US2028121A - High octane number gasoline and method of manufacture - Google Patents

Description

Jan. 14, 1936. 0, COTTRELL 2,028,1 21

HIGH OCTANE NUMBER GASOLINE AND METHOD OF MANUFACTURE Filed May 13, 1932 Fig 1.

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Patented Jan. 14, 1936 HIGH OCTANE NUMBER GASOLINE AND v METHOD OF MANUFACTURE Osceola P. Cottrell, Scarsdale, N. 'Y., assignor to Edeleanu Gesellschaft of Germany m. b. 11., a corporation Application May 13, 1932, Serial No. 611,217

5 Claims. (01. 196-50) This invention relates to the manufacture of a motor fuel characterized by an especially high anti-knocking quality and consequent high 'octane number.

More specific-ally, it relates to a process which combines steps of cracking and treating with selective solvents, such as liquid-S02, or others, such as are known in the'industry, in suchmannet that a given amount of low boiling hydropurposes of illustration,

Fig. 1 is a flow diagram showing a multi-stage system of treatment; and

Fig. 2 is a flow diagram showing a recycling system of treatment.

Referring to Fig. 1, a cracking stock is cracked so as to form a cracked gasoline. Any method of cracking, liquid phase or vapor phase, at any temperature and pressure may be used.

The cracked gasoline is then separated into a low boiling fraction and a high boiling fraction.

, This may be done by distillation of the condensed gasoline, or may be. accomplished directly by taking the higher boiling fraction oil the usual bubble tower of the cracking apparatus as a liquid side stream, while the lower boiling fraction is taken from the top of the bubble tower as a vapor, and subsequently condensed. The cut may be made at any point, depending on the type of stock and the desired quality of the finished high octane number gasoline product, and is not restricted to any special temperature or gravity. 1

The high boiling fraction is then treated with a selective solvent, such as liquid-S02, or mixed solvent, in the well known manner. The liquid- S02, or like solvent, dissolves out the unsaturated and aromatic constituents and these are known as the extract, which is characterized by having a high octane number. The remainder, comprising substantially the saturated constituents, is known as the rafiinate, and being knock producing is characterized by having a low octane number. Both portions will contain some of the solvent and this is removed by evaporation in the usual manner.

The extract from the high boiling fraction is subjected to a suitable finishing treatment for the removal of impurities-such as sulfur compounds, gums, etc.,--and is blended with the low boiling fraction which has been similarly finished. The blend is a finished high octane number gasoline, and constitutes a very high quality of motor fuel. As a modification of this method, the low boiling fraction and the extract may be first-blended and then finished to produce the high octane number product.

Thus far the process is the same asthat de- 15 scribed in the patent to Edeleanu, No. 1,661,566, upon which it is an improvement. The present process, however, provides for converting the entire stock into high octane number motor fuel, that is, the raflinate from the high boiling fraction heretofore considered unsuitable for motor fuel because of its high boiling point and its knocking characteristic is also converted into a I high octane number gasoline suitable for motor fuel. This is accomplished according to the fol- 25 lowing method.

The rafiinate from the treatment with liquid- S02 or like solvent, applied to the high boiling fraction of the cracked gasoline is subjected to a cracking operation. This is readily and economically effected since the raflinate is comprised substantially of saturated hydrocarbons. The product, a cracked gasoline, is then subjected to the same process steps as was the original cracked gasoline stock. It is separated into a low boiling fraction and a high boiling fraction. The high boiling fraction is treated with liquid- $02 or the like, and the extract, after freeing from solvent and finishing, is blended with the finished low boiling extract to form a finished high octane number gasoline suitable for use as a high quality motor fuel. .The raifinate is treated in the same manner as the rafiinate from the original treatment, and so on over and over, until all of the original raifinate has-been converted into high octane number gasoline. v

The foregoing method illustrates my invention in its simplest form. In actual practice, however, instead of confining the successive stages of treatment to the successive rafiinats, each successive raiiinate would be mixed with a cracking stock and the admixture sotreated. This methad is shown in Fig. 1, by including the step of adding cracking stock represented by the dotted flow line. An'advantage of this procedure is sults in a cracked low sulfur gasoline.

Example -A Midcontinent cracked gasoline was separated by distillation into two portions, a fraction boiling below 347 F., and a higher boiling fraction. The yield of the low boiling fraction was 64.0% and that of the higher boiling fraction was 35.2% (distillation loss amounting to 0.8%). The high boiling fraction was treated with liquid- S02, resulting in an extract yield of 42% and a raifinate yield of 58%. The extract was finished and blended with the low boiling fraction which was first finished. The blend resulted in a 'finished gasoline having a greatly improved distillation range and a 45% increase in octane number over the original cracked gasoline. The end point of the finished gasoline thus manufactured was 444 F. and its octane number was 83.

The rafiinate, representing over 20% of the original cracked gasoline, was mixed with cracking stock and recracked together with such stock, and the resulting cracked'gasoline was subjected to the same series of steps as was the original cracked gasoline; and this procedure was repeated with each successive raffinate.

In this manner substantially all of the original cracked gasoline was converted into finished high octane number gasoline, whereas if my improved method had not been used, over 20% of the orig- -inal stock-the first rafiinatecould have been yield. The present invention resultsin a finished gasoline of such a favorable composition and distillation range that the end point may be considerably increased without adversely aifecting its volatility in the motor or octane number.

Previously it was necessary to produce cracked gasoline having an end point of 390-400 F. to obtain a desired octane number which by the present method is obtained from a 437 F. or higher, end point gasoline.

Fig. 2 shows a continuous recycling method for carrying out my invention. This process results in substantially all of a'cracked gasoline being converted into a high octane number gasoline, and all of the cracking stock employed is mixed with raffinate, so that cracking conditions are superior in .all cracking operations.

As in the first described method, the cracking stock is cracked into gasoline which is then separated into a low-boiling fraction and a high boiling fraction. The high boiling fraction is treated withliquid-SOg, or like solvent, and the extract blended with the low boiling fraction to produce the high octane number gasoline.

The distinguishing feature of this form of my invention is that the rafiinate is led back and introduced into the original cracking stock enter.- ing the cracking step of the process. Thus the rafiinate is continuously recycled and a given portion is therefore gradually converted substan tially in its entirety into high-octane number gasoline as a result of the successive crackings,

fractionations and selective solvent treatments.

to which it is subjected.

Fig. 2 also illustrates how the same principle may be used-for converting either a cracked gasoline or a straight run gasoline into high octane number gasoline. In this case the raflinate is cracked and'the resulting cracked raftinate mixed with the cracked gasoline or straight run gasoline entering the cycle (as shown by broken-line b'in Fig. 2), the mixture then being separated into a low boiling fraction and a high boiling fraction which are disposed of in the manner already described. No cracking stock is made use of, although, if desired, cracking stock may be simultaneously converted into high octane number gasoline by mixing it with the rafiinate'to be cracked, as is evident from Fig. 2 and the foregoing description.

It will be apparent to those skilled in the art that my invention may be applied in many other ways. For example, in practically all cracking processes a recycle stock is obtained, being generally drawn off from the bottom of the bubble 'tower of the cracking plant. This recycle stock, containing such high boiling hydrocarbons as are not normally usable, is led back and recracked with raw cracking stock in order that it may be broken up into lower boiling hydrocarbons. As shown in Fig. 2, this procedure may be combined with the foregoing embodiments of myinvention as follows: Instead of mixing the raifinate directly with new cracking stock and cracking the admixture, the raffinate is mixed with the recycle stock from the cracking plant (indicated by broken line a in Fig. 2) and this admixture is mixed with new raw cracking stock and the combined mixture subjected to cracking. The cracked gasoline product is then subjected to the same process steps already described.

My invention obviously is not restricted to the embodiments thereof illustrated and described,

but what I claim is as follows:

1. A continuous process for converting sub-' stantially all of a straight run gasoline into high octane number gasoline, comprising the steps of separating the gasoline into a low boiling fraction and a high boiling fraction, treating the high boiling fraction .with liquid-S02 or like solvent, separating the raflinate and extract, removing the solvent therefrom, cracking the rafiinate, re-

, cycling the cracked raflinate by mixing it with the straight run gasoline stock entering the cycle and blending said extract with said low boiling fraction to produce the high octane number' gasoline.

2. A process for the manufacture of high octane number gasoline comprising mixing the liq- Hid-S02 insoluble hydrocarbons from the high boiling portion of a straight run gasoline with cracking stock containing both saturated and unsaturated hydrocarbons, cracking the mixture to form a cracked gasoline, dividing the latter 2,oae,121

boiling fraction with liquid-S02 or like solvent,

separating the raflinate and extract, removing the solvent therefrom, blending said extract with said low boiling fraction to form a high octane number gasoline, mixing said raflinate with cracking-stock containing both saturated and unsaturated hydrocarbons, cracking the mixture so as to form a cracked gasoline, subjecting the latter to the foregoing sequence of steps described for the straight run gasoline, and in like manner treating the successive rafiinates resulting from continuing the process herein set forth.

4. A continuous process for converting substantially' all of a straight run gasoline into high octane number gasoline, comprising the steps of separating the gasoline into a low boiling fraction and a high boiling fraction, treating the high boiling fraction with liquid-SO: or like solvent, separating the raffinate and extract, removing an the solvent therefrom, mixing the rafiinate with cracking stock and cracking the mixture to form a cracked gasoline, mixing the latter with straight run gasoline entering the cycle, and blending said extract with said low boiling fractionto produce the high octane number gasoline.

5. A continuous process for converting substantially all of a straight run gasoline into high octane number gasoline, comprising the steps of separating the gasoline into a low boiling fraction and a high boiling fraction, treating the high boiling fraction with liquid-S02 or like solvent, separating the raflinate and extract, removing the solvents therefrom, cracking the raflinate in admixture with recycle stock from the cracking step to form a cracked gasoline, mixing the latter with straight run gasoline entering the cycle, and blending said extract with said low boiling fraction to produce the high octane number gasoline.

OSCEOLA P. CO'I'I'RELL.

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