USE OF ORGANIC FLUOROCHEMICAL COMPOUNDS WITH OLEOPHOBIC AND HYDROPHOBIC GROUPS IN CRUDE OILS AS ANTI-DEPOSITIN AGENTS, AND SAID COMPOSITIONS

Abstract: A method of inhibiting the deposition of paraffin wax, asphaltene, or mixtures thereof in a crude oil contaminated with paraffin wax, asphaltene, or mixtures thereof and susceptible to such depositions comprising the step of incorporating into said crude oil an effective deposition inhibiting amount of an oil soluble organic compound having at least one oleophobic and hydrophobic fluoro­ aliphatic group, and antideposition stabilized crude oil compo­ sitions containing said compound, are disclosed.

Description: The present invention relates to the introduction of an effective deposition inhibiting amount of an oil soluble organic compound having at least one oleophobic and hydrophobic fluoroaliphatic group crude oils contaminated with paraffin wax, asphaltenes, or mixtures thereof, and which oils are normally susceptible to deposition by such contaminants. The present invention relates to crude oils compositions contaminated with deposition susceptible paraffins, asphaltenes, or mixtures thereof, and containing an effective deposition inhibiting amount of such oleophobic and hydrophobic fluoroaliphatic group containing oil soluble organic compounds. Crude oils are complex mixtures comprising hydrocarbons of widely varying molecular weights, i.e. from the very simple low molecular weight species including methane, propane, octane and the like to those complex structures whose molecular weights approach 100,000. In addition, sulfur, oxygen and nitrogen containing compounds may characteristically be present. Further, the hydrocarbyl constituents may comprise saturated and unsaturated aliphatic species and those having aromatic character. Crude oils are normally contaminated with paraffine waxes and asphaltenes which can precipitate and create many problems for the oil producer. It is desirable to inhibit or to prevent the depo­ sition of said waxes and asphaltenes. Moreover low amounts of an additive are desirable to avoid separation problems. One embodiment of the present invention relates to a method of inhibiting paraffin wax or asphaltene deposition from a low water hydrocarbon crude oil contaminated with such paraffin wax or asphaltene or mixtures thereof by contacting said oil with an effective deposition inhibiting amount of an oil soluble organic compound having at least one oleophobic and hydrophobic fluoroaliphatic group, said group having between about 4 to about 20 carbon atoms. A further embodiment of the present invention relates to a deposition stabilized composition comprising crude oil contaminated with paraffin wax, asphaltene, or mixtures thereof and susceptible to deposition by such contaminants and an effective deposition inhibiting amount of an oil soluble organic compound, having at least one oleophobic and hydrophobic fluoroaliphatic group, dissolved therein. Preferably, the fluoroaliphatic group-containing oil soluble organic compound is added to the pipeline or well bore of the wax or asphaltene contaminated hydrocarbon crude oil. In order to insure rapid and efficient dissolution and dispersion of the fluoro­ aliphatic oil soluble organic compound, the deposition inhibitor may conveniently be added to the crude oil as a solution or semiliquid by dilution of the deposition inhibitor in a liquid oil soluble carrier. The amount used is preferably at least 10 parts by weight of fluoroaliphatic compound per milion parts by weight crude oil, especially 10 to 5000 and particularly 100 to 5000. Using fluoroaliphatic groups containing polymers from vinylmonomers, especially acrylates, the upper amount is preferably less than 5000 ppm. In a preferred embodiment are incorpoarted from 100 to 2000 ppm of the fluoroaliphatic compound. Advantageously, useful fluoroaliphatic oils soluble organic com­ pounds are those exhibiting a solubility in the crude oil to be treated of at least 10 ppm by weight at 80°C; which are sufficiently oleophobic such that a steel coupon treated with the fluoroaliphatic compound gives a contact angle with hexadecane of fifteen degrees or more; and wherein the fluorine content is generally between about 1 and about 70 weight percent of the fluoroaliphatic compound. Useful guides in selecting highly preferred fluoroaliphatic compounds useful in deposition inhibition are found in the laboratory screening techniques for paraffin and asphaltene deposition inhibition tests described hereinafter. Generally, suitable oil soluble organic compounds containing at least one oleophobic and hydrophobic fluoroaliphatic group can be represented by the formula [(R f ) n R′] m Z (I) wherein R f is an inert, stable, oleophobic and hydrophobic fluoroaliphatic group having about 4 to about 20 carbon atoms; n is an integer from 1 to 3; R′ is a direct bond or an organic linking group having a valency of n+1 and is covalently bonded to both R f and Z; m is an integer of from 1 to about 5000; and Z is a hydrocarbyl containing residue having a valency of m and being sufficiently oleophilic so as to impart an oil solubility to said compounds of at least 10 parts by weight per million parts of hydrocarbon crude oil. Suitable R f groups include straight or branched chain perfluoroalkyl having 4 to 20 carbon atoms, perfluoroalkoxy substituted perfluoro­ alkyl having a total of 4 to 20 carbon atoms, omega-hydro perfluoro­ alkyl of 4 to 20 carbon atoms, or perfluoroalkenyl of 4 to 20 carbon atoms. If desired, the R f group may be a mixture of such moieties. The integer n is preferably 1 or 2. Where n is 1, R′ may be a direct bond or a divalent organic linking group. The nature of the divalent organic linking group R′, when present, is not critical as long as it performs the essential function of bonding the fluoroaliphatic group, R f , to the oleophilic organic radical Z. In one sub-embodiment, R′ is an organic divalent linking group which covalently bonds the R f group to the group Z. Thus, R′ may, for example, be a divalent group, R o , selected from the following: -C₁-C₈alkylene-, -phenylene-, -C₁-C₈alkylene-R₁-C₁-C₈alkylene-, -C₁-C₈alkylene-R₁-, -R₁-C₁-C₈alkylene-, -R₁-C₁-C₈alkylene-R, -R₁-, -R₁-phenylene-, -R₁-phenylene-R₁-, -R₁-phenylene-C₁-C₈alkylene-, or -phenylene-R₁-, wherein, in each case said alkylene and phenylene are independently unsubstituted or substituted by hydroxy, halo, nitro, carboxy, C₁-C₆alkoxy, amino, C₁-C₆alkanoyl, C₁-C₆carbalkoxy, C₁-C₆alkanoyloxy or C₁-C₆alkanoylamino. The alkylene moiety may be straight or branched chain or contain cyclic alkylene moieties, such as cycloalkylene or norbornylene. R₁ and R independently represent: -N(R₂)-, -CO-, -N(R₂)CO-, -CON(R₂)-, N-(R₂)COO-, -OCO-N(R₂)-, -S-, -SO-, -SO₂-, -N(R₂)SO₂-, -SO₂N(R₂-, N(R₂)CON(R₂)-, -COO-, -OCO-, -SO₂O-, -OSO₂-, -OSO₂O-, -OCOO-, -O-, where R₂ is hydrogen, C₁-C₆alkyl or C₁-C₆alkyl substituted by: C₁-C₆aloxy, halo, hydroxy, carboxy, C₁-C₆carbalkoxy, C₁-C₆alkanoyl­ oxy or C₁-C₆alkanoylamino. Also, if desired, the amino group -N(R₂)-, above, may be in quaternized form, for example of the formula wherein a is 1, R₃ is hydrogen or C₁-C₆alkyl which is unsubstituted or substituted by hydroxy, C₁-C₆alkoxy, C₁-C₆alkanoyloxy or C₁-C₆­ carbalkoxy and X is an anion, such as halo, sulfato, lower alkyl­ sulfato such as methylsulfato, lower alkyl-sulfonyloxy such as methylsulfonyloxy, lower alkanoyloxy such as acetoxy or the like. Lower means a content of 1 to 6 carbon atoms. As an alternate sub-embodiment, R′, while being covalently bonded to both R f and Z may contain an ionic bridging group as an integral part of the chain linking R f to Z. Thus, for example, R′ may be selected from the following: or where R is -C₁-C₈alkylene-, -phenylene, -C₁-C₈alkylene-R₁-C₁-C₈­ alkylene-, -R₁-C₁-C₈alkylene-, -R₁-phenylene- or -R₁-phenylene-­ C₁-C₈alkylene-; where R is -C₁-C₈alkylene-, -phenylene, -C₁-C₈alkylene-R₁-C₁-C₈­ alkylene-, -C₁-C₈alkylene-R₁-, -phenylene-R₁- or C₁-C₈alkylene-­ phenylene-R₁-; s and t are independently 0 or 1; T is an anionic group, R f is as defined above and Q is a cationic group and wherein said alkylene and phenylene unsubstituted or substituted by hydroxy, halo, nitro, carboxy, C₁-C₆alkoxy, amino, C₁-C₆alkanoyl, C₁-C₆carbalkoxy, C₁-C₆alkanoyloxy or C₁-C₆alkanoylamino. Suitable anionic groups for T include carboxy, sulfoxy, sulfato, phosphono, and phenolic hydroxy. Suitable cationic groups for Q include amino and alkylated amino, such as those of the formula where each R₂ and R₃ are as defined above. Where n is 2 and m is 1, R′ is an organic trivalent group. Suitable such groups include those of the formula: wherein R₁ and R₂ are defined above; v and w are independently 1 or 0 and R o is alkanetriyl, arenetriyl or aralkanetriyl of up to 18 carbon atoms which may be interrupted by one or more hetero atoms, such as oxygen, sulfur or imino. The oleophilic organic radical Z can vary widely and is, in general, not critical, as long as the group performs the essential function of conferring the requisite oil solubility to the compound. For example, suitable oleophilic organic radicals, when m is 1 include, without limitation, conventional hydrophobic-oleophilic higher alky or alkenyl of 6-24 carbon atoms which are unsubstituted or substituted e.g. by chloro, bromo, alkoxy of up to 18 carbon atoms, nitro, alkanoyl of up to 18 carbon atoms, alkylmercapto of up to 18 carbon atoms, amino, C₁-C₁₈alkylamino, or di-C₁-C₁₈alkylamino; an aryl group, such as phenyl or naphthyl, the phenyl and naphthyl moiety of which is unsubstituted or substituted by alkyl of up to 20 carbon atoms, alkoxy of up to 20 carbon atoms, alkanoyl of up to 20 carbon atoms, alkanoyloxy of up to 20 carbon atoms or mono- or di-alkylamino of up to 20 carbon atoms; mono- or di-C₆-C₂₄alkyl­ amino-C₂-C₇alkylene; alkoxyalkylene of 4-20 carbon atoms which is unsubstituted or substituted by one or two C₆-C₂₄carbalkoxy or C₆-C₂₄carbamoyl groups; poly-C₆-C₂₄alkoxy-higher alkyl or akenyl of 6-24 carbon atoms; a heterocyclic group such as piperidino, pipera­ zino, azepino, N-pyridinium, morpholino, benztriazolyl, triazinyl, pyrrolidino, furanyl, tetrahydrofuranyl and the like, which are unsubstituted or substituted e.g. by halo, alkoxy of up to 18 carbon atoms, nitro, alkanoyl of up to 18 carbon atoms, alkylmercapto of up to 18 carbon atoms, amino or alkylamino of up to 18 carbon atoms; poly-C₂-C₃alkoxy-phenyl, the phenyl group of which is unsubstituted or substituted by alkyl of up to 20 carbon atoms; a group of the formula -(CH₂CH₂CH₂CH₂) g H and g is 2-80; a group of the formula -(CH₂CH₂O) b (CH₂) c (CH₂CH₂O) d H wherein b is 2-40, c is 2-80, and d is 2-40; a group of the formula wherein each e is 3-20, and each f is 3-20 and A is an anion; a group of the formula where p is 1-15 and q is 1-15 and R″ is alkyl of 6 to 22 carbon atoms or alkanoyl of 6 to 22 carbon atoms; or a group of the formula where R o , b, c and d are as defined above. Also, where m is 2 or 3, Z represents an oleophilic organic divalent or trivalent radical. Suitable such radicals include those wherein Z is an oleophilic di- or trivalent aliphatic, carbocyclic, hetero­ cyclic or aromatic group. For example, when m is 2, Z may represent an oleophilic polyalkyleneoxy containing group, the terminal members of which are covalently bonded to R′; an arylene group, such as phenylene or naphthalene which are unsubstituted or substituted, e.g. by alkyl of up to 20 carbon atoms, alkoxy of up to 20 carbon atoms, alkanoyloxy of up to 20 carbon atoms, alkanoylamino of up to 20 carbon atoms, halo, amino or alkylamino of up to 20 carbon atoms, or the like; an alkylene or alkenylene group of up to 20 carbon atoms which is unsubstituted or substituted, e.g. by alkoxy of up to 20 carbon atoms alkylamino of up to 10 carbon atoms, alkanoyl of up to 20 carbon atoms, alkanoylamino of up to 20 carbon atoms, or alkanoyloxy of up to 20 carbon atoms; a heterocyclic group, such as N,N′-piperazinylene, triazinylene, or the like. An alternate group of oil soluble compounds according to formula I are those wherein the R f group is pendant to an oleophilic polymer backbone. Suitable oleophilic backbones are those derived from condensation polymers and addition polymers. For example, the group Z may contain condensation units of the formula: (O-R₃-OCONH-D-NHCO) m wherein R₃ is an aliphatic triradical or tetraradical of 2-50 carbon atoms which is covalently bonded to the (R f ) n R′ groups and is selected from the group consisting of branched or straight chain alkylene, alkylenethioalkylene, alkyleneoxyalkylene or alkylene­ iminoalkylene; and D, together with the -NHCO groups to which it is attached, is the organic divalent radical of a diisocyanate. In a preferred subembodiment, D is alkylene of 2 to 16 carbon atoms; cycloaliphatic of 6 to 24 carbon atoms; phenylene that is unsubsti­ tuted or substituted by lower alkyl, lower alkoxy or chlor; dipheny­ lene, phenyleneoxyphenyl, phenylene (lower alkylene) phenylene, or naphthylene, where the aromatic ring is otherwise unsubstituted or substituted by lower alkyl, lower alkoxy or chloro. In an alternate embodiment, up to about 85 percent of the [(R f ) n R′] m R₃ groups may be replaced by the biradical of a bis-(2-aminopropyl)ether of a polyethylene oxide; an aliphatic polyol of up to 18 carbon atroms; a di- or polyalkoxylated aliphatic or aromatic tertiary amine of up to 18 carbon atoms; a lower alkylene polyether; or a hydroxy-terminated polyester having a hydroxyl number from 40 to 500. Suitable preferred condensation polymers and their preparations are described, inter alia , in U.S. Patent Nos. 3,935,277, 4,001,305, 4,046,944 and 4,054,592. Suitable oleophilic polymer backbones derived from addition polymers comprising the group Z include those wherein up to about 5000 groups of the formula (R f ) n R′- are attached to an oleophilic hydrocarbyl containing polymeric backbone. Suitable polymers include those wherein the additon polymer contains up to about 5000 units of the formula wherin R f , n and R′ are defined above, and R a is hydrogen or lower alkyl. Preferably R a is hydrogen or methyl. Such addition polymers are generally prepared, by methods known in the art, e.g. in U.S. 3,282,905, U.S. 3,491,169 and U.S. 4,060,681, by homo- or co-polymerizing the corresponding monomer of the formula wherein R f , n, R′, and R a are defined above, optionally with polymerizable vinylic comonomers. Suitable comonomers include: Ethylene and chloro, fluoro- and cyano-derivatives of ethylene such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, acrylonitrile, methacrylonitrile, tetrafluoroethylene, trifluorochlorethylene, hexafluoropropylene, acrylate and methacrylate monomers, particularly those with 1 or 12 or 18 carbon atoms in the ester groups such as n-propyl methacrylate, 2-methyl cclohexyl methacrylate, methyl methacrylate, t-butyl methacrylate, n-butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 3-methyl-1-pentyl acrylate, octyl acrylate, tetradecyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl acrylate, and phenyl acrylate; dienes particularly 1, 3-butadiene, isoprene, and chlorprene, 2-fluoro-butadiene, 1,1,3-trifluorobutadiene, 1,1,2,3-tetrafluoro butadiene, 1,1,2-trifluoro-3,4-dichlorobutadiene and tri- and pentafluoro butadiene and isoprene; nitrogen-vinyl monomers such as vinyl pyridine, N-vinylimides, amides, vinyl succinimides, vinyl pyrrolidone, N-vinyl carbazole and the like; styrene and related monomers such as o-methylstyrene, p-methyl­ styrene, 3,4-dimethyl styrene, 2,4,6-trimethyl styrene, m-ethyl styrene, 2,5-diethyl styrene; vinyl esters, e.g. vinyl acetate, vinyl esters of substituted acids, such as for example, vinyl methoxyacetate, vinyl trimethylacetate, vinyl isobutyrane, isopropenyl butyrate, vinyl lactate, vinyl caprylate, vinyl pelargonate, vinyl myristate, vinyl oleate and vinyl linoleate; vinyl esters of aromatic acids, such as vinyl benzoate; alkyl vinylethers, such as methyl vinyl ether, isopropyl vinyl ether, isobutyl vinyl ether, 2-methoxy ethyl vinyl ether, n-propyl vinyl ether, t-butyl vinyl ether, isoamyl vinyl ether, n-hexyl vinyl ether, 2-ethylbutyl vinyl ether, diisopropyl vinyl ether, 1-methyl-heptyl vinyl ether, n-decyl vinyl ether, n-tetradecyl vinyl ether, and n-octadecyl vinyl ether. Propylene, butylene and isobutylene are preferred α-olefins useful as comonomers. Suitable candidate compounds of the formula I containing one or more inert stble oleophilic and hydrophobic fluoroaliphatic groups, R f , and an oleophilic hydrocarbyl containing residue, represent a well known class of compounds widely described in the literature. For example, compounds of the formula I wherein n and m are 1 are described in U.S. 4,460,791; U.S. 4,302,378; U.S. 3,575,899; U.S. 3,575,890, U.S. 4,202,706; U.S. 3,346,612; U.S. 3,989,725; U.S. 4,243,658; U.S. 4,107,055; U.S. 3,993,744; U.S. 4,293,441; U.S. 4,107,055; U.S. 3,839,343; JP 77/88,592; Ger. Offen. 1,966,931; Ger. Offen. 2,245,722; JP 60/181,141; EP 140,525; JP 53/31582; CH 549,551; EP 74,057; FR 2,530,623; Ger. Offen. 2,357,780; JP 58/70806; Ger. Offen. 2,344,889; U.S. 3,575,890; U.S. 3,681,329; Ger. Offen. 2,559,189; U.S. 3,708,537; U.S. 3,838,165; U.S. 3,398,182; Ger. Offen. 2,016,423; Ger. Offen. 2,753,095; Ger. Offen. 2,941,473; Ger. Offen. 3,233,830; JP 45/38,759; JP 51/144,730; Ger. Offen. 3,856,616; Ger. Offen. 2,744,044; JP 60/151,378; Ger. Offen. 1,956,198 and GB 1,106,641. Compounds of the formula I wherein n is 2 or 3, or m is 2 to 4 are described, for example, in U.S. 4,219,625; Ger. Offen. 2,154,574; Ger. Offen. 2,628,776; Text. Res. J., 47 (8), 551-61 (1977); U.S. 4,268,598; U.S. 3,828,098; Ger. Offen. 1,938,544; Ger. Offen. 2,017,399; Ger. Offen. 2,628,776; Ger. Offen. 1,956,198; JP 47/16279; Ger. Offen. 1,938,545; Ger. Offen. 1,916,651; U.S. 3,492,374; U.S. 4,195,105; Ger. Offen. 2,009,781; U.S. 4,001,305 and GB 1,296,426. Compounds where n is 1 to 3 and m is in excess of 4, up to for example about 500, are described, inter alia , in U.S. 3,935,277; U.S. 2,732,370; U.S. 2,828,025; U.S. 2,592,069; U.S. 2,436,144; U.S. 4,001,305; U.S. 4,046,944; U.S. 4,054,592; U.S. 4,557,837; U.S. 3,282,905; U.S. 3,491,169 and U.S. 4,060,681. In a preferred embodiement of the invention, highly suitable candidate oil soluble organic compounds, containing at least one oleophobic and hydrophobic group, of formula I useful as antideposition agents in crude oils contaminated with paraffin wax, asphaltenes, or mixtures thereof, contain 1-70 % fluorine and have a solubility in crude oil of at least 10 ppm at 80°C and are advantageously screened for efficacy using simple laboratory techniques as described hereinafter. For example, in screening oil soluble candidate compounds of formula I for paraffin antideposition properties, it has been found that those compounds repeatedly applied to the surface of steel coupons from e.g. a 5 % by weight solution of candidate compound in a suitable volatile inert solvent, such as xylene, toluene, isopropyl acetate, methylene chloride, ethanol, watere or miscible mixtures thereof, and air dried after each application, which render the metal coupon sufficiently oleophobic such that hexadecane exhibits a contact angle with the treated coupon of fifteen degrees or more, are characteristically suitable for use in the instant invention. A second screening technique for oil soluble candidate compounds of formula I for paraffin deposition involves the determination of the comparative deposition reduction the paraffin contaminated crude oil to be treated by comparing the wax deposition of a treated oil, containing from 10 to 500 parts by weight of the compound of formula I per million parts oil, with a crude oil identical to the treated oil but without the fluorochemical candiate, in respect to the amount of residue retained on the walls of standard laboratory beakers in accordance with the Beaker Method more fully described hereinafter. While 100 ml Pyrex beakers are employed, the test may be run using, e.g. degreased stainless steel 100 ml beakers. Under the test conditions, those compounds in which the treated crude oil composition exhibits reduction in total beaker weight gain due to rsidual oil on the beaker surface have characteristically been found to be highly preferred. An alternate and generally efficient laboratory technique for screening preferred oil soluble candidate compounds of formula I for paraffin antideposition properties in the paraffin contaminated crude oil to be treated is the Static Cold Finger Method, described hereinafter. In this test 500 parts by weight of fluorochemical are added per million parts of crude oil. Depending upon the solubility of the fluorochemical under the test conditions, it is recognized that lesser amounts may be employed, to a minimum of about 10 parts by weight of fluorochemical per million parts crude oil, in the event that the candidate possesses but limited solubility. Those treated crude oil compositions exhibiting a reduction in the percent decrease in weight gain of the cold finger coil of at least 10 % vis-a-vis crude oil not containing the fluorochemical candidate qualifies such candidate as characteristically suitable for use in the instant invention. Preferred compounds generally inhibit paraffin deposition of crude oils in this method by a percent decrease in weight gain of the coil of at least 20 %, most preferably at least 40 %. A convenient laboratory screening technique for oil soluble candidate compounds of formula I for asphaltene deposition inhibition is the Asphaltene Deposition test described hereinafter, wherein a crude oil contaminated with deposition succeptible amounts of asphaltene is treated by dissolving 10 to 200 parts per million by weight of a compound of formula I to such oil and comparing the amount of asphaltene precipitate occassionaled by the addition of hexane as compared to an otherwise identical control sample of crude oil not containing the candiate. Preferably, 200 parts per million by weight of candidate compound is employed per part crude oil. It has been found that under the best conditions, those compounds which significantly inhibited the precipitation of asphaltene, e.g. at least 10 percent decrease by weight of asphaltenes collected on the filter paper, preferably at least 20 % and most preferably 50 %, characteristically result in the compound of highly suitable for use as an asphaltene inhibitor in the instant invention. It is to be understood that for purposes of easily and efficiently dispersing and dissolving the fluorochemical in the crude oil to be treated, it is generally advantageous to first dissolve or disperse the fluorochemical of formula I in suitable solvent which is generally compatable with the crude oil in the amounts employed. Suitable solvents vary widely but include, inter alia , conventional organic solvents such as toluene, xylene, cumene, aliphatic and or aromatic oil fractions, petroleum ether, isopropyl acetate, methylene chloride, alkanols and the like. In the following test descriptions and examples, all temperatures are given in degrees Centigrade and all parts are given in parts by weight unless otherwise indicated. Description of crude oils Crude oil A is paraffinic; originating from Utah, it has a pour point of 31°C, a paraffin content of 22 %, and a cloud point of 50°C. Its water content is 0.4 %, it is black and it has an API gravity of 35 %. Crude oil B is paraffinic; originating from Utah, it has a pour point of 45°C, a paraffin content of 35 %, and a cloud point of 66°C. Its water content is 0.05 %, it is yellow and it has an API gravity of 42 %. Crude oil C is paraffinic; originating from Utah, it has a pour point of 35°C, a paraffin content of 25 %, and a cloud point of 57°C. Its water content is 0.05 %, it is yellow and it has an API gravity of 36 %. Crude oil D is asphaltenic from off shore Italy; it has a viscosity of 39,500 cP at 25°C. Its estimated asphaltene content is 9 % and it has an API gravity of 14°. Description of laboratory test methods A. Paraffin Deposition 1. Hexadecane Contact Angles Degreased steel coupons (SAE 1010 1/2"x3"x1/8") are dipped for one minute in a 5 % solution of fluorochemical in a suitable solvent, then are removed and air-dried for one minute. The procedure is repeated five times and the coupons are air-dried for at least 30 minutes. Contact angles with hexadecane are determined using a Raume-Hart contact angle goniometer. Hexadecane is used as a testing liquid due to its structural resemblance to paraffin wax and ease of handling. The contact angle of hexadecane with untreated steel coupons is zero degrees; for a fluorochemical to be considered effective the contact angle for the coated coupon should be at least fifteen degrees. 2. Beaker method One hundred grams of crude oil are placed in a one-liter-bottle and heated to a temperature 10°C higher than its cloud point for five minutes. Seven 100 ml beakers are pre-weighed and left standing at room temperature. The crude oil is poured into the first beaker. After the first beaker is filled, its contents are immediately transferred to the secon beaker and the first beaker is put upside down. The procedure is repeated five times and the contents of the seventh beaker are tansferred to the bottle and the beaker is placed upside down. The total weight gain of the seven beakers is determined. Potential paraffin deposition inhibitors are added to a new sample of oil during the heating stage and the procedure is repeated. Deposition inhibitions is expressed as % decrease in beaker weight gain. 3. Static cold finger method A method similar to the one described by Hunt (Journal of Petroleum Technology), 1962, pp 1259-1269) is used: Nine hundred ml of a high paraffin crude oil are placed in a liter vessel and heated with gentle agitation to a temperature 10°C below its cloud point. A pre-weighed stainless stell coil of 0.25 inch outer diameter and a total surface area of 26 square inches is immersed in the oil for 45 minutes. Water circulating through the coil maintains its temperature 15°C below the cloud point of the crude oil. The coil is removed and the weight gain due to paraffin deposition is recorded. Potential paraffin deposition inhibitors are added to a new sample of crude oil and the procedure is repeated. Deposition inhibition is expressed as percent decrease in weight gain of the coil. B. Asphaltene Deposition As mentioned earlier, addition of low surface tension hydrocarbons depeptizes the asphaltene micelle and causes asphaltene deposition: Fifty grams of low gravity asphaltic crude are mixed with 50 grams of hexane and the mixture is heated at 50°C with gentle agitation for fifteen minutes. The diluted oil is then filtered through a Whatman # 2 filter paper and the asphaltene deposit collected is air dried and weighed. Potential asphaltene deposition inhibitors are added to a new sample of crude oil and the procedure is repeated. Deposition inhibition is expressed as percent decrease of asphaltenes collected on the filter paper. Examples 1-10: Hexadecane contact angles for compounds of the formula are determined employing the procedure previously described. Steel coupons are coated using toluene solutions. All contact angles are greater than fifteen degrees indicating that the tested compounds are useful as deposition inhibitors. Since many of the above compounds are soluble in hexadecane the angle may decrease as the coating dissolves in hexadecane; therefore only initial angles should be considered. Examples 11-13: Hexadecane contact angles are determined for some commercial fluorochemicals. Steel coupons are coatd using toluene solutions. The above contact angles indicate that the compounds of the examples are useful as paraffin deposition inhibitors. The rapid contact angle decrease (from 45° to 20°) for the FC 740 coated coupon is attributed to the dissolution of FC 740 hexadecane. Examples 14-21: The efficiency of compounds of the formula as paraffin deposition inhibitors is determined by the previously described static cold finer method. Crude A is used and it is held at 40°C. The water circulating through the coil is at 35°C and treating level of inhibitor in crude oil is 500 ppm. The above examples demonstrate great decreases in paraffin deposition. It should be noted that this is a static evaluation and even greater decreases may be observed in a dynamic system where precipitated paraffins are carried by the flowing crude oil. Example 22: A mixture of 1,58 g benzotriazole (0.0131 mole), 7.0 g C₉F₁₇CH₂CH₂SCH₂CH₂CH₂OCH₂CH₂ (0.0114 mole) and 34.24 g toluene, is heated to reflux (110-111°C) for 10.25 hours. Then 0.02 g boron trifluoride etherate are added and the reaction mixture is heated under reflux for 45 minutes. Removal of the toluene affords a product containing a mix of two isomers with the following structures I and II, as determined by ¹³C-NMR: Analysis: Calculated (percent): C 37.0; H 2.8; N 6.7; F 45.3. Found (percent): C 37.3; H 2.8; N 6.7; F 43.6. Example 23: A mixture of 26.8 g (0.05 moles) of 3-(1,1,2,2-tetra­ hydroperfluorodecanethio)-1,2-epoxypropane is reacted with 14.9 g (0.05 moles) of octadecyldimethylamine and 3.35 g (0.055 moles) of acetic acid in 179 grams toluene at 50-60° for 18 hours. The clear reaction product has the structure C₈F₁₇CH₂CH₂SCH₂CH(OH)CH₂(CH₃)₂C₁₈H₃₇O₂CCH₃ and is soluble at a 20 % concentration in toluene to 0°C. The product is coated on a coupon of cold rolled mild steel SAE 1010 and contact angle measurements are run. For hexadecane the angle is 50° (untreated steel = 0°, i.e. it wets completely). Its surface tension in toluene at 1 % is 26.0 dynes/cm (toluene = 28.2). Example 24: A 300 ml 3-neck reaction flask equipped with stirrer, nitrogen inlet, condenser and thermometer is charged with 30 g (0.03 mol) (R f2 -diol* and 35 g methylethyl ketone (MEK) which is dried over molecular sieves. After all diol has dissolved, 4.4 g 3,3,4-trimethyl hexane-1,6-diisocyanate (TMDI) (0.002 mol) are added followed by 0.01 g triethylamine. The mixture is heated to reflux for three hours, after which time free -NCO groups are not detected by IR. Then another 4.4 g TMDI are added, dissolved in 4.4 g MEK following after 1/2 hour by 4.5 g bis 2-aminopropyl ether of polyethylene glycol of MW 900 (BAPG-900) (0.05 mol) and 8.8 g TMDI together with 54 g MEK. The mixture is kept at reflux for 4 more hours at which time no -NCO are detectable by IR. Heating is discontinued and 93 g water were slowly added under vigorous stirring. A yellowish, slightly turbid solution resulted, whose solids content is adjusted to 25 %. *The diol has the formula where R f is a mixture of perfluoroalkyl chains consisting of C₆F₁₃, C₈F₁₇ and C₁₀F₂₁ (U.S. Pat. No. 4,001,305). Example 25: Methyl ethyl ketone (600 g) is charged to a 2 ℓ flask fitted with a stirrer, thermometer, nitrogen inlet and a condenser protected with a drying tube. 2,3-Bis(1,1,2,2-tetrahydroperfluoro­ alkylthio)butane-1,4-diol (600 g; 0.571 mole) (see example 25), is added together with a 1:1 mixture of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylenediisocyanate (80.16 g; 0.381 mole). All reagents are rinsed in with an additional 50 g MEK. The solution is heated to boiling and 50 g solvent is removed by distillation to effect azeotropic drying of all materials. Then dibutyltindilaurate (0.692 g; 1.14 x 10⁻³ mole; 2 mole % based on diol) is added as a catalyst and the solution is heated under reflux for 6 hours, when the reaction is judged to be complete by the absence of the N=C=O infrared band at 2270 cm⁻¹. The solution is cooled to room tempera­ ture (25°C) and diluted with MEK to a total of 2042 g (33 1/3 % solids). A portion of the above material is taken to dryness. A quantitative recovery of a resinous material is obtained. Elemental analysis showed 52.8 % F (theory: 53.4 % F). Infrared bands at 3460 cm⁻¹ (O-H str.), 3340 cm⁻¹ and 1705 cm⁻¹ (C=) str.) confirm the structure of the hydroxy-terminated urethane prepolymer. The hydroxy-terminated prepolymer (53.7 g solution, 17.9 g solids) is treated further at 75°C with dimer acid derived diisocyanate (6.0 g; 0.01 mole) (DDI, HENKEL Company) for two hours, then the urethane chain is completed by the addition of trimethylhexa­ methylene diisocyanate (2,2,4- and 2,4,4 isomer mixture) (1.05 g; 0.005 mole) and N-methyl-diethanolamine (1.19 g; 0.01 mole). Reaction is complete in three hours, as shown by the disappearance of the N=C=O band (2270⁻¹) in the infrared spectrum. Hexadecane contact angle on steel coupons is 73 ± 1 degrees. Example 26-29: The efficiency of the compounds whose prepartion is described in examples 22-25 as paraffin deposition inhibitors is determined by the previously described static cold finger method. Crude A is used and it is held at 40°C. The water circulating through coil is at 35°C and treating level of inhibitor in crude oil is 500 ppm. Examples 30-33: Potential paraffin deposition inhibitors are evaluated using the previously described beaker method. Testing levels of inhibitor in crude oil are 500 ppm. A comparison of example 30 with example 20 reveals that although 65 % inhibition is recorded by the coil method, the beaker method yields only 9.7 % inhibition for the same compound. This is an indication of the severity of the beaker method and any inhibition recorded using this method is an indication of the usefulness for a compound.

Claims: 1. A method of inhibiting the deposition of paraffin wax, asphaltene, or mixtures thereof in a crude oil contaminated with paraffin wax, asphaltene, or mixtures thereof and susceptible to such deposition comprising the step of incorporating into said crude oil an effective deposition inhibiting amount of an oil soluble organic compound having as least one oleophobic and hydrophobic fluoroaliphatic group. 2. A method according to Claim 1, wherein said compound has a solubiity in said crude oil of at least 10 parts by weight per million parts by weight crude oil. 3. A method according to Claim 1, wherein said fluoroaliphatic group contains between about 4 and about 20 carbon atoms. 4. A method according to Claim 1, wherein the oil soluble organic compound containing at least one oleophobic and hydrophobic fluoro­ aliphatic group is inocrporated into said crude oil by adding said compound to the crude oil as a solution or semiliquid containing the compound in a liquid organic soluble carrier. 5. A method according to Claim 1, wherein said oil soluble compound is of the formula [(Rf)nR′]mZ wherein Rf is an inert, stable, oleophobic and hydrophobic fluoroaliphatic group having up to 20 carbon atoms; n is an integer from 1 to 3; R′ is a direct bond or an organic linking group having a valency of n+1 and is covalently bonded to both Rf and Z; m is an integer of from 1 about 5000; and Z is a hydrocarbyl containing residue having a valency of m and being sufficiently oleophilic so as to impart an oil solubility to said compounds of at least 10 parts by weight per million parts of hydrocarbon crude oil. 6. A method according to Claim 5, wherein Rf is straight or branched chain perfluoroalkyl of 4 to 20 carbon atoms, perluforoalkoxy substituted perfluoroalkyl having a total of 4 to 20 carbon atoms, omega-hydro perfluoroalkyl of 4 to 20 carbon atoms, or perfluoro­ alkenyl of 4 to 20 carbon atoms, or a mixture thereof. 7. A deposition stabilized composition comprising crude oil conta­ minated with paraffin wax, asphaltene, or mixtures thereof and susceptible to deposition by such contaminants and an effective deposition inhibiting amount of an oil soluble organic compound, having at least one oleophobic and hydrophobic fluoroaliphatic group, dissolved therein.

Inventors: COOKE, THOMAS W., FALK, ROBERT A., KARYDAS, ATHANASIOS
Applicants: CIBA-GEIGY AG
Application year: 1987
Main classification: C10L1
IPC codes: C09K3, C10L1