US2892690A - Compounded hydrocarbon fuels - Google Patents

Description

United COMPOUNDED HYDRGCARBGN FUELS No Drawing. Application March 22, 1955 Serial No. 496,077

' Claims. (Cl. 44-62) This invention relates to an improvement in hydrocarbon fuels, and particularly hydrocarbon distillate fuels, to the extentthat they are stabilized against deposit formation under varying conditions of static and dynamic flow incident to ultimate introduction into a combustion zone.

The. deposit-forming tendencies of hydrocarbon fuels, and particularly the petroleum distillate fuels, are largely dependent upon their composition and the conditions to which they are subjected prior to energy-release through combustion in :a combustion zone. Compositionwise, the deposit-forming tendencies or instability of the fuel are usually associated with the presence of thermally and/or catalytically cracked componentsin the fuel and" become. increasingly pronounced in the higher boiling 'range'fuels. However, in:addition to the effect of the organic components of the fuel, certain conditionsof storage, transportation and serviceprior to combustion also contribute materially to the deposit-forming tendencies of the. fuel. These conditions are generally conditions of: oxidation and result in the formation of solublev and insoluble oxidation products which form the bulk of the deposits laid dovm on the various metal and other surfaces within the fuel system. Additionally,:the presence of nonhydrocarbon contaminants in the fuel, and particularly metals such as copper and iron, accelerates-the oxidative reactionsand coincident deposit formation.

The more general oxidative' deterioration. is obtained asa low temperature oxidation during storage in the presence of air, and the resulting deposit formation is substantially dependent upon the composition or stability of the fuel. Other types of oxidative conditions which, in addition, promote deposit formation are encountered in the conditions and fuel systems specificto'the various types of hydrocarbon fuels. Thus,.in: the operation of internal combustion: engines,.whether compression-igni tion or spark-ignition, deposit formation is encountered within the inductionsystem. and particularly at the intake valves, injector nozzles, and injection plungers. At the areas of deposit formation, the hydrocarbon fuel is subjected to comparatively high temperatures and comes in contact with combustion and exhaust gases'containing oxidation precursors, etc. Another illustration of specific deposit formation of hydrocarbon fuels isin the opera tion of aircraft gas turbine engines wherein the fuel may be employed as a. coolant and in heat exchange with the circulating lubricating oil. In such situations, the fuel is subjected to skin temperatures of up to 500 F. and results in the deposition of coke-like deposits on the heat exchanger surfaces.

Although certain of these deposit-forming tendencies of the hydrocarbon distillate fuels maybe eliminated or minimized by additional refinery processing designedto extract, alter, and/ or remove the oxidation-sensitive and/ or unstable components of the fuel, such practices great- 1y depreciate theyield of fuel and materially increase the unit fuel costs. However, contrasting the disadvantages of additional process refining ofthe distillate fuels, it has ties Patent 2,892,690 Patented June 30, 1959 now beendiscovered that hydrocarbon fuels-may be stabilized against objectionable deposit formation prior to combustion by the incorporation of a unique class of. addition agents.

According to thepresent invention, it has been found that the incorporation in a hydrocarbon fuel, and pref: erably a petroleum hydrocarbon distillate fuel, of a minor amount of a specific class of relatively high molecular weight copolymer compositions will effect a material reduction in the formation of insoluble sludges, etc., which" may be precipitated or carried with the fuel to form'deposits'within the fuel system and thereby reduce the operating efficiency of the combustion engine or burner; The class of copolymer compositions which have been determined to be unique in these improving character-- istics may be defined as arelatively high molecular weight copolymer composition which may be obtained by thecopolymerization of (A)'at least one compound containing. an ethylenic linkage and 8 to 30 aliphatic or cyclo-- aliphatic carbon atoms which is copolymerizablethrough the'ethylenic'linkage, and (B) at least one il-unsaturated monocarboxylic acid, and preferably an a ti-unsaturated aliphatic monocarboxylic acid containingfromfi to 81 carbon atoms, which copolymer is so constituted that the ratio of (A) to (B) is within the range of 0.5 to 10, and' in which 0 to about of the carboxyl groups of; component (B) are present in the form of a polar-substituted derivative.

Within the foregoing definition of the hydrocarbon fuel improving. agent, the particular composition chosen foroptimumelfectiveness is dependent largely upon the particular. type of hydrocarbon'fuel, its composition, and the environmental conditions to which the fuel is subjected prior to-introduction into a'combustionzone. Thus, the specific copolymer composition employed in a motor gasoline for maximum effectiveness in reducing the intake manifold deposits in a spark-ignition, internal combustion engine will usually. differ chemically within the foregoing classification from the copolymer additives incorporated in a high boiling burner fuel containing high concentrations of cracked gas oil stocks to eflfect the maximum reduction in clogging: and plugging of filters, screens, pumps, and the like. In general, the greatest improvement in reduction of deposit-forming characteristics of a hydrocarbon distillate fuel by the incorporation of the subject copolymer addition agentis obtained with distillate fuels composed predominantly of hydrocarbons boil ing above about 300 F., and the effective concentration of the copolymer additive will usually vary between 0.0005 to 1.0% by weight.

For specific illustration of the effectiveness of these addition agents in reducing the deposit-forming tendencies of a hydrocarbon fuel, reference is made. to the higher boiling range fuels, such as the aircraft gas turbine engine fuels, commonly referred to as jet fuels; kerosene; gas oils, and particularly the thermal and catalytically cracked gas oils; compression-ignition, internal combustion fuels, such as diesel fuels; and the conventional burner or furnace oils. Particularly for these types of fuel applications, it is desirable to employ an addition agent within the class of relatively high molecular weight copolymers, which may be produced through copolymerization of (A) at least one compound comprising analiphatic ester containing 8 to 30 carbon atoms and a copolymerizable ethylenic linkage alpha or beta to the carboxylgroup, and (B) at least one copolymerizable compound comprising an a ti-unsaturated aliphatic mono, carboxylic acid containing from 3 to 8 carbon atoms, .to produce'a copolymer composition in which the compo, nents (A) and (B) are present in the ratio of (A) to (B) within the range of 0.5 to 7, and in which 5- tov 60%. of .thecarboxyl groups of the component (B) are present in the form of a polar-substituted derivative such as the oxygenand/or nitrogen-containing esters, amides, and/ or amine salt derivatives.

The copolymerizable component (A) is primarily employed to impart the required degree of oil solubility to the copolymer composition, and, according to the aforementioned definitions, includes the following: olefin hydrocarbons and particularly alkenes such as polyisobutylene and dodecene-l, cycloalkenes such as cyclohexene and vinylcyclohexane, and styrenes such as p-octylstyrene and p-t-butylstyrene; olefinic ethers, representative of which are the vinyl ethers such as vinyl n-butyl ether, vinyl Z-ethylhexyl ether, and vinyl p-octylphenyl ether, allyl ethers such as allyl cyclohexyl ether and allyl isobutyl ether, and methallyl ethers, such as methallyl nhexyl ether and methallyl octadecyl ether; organic esters in which the copolymerizable ethylenic linkage is contained in the ester radical, such as the vinyl, allyl, methallyl and crotyl esters of long-chain aliphatic and cycloaliphatic monobasic acids, illustrative of which are vinyl oleate, vinyl palmitate, allyl laurate, allyl stearate, allyl ricinoleate, allyl naphthenate, methallyl caproate, methallyl palmitate, crotyl oleate, crotyl naphthenate, a-methylcrotyl palmitate; organic esters in which the copolymerizable ethylenic linkage is contained in the acid portion of the molecule, such as the esters of acrylic, methacrylic, crotonic, maleic, citraconic acids, etc., representative of which are dodecyl acrylate, dodecyl methacrylate, cyclohexyl methacrylate, decyl vinylacetate, octadecyl isocrotonate, didodecyl maleate, di-2-ethylhexyl fumarate, didodecyl citraconate, etc.

The other copolymerizable component, identified for convenience as component (B), is employed for the purpose of supplying the requisite active polar constituents in the copolymer composition. As previously indicated, the fundamental structure of component (B) consists of a monocarboxylic acid, and preferably an aliphatic monocarboxylic acid, with a copolymerizable olefinic linkage in the a,fl-position to the'carboxyl group. More specifically, component (B) is preferably selected from the 18- unsaturated aliphatic monocarboxylic acids which contain [from 3 to 8 carbon atoms in molecule. Particularly preferred as component (B) are the acrylic and methacrylic acids with their substituted derivatives falling within the scope of the general formula:

in which R; and R are either hydrogen or lower alkyl radicals containing from 1 to 3 carbon atoms.

While component (B) has here been defined in terms of a free monocarboxylic acid, the final copolymer composition may present up to 80% of the carboxyl groups of component (B) in the copolymer in the form of their polar-substituted derivatives. These derivatives may be introduced initially into the copolymerization reaction by employing as the monomer (B) appropriate mixtures of the monocarboxylic acid derivatives and the free monocarboxylic acid, or the copolymerization may be effected with the monocarboxylic acid monomer and the resulting copolymer reacted with the desired polar-substituted alcohol or an amine in appropriate ratio to effect the desired degree of derivative formation.

The desirability of modifying the basic copolymer structure through the use or by the formation of the carboxylic acid derivatives is primarily dependent upon the environmental conditions to which the compounded hydrocarbon fuel is subjected. In addition to the previous variables in composition of the base fuel and projected service conditions, a further selection of optimum copolymer composition is predicated upon the presence or absence of water in the fuel system, e.g., wet or dry fuel system. It has been found that, in general, the modified copolymers in which up to 80%, and preferably from about 5 to 60%, of the carboxyl groups of component (B) are presented in the form of their oxygenor nitrogencontaining esters or aminated derivatives possess certain performance advantages when employed as an improving agent for hydrocarbon fuels in a wet fuel system. Aside from the improved deposit reduction noted in performance tests in a wet burner fuel system, other collateral improvements, such as corrosion inhibition and improved demulsibility, are attained with proper selection of the copolymer derivatives.

The derivatives contemplated within the scope of the invention are such derivatives as may be produced by conventional esterification or amination reactions with the carboxyl groups of component (B). By amination" reaction is meant the generalized reaction of ammonia and its substituted derivatives, e.g., primary, secondary, and tertiary amines, with a carboxyl group, including the various stages of dehydration, e.g., amine salt, amide, imide, etc., formation. Although these derivatives may be initially presented as an integral function of the monomer (B) to the copolymerization reaction, it is preferred to conduct the copolymerization reaction with the free monocarboxylic acid as the copolymerizable monomer (B) and subsequently modify the resulting copolymer by the partial esterification or amination reactions to introduce the particular derivative functions in the desired degree. This preferred mode of preparation facilitates the conduct of a copolymerization reaction, yields a more uniform copolymer backbone, and permits more latitude in the degree of derivative formation.

Since one of the primary objectives in the modification of a given copolymer backbone is to increase the polar ratio of the copolymer composition, the partial esterification and amination reaction are preferably conducted to form derivatives containing at least one active polar group. To this end, the partial esterification may be conducted with aliphatic, cycloaliphatic, or aromatic monoand polyhydric alcohols, and the partial amination reactions with ammonia or monoand polyamines within a wide range of structural deviation and molecular weight.

For the purpose of illustrating the preferred form of derivatives, the following representative types of alcohols may be employed in the formation of the esters. For the introduction of multiple polar groups, the glycols, glycerols, pentaerythritols, sorbitans, and polyalkylene glycols and their condensation products may be employed. In the polyalkylene glycols, the polyethylene and polypropylene glycols, either per se or in combination with varying molecular weights up to about 800, may be used. Additionally, the ethylene oxide condensation products with fatty amines, fatty acids, and fatty acid amides may also be employed. When esterifying with the polyhydric alcohols, for example, glycols and polyethylene glycols, it is preferred to avoid the presence of a free terminal hydroxyl group which may result in cross linkage within the polymer structure as evidenced by gel formation.- This has been avoided in the case of the polyethylene glycols by capping the residual or terminal hydroxyl radical with alkyl or other radicals.

On the other hand, representative amines which may be employed to form the aminated derivatives include the monoand polyfunctional amines as represented by the primary, secondary, and tertiary aliphatic, aromatic, or alicyclic amines, which preferably contain up to 18 carbon atoms, as well as the polyamines and polyfunctional amines including the amino acids, amino alcohols, amino phenols, polyalkylenepolyamines, glyoxalidines or imidazolines and substituted derivatives thereof.

It has been particularly noted in the preferred application of the subject copolymer improving agents in the higher boiling range fuels, such as those boiling predominantly within the range of from 300 to 700 F., and preferably such fuels as contain appreciable concentrations of catalytically cracked gas oil stocks, that a certain optimum relationship between the total number of aliphatic carbon atoms to polar groups within the molecule appears to exist. Evidence has been obtained that fora .given concentration the copolymer compositions containing a ratio of aliphatic carbon atoms to polar groups within the range of from 7 to 70 appear to embrace the optimum composition for deposit reduction efiectiveness. In determining this apparent balance between the polar and nonpolar constituents, the aliphatic carbon atoms to be considered are the following: CH CH and excluding aromatic ring carbon atoms or the carbon atom of the carbonyl groups. As polar groups, the following representative radicals are included: --O, OH (either acid, alcohol or phenol), NH

Am, .1 1 and excluding the carboxyl group of the substituted derivatives.

Although considerable variation in ratio of component (A) and component (B) may be indulged, it has been found that the optimum performance characteristics of these copolymer improving agents, which may be represented as A B are obtained when the ratio of component (A) to component (B) lies within the range of from s 0.5 to 10, and preferably from 1 to 7, or where m equals 0.5 to m, and preferably 1 to 7n. In order to attain the optimum ratios of (A) to (B) in the final copolymer composition, it may be necessary or desirable to employ :a mixture of monomers for either or both components (A) and (B). For example, it is recognized that certain monomers falling within the scope of the definition of component (A), such as the allyl esters, allyl ethers, vinyl esters, vinyl ethers, and alkenes, are difficult to copolymerize with a component (B) monomer to a greater than l/l ratio. However, in the event a ratio, (A) to (B), greater than 1 is desired, this may be accomplished by employing a mixture of monomers using as the additional monomer (A'), for example, the acrylate esters, methacrylate esters, and/ or diesters of maleic, fumaric, citraconic, etc., acids, to result in a copolymer composition A A 'B where m-l-m' equals 0.5 to 10.

The copolymerization of the monomers of component (A) and component (B) may be conducted in accordance with the conventional bulk, solution or emulsion methods of polymerization, with or without the presence of a polymerization catalyst or initiator, and the choice of the particular method of preparation will depend largely upon practical considerations and the particular types of monomers to be copolymerized. However, the reaction is preferably effected in the presence of an inert organic solvent, such as benzene, toluene, xylene, or petroleum naphtha, to facilitate control of the reaction and handling of the resulting copolymer. Various conventional types of'free radical-liberating initiators or polymerization catalysts may be employed; as, for example, the organic peroxides such as benzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide, or di'benzoyl peroxide; or an azonitrile such as 1,1'-azodicyclohexane-carbonitrile or a, x-azodiisobutyronitrile. In addition, other means for initiating the copolymerization reaction may be employed, such as the use of ultraviolet or gamma radiation, as may be obtained from irradiation with a cobalt 60 source. The organic catalyst or initiator may be employed in amounts of 0.1 to 10% by weight, and preferably in the range of 0.25 to 2%, which amounts may be incorporated in increments as the reaction proceeds. The temperature of copolymerization will vary, depending upon the selected monomeric reactants and solvent employed, and may vary from about 75 to 150 C. The .copolymers formed may have a wide range of apparent g molecular weight, and usually of the order of' at least several thousands.

The majority of the desired copolymer compositions to be employed as improving agents are substantially miscible in hydrocarbon oils, and may be compounded into additive concentrates of at least 10% by weight, and preferably up to 70% by weight. In the preparation of additive concentrates, the concentration of copolymer in the hydrocarbon vehicle, such as toluene, mixed xylenes, kerosene, or other petroleum fractions, may be limited by the tendency toward gel formation, and in such instances it has been found desirable to incorporate a modifying agent or polar solvent, such as dimethyl formamide, tetrahydrofuran, Z-methyltetrahydrofuran, dioxane, cresylic acids, propylene carbonate, etc., which function as solubilizing agents and cosolvents in the copolymer concentrate. These modifying agents or cosolvents are generally employed in concentrations rang ing from 1 to 25% of the concentrate. In addition to the copolymer improving agent of this invention, other conventional fuel additives which are compatible with the copolymer improving agent may be incorporated into the concentrate for the purpose of facilitating the handling and blending problems involved in the production of the finished hydrocarbon fuel.

As an illustration of the preparation of representative copolymers of the invention, together with their derivatives, the following examples are presented. It is to be understood, however, that these examples are presented solely for illustration and are not to be construed as limitations of the invention compositions.

EXAMPLE 1 In this preparation of a copolymer of dodecyl (lauryl) methacrylate and methacrylic acid, the starting material employed was a homopolymer of lauryl methacrylate (Acryloid 710). A solution of 14 grams of potassium hydroxide in 300 milliliters of Z-ethylhexanol was prepared, and to this solution was added 800 milliliters of a 40% solution in mineral oil of the methacrylate homopolymer. The amount ofpotassium hydroxide employed constitutes a slight excess over that theoretically required to eifect the desired saponification of approxi mately 15% of the ester groups present in the polymer.

The resulting solution was heated to 320 F. and maintained at this temperature with stirring for 10 hours. To this solution was then added 50 milliliters of benzene along with a 50% excess of 6 N-hydrochloric acid, theoretically required to liberate the free carboxyl groups from the corresponding salt. 'The acidified solution was then refluxed for over 8 hours, after which it was cooled, diluted with ethyl ether and Water washed (along with a small amount of ethyl alcohol to break the emulsion) until neutral to litmus. The solution was then placed in a steam bath to remove the ether, and thereafter distilled in vacuo until a pot temperature of 350 F. at 3 millimeters mercury was reached in order to remove the Z-ethylhexanol and the dodecyl alcohol present. The resulting copolymer of dodecyl (lauryl) methacrylate and methacrylic acid contained the approximate ratio, A /B Variations in the ratio of lauryl methacrylate to methacrylic acid or, in other words, component (A) to component (B), were obtained in accordance with the foregoing procedure by modifications in the degree of saponification and hydrolysis.

EXAMPLE 2 The copolymer of dodecyl methacrylate and methacrylic acid, A7/B1, prepared in accordance with Example. 1, was dissolved in 300 milliliters of a mixed toluene-xylene solvent, along with 0.15% (based on the weight of the polymer) of toluene sulfonic acid and an amount of n-octylamine, theoretically required to amidize 50% of the free carboxyl groups in the copolymer. The resulting solution was then refluxed for 8 hours 7 while distilling off as an azeotrope the water formed during the amidization reaction.

The modified copolymer composition was then precipitated by the addition of an excess of an acetonemethanol mixture, following which the composition was acetone washed and stripped in vacuo to remove lowboiling constituents. The resulting oil-soluble copolymer composition so obtained was found to contain approximately 50% of the carboxyl groups in the methacrylic acid, component (B), in the form of their noctylamide derivative.

Similar preparations were conducted, employing the same basic copolymer and reacted to form the amides and amine salts using various types of amines, such as monoethanolamine, dihydroxyethyl ethylenediamine, etc., in varying degrees of derivative formation and stages of dehydration.

EXAMPLE 3 Into a 1-liter condensation flask, equipped with agitating means, heat control and automatic water separator, was charged 350 grams of dodecyl methacrylate-methacrylic acid copolymer (A /B 178 grams of a dodecyl ether of a polyoxyethylene glycol containing an average of 10 ethylene oxide units, 1 gram of p-toluene sulfonic acid, and 100 milliliters of refined kerosene. The reaction mixture was continuously agitated for about 36 hours while maintaining a temperature of 400 F. and automatically separating the water of reaction. To a mixture of 570 grams of the resulting reaction product and 50 milliliters of benzene undergoing Vigorous agitation was added 500 milliliters of methanol and 2000 milliliters of acetone for the purpose of extracting the excess alcohol and precipitating the copolymer composition. This total mixture was then stirred for 5 minutes and allowed to settle for 30 minutes. The methanolacetone extract was decanted. The precipitation procedure was repeated five additional times. The precipitated copolymer composition was then dissolved in a 140 neutral lubricating oil from a California waxy crude to yield a 45.25% concentrate. Electrometric titration (sodium methylate procedure) indicated that the carboxyl groups of component (B) were esterified to the extent of 25.8%.

Further preparations were repeated in accordance with the foregoing procedure employing copolymer backbones of varying composition and ratio to esterify the carboxyl groups of component (B) with representative types of alcohols and in varying degrees of esterification.

EXAMPLE 4 This example illustrates the copolymerization of the monomeric components, dodecyl methacrylate and meth acrylic acid. Into a 1-liter condensation flask, equipped with agitation, heat control, etc., was charged 300 grams of dodecyl methacrylate, 100 grams of toluene, 50 grams of benzene, and 17.55 grams of glacial methacrylic acid. This mixture was stirred and heated to 226-230 F. A catalyst solution containing 6.43 grams of benzoyl peroxide dissolved in 100 grams of toluene was slowly added. After all the catalyst was added, the total reaction mixture was stirred at 220230 F. for 8 hours.

At the conclusion of the polymerization reaction, 100 grams of the reaction mixture was dissolved in 70 grams of benzene, and vigorously agitated. While stirring vigorously, 316 grams of acetone and 78 grams of methanol were added to precipitate the dodecyl methacrylate-methacrylic acid copolymer. The precipitated copolymer was recovered and dissolved in a solvent-refined lubricating oil of an SAE 30 grade to result in a 39.4% concentrate. Electrometric titration indicated a ratio of dodecyl methacrylate to methacrylic acid of 5.5/1, or, in other words, 5.5 1-

To ascertain the merits of the subject improving agents, and particularly their merits in regard to deposit reduction in unstable, high-boiling fuels, such as those as con tain appreciable concentrations of cracked gas oils, a test procedure was established which has been determined to correlate with actual service conditions' This test involves the determination of the filter residue, or, in other words, the amount of insoluble solids of less than 100- mesh particle size present in distillate fuels as received and the amount of insoluble solids which form in distillate fuels during aging at elevated temperature. The aging conditions are for 4 weeks at 140 F.

In determining the filter residue of fuels as received, the sample is screenedthrough a 100-mesh sieve, and 500 milliliters are filtered through a tared Gooch crucible without adding diluent. The crucible is washed with 500 milliliters of petroleum ether, dried in an oven at 190 F., cooled in a constant-humidity vessel, and weighed. The filter residue is calculated as parts per million.

In determining the filter residue of the fuel on aging, an additional 500 milliliter sample of the fuel is filtered through filter paperinto an unstoppered l-quart bottle and stored at 140 F. for 4 weeks. At the end of this time, the sample is filtered through a tared Gooch crucible. The material adhering to the container is dissolved in 25 milliliters of an /20 benzene-alcohol solution. The gums are precipitated by the addition of 500 milliliters of petroleum ether, and the mixture is also filtered through the Gooch crucible. The crucible is then washed, dried, and weighed as previous.

The following filter residue test results were obtained with a number of copolymer improving agents of the invention, illustrating the effect of variations in mole ratio of the (A) and (B) components and modification of the copolymer base by esterification and amination reaction with the carboxyl groups of component (B) to form partial derivatives thereof. In these tests, the base fuel employed was a 50/50 blend of a raw Thermofor catalytically cracked gas oil and a straight-run gas oil, blended to meet the US. Commercial Standards specifications of a No. 2 fuel oil, and the copolymer improving agents were incorporated in each instance in a concentration of parts per million. The data are reported in terms of the percent improvement or percent reduction in filter residue over the uncompounded base fuel. For the sake of convenience, the base monomers of the copolymer compositions will be identified as A-lauryl methacrylate, B-methacrylic acid, and B'acrylic acid; and the subscript following the respective monomer indicates the approximate mole ratio of the monomer in the copolymer backbone. Following the designation of the modifying agent in the case where the copolymer backbone is esterified or aminated, the percentage figure in parentheses will indicate the degree of esterification or amination.

Table I [Filter residue after storage 4 weeks at F.]

Reduction in Deposit Formation, Percent Additive Polyethylene glycol of indicated molecular weight.

Further test data were obtained to illustrate the effectiveness of the copolymer compositions in aircraft gas turbine engine fuels. As previously indicated, certain recent models of aircraft gas turbine engines utilize the fuel as a coolant for the engine lubricating oil, and as a result have developed a problem of deposit formation on the fuel side of the heat exchanger. In this type of service, the fuel is subjected to temperatures in the range of 300 to 500 F., and to a greater or lesser extent gradually results in the fouling of the heat exchanger and fuel system lines with a coke-like deposit.

A test procedure was developed to correlate the effect of addition agents upon the stability of the engine fuel at elevated temperatures maintained over varying periods of time. In this test, open Erlenmeyer flasks containing 100 milliliters of test fuel are partially submerged in a heated oil bath. The temperature of the bath and time in the bath are varied to obtain the desired severity. After the samples are removed and cooled, they are filtered through No. 2 Watman paper disks. The disks are then rinsed with mixed hexanes, and the deposits rated visually. A rating scale is used which assigns a zero to a perectly clean filter disk and 9 to a heavily deposited dis In the subject tests, the base fuel employed was a JP-3 fuel meeting military specifications MTL-F-5624B. With the compounded fuels, the temperature was maintained at 400 F. for 6 hours. As indicated in the following table, one test fuel was continued with hourly examinations to 10 hours. As previously, the base monomers of the copolymer compositions are identified as A-laury1 methacrylate, B-methacrylic acid. The following test results were obtained; and the subscripts following the respective monomers indicate the approxiigaate mole ratio of the monomer in the copolymer backone.

Polyethylene glycol of indicated molecular weight.

Base fuel gave a rating of 9 at 350 F. for 2 hours.

Obviously, many modifications and variations of the invention as hereinbcfore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. An improved fuel composition comprising a major portion of a hydrocarbon fuel and a minor portion, sufficient to reduce the deposit-forming characteristics of said fuel, of a relatively high molecular weight copolymer obtained by the copolymerization of (A) monomers selected from the group consisting of aliphatic esters of methacrylic acid and acrylic acid containing 8 to 30 carbon atoms and (B) monomers selected from the group consisting of methacrylic acid and acrylic acid in which the ratio of (A) to (B) is within the range of 0.5 to

10, and in which from about to 60% of the carboxyl,

groups of (B) are present in the form of monoesters of polyalkylene glycols selected from the group consisting of polyethylene glycol having a molecular weight up to about 800 and monoalkyl ethers of said polyethylene glycol.

2. An improved hydrocarbon fuel composition comprising a major portion of a hydrocarbon fuel predominantly boiling above 300 F. and a minor portion, sufficient to reduce the deposit-forming characteristics of said fuel, of a relatively high molecular weight copolymer produced through copolymerization of (A) dodecyl methacrylate, and (B) methacrylic acid to produce a copolymer composition in which the components (A) and (B) are present in the ratio of (A) to (B) within the range of 0.5 to 10, and in which from about 5 to 60% of the carboxyl groups of component (B) are present in the form of monoestersof polyethylene glycol having a molecular weight of about 400.

3. An improved hydrocarbon fuel composition comprising a major portion of a hydrocarbon fuel predominantly boiling above 300 F. and a minor portion, sufficient to reduce the deposit-forming characteristics of said fuel, of a relatively high molecular weight copolymer produced through copolymerization of (A) dodecyl methacrylate, and (B) methacrylic acid to produce a copolymer composition in which the components (A) and (B) are present in the ratio of (A) to (B) within the range of 0.5 to 10, and in which from about 5 to 60% of the carboxyl groups of component (B) are present in the form of monoesters of the dodecyl ether of polyethylene glycol having a molecular weight of about 704.

4. An improved hydrocarbon fuel composition comprising a major portion of a hydrocarbon fuel predominantly boiling above 300 F. and a minor portion, sufficient to reduce the deposit-forming characteristics of said fuel, of a relatively high molecular weight copolymer produced through copolymerization of (A) dodecyl methacrylate, and (B) methacrylic acid to producea copolymer composition in which the components (A) and (B) are present in the ratio of (A) to (B) within the range of 0.5 to 10, and in which from about 5 to 60% of the carboxyl groups of component (B) are present in the form of a monoester of octadecyl ether of a polyethylene glycol having a molecular weight of about 400.

5. A concentrate adapted to be incorporated in by drocarbon fuels in concentration elfective to reduce the deposit-forming characteristics of said fuels consisting essentially of a hydrocarbon vehicle containing from 10 to by weight of a relatively high molecular weight copolymer obtained by copolymerization of (A) monomers selected from the group consisting of aliphatic esters of methacrylic acid and acrylic acid containing 8 to 30 carbon atoms, and (B) monomers selected from the group consisting of methacrylic acid and acrylic acid in which the ratio of (A) to (B) is within the range of 0.5 to 10, and in which from about 5 to 60% of the carboxyl groups of (B) are present in the form of monoesters of polyalkylene glycols selected from the group consisting of polyethylene glycol having a molecular weight up to about 800, and monoalkyl ethers of said polyethylene glycol.

References Cited in the file of this patent UNITED STATES PATENTS 2,366,517 Gleason Jan. 2, 1945 2,370,943 Dietrich Mar. 2, 1945 2,469,737 McNab et a1. May 10, 1949 2,584,968 Catlin Feb. 12, 1952 2,615,845 Lippincott et a1. Oct. 28, 1952 2,666,044 Catlin Jan. 12, 1954 2,728,751 Catlin et a1. Dec. 27, 1955 FOREIGN PATENTS 719,648 Great Britain Dec. 8, 1954

Claims (1)

1. AN IMPROVED FUEL COMPOSITION COMPRISING A MAJOR PORTION OF A HYDROCARBON FUEL AND A MINOR PORTION, SURFFICIENT TO REDUCE THE DEPOSIT-FORMING CHARACTERTISTICS OF SAID FUEL, OF A RELATIVELY HIGH MOLECULAR WEIGHT COPOLYMER OBTAINED BY THE COPOLYMERIZATION OF (A) MONOMERS SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC ESTERS OF METHACRYLIC ACID AND ACRYLIC ACID CONTAINING 8 TO 30 CARBON ATOMS AND (B) MONOMERS SELECTED FROM THE GROUP CONSISTING OF METHACRYLIC ACID AND ACRYLIC ACID IN WHICH THE RATIO OF (A) TO (B) IN WITHIN THE RANGE OF 0.5 TO 10, AND IN WHICH ABOUT ABOUT 5 TO 60% OF THE CARBOXYL GROUPS OF (B) ARE PRESENTED IN THE FORM OF MONOCESTERS OF POLYALKYLENE GLYCOLS SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT UP TO ABOUT 800 AND MONOALKYL ETHERS OF SAID POLYETHYLENE GLYCOL.