US2411307A - Stabilized aromatic amines - Google Patents

Description

Patented Nov. 19, 1946 STABILIZED AROMATIO AMINES Ernest L. Walters, San Francisco, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application September 15, 1943, Serial No. 502,707

8 Claims. (01. 260-578) i This invention relates to gasolines having improved oxidation stability and knock rating.

A principal object is to provide motor fuel of greater stability and decreased age deterioration.

Another purpose is to produce aviation gasolines which are both high in octane rating and low in gum forming or precipitating tendencies. Other objectives will be apparent from the following description.

In my copending application Serial No. 441,876, filed May 5, 1942, I showed that 2,4-dimethyl-6- tertiary butyl phenol possesses unique and extraordinary inhibitor powers for tetra-alkyl lead fluid as well as for an initially stable gasoline (such as substantially saturate gasolines, for example aviation gasoline, as distinguished from unstable or cracked gasoline), which stable gasoline has been rendered unstable by the addition of tetra-alkyl lead.

I have now found that aniline Or an alkyl aniline having not more than 6 carbon atoms in the alkyl radicals, in a relatively small amount but substantially greater than that'of the 2,4- diniethyl-G-tertiary butyl phenol unexpectedly accelerates or increases the inhibiting effect of e the 2,4-dimethyl-6-tertiary butyl phenol in addition to materially raising the anti-knock rating. This is especially true in initially stable leaded motor fuels such as aviation gasoline in which 2,4-dimethyl-6-tertiary butyl phenol is used with particular eifectiveness as an anti-oxidant. However, this cumulative inhibiting efiect of anilines and 2,4-dimethyl-6-tertlary butyl phenol may also be observed in normally unstable or cracked gasolines which may or may not contain lead.

The apparent reason for this cumulative effect is that 2,4-dimethyl-6-tertiary butyl phenol stabilizes the aromatic amines by themselves. Therefore the same inhibitor can be used to stabilize the amines, not only when they are dissolved in gasoline in relatively low concentration, but also when they are in the substantially pure state, i. e. undiluted, or else are in the form of concentrates.

Moreover, the inhibitor will also stabilize amines having a greater number of carbon atoms than indicated above, i. e. greater than 12, as well as polycyclic 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, if the amine is a liquid under normal conditions, the inhibitor should be a true 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.

The ability of 2,4-dimethyl-6-tertiary butyl phenol to inhibit the deterioration of aromatic amines is very outstanding, in that it is the only gasoline inhibitor found among a large number tested which effectively protects the amines themselves.

Among the many mono nuclear aromatic hydrocarbon amines useful for blending with gasolines, particular mention may be made of the following: aniline, N-monoand dimethyl or higher alkyl anilines (which may also be substituted in the nucleus), mono-, di-, and trimethyl and higher alkylated anilines (which may also be substituted on the N atom), toluidines, xylidines, cymidine, cumidine, pseudo cumidine, etc. as well as suitable substituted derivatives. Obviously, mixtures of aromatic amines, as well as the individual amines may be thus employed. 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 may be blended in a motor fuel according to the present invention. These amines by themselves have little if any anti-oxidant eifect.

Amounts of mono nuclear aromatic amines in gasolines between about 25% and 3% are quite effective, although at times higher or lower quantitles may be employed. The upper limit is usually prescribed by maximum boiling range specifications of the gasolines. Since the aromatic amines are relatively high boiling, they may raise the upper boiling range of the gasoline above permissible limits if used in excessive amounts. On the other hand, amounts of the amines below the lower limit indicated give, as a rule, insuflicient improvement to warrant their use. A content of about 1% has been found to be particularly advantageous.

An effective range for the 2,4-dimethyl-6-tertiary butyl phenol in gasoline is between about .0001 and .1%. The gasoline if desired may contain up to about 6 c. c. of tetra alkyl lead per gallon.

In undiluted aromatic amines, the content of the 2,4-dimethyl-6-tertiary butyl phenol may range from about .01 to .1%, preferably .1 to .5%.

A further advantage in the use of my combination of aromatic amine and 2,4-dimethyl-6- tertiary butyl phenol in gasoline is that when Most available commercial inhibitors failed to materially improve the color stability, and on the rioration 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 eflectiveness 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.

The invention may be further illustrated by reference to tests made with pure xylidine (5-amino- 1,3-dimethy1 benzene) in a 100 octane aviation gasoline composed of approximately 45% straight run gasoline, 45% alkylate and cyclopentane and containing 4 cc. of tetra ethyl lead fluid per gallon.

Stabilization of typical amines is shown by the following data. A liquid mixture of amino xylenes was examined for color at intervals, and the time elapsed to allow the darkening from 2 to 6 A. S. T. M. color at 90 F. in the presence of air was determined. The following results were obtained:

Inhibitor Time No inhibitor About 1 week. .2% 2,4-dlmethyi-6-iertlary butyl phenol 3 months.

contrary many reduced the time of darkening to about one day.

This is a continuation in part of my copenciing application, Serial No. 478,290, filed March 6, 1943.

I claim as my invention:

1. An aromatic hydrocarbon amine of improved stability containing finely distributed 2,4-dimethyl-fi-tertiary butyl phenol in amounts of .01 to 1% calculated on the amine.

2. The composition of claim 1 wherein said amount is between .1 and .5%.

3. Normally liquid aromatic hydrocarbon amine of improved stability containing dissolved 2,4-dimethyl-6-tertiary butyl phenol in an amount of .01 to 1% calculated on the amine.

4. A mono nuclear aromatic hydrocarbon amine of improved stability in which the total number of carbon atoms in all alkyl radicals is less than '7, containing finely distributed 2,4-dimethyl-6-' tertiary butyl phenol in amounts oi. .01 to 1% calculated on the amines.

5. A composition of improved stability comprising a mononuclear aromatic hydrocarbon amine selected from the group consisting of aniline, N-alky] aniline, and nuclear alkyl-substituted aniline, and containing dissolved 2,4-dimethylfi-tertiary butyl phenol in amounts of .01 to 1% calculated on the aniline.

6. .Toluidine of improved stability containing dissolved 2,4-dimethyl-6-tertiary butyl phenol in amounts of .01 to 1% calculated on the toluidine.

'7. Xylidine of improved stability containing finely distributed 2,4-dimethyl-6-tertiary butyl phenol in amounts of .01 to 1% calculated on the xylidine.

8. Normally liquid xylidines of improved stability containing dissolved 2,4-dimethyl-6-tertlary butyl phenol in amounts of .01 to 1% calculated on the xylidine.

ERNEST L. WALTERS.