FUEL OIL COMPOSITIONS

Abstract: Chemical markers are used in a fuel oil composition to inhibit the tendency of the composition to foam.

Description: Fuel Oil Compositions This invention relates to oil compositions, primarily to fuel oil compositions, and more especially to the control of foaming in such compositions. In the processing and transport of liquid fuels, foaming frequently occurs as the fuel is passed from one vessel to another. The foaming may interfere with the pumping of the fuel, and may be such as to require a reduction in pumping rate to allow foam collapse to avoid fuel spills. It is desirable to control foaming to permit higher rates of fuel transfer. US-A-3,233,986 describes certain organosilicon compounds as additives for reducing the foaming tendency of organic liquids such as liquid hydrocarbon fuels. Additives having the ability to reduce foaming tendency are generally known as "antifoams". A problem in using antifoams is that relatively large proportions thereof may be needed to give rise to a desired antifoaming effect. It has now surprisingly been found that chemical markers are able to control the foaming of additive-containing fuel oil compositions, advantageously at low concentrations in the fuel. Thus, a first aspect of the invention is use of an additive comprising a chemical marker for fuel oil that is detectable therein either by conversion to a colorimetrically identifiable tautomeric form thereof or by conversion to a colorimetrically identifiable reaction product thereof, as an anti-foam in a fuel oil. In a preferred embodiment of the first aspect of the invention, the additive also comprises one or more co-additives selected from a cetaπe improver; a stabiliser; a demulsifier; an anti-foam agent; and an anti-corrosion agent. The features of the invention will now be discussed in further detail as follows. THE CHEMICAL MARKERS Examples of these are known in the art. See, for example US-A-4,209,302; US-A-4,735,631 ; EP-A-509,818; and EP-A-609,591. They are chemical compounds that are dissolved in a liquid to be identified and which are then subsequently detected by an appropriate colorimetric test. Such tests maybe quantitative or qualitative and are known in the art. The present invention envisages two classes of chemical marker: one where identification is effected by a chemical reaction which converts the marker to a colorimetrically detectable product; and the other where the marker is capable of existing in two or more tautomeric forms, at least one of which forms is colorimetrically detectable. In the latter, which is preferred, identification is effected by changing conditions to convert the marker from a non-detectable tautomeric form to a detectable tautomeric form. A preferred chemical marker is an organic base capable of existing in the following tautomeric forms: a non-ionic form; and one or more ionic tautomeric forms such as an ammonium ion, an oxonium ion and a carbonium ion. A specific example is 'Rhodamine Base B' which is capable of existing in the following tautomeric forms. CETANE IMPROVER Examples are organic nitrates such as nitrate esters containing aliphatic or cycloaliphatic groups with up to 30 carbon atoms, preferably saturated groups and preferably with up to 12 carbon atoms. Examples of such nitrates are methyl, ethyl, propyl, isopropyl, butyl, amyl, hexyl, heptyl, octyl, iso-octyl, 2-ethylhexyl, nonyl , decyl, alkyl, cyclo-pentyl, cyclohexyl, methylcyclohexyl, cyclodecyl, 2ethoxyethyl, and 2-(2-ethoxyethoxy)ethyl nitrates. Octyl and 2-ethyl hexyl nitrates are preferred. Other examples of cetane improvers are fuel soluble peroxides, hydroperoxides and peroxyesters. STABILISER Fuel oxidation and other degradative reactions can lead to formation of sediment and increase the colour of the fuel. Such reactions may occur in some refinery streams, particularly from conversion/cracking processes. Moreover, continuous contact with air, dust and reactive metallic surfaces can further enhance degradation processes; this happens during fuel storage, particularly when fuel is stored for a long time. Examples of anti-oxidant/stabilisers that are known are hindered phenols and N.N'-di-sec-butyl-p-phenyienediamine, phenyl-α-naphthylamine, and 4-isopropylaminodiphenylamine. DEMULSIFIER Exemplary demulsifiers which may be employed in the practice of this invention include poly(alkylphenol) formaldehyde condensates and the polyalkyleneoxy modified reaction products thereof. These compounds are prepared by reacting an alkylphenol with formaldehyde and thereafter reacting the reaction product of the above with a C2 to CQ alkylene oxide such as ethylene oxide and propylene oxide. The demulsifiers have a generalized structural formula: wherein U is an alkylene of 2 to 6 carbons; y is an integer averaging between 4 and 10; x is an integer averaging between 4 and 10; and R5 is an alkyl having from 4 to 15 carbon atoms. Preferred demulsifiers described by the above formula are polyethyleneoxy modified methylene bridged poly(alkylphenol) polymers having a polyethyleneoxy chain of 8 to 20 carbons and preferably from 10 to 16 carbons and at least about 75 number percent of the polyethyleneoxy chains being within the range specified. The methylene bridged poly(alkylphenol) portion of the polymer has from 4 to 10 and preferably from 5 to 8 repeating methylene bridged alkylphenol units with 4 to 15 and preferably 6 to 12 carbons in the alkyl group, in preferred embodiments, the alkyl groups are a mixture of alkyls having between 4 and 12 carbon atoms. Illustrative alkylphenols include p-isobutylphenol, p-diisobutylphenol, p-hexylphenol, p-heptylphenol, p-octylphenol, p-tripropylenephenol, and p-dipropylenephenol, etc. Another type of demulsifier component is an ammonia-neutralised sulphonated alkylphenol. These compounds have the general structure: wherein R-| is a hydrocarbyl group having from 4 to 15 carbon atoms, preferably from 6 to 12. These compounds are prepared by sulphonating an alkylated phenol and thereafter neutralising the sulphonated product with ammonia. Another type of demulsifier is an oxyalkylated glycol. These compounds are prepared by reacting a polyhydroxy alcohol such as ethylene glycol, trimethylene glycol, etc., with ethylene or propylene oxide. Many of the compounds are commercially available from BASF-Wyandotte Chemical Company under the PLURONIC trademark. They are polyethers terminated by hydroxy groups and produced by the block copolymerisation of ethylene oxide and propylene oxide. The ethylene oxide blocks act as the hydrophiles and the propylene oxide blocks as the hydrophobes. They are available in a wide range of molecular weights and with varying ratios of ethylene oxide to propylene oxide. A further type of commercially available demulsifier comprises a mixture of alkylaryl sulphonates, polyoxyalkylene glycols and oxyalkylated alkylphenolic resins. Such products are supplied by Petrolite Corporation under the TOLAD trademark. One such propriety product, identified as TOLAD 286K is understood to be a mixture of these components dissolved in a solvent composed of alkyl benzenes. A related product, TOLAD 286, is also suitable. In this case the product apparently contains the same kind of active ingredients dissolved in a solvent composed of heavy aromatic naphtha and isopropanol. However, other known demulsifiers can be used. A demulsifier is a material that can cause an oil-water emulsion to break down to form discrete, separable oil and water phases, the oil being a fuel oil of this invention, for example at a concentration of 0.1 to 2,000 ppm by weight based on the weight of the fuel. It requires a balance between hydrophilic and hydrophobic properties. Thus, it must be sufficiently hydrophobic to dissolve in the oil of an oil/water emulsion to break the emulsion, and must be sufficiently hydrophilic to prefer the aqueous phase which separates from the oil phase after the emulsion breaks. The demulsifier may be a surfactant that alters the surface or interfacial tension of the droplets in the disperse phase of the emulsion to make them unstable, e.g. by raising the surface or interfacial energy. Demulsifiers may have a hydrophilic part and a hydrophobic part. They may, for example, be divided into two groups as follows: Group 1 is a condensate comprising a hydrophobic part and one or more oxyalkylated groups comprising the hydrophilic part. The hydrophobic part is derived from a precursor having one or more groups such as hydroxy groups; amino groups, i.e. primary, secondary, tertiary and quaternary ammonium groups; and halogen groups capable of a condensation reaction to form the oxyalkylated groups. The oxyalkylated group may, for example, have up to 50 oxyalkyl units per group capable of a condensation reaction, and each such oxyalkylated unit may, for example, have from 2 to 6 carbon atoms and may for example be ethoxy, propoxy, or butoxy. The oxyalkylated units in a particular oxyalkylated group may be the same or different. One example of demulsifier within Group 1 is a phenolic resin of the general formula below, being a precursor for the hydrophobic part, the hydroxy groups of which have been condensed to form oxyalkylated groups: where R represents an aliphatic hydrocarbyl group having from 3 to 24 carbon atoms such as 9 or 15, and n represents an integer from 1 to 20 such as 4 to 10. The hydrocarbyl group contains C and H atoms and is bonded to the rest of the molecule by a carbon atom. It may be straight chain or branched, be saturated or unsaturated, or by alicylic and may contain one or more hetero atoms (e.g. O, S, N) provided that such hetero atoms do not substantially alter the hydrocarbyl nature of the group. Preferably, R is an alkyl group. Such phenolic resins may be made by the base catalysed oxyalkylation of an alkyl phenol-formaldehyde resin made by acid catalysis. They are described in, for example, US-A-2,499,367. US-A-3-424,565; and US-A-3,752,657. The number average molecular weight of such oxyalkylated phenolic resins as measured by Gel Permeation Chromatography (GPC) may, for example, be up to 200,000 such as up to 150,000, preferably up to 50,000, more preferably up to 25,000, even more preferably up to 10,000. Another example of demulsifier within Group 1 is a linear mono or polyhydroxy compound, being a precursor for the hydrophobic part, the hydroxy group(s) of which has or have been condensed to form oxyalkylated groups. Such linear compounds may be mono or polyhydroxy alcohols such as mono or polyalkylene glycols, e.g. where the alkylene groups have from 1 to 6 carbon atoms, or pentaerythritol, or mono or polycarboxylic acids such as aliphatic fatty acids or adipic acid. Another example of demulsifier within Group 1 is a diglycidyl ether, the epoxide groups of which being ring opened with a hydroxy moiety, e.g. a polyoxyalkylene such as polyethylene glycol or polypropylene glycol to generate, in addition to the oxyalkyl groups, hydroxy groups which themselves can optionally be oxyalkylated to form a branched or cross-linked demulsifier. Another example of demulsifier within Group 1 is an oxyalkylated amine (primary, secondary, tertiary or quaternary) analogous to the above-mentioned oxyalkylated hydroxy compounds, and oxyalkylated fatty amines reacted with adipic acid. Examples of demulsifiers are also described in US-A-4,836,829. Group 2 is a compound having a sulphonate or sulphonic acid group as the hydrophilic part, attached to a hydrophobic part which may, for example, be a long chain alkyl group. Specific examples are alkyl aryl sulphonates. The demulsifiers used in this invention may also be characterised by their relative solubility numbers, referred to herein as RSN. The RSN can be correlated to the hydrolipophilic balance (HLB). RSN is determined by dissolving 1 g of the demulsifier in 50 ml of acetone and titrating distilled water into the solution until a permanent haze occurs. The number of mis of water added is the RSN. The RSN range of demulsifiers used in this invention is suitably from about 4 to about 25, preferably to about 20, typically between 8 and 11. Examples of demulsifiers that may be used in this invention are ethylene oxide/propylene oxide copolymers; p-alkylphenolformaldehyde resins of such copolymers and modifications thereof; polyester amines; amineoxyalkylates; oxyalkylates; cyclic-p-alkylphenolformaldehyde resins and complex modifications thereof; cross-linked polyols such as polyol esters, polymeric esters and resins, chain extended polyols, oxyalkylated chain extended polyols, alkoxylated fatty acids, and heteropolyols; amines such as oxyalkylated amines (e.g. ethoxylated amines) and polyester amines; oxyalkylated phenol-formaldehyde resins; sulphonates; sulphosuccinic acid esters; oxyalkylated phenols, polyalphaolefins; and blocked polyols. The above specified demulsifiers are not necessarily mutually exclusive. The demulsifiers may be used in this invention singly or as mixtures of more than one demulsifier. ANTIFOAM AGENT Suitable antifoam agents include silicones and organic polymers such as acrylate polymers. Various antifoam agents are described in Foam Control Agents by H.T. Kerner (Noyes Data Corporation, 1976, pages 125-176). The use of silicone oils such as are available as articles of commerce is generally preferred. Thus, among foam inhibitors there may be mentioned siloxane-polyoxyalkylene copolymers, for example those described in U.S. Patent No. 3,233,986, the disclosure of which is incorporated by reference herein, which comprise at least one siloxane block containing at least two siloxane groups of the formula R2SiOtj.5(4-b) wherein R represents a halogen atom or an optionally halogenated hydrocarbon group and b represents from 1 to 3, and at least one polyoxyalkylene block containing at least two oxyalkylene groups. Generally, the alkylene groups have 2 or 3 carbon atoms, and usually both ethyleneoxy and propyleneoxy groups are present. Advantageously, the copolymer is a polymethylsiloxane- polyoxyalkylene copolymer, preferably of the general formula: (CH 3 )3SiO[CH3(A)SiO] m [(CH3)2SiO] n Si(CH 3 )3 in which A represents -(CH2)pO(C 2 H 4 O) x (C3H 6 O) y Z in which Z represents hydrocarbyl, OC(hydrocarbyl) or, preferably, hydrogen, and in which the absolute values of m and n, and their ratios, and the values of p, x, and y, and their ratios, may vary widely but total values advantageously give a weight average molecular weight in the range of from 600 to 25000. The ratio of m:n is advantageously in the range of from 10:1 to 1:20, or the value of n may be zero, and the ratio of x:y is advantageously in the range of from 1 : 100 to 100: 1 , preferably 20:80 to 100:1 , or one of x or y, but not both, may be zero. Preferred foam inhibitors are those sold under the trade mark TEGOPREN by Th. Goldschmidt AG. Advantageously, the foam inhibitor is present in the fuel in a proportion in the range of from 0.0001 to 0.2%, preferably from 0.005 to 0.2%, by weight. DE-C-4,343,235 describes polysiloxanes with methyl and polar organic substituents that are used to defoam diesel fuel. Other examples of silicon containing anti-foams are silicone terpolymers, when at below 1.2 ppm silicon, comprising a silicone backbone co-grafted with a phenol derivative (especially eugonol) as well as a polyether. Such anti-foams are described in US-A-5,334,227. Other anti-foams may be non-silicon containing, such as those made by acylating polyamines as described in WO 94/06894. ANTI-CORROSION AGENT A corrosion (or rust inhibitor) may be a single compound or a mixture of compounds having the property of inhibiting corrosion of metallic surfaces. In some cases compounds are known which act not only as corrosion inhibitors but as metal deactivators in passivating the surface of the metal and thereby inhibiting corrosion. Among suitable corrosion inhibitors for use in accordance with this invention are the thiazoles, triazoles and thiadizoles. Examples of such compounds include benzotriazole, tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-mercapto benzothiazole, 2,5-dimercapto-1 ,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio- 1 ,3,4-thiadiazoles, 2-mercapto-5-hydrocarbyldithio-1 ,3,4-thiadiazoles, 2,5- bis(hydrocarbylthio)-1 ,3,4-thiadiazoles, and 2,5(bis)-hydrocarbyldithio)-1 ,3,4- thiadiazoles. A number of these materials are available as articles of commerce. Other types of useful corrosion inhibitors include dimer and trimer acids such as are produced from tall oil fatty acids, oleic acid, linoleic acid, etc.; alkenyl succinic acid and alkenyl succinic anhydride corrosion inhibitors such as tetrapropenylsuccinic acid, tetrapropylsuccinic anhydride, dodecenylsuccinic acid, dodecenylsuccinic anhydride, hexadecenylsuccinic acid, and similar compounds. Also useful are derivatives of alkenyl succinic acids and anhydrides such as half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as diols and polyglycols and imides and amides of alkenyl succinic acids and anhydrides having 8 to 24 carbon atoms in the alkenyl group, for example the reaction product of dodecenyl succinic acid or anhydride with a polyethylene polyamine, further reacted with a fatty acid such as olefic acid. Also useful are aminosuccinic acids or derivatives thereof represented by the formula: R 6 o R 7 - C - C - OR 5 R 4 \ N - C - C — OR 1 / R 3 R 2 O wherein each of R 1 , R 2 , R5, R6 anc j R7 J S independently, a hydrogen group containing 1 to 30 carbon atoms, and wherein each of R 3 and R 4 is, independently, a hydrogen atom, a hydrocarbyl group containing 1 to 30 carbon atoms. The groups R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 , when in the form of hydrocarbyl groups, can be, for example, alkyl, cycloalkyl or aromatic containing groups. Preferably R^ and R5 are the same or different straight-chain .or branched-chain hydrocarbon radicals containing 1-20 carbon atoms. Most preferably, R 1 and R 5 are saturated hydrocarbon radicals containing 3-6 carbon atoms. R2, either R 3 or R 4 , R6 and R 7 , when in the form of hydrocarbyl groups, are preferably the same or different straight-chain or branched-chain saturated hydrocarbon radicals. Preferably a dialkyl ester of an aminosuccinic acid is used in which R 1 and R§ are the same or different alkyl groups containing 3-6 carbon atoms, R2 is a hydrogen atom, and either R 3 or R 4 is an alkyl group containing 15-20 carbon atoms or an acyl group which is derived from a saturated or unsaturated carboxylic acid containing 2-10 carbon atoms. Most preferred of the aminosuccinic acid derivative is a dialkylester of an aminosuccinic acid of the above formula wherein R1 and R5 are isobutyl, R2 is a hydrogen atom, R 3 is octadecyl and/or octadecenyl and R 4 is 3-carboxy-1-oxo-2- propenyl. In such ester R6 and R 7 are most preferably hydrogen atoms. FUEL OIL The fuel oil may be a hydrocarbon fuel such as a petroleum-based fuel oil, for example kerosene or distillate fuel oil, suitably a middle distillate fuel oil, i.e. a fuel oil obtained in refining crude oil as the fraction between the lighter kerosene and jet fuels fraction and the heavier fuel oil fraction. Such distillate fuel oils generally boil within the range of about 100°C to 500°C, e.g. 150°C to 400°C, for example, those having a relatively high Final Boiling Point of above 360°C (ASTM-D86). The fuel oil can comprise atmospheric distillate or vacuum distillate, or cracked gas oil or a blend in any proportion of straight run and thermally and/or catalytically cracked distillates. The most common petroleum distillate fuels ' are kerosene, jet fuels, diesel fuels, heating oils and heavy fuel oils. The heating oil may be a straight atmospheric distillate, or it may contain minor amounts, e.g. up to 35 wt %, of vacuum gas oil or cracked gas oils or of both. Heating oils may be made of a blend of virgin distillate, e.g. gas oil, naphtha, etc. and cracked distillates, e.g. catalytic cycle shock. A representative specification for a diesel fuel includes a minimum flash point of 38°C and a 90% distillation point between 282°C and 380°C (see ASTM Designations D-396 and D-975). Also, the fuel oil may be an animal or vegetable oil, or a fuel oil as described above in combination with an animal or vegetable oil. The concentration of the marker in the oil by weight per weight of fuel may for example be 0.001 to 1000 ppm, such as 0.005 to 10 ppm, preferably 0.008 to 1 ppm. The concentration of the additive comprising marker and co-additives in the oil may for example be in the range of 1 to 5,000 ppm of additive (active ingredient) by weight per weight of fuel, for example 10 to 5,000 ppm such as 10 to 2,000 ppm (active ingredient) by weight per weight of fuel, preferably 25 to 500 ppm, more preferably 100 to 200 ppm. CONCENTRATE Concentrates comprising the additive in admixture (e.g. solution or dispersion) in a carrier liquid are convenient as a means for incorporating the additive into bulk fuel oil such as distillate fuel, which incorporation may be done by methods known in the art. The concentrates may also contain other additives as required and preferably contain from 3 to 75 wt %, more preferably 3 to 60 wt %, most preferably 10 to 50 wt % of the additives preferably in solution in oil. Examples of carrier liquid are organic solvents including hydrocarbon solvents, for example petroleum fractions such as naphtha, kerosene, diesel and heater oil; aromatic hydrocarbons such as aromatic fractions, e.g. those sold under the 'SOLVESSO' tradename; alkanols; and paraffinic hydrocarbons such as hexane and pentane and isoparaffins. The carrier liquid must, of course, be selected having regard to its compatibility with the additive and with the fuel. For example, a concentrate may contain both marker and co-additives, or separate concentrates, one containing marker and the other containing co-additives, may be provided. The additives of the invention may be incorporated into bulk fuel oil by other methods such as those known in the art. If co-additives are required, they may be incorporated into the bulk fuel oil at the same time as the additives of the invention or at a different time. CO-ADDITIVES The additives of the invention may be used singly or as mixtures. They may also be used in combination with one or more co-additives such as known in the art, for example the following, detergents, antioxidants, dehazers, metal deactivators, cosolvents, package compatibilisers, and antistatic additives, provided that such co-additives are different from any of the co-additives herein before described in relation to the invention. The following examples illustrate the invention. MATERIALS USED Additive Components A: Rhodamine Base B B. dilinoleic acid (anti-corrosion agent) C. 2-ethyl hexyl nitrate (cetane improver) D. methyl siloxane/polyglycol copolymer (anti-foam) E. ethoxylated alkyl phenol/formaldehyde resin plus ethylene diamine (stabiliser) F. glycol ester of Cg oxyalkylated and C4 phenol/formaldehyde resin (demulsifier) Fuel A middle distillate fuel having the following distillation characteristics: 50% : 276.7°C; 90% : 333.7°C Final Boiling Point: 358.8°C TESTMETHODANDPROCEDURE Samples of the fuel were treated with various additive combinations and, in each test, agitated vigorously and the time, in seconds, for the foam to collapse observed. The initial foam height was also measured and the untreated and treated fuels compared. The examples were carried out at ambient temperature. RESULTS Results I represent those of one set of experiments carried out sequentially, and Results II represent those of another set of experiments carried out sequentially. It is apparent for the results that low concentrations of marker A significantly reduced the foaming tendency of base fuel, both alone and in combination with other additives. In particular, the presence of co-additives B, C, D, E and F led to enhanced antifoam performance.

Claims: CLAIMS 1. Use of an additive comprising a chemical marker for fuel oil that is detectable therein either by conversion to a colorimetrically identifiable tautomeric form thereof or by conversion to a colorimetrically identifiable reaction product thereof, as an anti-foam in a fuel oil. 2. The use of claim 1 wherein the additive also comprises one or more co- additives selected from a cetane improver; a stabiliser; a demulsifier; an anti-foam agent; and an anti-corrosion agent. 3. The use of claim 1 or claim 2 wherein the marker is Rhodamine Base B.

Inventors: CAPROTTI RINALDO, HENDERSON IAN, SEARIS STEVEN, TANNER TRACY, CAPROTTI, RINALDO, HENDERSON, IAN, SEARIS, STEVEN, TANNER, TRACY
Applicants: EXXON CHEMICAL LTD, EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL LIMITED, EXXON CHEMICAL PATENTS INC.
Application year: 1996
Main classification: C10L1
IPC codes: C10L1