US2146039A - Method of improving naphtha - Google Patents

Description

Feb; 7, 1939. J. M. WH|TELE Y 2,146,039

METHOD OF IMPROVING NAPHTHA Filed Nov. 29, 1935 LIGHT ENDS SUPER HIGH TANE GA SOLINE RAW AVIATION GASOLINE. FINAL k' GASQLlNE TREATERS EXTRACT HIGH ocmue EXTRAQTR on TANKS EXTRHCT OCTF? NE Patented Feb. '7, 1939 UNITED STATES METHOD OF IMPROVING NAPHTHA James M. Whiteley, Roselle, N. .L, assignor to Standard Oil Development Compa y, a corporation of Delaware Application November 29, 1935, Serial No. 52,048

3 Claims.

My invention relates to methods for treating motor fuels or hydrocarbon mixtures of the naphtha boiling range which are converted into motor fuels for the production therefrom of motor fuels 5 of high octane number. More particularly, my

invention is directed to improvements in processes in which a naphtha is extracted witha selective solvent for the production of an extract having a high knock rating.

In recent years, due to the development of high .compresslon engines, one of the chief problems of the oil refiner has been to eliminate from motor fuels the tendency to knock, which is intensified in high compression motors. To that end considerable research has been conducted to devise methods for imparting to motor fuels the highest possible immunity to knocking. The tendency of a fuel to knock is indicated by its knock rating,

' which is usually given as an octane number and is based on the knocking caused by a given fuel and to employ the extract so obtained as a blend- 1 ing agent for fuels which require octane number 30 improvement. A common practice has been to send the rafiinate of such an extraction, particularly that portion thereof which boils above 200 F., to an ordinary cracking coil where it is mixed with the cracking stock and subjected to high 5 temperature and pressure.

I have found that the rafilnate from such an extraction, whether the solvent be liquid sulfur di-oxide or a solvent having similar selectivity;-

constitutes an excellent material for treatment 40 with a catalyst under conditions conducive to dehydrogenation. When so treated, the raifinate is converted into a material having a high octane blending value and may be further extracted with sulfur di-oxide, or a similar solvent, to yield an 45 extract having an even higher octane blending value.

When a highly naphthenic naphtha is subjected to my process it is preferable to subject the product of the dehydrogenation to extraction 50 with liquid sulfur di-oxide, or a similar solvent, and then again subject the rafiinate of such an extraction to dehydrogenation. When the stock to be treated contains appreciable percentages of open chain unsaturates, it will be preferable to 55 pass it in the vapor phase over clay at a temperature of about 500 1". before introducing it into the dehydrogenation chamber. In this way the activity for the dehydrogenation catalyst can be prolonged.

In general, the catalytic treatment employed 5 according to my invention is conducted at temperatures between about 900 and 1100 F., preferably between 950 and 1050 F. The pressure most commonly employed is atmospheric, but may be reduced to any desired extent. The catalyst 10 employed is one of the known dehydrogenation catalysts. Among these may be mentioned refractory metal oxides, such as alumina, thoria, oxides of metals of Groups V and VI, and mixtures of such refractoryoxides. Phosphates and meta- 15 phosphates exhibit activity in the desired direction. vaporous catalysts, such as readily vapor- -tion are disclosed in Patent Nos. 1,844,998,

1,851,726, 1,881,692, 1,900,739, 1,910,910, 1,913,940, 1,913,941, 1,937,619, 1,938,086, 1,955,829, 1,975,476. A particularly desirable procedure giving very high yields of high anti-knock gasoline, according to my invention, consists in first removing the light ends from a naphtha, such as a raw aviation gasoline, subjecting the heavy ends; to extraction. with sulfur dioxide, adding the extract to the light ends'initially recovered, subjecting the rafilnate to the catalytic treatment described above, and adding the thus treated rafiinate to the mixtureof light ends and initial extract. A fuel having an evenbetter knock rating can be obtained by subjecting the catalytically treated raflinate to a second extraction and returning only this second extract to the blend of the first extract and the light ends initially recovered.

The hydrocarbon mixture may be subjected to the solvent extraction step'in either the liquid 40 or the vapor phase. The latter procedure may be readily effected by conducting the vaporous products from the catalytic dehydrogenation step upwardly through a packed tower in countercurrent to the solvent, or by bubbling saidvaporous products through a deep layer of the solvent,

2 preferably while the latter is maintained in a state of violent agitation. When the solvent employed is normally a gas, such as sulfur dioxide, it is convenient to mix it with the vaporous products of the catalytic dehydrogenation step and subject the mixture to compression and cooling to form two layers of condensate. The lower the temperature to which the mixture is cooled the smaller will be the volume of extract and the better .55

will be the octane number blending value of the extract.

In the accompanying drawing a front elevation of a plant adapted for the carrying out of either of the above referred to processes is illus trated in diagrammatic form. The drawing bears appropriate legends which render unnecessary further description thereof.

In a practical embodiment of the present invention two samples of aviation naphtha heavy ends, derived from QuiriQuiri. crude and Lagunillas crude respectively, were extracted with S02 at 22 F. The rafiinates were catalytically dehydrogenated in a once-through operation in the vapor phase at atmospheric pressure and at 1000 F. in the presence of a catalyst composed of magnesite carrying oxides of zinc, lead and chromium. The dehydrogenated rafiinate thus obtained was extracted with aniline at F. The extracted naphtha was recovered from the aniline extract by distillation. The results of this procedure were as follows:

It will be noted that from the QuiriQuirl naphtha only 4.2% of a naphtha, having an octane number of 79.4, was obtained, and that whereas the S02 rafiinate had an octane number of only 67.0 and the catalytically reformed rafiinate had an octane number of only 65.0, this raffinate, on extraction with aniline, yielded 22.6% of a naphtha having an octane number of 74. Thus the catalytic dehydrogenation and extraction of the S02 raffinate increased the yield of high octane number gasoline by over 500%. A similar comparison of the data on Lagunillas naphtha shows that the catalytic dehydrogenation and solvent extraction of the S02 raffinate increased the yield of good octane number gasoline by 200%.

A 200-300 F. cut of a West Texas naphtha, said out having an octane number according to the C. F. R. method of 58.4, was passed over a catalyst prepared by impregnating magnesium oxide with water-soluble salts of lead, zinc, and chromium, and roasting the composition so produced to form the oxides of the metals at a temperature of about 1020 F. The resulting product was extracted with of aniline at 74 .F. The extract, on separation from the aniline, constituted 48% of the original 200-300 cut and had an octane number of 62. When the extraction with aniline was carried out at 25 F. the resulting extract constituted 28% of the ZOO-300 cut and had an octane number of 66.4.

A Lagunillas naphtha having an octane number of 52 C. F. R. method was passed over the same catalyst employed in the preceding example under the same conditions. A 200-300" F cut of the product had an octane number of 66. This cut was extracted with of aniline at 71 F. A product constituting 25% of the out had an octane number C. F. R. of 76.4. The original Lagunillas naphtha, when extracted with aniline under the same conditions, gave 25% of an extract having an octane number of 70.1.

The above examples illustrate the nature of the improvement effected by the present process. They are not intended toneijne the extent of the improvement which may' beeffected according to this process. The extent to which octane number improvement can be eifected will vary with the catalyst employed in the reforming step, and the solvent and the temperature employed in the extraction step. A great variety of catalysts and a very large number of solvents are available for use in this process. The 'use of these various catalysts and of these various solvents is contemplated for the exercise of the present inventanol method, can, in some cases, be almost doubled. This improvement in solvent power by the same method which improves octane number is not readily explainable because improvement in solvent power is not necessarily concomitant with improvement in octane number. It is known, for example, that an increase in'the branchiness of open chain, compounds increases octane number but does not affect solvent power as measured by the kauri butanol value.

Without attempting to ofler an explanation for the utility of the present process both for increasing octane number and increasing solvent power, I wish it to be understood that I contemplate the use of the process for both purposes.

A Conroe naphtha was extracted with liquid I sulfur dioxide. The raflinate obtained by separation of the layers had a solvent power, as measured by the kauri butanol value of 34, an octane number of 51.5, an A. P. I. gravity number of 57.4 and an aniline point of 131 F. This ramnate was subjected to dehydrogenation under the conditions and in the presence of a catalyst in the first example above. The product of the dehydrogenation had a solvent power, as measured by the kauri butanol value, of 43, an octane number of 66.5, an A. P. I. gravity number of 52.5, and an aniline point of 87.5. In general, the dehydrogenated stock best suited for solvent purposes is a fraction boiling between 100 and 350 F. For certain purposes a narrower fraction boiling between 200 and 300 F. is most desirable.

- Having thus described the nature and objects of my invention and given practical illustrations of the same which, however, are not intended to define the scopeof my invention, what I claim as new and useful and desire to be secured by Letters Patent is:

1. The process of improving the octane number of motor fuel containing parafinic and nonparaffinic constituents which comprises treating said motor fuel with a selective solvent having a relatively higher solvent power for nonparaflinic constituents than for said paraffinic constituents to thereby separate said motor fuel into a fraction relatively rich in paraffinic constituents and a fraction containing said nonparaflinic constitu- -ents and solvent, passing said paraffinic fraction at a temperature between about 900 and 1050 FL over a dehydrogenating catalyst for a time sufllcient to materially improve the anti-knock properties of said fraction.

2. A process for increasing the octane number of motor fuel containing parailinic and nonparaflinic constituents. which comprises initially treating said motor fuel with a selective solvent having a relatively higher solvent power for nonparafilnic constituents than for parafiinic constituents to thereby separate the motor fuel into a paraflinic raifinate fraction and a nonparaffinic extract fraction, passing said raflinate fraction at a temperture of between 950 and 1050 F. over a dehydrogenating catalyst, and regulating the time of contact of said catalyst to materially improve the octane number of said fraction.

3. In a process for improving the octane number of motor fuel containing paraflinic and nonparaflinic constituents wherein the motor fuel is initially separated into a light naphtha fraction and. a heavy naphtha fraction and the heavy naphtha fraction subjected to treatment to improve the anti-knock properties; the improvement which comprises treating said heavy naphtha fraction with a selective solvent having a relativelyhigher solvent power for nonparafiinic constituents than for paraffinic constituents to thereby separate said fraction into paraflinic raflinate fraction and a nonparaffinic extract fraction, passing said paraflinic raifinate fraction over a dehydrogenating catalyst and regulating the temperature and time of contact of -said catalyst to materially improve the octane number of said fraction and thereafter blending the product resulting from said treatment with said light'naphtha fraction to produce the desired motor fuel.

JAMES M. WHITELEY.

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