US2875029A - Stabilized liquid fuel - Google Patents

Description

2,875,029 STABILIZED LIQUID FUEL Leo A. McReynolds," Barflesville, kla., assignor to Phil lips Petroleum Company, a corporation of Delaware No Drawing. Application May 21, 1953 Serial No. 356,589

sclaims." c1: mu-

- This invention relates to the stabilization of liquid hydrocarbon fuels. In one of its more specific aspects, the invention relates to the prevention of gum formation in liquid fuels. In another of its more specific aspects, the invention relates to the prevention of gum formation in liquid fuels during periods of storage, especially under the influence of light'and/ or oxygen.

It is well known that when liquid fuels such as gasoline, diesel fuel, jet fuel, fuel oil and the like, are stored, especially under the influence of light and/or oxygen, chemical changes occur which affect the color and increase the gum formation. Gum formation in liquid fuels adversely affects the operation of equipment in which such fuels are used, such as internal combustion engines, domestic and industrial burner systems, etc., by clogging feed lines, screens, nozzles and the like. It is conventional practice to add gum inhibitors to hydrocarbon materials ranging from the gasoline boiling range through the furnace oils and diesel fuels range. The hydrocarbon fuels which contain large amounts of cracked distillates are particularly subject to the problem of gum formation.

Each of the following objects will be attained by at least one of the aspects of this invention.

.An object of this invention is to provide a stabilized liquid fuel. Another object of the invention is to provide a liquid fuel stabilized by the addition of a minor portion of a product ofthe oxidation of selected high molecular weight hydrocarbons to, such fuel. Another object of the invention is to provide a method for enhancing'storage stability of liquid hydrocarbon fuels.

Other and further objects of this invention will be apparent to those skilled in the art upon study of the accompanying disclosure. 1

Broadly speaking, this invention comprises the stabilization of liquid hydrocarbon fuels by the addition thereto of between 0.0001 and 0.1 weight percent based on the liquid hydrocarbon, preferably between 0.001- and 0.01

2,875,029 Patented Feb. 24, 1959 r 2 boiling in the range ofabout 380 F. to 640 F.,' include Pennsylvania, Mid-Continent, Califorina, East Texas, Gulf Coast, Venezuela, Borneo, and Arabic crudes. The source of the crude from which the petroleum fraction is derived does not significantly influence the preparation or properties of the stabilizing additive, provided the petroleum fraction has been prepared by subjecting the crude to certain necessary treatments to exclude undesired materials therefrom.- a

In the preparation of the preferred petroleum fraction from which the stabilizing additive is produced, a crude oil is topped, i. e., distilled to remove therefrom the more volatile, lower molecular weight hydrocarbons such as gasoline and light gas oil, and then vacuum reduced to remove heavy gas oil and light lubricating oil of the SAE 10 and 20 viscosity grade. The vacuum reduced crude is then propane fractionated to remove an overhead fraction of about 100 SUS at 210 F. viscosity. The residue from the second fractionation may be subjected to a propane fractionation to remove still another overhead fraction of about 575 SUS at 210 F. viscosity. Propane fractionation maybe modified by the presence of butane, ethane,

weight percent of a product of the oxidation of a selected preparation of this additive includes substantially saturated diene polymers, such as polybutadiene, and olefin polymers having from 2to 12 carbon atoms, per monomer molecule, such as polypentadiene, polypropylene, polyethylene, polyisobutylene, etc., preferably having a ratio of carbon atoms to olefin bonds ofat least 40:1 and not less than 16:1, copolymers such as styrene-olefin copolymers, alkylated polystyrene, and a petroleum lubricating oil fraction which has substantially no asphalt within its natural state orwhen deasphalted and which has been solvent extracted to reduce the content of aromatic hydrocarbonstherein and preferably dewaxed. Petroleum fractions which are suitable for oxidation to produce the stabilizing additive, i. e., a stabilizer. for normally liquid hydrocarbon fuels ranging from the gasoline boiling range to about 720? F., preferablythe furnace oils andfueloils 1 or methane to the extent desired.

Following the propane fractionation step the overhead oil fraction is solvent extracted with a selective solvent which will separate the paraflinic hydrocarbons from the more aromatic-type hydrocarbons. Suitable selective solvents for aromatic hydrocarbons include among others the various phenols, sulfur dioxide, furfural and ;8,B'-dichlorodiethyl ether. This solvent extraction step for the removal of the more highly aromatic compounds can be carried out in accordance with the well-known concurrent or countercurrent solvent extraction techniques as well as by the well-known dual solvent technique. The resulting solvent extracted material, before or after the removal of the more aromatic hydrocarbons, is preferably dewaxed. Dewaxing may be carried out by any conventional method, e. g., by solvent dewaxing using propane or solvent mixture such as methyl ethyl ketone or methyl isobutyl ketone with benzene at a suitable temperature.

Each of the phenol extracted, dewaxed, propane-fractionated oils have been used in preparing the additive material of this'invention with goodresults but the oil fraction from the second propane fractionation is preferred. It will be recognized by those skilled in the art that propane fractionated oils differing from those described may be used or a single broad viscosity out can be used. The residual material from the final propane fractionation contains the rejected asphalt and more aromatic oils.

Although the preferred method for preparation of feed stock is as above described, other methods may be used to bu'tadiene which is prepared by sodium-catalyzed polyrnerization of butadiene and which material is subsequently hydrogenated so as to reduce the olefinic unsaturation thereof to a desired amount, is another suitable feed stock for use in the production of the additive material of this invention. When butadiene is polymerized, only one double bond remains therein for each butadiene group of the polymer. The feed material of this invention should be hydrogenated suflicientlyso that the ratio of carbon atoms to double bonds is at least 167to 1. Preparation of liquid polybutadiene may be obtained bymeans of the process set forth in U. S. application Serial No. 67,098, filed De camber 23, 1948, by W. W. Crouch, now-- PatentNo.

ciently to increase the ease of oxidation and to'increase the oil solubility.

Another suitable feed material is a high molecular weight polymer prepared by zirconium tetrachloride polymerization of propylene. Still another material which has proved to be useful as a'feed-rnaterial for the oxidation step inthe preparation of the additive materialof this invention is a tacky polymer prepared by the polymerization of propylene over chromia-silica-alumina catalyst as more fully disclosed in U. S; applicationSerial No. 333,576, filed January 27, 1953, by John P. Hogan and'Robert L. Banks, now'abandoned (see U. S. Patent 2,825,721, March 4, 1958). Another suitable feed material is a copolymer of styrene with olefins in which the olefin portion constitutes at least 50 percent of the total molecular weight of the molecule. With any of these feed materials, it is desired to reduce the amount of olefinic unsaturation to such an extent that theratioof carbon atoms to olefinic bonds is preferably at least 40:1 and not less than 16:1. The hydrocarbon stocks which are useful in the practice of this invention include those materials which are identifiable as having the following properties set-forth in Table 1.

1 Viscosity index not determinable for non-Newtonian materials.

The lubricating oil and polymers having a similar viscosity which are suitable as feed stocks for the production of the oxidation product used as the stabilzcdadditive of my invention, are set forth as follows in Table 2.

TABLE 2 Property Broad Preferred Range Range Refractive Index no 1.4401.520... 1.480-1.515. Average Molecular Weight. 5501,300.-.- 600-900. Minimum Molecular We1gl1t.. 450

Viscosity, SUS at 210 F Viscosity Index Carbon Atom Content per Molecule;

It appears that during; oxidation, scission takes plac'e'in the large hydrocarbon molecules. This is substantiated by passing nitrogen gas through the oil at 250 C. and collecting the volatile products which were negligible. Only a very small amount was collected when the temperature was raised to 300 C., thus'demonstrating that the major cause of the formation of the volatile products is oxidation and not thermal decomposition nor stripping of'light ends originally present in the oil. With oils of moderate molecular weight, scission cannot take place in any position but what one or'all of the fragments is sufficiently small that distillation takes place, thus preventing accumulation of molecules appreciably smaller than those originally present. Hence, the viscosity is not de-. creased to any great extent. Concomitant with theoxidative scissionreaction there is a'polymerizationor condensation reaction resulting in an increase inviscosi'ty. The

net change in viscosity is "apparently dueto the"re'lative 7 magnitude of eachreaetiom- In very high molecular weight hydrocarbons the oxidative scission more frequently results in fragments which have molecular weights too large to be removed by distillation and, hence. the molecular weight decreases causing a decrease in viscosity especially during the initial portions of the oxidation period. As the oxidation reaction proceeds, the reactions causing increa'sedmolecular weight may ofiset,

more or less, those, causing a decrease in molecularweight; As a result, the molecular weights of cna'rge oils" having molecular weights in the lower range tend toincrease and those in the higher'range tend to decrease during the initial oxidation period;

If desired, the petroleum oil fraction which has been highly refined as described above may be further subjected to additional refining treatments, for example, these petroleum fractions may be hydrogenated to convert any aromatic compounds therein to the correspondingnaphthe'nic' and saturated hydrocarbon, or if desi:ed, these petroleum fractions may be subjected to contact with silica gel for thepreferential adsorption and removal of the more aromatic hydrocarbons therefrom.- Generally, the petroleum fraction which is oxidized for the production of the stabilizing additive of this invention should contain not more than 20 percent of the carbon atoms in aromatic rings asdetermined by ring analysis. It is preferred that the aromatic content of the petroleum fraction be reduced to an economically feasible'cxtent by refining procedures since oxidation of aromatic type hydrocarbons tend to result in the formation of oil-insoluble products not suitable for the present invention. It 'also appears that aromatic constituents oxidize more readily' than do the non-aromatic components. Thus, failure to remove the most aromatic materials from the feed before oxidation results in formation of considerable oil-insoluble materials. Usually a suitable petroleum fraction, upon distillation under reduced pressure, e. g., molecular distillation, will produce a first 10 percent by weight fraction which has a viscosity of more than 50 SUS at 210 F., preferably more than SUS at 210 F.

Thelubricating oils, such as highly refined petroleum bright stocks which'are employed in the oxidation reactionto prepare the stabilizing additive, can be additionally treated so as to yield a desired solid product of improved color properties as more fully disclosed and claimed in the U. S. application by W. B. Whitney, Serial No. 264,840, filed January 3, 1952, now U. S. Patent No. 2,786,803 issued March 26, 1957. The additive material which is produced without this type of treatment is very dark red in color. An outstanding improvement resulting from this additional treatment is that the stabilized additive is much lighter in color than a product obtained without this treatment and does not produce as dark a color in a" liquid hydrocarbon fuel composition containing the same; I

Broadly speaking, this additional treatm'ent comprises treating'the'charge'stock prior to oxidation by contacting itwith silica'gel o'ra similar solid-selectiveadsorbent for the removal of the more" aromatic hydrocarbon types. Accordingly 'a' lubricating'oil stocksuch as a petroleum bright stock'which has substantially no asphalt, a low aromatic content and, preferably, low waxcontent, is additionally treated with silica gel at about room-temperature, usually in the range 40 F. to 70 F., and a suflicient pressure differential is maintained" across-the bed or mass of silica gel so asto cause 'asatisfact'ory flow therethrough of the lubricatingoil fraction being treated. The charge stock which is thus treated may be any-hydrocarbon fraction suitable for the production of the additive of this invention, usually a hydrocarbon fractian having a viscosity in the range 70 to 700 SUS at 210 F., preferablya lubricating" oil fraction inthe'rang'e 1l5"to 300 S US at"210 F. A highly refined lubricatin'g'oil in these ranges will generally have an averagemolecular 'we ight in'tliera'nge'SSO 'to"1100. It is preferred that the hydrof fractionating conditions ozone.

(1) An increase in the carbon to hydrogenweight ratio (2) An increase in molecular weight (3) An increase in the oxygen content (4) A decreased solubility inpropane under propane Allthese changes are broughtabout by contacting an above-described selected hydrocarbon fraction undersuitable conditions of temperature and pressure with an oxidizing agent such as free oxygen, sulfur trioxide, nitrogen dioxide, nitrogen trioxide," nitrogen pentoxide,.aci dified chromium oxides and 'chromates', permanganates, peroxides such as hydrogen peroxide, sodium peroxide and Any oxygen containing material capable of releasing free oxygen under the oxidizing conditions may be used. Suitable other specific oxidizing agents include air, relatively pure commercial grade oxygen, oxygen enriched air, and a mixture of oxygen with an inert gas,

such as. carbon dioxide and nitrogen. Even oxygen admixed with natural gas or methane is satisfactory. Air

having less than the usual amount of oxygen may also be usedi Air iseconomically a preferred oxidizing agent.

Generally the oxidation reaction is carried out at a temperature in the range of from ---40? F. to 800 F.

' When using an' active oxidizing agent such as sulfur trioxide, temperatures in the'range of 40 F. to 400 F.,

preferably 70 F. to 200 Frare used. With less active oxidizing. agents, such as air, higher temperatures are used, such as .100 F. to 800 F., preferably 390? F. to

575?. F. Higher oxidaitiodtemperatures result in a faster oxidation reaction. when the oxidizing. agent is in the gaseous phase, another variable whichafiects the rate of the oxidation reaction is the partial pressure of the oxidizing agent. Accordingly, as the pressure at which the oxidation reaction is vcarried out is increased,

other conditions remainingfthe same, theoxidation re action proceeds at a faster'rate. Therefore, depending 6 minimize reaction. time while readilyand easily controlling the reaction.- j T Conditions. which have'been found to be satisfactory for producing the stabilizing additive from a selected hydrocarbon fraction when using a moderate oxidizing agent, such as air, are set forth Table 3.

'reached (as measured by increase in viscosity). 25'

: diluted with a modifying solvent.

utilized in this operation undersuitable temperature con- TABLE- 3 Reaction Condition Broad Preferred M Range 1 Temperature," F 375-5 76 Time of Oxidation, hrs 5-50. Pressure, p. s. i. a 15-100; Rate of introduction of oxidizing agent in a. c. f. (standard cubic feet) per pound of oil per hour 0.01'-3.0.'.-- 0.040.4.

' Exemplary of the influence of various variables upon the oxidation reaction, it is pointed out that at a temperature of 482 F. and at an air introduction rate of about-0.32 s. c. f; per pound of oil per hour and'at about atmospheric pressure, the oxidation reaction requires about '20, hours before the desired degree of completion is 7 When the air rate was increased to 1x44 s. c. f. per pound of oil per hour,"o nly 16 hours were required to convert the ;oil to an oxidized product of similar viscosity. Increas- 'ing*the reaction temperature to 572 F. decreased the time required for oxidation appreciably- Reducing the reaction temperature to below 390 F. increased the re- ,action time under these conditions.

' More active oxidizing agents, such as sulfur trioxide may also be used in the oxidation step as pointed out above. When liquid sulfur trioxide' is utilized as the oxidizing agent; the reaction is most readily carried out when both the oil and sulfur trioxide are separately Solvents which may be ditionsinclude liquid sulfur" dioxide, .hexane, tetrachloroethylene, ethylene dichloride, pyridine,-nitrobenzene and dioxan'ev a Liquid sulfur trioxide'is an cxtremely'reactivc compound and, ifadded directlyto the oil, will cause excessive eharring and violent splattering. It' is necessary to upon the rate of oxidation desired, the oxidation reaction" is carried out at sub-atmospheric, atmospheric or superatmospheric pressure. Usually it is preferred to carry out. the oxidationreaction at apressure betweenabout 10--and..10O lbs. per square inch absolute depending up on t he composition or. oxygen content'of the oxidizing gas. Lower or higher. absolute pressures maybe satisfactorily used if desired; :Lower'oxidat'ion pressures are useful in that they facilitate 1 release and rem oval of the more volatile, andzother, undesirable materials, e. g.,

-H O'from the reaction mixture.

The rate of oxidation is also dependent upon and: in-

.fluenced by the distribution of the'oxidizing gas within thereactionmixture and the rate of introductionof the 1. oxidizing gas] thereto. Theoxidizing agent is preferably introduced and; present .in the reaction mixtu r'e in a finely .dispersed state in order, to achieve bettercontact with the 1 materials undergoing, oxidation, and bettermixing therexwith sAn increase in the rate of introduction of the toxidizing gas of course increases the rate ofoxidation,

moderate this excessive reactivity by dilution with -a solvent such as those disclosed above.- A'molar'ratio of solvent to sulfur 'trioxide of at least about 1:1 appears to be necessary and it is preferred to use a ratio of 2:1 or greater; Dilution of the oil is also very desirable for the reduction of viscosity and to facilitate mixing, but

such a dilution is'not required. Dilution of the oil may .be obtained withsome non-reactive solvent other than that utilized for the dilution of the sulfur trioxide.

Use ofthe same diluent, however, simplifies thefrecovery problem. Gaseous 50;, may be introduced into the oil vdirectly or mixed with a-carrier gas such as air, nitrogen or other inert gas. In the case of gaseousSO an elevated temperature, e; g., 200 to 300 C., may be used.

The extent of oxidation is determined by theratio of oil to sulfur trioxide. The weight ratio may be varied frornhl to 3,051 but ispreferably maintained the range of between3:l to 18:1; -;Ratios from 3:1 to

.j The initial reactionof the other conditions remaining unchanged. The, conditions ;of temperature, pressure, oxygen content of; the oxidizing gas, rate of introductionof:oxidizing gas, ctc.,:are ,',correlated, adjusted. andlcontrolled so as ,to carry out i he c d i u b tasvf sntl r v d it",

8:1 are the most desirable. Very low ratios result in the use of excessive amounts-of sulfur trioxide without obtaining a corresponding increase in useful product. Very high ratios fail to obtainsuflicient oxidation to be economical;

' sulfur trioxide with oil is almostfinstantaneous at room temperature or above, butreaction continues for extended periods of time, c. g.,

fup to asniuchastl tthoursor more. 'At'hi'gher tem- ,pe raturcs, the time of I the slower secondary reactions is shortened to less thanj24 hours. The evolution of sulfur dioxide and other 'gaseseausesmuchfoaming and the rat, t r ctioni mus h icg i tolles .sut iqm y permit the ea-pastry er the apparatus warn-aliens aimi- -ing. reaction mixture. .The time requiredto'r reaction may beishortened to unless thIeeminu'tes,"in tvliiehcase, secondary reac'tionsdono take place to any great extent. 'The quality ofthe product is not materially affected by the leng'thof reaction time orbythe absence or occurrence of the secondary reactions.

The-temperatures-which may-generally be utilized .in theoxidationreaction, whereinrsulfur trioxide is used as the oxidizing agent, range from -40 F. to 400 F., preferablyfrom' 70F. to'200'F. A very short period of time, usually'less than three hours, is required 'for the initial reaction. l I 7 After the reaction, the"projductis .treatedifor the-removal'of' acid and other. impurities. Acid'isconveniently removed "from the product by water washing. .Thenproduct is concentrated :in' the manner. discussed --later .in connectionwithl zthe product obtained in a. process .utilizing .a less activeioxidizing agent. Theadditive produced .bysulfur .trioxide oxidation is somewhat improvedin colorby-reduction. This-is preferably accomplished by? treatment in. alcohol-, with lithium .hydride'or withzinc. and hydrochloricsacid. Catalytic .hydrogenation'or chemical reduction may also .be used.

I The extent: to which the;.oxidation reaction is. carried out is dependent uponlthe selected -oil fraction being oxidizedan'd .the-yi'eldof additivematerial desired. -I have found that if :the oil, being oxidized contains a relatively low concentration oflower molecular .weight hy- 30 drocarbons the oil maybe oxidized to a considerable ex- :-tent, upto as'high as 75 percentbyweightofthe oil charged, without any deleterious effects-.npon thereaction itself or the-:additive ,material. AlsQzI .have observed that when the aromatic contentof the charge stocloislow,

- suchqas below about 5. percent byweightof carbonatoms in aromatic rings and especially below; about 2-.'.pe,r.. nt --by weight-the. charge stock can be oxidizedto; agreater extent without .any undesirable efiects or .adversely .:af-

.-fecting the-yield such as may.happen-whenthereis an appreciable amount, above about percent by weight of aromatic -carbon atoms present therein. V-iugeneral, the oxidation reactionds carried out. until the oxidized oil has increased in viscosity, when expressed in'Saybolt Universal seconds SUS)'.at,2l0F., from 70.5 to-SO fold,

preferably from 3:10 .10 fold, over that of (the originally a charged :unoxidized .oil. When the oxidation. reactionis carried out to-a 3 to 10.fold-inerea se-;in, viscosity the yield of active 'stabilizingadditive recovered from the oxidized oil-amounts .to about to 50 percent by weight "of the original unoxidizedoil. .Continuedoxidation, es-

pecially aboveabout 1. 60 ipercent, ,tends to produce; a 'certain amount of oil-insoluble; oxidized-materials.Which,

although they do 1not-adverselyafiect the eflectivenessof ithefoilfsoluble; additive, .dowadversely affect the yield. of; 4 :.;the. desired product. -:;Also; since vit is; often necessaryto eremovethese.oileinsoluble oxidized materials, itis desir- E :able therefore. notfto continue the oxidation. reaction (beyond 'that point. .at which the oil-insoluble .materials are *:.produced.

The stabilizing-. additiveof this inventionproduced vduring the oxidation reaction zdissolyes-in the lubricating --Ioil;frorn which it isvprepared since it is.oil soluble. The oxidized reaction. mixture itself, is useful. .as .the hydrocar- .--bon. fuel1 additive since itpossesses. thestabili'zing proper- -.rties when added to -or compounded with; that.;-fuel. Itis often desirable to prepare a concentrate or theactive0lid additive. material which comprises. substantially-only the-solid additive-material. Irritant/maria additive rnaterial can: be recovereddirectly from the. oxidized .reaction: mixture.-, by. solvent.,,extract ion= 1 whiehjs selective forulthe. re1ative1v..iui1 ized, :,es s;en

ti y vl b t is atnthe sameatirneessentiallstano" solventlf -actives-additive material ,in the... ,i'eactionwinixture.

a ,solvent n: material itherem.

and ivhichsqly m able solvents forthere'coveryof the "solid active additive preferred in the pra'ctice;of. this invention to employ material *fi'oni use oxidized {reaction -.mixture include propane, isopropyl alcohol, a solvent mixtureotpropane:

with 'rifioditying-amounts (up to about150 .p'ercent-Tby Weight) of other low-boiling hydrocarbons .such .as methane, ethane, and; butane. Other selective :solvents. such as methyl ethyl ketone, methyl isobutyl ketone, tertiary "'butyl alcohol, isobutyl alcohol, ethyl acetate,

,dioxane, morpholine, dimethyllformamide, phe'nol and I t1.1res;of,. the two at appropriate temperatures so asto 120 dissolve pmyrhe oil, and lower molecular weight oxida- .tion, material. The proper temperature will dependupon the ratio inf-solvents andjthe percentage of product to be dissolved. 'I he undissolved material is thereafter 'me- Vchanically,separated from the dissolved material.

I Whenthesematerialsare used in obtaining the active additive material from the oxidized reaction mixture the active, solid additive is recovered as a propane insoluble,

oil-soluble, solid phase (raffinate) the inefiective substantially hydrocarbon material of the reaction mixture beingdissolved in tli'e treating materialas an extract.

,Thepropane soluble phase from which the active additive materialis. separated has a viscosity index much .higher than that of the unoxidized oil This p'ropane soluble phase may be used toblend with an o'ilforlthe purpose of imp'roving the viscosity index of that oil.

In the recovery of the active additive material, itis propaneas aselective solvent, the solid active additive .being recovered as a separate propane insoluble phase .un'denpropane fractionating conditions of temperature,

[pressure and ratio of solvent to material being treated (usually 5:1 to, 25:1 by vol.). The solvent extraction operation forthe recovery of theactive additive material 1s usually'ca'rried on ata temperature in the range F. to.250 F. especially in the range F. to F. and a pressure ofbetween200 p. s. i. g. to 500 p. s. i. g. Countercurrent solvent extraction techniques are usefully employed as well as multiple, solvent extraction stepsof separately contacting and recovering'the undissolved active additive. I

In many instances, the activity of the additive'material is considerably increased by additionally treating this recovered solid additive material with. an aliphatic al oho int e C3 to .Ca anse has isoprbpyl o .an Jrfl t v n fa Pur fied an m wire 7 iro ie ars l d' t at e t. h a.

ald'eh yde sgaiid fth'e like which may be oxidation proadditive there eohol insoluble phase. The alcohol two=fold purpose. "Traces of peroxides,

motors 'are removed thereby. In addition thereto, -1t appears that a beneficial chemical change takes place during stripping of residual, alcohol solvent'from the I additive material.

The'above-described sequence of recovery and purification stepsdoes not in some i nstances greatly influence the quality and efiectiveness of the solid; finaladditive product. It is preferred to employ a propane fractiona- 'tionstep prior-to the organiepola'r' compound-heating "step to avoid emulsions which arediflicult to break-and which present operational difiicultieswhen' the alcohol or ketone-treatin'gstep precedes the propane. solvent. ex-

- tractionstep.

Normally liquid -hydrocar bon-fuel-- to whiche'thi'ssta bilizing 'additiveis added'may be any of thefuelsrangi ingthrou'gh ,the gasoline boiling range to and;through the fuel oil's and dieselfuel range and even as high as -720 F." Althoughfairly large'quantities of this. additive .will tend to discolor the fuel towhich it is added, it should liquid hydrocarbon fuel. a

The stabilizing additive disclosed hereinabove is more fully disclosed and discussed in the U. S. application of W. B.- Whitney, Serial No. 304,659, filed August 15,

.1952, now abandoned. In that application, the product of oxidation has been disclosed as being useful as an ashlessdetergent in lubricating oil. 1

The following examples are illustrativeof the subject invention and of the advantages to be obtained in the practice thereof; These examples are not intended to be unduly limitative of this invention.

Example I The stabilized additiveused in the following examples was preparedas follows: 403 pounds. of finished 250 lubricating oil blending .stock were charged to a 50 gallon still. Air was passed through the oil in the still at a rate of 7 standard cubic feetper minute; The pressure was adjusted to 25 p. s. i. g. and the temperature to 482 F. and held there throughout'the ,run. The run was continued until the viscosity of the oil had increased to about 350 SUS at 210 F. At the conclusion of the run, which required 10.6 hours, a liquid overhead product of 12.9 pounds had been collected and consisted of two phases, 1. ve., an aqueous phase of 8.4 pounds and an oil phase of 4.5 pounds. 7 The oxidized oil was withdrawn from the still and was charged to a propane fraction column which was operated under the conditions and with the results set forth in Table I N TABLE I.--PRIMARY PROPANE FBACTIONATION Top columntemp fF 150 Oil charge temp., F .132 Propane charge temp., F 115 Bottom column temp., F.. 110 Column pressure, p. s. i. g 450 Oil charge rate, G. P. H. 60 F 2.2 Propaneto oil ratio, vol. (estimate) 5.8 On stream time, hr 21 wt. per- 2.0 Vls., Rd Products lbs. cent of SUS 70 0. Color charge overhead 283.1 80.6 134.7 1. 4806 25+ bottoms 68. a 19. 4

All of the overhead product from the above described propane fractionation was charged to a 50 gallon batch still. The oxidation air rate was adjusted to 5.8 s. c. f. per minute. The pressure raised to 25 p. s. i. and the temperature raised to 482 F. and held there throughout the run. The run was-continued until the viscosity of the oil had increased to about 600 SUS at 210 F; At the conclusion of the'run, 21.1 pounds of liquid overhead product had been collected which consisted of 12.2 pounds of aqueous phase and 8.9 pounds of oil phase.

The oxidized oil from the secondary oxidation was charged to a propane fractionation column. Table II presents data on this fractionation step.

TABLE II.SECONDARY PROPANE FRACTIONATION Top column temp., F 150 Oil charge temp., F 132 The bottoms product of this fractionation constituted the stabilizing additive and themateriaL used in the following examples.

Example Il Filtering tests were made on a fuel oilwith and without the stabilizing additive of a fuel with a 50:50 blend of light cycle oil and straight run stove oil. Thefilter test was conducted in a jet fuel filtering apparatus.

The test procedure utilized was as follows: A-fuel reservoir containing a sample of the fuel was connected to the apparatus and a slight air pressure was applied to the. fuel so as to force it into the filtering system. Bubbles were worked out of the flow lines and the flow regulator was adjusted so. that a flow of 6.0n'1illiliters per minute per square centimeter of square filter area was obtained. A total of 50-100 milliliters of fuel-was allowed to pass throughthe system at room temperature to equilibrate it. The relay was deactivated and the pinch clamp was closed. The temperature of the filter bath was adjusted to 70 Rand after the fuelin the filter bath had been raised to the desired temperature, flow-was resumed by reactivating the relay and opening the pinch clamp. The filtrate was received in a graduated cylinder and readings were taken for each 10 milliliters filtered so that a' curve relating pressure and volume could be plotted. The filter is considered clogged TABLE DBL-VOLUME FILTERED VBJPRESSURE DROP Pressure Drop (mm. Hg)

Volume Filtered ml. of fuel oil Aged Fuel Aged Fuel Aged Fuel (No De 0.0005 wt. +0.001 wt. tergent) Percent Percent Detergent Detergent insoluble residue lay-filtration A. Apparatus: r

(1) Gooch-typePyrex, crucible with fritted glass disk having a porosity of 14 microns v (2) Filter flask, 250 nil., equipped with funnels and 3 rubber crucible holders B. Reagents:

(1) ASTM naphtha (2) Acetone v (3) Nitric acid, concentrated (4) Sulfuric acid, concentrated A Gooch crucible was thoroughly cleaned by immersing it in a hot acid bath (maintained at 240 F. to 280 F.) consisting of approximately 3 parts concentrated nitric acid and one part concentrated hydrochloric acid. After the crucible was allowed to remain in the hot bath for 2 hours, it wasco'oled and rinsed thoroughly with tap water-{distilled water, and finallywith acetone. This was followed with a one-hour drying period in an oven at 150 C. Crucible was then transferred to a cooling vessel and allowed to cool for at least one hour before weighing. A sample of distillate fuel in the amount of 100 ml; was filtered by suctionthrough the weighed Gooch .crucible.

Crucible was then transferred to an other filter flask. .The vessel which containedthe sample of vfuel oil was then washed with three portions of ASTM naphtha and the washings were added to the crucible after each rinse. Following this step, the outside and the bottom of the Gooch crucible werecarefully washed with AST M naphtha to remove all traces of oil. Crucible was thendried forone hour at 150 C., tranferred'to a cooling ves'sel and allowed to cool for 2 hours before reweighing. Residuewastheincrease in weight calculated as milligrams per 100 1. of sample. The data are giveni'n Table IV.

V TABLE. IV.'INSVOLUBL E GUM ged at 150 F. for 14 days in dark glass bottles] Insolu- (mg/100 ble Gum ml.)

Before After Aging Aging (1) Blend with no additive 0.9 4. 7 (2) (1) 0.0005 wt. percent'detergent..- 0. 4 2. 1 (3) (1) 0.001 wt. percent detergent 1.8 1. 9

- From the dataset forth in thefabove examples, it is clear that gum formation is readily inhibited in the 'normally'liquldhydrocarbonfuel. warren-Salutations {of this invention will be apparent to those "skilled in "the art, but su ch modifications are believed tobe clearly within the spirit and the scope of this invention.

1. A stabilized fuel consisting essentially of normally liquid hydrocarbon and between 0.0001 and 0.01 weight percent of a -gum-formation-inhibiting oxygenated component obtained by oxidation of an aliphatic hydrocarbon fraction in which the ratio of carbon atoms to olefinic bonds is at least 16:1, having a refractive index n in the range of 1.440 to 1.520, an average molecular weight in the range of- 550 to 10,000-and substantially all components thereof having a minimum molecular weight of 450, a viscosity in the range of 50 to 1400 SUS 'at'210 F.', a viscosity index (when determinable) inthe range of 50 to and an average carbon atom content per molecule in the range of 40 to 720.

2. The fuel of claim '1 'in which said component has an acid number below 50, a 'sapon'ification number in the range of 0-100, and an oxygen content in the range of 1 to 15 weight percent. a

3. The stabilized fuel of claim 1 wherein said normally liquid hydrocarbon hasa boiling range below 720 F.

4. The fuel defined in claim 1 further. characterized in that saidhydrocarbon fraction is obtained from a topped, distilled, and vacuum reduced crude and is substantially free of asphalt.

5. The fuel'defined in claim '1 further characterized in that said hydrocarbon fraction is obtained from a topped, distilled, and vacuum reduced crude substantially free of asphalt by propane fractionation and solvent extraction to remove aromatics.

6. A gasoline having dissolved therein a small but gum inhibiting amount of an oil/soluble, propane insoluble, isopropyl alcohol insoluble, solid, oxygenated hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2 ,875 ,029 February 24, 1959 Leo A, McReynolds It s hereby certified that error appears in the printed specification i of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 4, line 64, for "40 Fm to 70 F," read 40 F., to 170 it,

Signed and sealed this 29th day of December 1959 (SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,875,029 February 24., 1959 Leo A. McReynolds It is hereby certified that error a of the above numbered patent requiring 0 Patent should read as corrected below.

ppears in the printed specification orrection and that the said Letters Column 4, line 6 fer "40 1 to 70 F," read 0 F.,, to 170 F,

Signed and sealed this 29th day of December 1959,

E Attest:

KARL Ho AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents

Claims (1)

1.A STABILIZED FUEL CONSISTING ESSENTIALLY OF NORMALLY LIQUID HYDROCARBON AND BETWEEN 0.0001 AND 0.01 WEIGHT PERCENT OF A GUM-FORMATION-INHIBITING OXYGENATED COMPONENT OBTAINED BY OXIDATION OF AN ALIPHATIC HYDROCARBON FRACTION IN WHICH THE RATIO OF CARBON ATOMS TO OLEFINIC BONDS IS AT LEAST 16:1, HAVING A REFRACTIVE INDEX ND20 IN THE RANGE OF 1.440 TO 1.520, AN AVERAGE MOLECULAR WEIGHT IN THE RANGE OF 550 TO 10.000 AND SUBSTANTIALLY ALL COMPONENTS THEREOF HAVING A MINIMUM MOLECULAR WEIGHT OF 450, A VISCOSITY IN THE RANGE OF 50 TO 1400 SUS AT 210*F., A VISCOSITY IN THE RANGE OF 50 TO 1400 IN THE RANGE OF 50 TO 125 AND AN AVERAGE CARBON ATOM CONTENT PER MOLECULE IN THE RANGE OF 40 TO 720.