US2317968A - Compression ignition motor fuel - Google Patents

Description

. ignition qualit Patented Apr. 27, 1943 7 2,317,968 COLDRESSION IGNITION MOTOR FUEL Thomas H. Schultz,

, Levine and Homer B assignors to Standar fornia, San Francisc Delaware Richmond, and Irving E. Wellman, Berkeley, Calii.,

d Oil Company of Call-. 0, Calif a corporation of No Drawing. Application May 12. 1941,- Serial No. 898,076

9 Claims.

This invention relates to fuels for internal combustion engines of the Diesel type, in which a liquid fuel is injected into the combustion chamber and ignited by compression; it has particularly to do with the modification of hydrocarbon fuels more volatile than those ordinarily employed in compression ignition motor service and the admixture of such modified volatile fuelswith ordinary or special hydrocarbon fuels of the Diesel type in such a manner as to enhance the combustion characteristics of the latter for Diesel motor purposes.

In the attainment of minimum engine knocking, the time interval between the instant of liquid fuel injection and the instant of ignition, referred to as the "delay period," should be as brief as possible, and this delay period is known to be affected by the type or character and the volatility of the hydrocarbons composing the fuel. In the present invention, fuels of high as measured by decrease in delay period, are prepared by admixing with petroleum hydrocarbons of otherwise satisfactory character a modified hydrocarbon fuel of originally somewhat higher volatility than the usual whole Diesel fuel or fractions thereof. This modified hydrocarbon fuel originally of higher than the usual Diesel fuel volatility is derived, in its simplest terms, by a carefully controlled partial oxidation of a relatively highly volatile petroleum fuel, under definitely ascertained circumstances, followed by a supplementary treatment designed to stabilize the composition which is produced and to free it from components adverse in their effects upon Diesel engine operation, upon deterioration in storage, upon physical homogeneity and the like. As prepared, this modified fuel may be promptly admixed with an ordinary or special hydrocarbon Diesel fuel for the improvement of the latters combustion characteristics, or it may be stored or transported as such, to be admixed with an ordinary Diesel fuel, when convenient, for the improvement of the latters com-' bustion characteristics.

In their barestoutline, the products of the invention are prepared by processes which provide for the preliminary selection or treatment of a petroleum fuel of higher than kerosene volatility, by such means as will produce a set of hydrocarbons capable upon oxidation with air or an oxygen-carrying gas of attaining an oxygen factor" of higher than about 800 and generally between about 800 and about 1450; treating the said selected or preliminarily prepared set of hydrocarbons with air, oxygen oran oxygencarrying gas under such conditions as will allow.

it to attain an oxygen factor of about 800 or more and generally between about 800 and about 1450, usually without concomitant increase in neutralization number of more than about 20; arresting the progress of said oxidizing treatment before the oxygen factor of the oil has decreased to below about 800 (after through a maximum); and removing acidic and other oxidation products that have been ascertained to be detrimental for the purposes of the invention. This modified or partially oxidized oil may, when desirable, be blended with one or more ordinary or special hydrocarbon fractions of the Diesel fuel class to produce a fuel of a desired high ignition quality or it may be stored or transported for such blending at a later time. The modified or partially oxidized oils contain chemically combined oxygen in significant quantities, dependent upon the oxygen factors obtained in the modifying processes themselves; for example, a modified oil of an oxygen factor between about 800 and about 1450 may contain from about 4% to about 14% of chemically combined oxygen.

The processes and the compositions of the invention may best be described by reference to a. number of specific examples.

Example 1.-A straight run petroleum distillate fraction having the following characteristics:

Gravity, A. P. I 46.6 Initial boiling point 312 50% boiling point 327 End boiling point 369 U. 0. P. characterization factor 11.60

was treated at-crdinary temperature with about 0.5 pound of 98% H2804 per gallon. The sludge was settled and removed and the treated oil was washed with water, neutralized with caustic soda solution and again washed with water in a usual gasoline'- or petroleum solvent-type of treatment. About 10 gallons of this preliminarily treated c was heated to a temperature of 300-310 F. and transferred to a vertical cylindrical vessel or still about 8 inches internal diameter and 96 inches in height, of chrome-nickel steel and equipped with a'horizontal porous plate partition about limb from its bottom (Filtros plate, grade R, manufactured by Filtros Inc., East Rochester, New York) and provided with a heating and cooling jacket and with a vapor condenser. The designated volume of oil filled the vessel; above the plate, to a depth of about 48 inches. About 2% by volume of a modified, partially oxidized oil of the invention,

the same has passed seedstock (a completely as possibleto a 2. from an earlier preparation) was added to the treated distillate introduced to the vessel. During the charging of the vessel, air was passed upwardly through the porous plate partition at a rate of about 0.3 volume per volume of oil to be charged, per minute, to prevent the charged oil from passing downwardly through the plate. The air rate was increased as rapidly as possible, following the completion of the charging operation, without decreasing the temperature appreciably below about 300 F.; this rate should be 2 or more volumes per volume of oil per minute, and may be as high as 3 or more volumes per volume of oil per minute, depending somewhat upon the tendency of the material to foam into the condenser. Blowing was continued for 5 hours at an oil temperature of 295-305 F. (it may advantageously be held between 290 and 295' F. for the latter half of the operation). During the first part of the reaction heat was supplied to compensate for the cooling caused by evaporation; during the latter part of the reaction less heat was needed (and cooling is indeed sometimes required), as the reaction is exothermic. Such oil as evaporated was liquefied in a stainless steel condenser, condensed water was trapped out, and the condensed oil was returned directly to the main reaction mixture. After 5 hours of blowing under these conditions, the oil had an oxygen factor of 1210, a neutralization number of -11 and a saponification number of 30.5.

The partially oxidized oil was cooled as rapidly temperature of 100 F., while discharging from the treating vessel, by circulating cool water through the coils and passage of the treated stock through heatexchanger; the air rate through the porous plate was reduced to about 0.3 volume per volume of charged oil per minute at the end of the discharging operation (and may be maintained at this rate during the charging of the next batch of oil to be treated).

The modified oil was washed at atmospheric temperature with 5% aqueous caustic soda solution, to remove such acidic products as were present in the oil; the caustic soda solution was added in only small excess of that calculated to be required, from the neutralization number. Finally, the oil was washed with water and settled bright in the usual manner. The characteristics of this modified oil were as follows:

Gravity A. P. I 42.8 Oxygen factor 985 saponification number 19.4 Neutralization number 0.1

Example 2.A clean straight run gas oil distillate of California origin having the following characteristics:

stability of the blend. The characteristics of this blended Diesel fuel were as follows:

Gravity A. P. I 39.0 Pour point F' -30 Cetane number 63 Oxygen factor 148 Example 3.-A rafllnate from an SOs-treated petroleum distillate of California origin having the following characteristics:

Gravity A. P. I 43.8 Pour point F 30 Cetane number 53 Initial boiling point F 350 50% boiling point F 435 End boiling point F 580 was blended with the finished modified oil as described in Example 1, the proportions of the blend being 97.5% by volume of the S02 raifinate and 2.5% by volume of the 985 oxygen factor 011 prepared in accordance with Example 1. This blend was washed with 3% of its volume of 5% Gravity A. P. 38.2 Pour point F -30 Cetane number 44 Initial boiling point ..F 355 50% boiling point F 455 End boiling point F 565 was blended with the finished modified oil prepared as described in Example 1, the proportions of the blend being 80 volume per cent of the clean gas oil distillate and 20 volume per cent of the 985oygxen factor oil prepared in accordance with Example 1. This mixture was carefully washed with 3% of its volume of 5% aqueous caustic soda solution, then washed with water and allowed to settle bright, such final treatment being desirable to enhance the storage aqueous caustic soda solution, washed with water and settled bright. The characteristics of this blended Diesel fuel were as follows:

Gravity A. P. L- 43.8 Pour point F 30 Cetane number 60 Oxygen factor 19 volumes per volume of oil per minute, without appreciable lowering of the temperature of the oil. Blowing was continued for about 4 hours at an oil temperature of 295-305" F., and after treatment for this period of time, under these conditions, the oil had an oxygen factor ofv 950, a neutralization number of 6 and a saponification number. of 22.5. The partially oxidized oil was rapidly cooled to a temperature below 100 F. during the emptying of the treating vessel, maintaining an air rate of about 0.3 volume per volume of charged oil per minute. The modified oil was washed with aqueous caustic soda solution in the manner described in Example 1 and was finally washed with water and settled bright. The characteristics of this modified oil were as follows:

Gravity A. P. I 43.4 Oxygen factor 800 saponification number 16.5 Neutralization number 0.1

Example 5.A rafiinate from a liquid sulfur dioxide treated distillate having characteristics similar to those of the SO-i-raillnate referred to in Example 3 was blended with the finished modifled oil prepared as described in Example 4, the proportions of the blend being volume per cent of the SOz-raflinate and 5 volume per cent of the 800 oxygen factor oil prepared in accordance with Example 4. This blend was washed with 3 volume per cent of 5% aqueous caustic soda solution, washed with water and settled bright. The

characteristics of this blended Diesel fuel were as follows: Gravity A. P. I 43.8 Pour point F 30 Cetane number 62 Oxygen factor 32 Example 6.A preliminarily treated petroleum fraction of characteristics similar to those of the stock exemplified in Example '1, with the addition of about 2% by volume of a seed stock taken from a previously prepared batch .of partially oxidized oil, was treated in the manner described in Example 1, for about 1 hour at an average air rate of 1.0 volume of air per volume of oil at 300-305 F., and for about 4 hours at an average air rate of 2 volumes per volume of oil per minute and at 280-290 F. At the end of this treatment, the partially oxidized oil had an oxygen factor of 1430, a neutralization number of 14 and a saponification number of 39; the blown oil was cooled rapidly to 100 F. by passage through a heat exchanger, air passage being continued in the main vessel until it was empty of oil. After washing with water, dilute aqueous caustic soda solution in an amount only slightly greater than that required and a final water washing and brightening, the characteristics of the finished modified oil were as follows:

Gravity A. P. I 42.0 Oxygen factor 1210 Saponification number 25 Neutralization number 0.1

Example 7.A solvent refined light gas oil disous solution of potassium iodide.

of, ethyl ether in place of alcohol.

tillate of California origin, having characteristics similar to those of the rafiinate from an SO2- treated distillate referred to in Example 3, was blended with the finished modified oil prepared as' described in Example 6, the proportions of the blend being 85 volume per cent of the solvent refined distillate and volume per cent of the 1210 oxygen factor oil prepared in accordance with Example 3, and the blend was given a final caustic soda washing as heretofore described. The characteristics of this blended Diesel fuel were as follows:

Gravity A. P. I 43.6 Pour point F Cetane number 70 Oxygen factor 140 Deflm'tions.For the purposes of this invention, the following characteristics have the following meanings or derivations:

The cetane number determinations given herein are determined by a procedure known as the Standard Oil Company of California delay method, employing a Fairbanks Morse Diesel engine. in which the ignition delay with combustion occurring at top dead center is utilized as the test criterion and in which the operating variable is the injection advance, equivalent to the ignition delay when firing is made to-occur at top dead center. In brief, this procedure is characterized as follows: The fuel to be tested is introduced into the engine and the injection is then advanced or retarded until firing occurs at top center; the ignition delay is read and recorded. The procedure is then repeated for a series of cetane-alphamethylnaphthalene blends which produce greater and lesser ignition delays than the fuel under test. A plot is made of the ignition delays of the cetane-alphamethylnaphcetane in the blends. fuel under test is placed on this plot and its corresponding cetane number is determined. The

I method may be employed on service engines capable of sufiicient control of all operating variables, other than Fairbanks Morse; as described. the method yields results which correlate well with service performance.

For the purposes of this invention, the factor" to 10 ml. sample of the oil, at approximately 68 F., is accurately pipetted into a 250 ml. glassstoppered flask. 20 ml. of a mixture consisting of volume per cent of C. P. glacial acetic acid and 40 volume per cent of chloroform are added to the oil, followed by 2.0 m1. of a saturated aque- The mixture is shaken vigorously for three minutes and then diluted with about 50 ml. of distilled water. The liberated iodine is titrated with 0.1 normal standardized sodium thiosulfate solution, adding starch indicator just before the end point is reached. Considerable shaking is necessary near the end of the titration. Oxygen factor=(titer in mi. normality of thiosulfate X 1120) (volume oxygen of sample in ml).

Saponification numbers are determined in accordance with A. S. T. Neutralization numbers are determined in accordance with A. S. T. M. D188-27T, method B. modified by titration at room temperature, by the use of alcoholic hydroxide and by the use U. 0. P. characterization factorsv are discussed in Watson, Nelson and Murphy, Industrial and Engineering Chemistry, volume 27, pages 1460-1464 (1935).

The precise character of the oil contemplated for use has been found to be of considerable consequence in providing a set of hydrocarbons capable of attaining high oxygen factors upon being subjected to the action of oxygen or an oxygencontaining gas such as air, under the circumstances disclosed for the practice of the invention. In general, the factors which have been found of greatest. significance in this choice or preliminary preparation of an oil are: relative freedom from large proportions of aromatic ring structures amongthe hydrocarbons themselves; relative freedom from asphaltic or resinous materials; and relative volatility of the set of hydrocarbons as a whole. Straight run petroleum distillates are preferred as initial materials, and such distillates shoul be sulfuric acid-treated as described hereinabove, before subjection to oxidizing modification, or, alternatively, they may be extracted with a selective solvent refining agent such as liquid sulfur dioxide, aqueous phenol, aqueous aniline or equivalent material; in the absence of such preliminary treatment, it has been found that only indifferently high oxygen factor treated products are obtainable.

' Straight run distillates of initial and end boiling thalene blends in terms of the percentage of 76 point within the range 200 and 450 F. are preferred, and cuts thereof boiling within the following exemplary ranges are suitable: 250- 350 F.; 300-375 F.; 200400 F.; 350-450 F. Due to the volatile character of these distillates, particularly at the temperatures preferred in the modifying operations, superatmospheric pressures may be maintained if desired and such superatmospheric pressure may be at or slightly higher than the vapor pressure of the hydrocarbon stock being treated, at the temperature of treatment; in such an event, the air rates (herein The ignition delay of theof an oil is determined as follows: A 2

M. D94-38T, method A..

given as at atmospheric pressure) may be modified accordingly.

In preparing the partially oxidized, modified oils in the manner described, no oxidation catalysts and particularly no oxidation catalysts such as salts or soaps of the metals are required or desirable. A small amount of a previously oxidized oil is desirable when a clean reaction vessel is put into operation, and even this may be advantageously dispensed with in the event that the treating vessel is not cleansed between blowing operations.

For the best preservation of the benefits above mentioned, the Diesel-type distillates, treated distillates or rafiinates to be blended with the modified, partially oxidized oils should be clean and relatively free from asphaltic and resinous bodies, as small amounts of such reactive materials destroy the substances measurable in terms of oxygen factor. When acidic reaction products are substantially completely removed from the modified, partially oxidized oil before storage and before blending with straight hydrocarbon Diesel-type distillates, the materials are sufficiently stable in storage in ordinary fuel containers under all ordinary circumstances, without undue deterioration in the qualities determinable by engine performance. The final blends may also, and further, be washed with aqueous caustic soda solution, and with'water, as hereinabove exemplified, with great advantage to stability in storage.

As used in this specification and in the appended claims, the term Diesel-type fuel refers to distillate and treated or solvent refined distillate fractions only, but it includes hydrocarbon distillate fractions of kerosene or illuminating oil boiling range and fractions of such fractions, as well as the somewhat less volatile distillates in more usual present use in internal combustion engines of the mediumand high-speed Diesel type; the term accordingly includes hydrocarbon fractions whose A. S. T. M. 50% boiling points at atmospheric pressure are within the range 325 650 F. As thus used herein, this term includes fractions of relatively narrow boiling point range (so-called as fractions of wider boiling point range (socalled long cuts).

This application of a continuation-in-part of our application Serial No. 283,636, flied July 10, 1939, Diesel fuels of improved combustion characteristics.

While various specific embodiments of the invention have been illustrated and described above it is obvious that many modifications and adaptations may be made without departing therefrom, and all such changes as are included within the scope of the appended claims are embraced thereby.

We claim:

1. A process of preparing an improved Diesel type motor fuel containing-substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and of higher than kerosene volatility to treatment in liquid phase with an oxygen-containing gas at a temperature 275- 310 F. for a period of time suflicient to produce an oil having an oxygen factor of higher than about 800 but insufficient to increase the neushortcuts or "heart cuts) as well' without reducing the tralization number of the oil by more than about 20, arresting the said treatment before the owgen factor of the produced 011 decreases to below about 800, and removing acidic reaction products oxygen factor of the produced substantially acid-free oil to below about 800.

2. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen. which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of arcmatic ring hydrocarbons and boiling within the range 200-450 F. to treatment in liquid phase with an oxygen-containing gas at a temperature 285-310 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 800 but insufiicient to increase the neutralization number of the oil by more than,

about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, and removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800.

3. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically, combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel', comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and boiling in major part within the range 300-375 F. to treatment in liquid phase with an oxygen-containing gas at a temperature 285310 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 800 but insufficient to increase the neutralization number of the oil 'by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, and removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800.

4. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and of higher than kerosene volatility to treatment in liquid phase with an oxygen-containing gas at a temperature 285- 310 F. for a period of time sufficient to produce an oil having an oxygen factor within the range 800-1450 but insufficient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, and removing acidic reaction products without reducing the oxygen factor of the produged substantially acid-free oil to below about 5. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of an oxygen-containing gas at a temperature 285- 310 F. for a period of time suificient to produce an oil having an oxygen factor of higher than about 1,000 but insuflicient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, and removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800.

6. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and of higher than kerosene volatility to treatment in liquid phase with an oxygen-containing gas at a temperature 285- 310 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 800 but insumcient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800, and admixing the produced oil with a Diesel type fuel in amounts suflicient to enhance materially its combustion characteristics.

'7. .A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and boiling in major part within the range 300-875 F. to treatment in liquid phase with an oxygen-containing gas at a temperature 285-3l0 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 800 but insufficient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, removing acidic reac- 5 tion products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800, and admixing the produced oil with a Diesel type fuel in amounts sufficient to enhance materially its combustion characteristics.

8. A process of preparing an improved Diesel type motor fuel containing substantial propor tions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and of higher than kerosene volatility to treatment in liquid phase with an oxygen-containing gas at a temperature 285- 310 F. for a period of time sufflcient to produce an oil having an oxygen factor of higher than about 1,000 but insuilicient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 800, removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800, and admixing the produced oil with a Diesel type fuel in amounts suflicient to enhance materially its combustion characteristics.

9. A process of preparing an improved Diesel type motor fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the-said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring hydrocarbons and of higher than kerosene volatility to treatment in liquid phase with an oxygen-containing gas at a temperature 285- 310" F. for a period of time suificient to produce an oil having an oxygen factor within the range 800-1450 but insufiicient to increase the neutralization number of the oil by more than about 20, arresting the said treatment before the oxygen factor of the produced 011 decreases to below about 800, removing acidic reaction products without reducing the oxygen factor of the produced substantially acid-free oil to below about 800, admixing the produced oil with a Diesel type fuel in amounts sufficient to enhance materially its combustion characteristics, and treating the admixture with a dilute aqueous alkaline solution.

- THOMAS H. SCHULTZ.

IRVING E. LEVINE. HOMER B. WELLMAN.