US2479901A - Antiknock mixtures - Google Patents

Description

} Fatented Aug. 23, 1949 ANTIKNOCK MIXTURES George Calingaert, Detroit, and John S. Wintringham, Blrmin gham, Mich., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing Application July 31, 1948, erial No. 41,897

8 Claims. (Cl. 252-386) This invention relates to mono-bromo-aromatic hydrocarbons for use as scavengers with lead antiknock compounds. The bromo-hydrocarbons may be used alone in fuels generally, and are preferred for use in aviation fuels. According to Bartholomew Patent No. 2,398,281, issued April 9, 1946, a preferred motor fuel contains both bromoand chloro-hydrocarbon scavengers. For this use our invention is a mixture of one or more of our bromo-hydrocarbons with one or more chimp-hydrocarbons having a particular vapor pressure.

Scavengers are materials employed with lead antiknock compounds in fuels for internal combustion engines to produce, during combustion, volatile lead compounds which are exhausted from the engine. Scavengers reduce the amount of less volatile lead compounds which otherwise form during combustion and collect on engine parts. For satisfactory operation of an engine employing leaded gasoline, it is essential that a scavenger be used. Commercially used scavengers are ethylene dibromide and ethylene dichloride.

It has generally been believed that in an engine cylinder all scavengers containing a given quantity of a specific halogen are equally eflicacious. This property of unit effectiveness with in the cylinder we call intrinsic scavenging efficiency, and we have found that it varies widely for different halogen compounds. Other desirable properties of scavengers include stability when stored in admixture with lead antiknock compounds, miscibility with lead antiknock compounds, freedom from reduction ineffectiveness of lead antiknock compounds, and volatility giving a suitable pattern of distribution in the engine relative to that of lead antiknock compounds under the range of intake manifold conditions encountered in service.

It is an object of our invention to provide a new class of scavengers having not only good intrinsic scavenging efliciency but also other properties desirable for commercial use.

Our invention is the use as scavengers of monobromo-derivatives of benzene. In a more restricted'sense, this invention relates to monobromo-derivatives of alkyl benzenes having eight carbon atoms, in which the bromine atom is attached to the benzene nucleus such as monobromo-xlylenes and mono-bromoethylbenzenes. Our invention also includes the use of these scavengers with chloro-hydrocarbons having a vapor pressure at 50 C. of substantially 0.2 to 6 millimeters of. mercury. Among the mono-bromoalkylbenzene derivatives within the scope of our invention may be mentioned the following:

4-bromo-1,2-dimethylbenzene 3-bromo-1,2-dimethylbenzene Mono-bromo-dimethylbenzenes (mixed) 4-bromo-1,3-dimethylbenzene Z-bromo-l,S-dimethylbenzene 1-bromo-4-ethylbenzene 5-brom0-1,3-dimethylbenzene Mono-bromo-ethylbenzene (mixed) l-bromo-S-ethylbenzene It is to be understood that mixtures of these compounds may be used, and this is frequently more economical since manufacturing processes may produce mixtures, and the expense of isolating one compound from the others may be avoided. One theory of any of the above compounds employed with tetraethyllead in gasoline gives good results in aviation engines.

A representative group of chloro-hydrocarbons, to be used with our bromo-hydrocarbons, with their vapor pressures at 50 C., is as follows:

Ap roximate apor Pressure at 50 C.

Chime-hydrocarbons l-Ohlorouaphthalene Q. 4-Chloro-l-(B-chlorocthy1) benzene 1,8;Dichlorooctane. ".65"-..

3,4-D hlorocnmene Pentachlorobutanes (mixed Hexachloropropylene v 1.2,4-Trichlorobenzene Dichloroheptanes (mixedL. 2,4-Dichlorotoluene 1,2-Dichlorocyclohexane. l-Chloroctane One-half theory of mono-bromoxylenes (mixed), or of others of our bromo-hydrocarbons, and one theory of 1,2,4-trichlorobenzene or others of our chloro-hydrocarbons employed with tetraethylenger showed that our compounds were always effective scavengers and were at least as good as those now in commercial use.

The quantity of scavenger theoretically required for reaction with the lead to form the lead halide, which quantity is two atoms of halogen per atom of lead, is called one theory of halogen. Present practice is to use one theory of bromine in aviation fuels, while for motor fuels one-half theory of bromine plus one theory of chlorine is used. In the engine operation described below, the scavengers were used in amounts providing the number of theories of halogen employed in commercial practice.

In road operation our scavengers were compared with ethylene dibromide and ethylene dichloride. Brom-ethyl-benzene, in combination with a chlorine scavenger, benzotrichloride, was blended with tetraethyllead and incorporated in a gasoline. Comparison was made in operations on the road with the same gasoline containing a'mixture of tetraethyllead, ethylene dibromide, and ethylene dichloride. The fuels were used in automobiles of the same standard make, which were driven many thousands of miles. Our scavenger was found to have good intrinsic scavenging emciency as indicated by measurements of engine deposits, and by visual inspection.

To illustrate that in some engines under certain conditions our scavengers have an intrinsic scavenging efficiency superior to those heretofore used, results may be reported from operation of single-cylinder, aviation-type engines comparing mono-bromoxylenes (mixed) with ethylene dibromide. Under comparable conditions for both scavengers the bromoxylenes (mixed) produced only about 92% .of the amount of combustion chamber deposit that was found with ethylene dibromide. Also a reduction was found in deposits on the exhaust valves and spark plugs.

In addition to good intrinsic scavenging efficiency, our compounds possess the other desirable properties mentioned above. For example, for use in certain engines, especially in certain highoutput aviation engines, we have found that the scavengers of our invention have evaporation characteristics under the conditions existing in the intake manifold sufliciently close to those of tetraethyllead. This ensures good distribution of the scavenger relative to tetraethyllead between the diiferent cylinders of the engine and avoids the harmful effects caused either by an excess or a deficiencyin the theories of halogen for the lead in any cylinder. On the other hand, ethylene dibromide and ethylene dichloride have vapor pressure so much higher than that of tetraethyllead that they tend to give relatively poor patterns of distribution. Measurements made during operation of an engine show the marked superiority of our scavengers to ethylene dibromide and ethylene dichloride in this respect.

To illustrate the relative quantities of various scavengers present in the liquid portion of the fuel flowing along the wall of the maniifold, a currently-produced eight-cylinder, valve-in-heacl automotive engine was used in which the liquid flowing along the walls of the manifold branches for each pair .of cylinders was collected for analysis. A considerable proportion of the total tetraethyllead content of the input fuel was found in this unevaporated liquid, but when ethylene dibromide was used, the concentration of that scavenger in the liquid was only 0.05 theory. From these results a different pattern of distribution of tetraethyllead and ethylene dibromide to the cylinders would be expected, and this was confirmed in other operation of the same engine. In contrast, in operation with monobromoxylenes (mixed), the manifold liquid contained 0.85 theory of the scavenger, which is near enough to the ideal value to assure the attainment of very close to 1.00 theory in the total input to each cylinder. This performance illustrates the improvement in distribution relative to the lead antiknock compound which can occur with our scavengers.

The storage stability of antiknock fluids containing scavengers is highly important in the shipping and storage of such fluids, either alone or in gasolines. When the antiknock fluid decomposes, lead salts are either precipitated or remain in solution in the fluid, from which they may precipitate when the fluid is blended with gasoline. Decomposition is accompanied by evolution of gas which causes pressure to be built up in the containing drum or tank car. The bromo-aromatic and chloro-hydrocarbon scavengers of our invention are generally superior to ethylene dibromide and ethylene dichloride in respect to storage stability.

Our scavengers may be used with lead compounds other than tetraethyllead, such as tetrapropyllead, dimethyldiethyllead, and methyltriethyllead. When a mixture of lead antiknock compounds in employed, the scavenger may be one of our bromohydrocarbons or a mixture of two .or more of them, a mixture of one bromohydrocarbon with one chloro-hydrocarbon, or a mixture of two or more bromohydrocarbons with two or more chlorohydrocarbons. It is custom ary to make a blend of the lead antiknock compound and the scavenger and then to add this mixture to a gasoline. However, the scavenger and the antiknock compound may be added sepa-- rately to the fuel.

Miscibility of scavengers with lead antiknock compounds and freedom from reduction in the effectiveness of lead antiknock compounds are important commercially. Our scavengers generally are satisfactory in these respects.

For purposes of comparison, the proportions of scavengers used in the above examples have been the same, i. e., one theory of bromo-hydrocarbon for the lead compounds in aviation gasolines, and a mixture of one-half theory of a'bromo-hydrocarbon and one theory of a chloro-hydrocarbon for the lead compounds in motor fuels. The concentration of our scavengers is not critical, and therefore is not so limited. For aviation fuels. best results have been obtained with proportions varying from 0.8 theory to 1.5 theories, and a wider variation may be used. For motor fuels we recommend the proportions of scavengers set forth in Bartholomew Patent No. 2,398,281.

Our scavengers may be used in admixture with one another as well as in admixture with other scavengers.

We claim:

1. An antiknock composition consisting essentially of a lead antiknock compound and a scavenger in an amount sufllcient to reduce the deposition of lead in the engine by forming volatile lead compounds, a principal active scavenging ingredient of which is a mono-bromoalkylbenzene having eight carbon atoms and having the bromine atom attached to the benzene ring.

2. An antiknock composition consisting essentially oi tetraethyllead and a scavenger in an amount suflicient to reduce the deposition of lead in the engine by forming volatile lead compounds.

--tached to the benzene ring.

3. An antiknock composition consisting essentially of tetraethyllead and a scavenger in an amount sufiicient to reduce the deposition of lead in the engine by forming volatile lead compounds, a principal active scavenging ingredient of which is a mono-bromo-xylene.

4. An antiknock composition consisting essentially of tetraethyllead and a scavenger, in an amount sufficient to reduce the deposition of lead in the engine by forming volatile lead compounds, the principal active scavenging ingredient of which is a monobromo-ethylbenzene having the bromine atom attached to the benzene ring.

5. An antiknock composition consisting essentially of a lead antiknock compound and a mixture oi scavengers each of which is present in an amount sufilcient to reduce the deposition of lead in the engine by forming volatile lead compounds, the principal active ingredients of which are a mono-bromo-alkylbenzene having eight carbon atoms and having the bromine atom attached to the benzene ring, and a chlorohydrocarbon having a vapor pressure at 50 C. of substantially 0.2 to 6 millimeters of mercury.

6. A composition or matter consisting essentially of a lead alkyl anti-knock compound and a monobromo alkylbenzene having eight carbon atoms and having the bromine atom attached to the benzene ring, in a proportion in the range providing 0.8-1.5 mols of bromine per mol of lead. 7. The composition of claim 5 wherein the chloro-hydrocarbon scavenger is 1,2,4-trichlorobenzene.

8. An antiknock composition consisting essentially of a lead antiknock compound and a mixture of scavengers each of which is present in an amount suificient to reduce the deposition of lead in the engine by forming volatile lead compounds, the principal active ingredients of which are mono-bromoxylene and 1,2,4-trichlorobenzene.

GEORGE CALINGAERT. JOHN S. WINTRINGHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,668,022 Midgley, Jr May 1, 1928 2,364,921 Shokal Dec. 12, 1944 2,447,926 Wiczer Aug. 24, 1948