US3407051A - Thermally stabilized, liquid hydrocarbon fuels - Google Patents

Description

United States Patent 7 2 Claims. (Cl. 44-63) ABSTRACT OF THE DISCLOSURE A composition including a major amount of a petroleum oil fraction of the gasoline-kerosene boiling range and a stabilizing amount of the imide-amide reaction product obtained by reacting ethylenediamine tctraacetic acid with an aliphatic primary amine having 4-24 carbon atoms per molecule.

This application is a division of the U.S. patent application of John W. Thompson et al., Ser. No. 65,954, filed Oct. 31, 1960, for imide-Amide Derivatives of Ethylenediamine Tetraacetic Acid, and abandoned after the filing of the instant application.

This invention relates to new compositions of matter useful as additives for petroleum oil fractions and especially adapted as thermal stabilizers for jet fuels and other liquid hydrocarbon fuels that are subject to degradation at elevated temperature. More, particularly the invention relates to imide and amide products obtained by reacting ethylenediamine tetraacetic acid with aliphatic primary amines at elevated temperature and to compositions comprising such imide and amide products in admixture with petroleum oil fractions.

A recent development in the operation of jet aircraft is the use of the liquid hydrocarbon jet fuel as a so-called heat sink or, in other words, as a coolant to aid in dissipating the large amount of heat developed in operation of the aircraft at supersonic speeds. For instance, the engine lubricating oil is cooled by indirect heat exchange with the liquid fuel as it passes from the fuel tanks to the engine. To be satisfactory for such coolant use, the jet fuel must be stable at temperatures of 400 F. or higher. At such high temperatures it should not form degradation products such as sludges which clog the fuel filters, flow lines, nozzles and heat exchangers.

The current jet aircraft fuels are petroleum oil fractions, some types of which are fractions generally of the kerosene boiling range and others of which are wide-range mixtures of kerosene and gasoline fractions. The military services and industrial laboratories have studied the thermal stability of these fuels. They have found that some jet fuels, and particularly those that contain cracked stocks, are too unstable thermally for contemplated high temperature uses.

We have now discovered that the thermal stability of petroleum oil fractions, such as unstable jet fuels, can be markedly improved by the addition thereto of minor amounts of certain novel imide and amide derivatives of ethylenediamine tetraacetic acid, which is also known as ethylenedinitrilotetraacetic acid and is abbreviated hereinafter as EDTA.

In general the compositions of our invention comprise the products obtained by reacting EDTA with a C C primary aliphatic amine under conditions adapted to yield a reaction product that consists essentially of imide and amide compounds, such product having an average of no more than one amine salt group or unreacted carboxyl group per molecule. Our invention further includes com- 3,407,051 Patented Oct. 22, 1968 positions comprising a major amount of hydrocarbon oil and a minor amount of our novel reaction products. A preferred embodiment of the invention comprises a major amount of a jet aircraft liquid hydrocarbon fuel which has a substantial content of unsaturated hydrocarbons and/or sulfur and nitrogen compounds and a minor amount of our novel imide or amide reaction product.

Our novel products are obtained by reacting EDTA with an aliphatic primary amine having from 4 to 24 carbon atoms per molecule under selected reaction conditions. The most important reaction conditions are temperature, reaction time and mole ratio of amine and EDTA. These conditions are so selected that the imide or amide compounds of the invention are formed. By imide and amide and and by the term imide-amide we mean to include several possible derivatives of EDTA that contain imide or amide groups. We include the compounds resulting from reaction of all of the carboxyl groups of EDTA, such as the tetraamide and the diimide, and the mixed amide-imide compounds, i.e., imide-diamide. We also include the triamide and the imide monoamide compounds. The latter compounds can contain an amine salt group or an unreacted carboxyl group in addition to the amide or imide groups. A feature that distinguishes our product from other EDTA derivatives that do not possess all of its valuable properties is that the average content of amine salt groups and carboxyl groups in our reaction product is no more than one of such groups per molecule. In other words, an average of at least three of the carboxyl groups of EDTA are converted to amide or imide groups in forming our novel product.

Compounds present in the products of our invention are illustrated by the following general structures:

wherein R is an aliphatic group of 4 to 24 carbon atoms and X is NHR, -OH.RNH or -OH.

Amines suitable for reaction with EDTA to form the products of our invention are primary aliphatic amines having from 4 to 24 carbon atoms per molecule. An especially preferred amine is the product known as Primene 81-R. This is a mixture of branched chain, primary, alkyl amines in which the amine group is attached to a tertiary carbon atom and which have 12 to 15 carbon atoms per molecule and an average molecular weight of about 200. When this type of amine is employed, products of the invention according to the structural Formulae I, II or III above are formed in which R is a branched chain alkyl group of 12 to 15 carbon atoms.

Another commercial mixture of amines suitable for making our products is the product known as Primene JM-T. This is essentially a mixture of branched chain,

primary alkyl amines of structure similar to the amines of Primene 81-R, but containing 18 to 24 carbon atoms per molecule. Typical examples of other suitable amines are 2-et-hylhexylamine, octylamine and dodecylamine.

In the products of the invention made from amines of the types descried above, R is an aliphatic hydrocarbon group of 4 to 24 carbon atoms. Other amines can also be used which form products of the invention in which R is an aliphatic group of 4 to 24 carbon atoms but not necessarily an aliphatic hydrocarbon group. Thus a suitable class of amine includes the Duomeen products. One of such products, known as Duomeen 12, is a propylenediamine derivative having the structure,

This type of amine fits the definition of primary amines used for making the products of the invention, the primary amino group being the reactive group of the molecule. In products of the invention of the Formula-e I, II, or III prepared from this type of amine the substituent R has the structure, -(CH NHR', wherein n is 2 or 3 and R is an aliphatic hydrocarbon group of 8 to 18 carbon atoms.

An especially preferred product of our invention is made by heating a mixture of 3 moles of Primene 81-R and 1 mole of EDTA in kerosene solution at the boiling point of the solution, about 220 C., until a product acid number of about 50 is obtained. Time required is about 6 to =8 hours. The approximate composition of the product, in terms of conversion of the carboxyl groups of EDTA, is: 50 to 30% of carboxyl groups in imide form; 30 to 50% of carboxyl groups in amide form; 20% of carboxyl groups in salt form.

Of the selected reaction conditions used in forming the products of our invention, reaction temperature is particularly important. The temperature must be above about 200 C. and preferably is in the range of about 200 to 220 C.

Reaction time is also important and must be suflicient to yield the imide or amide products of the invention. When the reaction temperature is in the range of 200 to 220 C. the reaction time must be at least about 3 hours to yield the products of the invention. For the preferred products of the invention the reaction time should be at least about 6 hours, e.g. 6 to 8 hours. It should be understood that not all combinations of reaction temperature and reaction time within the disclosed ranges will produce the same results and that to form products of the invention with the shorter reaction times indicated the higher temperatures should be used.

Another important variable is the molar ratio of amine to EDTA. The amount of amine must be sufiicient to convert at least three of the carboxyl groups of EDTA to the imide or amide forms. Therefore, the minimum mole ratio of amine to EDTA is 2:1, which is the minimum stoichiometric ratio for producing the imide-monoamide or the diimide compounds. For producing the tetraamide the preferred upper limit is 4:1. A higher mole ratio of amine to EDTA can be employed but an excess of amine, particularly at the lower temperatures of the reaction, can lead to production of the undesired amine salts. In summary, the amine to EDTA mole ratio for preparing our products is at least about 2:1 and preferably is in the range of about 2:1 to 4: 1.

A suitable procedure for preparing the products of the invention comprises charging the EDTA in the liquid phase to a reaction vessel equipped with an agitator and heating means. The amine is then introduced into the vessel in an amount sufiicient to provide the proper mole ratio of amine to EDTA, e.g., 2:1 to 4:1. The mixture is heated at atmospheric pressure to a temperature in the range of 200 to 220 C. Heating is continued until the acid number (ASTM D974) is less than 60 or approximatel that of the desired product, for example, zero for the fully amidized products, i.e., the diimide, the tetraamide and the imide-diamide. This will require about 3 to 8 hours. Normally, heating is continued until no more water is evolved from the reaction mixture.

We prefer to carry out the reaction in the presence of an inert solvent that boils above 200 C. to remove by azeotropic distillation the water formed in the reaction. The EDTA is mixed with the solvent in the reaction vessel and the amine isthen added. Suitable solvents include hydrocarbon fractions such as kerosene or Stoddard solvent thathave endpoints substantially higher than 200 C. By using such a high boiling solvent, essentially complete dehydration'is obtained in about 3 hours and the amine salt compounds areeliminated from the product or at least reduced to a low level such that the acid number is less than and the imide-amide products contain no more than one salt group per molecule.

Typical products of the invention and a method that we have used in their preparation are described in the following examples.

Example 1 In a flask fitted with a mechanical stirrer and a water trap were placed 73 g. (0.25 mole) of ethylenediamine tetraacetic acid, g. (excess) of Z-ethylhexylamine, and 10 ml. of water. This mixture was refluxed until 28 ml. of water had been collected, which required about two hours. During this period the temperature of the reactants was in the range of 200 to 220 C. The excess amine was stripped under vacuum. The product obtained was a clear, light amber, viscous liquid. Elemental analysis of the product and its comparison with the theoretical analysis for the tetraamide, 2,2',2",2'(ethylenedinitrilo) tetrakis(2-ethylhexylacetamide) was as follows: Theory 68.41% C, 11.51% H, 11.40% N. Found: 68.60% C, 11.58% H, 11.30% N. The fact that the product was fully amidized and contained essentially no amine salt groups or residual carboxyl groups was established by acid number determination according to ASTM D974, which measures the mg. of KOH required in titrate the acidity of 1 g. of sample. The acid number of the reaction product was only 1.16.

Example 2 EDTA was reacted with dodecylamine in a mole ratio of about four moles of amine per mole of EDTA and at a temperature in the range of 200 to 220 C., substantially according to the procedure of Example 1. The reaction product was a hard tan wax. The product was fully amidized as indicated by an acid number of only 0.32.

Example 3 EDTA was reacted with the commercial amine mixture known as Primene 81-R in a mole ratio of 4 moles of amine per mole of EDTA and at a temperature of 200 to 220 C., substantially according to Example 1. The product was a viscous brown liquid and was partially amidized, as indicated by an acid number of 53.1.

Example 5 EDTA was reacted with the commercial amine mixture known as Primene JM-T in a mole ratio of 4 moles of the amine per mole of EDTA at a temperature of 200 to 220 C., substantially according to Example 1. The reaction product was a viscous brown liquid and was partially amidized, as indicated by an acid number of 29.8.

5 Example 6 EDTA was reacted with the commercial aimine mixture known as Duomeen 12 in a mole ratio of 4 moles of amine per mole of EDTA at a temperature of 200 to 220 C., subsantially according to Example 1. The reaction product was a viscous brown liquid and was partially amidized as indicated by an acid number of 12.9.

Example 7 EDTA was reacted with Primene 81-R in a mole ratio of 3 moles of amine per mole of EDTA and at a temperature of 200 to 220 C., substantially as in Example 4. The product was an amber sticky solid with an acid number of 54. This acid number indicated that approximately one carboxyl group per EDTA molecule was present. The product. was easily and completely soluble in Stoddard solvent.

We have tested the ability of the products of the above examples to improve the thermal stability of jet fuels in the CFR Fuel Coker test. A discussion of the test was given by Crampton et al. in a paper entitled Thermal Stabilitya New Frontier for Jet Fuel, at the SAE Summer Meeting in 1955. Instructions for operating the CFR Fuel Coker are contained in Manual No. 3 of Coordinating Research Council, Inc.

The test involves pumping the jet fuel at 150 p.s.i. and a flow rate of 4-6 pounds/hour through a preheater assembly and then through a furnace assembly which contains a 20 micron sintered, stainless steel filter. The fuel is heated to 300-400 F. in the preheater and to 400- 500 F. in the furnace. Fuel degradation products appear as deposits on the preheater. They are also trapped on the furnace filter where they cause a pressure drop on a mercury manometer connected across the filter. Usually is a kerosene of high flash point (140 F.). JP-6 is a wide cut kerosene. The five fuel compositions employed in our tests will be referred to as jet fuels A, B, C, D, and E. Fuel A was a blend of several commercial unstable and stable JP-S fuels. Fuel B was a commercial JP-S fuel, Fuel C wass a JP-6 fuel, Fuel D was a JP-4 fuel, and Fuel E was a JP-5 fuel. Inspection data for specific fuels of the three different grades used in our tests are as follows:

TABLE I.-INSPECIION DATA ON JET FUELS Jet Fuel Jet Fuel Jet Fuel 13 JP-5 JP-6 "D JP-4 Gravity, API 41. 6 46. 55. 1 Distillation:

Initial boiling point, F 320 146 evaported, F 390 341 208 50% evaporated, F- 432 3 57 90% evaporated, F- 488 377 End point, F- 548 404 384 Sulfur, wt. pereent 0. 178 0. 02 0. 043 Freezing point, F -50 --70 -80 Aromatics, v01. percent 19 9. 6 16. 9 Olefins, vol. eroent 3. 37 1. 5 1. 1 Flash point, F 141 The CFR Fuel Coker conditions used for the different fuels in our tests were:

The following table shows the CFR Fuel Coker test results for Fuels A, B, C, D, and E with and without our additives. The table identifies each additive by the number of the example above that describes its preparation.

TAB LE II Thermal stability additive Results of CFR iuel coker test Additive Goodness" Example No. Physlcal form Acid N 0. Jet fuel concn., rating lb./1,000 bbl.

None (controls) A(JP-5) None 40 B (J P-5) None 155 C (J P-fi) None 198 D(.TP4) None 230 1 Sl. viscous amber llqu1d 1. 16 B 10 870 Hard tan wax 0.32 A 2 8% 3 Soft ten wax 15.8 A 2 812 B 0 750 4 Very viscous brown liquid. 53. 1 A 2 609 B 25 800 C 820 D 5 700 5 .do 29. 8 A 2 385 6 Viscous brown liquid 12. 9 A 2 750 7 Amber sticky solid 54 B 5 680 E 850 the test is run until a pressure drop of 25 in. Hg is indicated on the manometer, or for 300 minutes, whichever occurs first. Fuel stability is expressed in goodness" units which are a measure of time required for the pressure drop to reach 25 in. Hg, or of the actual pressure drop if less than 25 in. Hg at 300 minutes. The ratings range from 0 for immediate clogging to 900 for no manometer pressure drop at 300 minutes. After the test the preheater is dismantled and the inner aluminum tube around which the fuel flows is inspected for deposits. These are rated as to extent and color.

We have applied the CFR Fuel Coker test to five different jet fuel compositions containing our thermal stability additives. The fuels were liquid hydrocarbon fractions of the JP-4, JP-5 and JP-6 grades. The characteristics of these jet fuels are well known. See military specification v MIL-J-5624D and ASTM Dl655-59T. JP-4 is essential- Table II shows that the Example 1 imide-amide reaction product of EDTA and 2-ethy1hexylamine (amine: EDTA mole ratio of 4:1) was effective in retarding both filter plugging and preheater deposits. Jet Fuel B, before the addition of our product, had a goodness rating of only 155 and a preheater tube deposit rated as dark brown stain. The same fuel containing 10 lb./ 1,000 bbl. of our Example 1 product was greatly improved in stability, having a goodness rating of 870 and a preheater tube deposit rating of only 48% light brown stain.

Table II shows that the imide-amide product of Example 2 obtained by reacting dodecylamine with EDTA (4:1 ratio) was a very effective thermal stabilizer. The product was fully amidized, as indicated by an acid number of only 0.32. Jet Fuel A without the additive had a goodness rating of only 40. A concentration of only 2 lb./ 1,000 bbl. of the additive increased the goodness rating of Fuel A to 828.

Example 3 of Table II shows that the partial imideamide reaction product obtained by reacting n-octylamine 7 with EDTA was an effective thermal stabilizer for Fuel A. An additive concentration of 2 1b./ 1,000 bbl. increased the goodness rating from 40 to 812.

Example 4 of the table shows that the partially amidized product obtained by reacting EDTA with Primene 81-R was an effective stabilizer for all four of the fuel compositions in concentrations ranging from 2 to lb./1,000 bbl. Thus, Fuel A without the additive had a goodness rating of only 40 (25 in. Hg pressure drop in 20 minutes). With the addition of only 2 lb./ 1,000 bbl. of the Example 4 partial imide-amide product the goodness rating increased to 609 (pressure drop of only 3 in. Hg after 300 minutes). This low concentration of the additive markedly reduced the filter plugging tendency of Fuel A. Preheater tube deposits were not measured for Fuel A. However, the Example 4 product'was very effective in retarding both filter plugging and preheater deposits of Fuel C. When tested under the conditions for JP-6 fuels, Fuel C without the additive had a goodness rating of 198 and preheater tube deposits rated as dark brown. Upon addition of 20 lb./ 1,000 bbl. of this partial imideamide reaction product the goodness rating increased to 820 and the preheater contained only 10% of a very light tan stain. The improvement in preheater tube condition was particularly impressive. Fuel D when tested under JP-4 conditions had a goodness rating of 230. Upon addition of 5 lb./ 1,000 bbl. of the Example 4 product, the goodness rating increased to 700. The additive also caused a decrease in preheater tube deposits.

Table II shows that the partially amidized Example 5 product obtained by reacting EDTA with Primene JMT improved the thermal stability of jet Fuel A in a concentration of only 2 lb./ 1,000 bbl.

Table II further shows that even a small concentration of the low acid number (12.9) imide-amide product of Example 6 obtained by reacting EDTA with Duomene 12 was very effective in increasing the thermal stability of Fuel A.

Still further, Table II shows that the imide-amide product of Example 7, obtained by reacting EDTA with Primene 81R in a 3:1 mole ratio, markedly increased thermal stability of two jet fuels. The goodness rating of Fuel E increased from 590 to 850 with addition of 25 lb./ 1,000 gal. of the additive. The rating of Fuel B was increased to 680 by 5 lb./1,000 gal. of the additive. In both fuels this additive significantly reduced the preheater deposits.

We have emphasized that in preparing the novel products of our invention at least three-fourths of the carboxyl groups of EDTA are converted to amide or imide forms. In other words, the product has an average of no more than one carboxyl or one amine salt group per molecule.

We have found that EDTA-amine reaction products that are predominantly amine salts are inferior to our products as thermal stability additives for hydrocarbon oils. Our products have the important advantage that they are less readily extractable from hydrocarbon oils by water, acidic solutions or alkaline solutions than the products that are predominantly amine salts. Furthermore, the EDTA-amine derivatives containing more than one salt group per molecule promote the formation of oil-water emulsions to such an extent that they are not of practical use.

The military specifications for jet fuels require that fuelwater mixtures separate quickly and completely (MIL-J- 5624D and MILF-25656). Many petroleum additives are surface-active compounds which promote emulsions and do not meet the military specifications. We have found that EDTA-amine reaction products which contain more than one salt group per molecule or that have an acid number higher than 60 fail the emulsion test, Method 3251.6 of Federal Test Method STD 791, which involves shaking isooctane (plus additive) with water. The following table lists the emulsion test results for a series of reaction products of EDTA with Primene 81-R.

TABLE III Response to Federal 791 EDTA-Primene 81-R product: Water tolerance test Diirnide Pass Imide-monoamide-monosalt Do.

Imide-monoamide-monoacid Do. Imide-diacid Fail Imide-disalt Do.

Monoamide-trisalt Do. Tetrasalt Do It should be understood that the products designated in Table III as imides arenot necessarily. entirely in the imide form but can include such imides in admixture with compounds in which two amide groups are present in lieu of an imide group. In any event, the products that have an' average content of more than one" salt group per molecule failed the emulsion test.

We have indicated that an advantage of our imideamide derivatives of EDTA is that they are not as easily extractable from petroleum oil fraction by water, caustic solutions and mineral acid solutions as are other derivatives of EDTA such as the predominantly amine salt de-' rivatives. This advantage over the predominantly amine salt type of reaction product of EDTA with amines is demonstrated by a series of tests that we have carried out with three types of reaction products of EDTA with Primene 81-R. One of these products, which we call the tetra salt, had an acid number that indicated that essentially all of the carboxyl groups of EDTA were converted to amine salt groups. Another product, which we call the disalt-diamide, had a somewhat lower acid number indicating that two of the four carboxyl groups of EDTA were converted to amine salt groups, and two were converted to the amide or imide forms. The third product was a product within the scope of the invention. It had a still lower acid number, that indicated that three of the four carboxyl'groups of EDTA were converted to the amide or imide forms and only one to the amine salt form. In the test procedure, 0.2 g. of the particular additive product was added to a ml. sample of isooctane. Then the isooctane sample containing the additive was shaken vigorously with an equal volume of tap water. The oil mixture was allowed to separate and 50 ml. of the supernatant isooctane layer was pipetted into a tared 100 ml. beaker. This liquid was evaporated at 230 F. under a current of heated air for 20 minutes. After cooling a desiccator, the beakers were again weighed. The percent extraction of the additive from the isooctane was calculated from the weight of the residue. Control evaporation tests showed no residue in the evaporated isooctane and quantitative recovery of the additives from unextracted isooctane solutions. This test procedure for each additive was repeated with acid and alkaline solutions substituted for the tap water. One solution was a 1% aqueous solution of HCl. The other was a 1% aqueous solution of NaOH. The results of the tests with the three different additives and with the three types of extracting liquids, i.e., tap water, 1% HCl and 1% NaOH, are given in Table IV below.

TABLE IV.EXTRACTABILITY OF EDTA-PRIMER Sl-R PRODUCTS FROM HYDRO'CARBONS Percent loss of additive from isooctane after shaking 5 minutes with equal volume Table IV shows that the tetra salt product was almost .entirely extracted from the isooctane by tap water and by the dilute acid and alkaline solutions. The disalt product was less easily extractable by tap water and dilute 9 HCl although the loss was still too large. The loss by extraction with dilute alkaline solution was almost as great as with the tetra salt. In contrast, the table shows that products of the invention as exemplified by the triamide-monosalt product are much more resistant to extraction by tap water or by acid or alkaline solutions. An important practical advantage for the products of the invention is thus demonstrated.

The following example illustrates the significance of reaction temperature and the length of the reaction period for obtaining the imide-amide products of our invention.

Example 8 A mixture of Primene 81-R and EDTA (4:1 mole ratio) was heated at 170 to 175 C. After 15 minutes only amine salt was formed. After 8 hours only a small amount of amide had been formed and the product was too insoluble to test as a jet fuel additive. In another test the same materials were reacted in the same manner as above except that the temperature was maintained in the range of 198 to 205 C. The product obtained after a reaction period of 3 hours had an average composition corresponding to the diamide-disalt compounds which does not pass the water-oil emulsion test.

The following table lists acid numbers determined for the reaction products of Primene 81-R and EDTA (4:1 mole ratio) at different time intervals during reaction periods of 8 hours at two different temperatures, 170 C. and 200 C. The measured acid numbers can be compared with the theoretical acid numbers for the various possible products of different degrees of amidization, namely, the tetrasalt (186), the trisalt-monoamide (140), the disalt (95), the monosalt-triamide (50), and the tetraamide TABLE V.ACID NUMBERS OF EDTAPRIMENE 81-R PRODUCTS AT DIFFERENT REACTION TIMES AND TEMPERATURES Acid Number, Reaction at- Reaction period, hours Example 8 and Table V demonstrate that a temperature below abuot 200 C. will not yield the products of our invention even though the reaction period is very long, e.g., 8 hours. The example also demonstrates that when the reaction temperature is at the lower end of the permissible range for making the products of the invention, i.e., about 200 C., the reaction period must be considerably longer than the minimum that is suitable for higher temperatures.

We have illustrated the utility of our new products as thermal stabilizers for JP4, JP-S, and JP-6 jet fuels. In general they are useful as thermal stability additives for various petroleum oil fractions. For example, they can be used in special jet fuels (MIL-F-25524), in ram jet fuels (MIL-F-2555 8), in rocket engine fuels (MIL-F-25576) and in other kerosene and gasoline fractions, including conventional automotive and aviation gasoline, as well as in other types of petroleum oil fuels such as diesel oil and Numbers 1, 2, and 3 fuel oils. Our additives are particularly valuable for improving any of such fuels that contain olefins or that are otherwise unstable.

The concentration of stabilizer in the petroleum oil will depend upon the composition of the particular oil and on the degree of thermal stability desired. Ordinarily,

concentrations of about 1 to 100 lb./ 1,000 bbl. of oil (about 0.00038 to 0.038 weight percent) will suffice, although for some applications larger or smaller amounts can be used, e.g., 0.001 to 0.05 weight percent. Our stabilizers can be used alone or with other additives such as dyes, dispersants, metal deactivators, antioxidants, anticor-rosion agents, and antiknock agents. They can be added to fuels in the pure form or as concentrates in solvents such as alcohols, Stoddard solvent, kerosene, etc. The concentrates can also contain other additives such as those mentioned.

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A composition containing a petroleum oil fraction of the gasoline-kerosene range, which has a substantial content of unsaturated hydrocarbons, and an amount sufiicient to improve the thermal stability of said fraction of a reaction product consisting essentially of compounds selected from the group consisting of each R is an aliphatic hydrocarbon group of 4 to 24 carbon atoms or (CH ),,----NI-I--R wherein n is 2 or 3 and R is an aliphatic hydrocarbon group of 8 to 18 carbon atoms and X is a radical selected from the group consisting of -NHR, -OH.RNH and OH, R being defined above, said reaction product having an average content of amine salt groups and carboxyl groups of no more than one of such groups per molecule.

2. A composition according to claim 1 wherein said reaction product is present in an amount of about 0.0001 to about 0.05 weight percent of said fraction.

References Cited UNITED STATES PATENTS 3,024,277 3/ 1962 I-Iotten.

2,794,000 5/1957 Moritz 2525l.5 3,173,770 3/1965 Thompson et a1 44-71 3,202,491 8/1965 Maxwell et al. 44-71 PATRICK 'P. GARVIN, Primary Examiner.

Y. H. SMITH, Assistant Examiner.