Additives are often used in petroleum fuels to provide specific effects during processing or to provide particular properties in the fuel. Fuel additives are usually formulated as solutions in a suitable carrier fluid, which is commonly heavy aromatic naphtha (HAN-a mixture of mainly Cg and C10 aromatic hydrocarbons-predominantly trimethyl benzenes, diethyl benzenes and dimethyl ethyl benzenes).

HAN is a very effective solvent and is readily and widely available. Environmental considerations are leading to pressure to reduce the proportion of volatile aromatic compounds used in such applications, but to date no satisfactory substitute for HAN or similar highly aromatic solvents has been found.

The present invention is based on the discovery that certain esters of aromatic carboxylic acids, particularly benzoic acid, are very effective solvents for fuel additives and are environmentally much less objectionable than HAN. In referring to"petroleum fuel"herein we mean refined petroleum products for use as fuels, particularly in engines, including gasoline, diesel and fuel oil, and related phrases have corresponding meanings.

The present invention accordingly provides a petroleum fuel additive formulation which includes at least one petroleum fuel additive, particularly at least one paraffin wax pour point depressant and/or at least one dehazing agent dissolved in a carrier fluid including at least one compound of the formula (I) : Rl- (AO) n-OOC- (CH2) m-Ph- (R2) p (I) where R1 is a C1 to C10 alkyl group, particularly a C1 to C6 alkyl group, more particularly a C3 to C5 branched alkyl group ; AO is an alkyleneoxy group, particularly an ethyleneoxy or a propyleneoxy group, and may vary along the (poly) alkyleneoxy chain ; n 0 or from 1 to 100, desirably 0 ; m is 0, 1 or 2, desirably 0 ; and Ph is a phenyl group, which may be substituted with groups (R2) p ; where each R2 is independently a C1 to C4 alkyl or alkoxy group ; and p is 0, 1 or 2, desirably 0.

The invention includes a method of treating a petroleum fuel, in which at least one petroleum fuel additive dissolved in a carrier fluid, including at least one compound of the formula (I), as defined above, is introduced into the petroleum fuel. The invention further includes the use of compounds of the formula (I), as defined above, as carrier fluids for petroleum fuel additives. As is discussed below, desirably the carrier fluid is or includes iso-propyl benzoate.

The petroleum fuel additive is, in particular at least one wax pour point depressant (dewaxer) and/or at least one dehazing agent. Accordingly the invention includes a petroleum fuel additive formulation including one or more of at least one wax pour point depressant and/or at least one at least one dehazing agent, dissolved in a carrier fluid including at least one compound of the formula (I) as defined above, in particular where the carrier fluid is or includes iso-propyl benzoate. Further, the invention includes a method of treating a petroleum fuel, in which at least one fuel additive, dissolved in a carrier fluid including at least one compound of the formula (I) as defined above, in particular where the carrier fluid is or includes iso-propyl benzoate, is introduced into the petroleum fuel. The invention also includes petroleum fuel including an additive formulation of the invention. Other petroleum fuel additives that can be included in compositins of the invention include detergents, anti- deposition agents, lubricants, corrosion inhibitors and cetane improvers.

Desirably in the compound of the formula (I) used in the invention R1 is a branched alkyl group, particularly a C3 to C8 branched, such as a C3 to C5 secondary, alkyl group, e. g. an iso-propyl (prop- 2-yl), sec-but (but-2-yl), iso-butyl (2-methyl-prop1-yl) and/or tert-butyl, or a 2-ethyl hexyl group, the branching reducing the ease with which the ester can be hydrolysed. Esters with secondary alcools are particularly useful in this regard and R1 is thus especially a C3 to C5 secondary alkyl group and very desirably an iso-propyl group. Although the carboxylic acid used in the ester can be a dihydrocinnamic acid or a phenylacetic acid, it is very desirably a benzoic acid i. e. desirably m is 0.

Similarly, although the phenyl ring of the acid may be substituted, it is desirable that it is unsubstituted i. e. desirably p is 0.

The esters used in the invention may include a (poly) alkyleneoxy chain, (AO) n in formula (I), between the carboxyl group and the group R. When present the (poly) alkyleneoxy chain is desirably a (poly) ethyleneoxy, a (poly) propyleneoxy chain or a chain including both ethyleneoxy and propyleneoxy residues. Generally, it is desirably not to include such a chain in the ester i. e. desirably n is 0.

Esters of the formula (I) that can be used in the invention include ethyl benzoate, propyl benzoate, iso-propyl benzoate, sec-butyl benzoate, iso-butyl benzoate, tert-butyl benzoate, 2-ethyl hexyl benzoate and nonyl benzoate. Among these particularly useful esters are iso-propyl benzoate and 2- ethlyhexyl benzoate and the invention specifically includes a petroleum fuel additive formulation, particularly a formulation of at least one of the additives set out above, in which at least one petroleum fuel additive is dissolved in iso-propyl benzoate and/or 2-ethlyhexyl benzoate as a carrier fluid. Iso- propyl benzoate has a combination of properties that make it exceptionally useful in the carrier fluid role. As a pure material, it has a wide liquid range having a high boiling point (BP ca 219°C) and remaining fluid at temperatures below normally expected environmental temperatures (pour point <- 60°C) ; it has a flash point (ca 99°C) so that it is classified as non-flammable and under normal use conditions it has a low vapour pressure ; it has a density similar to that of water (1. 008 kg. l~1 at 25°C) ; and a low viscosity (2. 32 cSt at 25°C ; measured by the U tube method, equivalent to 2. 34 mPa. s).

Desirably, the carrier fluid used in formulations of the invention is wholly of one or more compounds of the formula (I). However, if desired other solvents or carrier fluids may be used in admixture.

Examples of other such fluids include propylene tetramer and ethyl lactate. Although HAN can be included it is unlikely that HAN or other carrier fluid or solvent including a substantial proportion of aromatic hydrocarbons will be used as a major component of any such mixed carrier fluid, because of its adverse environmental impact. When mixtures are used, compounds of the formula (I) will usually be present in at least 40%, more usually at least 50%, desirably at least 60%, and particularly at least 75%, by weight of the total carrier fluid used. When present, other carrier fluid components or solvents will desirably be used at level of from 1 to 40%, more desirably 2 to 25, and particularly 5 to 15% by weight of the total carrier fluid used.

Fuel additives are materials added to petroleum fuel materials e. g. diesel fuel, heating oil and gasoline, to provide particular effects such as pour point depression (dewaxing) and dehazing.

The amount of the fuel additive included in the formulation is typically from 1 to 99, more usually from 5 to 90% by weight of the formulation. Generally the amount of additive added to the fuel is within the range 1 to 5000 ppm by weight of the treated fuel, more usually from 5 to 2500 ppm. Accordingly the amount of additive formulation added to the fuel is usually from 5 to 10000 ppm, more usually from 10 to 5000 ppm by weight of the treated fuel. Within these general ranges, the amounts for particular additives may vary as is described below.

Middle distillate fuels (diesel fuel) are complex mixtures of hydrocarbon molecules including normal (straight chain) paraffins with carbon chains mainly from Cg to C28 but possibly with some compounds up to C36. At low temperatures the heavier (longer chain) paraffins tend to precipitate wax crystals, typically as thin, flat, rhomboid plates and at very low temperature decreases these can grow to 0. 5 to 1. 0 mm across. Such wax crystals can directly cause fuel filter blockage and indirectly the wax crystals can build a gel structure in the fuel trapping liquid fuel between interlocking wax crystals so that as little as 0. 5 to 1 % of precipitated wax may cause fuel solidification, thus blocking fuel lines etc.

Paraffin wax pour point depressants are commonly added to the fuel to inhibit or prevent wax precipitation. This resulting effect is similar to the removal e. g. by catalytic cracking, of waxes in refinery operations and is sometimes colloquially referred to as dewaxing. Such additives are usually presented as solutions in a carrier fluid. Examples of suitable additives include ethylene vinyl acetate copolymers and polyalkylmethacrylate copolymers.

Where the fuel additive is a pour point depressant, the concentration in the carrier fluid, or solvent, is typically from 1 to 99%, particularly from 5 to 50% by weight of the total formulation and the formulations will typically include from 99 to 1 %, particularly from 50 to 5% of the carrier fluid by weight of the total formulation. The amount of pour point depressant included in an oil fuel is typically from 1 to 5000 ppm, particularly from 5 to 2500 ppm, by weight of the oil stream. Accordingly, the addition

rate of the pour point depressant formulation to the oil fuel will typically be from 5 to 10000 ppm, particularly from 10 to 5000 ppm, by weight of the total oil fuel.

Fuels such as diesel fuel, heating oil and gasoline can contain minor amounts of water or aqueous material which separates during and/or after manufacture with even small amounts of water becoming visible as haziness in the fuel. Dehazers are added to remove the haze, probably either by solublizing or microemulsifying the aqueous material to give a clear, stable fuel, or by encouraging fuller phase separation of the water so it can be more easily removed form the fuel. The use of dehazers contributes to water being present as a separate phase where this is undesirable e. g. in storage tanks where separated water may lead to corrosion or in engines where it may cause corrosion or block fine nozzles or jets. The presence of detergent surfactants in fuel may act to stabilise emulsions of water in fuel thus increasing the tendency to form haze.

Dehazers chemically typically have surfactant properties and examples include alkyl phenol formaldehyde resin alkoxylates and EO/PO, block or random, co-polymers, which usually have molecular weights of from 1000 to 5000 ; post reacted EO/PO block co-polymers, particularly post reacted with isocyanate materials such as MDI [4, 4'-methylenebis (phenyl-isocyanate)] and polyamine, particularly alkylene, especially ethylene, diamine, alkoxylates, which usually have molecular weights of from 10000 to 100000 ; and polyol, particularly glycerol, alkoxylates, which can have a wide range of molecular weights from 1000 to 20000 or higher. It is common to use combinations of two or more dehazer materials to suit particular conditions in an oil stream, e. g. combinations of coalescence and flocculation enhancing agents.

The concentration of dehazer components in the carrier fluid, or solvent, is typically from 10 to 90%, more usually from 15 to 85%, particularly from 25 to 80% by weight of the total formulation.

Correspondingly, dehazer formulations of the invention will typically include from 90 to 10%, more usually from 85 to 15%, particularly from 75 to 20% of the carrier fluid by weight of the total formulation. In use the amount of dehazer included in an oil fuel is typically from 1 to 500 ppm, particularly from 5 to 150 ppm, by weight of the fuel. Accordingly, the addition rate of the dehazer formulation to the fuel will typically be from 5 to 1000 ppm, particularly from 10 to 300 ppm, by weight of the total fuel.

Accordingly, the invention includes a fuel additive formulation which includes at least one fuel additive agent, particularly at least one paraffin wax pour point depressants and/or at least one dehazing agent, dissolved in a carrier fluid including at least one compound of the formula (I) as defined above, in particular where the carrier fluid is or includes iso-propyl benzoate. Additionally, the invention includes a petroleum based fuel which includes an additive formulation of at least one fuel additive agent, particularly at least one paraffin wax pour point depressant and/or at least one dehazing agent, dissolved in a carrier fluid including at least one compound of the formula (I) as defined above, in

particular where the carrier fluid is or includes iso-propyl benzoate. The invention further includes a method of treating a petroleum based fuel, in which at least one petroleum additive dissolved in a carrier fluid, including at least one compound of the formula (I), as defined above, is introduced into the fuel, in particular where the carrier fluid is or includes iso-propyl benzoate. The invention further includes the use of compounds of the formula (I), as defined above, as carrier fluids for fuel additives, in particular where the carrier fluid is or includes iso-propyl benzoate.

The following Examples illustrate the invention. All parts and percentages are by weight unless otherwise stated.

Materials Sol1 isopropyl benzoate Sol2 ethyl benzoate Sol3 nonyl benzoate Sol4 2-ethyl hexyl benzoate CSol1 heavy aromatic naphtha DH1 Kemelix 3422X-polyethyleneimine propoxylate ex Uniqema DH2 Kemelix D510-polyethyleneimine alkoxylate ex Uniqema Example 1 A diesel fuel wax pour point depressant additive formulation was made up from 90 parts by weight iso- propyl benzoate and 10 parts by weight ethylene vinyl acetate co-polymers. The fluid was a clear, one phase, stable liquid.

Example 2 A diesel fuel wax pour point depressant additive formulation was made up from 40 parts by weight iso- propyl benzoate and 60 parts by weight ethylene vinyl acetate co-polymers. The fluid was a hazy, one phase, stable liquid.

Exampie 3 A dehazer additive formulation was made up from 20 parts by weight iso-propyl benzoate and 80 parts by weight of a mixture of alkyl (mainly C5, Cg and Cg alkyl) phenol formaldehyde resin alkoxylates.

The fluid was a clear, one phase, stable liquid.

Example 4 A dehazer additive formulation was made up from 60 parts by weight iso-propyl benzoate, 20 parts by weight nonyl phenol formaldehyde resin ethoxylate and 20 parts by weight ethylene diamine alkoxylate. The fluid was a clear, one phase, stable liquid.

Example 5 A dehazer additive formulation was made up from 29 parts by weight iso-propyl benzoate, 54 parts by weight nonyl phenol formaldehyde resin ethoxylate and 17 parts by weight ethylene diamine alkoxylate. The fluid was a clear, one phase, stable liquid.

Example 6 Two commercial available dehazers, DH1 and DH2, were tested in diesel using Sol1 (isopropyl benzoate) or CSol1 (heavy aromatic naphtha) as the additive solvent. From previous testing it was known that DH1 and DH2 are effective as dehazers. The additives were made up as 40% solutions in the solvents and tested in dehazing diesel fuel oil using the following method (modification of ASTM D 1094) : i add 150ppm (vol/vol) conventional commercial detergent to dry diesel fuel oil and place 40mis of the diesel in a 50 mi measuring cylinder ; ii add 8 jli dehazer solution (2. 5% wt/wt* dehazer in solvent-to give dehazer test concentration of 5 ppm wt/vol), followed by 10moi pH7 aqueous phosphate buffer solution ; iii cap the cylinder, shake for 2 minutes (2/3 strokes per second) and then leave to stand for 5 minutes ; iv pipette sample of diesel oil (from the middle of the cylinder) to a spectrophotometric cell and measure the (UV/visible) absorbance.

* The dehazer solution was diluted to 2. 5% before dosing the fuel to improve the precision in the amount of additive used in the test.

The results are recorded as the difference in absorbance (Delta A) between test samples and dry untreated diesel and are given in Table 1 below.

Table 1 Ex No Additive Solvent Delta A C6. 1 Blank 2. 50 C6. 2 DH1 CSol1 0. 80 6. 1 DH1 Sol1 0. 80 C6. 3 DH2 CSol 1 1. 00 6. 2 DH2 Sol 1 1. 00 Example 7 The commercially available dehazers, DH1 and DH2, were tested in diesel using Sol1, Sol2, Sol3 and Sol4 as solvents using the experimental and test method described in Example 3. The test results are set out in Table 2 below.

Table 2 Ex No Additive Solvent Delta A C4. 1 Blank 2. 44 4. 1a DH1 Sol1 1. 51 4. 1 b DH1 Sol2 1. 62 4. 1c DH1 Sol3 1. 63 4. 1d DH1 Sol4 1. 82 4. 2a DH2 Soll 1. 69 4. 2b DH2 Sol2 1. 81 4. 2c DH2 Sol3 1. 63 4. 2d DH2 Sol4 1. 64