US2283603A - Manufacture of motor fuel - Google Patents

Description

i May 19, 12942. AIR. GoLDsBY x-:T Al. 2,283,603

MANUEACTURE OF MOTOR FUEL Filed March 18, 1938 FRANK H. BRUNER INVENTORS ATTORNEY E nl si s III w mul-.Thum

-ARTHuh R. GoLoseY BY I may Patented May 19, 194.2

UNITED STATES PATENT OFFICE 2,233,603 y IMANUFACTUBE or Moron FUEL Arthur R. Goldsby and Frank H. Bruner, Beacon, N. Y., assignors, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application` March 18, 1938, Serial No. 196,669

v 8 Claims. This invention relates to the manufacture of high antiknock hydrocarbons, particularly liquid it is desirable to maintain an excess of isobutane in the reaction mixture and the principal object of the present invention is to provide means for a continuous recycle process in which the excess isoparaiiins are recycled.

The present invention contemplates broadly 20 (Cl. 19E-10) in the presence of sulfuric acid catalyst and a recycle fraction containing the excess isobutane is separated from the reaction products and recycled. Ordinarily the reaction products, after separation from the acid, are fractionated to separate the normally liquid hydrocarbons, and then unreacted normally gaseous hydrocarbons,

, all or in part, are fractionated v'to obtain a fracthe treatment of isoparailins with oleilnic hydrocarbons wherein the excess isoparaftlns may be separated and recycled in the process. The invention is speciiically intended for the alkylaliquid or normally gaseous, particularly normally gaseous olens, such as C4, C: or a mixture of C4 and C: olens, with or without the presence of paraiiins of the same number of carbon atoms. The invention is particularly suitable for the alkylation of isobutane with unsaturated nor-` mally gaseous hydrocarbon fractions, suchas C4 cracked hydrocarbon fractions or mixtures of Ca and C4 cracked gases.

In the alkylation of isoparains with oleiins, according to the herein described process, strong sulfuric acid of preferably about 92 to 98%, for example 94%, is used. Temperatures may range from around normal Vatmospheric temperatures to 120 F. or over, and preferably about 75 to 90 F. A ratio of acid to oleflns of about 1:1 or more may be used and the `acid may be recycled in a concurrent or countercurrent type of operation. The molar ratio of,v isobutane to oleiins may range between about 1:1 and 20:1, and preferably atleast about '3:1, and up to 5: 1 and higher is advantageous. The advantages of the high ratios of isoparafiin to olefin includean increased yield of alkylate within the aviation gasoline boiling range, and an improved octane of such alkylate.

According to one method of the present invention, a hydrocarbon charge containing an excess of isobutane above that which normally may be tion of isobutane with oleiins which are normally 25 tion-rich in isobutane which is recycled. The recycled fraction may contain, in addition to the isobutane, a small amount of normal paraiins, such as propane and butane. It is sometimes advantageous to retain all or part of the n-butane in the normally liquid products to impart volatility thereto. In case there is an excess of paraiiins, such as n-butane or propane, it is undesirable to retain the n-butane in the normally liquid products, and itmay be necessary to pro'- vlde means for eliminating the paraiilns such as n-butane or propane in the system in order to avoid the building up of such parailins therein. This may be done by fractionating the'gaseous hydrocarbons whereby a cut is made between the paratlins andisoparaffins, for example between the n-butane and isobutane. The isobutane or fraction rich in lsobutane is then recycled.V When operating as described above to fractionate lbetween the parafn and the isoparaflin hydrocarbons to provide an isobutane-rich fraction,

which fraction is recycled to the alkylation reaction zone, there is inherently effected a reduction in the proportion of normal parafn, such as normal butane, in the reaction zone during continuance of the process to a proportion substantially below that in the fresh hydrocarbon charge where the latter comprises a hydrocarbon fraction, such as a'customary refinery cracking gas, containing a substantial proportion ,of normal paraiiin. Certain advantages are inherent 40 in thisV disclosed method oi operation, since this avoids normal paraffin concentrations in the reaction zone which result in decreased yields of total alkylate and aviation fractions thereof onV the basis of the olefin charged while enabling available refinery cracking gas to be employed olens is present or the isobutane is insufficient aikylated with theV olefins present, 1s amylatea 55 to give the optimum results, particularly from the yield and antiknock standpoint. In such a case it is undesirable to recycle the small amount of unreacted isobutane. Since it is advantageous `to have a high proportion of isobutane, for ex- Y .,..,vided with a stirring mechanism 1|8.

`i ;.reactor the hydrocarbon mixture is intimately :contacted with Vfresh acid catalyst charged ample a molar. ratio of isobutane to oleiins of at least about 3:1 and up to 5:1 and higher, it is desirable when using such a charging stock to provide an auxiliary charging stock comprising isobutane in suiiicient amount to provide a mixture in which the desired ratio of isobutane to olens is obtained. This auxiliary charging stock may be substantially pure isobutane or a charging stock suitable for alkylation but containing a proportion of isobutane higher than the preferred range. It is intended that whenever using charging stocks deficient in isobutane, that this deficiency may be overcome by adjusting the proportion of isobutane or by the addition of auxiliary charging stocks or by the use of multiple charging stocks, whereby a mixture containing the desired proportion of isobutane is obtained. It is also intended that there will be an excess of isobutane which may be recycled in the process to maintain the desired ratio of isobutane to oleflns in the reaction mixture.

,l The invention will be further described in connectionA with the accompanying drawing which shows diagrammatically onel form of apparatus for carrying out the process of the invention.

Referring to. the drawing, a hydrocarbon charging stock is drawn'through the line I and valve 2 by the pump 3 and introduced into a reactor 5. In this reactor", the hydrocarbon is intimately contacted by means of stirring mech- Y anism 6 with used acid catalyst introduced through the line 8. The mixture of catalyst and hydrocarbon is transferredI by the pump 9 through the line l0 to a settler I2. wherein the spent acid is allowed to separate and collect in the lower portion thereof and may be withdrawn through the valve controlled line I4. The partially reacted hydrocarbon mixture flows through valved line I5 to a second reactor I6, also pro- In this through line 2li-.in which is located a valve 2| and pump 22,11-The mixture of acid and hydrocarbon Vis.. drawn from the bottom of the reactor l5 by thepump 23 and charged through the line 2| to a .settler 25. In this settler the acid is allowed .to separate from the hydrocarbon and collect-'in the lower portion thereof. This spent acid is withdrawn from the bottom of the settler bythe pump 26 and recycled to the reactor 5 `through the line 8. While acountercurrent type of operation for contacting the' hydrocarbon and through the line 32 in which is located valve 33V communicating with the line 28. The alkali so introduced is intimately contacted with the hydrocarbon in the scrubber 3l to effect neutralization of the acid bodies in the hydrocarbon. The scrubber 3| may contain suitable mixing deare . hereinafter.

vices, such as orifice plates or baltes."l The mixture of hydrocarbon and neutralizing agent is transferred from the upper portion of the scrubber 3l through the valve controlled line 34 to settler 35 in which the neutralizer is allowed" to settle out in the lower portion thereof. This spent neutralizer may be withdrawn through the line 35 or all or any part thereof recirculated v through the by-pass line. 38 by suitable regulation of valves 33 and 40. The neutralized hydrocarbons aretransferred from the settler 35 to a stabilizer-42 by means of the line 43 in which is located valve 44 and pump 45. In the stabilizer the normally liquid hydrocarbons and a portion or all of the butane are separated and transferred from the lower portion of the stabilizer to a fractionator I6 by means of the line 4l in which is located valve 48 and pump 50. The normally gaseous hydrocarbons including the isobutane, and all or a portion of the n-butane and hyc'irocarbons lighter than C4 hydrocarbons, are'removed as vapors from the upper portion yfof the stabilizer through the line 5|, in which is located a pump 49, and introduced into a fractionator 52.

The operation of the fractionator 52 may vary considerably. depending on the compositionfof the vapors to be fractionated therein. I'the vapors are low in butaiiLcQntent, it may be unnecessary to make a separation between the butane and isobutane and irisuch case the entire C4 fraction may be recycl'edgto the system. This fraction may be withdrawn Vasga liquid from the lower portion of the fractionatorthrough the line 53 while the lighter hydrocarbons may be removed from the upper portion of -the fractionator through line 54. If the hydrocarbon mixture contains substantial amounts of propane a portion of this may be retained in the lliquid fraction withdrawn through the line 53 for recycling to the system, although it is desirable to preventbuilding up of propane in the system, and most of such propane would be taken off overheadthrough line 55. If the hydrocarbons to be fractionated in the fractionator 52 contain an excess of n-butane, it is desirable to make a separation of the n-butane in orderv to avoid building up thereof in the system. Accordirigly,"l thebutane ma'yxbe fractionated and collected inf. the lower portion. of the fractionator and withdrawn through thelline 53.

A cut containingfthe isobutane may be removed as a side stream from the fractionator 52'4 through the valve controlled line 55'. This side stream may comprise essentially isobutane but ordinarily contains in addition some normal butane. Also if Ca hydrocarbons are present, the side stream may contain allor a portion of the C3 hydrocarbons. The lighter gases undesirable for recycling with the lsobutanel through line 55, are removed overhead from the fractionator through the line 54. 'I'he isobutane fraction removed in the side stream through the line 55 is forced by the pump 56 through line 58 to the 'charge line I through which it is introduced `into the reactor 5.

'I'he n-butane fraction removed from the lower portion of the fractionator 52 through the line 53 may be withdrawn from the system but it is preferably pumped by the pump 68 through the branch line 6| to the accumulator 52 referred to Branch line 63 connects the line 6I with the line 55 whereby all or a portion of the material withdrawn from the lower portion of the fractionator 52 may be recycled tothe system through line 55, pump 56 and line 58. This recycling of the fraction withdrawn from the lower' portion of the fractionator 52 may 1 recycle a portion .of the heavier fraction, .for exv` ample when there is poor fractionation between the 'r1-butane and isobutane.

The normally liquid' hydrocarbons introduced into the fractionator 46 arefractionated therein to make a separation between the gasoline fraction and fraction heavier than gasoline. They heavier fraction is withdrawn from the lower portion of the fractionator through the valved line 65 while the gasoline fraction is removed as vapors overhead through the vapor line 66. These vapors are condensed in the condenser 61 and pass through the run-down line 68 to accumulator 62 which is provided with a gas release line 69, and a liquid draw-off line 10. The gasoline fraction accumulated in the accumulator 62 may be deficient in butane for commercial gasoline specifications and accordingly any desired amount of excess butane from the system may be.

introduced therein through the line 6| referred to heretofore.

An auxiliary hydrocarbon charging line 12,'jin which is located a valve 13 and pump 15, is provided for introducing isobutane, o r any charging stock containing isobutane, in sufficient amount to make up any deficiencies in the isobutane content of the main charging stock, or for supplying an adequate amount of isobutane in the system,

' oleiins, which vcomprises continuously introducing settling zone-where the reaction .products separate into a hydrocarbon layer and a catalyst layer, continuously removing hydrocarbon from the hydrocarbon layer and catalyst from the catalyst layer, adding additional catalyst to the reaction zone to make up for that withdrawn,

.- stabilizing the removed hydrocarbon to separate to maintain the desired ratio of isobutane to The system is ordinarily operated under suiiicient pressure to maintain the hydrocarbons in the liquid phase, for example 25 to 150 pounds pressure. In some cases, for purposes of facilitatingv fractionation, the stabilizer 42 or the fractionator 52, or both, may be maintained under pressures which may vary somewhat from those maintained in the treating system.

vAs an example of the operation of the invention, an unsaturated C4 hydrocarbon charging stock, showing a ratio"of isobutane to olefns of ,f

about 1.221, was mixed with recycled isobutane to bring the ratio of isobutane to olen to about 3:1 and the mixture contacted with sulfuric acid of about 94% concentration at around 90 F., for suicient time, for example about an hour, to alkylate the isobutane with the olefins, whereby substantially all the olens were consumed. The

reaction products were neutralized and the hydrocarbons fractionated to separate the normallyy liquid hydrocarbons. The unreacted gaseous hydrocarbons were fractionated to form a fraction, rich in isobutane and low in normal butane, which was recycled to the system and another fraction, comprising essentially normal butane, which was added all or in part to the normally liquid hydrocarbon fraction to improve the volatility thereof. The normally liquid hydrocarbon fraction Was fractionated to separate a fraction containing hydrocarbons of gasoline boiling olf-gases therefrom, fractionating the off-gases fromthesaid stabilization to separate a fractiony rich insbutane and lean in normal butane, and continuously recycling the said isobutane fraction to the reaction zone to maintain a substantial excess of isobutane to olefin therein, the said isobutane fraction being sufficiently denuded of normal butane tothereby reduce the proportion of normal butane in the reaction zone during continuance 0f the process to a proportion subrstantially below` that in the fresh hydrocarbon fcharge tosaid zone.

2. A cyclic process for the manufacture of high anti-knock motor fuel from low-boiling hydrocarbons containing isobutane, normal butane and olefins, which comprises continuously introducing int'oan agitated reaction zone containing an alkylation catalyst af charge of the said lowboiling hydrocarbons, and reacting the hydrocarbons therein in liquid phase under conditions suchthat the isobutane is alkylated by the olefins to form normally liquid hydrocarbons within the gasoline boiling range, continuously withdrawing reaction products from the reaction zone to a settling zone where the reaction products separate into a hydrocarbon layer and a catalyst layer, adding additional catalyst to .the reaction zone to make up for that withdrawn, continurange. A gasoline yield of about 150%, based on the olens consumed, was obtained. The gasoline fraction consisted essentially of saturated hydrocarbons and had an antiknock value of layer, stabilizing the removedy hydrocarbon to vseparate off-gases therefrom, separating a fraction'rich in isobutane and lean in normal butane from the said off-gases, and continuously recycling the said isobutane fraction to the reac- .1 tion zone, the said fresh hydrocarbon feed being correlated with the recycle of the said isobutane fraction to continuously maintain in the reaction i zone a molar excess of isobutane over the of the olens which is about 5:1 and over.

3./A cyclic process according to claim 1, in which at least a portion of the normal butane fraction separated from the isobutane fraction in the fractionation of the olf-gases is blended back with'A the gasoline fraction of the alkylate to adjusty the volatilitythereof.

4. A cyclic process according to claim 1, in which the catalyst is strong sulfuric acid.

5. A'cyclic process for the manufacture of high anti-knockmotor fuel fi'om low-boiling hydrocarbons containing isobutane, normal butane and olens, which lcomprises continuously introducing into an agitated reaction zone containing an alkylation 'catalyst a charge@l of hydrocarbons containing substantial proportions of isobutane and oleflns and also a substantial proportion of normal butane, and reacting the hydrocarbons therein in liquid phase under conditions such that the isobutane is alkylated by the olefins to form normally liquid hydrocarbons within the gasoline boiling rama-'continuously withdrawing reaction products from the reaction zone to a settling zone where the reaction products separate into-a hydrocarbon layer and a catalyst layer, continuously removing hydrocarbon from the hydrocarbon layer and catalyst from the catalystV layer, adding additional catalyst to the Areaction .zone to make up for that withdrawn,

stabilizing the removed hydrocarbon to separate an off-gas fraction rich in isobutane and lan in normal butanewhile leaving a substantial proportion of the normal butane in the hydrocarbon to adjust the volatility thereof, fractionating the stabilized hydrocarbon into a gasoline fraction containing normal butane and a heavier fraction, and continuously recycling the said oil-gas fraction rich in isobutane to the reaction zone to maintain a substantial excess of isobutane to olen therein, the said isobutane fraction being suflicier'itly denuded of normal butane to thereby reduce the proportion of normal butane in the reaction zone during continuance of the process to a proportion substantially below that in the fresh hydrocarbon charge to said zone.

6. A cyclic process according to claim 5, in which the fresh hydrocarbon feed is correlated with the recycle of the isobutane fraction to maintain in the reaction zone a molar excess of isobutane over the stoichiometrical equivalent monomeric contents of the olens which is about 5:1 and over.

'7. A cyclic process according to claim 5, in which the catalyst is strong sulfuric acid.

8. A cyclic process for the manufacture of high anti-knock motor fuel from low-boiling hydrocarbons containing isobutane, oleflns and normal paraiiins including normal butane, which comprises continuously introducing into an agitated reaction zone containing an alkylation catalyst a charge of hydrocarbons containing substantial proportions of isobutane and olens and also some normal parailns including normal buta'ne, and reacting the hydrocarbons therein in liquid phase under conditions -such that isobutane is alkylated by the olefins to form normally liquid hydrocarbons within the gasoline boiling range, continuously withdrawing reaction products from the reaction zone to a settling zone where the reaction products separate into a hydrocarbon layer and a catalyst layer, continuously removing hydrocarbon from the hydrocarbon layer and catalystefrom the catalyst layer, adding additional catalyst to the `reaction zone to make up for that withdrawn, stabilizing the removed hydrocarbon to separate oigases therefrom, fractionating the offgases from the said stabilization to separate an isobutane-rich fraction from normal parain hydrocarbons, and continuously recycling the said isobutane-rich fraction to the reaction zone to maintain a substantial excess of isobutane to olefin therein and to avoid build-up of normal paraffin hydrocarbons in the system.

ARTHUR R. GOLDSBY. FRANK H. BRUNER.

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