US2456569A

US2456569A - Motor fuel

Info

Publication number: US2456569A
Application number: US568779A
Authority: US
Inventors: Andrew I Smith
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1944-12-18
Filing date: 1944-12-18
Publication date: 1948-12-14
Anticipated expiration: 1965-12-14

Description

Patented, Dec. 14, 1948 UNITED STATES PATENT OiFiCE MOTOR FUEL Andrew I. Smith, Long Beach, Calif., asslgnor to Union Oil Company of California, Los Angeles, Calif., a corporation of California lio Drawing.

This invention relates to an improvementin fuels for internal combustion engines, and it has particularly to do with the addition to liquid petroleum fuels of certain substances to modify the gum forming tendencies of the fuels.

It is well known that when certain types of gasoline, and particularly cracked gasoline are stored chemical changes occur, especially under the influence of light and oxygen, which effect the color, and increase the gum formation,

thereby reducing the anti-knock property. In

, comparable mixture.

Application December 18, 1944, Serial No.,568,'l79

the same time there is an increased usage of Diesel fuel additives for improvement of cetane number. Cetane numberis related *to the interval between the instant of fuel injection and the instant of ignition of the fuel in the comi bustion'chamberof an engine (the shorter the interval the greater the cetane number) and is determined by comparison of the ignition properties of a mixture of alpha-methyl naphthalene and normal cetane and is equal in numerical value to the volume per cent of cetane in the The concept of cetane number is described and the method of test defined on page 1'72 of the 1943 issue of the formation of peroxides which are believed to act as catalysts in the oxidation or polymerization which leads to gum formation. Inhibitors which have been used for this purpose include certain of the amines, diamines, phenols, amino phenols, and the like of molecular weight of less than about 250 and in most cases less than about 200. It should be stressed that these compounds '--are effective because of their suppression of oxidation reactions which would occur in their ab some in theparticular types of gasoline to which they are added.

Fuels employed'imthe Diesel type compression-ignition engines differ in 'rnany respects from ordinary spark ignition cnginefuels. Various qualities are necessary in each of these fuels to give the maximum effi-ciency in the particular types of motors in which they are employed. Regardless of these differences, however, the formation and precipitation of gums to be avoided in both types of fuel. Such gummy substances, uporfiiniection of-"the fuel into an internal combust on engine, whether it be Diesel or automotive, form hard residue polymers which are insoluble in the fuel, thus causing reduced engine efficiency by deposition on the walls of the inlet manifold, on the valves'of a spark ignition engine and the injectonlmechanism of a compression ignition engine;

Heretofore theiproblem of gum formation in Diesel fuels has not assumed a degree of importance inasmuch as, in most cases, these fuels have been of thestraight run type and therefore not particularly susceptible to gum formation by autocatalytic reactions therein. However, with increasing demands greater quantities of cracked fuels are being produced and at 'A. S. T. M. Standards on Petroleum Products and Lubricants prepared-by the A. S. T. M. 'committee D-2 on Petroleum Products and Lubricants. Ordinary Diesel fuels have a cetane humbar of about 40 to about 47 and it is desirable in many instances to increase this value to 50-55 or higher. special refining processes, such as extraction of ordinary distilled fuels with large quantities of liquid sulfur dioxide, heavy treatment with sulfuric acid and the like, it is possible to increase the cetane number of the fuel by removal of certain of the low cetane number constituents therein. However, such treatments are usually costly and wasteful of fuel clue to relatively high treating losses for a given increase in cetane number and emphasis is therefore switching to cetane number improvement by the addition of minor amounts of various compounds which have the effect of accelerating the ignition characteristics of the fuel which acceleration is concomitant with an increase in cetane number. Many compounds have been employed for this purpose such as the organic peroxides, nitrates of glycerols, nitrates of glycols, several low molecular weight alkyl nitrates and the like, certain of which compounds, however, have been shown to increase the formation of undesirable gums and sludges in otherwise clean fuels because of their properties of oxidation acceleration. This increased gum formation, as might be expected, is particularly evident, in Diesel fuels which have been doped with organic peroxides or hydroperoxides, and further it is not surprising that th addition to such a peroxide doped fuel of an an ioxidant type gum inhibitor employed in gasoline is relatively ineffectual in preventing the gum formation in the presence of such a powerful oxidizing agent as a peroxide or hydroperoxide.

Whereas, at the present time gum formation in undoped Diesel fuels is not a problem of paramount importance, it is encountered to a certain extent, and there is reason to believe that with the increase in the usages-of cracked and reformed fuels gum formation within said fuels It is known that by meansof I of peroxides which may form in storage.

It is therefore an object of this invention to prepare an improved petroleum fuel having reduced tendencies to deposit gums when used in internal combustion engines.

It is a more particular object of my invention to prepare a Diesel fuel of the same desirable properties.

It is a further object of this invention to modify the physical properties of the gums formed in petroleum fuel whereby their harmful .eflects on internal combustion engines are minimized.v

It is a specific object of my invention to prevent the precipitation of gums formed in petroleum fuels, and particularly in Diesel fuels, whereby their harmful effects on internal combustion engines are prevented. The reasons for gum formation within such fuels are immaterial for the purposes of this invention. I

It is a still further object of this invention to aid in a more wide spread usage of the oxidizing type additives in Diesel fuels by changing the character of the gums formed due to the presence of such additives in such a way as to render them innocuous in. the internal combustion engines.

for example the reaction products of substituted.

I have found that oil soluble detergent and surface active type compounds hereinafter disclosed can be used to prevent this gum formation or precipitation either partially or entirely depending upon the amount added to the Diesel fuel. By definition a surface active agent is one which modifies the properties of the surface of one phase in contact with another (Surface Active Agents, by Foster D. Snell, Industrial and Engineering Chemistry, volume 35, page 107, 1943).

For the purposes of my invention it is desirable to employ those surface active agents whichare comparatively low in their water-attracting properties in order to reduce the tendency to form emulsion in the presence of a wet fuel. In general the degree of water repelling property of such a surface acting agent is increased with an increase in the length of the carbon chain of the hydrocarbon group in such agent. Although in special cases short chains may impart this property. it is usually necessary to have chains of eight carbon atoms or more and preferably of twelve or more carbon atoms. I have found that those surface active agents which have molecular weights in the range above about 150 possess the desirable balance between their water attracting properties and their oil attracting properties to perform satisfactorily in the manner as disclosed hereinafter.

I have found that the addition of from about 0.01% to about 1% or 2% and preferably from about 0.05% to about 0.3% of the surface active agents as hereinafter disclosed has the effect of a number of ways such as for example by increasing the surface tension of any polymer or gum type material that may be formed thus preventing its agglomeration or by inducing a surface charge upon said gummy material causing it to remain in the fuel in a colloidal or physically dispersed state.

The surface active compounds which I may employ and which in a large number of experiments I have found to be satisfactory are usually long chain compounds containing at least one strong polar group. The general types of compounds to be employed are the soaps and detergents, sulfated aliphatic esters, aliphatic sulfates, amines, amides, substituted amines and amides, amide sulfonates, aliphatic sulfonates, and alkyl aryl sulfonates of various types having molecular weights in the approximate range of about 150 to about 450 and preferably in the range of about 150 to 350.

I have also found that certain classes of compounds having molecular weights considerably above 450 as for example from about 450 to about 650 are excellent surface active compounds for the purpose, of modifying the gum forming tendencies of petroleum fuels. weight compounds of polymer structure such as phenols with sulfur dichloride have been em-' ployed successfully as Diesel fuel additives according to my invention.

More specifically the surface active agents which I may employ in modifying the gum forming tendencies of liquid petroleum fuels and particularly peroxide doped Diesel fuels are obtained from the following classes of compounds.

1. Soaps consisting, not only of the metal salts of the higher fatty acids such as calcium stearate',

sodium pal'mitate, potassium oleate, barium stearate, and the like but also of the class of compounds formed by the neutralization of the fatty acids with amines which compounds may be represented by the empirical formula 0 Bri -0 NHIR' 4-,

in which I P R-c o represents the anion of the fatty acid, and R the group or groups, other than hydrogen, attached to the nitrogen in the amine employed in the neutralization and may be the same or different radicals, and :2: may be equal to one, two or three depending upon the use of a primary, secondary or tertiary amine. I prefer to employ mines for the neutralization having at least one R radical therein which includes a polar group such as greatly reducing the precipitated gum which normally occurs upon the addition of an oxidation type ignition accelerator compound to a Diesel fuel. I have discovered that additives of this nature act not only to decrease the amount of gums formed in such a doped fuel but also by f preventing the aggregation and consequent precipitation of the materials which form the gum and the sludge thereby maintaining such gums ,-OH, SH, Cl, Br, I, Noz, OPOzHz, OS2 O2H and the' like in its structure as for example the, soaps formed by the action of mono, di or triethanol amine on oleic acid to give o c. ormom)1-oH=oH' om ,Lonnwmomom; Other soaps are obtainable with a whole series High molecular in which R is the continuation of the triglyceride. Similar compounds in which R. is an aliphatic radical are also good additives.

3. Aliphatic sulfates may be employed which ccompounds include the metal and amino salts of the sulfated higher alcohols which alcohols may be derived by reduction of the fatty acids and may include oleyl, stearyl, mixed alcohols from the fatty acids derived from cocoanut oil, purified fractions of these alcohols consisting mainly of lauryl or myricyl alcohol or the like. Metal salts of these sulfated alcohols may be regarded as R-OSOaOY in which R represents a fatty acid chain which may vary in length from C to Cu or higher and may be branched or unbranched and Y consists of a metal cation. In a second class of aliphatic sulfates Y in the above formula may consist of an amino compound as HNHIR' (Cl-x) which may be employed in the neutralization of the sulfated fatty alcohols where a: may be 0. 1 or 2 depending upon the usage of a primary, secondary or tertiary amine. These compounds may be regarded as the amine salts of the high molec= ular weight aliphatic sulfonic acids and are there fore similar to the amine salts of the high molecular weight fatty acids as hereinbefore described. Compounds of the nature of the aliphatic sulfates may be synthesized and utilized as the additives according to my invention in which the sulfuric acid is replaced by phosphoric acid to give phosphoric acid esters in a manner similar to the above.

'4.'In sulfonating a petroleum oil or other oil fraction the sulfonation occurs at an active carbon group such as occurs in naphthenic or aromatic hydrocarbons, branched chain aliphatic hydrocarbons. with a tertiary carbon atom or in unsaturated hydrocarbons. In the sulfonation of olefins, sulfates or hydroxy sulfonates such as Hi l-8010B H I-OH may occur. The sulfonates obtained from such oil fractions are then neutralized with a suitable metal salt, as for example sodium carbonate, which resultant soap may be metathesized to of white oils by sulfuric acid treatment. structure of these oil soluble sulfonates has not,

substitute another metal for the one employed. For example the sodium sulfonate as above mentioned may be metathesized by digesting a water emulsion of an oil diluted sulfonate with a metal salt solution such as calcium chloride by which process the sodium will be replaced by the calcium to yield a calcium sulfonate. Mahogany sulfonates, perhaps the best known of these compounds are'obtained as a by product in the manufacture The as yet, been definitely established. but I have found them to be excellent surface active agents for the purposes of this invention for which usage they may be defined as described. The alkyl aryl sulfonates, which are active surface agents, ,are included in this group inasmuch as the alkylated aromatics contained in petroleum fractions may be sulfonated as described to yield alkyl aryl sulfonates. For purposes of this invention the alkyl group or groups attached to the aromatic ring should be of suificient sizes to impart a molecular weight thereto of at least about 150.

5. In addition to the amino soaps hereinbeiore described l have found that the high molecular weight amines possess the necessary requisites for a Diesel fuel additive to modify the gum. forming tendencies thereof which may be visualized by the empirical formulas in which R, R and R may be any high molecular weight straight or branched hydrocarbon chains which may or may not contain aromatic nuclei in the chain. In these amines it is necessary that R in each case be a hydrocarbon chain of at least eight carbon atoms and preferably of about twelve to about eighteen carbon atoms. Although R and B" may also be long hydrocarbon chains it is not necessary and in those cases where R and R" are less than five carbon atoms, polar groups may be included therein. Primary amines of C12 or higher may be employed such as octadecyl amines, oleyl amine and the like. The secondary amines may be characterized by such examples as dioctadecyl amine, octadecyl ethyl amine, oleyl ethanol amine and the like and the tertiary amines by such compounds as cctadecyl diethyl amine, lauryl dieiiiianol amine, dioctadecyl ethyl amine and the 11 e.

6, Conversion of the carboxyl group of a fatty acid to an amide produces the fatty acid amides. It is desirable in some cases to effect the substitution of either one or both of the hydrogens of the amide group with a radical containing a polar group, as for example in which R represents a fatty acid radical of at least 8 carbon atoms and preferably of more than 12 carbon atoms, a branched chain structure or a substituted aliphatic chain and R and B" may he any substituted group at least one or which preferably contains a polar group as for example O CzHaOH cn. om)1-cn=cnom)1- -N CIHIOH Diethanol oleamide O CrHaOH CHKCHzhq- N Ethyl ethanol stearamide We may also employ compounds of the general nature in which only one hydrogen of the amide is replaced by a radical containing a polar group such as'ethanol oleamide or a sulfonated amide salt in which a: is a metallic cation. It is to be understood that any polar groups may be substituted in compounds of this nature for the purpose of imparting the surface active properties necessary for usage according to my invention. I may also. employ the simple amides in which the carbon-nitrogen linkage furnishes the necessary polar groupage. The simple fatty amides are effective providing the molecular weight is above about 150 or preferably above about 200 such as octadecyl amide o OHKOHIhP -NHr or I may employ simple amides of the type in which may be any fatty acid chain impartin to the compound a molecular weight of at least 150, branched aliphatic or substituted aliphatic,

such asfor example 01 H 9 C H; (0 Hr) Pig-g- (C Hr) Pi -NH:

in which the double bond of the oleic acid radical is opened by the addition thereto of HCl or substitution products derived therefrom such as and the like.

7. Esters and ethers are representative of the simpler types of surface active agents and for polar group in connection with each ten carbon such purpose are comprised of long chain, high molecular weight hydrocarbon radicals containing a polar group or groups relatively close, from a structural standpoint, to the end of the molecule and may be represented by R-COOR' I R-COR.'

where R is again a fatty acid chain of at least 8 carbon atoms and preferably of more than 12 carbon atoms, branched chain aliphatic or sub.- stituted aliphatic chain, and B may be any substituted group preferably of comparatively low molecular weight and containing at. least one polar group as for example CriHssCOiCHr) 20H and compounds of similar nature.

8. High molecular weight surface acting compounds as hereinbefore mentioned having molecular weights ashigh as about 650 may be classed as polymer type products containing the necessary polar groupage to impart surface active properties. For example the calcium salt of the reaction product of tertiary amyl phenol and sulfur dichloride while not lending itself to classification in any of the above general groups is a high molecular weight surface active agent having one atoms Ca Ca and has been shown to satisfactorily perform thefunction of modifying gum forming characteristics of a petroleum fuel and particularly of a peroxide doped Diesel fuel. I

Another class of surface active compounds which I have employed is sometimes referred to as the reverse soaps or inverse soaps and is characterized by the fact that the major part of the molecule is positively charged. While the literature shows a large number of possibilities the commercial compounds of this nature are usually quaternary ammonium derivatives. As in the other types of surface active compounds the presence of a long chain hydrocarbon radical is essential. The simplest of this cetyl ammonium chloride.

.HlO-N-Cl Har m CH:

In this case the halide is replaceable by other strong acid radicals-N03 or HSO4- for example and in each case the compound ionizes group is trimethyl with the halide or'its eauivalent as the negative ion and the rest as the positive ion. Other types of quaternary ammonium salts. wh ch, however. are not cation active. are found to be good surface active agents such as for example such compounds as tetramethyl ammonium petronate.

The examples herein set forth are not meant to confine the scope of this invention to the particular compounds disclosed inasmuch as my invention lies in the discovery that surface active compounds selected from the classes disclosed above have the effect upon addition to petroleum fuels and particularly Diesel fuels to which Diesel fuels there may or may not have been added an ignition accelerator such as the organic peroxides, of not only reducing the gum forming tendency in said fuel but of modifying the character of the gums formed in such a manner as to prevent their precipitation and subsequent deposition-in the internal combustion engines in which they are employed, thereby rendering them innocuous in an internal combustion engine.

The amount of the surface active agent to be added to a particular Diesel fuel is dependent not only upon the type of surface active agent employed but upon the character of the Diesel fuel to be treated as well. As pointed out these Diesel fuels to which an ignition accelerator and particularly an organic peroxide has been added are particularly susceptible to improvement by the method of my invention inasmuch as compounds of this type present in Diesel fuels have the effect of catalyzing the formation of gums therein necessitating some action to minimize this condition. I have found that the addition of about 0.01% to about 1% or 2% and in most cases from about 0.05% to about 0.3% of the surface active agents hereinbefore described is sufficient to reduce the precipitation of gum from fuels as described.

The addition of these agents may be effected at any time prior to the usage of the fuel and in particular may be added either-"before, during or after the addition of any ignition type accelerator. Thus for example in using diethanol'oleamide as the surface active addition agent I may add the same to a Diesel fuel together with an ignition accelerator such as an organic peroxide or I may first add the ignition accelerator and subsequently the dlethanol oleamide or I may reverse this procedure and introduce the surface active compound into the Dlesehfuel and subsequently effect the addition of the ignition accelerator, or it may be added to a Diesel fuel to which no ignition accelerator has been or will be added such addition being made at any desirable time prior to usage.

It is to be understood that my invention is not limited to the treatment of Diesel fuels to which an ignition accelerator has been added inasmuch as the a ditives herein described are effective in any fuel in which gum form tion is encountered. The. doped fuels are however to be stressed inasm ch as the ignition accelerators and particularly the organ c peroxides have the effect of catalyzing the gum formation in the majority ofthe Diesel fuels to which they are added. or V The methods of addition-of-tlfese surface active compounds to the Diesel-fuels is also a-function of the additive to be employed, The desired compound may be added directly to the fuel in the required proportions or it may be dissolved in a portion of said fuel in a concentration considerably in excess of that required in the final analysis and this concentrated solution may subsequently be blended into the untreated fuel in the correct proportions to yield a final mixture of the desired proportions. In some cases it may be preferable to dissolve said surface active agent in an oil soluble solvent such as a hydrocarbon fraction different from the fuel to be treated, in a chlorinated hydrocarbon solvent, in an aromatic solvent such asbenzene, toluene. or the like, and in fact in any one of a large number of oil soluble solvents which are not detrimental to the fuel to which they are added. In this manner for example a surface active agent such as calcium stearate and an ignition accelerator such as an organic peroxide may be added to a Diesel fuel simultaneously by cosolution in a suitable oil soluble solvent or the calcium stearate may be added in the absence of said ignition accelerator by solution in such a solvent. I

Examples of the effects of these surface active compounds on gum formation in'Diesel fuels will serve to illustrate and emphasize the benefits which will accrue from their usage. The test method employed was standardized and consistent throughout with the exception of the exposure time and was as follows:

One hundred ml. of the Diesel fuel to be tested was placed in a Pyrex evaporating dish and maintained therein at C. for from 16 to 40 hours. This high temperature storage was employed to accelerate the normal gum formation. After the high temperature storage the samples were allowed to stand at room temperature for five hours to cool and to allow time for the last traces of gum to settle. The Diesel fuel was then poured out of the evaporating dish which was allowed to drain for a period of one-half hour, rinsed twice with a light hydrocarbon fraction to remove the last traces of the heavier fuel, allowed to dry for one-half hour and weighed, the increase in weight over that of the clean dish prior to the test being due to the gums that had precipitated during the test. In this manner untreated Diesel fuels, peroxide doped Diesel fuels, undoped Diesel fuels to which a surface active agent had been added according to my invention and peroxide doped Diesel fuels to which a surface active agent had been added were tested. Results of such tests upon a straight run-Diesel containing 1% by weight of dimethylcyclopentane peroxides to which hadbeen added various surface active compounds as gum preventives is shown in Table I. The values in Table I'were obtained on samples maintained at 100 C. for ten hours according to the above procedure. a

manner'with an exposure timeof 40 hours as compared to 16 hours employed above on samples of a Diesel fuel, to which no ignition accelerator had been added, containing varying amounts of the surface active agents as hereinbefore dis closed. fiepresentative data from these tests are given in 'llable II below.

Table II 7 Weight Per Additive Cent Added Mg. of gum to Fuel None 40 Calcium eteareie 0. l 1 a: 2

ad iemine Another series of 16 hour tests were made in the same manner upon a special Diesel fuel prepared by Edeleanu extraction of a straight run stock to remove the aromatic constituents therefrom. This Diesel fuel had a ce'tane number of approximately 50 as compared to a value of about 45 in the straight run diesel above. This special fuel was then doped with 1% by weight of a dimethylcyclopentane peroxide and subsequently with various surface active agents and tested for gum precipitation by the method as describedabove with the following results.

Prepared by mixing diethyiene triamine and oleic acid in mole ratio of 1 to 2, heating on a steam bath for twenty minutes and subsequently heating for 20 hours at 100 0. (K14 hours at l50 Cl to give an amideproduct.

A fourth series of 16 hour tests were conducted ona straight run Diesel engine fuel in which other types of surface active agents were employed. The results of these tests are shown in Table IV. It is understood that this series of vTableIV Mg. of

Sample gums A. straight Run Diesel 4 ins l. 1% of dimethylcyelopentane hydroperoxide. 2. 1% of dirrethylcyclopentane hydropcroxide plus a. 1% Ca salt of reaction product of tertiary amyl phenol and sulfur dicbloride..v.

. 0.5% Ca salt of reaction product of tertiary amyl phenol and sulfur dichloride 0.25% Ga salt ofreaction prodlctcf tertiary amyl phenol and sulfur dichloride 0.2? Sodium mahogany sulionate v 0.5 5 Sodium mahogany sulionate--. 0.1 a Lead 1 Mahogany petroleum sullonate. 1

A further verification of the utility of additives l2 of the surface active type is shown by the use of such an additive in a number of different Diesel fuels obtained throughout the country. These tests were again made in the same manner as the 5 above employing diethanol oleamide' as the surface active agent and a hydroperoxide derived from the oxidation of a petroleum fraction boiling between 200 F. and 260 F. as an ignition accelerator and a catalyst to increase gum formation. 1

Table V 8am 1e Desi tioii Per Pent r il? 1 M o p gm Peroxide g g gg Trace Trace F As a result oflextensive tests as above Ihave found thatieftain of the surface active com-" pounds are less efficient in some fuels than others and it is therefore a. matter of experimentation to determine which particular surface active agent is best suited for a particular type of Diesel fuel. The theory of their action in preventing the precipitation of the gums is not 'as' 40 yet well enough understood to be able to predict by a knowledge of the Diesel fuel composition whichof the many possible surface active agents should be employed.

The foregoing description and examples of my invention are not to be taken as limiting lna's-r much as many modifications thereof may occur to those skilled in the art without departing from the spirit and scope of the following claims.

I claim:

1. A hydrocarbon Diesel fuel consisting essentially of a Diesel fuel normally subject to the formation of gums, containing from about 0.0 to about 2.0% of an oil soluble surface active agent selected from the alkyl monoamines and fatty acid amides characterized by molecular weight greater than about 150 and the presence of at least one carbon vchain of more than eight carbon atoms for the purpose of preventing the precipitation of said gums.

2'. A hydrocarbon Diesel fuel according to claim 1 in which said surface active agent isof a molecular weight between about 150 and about 350.

3. A hydrocarbon Diesel fuel consisting essentially of a Diesel fuel normally subject to the formation of gums containing from about 0;01% to about 2.0% of an oil soluble surface active alkyl monoamine of molecular weight greater than 150 selected from the classes of amines consisting of primary, secondary and tertiary alkyl monoamines. which amines contain at leastone hydrocarbon chain of more than eight carbon atoms andwhich have the effect of preventing the precipitatlon of the gums formed within said Diesel fuel.

4. A hydrocarbon Diesel fuel according to claim 3 in which said monoamines have a molecular weight in the range of about 150 to about 350.

5. A hydrocarbon Diesel fuel consisting essentially of a Diesel fuel normally subject to the formation of gums to which there has been added from about 0.01% to about 2.0% of octadecyl amine to prevent the precipitation of the gums formed within said'Diesel fuel.

6. A hydrocarbon Diesel fuel consisting essentially of a Diesel fuel normally subject to the formation of gums to which there has been added from about 0.01% to about 2.0% of an oil soluble surface active fatty acid amide of a molecular weight greater than 150 and having at least one hydrocrabon chain of at least eight carbon atoms to prevent the precipitation of said gums.

7. A hydrocarbon Diesel fuel according to claim 6 wherein said surface active amide has a molecular weight between about 150 to about 350.

8. A hydrocarbon Diesel fuel according to claim 6 in which said surface active amide is obtained by the conversion of the carboxylic group of a fatty acid in which amide the hydrocarbon atoms of the amide group may be substituted by a hydrocarbon radical containing at least one polar group.

9. A hydrocarbon Diesel fuel according to Lii" hancl oleamide.

1D. A fuel as set forth in claim 1 containing an oxidation type ignition accelerator.

11. A fuel as set forth in claim 1 containing an organic peroxide as an oxidation type ignition y lm 6 in which said surface active amide is 13.,A fuel as set forth in claim 3 containing an organic peroxide as' an oxidation type igni-. tion accelerator.

14. A fuel as set forth in claim 3 containing dimethyl cyclopentane hydroperoxide as an oxidation type ignition accelerator.

15. A fuel as set forth in claim 6 containing an organic peroxide as anoxidation type ignition accelerator.

. 16. A fuel as set forth in claim 6 containing dimethyl cyclopentane hydroperoxide as an oxidation type ignition accelerator.

ANDREW I. SMITH.

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

UNITED STATES PATENTS Number Name Date 1,752,945 Evans Apr. 1, 1930 1,800,997 Greenstreet Apr. 14, 1931 1,940,445 Calcott Dec. 19, 1933 1,947,219 Murrill Feb, 13, 1934 2,115,473 Semon Apr. 26, 1938 2,197,851 Dietrich Apr. 23, 1940 2,208,105 Rathbun July 16, 1940 2,295,773 Chenicek Sept. 15, 1942 2,296,558 Kokatnur Sept. 22, 1942 2,316,739 Cook Apr. 13, 1943 2,322,007 Fischer June 15, 1943 2,343,766 'Gaylor Mar. 7, 1944 FOREIGN PATENTS Number Country Date 479,903 Great Britain Feb. 10, 1938 545,125 Great Britain May 12, 1942