Blends for use in fuel compositions

The present invention relates to a blend of a fuel additive mixture and one or more solvents. It also relates to a fuel composition comprising a base fuel, particularly a gas oil, such as an automotive gas oil, and such a blend.

A fuel composition includes a number of additive components, which impart various performance or handling advantages to the fuel composition. Such components are commonly provided and used in the form of an additive mixture containing one or more of said components and one or more solvents. Said solvents provide one or more functions to the mixtures, for example to reduce the concentration of an additive component to a level at which it is safe to handle, or to dissolve an additive component that exhibits low solubility in hydrocarbons, or for other reasons.

It has been found that certain commercially available products, that are marketed for use as solvents, have the properties that are required, but that it can be desirable, for cost or availability reasons, to find alternative materials that are suitable solvents for use in this context.

In one aspect of the invention, a blend composition comprising (i) one or more base fuels having an aromatics content of below 80% by weight, said one or more base fuels being present in the amount of 10 to 95% by weight of the blend composition; (ii) a fuel additive mixture comprising one or more fuel additives, wherein said additives include an anti-foam agent, said fuel additive mixture being present preferably in the amount of 0.01 to 80% by weight of the blend composition; (iii) an organic molecule containing a moiety CR₁R₂R₃(OH) wherein R₁, R₂ and R₃ are each independently hydrogen or an organic carbon-containing group; and optionally (iv) an aromatic solvent having an aromatics content of greater than 80% by weight.

In another aspect of the invention, a process for preparing the blend composition and a fuel composition containing the blend is provided.

It has now been found that the solvency properties of a commercially available solvent can be provided by a base fuel such as an automotive gas oil (diesel) or a jet fuel. In particular, it has been found that solvency properties of such a commercially available solvent when used in a blend containing a fuel additive mixture which comprises an anti-foam agent can be provided by at least partially replacing said solvent by a base fuel such as an automotive gas oil or jet fuel, each having a low aromatics content, when also including in said blend an organic molecule containing a moiety CR₁R₂R₃(OH) wherein R₁, R₂ and R₃ are each independently hydrogen or an organic carbon-containing group, an example of such a molecule being an alkyl alcohol. This enables such blends to maintain good stability even when using materials that are cheaper and more widely available than commercially available solvents.

For example, it has been found that the stability of a blend of a fuel additive mixture and ‘Caromax 20’ aromatic solvent (available ex. Petrochem Carless) can be provided when replacing at least some of said solvent in said blend by a low aromatics automotive gas oil and including in said blend 2-ethylhexanol.

U.S. Pat. No. 5,385,588 describes an additive concentrate package having an enhanced shelf-life stability which comprises a solvent stabiliser composition that contains at least one liquid aromatic hydrocarbon solvent and at least one liquid alkyl or cycloalkyl alcohol, e.g. 2-ethylhexanol. Preferred aromatic hydrocarbon solvents are described as being selected from toluene, ethylbenzene, xylene, and mixtures of o-, p- and m-xylenes, mesitylene, and higher boiling aromatic mixtures such as ‘Super High Flash Naphtha’, Aromatic 150’ and ‘Aromatic 100’. The aromatics contents of said commercially available higher boiling aromatic mixtures are >80%, >99 vol % and >99 vol %, respectively, i.e. high aromatics contents. However, there is no mention of the aromatic hydrocarbon solvent being a gas oil or jet fuel, nor of a low aromatics material. Solvents having low aromatics levels are known to be poor solvents for the types of additives in question.

Lack of stability of the blends can manifest itself as follows. As the atmospheric temperature falls, a blend that is a single-phase homogeneous liquid at normal temperatures may become a multiphase liquid as certain components either (i) freeze (forming a solid) or (ii) become immiscible in the bulk liquid and form a separate liquid layer. The onset of formation of a solid on cooling is characterised by a change in the transparency of the blend and the temperature at which this occurs is termed the “Cloud Point” of the fuel. If, on cooling, the Cloud Point is preceded by the formation of a separate liquid phase, the temperature at which this occurs is termed the “Phase separation temperature”.

In accordance with the present invention there is provided a blend composition comprising (i) one or more base fuels having an aromatics content of below 80% by weight, said one or more base fuels being present in the amount of 10 to 95% by weight of the blend composition; (ii) a fuel additive mixture comprising one or more fuel additives, wherein said additives include an anti-foam agent, said fuel additive mixture being present preferably in the amount of 0.01 to 80% by weight of the blend composition; (iii) an organic molecule containing a moiety CR₁R₂R₃(OH) wherein R₁, R₂ and R₃ are each independently hydrogen or an organic carbon-containing group; and optionally (iv) an aromatic solvent having an aromatics content of greater than 80% by weight.

In particular, it has been found that additive packages or mixtures containing a silicone anti-foam agent, for example a polyether-modified polysiloxane, have a tendency especially at low temperature to deposit a separate liquid phase containing silicone, plus all other components present which have partitioned themselves between the low aromatics hydrocarbon solvent phase and the silicone phase, but that this separation does not occur if the solvent system contains alcohol in addition to the low aromatics hydrocarbon.

“Base fuel” is defined as being a material that is in accordance with one or more published base fuel standard specifications.

Preferably, said aromatic solvent has an aromatics content of greater than 85% by weight, more preferably greater than 90% by weight, most preferably greater than 95% by weight. Suitable such aromatic solvents include ‘Caromax 20’ (ex. Petrochem Carless) and ‘Solvesso 200’ (ex. ExxonMobil).

Preferably, each said base fuel has an aromatics content of below 50% by weight, more preferably below 35% by weight. It is preferably selected from gas oils, such as automotive gas oils, and kerosene fuels, such as jet fuels.

Preferably, each said base fuel has a cloud point of below −5° C., more preferably below −15° C., yet more preferably below −20° C., most preferably below −25° C.

Preferably, said organic molecule is an alkyl alcohol, which more preferably is selected from C_3-30 alkyl alcohols, still more preferably from C_4-20 alkyl alcohols, yet more preferably from C_7-10 alkyl alcohols, such as 2-ethylhexanol, octan-1-ol and octan-2-ol, and is most preferably 2-ethylhexanol.

Preferably, said one or more published base fuel standard specifications are selected from EN 590, Swedish Class 1 (as defined by the Swedish Standard for EC1), ASTM D975 and Defence Standard 91-91 (Def Stan 91-91) specifications. EN 590:2004 is the current European Standard for diesel fuels. SS 155435:2006 is the current Swedish Standard for EC1. ASTM D975-07a is the current United States Standard Specification for Diesel Fuel Oils. Def Stan 91-91 Issue 5 Amendment 2 is the current UK standard for Turbine Fuel, Aviation Kerosine Type, Jet A-1.