USRE20596E - Process fob - Google Patents

Description

Reissued Dec. 21, 1937 UNITED STATES Re. 20,596 PATENT OFFICE PROCESS FOR Jack Francis Mahon Taylor MANUFACTURING MOTOR FUEL and Bernard Sutro reensfelder, San Francisco, and Russell Norman Shiras, Long Beach,

mesne assignments, of one-half to Shell Development Company,

direct and Cahf., assignors, by

San Francisco,

Calif., a corporation of Delaware, and one-half to Phillips Petroleum Company,

Bartlesville,

0kla., a corporation of Delaware No Drawing. Original No. 2,055,455, dated September 22,

Serial No. 167,250

11 Claims.

ties within comparatively wide limits can be obtained. The great importance attached to the anti-knock rating of a motor fuel is well known, while the means for developing this property are few generally known methods, such as cracking, hydrogenation, or suppressing the knocking tendency of a fuel by adding one of whose sole purpose, is to increase its anti-knock rating.

Being effective for this purpose to various degrees these compounds possess certain disadvantages such as toxic effects, tendencies to crystallize out at low temperatures, to form sludges or coatings in or on the engine, to cause deposition of gums from the fuels, or tocorrode parts of the apparatus. There has been, therefore, a constant trend in the art to develop a process for obtaining an anti-knock fuel without adding any foreign material, and investigators have turned more and more to the processes effecting certain changes in the constitution of mineral oils, which processes afford great possibilities in the field of producing the non-detonating fuels of high quality without employment of the extraneous agents.

These general methods of raising the antiknock ratings of gasolines are all improved upon by the instant invention, insofar as it provides a method for further raising the anti-knock ratings of gasoline with. simultaneous decrease in vapor pressure, if desired, and/or increase in volatility. The vapor pressure of a motor fuel, as measured under specific conditions, determines the tendency of this fuel to cause vapor lock; desirable, therefore, to produce a fuel with as low a vapor pressure as possible. On the other hand Application for reissue decreasing the vapor pressure. pentanes and lighter may be removed and the 40 1936, Serial No. 607,010, April 22,

October 4, 1937,

the requirement of a certain degree of volatility, as commonly measured by the 10% distillation point, in order to insure quick starting of, the motor at low temperature, sets a minimum limit beyond which the vapor pressure cannot be reduced. In the manufacturing of the light motor fuels the efforts are directed, therefore; to provalues. It is the compromise in meeting the opposing requirements of vapor pressure, volatility and anti-knock ratas is permissible by the vapor pressure limitations. The present invention solves the problem of This involves separation by fractional distillation into groups possessing well-defined influences upon the final character of the fuel, and subsequent selection substituted for butanes and lighter to maintain or increase the knock rating and volatility while Or, secondly the and volatility.

The light fractions suitable for this purpose must necessarily have a vapor pressure lower 45 7 present practice, therefore, to 15 certain light 35 the concentration of the components 50 removal of one or more of the scribe more fully one form tions, one or more compounds having compara-- tively high anti-knock ratings and low vapor pressures, and third, blending these narrow boiling fractions with the residual portion of the original distillate'which remained after the undesired detonating, and/or high vapor'pressure compounds were removed.

Accordingly, we can successfully treat by our method any mineral oil distillate either derived from a natural gas, or crude oil, or shale, or produced by one of the commercial processes such as pyrogenetic treatment or hydrogenation of the carbonaceous materials, including petroleum oils and fractions, derivatives, and mixtures of fractions and derivatives of such oils. Various properties of the treated distillate may be further modified by adding thereto one or more of the substances generally known as dopes.

As a matter of illustration, and in order to deof our invention, the manufacturing a following .speci c example of motor fuel of the improved quality is set forth.

and had the octane In this particular case, a normal aviation gasoline fraction was produced from natural gasoline. This fraction was at 50 C. still head temperature to effect substantial removal of the light hydrocarbons including propane, butanes and pentanes. The collected distillate was then fractionated and the fraction boiling at substantially 2832 C. separated; this fraction in which the iso-pentane predominated to a large extent is hereafter callediso-pentane fraction; as manufactured, it had a markedly low vapor pressure, viz, 255 mm. at 0 C., as compared to that of the next lower boiling component, n-butane, having vapor pressure 770 mm. at

C.; furthermore, it had a remarkably high anti-knock rating of 84 octane number, when compared to the next higher boiling n-pentane fraction which has been removed from gasoline number of about 60. These two properties, viz, low vapor pressure and high anti-knock rating, render theiso-pentane fraction a very desirable substitute for the 'n-pentane, and butane and lighter fractions in the finished gasoline. It is worthy of special note that the low vapor pressure of this fraction, or that of the pure iso-pentane, makes possible their use in large proportions in various fuel mixtures without an excessive rise in the vapor pressure of the resulting product, but with the corresponding marked increase in the volatility and anti-knock rating. particular illustrative case follows:

Fiendgefidygasm me: 0 ISO- Impection Mum Top d ntaneiraction gasoline gasom e topped gasoline Specific gravity F 7309 7m .7139 A. S. '1. M. distillation:

I. B. P 47 77 40 a" 96 87 W7 1H 1 ii! I. is. r 139 131 Percent distilled. 97. 5 V P. Reid at 5. 2 Octane Nbi' Dclco 74L 0 This illustrative example shows the manner in dephlegmated or. topped The specific information relative to this which the anti-knock rating and volatility of a gasoline has been increased by selective fractionation of the raw stock and subsequent. compounding'of the finished product.

The iso-pentane fraction which can be used for improving the properties of a gasoline may be defined by its composition which may be determined from the distillation in an efficient fractionating apparatus, and can be produced from various sources, such as natural-gas, crude oil, products of cracking and hydrogenation, chemical synthesis, etc. In general, it preferably should contain at least 60% (mol. basis) of isopentane (B. P. 27.95 0.), the balance consisting of. the slightly lower and higher boiling hydrocarbons; it is preferable, however, to employ fractions containing over 80% (mol. basis) isopentane, which fractions, being obtainable without difficulty, are very effective in producing gasolines of higher volatility and anti-knock rating, and comparatively low vapor pressure.

Aside from',blending the iso-pentane, or isopentane fraction,with the topped gasoline from which they may have been separated, these materials, i. e., iso-pentane, or iso-pentane fraction, can be admixed in concentrated or somewhat diluted form with the correspondingly favorable results, as knock suppressors to the gasolines of operation of our hereinbefore delimit ourselves to details thereof, as we have discovered that it is possible to successfully reduce by efficient fractionation, the content of such fractions in a gasoline distillate as those substantially comprising normal paraflin hydrocarbons such as n-hexane, n-heptane, etc., when these are present in appreciable quantities, so that their removal would markedly improve the anti-knock rating of the finished product.

In practice, we found, the removal of these hydrocarbons from a distillate may be considered satisfactory, or effective, when the fractions boiling within an A. S; T. M. range of about 10 C. and having end points about 1 C.-5 C. above the true B. P. of the corresponding normal hydrocarbons are removed from this distillate. The separation of these fractions can be conveniently carried out either while the distillate is produced, or by subsequent refractionation of the distillate in one or a number of operations. Some of the resulting fractions may be found in some cases to be contaminated with the valuable unsaturated, aromatic, or naphthenic compounds which should be retained in the motor fuel oil; the ordinary distillation was found to be ineffective in some of these cases to separate certain azeotropic mixtures, such, for example, as nheptane, toluene and cycloheptane"; to accomplish this separation, the extraction with liquid S0: was employed and the extract substantially hysically by means of fractionation, extraction, tc., and/or chemically by nitration, sulphonaion, etc., the said distillate, especially with regard to the hydrocarbons having markedly low or markedly high anti-knock rating. Knowing from these analyses that certain normal hydrocarbons are present in the distillate in comparatively large quantities, the narrow-boiling fractionated out in the experimental equipment and the effect of their removal on the anti-knock rating is determined by actual tests, from which the advisability of processing the original distillate on commercial scale can be determined. In one case, two fractions boiling respectively. at 60-70 C. and 90-97" C. were separated from a distillate; they constituted and 1% by volume of the original distillate, and contained about 60% mol., n-CsHu and mol. n-C'rHw, respectively; their knock-ratings expressed as octane numbers were 50 and 52. From this data the removal of the n-heptane cut did not appear worthwhile with this particular gasoline, the n-hexane out, however, was removed successfully, raising the octane number of the remaining gasoline from 65 to 67. As the compositions of difierent mineral oils vary within wide limits, cases have been encountered in practice in which either the heavier n-hydrocarbons, such as n-heptane,-noctane, etc., were present in sufficiently large quantities to warrant their removal. or the com--' bined effect of removing several fractions containing normal hydrocarbons was greatenough to Justify the expense of the fractionating operation. The removed portions do not constitute a waste in the refining industry, as they can be readily marketed as special solvents, blended with fuels not requiring a high anti-knock rating, etc.

While we have herein fully described the general principle of our invention, and have illustrated the specific manner in which our process can be carried out it-is to be distinctly understood that the particulars disclosed and referred to, have been introduced only by way of example, and that the process may be carried out under conditions somewhat different from those definitely stated in said examples without de-- parting from the spirit or scope of the appended claims.

5 We claim as our invention:

l. A process for manufacturing an anti-knock fuel of relatively low vapor pressure, comprising removing by distillation a portion of the material containing hydrocarbons lower than and including n-pentane, separating from the produced v distillate the iso-pentane fraction, and returning the same to the residue from the first distillation;

2. A process of increasing the volatility and anti-knock rating of a motor fuel distillate 60mprising distilling off the lighter portion of the distillate boiling up to and including n-pentane, and adding to the residual portion a suilicient quantity of the iso-pentane fraction to obtain finished product having substantially the same vapor pressure as the original distillate and a higher. anti-knock rating.

. 3. A process of increasing the volatility and anti-knock rating of a motor fuel distillate without increasing its vapor pressure, comprising distilling oil the lighter portio'n of thedistillate boiling up to and including n-pentane, and adding cient quantity of'the iso-pentane fraction to restore vapor pressure of the finished product and enhance its anti-knock rating.

tions containing said hydrocarbons are frac-.

to the residual'portion of the distillate a suill- 4. In theprocess of manufacturing a motor fuel of the type of commercial gasolines, which gasolines normally contain pentanes and the lighter hydrocarbons responsible for the effective vapor pressure thereof, the steps comprising producing by fractionation of a hydrocarbon mixture a fraction boiling within a gasoline range and free of pentanes and the lighter hydrocarbons, and therefore having a. relatively low vapor pressure, then incorporating into thesaid fraction a sufficient quantity of iso-pentane to raise its vapor pressure to correspond to that of the commercial gasoline normally containing pentanes and the lighter hydrocarbons.

5. In the process of manufacturing a gasoline having a vapor pressure of about 5 lbs/sq. in. at 100 F. and whose initial boiling point is about 40 C., the steps which comprise producing a hydrocarbon mixture free of n-pentane, n-butane and the lighter hydrocarbons, thereby causing the vapor pressure to be substantially below 5 lbs/sq. in. at 100 F., and theinitial boiling point to be substantially above 40 0., and then incorporating a sumcient quantity of an iso-pensteps which comprise fractionating a hydrocarbon mixture to produce a hydrocarbon fraction substantially free from n-pentane and the lighter hydrocarbons, and having a relatively low antiknock rating and the end point of gasoline and incorporating with said fraction a quantity of isopentane to raise the vapor pressure of the fraction to that of gasoline and raise its anti-knock rating. 7. A gasoline whose active fuel component con sists of a mixture of a hydrocarbon fraction containing saturated and unsaturated hydrocarbons boiling withinthe gasoline range, and which is substantially free of the normal hydrocarbons containing less than six carbon atoms in a molecule, said fractions having a vapor pressure lower than that of the normal gasoline and a quantity of an iso-pentane fraction which is in excess of that normally present in the gasoline and is sufficient to raise the vapor pressure of the fuel to that of the normal gasoline and to enhance its anti-knock rating.

8. A gasoline whose active fuel component consists of a mixture of a hydrocarbon fraction containing saturated and unsaturated hydrocarbons boiling within the gasoline range, andwhich is substantially free of the normal hydrocarbons containing less than six carbon atoms in a molecule, said fraction having a vapor pressure lower than that of the normal gasoline, and a quantity of an iso-pentane fraction in excess of that normally present in the gasoline and sufilcient to raise the vapor pressure of the fuel to that of the normal gasoline and enhance the anti-knock,

distillation and replaced by another light hydro-' carbon fraction comprising-substantially iso-pentane.

10. A gasoline whose active fuel component consists of a mixture of a hydrocarbon fraction containing hydrocarbons boiling within the gasoline range, and which is substantially free of the normal iwclrocarbons containing less than six carbon atoms in a molecule, said fractions having a vaporpressure lower than that of the normal gasoline and a quantity of an iso-pentane fraction which is in excess of that normally present in the gasoline and is sufficient to raise the vapor pressure of the fuel to that of the normal gasoline and to enhance its anti-knock rating.

11. A gasoline whose active fuel component consists of a mixture of a hydrocarbon fraction comprising saturated hydrocarbons boiling within the gasoline range, and which is substantially free of the normal hydrocarbons containing less than six carbon atoms in a molecule, said fractions having a vapor pressure lower than that of the normal gasoline and a quantity of an isopentane fraction which is in excess of that normally present in the gasoline and is sumcient to raise the vapor pressure of the fuel to that of the normal gasoline and to enhance its antiknock rating.

JACK FRANCIS MAHON TAYLOR. BERNARD sumo GREENSFEIDER. RUSSELL NORMAN SHIRAS.