US2881061A - Anti-knock gasoline containing hydrogenated quinolines and indoles - Google Patents

Description

United States Patent 2,881,061 ANTI-KNOCK GASOLINE CONTAINING HYDRO- GENATED QUINOLINES AND INDOLES James A. Brennan, Camden, N.J., and Charles C. Price,

Lansdowne, Pa., assignors to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Application March 12, 1956 Serial No. 570,712 12 Claims. (Cl. 44-63) This invention relates generally to improved fuels for internal combustion engines of the spark-ignition type. More particularly, it is concerned with the provision of gasolines having improved anti-knock properties.

It is now well known that knock in spark-fired engines is due to the relatively slow oxidation of the endgas prior to the arrival of the flame front, the immediate (cause being the extremely rapid combustion of the last ,"part of the charge to burn. It is also known that certain :factors such as fuel/air ratio, compression ratio, spark :setting, engine speed, etc., affect the fuel combustion. Furthermore, it has been determined that the most economical burning of the gasoline is obtained at the higher compression ratios. The higher the compression ratio, however, the higher the octane number of the gasoline necessary for knock-free operation. Because the design of modern automobile engines, particularly in recent years, has been towards increased compression ratios, the demand has been for gasolines of constantly improved anti-knock quality. Refiners have kept abreast of this demand through (a) the development of new refining techniques, such as alkylation, isomerization, catalytic cracking, reforming, etc., and (b) the use of anti-knock agents which are added to the gasoline. As is well known, either or both of these means can be used to improve the anti-knock quality of gasoline fuels. The present invention is concerned particularly with the improvement of gasoline octane rating by means of addition agents.

Anti-knock agents most widely used in the past have been those of the so-called metallic type, of which a prime example is tetraethyl lead. It has been recognized, however, that the use of metal-containing anti-knock agents, such as tetraethyl lead, contributes to other difliculties associated with the operation of high compression engines, such as spark plug fouling, preignition, etc., which have been found to be due to the formation of metallic deposits on the engine parts. The art has, therefore, turned to the development of non-metallic antiknock agents which can be used either alone or in conjunction with metallic-type anti-knock agents. The use of such non-metallic compounds in the gasoline in conjunction with metallic anti-knock agents reduces the formation of the deleterious metallic deposits in the engine; or, if the non-metallic agent is used as the sole anti-knock additive the metallic deposits are eliminated entirely.

The best presently known non-metallics are aniline and certain alkyl derivatives thereof. These compounds vary greatly in their ability to suppress knock. The class as a whole is represented by the following structural formula:

where R, R and R" represent hydrogen or lower alkyl groups. If either R or R, or, both, are hydrogemsthe alkyl or alkoxy groups,

2,881,061 Patented Apr. 7, 1959 substance has knock-inhibitive ability, R and R are alkyl groups the compound has no anti-knock property. Probably the best known non-metallic is N-methylaniline. In the series where R and R" are hydrogen and R is alkyl, a decrease in anti-knock effectiveness with increasing length of the alkyl group occurs. The data in the following table illustrates the foregoing.

whereas if both ASTM Designation D908-53, ASTM Manual of Engine Test Methods for Rating Fuels, 1953 supplement.

AS'IDM Primary Reference Fuel (60% iso-octane40% n-heptane).

A recent publication by J. E. Brown et al., Ind. and Eng. Chem. 47, 2141 (1955), summarizes the known information on amine type anti-knocks. These authors state that the substitution of groups larger than methyl in the ortho position in aniline results in decreased antiknock efiectiveness. Furthermore, they have shown that the substitution of only one ortho-methyl group in N- methylaniline will cause decreased eifectiveness.

It has now been found, however, that if the N-alkyl group is made to form a ring attached to the benzene ring ortho to the amine function, the resulting substance is an This compound is an anti-knock equal in effectiveness to N-methyl aniline. Furthermore, replacement of the nuclear hydrogens of the aromatic ring with lower alkyl or alkoxy groups, such as methyl or methoxy groups, has been found not to lower the anti-knock effectiveness of the compound at all when the substitution is meta (5 or 7) or para (6) to the amine function and the reduction is only slight when the replacement is in the ortho (8) position. Substitution of the non-aromatic ring by lower does decrease the anti-knock activity somewhat, however, the resulting compounds are still highly effective anti-knock agents.

It will be appreciated from the foregoing, that the present invention provides an entirely new class of compounds having anti-knock ability. It is, therefore, the principal object of this invention to provide a new class of non-metallic anti-knock agents. It is a further object to provide improved I these new anti-knock agents. Other and further objects will become apparent from the following description of the invention.

Broadly, the compounds of the invention are defined by the following general formula:

12-0 0 c n-i: ii La gasoline compositions containingwhere R is selected from-.the.-group consisting of hydrogen, alkyl groups having from 1 to about 4 carbon atoms These compounds are dihydroindoles.

Specific examples of compounds of the character contemplated by this invention include the following (py =pyridine).

(a) Py-tetrahydroquinolines such as: py-tetrahydroquinoline;. 2-methyl-py-tetraquinoline; 2,4-dimethyl-pytetraquinoline; 2,2,4-trimethyl-py-tetraquinoline; 4-ethy1- py-tetraquinoline; 4,6-diethyl-py-tetraquinoline; 4,5,6-tripropyl-py-tetraquinoline; 4,5,6-tributyl-py-tetraquinoline; 6methyl-py-tetrahydroquinoline; 8-methyl-py-tetrahydro quinoline; 2 methyl-6-methoxy-py-tetrahydroquinoline;

2-methyl-6-butoxy-py-tetrahydroquinoline; and, 6-methyl,

8-methoxy-py-tetrahydroquinoline.

(b) Dihydroindoles such as: Z-methyldihydroindole; 3-ethyldihydroindole; 5-methoxydihydroindole; G-methyldihydroindole; 3-ethyldihydroindole; 5-propyldihydroindole; S-butyl-dihydroindole; S-butoxydihydroindole;wand Z-methyl-6-butyldihydroindole.

The py-tetrahydroquinoline;compounds of the invention can be prepared by a variety of methods. The reduction of the pyridine ring inquinoline or alkyl-substituted quinolines by either catalytic or chemical means is the preferred method of synthesis. Procedures for this reduction maybe found in the literature. A typical reduction is given in Example III, below. The dihydroindoles, on the other hand, may be-conveniently prepared by any of the known methods, such as the catalytic reduction of indole or appropriately substituted indoles.

The following examples and test results will serve to further illustrate the present invention.

Example I.-Py-tetrahydroquinoline as white label re- C. It had the fol- This compound was purchased agent. Its melting point is 15-l6 lowing analysis:

Example l1.-Acetne-Anil CHI 4 Prepared from aniline and acetone in the presence of iodine according to W. RJ'Vaughan, Org. Syn. 28, 49

(1948). Its boiling point is131132 C. at 13 mm.

Example Ill.-2,2,4-trimethyl-py-tetrahydr0quin0line i CH;

Twenty grams (0.116 mole) of acetone-anil were dissolved in 250 milliliters of absolute alcohol. Twenty grams (0.87 g. atom) of sodium were added at such a rate as to maintain steady reflux. Near the end of the metal addition it became necessary to heat the mixture to maintain rapid reaction, After all the sodium had been added, the reaction mixture was refluxed an additional two hours. The solution was cooled to room temperature (crystalline solid), dissolved in water, made acid with 6 N HCl and most of the alcohol removed by distillation. The residue was made basic with concentrated NaOH then extracted with ether. The com-. bined ether extracts were dried over anhydrous Na SO After removal of the ether, the residue was distilled at reduced pressure, yielding 15 grams of a colorless oil, with a boiling point of 108-110 C. at 8-9 mm.

Example IV.2,4-dimethyl-py-tetrahydroquinoline 2,4-dimethylquinoline was prepared from acetone-anil (W. R.Vaughan, ibid.). The quinoline was then reduced as described in Example HI. The boiling point of 2,4-dimethyl-py-tetrahydroquinoline is 126130 C. at i 11 mm.

Example V.--2-methyl-py-tetrahydroquinoline Prepared by the reduction of Z-methyl-quinoline as described in Example 111. Thereduced quinoline boils at .110113 C. at 3-4 mm.

Example VI.-6-methyl-py-tetrahydroquinoline Prepared from 6-methyl-quinoline by reduction with sodium and alcohol (Example III). The product had a boiling point of 93-96 C. at 3-4 mm.

Example VIl.8-methyl-py-tetrahydroquinoline CH3 H Prepared by the reduction of S-methyl-quinoline as described-in Example III. 8-methyl-py; t etrahydroquipQ-. ueeiboikat 1341 0. m

Example VIIL-ti-methoxy-py-telrehydroquinoline CHsO This compound was purchased as white label reagent. Its melting point is 40-42 C.

ANTI-KNOCK ABILITY Fuel blends of the compounds described in the foregoing examples were prepared and the Research octane numbers thereof were determined. The pertinent data and the results obtained are recorded in Table II. These data show that all of the py-tetrahydroquinolines are octane improvers and that this improvement applies in both clear and leaded fuels.

It will be seen from the table that acetone-anil (Example H), which differs from the py-tetrahydroquinolines only by an olefinic bond in the non-aromatic ring, is a pro-knock. The reduction of this bond results in 2,2,4- trimethyl-py-tetrahydroquinoline (Example HI), a substance with anti-knock properties.

TABLE II Amount of Research additive octane number Compound added Weight Mole 3 cc.

perper- Clear TEL/ cent cent gal.

Base fuel 1 60.0 84. 3 N -methylaniline 3 3. 3 78. 93. 4 py-Tetrahydroquinollne (Ex. I) 3 2. 7 77.3 94.4 Acetone-anll (Ex. II) 3 2.0 48.3 79.1 2,2,4-trimethyl-py-tetrahydroquinoline (Ex. II 3 2.0 64. 86.3 2,4-dtmethyl-py-tetrahydroquinoline (Ex. IV) 3 2. 3 70. 7 88. 3 Z-methyI-p ttrahydroquinollne (Ex. 3 2. 5 72. 2 90. 5 S-methyl-p trahydroquinoline (Ex. I) 3 2. 5 74. 6 6-methyl-py-tetrahydroquinoline (Ex. VII 3 2. 5 77. 5 93.1 6 methoxy py tetrahydroqulnoline (Ex. VIII) 3 2. 2 78.0 92. 5

1 ASIM primary reference fuel: 60/40 lsooctanelmheptane.

Also, it will be seen that the substitution of methyl groups in the parent compound affects its anti-knock properties. Thus, 2,2,4-trimethyl-py-tetrahydroquinoline (Example III) was the poorest anti-knock of the series. The removal of one of the methyl groups in 2,2,4-trimethyl-py-tetrahydroquinoline, however, results in the 2,4-dimethyl derivative and an increase in anti-knock effectiveness (Example IV). Also, Z-methyl-py-tetrahydroquinoline (Example V) was found to be superior, as an anti-knock, to the 2,4-dimethyl derivative. The parent compound was better than any of its methyl derivatives, when the methyl was substituted in the non-aromatic ring.

Methyl substitution in the 8-position of the aromatic ring lowered the anti-knock effect of py-tetrahydroquinoline somewhat as shown by 8-rnethyl-py-tetrahydroquinoline (Example VI). Methyl substitution in the 6-position, however, resulted in an anti-knock comparable to py-tetrahydroquinoline on a weight basis (Example VII).

The py-tetrahydroquinoline (Example I) was 10% better on a mole basis and the 8-methyl derivative (Example VI) was identical in effectiveness to N-methylaniline. The 6-methyl-py-tetrahydroquinoline (Example VII) and 6-methoxy-py-tetrahydroquinoline (Example VIII) were the best of the py-tetrahydroquinolines investigated. They were 30% better than N-methylaniline on a mole basis.

It will be understood that the additives of the invn tion may be advantageously utilized in any hydrocarbon fuel suitable for use in internal combustion engines of the spark-ignition type. In general, these fuels are comprised of mixtures of hydrocarbons having suitable volatility characteristics. For example, automotive gasolines generally comprise hydrocarbon mixtures having initial boiling points of around F. and end-boiling points of around 440 F. and which boil substantially continuously between these points. These motor gasolines usually show a clear octane number of from about 70 to about 90.

Aviation gasolines, on the other hand, are mixtures of hydrocarbons which have an initial boiling point of around 80 F. and an end boiling point of about 330 F. and which boil substantially continuously between these points. Aviation fuels have octane ratings of from about 80 to about 100.

The data in Table III illustrate the octane rating improvement obtained by the use of py-tetrahydroquinoline in two types of base fuels, as follows.

Fuel A is a blend of 70% catalytically-cracked and 30% thermally-reformed gasolines having an initial boil ing point of 104 F., a 50% point of 226 F. and a point of 350 F.

Fuel B is a catalytically-reformed gasoline. It contained 44% parafiin, 3% olefin and naphthalene and 53% aromatics. It had an initial boiling point of F., a 50% point of 250 F. and a 90% point of 320 F.

TABLE HI Research octane number (F-l) Fuel blend Clear 3 cc. TEL/ gal.

BaseFue1 A 83. 3 93. 2 Fuel A+1.5% py-tetrahydroqninoline 87. 6 95.9 BaseFuel B 89.0 97.7 Fuel B+3% py-tetrahydroquinoline 95. 2 iso+0. 13

1 Indicates fuel of same value as isooctane plus 0.13 ml. TEL.

The anti-knock action of thecompounds of the present invention is independent of other anti-knock agents of either the metallic or non-metallic type. Hence, they can be used to increase the octane ratings of fuels containing other anti-knocks.

Other additives designed to impart various improved properties to the fuel may also be used in the fuels containing the anti-knock agents of this invention. Thus, anti-oxidants, metal deactivators, anti-rust, anti-stalling and ignition control compounds may be used in the fuel composition.

The amount of the additives of the invention which is added to the gasoline will depend upon the particular gasoline and the amount of improvement desired. In general, from about 0.1% to about 10%, by weight, of additive may be used. Also, as indicated herein, the additives of the invention are advantageous when used in the fuels in conjunction with tetraethyl lead. In general, the amount of tetraethyl lead to be used in conjunction with the new additives may range from about 0.1 cc. to about 10 cc. per gallon. The conjoint use of the new additives and tetraethyl lead is particularly indicated where aviation gasolines of high octane ratings are desired.

Although the present invention has been illustrated herein by means of specific embodiments and examples, it is not intended that the scope of the invention be limited thereby but only as indicated in the following claims.

We claim:

1. A gasoline containing a minor amount, from about 7 0.1% toabout 10%, by weight, of a compound having the general formula MAW I n f where R is selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 4 carbon atoms and alkoxy groups having from 1 to about 4 carbon atoms, with not more than three R groups, other than hydrogen, being substituted on the non-aromatic ring and n represents an integer selected from and 1.

2. A gasoline containing a minor amount, from about 0.1% to about by weight, of tetrahydroquinoline.

3. A gasoline containing a minor amount, from about 0.1% to about 10%, by weight, of 1,2-dihydroindo1e.

4. A gasoline containing a minor amount, from about 0.1% to about 10%, by weight, of .8-methyl-py-tetrahydroquinoline.

5., A gasoline containing a minor amount, from about 0.1% to about 10%, by weight, of 6-methyl-py-tetra hydroquinoline.

6. A gasoline containing a minor amount, from about 0.1% to about 10%, by weight, of 6-methoxy-py-tetrahydroquinoline.

7. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetraethyl lead and from about 0.1% to about. 10%, by weight, of a compound having the where R is selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 4 carbon atoms and alkoxy groups having 1 to about 4 carbon atoms, with not more than three R groups, other than hydrogen, being substituted on the non-aromatic ring and n represents an integer selected from O and 1.

8. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetraethyl lead and from about 0.1% to about 10%, by weight, of tetrahydroquinoline.

9. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetraethyl lead and from about 0.1% to about 10%, by weight, of 1,2-dihydroindole.

10. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetraethyl lead and from about 0.1% to about 10%, by weight, of S-methyl-py-tetrahydroquinoline.

11. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetraethyl lead and from about 0.1% to about 10%, by weight, of ,-methyl-py-tetrahydroquinoline.

12. A gasoline containing from about 0.1 cc. to about 10 cc. per gallon of tetaethyl lead and from about 0.1% to about 10%, by weight, of 6-methoxy-py-tetrahydroquinoline.

References Cited in the file of this patent UNITED STATES PATENTS 2,030,033 McConnell Feb. 4, 1936 2,560,898 Schulze et a1. July 17, 1951 2,647,824 Jones et a1. Aug. 4, 1953 2,787,551 Bell et a1 Apr. 2, 1957

Claims (1)

1. A GASOLINE CONTAINING A MINOR AMOUNT, FROM ABOUT 0.1% TO ABOUT 10%, BY WEIGHT, OF A COMPOUND HAVING THE GENERAL FORMULA