US2296200A - Stabilizing solution of tetra-alkyl lead compounds - Google Patents

Description

Patented Sept. 15, 1942 STABILIZING SOLUTION 0F TETRA-ALKYL LEAD CODI'POUNDS Troy Lee Cantrell, Lansdowne, and Carlton Louis Suplee, Malvern, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application February 27, 1940, Serial No. 321,132

6 Claims.

This invention relates to stabilizing solutions of tetra-alkyl lead compounds; and it comprises a method of stabilizing liquids containing such compounds, particularly ethyl gasoline, to inhibit the development of a hazy appearance, wherein small quantities of certain amino salts of fatty acids are added'to such liquids; and it also comprises as an anti-knock motor fuel stable to light, a gasoline containing a tetra-alkyl lead compound and a small quantity of such an amino salt of a fatty acid; all as more fully hereinafter set forth and as claimed.

It is customary in the production of so-called ethyl gasoline'f to add a small amount of a tetra-alkyl lead compound, usually tetra-ethyl lead, to a good grade of gasoline to reduce knocking in high compression gasoline engines. The amountof tetra-alkyl lead compound added to a gasoline depends upon the nature of the gasoline and the desired anti-knock rating. Tetra-ethyl lead is customarily added to the gasoline in the "form of a liquid preparation called ethyl fluid," which usually is a solution containing a mixture of tetra-ethyl lead, alkylene di-halide (e. g. ethylene di-bromide or ethylene di-chloride or both). Usually a small amount of a dye' is also added to impart a distinctive color; addition being either to the fluid or to the gasoline. The ethyl fluid is added to the gasoline in a quantity sufiicient to produce the desired anti-knock rating. In some cases only a relatively small amount is added, but sometimes, as with certain aviation grades of gasoline, a large amount is used. Gasoline to which a large amount of tetra-ethyl or other tetra-alkyl lead has been added is often referred to as a heavily leaded gasoline.

Although tetra-alkyl lead compounds, and in particular tetra-ethyl lead, are particularly efficient for imparting anti-knock properties to gasoline, their employment is not entirely free from disadvantage. For one thing, leaded gasoline tends to develop a hazy appearance upon standing, particularly in strong sunlight. In direct sunlight in the summer time, any ethyl gasoline 4 may develop a perceptible haziness after an hour or two of exposure, and longer periods of exposure may result in a very marked haziness. Precipitation finally occurs. This hazing phenomenon is also sometimes observed in the ethyl fluid itself.

The formation of haze in gasoline is objectionable. Customers prefer a product which is clear and transparent; free from haze or muddiness. A further and perhaps more important objecgasoline often develops with haze formation. Also, damage is likely to occur in the fuel lines and carbureter. The development of haze in ethyl fluid itself is also objectionable, because when a hazy ethyl fluid is blended with gasoline to form ethyl gasoline, the haze is at once introduced into the fuel with all its attendant disadvantages.

An object achieved by this invention is to achieve a stabilization against haze formation in liquids containing tetra-alkyl lead compounds, such as ethyl fluid and ethyl gasoline.

We have found that haze formation in solutions of tetra-alkyl lead compounds, such as ethyl fluid and ethyl gasolines, can be retarded or obviated by incorporating in such solutions small quantities, proportioned on the amount of tetra-alkyl lead in solution, of salts or soaps formed by fatty acids higher than acetic acid.

with cycloaliphatic amines or with the aliphatic amines higher than the methyl amines.

' These higher amino salts of higher fatty acids 7 may be added with advantage to liquids containing tetra-alkyl lead compounds generally. They are particularly advantageous in stabilizing moderately leaded gasolines such as ordinary ethyl gasoline of automobile grades. However, they effect a stabilization of even heavily leaded grades of gasoline, such as certain aviation grades of gasoline. The salts being soluble in gasoline and the like, the manner of incorporating them in solutions of tetra alkyl lead compounds is not critical. For example they may be incorporated in ethyl fluid at any stage during the preparation thereof or they may be incorporated in gasoline, prior to the addition of ethyl fluid, along with the ethyl fluid, or subsequent to blending the ethyl fluid with the gasoline.

Even very small proportions of these salts arev sumcient to exert a substantial stabilizing effect against light in fluids containing .tetra-alkyl lead compounds. In practically all cases an addition of from 3 to 80 pounds of salt per 1000 barrels of gasoline containing from 0.01 to 1.0 per cent by weight of tetra ethyl lead exerts a marked stabilizing'efiect against light; to produce an ethyl gasoline stable to light under the usual conditions of exposure. In general, commercial ethyl gasoline containing from 0.02 to 0.40 per cent by tion is that a reduction in the octane rating of 55 weight of tetra-ethyl lead requires only about 5 to about 30 poundsof these amino salts of fatty acids per barrel of gasoline to produce a satisfactorily stabilized product with ordinary conditions of storage and handling. Mostly 5 to 20 pounds of such salts per 1000 barrels of gasoline carrying from 0.02 to 0.40 per cent of tetra-ethyl lead suflices. However, as there is some variance in the stabilizing power of the difl'erent salts, the amounts to be added vary accordingly.

The application of the higher amino salts of higher fatty acids to the stabilization of solutions of tetra-alkyl lead compounds against haze formation is not limited to leaded gasoline, but they may be incorporated directly in the ethyl fluid or concentrate" with advantage. When these salts are incorporated in the tetra-alkyl lead concentrate, they stabilize it during storage and shipment, and a concentrate containing such a salt can then be added to gasoline to impart thereto both anti-knock properties and resistance to hazeformation. Ordinarily the proportion of salt added .to ethyl fluid is somewhat greater than is required for its stabilization so that by the addition of the usual small amount of ethyl fluid to the gasoline a suitablestabilizing amount of the salt will be incorporated in the gasoline. Generally from 1 to 10 per cent by weight, based on the tetra-ethyl lead, of a higher amino salt of a higher fatty acid stabilizes commercial tetraethyl lead concentrates, such as ethyl fluid, and on adding the stabilized concentrate to gasoline to produce ethyl gasoline, a satisfactory stabilized ethyl gasoline is obtained.

A large variety of amino salts of fatty acids may be advantageously employed to stabilize solutions of tetra-alkyl lead compounds against haze formation. However, we have found that there is a considerable variance in the stabilizing potencies of these salts. Thus we have found that the amino salts of acetic acid, and the fatty acid salts of the methyl amines (mono-, diand trimethyl amines) do not constitute wholly satis-- factory stabilizers for ethyl fluid, ethyl gasoline and the like. However, salts formed by fatty acids higher than acetic acid with aliphatic amines higher than the methyl amines (i. e., amines containing at least one alkyl group higher than the methyl group) or with cycloaliphatic amines do constitute satisfactory stabilizers. Of these higher amino salts of higher fatty acids we have found that those containing large hydrocarbon radicals are more eflective stabilizers than those containing only small hydrocarbon radicals. For example, butylamine laurate, cyclohexylamine oleate and amyl cyclohexyl amine stearate constitute more effective stabilizers than ethylamine propionate. The higher compounds have a greater solubility in gasoline.

We have found, moreover, that the aliphatic amines higher than the methyl amines, and the cycloaliphatic amines form more effective sta-' bilizers with fatty acids than do the aromatic amines, such as aniline and the naphthylamines. This may be due to the low basicity of the aromatic amines as compared with the aliphatic and cycloalipathic amines. The ionization constants of the aromatic amines are of the order 10 The higher aliphatic and the cycloaliphatic amines, 'on the other hand, have ionization con-- stants of the order of 10-- to i; e. they are much stronger bases.

The secondary amines such as di-butylamine, di-cyclohexylamine and amyl cyclohexyl amine are best adapted for the present purposes. Oleic and stearic acid are particularly effective fatty acids, and of the two, oleic is the more effective.

The oleates, stearates and laurates of di-cyclohexylamine and amyl cyclohexyl amine are particularly useful stabilizers because of their high inhibiting power. From 5 to 20 pounds of .these salts per 1000 barrels of ethyl gasoline containing 0.02 to 0.40 per cent by weight of tetra-ethyl lead produces a gasoline which is perfectly bright after 5 hours exposure to bright sunlight. Also, they are only slightly soluble in water; less so than most of the other amine-fatty acid salts. Ethyl fluid and ethyl gasoline containing them are less damaged on contact with water.

Many other salts, however, are .also satisfactory, for example, butylamine and di-butylamine oleates, amylamlne oleate, di-butylamine stearate, cyclohexylamine oleate, benzylamine oleate, N-phenyl cyclohexylamine oleate, and piperidine oleate.

It is an advantageous property of many of the higher amine-higher fatty acid salts that they are liquid or semi-liquid in character and hence are readily blended with gasoline, ethyl fluid and the like. They are freely mixable.

Besides individual amines and individual fatty acids, mixtures of amines and of fatty acids may be used in forming the stabilizers of this invention. Thus,commercial mixtures of fatty acids derived from the ordinary fatty oils, such as coconut oil, may be employed in place of a single fatty acid such as oleic acid.

A particular advantage of the stabilizers used in this invention is their cheapness and ease of production. The source materials-amines and fatty acids-are in many cases available in large quantities at very low cost. The method of manufacture of the salts therefrom consists merely of mixing the ingredients and sometimes heating the mixture during the reaction.

The stabilizing salts used in this invention also have other properties which make them desirable. They do not injuriously aflect the oxygen stability of gasoline or promote gum formation therein. Samples of cracked ethyl gasoline containing these amine-fatty acid salts have been aged and tested for oxygen stability and by the copper dish method for gum formation. The presence of the salts did not promote either oxygen instability or gum formation. The salts are non-corrosive to common packaging materials such as steel, zinc, copper and tin, and are compatible with the dyes commonly used in ethyl gasoline. All of them are sufficiently soluble in gasoline to accomplish the intended stabilization. Continued storage of gasoline containing these salts does not affect their stabilizing properties.

The following specific examples will serve to illustrate the excellent haze-inhibiting properties of the higher amine-higher fatty acid salts; Example 1.-Ethyl gasoline containing 0.1 per cent by weight .of tetra-ethyl lead (added in the form of ethyl fluid comprising tetra-ethyl lead, ethylene dibromide, ethylene dichloride, and a dye) was treated with butylamine oleate in the proportion of 10 pounds of the latter per 1000 barrels of gasoline. exposed for 5 hours to sunlight and the appearance of the gasoline was noted. At the end of the 5-hour exposure no haziness whatever could be observed. In contrast to this result, a sample of the same ethyl gasoline, exposed under identical conditions but containing no inhibitor, showed a large degree of haziness at the end of the 5-hour period, and a heavy precipitate resulted.

Example 2 .Benzylamine oleate, N-phenyl cyclohexyl amine oleate and di-butylamlne stearate were tested in the same amounts and The resulting mixture was The results obtained with them were satisfactory.

Benzylamine oleate, the least potent of the threestabilizers, stabilized ethyl gasoline to such a point that at the end of the -hour exposure to sunlight only a small degree of haziness was observed, whereas the unstabilized gasoline developed a heavyprecipitate.

Example 3.-Di-cyclohexylamine oleate, amyl cyclohexyl amine oleate and di-cyclohexylamine stearate were tested in a manner identical with that of Example 1. In each case, at the end of I the 5-hour exposure to sunlight no haziness whatever was noted; the ethyl gasoline was perfectly bright and clear.

While our invention has been described herein with reference to particular embodiments and specific examples thereof, we do not intend that our invention shall be limited to such embodiments and examples except as hereinafter defined in the appended claims.

What we claim is:

1. A method of stabilizing a solution of a tetra-alkyl lead compound against haze formation, which comprises incorporating in said solution an amine salt of a fatty acid, in an amount, proportioned on the amount of tetra-alkyl lead present, suflicient to inhibit haze formation due to the presence of said amount of tetra-alkyl lead, said amine salt being a salt of a secondary amine selected from the group consisting of dibutylamine, di-cyclohexylamine and amyl cyclohexyl amine and a fatty acid selected from the group consisting of oleic, stearic and lauric acids.

2. A method of stabilizing a motor fuel containing about 0.01 to 1.0 per cent of tetra-alkyl lead against haze formation, which comprises incorporating in said motor fuel di-butylamine oleate in an amount between 3 and 80 pounds per 1000 barrels, sufficient to inhibit haze formation due to the presence of said amount of tetraalkyl lead.

3. A method of stabilizing a motor fuel containing about 0.01 to 1.0 per cent of tetra-alkyl lead against haze formation, which comprises incorporating in said motor fuel di-cyclohexylamine oleate in an amount between 3 and 0 pounds per 1000 barrels, sufiicient to inhibit haze formation due to the presence of said amount of tetra-alkyl lead.

4. As an improved anti-knock motor fuel stable to light, a gasoline containing a tetra-alkyl lead compound in amount suflicient to impart antiknock properties to said gasoline and an amine salt of a fatty acid in amount suflicient to inhibit haze formation due to the presence of said amount of tetra-alkyl lead, said amine salt be-' ing a salt of a secondary amine selected from the group consisting of. di-butylamine, di-cyclohexylamine and amyl cyclohexyl amine and a fatty acid selected from the group consisting of oleic, stearic and lauric acids.

5. As an improved anti-knock motor fuel stable to light, a gasoline containing about 0.01 to 1.0 per cent of tetra-alkyl lead and dibutylamine oleate in an amount between 3 and pounds per 1000 barrels, sufiicient to inhibit haze formation due to the presence of said amount of tetra-alkyl lead.

6. As an improved anti-knock motor fuel stable to light, a gasoline containing about 0.01 to 1.0 per cent of tetra-alkyl lead and di-cyclohexylamine oleate in an amount between 3 and 80 pounds per 1000 barrels, suflicient to inhibit haze formation due to the presence of said amount of tetra-alkyl lead.

, TROY LEE CANTREEL.

CARLTQN L. SUPLEE.