US2990363A

US2990363A - Method of reducing variation in antiknock characteristics of fractions of full boiling range naphtha

Info

Publication number: US2990363A
Application number: US790868A
Authority: US
Inventors: Louis P Evans
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1959-02-03
Filing date: 1959-02-03
Publication date: 1961-06-27
Anticipated expiration: 1978-06-27
Also published as: FR1246639A; GB892250A; DE1163477B

Description

June 27, 1961 L, METHOD OF REDUCING VARIATION OF FRACTION Filed Feb. 3, 1959 P EVANS 2 Sheets-Sheet 1 o 95 Tcrge'r ON 9;, 2 C 2 8 U a so 0 o 50 I00 I50 200 250 300 350 400 450 500 I MEAN AVERAGE Boiling PoinfF 42c ASTM Distillation Curve Middle East Nophthu 5 -B.R. 05m 400F. 1 340 I g 300 charge 20 40 so 0 EP /,overheo lNl/E/VTOR.

FIG.2

Louis P. Evuns AGENT- June 27, 1961 VANS 2,990,363

L. P. E METHOD OF REDUCING VARIATION IN ANTI-KNOCK CHARACTERISTICS OF FRACTIONS OF FULL BOILING RANGE NAPHTHA 2 Sheets-Sheet 2 Filed Feb. 3, I959 SPLITTER Full Range Naphfho To Stabilization other Finishing Operations FIG.3

lNVE/VTO/i. Louis F! Evans AG E NT.

2,990,363 METHOD OF REDUCING VARIATION IN ANTI- KNOCK CHARACTERISTICS OF FRACTIONS OF FULL BOILING RANGE NAP A Louis P. Evans, Woodbury, N.J., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Filed Feb. 3, 1959, Ser. No. 790,868 9*Claims. (Cl. 208-65) The present invention relates to the reduction in variation of the octane rating of fractions of reformed naphtha and, more particularly, to a method of reforming naphtha to reduce the road-octane depreciation of reformed naphtha.

It has been discovered that while the octane rating of a full boiling range gasoline containing tetraethyl lead meets the requirements of a specification nevertheless fractions of that gasoline have octane ratings far below the target octane rating of the blend. When the manifolding system of the gasoline feed of an internal combustion system is such that a uniform mixture of the gasoline is not delivered to all cylinders of the engine some cylinders receive a gasoline mixture of lower octane rating than required for knock-free operation, whereas other cylinders of the same engine receive a gasoline mixture of higher octane rating than required for knockfree operation.

The variation of octane rating with mean average boiling point of the fractions of a full boiling range leaded gasoline having an octane rating of 90 (R+1.9 cc. TEL) is illustrated by the curve presented in FIGURE 1 of the drawings.

Inspection of FIGURE 1 makes it manifest that the fractions of the full boiling range gasoline having mean average boiling points between about 120 F. and about 25 8 F. have octane ratings below 90 while the fractions having mean average boiling points between about 70 F. and 120 F. and about 258 F. and the end boiling point of the full boiling range gasoline have octane ratings in excess of the 90 octane rating of the full boiling range gasoline.

When a full boiling range naphtha is reformed to an octane rating of 100 (Research +1.9 cc. TEL) the road octane depreciation, i.e., Research Octane minus Road Octane, is about 9 units. On the other hand, when the same full boiling range naphtha is reformed in the manner described hereinafter to an octane rating of 100 (Research +1.9 cc. TEL) the road-octane depreciation is only about or less octane units.

Accordingly, the present invention provides a method for reducing the variation in octane rating with the mean average boiling point of fractions of full boiling range naphtha which comprises fractionating a full boiling range naphtha into a light fraction and a heavy fraction, contacting said light fraction with all of the particle-form reforming catalyst in the presence of hydrogen and mixing the heavy fraction with the effiuent from at least the first thirty percent of said catalyst.

It is another object of the present invention to provide a method for reducing the road-octane depreciation of a full boiling range naphtha which comprises fractionating a full boiling range naphtha into a light fraction and a heavy fraction, passing said light fraction through at least three reaction zones in the presence of hydrogen and a particle-form reforming catalyst and mixing the heavy fraction with the efiiuent from at least the penultimate reaction zone. It is a further object of the present invention to provide a method of reforming full boiling range naphtha which comprises fractionating a full boiling range naphtha into a light fraction and a heavy fraction, passing said light fraction through at least three reaction zones in the presence of hydrogen and a particle-form reforming catalyst, and mixing the heavy fraction with the efiluent from the penultimate reaction zone. It is also an object of the present invention to provide a method of reforming full boiling range naphtha which comprises fractionating a full boiling range naphtha containing only innocuous concentrations of catalyst poison into a light fraction and a heavy fraction, contacting said light fraction in at least three reaction zones with particle-form reforming catalyst in the presence of hydrogen, and admixing the heavy naphtha fraction with the effluent from at least the penultimate reaction zone. The present invention also provides for fractionating a full boiling range naphtha into a light fraction and a heavy fraction, contacting said light fraction in at least three reaction zones in the presence of hydrogen, admixing said heavy fraction with the effluent from at least the penultimate reaction zone, maintaining a hydrogento-naphtha mol ratio in the reaction zones through which both light and heavy naphtha pass of about 4 to 20 and maintaining a hydrogen-to-naphtha mol ratio in the reaction zones through which only the light fraction passes at least 1.7 times the hydrogen-to-naphtha rnol ratio in the reaction zones through which both the light and heavy fractions pass. Other objects and advantages will become apparent to those skilled in the art from the following description of the present invention taken in conjunction with the drawings in which:

FIGURE 1 is a graph showing the relation between the octane rating (Research +1.9 cc. TEL) and the mean average boiling point of a plurality of fractions of a reformate having an octane rating of (Research +1.9 cc. TEL).

FIGURE 2 is a graph of the temperatures at which successive ten percent fractions of a C 400 F. Middle East naphtha were distilled in an A.S.T.M. distillation, and

FIGURE 3 is a flow sheet illustrating the flow of liquids and vapors through a reforming unit employing the preferred catalyst.

Illustrative of the C to 400 F. boiling range full boiling range naphtha to be treated in accordance with the principles of the present invention is a Middle East naphtha, the A.S .T.M. distillation curve for which is presented in FIGURE 2. FIGURE 2 was plotted from the data in Table I.

TABLE I A.S.T.M. distillation of pretreated Middle East C 400 F. full boiling naphtha The charge naphtha, pretreated to reduce the concentration of catalyst poisons to innocuous concentrations, is fractionated to provide a light fraction having an end boiling point of about 220 to about 270 F. That is to say, the light fraction is about 40 to about 60 percent of the naphtha charged to the fractionator.

When employing a catalyst sensitive to nitrogen, arsenic, and the like, the concentrations of these poisons are reduced to innocuous levels before introducing the naphtha into the reaction zones. Thus, for example, when the naphtha is to be reformed in the presence of a platinum group catalyst, e.g., a catalyst comprising 0.1 to about 2 percent, preferably about 0.3 to about 0.6 percent platirine supported on a carrier comprising alumina, the nitrogen content of the feed to the reaction zones is not more than about 1 p.p.m. and the feed to the reaction zones is essentially free from arsenic, i.e., arsenic deactivation of the catalyst does not occur before the catalyst is replaced because of mechanical failure or temperature required to produce a reformate having an octane rating of at least 100, to ensure a practical Von-stream life for the catalyst. In order to reduce corrosion of the reforming unit to practical levels the sulfuric content of the naphtha charged to the unit is not more than about 20 ppm. On the other hand, when employing a catalyst comprising a mixture of oxides of chromium and aluminum the arsenic and nitrogen content of the charge naphtha can be higher.

As illustrated in FIGURE 3 the present invention provides for reforming the naphtha in a reforming unit comprising a plurality of reaction zones, preferably three, employing fixed beds of catalyst. However, the moving bed technique or the fluidized technique can be employed throughout the reforming unit. Furthermore, moving bed technique or fluidized technique can be employed for the initial reaction of the light naphtha and static bed technique employed for the final stages of the reaction when the light and heavy fractions are reformed together without departing from the principles of the present invention. Thus, the light fraction can be contacted with a moving bed of chromia-alumina reforming catalyst, the efiluent therefrom admixed with the heavy fraction and the mixture contacted with a static bed of platinum group reforming catalyst. Alternatively, the heavy naphtha can be in jected into the moving bed of catalyst at a point spaced from the light naphtha inlet about 30 to about 70 percent of the distance between the light naphtha inlet and the vapor out-let. The fluidized technique can be used alone or in conjunction with a static bed of platinum-group re-j forming catalyst in a similar manner.

Suitable reforming catalyst can be classified as nonnoble metal reforming catalysts and platinum-group metal reforming catalysts. Illustrative of the non-noble metal reforming catalysts are mixtures of oxides of chromium and alumina, and molybdenum and alumina with or without chlorine and/or fluorine. Typical of the platinumgroup metal reforming catalysts are catalysts comprising about 0.1 to about 2 percent by weight platinum, about 0.1 to about 0.8 percent by weight of chlorine and/ or fluorine on alumina, and about 0.1 to about 2 percent by weight plantinum on a silica-alumina support.

Illustrative of the present invention is the reforming of the -400 F. Middle East naphtha to which reference has been made hereinbefore. As illustrated in FIGURE 3 the decontaminated naphtha is drawn from a source not shown through pipe 1 by pump 2. Pump 2 discharges the full boiling range naphtha into pipe 3. The C 400" F. naphtha flows through pipe 3 to fractionator 4. In fractionator 4 an overhead having an end point of about 220 to about 270 F. is taken. The overhead, hereinafter designated light naphtha, flows through pipe 5 to heat exchanger 6 where the light naphtha is in indirect heat exchange relation with the total efiluent of reactor 23 flowing through conduit 34. From heat exchanger 6 the light naphtha flows through pipe 7 to the suction side of pump 8. Pump 8 discharges the light naphtha into conduit 9 at a pressure higher than the pressure in reactor 13. The light naphtha flows through conduit 9 to coil 10 in heater 11. At some point in conduit 9 intermediate to pump 8 and to coil 10, hydrogen-containing recycle gas is admixed with the light naphtha. The charge mixture thus formed aaa aess I a l e num and about 0.1 to about 0.8 of chlorine and/or fluo- 4 comprising light naphtha and hydrogen flows through conduit 9 to coil 10. Preferably, after start-up the hydrogencontaining gas is recycle gas discharged by compressor 40 into conduit 41 through which the recycle gas flows to conduit 9. r

In heater '11 the charge mixture, e.g., light naphtha and hydrogen-containing recycle gas is heated to a reforming temperature primarily dependent upon the catalyst, the age of the catalyst, and the required octane of the reformate. For a platinum reforming catalyst comprising 0.6 percent by weight platinum and 0.6 weight percent chlorine on alumina, the light naphtha charge mixture is heated to a temperature within the range of about 900 to about 980 F., the limiting temperature being the temperature at which the catalyst is irreversibly deactivated by heat alone. From heater 11 the light naphtha charge mixture flows through conduit 12 to reactor 13.

In reactor 13 the charge mixture flows downwardly in contact with the particle-form reforming catalyst. The first reactor effiuent flows through conduit 14 to coil 15 in heater 16. In accordance with the present inventive concept a portion or all of the heavy naphtha can be admixed with the first reactor eflluent.

Thus (returning to fractionator 4), as noted hereinbefore, an overhead, designated light naphtha, having an end point within the range of about 220 to about 270 F. is taken at fractionator 4, leaving a bottoms, designated heavy naphtha, having an initial boiling point about 5 to 10 F. lower than the end point of the light naphtha depending upon the efiiciency of the fractionator. The heavy naphtha has an initial boiling point within the range of about 240 to about 270 F. The heavy naphtha flows from fractionator 4 through pipe 26 to heat exchanger 25 where the heavy naphtha is in indirect heat exchange relation with the total eflluent of reactor 23, designated hereinafter final eflluent, flowing to heat exchanger 25 through conduit 24. The heavy naphtha flows from heat exchanger 25 through pipe 27 to the suction side of pump 23. Pump 28 discharges the heavy naphtha into pipe 29 at a pressure higher than the pressure in reactor 18.

Dependent upon the naphthene content of the C -l00 F. naphtha a portion or all of the heavy naphtha flows through pipe 29 through pipe 32 under control of valve 33 to conduit 14 or a part or all of the heavy naphtha flows from pipe 29 through pipe 30 under control of valve 31 to conduit 19. Thus, when reforming a 0 -400 F. naphtha containing less than 30 percent naphthenes in the manner disclosed herein all of the heavy naphtha flows from pipe 29 through pipe 30 to conduit 19. On the other hand, when reforming a C 400 F. naphtha containing about 30 to about 50 percent naphthenes in the manner disclosed herein about 40 to about 50 percent of the heavy naphtha flows from pipe 29 through pipe 32 to conduit 14 and the balance flows through pipe 30 to conduit 19. When reforming a C 400 F. naphtha containing more than about 50 percent naphthenes, about 60 to 70 percent of the heavy naphtha flows from pipe 29 through pipe 32 to conduit 14 and the balance through pipe 30 to conduit 19.

The first reactor effluent with the admixed heavy naphtha, if any, flows through conduit 14 to coil 15 in heater 16. In heater 16 the light naphtha charge mixture and admixed heavy naphtha, if any, is heated to a reforming temperature the same as, higher or lower than, the reforming temperature to which the light naphtha charge mixture has been heated in heater 11. The first reactor efiluent and admixed heavy naphtha, if any, designated second reactor charge mixture, flows from heater 16 through conduit 17 to reactor 18.

In reactor 18 the second reactor charge mixture flows downwardly in contact with the particle-form solid reforming catalyst. The effluent of reactor 18, designated second reactor effluent, flows through conduit 19 to coil 20 in heater 21. In conduit 19 the second reactor efiluent is admixed with heavy naphtha as described hereinbefore to form a third charge mixture comprising unreacted light naphtha, if any, unreacted heavy naphtha, if any, reaction products and the balance, if any, of the heavy naphtha fraction. The third charge mixture is heated to a reforming temperature the same as, higher or lower than, the temperature to which the first and second charge mixtures have been heated. The heated third charge mixture flows from heater 21 through conduit 22 to reactor 23.

In reactor 23 the third charge mixture flows downwardly in contact with particle-form solid reforming catalyst. The efiluent from reactor 23, designated final eflluent, flows through conduit 24 to heat exchanger 25 Where the final efifiuent is in indirect heat exchange relation with the heavy naphtha flowing from fractionator 4 as described hereinbefore. From heat exchanger 25 the final eflluent flows through conduit 34 to heat exchanger 6 where the final efiluent is in indirect heat exchange relation with the light naphtha flowing from fractionator 4 as described hereinbefore. From heat exchanger 6 the final efiluent flows through conduit 35 to cooler 36 where the temperature of the final effluent is reduced to approximately that at which C and heavier hydrocarbons are condensed. From cooler 36 the uncondensed and condensed final efiluent flows through conduit 37 to liquidgas separator 38.

In liquid-gas separator 38 the uncondensed final effluent separates from the condensed final effiuent, i.e., C and heavier hydrocarbons. The uncondensed final effiuent, now termed recycle gas, flows from separator 38 through conduit 39 to compressor -40. A portion about equivalent to the net make of gas in the reforming reaction is diverted from conduit 39 through conduit 43 under control of valve 44 to other processes such as pretreating the C -400 F. naphtha, in which hydrogen-containing gas of this or similar composition can be used, or to the refinery fuel main. The balance of the hydrogencontaining recycle gas flows through conduit 39 to the suction side of compressor 40. Compressor 40 compresses the recycle gas to a pressure at least equal to that in conduit 9. The compressed recycle gas is discharged by compressor 40 into conduit 41 through which the compressed recycle gas flows to conduit 9 as described hereinbefore.

The condensed final effluent, i.e., C and heavier hydrocarbons, flows from separator 38 through pipe 42 to stabilization and other finishing operations.

It has been disclosed that the total amount of platinum catalyst can be distributed among three reactors so that the amount of catalyst in the second reactor is at least equal to the amount of catalyst in the first reactor and the amount of catalyst in the third reactor is greater than the amount of catalyst in the second reactor (US. Patent No. 2,654,694). In co-pending application for United States Letters Patent Serial No. 682,361, filed September 6, 1957, in the name of Anthony E. Potas, there is disclosed the use of at least two reactors and distribution of the catalyst between the reactors so as to provide 2-5 tons per 10,000 barrels of naphtha contacted per day in the first reactor and the amount of catalyst in the reactor(s) succeeding the first is that required to produce reformate of the required octane rating. In co-pending application for United States Letters Patent Serial No. 739,065, filed June 2, 1958, there is disclosed a method of reforming in which the platinum catalyst is distributed in two or more reactors to provide 2 to 5 tons of catalyst per 10,000 barrels of naphtha contacted per day in the first reactor and to provide an amount of catalyst in the reactors succeeding the first dependent upon the hydrogen partial pressure at the outlet of the last reactor. In the present invention the platinum catalyst can be distributed as disclosed in the aforesaid US. patent and patent applications. However, it is preferred to distribute the catalyst in substantially equal amounts in each reactor. Thus, for a reforming unit treating 10,000 barrels of C -400 F. naphtha per day at a space velocity of about 1, about 53 tons of catalyst comprising 0.6 Weight percent platinum and about 0.6 weight percent chlorine on a support comprising alumina is distributed among three reactors, R R and R to provide about 18 tons or 417 barrels of catalyst in each reactor.

lit will be recognized by those skilled in the art that, in a reforming unit in which the overall liquid hourly space velocity is one when the entire full boiling range, i.e., C 400 F. naphtha, passes through all reactors, the liquid hourly space velocity will be less in those reactors in which only the light naphtha fraction or a mixture of the light naphtha fraction and a portion of the heavy naphtha fraction pass. In the method of the present invention the liquid hourly space velocity in reactors R and R will be less than in R and dependent (1) upon volume of the fraction of the C 400 F. taken as light naphtha, and (2) the portion of the fraction of heavy naphtha charged to the second reactor (R in admixture with the first reactor eflluent. The variation in liquid hourly space velocity 'for different values of the foregoing variables is recognized from the following tabula- TABLE 11 Overall space velocity full boiling range naph5tlia (Os-400 F.)1

Full boiling range naphtha-10,000 b./d. (416 Catalyst distributionl:1:1; 138.8 bbl. cat/reactor (416.5 total bbls.)

Heavy Naphtha to R2 Liquid Hourly Space Velocity Balance to R3 (v./hr./v.)

Light Naphtha Percent as percent of Heavy R1 R2 R3 (la-400 F. Naphtha Naphtha to B2 0.90 0. 90 3 1. 20 1. 20 3 1. 50 1. 50 3 1. 1.80 3 0. 1. 74 3 0.90 1. 3 0. 90 2. 16 3 0. 90 2. 37 3 1. 20 1. 92 3 1. 20 2. l0 3 l. 20 2. 28 3 1. 20 2. 46 3 1. 50 2. 10 3 1. 50 2. 25 3 1. 50 2. 40 3 1. 50 2. 55 3 1. 80 2. 28 3 1. 80 2. 4O 3 1. 80 2. 52 3 1. 80 2. 64 3 Furthermore, the hydrogen to naphtha ratio in reactors R and R Will vary with the volume of the light naphtha introduced into R and the volume of heavy naphtha introduced into R as shown in Table III.

TABLE HI H N Hdr-o entoNahh Light Naphtha Percent M ol y g Ratio t a M01 as percent by Heavy Ratio vol. of C 400 F. Naphtha O to R 400 F R; R1 R Naphtha None 4 11.0 11.0 4 None 15 41.0 41.0 15 None 4 5. 9 5. 9 4 None 15 22. 1 22. l 15 40 4 11.0 6. 8 4 40 15 41.0 25. 6 15 70 4 11.0 5.0 4 70 15 41.0 19.0 15 40 4 5. 9 5.1 4 40 15 22.1 19.3 15 70 4 5. 9 4. 6 4 70 15 22.1 17.0 15

1 Balance to R Admstmeut made for different molecular weights of fractions.

Illustrative of the fractionation' of'a (E -400 F. Middle East naphtha and resultant C reformates are the compositions presented in Table IV. Since the C -400 F.

naphtha contained about 25 percent naphthenes the entire heavy naphtha fraction was introduced into reactor R 23).

Those skilled in the will understand that the diflfer ences in vapor inlet temperature result primarily from the difierences in severity, although the various runs were made on successive days.

Accordingly, the present invention provides for fractionating a naphtha, particularly a straight run naphtha,

TABLE IV O +Reformate at Indicated Severity (R+3) C +Components, per- (J -400 13. Light Heavy cent Vol. (P ONA+Ped)* Naphtha Naphtha Naphtha Paraflins 68. 2 82. 1 61. 3 56. 2 55. 5 54. 2 40. 4 42. 9 l0. 2 3. 5 13. 5 40. 8 41. 1 43. 2 57. 55.0 20.2 13. 6 24. 9 2.1 2.4 1.7 1.1 1.2 0.1 0.2 0.3 0.8 1.0 0.9 1.5 0.9 1. 3 0. 0. 1

Total 100. 0 100. 0 100. 0 100.0 100. 0 100. 0 100. 0 100. 0

Percent of 05-400 F.

Naphtha 100.0 46.0 54. 0

1 Made at 6:1 Ely/naphtha recycle mol ratio for 0 -400 F. 1 Made at 10:1 lib/naphtha recycle mol ratio for 0 400" F. 5 Made at 9:1 El /naphtha recycle moi ratio for (la-400 F. 1? 0NALiquid hydrocarbon type analysis.

Pod-C and lighter individual hydrocarbon analysis.

The reformates for which analyses are presented in Table IV were reformed under the conditions set forth into a light naphtha fraction having an end boiling point within the range of about 220 to about 270 F. and a 1n Table V. heavy naphtha fraction having an initlal boiling point TABLE V Operating Conditions Catalyst Fill 1:1:1 05-400 F. Light Heavy c -l-Retormates N aphtha N aphtha Naphtha Octane No. Severity (3+3 cc.) 93 96 98 101 101 Inlet Temp. F.:

R: 1 964 2 922 3 93a 4 965 5 965 Re 964 922 935 965 965 R1 901 922 935 965 965 Space Velocity (Ck-400 F) 1.02 0. 98 0.97 0.98 1.00 H /Naphtha M01 Ratio". 5. 3 10. 8 9.6 9. 2 6.2 Yield, percent vol. of C 400 F.. 70.4 74.7 71.6 59.6 64.0 Distillation, ASTM: IBP F 112 107 268 110 105 100 103 105 162 133 285 162 140 142 148 151 257 171 321 280 258 264 271 270 364 224 380 364 365 360 369 369 E.P. F 398 344 398 425 426 440 459 455 Research (Clear) 0. N. of C5220 RT. r

Fmt'l'lm'l 79. 7 78. 3 79.0 79. 5 78.0 Research (+3 cc. TEL) O.N. of (ls-220 F.

T.B.P. Fraction 95. 5 95. 2 94. 95. 2 94. 6 Road Octane Depr n 2. 2 4. 8 4. 6 5. 5 5. 2

1 Catalyst age 14 days. 1| Catalyst age 10 days. I Catalyst age 11 days. 4 Catalyst age 12 days. 5 Catalyst age 13 days. Based on total naphtha charged, i.e., light and heavy naphtha.

It will be observed that, although the leaded octane rating of the C -22O F. TBP fraction in all cases is 95.0 (within the accuracy of the test), nevertheless the road octane depreciation is much greater for those gasolines in which the vapor inlet temperature of the last reactor is the same as those of the first and second reactors. This is manifest from the following summary of pertinent data presented in Table VI.

higher than the percent point of the light naphtha fraction and an end boiling point about that of the full boiling range naphtha, contacting said light naphtha fraction at an overall space velocity of .1 to 2 with at least about 27 to about 53 tons of particle-form platinum reforming catalyst at reforming temperatures dependent upon the activity of the reforming catalyst and the required octanerating of the C reformate. The reforming catalyst is confined in at least two, preferably three, reaction zones and the light naphtha is reheated to reforming temperatures between successive reaction zones. The heavy. naphtha fraction is admixed with the light naphtha fraction prior to contacting the mixture with the last 30 to 70 percent of the catalyst. Furthermore, the temperature of the mixture of partly treated light naphtha and the unreformed heavy naphtha is dependent upon the naphthene content of the heavy naphtha fraction and is at least about 850 to about 930 F. for naphthas containing about twenty percent naphthenes and at least about 900 9 to about 965 F. for naphthas containing about fifty percent or more of naphthenes.

Those skilled in the art will understand that the present invention comprises fractionating a full boiling range naphtha into a light naphtha fraction and a heavy naphtha fraction, the light naphtha fraction preferably having an end boiling point within the range of about 220 to about 270 F. and the heavy naphtha having an initial boiling point not lower than the 90% point of the light naphtha, contacting the light naphtha fraction with a total of one volume of particle-form reforming catalyst per one volume of full boiling range naphtha per hour, admixing said heavy naphtha fraction with partially treated light naphtha fraction after the light naphtha fraction has contacted at least about one-third of the total amount of particle-form reforming catalyst, preferably after the light naphtha has contacted about two-thirds of the total amount of particle-form reforming catalyst, and particularly after the light naphtha has contacted about 85 to about 90 percent of the total amount of particleform reforming catalyst, maintaining substantially the same vapor inlet reforming temperature while the naphtha fractions are in contact with the total amount of particleform reforming catalyst when admixing said heavy naphtha fraction with said light naphtha fraction after con tacting said light naphtha fraction with at least 85 percent of the total amount of particle-form reforming catalyst and maintaining a lower reforming temperature in that portion of the total reforming catalyst contacted by both light and heavy naphtha fractions when the heavy naphtha fraction is admixed with the light naphtha fraction after the latter has contacted at least about two-thirds of the total amount of particle-form reforming catalyst, contacting said mixture of heavy naphtha and partially reformed light naphtha with said particle-form reforming catalyst in the presence of hydrogen-containing gas at a hydrogen to total naphtha mol ratio about 4 to 20, preferably about 6 to 15, contacting said light naphtha fraction only with said particle-form reforming catalyst in the presence of hydrogen-containing gas at a hydrogen to naphtha mol ratio which is the aforesaid mol ratio divided by volume percent which the light naphtha fraction is of the full boiling range naphtha, the space velocity of the mixture of heavy naphtha and partially treated naphtha being about 1.0 to about 20, preferably about 3 to 10, vol./hr./ v. catalyst, and the space velocity when the light naphtha fraction is only in contact with the particle-form reforming catalyst being that of the overall space velocity multiplied by the volume fraction which the light naphtha is of the full boiling range naphtha and divided by the percent of the total catalyst fill contacted only by the light naphtha fraction when the catalyst is distributed equally among a plurality of reaction Zones, and when the mixture of heavy naphtha fraction is contacted with only 10 to percent of the total volume of catalyst, the space velocity when the light naphtha fraction is only in contact with the particle-form reforming catalyst is a fraction of the space velocity of said mixture of light and heavy naphthe. equal to the multiple of the volume per cent which the light naphtha is of the full boiling range naphtha divided by percent of total catalyst fill contacted by the light naphtha, and the pressure is a reforming pressure within the range of 100 to 1000 p.s.i.g., preferably within the range of about 200 to 600 p.s.i.g.

Particularly, the present invention provides a method of reforming full boiling range naphtha at a reforming pressure within the range of 100 to 1000, preferably 200 to 600 p.s.i.g., in the presence of particle-form platinum group reforming catalyst, e.g., comprising 0.1 to 2.0, preferably about 0.3 to about 0.6, percent by weight of platinum on alumina in the ratio of about 27 to about 106 tons total of said platinum catalyst per 10,000 barrels of full boiling range naphtha reformed per day, wherein said catalyst is distributed equally among three reaction zones R R and R (numbered in the direction of flow of light naphtha fraction of the full boiling range naphtha), wherein said full boiling range naphtha containing not more than about 1 ppm. of nitrogen, not more than about 20 p.p.m. of sulfur, and essentially free of arsenic is fractionated into a light naphtha having an end boiling point within the range of about 220 to about 270 F. and a heavy naphtha having an end boiling point within the range of about 320 to about 400 F, wherein the said light naphtha is contacted with said total amount of catalyst, wherein said heavy naphtha is contacted in admixture with said light naphtha with not more than about 70 percent of said total amount of particle-form reforming catalyst after said light naphtha has contacted at least 30 percent of said catalyst, wherein the hydrogen to naphtha mol ratio is about 4 to 20, preferably about 6 to 15, while the mixture of heavy naphtha and partially treated naphtha is in contact with said reforming catalyst, and a multiple thereof when contacting only said light naphtha with said reforming catalyst equal to A/B, where A equals the mol ratio of hydrogen to naphtha when the aforesaid mixture is in contact With the catalyst, and B is the fraction which the light naphtha is of the full boiling range naphtha, wherein the space velocity when the aforesaid mixture of light and heavy naphtha is contacted with the aforesaid catalyst is about 1.0 to 20, preferably about 3 to 10 vol. naphtha/-hr./vol. catalyst, and the space velocity when the light naphtha only is in contact with the aforesaid catalyst is equal to CD/E, Where C is the overall space velocity of the full boiling range naphtha passing through all of the reaction zones, D is the fraction which the light naphtha is of the full boiling range naphtha, and E is the fraction of the total catalyst fill contacted by the light naphtha only, and wherein the temperature is a reforming tempera-ture dependent upon the activity of the catalyst and the required octane rating of the C reformate within the range of about 800 to about 1000 F., preferably about 900 to about 980 F.

I claim:

1. In the method of reforming naphtha wherein a full boiling range naphtha is contacted in at least one reaction zone with particle-form solid reforming catalyst in the presence of hydrogen at a hydrogen to naphtha mol ratio of about 4 to about 20, at a space velocity vol. naphtha/ hr./vol. of the aforesaid particle-form solid reforming catalyst of about 0.5 to about 3, under pressures of about to about 1000 p.s.i.g., at reforming temperatures to obtain a mixture of hydrogen and C hydrocarbons, separating a-recycle gas comprising hydrogen and C to-C' hydrocarbons from C and heavier hydrocarbons, and "wherein a major portion of said recycle gas comprising hydrogen and C to C hydrocarbons is returned to said reaction zone, the improvement which consists essentially of fractionating said full boiling range naphtha into a light naphtha having an end boiling point within the range of about 220 to about 270 F. and a heavy naphtha having an initial boiling point not lower than the ninety percent point of the aforesaid light naphtha, contacting said light naphtha with all of said reforming catalyst, admixing said heavy naphtha with partially reacted light naphtha after said light naphtha has contacted at least 30 percent of the total volume of the aforesaid particleform solid reforming catalyst, and contacting said mixture of the aforesaid heavy naphtha and the aforesaid partially reacted light naphtha with the balance of said particleform reforming catalyst.

2. In the method of reforming naphtha the improvement set forth in claim 1 wherein the particle-form reforming catalyst is a platinum group catalyst comprising about 0.1 to about 2 percent by weight platinum, and about 0.1 to about 0.8 percent by weight halogen, on alumina support.

3. In the method of reforming naphtha the improvement set forth in claim 1 wherein the particle-form re- 11 forming catalyst comprises about 0.1 to about 2 percent by weight platinum on alumina support, and the heavy naphtha is mixed with the partially reacted light naphtha after the light naphtha has contacted about 60 to about 70 percent of the aforesaid particle-form solid reforming catalyst.

4. In the method of reforming naphtha the improvement set forth in claim 1 wherein the particle-form reforming catalyst comprises about 0.1 to about .2 percent by weight of platinum on alumina support, the heavy naphtha is mixed with the partially reacted light naphtha after the light naphtha has contacted about 60 to about 70 percent of the catalyst, and the mixture of heavy naphtha and partially reacted light naphtha is contacted with the balance of the aforesaid particle-form reforming catalyst at a temperature lower than the temperature at which said light naphtha only contacted the aforesaid particle-form reforming catalyst and high enough that the temperature of the eflluent mixture of treated light naphtha and treated heavy naphtha is not less than about 800 F.

5. In the method of reforming naphtha the improvement set forth in claim 1 wherein the particle-form reforming catalyst comprises about 0.1 to about 2 percent by weight of platinum on alumina support, the heavy naphtha is mixed with the partially reacted light naphtha after the light naphtha has contacted about 60 to about 70 percent of the catalyst, and the mixture of heavy naphtha and partially reacted light naphtha is contacted with the balance of the aforesaid particle-form reforming catalyst at a temperature lower than the temperature at which said light naphtha only contacted the aforesaid particle-form reforming catalyst and high enough that the difference between the temperature of the mixture of heavy naphtha and partially reacted naphtha when said mixture first contacts the balance of the aforesaid particleform reforming catalyst and the temperature of the chinent mixture of reacted light naphtha and reacted heavy naphtha is a maximum and the temperature of said eflluent mixture is not less than about 800 F.

6. In the method of reforming full boiling range naph tha which comprises passing heated full boiling range naphtha successively through three reaction zones, at reforming temperature and pressure, each of said reaction zones containing substantially the same amount of catalyst comprising about 0.1 to about 2 percent by weight of platinum on alumina support, to obtain a final effluent from said third reaction zone comprising hydrogen and C hydrocarbons, separating a recycle gas comprising hydrogen and C to C hydrocarbons from reformate comprising C and heavier hydrocarbons, and returning said recycle gas to said first reaction zone, the improvement which consists essentially of fractionating said full boiling range naphtha into a light naphtha being about 40 to about percent of the full boiling range naphtha and a heavy naphtha having an initial boiling point 5 to 10 F. lower than the end boiling point and not lower than the ninety percent point of the aforesaid night naphtha, passing said light naphtha only through the first and second reaction zones, mixing the efiluent of said second reaction zone with said heavy naphtha, and passing said mixture of said heavy naphtha and said second reaction zone effluent through said third reaction zone.

7. The improvement in the method of reforming full boiling range naphtha as set forth in claim 6 wherein the hydrogen to naphtha mol ratio in said third reaction zone is about 4 to 20.

8. The improvement in the method of reforming full boiling range naphtha as set forth in claim 6 wherein the mixture of said second reaction zone effluent and said heavy naphtha is contacted with said catalyst in said third reaction zone at a reforming temperature lower than the reforming temperatures in said first and second reaction zones, and the temperature of the effluent of said third reaction zone is not less than 800 F.

9. The improvement in the method of reforming full boiling range naphtha as set forth in claim 6 wherein the mixture of said second reaction zone effiuent and said heavy naphtha is contacted with said catalyst in said third reaction zone at a reforming temperature lower than the reforming temperatures in said first and second reaction zones, the difierence between the vapor inlet temperature of the said third reaction zone and the temperature of the efiluent of said third reaction zone is a maximum, and the temperature of said effluent of said third reaction zone is not less than about 800 F.

References Cited in the file of this patent UNITED STATES PATENTS 4.. when,

Claims

1. IN THE METHOD OF REFORMING NAPHTHA WHEREIN A FULL BOILING RANGE NAPHTHA IS CONTACTED IN AT LEAST ONE REACTION ZONE WITH PARTICLE-FORM SOLID REFORMING CATALYST IN THE PRESENCE OF HYDROGEN AT A HYDROGEN TO NAPHTHA MOL RATIO OF ABOUT 4 TO ABOUT 20, AT A SPACE VELOCITY VOL. NAPHTHA HR./VOL. OF THE AFORESAID PARTICLE-FORM SOLID REFORMING CATALYST OF ABOUT 0.5 TO ABOUT 3, UNDER PRESSURES OF ABOUT 100 TO ABOUT 1000 P.S.I.G., AT REFORMING TEMPERATURES TO OBTAIN A MIXTURE OF HYDROGEN AND C1+ HYDROCARBONS, SEPARATING A RECYCLE GAS COMPRISING HYDROGEN AND C1 TO C3 HYDROCARBONS FROM C4 AND HEAVIER HYDROCARBONS, AND WHEREIN A MAJOR PORTION OF SAID RECYCLE GAS COMPRISING HYDROGEN AND C1 TO C3 HYDROCARBON, AND REACTION ZONE, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF FRACTIONATING SAID FULL BOILING POINT WITHIN THE RANGE LIGHT NAPHTHA HAVING AN END BOILING POINT WITHIN THE RANGE OF ABOUT 220* TO ABOUT 270* F. AND A HEAVY NAPHTHA HAVING AN INITIAL BOILING POINT NOT LOWER THAN THE NINETY PERCENT POINT OF THE AFORESAID LIGHT NAPHTHA, CONTACTING SAID LIGHT NAPHTHA WITH ALL OF SAID REFORMING CATALYST, ADMIXING SAID HEAVY NAPHTHA WITH PARTIALLY REACTED LIGHT NAPHTHA AFTER SAID LIGHT NAPHTHA HAS CONTACTED AT LEAST 30 PERCENT OF THE TOTAL VOLUME OF THE AFORESAID PARTICLEFORM SOLID REFORMING CATALYST, AND CONTACTING SAID MIXTURE OF THE AFORESAID HEAVY NAPHTHA AND THE AFORESAID PARTIALLY REACTED LIGHT NAPHTHA WITH THE BALANCE OF SAID PARTICLEFORM REFORMING CATALYST.