US3111480A - Sequential high pressure-low pressure reforming - Google Patents

Description

Nov. 19, 1963 v. o. BOWLES ETAL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6 Sheets-Sheet 1 IIO 2- 209 PSIG N 500 C so PSIG 94 95 53 I00 I02 04 I08 0.N. (R+3cc T.E.L.)

FIG. I

O U 5 .C o "6 a 2 Fl G. 2 (I) O U a. a: 5 E

INVENTORS VERNON O.BOWLES 00 I02 I04 I05 o WALTER F. READ Octane Number of IO# RVP Product Nov. 19, 1963 v. o. BOWLES ETAL 3,111,480

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6 Sheets-Sheet 2 0 o u 92 Hlgh Pressure 5 Effluent O.N.=9O z N H hPressure m '9 Fl G. 3 Effluent 0.N.=98

5 3 860 High Pressure 3 Effluent O.N.=94 g 040 O o 94 96 98 '00 I02 I04 I06 I08 O.N.PRODUCT ago's mo e Octane Number (Rl3cc)of l0 RVP Product INVENTORJ veauon 0.80WLES O.N.of FEED to Low Pressure Stage AGENT Nov. 19, 1963 v. o. BOWLES EI'AL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Filed March 31, 1958 6 Sheets-Sheet 3 as as V I IOI 0.N. IO RVP Product 2 (Low Pressure 1 I PrOdl-ICT) '04 II II I '05 a n Octane No. of High Pressure ProducHFeed to Low Pressure Stage) 0 a o N Io 203040506070 BOSOIOOI'OIZOBOHO DAYSon STREAM INVENTURS vznuou o.a0wuzs warren P. am FIG.5

AGEN'IZ Nov. 19, 1963 v. o. BOWLES ETAL 3,111,430

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING 6 Sheets-Sheet 4 Filed March 31, 1958 5 Ma J M83 E Van m WM: NT n ww w @E b E N n. 7 GM N 0 20 3 2 1 2 u :50 A 0 mm a M m ONA d n w 0 H ud m mm w m M Q m m m m 3 M 5 Q u m 1 u m 5 m \J 5 8 nu Q wil m1 my r m 5 353 o.

Nov. 19, 1963 v. o. BOWLES ETAL 3,111,480

SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFGRMING Filed March 31. 1958 6 Sheets-Sheet 6 ms 31 m! we 3. 5 N! 3 5 o: .5 3 x. u \u Mm we m2 ZUIIOENE fimfim Mfimfi :3 33

3 \J on. w! my E 8. 5. n0. N2 .w. h m 1 m. 5. 3 m:

WALTER EREAD AGENT.

United States Patent 3,111,480 SEQUENTIAL HIGH PRESSURE-LOW PRESSURE REFORMING Vernon 0. Bowles, Rye, N.Y., and Walter F. Read, Westfield, N.J., assignors to Socony Mobil Oil Company, Inc., a corporation of New York Filed Mar. 31, 1958, Ser. No. 725,398 13 Claims. (Cl. 208-65) The present invention relates to the production of gasolines having super-octane ratings (research+3 cc. TEL) of 100 or more, particularly 102 or higher and more particularly to the production of gasolines having the aforesaid super-octane ratings in a low pressure reforming operation in which the octane rating research+3 cc. TEL) of the feed to the low pressure reforming unit is within the range of about 81 to about 98, preferably not greater than about 96, and the reaction temperature and/or catalyst volume in the low pressure reforming unit is correlated with the octane rating (research-+3 cc. TEL) of the product and the octane rating (research-H cc. TEL) of the feed to the aforesaid low pressure reforming unit.

The present invention also relates to the production of gasolines having super-octane ratings (research-H cc. TEL) of 100 or more particularly 102 or higher, in which the naphtha is first reformed to a critical octane rating (research-{J cc. TEL) of 81 to 98, preferably not greater than 96, under high pressure, e.g., 500 p.s.i.g. or more and the product of the high pressure reforming operation is reformed at low pressure of less than 500 p.s.i.g., e.g., p.s.i.g. to 450 p.s.i.g., to the required super-octane rating of 100 or more.

The present invention also relates to a combination of high pressure reforming (at 500 p.s.i.g. or more) with low pressure reforming (at less than 500 p.s.i.g.) in which the algebraic sum (EAT of the difference between the temperature of the vapors entering each reactor and the temperature of the vapors leaving each reactor in the high pressure unit is equal to at least 2N R, where N is the volume percent of naphthenes in the naphtha charged to the high pressure unit and the algebraic sum (EAT of the difference between the temperature of the vapors entering each reactor and the vapors leaving each reactor in the low pressure unit is algebraically not more than N R, where N is the volume percent of naphthenes in the naphtha charged to the high pressure unit. In other words, where AT, is the difference between the temperature of the vapors entering and the temperature of the vapors leaving reaction zone 1 of the high pressure unit, or the temperature drop across reaction zone 1, AT is the temperature drop across reaction zone 2 of the high pressure unit, and AT is the temperature drop across reaction zone 3 of the high pressure unit, then the sum of AT AT and AT is at least 2N.

Similarly, if AT is the temperature drop across reaction zone A of the low pressure unit, and AT is the temperature drop across reaction zone B of the low pressure unit, then the algebraic sum of AT and AT is not greater than N R, where N is the volume percent of naphthenes in the naphtha charged to the high pressure unit. The foregoing can be expressed by two equations as follows:

The present invention relates specifically to the production of gasolines having octane ratings (research+3 cc. TEL) of at least 100 by reforming a charge naphtha in the presence of hydrogen and a particle-form platinumice type reforming catalyst at a reactor pressure of 500 p.s.i.g. or more and passing the high pressure effluent after reduction of the pressure over a particle-form platinumtype catalyst at pressures less than 500 p.s.i.g., for example, 200 p.s.i.g.

The present invention provides a considerable saving in the total amount of reforming catalyst required in a combination unit comprising a high pressure reforming unit of one or more reactors and a low pressure unit of one or more reactors to produce a gasoline having a given super-octane rating from a given napththa when compared to the total amount of reforming catalyst required to produce a gasoline of the same given superoctane rating from the same given naphtha wholly in a high pressure reforming unit or wholly in a low pressure reforming unit. Thus, the total reforming catalyst requirement of platinum-type catalyst for the present combination unit is about 25 to about 50 percent less than that required in a high pressure unit and about 35 to about 60 percent less than that required in a low pressure unit.

The present invention also provides an advantage in increased on-stream time between regencrations of at least 7 days when producing products having super-octane ratings (research-{4 cc. TEL) of about 104 or greater and at least about 30 days when producing gasolines having octane ratings (research-k3 cc. TEL) of 104 or less, depending upon the space velocity. As will be described later, less catalyst can be used, resulting in a higher space velocity and more rapid aging which is of minor consequence when a regenerative system with a swing reactor is employed.

The suggestion has been made in the past to reform naphtha sequentially at two reactor pressures. Thus, in 1943 Komarewsky and Riesz published an article in the Oil and Gas Journal in which they described a twostage process involving the use of relatively high and low reactor pressures. The following US. patents are directed to multi-stage reforming processes: 2,320,147; 2,338,573; 2,374,109; 2,409,695; 2,596,145; 2,629,683; 2,654,694; 2,659,692; 2,664,386; 2,698,829; 2,710,826; 2,710,827; 2,758,062; 2,773,013 and 2,773,014. The following British patents also describe multi-stage reforming processes: 731,094; 742,966; 745,520; 745,522; 773,- 476 and 775,961. However, the present invention is not the discovery that the reforming reaction can be carried out at high or low pressure or at high pressure and low pressure. The present invention results from the discovery that it is advantageous to control the octane rating of the feed to a low pressure reforming zone and that the reforming catalyst requirements are less for a combination unit than for a high pressure or a low pressure unit as described hereinbefore.

At the outset it is desirable to establish that the yield of 10 RVP gasoline at any octane rating is greater when the charge naphtha is reformed at relatively low reactor pressure, e.g., 200 p.s.i.g. than when reformed at higher pressures, e.g., 500 p.s.i.g. Thus, a Mid-Continent naphtha having a boiling range of F. to 380 F. was reformed over a platinum-type catalyst comprising about 0.6 percent by weight platinum, about 0.6 percent by weight chlorine and the balance alumina at a reactor pressure of 500 psig. and a hydrogen-to-naphtha ratio of 6 to l to produce 10 RVP gasolines of various octane ratings. The same charge stock was reformed over the same catalyst at a reactor pressure of 200 p.s.i.g. and a hydrogen-to-naphtha ratio of 6 to 1 to produce 10 RVP gasolines having octane ratings of the same order of magnitude. The data thus obtained have been plotted to provide the graph FIGURE 1 in which curve A and curve B express the relationship between octane number (research+3 cc. TEL) and the recovery of 10 RVP gasoline as percent by volume of the charge naphtha at a reactor pressure of 500 p.s.i.g. and at a reactor pressure of 200 p.s.i.g. respectively.

It will be observed that at any octane number (research+3 cc. TEL) the yield of 10 RVP gasoline is greater when operating at 200 p.s.i.g. than when operating at 500 p.s.i.g. (All octane ratings set forth hereinafter, unless noted otherwise, are research ratings with 3 cc. per gallon of tetraethy] lead added, i.e., research+3 cc. TEL.) The increased yield varies from 4 percent at 97 octane number to 8 percent at 105 octane number. Such an increased yield is of commercially important magnitude. However, reforming at relatively low reactor pressures, such as 200 p.s.i.g. while providing an increase of 10 RVP gasoline at octane ratings of the order of 90 to 108 also has the disadvantages of (l) shorter catalyst life between regenerations, even at lower space velocities, (2) more complex and more expensive process facilities, (3) greater catalyst requirement, or (4) shorter on-stream time per unit if non-regenerative.

The platinum-type catalyst described hereinbefore when used to reform naphtha having an octane rating of 70 to 104 octane at 500 p.s.i.g. at a given space velocity has an on-stream life between regenerations of at least 180 days. On the other hand, the life of a platinum-type catalyst when used to reform naphtha feed having an octane number of 70 to gasoline having an octane number of 104 at pressures of the order of 200 p.s.i.g. and at a given space velocity has an on-stream life between regenerations of only about 3 days.

It has now been discovered that, when producing 10 RVP gasolines having octane ratings within the range of about 100 to about 108, the on-stream time between regenerations can be increased an industrially important amount or the amount of catalyst required can be reduced considerably for substantially the same on-stream time by correlating the octane rating of the feed to a low pressure reforming unit with the octane rating of the 10 RVP gasoline to be produced in the low pressure reforming unit and with the reaction temperature and/or catalyst volume of the low pressure reforming unit.

Thus, when producing 10 RVP gasoline having an octane rating of 106 at a space velocity of 1.5 and a pressure of 200 p.s.i.g., an optimum on-stream time between regenerations of about 18 days can be obtained by ensuring that the naphtha feed to a low pressure reforming unit has an octane rating of about 95. Illustrative of the foregoing are the following data:

Low Prcs- Low Pres- Days On- 10 RVP sure Reiormsure Reiormstream Be- Product ing Unit ing Unit, tween Re- Octane No. Charge Oc- 'lomp., F. generations tune N 0.

Compared with the on-stream period of 3 days when naphtha such as straight run naphtha, having an octane number of about 70 is charged to a low pressure reforming unit, the on-stream period of 18 days represents an increase of about 600 percent in the on-stream time. In other words, when reforming naphtha to super-octane ratings of 100 or more over a given amount of reforming catalyst a commercially important increase in the onstream time between regenerations can be obtained by regulating the octane number of the feed within critical limits dependent upon the required octane rating of the product.

It is to be observed that when the naphtha is partially reformed under high pressure, i.e., 500 p.s.i.g., and then reformed to the required octane rating under low pressure, i.e., 200 p.s.i.g., the yield of gasoline from the combination unit is at least substantially the same as that produced when the naphtha is reformed solely at a low pressure of 200 p.s.i.g., for example, to super octane ratings of and more and in any event is substantially greater than when the naphtha is reformed wholly at a high pressure, e.g., 500 p.s.i.g. This is graphically illustrated by curve C in FIGURE 1.

Curve C in FIGURE 1 was plotted from the data obtained when a Mid-Continent naphtha having a boiling range of F. to 380 F. was reformed under the conditions set forth in Table I.

wt. percent Cl; balance alumina.

Operating Conditions High Prcs- Low Pressure Unit sure Unit Pressure, p.s.ig 500 200 llydrogen-to-naplitlia ratio 6 6 Space Velocity, vJhn/v .5 1. 5

l0 RVP GASOLINE Run No. Octane N umber Yield Volume Percent 05. 2 105. 3 90. 2 97. 8 99. 9 JG. 3 101. 0 94. 3 101. 2 .13. 2 102. 4 91. 2 I03. 0 80. 3 103. 8 88. 7 107. 0 81. 7

Table 11 Charge to reforming unit Mid-Continent naphtha. Boiling range 180 to 380 F.

Sulfur Not 20 p.p.m. Nitrogen Not 1.0 p.p.m. Arsenic Not 0.005 p.p.m. Catalyst (both units) 0.6 wt. percent Pt; 0.6

wt. percent Cl; balance alumina.

Operating Conditions High Prcs- Low Pros sure Unit sure Unit Pressure, p.s.Lg 1. 500 200 1Iydrogen-to-naplitlia ratio [111 (111 Space Velocity, v .lhr/v 3 1. 5

Table II-Continued Yield 10# Octane No. RVP Gaso Octane No. Run Number of Product line, Percent ol'lligh Pres- Volurnc of sure Efiiucnt Charge Although the severity, i.e., octane number, of the conditions in the high pressure unit has no important effect upon the yield of 10 RVP product at any octane rating, it has been found that the octane number of the efiiuent from the high presure unit does have an elfect upon the reactor temperature in the low pressure unit. The data establishing the foregoing are presented in Table III and plotted in FIGURE 3.

Table III Reactor Octane No. Octane No. 'Icrnnera- Run N0. High lrer- Product ture Low surc Elflucnt Pressure Unit 90. 7 05. 2 S02 90. 1 9?. 3 834 91. 0 08. 9 848 90. 1 101. 0 809 90. (J 102. 1 858 00. 0 104 2 915 93. 6 99. 9 842 94. 4 102. 4 80G 93. 6 103. 2 885 94. ii 104. 3 899 94. 8 105. 2 921 94. l 107. 0 952 97. 8 90. 9 848 97. 0 101. 2 S63 97. 8 100. 0 800 98. 104. 5 924 99. 0 105. 7 952 It has now been discovered that the octane number of the effluent of the high pressure stage is a critical factor in determining the reactor temperature required in the low pressure stage to produce a 10 RVP product having a required octane number. This is important because the lower the reactor temperature to produce a 10 RVP product having a required octane rating the longer the period between regenerations, i.e., the longer the on-stream period.

The on-stream period between regenerations is limited by the maximum temperature to which the catalyst can be exposed during the reaction without permanent loss of activity and selectivity, hereinafter designated catalyst damaging temperature, and by the incremental increase in the reactor temperature required during the on-stream period to produce a 10 RVP product having the required octane rating. Thus, for example, some platinum-type catalysts are permanently deactivated when exposed to temperatures of 1000 F. Therefore, in commercial operation to ensure that there will be a minimum likelihood that permanent deactivation will occur an upper temperature limit of 980 F. is placed upon the reactor inlet temperature. To cotninue to produce a 10 RVP product having a required octane rating employing the aforesaid platinum-type catalyst it has been found that the average reactor temperature must be raised a fraction of a degree to as much as a few degrees Fahrenheit per day, depending upon the severity level. As a consequence, the on-stream period between regenerations is dependent upon the initial reactor temperature required to produce a 10 RVP product having the required octane rating employing fresh or freshly regenerated catalyst, hereinafter designated fresh catalyst. Thus, assume that to produce a 10 RVP product having an octane rating of 104 the initial reactor temperature (employing fresh catalyst) is 900 F. and that the limiting temperature is 980 F. Further, assume that the incremental temperature increase is 1.8F. per day. Then the on-stream period will be Thus, the lower the initial reactor temperature required to produce a 10 RVP product having the required octane rating when employing fresh catalyst, the other factors, permissible maximum reactor temperature and incremental rise in temperature being the same, the longer the on-stream period between regenerations.

By an examination of the graph of FIGURE 4 those skilled in the art of reforming will be assured that the maximum oil-stream time is correlated with the octane number of the feed and the octane number of the product.

The graph of FIGURE 4 of the drawings demonstrates the relation between the octane number of the charge to the low pressure reforming unit and the octane number of the 10 RVP product from the low pressure unit as a function of the reactor temperature in the low pressure unit. That is to say, the family of curves presented in FIGURE 4 demonstrates that as a result of lower reaction temperatures, improved on-stream time between regenerations in a low pressure reforming unit employing a platinum-typc reforming catalyst is obtained by correlating the octane rating of the gasoline hydrocarbons of the charge to the low pressure reforming unit with the octane rating of the 10 RVP product and the reaction temperature with fresh catalyst. Thus, when a naphtha is subjected to conditions at 500 p.s.i.g. to produce a charge to a low pressure reforming unit having the octane ratings set forth in Table IV and the low pressure unit containing a platinum-type reforming catalyst is operated under conditions at 200 p.s.i.g. to produce 10 RVP prod ucts having the required octane rating in excess of 100, the reaction temperature in the low temperature reforming zone varies as the octane rating of the charge to the low pressure reforming unit varies.

The data presented in Table IV were read from the curves of FIGURE 3 and are plotted in FIGURE 4 as a family of curves for various average low pressure reactor temperatures between 800 and 960 F. required to reform stocks, having various octane ratings, charged to the low pressure reforming unit to 10 RVP products having various octane ratings between and 108. The on-stream time in days between regenerations for operations at each temperature are also presented in Table IV from the knowledge that the average reactor temperature must be raised each day to maintain the required product octane ratings. That is to say, the days on-stream, S at any reactor temperature, A, is determined from the relation between the permissible maximum average reactor temperature, P, the reactor temperature, A, and the incremental rise in the reactor temperature in degrees Fahrenheit per day F required to maintain the required octane rating of the 10 RVP product as follows:

In Table IV the value of P is 980 F. and the values of F are as indicated.

= 44 days T able IV 10 RVP Product Low Pressure Low Pressure Octane N0. Stage Charge Reaction, S

Octane N0. Temp, F.

100 (F=0.0 F./D.) 90.2 860 133 91. 2 850 92. 3 840 156 93. 7 830 167 95. 2 824 174 Q7, 1 830 167 97. 7 840 157 98.0 850 145 Table IVContinued 10 RVP Product Low Pressure Low Pressure Octane No. Stage Charge Reaction, S

Octane No. Temp, F.

101(F=1.07 F./D.) 89.5 880 93 90. 6 $70 103 102 (F=1.28 FJD.) 89. 7 s90 70 01. 2 880 T8 103 (F=1.52 F./D.)... 88.3 010 40 90. 1 900 53 104 (F=1.80 F./D.) 85. 8 930 28 88. 4 920 33 105 (F=2.15 F./D.). 86.1 940 19 89. 0 930 23 106 (F=".58 FJD.) 86.6 950 2 90. 0 940 15. 5

107 (F=3.05 RID.) 86. 8 060 7 9'2. 0 050 From the foregoing data it becomes manifest that the maximum on-stream time between regencrations is obtained when operating a low pressure, i.e., 100-4S0 p.s.i.g., preferably 200 p.s.i.g., reactor at the low pressure reactor temperatures correlated with the octane rating of the charge and the octane rating of the 10 RVP product.

The values for S in Table IV have been plotted in FIGURE 5 against the octane rating of the gasoline hydrocarbons of the charge for each 10 RVP product having an octane rating between 101 and 107. From the curves in FIGURE 5 broad and preferred ranges of the octane ratings of the gasoline hydrocarbons in the charge required to produce a RVP product having an octane rating within the range of about 101 to about 107 can be read off. These ranges are tabulated in Table V.

Table V Octane N0. 01 Reaction Temp, Gasoline Hydro- F. with Fresh carbons of Charge Days Orr-Stream Catalyst at Low Product to the Low Pres- Pressure sure Unit Broad Preferred Broad Preferred Broad Preferred Accordingly, the present invention provides a method for reforming naphtha to produce 10 RVP products having octane ratings of at least 100 which comprises reforming a charge stock having an octane number of at least about 87 and not more than about 98 and preferably at least about 91 and not greater than about 97 in the presence of hydrogen at a hydrogen-to-cliargestock mol ratio of about 2 to 10, preferably 3-6, and a platinum-type catalyst at initial reactor temperatures within the range of about 810 and on-stream final reactor temperature of the maximum temperature to which said platinum-type catalyst can be subjected without permanent loss of activity and selectivity and at a space velocity (v./hr./v.) of about 0.5 to about 5.0.

It will be observed that the present invention provides a method for reforming naphthas to produce 10 RVP products having an octane rating of 104 with an onstream time between regenerations of about 30 to about 40 days. The importance of this advance in the art will become manifest when it is understood that commercially a 10 RVP product having an octane rating (research clear) of 100 equivalent to 104 (research-H cc. TEL) is being produced employing five reactors and a swing reactor and regenerating two of the reactors in each 24 hours. Thus, the average on-stream time is 3 days. In addition, when the on-stream time is substantially the same, i.e., two days but the octane rating of the gasoline hydrocarbons of the feed to the low pressure reforming unit is correlated with reaction temperature in the low pressure reforming unit only about 35-50 percent as much catalyst is required as is required in the prior art low pressure reforming processes. (See Table VIII.)

It is also to be recognized that in the present sequential high pressure-low pressure combination the catalyst bed exposed to reforming conditions of high severity is doubly protected against contamination with arsenic and/ or lead and/or other metals in the feed naphtha. That is to say, the total unit, i.e., pretreater, high pressure reforming unit, and low pressure reforming unit, is designed to remove contaminants including arsenic, lead, etc. in the pretreater. However, in the event of failure, human or mechanical, of the prctreatcr, the catalyst employed in the low pressure unit where the catalyst is exposed to conditions of higher severity is still protected by catalyst in the high pressure unit.

The combination of sequential high pressure-low pressure reforming provides another advantage which is not obvious. Thus, while in prior art low pressure reforming units less hydrogen and light hydrocarbons were circulated, on the other hand, it was necessary to have a large number of reactors each containing substantially the same amount of catalyst to provide capacity necessary to take care of the large endothermicity. In contrast in the present sequential high pressure-low pressure combination it is not necessary to provide a low pressure unit of sufficient size to meet the requirements of the large endothermicity of the reaction. That is to say, in the present sequential high pressure-low pressure reforming process the algebraic sum of the differences between the vapor inlet temperatures and the vapor outlet temperatures of the reactors of the high pressure unit is at least about 2N F. (as defined hereinbefore) whereas in the low pressure unit of the combination unit the difference in temperature between the inlet temperatures and the vapor outlet temperatures of the reactors is not greater than about N F. In other words, sequential high pressure-low pressure reforming is a reforming process wherein in an adiabatic system the heat loss due to the endothermic heat of reaction is at least about 2N F. in the high pressure unit and not greater than about N F. in the low pressure unit.

The presently preferred method of applying the principles of the present invention to the production of 10 RVP product having octane ratings of the order of 100 and greater is that illustrated in FIGURE 6.

While the pretreatment of the naphtha to reduce the sulfur content to less than 20 p.p.m., the nitrogen content to less than 1 p.p.m., and the arsenic content to less than 0.005 p.p.m., preferably 0.002 ppm. is not a part of the present invention, the pretreatment of the naphtha, i.e., hydrotlecontamination of the naphtha, as well as the presently preferred method of producing 10 RVP gasoline having octane ratings in excess of 100 is illustrated in FIGURE 6. The flow sheet presented as FIGURE 6 illustrates decontamination of a charge naphtha and reforming of the hydrodecontaminated naphtha in the presence of a particle-form platinum-type reforming catalyst in the presence of hydrogen at high reactor pressures of at least 500 p.s.i.g. followed by reforming at low pressure, i.e., less than 500 p.s.i.g.

Thus, charge naphtha containing not more than about 12 p.p.m. of nitrogen flows from a source not shown through pipe 1 to the suction side of pump 2. Pump 2 discharges the charge naphtha into pipe 3 at a pressure to cause the naphtha to flow from pump 2 into absorber 6. The charge naphtha flows through pipe 3 to pipes 4 and 7 and thence to absorber 6. Gas containing hydrogen derivatives of the contaminants present in the charge naphtha flows from stripper 42 and separator 34 through conduits 43 and 35 respectively to conduits 10 and 12. The amount of gas flowing through conduit 10 is controlled by valve 11. The amount of charge naphtha flowing through pipe 4 is controlled by valve 5. These respective amounts of gas and charge naphtha are balanced to provide for the removal of light hydrocarbons from the gas and the removal of water and oxygen from the charge naphtha. This avoids recycling of the contaminant derivatives through the pretreating section.

The charge naphtha and absorbed hydrocarbons flow from absorber 6 through pipe 13 to the suction side of pump 14. Pump 14 discharges the charge naphtha into pipe 15 at a pressure greater than the pressure in reactor 26. The charge naphtha flows through pipe 15 to heat exchanger 16. In heat exchanger 16 the charge naphtha is in indirect heat exchange relation with the effluent from hydrodecontaminator 26 flowing thereto through conduit 30.

From heat exchanger 16 the charge naphtha flows through pipe 17 to heat exchanger 18 where the charge naphtha is in indirect heat exchange relation with the effluent from hydrodecontaminator 26 flowing through conduit 27. From heat exchanger 18 the charge naphtha flows through pipe 19 to coil 29 in furnace 21.

In coil 20 the charge naphtha is heated to a temperature within the range of about 600 to 750", preferably 675 to 725 F. The heated charge naphtha flows from coil 20 through pipe 22 to conduit 23 where it is mixed with hydrogen-containing gas flowing from compressor 69 and/or stripper 42 through conduits 100 and 24 or 43. 44 and 24 respectively.

The mixture of charge naphtha and hydrogen-containing gas flows through conduit 23 into hydrodecontamina tor 26. In hydrodecontaminator 26 the charge naphtha contacts catalyst having hydrogenating and desulfurizing and denitrogenizing capabilities. Typical of such catalysts are those comprising a mixture of oxides of cobalt and molybdenum well-known to the art. For example, a decontaminating catalyst comprising about 3 percent by weight of cobalt oxide, about 15 percent by Weight of molybdenum oxide and the balance substantially alumina can be used. Reaction temperatures within the range of about 600 to 800 F. are employed with space velocities of about 1 to 7 v./hr./v. in hydrodecontaminator 26.

The effluent from :hydrodecontaminator 26 flows through conduit 27 to heat exchanger 18 where the efliuent is in indirect heat exchange with the charge naphtha as described hereinbefore. From heat exchanger 18 the effluent flows through conduit 28 to heat exchanger 29 where the effluent is in indirect heat exchange relation with the hydrodecontaminator condensate flowing from pump 37 and heat exchanger 39 through pipe 40. From heat exchanger 29 the effluent flows through conduit 30 to heat exchanger 16 where it is in indirect heat exchange relationship with absorber bottoms. From heat exchanger 16 the effluent flows through conduit 31 to cooler 32 where the efiiuent is cooled to a temperature such that C and heavier hydrocarbons condense at the pressure existing in liquid-gas separator 34. The pressure in sep- 10 arator 34 is usually within the range of about 400 to about 450 psig.

In liquid-gas separator 34 the hydrogen and some of the derivatives of sulfur, nitrogen, arsenic and the like together with some of the C and lighter hydrocarbons separate and flow therefrom (as described briefly hereinbefore) through conduit 35 to conduits 10 and 12 and thence through absorber 6 to be vented through conduit 121 to the refinery fuel system.

The condensed and separated C and heavier hydrocarbons together with such amounts of the hydrogen derivatives of the contaminants as are soluble in the hydrodecontaminator condensate at the temperature and pressure existing in separator 34 flow from separator 34 through pipe 36 to the suction side of pump 37. Pump 37 pumps the hydrodecontaminator condensate through pipe 38 to heat exchanger 39 where the hydrodecontaminator condensate is in indirect heat exchange relationship with the bottoms of stripper 42 flowing therefrom through pipe 46. From heat exchanger 39 the hydrodecontaminator condensate flows through pipe 40 to heat exchanger 29 where the hydrodecontaminator condensate is in indirect heat exchange relation with the total efflu ent flowing from hydrodecontaminator 26 as described hereinbefore. In heat exchanger 29 the hydrodecontaminator condensate is heated to a temperature at which the dissolved hydrogen derivatives of the contaminants can be stripped from the hydrodecontaminator condensate with a stripping gas as hydrogen containing recycle gas. The hydrodecontaminator condensate usually is heated to about 300 to 400 F. in heat exchanger 29. From heat exchanger 29 the hydrodecontaminator condensate flows through pipe 41 to stripper 42. Hydrogen-containing recycle gas flowing from turbo-compressor 69 through conduits 100 and 95 strips the dissolved gases from the hydrodecontaminator condensate. The stripping gas and stripped volatiles flow from stripper 42 through conduit 43 to conduit 12 and absorber 6. When required the hydrogen stripping gas can be diverted wholly or in part through conduit 44 under control of valve 45 to supply all or part of the hydrogen required in hydrodecontaminator 26.

The bottoms of stripper 42 comprising C and heavier hydrocarbons containing less than 20 ppm. of sulfur, less than 1 ppm. of nitrogen, and less than 5 p.p.b., preferably 2 p.p.b., i.e., less than 0.005, preferably less than 0.002 ppm. of arsenic flows from stripper 42 through pipe 46 to heater exchanger 39 where the bottoms, hereinafter designated high pressure feed, is in indirect heat exchange relation with the hydrodecontaminator condensate as described hereinbefore. From heat exchanger 39 the high pressure feed flows through pipe 47 to the suction side of pump 48. Pump 48 discharges the high pressure feed into pipe 49 at a pressure greater than the pressure in high pressure reactor 58.

Low pressure hydrogen-containing recycle gas (obtained as hereinafter described) flows from steam driven compressor 98 through conduit 99 to conduit 50 at a pressure in excess of that of reactor 58. In conduit 50 the high pressure feed flowing thereto through pipe 49 and the hydrogen-containing recycle gas flowing thereto through conduit 99 are mixed in the ratio of about 2 to 10 mols of hydrogen per mol of naphtha in the high pressure feed to form a high pressure charge mixture.

The high pressure charge mixture flows through conduit 50 to heat exchanger 51 where the high pressure charge mixture is in indirect heat exchange relation with the low pressure effluent flowing from the low pressure reactor on-stream through conduits and 86. The high pressure charge mixture flows from heat exchanger 51 through conduit 52 to heat exchanger 53 where the high pressure charge mixture is in indirect heat exchange relation with the total low pressure efliuent flowing through conduit 89.

From heat exchanger 53 the high pressure charge mixture flows through conduit 54 to coil 55 in heater 56. In coil 55 the high pressure charge mixture is heated to a reforming reaction temperature below the maximum permissible catalyst temperature dependent upon the activity of the catalyst and the octane rating required for the feed to the low pressure unit to provide improved onstream time in the low pressure unit at the octane rating required for the 10 RVP product of the low pressure unit.

The following low pressure reaction temperatures have been found to give satisfactory results leading to improved on-strearn periods or to reduced catalyst requirements as described hereinbefore.

1 For incremental increase in reactor temperature to maintain required octane rating refer to Table IV.

However, the high pressure unit is oprated under conditions of temperature and space velocity to provide high pressure eflluent, i.e., low pressure feed, the gasoline hydrocarbons of which have the octane ratings required to give improved on-strcarn time for the low pressure reactor or reduced total catalyst requirements. Illustrative ranges of the octane ratings of the gasoline hydrocarbons in the feed to the low pressure reforming unit are given in Table VII.

Table VII Low Low Pressure Pressure 10 RVP Pl'OllllCt Octane. Relorin- Reform 5180" I S ing Unit ing Unit, A11, 1*.

Charge ]e|np., Octane F.

107 (Aging rate 3.05 F.fD.) 86. 952 28 .1 J0. 7 1 D48 32 11 93. 5 952 28 9 I06 (Aging rate 258" F./l).,l S7. 5 940 40 .13. l 1 H34 46 18 913.6 94.0 40 15 105 (Aging rate 215 F.."D.) S6. 8 s 50 23 U4. 1 tll l 66 31 U8. 2 930 50 23 101 (Aging ruin LEO F.ll).) 86. (l 920 (ill 33 94, 5 1 tlll Ni 48 100. 0 J30 5U 28 103 (Aging rate 162 11/17.)" 87.1 910 70 46 M. S 1 873 10? TL) 99. l 910 TU 46 102 (Aging ratc 128 Hill) 85. 3 910 70 55 15. 0 1 85-1 12G 98 E18. 0 S90 90 70 101 (Aging rate 107 F./D.) 83.8 910 70 05 95. 1 l 833 147 137 97, 8 860 120 112 100 (Aging rate 0.9 I., D.) 82. 4 H10 70 78 95. 2 1 M5 165 173 98. U 850 130 145 1 Presently preferred vapor inlet. temperature to low pressure reforming unit employing hereinbelore described platinum catalyst containing 0,6 weight percent platinum.

The heated high pressure charge mixture flows from coil 55 through conduit 57 to reactor 58 where the high pressure charge mixture is contacted with platinum-type reforming catalyst comprising, for example, 0.6 percent by weight platinum, 0.6 percent by weight chlorine, and the balance, to 100 percent by weight, alumina at an overall space velocity within the range 0.510 v./hr./v. The high pressure charge mixture flows downwardly through reactor 58. The eflluent of reactor 58 flows through conduit 59 to coil 60 in heater 56 where it is reheated to a reaction temperature the same as, lower or higher than, the temperature of reactor 58.

From coil 60 the reheated first reactor effiuent flows through conduit 61 to reactor 62 where the reheated first reactor efiiuent is contacted with a platinum-type catalyst preferably the same as that in reactor 58 for economic reasons. The efliuent of reactor 62 flows through conduit 63 to coil 64 in heater 56 Where the second reactor efiluent is reheated to reaction temperature the same as, or lower or higher than the temperatures in reactors 58 and 62.

From coil 64 the reheated second reactor effluent flows through conduit 65 to reactor 66. In reactor 66 the reheated second reactor efiluent is contacted with a platinum-type catalyst, preferably the same type of catalyst as used in reactor 58 and 62 for economic reasons. From reactor 66 the third reactor ei'liuent flows through conduit 67 to the turbine side 68 of turbo-compressor 69. In the turbine 68 the pressure of the third reactor efiluent is reduced to that of the low pressure reactor plus the pressure drop from turbine 68 t0 the low pressure reactors. The turbine 68 drives the compressor 69 which compresses the low pressure recycle gas (obtained as hereinafter described) to the pressure attainable from the power in turbine 68.

From turbine 68 the third reactor eflluent comprising naphtha having an octane rating dependent upon the octane rating required for the i0 RVP product of the low pressure unit to provide improved on-stream time for the low pressure unit for 10 RVP products having octane ratings of about 100 to about 107 and hydrogen, hereinafter designated low pressure charge mixture, flows through conduit 70 to coil 71 in heater 72. In coil 71 the low pressure charge mixture is heated to a reaction temperature required to produce a 10 RVP product having the required octane cating. Thus, the reaction temperature to which the low pressure charge mixture is heated in coil 71 is Within the range about 830 to 980 F.

From coil 71 the low pressure charge mixture flows through conduit 73 to manifold 74 and thence through manifold branch 75 or 76 to reactor 79 or 80 depending upon which reactor is on-stream. For purposes of illustration, reactor 79 is on-stream and reactor 80 is in the regeneration portion of the cycle. Accordingly, valves 73 and 84 are closed in conduits 76 and 82 respectively and valves 77 and 83 are open in conduits 75 and 81 respectively. With these valve settings the low pressure charge mixture flows from coil 71 through conduit 73. manifold 74, and manifold branch 75 to reactor 79. The effluent from reactor 79 flows through manifold branch 81 to manifold 85 and thence through conduit 86 to heat exchanger 51. In heat exchanger 51 the low pressure effluent is in indirect heat exchange relation with the low pressure charge mixture as described hereinbcfore.

From heat exchanger 51 the low pressure efilucnt flows through conduit 87 to heat exchanger 88. A part of the low pressure efiluent by-passes heat exchanger 88, flowing through conduit 90 under control of valve 91 to conduit 89. The balance or all of the low pressure effluent fiOWs through heat exchanger 88 where the low pressure effluent is in indirect heat exchange relation with a portion of the bottoms of stabilizer 104. The amount of low pressure efiluent flowing through heat exchanger 88 is proportioned to the fractionation desired in stabilizer 104 usually to maintain a temperature in stabilizer 104 at which n-C and lighter hydrocarbons are volatile. From heat exchanger 88 the low pressure eliluent flows through conduit 89 to heat exchanger 53 where the low pressure efilucnt is in indirect heat exchange relation with the high pressure charge mixture as described hercinbcforc. From heat exchanger 53 the low pressure effluent flows through 13 conduit 92 to cooler 93 where the temperature of the low pressure effluent is reduced to that at which C and heavier hydrocarbons condense. From cooler 93 the condensed and uncondensed constituents of the low pressure efiluent flow through conduit 94 to liquid-gas separator 95.

In liquid gas separator 95 the uncondensed constituents of the low pressure efiluent, i.e., propane and lower boiling hydrocarbons, and hydrogen separate from the higher boiling hydrocarbons. The uncondensed constituents of the low pressure effluent, hereinafter designated hydrogen-containing low pressure recycle gas, flow from liquidgas separator through conduit 96 to turbo-compressor 69.

In turbo-compressor 69 the hydrogen-containing low pressure recycle gas is recompressed to as high a pres sure as practical employing the high pressure reactor eflluent as the driving medium for turbo-compressor 69 as described hereinbefore. Turbocornpressor 69 discharges the compressed hydrogen-containing low pressure recycle gas into conduit 97. A portion of the compressed hydrogen-containing low pressure recycle gas, which is about equal to the gas produced in the reactors of the combination unit is diverted through conduit 100 under control of valve 122 to stripper 42 and to hydrodecontaminator 26 as required, as described hereinbefore. The balance and preponderant portion of the compressed hydrogen-containing low pressure recycle gas flows through conduit 97 to steam-driven compressor 98. In compressor 98 the compressed hydrogen-containing low pressure recycle gas is further compressed to a pressure greater than the pressure in reactor 58 to compensate for the pressure drop between compressor 98 and reactor 58. The pressurized hydrogen-containing low pressure recycle gas, hereinafter designated high pressure recycle gas, flows from compressor 98 through conduit 99 to conduit 50 where the high pressure recycle gas is mixed with the high pressure charge naphtha as previously described hereinbefore. (Those skilled in the art will recognize that the use of turbo-compressor 69 is not essential to the present invention and that the pressure of the high pressure recycle gas can be reduced to that of the low pressure system by means other than turbo-compressor 69, for example, a reducing valve.) However, it is presently preferred to use the high pressure recycle gas as the driving fluid in turbocompressor 69 to raise the pressure of the low-pressure recycle gas to a pressure somewhat less than that required in the high pressure unit and to complete the compression of the low pressure recycle gas to the pressure required in the high pressure unit with steam-driven compressor 98.

Returning to liquid-gas separator 95; the condensed constituents of the low pressure efiiuent, i.e., isob-utane and higher boiling hydrocarbons, hereinafter designated condensate, separate as a liquid in liquid-gas separator 95. The condensate flows from liquid-gas separator 95 through pipe 101 to heat exchanger 102 where the condensate is in indirect heat exchange relation with the bottoms of stabilizer 104. From heat exchanger 102 the heated condensate flows through pipe 103 to stabilizer 194. In stabilizer 104 C and lighter hydrocarbons are taken overhead through pipe 105 to cooler 106 and thence through pipe 107 to accumulator 108. The temperature in accumulator 108 is maintained to condense the heavier hydrocarbons. The condensed hydrocarbons, hereinafter designated accumulator condensate, flow through pipe 111 to the suction side of pump 112. Pump 112 discharges into pipe 113 through which the accumulator condensate flows to stabilizer 104 for use as reflux therein. A portion of the accumulator condensate is diverted through pipe 114 under control of valve 123 to suitable means for recovering isobutane for feed to an alkylation unit and for recovering normal butane for admixture with the higher boiling reformate to provide the required Reid vapor pressure of the super-octane product.

A portion of the bottoms of stabilizer 104 flows through pipe 119 to heat exchanger 88 where the stabilizer bottoms is in indirect heat exchange relation with the low pressure effluent. The stabilizer bottoms is heated in heat exchanger 88 to a temperature at which C hydrocarbons are volatilized. The heated stabilizer bottoms flows from heat exchanger 88 through pipe back to stabilizer 104. Any other form of re-boiler can be substituted for that illustrated. Furthermore, any other means for maintaining a temperature in stabilizer 104 at which C hydrocarbons are volatile can be substituted for the means illustrated.

The balance, and major portion of the stabilizer bottoms, flows from stabilizer 104 through pipe 115 to heat exchanger 102 where the stabilizer bottoms is in indirect heat exchange relation with the low pressure condensate flowing from separator 95 through pipe 101 as described hereinbefore. From heat exchanger 102 the stabilizer bottoms, hereinafter designated reformate, flows through pipe 116 to cooler 117. In cooler 117 the reformate is cooled to a temperature at which the lowest boiling constituent is liquid at atmospheric pressure. From cooler 117 the reformate flows through pipe 118 to storage.

Alternatively, as shown in FIGURE 7, the low pressure reforming unit can consist of two low pressure, e.g., 15 to 450 p.s.i.g., reactors plus a low pressure swing reactor, with means for reheating the effluent of the first reactor of the pair on-stream prior to introducing the effluent into the second reactor of the pair on-stream. The low pressure charge mixture is heated to the desired reaction temperature (as described hereinafter) in coil 124 of heater 125. The heated low pressure charge mixture fiows from coil 124 through conduit 126 to manifold 127 and thence through manifold branches 128 or 129 or 130 dependent upon which reactor of the pair on-stream is the first reactor to which the low pressure charge mixture flows. For the purpose of illustration, it will be assumed that reactor 133 (the swing reactor) is in the regeneration portion of the recycle and that reactor 131 is the first of the pair of reactors which is on-stream. Accordingly, with valves 134, 138, 147 and 161 open and with valves 135, 136, 137, 139, 146, 148, 162, and 163 closed, the low pressure charge mixture flows from manifold 127 through manifold branch 128 to reactor 131. The charge mixture flows downwardly through the bed of catalyst in reactor 131 to conduit (valve 134 open; valve 137 closed) to effluent reheat manifold 153. The efiluent from reactor 131, hereinafter designated first efiluent, flows through conduit 155 to coil 156 in heater 125.

In coil 156 the first effluent is reheated to a reaction temperature the same as, higher or lower than, the temperature to which the low pressure charge mixture was heated in coil 124. From coil 156 the re-heated first effluent flows through conduit 157 to manifold 152 having branches 149, and 151. The re-heated first effluent flows through manifold branch 150 (valves 146, 148, and 162 closed; valve 147 open) to reactor 132. The reheated first efiluent flows downwardly through the catalyst bed in reactor 132 to conduit 141. From conduit 141 the efiluent from reactor 132 hereinafter designated final low pressure efiiuent, flows through conduit 144 (valve 135 closed; valve 138 open) to low pressure final eflluent manifold 154. From low pressure final effluent manifold 154 the low pressure final efituent flows through conduit 86 to heat exchangers 51, 88 and S3 and cooler 93 to separator 95 for the purposes described in the discussion hereinbefore of the flow of the effluent from the alternate low pressure unit.

tI will be observed that the piping required for regeneration of the deactivated catalyst in the reactors of the high and low pressure units has not been illustrated in FIG- URES 6 and 7. Since the methods of regenerating fixed beds of catalyst are well known to those skilled in the art, it has been considered unnecessary to illustrate the piping required for regeneration of the catalyst in the low or high pressure reactors.

While the flow sheet of FIGURE 6 does not provide for the introduction of extraneous gasoline hydrocarbons having octane ratings of about 81 to 98 it is to be understood that the low pressure reforming unit can be designed for a capacity in excess of capacity required for treating the eflluent of the high pressure reforming unit and extraneous gasoline hydrocarbons treated in conjunction with the effluent of the high pressure reforming unit. Thus, a straight run naphtha or a fraction of cracked gasoline, for example, catalytically cracked gasoline, can be mixed with the effluent from the high pressure reforming unit in proportions to provide a feed to the low pressure reforming unit having an octane rating within the range 81 to 98 dependent upon the required octane rating of the 10 RVP gasoline (containing process butanes) produced in the low pressure unit and the mixture reformed in the low pressure reforming unit to the required octane rating.

Savings in catalyst inventory of considerable magnitude are provided by the hereinbefore described combination of sequential high pressure reforming-low pressure reforming when compared with catalyst inventories required for producing a product having the same octane rating either by reforming entirely at high pressure or by reforming entirely at low pressure. The data presented in Table VIII show that the differences in cost of catalyst inventory to produce the same amount of product having an octane number of about 106 can amount to as much as $719,000 to $1,580,000 in a unit processing 11,000 barrels of naphtha per day.

Table VIII Charge rate11,00tl b./s.d. Catalyst cost-$562 per cubic foot (c.l.)

a pressure of about 15 150 p.s.i.g. and an average reactor temperature within the range about 810 to about 980 F. to provide a maximum on-stream period between regenerations preferably of at least 3 days when producing products having an octane rating of about 106, and greater than 3 days when producing products having octane ratings of less than 106, dependent upon the space velocity, said reactor temperature being dependent upon the octane rating of said product and said gasoline boiling range constituents of said high pressure efiiuent.

Furthermore, the present invention provides for reforming naphtha in a low pressure reforming unit at low pressure, i.e., within the range of about 15 to about 450 p.s.i. g in the presence of hydrogen and particleform noble metal type reforming catalyst and correlating the octane rating of the gasoline hydrocarbons of the charge to said low pressure reforming unit with the required octane of the 10 RVP gasoline (containing process butanes) produced in said low pressure reforming unit and the reaction temperature in said low pressure unit, said gasoline hydrocarbons in said charge to said low pressure unit having an octane rating of at least about 81 and not greater than about 98 for loW pressure unit 10 RVP gasoline having octane ratings of about 100 to about 110.

On the other hand, the present invention provides for reforming naphtha in a low pressure reforming unit at low pressure, i.e., within the range of about 15 to about 450 psig in the presence of hydrogen employing a lligh Pressure Unit Combination Unit Low Pressure Unit Space Cost tlifTcr- C1. of (1.1. of Velocity 5 C1. 01' Ci. of 0.1. 01 (lost ential, 51M 1 Catalyst 1 Catalyst 7 Catalyst Catalyst Catalyst 2 Dlll at 0.75 at 0.6 antral S.V. 111 L1 S.V. .BM 1

1, 280 3, 430 3 3 2. 150 4, 290 2. 140 1, 200 1, 500 3, 430 4 3 1, 930 4, 200 2, 300 1, 325 l, 625 d, 430 5 3 1, 805 4, 290 2, 485 l, 400 1, 010 3. 430 3 4 1, 820 4, 200 2, 470 1, 390 l, 820 3. 430 4 4 1, 610 4. 200 2, 080 l. 505 l, 950 3, 430 5 4 1, 480 4. 200 2, 810 1, 580

$M=in thousands of dollars. I Additional catalyst. 3 1lP=high pressure; LP=low pressure.

The foregoing description of the present invention will be recognized by those skilled in the art as a description of an improvement in low pressure reforming in the presence of particle-form platinum-type reforming catalyst to produce gasoline containing process-butanes having octane ratings of at least 100 which comprises introducing into a reforming reactor under a pressure less than 500 p.s.i.g., for example, 100-300 p.s.i.g. containing particle-form platinum-type reforming catalyst, a charge stock having an octane rating of at least about 81 and not greater than about 98 and hydrogen and correlating the octane rating of said charge stock with the required octane rating of the product and the reaction temperature to provide a maximum on-stream period between regenerations preferably of at least about 3 days when producing products having an octane rating of about 106, and greater than 3 days when producing products having octane ratings of less than 106 depending upon the space velocity employed. The present invention also provides for reforming a charge stock having an octane rating less than 81 at pressure of at least 500 psig in the presence of particle-form reforming catalyst and hydrogen to produce a high pressure eflluent the gasoline hydrocarbons of which have an octane rating within the range of about 81 to about 98, reducing the pressure of said high pressure eflluent, reforming said high pressure ellluent in the presence Of pafliclerfwm Platinum-type reforming catalyst at particle-form solid noble metal reforming catalyst, relatively high reaction temperatures, and relatively short onstream periods, and correlating the octane rating of the gasoline hydrocarbons of the charge to said low pressure reforming unit with the required octane rating of the 10 RVP gasoline (containing process butanes) and the reaction temperature in said low pressure unit to employ less catalyst per unit throughput to produce said 10 RVP gasoline having said required octane rating than when naphtha is reformed to said 10 RVP gasoline having said required octane rating without correlating the aforesaid octane rating of the gasoline hydrocarbons of the charge to said low pressure unit with the octane rating of at least of the 10 RVP gasoline (containing process butanes) produced in said low pressure unit, said gasoline hydrocarbons in said charge to said low pressure unit having an octane rating of at least about 81 and not greater than about 98 for low pressure unit 10 RVP gasoline having octane ratings of about 100 to about 110. In addition, the present invention provides for reforming naphtha in a high pressure reforming unit in the presence of hydrogen and particle-form reforming catalyst and regulating the catalyst-to-oil ratio and reaction temperature to produce a EAT equal to at least 2N F. (as defined hereinbefore) across the reactor or reactors of the high pressure reforming unit to produce a high pressure unit elllucnt, reducing the pressure of said high pressure effluent to that of a low pressure reforming unit, reforming said high pressure effluent in said low pressure reforming unit at pressures less than 500 psig. in the presence of particle-form solid reforming catalyst and regulating the catalyst-to-oil ratio and the reaction temperature in said low pressure reforming unit to produce a EAT not greater than about N F. (as defined hereinbefore) across the reactor or reactors of said low pressure reforming unit, and recovering gasoline having an octane rating of at least 100. The present invention also provides for reforming naphtha comprising naphthenes and parafiins in a high pressure reforming unit at pressures of at least 500 p-.s.i.g. in the presence of hydrogen and particle form solid reforming catalyst at reforming temperature and space velocity to convert a preponderant portion of said naphthenes to aromatic hydrocarbons and to produce a high pressure effluent, reducing the pressure of said high pressure effluent to that of a low pressure rc forming unit, contacting said high pressure effluent under pressure less than about 509 p.s.i.g. with particle-form solid reforming catalyst under reforming conditions of temperature and space velocity to produce RVP gasoline (containing process butanes) having an octane rating of at least 100, and correlating the octane rating within the range of about 81 to about 98 of the gasoline hydrocarbons in said high pressure effluent with the volume of catalyst in said low pressure reforming unit to produce said 10 RVP gasoline having the required octane rating.

We claim:

1. The method of producing gasoline having an octane rating of 100 to about 110 which comprises establishing a plurality of high pressure reforming zones each containing particle-form solid reforming catalyst and piped for series flow of fluid reactant from the first high pressure reforming Zone to the last high pressure reforming zone of the aforesaid plurality of high pressure refonming zones, establishing a plurality of low pressure reforming zones each containing particle-form solid reforming catalyst and piped for series flow of fluid reactant from the first low pressure reforming zone to the last low pressure reforming zone of the aforesaid plurality of low pressure reforming zones, introducing charge naphtha into the aforesaid first high pressure reforming zone, contacting said charge naphtha in each of the aforesaid plurality of high pressure reforming zones with the aforesaid particleform solid reforming catalyst in the presence of hydrogen under reforming conditions of temperature, space velocity and pressure of at least 500 p.s.i.g., regulating the catalystto-naphtha ratio in each of the aforesaid high pressure reforming zones to obtain a difference in temperature between the temperature of the vapors entering each high pressure reforming zone and the temperature of the vapors leaving the same high pressure reforming zone and to obtain a sum in degrees Fahrenheit of the aforesaid differences in temperature for all of the aforesaid high pressure reforming zones equal to at least twice the numerical value of the concentration of naphthenes in the aforesaid charge naphtha, withdrawing the aforesaid last high pressure reforming zone a high pressure effluent comprising hydrogen and C and heavier hydrocarbons boiling in the gasoline boiling range, introducing at least that portion of the aforesaid high pressure comprising hydrocarbons boiling in the gasoline boiling range at a pressure less than 500 p.s.i.g. into the aforesaid first low pressure reforming zone, contacting the aforesaid portion of the aforesaid high pressure effluent in each of the low pressure reforming zones of the aforesaid plurality of low pressure reforming zones with partiole-fonm solid platinum-containing reforming catalyst in the presence of hydrogen under reforming conditions of temperature, space velocity and pressure less than 500 p.s.i.g., regulating the catalyst-to-naphtha ratio in each of the aforesaid low pressure reforming zones to obtain a difference in tempcrture between the temperature of the vapors entering each low pressure reforming zone and the temperature of the vapors leaving the same low pressure reforming zone and to obtain a sum in degrees Fahrenheit of the aforesaid dilferences in temperature for all of the aforesaid low pressure reforming zones not greater than the numerical value of the concentration of naphthenes in the aforesaid charge naphtha, withdrawing from the aforesaid last low pressure reforming zone of the aforesaid plurality of low pressure reforming zones a final effluent comprising hydrogen, and C and heavier hydrocarbons boiling in the gasoline boiling range and recovering from said final efiluent l0 RVP gasoline having an octane rating of with a yield of about 96 percent to about with a yield of about 76 percent.

2. A method of producing 10 RVP leaded gasoline having an octane rating of a least 100 which comprises contacting in a first reforming stage comprising a plurality of reforming zones piped for series flow of fluid reactant from a lead reforming zone to a tail reforming zone charge naphtha and particle-form solid noble metal reforming catalyst in the presence of hydrogen at reforming temperature, reforming pressure of at least 500 p.s.i.g. and a reforming space velocity of at least 3, withdrawing from the aforesaid tail reforming zone in said first reforming stage a high pressure effluent comprising hydrogen and hydrocarbons boiling in the gasoline boiling range having an octane rating within the range of about 86 to 98, contacting in the presence of hydrogen in a second reforming stage comprising a plurality of reforming zones piped for series flow of fluid reactant from a lead reforming zone to a tail reforming zone a second stage charge mixture comprising at least the hydrocarbons boiling in the gasoline boiling range of the aforesaid high pressure effluent with particle-form solid noble metal reforming catalyst at reforming temperature, reforming pressure less than 500 p.s.i.g., and reforming space velocity of at least 3, withdrawing from the aforesaid tail reforming zone in the aforesaid second stage a final effluent comprising hydrogen, and C and heavier hydrocarbons boiling in the gasoline boiling range, and recovering from said final efiluent 10 RV? leaded gasoline having an octane rating of 100 with a yield of about 96 percent to about 110 with a yield of about 76 percent.

3. The method set forth and described in claim '2 wherein the noble metal reforming catalyst is a platinum reforming catalyst.

4. The method set forth and described in claim 2 wherein the noble metal reforming catalyst is a platinum reforming catalyst, and wherein the second stage charge mixture comprises extraneous unreformed mixture of hydrocarbons boiling in the gasoline boiling range and at least the hydrocarbons boiling in the gasoline boiling range from the aforesaid high pressure effluent, the hydrocarbons boiling in the gasoline boiling range of thc aforesaid second stage charge mixture having an octane rating of 81 to 98.

5. A method of producing 10 RVP gasoline having an octane rating (research-k3 cc. TEL), hereinafter desig nated leaded gasoline, within the range of about 100 to about H0 in two stages to provide maximum on-stream time in the second of the aforesaid two stages when producing leaded gasoline having an octane rating within the aforesaid range which comprises contacting naphtha in a first, high pressure, stage with static particle-form solid reforming catalyst in the presence of hydrogen under reforming pressure of at least 509 p.s.i.g., at reforming temperature, and liquid hourly space velocity to produce a first, high pressure, stage eflluent, regulating the aforesaid temperature and space velocity to obtain hydrocarbons boiling in the gasoline boiling range, hereinafter designated gasoline hydrocarbons, having an octane rating within the range of about 90 to 98, contacting in the presence of hydrogen at least the gasoline hydrocarbons having an octane rating within the range of about 90 to 98 of the aforesaid first, high pressure, stage cfiluent in a second, low pressure stage with static particle-form solid reforming catalyst comprising 0.35 to 2.0 percent by weight of platinum on alumina support under reforming pressure less than 500 p.s.i.g., at reforming temperature and at reforming liquid hourly space velocity to obtain a second, low pressure, stage eflluent, and recovering from said second, low pressure, stage eflluent a gasoline comprising C and heavier hydrocarbons boiling in the gasoline boiling range having a Reid vapor pressure of ten pounds and having an octane rating (research-i-3 cc. TEL) within the range of 100 with a yield of about 96 percent to about 110 with a yield of about 76 percent.

6. The method of producing 10 RVP gasoline having an octane rating (research+3 cc. TEL) within the range of about 100 to about 110 as set forth and described in claim 5 wherein the reforming temperature and space velocity in the first, high pressure, stage are regulated to obtain gasoline hydrocarbons having an octane rating within the range of 94 to 95, wherein the RVP leaded gasoline has an octane rating of 101 to 107, and wherein the on-stream time in the second, low, pressure stage is about ten days when producing 10 RVP leaded gasoline having an octane rating of 107 to about 127 days when producing 10 RVP leaded gasoline having an octane rating of 101.

7. In the method of reforming naphtha at reactor pressures less than 500 p.s.i.g. to obtain 10 RVP leaded .gasoline having an octane rating of at least 100 which comprises contacting charge naphtha comprising naphthenes and paraflins with particle-form solid platinum-group metal reforming catalyst in the presence of hydrogen at reforming conditions of temperature and space velocity to produce 10 RVP leaded gasoline having an octane rating of 100 to 110, the improvement which comprises regulating the octane rating of the aforesaid charge naphtha Within the range of 85 to 98 dependent upon the required octane rating of at least 100 of the 10 RVP leaded gasoline product, and contacting the aforesaid charge naphtha having the aforesaid regulated octane rating with the aforesaid platinum-group metal reforming catalyst at the lowest reforming temperature, dependent upon the aforesaid regulated octane rating of the aforesaid charge naphtha and the octane rating of the aforesaid l0 RVP leaded gasoline product to produce the aforesaid 10 RVP leaded gasoline product in a yield greater than that obtained when reforming the aforesaid charge naphtha in the presence I of hydrogen and the aforesaid platinum-group metal reforming catalyst at 500 p.s.i.g. and for longer on-stream time between regenerations of the aforesaid platinumgroup metal reforming catalyst than is obtained when reforming the aforesaid charge naphtha without regulating the octane rating thereof within the range 85 to 98 dependent upon the octane rating of the 10 RVP leaded gasoline product in the presence of the aforesaid platinumgroup metal reforming catalyst at the same reforming pressure less than 500 p.s.i.g. to produce 10 RVP leaded gasoline having the same octane rating as the aforesaid 10 RVP leaded gasoline product.

8. The improvement in the method of reforming naphtha at reactor pressures less than 500 p.s.i.g. as set forth in claim 7 wherein the charge naphtha having the regulated octane rating within the range of 85 to 98 contains less than 20 parts per million of sulfur, less than 1 part per million of nitrogen, and less than 0.5 part per billion of arsenic.

9. The method of producing 10 RVP leaded gasoline product containing process produced butanes and having an octane rating of 100 to 110 from the product of the low pressure stage of a two-stage reforming process in which the pressure in the first high pressure stage is a reforming pressure of at least 500 p.s.i.g. and the pressure in the second low pressure stage is a reforming pressure less than 500 p.s.i.g. which comprises contacting naphtha containing naphthenes, less than 20 parts per million of sulfur, not more than 1 part per million of nitrogen, and less than 0.5 part per billion of arsenic in a first stage high pressure reforming zone in the presence of hydrogen with particle-form solid reforming catalyst at a reforming pressure of at least 500 p.s.i.g. at reforming conditions of temperature and space velocity dependent upon the activity of the aforesaid reforming catalyst to obtain a high pressure effluent the gasoline hydrocarbons of which have an octane rating dependent upon the octane rating of the product of the low pres-sure stage within the range of to 98, reducing the pressure of the aforesaid high pressure eflluent, contacting at least the gasoline hydrocarbons of the aforesaid high pressure effluent in a second stage low pressure reforming zone at a low pressure reforming zone pressure not greater than about 350 p.s.i.g. with particle-form noble metal reforming catalyst at reforming space velocity and minimum reforming temperature de pendent upon the octane rating of the gasoline hydro carbons of the aforesaid high pressure efiluent, the octane rating of the 10 RVP leaded gasoline product, and the aforesaid space velocity to produce 10 RVP leaded gasoline product having an octane rating of to 110, and recovering l0 RVP leaded gasoline, containing process produced butanes, having an octane rating of 100 to in a yield greater than the yield when the aforesaid charge naphtha is reformed at reforming pressure of at least 500 p.s.i.g. to 10 RVP leaded gasoline product in the presence of the aforesaid noble metal reforming catalyst and with an on-strearn time between regenerations of catalyst in the second low pressure stage reforming zone greater than the on-stream time between regenerations of the aforesaid noble metal reforming catalyst when reforming the aforesaid charge naphtha without regulating the octane rating thereof within the range 85 to 98 dependent upon the octane rating of the 10 RVP leaded gasoline in the presence of the aforesaid reforming catalyst at the same reforming pressure not greater than about 350 p.sig. to 10 RVP leaded gasoline having the same octane rating.

10. The method of producing 10 RVP leaded gasoline product containing process produced butanes and having an octane rating of 100 to 110 from the product of the low pressure stage of a two-stage reforming process as set forth and described in claim 9 wherein the particle'- form solid reforming catalyst in the first high pressure stage and the particle-form solid reforming catalyst in the second low pressure stage are platinum metal reforming catalysts comprising about 0.35 to about 1.0 percent by weight of platinum, about 0.35 to about 1.0 percent by weight of chlorine, on an alumina support.

11. The method of producing leaded gasoline having an octane rating of about 100 to 110 and containing process-produced butanes which comprises contacting gasoline hydrocarbons having an octane rating Within the range of 86 to 98 dependent upon the octane rating of the leaded gasoline product with particle form solid plattinum-group metal reforming catalyst in the presence of hydrogen at reaction pressures of 15 to 450 p.s.i.g., at space velocities of about 0.5 to 5.0, and at a reforming temperature dependent upon the octane rating of the aforesaid gasoline hydrocarbons and the octane rating of the aforesaid 10 RVP leaded gasoline product to obtain 10 RVP leaded gasoline product having an octane rating of 100 to 110 with longer on-stream periods between regenenations than when reforming at a pressure within the range of 15 to 450 p.s.i.g. gasoline hydrocarbons having an octane rating not dependent upon the octane rating of the 10 RVP leaded gasoline product.

12. The method set forth and described in claim 11 wherein the particle-form solid platinum-group metal reforming catalyst comprises 0.35 to 2 percent by weight of platinum on alumina support and the reforming temperature is within the range of 824 F. and 948 F. when using virgin or freshly regenerated catalyst.

13. The method set forth and described in claim 1 wherein the reforming catalyst in both the high pressure 21 22 reforming zones and the low pressure reforming zones 2,710,827 Gornowski June 14, 1955 comprises about 0.35 to about 2.0 percent by Weight of 2,758,062 Arundale et Allg- 1956 platinum on alumina support, 2,758,063 MacLaren et a1. Aug. 7, 1956 2,862,872 Beekberger Dec. 2, 1958 References Cited in the file of this patent 5 2,865,837 Holcomb et a1 Dec. 23, 1958 UNITED STATES PATENTS FOREIGN PATENTS 2,642,381 Dickinson June 16, 1953 714,061 Great Britain Aug. 25, 1954 2,642,384 Cox June 16, 1953 745,520 Great Britain Feb. 29, 1956 2,654,694 Berger et a1. Oct. 6, 1953 10 538,992 Canada Apr. 2, 1957

Claims (1)

1. THE METHOD OF PRODUCING GASOLINE HAVING AN OCTANE RATING OF 100 TO ABOUT 110 WHICH COMPRISES ESTABLISHING A PLURALTIY OF HIGH PRESSURE REFORMING ZONES EACH CONTAINING PARTRICLE-FORM SOLID REFORMING CATALYST AND PIPED FOR SERIES FLOW OF FLUID REACTANT FROM THE FIRST HIGH PRESSURE REFORMING ZONE TO THE LAST HIGH PRESSURE REFORMING ZONE OF THE AFORESAID PLURALITY OF HIGH PRESSURE REFORMING ZONES, ESTABLISHING A PLURALITY OF LOW PRESSURE REFORMING ZONES EACH CONTAINING PARTICLE-FORM SOLID REFORMING CATALYST AND PIPED FOR SERIES FLOW OF FLUID REACTANT FROM THE FIRST LOW PRESSURE REFOMING ZONE TO THE LAST LOW PRESSURE REFORMING ZONE OF THE AFORESAID PLURALITY OF LOW PRESSURE REFORMING ZONES, INTRODUCING CHARGE NAPHTHA INTO THE AFORESAID FIRST HIGH PRESSURE REFORMING ZONE, CONTACTING SAID CHARGE NAPHTHA IN EACH OF THE AFORESAID PLURALITY OF HIGH PRESSURE REFORMING ZONES WITH THE AFORESAID PARTICLEFORM SOLID REFORMING CATALYST IN THE PRESENCE OF HYDROGEN UNDER REFORMING CONDITIONS OF TEMPERATURE, SPACE VELOCITY AND PRESSURE OF AT LEAST 500 P.S.I.G., REGULATING THE CATALYSTTO-NAPHTHA RATIO IN EACH OF THE AFORESAID HIGH PRESSURE REFORMING ZONES TO OBTAIN A DIFFERENCE IN TEMPERATURE BETWEEN THE TEMPERATURE OF THE VAPORS ENTERING EACH HIGH PRESSURE REFORMING ZONE AND THE TEMPERATURE OF THE VAPORS LEAVING THE SAME HIGH PRESSURE REFORMING ZONE AND TO OBTAIN A SUM IN DEGREES FAHRENHEIT OF THE AFORESAID DIFFERENCES IN TEMPERATURE FOR ALL OF THE AFORESAID HIGH PRESSURE REFORMING ZONES EQUAL TO AT LEAST TWICE THE NUMERICAL VALUE OF THE CONCENTRATION OF NAPHTHENES IN THE AFORESAID CHARGE NAPHTHA, WITHDRAWIGN THE AFORESAID LAST HIGH PRESSURE REFORMING ZONE A HIGH PRESSURE EFFLUENT COMPRISING HYDROGEN AND C1 ANDHEAVIER HYDROCARBONS BOILING IN THE GASOLINE BOILING RANGE, INTRODUCING AT LEAST THAT PORTION OF THE AFORESAID HIGH PRESSURE COMPRISING HYDROCARBONS BOILING IN THE GASOLINE BOILING RANGE AT A PRESSURE LESS THAN 500 P.S.I.G. INTO THE AFORESAID FIRST LOW PRESSURE REFORMIGN ZONE, CONTACTING THE AFORESAID PORTION OF THE AFORESAID HIGH PRESSURE EFFLUENT IN EACH OF THE LOW PRESSURE REFORMING ZONES OF THE AFOESAID PLURALITY OF LOW PRESSURE REFORMING ZONES WITH PARTICLE-FORM SOLID PLATINUM-CONTAINING REFORMING CATALYST IN THE PRESENCE OF HYDROGEN UNDER REFORMING CONDITIONS OF TEMPERATURE, SPACE VELOCITY AND PRESSURE LESS THAN 500 P.S.I.G., REGULATING THE CATALYST-TO-NAPHTHA RATIO IN EACH OF THE AFORESAID LOW PRESSURE REFORMING ZONES TO OBTAIN A DIFFERENCE IN TEMPERTURE BVETWEEN THE TEMPERATURE OF THE VAPORS ENTERING EACH LOW PRESSURE REFORMING ZONE AND THE TEMPERATURE OF THE VAPORS LEAVING THE SAME LOW PRESSURE REFORMING ZONE AND TO OBTAIN A SUM IN DEGREES FAHRENHEIT OF THE AFORESAID DIFFERENCES IN TEMPERATURE FOR ALL OF THE AFORESAID LOW PRESSURE REFORMING ZONES NOT GREATER THAN THE NUMERICAL VALUE OF THE CONCENTRATION OF NAPHTHENES IN THE AFOESAID CHARGE NAPHTHA, WITHDRAWING FROM THE AFORESAID LAST LOW PRESSURE REFORMING ZONES A FINAL EFFLUENT COMPRISING HYDROGEN, AND C4 AND HEAVIER HYDROCARBONS BOILING IN THE GASOLINE BOILING RANGE AND RECOVERING FROM SAID FINAL EFFLUENT 10RVP GASOLINE HAVING ANOCTANE RATING OF 100 WITH A YIELD OF ABOUT 96 PERCENT TO ABOUT 110 WITH A YIELD OF ABOUT 76 PERCENT.

Images