2,410,829 Patented Nov. 12, 1946 UNITED STATES .tPATENT OFFICE 2,410,829 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. (Cl. 44-69) . This invention is based on the ?nding 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 2 , . , how difficult it may be to ?nd 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-oxidants‘for aromatic amines in 19 clude: para benzyl amino phenol, alpha-naphthol, 4-tertiary butyl catechol, hydroquinone, pyro gallol, beta-naphthol, para phenylene diamine and diphenyl phenylene diamine. Other pro; oxidant substances include thiophenol, thiodi dissolved in gasoline or other motor fuel; hence, it is an object of the invention to provide motor 15 glycollic acid, FeS, sulfanilic acid, salicyclic acid, fuels containing aromatic amino compounds brom benzene, dianisidine,-iodine, iron or gal which fuels are stabilized against oxidation or vanizeda iron surfaces, sodium nitrite, benzoyl decomposition. Another purpose is to provide peroxide, lead peroxide, copper phenyl pro motor fuels containing tetra alkyl lead and/or pionate, manganese oleate and stannous chloride. metallic carbonyl compounds which compounds 20 Gasoline inhibitors which were found to be with are stabilized by the additives of the present in out inhibiting e?fect on aromatic amines include: vention. ,An additional object is to provide im phenyl - alpha - naphthylamine, mixtures, ‘of proved motor fuels such as aviation' gasoline cresylic acids boiling between about 220° C. and having high antiknock ratings and improved 240° C., 2,3,5,6-tetra methyl phenol, penta-methyl oxidation or storage stability. Further objects 25 phenol, 2,3,5-trimethyl " phenol, para, para’ will be apparent from the following description. dihydroxy diphenyl, guaiacol, durohydroquinone, Aromatic amino compounds, upon exposure to thymol, resorcinol, anthraquinone, etc. air, often exhibit a tendency to change color as It has now been found, however, that‘ a their period of contact with oxygen lengthens. particular ‘group of di-alkyl phenols in which the This color change is the ?rst noticeable symptom 30 alkyl groups are attached at the 2 and 4 or ortbo of oxidative decomposition which, since it is ' and para positions, as hereafter more fully de catalytic in nature, proceeds, if unchecked, at an accelerated rate until the amino compounds are entirely altered in composition and useful ness. - scribed, have unique stabilizing properties for aromatic amino compounds, either when the amines are alone or when they are dissolved in 35 gasoline. The stabilizing agents of, the present A particular employment for aromatic amino invention are dialkyl phenols in which the 4 or compounds, especially those of low molecular‘ para position and one ortho position (2 or 6) are weight, is in motor fuels such as gasoline in which occupiedbya primary, secondary or tertiary alkyl they exert a bene?cial anti-knock effect. It will radical. Only one of the alkyl radicals may be be appreciated, therefore, that if such aromatic 40 tertiary, however, so one may have a di-primary amines are produced for incorporation in gaso alkyl, di-secondary alkyl, mono-primary mono line, it is especially desirable that they be secondary alkyl, mono-tertiary mono-primary stabilizedlagainst oxidation, since if such de alkyl, or mono-tertiary ‘mono-secondary alkyl' composition sets in either before or after their phenol. addition to the base fuel, it will not only decrease 45 The ortho and para alkyl radicals (only one of their own value as a fuel component but may which, as just stated, being a tertiary alkyl) also promote the decomposition of the base fuel, may conveniently be methyl, ethyl, n-propyl, iso resulting in gum ‘formation, increased knock ' propyl, n-, iso-,' secondary and tertiary butyl,' rating, volatility changes etc. and the various primary, secondary or tertiary Aromatic amines have also been added to 50 amyl, hexyl, heptyl, octyl, and homologous radi cracked gasolines in small quantities in order to cals. In general, radicals containing not more decrease the gum forming tendencies of the than about 16 or 20 carbonatoms are preferred, gasoline. Since such inhibition of the oxidation those 2,4 di-alkyl phenols containing a total of of the gasoline is achieved by the preferential not more than about 12 carbon atoms in all alkyl ' oxidation of the amino inhibitor, it will be realized 55 groups being particularly desirable (i. e. those 2,410,829 4 tion of colored products and oxidation of the xylidine occur simultaneously on aging, the de crease of light transmitted through the solution having a maximum of about 18 carbon atoms counting the nuclear'carbon atoms). The alkyl radicals should generally be such as to render the is an indication of the extent of oxidation. The are added. Too high a number of carbon atoms b1 following determinations were made at 70° 0., one atmosphere of air and employing inhibitor causes the compounds to be waxy and di?icultly phenols soluble in the composition to which they concentrations of 0.2% by weight. soluble. However, particularly in gasolines of appreciable aromatic contents, phenols with rela tively large wax radicals containing up to say 35 lncremc in 10% or 40 or even more carbon atoms may be suitable, 10 especially if those radicals contain branched chains. Time to reach 10% transmission inhibitor The ortho or para radicals may also transmission due to inhibition, as percent of blank comprise one or more aromatic groups such as phenyl, tolyl, benzyl, etc., although strictly ali ' None __________________________ .. Hours 35 0 butyl-‘i-methyl phenol. 78 120 phatic radicals are generally superior. 15 2~tertiary 2-tertiary butyl-i-cthyl phenol. . 66 89 The above limitations regarding the nature and 2,4-dimetl1yl phenol ___________ _ _ 54 54 2-metliyl-4-lertiary butyl phenol. 44 26 placement of the several hydrocarbon radicals on the phenol are very important. In this connec tion, it is of interest that 2,4,6-tri tertiary alkyl It has also been found that combinations of phenols, for example 2,4,6-tri tertiary butyl 20 the present poly alkyl phenols and aromatic phenol, have little anti-oxidant value for aro amines, such as the earlier ‘enumerated monocycle matic amines-some phenols are worse than no monocyclic aromatic amines having less than a inhibitor at all. Thus, some tri alkyl phenols total of about 7 carbon atoms in all alkyl groups, ' found to be pro-oxidants for aromatic amines are exhibit an inhibiting or stabilizing e?ect on gaso 2,6-ditertiary butyl-4-methyl or -ethyl phenols, 25 line, which e?ect is greater than the calculated 2,6-dimethyl-4-tertiary butyl pheno, 2,5-dimeth total of the inhibition produced by each additive yl-4-tertiary butyl phenol and 2,4-ditertiary alone. This effect is particularly noticeable in butyl-5-methyl phenol. saturate or initially stable gasoline such as avia The aromatic amines generally added to gaso line for their antiknock value are usually mono tion gasoline composed of straight run, cyclopen 30 tane,- aromatics, alkylate, hydroformed fractions and the like, which initially stable gasoline has ' nuclear monoamines having not more than a. total of 6 carbon atoms in all alkyl radicals. Par been rendered unstable by the incorporation of ticular mention may be made of the following: tetra alkyl lead. aniline, N-, mono- and di- methyl or higher Another tri alkyl phenol, 2,4-dimethyl-6-ter alkyl anilines (which may alsobe substituted in 35 tiary butyl‘ phenol is a singularly successful in the nucleus); -mono-, di-, and tri methyl and higher'nuclearly alkylated anilines (which may. hibitor of tetra alkyl lead ?uid or of initially stable gasoline composed of saturate fraction (such as enumerated above) which gasoline has been rendered unstable by tetra alkyl lead. This cumidine, etc., as well as suitable substituted de 40 phenol will also inhibit the oxidation of the pres rivatives. Mixtures of aromatic amines, as well ent aromatic amines. Hence when stabilizing as the individual amines, may be employed and ‘ amine-containing leaded gasoline or aromatic also be substituted on the N'atom), such as toluidines, xylidines, cymidine, cumidine, pseudo poly-amines may also be used. Likewise, aro- ' amines which are later to be incorporated into matic-rich petroleum fractions may be nitrated leaded gasoline (in particular into saturated type and reduced to give mixtures such as described 45 gasoline such as aviation gasoline) it may be ad vantageous to employ 2,4-dimethyl-6-tertiary in U. S. Patents 1,844,362 and 2,252,099, which butyl phenol together with a dialkyl phenol of the present invention. Thus, for example, the mixtures may be blended in a motor fuel ac cording to the present invention. However, the di-alkyl phenolic inhibitors will tetra ethyl lead will be stabilized by the 2,4-di also stabilize mcnonuclear amines having a 50 methyI-G-tertiary butyl phenol while the aromatic greater number of carbon atoms than indicated amines will be stabilized by one or more of the present dialkyl phenols such as 2-tertiary butyl above, i. e. greater than 6, as well as poly-cyclic 4-methyl phenol, Z-tertiary butyl-4-ethyl phenol, aromatic hydrocarbon amines, e. g. various naph 2,4-dimethyl phenol, 2-inethyl-4-tertiary butyl thylamines, alkyl naphthylamines, aryl naph thylamines, anthracylamines and the like. 55 phenol, etc. _ It is understood that the inhibitor must be well Effective total amounts of the poly alkyi phe distributed throughout the substance to be pro nolic inhibitors in a gasoline are generally be tected. Thus, it the amine is a liquid under nor tween about 0.001% to 0.1% (by weight), a pre ferred range being from about 0.001% to about mal conditions, the inhibitor should be in- true or colloidal solution. If it is a solid, the inhibitor 60 0.01% or 0.1%. The aromatic amines may be em may be incorporated by ?rst melting the amine, ployed in about 0.25% to 3% (by volume) in a gasoline although higher or lower quantities can distributing the necessary amount of inhibitor as by dissolving it, and then allowing the mixture to also be used. The upper limit is usually prescribed solidify; or else by merely spraying the inhibitor by maximum boiling range speci?cations of the or a solution thereof onto the solid amine. In 65 gasolines. Since the amines are relatively high boiling, they may raise the upper boiling range of undiluted aromatic amines, the content of the poly alkyl phenol may range from about 0.01% the gasoline above permissible limits it used in to 1% (by weight), preferably about 0.1% to - 0.5%. excessive amounts. On the other hand, amounts . of the amines below the lower limit indicated give, Quantitative determinations of the effective 70 as a rule, insuilicient improvement in knock rat ness of inhibitors of the present invention in sta ing to warrant their use. bilizing xylidine were made by determining the light transmission through various xylidine sam ples for a speci?c wave length 0:550 mu) using a Coleman spectrophotometer. Since the forma 76 found to be particularly advantaageous. The combination of aromatic amines and the speci?c poly alkyl phenols has a synergistic stabilizing About 1% has been e?'ect when applied particularly to saturated, 2,410,829 initially stable gasolines rendered unstable by the quate to stabilize the metallic carbonyl in a gas addition of metal antiknock compounds, as well oline.v Particularly when tetra alkyl lead is also present, a part of'the phenolic inhibitor content 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 an‘equivalent amount of another tetra alkyl lead may normally be added to gasoline. , \ . may be 2,4-dimethyl-6-tertiary butyl phenol. The invention claimed is: containing a knock-reducing amount of a mono ' nuclear aromatic amine in which the total num ber of carbon atoms in all alkyl radicals is less Solubilizers for the aromatic amines may also be present, particularly in gasolines which con tain but a small amount of aromatic constituents. v 1. _A composition comprising hydrocarbons 10 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 weight'alcohols, ethers, ketones (in particular ?ve 81nd tertiary alkyl radicals and the other alkyl or six carbon atom unsymmetrical ketones) ,_ varo substituent‘is selected from the group consisting matics such as benzene, toluene, etc. i _ 15 of primary and secondary alkyl radicals. Such mutual solvents may be low molecular 1 ‘A further advantage in the use of the combi nation of aromatic amine and poly alkyl phenol ' 2. A composition _ comprising hydrocarbons containing a knock-reducing amount of a mono nuolear aromatic amine in which the total num ber of carbon atoms in all alkyl radicals is less is that when the inhibitor e?ectiveness of the compounds begins to wear off, a sharp break in the induction period does not occur, but rather 20 than 7 and a stabilizing amount of a 2,4-dialkyl the formation of deterioration products proceeds phenol having a maximum of about 18 carbon slowly and a visible precipitate forms only after atoms and in which one alkyl. substituent is se extended aging. This is in marked contrast to lected from the group consisting of primary, sec the action of most oxidation inhibitors whose ondary and tertiary alkyl radicals and the other e?ectiveness is usually terminated quite sudden alkyl substituent is selected from the group con-. ly at the end of their period of stabilization with sisting of primary and secondary alkyl radicals. the rapid formation of degradation products in 3. A composititon comprising hydrocarbons the gasoline and the consequent prompt termina containing about 0.25% to 3% (by volume) of a tion of the usefulness of the motor fuel. ' mononuclear aromatic amine in which'the total It has also been found that the combination of 30 number of carbon atoms in all alkyl radicals is the present poly alkyl phenols withv aromatic ‘ less than 7_ and about 0.001% to 0.1% (by weight) amines shows extraordinary stabilizing power for of a 2,4-dialkyl phenol in which one alkyl sub metallic carbonyl compounds contained in gaso ' stituent is selected from the group consisting of line or other motor fuel. ‘primary, secondary and tertiary alkyl radicals It is known that numerous metallic carbonyl 35 and the other alkyl substituent is selected from compounds possess desirable antiknock proper the group consisting of primary and secondary ties when incorporated in a hydrocarbon fuel. alkyl radicals. However, various di?iculties have beset their par 4. A composititon comprising gasoline hy ticular utilization, notable among which has been drocarbons containinga tetra alkyl lead com their chemical instability and ease of decompo 40 pound, a knock-reducing amount of a mononu sition on standing, as well as their tendency to clear aromatic amine in which the total number catalyze the breakdown of the hydrocarbon fuel, of carbon atoms in all alkyl radicals is less than producing such e?ects as gum formation and the 7 and a stabilizing amount of a 2,4-dialkyl phenol V ‘ like. Although the anti-knock function of me having a maximum of about 18 carbon atoms and tallic carbonyls in gasoline may often be per- 45 in which one alkyl substituentis selected from formed in part by other compounds such as tetra the group consisting of primary, secondary and ethyl lead, there are particular applications in tertiary alkyl radicals and the other alkyl sub which such other substances are not applicable stituent is selected from the group consisting, of as in a “break in” fuel or in a heavily leaded fuel to which the addition of more tetra alkyl lead 50 would have little effect. ' 5. A composition of matter comprising a mix ture of gasoline hydrocarbons which has been rendered potentially unstable by the addition of tetra alkyl lead, about 0.25% to 3% (by volume) Metallic carbonylic compounds contemplated by the present application are, for example, the various carbonylic compoundsof iron, nickel, co 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% balt, molybdenum, mercury, etc., as well as their various applicable‘ derivatives.v Among these may be mentioned Fe(CO)4, Fe(CO)5, FE4(CO)15NO, FeNi(CO)9, Ni(CO)4, Co(CO)3NO, M0(CO)s, Hg(Co(CO)4)2. Compounds which decompose primary and secondary alkyl radicals. (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 under engine conditions’ to produce metallic car 60 about 18 carbon atoms and in which one alkyl bonyls may also be employed, such as complexes substituent is selected from the group consisting ‘of primary, secondary and tertiary alkyl radicals, of carbonyls with ammonia, amines, alkanol amines, etc. and the other alkyl substituent is selected from In general, an amount of metallic carbonylic the group consisting of primary and secondary compound in the range of about 0.25 to _3 'cc./gal 65 alkyl radicals. ' lon is adequate for a break-in fuel,'although up 6. A composition comprising gasoline hydro to about 10 cc./gallon may be used. In addition, carbons containing up to about 6 cc. tetra ethyl there may be present up to-about 6 cc. of commer cial tetra alkyl lead per gallon as well as various lead per gallon of-said composition, about 0.25% to 3% (by volume) of xylidine and about 0.001% solutizers such as alcohols, ketones, esters, pyri 70 to 0.1% (by‘weight) of a mixture of 2,4-dimethyl dine, aromatic constituents such as benzene and (i-tertiary butyl phenol and 2-tertiary butyl-4 the like. . '. methyl phenol. About 0.001% to 0.1% by weight of the alkyl 7. A composition suitable for addition to'a mix ated phenol in association with about 0.25% to ture of gasoline hydrocarbons containing a tetra 3% by volume aromatic amine is generally ade 75 alkyl lead compound, which comprises a xylidine 2,410,829 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 maxi mum of about 18 carbon atoms and in which one alkyl substituent is selected from the group con sisting of primary, secondary and tertiary alkyl , radicals and the other allwl substituent is selected 10. A composition consisting essentially of a mixture of normally stable saturated hydrocar bon 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-di alkyl phenol in which one alkyl substituent is selected from the group consisting of primary, secondary and tertiary alkyl radicals and the 8. A composition comprising gasoline hydro 10 other alkyl substituent is selected from the group from the group consisting of primary and second ary alkyl radicals. carbons containing a metal carbonyl, stabilized by an aromatic amine and by a 2,4-dialkyl phenol in which one alkyl substituent is selected from gzoanliisting of primary and secondary alkyl rad C . . ’ 11. A composition consisting essentially of a mixture of normally stable saturated hydrocar the group consisting of primary, secondary and bon fuels containing an amount ‘of tetra alkyl 15 tertiary alkyl radicals and the other alkyl sub stituent is selected from the group consisting of primary and secondary alkyl radicals. 9. A composition comprising gasoline hydro carbons containing iron carbonyl and tetra alkyl lead su?icient 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 lead which composition is stabilized by a mono 20 less than 7 and a total of about 0.001% to 0.1% (by weight) of two phenols, one of which is 2,4 nuclear aromatic amine in which the total num dimethyl-G-tertiary butyl phenol and the other 'ber of carbon atoms in all alkyl radicals is less ‘ being a 2,4-dialkyl phenol having a maximum of 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 sub stituent is selected from the group consisting of primary and secondary alkyl radicals. .30 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.