US2833634A - Synergistic antioxidants and their use - Google Patents

Description

ilnited, rates Patent SYNERGISTIC ANTEGXEANTS AND THEIR USE Eugene F. Hill, Birmingham, Mich, assignor to Ethyl Corporation, New York, N. Y, a corporation of Delaware No Drawing. Application January 26, 1953, Serial No. 333,371

Claims. (ill. 44-69) The present invention relates to the protection of materials that are subject to deterioration by contact with oxygen in any of its forms.

Certain hydrocarbon-type materials in wide use are subject to deterioration, sometimes fairly rapidly, when exposed to air and particularly where the air might have some ozone content. By way of example, gasolines and diesel engine fuels now enjoying wide-spread use are for practical reasons manufactured with a relatively high content of olefinic-type hydrocarbons. These materials, upon standing, will react with oxygen and will at least be partially converted to a form that is not desirable. Thus, olefinic gasolines will show a strong tendency to deposit gums which will interfere with the filtering of the gasoline by clogging up the filters and even cause fuel-passing valves to stick. In addition, gummy deposits often foul spark plugs and thereby cause misoperation of the engine. These same general type of dilficulties are experienced with diesel fuels.

In the past it has been found desirable to add antioxidants to the above types of oxygen-sensitive materials. However, with the progress of time, fuels have come to contain more and more olefins and engines have become more efficient and powerful so that the engine and fuel specifications are more rigid. The continuous use of prior art antioxidants accordingly results in the build-up of the antioxidant concentration to the point where it cannot be tolerated by some engines.

Among the objects of the present invention is the provision of novel antioxidant compositions that are more efiective than the prior art antioxidants.

Additional objects of the invention include the pro vision of mixtures of olefin-type hydrocarbons with a synergistic antioxidant composition that makes possible more effective protection of the hydrocarbons.

The above as well as still further objects of the present invention will be more clearly understood from the following description of several of its exemplifications.

It has been discovered that standard antioxidants selected from the class consisting of phenylenediamines, aminophenols and trialkylphenols, when mixed with a compound of the class consisting of ascorbic acid and its esters, show an unexpectedly high antioxidant etfect in protecting olefin-type hydrocarbons that are subject to deterioration by oxygen. This effect is particularly significant inasmuch as ascorbic acid and its esters show very little or no antioxidant value in connection with these materials when used as a primary antioxidant. The

synergistic etfect appears to extend to antioxidant compositions having from to 80 percent of ascorbic acid or its ester, the balance being essentially one or more of the above-named standard antioxidants. Best results are obtained, however, with an antioxidant composition having about twice as much of the standard antioxidant as ascorbic acid or its esters.

The following examples are typical of the improvements resulting from the present invention. In these examples the deterioration tendency has been measured by Pa nted Meta 91 5 2 determining the induction period various samples of materials require before beginning to react with oxygen under accelerated reaction conditions. The specific method used is a standard one adopted by the American Society of Testing Materials for determination of the oxidation stability of gasoline (induction period method), ASTM designation: D525-46, and is fully described in Part III-A, ASTM Standards for 1946. According to this method, the induction period is the period during which there is no absorption of oxygen by the test material as indicated by a time delay before the pressure drops in a testing bomb containing the test material at C. with oxygen at an initial pressure of 100 pounds per square inch gauge. All percentages are by weight.

Hydrocarbon Induction Material Tested Protecting Addition Period in Minutes G1 Gasoline- None 118 Do 0.0075% N .N-di-secbutyLp-phenylenedi- 394 amine A. 0.005% A +0.0025% ascorbic acid 533 N 90 260 315 A 340 0.005% A +0.0025% ascorbic acid 400 0.0025% A +0.00125% ascorbyl palrnitate 350 0.005% A +0.0025% ascorbyl palmitate 430 None 0.003725% A 310 0.0025% A +0.00125% ascorbyl palmitate. 355 0.0075 0 l v 400 0.005% A +0.0025%ascorbyl palmitate 490 In the above examples the G1, G2, and G3 gasolines are standard commercially available automotive gasolines which, when untreated, are normally susceptible to deterioration in the presence of oxygen. The characteristics of the above gasolines are as follows:

Distillation Range,

(29.5 in. Hg) (29.2 in. Hg)

Olefins; 18.4% Aromatics" 23. 6% Paraflins... 36. 5%

0100115 26.7% Aromatics" 18.1% Paraffins. 41.7%

Hydrocarbon-Type.

It should be noted that the ascorbic acid shown above to have a synergistic antioxidant eifect when combined with the N,N'-di-sec-butyl-p-phenylenediamine has when used by itself an antioxidant behavior which is very small, being about one-tenth that of the N,N'-di-secbutyl-p-phenylenediamine. The ascorbyl palmitate of these examples has, when used alone, no appreciable antioxidant effect.

Although the above examples show the value of the present invention in connection with stock gasolines, the same general improvements are obtainable with other olefin-type materials such as diesel fuels that tend to deteriorate in the presence of oxygen. The effect with gasolines is obtained whether or not the gasoline is leaded, that is contains added tetraethyllead along with its usual lead scavenger complement, as for example ethylene dibromide or ethylene dichloride.

When other of the above mentioned prior art standard antioxidants are substituted for the N,N'-di-sec-butyl-pphenylenediamine equally good synergistic improvement is obtained. Specific classes of suitable prior art antioxidants showing the synergism when admixed or otherwise used in conjunction with ascorbic acid and esters thereof are phenylenediamines, aminophenols and trialkylphenols. Illustrative examples of the phenylenediamines include such materials as unsubstituted p-phenylenediamine, unsubstituted o-phe'nylenediamine, as well as derivatives of these materials in which either or both amine groups are alkylated such as N,N-dimethyl-p-phenylenediamine, ethyl-p-phenylenediamine, N-methyl-N' n propyl pphenylenediamine, stearyl-p-phenylenediamine, N-methyl- N'-lauryl-p-phenylenediamine, N,N'-diethyl-o-phenylenediamine, N-methyl-o-phenylenediamine, N-butyl-N'-iso- 'propyl-o-phenylenediamine, N-stearyl o phenylenediamine, N-methyl-N'-lauryl-o-phenylenediamine, Z-aminodiphenylamine, 4-aminodiphenylamine, and the like. 11-

lustrative examples of aminophenols which can be ernor they are all difierent, and the groups range from methyl to decyl.

Instead of the ascorbic acid or ascorbyl palmitate other ascorbic acid esters can be used to give the equivalent results. Such other esters include such substances as ascorbyl formate, ascorbyl acetate, ascorbyl lactate,

ascorbyl succinate, ascorbyl maleate, ascorbyl propionate,

ascorbyl picrate, ascorbyl benzoate, ascorbyl salicylate,

ascorbyl monomalonate, ascorbyl dimalonate, and the like.

In all the above modifications, the same general formulation of ingredient proportion is effected. The concentration of antioxidant composition in the material being protected can be varied from about 0.01 percent down to the smallest concentration that will be elfective. Concentrations larger than 0.01 can be used but are not desirable.

As many apparently widely different embodiments of the invention may be made Without departing from the spirit and scope hereof, it is understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claims.

What is claimed is:

l. Gasoline normally tending to deterioriate in the presence of oxygen, and containing a mixture of an N,N' -dialkyl phenylene diarnine antioxidant and a synergist selected from the class of ascorbic acid and ascorbyl palmitate, said synergist being present in an amount of from 10 to 80 percent of the total amount of the mixture, the total mixture being present in an amount suificient to stabilize the gasoline.

2. The combination of claim 1 in which the N,N'-diallryl phenylene diamine is N,N'-di-s ec-butyl-p-phenylene diamine.

3. Thecombination of claim 2 in which the synergist is ascorbic acid.

4. The combination of claim 2 in which the synergist is ascorbyl'palmitate. l 7

5. A leaded olefinic gasoline containing about 0.005

' to about 0.01 percent by weight of a mixture of two parts of N,N'-di-sec-butyl-p-phenylenediamine with one part of a synergist selected from the class of ascorbic acid and ascorbyl palmitate.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Industrial and Engineering Chemistry, July 1926, page 691.

Riemenschneider:

Oil and Soap October 1944, pp. 307-309. I

Claims (1)

1. 5. A LEADED OLEFINIC GASOLINE CONTAINING ABOUT 0.005 TO ABOUT 0.01 PERCENT BY WEIGHT OF A MIXTURE OF TWO PARTS OF N,N''-DI-SEC-BUTYL-P-PHENYLENEDIAMINE WITH ONE PART OF A SYNERGIST SELECTED FROM THE CLASS OF ASCORBIC ACID AND ASCORYBL PALMITATE.