US 3389978 A
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United States Patent 3,389,978 DIESEL FUEL COMPOSITION CONTAINING DIMETHYL FORMAMIDE AND A METAL NAPHTHENATE John S. Mann, Medina, and William F. Reinhart Shaker Heights, Ohio, assignors to The Standard O1l Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Mar. 25, 1966, Ser. No. 537,281 5 Claims. (Cl. 44-57) ABSTRACT OF THE DISCLOSURE A diesel fuel additive containing 25-250 ppm. of dimethyl formamide and up to 500 ppm. on the basis of the metal portion of a material selected from the group of barium, calcium, strontium, zinc and magnesium naphthenates. The additive package improves nozzle cleanliness, increases the cetane number of the fuel and provides other benefits.
This invention relates to a novel diesel engine fuel composition containing performance-improving amounts of a metal naphthenate and dimethyl formamide (DMF). Metal naphthenates found to be effective for the purpose hereinafter described include barium, calcium, strontium, zinc and magnesium.
A metal naphthenate, as a diesel fuel additive, improves performance in terms of nozzle cleanliness and thus lowers exhaust smoke and increases power. Dimethyl formamide shortens the ignition delay period, which is a measure of cetane number, and thereby improves the cetane rating-of the fuel. It has now been discovered that cetane-improving property of dimethyl formamide is further enhanced by the metal naphthenate in the fuel additive composition.
Naphthenate soaps require some excess acid for fuel solubility, however, excess acid tends to etch injector nozzles. The addition of dimethyl formamide increases the solubility of the naphthenate soap in diesel fuel without the need of excess acid, thereby protecting injector nozzles against acid etching. An additional advantage of the diesel fuel oil additive composition resides in its ability to greatly reduce filter clogging caused by ice agglomeration.
By itself, dimethyl formamide has the disadvantage of promoting varnish formation and coking of the injector nozzles. The metal naphthenates, on the other hand, function as detergents and thus are capable of maintaining the nozzles clean. When combined into an additive package, the desirable properties of the components are retained and enhanced, while the undesirable properties are suppressed.
The naphthenic acids used in preparing the naphthenate soaps are conveniently of petroleum origin. Naphthenic acids from other sources may also be used at the disadvantage of higher cost. The useful petroleum-derived acids are principally those removed from the lubricating oil and gas oil fractions of petroleum which boil within the range from about 500 F. to about 1000 F. at atmospheric pressures. These acids normally contain from about 8 to about 30 carbon atoms per molecule and distill in the range of from about 250 F. to about 600 F. at 2 mm. of mercury absolute pressure. Such acids can range in saponification value from about 50 to about ice 300 mgs. of KOH per gram on an unsaponifiables-free basis. It is desirable that the soaps derived from mixtures of such acids have an average saponification value below 225 mgs. of KOH per gram.
For purposes of this invention, a metal naphthenate concentration level of 100 to 200 ppm. based on the metal is preferred, the higher amount being required for complete cleanliness of a pintle-type nozzle, while the lesser amount is satisfactory in integral injectors. In general, amounts in excess of 500 p.p.m. cannot be economically justified.
The amount of dimethyl formamide employed is dependent upon the concentration of the metal naphthenate. Equivalent amounts of DMF to metal as the naphthenate are desirable, however, from about 25 to 250 p.p.m. of dimethyl formamide may be employed.
The diesel fuel additives were tested in a single cylinder and in a multicylinder diesel engine. In the single cylinder engine, each test was run with an initially clean nozzle, and hourly readings were taken of engine performance. The engine conditions that were used were as follows:
Compression ratio 15:1.
Engine speed 600 rpm.
Rate of fuel injection 9 milliliters per 60:5
Injection timing 13,BTC.
Injector opening pressure 2000 p.s.i.
Injector jacket temperature 100 F.
Engine jacket temperature 212 F.
Inlet air temperature 150 F.
The properties of the diesel fuel employed are given in Table I.
TABLE I API gravity 35.4 Specific gravity at 60 F. 0.8477 Sulphur "Percent..- 0.24
At 100 F. cks 2.245 At 210 F. -cks 0.9685 IBP F 365 5% F... 414 10% F 425 20% F..- 444 30% F 458 40% F-.. 472 F 484 F 496 F-.. 511 F 528 F.- 552 F 574 E.P. F-.. 583 Saturates Percent 66 Olefins o 5 Aromatics 29 For the single cylinder tests, various mixtures of barium naphthenate and dimethyl formamide were added to the base fuel as indicated in Table II, and the engine was run on each treated fuel. The numbers recorded are the average of seven observations taken at timed intervals over a seven-hour period. The fuels were rated for exhaust smoke, ignition lag, and power. The lower the ratings for smoke or lag, the better the performance while the higher the rating of power, the better the performance.
As naphthenate (contains 11 weight percent barium).
The data in Table II indicate the improvement obtained with the combination of barium naphthenate and dimethyl formamide over the base fuel. The data show that with 100 p.p.m. of barium as barium naphthenate by itself, the exhaust smoke is lower and power is increased, but there is a greater time lag in ignition as compared with the base fuel. With 100 p.p.m. of dimethyl formamide by itself, there is almost no change in exhaust smoke, ignition lag or power ratings. The greatest amount of improvement in all three ratings was obtained with the use of equivalent amounts of barium as barium naphthenate and dimethyl formamide.
A comparison of calcium and barium naphthenates in diesel fuel is shown in Table 111. These data were generated from the same single cylinder test described above.
The results obtained for both metal naphthenates in combination with dimethyl formamide are very similar. Though smoke, ignition lag and power ratings are improved with 100 p.p.m. of either barium or calcium naphthenate, the ratings are further improved with the presence of dimethyl formamide.
The naphthenates of strontium, zinc and magnesium also were tested and compared favorably with the results obtained from barium and calcium naphthenates. From an economical standpoint, however, barium naphthenate is preferred.
In the multicylinder test, a General Motors 3-53 diesel truck engine was used. The engine was operated for two hours under steady driving conditions, i.e., 2000 r.p.m. at 75 HP, and then two hours under trafiic" cycling conditions as follows:
14 seconds-650 r.p.m. idle 35 seconds1500 r.p.m. at 50 HP 21 seconds-4200 rpm. at 38.5 HP
4 and then back to two hours of steady driving, etc., for a total run of 400 hours. The base fuel used as the blank was the same one employed in the single cylinder tests. The engine was run for 400 hours on the base fuel without the additives, and then for 400 hours on the same base fuel to which had been added p.p.m. of barium as barium naphthenate and 91 p.p.m. of DMF. The injectors of this engine have eight ports through which the fuel is sprayed. At the end of the run on the base fuel, at least one port was completely plugged with carbonaceous material and several other ports were partially closed, so that the spray pattern was distorted.
With the barium naphthenate and DMF present, the nozzle was as clean as when the test was started, and the spray pattern remained unmodified after 400 hours.
Various modifications of the instant invention will occur to those skilled in the art upon reading the foregoing disclosure. It is intended that all such modifications be covered which reasonably fall within the scope of the appended claims.
1. A fuel additive composition consisting essentially of from about 25 p.p.m. to about 250 p.p.m. of dimethyl formamide and a material in an amount of up to 500 p.p.m. 0n the basis of the metal portion, said material selected from the group consisting of barium, calcium, strontium, zinc, and magnesium naphthenates, and mixtures thereof.
2. The composition of claim 1 wherein the concentrations of dimethyl formamide and the metal portion of said material are on equal weight basis.
3. A diesel fuel oil containing a performance-improving additive consisting essentially of from about 25 p.p.m. to about 250 p.p.m. of dimethyl formamide and 11p to 500 p.p.m. on the basis of the metal portion of a material selected from the group consisting of barium, calcium, strontium, zinc, and magnesium naphthenates, and mixtures thereof.
4. The diesel fuel oil of claim 3 in which the concentrations of dimethyl formamide and the metal portion of said material are on equal weight basis.
5. The diesel fuel oil of claim 3 in which the concentrations of dimethyl formamide and the metal of the metal naphthenate are on equal weight basis and in the range of about p.p.m. to about 200 p.p.m.
References Cited UNITED STATES PATENTS 2,258,297 10/1941 Miller et a1. 44--57 XR 2,918,359 12/1959 Lovett et a1 447l XR FOREIGN PATENTS 205,842 5/1955 Australia.
DANIEL E. WYMAN, Primary Examiner.
W. J. SHINE, Assistant Examiner.