US2651597A - Process for improving the octane number of light naphthas - Google Patents

Description

Patented Sept. 8, 1953 PROCESS FOR IMPROVING; THE OCTANE NUMBER OF LIGHT NAPHTHAS Eugene S. Corner, Maplewood, and Fred B. Fischl,

Rahway, N. J assignors to Standard Oil Development Company, a corporation of Delaware I Application January 18, 1950, Serial No. 139,208

3 Claims. (Cl. 196-50) v This invention relates to the treatment of by I drocarbon oils boiling substantially in the gasoline boiling'range for the purpose of producing therefrom fuels of improved octane number. The invention is more particularly concerned with a flexible combination of fractionation and catalytic treatments whereby the nature and severity of "the respective catalytic treatments are adjusted according to the characteristics of the particular fraction treated so that a fuel of optimum quality may be produced. The catalytic treatments in question are catalytic hydroforming and catalytic isomerization and catalytic aromatization.

The term hydroforming wherever used in the specification and claims shall be understood to means any process of subjecting material consisting essentially-of hydrocarbons substantially boiling in the gasoline range to treatment at an elevated pressure above about 50 lbs/sq. in. at a temperature in excess of 500 F. and in the presence of catalysts and added hydrogen containing gas to produce a dehydrogenated or otherwise chemically reconstructed product, for

example, of anti-knock characteristics superior to those of the starting material. By the term chemically reconstructed" is meant something more than the, mere removal of impurities or ordinary finishing treatments. The amount of added hydrogen containing gasis in the range from 1000 and 5000 cubic feet per barrel, preferably from 1500 and 3000 cubic feet per barrel of feed. In the hydroforming reaction, various reactions occur, for example, reactions such ras dehydrogenation, aromatization or cyclization, cracking, hydrocracking, hydrogenation, desulfurization and alkylation, all or some of which may occur to a greater or lesser extent during the process. Hydrogen is one of the products of the hydroforming reaction.

The term catalytic isomerization wherever used in the specification and claims shall be understood to mean any process of subjecting materials consisting essentially of hydrocarbons substantially boiling in the gasoline range to heat treatment in the liquid or vapor phase and in the presence of a catalytic material to produce a product containing isomeric forms of the hydrocarbons.

The term catalytic aromatization wherever" used in the specification and claims shall be understood to mean any process of subjecting materials consisting essentially of hydrocarbons substantially boiling in the gasoline range to heat treatment at a temperature in excess of 500 F.- and in the presence of solid catalysts whereby cyclodehydrogenation reactions predominate to those of the starting material.

ample, a pressure in' the range from 0110," 50'.- lbs./sq. in. gage, preferably a pressure approach-. ing atmospheric. Optimum aromatization and conversion are obtained in the absence'of added hydrogen; However, small amounts of hydrogen. or hydrogen-rich gas such as from 0 to 1000i cubic feet per barrel of feed may be introduced for 'the purpose of lowering the carbon deposi tion on the catalyst.

In accordance with the present invention, a. hydrocarbon oil boiling in the gasoline range, such as light naphtha for example, is fraction-, ated into four fractions and each of these frac-; tions is subjected to one or more of the various catalytic treatments best suited to give the maximum increase in anti-knock value of the par,-,. ticular fraction. The manner in which the process is carried out will be more fully understood from the following description in connec--, tion with the accompanying drawingsin which- Figure 1 is a diagrammatic view of one type of suitable apparatus showing the lines of flow and Figure 2 is a diagrammatic view of a second embodiment of the present invention.

Referring to the drawing, a virgin naphtha from source I is passed by line 2'to distillation" zone 3, Where it is subjected to fractionation conditions to yield an overhead fraction boiling up to 158 F., a light side out boiling from 158 to 200 F., a heavy side out boiling from, 200 to" 211 F. and a bottoms fraction boiling. above. 211 F. The overhead fraction is passed by line 4 to reactionzone 5 which contains anhydrous aluminum chloride, aluminum chloride-hydrocarbon, sludge, aluminum bromide, or other isomerization catalysts.

Reaction zone 5 is maintained under isomeri za. tion conditions. When employing aluminum chloride catalyst, the pressure may be between 50 and 300 lbs/sq. in. and the average temper.-

* ature between 120 and 250 FL Small amounts of hydrogen and anhydrous hydrogen chloride or other catalyst modifiers and activators such as; water may be introduced through line 6. Reac-i tion products leave reaction zone 5 through line 1. v A light side stream fraction boiling at 158 to 200 F. is removed from distillation zone 3" through line 8. This fraction contains large amounts of alkyl-cyclo-pentanes', cyclo-hexanesi and methyl-hexanes. This fraction is passed to? isomerization reaction zone 9 similar in all re-- spects to reaction zone 5. In reaction zone 9 the C5 naphthenes are converted to C6 naphtheneswhich are very effective feed stocks for the hydroforming reaction. The isomerized materials are removed overhead from tower 9 through line 10 and combined with the bottoms from tower 3 boiling above 211 F. This mixture is then introduced by line I3 into hydroformingreaction zone l 4.. Reaction zone I4 is maintained under-'- pressure between 50 and 500 1bs../sq. prefer: ably between 150 and 400 lbs/sq. in. and at a temperature between 800 and 1050 F., preferably between 900 and 1000 F. The rate of flow of the mixture through the reaction zone is between 02 and volumes of liquid per volume of catalyst per hour. Rates between 0.3 and 3.0 volumes of liquid feed per volume of catalyst per hour are preferred in most. cases. An amount of gas containing free hydrogen should be intro duced along with the liquid mixture ranging between 1000 and 5000 cubic feet of gas per barrel of liquid feed, preferably between 1500 and 3000 cubic feet. The gas should contain between 20 and 90 mol percent of free hydrogen preferably between 50 and 80 mol percent. The catalyst in reaction zone I4 may comprise any one ormore of the many materials which promote hydroforming. Among these. may be mentioned compounds such as the oxides or sufides or the metals of the 4th, 5th, 6th and 8th, groups of the periodic system, especially the oxides of vanadium, molybdenum, chromium, tungsten, COball and nickel, These compounds may be used alone various mixtures or combinations with each other or in combination with carriers or supporting materials, such as alumina, alumina gel, Deptized alumina gel, zinc alumina spinel, vari- 011$ types of clays, etc. Particularly suitable catalysts are mixtures of aluminum and chrommm oxides, aluminum and molybdenum oxides, aluminumand vanadium oxides, in which the active metal oxide prefera ly c mp f m 1 to 50% by weight of the mixture. Products leave reaction zone l4 through line. and are co bined with the products. leaving reaction zone 5 through, line I.

Returning now to distillation zone 3. a heavy side stream fraction boiling between 200 and 211 F. is removed through line I6 and passed to aromatization reaction zone 11. Reaction zone [1 is maintained under relatively low pressure, preferably atmospheric but not above about 5.0 lbs/sq. in. gage and at a temperature between 800 and .1050 F., preferably between 90.0 and 1000" F. Asuitable catalyst for this reaction is a mixture of chromium and aluminum oxides, preferably containing promoters such as potassium and cerium oxides. Products from this reaction zone are removed through line l8 and combined with the products removed from reaction zones 5 and I4 flowing through line '1. The combined .eilluents from reaction zones 5, l4 and I1 are passed to storage and yield a motor fuel of optimum anti-knock properties.

In alternate embodiment of the invention, referred to in Figure 2, the heavy side out B. P. 200-211 .F. in Line 4 is combined with the overhead fraction in line 4 and the combined streams are isomerized in reaction zone 5. In this embodiment of the invention the aromatization reaction zone H of Figure 1 is omitted and the side out of ZOO-211 F. boiling point, consisting predominantly of low octane number normal heptane. is converted to high octane number isomers in isomerization zone 5. The efiluents from isomerization zone 5 and hydroforming zone H flowing through lines 1 and 15 respectively are combined to form the final motor fuel of high anti-knock quality.

The following data illustrate the advantages to be obtained according to this invention: u

,A light virgin naphtha was fractionated into 4 fractions. the first boiling up to 158: F.

and containing cyclopentane and normal and 4 branched hexanes; a ec nd. boiling be ween .158 and 200 F, and containing alkylcyclopentanes, cyclohexanes, and methylhexanes; a third -fraction boiling between 200 and 211 F. comprising normal heptane and a bottoms fraction consisting of virgin naphtha boiling above 211 F. The fraction boiling up to 158 F. consists almost entirely of normal and branched hexanes which have very poor hydroforming characteristios with the result that conventional hydroforming of this fraction is undesirable since the hydrocarbons are not converted readily to aromatios; and give excessive dry gas yields at elevated pressures as is illustrated by the following ata:

Hydroforming of isomeric hemdnes at 215 p. s. i. g.

[90ZnOi.A1iO=10-Mo0ica a yst; 900 F4 2.1-2.5 r/HQ mol ratio;

1.0 v./v.hr.; 1.0 hr. periods] Hydrocarbon n-Efexane 2-Methyl- 2,3-Di- 2,2-Di- D ntane methylmethylbutane. but ne Conversion, Percent 11 l3 l8 9. 0 Selecttivities, Wt. Per- 11, 6. 2 0.0 10 lefin 3. 7 18 11 3. 8. Gas 84 8d 86 Carbon 1. 0 1.5 3.3 6 3 Yields:

Aromatics, Vol. Percent 1. 3 0.6 0 0. 7 Oleflns, Vol. Percent 0.6 1. l, 1.9 0.4 Gas, Wt. Pereent-. 8. 9 11 15 7. 2 Carbon, Wt. Percent. 0 2 0.2 0.6 0.5

The fraction boiling between 158 and 200 F.

contains a large percentage of alkylcyclopentanes and is upgraded most effectively by isomerizing the C5 naphthenes to C6 naphthenes, the latter possessing very superior hydroforming characteristics. To show the effect of isomerization prior to h-ydroforming, a light East Texas naphtha fraction boiling between 150 and 200 F. was passed over a catalyst consisting of A1203;Z1JO and 10% M00; at a temperature of 950 E, at a rate of flow .of 0.75 volume of feed per volume of catalyst per hour and in the presence of 2.5 moles of hydrogen per mol of hydrocarbon. The following data were obtained:

fieeifi .Of isomerzzction prior to hydroforming on upgrading of a. light East Texas naphtha [Boiling range loo-200 F.; 90 Zl10.AhOa-1O M00; catalyst; 950 F.

0.7a v./-v. hm; 2.5 H1130 mol ratio; 24 hr. periods.)

Isomerization No Yes N 0 Yea Pressure, 1). s. i. gm, 5O 50 215 215 Conv sion, Forc 44 64 41 56 Selecfi-vitieg, Wt P roma 108., 55 74 64 79 Qlefins... 20 6.10 7. 7 2. 3 835i)... '1? 0 1; 9 27 17 or on 1. 5 Yields: 1 4

Aromatics, wt. Percent 20 38 21 37 lefins, Vol. P rcent...-

8. 5 3. 6 3. l 1. 3 Gas, wt. Perccnt.... 8.0 l0 l1 9. 5 Garbon, wt. Percent 3. 'l l. 8 0. 6 0.8 O +Liquid ie1d, Vol Percent .1. 8.6 84 '87 87 O. N.-GFR-R 72. 5 87. 0 94. 2 S3. 0 93. 0 Octane Number Increment.-- 14. 5 21. 1 1o. 5 20. 5

The above data show that when the fraction boiling between and 200 F. was isomerized prior to hydrotorm-ing a 10.5 CFR-Research Oc- 5 tane Number advantage was obtained over hydroforming without isomerization. Furthermore, the combination process resulted in a marked reduction in carbon formation at 50 lbs/sq. in. gage.

The fraction boiling between 200 and 211 F. (nearly pure normal heptane) was aromatized by passing it at relatively low pressures over a chromia-alumina catalyst promoted with potassium and cerium oxides having the following composition:

10.3% Cr2O3 1.04 potassium oxide 0.4% cerium oxide The results obtained by this process are compared with those obtained by hydroforming the same fraction at 215 lbs/sq. in. over the alumina zinc molybdena catalysts used in the hydroforming of the fraction boiling between 150 and 200 F. The results obtained are shown in the following table:

TABLE Comparison of memorization and hydroforming of n-heptane over promoted chromia-alumina and aZumina-zinc-molybdena catalysts [1.0 v./v. 1m; 1.0-1.5 hr. periods] Process Aromatization Hydroforming Catalyst Or/Al Or/AI" (Jr/Al Mo/Zn/Al" Temperature, F 900 900 950 900 Pressure, p. s. i. g 0 0 50 215 H9110, Mol Ratio 0 2. 2 -2. 5 -2. 5 Conversion, percent-. 52 27 15 23 Selectivities, Wt. percent:

Aromatics, vol.

percent 30 9. 6 0. 9 5. 1 Olefins, vol. percent 8. 5 10. 0 7. 6 1. 3 Gas, wt percent- 5. 2 3. 9 5. 5 15 Carbon, wt. percent 0. 9 0. 3 0. 2 0. 4

no.3 Cher-89.7 A1,o3+1.04% K and 0.4% Ge. "90 A1103. Zno-10 MoOa.

Equivalent to approximately 2,500 cu. ft. of hydrogen per barrel of liquid feed.

The above data indicate that the chromia-alumina catalyst is more than twice as active under low pressure aromatization conditions as the alumina-molybdena catalyst under conventional hydroforming conditions at high pressure and is more selective to aromatics as shown by aromatic selectivities of 71 and 29% respectively. The additional advantage of the chromia-alumina catalyst is its low dry as selectivity (10 weight percent at atmospheric pressure as compared with 63% for the alumina molybdena catalyst at 215 lbs/sq. in. gage). The data also show that the addition of relatively large amounts of hydrogen, forexample 2200-2500 cubic feet per barrel of feed in aromatization decreases both conversion and selectivity to aromatics. The data also show that better results are obtained when the pressure is maintained less than 50 lbs/sq. in.

The nature and objects of the present invention having been thus fully set forth, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. Process for improving the anti-knock value tane fraction boiling 158 to 200 F., a normal heptane fraction boiling 200 to 211 F., and a heavy naphtha fraction boiling above 211 F., isomerizing the hexane fraction, isomerizing the alkylcyclopentane fraction, combining the isomerized alkylcyclopentane fraction with the heavy naphtha fraction, hydroforming the combined fraction, aromatizing the normal heptane fraction and combining the isomerized normal hexane fraction, and the aromatized and hydroformed fractions as the final improved motor fuel.

2. Process according to claim 1 in which the isomerization steps are carried out in the presence of an aluminum chloride catalyst in which the aromatization step is carried out at a temperature in the range 900 to 1000 F., and substantially atmospheric pressure, in the presence of a chromia-alumina catalyst, and in which the hydroforming step is carried out at a pressure in the range from about to 400 pounds per square inch gage at 900-1000 F. in the presence of an alumina-molybdena catalyst.

3. Process according to claim 2 in which the chromia-alumina catalyst is promoted with p0- tassium and cerium oxides.

EUGENE S. CORNER. FRED B. FISCHL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,276,171 Ewell Mar. 10, 1942 2,304,187 Marschner Dec. 8, 1942 2,337,601 Hays Dec. 28, 1943 2,379,334 Atwell June 26, 1945 2,396,331 Marschner Mar. 12, 1946 2,417,699 McAllister et a1. Mar. 18, 1947 2,420,086 McAllister et a1. May 6, 1947 2,420,883 Johnson et a1. -1-" May 20, 1947

Claims (1)

1. PROCESS FOR IMPROVING THE ANTI-KNOCK VALUE OF LIGHT VIRGIN NAPHTHA AS MOTOR FUEL WHICH COMPRISES FRACTIONATING THE NAPHTHA INTO A HEXANE FRACTION BOILING UP TO 158* F., AND AN ALKYLCYCLOPENTANE FRACTION BOILING 158 TO 200* F., A NORMAL HEPTANE FRACTION BOILING 200 TO 211* F., AND A HEAVY NAPHTHA FRACTION BOILING ABOVE 211* F., ISOMERIZING THE HEXANE FRACTION, ISOMERIZING THE ALKYCYCLOPENTANE FRACTION, COMBINING THE ISOMERIZED ALKYLCYCLOPENTANE FRACTION WITH THE HEAVY NAPHTHA FRACTION, HYDROFORMING THE COMBINED FRACTION, AROMATIZING THE NORMAL HEPTANE FRACTION AND COMBINING THE ISOMERIZED NORMAL HEXANE FRACTION, AND THE ARMOMATIXED AND HYDROFORMED FRACTIONS AS THE FINAL IMPROVED MOTOR FUEL.

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