US3006747A - Hydrocarbon compositions - Google Patents

Description

hired. States i tent fifice 3,006,747 Patented Oct. 31, 1951 3,ilil6,747 t RUQARBGN CQMPOSITIGNS Theodore R. Lusehrinlr, Concord, alif., assignor to Shell Oil Company, a corporation of Delaware No Drawing. Filed Sept. 1 1959, Ser. No. 840,542 6 Claims. (Cl. -.5)

This invention relates to improved hydrocarbon compositions, more particularly hydrocarbon fuels for internal combustion engines.

Commercial hydrocarbon compositions such as those boiling in the gasoline, kerosene, and jet fuel boiling ranges invariably contain small amounts of water, either dissolved or dispersed in the product. This is because it is virtually impossible to prevent contact of the product with Water during some phase of its manufacture, blending, storage and transportation to the consumer. In processing, for example, the hydrocarbons are contacted with Water during desalting of the crude oil from which they are derived, during distillation in which stripping steam is used, and during scrubbing to remove hydrogen sulfide by dilute caustic washing. In addition water is also absorbed merely by contact with the atmosphere.

The presence of small amounts of Water is not usually deleterious at ordinary temperatures; however when the hydrocarbon product is cooled, ice particles are often formed. The formation of ice in hydrocarbon fuels is usually at least troublesome and often is extremely dangerous. For example, all vehicles powered with liquid hydrocarbon fuels are normally provided with filters, such as filter screens and microrric filters, in the fuel system, so as to prevent the passage of solid contaminants, for example, small particles of rust, into the engine. When ice is formed in the fuel used, it will often plug the filters, thus stopping the flow of fuel to the engine. In the case of vehicles operating on the ground or Water surface, this is at least inconvenient; but in aircraft such stoppage, of course, involves a grave risk to human life. Because of this danger, most aircraft are provided with an automatic by-pass around the filters. However, on the opening of the by-pass, the ice is passed through to injector mechanisms and the like, which contain close and critical tolerances. Here, the ice causes still further difficulties, including malfunctioning of these mechanisms.

Another fuel system mechanism which is particularly prone to malfunctioning due to plugging with ice is the carburetor. At this point in the fuel system, additional moisture is introduced with the air for combustion. Even though both liquid fuel and air temperatures are above 32 F., the evaporation of the fuel in the carburetor will often cool the system to 32 F. or below, especially soon after starting the engine, whereupon ice will form and will frequently cause the engine to stall because of the blocking of fuel and air passages by the ice.

Jet fuels of the kerosene type have even greater ability than gasoline to dissolve Water and the Warmer the fuel the greater amount of Water it can dissolve. At the low temperatures encountered during high altitude flights, dissolved water becomes free Water and tends to freeze. To illustrate the problem, at high altitude when the temperature may be as low as 50 R, over pounds of ice may be formed from 10,000 gallons of fuel which contained only 175 ppm. dissolved water.

Herctofore, these difiiculties have sometimes been alleviated by incorporating into the hydrocarbon fuel certain water-soluble freezing point depressants, such as alcohols (as in alcohol injection systems), glycols and the like. However, this requires relatively large concentrations of the freezing point depressant, for example, from about 0.1% to as high as 2 or 3% by volume. These large concentrations are not only uneconomical but also often adversely affect the chemical and physical properties of the fuel. Additionally, the high water solubility of these compounds makes them susceptible to removal from the fuel by the leaching action of the free water with which the fuel usually comes in contact during storage. Furthermore, such Water-soluble products when incorporated in the fuel, act as solubilizers for water, thus actually increasing the amount of Water which the fuel will absorb during commercial handling. Although this is by no means desirable, the alcohols, for example isopropyl alcohol, still are somewhat effective in decreasing the incidence of stalling of automobiles due to carburetor icing. But in the case of aircraft applications, wherein filter clogging is particularly critical, and temperatures are unusually low, the increased concentration of water in the fuel may over-balance the benefit of the freezing point depressant, so the addition of the latter often aggravates rather than alleviates the problem.

In jet aircraft, emergency alcohol injection systems have been installed for the pilots to use when symptoms of icing develop. However, the symptoms are diflicult to recognize. Flame-outs, engine speed fluctuations, frozen engine speed, and fuel filter warning lights are the symptoms by which a pilot may detect fuel icing. Nevertheless, despite such precautions, fuel icing has contributed to a number of fatal accidents. Moreover, the injection of alcohol in such emergencies is only a localized remedy and does not prevent ice formation in other parts of the fuel system.

In addition to alcohol injection, a further remedial action to fuel icing in jet aircraft has been to heat the fuel filter; however, this requires considerable power consumption and weight, both of which reduce the range of the aircraft. Furthermore, this is also merely a localized solution to the problem.

It is therefore a principal object of this invention to provide an improved composition of hydrocarbons boiling Within the jet fuel boiling range. A more particular object is to provide such a composition which has improved characteristics with respect to ice formation. Another object of the invention is to provide jet fuel composition with improved anti-icing characteristics. A further object of the invention is to provide a hydrocarbon composition with improved characteristics with respect to ice formation therein which does not require a high concentration of anti-icing additive. A still further object of the invention is the attainment of the foregoing objects in such a manner that the gross hydrocarbon composition has anti-corrosion properties when employed in the operation of continuous combustion engines. Other objects will be apparent from the description of the invention.

It has now been discovered that these and other objects are attained by the addition, to a hydrocarbon distillate fuel, of an extremely small concentration, for example, as little as one part per million by weight, of a mixture of certain aliphatic amino fatty acids, containing from 0 to 2 double bonds per molecule, and certain highly branched oil-soluble organic polymers, described with particularity hereinafter.

The hydrocarbon base material which is the major component of the composition of the invention can be any hydrocarbon or mixture of hydrocarbons boiling substantially within the liquified petroleum gas, gasoline, kerosene, aviation turbine fuel (jet fuel) and diesel fuel boiling range, that is, those within the ASTM boiling range of from about 60 F. to about 700 F. The invention is particularly directed to mixtures of hydrocarbons boiling Within an ASIM boiling range of from about F. to about 600 F, especially gasoline and jet fuel. In the case of a jet fuel the hydrocarbon base material may be of the kerosene type (e.g., J'P-S) or it may be a wide boiling range volatile distillate sometimes called gasoline type jet fuel (e.g., JP-4). Though the foregoing consist essentially of a mixture of many hydrocarbons of one or more hydrocarbon types (olefins, aromatics, paraflins and naphthenes), the base hydrocarbon may also be a fuel consisting of a single hydrocarbon composition, e.g., diethylcyclohexane, or defined mixtures of pure hydrocarbons.

The amino fatty acids to be utilized in accordance with the present invention have the general formula as follows:

In its broadest concept the class of amino fatty acids comprises those in which the aliphatic radical R, which contains from to 2 double bonds, and which is directly attached to the nitrogen atom contains from 8 to 24 carbon atoms and preferably from 10 to 18 carbon atoms, while the alkyl radical R, directly attached to both the carboxyl group and the nitrogen atom, contains from 3 to 17 carbon atoms, preferably from about 3 and 8 carbon atoms. Still more preferably, the aliphatic amino radical is attached to a carbon atom which is separated from the carboxyl group by a chain of from 1 to 3 intervening carbon atoms. Consequently, the preferred members to be employed in the present compositions comprise N hydrocarbyl-beta-, gamma, or delta-amino fatty acids containing 10 to 18 carbon atoms in the hydroc arbyl radical and 3 to 8 carbon atoms in the fatty acid hydrocarbon radical, especially such N-hydrocarbyl-beta-arnino fatty acids. Typical species falling with this class of compounds are as follows:

TABLE 1 N-ootylbeta-amino propionic acid N-octyl-beta-amino butyric acid N-decyl-beta-amino butyric acid N-dodecyl-beta-amino but ric acid N-tetradecyl-beta-amino butyric acid N-hexadecyl-beta-amino butyric acid N-octadecyl-beta-amino butyric acid N-octyl-gamma-amino v-aleric acid N-dodecyl-gamma-amino valeric acid N-octadecyl-gamma-amino valen'c acid N-dodecyl-delta-arnino caproic acid N-octadecyl-delta-amino caproic acid N-tetnadecyl-delta-amino caproic acid N-nonyl-beta-amino laun'c acid N-Z-ethylhexyl-gamma-anfino capric acid N-4-butyloctyl-delta-amino caprylic acid N-3-propylnonyl-beta-amino butyric acid N-hexadecenyl-beta-amino butyric acid N-octadecenyl-beta-amino Valerie acid N-octadecadienyl-gamma amino butyric acid While the aliphatic radical attached to the nitrogen atom (R) may be either straight chain or branched chain alkyl, the straight chain species are preferred. Only one aliphatic radical should be directly attached to the nitrogen atom since it has been found that the amino fatty acids having two aliphatic groups attached to the nitrogen atoms exhibit sharply reduced anti-icing properties.

The amino fatty acids as defined above are dispersible either in gasoline or in water or both and remain in a highly dispersed condition in gasoline compositions Whether or not substantial proportions of water are present.

While a single N-aliphatic amino fatty acid may be employed for the purposes of the invention, it will be understood that mixtures of the same in the above total concentrations are also suitable. For example, a mixture of N-dodecyland N-tetradecyl-beta-arnino butyrie acids is especially suitable for use as a gasoline corrosion inhibitor and anti-icing additive. A particularly preferred mixture of amino fatty acids is a mixture of N-alkylbeta-amino butyric acids, such as may be obtained from Armour and Company under the trade name of Armeen-Z, wherein the aliphatic groups are derived from coconut oil fatty acids, i.e., the aliphatic groups contain from 8 to 18 carbon atoms and predominate in alkyl groups of 12 and 14 carbon atoms.

The polymeric additive of the invention is a hydrolyzed reaction product of vinyl ester of a lower molecular weight alklyl carboxylic acid, or a mixture of such esters, and an acyclic alpha-monoolefinic hydrocarbon containing a terminal CH :CH group and containing at least 10 and no more than 42 carbon atoms, or a mixture of such alpha-olefins. The hydrolyzed reaction product is a mixture of compounds having an average molecular weight of from about 4000 to about 100,000, each molecule thereof containing a linear backbone hydrocarbon chain of from about 40 to about 4000 carbon atoms substituted on about half the carbon atoms of this chain by randomly or uniformly located polar and non-polar groups, the polar groups being hydroxyl groups and alkanoyloxy where R= H or alkyl) groups, the alkyl subgroup of the latter containing no more than 4 carbon atoms, at least about 30% of the polar groups being hydroxyl groups, and the non-polar groups being acylic hydrocarbyl groups containing from S to 40 carbon atoms, wherein the ratio of the number of polar groups to the number of non-polar groups is from about 0.521 to about 10: 1.

The alkyl groups of the copolymer are, of course, determined by the particular acyclic alpha-monoolefin used. Since the terminal CH =CH- group of this monomer enters the backbone chain of the copolymer, the alkyl group derived from a particular olefin molecule will be the remainder of the molecule. it is preferred that these alkyl groups be straight chain groups and it is also preferred that they contain at least 10 carbon atoms, especially at least 12 carbon atoms. However, these groups should not be too long and preferably should contain no more than 30 carbons. Still better results Will be obtained with alkyl groups containing no more than about 20 carbon atoms.

The acid from which the vinyl ester is derived can generally be any of the lower molecular weight alkyl carboxylic acids, preferably mono-carboxylic acids, containing up to 5 carbon atoms. The vinyl ester can thus be vinyl formate, vinyl acetate, vinyl propionate or the like. Vinyl acetate is a cheap, readily available and especially preferable ester for the purposes of the invention.

It is preferred that the average molecular weight of the hydrolyzed copolymer be at least 8000 and even better results will be generally obtained with molecular weights above about 10,000. On the other hand, although molecular weights up to about 100,000 can be used, better results will be generally obtained with average molecular Weights no greater than about 50,000, and especially no greater than 25,000.

Generally, superior results are obtained with hydrolyzed copolymers of the invention wherein the ratio of the number of polar groups to the number of non-polar groups (i.e., the mol ratio of the vinyl ester to the alphaolefin in the copolymer before hydrolysis) is at least 1:1, especially at least 3:1. On the other hand, this ratio is preferably not greater than 8: 1, and especially not greater than 5: 1.

The degree of hydrolysis of the copolymer, of course, determines the proportion of the polar groups which will be hydroxyl groups. It is preferred that at least 50%, and especially at least of the polar groups be hydroxyl groups. Generally, best results will be obtained if nearly all are hydroxyl groups; however, practical considerations in the hydrolysis of the copolymer will usually limit the economic proportion of hydroxyl groups to about or of the total of the hydroxyl and alkanoyloxy groups in the hydrolyzed copolymer.

The preparation of the foregoing organic polymers is described in US. Patent 2,800,401, issued July 23, 1957.

As mentioned before, the effective concentrations of the mixture of N-aliphatic amino fatty acid and organic polymer are extremely small. The concentration can be as low as 0.5 part per million (wt.), although it is preferred that at least 1 and especially at least 5 parts per million be used. Higher concentrations may, of course, be used. It is preferred that no more than about 50 parts per million be used,

Most prior additives for hydrocarbons which are effective at extremely small concentrations, such as corrosion inhibitors, oxidation inhibitors, anti-icants, etc., exhibit sharp reduction of effectiveness when they are added at significantly higher concentrations. However, it has been found that the incremental effectiveness of the mixture of amino fatty acid and organic polymer of the invention is reduced only partially at concentrations nearly 500 times their minimum effective concentration. Thus the addition of the mixture of the invention is effective at concentrations as high as 250 parts per million. Above this concentration, the incremental effectiveness of the mixture falls off more sharply. The wide range of effective additive concentration is important in that it enables a wide range of hydrocarbons, containing higher amounts of water, to be reduced in anti-icing tendencies by the addition of the mixture of this invention. Another important advantage of the invention is that the water contained in the hydrocarbon fuels to which the mixture of amino acid and organic polymer is added may be either dissolved water or it may also be dispersed water. The mixture is therefore effective in jet fuels containing dissolved water, dispersed water, or both.

Within the foregoing range of total concentration of the additives mixture, a wide range of relative amounts of amino acid and organic polymer may be used. It is preferred, however, that both of the component classes of materials be present in the additive mixture at a concentration of at least 30% by weight. For most jet fuel applications, in which both dissolved and free water are usually present, it is preferred that the mixture contain about 40 to 60% by weight of the amino acid and from 60 to 40% of the organic polymers. When the hydrocarbon composition contains or is likely to contain excessive amounts of dissolved water before ultimate consumption, for example from storage at tropical temperatures in the presence of tank bottoms containing water, it is preferred that the concentration of amino acid be at least 45% by weight. On the other hand, when the hydrocarbon composition contains or is likely to contain large amounts of dispersed or free water, as, for example, during low ambient storage temperatures, it is preferred that the concentration of organic polymer be at last 50% by weight.

The invention is illustrated in the following example.

Example I The following test procedure was employed to determine the anti-icing ability of the hydrocarbon fuels of the invention:

Two hundred fifteen gallons of hydrocarbon jet fuel containing no inhibitors, deactivators, or additives are added to a round bottom tank and circulated by means of a circulating loop consisting of a drawoif line, pump, and return line. The circulating loop passes through a heat transfer tank. If the fuel temperature is below 75 F it is warmed to that temperature by circulating warm solvent through coils contained in the heat transfer tank. When the fuel has reached a temperature of 75 F., 150 milliliters of water are added dropwise to the fuel as it is circulated for two hours. Circulation is then discontinued and the fuel is allowed to settle for one-half hour during which large droplets ,of dispersed water are settled out and drained. The fueljs-th en sampled for water content by a Karl Fischer analysis. Moisture content of the fuel averages from 115 to 130 parts per million by weight.

The fuel is then circulated and cooled until the test temperature, here 15 F., is reached. Cooling is accomplished by passing Dry Ice-cooled solvent through the coils of the heat transfer tank. After the test temperature is reached, the fuel is circulated through a filter unit containing a 200 mesh screen. The initial flow rate is set at 1,000 pounds per hour and the flow rate, temperatures of the tank and filter, pressure drop across the filter, and the time of flow are recorded. Ice formation is noted by checking the pressure drop across the screen and the decrease in flow rate until complete plugging of the screen occurred. When additives are tested, the same process is followed except that the additives are introduced into the fuel after the sampling for water content has been completed.

The foregoing procedure was followed during which 30 runs were made to determine the icing tendency of a military jet fuel composition containing no additives. The foregoing procedure was also followed in testing the icing tendency of the same jet fuel to which were added in separate tests (1) only the organic polymer; (2) only N-alkylamino acid, and (3) a 50/50 mixture of polymer and fatty acid, in accordance with the invention. Five tests were performed on each of the three additive-containing fuels. The times for complete plugging in each of the foregoing tests were then averaged. The results were as follows:

1 92% Hydrolyzed reaction product of vinyl acetate and l-dodeccne, mole ratio of vinyl ester to alpha olefin 3.521 before hydrolysis.

2 N-coco-beta-amino butyric acid.

Thus, even though the separate components of the additive mixture exhibited significant anti-icing effects, the combination of the organic polymer and amino acid had 9.5 to 26 times the individual effects of the separate components in increasing the length of time before plugging of the filter with ice. Conversely, less than 10% of the mixture of polymer and acid are required to attain the same anti-icing effect of either component by itself.

In addition to the above superior anti-icing benefits, the fuel composition in accordance with the invention also possesses outstanding high temperature stability (as measured by the CFR Fuel Coker test procedure) and excellent anti-corrosion properties. The importance of these auxiliary properties will, of course, be recognized by anyone familiar with the requirements of jet fuels.

In the foregoing tests of the invention, no other additives were present in the jet fuel but the jet fuel compositions can and will ordinarily contain additives for other purposes. Suitable compatible auxiliary additives include anti-oxidants, corrosion inhibitors, and metal deactivators. Examples of such additives are 2,6-ditertiary butyl 4-methy1 phenol, N,N' disecondary butyl paraphenylene diamine, 2,4-dimethyl-o-tertiary-butyl phenol, N,N-disalicylidine-1,2-propane diamine, N,N'-disalicylidene-1 .2-ethylened.iamine, polymerized linoleic acids and N,C-disubstituted imidazolines. It is to be noted, however, that the fuel compositions of the invention will not ordinarily contain added corrosion inhibitors, since the compositions themselves possess sufficient anti-corrosive properties.

The order of mixing of the various constituents of the compositions of this invention is immaterial. For example, either the organic polymer or the N-alkylamino acid may be added to the hydrocarbon which already contains the other or they may be added together. Likewise, both may be first mixed, stored, and handled as a concentrate, and added to the fuel at a later time.

From the standpoint of ease of handling it is particularly advantageous to handle both the organic polymer and the N-alkylamino acid as a concentrate either with or without the aforementioned additives, for example, antioxidants, metal deactivators and the like. Because of the consistency of some of the preferred N-alkylamino acids, they are normally handled in solution with, for example, isopropyl alcohol. Therefore, such an additive concentrate will normally contain a small amount of isopropyl alcohol. In addition, aromatic solvents such as toluene may also be added in order to increase the solubility of the additive concentrate. A typical additive concentrate, which is suitable for use in jet fuels in accordance with the invention, has the following composition:

Percent by Weight Organic polymer l Though the exemplary description of the invention has been directed primarily to hydrocarbon fuels of the jet fuel boiling range, it will be recognized by those skilled in the art of fuels that the additives of the invention are also eifective in combatting the icing difiiculties encountered in carburetted and fuel injection systems such as are used with gasoline-powered vehicles and pistontype aircraft power plants. In such a situation, the hydrocarbon composition may also contain, in addition to the foregoing discussed classes of additives, anti-detonants, scavenging agents, spark plug anti-foulants, and combustion modifiers.

I claim as my invention:

1. A hydrocarbon composition consisting essentially of hydrocarbon base material boiling within the range of from about 6 F. to about 700 F. and at least 1 and less than about 250 parts per million by weight of an additive mixture consisting essentially of (a) N-aliphatic amino fatty acid having the general formula wherein R is an aliphatic radical of the group consisting of alkyl and alkenyl, said radical having 824 carbon atoms and containing from O to 2 double bonds and R is an alkyl hydrocarbon radical having 3-17 carbon atoms and being attached to the nitrogen atom by a carbon atom which is separated from the COOH group by l to 3 intervening carbon atoms and (b) an organic polymer which is the at least hydrolyzed reaction product of a vinyl ester of lower molecular weight alkyl carboxylic acid and an acylic monoolefinic hydrocarbon material with a terminal CH CH group and containing from 10 to 40 carbon atoms per molecule, said reaction product, before hydrolysis, containing said vinyl ester and said monoolefinic hydrocarbon material in a mol ratio of from about 0.5:1 to about 10: 1, said hydrolyzed reaction product having an average molecular weight of about 4,000 to 100,000.

2. A hydrocarbon composition in accordance with claim 1 in which the additive mixture contains from 30 to of the N-aliphatic amino fatty acid and from 70 to 30% of the organic polymer.

3. A hydrocarbon composition in accordance with claim 1 in which R contains from 10 to 18 carbon atoms and R contains from 3 to 8 carbon atoms.

4. A hydrocarbon composition in accordance with claim 1 in which the acid is an N-alkyl beta-amino fatty acid.

5. A hydrocarbon composition in accordance with claim 4 in which the acid is a mixture of N-alkyl betaarnino butyric acids wherein the alkyl groups are derived from coconut oil fatty acids.

6. A hydrocarbon composition in accordance with claim 1 in which the organic polymer is the at least hydrolyzed reaction product of vinyl acetate and a mixture of monoolefinic hydrocarbons substantially most molecules of which hydrocarbons have a terminal CH =CH group and from 14 to 18 carbon atoms, said reaction product, before hydrolysis, containing said vinyl acetate and said mixture of monoolefinic hydrocarbons in a mol ratio of from about 3:1 to about 5:1, said hydrolyzed reaction product having an average molecular weight of from about 10,000 to about 25,000.

References Cited in the file of this patent UNITED STATES PATENTS 2,800,401 L-usebrink et a1 July 23, 1957

Claims (1)

1. A HYDROCARBON COMPOSITION CONSISTING ESSENTIALLY OF HYDROCARBON BASE MATERIAL BOILING WITHIN THE RANGE OF FROM ABOUT -60*F. TO ABOUT 700*F. AND AT LEAST 1 AND LESS THAN ABOUT 250 PARTS PER MILLION BY WEIGHT OF AN ADDITIVE MIXTURE CONSISTING ESSENTIALLY OF (A) N-ALIPHATIC AMINO FATTY ACID HAVING THE GENERAL FORMULA