US2689822A - Quenched hydrofluoric acid conversion - Google Patents

Description

Sept. 21, 1954 J. E. PENICK 2,689,822

QUENCHED HYDROFLUORIC ACID CONVERSION Filed Aug. 17, 1950 5 Sheets-Sheet l V Ln vs INVENTOR. .Jae Pe l BY Z )26E/vr m Hrm/mfr LIS QUENCHED HYDROFLUORIC ACID Filed Aug. 17, 1950 CONVERSION 5 Sheets-Sheet 2 /f' 7 VENT 6,45 f J 63 z Jimi/e 47 .sm/Pfff? avm/11540 /lm/MUmm/e 70 71 @6 67 Sept. 21,` 1954 J. E. PENICK QUENCHED HYDROFLUORIC ACID CONVERSION 5 Sheets-Sheet 3 Filed Aug. 17, 195o J. E. PENICK QUENCHED HYDROFLUORIC ACID CONVERSION Sept. 21, 1954 5 Sheets-Sheet 4 Filed Aug. 17. 1950 E mir/0, Wfl/WL,

INVENTOR. ./e E fen/ff Buwx vm Sept. 21, 1954 E lPENlCK l 2,689,822

QUENCHED HYDROFLUORIC ACID CONVERSION Filed Aug. 17. 1950 5 Sheets-Sheet 5 mk) e IN V EN TOR.

Patented Sept. 21, 1954 QUENCHED HYDROFILUORIC VACID CONVERSION Joe E. Penick, Woodbury, N.` J., assignorto. Soy cony-VacuumOil. Company, Incorporated, a`

corporation offNew York Application August 17, 1950; Serial No. 17 9,924V

4 Claims.. (Cl. 196-50) The present invention relates to thelconversion of hydrocarbons employing hydroiiuoric acid as a catalyst and, more particularly to the conversion in liquid phase of mixtures of hydrocarbons having relatively low octane numbers to mixtures of hydrocarbons having relatively high octane numbers; the conversion being carried out in the presence of hydrogen fluoride and `at elevated temperatures.

While the conversion of hydrocarbonsl employinghydroiiuoric acid as a catalyst has been disclosed in various patents, notably U. S. Patents Nos. 2,403,649; 2,454,615; 2,450,588; and 2,449,463, it is preferred to subject the hydrocarbon mixture to be converted to the conditions describedinco` pending application Serial No. 94,955, filedMay 24, 1949, now Patent No. 2,606,860 in thename of Joe E. Penick. The present application is a continuation-inpart of the aforesaid application Serial No. 94,955 and provides for improved results thereover.

As disclosed in the aforesaid pending application, the conversion of hydrocarbon mixtures hav-4 ing low octane numbers tohydrocarbon mixtures havin@ relatively high octane numbers is carried out by contacting such hy-drocarbon mixtures; naphthas for example, with hydrogen fluoride in the liquid state in amounts greater than that required to saturate the hydrocarboncharge with hydrogen fluoride but not more than in the ratio of two volumes of hydrouoric acid toone volume of hydrocarbon charge stock at temperatures of the order of 270 F. to 470 F. and preferably in the range of 320 F. to 450 F.

It has been found that operational difficulties can be avoided and improved yields can be obtained by quenching the reaction mixture before separating the acid phase from thehydrocarbon phase.

It has been discovered that (l) the mutual solubilities of hydrogen fluoride and saturated hy-` drocarbons increase logarithmically with increasing temperature and (2) the coeicient of thermal expansion for hydrogen fluoride is greater than that for `hydrocarbons so that as the temperature is increased the density: of hydrogen fluoride decreases more rapidly than the density of hydrocarbons. At temperaturesin the range of 300 F, to 450 F. the density of. hydrogen fluoride is in the range of densities of hydrocarbons so that the density of hydrogen fluoride under` these conditions may be the same, evenless' or only slightly higher than: thedensitygof the hydrocarbon phase.` Consequentlyu afclean separary 2 tion-of thethydrogen uoride phase from the hydrocarbon phase. in this tempearture range is impossible.

The relation between the density of hydrogen fluoride and the density of hydrocarbon mixtures as inuenced by the temperature is clearly demonstrated'by the curves of Figure I. It is manifest that at temperatures between about 300 F. and about 450 E'. the densityof hydrogen fluoride is such as to preclude vgravity separation of hydrogen` fluoride from a hydrocarbon mixture. For example, at 300fF. hydrogen fluoride has a density ofl about 6.161pounds per gallon and the densities of .hydrocarbon mixtures having gravities of 452.52" and 54 A. P. I. are respectively, 5.84, 5.58 and. 5.49. pounds per gallon. Furthermore, hydrogen fluoride has the same density as a. A. P.` I. hydrocarbon mixture at 360 F., as a 52 A. P. I. hydrocarbon mixture at 412 F., and as a 54 A. P. I. hydrocarbonmxture at about 434 F.

Whenever an attempt is made to separate hydrogen iiuoride from a hydrocarbon phase at temperatures abovecabout25`0 F., say at 300 F., separation of the two phases is so poor that it is impossible to achieveV the steady operation so necessary to a conversion process involving continuous operation.` For example, the amount of hydrogen fluoride in the hydrocarbon phase becomesso large thatthe main fractionator has insuflicent capacity to obtain the desired fractionation andthe fractonator bottoms contain considerable amounts of both hydrogen fluoride and tar. At the same time the interface between the hydrocarbon mixture and the hydrogen fluoride -in the settler (as determined by electrical conductivity measurements) is less distinct and even disappears completely at times.

As a result of the increased solubility of hydrogen fluoride in hydrocarbon mixtures at high temperatures (300 F. and greater) a greater amount of heatis required. The hydrogen uoridenot separated from the` hydrocarbon phase by gravity separation must be removed by Vaporizatonin the main` fractionator and the hydrogen fluoride stripper. Since ythe hydrocarbon phase leaving the settler operating at temperatures above about 250 F. will contain from 5 to 40 per cent. hydrogen-fluoride, the quantity of heat requiredfto vaporize this .amount of hydrogen nuorde is quite large and.` often exceeds all the other heat requirements `for i the` process. The heat used in vaporizing'dissolvedand/or entrained hydrogen: yiuoride` from .the hydrocarbon phase is wastedbecauseA nothing vis gained from the vaporization except freeing the hydrocarbon mixture of hydrogen fluoride.

The hydrogen iluoride dissolved and/or entrained in the hydrocarbon phase coming from a gravity separation at temperatuers above about 250 F. carries substantial amounts of tar. When the hydrogen fluoride is vaporized in the main fractionator the tar remains in the bottoms and is recycled in solution in the hydrocarbon recycle stock. This tar is readily eX- tracted from the recycle stock when the recycle stock contacts the hydrogen fluoride in the reactor. This dilutes the hydrogen fluoride and reduces its effectiveness as a catalyst. Since tar dissolved in the hydrogen fluoride in the hydrocarbon phase coming from a settler operating at temperatures above about 250 F. cannot be withdrawn from the process save by fractionation of the bottoms of the main fractionator, i. e., a second vaporization operation, it is manifest that in the absence of quenching prior to gravity separation of the hydrogen fluoride phase from the hydrocarbon phase vaporization does not serve to improve in any way the effectiveness of the catalyst. This problem can become so great due to the increase in the quantity of hydrogen uoride and tar dissolved therein present in the hydrocarbon phase and the resultant increase in the internal recycle of the tar that the process becomes inoperative.

`vihen the gravity separation of the hydrogen fluoride phase and the hydrocarbon phase takes place at temperatures above about 250 F. the hydrocarbon phase leaving the settler contains more than 2 per cent of dissolved hydrogen iiuoride. The vaporization of such large quantities of hydrogen iiuoride in the fractionator results in excessive corrosion of the fractionator.

When the gravity separation of hydrogen fluoride from a hydrocarbon mixture takes place at temperatures in excess of about 250 F., 5 to 20 per cent and even more of the hydrocarbon phase is dissolved or entrained in the hydrogen fluoride phase. The dissolved or entrained hydrocarbon material is lost as tar in the acid regenerator and the volume of material which must be handled to process a given weight of hydrogen fluoride is increased. Both of these end results are undesirable from a standpoint of economics.

From the foregoing discussion of the disadvantages arising from attempting gravity separation of hydrogen fluoride from hydrocarbon mixtures at temperatures above about 250 F., it will be manifest to those skilled in the art that the present invention provides an improvement in prior art hydrocarbon conversion processes employing hydrogen iluoride as a catalyst and reaction temperatures in excess of about 250 F. The aforesaid improvement, broadly stated, comprises carrying out a gravity separation of hydrogen fluoride from the hydrocarbon phase of the reaction mixture at temperatures not greater than about 250 F. and preferably at temperatures of about 150 F. to about 200 F.

The sequence of operations described in copending application Serial No. 94,955 can be modified by interposing a cooler between the reactor i3 and the settler I6 of Figure I of that disclosure. However it is preferred to modify the procedure therein described in a manner such as illustrated in either Figure II or Figure III of the drawings of the present application in which Figure I is a graph showing the relation between temperature and the density of hydrogen fluoride and the densities of various hydrocarbon mixtures;

Figure II is a flowsheet, in more or less diagrammatic form, of one embodiment of the present invention;

Figure III is a flowsheet, in more or less diagrammatic form, of another embodiment of the present invention, and

Figure IV is a flowsheet, in more or less diagrammatic form, showing the application of the separation of the hydrogen fluoride phase from the hydrocarbon phase at temperatures not greater than 250 F. and preferably below 200 F. to the invention described in the co-pending application Serial No. 94,955.

Illustrative broadly of the effect of separating liquid hydrogen iluoride from a liquid hydrocarbon phase at temperatures not greater than 250 F. and preferably at temperatures not greater than 200 F. and especially at temperatures of about to about 200 F. is the following data.

A hydrocarbon conversion unit wherein the hydrocarbon conversion took place at a temperature above 300 F. and the gravity separation of the hydrogen fluoride and hydrocarbon phases took place at about 290 F. Was operated for about 6 hours. The hydrocarbon phase passed through the settler at the rate of 23.2 gallons per hour and contained 5.6 Weight per cent hydrogen iluoride. In other words, 5.71 pounds .056=0.32 pound of hydrogen uoride were dissolved or entrained in a gallon of hydrocarbon phase when the separation was carried out at 290 F. On the other hand, when the separation of the liquid hydrogen fluoride phase from the liquid hydrocarbon phase was carried out at 200 F. the liquid hydrocarbon phase contained only 0.06 pound of hydrogen fluoride per gallon. In other Words, separation of the liquid hydrogen fluoride phase from the liquid hydrocarbon phase at a temperature not greater than 250 F. and preferably at a temperature of 200 F. or less resulted in a reduction of 8l per cent in the amount of hydrogen fluoride dissolved or entrained in the hydrocarbon phase. In addition, it was possible at the lower separation temperature to treat about 15 volume per cent more hydrocarbon in the same equipment.

In accordance with the principles of the present invention hydrocarbons can be subjected to conversion in accordance with operations schematically illustrated in Figures II, III and IV. Referring to Figure II, it will be seen that fresh hydrocarbon feed, for example a naphtha of low octane number, is withdrawn from a source not shown through lines I and E by pump 3. The charge or feed is passed through line l to reactor 5. Fresh hydrogen iiuoride is withdrawn from a source not shown through line t by pump l and discharged through line 8 into line 9. Recycle hydrogen fluoride is Withdrawn from settler I0 through line Il by pump l2 and discharged into line 9. At point i3 on line S the fresh hydrogen fluoride joins the recycle hydrogen fluoride and the mixed fresh and recycle hydrogen fluoride passes through a heat exchanger I4 or other means for raising the temperature of the stream of hydrogen uoride. The heated stream of hydrogen fluoride leaves heater I4 by pipe I5 which joins line d at point I6.

A secondary recycle stream of hydrogen iiuoride is withdrawn from stripper overhead accharged through line into pipe 4 at point I6.

The mixture of hydrogen-'fluoride andvhydrocar-- bon passes upwardly through'reactorf5, operated at temperatures of about 270 F. to about 470 F. and preferably of about '320 F. to about 450 F. and pressure sufficient to maintain the hydrogen fluoride in the liquid state and preferably at a pressure at least 125`p. s. ir'greater than'thepressure of the reaction, and .through conduit 121| to heat exchanger or cooler 22 in which thetemperature `of the liquid` hydrocarbon-hydrogen fluoride stream is` reduced to not greater than about 250 F. and vpreferably to about.200:Fl or less. The liquid hydrocarbon-liquid'. hydrogen fluoride stream after cooling to at least 250 F. and preferably after=cooling toat least ZOOP-5F. passes through, pipe 23 intoA settler l0. ff.

In settler I0 the liquid hydrogen fluoride (when the temperature is below about 250 F.) forms the lower: stratum and the liquid: hydrocarbons the upper stratumor phase.

The liquid hydrocarbons leave the settler l0 through line 24 and pass therethrough to the hydrogen fluoridestripper 25'. In stripper 25 the hydrogen fluoride, light' hydrocarbons' and noncondensable gases escape as overhead through line 23, cooler 21 and line 28 tostripper'foverhead accumulator 1. Vent gas escapesfrom accumulator I1 through line 23.

The hydrocarbon bottoms in stripper 25. flow through line to fractionato-r'3l wherein an overhead hydrocarbon product isseparatedifrom a recycle bottoms product. The overhead product leaves fractionator 3| by pipe 32, cooler 33 and line 34 to storage or other use.

The hydrocarbon recycle bottoms are withdrawn from fractionator 3| through lines 35 and 2 by pump 3. At point `36 on line 2 fresh hydrocarbon feed joins the recycle bottoms.v

At times it will be desirable to bleed some hydrogen fluoride continuously or intermittently from the hydrogen fluoride recycle streami and send the spent hydrogen fluoride tothe hydrogen fluoride regenerator. To this end spent hydrogen fluoride, i. e., anacid stream containinglessthan 96 per cent hydrogen fluoride and preferably less than 90 per cent hydrogen fluorideis withdrawn from line at some point say. 31 and passed throughiline 38 to the hydrogeniuoride.Y regenerator.

Since the owsheet of Figure II` is,.essentially diagranunatic in nature the necessary and desirable valves have not been illustrated. Furthermore, the location of such. valves .beingamatter of choice, those skilled inthe artare able to. place the valves in the `desirable necessary positions.

Figure III is a diagrammatic illustration of a modification of the. sequence of operationsillustrated in Figure `II Which nevertheless is illustrative of the spirit of the present invention. The primary difference .betweenthe sequence of operations illustrated in Figure III and that illustrated in Figure II is the use of thefresh hydrocarbon feed as a reilux:in the fractionator. `In other respects the operations .are the: same.-

Thus, fresh hydrocarbon feed, for `example coker gasoline is withdrawn `from a` sourcenot shown through line 4| and introduced into vfractionator 42 as a reflux. When the fresh feed has components having boiling ranges.- of the-same order as the overheadof fractionator 42 those components are distilled `off i with ther-.reaction product overhead. The `bottoms-:of the; hydro,-`

carbon phase of the reaction mixture together with the higher boiling constituents of the fresh hydrocarbon feedf iswithdrawn `fron1Ifractionatcr 42 through line 43 by pump 44' and discharged into reactor 45 through line 46. vRecycle hydrogen fluoride forms the' bottom layer of the reaction mixture in settler 41 when the contents of the settler are at a temperature of.` 250. FQ or less and preferably iat a temperature1of20'0'? F. or less. Thet recycle hydrogen fluoride Vis `withdrawn vfrom settler 41 through pipe 48 by pump |49. At a point intermediate settler 41l and pump49, a portion of the recycle hydrogen fluoride is continuously or intermittently Withdrawn'throughcon- Iduit' 53 for regeneration in a. hydrogen fluoride regenerator (not shown).

Recycle hydrogen fiuoridecis discharged by pump 49 into llinef5| leadingLinto heater 52. At a point intermediate pump-49 and heater 52, fresh hydrogen fluoride drawn through -line 53.by pump 54 from the hydrogen. fluoride regenerator. (not shown) joins the stream of recycle hydrogen fluoride. The recycle hydrogen fluoride and fresh hydrogen fluoride passes .from heater 52 through line55 to reactor 45.

Some recyclehydrogen fluoride accumulates in stripper-overhead accumulator 5S. This recycle hydrogen fluoride is Withdrawn from accumulator56 through line 51 by pump 58 and. discharged through line 59 into reactor 45. (It will.

be noted that the streams in lines 46, 55 and 59 are all joined before entering reactor 45.) The reaction mixture of liquid hydrogen fluoride and hydrocarbons passes upwardly through reactor 45 at elevated temperatures in excess of 250 usually at temperatures above 300 F., and at a pressure sumcient to maintain the hydrogen fluoride `in the liquid state. However, it is preferred to employ pressures at least 125, andpreferably p. s. i. greater than the vapor pressure of the reaction mixture at the reaction 'temperature.

The reaction mixture leaves reactor 45 through pipe 50, passes through cooler 6|, in which the stream is cooled `to at least 250 F. and preferably to 200. F. or less, and liner62 to settler 41. The hydrocarbon phaseleaves the` settler through line 53 and passes to hydrogen-fluoride stripper B4.

In stripper 64 dissolved and/or entrained hydrogen fluorideisA takenas an overheadtogether with non-condensable gases suchf as hydrogen, nitrogen, hydrogentsulde, carbon-` dioxide and light hydrocarbons suchas methane-'and ethane. The hydrogen fluoride and non-'condensable `gases `pass as overhead vialine 65, cooler G5 and line 61 to stripper overhead accumulator 55 from which the non-condensable gases are removed by pipe 53.

The" bottoms of stripper 64 is. the. hydrocarbon phase substantially.k free from hydrogen. iuoride. The bottoms is removed from stripper 64| through conduit 59 as feedfor fractionator y42. vThe overhead for `fractionator 42 is removed therefrom through pipe 1.0 and cooler 1-| to storage or further treatment. i

There is some dierence between the characteristics of theproduct producedby following the sequence of operations-illustrated by Figure Il and those of the product `produced in accordance with the iiowsheet of Figure III.` These/differences areillustrated Vby .the.y dataff' presented in Table It 1 TABLE I Hydrogen jluortde converszon of coker gasolzne 'wzth separation of hydrogen fluorzde at about 200 F operation of Figure Csbgi n 111 n n n1 n n 11 n In 111 Run No 27 28 31 32 30 35 36 37 37A 29 34 Processing Conditions:

ReactiOn Temp., F. 385 385 335 340 330 430 430 430 430 425 430 Contact Time, Min 4. 3. 6 4. 0 3. 6 4. 8 8. 0 8. l 8. 0 8. 1 3. 8 8. 0

HF/HC v01/vol. 60 F 1.0 1.1 1.0 1.0 1.1 1.1 1. l 1.1 1. 1 1. 1 1.1

Acid Strength, Wt. percent HF 70. 9 70. 8 72.7 76. 0 75. 9 71.1 78. 1 69.1 70.0 67. 8 71.6

Pressure, p. s. i. g 1, 600 1,600 1, 600 1, 600 l, 600 1, 600 1, 200 l, 800 2,000 1, 600 1, 600 Ulinate Yield, vol. percent of arge:

10 RVP Gasoline 65. 5 76. 2 59. 0 67.1 67. 5 71.6 62. 3 68. 4 75.1 81. 7 80.2

Excess C4 and lighter; 12.4 9.8 8.0 8. 7 12. 5 8. 3 11.3 9.0 6.6 6` 7 7. 6

Tar 24. 8 20. 2 33. 0 25. 2 24. 3 21. 0 24. 5 22. 5 19. 2 18. 5 16. 4: Conversion, vol. percent/Pass 1 22. 3 27.1 13. 8 13.8 15. 5 51. 7 28. 0 53. 0 57. 4 35. 5 67. 7 Gasoline Properties:

Gravity, A. P. I 51. 4 72. 7 68. 3 70. 5 70. 3 69. 2 71. 7 72. 6 70. 7 70.9 69. 8 67. 8

RVP 2. 8 13. 0 12. 6 11. 1 10. 2 14. 3 12. 5 18. 1 9. 0 9. 4 13. 1 11. 3

ASTM Boiling Range, F 12C-454 81-287 87-305 92-292 90-296 74-314 76-303 66-303 94-287 88-296 85-291 92-292 NOrWOOd Bromine N0 80. 9 0.0 56. 4 1. 4 0. 0 48. 2 2. 4 1. 2 0. 0 0. 5 58. 9 62. 0

Sulfur, Wt. percent 0. 94 O. 05 0. 3G 0. 09 0. 10 0. S4 0. 05 0. 07 0. 04 0. 04 0. 32 0. 45 Octane No. of l0 RVP Gasoline:

CFRR, Clear 72. 0 72. 1 80. 2 69. 0 69. 3 81. 3 71, 3 82. 8 83. 6

+ m1. TEL 81. 0 86. 3 89. 5 83. 5 84. 0 89. 5 86. 6 91. 5 90. 3

1 Volume 300 EP Gasoline produced/hydrocarbon charge to reactor X100. In general, the present method provides for the 25 ture is reduced to not greater than about 250 F.

treatment of mixtures or hydrocarbons, especially naphthas, With hydrogen fluoride in liquid state in amounts greater than that required to saturate the hydrocarbon charge with hydrogen fluoride and not more than in the ratio of tvo volumes of hydrofluoric acid to one volume of hydrocarbon charge stock at temperatures of the order of 270 F. to 470 F. and preferably in the range of 320 F. -to 450 F.

It has been found that the hydroluoric acid should contain at least 4 per cent by Weight and not more than about 40 per cent by weight of acid soluble oil and not more than about 10 per cent o Water.

It has been found that, generally, the hydro carbon stock at room temperature is saturated with hydrogen fluoride when a concentration of about 0.5 per cent hydrogen lfluoride is attained. Consequently, an amount or' hydrogen fiuoride in excess of about 0.5 per cent by Weight of the hydrocarbon charge is in excess of that amount required to saturate the hydrocarbon charge.

Although any mixture of hydrocarbons can be treated, the present method is very readily illustrated by discussion of the treatment of naphthas. Thus, for example, the treatment of naphthas having a boiling range of about 250 to 400 F. and naphthas having a boiling range of about 315 to 400 E. Will be used to illustrate the basic principles of the present method of converting hydrocarbons.

As shown in a more or less diagrammatic manner in Figure IV, the fresh hydrocarbon charge from a source not shown is passed by means of line 80 through heat exchanger 8| and line 02 to reactor 83. Liquid hydrogen fluoride or hydroiluoric acid is introduced into reactor 03 by conduit Sli under the pressure required by the pressure in reactor 83. Reactor 03 is of suflicient capacity to provide a residence time sucient that a conversion of less than 40 per Cent to liquid products having a 90 per cent point below the l0 per cent point of the charge stock is obtained at temperatures of 270 F. to 470 F. and at pres sures sufiicient to maintain the reactants in the liquid state at the reaction temperature.

The reaction mixture comprising reactants, catalyst and reaction products is passed via line to vcooler 05A and thence to settler 80. In cooler 85A the temperature of the reaction mixand preferably to a temperature not greater than about 200 F. In settler 86 the hydrogen fiuoride phase is the lower phase and is drawn-oh through iine 8l by pump 8S.

The hydrocarbon products being lighter than the hydrofluoric acid phase at temperatures below about 250 F. form the upper layer in settler 236 and are withdrawn through line 29, pressure reducing valve 00 and line 9| to the main fractionating tower 92 in which the hydrocarbon products, Whose per cent point is at least below the 10 per cent point of the charge stock and saturated with hydrogen fluoride, are Withdrawn through line 93, heat exchanger S and line 95 to the hydrogen fluoride stripper 06. The remaining higher boiling hydrocarbons are withdrawn from fractionating column 92 through line 9'! by pump 98 and recycled to reactor 03 through lines te and 82.

In the stripper 00 hydrogen fluoride and light hydrocarbons are taken as overhead and passed through line |00, heat exchanger 10| and line |02 to settler |03 in Which the hydrogen fluoride forms the lower liquid phase and the light hydrocarbons the upper liquid phase.

The hydrocarbon phase in settler |03 is returned through line |05 to stripper 96 to serve relux While the hydrogen fluoride is withdrawn from settler |03 through line |05 to line |06.

The hydrogen iluoride phase Withdrawn from settler 85 through line 81 in part is transferred to the hydrogen fluoride regenerator 07 through line H0 under the control of valve ||0A. In regenerator |01 hydrogen nuoride is taken as an overhead through line |08 and heat exchanger 909 and with the hydrogen uoride from settler 03 returned through lines |05 and 84 to the reactor 83. Tar is withdrawn from regenerator l 0l through line l2.

Returning now to the hydrogen fluoride stripping operation, the overhead from stripper 96 is hydrogen uoride and light fractions of the desired product. This overhead is withdrawn as described hereinbefore through line |00. The bottoms, i. e., the desired'product having a 90 per cent point lower than the 10 per cent point of the charge stock is withdrawn from stripper 96 through line to storage or for further treatment or other use as the situation requires.

`the catalytic hydrofluoric acid.

`9 Theforegoing has been a description ofthe general operation 'of the present method: However, certain factors aiect the results of `thelpresent method of converting hydrocarbons and require discussion. Thus,l for examplait has been established that the acid to hydrocarbon; i. e.,

hydrofluoric acid to charge stock` ratio has a marked effect upon the amountfof high boiling or tarry material produced. This is'aptly 'illustrated by the curves of Figure V. -The -materials treated to illustrate thiseffect ywere two `naphthas; one having a boiling range of 25W-'400 F. and the other having aboi'ling range of 315- 400" F'. The curves of Figure V establish that as the ratio of hydrogen fluoride'to charge stock is increased from about 0.4 -to 5.0 volumes of hydrofluoric acid per volume of charge stock the ratio of converted railinati. e., material having a 90 per cent point `below -the 10 per cent point of the charge stock, `to organic material soluble in the hydrofluoric `acid phase; i. e.; tarry material, decreases from 6 to 1 to 1 to 1. In -other words, when treating `a charge stock at a given temperature and under a pressure suiiicient to maintain the reactants inthe liquidphase,the ratio of desired products to undesirable products decreases as the ratio of hydrofluoric acid to charge stock decreases. Thus, lata I-IFzHC ratio of 0.4-0.5 volumes to one vo1ume,- the volume of the hydrocarbon product was 6 times the volume of the acid soluble oil. In contrast, when l3 volumes of hydrofluoric -acid fwere used per one volume of charge, the ratio "of desiredproduct to acid soluble oil was 1 to l. The foregoing can be stated in another manner.. When the hydrouoric `acid to charge stock ratio was 0.4-0.5 1 the desired product was aboutf. percent of the charge stock converted and the acid soluble oil about 14 per cent. However, when the hydrouoric acid to charge stock ratio `was 3:1.-about .l

54 per `cent of the charge was converted to desired `product and about 46 per cent to acid soluble oil.

The curves in Figure VI. establish that in the treatment of naphthas as the ratio of` acid -to charge stock is increased .from about 0.5 to about 4.6 to 1 (by volume), the ultimate conversion decreases from about 90 per cent to about 55 per cent.

The foregoing leads to the expression of the preferred conditions as those in which the ratio of hydrofiuoric acid or hydrogen fluoride to charge stock is not greater than about 2.0 to 1 and not less than an excess of that amount of hydrogen fluoride required to saturate the charge stock therewith.

A further modification of the basic concept is control of the water and soluble oil content of It has been found that improved results are obtained when the acid contains at least 4 per cent by weight of organic material soluble in the acid catalyst and termed herein acid soluble oil. Figures VII and VIII illustrate the fact that with fresh hydrouoric acid about 9.2 per cent of the charge is converted to organic material soluble in the acid; i. e., acid soluble oil although that represents only about 4 weight per cent of the acid phase. When that acid is recycled only about 8 weight 'per cent of the charge is converted to acid soluble oil in the second pass and about weight per cent in the third and subsequent passes, although the total amount of acid soluble oil reaches about 9 weight per cent of the acid phase in the fourth and subsequent passes. In other words, when `10 i ltheV hydrofluoric acidv contains about V3 to about 10 'weight per cent of acid soluble oil-the conversion of chargestock to acidsoluble oil is a minimum.

The results produced by the basic method of operation can be still furtherimproved by carrying out the conversion in the liquid phase at a pressure more than at least `150 p. as. i. greater than the vapor pressure of the products of conversion at the reaction temperature. Thus, for examplawhenV treating a heavy naphtha from a Mid-Continent crude, it wasfound that the octane number of the gasoline produced could be raised about 7 numbers by resorting to this variation in operation. These data are presented in tabular form as follows:

p TABLE 1I Charge stock 314`400 F., heavy naphtha. Reaction temperature 340 F Contact time About 7 minutes.

HF/HC ratio (volume) 0.5:1.

Vapor pressure of conversion products at reaction temperature 780 p. s. i.

It is manifest that not only is the improvement in octane numberA markedly greater but i the ultimate` yield of gasoline .is about 18 volurne per centgreater as a result of operating at a reactionpressure greater 4than about 150 p. s. i. greater than the vapor pressure ofthe conversion products.

` The residencetirne for the conversion reaction varies with the temperature and in general is `less theA higher the temperature within the interval 270 F. to 470 F. 4'The preferred conditionsare a reaction temperature of about `300" F. to `450 F., a residence `timersuicient to `secure not `more .than about 40-volume per cent conversionto Vproducts having a percent point lower than the 10 per cent point of the charge stock and preferably a residence time sufficient to obtain only about 20 to 30 per cent conversion to products having a 90 per cent point lower than the 10 per cent point of the charge stock. In general, a residence time of not more than 20 minutes and preferably of the order of 2 to l0 minutes dependent upon the reaction temperature is desirable. With the reaction conditions described hereinbefore, satisfactory results will be obtained employing at least sumcient hydrouoric acid to form a second liquid phase; i. e., an amount in excess of that required to saturate the charge stock with hydrofluoric acid and not more than about 2.0 volumes of hydrofluoric acid per volume of charge stock and preferably about 0.4 volume to about 1.5 volumes of hydroiiuoric acid per volume of charge stock. The results described herein can only be obtained when the reactants are in the liquid state. Consequently, the conversion reaction must be carried out at a pressure at least suflicient at the reaction temperature to maintain liquid state conditions and preferably at least 150 pounds per square inch (p. s. i.) higher than the vapor pressure of the effluent from the reactor at the reaction temperature.

While the present conversion method may be carried out with total recycle or without recycle of the hydroiluoric acid, it is preferred to recycle at least 25 per cent of the hydrofluoric acid. Similarly, while 100 per cent hydrofluoric acid may be used and the concentration of hydrogen fluoride in the catalytic acid should be more than 50 per cent with a maximum of 10 per cent of Water, it is preferred that the acid catalyst contain not more than per cent of water and at least 4 per cent of soluble organic material herein termed acid soluble oil. Thus, acid catalyst containing not more than 5 per cent Water and preiu erably less than 3 per cent Water and having a titratable acidity of at least 50 per cent to about 90 per cent hydrogen iluoride gives satisfactory results.

I claim:

1. A method of raising the octane rating of naphtha Which comprises contacting naphtha With an amount of hydrogen uoride in excess of that required to saturate said naphtha and not more than about 2.0 Volumes of hydrogen fluoride per volume of naphtha, said hydrogen fluoride containing about 4 to about 10 per cent acid soluble oil, at a reaction temperature of about 270 to about 470 F., at a presure at least 125 p. s. i. greater than the vapor pressure of the reaction mixture at the aforesaid reaction temperature and for not more than about minutes, cooling the liquid reaction mixture to about 150 to about 250 and separating a hydrocarbon conversion product having a 90 per cent point below the 10 per cent point of said charge naphtha and containing less than 5 per cent hydrogen fiuoride from a liquid hydrogen fluoride phase.

2. A method of raising the octane number of naphtha which comprises contacting naphtha with a liquid catalyst comprising hydrogen fluoride about 50 to about 90 per cent, about 4 to about 10 per cent of acid soluble oil and the balance, to make 100 per cent, water, in the ratio of about 0.4 to about 2.0 volumes of catalyst per volume of naphtha, to form a reaction mixture, holding said reaction mixture at a reaction temperature of about 270 to about 470 F. for about 2 to about 10 minutes at a pressure at least 125 p. s. i. greater than the vapor pressure of said reaction mixture at said reaction temperature, cooling said reaction mixture to about 150 to about 250 F., and separating a hydrocarbon con- Version product having a per cent point below the 10 per cent point of said charge naphtha and containing less than 5 per cent hydrogen uoride from a liquid hydrogen iiuoride phase.

3. A method of raising the octane number of naphtha which comprises contacting naphtha with a liquid catalyst comprising about 8 to about 10 per cent acid soluble oil, about 3 to about 5 per cent Water and the balance to make per cent hydrogen fluoride in the ratio of about 0.4 to about 1.5 volumes of hydrogen fluoride per volume of naphtha to form a reaction mixture, maintaining said reaction mixture at a reaction temperature of about 270 to about 470 F. andat a pressure at least p. s. i. greater l than the vapor pressure of said reaction mixture for about 2 to about 10 minutes, cooling said reaction mixture to about to about 250 F., and separating a hydrocarbon conversion product having a 90 per cent point below the 10 per cent point of said charge naphtha and containing not more than 2 per cent hydrogen fluoride from a liquid hydrogen fluoride phase.

4. The method of raising the octane number oi naphtha as set forth and described in claim 3 wherein the reaction temperature is about 300 to about 450 l., the reaction pressure is about 150 to about 820 p. s. i. greater than the vapor pressure of the'reaction mixture, and the reaction mixture is cooled to about 150 to about 200 F.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,403,649 Frey July 9, 1946 2,427,865 Lien et al Sept. 23, 1947 2,433,020 Becker Dec. 23, 1947 2,454,615 Ridgway et al. Nov. 23, 1948 2,504,280 Shoemaker Apr. 18, 1950 2,509,028 Abrams et al. May 23, 1950 2,577,799 ONeal Dec. 11, 1951

Claims (1)

1. A METHOD OF RAISING THE OCTANE RATING OF NAPHTHA WHICH COMPRISES CONTACTING NAPHTHA WITH AN AMOUNT OF HYDROGEN FLUORIDE IN EXCESS OF THAT REQUIRED TO SATURATE SAID NAPHTHA AND NOT MORE THAN ABOUT 2.0 VOLUMES OF HYDROGEN FLUORIDE PER VOLUME OF NAPHTHA, SAID HYDROGEN FLUORIDE CONTAINING ABOUT 4 TO ABOUT 10 PER CENT ACID SOLUBLE OIL, AT A REACTION TEMPERATURE OF ABOUT 270* TO ABOUT 470* F., AT A PRESURE AT LEAST 125 P.S.I. GREATER THAN THE VAPOR PRESSURE OF THE REACTION MIXTURE AT THE AFORESAID REACTION TEMPERATURE AND FOR NOT MORE THAN ABOUT 20 MINUTES, COOLING THE LIQUID REACTION MIXTURE TO ABOUT 150* TO ABOUT 250* F., AND SEPARATING A HYDROCARBON CONVERSION PRODUCT HAVING A 90 PER CENT POINT BELOW THE 10 PER CENT POINT OF SAID CHARGE NAPHTHA AND CONTAINING LESS THAN 5 PER CENT HYDROGEN FLUORIDE FROM A LIQUID HYDROGEN FLUORIDE PHASE.

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