertheless contain appre# ciable quantities of hydrocarbons, both heavier and lighter than those vcorresponding to the simple addition reaction. Even so, the alkymer product as produced seldom has satisfactorily balanced volatility characteristics for use as motor fuel, and particularly for use inaviation service, without the addition of considerable quantities of either heavier -or lighter blending materials from other sources. kAnother disadvantage of the alkylation processes as previously disclosed has been that when the simple addition product is well adapted in volatility to constitute the major portion oi the desired fuel and a sufdcient quantity oi the components more Volatile than the simple addition product are simultaneously produced to give the mixture a satisfactory initial boiling point, the end boilpoint is invariably too high due to the presence of a substantial quantity oi. heavy components. Since the most widely used raw material for the alkylation reaction has beenthe butanelou-tene or C4 fraction produced during the cracking ci petroleum oil, the simple addition product has been an octane or a mixture of the isomeric octanes, much of the material boiling above the major component has been too heavy for inclusion in an aviation fuel and has thus constituted waste raw material with respect to such fuel.

lt was, however, soon discovered that if the alkymer fractions boiling above or below a desired range A are returned to the alkylation reaction they are, in part at least, used up for the production of components boiling within the desired range, and in addition they appear by their presence in the zone oi' alkylation to repress the'iurther production of components of the same boiling range. In other words, when excess light alkymers are recycled to the alkylation reactionv they repress the further production of light alkymers and are at the same time themselves further alkylated to give higher boiling products. Likewise, when heavy alkymers are returned to the alkylatlon zone they repress the formation of additional heavy alkymers and are at the same time apparently/themselves "destructively alkylated with t e production of lighter products. It has now en discovered that the same or superior results may be obtained in a more desirable andv expeditious manner and with considerable economy if-a portion of the heavy ,alkymers is subjected to catalyticv decompositionin a zone which is separate from thealkylation reaction and which is usually, though not necessarily, at a' different temperature than that at which low molecular weight oleflns with isoparaiiins and/or normal parailins of less than six carbon atoms per molecule.

' It is another object oi this invention to pro` vide a process for the production of high antlknock 4motor fuel of high volatility characteristics by alkylating isoparamns and/or normal paraiiins-'of less lthan six carbon atoms per mole'- cule with normally gaseous olelns and catalytically decomposing the product boiling above the ,desired range in a zone separate from the alkylation reaction.

It is a more specific object of the invention to provide a process for the production of high antiknock aviation fuel by the reaction of low boiling isoparamns with oleflns under conditions such that the production of fuel having a boiling point above the end point of aviation gasoline is materially reduced.

It is another specific object of this invention to provide a process for the alkylation of isoparamns of less than six carbon atoms per molecule and/or normal paramns of less than six but more than two carbon atoms per molecule by olens of less than six carbon atoms per molecule to produce a maximum of light liquid hydrocarbons boiling in the general'range of motor fuels through subjecting the heavier alkymer products in part to destructive alkylation and in part to catalytic decomposition in a separate zone and at a different temperature. y

Other objects of the invention will be apparent from the following description and the appended claims. y

The previously disclosedreaction of an isoparaln with an olefin in the presence of a catalyst, such as sulfuric acid, aluminum chloride, etc., to produce largely a single addition product together withla substantially uncontrolled amount of both lighter and heavier products has been referred to broadly as one of alkylation" and the products have been called alkymers The reaction by which heavy alkymers are converted to lighter products when returned to the alkylation zone may thus be referred to as destructive alkylation. The reaction in the separate process stage of the present invention, in which heavy' alkymers are reacted with additional alkylation catalyst to form lighter products, will be referred to as "catalytic decomposition since even though it appears that the mechanismI of the. reaction may be in part the same as that of the destructive alkylation reaction, the conditions are so different that the reaction cannot be wholly the same. It will also be found convenient to refer to the product of simple union between the principal olefin and paraffin of any given charge as the main alkymer." Thus in the case of the alkylation of isobutane with butene the main alkymer will consist of an octane or a mixture of isomeric octanes.

'Ihe alkylation of an isoparaiiin by an olefin may be effected by bringing the two together, or in proper sequence, into intimate contact with one of several alkylation catalysts at temperatures below about 200 F. and usually below 150 F. under sufficient pressure to maintain the reactants in liquid phase. Catalysts that have been found active in promoting this reaction are of what will herein be referred to as the sulfuric acid type comprising concentrated sulfuric acid, chlorosulfonic acid, mixed sulfuric and chlorosulfonic acid, mixed sulfuric and phosphoric acids, etc., and of the well-known Friedel and Crafts type comprising aluminum chloride, boron fluoride and the like. Due to the greater ease and economy of operation, the liquid catalysts of the sulfuric acid type have been more extensively employed than the solid or gaseous halide catalysts of the Friedel and Crafts type. Onthe other hand, since the catalysts .of the latter type are capable of effecting the alkylation of normal parafilns with olefins whereas those of the former type usually are not. they may be used to considerable advantage in certain circumstances. In the process of the present invention either of these types of alkylation catalysts may be employed with good results, the greater convenience of operation with a liquid .acid catalyst being oifset by the greater range of raw material available for the alkylation re- `action when catalyzed by the Friedel and Crafts type of catalyst which, as above mentioned, will effect the alkylation-not only of visoparaflins but also to a considerable extent of normal paramns by the olenns of ive or less carbon atoms per molecule at temperatures of about 200 F. or be- The rather surprising discovery upon which the process of the present invention is based is `that when the heavy allwmers produced by either of the above types of catalysts are separated and -given a further treatment' with an alkylation.

catalyst under appropriate conditions in a Se@ asoaooa ondary zone they are converted in substantial Dart to more volatileproducts entirely analogous to the light alkymers produced in the main reaction. While the over-all production of iight alkymers and the quality of the light alkymers thus produced are substantially the same as when the heavy alkymers are all returned to the alkylation zone for destructive alkylation the total quantity of alkylation catalyst required per unit of light alkymer product is materially reduced. In actual operation it maybe found desirable to return a portion of the heavy alkymer product to the alkylation zone for destructive alkylation, in order to repress the further production of heavy alkymers, and to submit the remainder of the heavy alkymers to catalytic decomposition, al further explained hereinafter. In this way substantially the whole of the olefin-paraffin hydrocarbon raw material consumed may be converted to light alkymers boiling in the more volatile motor fuel range.

For example, in the alkylation of butane -by a butene it maybe desired to produce a narrow boiling product of high volatility for aviation or other special service having. for instance, an end boiling pointof 250 F. The primary alkymer. product would then be separated by distillation and the fraction boiling above 250 F. would be submitted to catalytic decomposition or would be divided and one part returned to the alkylation zone for destructive alkylation and repression o! the further production of alkymers boiling above 250 F., while the remainder would be submitted to catalytic decomposition.

Various specific methods have previously been disclosed for effecting the parailin-olefin alkylation reaction. In one the paraffin, olefin and catalyst are brought together simultaneously info intimate contact in an appropriate reaction vessel and the product then separated by appropriate means. In another specific method which has been referred to as the "two-stage process" and which is particularly applicable with a fluid acid catalyst of the sulfuric acid type, the olefin is caused to alkylate the acid in a first stage and the alkylated acid solution thus produced is contacted, usually under somewhat different conditions of temperature, pressure, etc., with the isoperamn to be alkylated in a. second or hydrocarbon alkylation stage wherein alkylation of the isoparamn is effected. The alkylation stage of the present invention may employ either of the foregoing methods of operation, the portion of heavy alkymer recycled being returned in the former to the zone of simultaneous contact between paranln, olefin and catalyst while in the two-stage method it is added to the second or hydrocarbon alkylation stage while the portion of heavy alkymer which is to be catalytically decomposed is sent forward to a separate secondary reaction zone.A In this secondary reaction zone the heavy alkymer product is intimately contacted with additional alkylation catalyst and usually with additional isoparaflin ln'a manner very similar to the operation employed in the primary alkylation zone when operated according to the single-stage principle, the most significant point of difference being that in the secondary zone no olefin is added and the temperature is usually maintained some- Stabilized for the removal of butanes and lighter, and is then distilled to produce a fraction boi-ling below 250 F. and a bottoms fraction which may then be recycled to the secondary reaction zone, returned to theprimary alkylation zone or discharged from the system as desired.

In one preferred method of operation the heavy alkymers from the alkylation stage are divided into two portions, the one, sufcient in amount to substantially repress the further production off heavy alkymers, is returned to the primary alkylation zone while the second is subjected to catalytic decomposition in the secondary reaction zone. In this method of operation the heavy seclondary product would Ibe recycled to the secondvery satisfactory vtemperature for the alkylation of isobutane with butene is from 32 to 50 F., whereas the decomposition reaction may be satisfactorily effected at temperatures of the order of 100 F. or even slightly higher. The same alkylation reaction may be advantageously effected by aluminum chloride at temperatures in the neighborhood of 50 F. while the decomposition reacing wherein is shown the -alkylation of isobutane l catalyst separating zone, etc., as previously disclosed for effecting the alkylation reaction. Butene may be charged to the reaction zone at 2, fresh acid catalyst at 3 and isobutane and heavy urecycle alkymers at 4, while the alkymer product is removed at'5 and the used acid catalystat 6. The alkymer product is conveyed to a stabilizer I wherein unreacted isobutane and lighter hydrocarbons, when present, are separated 'and vdischarged at 8 while the alkymer product is removed at 9 to the rerun still I0 for fractionation to produce a light alkymer product of the desired end point, which may be removed at II, and a heavy alkymer fraction which is removed at I2. s

The heavy alkymer fraction removed at I2 may be divided as previously mentioned, a portion being returned by way of I5 and 4 to the alkylation zone I while the remainderis passed by way of i3 to the secondary reaction zone I4. In an alternative method of operation the total heavy alkymer product may be passed to the secondary reaction zone I4 wherein it is intimately ccn-l tacted with the acid catalyst. The latter may be that which was removed from the alkylation zone at t and conducted .to the zone I4 lby line llt, it may be in part such used acid and in part fresh acid added at i8 or it may be entirely the latter. Usually it will be found desirable to add to the reaction mixture in zone I4 a substantial amount of isobutane which may be added at I9. While the presence of isobutane in this stage of the process is not essential to the decomposition reaction. it has been found to contribute to better yields yoi the desired light product and to permit better control of the reaction. The temperature to be maintained in the catalytic decomposi :on

reaction ofA zone I4 is usually somewhat higher than that which is found desirable in a primary alwlation reaction employing the same catalyst.

When the catalyst is 96 to 98% sulfuric acid a tion vis preferably effected with this catalyst at somewhat higher temperatures, for instance at gobgit F. or sometimes even up to about The hydrocarbon products from the decomposition reaction in zone I 4 are separated from the catalyst and passed by way of 20 to the stabilizer 2I while the used catalyst is withdrawn at 22. When isobutane has been added tothe reaction in zone I4lthe excess, together with other C4 and lighter hydrocarbons that may have been produced, is removed from stabilizer 2I through 23 and discarded, recycled through 24 and'IB for further usein zone I4 or otherwise disposed of. The stabilized product is then conducted through 25 to rerun still 25 wherein it is separated into a light product, which is removed at 2'I, and a heavy product, which is removed at 28 and discharged through 29 or recycled through 30 to a point 3| where lines I3 and I5 connect. At 3l the heavy secondary product may be divided and part passed through I3 to the secondary or catalytic decomposition zone I4 and the remainder through I5 to the primary alkyla'tion zone I,' or the whole product m-ay be directed either way, depending,

as above indicated, on whether some of the heavy alkymers from I2 are being recycled for destruc tive alleviation or whether all are being subjected to the catalytic decomposition reaction in zone I4. In the latter case a substantial portion of the heavy secondary product-.would be added to the alkylation zone I for the previously mentioned repression effect.

While under most circumstances it may be found desirable to keep the alkylation reaction and the catalytic decomposition reaction substantially or entirely separated, as above described, when such is not necessary substantial plant equipment may be eliminated Iby icy-passing units I and I0 by, means of line 32, the hydrocarbon product from alkylation zone I being thus led through 5 and 32and combined with the hydrocarbon product from zone I4, either directly in line 20 or indirectly by passing through zone I4,

the combined product then passing through' 20 to stabilizer 2I and still 26 as previously described for the product from I4 alone.A When operating in this manner the light alkymers and light decomposition vproduct will, of course, be removed together at 2'I and the heavy alkymers and heavy secondary product at 28 for recycling to zone I and/or I4 as previously described.

One very worthwhile beneiit of operating according to the present invention will be seen from the following data which may be taken as representative when operating to produce a 200 F. end point blending stock by alkylating isob-utane with butene by means of a sulfuric acid catalyst:

When the alleylation reaction was effected at 32 F. in the usual manner the 200 F. end point fraction amounted to about 30% by weight of the oleflns charged. When the alkymers boiling above 200 F. were recycled the yield of light When the same operation with heavy alkymer recycle was carried out at 100 F. th'e yield of light alkymer product amounted to about EJO-113% by weight of the olen charged and the acid requirement was 4about 19 pounds per gallon of light product. When operating according to the method of the present invention, keeping the alkylation reaction 'at 32 F., recycling a portion of the resulting heavy Iallrymers and catalytically decomposing the remainder at 10D" F., the combined yield of 200 F. end point product amounted to 102% by weight of the oleflns charged, which was substantially the same as produced by recycle operation alone at 100 F., but the acid requirement, was only 8.4

pounds per gallon of light product, which was less than half that required in the former method of operation.

In another and sometimes preferred method of operation the 'division of the alkymer product effected in stills I0 and/or.26 would be made at about 220 F. in order to recycle and/or catalytically decompose only the alkymers higher boiling than the preferred octanes, such as 2,2,4-trmethyl pentane, and hence to conserve to the maximum degree compounds of the highest antiknock value.

While the foregoing explanation and data and the accompanying drawing illustrating the process of the present invention have referred particularly to the alkylation of isobutane with butene by means of a sulfuric acid catalyst, the process is equally applicable to the alkylation of other isoparaillns with other olens by means of the several catalysts of the sulfuric acid, type and the alkylation of both normal andv iscparamns'with the oleflns by means of catalysts of the Friedel and Crafts type.'

While it will usually not be found convenient tc so operate, it is entirely possible to operate the process employing different alkylation catalysts in the alkylation stage and in the catalytic decomposition stage and such modification is contemplated within the scope of the present invention. f i

Having now described and illustrated a proc- 4 ess for the eflicient production of light hydro- -carbon blending materials in improved yield from the alkylation of parafllns .with oleiins wherein heavy alkymers are in substantial part' catalytically' decomposed by an alkylation `catalyst in a zone separated from the alkylation4 zone, I claim as my invention: 4

1. In a process for alkylating isoparamns with olefins by means oi' an alkylation caatalys1r`ofvw l the sulfuric acid type in which the hydrocarbon` phase is substantially freed of C4 and lighter hydrocarbons and the remainder fractionated f into a cut consisting essentially of desired gasoline constituents and another cut of constituents heavier than the desired gasoline constituents, the improvement for increasing the yield of constituents Iboiling within the desired gasoline range which comprises treating said cut of constituents heavier than the desired gasoline constituents in a second zone separate from said alkylation zone and to which said second zone no other hydrocarbon reactants are added, using sulfuric acid of alkylating strength under alkylating conditions in said second zone at a higher temperature than that prevailing in said alkylation zone, fractionating the hydrocarbon phase produced in said second zone and recovering desired gasoline constituents not present in said heavier cut supplied to said second zone.

2. A process 'for producing volatile motor fuel hydrocarbons of high anti-knock value comprising alkylating. an isoparaiiln of less than 6 carbon atoms per molecule with av normally gaseous olefin in an alkylation zone by means of an alkylation catalyst of the sulfuric acid type under alkylating conditions, separating the resulting alkymers from the catalyst, fractionating the hydrocarbon phase to obtain a cut heavier than the desired gasoline constituent,

30 and catalytically decomposing said heavier cut of alkymer product by means of4 an alkylation catalyst of the sulfuric acid type in a separate zone, to which no other hydrocarbon reactants are added, at a temperature higher than that maintained in said alkylation zone.

3. A process for producing volatile motor fuel hydrocarbons of high anti-knock value comprising alkylating an isoparafiin of less than 6 carbon atoms per molecule with a normally gaseous olefin in a primary alkylation zone by means of an alkylation catalyst of the sulfuric acid type,.separating the resulting alkymer from the catalyst, fractionating such resulting alkymer to separate a heavier alkymer out composed of 5 constituents heavier than the desired volatile arate zone, to which no other hydrocarbon reactants are supplied, employing an alkylation catalyst of the sulfuric acid type in said separate zone and maintaining a higher temper- ',aturc condition in said separate zone than in the primary alkylation zone.

LAVERNE P. Ermo'r'r.

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