US2244556A - Reaction of hydrocarbons - Google Patents

Description

M. M. HOLM ET AL REACTION OF HYDROCARBONS Filed Oct. 12, 1,940

.June 3, l9`41.

"duced and the product Patented June 3, 19,41

f uNl'rEosTArEs PATENT oFFlcl-z.

` chiasso l i i Melvin M. Holm,

ley, El Cerrito, SegundmCs San Francisco, Eugene H. Oaki and llaobert LJHumphrcys, El assignors to 'Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware.

Application October 12, 1940, Serial No. 360,871 s claims. (ci. rss-lio) This invention relates ,to an improved process for the manufacture of high antiknock motorfuel hydrocarbons by the reaction of paramnic hydrocarbons with olefinic hydrocarbons in the presenceof a sulfuric acid catalyst.

This application is a continuation-in-part of our copending application Serial. No. 281,168 vfiled June 26, 1939, now Patent No. 2,224,102.

It is known that isoparafiinic hydrocarbons can be reacted with oleflnic hydrocarbons to produce pounds having a number of carbon atoms equal to the sum of the carbon atoms in the reacting isopraiiln and olen molecules. For example, the alkylation of isobutane with a butene to make a product rich in isooctane by contact and vigorous agitation with a strong sulfuric acid catalyst is.

now an established commercial process. The

product of such alkylation reactions will be referred to herein as an alkymen In the application of this general alkylation reaction to the manufacture of motor fuel from the isoparaillns and olens of low molecular weight, especially in the manufacture of aviation gasoline from the normally gaseous isoparailins and oleiins, it is necessary that the product meet certain rigorous standards as to quality, `such as Y isoparalnic hydrocarbons predominating in com; i

' tion of isoparaifins a new and improved process for the alkylation of isoparaiiins with oleiins to produce saturated high antiknock motor fuel hydrocarbons. y

Still another object of this invention is to provide a new and improved process for the `allrylarated high antiknockmotor fuel hydrocarbons, the product of which process contains a high proportion of such hydrocarbons boiling inthe range of aviation gasoline. g

Another object of t is invention is to provide a new and improved prdcess for the alkylation of isoparamns with olefins to produce an alkymer product having a low bromine number and a high those relating to antiknock value, brominenumber, gravity and boiling range. Due, however, to numerous difficulties and to the large number of unsuspected variables encountered in the operation of an alkylation process for the production vof'good quality alkymer motor fuel, it has heretofore been impossible to obtain a product having as high a quality as desired.

In our copending application, Serial No. 281,168, we have disclosed that by keeping the concentration of alkyl acid sulfate inthe sulfuric acid catalyst at a low value, which is always below 2% by weight of the acid and usually ,is substantially below 1%, larger yields of alkymer products boiling in the range of aviation motor fuels areprohas a lower bromine number and a higher antiknock value .than when higher concentrations of alkyl acid sulfate are permitted to build up in the catalyst, It was also disclosed that the desired low concentration of alkyl lacid ester may be maintained by controlling the Vrateof addition of'fresh acid to the process, by controlling the feed rate and the composition of the charge to be alkylated and thereby the ratio of olefin to sulfuric acid and of isoparaiiln to olefin, by controlling the degree of contacting of the hydrocarbon reaction mixture with the acid cata- A. P. I. gravity.

Still another object of 'our invention is to provide anl improved process for the alkylation of isobutane with butene by means of a sulfuric acid catalyst to produce a substantially saturated alky. mer product of the highest antiknock value yet obtained boiling substantially entirely in* the` rangeof aviation gasoline. *l

Other and further important objects of this invention will1 become apparent from the following description and the appended claims.

In one method of effecting the alkylation of isoparafilns with oleiins by means of a sulfuric acid catalyst the olefin or oleiins and the isoparafiln or isoparaillns to be alkylated are continuously mixed with the sulfuric acid catalyst at a relatively low temperature, usually below F., and under lsuiilcient pressure to maintain the reactants4 in liquid phase. This mixture is agitated to assist in obtaining contact between the acid catalyst and the hydrocarbon reactants and thus to assist in effecting the alkylation reaction The mixture is then passed to a separating zone whereinthe sulfuric acid catalyst is separated from the hydrocarbon phase comprising unused reactants and products.

The absorption of an weight by strong sulfuric olen of low molecular Mld i8 B Substantially with olenns to produce satuinstantaneous reaction while the alkylation of an isoparaiiin by an olefin, at least under conditions hitherto disclosed, appears to be a relatively slow reaction and consequently the vconcentration of alkyl acid sulfate in the sulfuric acid catalyst will have a tendency to increase unless special precautions are taken to prevent it. However, irrespective of the theoretical explanation of why the alkyl sulfate concentration tends to increase, we have found that certain undesirable results, such. as low yields of aviation gasoline fraction and relatively low antiknock value of the alkymer product, are associated with too high concentrations of alkyl acid sulfate in the acid catalyst and we have now discovered a new and eiective process for isoparafiin alkylation in which novel means are employed for eliminating these diiiiculties and whereby an improved alkymer product, of higher aviation gasoline content, higher antiknock value and higher degree of saturation ls produced.

The process oi this invention contemplates the alkylation of isoparaiiins with oleiins by intimately contacting them, preferably in liquid phase, with sulfuric acid of alkylation strength and controlling the alkyl acid sulfate concentration in the sulfuric acid at a low value and always below certain critical concentrations, so that the maximum production of alkymers of the highest possible quality may be obtained, by regulating and coordinating the composition of the reaction mixture.

According to one embodiment of our invention the concentration of alkyl acid sulfate, resulting ,from the reaction of sulfuric acid and olefin, is

maintained below certain critical values, which are related to the quality of the product, and especially the antiknock value. bromine number and content of aviation gasoline fractions in the product. The concentration of alkyl acid sulfate in the sulfuric acid'catalyst is maintained continually b'elcw ,about 2% by weight of the acid for all temperatures of operation and below about 1% by weight of the acid for temperatures of operation above about 40 F. Even'when the temperature of operation is maintained below 40 F. it is preferable, in order to realize the maximum utility of the sulfuric acid as an alkylation catalyst and to produce alkymers of the highest quality, that the concentration of the alkyl acid sulfate be maintained always below about 1% by weight of the acid. This is effected by maintaining in the reaction mixture a high concentration of isoparafiin, a high ratio of isonaraiin to olefin, a high relative proportion of acid catalyst in the reaction mixture at the point of its initial con-f tact with the oleiin and the highest practical degree of contact between the hydrocarbon and acid catalyst phases.

We have found that when the composition of the reaction mixture is so controlled and maintained within the limits presently to be discussed an alkymer product may be produced which boils substantially 100% within the range of aviation gasoline, has a bromine number substantially less than 1.0 and has an voctane number usually between about 96 and 97.5 by the research motor method. whereas the product produced under conditions not particularly designed to maintain a low alkyl sulfate concentration may contain a maximum of 85 to 90% of aviation gasoline having an octane number of about 92 to 93.

While itis customary in effecting the alkylation of an isoparaiiin with an olen by means of a sulfuric acid catalyst to maintain a molecularexcess of the isoparamn over the olen in the reac- `instance in the range between 100 and 700 to 1 or even higher at the'point of intial contact between the oleiin and the acid catalyst and at the same time maintaining the concentration of the isoparaiiin to be alkylated in the hydrocarbon phase of the reaction mixture always above 50% and usually above about 60% by liquid volume While effecting a high degree of mechanical agitation and thus producing a maximum surface of contact between the hydrocarbon and acid catalyst phases by means of an efficient mechanical contacter, an alkymer product of high antiknock value, above octane number, and high aviation gasoline content, usually 99% or better, may be produced.

This invention may be better understood by reference to the accompanying drawing wherein one specific embodiment exemplifying the invention is shown in the figure. In this embodiment a mixture of normally gaseous hydrocarbons containing an lsoparailin to be alkylated and the olen for effecting the alkylation may be introduced through line I while the catalyst, sulfuric acid usually of about 96% to 98%v H2804, is introduced through line 2. The mixture of catalyst, olefin and isoparain is rapidly passed through line 3 to a mixing or agitating device d, which maybe a centrifugal pump, turbo-mixer, etc. operated at high speed or other appropriate device for eecting a. high degree of contact between the hydrocarbon phase and the acid vcatalyst phase. In this mixing pump the acid catalyst and the hydrocarbon phase, including the olefin and isoparaiiin reactants, are thoroughly. mixed to give the largest practical surface of contact and thus to effect the alkylation reaction quickly and the sulfuric acid'catalyst may be separated from the hydrocarbon phase by gravity.

From the separator 6 hydrocarbons and any unseparated sulfuric acid catalyst withdrawn through line 7, controlled by valve 29, may be passed into a neutralizer 8 in which the hydrocarbons are contacted with a neutralizing agent, such as a caustic alkaline material or the like, introduced into 8 through line 9, to remove the acid and acid reacting bodies, `such as alkyl esters present in the hydrocarbon phase. Used caustic solution which has settled in neutralizer d may be withdrawn through line i 0 or may be recirculated by pump ii through lines i2 and 9. From the neutralizer t the hydrocarbons may be passed through line to a settling tower,A i3 where the used alkaline solution settles out from the hydrocarbons and is withdrawn through line it or may be recirculated to the neutralizer 8 by pump i5 through lines it and 9. Fresh caustic may be added when required through line i7 communieating with lines it and 9.

Some of the hydrocarbon phase withdrawn from the separator t through line 'i may be passed into line iii, controlled by Valve i9 and recirculated through the mixer i and the separator t. These hydrocarbons will include some of the alkymer product and a substantial quantity of unreacted isoparafdn'which will materially' d essential features of the present invention.

Used acid may be removed from the lower part of separator l through line 2| and discharged from the system through valve 22 or recirculated through line 2, controlled by valve 23. Fresh acid to replace that which is discharged from the l, 2,244, I alkylation which, as pointed out above, constitute system maybe added through line 24, controlled f by valve 43, which communicates with line 2.

Instead oi' operating the separator 6 so as to eifect the substantially complete separation of acid and hydrocarbons and then recycling the separated acid and hydrocarbons, as just described, it is frequently found preferable to pass the reaction mixture through the separator 6 at'such a rate that while a very substantial amount of coalescence isfeifected, no continuous acid phase is ever actually separated therein and the recycle stream returned through 4valve 23 and line 2 to the initial alkylation none in mixing pump 4 is thus composed of both acid and hydrocarbons.

When, due to the more rapid passage of the I reaction mixture as just described or for other reasons, the stream passing from the separator 6 through line 1 contains any considerable quanuse, 3

mal and isobutane in a ratio of about three to one and about 45% of normal and isobutenes also in the ratio of roughly three to one. It will thus be readily seen that the hydrocarbon phase of the reaction mixture in the zone of active alkylation in pump 4 and immediately thereafter would contain, after the substantially instantaneous and complete absorption of the olens by the sulfuric acid, a several fold excess oi hydrocarbons other 'than isobutane unless precautions were taken to`prevent it. Due to the recirculation of normal butane and alkymer products through lines 2 and I3, as above described, the concentration of isobutane in the reaction mixture would thus `quickly be reduced to a very low value. We have discovered. howy ever, and it is an essential feature of the present invention, that in order to maintain the desired low concentration of alkyl acid sulfate in the sulfuric acid catalyst and thereby to produce an alkymer product of the highest possible quality, the concentration of isobutane in the hydrocarbon phase in the zone of active alkylation must bemaintained in excess of 50% and preferably in excess of about 60%. This condition may be realized by charging auxiliary isobutane through i line 46 and by separating the mixture of isovalve 58 and the hydrocarbon led directly to line l 25 and stabilizer 26.

Hydrocarbons, which include the alkymers and unreacted normally gaseous hydrocarbons, may be removed from the upper part of settler I3 or from line 51 through line 25 and passed to an alkymer stabilizer 26 which contains heating coil 21 or equivalent heating means, II the oleflnic or isoparaiilnic charge to. the system contains normal paraiilns, a mixture of normal and isoparaftln, such as normal and isobutane, may be removed from the stabilizer 26 overhead through line 28, condensed in condenser 29 and collectedA in receiver 30. Some of the condensate in receiver 30 may be returned to the upper part of stabilizer 26 through Aline 3l in order to provide adequate reilux liquid. On the other hand, should the hydrocarbons charged to the system contain no normal paraffin, such as normal butane, the unreacted isoparailln, such as isobutane, may be passed Vdirectly from the stabilizer 26 through line 32, controlled by valve 33 and returned to the mixing zone through line l. Alternatively, the mixture of normall and iso- "parailln may be passed directly to mixer 4 through lines 32 and 3 if desired. The material being returned through line 32 may be liquitled when necessary by any known means, such as a condenser or compressor not shown in the drawing. The alkymer product may be withdrawn from stabilizer 26 through line 34, controlled -by valve 35 and passed into a still 36 where the alkymr product may be distilled into any de-` sired cuts, such as van aviation gasoline cut and i a bottoms cut.

When the hydrocarbon charged to the system through line I is, as is frequently the case, a usual fraction from a cracking reaction, such as the C4 or butane-butane cut, it will contain norbutane and normal butane, collected in receiver 30 by passing it through line 31 to an isoparailln still 36 from which normal paraffin is removed as bottoms through line 33 and isoparailln is taken of! overhead through line 40, condensed in cooler 4| and collected in receiver 42, and returning a portion of the isoparailin from receiver 42 to the mixing zone through lines 44 and 32. Isoparail'in withdrawn from receiver 42 may be returned to still 38 as reflux through valve con-4 trolled line 43, or withdrawn through valve controlled line 45, as desired.

The amount of recirculation of reaction mixture through lines 2 and I3 and the amount of recirculation of isobutane through line 32 necessary to maintain a minimum concentration of isobutane above about 50% in the hydrocarbon phase will,'of course, depend to a large extent upon the composition of the feed entering through lines i and 46'. When this feed contains no normal butane the amount of recirculation' may obviously be materially less than when the relatively high proportion of normal butane orf dinarily contained in the C4 cut produced in the cracking operation is present.

It might at first lglance appear that by keeping the ratio of isoparailin to olefin at the high ratio, of above 50 to l, as in one feature of the present invention the high isoparamn concentration constituting the other essential feature of the invention would be automatically fixed. The two quantities are, however, entirely independent andboth require to be adjusted in order to produce anything like the highest quality allwmer product from a given reaction. This may be illustrated by the following two hypothetical reaction mixtures, I and 1I:

The isoparailln to olefin ratio is to l in both. v

while the concentration of isoparaiiln is 30% and 70%, respectively. When submitted to the same conditions of alkylation the -aviation gasoline fractions (initial boiling point about 85 i?. and

90% off at 275" F.) produced from raw materials of these compositions might be expected to be of the order of 93.0 and 96.1 octane number, respectively. This point is further illustrated by the following two examples from actual plant opera- M Although the alkylation reaction of the present invention may be edected with the isoparaiilns and olens in the gas phasa, it is preiierred to operate with these reactants in the liquid phase. The sulfuric acid used may be of any concentration known to eiiectthe alhylation re" action, though it is preferred to use sulfuric acid of a concentration between about 95 and about 98% H2SO4. The temperature of the reaction may be any temperature known for the alkylation of an. isoparafdn by an olen with sulfuric acid as the catalyst, though it is preferred to operate between 15 F. and 150 F. While the process of our invention may be used to eiect the ailsylation of any isoparain with any oleiin known tobe capable of such reaction, it is especially suitable for the alkylation of normally gaseous isoparamns with normally gaseous oleins, such as are usually present in gases obtained from the cracking oi' petroleum, for example the alkylation oi isobutane or isopentane with propylene or any of the butenes.

It will be understood that whenever reference is made herein to the ratio of isoparamn to olen it is intended to mean the molecular ratio of light isoparalln, such as isobutane, to be alkylated to oleiin capable of effecting the alkylation, such as normal butene or its equivalent in polybutene. It is also to be understood that whenever the concentration of isoparamn in the hydrocarbon phase is mentioned it is intended to mean the percentage isoparafiin by liquid Volume of the total hydrocarbon in the reaction mixture even though a portion or all of the hydrocarbon may actually exist in the vapor phase.

Having thus disclosed and described our invention which comprises the allrylation oi' isoparailins with olei'lns by means of a sulfuric: acid catalyst in which the concentration oi alhyl acid lsulfate is maintained at a low value by maintaining the ratio of isoparaln to ol at the point of initial contact between the olen and acid above a ratio of about 50 to l andthe concentration of isoparamn in the hydrocarbon phase in the alkylation zone above about 50% and preferably above 60% by liquid volume and submitting the reaction mixture to vigorous mechanical agitation in order to provide a maximum surface of reaction between the hydrocarbon and the acid catalyst phases, we claim as our invention: l y I 1. Process of manufacturing high anti-knock ams, and olefin, which comprises charging said gaseous mixture to a reaction zone wherein isoparamn is alkylated with oleiin by contact with an alkylatlon catalyst comprising sulfuric acid oi alkylating concentration, simultaneously maintaining the concentration` of isoparamn to be alkylated in the hydrocarbon phase oit said reso# tion zone above 60% by liquid volume of the hydrocarbons, maintaining the ratio of isoparan to olefin at the point where the olein initially contacts the catalyst above to 1, and maintaining a high degree of contact between the acid and hydrocarbon phases to produce a high yield of high anti-knock motor fuel hydrocarbons boiling in the aviation gasoline boiling range;

2. Process of manufacturing high anti-knock motor fuel constituents boiling in the aviation gasoline boiling range from isobutane and butene which comprises alkylating isobutane with butene by Contact with an alkylation catalyst comprising sulfuric acid 'of alkylating concentration, simultaneously maintaining the concentration of isobutane in the hydrocarbon phase in said reactionizone above 60% by liquid volume of the hydrocarbons, maintaining theratio of isobutane to butene at the point where the butene initially contacts the acid catalyst bove 100 to l, and maintaining a high degree o contact between the acid and hydrocarbon phases to produce a high yield of high anti-knock motor fuel hydrocarbons boiling in the aviation gasoline boiling range.

3. The improvement in the process of allryiating isoparaiiins with olens by means of an alkylation catalyst comprising sulfuric acid of allryiating concentration which comprises maintaining the alkyl acid sulfate concentration in the catalyst suiiiciently low to produce a high quality product by eiecting a sumciently high degree of mixing of hydrocarbon and acid catalyst phases thus producing a sumciently large surface of contact between said hydrocarbon and acid catalyst phases while simultaneously maintaining the molecular ratio of isoparan to. be alkylated to olefin at the point where oleiin initially contacts the acid catalyst above 100 to l and maintaining the concentration of the isoparaiiin to be alkylated in .the hydrocarbon phase oi the reaction mixture above 60% by liquid volume of the hydrocarbons.

a. The improvement in the process of alkylating isobutane with butene by means of an alkylation catalyst comprising sulfuric acid of alkylating concentration which comprises maintaining the butyl acid sulphate concentration in the catalyst sufliciently low to produce a high quality product vby effecting a sumciently high degrec ci. mechanical agitation of hydrocarbon and acid catalyst phases thus producing a sumciently large surface of contact between said hydrocarbon and acid catalyst phases while simultane- 1 ously maintaining the molecular ratio of isobutane to butene at the point where butene initially contacts the acid catalyst above 100 to l and maintaining the concentration of the isobutane in the hydrocarbon phase of the reaction mixture above 60% by liquid volume of the hydrocarbons. i

f5. 'liheimprovement in the process of alklating isoparamns with olens by means of an alkylation catalyst comprising sulfuric acid oi' alkylating concentration which comprises maintaining the alkyl acid sulfate concentration in the catalyst Vbelow about 2% to produce a high quality product by effecting a sumciently high degree of mixing oi.' hydrocarbon and acid catalyst phases thus producing' a suiiiciently large surface of contact between said hydrocarbon and acid catalyst phases while simultaneously maintaining the molecular ratio of isoparafiln to be tially contacts the acid catalyst above 100 to 1 and maintaining the concentration of the isoparaffin to be alkylated in the hydrocarbon phase of the reaction mixture above 60% by liquid voiume of the hydrocarbons.

6. The improvement in the process cf alkylating isobutane with butene by means of an alkylation catalyst comprising sulfuric acid of alkylating concentration which comprises maintaining the butyl acid sulfate concentration in the catalyst below about 1% to produce a high quality product by effecting a suiilciently high degree of mechanical agitation oi.' hydrocarbon and acid catalyst phases thus producing a suiiciently large surface of contact between said hydrocarbou and acid catalyst phases while simultaneously maintaining the molecular ratio of iso- .butane to butene at the point where butene initially contacts the acid catalyst between 100 to 1 and 100 to 1, and maintaining the concentration ci the isobutane in the hydrocarbon phase o! the reaction mixture above 60% by liquid volume of the hydrocarbons.

7. Process as deiined in'claim 2 in which the concentration of 'isobutane in the hydrocarbon phase in said reaction zone is maintained about 70% by liquid volume of the hydrocarbons.

8. Process as deined in claim 3 in which the concentration of the isoparaln to be alkylated in the hydrocarbon phase of the reaction mixture is maintained about 70% by liquid volume of the hydrocarbons.

MELVIN M. HOLM. EUGENE H. OAKLEY. ROBERT L. HUNIPHREYS.

DlscLAlM'ER.

2,244,556.-Melvin M. Holm, San Francisco, Eugene H Oakley, El Cerrito, and Robert' L. Humphreys, El Se do, Calif. REACTION oF HYDRoCARBoNs.. Patent dated June 3, 1941. liclaimer ld April 3, 1943, by the assignee, Standard Oil ompany of California. f Hereby enters this disclaimer to claims l, 2, 3, and 4 of. said patent.

[Q'Clll Gazette May 4, 1.943,]

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