US2496930A - Composition useful as gum inhibitor for motor fuels - Google Patents

Description

Feb 7, 1950 M. R. BRIMER 2,496,930

COMPOSITION USEFUL AS GUM INHIBITOR FOR MOTOR FUELS Filed July 9, 194e Effect/vengas Effectiveness Mans/7a NTOR Effectiveness Patented Feb. 7, .1950.

COMPOSITION USEFUL AS GUM INHIBITOR FOR MOTOR FUELS Marshall R. Brimer, Kingsport, Tenn., assigner to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 9, 1946, Serial No. 682,248

This invention relates to a composition useful as a gum inhibitor for motor fuels and to motor fuels stabilized against gum formation.

It is well known that many motor fuels which are produced to possess a high octane rating are susceptible to deterioration during storage, owing to a tendency to react with atmospheric oxygen. The result of the oxidation-is formation of gum which may actually render inoperable the motor in which the fuel is used. and in any event the fuel loses in octane rating. Certain substances are known to act to prevent or inhibit oxidation of deteriorable motor fuels when added to the fuels in relatively low concentrations. The addition of the inhibitor to themotor fuel must be made as soon as possible in order to achieve the maximum inhibiting effect. Therefore, the addition of the inhibitor is customarily part of the manufacturing process and is carried out at the refinery. l

- v4The practical use of gum inhibitors places cer tain limitations upon the properties of such substances which may be considered for practical use. Of primary importance, of course, is the effectiveness of a given substance as an inhibitor of gum formation in the motor fuel.

However, substances possessing high effectiveness as inhibitors of gum formation in motor fuels must have certain 'additional properties in order to be of practical use. The inhibitor should be a liquid, in order to permit ready blending with the motor fuel.

A typical example of a highly eiiicacious gum inhibitor is N,N'diisopropyl p phenylenediamine (hereinafter sometimes called DIPDA). DIPDA is a solid and must be dissolved in a suitable solvent before blending with the motor fuel, e. g. isopropyl alcohol or toluene. The gum inhibitor effectiveness of solutions of DIPDA in these commonly employed solvents is directly proportionalA to the concentration of the DIPDA 7 Claims. (Cl. 252-401) in solution, the solvent having substantially no gum inhibitor effectiveness.

I have now found that by mixing DIPDA with at least one primary aromatic monoamine of the benzene series which is devoid of -XH groups wherein X represents a divalent atom, a composition is obtained, which, when dissolved in a solvent having substantially no gum inhibitor effectiveness, e. g. isopropyl alcohol or toluene, gives an inhibitor solution which has an effectiveness substantially greater than a solution of only DIPDA in the same solvents containing the same concentration of DIPDA. This is surprising, since primary aromatic monoamines of the benzene series devoid of XH groups have only a slight gum inhibitor effectiveness, in and of themselves, in the concentrations used in commercial practice. I have also found that primary aromatic monoamines of the benzene series have the same synergistic effect on other N,N-dialkyl-pphenylenediamines, e. g. N,N di-secondary butyl-p-phenylenediamine.

It is, accordingly, an object of my invention to provide new compositions useful as gum inhibitors for motor fuels. A further object is to provide motor fuels stabilized against gum formation with such compositions. Other objects will become apparent hereinafter.

In preparing my new compositions, I mix t\ gether to give an intimate mixture or solution, at least one N,N'dialkyl-p-phenylenediamine, e. g. N,N diisopropyl p phenylenediamine, N,N'disecondary butyl p phenylenediamne, etc., and at least one primary aromatic monoamine of the benzene series, e. g. aniline, a toluidine, a xylidine, etc. In my more useful compositions, the primary aromatic monoamine of the benzene series constitutes from about 0.5 to about by weight of the mixture. Primary aromatic monoamines of the benzene series containing only carbon, hydrogen and of aniline.

nitrogen atoms are advantageously employed. The resulting mixture vis advantageously dissolved in a solvent before blending with the motor fuels. Typical solvents include methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl alcohols,v n-propyl ethyl ether, n-propyl isopropyl ether, diisopropyl ether. di-n-propyl ether, benzene, toluene, xylenes, heptane, mixtures of petroleum hydrocarbons, e. g. straightrun gasoline, etc. These solvents are inert solvents, i. e. they have substantially no gum inhibitor eectiveness, in and of themselves and substantially no synergistic effect on the zum inhibitor effectiveness of the N,N'dialkylp phenylenediamines.

'I'he eifects which I obtain in practicing my invention can be illustrated first with reference to a solution of DIPDA in. isopropyl alcohol or toluene. The gum inhibitor effectiveness of such solutions of DIPDA in a standard reference gasoline is represented by curve A in Fig. 1 of the accompanying drawing. (As used herein, the effectiveness of an inhibitor is defined as the number of pounds of a standard comparison material required to produce the same induction period in an oxygen bomb-test as is produced by one pound of the inhibitor being tested, the oxygen bomb test being that described by Eglo, Morell, Lowry and Dryer in Ind. Eng. Chem. 24, 1375-1378, 1932.) The scale vused in Fig. 1 is such that the effectiveness of a 50% (by weight) solution of DIPDA in isopropyl alcohol or toluene is 1.0. On this scale the eil'ectiveness of the isopropyl alcohol solution of N-butyl-p-aminophenol. which is commonly used as a commercial gum inhibitor for motor fuels, is approximately 1.0. Curve A of Fig. l shows that, for example, a 75% solution of DIPDA in isopropyl alcohol or toluene possesses an effectiveness of 1.5, and a 25% solution of DIPDA in the same solvents possesses an eilectiveness of 0.5. In other words, the effectiveness of DIPDA solutions in solvents known to the art is equal to the effectiveness of pure DIPDA multiplied by the concentration of DIPDA in the solution, when the DIPDA concentration is expressed as a fraction of the weight of the solution in question.

Comparing the above DIPDA solutions with solutions of DIPDA in aniline, the DIPDA solutions in aniline possess effectiveness far in excess of that calculated by multiplyingthe effectiveness of pure DlPDA by the concentration of DIPDA in the aniline solution, yet the effectiveness of aniline alone as a sum inhibitor is less than 0.05.

Curve B in Fig. 1 of the accompanying drawing gives the eectiveness of solutions of DIPDA in aniline in the same standard reference gasoline, and it will be seen that curve B departs greatly'in a positive direction from curve A. The shape of curve B can be explained if the presence of aniline enhances the effectiveness of DIPDA, or if DIPDA enhances the eiectiveness The unexpected nature of my discovery can be more clearly understood if the difference between curve B and curve A is ascribed to inhibitor effectiveness exerted by aniline in the aniline solutions of DIPDA. For example, at a given concentration of DIPDA, the diilerence between curve A and curve B represents the 'inhibitor effectiveness contributed by the aniline in the solution. When the effectiveness contributed by the aniline is divided by the weight fraction of the aniline in the solu- 55 wise, in the group ha tion, the quotient represents the apparent inhibitor eectiveness of the aniline in the solution. Representative values are as follows:

wenn: rmcwn Apparent Effectiveness mrns Annina f Anm 0.00 1.00 0.00 .a0 .10 0.44 .so .so 0. s4 .1o .a0 1.43 .so .so 1. 70 .o0 .i0 1.80

Thus. when aniline is mixed vwith DIPDA, the effectiveness of the aniline appears to increase from less than 0.05 to more vthan 1.80, an increase of more than 3600 per cent.

As pointed out above, a practical inhibitor should be liquid, in order to facilitate blending with the motor fuels. Not only should thevinhibitor be liquid, but the liquidfshouldfnot be susceptible to freezing at temperatures normally encounteredin retlnerles, and if the j inhibitor is .susceptible tofreezing above 10 C., its freezl ing point may.' handicap its practicability.v

I measure the freezing point of an inhibitor by cooling it to a temperature below its freezing point, inducing the formation of solid (by agitation or seeding), and then allowing the temperature of the liquid-solid mixture to rise slowly. I record the temperature at which the solid disappears as the freezing point.

In order vto vshow the' importance of this invention, I lhave prepared Table I (see below) Awhich shows howthe freezing points of practical inhibitors caribe improved by taking advantage of the fapparent effectiveness of aniline. Table I shows seven groups of five solutions each, the

solutionsV being grouped laccording to inhibitor eectiveness. The iirstfour columns of Table I show the` composition of the solutions which were tested, the fifth column shows the effectiveness of the solutions, andthe sixth column shows the,

freezlngpoint of the solutions. Pure DIPDA is included ,forcomparisom In each group, it will beobserved that,the inhibitors which Vdo not con-v tain anilineehav'e freezing points which are much higher than thefreezing'point of the inhibitor solutions which do aniline. For example in:v theV group.L whichffhasg/anc iectiveness of l 1.6'. the' lowering of` the ,-ireezingrpoint, made possible by utilizing 'thisidisco the freezing point of arr-inhibitor can be achieved withoutsacriicefof inhibitor potency, as'would be necessary ifthe freezingpolnt wereimproved by the use of other solvents. Likewise. Table I showsthat if it-be desired to 'maintain a lcertain maximum freezing"4 point,the effectiveness can be greatly increased. Ifgforexample, 10-C.'is set as the maximum practical allowablev freezing point, without using aniline, the attainable eil'ectiveness is 0.9 l`(45% DIPDA+`55% toluene, freezing point 9 C.) or 0.7 (3,5% DIPDA-,-65% isopropyl alcohol. freezing pointe C.) but by using my invention, the `attainableeffectiveness `.can be raised to 1.4',(either"53%-DIPDA-20% isopropyl alcohol-27% aniline, `freezing point 10 C. or

53% DIPDA20% toluene-27% aniline, freezing Thus the attainable effectiveness point 6 C), lower 20% separation temperature" with the same effectiveness as inhibitors prepared accordcan be doubled using my invention.

Table I ing to the prior art. For example, if an inhibitor with an eiectiveness of 1.0 (comparable to ln- .eS. o...... )1..8 n. .d albwcmauecwmsmw mm a s e a 05o. ulm .owoohmtv 8mm. 94.42 4015 1587 4569.. 8.54.0 Mmznl wwofa .w MMTNCMPMDWW hafpan mmm 1 1 n 1 a n 1. a I o i ammwmmamgwmawmmm Wa. d e 1 .1 p y 2 DS S e dav; mm%mm%e% mime f a b .pws anUXoxmmAr .edqo Nu 0 6066 4444 2222 1111 0000 9999 7777 )mm V, .un-um llm DMCW e mm 2. LLLL .LLLL LLLL LLL,... 1.11.1. 0.0.0.0. 000.0 am etOhMWAemAaAEmmu.eW E e m .th2Dh1 DDonshn g nn .m0 PtaS% 0C @eta e am .1.m% ISM-.lm7)ydhgv H .m 0 00 0 O70 5 n ymzdannapznometmm e m m soa 2 .a 020% nana nana nana onen a ai elm im uam.. w a. A a lpAmwla/s ao4aa wm a w a mnpowmnwawhsi. terni T y m t e mmmqo( C. m m 0 00mm OOMM 00M@ 006% DOWN 00%.41 OCMW 1 l t mc. afnnluw a a .n 00 .1 no e ).1 AdOb r 0 c2 n when nh a 1 p 7%A4 bur DA .a y mlm m wemmonhnmwmwwaDmw m www o anno mavo @woo anon anon nooo waoo i n1(1=. t no. P mu c r s .m mmamwaba a I ...a mmcamndwamaaaznuem a m A a n o la D. can o .D mm5%.wmee%mm wrommm c n m @www mama mama aan mama nana aman n a l minnpmamaawemmaa D 5 m n a .a a a 0. e m a .r L .n at. nmmwomewdmwnmw .MDC 874 06 64 2 2 .1.0 litrulomri. Otanmr mm. a all am? ma a 1. s all... a: ii mamammmfmaaagwma er us arun gywraghcwko mmwmi, m s s... n m Hmomdm ESWDM .W 0 66606 44.4.4.4 22222 131111 00000 00099 77777 nWC m mw a LLLLL LLLLL LLLLL LLLLL LLLLL 0.0.00.0.. 0000.0. auta mn.md amm n P alum m.. E firm onwo oamammna O aMMZl e hSWE e V..pguein Yeurn%t.k d tcemmmeuhmmoodm, 0 o Douma nonna otaaa enana ooaa comma nonna ummpnsfihat s n2 nt ,n a wpaaomtmamaa Sem e t .l I d rf.. w meymmmtammtewmeaowm v. n apr stnm smetwao m m 0 O,m00w 0%00@ 040200@ OOOw OwOOQ OMOO OMOOW Wxamm S w T mw mmmwrmndmtmw .wmm r l Msnrml .mi0nmvem5-tew a plmmnmmaama pwdts m. o @DONO wOOmO mOOmO 6.000%0 MOOQW OOUO MOOW manif.. mn e 8% .h A J mat fte S urwo 1 .m uwpawosmhepimmamw e. w l mramanmaammwgmm 0 D O .1. dpO y e an 61V... c u m naamw mmaa wanna wanna maman aman naman @mw/0m uma nmmmmmmmmwm D r0.1 000 m mapamtaadnmmsm corded as the 20% separation temperature.T from by invention can be seen at once. If it is By taking advantage of the present invention. 60 desired to prepare an inhibitor with an effective'- it is possible to improve the 20% separation ness equivalent to commercial inhibitors now temperature greatly. Table II (see below) comcommonly used, for example, an effectiveness of pares the 20% separation temperature o f a 1.0, by using my invention very great savings can number of groups of solutions of DIPDA. e be achieved, in addition to attaining greatly imsolutions within each effectiveness group in Iable 65 proved properties already described. It is obvious II are arranged in order such that a solution that an inhibitor containing 37% D1PDA-42% containing no a-niline can be readily compared isopropyl alcohol or toluene- 21% aniline,ismuch with the solution containing aniline, and it will be seen that in every case (except where the cheaper than one containing 50% DIPDA-50% isopropyl alcohol or toluene, but the effectiveness 20% separation temperature" is below 50 C.) 70 of both is 1.0. This is true because DIPDA conthe lowering of the 20% separation temperatent of the inhibitor solution can be reduced from ture" is 13 C. or more. In other words, gum 50% to 37%, a saving of 26% of the most exinhibitors prepared according to my invention pensive component of the solution. In other can be made to possess a higher eiectiveness with words 13% of DIPDA and 8% of inert' solvents the same 20% separation temperature" or a 76 have been replaced by 21% of aniline without line.

Yet another important advantage to be derived from the use of my invention is the improvement `rwhich can be attained with respect to color sta- Y bility. The color stability of the inhibitor is important from the standpoint of practical use. Inhibitor and inhibitor solutions commonly are in contact with air before and after addition to motor fuels If an inhibitor under consideration is found to produce strong color upon atmospheric oxidation, it is said to lack color stability, and if it does not produce deep color upon atmospheric oxidation, it is said to be color-stable. Inhibitors which show color instability are ordinarily not suitable for practical use because the color produced interferes with the saleability of the motor fuel. an inhibitor by observing the shade and depth of color produced when one ounce of fresh inhibitor is allowed to stand in a Z-ounce bottle, in the neck of which is fitted a stopper bearing a, 1-inch length of 0.5 mm. tubing to permit access of air to the interior of the bottle. If a strong color developsupon a few hours exposure. the inhibitor is unsatisfactory for practical use, while if the inhibitor merely darkens after standing several days, it is satisfactory for practical use.

Heretofore. DIPDA has not been used commercially as an inhibitor because of the fact that it lacks color stability when dissolved in solvents commonly used in the art. An isopropyl alcohol solution of DIPDA becomes very dark in color after only a few hours, even though the exposure of the solution to atmospheric oxygen has been slight. On the other hand, solutions of DIPDA in isopropyl alcohol and aniline are color-stable for several days, even when exposed continuously to atmospheric oxygen by the procedure described above. As little as aniline in the solution is adequate to provide color stability and, since larger proportions of aniline are desirable in order to take full advantage of my invention with regards to other desirable properties described herein, color stability is no longer a problem with DIPDA when my invention is used.

It has been found that other aromatic amines are useful in practicing my invention. For example, curves C and D in Figure 2 of the accompanying drawing show the effectiveness of DIPDA solutions in inert solvents, such as, isopropyl alcohol and toluene compared with solutions of DIPDA in o-toluidine. The other important properties, such as, freezing point, 20% separation temperature, and color, as well as cost, are improved 'by the use of o-toluidine in the manner similar to aniline. The xylidines are likewise effective when used in accord-ance with my invention.

Other substituted phenylene diamines, such as N,N'di-secondary-butyl-p-phenylene diamines are also effective in practicing my invention when used with the aromatic amines described above. For example, curves E and F in Figure 3 of the yaccompanying drawings shows the comparison between effectiveness of solutions of N,Ndi secondary-butyl-p-phenylene diamines in inert solvents, e. g. isopropyl alcohol or toluene, and the effectiveness of mixtures of N,N'disecondary butyl-p-phenylenediamine in aniline. Other important properties, such as, freezing point, 20% separation temperature, and color, are effective I measure the color stability of i'ful. dissolved in an inert solvent to give a solution advantages in this case also. As in 'the case of DIPDA, the toluidines and the xylidines behave in a similar manner as aniline does.

As set forth above, primary aromatic monoamines of the benzene series containing -XH groups, wherein X represents a divalent atom, are excluded from my invention. Thus, p-hydroxy aniiine (p-aminophenol) p-mercapto aniline, etc. are excluded, but o-anisidine, m-chloroanlline, etc. are included;

Of my new compositions comprising a mixture of at least one N.Ndisecondary alkyl-p-phenylenediamine and at least one primary aromatic monoamine ofthe benzene series which contains only carbon, hydrogen and nitrogen atoms, those in which the nmonoamine constitutes from about l5A to 45% by weight of the mixture are especially Such compositions are advantageously containing from about 20 to about 45% by weight of the inert solvent.

My invention is directed to the stabilization of hydrocarbon motor fuels against deterioration. By the term hydrocarbon motor fuel, I mean not only motor fuels constituted entirely of hydrocarbons but also motor fuels containing hydrocarbon and appreciable amounts of other combustible substances, such as alcohols. Cracked gasoline, as is well known, has an undesirable tendency to undergo deterioration upon storage. Straight-run gasolines, on the other hand, do not have the same undesirable tendency to deteriorate, although blended stock containing cracked gasoline and straight-run gasoline usually show thel undesirable tendency to deteriorate. It is to the stabilization of any unstable liquid motor fuels comprising light hydrocarbons and normally tending to deteriorate that my invention is directed. To stabilize motor fuels against deterioration with my new composition, I dissolve a small amount of the composition in the motor fuel. Ordinarily an amountsufllcient to give a concentration of from about 0.000l% to about 0.1% (by weight) of the composition in the motor fuel will suflice to give a motor fuel of suitable stability against deterioration. Of course, the quantity of any one of my new compositions which is actually employed will depend upon the nature of the motor fuel being stabilized and the conditions under which the fuel is stored. The tendency of the motor fuel to'form gum can be determined among other methods by an accelerated oxidation test. The test described by Egloff et al., supra, is very satisfactory and is widely used. In accordance with this test, a sample of the motor fuel being tested, in an open 8ounce bottle, is placed in a suitable metal bomb surrounded by a water bath. Oxygen is introduced to pounds per square inch ('7 kg. per square centimeter pressure). The bath is then heated to 100 C. As the temperature increases, the pressure rises, reaches a maximum and continues near this maximum for a shorter or longer period of time. 'I'he testis continued for 4 hours or until a drop in pressure is noted. The period from slightly before the attainment of maximum pressure (approximately 15 minutes from the beginning of heating), until more than a slight drop in pressure takes place (usually a sharp break in the pressure occurs), is recorded as the induction period.

An induction period of less than 75 minutes is usually indicative of very low stability, while an induction of 300 or more minutes, for freshly made motor fuels, represents a fuel possessing suitable stability for from 6 to 12 months storage in the northern half of the United States. For more southern or Warmer climates, the induction period should be increased somewhat for satisfactory bulk storage of about one year duration.

My new composition can be employed to retard gun formation in hydrocarbon motor fuels which tend to undergo deterioration whether the motor fuel contains small or large amounts of addition agents, such as tetraalkyl lead compositions. It is, of course, known that tetraalkyl lead compounds, such as tetraet-hyl lead, are added to hydrocarbon motor fuels to improve the octane rating of the motor fuels. In some cases only a relatively small amount of the tetraalkyl lead compound is added, but sometimes with certain aviation grades of gasoline, a larger amount is used, such as with aviation gasoline having an octane number above 80 and comprising essentially non-gum-forming yhydrocarbons containing less than 1% by volume of oleflnic or diolenic hydrocarbons. Motor fuels having a relatively large amount of tetraalkyl lead compounds are usually referred to as heavily leaded gasoline.

Not only can my new compositions be used in all types of leaded gasoline, but my new compositions can, if desired, be added to the ethyl fluid itself. Ethyl fluid usually is a solution containing a mixture of tetraalkyl lead compound and a halogenated hydrocarbon, such as ethylene dibromide or ethylene dichloride, or both. My new compositions serve to retard the formation of haze in ethyl fluid or in hydrocarbon motor fuels containing the "ethyl fluid, whether the hydrocarbon motor fuel is one which forms gum upon storage or is one which is composed essentially of non-gum-forming hydrocarbons.

What I claim as my invention and desire to be secured by Letters Patent of the `United States is:

1. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of a N,Ndi secondary alkyl-p-phenylenediamine in which each alkyl group contains from 3 to 4 carbon atoms and a primary aromatic amine selected from the group consisting of aniline and o-toluidine, the primary aromatic amine constituting 10 from about 0.5 to about by weight of the mixture. A

2. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,Ndi isopropyl-p-phenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by weight of the mixture.

3. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,N'di secondary butyl-p-phenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by weight of the mixture.

4. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,N'di isopropyl-pphenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by weight of the mixture, the mixture being dissolved in an inert solvent.-

5. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,N'di isopropyl-p-phenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by Weight of the mixture, the mixture being dissolved in isopropyl alcohol.

6. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,N'di isopropyl-p-phenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by weight of the mixture, the mixture being dissolved in toluene.

'7. A composition useful as a gum inhibitor for motor fuels consisting of a mixture of N,N'-di secondary butyl-p-phenylenediamine and aniline, the aniline constituting from about 0.5 to about 85% by weight of the mixture, the mixture being dissolved in an inert solvent.

MARSHALL R. BRIMIER.

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

UNITED STATES PATENTS

Claims (1)

1. 2. A COMPOSITION USEFUL AS A GUM INHIBITOR FOR MOTOR FUELS CONSISTING OF A MIXTURE OF N,N'' -DIISOPROPYL-P-PHENYLENEDIAMINE AND ANILINE, THE ANILINE CONSTITUTING FROM ABOUT 0.5 TO ABOUT 85% BY WEIGHT OF THE MIXTURE.

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