US2410829A - Stabilization of gasoline and of addition agents therefor - Google Patents

Description

Patented Nov. 12, 1946 STABILIZATION OF GASOLINE AND OF ADDITION AGENTS THEREFOR Daniel B. Luten, Jr., Berkeley, Calif., assigno'r to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application January 17, 1944, Serial No. 518,667

11 Claims.

This invention is based on the finding of the unique and unusual properties of certain ortho, para or di-alkyl phenols in stabilizing certain substances commonly employed as motor fuel or gasoline additives. In particular, it pertains to the stabilization of aromatic amines and to the stabilization of hydrocarbon compositions such as gasoline which contain these amines alone or in combination with metal antiknock additives such as tetra alkyl lead, metallic carbonyls, etc.

It is an object of the invention to produce stabilized aromatic hydrocarbon amines. These stabilized or inhibited aromatic amines may be dissolved in gasoline or other motor fuel; hence, it is an object of the invention to provide motor fuels containing aromatic amino compounds which fuels are stabilized against oxidation or decomposition. Another purpose is to provide motor fuels containing tetra alkyl lead and/or metallic carbonyl compounds which compounds are stabilized by the additives of the present invention. An additional object is to provide improved motor fuels such as aviation' gasoline having high antiknock ratings and improved oxidation or storage stability. Further objects will be apparent from the following description.

Aromatic amino compounds, upon exposure to air, often exhibit a tendency to change color as their period of contact with oxygen lengthens. This color change is the first noticeable symptom of oxidative decomposition which, since it is catalytic in nature, proceeds, if unchecked, at an accelerated rate until the amino compounds are entirely altered in composition and usefulness.

A particular employment for aromatic amino compounds, especially those of low molecular weight, is in motor fuels such as gasoline in which they exert a beneficial anti-knock effect. It will be appreciated, therefore, that if such aromatic amines are produced for incorporation in gasoline, it is especially desirable that they be stabilized against oxidation, since if such decomposition sets in either before or after their addition to the base fuel, it will not only decrease their own value as a fuel component but may also promote the decomposition of the base fuel,

resulting in gum formation, increased knock rating, volatility changes etc.

Aromatic amines have also been added to cracked gasolines in small quantities in order to decrease the gum forming tendencies of the gasoline. Since such inhibition of the oxidation of the gasoline is achieved by the preferential oxidation of the amino inhibitor, it will be realized how difficult it may be to find a substance which will stabilize such aromatic amines themselves, both before and after their addition to'gasoline.

For this problem, the broad class of known gasoline inhibitors has been found ineffective.

Indeed many of them act as pro-oxidants or oxidation accelerators for the amino compounds. Commonly used gasoline stabilizers which were found to be pro-oxidantsfor aromatic amines in- 19 clude: para benzyl amino phenol, alpha-naphthol,

4-tertiary butyl catechol, hydroquinone, pyrogallol, beta-naphthol, para phenylene diamine and diphenyl phenylene diamine. Other pro oxidant substances include thiophenol, thiodiglycollic acid, FeS, sulfanilic acid, salicyclic acid,

brom benzene, dianisidine,-iodine, iron or galvanized iron surfaces, sodium nitrite, benzoyl peroxide, lead peroxide, copper phenyl propionate, manganese oleate and stannous chloride.

Gasoline inhibitors which were found to be without inhibiting eflfect on aromatic amines include: phenyl alpha naphthylamine, mixtures of cresylic acids boiling between about 220 C. and 240 C., 2,3,5,6-tetra methyl phenol, penta-methyl phenol, 2,3,5-trimethyl phenol, para, para dihydroxy diphenyl, guaiacol, durohydroquinone, thymol, resorcinol, anthraquinone, etc.

It has now been found, however, that a particular group of di-alkyl phenols in which the alkyl groups are attached at the 2 and 4 or ortbo and para positions, as hereafter more fully described, have unique stabilizing properties for aromatic amino compounds, either when the amines are alone or when they are dissolved in gasoline. The stabilizing agents of the present invention are dialkyl phenols in which the 4 or para position and one ortho position (2 or 6) are occupiedbya primary, secondary or tertiary alkyl radical. Only one of the alkyl radicals may be 40 tertiary, however, so one may have a di-primary alkyl, di-secondary alkyl, mono-primary monosecondary alkyl, mono-tertiary mono-primary alkyl, or mono-tertiary mono-secondary alkyl' phenol.

The ortho and para alkyl radicals (only one of which, as just stated, being a tertiary alkyl) may conveniently be methyl, ethyl, n-propyl, isopropyl, n-, iso-,' secondary and tertiary butyl,'

and the various primary, secondary or tertiary amyl, hexyl, heptyl, octyl, and homologous radicals. In general, radicals containing not more than about 16 or 20 carbonatoms are preferred, those 2,4 di-alkyl phenols containing a total of not more than about 12 carbon atoms in all alkyl groups being particularly desirable (i. e. those having a maximum of about 18 carbon atoms counting the nuclear'carbon atoms). The alkyl radicals should generally be such as to render the phenols soluble in the composition to which they are added. Too high a number of carbon atoms causes the compounds to be waxy and diflicultly soluble. However, particularly in gasolines of appreciable aromatic contents, phenols with relatively large wax radicals containing up to say 35 or 40 or even more carbon atoms may be suitable, especially if those radicals contain branched chains. The ortho or para radicals may also comprise one or more aromatic groups such as phenyl, tolyl, benzyl, etc., although strictly aliphatic radicals are generally superior.

The above limitations regarding the nature and placement of the several hydrocarbon radicals on the phenol are very important. In this connection, it is of interest that 2,4,6-tri tertiary alkyl phenols, for example 2,4,6-tri tertiary butyl phenol, have little anti-oxidant value for aromatic amines-some phenols are worse than no inhibitor at all. Thus, some tri alkyl phenols found to be pro-oxidants for aromatic amines are 2,6-ditertiary butyl-4-methyl or -ethyl phenols, 2,6-dimethyl-4-tertiary butyl pheno, 2,5-dimethyl-4-tertiary butyl phenol and 2,4-ditertiary butyl-5-methyl phenol.

The aromatic amines generally added to gasoline for their antiknock value are usually mononuclear monoamines having not more than a.

higher'nuclearly alkylated anilines (which may.

also be substituted on the N'atom), such as toluidines, xylidines, cymidine, cumidine, pseudo cumidine, etc., as well as suitable substituted derivatives. Mixtures of aromatic amines, as well as the individual amines, may be employed and tion of colored products and oxidation of the xylidine occur simultaneously on aging, the decrease of light transmitted through the solution is an indication of the extent of oxidation. The following determinations were made at 70 0., one atmosphere of air and employing inhibitor concentrations of 0.2% by weight.

amines, such as the earlier enumerated monocycle monocyclic aromatic amines having less than a total of about 7 carbon atoms in all alkyl groups,

exhibit an inhibiting or stabilizing efiect on gasoline, which efiect is greater than the calculated total of the inhibition produced by each additive alone. This effect is particularly noticeable in saturate or initially stable gasoline such as aviation gasoline composed of straight run, cyclopentane,- aromatics, alkylate, hydroformed fractions and the like, which initially stable gasoline has been rendered unstable by the incorporation of tetra alkyl lead.

Another tri alkyl phenol, 2,4-dimethyl-6-tertiary butyl phenol is a singularly successful inhibitor of tetra alkyl lead fluid or of initially stable gasoline composed of saturate fraction (such as enumerated above) which gasoline has been rendered unstable by tetra alkyl lead. This phenol will also inhibit the oxidation of the present aromatic amines. Hence when stabilizing amine-containing leaded gasoline or aromatic poly-amines may also be used. Likewise, aromatic-rich petroleum fractions may be nitrated and reduced to give mixtures such as described in U. S. Patents 1,844,362 and 2,252,099, which mixtures may be blended in a motor fuel according to the present invention.

However, the di-alkyl phenolic inhibitors will also stabilize mcnonuclear amines having a greater number of carbon atoms than indicated above, i. e. greater than 6, as well as poly-cyclic aromatic hydrocarbon amines, e. g. various naphthylamines, alkyl naphthylamines, aryl naphthylamines, anthracylamines and the like.

It is understood that the inhibitor must be well distributed throughout the substance to be protected. Thus, it the amine is a liquid under normal conditions, the inhibitor should be intrue or colloidal solution. If it is a solid, the inhibitor may be incorporated by first melting the amine, distributing the necessary amount of inhibitor as by dissolving it, and then allowing the mixture to solidify; or else by merely spraying the inhibitor or a solution thereof onto the solid amine. In undiluted aromatic amines, the content of the poly alkyl phenol may range from about 0.01% to 1% (by weight), preferably about 0.1% to Quantitative determinations of the effectiveness of inhibitors of the present invention in stabilizing xylidine were made by determining the light transmission through various xylidine samples for a specific wave length 0:550 mu) using a Coleman spectrophotometer. Since the formaamines which are later to be incorporated into leaded gasoline (in particular into saturated type gasoline such as aviation gasoline) it may be advantageous to employ 2,4-dimethyl-6-tertiary butyl phenol together with a dialkyl phenol of the present invention. Thus, for example, the tetra ethyl lead will be stabilized by the 2,4-dimethyI-G-tertiary butyl phenol while the aromatic amines will be stabilized by one or more of the present dialkyl phenols such as 2-tertiary butyl- 4-methyl phenol, Z-tertiary butyl-4-ethyl phenol, 2,4-dimethyl phenol, 2-inethyl-4-tertiary butyl phenol, etc.

Effective total amounts of the poly alkyi phenolic inhibitors in a gasoline are generally between about 0.001% to 0.1% (by weight), a preferred range being from about 0.001% to about 0.01% or 0.1%. The aromatic amines may be employed in about 0.25% to 3% (by volume) in a gasoline although higher or lower quantities can also be used. The upper limit is usually prescribed by maximum boiling range specifications of the gasolines. Since the amines are relatively high boiling, they may raise the upper boiling range of the gasoline above permissible limits it used in excessive amounts. On the other hand, amounts efl'ect when applied particularly to saturated,

' like.

tallic carbonyls in gasoline may often be per-- initially stable gasolines rendered unstable by the addition of metal antiknock compounds, as well as to unsaturated, initially unstable gasolines (such as cracked gasolines). with or without metal anti-knock compounds. Up to about 6 cc. per gallon of tetra ethyl lead or anequivalent amount of another tetra alkyl lead may normally be added to gasoline.

Solubilizers for the aromatic amines may also be present, particularly in gasolines which contain but a small amount of aromatic constituents. Such mutual solvents may be low molecular weight'alcohols, ethers, ketones (in particular five or six carbon atom unsymmetrical ketones) aromatics such as benzene, toluene, etc. i 1 A further advantage in the use of the combination of aromatic amine and poly alkyl phenol is that when the inhibitor efiectiveness of the compounds begins to wear off, a sharp break in the induction period does not occur, but rather the formation of deterioration products proceeds slowly and a visible precipitate forms only after extended aging. This is in marked contrast to the action of most oxidation inhibitors whose efiectiveness is usually terminated quite suddenly at the end of their period of stabilization with the rapid formation of degradation products in the gasoline and the consequent prompt termination of the usefulness of the motor fuel.

It has also been found that the combination of the present poly alkyl phenols withv aromatic amines shows extraordinary stabilizing power for metallic carbonyl compounds contained in gasoline or other motor fuel.

It is known that numerous metallic carbonyl compounds possess desirable antiknock properties when incorporated in a hydrocarbon fuel. However, various difliculties have beset their particular utilization, notable among which has been their chemical instability and ease of decomposition on standing, as well as their tendency to catalyze the breakdown of the hydrocarbon fuel, producing such efiects as gum formation and the Although the anti-knock function of meformed in part by other compounds such as tetra ethyl lead, there are particular applications in which such other substances are not applicable as in a break in fuel or in a heavily leaded fuel to which the addition of more tetra alkyl lead would have little effect.

Metallic carbonylic compounds contemplated by the present application are, for example, the various carbonylic compoundsof iron, nickel, cobalt, molybdenum, mercury, etc., as well as their various applicable derivatives. Among these may be mentioned Fe(CO)4, Fe(CO)5, FE4(CO)15NO, FeNi(CO)9, Ni(CO)4, Co(CO)3NO, M(CO)s, Hg(Co(CO)4)2. under engine conditions to produce metallic carbonyls may also be employed, such as complexes of carbonyls with ammonia, amines, alkanol amines, etc.

In general, an amount of metallic carbonylic compound in the range of about 0.25 to 3 'cc./gallon is adequate for a break-in fuel,'although up to about cc./gallon may be used. In addition, there may be present up to-about 6 cc. of commercial tetra alkyl lead per gallon as well as various solutizers such as alcohols, ketones, esters, pyridine, aromatic constituents such as benzene and the like.

About 0.001% to 0.1% by weight of the alkylated phenol in association with about 0.25% to 3% by volume aromatic amine is generally adequate to stabilize the metallic carbonyl in a gasoline. Particularly when tetra alkyl lead is also present, a part of'the phenolic inhibitor content may be 2,4-dimethyl-6-tertiary butyl phenol.

The invention claimed is: v

1. A composition comprising hydrocarbons containing a knock-reducing amount of a mononuclear aromatic amine in which the total number of carbon atoms in all alkyl radicals is less than 7 and a stabilizing amount of a 2,4-dialkyl phenol in which one alkyl substituent is selected from the group consisting of primary, secondary nd tertiary alkyl radicals and the other alkyl substituent is selected from the group consisting of primary and secondary alkyl radicals.

2. A composition comprising hydrocarbons containing a knock-reducing amount of a mononuolear aromatic amine in which the total number of carbon atoms in all alkyl radicals is less than 7 and a stabilizing amount of a 2,4-dialkyl phenol having a maximum of about 18 carbon atoms and in which one alkyl substituent is selected from the group consisting of primary, secondary and tertiary alkyl radicals and the other alkyl substituent is selected from the group con-.

sisting of primary and secondary alkyl radicals.

3. A composititon comprising hydrocarbons containing about 0.25% to 3% (by volume) of a mononuclear aromatic amine in which'the total number of carbon atoms in all alkyl radicals is less than 7 and about 0.001% to 0.1% (by weight) of a 2,4-dialkyl phenol in which one alkyl substituent is selected from the group consisting of Compounds which decompose of primary,

the group consisting of primary, secondary and tertiary alkyl radicals and the other alkyl substituent is selected from the group consisting of primary and secondary alkyl radicals.

4. A composititon comprising gasoline hydrocarbons containinga tetra alkyl lead compound, a knock-reducing amount of a mononuclear aromatic amine in which the total number of carbon atoms in all alkyl radicals is less than 7 and a stabilizing amount of a 2,4-dialkyl phenol V having a maximum of about 18 carbon atoms and in which one alkyl substituentis selected from the group consisting of primary, secondary and tertiary alkyl radicals and the other alkyl substituent is selected from the group consisting, of primary and secondary alkyl radicals.

5. A composition of matter comprising a mixture of gasoline hydrocarbons which has been rendered potentially unstable by the addition of tetra alkyl lead, about 0.25% to 3% (by volume) of a mononuclear aromatic amine in which the total number of-carbon atoms in all alkyl radicals is less than 7 and a total of about 0.001% to 0.1% (by weight) of two phenols, one of which is 2,4- dimethyl-G-tertiary butyl phenol and the other being a 2,4-dialkyl phenol having a maximum of about 18 carbon atoms and in which one alkyl substituent is selected from the group consisting and the other alkyl substituent is selected from primary and secondary alkyl radicals.

6. A composition comprising gasoline hydrocarbons containing up to about 6 cc. tetra ethyl lead per gallon of-said composition, about 0.25% to 3% (by volume) of xylidine and about 0.001% to 0.1% (byweight) of a mixture of 2,4-dimethyl- (i-tertiary butyl phenol and 2-tertiary butyl-4- methyl phenol.

secondary and tertiary alkyl radicals,

and a total of about 0.01% to 1% (based on the xylidine weight) of 2,4-dimethyl-6-tertiary butyl phenol and a 2,4-dialkyl phenol having a maximum of about 18 carbon atoms and in which one alkyl substituent is selected from the group consisting of primary, secondary and tertiary alkyl carbons containing iron carbonyl and tetra alkyl lead which composition is stabilized by a mononuclear aromatic amine in which the total num- 'ber of carbon atoms in all alkyl radicals is less than 7, by 2,4-dimethyl-6-tertiary butyl phenol and by a 2,4-dialkyl phenol having a maximum of about 12 carbon atoms in all alkyi radicals and in which one alkyl substituent is selected from the group consisting of primary, secondary-and tertiary alkyl radicals and the other alkyl substituent is selected from the group consisting of primary and secondary alkyl radicals.

10. A composition consisting essentially of a mixture of normally stable saturated hydrocarbon fuels containing a knock-reducing amount of a mononuclear aromatic amine in which the total number of carbon atoms in all alkyl radicals is less than 7 and a stabilizing amount of a 2,4-dialkyl phenol in which one alkyl substituent is selected from the group consisting of primary, secondary and tertiary alkyl radicals and the other alkyl substituent is selected from the group gzoanliisting of primary and secondary alkyl rad- 11. A composition consisting essentially of a mixture of normally stable saturated hydrocarbon fuels containing an amount of tetra alkyl lead sufiicient to render it relatively unstable on storage, about 0.25% to 3% (by volume) of a mononuclear aromatic amine in which the total number of carbon atoms in all alkyl radicals is less than 7 and a total of about 0.001% to 0.1% (by weight) of two phenols, one of which is 2,4- dimethyl-G-tertiary butyl phenol and the other being a 2,4-dialkyl phenol having a maximum of about 18 carbon atoms and in which one alkyl substituent is selected from the group consisting of primary, secondary and tertiary alkyi radicals, and the other alkyl substituent is selected from the group consisting of primary and secondary alkyl radicals.

DANIEL B. LU'I'EN, J a.