US 2978302 A
Description (OCR text may contain errors)
r 2,973,302 Patented Apta, 19 61 STABHJZED nisriLLArE FUELS Joel R. Siege], Irviugton, and John V. Clarke, Jr., Cranford, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware N Drawing. Filed Feb. 28, 1958, Ser. No. 718,120
17 Claims. (Cl. 44-62) The present invention relates to improvements in the stability ofhydrocarbon oil products and more particularly relates to improved petroleum distillate fuels boiling in the range between about 300 F. and about 900 F. which have been stabilized against deterioration during storage by the incorporation therein-of small amounts of certain alkyl and acyl derivatives of hydrazine.
Petroleum distillate fuels boiling in the range between about 300 F. and about 900 P. such as heating oils, diesel engine fuels and fuels for turbo-jet aircraft engines, particularly distillate fuels derived in part from thermal or catalytically cracked petroleum fractions, generally contain unsaturated hydrocarbons and other relatively unstable compounds. During the storage of such fuels these unstable constituents often undergo oxidation, polymerization or other reactions and form sludge and sediment which, upon subsequent introduction of the fuels into engines and burner systems, may lead to the plugging and fouling of fuel lines, filters and orifices.
These difficulties attributable to the presence of unstable constituents in petroleum distillate fuels are partic- ,'ularly pronounced in the case of fuels used in turbojet aircraft engines. Because of the high temperatures at which turbo-jet engines operate, it is necessary to continuously cool the lubricating oil used in order to prevent its thermal degradation. conventionally this is accomplished by providing such engines with heat exchangers through which the fuel and the lubricating oil are circulated. The fuel is thus employed as a cooling medium for the oil and may be subjected to temperatures as high as 400 F. for extended periods of time before it'is actually burned. This prolonged exposure to high temperaturesaccelerates reaction of the unstable constitutents in the fuel and leads'to a buildup of varnish and deposits upon the heat exchanger surfaces and the formation of increased quantities of sludge and sediment. Decreased cooling of the lubricating oil, reduced fuel flow and engine power, and in extreme cases flameouts may thus occur as a direct result of turbo-jet fuel instability. The serious consequences which may ensue are obvious.
Because of the growing demand for turbo-jet fuels and similar fuels products and the necessity for using increasing quantities of crackedpetroleum fractions in order to supply that demand, there has been a great deal of activity in the development and use of additives for stabilizing purposes. The additives most widely used to date have metallic compounds such as calcium andv barium sulfonates and naphthenates. Such additives are reasonably effective in reducing sludge and sediment formation to acceptable levels under ordinary storage conditions but they are not satisfactory for use under very severe conditions such as those encountered in turbo-jet engines and do not overcome the problem of heat exchanger tube deposits in such engines. Moreover, such additives are undersirable because they leave a residue when burned and hence cause a buildup of car- 1 bonaceous deposits in engine combustion chambers and upon burner nozzles. Such deposits are very undesirable in jet engines because they disrupt the desired fuel spray pattern in the combustors, cause warping of the liners and thus reduce the thrust'which can be generated. Similarly adverse effects; are experienced indieselengines and in heating systems. particularly certain polymeric dispersant compositions, have been suggested for use asstabilizing additives but it has been found that these are not wholly effective and that they do not lend suflicient stability to petroleum distillate fuels for use in turbo-jet aircraft engines to overcome the problem of varnish and deposit formation.
The present invention provides a new and improved class of additives which may be incorporated into petroleum distillate fuels boiling in the range between 300 and about 900 F. in order to improve the stability of such fuels. It has now been discovered that the addition of small amounts of certain alkyl or acyl derivatives of hydrazine to suchfuels either alone or in combination with certain polymeric dispersant compositions permits their storage for extended periods of time at high temperatures or under otheradverse conditions without the formation of appreciable quantities of sludge, sediment and varnish such as are otherwise encountered. It has been found that combinations of the hydrazine derivatives and polymeric stabilizing additives exhibit a synergistic effect and at a given concentration produce a more stable fuel than can be obtained by using either the hydrazine derivatives or the dispersant polymers alone; The invention thus providesa new and improved class of stabilizing additives for use in petroleum distillate fuels'boiling be tween about 300 and about 900 F. which are surprisingly more effective than additive materials which have been employed heretofore.
The hydrazine derivatives which are employed as stabilizing additives for petroleum distillate fuels in accordance with the present invention are compounds having the general formula 6 carbon atoms and the mono-substituted hydrazides derived from straight chain fatty acids having from about '8 to about 18 carbon atoms per molecule are particularly preferred.
Specific examples of hydrazine derivatives coming within the abovedefinitions and suitable for use as distillate fuel stabilizing additives in accordance with the present invention include methyl hydrazine, ethyl hydrazine, propyl hydrazine, butyl hydrazine, hexyl hydrazine, decyl hydrazine, octadecyl hydrazine, N,N-dirnethyl hydrazine, N-ethyl-N-butyl hydrazine, acetic hydrazide, decanoic hydrazide, octadecanoic hydrazide, and butyric hydrazide.
The hydrazine derivatives represented by the above formula may be prepared in a number of different ways by reactions familiar to those skilled in the art of nitrogen chemistry. The monalkyl hydrazines such as methyl Various ashless compounds,
and ethyl hydrazine may be prepared, for example, by means of the Hofmann reaction wherein an N-alkyl urea is treated with sodium hypochlorite. Dimethyl hydrazine and other N,N-dialkyl compounds can be prepared by reducing the corresponding nitrosamines with zinc and acetic acid or a similar reducing agent. The hydrazides can be prepared by a number of the methods used for preparing amides by merely substituting hydrazine in place of the ammoniaused to form the amides. The action of hydrazine on acid chlorides, esters and anhydrides, for example, yields the corresponding liydrazides. The above are all well known reactions and need not be discussed in detail for purposes of this invention. Descriptions of these and other methods for preparing hydrazine derivatives may be readily found in the chemical and patent literature.
A number of polymeric dispersant additives suitable for stabilizing petroleum distillate fuels are available commercially or known to those skilled in the fuels art and may be employed in conjunction with the hydrazine derivatives in accordance with the present invention.
A preferred class of such polymeric stabilizing additives for use with the hydrazine derivatives are those prepared by the copolymerization of an alkyl chloropropyleneoxy mixed ester of an unsaturated conjugated dibasic acid with a polymerizable organic monomer containing a vinylidene linkage. The alkyl chloropropyleneoxy mixed esters used as one of the components of such copolymers are prepared by first reacting a C to C unsaturated conjugated dibasic acid such as maleic acid, fumaric acid, citraconic acid, mesaconic acid or a mixture of such acids or their anhydrides, when they exist, with a long chain saturated aliphatic alcohol to produce a half ester. Suitable alcohols for this purpose are those containing from about 8 to about 24 carbon atoms per molecule, preferably about 8 to 18 carbon atoms per molecule. Straight chain primary alcohols such as dodecyl, cetyl, eicosyl and docosyl alcohols are preferred but branched chain alcohols such as 2-ethylhexanol-1 and C oxo-alcohols, secondary alcohols such as capryl alcohol and mixtures of straight and branched-chain alcohols may also be used. Commercially marketed mixtures of alcohols of the requisite chain length, such as those obtained by the hydrogenation of coconut oil, may also be used.
The half ester produced in the above manner is then reacted with epichlorohydrin in the presence of either an acidic or a basic catalyst such as boron fluoride or sodium hydroxide to produce the mixed ester. The ratio of the half ester to epichlorohydrin in the reaction mixture may range from about 1:1 to 1: 4. Addition of the epichlorohydrin takes place through the epoxy group and the chlorine atom is unaffected. Themixed ester may thus contain from 1 to about 3 chlorine atoms.
The mixed ester prepared as described above is then copolymerized with from about /2 to about 20 parts of an unsaturated organic monomer containing a vinylidene group in the presence of gamma radiation, a peroxide type catalyst such as benzoyl peroxide, or an azo catalyst such as alpha-alpha azo-bisisobutyronitrile. Suitable monomers containing vinylidene groups include hydrocarbons such as styrene, isobutylene and butadiene; esters such as vinyl propionate and methyl methacrylate; ethers such as divinyl ether; and nitriles such as acrylonitrile and vinyl-acetronitrile. Mixtures of such monomers containing vinylidene groups with other copolymerizable materials, long chain alcohol esters of unsaturated conjugated dibasic acids such as lauryl maleate and tallow fumarate for example, may also be used. Vinyl esters of short chain fatty acids, particularly vinyl acetate and mixtures of such esters with fumarate or maleate esters of long chain aliphatic alcohols containing from about 8 to about 20 carbon atoms'per molecule are preferred monomers for preparation of the copolymers withthe mixed esters.
The resulting copolymers are oil-soluble and preferably have molecular weights between about 6000 and about 20,000 Staudinger. Such copolymers are described in copending application S.N. 673,156, filed July 22, 1957.
A second class of dispersant polymeric additives which are preferred for use with the hydrazine derivatives in accordance with the invention are the oil-soluble, nitrogen-containing addition type copolymers prepared by copolymerizing an amine-free monomer containing one polymerizable ethylenic linkage and an aliphatic hydrocarbon chain of from 8 to 18 carbon atoms with a monomer containing a nitrogen atom and one polymerizable ethylenic linkage. Such copolymers may be prepared, for example, by the copolymerization of an acrylic or alpha-substituted acrylic esterof an aliphatic alcohol containing an average of from 8 to 18 carbon atoms, such as lauryl methacrylate, with an ethylenically unsaturated compound containing a basic amino group, such as beta dimethylamino-ethyl methacrylate. Other specific examples of the amine-free monomers containing a polymerizable ethylenic linkage and a C -C aliphatic chain include the tridecyl, cetyl and octadecyl esters of acrylic and methacrylic acids. Also suitable are esters of these acids prepared from mixtures of alcohols such as those containing primary alcohols of from 10 to 18 carbon atoms derived by the hydrogenation of coconut oil and sold under the trade name Lorol. A typical mixture consists chiefly of lauryl alcohol having 12 carbon atoms per molecule and has the following approximate com- The polymerizable ethylenically unsaturated compounds containing a nitrogen-containing group which are used in forming the second class of preferred copolymers suitable for use in accordance with the invention include the basic tertiary amino-alkyl acrylates, such as the dialkyl amino-alkyl acrylates and alpha hydrocarbon-substituted acrylates, beta dimethylaminoethyl acrylate and methacrylate, and their homologs and analogs. The nitrogen may be a member of a heterocycle where the polymerizable ethylenic unsaturation is extranuclearly bonded to the heterocycle, such as the vinyl pyridines, vinyl pyrrolidone.
Limited amounts of other copolymerizable monomers in addition to those described above may be incorporated into the copolymers of the second preferred class as filler materials. Such filler materials include vinyl and allyl formates, acetates, propionates; isobutylene; styrene; methyl methacrylate; ethyl vinyl ether and the like. The final copolymer may contain from about 20% to about 99% of the nitrogen-free monomer, from about 0.5% to 50% of the nitrogen-containing monomer, and from about 0 to about 79% of the monomer used as a filler material. Many of the polymeric additives falling within the second preferred class described above are described in detail in US. Patent No. 2,737,452, issued March 6, 1956.
The copolymers described above and the hydrazine derivatives may each be employed in petroleum distillate fuels in concentrations ranging between about 0.001% and about 2% by weight. The ratio of the copolymer to the hydrazine derivative will preferably range between about 1 :5 to 1 :0.5. A ratio of 1 to 1 is particularly preferred.
The petroleum distillate fuels in which the additive materials are employed in accordance with the invention consist of a major proportion, at least of liquid both military and commercial aircraft.
such as JP-4, ]P5 and JP-6; diesel fuels for use in stationary, marine and automotive type diesel engines;
and heating oils suitable for use in both domestic and industrial heating systems. Aviation turbo-jet engine defined by US. Military Specifications MILF5624C, MIL-'-F25524A and MILF25558A and are used in Diesel fuels as contemplated herein are defined by ASTM Specification D-975-53T and fall into Grades 1D, 2D and 4D, in all of which the additive materials of the invention may be Y used. Typical of the heating oils in which the additives may be employed are those covered by ASTM Specification D396-48T and falling within Grades 1 and 2 thereof.
The additive materials of the invention are effective when incorporated into fuels such as those described above in concentrations ranging from about 0.001% to about 2% by weight. Concentrations between about 0.005% and about 1% by weight are usually sufficient for stabilizing most petroleum distillate fuels and are therefore preferred. The additives may in most cases be incorporated directly into the fuels but in some cases it may be preferred to first dissolve them in a suitable solvent such as hexane, benzene, toluene or xylene and then add the solution to the fuels in quantities sufficient to give the desired additive concentration. The additives may be employed in conjunctionwith other additive agents commonly used in distillate fuels boiling between about 300 F. and about 900 F., includingrust inhibitors, anti-emulsifying agents, anti-static additives, dyes, dye stabilizers and the like. If desired a concentrate of these additives and the additives of the invention may be prepared and then added to the fuels.
The invention may be further illustrated by the following examples. a
Example 1 Stearic hydrazide prepared by heating together equal molar quantities of aqueous hydrazine hydrate and the methyl ester of'stearic acid was added in a concentration of 0.0075% to a heating oil consisting of about 50 per- -cent of virgindistillate and about 50 percent of catalytically cracked stock. Typical pro'perties of such a heating oil are as follows: i
Distillation, API? Samples of this heating oil containing the stearic hydrazide and samples of the same base heating oila without stearic hydrazide were then subjected to an Accelerated Storage Stability Test in order to determine their relative stabilities. The test comprised heating the samples for a period of 16 hours at a temperature of 210 F. in order to accelerate the formation of sediment due to the presence of unstable constituentsand then filtering each sample through asintered glass filter. The sediment collected from each sample was weighed fuels as referred to in connection with the invention are and the light transmission of each sample was determined. The following results were obtained.
Sample g-K oil Base Heating Oil Base Heating Oilj0.0075% Stearic Hydrazide.
the amount of suspended material and soluble color I bodies present in the oil, was similarly improved by the addition of the stearic hydrazide.
Example 2 was a copolymer of 20 parts of vinyl acetate, 40 parts of a C -C alkyl maleofumarate (mixture of C -C alkyl esters of maleic and fumaric acid), 10 parts of an isooctyl ethyleneoxy maleate and 30 parts of di C oxo maleofumarate.
The polymeric additive was diluted with an equal quantity of a petroleum distillate having an API gravity of 56. A total additive concentration of 0.000625 weight percent was .used'in 'each instance.
-These Samples were then subjected to the Accelerated Storage Stability Test as described in the' preceding I example. The results obtained were as follows:
Base Oil|-,0.0003125% Polymeric Add tive+ 0.0003l25% Stearic Hydrazide The above-test was carried out at additive concentrations well below the range in which the additives are preferably used in petroleum distillate fuels. At the very low concentration of 0.000625% the stearic hydrazide actually caused an increase in sediment. Despite the extremely low concentration, however, when the stearic hydrazide and the polymeric additive were used in combination a synergistic effect occurred. The sedi-, rnent formed when the combination of additives was used was less than that formed when the individual additives were employed at the same total concentration. The addition of the hydrazide to the polymeric additive produced little change in the light transmission, although the hydrazide alone substantially improved the transmission of light through the oil.
Example 3 Samples of a turbo-jet aircraft engine fuel were subjected to a fuel stability test in order to determine the aerasoa Heat content, B.t.u./lb 18551 To samples of this fuel were added the following dispersant polymer additives:
Additive A.-A copolymer consisting of one part of vinyl acetate, 0.25 part of isooctyl chloropropyleneoxy maleate and 0.75 part of mixed C C alkyl fumarate.
Additive B.-A nitrogen-containing copolymer used commercially as a stabilizer for distillate fuels consisting of 8 parts of Lorol methacrylate and 2 parts of beta diethylaminoethyl methacrylate.
Additive C.--A copolymer used commercially as a stabilizer for distillate fuels consisting of a methacrylate copolymer containing nitrogen in a neutral, i.e. non-basic form.
The fuel stability tests were carried out in apparatus closely resembling a scaled-down turbo-jet fuel system, the CFR Fuel Coker. The fuel samples, containing each of the above polymeric additives, were pumped from a supply tank through a screen and rotameter to an annular aluminum he at exchanger where they were heated to a temperature of 400 F. They were then passed through a sintered metal filter held at a temperature of 500 F. Fuel performance was measured by the time required for the pressure drop across the filter to increase by 25 inches of mercury or by the pressure increase which occurred in 300 minutes, depending upon which took place first. Upon the basis of the pressure drop and the length of the run, a merit rating was assigned to each fuel sample. A merit rating of 500 in this standardized test is equivalent to a pressure drop of 12 inches of mercury across the filter in 300 minutes and has been established by actual service tests as an acceptable stability level for turbo-jet fuels for aircraft.
The percentage of the heat exchanger tubes covered byvarnish deposits and the color of the deposits at the conclusion of each test were also noted, since this serves as an indication of the extent to which similar deposits will be formed in an actual turbo-jet engine.
Following tests of the fuels containing the polymeric additives as described above, N,N-dimethyl hydrazine and the same polymeric additives were added to samples of the same fuel and the tests were repeated. The results obtained in these tests were as follows:
Merit Preheater Fuel Rating 1 Tube Deposits 2 Base Fuel 100 50/8 Base Fuel+0.005% of Additive A 710 75/5 Base Fuel+0.01% of Additive A 740 35/7 Base Fuel+0.0l% N,N-Dimethyl Hydrazine 370 30/8 Base Fuel+0.005% of Additive A+0.005%
N,N-Dirnethyl Hydrazine 765 15/5 Base Fuel+0.0025% of Additive B 770 60/7 Base Fuel+0.0l% of Additive B+0.01%
N, N-Dimethyl Hydrazine 890 /2 Base Fuel+0.0l% of Additive C 255 3 60/8 Base Fuel-+0.01% of Additive C+0.01%
N,N-Dimethyl Hydrazlne 320 4 /2 I The data obtained in these tests clearly show the effect of the hydrazine derivatives upon the stability of petroleum distillate fuels containing polymeric type stabilizing additives. In every case, even where a poor polymeric ASTM distillation! Initial boiling point, F 338 10% point, F 37 6 50% point, F 450 90% point, F 510 Final boiling point, F 540 Smoke point, mm 22 Olefins, vol. percent 1.7 Aromatics, vol. percent 11.3 Sulfur, wt. percent 0.073 Flash point, F 130 groups are selected from the additive, Additive C, was employed, the addition of the hydrazine derivative brought about an appreciable increase in merit rating and a surprising decrease in tube deposits. The advantages of using such hydrazine derivatives in combination with polymericstabilizing additives in turbo-jet aircraft engine fuels are thus apparent.
What is claimed is:
l. A petroleum distillate fuel boiling ,in the range between about 300 F. and about 600 F. containing from about 0.001% to about 2% by weight of an oil-soluble polymeric dispersant selected from the group consisting of (a) a 6000 to 20,000 molecular weight copolymer of a C to C alkyl aliphatic oxy mixed ester of an unsaturated conjugated C to C dibasic acid and avinyl ester of a short chain fatty acid wherein said aliphatic class consisting of a C to C alkylene and a C to C halogenated alkylene, and (b) a copolymer of from 20 to 99% by weight of a C to C aliphatic alcohol ester of an acid selected from the group consisting of acrylic acid and'an alpha substituted acrylic acid in which the alpha substituent is a lower alkyl group, from 0.5 to 50% by weight of a basic tertiary amino alkyl acrylate, and from 0 to 79% by weight of a copolymerizable olefinically unsaturated organic monomer and from about 0.001% toabout 2% by weight of a hydrazine derivative having the formula at least one carbon atom attached directly to the primary,
2. A fuel as specified in claim 1 wherein said dispersant and said hydrazine derivative are present in a ratio of from 1 5 to 1 0.5 parts by weight.
3. A fuel as specified in claim 1 wherein said dispersant and said hydrazine derivative are each present in a concentration of from about 0.005 to about 1% by Weight.
4. A fuel as specified in claim 1 wherein said dispersant is a copolymer of one part of, isooctyl chloropropyleneoxy maleate and from /1 to 20 parts of a mixture of vinyl acetate and C -C alkyl fumarate, said copolymer having a molecular weight of from about 6000 to about 20,000.
5. A fuel as specified in claim 1 wherein said dispersant is a copolymer of mixed C to C alkyl methacrylate and beta-diethylaminoethyl methacrylate, said copolymer being made up of from 0.5 to 50 percent of betadiethylarninoethyl methacrylate.
6. A petroleum distillate fuel boiling in the aviation turbo-jet fuel, diesel fuel and heating oil boiling range having incorporated therein from about 0.001% to about 2% by weight of an unsymmetrical dialkyl hydrazine having alkyl groups of from about 1 to 6 carbon atoms in length and from about 0.001% to about 2% by weight of a 6000 to 20,000 molecular weight copolymer of a C to C alkyl-chloropropyleneoxy ester of a C to C un- 9. A petroleum distillate fuel boiling in the aviation turbo-jet fuel, diesel fuel and heating oil boiling range having incorporated therein from about 0.001% to about 2% by weight of an unsymmetrical dialkyl hydrazine having alkyl groups of from about 1 to 6 carbon atoms in length and from about 0.001% to about 2% by weight of an oil-soluble coploymer of from 20 to 99% by weight of a C to C aliphatic alcohol ester of methacrylic acid, from 0.5 to 50% by weight of a basic tertiary amino alkyl methacrylate, and from to 79% by weight of a copolymerizable olefinically unsaturated organic monomer.
10. A fuel as specified in claim 9 wherein said copolymer is a copolymer of about 80% of mixed 0 to C alkyl methacrylates and about 20% of beta-diethylaminoethyl methacrylate.
11. A fuel as specified in claim 10 wherein said hydrazine is N,N-dimethyl hydrazine.
12. A fuel as specified in claim 1 wherein said hydrazine is N,N-dimethyl hydrazine.
13. A fuel as specified is claim 1 wherein said hydrazine is stearic hydrazine.
14. A fuel as specified in claim 1 wherein said dispersant is a copolymer of one part of isooctyl ethyleneoxy maleate and from /2 to 20 parts of a mixture of vinyl acetate and a C to C alkyl maleofumarate, said copolymer having a molecular weight of fi'om about 6000 to about 20,000.
15. A petroleum distillate fuel boiling in the aviation turbo-jet fuel, diesel fuel and heating oil boiling range having incorporated therein from about 0.001% to about 2% by weight of an unsymmetrical mono-substituted hydrazine having acyl groups derived from fatty acids of from about 8 to 18 carbon atoms in length and from about 0.001% to about 2% by weight of a 6000 to 20,000 molecular weight copolymer of a C to C alkyl ethyleneoxy ester of a C to C unsaturated conjugated dibasic acid with a vinyl ester of a short chain fatty acid, said ethyleneoxy ester comprising about to about /3 of the total monomers making up said copolymer.
16. A fuel as specified in claim 15 wherein said copolymer is -a coploymer of about 20 parts of vinyl actate, about parts of a C to C alkyl maleofumarate, about 10 parts of an isooctyl ethyleneoxy maleate, and about 30 parts of a di C oxo maleofumarate.
17. A fuel as specified in claim 15 where said hydrazide is stearic hydrazide.
References Cited in the file of this patent UNITED STATES PATENTS 1,906,044 Burk Apr. 25, 1933 2,027,394 McMullan Ian. 14, 1936 2,607,761 Seymour Aug. 19, 1952 2,615,845 Lippincott Oct. 28, 1952 2,729,690 Oldenburg Jan. 3, 1956 2,737,452 Catlin et al Mar. 6, 1956 2,808,416 Bell et a1 Oct. 1, 1957 OTHER REFERENCES The Chemistry of Hydrazine, by Audrieth and Ogg; John Wiley and Sons Inc., 1951, pages 225, 226, and 227.
Ind. and Eng. Chem., vol. 42, September 1950, Hydrazine in Organic Chemistry, by Byrkit and Michalek, pages 1862 to 1875.