US2889212A - Lead scavenger compositions - Google Patents

Description

LEAD SCAVENGER COB POSITIONS Jenard E. Yust, Alton, and John L. Bame, East Alton,

HL, assignors to Shell Development Company, Emeryville, Calif, a corporation of Delaware No Drawing. Application July 22, 1952 Serial No. 300,337

14 Claims. (Cl. 44-69) This invention relates to compositions which are useful as scavengers with lead anti-knock compounds.

The use of lead compounds in gasolines to increase the octane ratings thereof is extremely widespread. There are, however, several rather serious adverse efiects which accompany the use of leaded gasolines. One of these eifects, the deposition of various lead compounds within the combustion chambers of the engines, has been at least partially remedied by the use of halohydrocarbon scavengers such as ethylene dibromide. Another adverse effect, which has been attributed to the lead anti-knock compounds, is mis-firing of the engine due to spark plug fouling. This spark plug fouling is quite prevalent under conditions of high temperature engine operation and, particularly in the caseof aircraft engines, is a very serious type of trouble.

It is, therefore, an object of the present invention to overcome the previous shortcomings arising from the use of leaded gasolines. It is a further object to provide novel scavenger compositions for use with lead anti-knock compounds and in gasoline fuels. Another object is to provide novel fuel compositions containing said scavenger compositions. Other objects will be apparent hereinafter.

it has now been found that the use, as a lead scavenger in stable leaded gasoline fuel compositions, of a mixture of a halohydrocarbon scavenger and of a smaller'arnount of an alkaryl phosphate or phosphite will result in greatly improved operation of spark ignition internal combustion engines. More particularly, the use of such scavenger compositions substantially eliminates spark plug fouling, or at least minimizes such fouling to a point where it is no longer a material consideration in engine operation. This outstanding advantage is obtained without having the anti-knock characteristics of the fuel deleteriously aflected by the presence of the scavenger compositions.

The phosphorous compounds in the present scavenger compositions will be referred to hereinafter as anti-fouling compounds.

The halohydrocarbon scavenger which makes up the major proportion of the scavenger compositions of the present invention may be, for example, any of the numerous halogen scavenger compounds already known, such as ethylene dibrornide and ethylene dichloride (U.S. 2,398,281), acetylene tetrabromide (U.S. 2,490,606), hexachloro-propylene, monoand polyhalo propanes, butanes and pentanes (U.S. 2,479,900 and U.S. 2,479,902), polyhalo alkyl benzenes (U.S. 2,479,901 and U.S. 2,479,- 903), and the like, having a volatility between about 100 and about 0.1 mm. Hg. at 50 C.

The alkaryl phosphates and phosphites of the present invention are the esters of phosphoric and phosphorous acids, respectively. They may be readily prepared by reacting alkyl phenols with phosphoric acid to form the phosphates or with phosphorus trichloride to form the phosphites. Examples of suitable alkyl phenols are ortho-, meta-, and para-cresol; 2,4- and 2,5-xylenol; 2,4-dimethyl- 6-tert-butylphenol; octyl and nonyl phenols prepared by alkylation of phenol with diisobutylene or propylene trimited States Patent "ice 2,889,212 Patented June 2, 19 5 9 er, respectively. In general, any phenol containing a hydrocarbon side chain of non-aromatic character is a suitable esterifying agent for making suitable alkaryl phosphates and phosphites.

The trialkaryl esters are generally the most suitable anti-fouling agents, but the monoand dialkaryl esters as well as mixed esters containing only one or two alkaryl groups can also be used.

Of the alkaryl radicals the di-, tri-, and higher polyalkylated aromatic radicals are preferred over the monoalkyl aromatic radicals. Higher molecular weight alkyl groups, up to about 12 or 15 carbon atoms, are desirable.

The following are a few examples of suitable antifouling additives of the present invention: tri-(m-cresyl) phosphate, tri-(2,4-dimethylphenyl) phosphate, tri-(pethylphenyl) phosphate, tri-(2-methyl-4-isopropyl phenyl) phosphate, tri-(p-tert-butylphenyl) phosphate, tri-(2,6-dimethyl-4-tert-butylphenyl) phosphate, tri-(4-methyl-lnaphthyl) phosphate, ethyl di-(p-cresyl) phosphate, 2,6- xylenyl di-(n-butyl) phosphate, di-(2-methyl-4-ethylphenyl) phosphate, mono-(o-cresyl) diacid phosphate, tri- [p-(n-propyl) phenyl] phosphite, tri [p (1,1,3,3-tetramethylbutyl) phenyll phosphite, tri (2,4,6-trimethylphenyl) phosphite, tri-(p-allylphenyl) phosphite, di-(tertamylphenyl acid) phosphite, i-propyl di-(2,5-dimethylphenyl) phosphite, tri-(3,5-dimethylphenyl) phosphite, e C.

While substituents other than hydrocarbon radicals do not adversely affect the efficiency of the phosphates and phosphites as anti-fouling agents, it is preferred that the estler groups thereon be unsubstituted'hydrocarbon radica s.

When using the scavenger compositions of the present invention, the total amount of halogen scavenger plus anti-fouling agent will generally fall between about 0.6 and about 1.5 theories, based upon'the lead content of the gasoline, but may advantageously be as low as 0.4 or as high as 2.0 in some cases. The preferred range is from about 0.9 to about 1.2 theories.

The ratio of the two components of the scavenger composition is rather important. For example, if the proportion of halogen scavenger present is too large, excessive wear and corrosion of certain operating parts, such as exhaust valves and valve guides, is noted. If too small a quantity of halogen scavenger is used, the lead deposits are not efiectively scavenged. If too small a quantity of the anti-fouling compound is used, the spark plug fouling will not be materially reduced; and if too much of that compound is present the amounts of deposits and the plug fouling are both increased. In general, the theory ratio of the halogen scavenger or scavengers to the antifouling agents should be between about 3:2 and about :1. For best results this ratio should be between about 2:1 and about 15:1. As an additional limitation, the total scavenger mixture and the ratio of components therein should be adjusted so that the anti-fouling compound is present in an amount of between about 0.01 and about 0.6 theories, and preferably between about 0.05 and about 0.4 theories. Thus for the preferred minimum of 0.05 theory for the phosphorus anti-fouling agent and the maximum of 2.0 theories of total halogen scavenger and anti-fouling agent, it is seen that a ratio of 2.0 to 0.05, namely 40:1 represents a preferred maximum ratio of the sum of the two to the anti-fouling agent. A particularly desirable composition comprises 1 theory of the halogen scavenger and 0.1 theory of the anti-fouling compound. It is preferred that the weight concentration of the anti-fouling additive in the fuel be kept below 0.1%. It is to be understood that more than one of the compounds from each class (i.e., halogen scavenger or anti-fouling agent), may housed in any single composi- 3 tion, just so the total quantity of each type falls within the limits set forth above.

The term theory," when used in conjunction with a halogen scavenger compound, designates the amount of scavenger required to react stoichiometrically with a given amount of lead anti-detonant so that all of the lead atoms and all of the halogen atoms form PbBr or PbCl In orther words, a theory of scavenger is an amount which contains two atomic proportions of halogen for each atomic proportion of lead in the anti-detonant, or, a theory of the halohydrocarbon scavenger is one mol of the halohydrocarbon scavenger divided by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and therefore, the number of theories of halohydrocarbon scavenger present in a given composition is equal to the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead antidetonant present. As applied to the anti-fouling compounds, the term theory designates the amount required to react stoichiometrically with the lead so that all of the lead atoms and all of the phosphorus atoms form Pb (PO or, a theory of the phosphorus anti-fouling compound is one mol of the phosphorus anti-fouling compound multiplied by two-thirds (that is, two-thirds of a mol of the phosphorus anti-fouling compound), for each gram atom of lead in the lead anti-detonant present, and therefore the number of theories of the phosphorus antifouling compound present in a given composition is equal to the number of mols of the phosphorus anti-fouling compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonant present.

While it is to be understood that the present compositions may be utilized in any leaded gasoline fuel, the compositions are of particular importance with respect to use in reciprocating internal combustion engine gasoline fuels, and especially such aviation fuels. This is true because of the relatively more frequent occurrence of spark plug fouling in aviation engines, with the greater inherent danger to human life in the case of failures of such engines. In addition to the lead anti-detonant and the scavenger composition, the gasoline fuels, or the concentrates for addition thereto may also contain corrosion inhibitors and stabilizers, such as 2,4-dimethyl-6-tertia1'ybutylphenol and other alkyl phenols, N,N-dibutyl pphenylene diamine, hydroquinone, phenyl-alpha-naphthylamine, N-butyl-p-aminophenol, alpha-naphthol, etc., dyes and the like.

By the term leaded gasoline, and the terms of similar import, is meant a petroleum fraction boiling in the gasoline hydrocarbon range (between about 50 F. and about 450 F.) to which has been added a small amount, usually between about 1 and about 6 cc. per gallon, of a metallo-organic, usually an organo-lead, anti-knock compound, such as a tetra-alkyl lead, e.g., tetra-ethyl lead, tetra-i-propyl lead, etc.

The fuels to which the present scavenger compositions are added are preferably those which are relatively stable with respect to oxidation or gum formation. The stability may result from the use of stable base stocks such as aviation alkylate, straight run gasoline fractions, or other fractions which have been highly refined to remove olefins, or the stability may result from the use of oxidation stabilizers, such as those mentioned above. A few of the phosphorus compound anti-fouling agents of the present invention are known to have slight oxidation inhibiting properties, but these properties are very weak. It is much preferred that an additional oxidation inhibitor, i.e., a non-phosphorus stabilizer, be used in the present gasoline compositions. Thus, the gasoline fuels to which the present anti-fouling agents are added should be sufiiciently stable that the addition of the normal amount of anti-fouling agent will have no substantial effect upon the oxidation stability of the fuele.g., the

4 antiafouling' agents will not decrease gum formation in such fuels by more than about 5 or 10% As indicated above, the scavenger compositions of this invention are particularly useful in aviation gasoline. By the term aviation gasoline" is meant a relatively high grade of gasoline fuel used in aviation engines, as distinguished from the lower quality gasolines, or motor fuels used in automotive engines. Aviation fuels have a more closely specified boiling range, generally running from a minimum of about 100 F. to a maximum of about 350 F. The octane number of such fuels is generally in excess of 100. Because of the demand for high quality, thermally cracked fractions are never used in aviation gasolines. Catalytically cracked fractions may sometimes be used, but only after treatment to remove olefins. One of the reasons for the restrictions upon incorporation of cracked gasolines in aviation fuels is that the oxidation stability of aviation fuels must be much greater than that required for motor fuels. For example, when tested according to a method such as described in the patent issued to Thomas W. Bartram, U.S. 2,256,187, an aviation fuel base stock will go well beyond 4 or 5 hours before the oxygen pressure will have decreased by 5 pounds per square inch.

The following example is presented as illustrative of the outstanding results obtained with fuels containing the compositions of the present invention.

Example A Franklin 4AC-l76 engine was operated upon a 100/130 grade aviation fuel containing 4 cc. of tetraethyl lead per gallon of fuel and l theory of ethylene dibromide (EDB) scavenger. The engine was operated under lean mixture cruise conditions, but with 5 minutes of rich mixture idling every half-hour, and the elapsed time before spark plug fouling (as evidenced by the engine mis-firing), was noted.

The test was then repeated using different scavenger It is to be understood that the order of mixing the various constituents of the present compositions is immaterial. For example, the anti-fouling compound may be added to a gasoline which already contains the antiknock compound and halogen scavenger. Likewise, the metallo-organic anti-knock agent, the halogen scavenger and the anti-fouling compound may be first mixed, stored and handled as a concentrate, and added to the gasoline at a later time. A typical concentrate of this latter type has approximately the following composition:

Wt. percent Tetra-ethyl lead 50-65 Ethylene dibromide 25-40 Tricresyl phosphate 3-15 Kerosene, inhibitor, dye stabilizer, etc. 3-6

Under other circumstances it may be desirable to mix the halogen scavenger and the anti-fouling agent, or the antrknock agent and the anti-fouling agent, in the desired relative proportions and handle or store this mixture,

with or without stabilizers, inhibitors, etc., as a concentrate for later incorporation with the other components of the ultimate fuel composition. Thus, a typical suitable scavenger concentrate consists essentially of ethylene dibromide and tricresyl phosphate in the relative proportions of 25-40 and 315 parts by weight, respectively.

The present application is a continuation-in-part of our copending application, Serial No. 242,309, filed August 17, 1951, now abandoned which is in turn a continuation of our application, Serial No. 167,376, filed June 10, 1950, now abandoned.

We claim as our invention:

1. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor suificiently effective anti-detonant amount of an organo-lead auti-detonant, and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and of a phosphorus compound selected from the group consisting of alkaryl phosphates and alkaryl phosphites, each alkaryl group of which contains from 7 through carbon atoms, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that, where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of the phosphorus compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonant present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.01 to about 0.6, and the ratio of (a) to (b) is from about 3:2 to about 40:1.

2. A composition according to claim 1 wherein the phosphorus compound is a tri(alkaryl) phosphate.

3. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor sufliciently eifective anti-detonant amount of an organo-lead anti-detonant, and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and of a phosphorus compound selected from the group consisting of alkaryl phosphates and alkaryl phosphites, each alkaryl group of which contains from 7 through 15 carbon atoms, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that, where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of the phosphorus compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonant present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.05 to about 0.4, and the ratio of (a) to (b) is from about 3:2 to about 40:1.

4. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, from about 1 to about 6 cc.. of tetraethyl lead per gallon of fuel and a scavenger mixture for said tetraethyl lead consisting essentially of a halohydrocarbono scavenger and tricresyl phosphate, said halohydrocarbon scavenger being present in an amount such that the number of mols of halohydrocarbon scavenger multiplied by onehalf the number of halogen atoms per molecule, for each mol of tetraethyl lead present, is about 1.0, and said tricresyl phosphate being present in an amount such that the number of mols of tricresyl phosphate multiplied by three-halves, for each mol of tetraethyl lead present, is about 0.1.

5. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, from about 1 to about 6 cc. of tetraethyl lead per gallon of fuel and a scavenger mixture for said tetraethyl lead consisting essentially of a halohydrocarbon scavenger and tricresyl phosphate, said halohydrocarbon scavenger being present in an amount such that the number of mols of halohydrocarbon scavenger multiplied by one-half the number of halogen atoms per molecule, for each mol of tetraethyl lead present, is about 1.0, and said tricresyl phosphate being present in an amount such that the number of mols of tricresyl phosphate multiplied by three halves, for each mol of tetraethyl lead present, is about 0.2.

6. A fuel composition for internal combustion engines consisting essentially of a stabilized gasoline, a minor sufficiently effective anti-detonant amount of tetraethyl lead and a scavenger mixture for said tetraethyl lead consisting essentially of ethylene dibromide, ethylene dichloride and tricresyl phosphate, said ethylene dichloride, ethylene dibromide and tricresyl phosphate being present in amounts such that, where (a) is the total number of mols of ethylene dibromide and ethylene dichloride present, for each mol of tetraethyl lead present, and (b) is the number of mols of tricresyl phosphate present multiplied by three-halves, for each mol of tetraethyl lead present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.05 to about 0.4, and the ratio of (a) to (b) is from about 3:2 to about 40: 1.

7. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor sufiiciently eifective anti-detonant amount of tetraethyl lead, and a scavenger mixture for said tetraethyl lead consisting essentially of a halohydrocarbon scavenger and tri(2,5-dimethylphenyl) phosphate, said halohydrocarbon scavenger and said tri(2,5-dimethylphenyl) phosphate being present in amounts such that, where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each mol of tetraethyl lead present, and (b) is the number of mols of tri(2,5-dimethylphenyl) phosphate present multiplied by three-halves, for each mol of tetraethyl lead present, the total of (a) plus (b) is from about 0.4 to about 2.0, and (b) is from about 0.1 to about 0.2.

8. A composition according to claim 3, wherein the alkaryl groups of the phosphorus compound are polyalkaryl groups.

9. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor sufnciently effective anti-detonant amount of an organo-lead anti-detonant, and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and of a phosphorus compound selected from the group consisting of alkaryl phosphates and alkaryl phosphites, each alkaryl group of which contains from 7 through 8 carbon atoms, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that, Where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of the phosphorus compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonant present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.05 to about 0.6 and the ratio of (a) to (b) is from about 3:2 to about 40:1.

10. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor sufiiciently effective anti-detonant amount of an organo-lead anti-detonant, and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and of an alkaryl phosphate each alkaryl group of which contains from 7 through 8 carbon atoms, said halohydrocarbon scavenger and said phosphate being present in amounts such that, where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of the phosphate present multiplied by three-halves, for each gram atom 7 of lead in the lead anti-detonant present, the total of (a) plus (12) is from about 0.4 to about 2.0, (b) is from about 0.05 to about 0.4, and the ratio of (a) to (b) is from about 3:2 to about 40:1.

11. A composition according to claim 10, wherein the phosphate is a tri(alkaryl) phosphate.

12. A composition according to claim 10, wherein the phosphate is a tri-hydrocarbon phosphate.

13. A composition according to claim 10, wherein the phosphate is tricresyl phosphate.

14. A fuel composition for internal combustion engines consisting essentially of a stable gasoline composition, a minor sufiiciently efieetive anti-detonant amount of tetraethyl lead and a scavenger mixture for said tetraethyl lead consisting essentially of a halohydrocarbon scavenger and tricresyl phosphate, said halohydrocarbon scavenger being present in an amount such that the number of mols of halohydrocarbon scavenger multiplied by one-half the number of halogen atoms per molecule, for each mol of tetraethyl lead present, is about 1.0, and said References Cited in the file of this patent UNITED STATES PATENTS 2,155,678 Oosterbout Aug. 25, 1939 2,256,187 Bartram Sept. 16, 1941 2,301,370 Cook et a1 Nov. 10, 1942 2,364,921 Shokal Dec. 12, 1944 2,398,281 Bartholomew Apr. 9, 1946 2,405,560 Campbell Aug. 13, 1946 2,427,173 Withrow Sept. 9, 1947 FOREIGN PATENTS 421,568 Canada July 18, 1944 600,191 Great Britain Apr. 2, 1948

Claims (1)

1. A FUEL COMPOSITION FOR INTERNAL COMBUSTION ENGINES CONSISTING ESSENTIALLY OF A STABLE GASOLINE COMPOSITION, A MINOR SUFFICIENTLY EFFECTIVE ANTI-DETONANT AMOUNT OF AN ORGANO-LEAD ANTI-DETONANT, AND A SCAVENGER MIXTURE FOR SAID ANTI-DETONANT CONSISTING ESSENTIALLY OF HALOHYDROCARBON SCAVENGER AND OF A PHOSPHORUS COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKARYL PHOSPHATES AND ALKARYL PHOSPHITES, EACH ALKARYL GROUP OF WHICH CONTAINS FROM 7 THROUGH 15 CARBON ATOMS, SAID HALOHYDROCARBON SCAVENGER AND SAID PHOSPHORUS COMPOUND BEING PRESENT IN AMOUNTS SUCH THAT, WHERE (A) IS THE NUMBER OF MOLS OF HALOHYDROCARBON SCAVENGER PRESENT MULTIPLIED BY ONE-HALF THE NUMBER OF HALOGEN ATOMS PER MOLECULE, FOR EACH GRAM ATOM OF LEAD IN THE LEAD ANTI-DETONANT PRESENT, AND (B) IS THE NUMBER OF MOLS OF THE PHOSPHORUS COMPOUND PRESENT MULTIPLIED BY THREE-HALVES, FOR EACH GRAM ATOM OF LEAD IN THE LEAD ANTI-DETONANT PRESENT, THE TOTAL OF (A) PLUS (B) IS FROM ABOUT 0.4 TO ABOUT 2.0, (B) IS FROM ABOUT 0.01 TO ABOUT 0.6, AND THE RATIO OF (A) TO (B) IS FROM ABOUT 3:2 TO ABOUT 40:1.