US2618612A - Concentrated lead fluids - Google Patents

Description

Patented Nov. 18, 1952 CONCENTRATED LEAD FLUIDS William C. Howell, J12, Union, Allen R. Jones,

Roselle, and John 0. Smith, Jr., North Plainfield, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application June 1, 1950, Serial No. 165,602

6 Claims. 1

This invention relates to an improved composition consisting of a concentrated lead alkyl anti-detonant. The compositions of this invention include concentrated tetraethyl lead fluids containing amines, and particularly concern such compositions which also contain 2,6-ditertiary butyli-methyl phenol.

For many years it has been known that lead alkyl compounds, such as tetraethyl lead, effect a more or less catalytic action upon the detonation of fuels in which the compounds are employed in minor quantities. Thus, the lead alkyl compounds act to markedly improve the anti-knock characteristics of fuels. As a result of this discovery, compositions have been developed, and are commercially available consisting of concentrated mixtures of tetraethyl lead, or other lead alkyls, together with certain other compounds. It is the principal object of this invention to improve the concentrated lead fluids presently known, and to provide new and novel compositions having improved properties. Throughout the ensuing disclosure, the term lead fluid will be employed to refer to the general compositions embraced in this invention, and will designate concentrated lead alkyl solutions intended ultimately for addition to gasolines.

Attempts of the prior art to provide a composition of lead alkyls suitable for addition to gasoline have failed to meet certain requirements. First, the presently known concentrated lead fluids have been subject to instability, resulting in the precipitation of insoluble material. This precipitate formation materially decreases the value of the lead fluid by lowering the effectiveness of the fluid when added to gasoline, and by necessitating exten sive reconditioning prior to use in gasoline to prevent clogging of fuel systems. This latter condition is particularly acute in the case of aviation engines, as decomposition of lead fluids prior to, or after addition to an aviation gasoline can, and has caused failure of aviation engines in the air. Consequently, it is one of the principal objectives in this invention to provide lead fluids having hitherto unobtainable stability characteristics. The lead fluids of this invention may consequently be stored for longer periods of time and at adverse temperatures without the decomposition and precipitate formation heretofore frequently encountered.

A second problem ordinarily associated with present lead fluids, concerns the lead scavenger ordinarily contained in the lead fluid. In employing a lead fluid it has long been known that addition of the fluid to a gasoline will result in the formation of lead deposits in the combustion zone, and on ports, valves, and spark plugs associated with the combustion zone. These deposits are so objectionable that it has been the practice to combine a "lead scavenging agent in the concentrated lead fluid. The lead scavenging agent consists of a halogenated hydrocarbon capable of forming volatile lead halides upon combustion, so as to minimize the deposit of lead compounds. However, it appears to be an inherent characteristic of lead scavengers, or of halogenated hydrocarbons, to decrease the anti-knock properties of a lead fluid. Thus, if a lead fluid containing a scavenger, such as ethylene dibromide, is blended with a gasoline, the anti-knock rating of this gasoline will be substantially lower than in the case in which the scavenging agent is not contained in the lead fluid. This effect 'may be said to be a pro-knock effect resulting from the presence of halogenated hydrocarbons in a lead fluid. Insofar as this effect decreases the ultimate value of the lead fluid, by in part canceling the anti-detonation properties of the lead compound, it is apparent that means to overcome the pro-knock effect of lead scavengers in the fluid are desirable. Consequently, it is a further object of this invention to provide a lead fluid containing additives capable of coacting with lead scavengers agents so as to decrease the pro-knock effect of the lead scavenging agents in the fluid.

Still another problem which has arisen in connection with lead fluids, concerns the stability of the lead scavenger contained in the fluid. Insofar as the scavengers employed are halogenated hydrocarbons having sufficient reactivity to readily form metallic halides, it appears that this property permits decomposition of the halogenated hydrocarbons in the lead fluid during storage. This decomposition of the lead scavenging agent is undesirable since it decreases the critically adjusted concentration of the lead scavenger, permits corrosion of storage drums, and particularly galvenized storage drums in which the fluid is stored, and causes chemical changes affecting other additives such as dyes. A manifestation of this latter type of effect is exemplified by fading of the dyes added to impart color to the gasoline, this fading being due to changes in the chemical structure of the dyes resulting from the reactivity of the lead scavenging agent.

Consequently, it is a still further object of this invention to provide a lead fluid containing additives capable of stabilizing lead scavengin agents present in the fluid.

The manner in which the indicated objects of this invention may be attained will be appreciated from the following examples embodying the invention.

12,6-ditertiary butyll-methyl phenol.

EXAMPLE 1 A commercial tetraethyl lead anti-knock fluid known as Ethyl-l-T Aviation mix and containing one theory of the conventional lead scavenging agent, ethylene dibromide, was stored in a brown bottle containing a steel strip at 120 F., for a number of days. This quantity of ethylene dibromide is the quantity required to stoichiometrically react with the tetraethyl lead to form lead bromide. The steel strip was included in the test to simulate the contact of the fluid with a ferrous metal as ordinarily encountered in storage drums. It was found that after a period of one day an arbitrary quantity. of deposit was obtained which was visually characterized asbeing moderate. After a period of forty days storage, under the indicated conditions, the deposit had increased to a point which was characterizedas being a heavy deposit.

It is apparent from this data that a lead fluid 0.1 weight per cent of 2,6-ditertiary butyl-4- methy1 phenol was included in the composition ofExample l, and the number of days required to obtain comparable deposits was determined.

It was found that under conditions of storage identicalto those given in Example 1, ten days .time was required to form a moderate deposit comparable to the deposit formed in one day I when employing the composition used in Example However, only 15 days were required to form 1. a heavy deposit in the composition containing 2,-6-ditertiary butyll-methyl phenol, as compared to forty'days in the compositioncontainwing no inhibitor. It will be seen f-romthis .data that 2,6-ditertiary butyl-l-methyl phenol was -capable of inhibiting the decomposition of the lead fluid so as to extend the time required to obtain a moderate precipitate by a factor of about ten, although it actually accelerated .the timerequired to obtain .aheavy deposit.

EXAMPLE 3 .An-experiment similar to Example 2 was conducted in which 0.1 weight per cent of a mixture of isomeric xylidines was substituted for the In this case it was found that a heavy deposit was .obtained'after a period of only six days, indicating' that the xylidines were not satisfactory for preventing thedecomposition of the lead fluid.

EXAMPLE 4 Finally .05 weight per cent of 2,6-ditertiary .,butyl-4-methyl phenol and .05 weight percent of .xylidines wereadded to the compo ition'employed in Example 1. The resultant composition consisting. of. tetraethyl lead, .ethylene dibromide, I xylidines .phenol was materially more stable than any and 2,6-ditertiary butyll-methyl ofthe compositions tested in the preceding examples. 'Thus, it was found that even after a period of forty-three days, the quantity of de- It is significant that while Xyli-- not successful in stabilizing the lead fluid, when the two were employed together excellent stabilization was achie ed. It is a parent, therefore, that in some fashion not fully understood, the xylidines and 2,6-ditertiary butyl-e-methyl phenol co-act together in a synergistic manner to effectively stabilize the lead fluid.

amine.

.As indicated in the preceding examples, therefore, a specific embodiment of this invention con- .cerns a concentrated lead fluid containing both xylidine and 2,6-ditertiary butyl-4-methyl phenol. Such a composition as indicated by the 'data presented is :remarkably stable during prolonged storage. It is apparent that real improvements. instorage stability of lead fluids, as exemplified by the storage time permissible before precipitation reaches the objectionable stage of being classed as moderate, may also be achieved in the case in which the xylidines are not included in the composition. Consequently, the composition consisting of a lead fluid containing '2,6-ditertiary'butyl-i-methyl phenol is also embraced within the scope of this invention.

Experiments were also conducted to determine the effect on the properties of a lead fluid, achieved by combining amines other than xylidine in the fluid. These experiments are outlined in Examples 5-9, presented hereinafter.

EXAMPLE 5 In one application of this invention, a blend of 65% iso-octane and 35% normal heptane was prepared, and 4.11 cc.s of pure tetraethyl lead per gallon were added to this blend. The resulting ASTM-Motor octane number was found to be 87.8.

EXAMPLE 6 To the composition of Example 5, consisting of 65% iso-octane, 35% normal heptane and 4.11 cc.s per gallon of tetraethyl lead, was added four theories of halogen in the form of tertiary octyl bromide. In other words, the quantity of bromide used was four times the quantity of bromide stoichiometrically required to react with the lead present. It was found that the motor octane number of this fuel blend was 71.8 or 16 octane numbers below that of the fuel composition of Example 5. It is, therefore, to be seen that the addition of the halogenated hydrocarbon as a scavenger agent markedly decreased the octane number of the fuel.

EXAMPLE 7 To the fuel composition of Example 6, 0.5% by volume of di-isobutyl amine was added. It was found that the motor octane number of this fuel was 76.8. This indicates an octane number increase over the fuel of Example 60f five octane numbers, which must be attributed to the dieisobutyl amine.

EXAMPLE 8 Similarly, 0.5% of diethylene triamine was added to the fuel composition of Example 6. It was found the resulting motor octane number was 76.0 or was 4.2 octane numbers higher than the same fuel composition not containing the amine.

EXAMPLE 9 Finally, 0.5 volume per cent of phenyl amine was added to the fuel composition of Example 6. It was found that the motor octane number was 74.5 as compared to the octane rating of the fuel of Example 6 which was 71.8.

As indicated by the preceding examples, a marked increase in the octane rating of a leaded gasoline containing a scavenger can be obtained by incorporating therein a small amount of an Further experiments were conducted in order to determine whether the amine contributed an anti-knock effect to the gasoline or whether the amine offset the pro-knock efiect of the lead scavenger agent. Results of these tests are indicated in Table I and Table II below:

Table I NO LEAD SCAVENGING AGENT PRESENT Amine used None 2 E235" Phenyl- Leaded Octane No... 87.8 87.1 88. 5 88. 5

Increment 7 7 7 Table II 4 THEORIES OF TERTIARY OCTYL BROMIDE PRES- ENI. AS LEAD SCAVENGING AGENT Amine used None Phenyl- Leaded Octane No... 71.8 76. 8 76.0 74. 5 Increment, gross +5.0 +4. 2 +2. 7 Net, Unexpected +5. 7 +3. 5 +2.0

It will be noted from Table I that a blend consisting of 65% iso-octane and 35% normal heptane to which has been added 4.11 cc.s of pure fore, to be seen from the data of Table I that the efiect of the amines employed as in the indicated examples, is not due to the anti-knock effect of th amines but is in some way due to an interaction with the lead scavenger employed, resulting in an offsetting of the pro-knock effect of the scavenger. The octane number gain resulting from this effect is tabulated in Table It is also within the scope of this invention to obtain the beneficial effect of the amine type compound in offsetting th pro-knock effect of organic halides, by incorporating the amine grouping directly in the same molecule to which the halogen group is attached in the lead scavenging agent. type are bromo or chloro aminobenzene, bromo or chloro amino toluenes, bromo or chloro amino xylidines, bromo or chloro aminoethylbenzenes,

bromo or chloro amino mesitylene, bromo or chloro amino isopropyl benzene, and the like. The following example is illustrative of the manner in which this specific embodiment of the invention is applicable.

EXAMPLE 10 Blends of aviation gasoline containing 4.0 ml. of pure TEL per gallon were prepared, to which were added on the one hand, first bromo toluene and then 3-bromo-4-amino-toluene, and on the other hand, first bromo xylenes and then bromo amino xylenes. ASTM-aviation octane numbers were obtained on these blends, with the results shown in Table III.

However,

Examples of compounds of this 1 Data based on average of two tests on each blend. 1 Aviation gasoline plus 4.0 ml. pure TEL/gallon. 3 Additive present in 4.0 theories concentration.

It is evident from these data that not only did the incorporation of the amino grouping in the molecule completely counteract the proknock effect of th halogen, but actually a no ticeable increase in anti-knock quality was attained with these compounds.

As indicated by Examples 5 through 10, therefore, the properties of a lead fluid may be materially enhanced by including amines or an amine grouping in the lead fluid. It is particularly significant, that while the addition of amines would not be desirable in the case in which scavenging agents are not employed, when scavenging agents are employed, the amines are capable of overcoming the pro-knock effect of the scavenging agents. For this reason by combining the amines in the lead fluid prior to addition to gasolines, the desired quantities of amines may be provided in the ultimate fuel since this quantity depends upon the type and quantity of lead scavenger employed in the lead fluid. This quantity is the amount of amine equivalent to about 0.2 to 15 times the weight of the elemental lead present in the lead fluid employed. If the halide scavenger possesses a high degree of thermal stability, 2. lower concentration of amine in the lead mix may be used.

As a further example of the compositions of this invention, experiments were conducted to evaluate the stabilization of unstable scavenging agents which may be achieved by employing the additives heretofore described. It may be observed that the instability of lead scavenging agents has long been appreciated as an undesirable characteristic of lead fluids. Thus lead fluids containing the conventional scavenger, ethylene dibromide, have undergone storage changes resulting in the decomposition of as much as one-third of the ethylene dibromide present after prolonged storage. As an indication of the improvement which can be obtained, experiments were conducted employing one of the most unstable scavenging agents known; that is, acetlylene tetrabromide. This data is given in the following example:

EXAMPLE 1 1 lead fluid, it was found that no precipitate formation whatever could be observed, even after S0 days of storage. It is to be seen, therefore, that lead fluids containing 2,6-ditertiary butyl- 4-methyl phenol are particularly desirable as regards the improvement in the stability of the lead fluid which may be obtained.

' genated hydrocarbon scavenging agents.

7 In addition to the advantages of incorporating amines in lead fluids heretofore brought out, a further advantage of such compositions is that their use in internal combustion engines results in the formation of less engine deposits. It appears that amines have the property of promoting the formation of lead halides during combustion, when used in conjunction with halo- Consequently, lead fluids containing amines as well as lead scavengers exert better scavenging effects than in the case in which amines are not em-- ployed. Example 12 presents data showing this effect.

. EXAMPLE .12

Forty-hour engine tests were conducted employing a fuel .base'consisting of Grade 80 commercial aviation gasoline. A lead mix was added to this gasoline so as to provide 4 mls. per gallon of tetraethyl lead, and so as to provide one theory of monobromo xylenes; the monobromo xylenes being halogenated hydrocarbons which. are effective as a lead scavenging agent. At the end of a forty hour period of operation, the weights of deposits accumulating in the combustion chamber and on various parts of the engine were determined. The deposits were also analyzed and on the basis of these analyses the lead distribution was calculated. The test conditions employed in these tests were purposely made relatively mild in order to favor retention of deposits in the engine so that they could be analyzed. It is visualized that a high concentration of bromine in the retained deposit is very desirable, since this indicates a high concentration of lead bromide which under the more severe (hot) engine conditions encountered in practice, is scavenged through the exhaust, due to its relatively high volatility. Formation of lead sulfate and lead oxide, on the other hand, is undersirable, since these salts are relatively non-volatile and difficult to scavenge, even under relatively hot engine conditions. The data obtained in these tests are indicated in Table IV.

Table IV Fuel Base (grade 80 avia- Base-{-05 tion gasoline-+4 ml. vol. per- TEL/gallon-i-l theocent xyliry of bromo xylenes) dines "F/A-Ratio 0.074 0.060 0. 000

Deposit Weight, grams:

Combustion chamber..." 11 11 12 Spark plug 46 62 63 Exhaust valve 2 55 .35 .Grams of element incombustion chamber deposit:

71 7. 1 7. 5 2.7 1.7 2.4 Suliu .07 .15 .07 Calculated lead (1 bu Percent in form of PbBr 51 31 41 Percentin form of PbSO 7 13 6 Percent in form of PbO 43 56 53 1 0.060 is 90% and 0.074 is 111% of the stoichiometric fuel-air'ratio. The deposit Weight data shown here are corrected for the smaller amount of fuel consumed at 0.000 fuel-euratlo.

E (alculaled on the basis of simple lead salts.

N. B.dat:1 shown represent average oftwo engine tests on each fuel.

It is apparent from these data that when the fuel/air ratio was decreased from 0.074 to 0.060, an increase in the relative proportion of the non-volatile lead sulfate and lead oxide occurred, atthe expense of the relatively volatile lead. bromide' This is .also. indicated by a. decrease-in.

the grams of bromine found in the combustion chamber deposit and an increase in sulfur content. The weight of the spark plug. and exhaust valve deposits also increased when going to the leaner fuel/air ratio. When 0.5 vol.% xylidines was added to the fuel, however, and at the lean fuel/air ratio of 0.060 employed, the composition of the combustion chamber deposit obtained more nearly resembled that obtained at 0.074 fuel/air ratio with no 'xylidines. That is, the proportion of lead bromide was increased and the proportions of lead sulfate and lead oxide decreased. Likewise, the deposit of harmful exhaust valve deposits was also decreased. It is evident, therefore, that the inc usion of 0.5% xylidines in the fuel tended to counteract the harmuful effect with regard to deposit formation obtained by decreasing the fuel/air ratio from 0.074 to 0.060.

EXAMPLE 12 As a further indication of' the advantage to be gained by the inclusion of amines in gasoline, tests were conducted in a full-scale Pratt 82 Whitney aircraft engine-cylinder, model R-2800. It has been found that with engines of this type, one type'of difficulty experienced with operation at lean mixture strengths is failure of spark plugs after relatively short periods of operation. It has been found that when employing fuels of the composition of this invention, spark-plug failure attributable to lean-mixture operation can be markedly reduced. Thus, when an aviation gasoline containing 4.5 ml. of tetraethyl lead per gallon and 1 theory of ethylene dibromide was employed in the full scale single cylinder engine tests, failure of the spark plugs as evidenced by serious misfiring, occurred after only 37 hours of operation. Under similar test conditions, when employing a similar fuel to which had been added 1.0 vol.% xylidines, no evidence of spark plug failure was evident even after 43 hours on test. These test data are summarized in Table V.

Table V FULL SCALE, SINGLE CYLINDER. PRATT & XVHITNEY R-2800 ENGINE TESIS Conditions 01' test: 100 F. Intake air temperature, 140-145 p. s. i.

Indicated moan effective pressure, 30-38 inches hg. Manifold pressure, 300 F. Cylinder head'temperature, 1800 R. P. M.

Operation on rear spark plug only, with fuel injection through front spark plug lfirst plug failed at 24 hours. New plug installed and test rcsumed; this plug failed after 21 'hours operation.

It is evident from these data that the incorporation of 0.5% xylidines in the fuel caused a marked improvement in spark plug life when employing leaded gasoline under lean mixture operating conditions.

As heretofore described, therefore, the compositions of this invention embrace lead fluids containing amines, lead fluids containing 2,6- ditertiary butyl-4-methyl'phenol, and. in their preferred form compositions containing both amines and 2,6-ditertiary butyl-4-methy1 phenol. It is apparent that the actual composition of the lead fluid may be greatly varied within the scope of this invention. Thus, while lead tetraethyl is the lead anti-detonant ordinarily employed in lead fluids, if desired the lead tetraethyl can in part or whole be replaced with other lead alkyl compounds. For example, the following lead alkyl compounds may be employed: Tetramethyl lead, trimethyl-ethyl lead, dimethyl-diethyl lead, tri-ethyl-methyl lead, trimethyl propyl lead, trimethyl-isopropyl lead, dimethyl-di-n-propyl lead, di-methyl-di-isopropyl lead, tri-methyl-n-butyl lead.

In addition to these individual compounds, mixtures thereof obtained either by blending pure compounds or by using a reaction product composed of mixed lead alkyls may be employed. Again, the lead scavenging agent contained in the lead fluid may be selected from a large number of halogenated hydrocarbons. While the present lead scavenging agents in commercial use generally consist of either ethylene dibromide or a mixture of ethylene dibromide and ethylene dichloride, most broadly any halogenated hydrocarbon can be employed in lead fluids as lead scavengers. A preferred class of these compounds are C3 to C9 aliphatic and aromatic hydrocarbons containing from 1 to 3 bromine atoms. Examples of this general class of scavenging agent are the monobromo xylenes and dibromo toluene. The scavenging agent, or mixture of scavenging agents employed should be present in proportions advantageous to provide about one to two theories of halogen based on the lead in the fluid. It is also to be understood that if desired the lead fluids may contain dyes and other additives which may conventionally be added to gasolines.

The amines to be included in the lead fluids are generally contemplated to be aromatic amines, aliphatic amines and alkylene polyamines. Aniline, toluidine, and xylidine are examples of suitable aromatic amines. The aliphatic amines may be chosen from the class consisting of aliphatic monoamines having from 5 to 12 carbon atoms. Diethylene diamine, and diethylene triamine are examples of suitable alkylene polyamines. It is important, however, that the particular amine or amines chosen have boiling points falling within the gasoline boiling range, or in the range of about 150 to 500 F. Thus, if the boiling point of the amine employed falls below the indicated limit, loss of the amine will occur during transportation and storage of the lead fluid. If the amine has a boiling point above the limit indicated, undesirable deposits will result in the inductance system of engines in which the lead fluid may be employed. The quantities of amines to be added to the lead fluids are about 0.01 to 1000 weight per cent based on elemental lead.

When lead scavengers having a low proknocking tendency such as p-bromo toluene, bromo xylenes, 1,2,4-trichloro benzene, p-dibromo benzene, and hexochlorobutadiene are employed, the amount of amine needed to prevent a given octane number loss is less than that required when other scavengers are used. For example, the preferred range is about 1 to 100 weight per cent based on elemental lead. If scavengers having a pro-knocking tendency are used the preferred range is about to 1000 weight per cent.

Examples of scavengers having a large proknocking effect are benzyl bromide, benzo trichloride, and 2-chloro-2,3-dibromo butane.

As indicated, it is particularly preferred that 2,6-ditertiary butyl-4-methyl phenol be included in the lead mixes of this invention. This compound should be employed in Weight proportions of about 0.01 to 0.5 per cent, or preferably 0.05 to 0.2 per cent based on the elemental lead in the fluid.

It is further contemplated that the advantages of this invention may be obtained by employing amino-aryl halides as additives. Insofar as these compounds are halogenated compounds, this class of compound acts as a scavenging agent, and at the same time the amine group of the compounds provide the desirable effects demonstrated for the amines in lead fluid compositions. It is necessary, however, that the halogen atom in the amino-aryl halide be attached directly to a carbon atom.

It is also contemplated that in place of the 2,6- ditertiary buty1-4-methyl phenol anti-oxidants such as the alkylated phenylene diamine type may be employed.

What is claimed is:

1. A composition consisting essentially of lead tetraethyl and a compound selected from the group consisting of bromo-amino toluene; chloroamino toluene; bromo-amino xylene, and chloroamino xylene in which the proportion of the said amino compound is sufficient to provide about 0.5 to 2 theories of halogen based on the lead.

2. The composition defined by claim 1 in which the said halogenated amine consists of bromoamino toluene.

3. The composition defined by claim 1 in which the said halogenated amine consists of chloroamino toluene.

4. The composition defined by claim 1 in which the said halogenated amine consists of bromoamino xylene.

5. The composition defined by claim 1 in which the said halogenated amine consists of chloroamino xylene.

6. A composition consisting essentially of lead tetraethyl and a compound selected from the group consisting of bromo-amino toluene; chloroamino toluene; bromo-amino xylene, and chloroamino xylene in which the proportion of the said amino compound is sufficient to provide about 0.5 to 2 theories of halogen based on the lead, and about 0.01 to 0.5% (based on elemental lead) of 2,6-ditertiary butyl-4-methyl phenol.

WILLIAM C. HOWELL, JR. ALLEN R. JONES. JOHN 0. SMITH, JR.

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

UNITED STATES PATENTS Number Name Date 1,668,022 Midgley May 1, 1928 1,724,640 Calcott Aug. 13, 1929 2,230,844 Miller et al Feb. 4, 1941 2,324,118 Sweeney July 13, 1943 2,364,921 Shokal Dec. 12,1944 2,410,846 Walters Nov. 12, 1946 2,413,262 Stirton Dec. 24, 1946

Claims (1)

1. A COMPOSITION CONSISTING ESSENTIALLY OF LEAD TETRAETHYL AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF BROMO-AMINO TOLUENE; CHLOROAMINO TOLUENE; BROMO-AMINO XYLENE, AND CHLOROAMINO XYLENE IN WHICH THE PROPORTION OF THE SAID AMINO COMPOUND IS SUFFICIENT TO PROVIDE ABOUT 0.5 TO 2 THEORIES OF HALOGEN BASED ON THE LEAD.