US2692821A - Stable fuel oil compositions - Google Patents

Description

Patented Oct. 26, 1954 UNITED STATES PATENT OFFICE STABLE FUEL OIL COMPOSITIONS Henry A. Ambrose, Penn Township,

. Allegheny I County, and Oliver L. Brandes, Gibsonia, Pa.,

assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application June 1, 1951, Serial N 0. 229,528

'7 Claims.

This invention relates to stable fuel oil compositions. More particularly, the invention relates to stable fuel oil compositions which are composed of straight run and cracked oils.

When a heavy petroleum oil is subjected to catalytic cracking by any of the conventional processes such as the fixed bed, moving bed or fluid processes, wherein the heavy oil is contacted with a cracking catalyst such as a natural clay catalyst or a synthetic silica-alumina or silicamagnesia catalyst, the conversion products comprise not only gasoline hydrocarbons but also heavier distillate hydrocarbons, such as hydrocarbons boiling in the fuel oil range, that is, hydro-carbons boiling within the range of about 350 to about 750 F. Although the burning characteristics of such oils are fairly good, it is gen 1 erally the practice when using these catalytically cracked oils as fuels to mix them with straight run distillate oils of similar boiling range in order to produce mixed oils having better burning characteristics than catalytically cracked oils, and also in order to balance refinery production. In addition, thermally cracked distillates are sometimes mixed with straight run distillate oils of similar boiling range to produce fuel oils.

The problem of instability, as a practical matter, is troublesome primarily in the case of fuel oils consisting of mixed cracked and straight run oils. In the case of straight run distillates sludging or precipitation is not normally troublesome. However, in certain instances some straight run fuel oils will deposit sludge and may give trouble in service because of either inadequate or im- .proper refining, or due to a natural instability contribute to instability and the formation of.

precipitates in the subsequent storage and handling of such straight run fuels. It is believed that the problem encountered with straight run fuels is essentially one of oxidation and the formation of insoluble oxygenated compounds which result from contact with atmospheric and dissolved oxygen in the distillate. This problem is a dififerent one from that encountered in the storage and use of mixed cracked and straight run oils.

In the case of cracked distillates the chemical 1 nature of the components is considerably different from that of straight run materials, cracked distillates being, as a rule, highly aromatic and containing appreciable amounts of olefins and aromatic-olefin mixed-type compounds. Such compounds by virtue of their unsaturated character are particularly susceptible to polymerization reactions leading to the formation of relatively high molecular weight'resinous or gum-like materials which may or maynot contain appreciable amountsof oxygen. Although catalytically cracked stocks are relatively stable, thermally cracked stocks, depending upon the degree of cracking and on the type of charge stock, will precipitate sludge during storage. It is believed that this precipitation of sludge in thermally cracked stocks is mainly a result polymerization.

The tendency of fuel oils to cause the clogging of screens, conduits, and other parts of burners,

of oxidation and therefore, varies with different fuel oils. However, it has been found that the tendency of a mixed cracked and straight run fuel oil to form objectionable sedimentis greater than that of either oil alone. This is probably due to the fact that the decomposition products are less soluble in the mixed oil and therefore tend to precipitate out. Since the straight run component, being essentially paraflinic in nature, is a very poor solvent for the highly polymerized aromaticolefin type compounds which are formed from the cracked component, it probably has the effect of reducing the solvent power of the cracked distillate itself for such gum-like material. As a result, precipitation of those materials will occur.

It is believed that the sludge formed in such cases is of a different character from the sludge formed as a result of oxidationof straight run fuel oils.

t The present invention relates to fuel oil compositions comprising rnixedcracked and straight run distillate fuel oils, which compositions are of improved stability with respect to sludging and therefore of good appearance and adapted for effective use in fuel oil furnaces and as diesel fuels even after being stored for extended periods.

It has been discovered that such an improved mixed fuel oil composition can be obtained by incorporating in the mixed fuel oils a small amount of a divalent metal salt of a hydrogenated rosin, said metal being selected from the group of metals whose only simple salts are the divalent metal salts.

It is not clear as to what way the divalent metal salts of the class described function to improve the characteristics of the mixed fuel oil and therefore the invention is not limited to any theory of operation. It might appear that they function as solubilizing agents for the sludge, but this function is more or less negatived by the fact that whereas a mixed fuel oil in the absence of such a compound forms additional amounts of sludge so long as it is stored, at least over any feasible test storage period, the incorporation of a compound of this class in the oil inhibits the formation of additional sludge even after some sludge has been formed, although the already formed sludge does not disappear. We have discovered, however, that by adding a small amount of a compound of this class to a mixed fuel oil containing an amount of sludge making the oil undesirable for use in a household burner because of sludge deposits, the oil can be employed in such a burner without leaving the undesirable deposits. In this case it appears that although the sludge does not disappear, its characteristics are so changed as to prevent its deposition on a typical burner screen or on other parts of a burner.

Inasmuch as the hydrogenated rosins from which the salts of this invention are prepared are commercially available, their preparation does not form any part of this invention and need be only briefly considered. If desired, however, the hydrogenated rosin may be obtained by any of the well-known methods of preparation. For example, rosin may be heated and treated with hydrogen in the presence of a metallic catalyst. Moreover it may be either partially or completely saturated. The divalent metal salts of these more saturated rosin acids can then be formed by well-known methods such as by the addition of the metal oxide or hydroxide. If desired, the metal salts can also be prepared indirectly by substitution. The term rosin is intended to include all rosin acids, abietic acids and similar rosin materials.

It has been pointed out that useful salts are salts of metals selected from the group whose only simple salts are divalent metal salts. Thus, suitable salts include barium, calcium and magnesium salts of hydrogenated or partially hydrogenated rosin. Other metals normally forming simple divalent salts are zinc, cadmium, nickel, cobalt and strontium. Because of ease of availability, barium and calcium salts of hydrogenated or partially hydrogenated rosin naturally are preferred.

The addition of the compound in very small amounts has been found to produce excellent results. Thus, our composition comprises a major amount of the mixed straight run and cracked distillate fuel oils and a minor amount suincient to inhibit sludge deposition of the divalent metal salt of an at least partially hydrogenated rosin. Fully effective results are obtained when using between about 0.01 and about 0.1 per cent of the additive by weight of the mixed fuel oil for addition even to mixed oils having high sulfur content and pronounced sludging tendencies. Moreover, satisfactory results are obtained when using as little as 0.005 per cent. In this instance, in many cases full inhibition of sludge formation is not obtained but the mixed oil is satisfactory for use because the additive changes the physical, and perhaps chemical, nature of the sludge so that it does not cause rapid clogging of screens and other parts of burners. While larger quantities than 0.1 per cent can be used,

no advantage appears to result. The use of larger quantities necessarily increases the ash and carbon residue test values of the mixed oils, and may also cause darkening.

The divalent metal salt of hydrogenated rosin may be incorporated in the mixed fuel oil in any suitable manner. For example, it may be added to either or both of the cracked or straight run oils prior to mixing the two or it may be added to the mixed oil. When the compound is incorporated in the mixed oil, it is unnecessary to do this immediately after mixing the oil as the compound is effective even after some sludge has formed. It will usually be preferable to add the compound prior to any sludge formation as this will either eliminate sludge formation, or reduce the amount of sludge which will be formed, depending upon the specific characteristics of the oils employed in making up the mixed oil and upon the amount of the compound added. The compound can be added as such but it is preferred to employ it in the form of a concentrated solution in an oil carrier. After addition, some circulation of the mixed oil is desirable to insure the early production of a uniform composition, but this is not absolutely necessary.

It is emphasized that the problem with which the present invention is concerned exists primarily when a cracked oil and a straight run oil are combined in such proportions as to cause a substantial effect such as previously described. The invention is important when the ratio of the volume of the cracked oil to the straight run oil is within the range of 9:1 to 1:9. It is especially advantageous when applied to mixed oils containing these oils in a volume ratio within the range of 4:1 to 1:4.

In the following tables there are given the results of light stability tests made on the mixed fuel oils of the character indicated, in the absence of an additive, and containing compounds of the class disclosed above. The compounds employed in these tests were the calcium barium salts of a hydrogenated rosin. The percentages of each compound used in the tests are weight percentages of the compound in the oil.

A No. 2 oil is defined in ASTM Standards on Petroleum Products and Lubricants D396-48T. The No. 2 indicates a distillate oil for general purpose domestic heating for use in burners not requiring a No. 1 fuel oil, and having the following properties: Flash point, F.--l00 or legal (min); pour point, F.--20 (max); water and sediment, percent by volume0.l (max); carbon residue, percent by weight-0.35 on 10% residuum; distillation temperature, F.-90% point 675 (max); viscosity, Saybolt Universal seconds at F.-40 (max) gravity, API-26 (min); and maximum sulfur content-1 per cent.

The light stability test was carried out by exposing a 100 cc. sample of the oil to be tested to a light source rich in ultra-violet rays, for periods of 4 hours alternated with periods of 20 hours during which the oil was stored in the dark. The test was completed after 40 hours exposure to the light. At the end of each dark storage period the samples were examined for the presence of precipitated sediment or sludge. The exposure to light was accomplished by putting samples of fuel oil in 4-ounce bottles which were unstoppered to allow access of air. These bottles were placed within a circular metal enclosure at a distance of 22 inches from the light source which was a Westinghouse 400 watt type DH-l mercury vapor lamp mounted vertically in the center of the housing. It was found that a temperature rise of approximately 20 F. occurs during the exposure period. The interval of darkness was necessary to allow any dispersed sludge to settle and to permit oxygen to replace any used up in the light-induced reaction. The effect of the exposure to light was judged by swirling the bottle and estimating the quantity of precipitate which had settled. This was recorded as Trace, Light, Medium or Heavy. In

this light stability test the calcium and barium salts of this invention are used. The salt employed in the storage tests tabulated below is the calcium salt of hydrogenated rosin. Suitable hydrogenated resins are rosins of at least.

about 40 per cent saturation to and including fully hydrogenated rosin. A particularly useful hydrogenated rosin is one which has been hydrogenated to about 60 per cent of capacity.

TABLE I Light stability test Hours of exposure g gg' g Oil reqmred at end 01' to sluldgte 40 Hrs samp e o exp.

50/50 Blend Eastern Venezuela Straight Run 12 Heavy.

No. 2 Fuel Oil Distillate and Fluid Catagrrticiigly Cracked No. 2 Distillate (Blend 0. Blend No. 1 Plus 0.025% Calcium Salt of 44 Light-.

Hydrogenated Rosin. Blend No. 1 Plus 0.05% Calcium Salt of 44 'lrace+.

Hydrogenated Rosin. Blend No. 1 Plus 0.1% Calcium Salt of 60 Do.

Hydrogenated Rosin.

Make-up of Fuels, Percent by Vol.:

Straight-Run Fuel Distillate No. 2, Doctor-Sweetened.

Thermofor Cat-Cracked No. 2 Fuel Oil D late istil Concentration of Additive: Percent by West Texas weight on oil. Storage Time: 1 month Sludge AppearancebfSttlIII:II:

2 months Slud e g A glrliearance of Steel l 3 mon s Sludge 4 mon s Sludge Apl liearance of SteeL.

5 mont s Sludge A ggearance of Steel 6 mon s- Sludge ApEeaI anceo SteeIIIIIII:I

7 mont s-- Sludge AppearanceEr'sEEiIIIIIIIII:

TABLE II Light stability test No. of hours of ultraviolet light required to sludge $32 52: Sample Description samples at End of Test (40 Trace Light Medium hours) /50 Blend Eastern Vene- 4 12 28 Medium+.

zuela Straight Run and Fluid Catalytically Cracked (Blend No. 2).

Blend No. 2 Plus 0.025% 4 40 Light.

Calcium Salt of Hydrogenated Rosin.

Blend No. 2 Plus 0.05% 4 Traee+.

Calcium Salt of Hydrogenated Rosin.

Blend No. 2 Plus 0.05% 4 vDo.

Barium Salt of Hydrogenated Rosin.

A storage test was also carried out to determine the stability of the fuel oil compositions disclosed herein. This test was carried out by pouring 1500 cubic centimeters of the fuel to be tested into a two-quart Mason jar and immersing an 8 inch by 1 inch by inch SAE 1020 cold rolled steel strip in the oil. The steel surface to oil ratio approximates that existing in a 55 gallon steel drum. The jar was then closed with a vented lid and was stored in total darkness. Periodically sampling and testing were carried out as rapidly as possible in subdue light. The extent of deterioration of the fuel was determined by the amount of precipitate observed and designated as Trace, Light, Medium or Heavy. Any staining or corrosion of the steel strip was also noted.

In the following tables there are tabulated the results obtained in storage tests on the oils alone and stabilized fuel oil compositions of the invention.

TABLE IV Laboratory storage tests Make-up of Fuels, Percent by Vol.2

West Texas Straight-Run Fuel Dis- 50 50 tillate No. 2, Doctor-Sweetened. Thermofor Cat-Cracked No. 2 Fuel 50 50 Oil Distillate. Concentration of Additive: Percent by 0.005

weight on oil. Storage Time: 1 month Sludge S1. Trace.-. Appearance of Steel. K 2 months Sludge Appearance of Steel 3 months- Sludge Medium+.. Appearance of Steel. S1. Stain.- OK 4 months- Sludge Medium+.. Light.. Appearance of Steel Stained-.- Sl. Stain.- 5 months- Sludge Medium+... Medium..- Appearance of Steel--. Stained.. Stained.-- 6 months- Sludge Medium+... Medium Appearance of Steel Stained Stained...

S1. Trace... S1. Trace.

K OK.

Trace Light. K OK.

Trace Light.

Light Light.

S]. Stain- Stained.

Light+ Light.

Stained. Stained.

From the results given. in the foregoing tables it will be seen that the mixed oils possess poor stability properties. These results also show that mixtures of straight run and catalytically cracked oils are materially improved with respect to stability to sludge formation by the addition of certain divalent metal salts of at least partially hydrogenated resins. The stability of the mixed oil to sludge formation is improved with the addition of as little as 0.005 per cent of a compound of this class; however, major improvement is obtained by the addition of 0.01 per cent. Even greater improvement may be obtained in some cases by the addition of 0.05 per cent. Also stabi ity to sludge formation is obtained when larger amounts are employed but the addition of excessive amounts will necessarily increase the ash and undistillable residue in the oil and is not usually required for normal storage conditions. Therefore, when positive control of sludge formation is desired, it is preferred to employ at least 0.005 per cent of the divalent metal salt of at least partially hydrogenated rosin and it is not necessary to employ more than 0.05 per cent. In any case, the total amount of the hydrogenated rosin salt need not exceed 0.1 per cent of the mixed oils.

The tests employed in obtaining the data set out in the tables are especially severe tests of the compounded oils and the results are given in terms of the quantity of sludge deposited without regard to the nature of the sludge. In practice, however, the quantity of sludge formed is frequently not as important as the physical characteristics of the sludge. The addition of a very small amount of a compound of the class described to a mixed fuel oil affects the characteristics of the sludge, making it lighter and apparently more easily dispersed so that the sludge deposition is avoided or at least materially lessened. To accomplish variation in the nature of the sludge as well as some control over the actual formation of sludge, as little as 0.005 per cent by weight of the mixed oils of the divalent metal salt of at least partially hydrogenated rosin can be used. Consequently, as previously pointed out, we generally prefer to employ the salt in an amount equal to about 0.005 to about 0.05 per cent by Weight of the mixed oils.

Although the compounds employed in the tests, the results of which are given in the tables, are preferred for use in the fuel oil compositions of the invention, it will be understood that other members of the class of compounds disclosed above may be used to prepare fuel oil compositions of the invention, it will be understood that other members of the class of compounds disclosed above may be used to prepare fuel oil compositions of substantially the same improved properties. In other words, the invention includes other hydrogenated rosin metal salts wherein the metal is selected from the group whose only simple metal salts are divalent metal salts. Nickel, for example, is suitable.

If desired, the stable fuel oil compositions may contain in addition to the compounds previously discussed oxidation inhibitors, flash point control agents, corrosion inhibitors, anti-foam agents, ignition quality improvers, combustion improvers and other additives adapted to improve the oils in one or more respects.

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

We claim:

1. A fuel oil composition comprising a major proportion of a mixture of straight run and cracked distillate fuel oils tending to deposit sludge and a minor amount, sufficient to inhibit sludge deposition from said mixture of oils, of a divalent metal salt of a hydrogenated rosin of at least about 40 per cent saturation, wherein said metal is selected from the group of metals whose only simple salts are divalent metal salts.

2. A fuel oil composition comprising a major amount of a mixture of straight run and cracked distillate fuel oils tending to deposit sludge and a minor amount of from 0.005 per cent to 0.1 per cent by weight of the mixture of a divalent metal 'j salt of a hydrogenated rosin of at least about 40 per cent saturation, wherein said metal is selected from the group of metals whose only simple salts are divalent metal salts.

3. A fuel oil composition comprising a major amount of a mixture of straight run and cracked distillate fuel oils tending to deposit sludge and a minor amount of from 0.01 per cent to 0.1 per cent by weight of the mixed fuel oil of the calcium salt of a hydrogenated rosin of at least about 40 per cent saturation.

4. A fuel oil composition comprising a major amount of a mixture of straight run and cracked distillate fuel oils tending to deposit sludge and a minor amount of 0.01 per cent by weight of the mixed fuel oil of the barium salt of a hydrogenated rosin of at least about 40 per cent saturation.

5. A fuel oil composition comprising a major amount of a mixture of straight run and cracked distillate fuel oils tending to deposit sludge and a minor amount of at least 0.005 per cent by weight of the mixed fuel oil of the nickel salt of hydrogenated rosin of at least about 40 per cent saturation.

6. A process for treating a composition consisting essentially of a mixture of straight run and cracked distillate fuel oils from which sludge has begun to deposit to prevent further substantial deposition of sludge which comprises introducing into said fuel oil composition containing sludge a minor amount sufiicient to inhibit further sludge deposition of a divalent metal salt of a hydrogenated rosin of at least about 40 per cent saturation, wherein said metal is selected from 10 the group of metals whose only simple salts are divalent metal salts.

7. A process for treating a composition consisting essentially of a mixture of straight run and cracked distillate fuel oils from which sludge has begun to deposit to prevent further substantial deposition of sludge which comprises introducing into said fuel oil composition containing sludge a minor amount of from 0.005 to 0.1 per cent by weight of a divalent metal salt of a hydrogenated rosin of at least about 40 per cent saturation, wherein said metal is selected from the group of metals whose only simple salts are divalent metal salts.

Name Date Bartleson et al July 17, 1951 Number

Claims (1)

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF A MIXTURE OF STRAIGHT RUN AND CRACKED DISTILLATE FUEL OILS TENDING TO DEPOSIT SLUDGE AND A MINOR AMOUNT, SUFFICIENT TO INHIBIT SLUDGE DEPOSITION FROM SAID MIXTURE OF OILS, OF A DIVALENT METAL SALT OF A HYDROGENATED ROSIN OF AT LEAST ABOUT 40 PER CENT SATURATION, WHEREIN SAID METAL IS SELECTED FROM THE GROUP OF METALS WHOSE ONLY SIMPLE SALTS ARE DIVALENT METAL SALTS.