US3242066A - Method of producing high octane gasoline and jet fuels having a luminometer number of at least 150 - Google Patents

Description

March 22, 1966 H, C, MYERS 3,242,066

METHOD OF PRODUCING HIGH OCTANE GASOLINE AND JET FUELS HAVING A LUMINOMETER NUMBER OF AT LEAST 150 REACTOR ISOTHERMAL HEAVY NAPHTRA INVENTOR. 29 HU/O/C 7 39; BY

March 22, Q H, C, MYERS 3,242,066

METHOD OF PRODUCING HIGH OCTANE GASOLINE AND JET FUELS HAVING A LUMINOMETER NUMBER OF AT LEAST 150 Mm'ch 22, E966 H, C, MYERS LT METHOD 0E PHODUCING HIGH OCTANE GHSOLINE AND JET FUELS HAVING A LUMINOMETER NUMBER 0E AT LEAST 150 United States Patent O METHOD F PRODUCING HIGH CTANE GASG- LINE AND JET FUELS HAVING A LUMHNOM- ETER NUMBER 0F AT LEAST 150 Harold C. Myers, Woodbury, N..l. assignor to Socony Mobil Oil Company, Inc., a corporation of New York Filed Nov. 1, 1961, Ser. No. 149,251 3 Claims. (Cl. 208-93) The present invention relates to a method of producing gasoline having an octane rating of at least 100 (Research +3 cc. TEL) and, alternatively, of producing gasoline having an octane rating of at least 100 and jet fuel having a luminometer number of at least 150 and more particularly, to a method of producing gasoline having an octane rating of at least 100 (Research +3 cc'. TEL) and, alternatively, of producing gasoline having an octane rating of at least 100 and jet fuel having a luminometer number of at least 150 wherein a C5 to 380 F. naphtha comprising parailns and naphthenes and containing not more than innocuous concentrations of sulfur, nitrogen and arsenic (as hereinafter defined) is fractionated into a light naphtha having an end point of about 250 F. and a heavy naphtha having an initial lboiling point not lower than the 90 percent point of the aforesaid light naphtha and an end boiling point of about 380 F. but not higher than about 420 F. The light naphtha is reformed in the presence of particle-form solid platinum-group metal reforming catalyst at reaction pressures in the range of 15 to 350 p.s.i.g. at a liquid hourly space velocity in the range 0.5 to 5 at reforming temperatures measured at the vapor inlet of the reaction zone(s) in the range of 800 to 1025 F. and in the presence of up to mols of hydrogen per mol of light naphtha to produce a low pressure reaction zone eilluent or a light naphtha reaction product comprising hydrogen and C1 and heavier hydrocarbons. The lolw pressure reaction zone eiiiuent is treated tot separate the low octane rating components having iive or more carbon atoms in the molecule from high octane rating components boiling in the gasoline range. The low octane rating components are used in whole or in part as jet fuel blending stock or recycled to the low pressure reforming zone(s) to extinction. The heavy naphtha is reformed under isothermal conditions (as dened hereinafter) of temperature in the range of about 900 to l025 F. as measured at the vapor inlet of the isothermal reaction zone at a pressure of at least about p.s.i.g., up to 1200 p.s.i.g. at a hydrogen-to-heavy naphtha mol ratio in the range of 1 to 20, preferably 4 to l0, and at a liquid hourly space velocity of at least about 15 upto about 150 to produce a high pressure isothermal effluent comprising hydrogen and C1 and heavier hydrocarbons. The isothermal etfluent is treated to separate C5 and heavier high octane rating component from C5 and heavier low octane rating components boiling in the gasoline range. The isothermal C5 and heavier low octane rating components are a jet fuel blending stock. Alternatively, all or a part of the isothermal C5 and heavier low octance rating components are recycled to the lo-w pressure reforming zone(s) to extinction.

The literature of the art of upgrading gasoline hydrocarbons is replete with descriptions involving fractionation of naphtha into two or more fractions followed by reforming of the fractions separately under reforming conditions of different severity. Thus, for example, in 1938 U.S. Patent No. 2,141,185 issuedin which a method ICC of reforming naphtha is described. The patented method comprises fractionating low octane naphtha into a lower boiling fraction and a higher boiling fraction. Each of these fractions is reformed three times separately, the high octane fractio-n of each reformate being separated by fractionation. In 1941 U.S. Patent No. 2,249,461 issued with a description of a method of manufacturing anti-knock gasoline which involved fractionating naphtha into seventy closely cut fractions, discarding the lowest boiling eleven fractions, segregating the balance into fractions having an octane rating above 68 and fractions having an octane rating below 68, and reforming the fractions having octane ratings below 68. Other U.S. patents describing methods of upgrading naphtha involving fractionating into two or more fractions are the following: 2,304,187; 2,324,165; 2,659,692; 2,740,751; 2,767,124; 2,773,809; 2,866,745; 2,905,619; 2,944,959. U.S. patents disclosing the production of two or more fuel products include U.S. Patent No. 2,401,649 issued in 1946 teaching a process for producing alkymer gasoline and aviation base gasoline of high aromatic and low parallin content; U.S. Patent No. 2,729,596 issued in 1956 and describing the production of diesel and jet fuels; U.S. Patent No. 2,740,751 issued in 19'56 and describing a method of producing motor fuel and aviation fuel; U.S. Patent No. 2,945,802 issued in 1960 and describing a method of producing jet fuel and aromatics by hydrocracking a hydrocarbon charge stock to convert at least a portion of the stock into jet fuel boiling range material, separating cracked naphtha and reforming the separated cracked naphtha.

Thus, while the art has been concerned with upgrading naphthas, the production of jet fuels and diesel fuels by processes involving fractionation either of the charge naphtha or the reformates produced, none has described a method in which the yield of gasoline having an octane rating of at least and, alternatively, a method in which gasoline having an octane rating of at least 100 and jet fuel having a luminometer number of at least are produced in greater yield of saleable high quality product than that of the conventional industrially practiced manipulations.

Before describing in general terms the method of the present invention, the use of certain terms will be clarilied. Thus, a naphtha contains not more than innocuous concentrations of sulfur, nitrogen, and arsenic when the concentration of sulfur does not exceed 20` ppm. (parts per million), when the concentration of nitrogen does not exceed l p.p.m., and when the naphtha is essentially free of arsenic .and in any event does not contain more than 2 p.p.b. (parts per 109) of arsenic. As used herein, essentially free of arsenic designates a concentration of arsenic in a reformer feed which, when said reformer feed is contacted with a bed of reforming catalyst comprising 0.35 percent of platinum by weight, is insufficient to deactivate said catalyst within the life of the catalyst, for example two years, as determined by other factors such as the temperature required to produce a reformate having an octane rating of at least 100 (Research4-3 cc. TEL), the yield of reformate, and the mechanical strength of the catalyst. As used herein, the terms isothermal conditions of temperature, isothermal reactor, isothermal reaction zone, isothermicity or in general any reference to temperature ras being isothermal designates conditions within a Zone such that the temperature of the reaction vapors leaving the zone, as measured at the vapor outlet thereof, is not more than 20 degrees Fahrenheit lower than the temperature of the reactant vapors entering the reaction zone as measured at the vapor inlet thereof.

In general, the present invention provides for fractionating a naphtha into a light fraction or light naphtha and a bottoms or heavy fraction or heavy naphtha. The light naphtha is reformed at low pressure in the range of 15 to 350 p.s.i.g. while the heavy naphtha is reformed at pressures in the range of 15 to 1,200 p.s.i.g. at conditions of isothermicity. The low presure or light naphtha reformate and the isothermal or heavy naphtha reformate each is treated in a manner to produce a jet fuel of high luminosity and a highly aromatic blending stock or a highly aromatic blending stock and aromatic hydrocarbons of relatively high purity. Thus, as indicated in a highly schematic manner in the drawing, the flow sheet illustrates fractionation of naphtha, low pressure reforming of the light naphtha and isothermal reforming of the heavy naphtha and four preferred embodiments of the treatments of the light and heavy reformates. For example, Embodiment (A) provides for contacting both reformates with molecular sieve material to obtain a sieve effluent comprising cyclic hydrocarbons, i.e., naphthenes and aromatics, and isoparatlins. The sieve is unloaded or regenerated, i.e., the sorbate comprising norrnal parains is displaced, by contacting the loaded sieve material with suitable desorbant, preferably with hydrogen and especially with reformer gas comprising hydrogen and C1 to C2 hydrocarbons.

The molecular sieve material is an alkali metal alumino-silicate having pores the diameters of which are somewhat larger than the diameters of the molecules of normal paratiins but smaller than the diameters of isoparans, naphthenes and aromatic hydrocarbons and usually in the range of 4 to 5 Angstroms.

In Embodiment (B) the isothermal or heavy reformate only is contacted with the molecular sieve material an-d the sieve eHuent blended with the total liquid, i.e., C5 and heavier, low pressure or light reformate.

In Embodiment (C) the light reformate is contacted with molecular sieve material to provide light reformate sieve effluent and light reformate sieve sorbate. The heavy reformate is extracted with a selective solvent having greater solvency for non-parafnic hydrocarbons than for parai'linic hydrocarbons to obtain a parainic raffinate and an aromatic extract. The aromatic hydrocarbons of the aromatic extract are separated from the selective solvent. The extracted aromatic hydrocarbons and the light reforrntae sieve eluent provide one or more products. The sieve sorbate and the heavy rainate paraffns provide a jet fuel. In Embodiment (D) the light reformate is fractionated to obtain a C5 or a C5-C6 fraction as an overhead and a bottoms comprising C7 and heavier hydrocarbons. The heavy reformate together with the light reformate overhead is contacted with molecular sieve material to provide a sieve effluent. The sieve effluent and the light reformate bottoms are products. The sieve sorbate is recycled to the low pressure reforming zone.

Alternatively, in Embodiments A, B and C supra all or a portion of the sieve sorbate can be recycled to the low pressure reforming zone. It is to be observed that in Embodiment A when the sieve sorbate of both reformates is recycled to the low pressure reforming or reaction zone the yield at 102 octane (Research-l cc. TEL) is about five percent higher than the most efficient combination of low pressure reforming of the light naphtha and high pressure reforming of the heavy naphtha. That is to say, when C5 to 380 F. Mid-Continent naphtha is processed in `accordance with the combination of operations designated embodiment A, gasoline having an octane rating (R4-3 cc. TEL) of 102.2 is produced in a yield of 83.2 percent by volume based on the charge. The most efficient combination of low pressure reforming of the light naphtha `and high pressure reform ing of the heavy naphtha provided a yield of only 78.4 percent by volume based on the charges. Thus, processing in accordance with the `combination of operations designated Embodiment A provides a yield incease of about 5 percent (4.8%) by volume. Furthermore, the reforming of the heavy fraction under conditions of isothermicity at a liquid hourly space velocity of 30 is an added advantage. Under these condtions 93 percent of the naphthenes of the 250 to 380 F. heavy naphtha from Mid-Continent straight run naphtha was converted to aromatic hydrocarbons with no substantial cracking of naphthenes and paraftins when the vapor inlet temperature was 980 F. and the vapor outlet temperature was about 965 F. It will be observed that at a liquid hourly space velocity of 30 the catalyst requirements for a unit treating 20,000 barrels of naphtha per day for both the low pressure reforming of the light naphtha and the isothermal reforming of the heavy naphtha is but 42 percent of the quantity normally employed. Thus, there is a saving in capital investment of about $625,000 and an increased income of about $700,000 per year in a unit treating 20,000 barrels of naphtha per day to produce 10 RVP gasoline having an octaine rating of 102 (Research+3 cc. TEL). In the illustrative example, the stream of normal parains, i.e., the molecular sieve sorbate, comprises about 12.6 percent by volume of the `C5 to 380 F. charge naphtha. When charging 20,000 barrels of said charge naphtha per day about 2,520 barrels of jet fuel are obtained per day. The jet fuel thus produced has the properties essentially as set forth in Table A.

TABLE A Yield, Percent Volulrnne C to 380 F. Naphtha Freezing Point, F Composition, Volume Percent:

When processing C5 to `3 80 F. straight run Mid-Continent naphtha the products are produced in the volumetric proportions set forth in Table B.

TABLE B Volume, percent C5-380 F. Naphtha 100 20 p.p.m. of sulfur. l p.p.m. of nitrogen. 2/10-9 of arsenic.

C5 to 250 F. light naphtha 40.2 250 to 380 F. heavy naphtha 59.8 Molecular sieve effluent (recycling n-paratlins to extinction) 83.2 Molecular sieve eluent (n-parafiins to jet fuel) 74.6 n-Parain recycle 12.6

ln illustrative Embodiment B only the heavy reformate, i.e., the isothermal reformate, is contacted with molecular sieve material and the heavy reformate sorbate, i.e., n-paraiins, recycled to the low pressure reforming Zone. However, the yields of C5+ (C5 and heavier) product from the low pressure reforming of the light naphtha in the presence of the recycle of only the n-paraffins from the heavy reformate is substantially higher than that obtained when the light naphtha is reformed in the presence of the t recycled n-parafiins sorbate from the total low pressure and high pressure reformate. Thus, when producing C5|- product having an octane rating of 100.7 (Research-f6 cc.Y TEL) recycle of only the sorbate of the heavy reformate to the low pressure reforming zone provides a C5-lproduct yield (by volume) of 84.4 percent as compared to a C5| product yield (by Volume) of 80.5 percent when the n-parains, i.e., sorbates, from both reformates are reformed in admixture With the light naphtha. The yield advantage `at 102 O.N. (R4-3 cc. TEL) over low pressure reforming of the light fraction and high pressure `reforming of the heavy fraction is about ve percent. The volumetric proportions of the different streams are given in Table C.

TABLE C Volume, percent C5 to 380 F. naphtha charge 100.0

20 p.p.m. of sulfur. 1 p.p.m. of nitrogen. 2/109 of arsenic. C5 to 250 F. light naphtha 40.2 250 to 380 F. heavy naphtha 59.8 Light reformate C54- product 31.4 Heavy reformate sieve el'lluent 44.2 n-Paraflin recycle 8.4

Combined C5-lreformate (102.7 O.N. R|3 cc.) 82.7

It is to be noted that, when the heavy naphtha is contacted with molecular sieve material before isothermally reforming the heavy naphtha, the yield of C54- product at an octane rating of 103.4 (Research-l-.S cc. TEL) is 76.1 percent by volume while the manipulation described briefly hereinbefore as Embodirnent B yields C5-lproduct in the proportion of 79.9 percent by volume. In addition, the contacting of the heavy naphtha before reforming requires a larger molecular sieve unit and concomitantly larger quantities of purge gas. Since the overall yield advantage for Embodirnent B is practically the same as for Embodirnent A, it is preferred to treat the C5 to 380 F. naphtha in accordance with the combination of operations designated Embodirnent B when the sorbate is to be recycled to extinction. The quantity of molecular sieve and the volume of hydrogen for regeneration are substantially lower for Embodirnent B than for Embodirnent A.

In Embodirnent C when the light reformate is contacted with molecular sieve material to obtain light reformate sieve effluent and light reformate sorbate while the heavy reformate is extracted with a selective solvent for nonparailinic hydrocarbons to provide a parainic rainate `and an aromatic extract, and the sieve effluent and the extracted aromatic hydrocarbon combined to provide a 105.5 octane (Research-H cc. TEL) C54- product the overall yield is 67 percent by volume of the charge naphtha and the yield of 150 luminometer number jet fuel is 20.2 percent by volume on the C5 to 380 F. charge naphtha. Only a 72 percent by volume yield of 105.5 octane C54- reformate and no jet fuel is obtained by combined low pressure reforming of the light naphtha and adiabatic high pressure reforming of the heavy naphtha.

In a modification of Embodirnent C when the hydrocarbons of the heavy paraffinic rafnate are combined with the light reformate sorbate and recycled to extinction in the low pressure reforming zone a 7.6 percent increase in yield of C54- reformate product is obtained at an octane rating level of 104.3 (Research-l-S cc. TEL) cornpared to the yield (by volume) of C54- reformate product when reforming the light naphtha at low pressure and the heavy naphtha adiabatically at high pressure.

In a further modification of Embodirnent C when the light reformate and the heavy reformate are extracted with selective solvent for non-parafinic hydrocarbons to produce a parainic raffinate and a non-parainic extract and the parafns of the raffinate are recycled to extinction in the loW pressure reforming zone there is a 7.7 percent advantage (by volume) at the octane rating level of 105.2 (Research-i-S cc. TEL) over low pressure reforming of the light naphtha and adiabatic reforming of the heavy naphtha at high pressure. Volumetric proportions of the dierent streams in the three illustrative variations of Embed-intent C based on the C5 to 380 F.

charge naphtha are tabulated in Table D.

TABLE D Modification Embodiment C C5 to 380 F. straight run naphtha' 20 p.p.m. of sulfur 1 ppm. of nitrogen 2/10- of arsenic C5 to 250 F. light naphtha 250 to 380 F. heavy naphtha LoW pressure reformate sieve ettluent Solvent extracted isothermal reformate n-Paraffin sorbate n-Paian raffinate from isothermal reforma e n-Paran raffinate from combined light and heavy reformfztp 05+ reformate product. .Tet fuel product Total yield of liquid product The embodiment D provides for excluding low octane rating C5 and C6 or C5 paraflins from the 05+ reformate product. At an octane level of 102` (Research-F3 cc. TEL) a yield of 82.8 percent -by volume is obtained. Combined low pressure reforming of the light naphtha and adiabatic high pressure reforming of the heavy naphtha produces only a 78.8 percent (by volume) yield of `C5|-reformate5 i.e., a yield advantage of 4 percent. The volumetric proportions of the different streams produced by use of Embodiment D are given in Table E.

A further Embodirnent E of the present invention provides for fractionating C6 to 380 F. naphtha to produce light naphtha BR C6 to 250 F. and heavy naphtha BR 250 to 380 F. The heavy naphtha is contacted with molecular sieve material to provide a heavy effluent and a heavy sorbate. The heavy eluent is reformed isothermally to provide a C5|- reformate of required octane rating (Research-|-3 cc. TEL). The heavy sorbate is combined with all or `a portion of the light fraction to provide a jet fuel having a luminometer number of at least 150. The balance of the light fraction is reformed adiabatically at low pressure. A C6 toi 380 F. Mid- Continent straight run naphtha was fractionated to provide a light naphtha and a heavy naphtha in the proportions and having the compositions set forth in Table F.

TABLE F C to 250 to 250 F. 380 F.

Volume percent of Ct to 380 F. Naphtha containing- 35. 4 64. 6 n-Paralins 27.0 17. 7 i-Parafns 25. 2 28. 4 N aphthenes 45. 2 42. 8 Aromatics-. 2. 6 10. 6 Other 0.5 100. 0 100. 0 Luminomcter No. C@ to 250 136.0 Luminometer No. 250 to 380 F. sorbate 0 TABLE G Volume percent Ou to 380 F. straight run naphtha:

Sulfur, 200 p.p.m

Nitrogen, 1 ppm 100.0

' Arsenic, 1/10-0 Cn to 250 F. light naphtha Volume percent:

n-Parafns i-Parafns Naphthcnes A romatics Other Luminometer No. 136, 250 to 380 F. heavy naphtha Volume percent:

n-Paraffins i-Parains Naphthenes Aromatics-- Other Molecular sieve eii'luent, volume percent Molecular sieve sorbate, volume percent (Luminometer No. 190) Jet Fuel (56% C@ to 250 F., 44% molecular sieve sorbate), Lumi- 'nometer No. 150 25.9 Gasoline Product (C5 and heavier), Octane No. (R plus 3 cc.

TEL) 104-- 57. 3

Hence, the yield of 104 octane number gasoline is 573 barrels and the yield of 150 luminometer number jet fuel is 259 barrels from each 1000 barrels of C6-3 80 F. Mid- Continent naphtha charged to the splitter.

By extraction of the C5 to 250 F. light naphtha with `silica gel before admixing with the sorbate from the heavy naphtha a jet fuel having a luminometer number in the range of 160 to 165 can be obtained with a slight sacriice of gasoline production.

One important feature of the present method of producing highloctane gasoline or high octane gasoline and jet fuel `or aromatic hydrocarbons and jet fuel is the use of isothermal conditions for the reforming of the heavy naphtha. At minimum liquid hourly space velocity in the isothermal reactor only about 0.03 to 0.035 barrel of reforming catalyst per barrel of heavy naphtha or 30 to 35 barrels of catalyst per 1000 barrels of heavy naphtha charged per day are required. At maximum liquid hourly space velocity (150) the values are 0.00665 per barrel and 6.65 per 1000 barrels of heavy naphtha charged per day.

Illustrative of some modifications of the basic concept of the present invention are, to wit: (l) fractionate C5 to 420 F., preferably C5 to 380 F. mixture of hydrocarb-ons comprising parans and naphthenes to obtain light naphtha comprising parains and naphthenes having an end boiling point (EBP.) of about 250 F. and containing C5 or C6 and heavier hydrocarbons and a heavy naphtha comprising hydrocarbons boiling in the range of about 250 F. to about 420 F., preferably about 250 F. to about 380 F., (2) adiabatically reform at least the naphthenes of the aforesaid light naphtha at a pressure in the range of about to about 350 p.s.i.g., preferab-ly Vabout 100 to about 300 p.s.i.g., (3) isothermally reform the heavy naphtha, and (4) treat the reformates so produced to obtain (l) only gasoline having an 'octane rating of ait least 100 (Research-Ha cc. TEL), (2) aromatic hydrocarbons and jet fuel having a luminometer number of at least 150, or (3) gasoline having an octane rating of at least 100 (Research-|-3 cc. TEL), and jet fuel having a luminometer number of at least 150.

S TABLE H Properties and compositions of full boiling range Mid- Continent naphtha and of light and heavy naphtha therefrom Full Light Heavy Boiling Naphtha Naphtha Range Percent Full Boiling Range 118 177 166 294 199 172 297 258 191 314 90% 337 217 358 EBP-Octane Rating:

Research, Clear 46. 5 65.7 29.2 Research -I- 3 cc. TEL 72.0 84. 9 53. 2 Motor, Clear 46. 7 63.1 33.8 Motor, 3 ce. TEL 73.0 83.8 57. 5

Hydrocarbon Distribution:

Paraiiins 52.1 58. 8 46.1 40. 2 39. 1 42. 8 7. 4 2. 1 10. 6 0.3 0.0 0.5

In this embodiment the effluents of both the low pressure reforming zone and the isothermal reforming zone are treated at temperatures in the range of about 600 to about 800 F., i.e., at a temperature above the deW point and below cracking temperature of the C5 and heavier hydrocarbons by contact with molecular sieve material. In the following description of the ow of liquids and gases as illustrated by the drawing only a brief description of the separation of low octane from high octane components of the C5 and heavier reformate is provided. For a more exhaustive trreatment of this subject and the recovery of the sorbate, i.e., for regeneration or unloading of the sieve material by the thermal Swing, pressure swing, liquid displacement, or vacuum techniques reference is made to the brochure published by Linde and Co. entitled, Octane Improvement; U.S. Patents Nos. 2,858,901; 2,859,170; 2,859,173; 2,859,256; 2,859,257; and 2,901,519; Oil and Gas Journal, 57, No. 13, pp. 52 and 53 (March 23, 1959); World Petroleum, April 1959; Petroleum Renner, 38, No. 4, pp. -134 (April 1959); and Chemical Engineering, 66, 104, 1959, No. 16, August 10, 1959.

Thus, C5 to 380 F. naphtha comprising parafiins and naphthenes and containing not more than innocuous concentrations of sulfur, nitrogen, and arsenic is drawn from a source not shown through pipe 1 by pump 2. The charge naphtha is discharged into pipe 3 and heated by means not shown to a temperature at which the components thereof boiling up to about 250 F. are volatile. The heated naphtha flows to fractionator, e.g., a splitter, 4. In fractionator 4 an overhead comprising C5 and heavier hydrocarbons having an E.B.P. of about 250 F. is taken through pipe 5. The light naphtha so obtained comprises paraffins and naphthenes. A bottoms, i.e., heavy naphtha having an initial boiling point (LBP.) of about 250 F. and not lower than the 90 percent point of the light naphtha and an E.B.P. substantially that of the charge naphtha and preferably not higher than 380 F. is Withdrawn from fractionator 4 through pipe 6.

The flow of light naphtha from fractionator 4 to effluent main 42 will be described iirst. Thereafter, the ow of heavy naphtha from fractionator 4 to euent main 4Z will be described.

The light naphtha flows from fractionator 4 through pipe 5 to the suction side of pump 7. Pump 7 discharges the light naphtha into pipe 8 at a pressure in exess of the pressure in low pressure reactor 16. The light naphtha flows through pipe 8 to indirect heat exchanger 9 where the light naphtha is in heat transfer relation with the low pressure ellluent flowing from indirect heat exchanger 11 through conduit 22. From indirect heat exchanger 9 the light naphtha flows through pipe 10 to indirect heat exchanger 11. In heat exchanger 11 the light naphtha is in heat transfer relation with the low pressure eilluent flowing from reactor 20 through conduit 21. From indirect heat exchanger 11 the light naphtha flows through conduit 12 to coil 13 in heater or furnace 14. At a point in conduit 12 intermediate to heat exchanger 11 and coil 13 hydrogen containing reformer recycle gas is admixed with the light naphtha to form a light naphtha charge mixture. After start-up and when the pressure at isothermal reactor 36 is higher than the pressure at reactor 16 the hydrogen-containing gas is reformer gas, recovered, when employing molecular sieves as a means of separating n-parafns from other constituents of reformates, at liquid-gas separator 61 (FIGURE 2S) flowing therefrom through conduit 63 to compressor 64 and thence through conduits 65, 66, 67, lcoil 68, and conduit 70 under control `of valve 91 to reducing valve 92 and conduit 93.

When the isothermal reactor 36 and reactor 16 are at substantially the same pressure the reformer recycle 4gas lbypasses reducing valve 92 and with Valves 94 and 95 open ilows through conduit 96 in part to conduit 93 and conduit 12 and in part to conduits 97 and 32. When the isothermal reactor is at a pressure substantially higher than that of reactor 16 a portion lof the reformer recycle 4gas bypasses reducing valve 92 and with valve 94 open and valve `95 closed ilows in part through conduits 96 and 97 to conduit 32 and in part through reducing valve `92 through conduits 93 and 12. In conduit 12 the hydrogen-containing reformer recycle gas is admixed with the light naphtha to provide a light naphtha charge mixture having a hydrogen-to-light naphtha mol ratio of 0.25 to l0. Alternatively, compressor 64 can compress the hyrogen-containing reformer recycle gas to a pressure in excess of that at reactor 16 but below the pressure at isothermal reactor 36. The hydrogencontaining gas in excess of that used in reactor 16 is then reconipressed by a compressor not shown to a pressure in excess of that at isothermal reactor 36.

The light naphtha charge mixture flows through conduit 12 to coil 13 in heater 14. In coil 13 the light naphtha charge mixture is heated to a reforming temperature to provide a temperature at the vapor inlet of low pressure reactor 16 in the range of 800 to about 1000 F., preferably about 900 to about 980 F.

The heated light naphtha charge mixture llows from coil 13 through conduit 15 to low pressure reactor (L1). In low pressure reactor 16 the light naphtha charge mixture is contacted with particle-form solid platinum-group metal reforming catalyst, preferably platinum-group metal reforming catalyst comprising about 0.35 to abo-ut 0.6 percent by weight of platinum on refractory oxide, preferably alumina, support. The liquid hourly space Velocity (v./hr./v.) and the reforming temperature are interdependent and dependent upon the target or required octane rating of the C and heavier cyclic hydrocarbons and branched-chain parailins of the low pressure eflluent. The light naphtha charge mixture flows through reactors 16 and 20 at a liquid hourly space velocity of the light naphtha in the range of 0.5 to 2. The llrst low pressure eflluent flows from reactor 16 through conduit 17 to coil 18 in furnace 14. In coil 18 the first low pressure effluent is reheated to a reforming temperature to provide a temperature at the vapor inlet of reactor 20, the same as, lower or higher than, the temperature at the vapor inlet of reactor 16. The reheated rst low pressure ellluent flows from coil 18 through iconduit 19 to low pressure reactor 20. The liquid space velocity employed in low pressure reactor 20 is dependent upon the activity of the catalyst (preferably of the same coimposition as that in reactor 16), and the extent to which the parafllns in the ilrst low lpressure eilluent are to be isomerized and dehydrocyclized. At any given inlet temperature and with a catalyst having substantially the same activity the liquid hourly space velocity will be lower the higher the required conversion of the parafins. The overall liquid hourly space velocity for reactors 16 and 20 is in the range of about 0.5 to about 2.0.

The eilluent of reactor 20, designated final low pressure effluent, flows from low pressure reactor 20 through conduit 21 to indirect heat exchanger 11, through conduit 22, indirect heat exchanger 9 and through conduits 23 and 24 (valve 25 open, valve 26 closed) to eflluent main 42 (FIGURE 2s).

The ilow of the heavy naphtha from fractionator 4 to the elluent main 42 will Ibe described now. The bot toms of fractionator 4 having an initial boiling point of about 250 F. and not lower than the 90 percent point of the light naphtha and an end boiling point preferably of about 380 F. and by choice as ,high as 420 F. flows `from fractionator 4 through pipe 6 to the suction side of pump 27 (FIGURE 1h). Purnp 27 discharges the heavy naphtha into pipe 28 at a pressure in excess of that in isothermal reactor 36. The pressure in reactor 36 is in the range 15 to 120'0 p.s.i.g. and preferably in the range 500 to 1200 p.s.i.g.

The heavy naphtha flows through pipe 28 to indirect heat exchanger 29 where the heavy naphtha is in heat transfer relation with the isothermal ellluent flowing from indirect heat exchanger 31 through conduit 38. From heat exchanger 29 the heavy naphtha il'ows through pipe 30 to indirect heat exchanger 31. In indirect heat exchanger 31 the heavy naphtha is in heat transfer relation with the isothermal eflluent flowing from isothermal reactor 36 through conduit 37. From exchanger 31 the heavy naphtha flows through conduit 32 to coil 33 in heater 34. At a point in conduit 32 intermediate to exchanger 31 and to coil 33 reformer recycle gas flowing from compressor 64 (FIGURE 2S) through conduits 65, 66, 67, coil 68 (FIGURE 2S) and conduit 70 under control of valve 91 (FIGURE 1L), conduit 96, conduit 97 and conduit 32 (FIGURE 1L) is admixed with the heavy naphtha to provide a heavy naphtha charge mixture having a hydrogento-heavy naphtha mol ratio in the range of 1 to 10, preferably 4 to 6. The heavy naphtha charge mixture flows through conduit 32 to coil 33.. In coil 33 the heavy naphtha charge mixture is heated to a temperature to provide at the vapor inlet of isothermal reactor 36 a reforming temperature in the range of about 940 to about 10.20 F. rand preferably about 960 to about 980 F. The heated heavy naphtha charge mixture flows from heater 34 through conduit 35 (valve 98 open; valve 99 closed) to isothermal reactor 36.

In isothermal reactor 36 the temperature and liquid hourly space velocity are correlated to convert substantially all of the naphthenes to aromatic hydrocarbons with a minimum of hydrocracking. Vapor inlet temperatures in the range of 940 to 1020 F. with liquid hourly space velocities in the range of 30 to 150, preferably 30 to about 100 are usually employed. The yheavy naphtha charge mixture is in -contact with particle-form platinum-group metal reforming catalyst, preferably platinumgroup metal reforming catalyst comprising about 0.35 to about 0.6 percent by weight of platinum on a refractory oxide support, preferably alumina.

The heavy naphtha charge mixture llows downwardly in isothermal reactor 36 to produce an isothermal ellluent. The isothermal ellluent ilows from reactor 36 through conduit 37 to heat exchanger 31 through conduit 38 to heat exchanger 29 and through conduit 39 to isothermal ellluent main 40.

When the pressure in isothermal eflluent main 40 is greater than the pressure at which the low pressure ellluent enters eflluent main 42 by substantially more than the pressure drop from conduit 39 to effluent main 42, the pressure of the isothermal eflluent is reduced by means of pressure reducing valve 41 (FIG. 2s). When the pressure of the isothermal effluent is not greater by 1 l more than the pressure drop between conduit 39 and effluent main 42, the isothermal effluent flows from conduit 39 to conduit 40 (FIGURE 2s), conduit 45 ( valves 43 and 44 open) to conduit 42. Under the alternative pressure conditions the flow is from conduit 39 to conduit 40, and pressure reducing valve 41 to conduit 42.

In the embodiment of the present invention presently being described the low pressure effluent and the isothermal effluent are mixed and contacted with molecular sieve material. Accordingly, for purpose of description, the isothermal effluent and the low pressure effluent cooled by the heat exchange described hereinbefore to not higher than 800 F. and not lower than the dew point of the mixture at the pressure in effluent main 42, usually not lower than about 600 F. flow through effluent main 42 to sieve manifold 46 (FIGURE 2s) A plurality of sieves are required to make the separation continuous and to integrate the sieve separation with the reforming operation. Accordingly, while one or more sieves are being loaded other sieves are being unloaded or regenerated. For the purpose of this description it will be `assumed that sieve 49 is unloaded and sieve 101 is loaded and being unloaded contemporaneously employing the hydrogen-containing reformer gas as a purge.

Thus, the mixed low pressure effluent and isothermal effluent, designated mixed effluent, flows through effluent main 42 to sieve manifold 46. With valves 74, 77 and 52 closed and valves 48 and 51 open the mixed effluents flow from sieve manifold 46 through branch 47 into sieve 49. The mixed effluents flow downwardly through the sieve material having pores 4 to 5 Angstroms in diameter leaving as a sorbate in the sieve material the straight chain paraflns and producing a sieve effluent comprising isoparaflins, aromatics, and any unconverted naphthenes. The sieve effluent having a temperature in the range of 600 to 800 F. flows from sieve 49 through conduit 50 (valve 51 open; valves 52 and 80 closed) to sieve effluent manifold 53. From manifold 53 the sieve effluent flows through conduit 54 to indirect heat exchanger 55. In heat exchanger 55 the sieve effluent is in heat transfer relation with the purge gas (described hereinafter) flowing from indirect heat exchanger 57 through conduit 66. From heat exchanger 55 the sieve effluent flows through conduit 56 to indirect heat exchanger 57. In indirect heat exchanger 57 the sieve effluent is in heat transfer relation with the purge gas flowing from compressor 64 through conduit 65. From heat exchanger 57 the sieve effluent comprising hydrogen, isoparaffins, and cyclic hydrocarbons of the mixed ellluent flows through conduit S to cooler 59. In cooler 59 the sieve effluent is cooled to a temperature at which C4 and heavier isoparaflns and aromatics are condensed at the existing pressure. The cooled sieve effluent flows yfrom cooler 59 through conduit 60 to effluent liquid-gas separator 61.

In separator 61 the uncondensed sieve effluent, designated reformer gas, comprising hydrogen and C1 to C3 hydrocarbons not sorbed by the sieve separates from the C4 and heavier isoparaffins and aromatics, designated gasoline product. The gasoline product flows from sieve separator 61 through pipe 62 to means for recovering aromatic hydrocarbons, to gasoline blending, etc. not shown. The reformer gas flows from sieve separator 61 through conduit 63 to compressor 64. Compressor 64 recompresses the reformer gas to a pressure required for purging sieve 101 or preferably to a pressure in excess of that at reactor 16 (FIGURE 1L).

As stated before, it has been assumed for the purpose of this illustration that sieve 101 is being unloaded or purged or regenerated while sieve 49 is being loaded. In other words, the sorbate comprising n-paraflins is removed in any suitable manner known to the art. The method selected for illustration is that of displacing the paraffinic sorbate with hydrogen-containing reformer gras separated 'from the sieve effluent in effluent separator 61. Accordingly, a portion of the reformer gas flowing from compressor 64 through conduits 65, 66, 67 and coil 68 in which the reformer gas is heated to substantially the temperature of the sieve material in sieve 101 and usually in the range of about 600 to about 800 F. flows from coil 68 through conduit 70 to purge manifold 71. From purge manifold 71 the purge gas flows through purge branch 72 under control of valve 73 which is regulated to pass the portion of the reformer gas not required in the low pressure reactors and the isothermal reactor to maintain the required hydrogen-to-naphtha mol ratios set forth herein. The hydrogen-containing purge gas flows from purge branch 72 to reactor effluent branch 75, downwardly through the sieve material in sieve 101 to sieve effluent branch 7 8 removing the n-paraflln sorbate during its passage. With valve 81 closed and valve S6 open the purge gas and sorbate flow through sieve purge branch '79 to purge manifold 82. The purge gas and sorbate flow through purge manifold 82 to cooler 83 where the purge gas-sorbate mixture is cooled to a temperature at which C4 and heavier n-paraflins are condensed at the existing pressure. From cooler 33 the condensed and uncondensed purge gas-sorbate mixture flows through conduit 98 to sorbate liquid-gas separator 84.

In sorbate liquid-gas separator 84 the uncondensed purge gas-sorbate mixture comprising C4 to C3 paraflins and hydrogen, designated hydrogen-containing purge gas, separates from sorbate comprising C4 and heavier paraffins. The purge gas flows from sorbate separator 84 through conduit S5 to other hydroprocesses or fuel main.

The n-parafn sorbate comprising C4 and heavier n paraffins in whole or in part flows from separator 84 through pipes 86 and S7 under control of valve 88 to iet fuel storage. Alternatively, the n-paraflin sorbate flows in whole or in part from separator 84 through pipes 86 and 89 under control of valve 90 to the suction side of pump 99. Pump 99 discharges the sorbate into pipe 100 through which the sorbate flows to pipe 8 (FIGURFJ 1L) to mix with the light naphtha charge mixture.

EMBODIMENT B In the modification of the basic concept -of the present invention designated Embodiment B only the isothermal effluent is contacted with the molecular sieve material. Accordingly, the light naphtha is reformed as previously described to produce a low pressure final effluent flowing from low pressure reactor 20 through conduit 21 to heat exchanger 11, conduit 22, heat exchanger 9, and conduit 23 (valve 26 open; valve 25 closed) to conduit 102. The low pressure final effluent flows through conduit 102 to Conduit 54 (FIGURE 2S) where it mixed with the sieve effluent of the isothermal effluent.

The heavy naphtha is reformed isothermally as previously described to obtain an isothermal efiluent flowing from isothermal reactor 36 (FIGURE 1h) through conduit 37 to heat exchanger 31, conduit 3S, heat exchanger 29 and conduit 39 to conduit 40 (FIGURE 2S), eflluent main 42, sieve manifold 46, and sieve branch (valve 74 open; valve 48 closed) to sieve 101. The isothermal effluent flows downwardly through sieve 101 which sorbs the n-paraflins in the isothermal effluent to produce a sieve effluent comprising isoparaflins and aromatics. The sieve effluent flows from sieve 101 through sieve effluent branch 78 (valve 81 open; valve 80 closed) to effluent manifold 53 and thence to conduit 54 where the isothermal sieve effluent mixes with the low pressure final effluent as stated before.

The mixture of isothermal sieve effluent and low pressure final effluent flows through conduit 54 to heat exchanger 55, conduit 56, heat exchanger 57 and conduit 5S to cooler 59. In cooler 59 the mixture of isothermal sieve effluent and low pressure final eflluent comprising hydrogen and C1 and heavier isoparaffins, aromatics and n-paraflins from the low pressure final effluent is cooled to a temperature at which the C4 and yheavier hydrocar- 'bons are condensed. The cooled mixture of isothermal sieve effluent and low pressure final effluent flows from cooler 59 through conduit 60 to effluent gas-liquid separator 61.

In eluent separator 61 the uncondensed mixture, designated reformer gas and comprising hydrogen and C1 to C3 hydrocarbons flows from separator 61 through conduit 63 to compressor 64.

The condensate, designated gasoline product, hows from elluent separat-or 61 through pipe 62 to stabilization, gasoline blending, storage, distribution, etc.

The reformer gas flowing from separator `61 to compressor 64 is recompressed and discharged into conduit 65 through which the recompressed reformer gas flows to exchanger 57, conduit 66, exchanger 55 and conduit 67 to coil 68 in heater 9` as previously described herein. The reheated lreformer gas ows from heater 69 through conduit 70 under control of valve 91 (FIGURE 1L) to the low pressure reformer 16 and the isothermal reformer 36 as previously described herein. The balance of the reformer gas is used to purge the loaded sieve. Since in `Eni-bodirnent B as described hereinbefore sieve 101 has been loaded, the unloading or purging of sieve 49 will be described.

A portion, i.e., the balance, of the reformer gas not used in reactors 16, 20, and 36, tiows from conduit 70 to purge manifold 71 rand thence through purge branch 76 (valve 77 open; valves 73 and 48 closed) to sieve 49. The purge gas flows downwardly through sieve t9 displacing the n-paraftin sorbate to effluent branch 50 and purge branch 103 ( valves 51 and 80 closed; valve 52 open). The purge gas and n-parain :sorbate flow from purge branch 103 to purge manifold 82 and thence to cooler 83. In cooler 83 the temperature of the purge gas-s-orbate mixture is reduced to that yat which at the existing pressure C4 and heavier hydrocarbons are condensed. The cooled mixture Hows from cooler 83 through conduit 93 to sorbate gas-liquid separator 84. In sorbate liquid-gas separator 84 the uncondensed mixture comprising hydrogen and C1 to C3 hydrocarbons separates from the con- `densed sorbate and Hows through conduit 85 to other hydroprocesses or fuel. The condensed sorbate comprising C4 and heavier n-parans ows from separator 84 through pipe S6 in whole or in part through pipe S7 under control of valve 88 to storage as jet fuel or in whole or in part through pipe S9 under control of valve 90 to the suction side of pump 99 for recycle through pipe 100 to pipe 8 and the low pressure reactors 16 `and 20.

EMBODIMENT C In Enrbodiment C the low pressure iinal eiiluent is contacted with the molecular sieve material while the isothermal eiliuent is extracted with a selective solvent having greater solvency for nonparafnic hydrocarbons than for paraffin-ic hydrocarbons. There are numerous selective solvents useful for this purpose known to those skilled in the art. These selective solvents include liquid sulfur dioxide, the polyalkylene glycols, and others. For illustrative purposes diethylene glycol has been chosen as the selective solvent. Since the manipulation of these selective solvents is well known to those skilled in the art only a brief description is provided.

The light naphtha is reformed as previously described to obtain a low pressure fin-al eluent flowing rfrom loW pressure reactor 20 (FIGURE 1L) through conduit 21, exchanger 11, conduit 22, exchanger 9 and conduit 23 to conduit 24 (valve 25 open; valve 26 closed). The low pressure final efliuent flows through conduit 24 to effluent main 42 and thence to sieve manifold 46. Sieve 49 being yon-stream the low pressure nal effluent ows from sieve manifold 46 through branch 47 to sieve 49. The low pressure iinal efuent ows downwardly through sieve 49 depositing n-parailns to provide a sieve effluent comprising iso-parafins, aromatics, and hydrogen. The sieve effluent flows from sieve 49 through sieve eiuent branch 50 (valve 51 open; valve 52 closed) to sieve eluent manifold 53, conduit 54, exchanger 55, conduit 56, exchanger S7 and conduit S8 to cooler 59. In -cooler 59 the sieve effluent is cooled to a temperature at which yC4 and heavier hydrocarbons areA condensed at the existing pressure. From cooler 59 the cooled sieve eiiluent flows through conduit `60 to effluent separator 61. In separator 61 the uncondensed sieve effluent, designated reformer gas, separates and flows through conduit 63 to compressor 64- and thence in major part to reactors 16 and 36 and in minor part to regenerate or unload sieve 1.01. The condensed sieve etiiuent flows from separator 61 through pipe 62 as gasoline product.

The heavy naphtha is reformed in isothermal reactor 36 to produce isothermal eluent which flows from reactor 36 through conduit 37, exchanger 31, conduit 38, exchanger `29, and conduit 39 to conduit 40. When the pressure of the isothermal efliuent is greater than the pressure drop plus `the pressure at extractor `112 (FIG- URE 2e) the isothermal efliuent ows through conduit 40, pressure reducing valve 41, effluent main 42 (valve 103 closed; valve open) and conduit `104` to cooler 106 (FIGURE 2e). In cooler 106 the isothermal effluent is cooled to a temperature at which C5 and heavier hydrocarbons are condensed at the existing pressure. The cooled isothermal eflluent flows from cooler 106 through conduit 107 to isothermal Iliquid-gas separator 108.

In isothermal liquid-gas separator 108 the 4uncondensed isothermal eflluent comprising hydrogen and C1 to C5 hydrocarbons separates `from the condensed isothermal ef'duent comprising C5 and heavier paraitins, naphthenes (if any), and aromatics. The uncondensed or gaseous isothermal eiiluent hows from separator 108 through conduit `109 (valve 110 open) to conduit 54 (FIGURE 2s) and thence with the sieve efliuent to effluent separator 61 (FIGURE 2S).

The condensed isothermal effluent, designated isothermal reformate, tiows from separator `108 through conduit 11.1 to extractor 112. During the passage from separator 108 to extractor 112 the isothermal reformate is heated in any suitable manner to extraction temperature which, for diethylene glycol, is in t-he range of about 200 F. to 350 F. In extractor 112 the isothermal reformate is contacted with selective solvent having a greater solvency for nonparainic hydrocarbons than for paraf-nic hydrocarbons. For the purpose of this illustration the selective solvent :diethylene glycol will lbe used. Thus, the selective solvent, diethylene glycol, Hows from fractionator through pipe 127 to indirect heat exchanger 1213. In heat exchanger 123 the selective solvent is in heat transfer relation with the isothermal extract flowing from extractor 112 through pipe 122. From indirect heat exchanger 12'3 the selective solvent flows through pipe 128 to pli/pe 121 being heated to extraction temperature if necessary by any suitable means during passage to pipe 121 or thereafter. Selective solvent separated from the isothermal ranate flows `from fractionator 114 through pipe 120l to pipe 12:1. The selective solvent at extraction temperature flows from pipe 121 into extractor 1112. The selective solvent ows counterourrently downward through extractor 1112 in intimate contact with the upwardly owing isothermal reformate extracting the aromatic hydrocarbons of the isothermal reforrnate therefrom to produce isothermal extract comprising selective solvent and aromatic hydrocarbons and isothermal ranate comprising unextracted parainic hydrocarbons. The isothermal rainate leaves extractor 112 through pipe 113 and flows therethrough to fractionator 114. In yfractionator 114 the piaraiinic hydrocarbons separate from entrained selective solvent and how therefrom through pipe ,1115 in whole or part to pipe .1:16 (FIGURE 12s) under control of valve 11.7 -to conduit `32 and admixture with sieve sorbate `or in whole or part to pipe 1118 under control of valve 119 to pipe v89 andr the suction side of pump 99 for recycle to the low pressure reforming reactor 16 (FIGURE 1L). rPhe isothermal extract ows from extractor 112 through pipe 122 to indirect heat exchanger 123, and pipe y124 to fractionator 125. 1n fractionator 125 the non-parafnic hydrocarbons of ,thelisot-herrnalextract separate from the selective solvent fand flow through pipe 126 to recovery of substantially pure aromatic hydrocarbons boiling in the range of 176 to 380 F., to adrnixture with the gasoline produlct flowing through pipe '62 (FIGURE 2s), or to storage or distribution per se as gasoline product. The selective solvent separated in fractionator 125 returns to the extractor via pipe 127, exchanger 123, and pipes 128 and 121 as previously described.

In a modification of Embodiment C the low pressure effluent and the isothermal efiiuent are condensed and the C5 and heavier fraction of each effluent extracted with a selective solvent for non-parafiinic hydrocarbons.

In this instance the low pressure effluent flows from reactor 20 through conduit 21, exchanger 11, conduit 22, exchanger 9, conduit 23 (valve 2,5 closed; valve 26 open), conduit 102, (FIGS. 1L and 2s), conduit 129, (FIGS. 2s land 2e); (valve 130 open; valve 168 closed) cooler 161, and conduit 162 to cooler 106.

`The heavy naphtha is reformed isothermally as previously described. The isothermal effluent fiows from isothermal reactor 36 through conduit 37, exchanger 31, conduit 38, exchanger 29, and conduit 39 to conduit 40, (FIG. 2S). When the isothermal efliuent is at a pressure not substantially greater than that in conduit 104 the isothermal effluent iiows from conduit 40 through conduits 45 and 162 to conduit `104 ( valves 43 and 163 open; valve 44 closed). When the pressure of the isothermal efuent is substantially greater than that in conduit 104, the isolthermal effluent fiows from conduit 40 through pressure reducing valve 4'1, conduit 42 (valve I103 closed; vallve 105 open) to conduit 104. The isothermal effluent ovvs through conduit 104 to cooler 106. In cooler 106 the isothermal effluent .and the 'low pressure effluent are cooled to a temperature at which C5 and heavier hydrocarbons are condensed. The cooled mixed efliuents flow from cooler 106 through cond-uit 107 to separator i108.

In separator 108 the uncondensed mixed effluents comprising hydrogen and C1 yto C., hydrocarbons separate from the condensed mixed effluents comprising paraffinic and non-paraiiinic C5 and heavier hydrocarbons. The uncondensed mixed efiiuents flow from separator 108 through conduit 109 to cond-uit 54 (FIG. 2s; valve 1.10 open) and thence through conduit 54 to exchanger 55, conduit 56, exchanger 57, conduit 58, cooler 59 and conduit 60 to separator 61. In separator 61 the hydrogen and C1 to C3 hydrocarbons separate and flow from separator 61 through conduit 63 to compressor 64 and is thereby recycled to the reactors 16 and 36. The C4 and heavier hydrocarbons flow from separator 61 through conduit 62 to recovery. The condensed mixed effiuents, designated extractor feed, fioW from separator 108 (FIG. 2e) through pipe 111 to extractor 112. In extractor 112 the extractor feed is contacted With a selective solvent for non-paraffinic hydrocarbons to provide a parafiinic raffinate which flows from extractor 112 through pipe 113 to fractionator 114 and non-plaraflinic extract Which flows from extractor 112 through pipe i122, exchanger 123, :and pipe 124 to fractionator 125.

In fractionator 11'4 the parafiinic hydrocarbons separate from selective solvent and flo-W through pipe 115 in Whole or in part to pipe :118 (FIG. 2s; Valve 117 closed; valve 119 open) and thence to pipe 89 and the suction side of pump 99 for recycle to the low pressure reactor 16 (FIG. 1L). The non-parafnic extract is fractionated in fractionator 125 to provide an overhead comprising aromatic hydrocarbons boiling in the range of 176 to 380 F. The aforesaid overhead fiows from fractionator 125 through pipe 126 to -means for the recovery of specific Aaromatic hydrocarbons, to means for blending to provide gasoline or to distribution as gasoline.

1 8 EMBoDrMEN'r D As stated hereinbefore Embodiment D of the present invention provides for excluding n-paraffins having six or less carbon atoms from the high octane Cyl-product. Accordingly, illustrative of the embodiment is the fractionation of naphtha to obtain a C5 to 250 F. E.B.P. light naphtha and a 250 to 380 F. heavy naphtha. The light naphtha is reformed at low pressure as previously described to produce low pressure effluent comprising hydrogen and C1 and heavier hydrocarbons. The low pressure efliuent ows from reactor 20 through conduit 21 to exchanger 11, conduit 22, exchanger 9, conduit 23 (valve 26 open; valve 2S closed) and conduit 102 to conduit 129 (FIGURE 2S; valve 130 open; valve 168 closed). The low pressure efiiuent flows through conduit 129 (FIGURE IZ) to indirect heat exchanger 131, conduit 132, indirect heat exchanger 133, conduit 134, cooler 135, and conduit 136 to fractionator 137 having a reboiler, e.g., pipe 138, pump 139, pipe 140, heat exchanger 141, and pipe 142. The flow of low pressure effluent `and accumulator liquid from accumulator 145 are controlled in conjunction With cooler and the reboiler to ensure that the accumulator liquid comprises substantially C5 and C5 paraffins and the bottoms C, and heavier hydrocarbons. Accordingly, the low pressure efliuent ows into fractionator 137. A temperature is maintained in fractionator 137 at which C5 and C5 hydrocarbons are volatile While C7 and heavier hydrocarbons are liquid. The C5 and C5 hydrocarbons together with hydrogen and C1 to C4 hydrocarbons are taken overhead through conduit 143 to cooler 144. In cooler 144 the overhead is cooled to a temperature at which C5 and heavier hydrocarbons are condensed. The cooled overhead flows from cooler 144 through conduit 165 to accumulator 145. In accumulator 145 the hydrogen and C1 to C4 hydrocarbons of the low pressure efliuent, designated LP. Hg-containing gas, flow therefrom through conduit 166 under control of valve 164 (FIGURE 2s) .to conduit 82 and thence to cooler 83 and conduit 98 to sorbate separator 84. The condensed C5 and heavier hydrocarbons, i.e., the accumulator liquid, flow from accumulator 145 through pipe 146 to the suction side of pump 147. Pump 147 discharges the accumulator liquid into pipe 150. A portion of the accumulator liquid, sufficient for redux, is diverted from pipe 150 through pipe 149 under con5 trol of valve 169 to fractionator 137. The balance and usually the major part of the accumulator liquid fiowing in pipe 150 flows in whole or in part under control of valves 152 and 154 to pipe 153, and pipe 156 or pipe 151, heat exchanger 133, pipe 155, heat exchanger 131 and pipe 156. The accumulator liquid i.e., C5 and C5 hydrocarbons, flows through pipe 156 under control of valve 157 (FIGURE 2s) to efiiuent main 42.

The 250 to 380 F. heavy naphtha is reformed isother-mally as previously described in isothermal reactor 36 (FIGURE 1h) to provide isothermal effluent flowing from reactor 36 through conduit 37 to heat exchanger 31, conduit 38, heat exchanger 29 and conduit 39 to conduit 40 (FIGURE 2s). Since the accumulator liquid usually is under a pressure of less than l5 p.s.i.g., the isothermal efuent usually flows through conduit 40 and pressure reducing valve 41 to effluent main 42. The isothermal effluent and the aforesaid accumulator liquid mix in effluent main 42 to provide a mixture having a temperature within the range of about 600 to about 800 F. The mixture .then is contacted with molecular sieve material in sieves 49 or 101 to produce sieve effluent which flows from sieve manifold 53 through conduit 54, exchanger 55, conduit 56, exchanger 57, conduit 58, cooler 59 and conduit 60 to effluent separator 61. In separator 61 the hydrogen and C1 to C4 hydrocarbons separate and flow therefrom through conduit 63 to compressor 64 for use as purge gas and reformer recycle gas. The condensed sieve effluent ilows from separator 61 through pipe 62 as ga-soline product.

The C7 and heavier hydrocarbons of the low pressure eluent flow from fractionator 137 (FIGURE 2f) through pipe 158 to the suction side of pump 159. Plump 159 discharges the C7 and heavier low pressure etlluent into pipe 160. The C7 and heavier low pressure efuent flows through pipe 160 under control of valve 167 (FIG- URE 25) to pipe 62 to mix with the sieve effluent flowing from separator 61 las stated hereinbefore.

Those 4skilled in the art will understand that the description provided hereinbefore `discloses fractionation of naphtha into light naphtha having an end boiling point of labout 250 F. `and a heavy naphtha having an initial :boiling point not lower than the 90 percent point of the light naphtha and not substantially higher than the end boiling point of the light naphtha. At least a portion of the light naphtha is reformed 4at a pressure in the range of about to about 300 p.s.i.g. and at least a portion of the soaproduced low pressure efll-uent is treated to separate low octane components of the low pressure effluent from the high octane components thereof.

The heavy naphtha is isothermally reformed at liquid hourly space velocities of at least 30 to produce isotherrmal eliluent. The isothermal eluent is treated to separate .the high octane components of the isothermal eil'luent from the low octane Icomponents thereof. The separated low octane components in whole or in part are blended to provide jet fuel having a luminometer number of at least 150 or in whole or in part recycled to the low pressure reforming zone(s).

Since reforming under essentially isothermal conditions results in less naphthene cracking than conventional adiabatic reforming, the yeld of C6 and heavier reformate is higher. A very economically attractive method for producing high quality jet fuels and contemporaneously producing higher volatility, high octane number gasoline is that described `as Embodiment E.

EMBODIMENT E In that embodiment of the present invention in which the normal parains of the 250 to 380 F. fraction of the naphtha are separated therefrom and mixed with a portion of the light naphtha, i.e., boiling range C6 to 250 F., the flow of liquids and gases is as illustrated in FIGURE 3. Thus, a C6 to 380 F. fraction comprising normal paraflins and naphthenes is drawn from a source not shown through pipe 170 by pump 171. Pump 171 discharges the C6 to 380 F. fraction of naphtha into pipe 172. The naphtha flows from pump 171 through pipe 172 to fractionator 173. Intermediate to pump 171 and fractionator 173 the C6 to 380 F. naphtha is heated in any suitable manner to a temperature at which hydrocarbons having a boiling point at atmospheric pressure not higher than 250 F. are volatile. The heated C6 to 380 F. naphtha is fractionated in fractionator 173 to provide a C6 to 250 F. overhead having a luminometer number of about 136 and a bottoms fraction having an initial boiling point not lower than the 90 percent point of the overhead and preferably about 250 F. and an end boiling point substantially the same as that of the highest boiling constituent of the charge to the fractionator and preferably about 380J F. The bottoms fraction flows from fractionator 173 through pipe 175 4to the suction side of pump 176. The bottoms fraction or heavy naphtha, i.e., boiling range about `250 to about 380 F. preferably, is discharged into pipe 177 at a pressure suciently in excess of the pressure in isothermal reactor 200 -to overcome the pressure drop between pump 176 and isothermal reactor 200. The heavy naphtha flows through pipe 177 to indirect heat exchanger 178 where the heavy naphtha is in indirect heat transfer relation with the effluent of the isothermal reactor flowing from indirect heat exchanger 180 to conduit 202. From indirect heat exchanger 178 the heavy naphtha flows through pipe 179, to heat exchanger 180. In heat exchanger 180 the heavy naphtha is in indirect heat transfer relation with the eiuent of isothermal reactor 200' flowing therefrom through conduit 201. The heavy naphtha flows from heat exchanger 180 through pipe 181 to coil 182 in heater 183 were it is heated to a temperature above the dewpoint thereof at the existing pressure.

The molecular sieves 187 and 188 can be loaded and unloaded in any suitable manner known to those skilled in the art. For the purpose of illustration loading at a temperature above the dewpoint of the highest boiling constituent of the heavy naphtha at the existing pressure and unloading by reducing the pressure has been schematically indicated. Accordingly, the heavy naphtha is heated in heater 183 to a temperature in excess of the dewpoint -of the heaviest constituent of the heavy naphtha at the pressure existing in pipe 181. Usually the heavy naphtha will be heated to a temperature in the range of about 400 to about 600 F. The heated heavy naphtha flows from hater 183 to sieve manifold 184 having branches 185 and 186. It will be assumed that sieve 187 is unloaded or regenerated and that sieve 188 is loaded or under regeneration. Accordingly, with valve 193 closed and valve 192 open the heated heavy naphtha ows downwardly through sieve 187 in contact with the molecular sieve material having pores of about 4 to 5 Angstroms in diameter. The sieve effluent flows from sieve 187 through pipe 189 (valve 209 closed; valve 194 open) to sieve manifold 191 and thence through pipe 196 to coil 197 in heater 198. At a point in conduit 196 intermediate to sieve manifold 191 and heater 198 hydrogen-containing gas, after startup, reformer gas flowing from separator 204 to compressor 207 and thence through conduit 208 to conduit 196 is admixed with the sieve euent. In conduit 196 the hydrogen-containing gas is mixed with the sieve eluent to provide an isothermal charge mixture comprising hydrogen and cyclic hydrocarbons in the mol ratio of about 7 to about '10 mols of hydrogen per mol of cyclic hydrocarbons in the heavy naphtha. The isothermal charge mixture is heated in furnace 198 to a reforming temperature in the range of about 960 to about 1000 F. The isothermal charge mixture flows from heater 198 through conduit 199 to isothermal reactor 200. The isothermal charge mixture enters reactor 200 at a reforming temperature within the range of 960 to 1000 F. The isothermal charge mixture flows downwardly through isothermal reactor 200 at a liquid hourly space velocity of at least about 15 and as high as 150. The efuent of the isothermal reactor 200, designated isothermal efuent, Hows fro misothermal reactor 200 through conduit 201 to indirect heat exchanger 180, conduit 202, indirect heat exchanger 178 and conduit 203. to cooler 254. In cooler 254 the isothermal efuent is cooled to a temperature at which C4 and heavier hydrocarbons are condensed at the existing pressure. The uncondensed isothermal eluent comprising hydrogen and C1 to C3 hydrocarbons separates from 4the condensed isothermal eliiuent comprising C4 and heavier hydrocarbons in liquid-gas separator 204.

The hydrogen and C1 to C3 hydrocarbons of the isothermal eluent, designated isothermal hydrogen, flows from separator 204 through conduit 206 to compressor 207. Compressor 207 recompresses the isothermal hydrogen to a pressure in excess of that in conduit 196. The recompressed isothermal hydrogen ows from compressor 207 through conduit 208 to conduit 196 to mix with the sieve effluent as described hereinbefore. Any isothermal hydrogen in excess of that required to maintain the aforesaid hydrogen to sieve effluent mol ratio is diverted from conduit 206 through conduit 256 under control of valve 253 and conduits 252 and 233 for use in the low pressure reforming unit.

The condensed C4 and hea'vier hydrocarbons of the isothermal reformate, designated isothermal condensate,

i9 flow from liquid gas separator 204 through pipe 205 to a stabilizer and high octane blending. l

As stated hereinbefore, an overhead comprising C6 to 250 F. E.B.P. hydrocarbons of the C6 to 380 F. naphtha ows from fractionator 173 through pipe 174 to pipe 225. A portion of the light naphtha, i.e., Cs to 250 F. fraction of the feed naphtha flows through pipe 228 to jet fuel storage tank 224. The balance of the light naphtha under control of valve 227 flows through pipe 226 to the suction side of pump 257. Pump 257 discharges the light naphtha into pipe 229 at a pressure in excess of the pressure in low pressure reactor 237. The light naphtha flows through pipe 229 to indirect heat exchanger 230 where the light naphtha is in indirect heat transfer relation with the effluent of low pressure reactor 242 flowing from indirect heat exchanger 232 through conduit 244. From indirect heat exchanger 230 the light naphtha flows through pipe 231 to indirect heat exchanger 232 where the light naphtha is in indirect heat transfer relation with the eiuent of low pressure reactor 242 flowing therefrom through conduit 243.

From indirect heat exchanger 232 the light naphtha iiows through conduit 233 to coil 234 in heater 235. At a point in conduit 233 intermediate to indirect heat exchanger 232 and heater 235 hydrogen-containing gas, such as reformer gas flowing from high pressure separator 204 through conduits 256 and 252 and low pressure reformer gas flowing from compressor 250 through coriduit 251 is mixed with the light naphtha in a proportion to provide a light naphtha charge mixture having a hydrogen to light naphtha mol ratio of about 4 to about l0. The light naphtha charge mixture ows from conduit 233 through coil 234 in heater 235 to conduit 236 and low pressure reactor 237.

The light naphtha charge mixture is heated in furnace 235 to a temperature to provide a vapor temperature at the vapor inlet of low pressure reactor 237 in the range of about 920 to about 980 F.

The light naphtha charge mixture ows downwardly through reactor 237 in contact with particle-form platinum-group metal reforming catalyst. The eiiiuent of low pressure reactor 237 flows through conduit 238 to coil 239 in heater 240 and thence through conduit 241 to low pressure reactor 242. In heater 240 the effluent of low pressure reactor 237, designated first low pressure etiiuent, is heated to a temperature such that the temperature of the reheated first low pressure effluent entering reactor 242 is the same as, lower than, or higher than, the temperature of the vapors at the inlet to the low pressure reactor 237 and in the range of about 900 to about 1025 F.

The reheated lirst low pressure eiiiuent flows downwardly through reactor 242 with particle-form platinum group metal reforming catalyst. The effluent of low pressure reactor 242 flows therefrom through conduit 243 to indirect heat exchanger 232, conduit 244, through heat exchanger 230, and conduit 245 to cooler 246.

In cooler 246 the effluent of low pressure reactor 242, designated final low pressure effluent, is cooled to a temperature at which at the existing pressure C4 and heavier hydrocarbons are condensed. The cooled final low pressure efuent iiows from cooler 246 through conduit 247 to liquid gas separator 248. In liquid gas separator 248 the uncondensed portion of the final low pressure eiiiuent, designated low pressure reformer gas, and comprising hydrogen and C1 to C3 hydrocarbons separates from the condensed final low pressure effluent. The low pressure reformer gas ows from liquid gas separator 248 through conduit 249 to compressor 250 where the low pressure reformer gas is recompressed to a pressure at least equal to that in conduit 233.

The condensed final low pressure eiuent comprising C4 yand heavier hydrocarbons flows from liquid gas separator 248 through pipe 258 to a stabilizer and thence to high octane blending.

As was stated hereinbefore vin the description of the treatment of the heavy naphtha it was assumed that sieve 188 was loaded with normal paraflins sorbed from a previous charge of heavy naphtha. The paratiinic sorbate is displaced from the molecular sieve material in 188 in any suitable manner. For the purpose of illustration, displacement of the sorbate is shown as by reducing the pressure. Thus, with valves 193 and 209 closed and valve 210 open the sieve 188 is connected to steam eductor 218. Accordingly, steam is introduced into eductor 218 and flows therefrom through conduit 219 to barometric condenser 220 and condensate pipe 221 thereby reducing the pressure in sieve 188 to a pressure less than atmospheric at which the sorbed normal parafiins of the heavy naphtha are volatilized at the temperature of the sieve. Accordingly, the volatilized normal paraflinic sorbate iiows from sieve 188 through pipe 190 (valve 195 closed; valve 210 open) to sieve sorbate manifold branch 212 and sieve sorbate manifold 213. The normal paraiiinic sorbate flows through sorbate manifold 213 to cooler 214 where the temperature of the sorbate is reduced to that at which hydrocarbons boiling in the range of 250 to 380 F. at atmospheric pressure are condensed. The condensed sorbate flows from cooler 214 through conduit 215 to liquid gas separator 216. In liquid gas separator 216 constituents of the sorbate boil-ing below 250 F. ow therefrom through pipe 217 to eductor 218. The condensed 250 to 380 F. hydrocarbons flow from separator 216 through pipe 222 under control of valve 223 to storage tank for jet fuel 224.

Reforming conditions in the low pressure reforming zone(s) and in the isothermal reforming zone are as set forth in Table I.

TABLE J Low PRESSURE SECTION Catalyst Broad Preferred Platinmtn-group metal, percent by 0.35 to 2.0 0.35 to 0.6.

weig Halogen, percent by weight Up to 1.0 Cllorine up to .7. Support, balance Rfratory Alumina.

Pressure, p.s.i.g

Temperature, F.

Liquid Hourly Space Velocity (v./hr./v.).

Hydrogen-to-light naphtha mol ratio.

10U-300. 920 to 980. l-2.

Up to 20 ISOTHERMAL SECTION 1. A method for producing a jet fuel having a luminometer number of at least about from a hydrocarbon fraction boiling in the range from about C5 hydrocarbons up to about 450 F. which comprises separating said hydrocarbon fraction at about its 250 F. boiling point into a lower boiling fraction and a higher boiling fraction, separately reforming said lower boiling fraction in the presence of particle-form solid platinum-group metal reforming catalyst at a liquid hourly space velocity below about 5, separately reforming said higher boiling fraction in the presence of particle-form solid platinumgroup metal reforming catalyst at a liquid hourly space velocity substantially above about 5, recovering a reformate product boiling above about C5 hydrocarbons from each of said separate reforming steps, separating the thus recovered reformate products into paraffinic and non-parainic hydrocarbons, and combining the separated paranic hydrocarbons obtained from said reformate products to produce a jet fuel having a luminometer number of at least about 150.

2. The method of claim 1 wherein the reformate prodnets are contacted with molecular sieve material having 4 to 5 Angstrom pores.

3. The method of 4claim 1 wherein the hydrocarbon fraction boils in the range of C5 hydrocarbons to about 380 F., wherein the higher boiling fraction is contacted with molecular sieve material having 4 to 5 Angstrom pores, wherein a sieve eluent comprising naphthenes substantially devoid of n-parans and a sieve sorbate hav-ing a luminomete-r number in excess of 150 are produced, and wherein said'sieve sorbate is mixed with the lower boiling fraction in proportions to produce jet fuel having a luminometer number of at least 150.

References Cited by the Examiner UNITED STATES PATENTS Barnum et al. 208-15 Hess et al. 208-93 Shuman 20S-310 Donnell et al. 20S-95 Ciapetta et al. 2018-15 Kimberlin et al. 20S-93 Hemminger 20S-95 Plummer 208-96 Franz 208-15 Kerr et al. 208-15 Woodle 208-15 Great Britain.

DELBERT E. GANTZ, Primary Examiner.

20 ALPHONSO D. SULLIVAN, Examiner.

Claims (1)

1. A METHOD FOR PRODUCING A JET FUEL HAVING A LUMINOMETER NUMBER OF AT LEAST ABOUT 150 FROM A HYDROCARBON FRACTION BOILING IN THE RANGE FROM ABOUT C5 HYDROCARBONS UP TO ABOUT 450*F. WHICH COMPRISES SEPARATING SAID HYDROCARBON FRACTION AT ABOUT ITS 250*F. BOILING POINT INTO A LOWER BOILING FRACTION AND A HIGHER BOILING FRACTION, SEPARATELY REFORMING SAID LOWER BOILING FRACTION IN THE PRESENCE OF PARTICLE-FORM SOLID PLATINUM-GROUP METAL REFORMING CATALYST AT A LIQUID HOURLY SPACE VELOCITY BELOW ABOUT 5, SEPARATELY REFORMING SAID HIGHER BOILING FRACTION IN THE PRESENCE OF PARTICLE-FORM SOLID PLATINUMGROUP METAL REFORMING CATALYST AT A LIQUID HOURLY SPACE VELOCITY SUBSTANTIALLY ABOVE ABOUT 5, RECOVERING A REFORMATE PRODUCT BOILING ABOVE ABOUT C5 HYDROCARBONS FROM EACH OF SAID SEPARATE REFORMING STEPS, SEPARATING THE THUS RECOVERED REFORMATE PRODUCS INTO PARAFFINIC AND NON-PARAFFINIC HYDROCARBONS, AND COMBINING THE SEPARATED PARAFFINIC HYDROCARBONS OBTAINED FROM SAID REFORMATE PRODUCTS TO PRODUCE A JET FUEL HAVING A LUMINOMETER NUMBER OF AT LEAST ABOUT 150.

Images