US2980517A - Stabilization of fuel oils - Google Patents

Description

'United. States Patent Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., acorporation of Delaware No Drawing. Filed May 31", 1957, Ser. No. 662,584

7 Claims. (Cl.-4462)' This invention relates to stabilization of blended distillate fuel oils. More particularly, the invention relates to stabilization of mixtures of catalytic'ally cracked and straight run fuel oil distillates during storage at ambient atmospheric temperatures. I

Uncompounded distillate fuel oil compositions are often troublesome with regard to sludge deposition and color degradation during storage at normal atmospheric temperatures. Sludge deposits in distillate fuel oils are objectionable in that such deposits can causeclogging of burner filters, screens, nozzles, etc., and thereby lead to improper functioning of the combustion apparatusi'n which the fuel oil is consumed.

. Although sludge deposition sometimes occurs in straight run distillate fuel oils and frequently occurs to a substantial degree in catalytically cracked fuel oil dis-v tillates, sludge deposition in blends of straight run and c'atalytically cracked fuel oil distillates presents an entirely distinct problem from that encountered with either component oil. While the sludge formed in such blended oils probably contains some sludge of the type formed by each component oil, the sludge formed in blended fuel oils is of different composition and is consistently greatly in excess of the amount that can be accounted for from the known sludging tendencies of the individual component oils.

It has heretofore been proposed to inhibit sludge deposition from mixed distillate fuel oils by incorporation therein of oil-soluble chemical inhibitors which are consumed during combustion of the oil.

It has now been found that sludge deposition in such mixed oils can be greatly alleviated by maintaining. the

oil in contact with an oil-insoluble inhibitor during;-

storage, which inhibitor can be used repeatedly and which is not consumed during combustion. The present invention, based on this discovery, relates to a process for improving the stability of mixed, catalytically cracked and straight run distillate fuel oils, and particularly to improving the stability of the mixed oils with respect to sludge deposition in order to improve the appearance of such oils and to render them more effective for use in fuel oil furnaces and the like, even after being stored for extended periods. We have found that improved storage stability in the mixed distillate fuel oils can be obtained by maintaining the mixed oils during storage at ambient atmospheric temperatures in contact with a sludge-inhibiting proportion of an oil-insoluble, strongly basic, anion exchange resin. Strongly basic anion exchange resins comprise a polymeric matrix having a. plurality of quaternary ammonium hydroxide groups 'associated therewith. Typical of the class are resins comprising the hydroxide form of a tertiary aminequaternized, haloalkylated copolymer of about 80 to 99.9 percent of a monovinyl aromatic hydrocarbon and about 0.1 to percent of a divinyl aromatic hydrocarbon. We"

have also found that the moisture content of the resin is important insofar as the stability of the fuel oil is concerned. For best results the resin should" contain at least about percent water, and preferably from about percent water up to the pointof saturation. Co' polymers containing 0.5 to 6 percent divinyl aromatic 2,980,517 Patented Apr. 18, 1961 reduced fouling tendencies and greater exchange capaci ties in fuel oils; By way of example, excellent results are obtainable with a strongly basic anion exchange resin that comprises the hydroxide form of a dimethyl ethanol amine-quaternized, chloromethylated copolymer of about 99 percent styrene and about 1 percent divinyl benzene, that contains about 55' percent moisture. Copolymers of other monovinyl and divinyl aromatic hydrocarbo'nscan be used: For example, monovinyl aromatic hydrocarbons capable of forming copolymers within the scope of the invention are typified by the following: styrene, orthometaand para-methyl styrenes, ortho'-, metaand para? ethyl styrenes, vinyl naphthalene, vinyl anthracen'e, and their homologues. Examples of divinyl aromatic hydrocarbons that can' form copolymers included within the scope of the invention include divinyl benzene, divinyl" toluenes, divinyl naphthalene, divinyl ethyl benzenes', divinyl xylenes, and their homologues. An example of a preferred'haloalkyl group is the chloromethyl group. Examples of other haloalkyl' groups include chlorobutyl, bromoethyl, and the like. Preferred tertiary amine quaternizing agents include dimethyl ethanol amine and trimethyl' amine. Other suitable quaternizing agents in: clude triethyl and tripropylamines, dimethyl ethyl amine} diethyl cyclohexyl amine, tricyclohexyl amine, triph'enyl amine, diphenyl ethyl amine, benzyl dimethyl amine, benzyl phenylmethyl amine, methyl diethanolamine, methyl ethyl propanol amine, etc; Additional examples of resins included by the process of this invention include the hydroxide form of a diethyl cyclohexyl amine quaternized chlorobutylated copolymer of 96 p'ercen meta-methyl styrene and 4 percent divinyl benzene,an"d" the hydroxide form of a benzyl phenyl methyl mine quaterni-zed bromoethylated copolymer of 94 percent vinyl naphthalene and 6 percent divinyl xylene, each in a moisture saturated condition. 7 i

The predominant non-crosslinked portion of the chin:- I

ride form of a tertiary amine-quaternized haloalkylatedcopolymer of vinyl and divinyl aromatic hydrocarbons, for example, a trimethyl amine-quaternized chloromethylated copolymer of styrene and divinyl benzene can be represented by the following structural formula:

whereas the crosslinked portion can be representedas In'the hydroxide form, the chlorine atoms are substituted with hydroxyl' groups in the above structures.

It has not been determined exactly in what way the strongly basic anion exchange resins function to improve the stability of the mixed fuel oils. Accordingly, the invention is not limited to any particular theory of op eration. exchange resins act toremove impurities of a non-hydrocarbon nature, such as mercaptans, naphthenic acids,

hydrocarbons are particularly valuable because of phenols, etc., from the oil. However, thispo s'sibility is mo're'or' less negatived by the fact that mere percolation It'might appear that the strongly basic anion :a'lyze formation of sludge and color bodies.

exchange resins definitely do not function as sludge dissurface area.

' mum proportion of the resin. tical standpoint, it will normally heu-ndesirable to employ more than about percent resin by'weight' of the cording to the method of'this invention showed no ,sig-,

see er? vtaining the desired stability in the fuel oils, or at any time nificant changes, as compared with an untreated sample may be that the anionexchang'e resins act to remove sludge and color precursors asthey are formed. The sludge and color precursors mayin and of: themselves form sludge and color bodies, or they may merely cat- The anion pe'rsants, as they are entirelyinsolublein fueloil.

' The resinzoil proportions that are effective for the purposes of this inventionwill vary' primarily accordingto the degree ofcontact betweenthe resin and the fuel oil.

'bef orethis pointlhas been reached, the resins can be regeneraetd by treatment with aqueous caustic, that is, sodium hydroxide- The. method of regenerating spent anion exchange resins with aqueous caustic is conventional andneed not be described. in detail here. I

The stability problem with which the present invention is concerned exists when, a catalytically cracked and a straight-run oil are combined in such proportions as to cause a substantial, combined sludging effect of the Y type described above. Theinvention is important when the ratio of the volume of the catalytically cracked oil to thestraight run oilis within the range of 9:1 to 1:9.

I The invention is especially advantageous when; applied to mixed fuel oils containing these oils in a volume ratio The commercial resins as purchased, before conversion in the shape of small granules or' beads of relatively large For this reason, the degree of interfacial' contact between oil andresin is potentially. large, particularly in the eased the porous resin particles. Under I r rich inultraviolet rays, for periods of 4 hours alternated r ample, an improvement instabilitycan be obtained using as little as about 0.004 weight percent resin, particularly where the oil or the resin is circulated'to' improve theinterfacial contact. Normally, about 0.05 to'5'weight perce ntresin will eltect a substantial improvement in the,

stability of theoil. Since the anion exchange resins are oil-insoluble, there is no need, other than as maybe imposed by "practical considerations, to' restrict the maxi- However, from a mad oil. t

The desired intercontact between oil' and resin can be obtained inany convenient way in the storage containers For example. one or a number of oil-permeable containers containing small portions of the resin can be suspended at suitably spaced locations in the oil. Alternatively, permeable containers containing the resin can be suspended from a plurality of radially disposed arms which can be rotated continuously or intermittently to obtain the desired intercontact. Suitable permeable containers have been prepared from muslin, linen and nylon fabric (woven and unwoven) and from stainless steelscreen. Another way of obtaining the desired intercon tact is to circulate the oil from the main storage ,vessel through a bypass containing the resin. Still another method is to provide a lining for the storage vessels having the anion exchange resin particles disposed thereon. Also, sheets or strips of oil-resistant material, e.g., plastic, having anion exchange resin particles adhering thereto can be suspended in the oil during storage. The resin in finely divided form, so as to minimize settling, can

a lso be metered into the oil as it is pumped into the' storage container and recovered from the oil by filtration:

as 'the oil is removed from storage.

While the invention can be used in large storage ves-:

sels of the type emp'oyed in petroleum refineries, it is well-adapted for use in the smaller tanks of jobbers or be maintained When the resins are no longer capable offmaina within the range of 4:1 to 1:4.

4 In order to demonstrate the effectiveness in mixed-dis tillate fuel" oils of stronglybasieanion exchange resins of the class disclosed above, various tests were carried out,vi;ncluding alight stability test and a long term storage test. The light stability test was carried out by exposing a 4 oz. sample of oil to be tested to a light source with periods of 7 hours, during'which the oil was stored in. the dark- Theltest was completed after 72 hours exposure'tovthelight. Visual estimates were made of the sludge and color after each complete, eleven hour, fonj off cycler The exposure to light was accomplished by putting samples of fuel oil in 4 oz. flint. glass bottles. These bottles were placed in an enclosure adjacent a light; I 7

source whichwas a Hanovia, 52353314 type burner;

Analytical Model quartz lamp. The light so urce was i made intermittent by passing light from thevahove lamp through a rotating, slitted drum. "A Corning polished glass filter No. 9863 (24004000 angstroms) was inter-r posed between the lightsource and the oil sample bot ties. Thespeed of the rotating drum was 1 revolution in 3,;seconds. The evenly spaced, light-transmitting slits The distance Trace, Light,. Medium or Heavy. Seventy-two hours exposure under the conditions ofthis test correspond ap-.

proximately to 1 /2 to 2 years of normal storage in actual usage. The long term storage stability test was carried out by pouring 1500 ml; of the fuel to be tested into a two-quart Mason jar and immersing an 8 x 1%" x & SAE 1020 cold rolled steel strip in the oil. The steel surface to oil ratio approximates that existing in a 5 5 gallon steel drum. The jar was then closed with a vented lid and was stored in ,total darkness at ambient atmospheric temperature.

--- Periodic sampling and testing were carried out as rapidly aspossible in subdued light. The extent of deterioration of, the fuel was determined by the amount of precipitate observed and designated as Trace, Light, Medium or. Heal/1y. Any staining or corrosion of the steel strip was note In the following table there are given the results of light stability and storagetests made on mixed fuel oils of the. character indicated, both in the absence of a resin, and in contact with a strongly basic anion exchange resin of the class disclosed above. The resin employed in these tests is adequately identified as the hydroxide form of a porous, quaternized chloromethylated copolymer ofaboutw97 percent styrene and, about 3 percent divinyl benzene, that has been quaternized with dimethyl ethanol amine. The chloride form of a resinessentially identical with the foregoing is marketed as Amberlitc IRA 411.". The chloromethylated copolymer, as such, contained in excess'of 2 percent chlorine. The hydroxide form of the resin used in the tests was prepared by placing the corresponding chloride form of the resin in a chromatographic tube to a depth such that the height to diameter 8 Total exchange capacity:

Meq./ml. wet resin- 0.7. Meq./g. dry resin 3.0.

Typical wet screen analysis ratio of the resin column was approximately 10 to l. 5

The resin was then washed with 10 times its, volume of Standard screens) a solution of percent sodium. hydroxide, which was 'Sizeof mesh; Percent retained followed with distilled water washing until the eluate was 19:1. no longer basic. The resin was. then dried under vacuum 7 for 3 hours. The relatively dry resin then. was, suitably 10 29,3 hydrated by stirring'in'a. container with an excess of water for 15 minutes. After decanting the excess water 70v w .7 l 0,5 the resin was filtered through. a Buchner funnel. (.under Finesicemem: Lessfljafl 2%.

suction) to remove surface water.- The. moist res1n',.pre- I pared essentially as indicated, was then placedin a per 15 No. 2 fuel oil distillate is defined in the ASTM Standimeable, muslin container and the latter was substantially centrally suspended by a cord in the fuel oils. The by droxide form of the resin as prepared aboveis referred tohereinafter as Resin A. i

ards on Petroleum Products and Lubricants for 1956 under the designation D396-48T.

The following Table I light stability tests:

TABLE I Blend A Example I Example II Example III Sample Make-up:

Fuel Oil Blend, Vol. Percent- A. 31.3% West Texas, Doctor-Sweetened, Straight Run No. 2 Fuel Oil Distillate; 21.3% Virgin S'.R. No. 2 Fuel Oil Distillate;

47.4% Distillate. B. 31.3% West Texas, Doctor-Sweetened, No.

Fuel Oil Distillate; 21.3% Virgin S.R. No.

Oat. Cracked No. 2 Fuel Oil Fuel Oil Distillate? 47.4% Cat. Cracked No. 2 Fuel Oil Distillate. Ion-Exchange Resin A in Contact with Fuel Oil- G./ Ml

1 Water Saturation of Resin A, Wt. Percent Inspections:

Color, ASTM Uni n Gravity, API

Specific Gravity, 60/60 F Neutralization Value Total Acid Number" Total Base No Stability Test, Intermittent Ultra gh Glass Container, After Exposure to Light, Appear- Trace of Stein on ance. Bottom. Qualitative Estimate of Sludge- I 36 Hours Med1um+... Tracel-... Med1um+ Trace-F... Trace-l 72 Hours Heavy-- Very Heavy- Light+ Heavy. Color, ASTM Union 4- 4- 3.5- 3.5.

The corresponding chloride form of the commercial resin has the following characteristics:

Physical form Uniform, bead-like porous particles. Density as supplied, lbs. per cu. ft..- 41.

Moisture content as supplied, per- It will be seen, from the foregoing table that a strongly basic anionexchange resin of the class disclosed will effect a substantial improvement in the stability of mixed cata lytically cracked and straight run fuel oil distillates. It willalso be seen that the stability imparted by contact with the resin is reduced when using a resinv of relatively lower moisture content.

cent 53-63. In the following Table II. there are tabulated the results.

Screen grading (wet) mesh (U.S. obtained in the long term storage tests carried out on a standard screens) 20-50- 55 mixed distillate fuel oil alone and stored in contact with Efiective size, mm- 0.35-0.50. Resin A.

TABLE II Blend 0 Example III- Sample Make-Up:

Fuel Oil Blend, Vol. Percent- C. 33.3% Doctor-Sweetened W.T.S.R. No. 100 100.

2 Fuel Oil Distillate; 33.3% Coastal S.R No. 2 Fuel Oil Distillate; 33.3% Fluid Cat. Cracked No. 2 Fuel Oil Distillate.

Resin A- Grams per 1500 M1. Fuel Oil Weight Percent Moisture Content of Resin, Wt. Percent (Approx). Storage Stability Test:

After 6 months- After 1 year- Existent Insolubles (Visual)- Steel Strip, Appearance Existent Insolubles, Mg./l00 M1 Color, ASTM Union presents the data obtained in the r answer? From the data presented in the foregoing table it will be apparent that mixtures of catalytically cracked and straight run fuel oil distillates are stabilized by. maintenance in contact during storage with a strongly basic anion exchange resin. It will be understood that the present invention is notlimited to the specific embodiments given herein, and that other distillate fuel oil blends and other strongly basic anionexchange resins of the class disclosed herein can be substituted for the corresponding substances in thespecificexamples in, the same or equivalent proportions. For example, for Resin Athere can be substituted the water-saturated, hydroxide formof a porous, trimethyl amine-quaternized chloromethylated copolymer of about 97 percent styrene and about 3 percent divinyl benzene, or the saturated hydroxide form of a trimethyl amine-quaternized chloromethylated copolymer of 97.5 percent styrene, 1 percent divinyl benzene, and 1.5 percent ethyl styrene, and the like. Examples of commercial quaternary ammonium type resins that can. be used include, in addition, to Amberlite IRA 411, Amberlite IRA 400, Amberlite IRA 401, "Amberlite IRA 410, Dowex 1 and Dowex 2.

As another example of the practice of our invention, 3000 grams of a moisture saturated, trimethyl aminequaternized chloromethylated copolymer of 96 percent styrene and 4 percent divinyl benzene, in the hydroxide form, prepared from the commercially obtained corresponding chloride form as described in connection with Resin A, is suspended in ten equal portions in muslin bags at about equally spaced locations near the bottom of a cylindrical, 500 gallon storage tank to which there is added 500 gallons of fresh, No. 2 fuel oil (50-50 by volume straight run and catalytically cracked distillate). After six months at ambient conditions, the tank is emptied. The resin is collected and after removal of its volume of 8 percent aqueous sodium hydroxide, water washed, and returned while Wet to the tank for further Ilse.

All of the resins disclosed are regeneratable by treat? ment with dilute caustic, for example, by the same procedure described in connection with the generation of resin A from its corresponding'chloride form.

The use of stronglybasic, anion exchange resins is essential to the invention. Thus, for example, when a weakly basic, oil-insoluble, anion exchange material,

on the other hand, is one which on titration under the same conditions will show a titration curve like that of a weak base, such as ammonium hydroxide.

If desired, there may be added to fuel oils of the class disclosed herein, preferably, but not necessarily, after storage in contact with the anion exchange resin, sludge inhibitors, oxidation inhibitors, corrosion inhibitors, ignition quality improvers, combustionimprovers and/or other additives adapted to improve the oils in one or more respects. 1

Many modifications and variations of the invention as described herein will suggest themselves to those skilled in the art. Obviously, these can be resorted to without departing from the spirit or scope of the invention. Therefore, only such limitations should be imposed in the present invention as are indicated in the appended claims. l

We claim: 1 t I? 1. A process for stabilizing fuel oil comprising maintaining a mixture of catalytically cracked and straight run fuel oil distillates that normally tends to deposit sludge during storage in contact with a minor proportion, suflicient to stabilize the oils, of a strongly basic anion exchange resin that comprises a polymeric matrix groups associated therewith substantially throughout the period of storage of said mixture of oils at ambient atmospheric temperature, where the moisture content of t the resin is at least about 25 weight percent.

2. A process for stabilizing fuel oil comprising maintaining a mixture of catalytically cracked and straight run fuel oil distillates that normally tends to deposit sludge during storage in contact with a minor proportion, sufiicient to stabilize the oils, of a strongly basic anion exchange resin substantially throughout the period adhering fuel on, the resin is regenerated with ten times jfpf storage of said mixture of oils at ambient atmospheric temperature, said resin being the hydroxide form of a tertiary aminequ'aternized haloalkylated copolymer of about 80 to 99.9 percent of a monovinyl aromatic hydrocarbon and about 0.1 to 20 percent divinyl aromatic hydrocarbon, where the moisture content of the resin is at least about 25 weight percent.

calcium hydroxyapatite, in the proportion of about 2 grams per 1500 ml. of oil, was suspended in a run-of the-refinery, mixed distillate fuel oil and subjected to the long term storage stability test, both the uninhibited and the inhibited oil showed heavy sludge deposits after four months. The explanation for this is believed to reside in the fact that weakly basic anion exchange materials.

are insufliciently basic to react completely with all of the weakly acidic sludge and color precursors pr'es'ent'in mixed distillate fuel oil. The resins of the class disclosed herein possess a basicity comparable to that of sodium hydroxide.

It is to be emphasized that the resins disclosed herein.

3. The process of claim 2 where the copolymer contains about 0.5 to 6 percent divinyl aromatic hydrocartaining a mixture of catalytically cracked and straight run fuel oil distillates that normally tends to deposit sludge during storage in contact with a minor proportion of a strongly basic anion exchange resin substantially throughout the period of storage of said mixture of oils at ambient atmospheric temperature, said resin being the hydroxide form of a tertiary amine-quaternized haloalkylated copolymer of about 94 to 99.5 percent of a bility of the oil. .Mere once-through contacting the oil with the resin, as by percolation through a bed of the latter, is not suflicient. As a matter of fact, when this procedure was followed with fuel oil blend C and resin A, the treated oil was found to deposit more sludge than the untreated oil.

Proportions mentioned herein are by weight where not specified otherwise.

Strongly basic anion exchange resins'may be defined as those which on titration in a concentrated potassium chloride water solution, e.g., an 0.5 normal solution, with an equivalent amount of hydrochloric acid, will show a titration eurve'like that of a strong base, such as sodium hydroxide. A weakly basic anion exchange resin,

monovinyl aromatic hydrocarbon and about 0.5 to 6 percent of a divinyl aromatic hydrocarbon, where the moisture content of the resin is at least about 35 percent, where the tertiary amine substituents each contain 1 to 7 carbon atoms, and where the haloalkyl group contains 1 to 4 carbon atoms.

6. The process of claim 5 where the tertiary amine is 'dirnethyl ethanol amine and the haloalkyl group is chloromethyl.

7. The process of claim 5 where the tertiary amine is trimethyl amine and the haloalkyl group is chloromethyl.

References Cited in the file of this patent UNITED STATES PATENTS Coonradt et al. Apr. 22. 1958

Claims (1)

1. A PROCESS FOR STABILIZING FUEL OIL COMPRISING MAINTAINING A MIXTURE OF CATALYTICALLY CRACKED AND STRAIGHT RUN FUEL OIL DISTILLATES THAT NORMALLY TENDS TO DEPOSIT SLUDGE DURING STORAGE IN CONTACT WITH A MINOR PROPORTION, SUFFICIENT TO STABILIZE THE OILS, OF A STRONGLY BASIC ANION EXCHANGE RESIN THAT COMPRISES A POLYMERIC MATRIX HAVING A PLURALITY OF QUATERNARY AMMONIUM HYDROXIDE GROUPS ASSOCIATED THEREWITH SUBSTANTIALLY THROUGHOUT THE PERIOD OF STORAGE OF SAID MIXTURE OF OILS AT AMBIENT ATMOSPHERIC TEMPERATURE, WHERE THE MOISTURE CONTENT OF THE RESIN IS AT LEAST ABOUT 25 WEIGHT PERCENT.