US2369497A - Method of preparing an improved motor fuel - Google Patents

Description

1 NI TE'Di-STA E EN Mn'rnon 0F PREPARING A'N 'IMPROVED MoronF-UnL .m' Albert L. S tanIyQBerk'eIey, CallL, assignor to Shel 1' I 'Development Company, sanfFrancisc'oycalil' acorporation of Delaware i Application n ceinb rzaial Serial No. 42 4,609-

' I No Drawing.

- more particularly deals with blendedfuels of reduced knocking tendencies in spark ignition engines. I

' Supercharging' is the most important known method of markedly raising the power output of internal combustion engines. For a given fuel, there is'a fuel mixturestrengthdeterminable by increasing. the cylinder pressure, as by supercharging. the engine, until a knock is perceptible, which mixture gives maximum detonation. Fuel admixture having approximately %--excess fuel over the correct stoichiometrical proportions, normally exhibitmaximum knock. Octane numbers are determined atthis fuel mixture strength.

Some: fuels having substantially the same octane rating, however, are known to give markedly different performancein engines which have'high compression ratios or are supercharged. It is known, for example, that the tendency of fuels to knock can be suppressedwithin limits by increasingthe ratio of fuel to air, with the result that higher pressures can be reached without encountering knockc Aromatics such as toluene, vcumene, benzene, ethylbenzene, -etc., and parafiin- ,ie fuels blended with these aromatics, are known to permit development of high pressures without knocking, andfto give particularly high power' outputs whenfed to engines in enriched mixtures.- However, aromatic blending agents are in general expensive and relatively difficult to obtain in technically pure form. Concentrated mixtures of aromatics obtained by extracting hydrocarbon fuels boiling within the range of the fuel with which ,the' extract is to .be blended, have been used although the maximum power outputs obtainable with. such materials are usually considerably lower than with certain pure'aromatic blending agents such as toluene, xylene, etc., be-

cause extracts normally include fairly large proportions of harmful; non-aromatic components which lower the obtainable power output.

Now I have discovered that concentrated mix tures of aromatics containing the harmful components in much lower concentrations and be ing capableof developing excellent maxium power outputs can be obtained by solvent extraction fractions boiling-withinthe gasolinesboilingrange containing a inen-percentage 'of aromatics, For

example, an extract, obtained by 'S'Oc' extraction of a 220 to 316. gasoline distillatbdiled from 237 F. to 341;[F/ This extract contained 67% by volume of aromatics, It-wasfractionally distilled and yielded fractions eontaining'the fol lowing percentages of aromatics: I

I Percent volume "of 1 extract Volume percent Boiling range H I I aromatics 1 As will be seen, the lowest boilingfractioncontains the lowest percentage ofaromatic material. Higher-boiling portions of extract contain higher percentages of aromatics and therefore by s'elec tion of a fraction of the proper boiling range, a blending stock may be obtained froman ex, tractobtainable by conventional solvent extrac; tion without the aid of an excessivenumber. of

extraction stages,-which-blending stocks coin;

prise at least about 40%1and preferably- -80% of the original extract and have acontentoi are} matics usually about '5 20% higherthan that of the e ra 1 ,1. 5:1 a

Blending stocks produced by first fractionally distilling to a narrow boilingunextracted fraction having a boiling range of from 25 to 5Q" F. and then extracting it under ,the same conditions does not result in extracts of the same high content of aromatics. The extracts thus ,obtained I contain larger quantities "of non-aromatic'comi ponents than. extracts produced by Imyi 'method. As is well known, to make possibl'e'theproduction of extractshaving aromatic content's of 8o'% to by a single extraction normally;v isfvery dinicult, requiring special equipment, I r

In carrying out my invention, I extract a gasoline distillate by any conventional method such as countercurrent liquid extraction with any selective solvent for aromatics useful under liquid phase extraction conditions. I, then, fractionally distil the extract so obtained under any convenient pressure in any conventional distillation apparatus. The resulting high boiling,highly concentrated aromatic fraction is then -'added ="to spark ignition engine fuels in quantities up' to about 50% by volume of the fuels. The choice of relative sizes .of low and higher boiling fractions depends on several considerations.- In the first place, the desired content of, aromatics in .the' high. boiling fractionsmust taken .intosaca easily be reduced by to .of that contained H in the extract, and the aromatic concentration canbeincreased proportionately.

The lower boiling fraction having the lower content of aromatics may, if desired, be further concentrated by re-extracting it; for example, by the process described in Egli, U; 8. 2,114,524. According to this process, the aromatic content of gasoline extracts is increased by re-extracting it in the presence of a higher boiling paraiiinic diluent. a j

Gasoline distillates, from which extracts can be produced containing appreciable quantities of 'aromatic'a may be obtained, ror example', by top ping certain crude oils, such as California, Texas, Oklahoma, Borneo; etc, crudes or occasionally-by cracking, particularly at temperatures in excess 011000" F.' For aviation gasolines, straight run gasoline distillates are in general" preferred for my purpose because normally they have a low content of undesirable unsaturated hydrocarbons.

QAS to the boiling range of suitable distillates, it is desirable that it be between about 150 F. and 450 F. Distillates boiling within this range are usually known as naphthaswhich term generally includes ma erials boiling within the gasoline range and-the-lower-ejnd of the light kerosene range. While the 'bfoii'ing range of suitable naphthas which may be extract-ed to Yield the desired extracts may be of any. breadth falling within the above limits} prefer boiling ranges of not more than about 100 F. spread. In conventional refining practice, gasoline distillates are generally separated into-'3 r more cuts, each of roughly 100%. boiling range orless, and it is'bot-h economicaiiycqnvenient and advantageous to extract these'somewhat relatively narrow boiling cuts. Some of the better known solvents having selective a'cticn'towardarcrnaticswhich 9.18 USEfl.11 for liquid-liquid;extraction in any for'm are liquid sulfur dioxide, furfuralfacetone; phenol, cresols, carbitols, beta-beta dichlordiethyl ether, nitroben'zerie, anilinajetc; "This group of solvents is not meantto"be"all=inclusive, and is given-merely y wer ex mp e.- f g Th aromatichlgh'boiling' fractions obtained by the abovej method ar useful as safety fuels, fuels for engines having "fuel injection systems where volatilityis'secondary; error blending with conventional; straight-run ojr'cracke'd automobile -ably 5% to 2,3,-dimethy1 butane, triptane, and other saturated hydrocarbons, particularly those boiling in the lower gasoline boiling range, such as isopentane, cyclopentane, cyclohexane, etc., or blends of any of the above fuels, or blends of the above fuels with branched-chain alkyl ethers.

The amounts of my aromatic fractions that may be blended into fuels will depend upon the power, volatility, freezing point, and other requirements specified for the particular fuel. Amounts will vary generally from about 5% to 50%, prefer- For automotive fuels, the factors controlling .the'amounts added are primarily the octane rating. In aviation fuels; on the other hand, the aromatic content generally should not exceed 30%, as fuel weight and economy on a weight basis which favor parafiinic fuels under "cruising conditions are of great importance. In

addition; concentrations of aromatics in excess of 30% are likely to cause damage to the self-sealing linings f air lane fuel tanks.

The anti=detonaticnproperties of fuel blended with my'aromatic fractions can be fortified or increased by addition of tetraethyl lead-and other organo-metallic anti-knock agents.

The following example further illustrates my invention:

' 7 Example 1 Two straight-run gasoline distillates boiling between 220 to 316 F. and 306 to 385 F.- obtained from a common stock, were subjected individually to countercurr'ent.extraction with S02 and yielded extracts boiling between 237 to 341 F. and 311 F. to 402 F. respectively. Both extracts were fractionally distilled to yield two fractions or substantially identical boiling ranges. The first of these fractions was obtained from "the low boiling extract and had a boiling. range from 281" to 339 F. The'iiecond fraction was Obtained from the higher boiling extract and had a boiling range from 270 to 339 F. The first fraction contained by volume of aromatics while'the second fraction 4 contained 59%- by volume of aromatics. e 1 Y 1 l Each of thefra'tions was blended to produce two-fuels-asshown in the table below in-the eel urnn Blended fuels.- The resulting four fuels [were tested on the C. F. engine. i

j The tests were made by running the-'C. F. R. engine on each of the fuels at a normal fuel-air ratio and then'raising the intake manifold pressure until a knock was perceptible, whereupon the power output was noted. The fuelm'ixture was then enriched and the intake pressure again increased until knocking was encountered. The maximum indicated mean eflective pressure (I. M. E. P.) permitted by detonation for enriched fuel mixtures was determined by varying the intake manifold ressure. Results were as follows:

Blended iuel 1 270-339 1". portion higher boiling extract +3 cc. 'l E. L

50% 13 octane number straight run linemen-50 231-439 1. 6561555? ii "281330' r. portion of low lioilingextract+3 cent. a.

' Per' nt M. E. 6f blended fuel) X 0 v aromatid .I. M. are: OPisooc'taue' 0 fuela aviationi fuel; or..- with synthetic, substan tidlly 'non aromatic fuels, which are useful alone "or in blends as aviation fuels such-- asalkylates,

mametcedrmtnnecne'xm.

components, with a selective solvent for aromatics, fractionally distilling the resulting extract to separate at least two fractions, a high boiling and a lower boiling one, the latter of tracting a gasoline distillate, boiling between about 150 F. and 450 F. and containing aromatic components, with a selective solvent for aromatics, iractionally distilling the resulting extract to separate a lower boiling fraction consisting of at least 20% of said extract and a high boiling fraction, and adding the highrboiling fraction comprising at least about 40% of the extract to gasoline.

3. The method of preparing an improved motor fuel for spark ignition engines comprising' extracting a gasoline distillate having a boiling range not greater than 100 F. and containing aromatic components, with a selective solvent for aromatics, fractionally distilling the resulting extract to separate a lower boiling fraction consisting of at least 20% of said extract and a high boiling fraction, and adding the high boiling fraction comprising at least about 40% of the extract to gasoline.

4. The method of preparing an improved motor fuel for spark ignition engines comprising extracting a gasoline distillate, boiling between about 150 F. and 450 F. and containing aromatic components, with a selective solvent for aromatics, fractionally distilling the resulting extract to separate a lower boiling fraction and a high boiling fraction containing not more than the upper boiling half of said extract, and adding the high boiling half of the extract to gasoline.

5. The method of preparing an improved motor fuel for spark ignition engines comprising extracting a gasoline distillate, boiling between about 150 F. and 450 F. and containing aromatic components, with a selective solvent for aromatics, fractionally distilling. the resulting extract to separate a lower boiling fraction, which is discarded, containing the material boiling in roughly the lower 20% of the extract boiling range and a high boiling fraction containing the balance ofsaid extract, and adding the high boiling fraction of the extract to gasoline.

6. The method of claim 1 wherein the gasoline distillate is a straight run gasoline distillate.

ALBERT L. STANLY.