Patented Aug. 23, 1949 ANTiKNOCK MIXTURES George Calingaert, Detroit, and John S. Wintringham, Birmingham, Mich., assignors to Ethyl Corporation, New York, N. Y., a corporation oi Delaware No Drawing. Application July 3i, 1948, Serial No. 41,898
This invention relates to dibromo-alkanes and dichloro-alkanes 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 chime-hydrocarbon scavengers. For this use our invention is a mixture of one or more of our bronco-hydrocarbons with one or more .of our chloro-hydrocarbons.
Scavengers are materials employed with lead antiknocir 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 dlbromide 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 efiicacious. This property of unit efiectiveness within 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, misclbility with lead antiknock compounds, freedom from reduction in effectiveness of lead antilmoclr 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 con- 1,4-dibromopentane 1,5-dlbromopentane 2,2-dibromopentane 2,3-dibromopentane 2/l-dibromopentane 3,3 -dibromopentane l,3-dibromo- 2,2 dimethylpropane 1,1-dibromobutane 1,2-dibromobutane 1,3-dibromobutane 1,4-dibromobutane 2,2-dibromobutane 2,3-dibromobutane l,l-dibromopentane 1,2-dlbromopentane LS-dibromopentane It is to be understood that mixtures of these compounds may be used. and this is frequently more cono ical s nce anufacturin p ocesses 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.
In addition our invention includes the corresponding dichloro-alkancs, when used in admix ture with the foregoing dibromoalkanes among which are:
1,1-dichlorobutane 1,2-dichlorobutane 1,3 -dichlorobutane 1,4-dichlorobutane 2,2-dich1orobutane 2,3 -dichlorobutane 1,1-dichloropentane 1,2-dichloropentane 1,3-dichloropentane One-half theory of one or a mixture of the above bromo-hydrocarbons with one theory of one or a mixture of the above chloro-hydrocarbons employed with tetraethyllead in motor fuel gives goods results in vehicles on the road.
Our scavengers, either alone or with other scavengers, in admixture with lead antiknock compounds have been added to different base gasolines. The resulting fuels have been used in extended operation in the laboratory and on the road in numerous engines, including vehlcular engines and single cylinder engines of the type commonly used for research on aviation fuels. At the end of each period of operation, examination of those engine parts which are adversely affected in the absence of a scavenger showed that our compounds were always eiiective scavengers and were at least as good as those now in commercial use.
The quantity of scavengergtheoretically required for reaction with the lead to 'form the lead halide, which quantity is two atoms of halo- .gen per atom of lead, is called one theory of halogen. Present practice is to useone 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, one of our scavengers mixed with a chlorine scavenger was compared with ethylene dibromide and ethylene dichloride. 1,4 dibromobutane, in combination with a chlorine scavenger, hexachloropropylene, 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 trucks of the same standard make operated in heavy-duty service for many thousands of miles. Our scavenger'was found to have good scavenging efliciency as indicated by measurements of engine deposits, by visual inspection and by an improvement in life of exhaust valves amounting 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 1,4-dibromobutane or 2,3-dibromobutane with ethylene dibromide. Under comparable conditions for all scavengers 1,4-dibromobutane or 2,3- dibromobutane produced only 80 and 95 percent respectively 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 g od intrinsic scavenging efilciency, our compounds possess 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 which are sumciently close to those of tetraethyllead. This ensures good distribution of the scavenger relative to tetraethyllead among the different cylinders of the engine and avoids the harmful effects caused either by an excess or a deficiency in the theories of halogen for the lead in any cylinder. On the other hand, ethylene dibromide and ethylene dichloride have vapor pressures so much higher than that of tetraethyllead that they tend to give relatively poor patterns of distribution. Measurements made during engine operation 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 manifold, a currently-produced eight-cylinder, valve-in-head automotive engine was used in which the liquid cylinders would be expected, and this was confirmed in other operations of the same engine. In contrast, in operation with 1,5-dibromopentane, the manifold liquid contained 0.92 theory of the scavenger, which is near enough to the ideal value to assure attainment of very close to 1.00 theory in the total input to each cylinder. This performance illustrates the improvement in distribution 4 relative to the lead antiknock compound which can occur with our scavengers.
The improved distribution pattern of our scavengers, indicated by the above measurements, is likewise shown by exhaust gas analysis. In the same engine without the equipment for collecting the liquid in the inlet manifold, representative samples of the exhaust gas from the individual cylinders were taken and analyzed for lead and halogen. The results are expressed in terms of the maximum percentage variation of one cylinder from the average of all cylinders. We found a pronounced maldistribution of tetraethyllead itself, the maximum variation being as much as 40 percent. Comparisons were made with one-half theory of ethylene dibromide plus one theory of ethylene dichloride, and with onehalf theory of one of our scavengers, 1,4-dibromobutane, plus one theory of a chlorine scavenger of similar, relatively low, volatility. The maximum variation in theories of bromine for the lead in the cylinders was 24 percent for ethylene dibromide and was only 4 percent for our bromine scavenger. From these results it is evident that scavengers of our invention are superior to ethylene dibromide in distribution characteristics relative to tetraethyllead.
The storage stability of antiknock fluids containing scavengers is highly important in the shipping and storage of such fluids, either alone or in gasoline. 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 dibromoalkane and dichloro-alkane scavengers of our invention are satisfactory in this respect.
Our scavengers may be used with lead compounds other than tetraethyllead, such as tetrapropyllead, dimethyldiethyllead, and methyltriethyllead. When a mixture of lead antiknock compounds is employed, the scavenger may be one of our halo-hydrocarbons or a mixture of two or more of them. It is customary 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 separately 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 bromohydrocarbon 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 range 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.
1. An antiknock composition consisting essentially of a lead antiknock compound and a scar enger in an amount sufllclent to reduce the dep sition of lead in the engine by forming volatile lead compounds, a principal activescavenging ingredient of which is a dibromo-alkane having four or five carbon atoms.
2. 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,
a principal active scavenging ingredient of which is a dibromoalkane having four or flve carbon atoms.
3. An antiknock composition consisting essentially of tetraethyllead and a scavenger in an amount sufilcient to reduce the deposition of lead in the engine by forming volatile lead compounds. a principal active scavenging ingredient of which is a dibromobutane.
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, a principal active scavenging ingredient of which is 1,4-dibromobutane.
5. An antiknock composition consisting of a lead antiknock compound and a mixture of scavengers each of which is-present in an amount sufllcient to reduce the deposition of lead in the engine by forming volatile lead compounds, the principal active scavenging ingredients of which are a dibromo-alkane and a dichloro-alkane, each of which has four or five carbon atoms.
6. An antiknock composition consisting essentially of tetraethyllead and a mixture of scavengers each of which is present in an amount sumcient to reduce the deposition of lead in the engine by forming volatile lead compounds, the principal active scavenging ingredients of which are 1,4-dibromobutane and dichloro-pentane.
7. A composition of matter consisting essentially of a lead alkyl anti-knock compound and 1,4-dibromobutane in a proportion in the range providing 0.8-1.5 mole of bromine per mol of lead.
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