Fuel and related compositions – Liquid fuels – Emulsion fuel
Reexamination Certificate
2002-07-25
2004-05-11
Meldey, Margaret B. (Department: 1714)
Fuel and related compositions
Liquid fuels
Emulsion fuel
C044S302000, C044S384000, C044S443000, C044S447000
Reexamination Certificate
active
06733549
ABSTRACT:
The present invention relates to fuels which are used in internal combustion engines, preferably diesel engines, and which are emulsions of the respective fuel type with water. Emulsifiers which are derived from polyisobutene are used for the preparation and stabilization of these emulsions, and polyisobutene ethoxylates are preferably used.
The internal combustion engines known today are operated with different fuels depending on the intended use. Most well known are gasoline engines which burn readily volatile gasoline fuels and diesel engines in which more sparingly volatile diesel fuels are used. However, there are also internal combustion engines in which other fuels are used and some of which have a design which differs from that of the abovementioned internal combustion engines. Only the use of light and heavy heating oil in, for example, ships' engines and of kerosene in aircraft engines is mentioned here.
In all these internal combustion engines, the object is to carry out the combustion of the fuel in such a way that high efficiency results and at the same time the emission of pollutants is as low as possible. The addition of water to the fuels has long been known for this purpose. The objects described above are in principle most simply and most economically achieved in this manner. The fundamental problem which arises with the use of such fuel/water mixtures is that the components which are immiscible with one another have to be fed to the engine in the form of a fine mixture, generally an emulsion. Emulsions of the water-in-oil type in which the water is present as the dispersed phase in the continuous oil phase, i.e. in the fuel, are generally used. Specific emulsifiers are used for the preparation and stabilization of the emulsion.
The use of particularly finely divided emulsions or of microemulsions is particularly preferred. These are emulsions in which the size of the droplets dispersed in the continuous phase is very small, preferably ≦1 &mgr;m.
The prior art contains several references which describe the preparation of fuel/water mixtures by various methods.
U.S. Pat. No. 2,111,100 discloses a clear engine fuel comprising at least 50% of fuel, at least 5% of water, at least 5% of an organic solvent selected from the group consisting of alcohols, ketones, ethers and aldehydes, and a fatty acid salt as emulsifier. The water content of the mixture may be up to 50%.
U.S. Pat. No. 3,346,494 describes an emulsifier system for water-in-oil emulsions which consists of from 1 to 10 parts of a fatty acid of 12 to 20 carbon atoms, from 1 to 10 parts of an alkylamino alcohol having 2 to 5 carbon atoms per alkyl group and from 1 to 10 parts of an alkylated phenol having at least one alkyl group of 8 to 12 carbon atoms. The emulsifier system can be used, inter alia, for stabilizing water-in-fuel microemulsions.
U.S. Pat. No. 3,902,869 describes a water-in-fuel microemulsion which contains from 5 to 40% by weight of water and from 1 to 35% by weight of an emulsifier which consists of a suitable carboxylic acid and a salt of this carboxylic acid. Suitable acids are, for example, naphthenic acids, resin acids and gallic acid. In order to increase the octane number, suitable metal salts are also added to the mixture.
WO 98/56878 discloses an emulsion of up to 37% of an aqueous C
1
-C
4
-alcohol in diesel fuel, at least one nonionic surfactant selected from alkoxyphenol, sorbitan monooleate, oleodiethanolamide and glyceryl monooleate being used as emulsifiers. The mixtures have a low soot pollutant emission during combustion.
Finally, WO 97/34969 discloses a water-in-fuel microemulsion which contains at least 5% by weight of water and which was prepared using an emulsifier system which has three fundamental components. These three components are (a) at least one specific sorbitol ester, (b) at least one specific fatty ester and (c) a specific polyalkoxylated alkylphenol. These emulsions have an HLB (hydrophilic-lipophilic balance) of from 6 to 8.
Up to the present, however, none of the water-in-fuel emulsions described in the prior art meet the requirements set for them. On the one hand, the emulsions frequently have insufficient stability, resulting in phase separation during storage. The emulsifier systems used are often complicated and expensive. The most important point, however, is that emulsifier systems used to date and required for the preparation and stabilization of the microemulsion lead to coking residues and deposits in the engine.
It is an object of the present invention to provide emulsifier systems which permit the preparation of water-in-fuel emulsions and do not have the disadvantages described above. In particular, these emulsifier systems should permit the preparation of water-in-diesel emulsions.
We have found that this object is achieved by using alkoxylated polyisobutene as an emulsifier in the preparation of water-in-fuel emulsions.
We have found that this object is furthermore achieved by a fuel-water emulsion containing from 95 to 60% by weight of fuel, from 3 to 35% by weight of water and from 0.2 to 10% by weight of an alkoxylated polyisobutene as emulsifier.
In a preferred embodiment of the present invention, the fuel which forms the continuous phase in the novel emulsions is diesel fuel.
The emulsifiers used in the present invention for the preparation of water-in-fuel emulsions are alkoxylates of polyisobutene. They belong to the surfactant group and can be described by the formula
R(CH
2
)
n
(O—A)
m
—OH.
Here, R is a polyisobutene having a weight average molar mass (Mn) of from 300 to 2300, preferably from 500 to 2000. A is an alkylene radical of 2 to 8 carbon atoms, m is a number from 1 to 200 which is chosen so that the alkoxylated polyisobutene contains from 0.2 to 1.5 alkylene oxide units per C
4
unit, preferably 0.5 alkylene oxide unit per C
4
unit, n is either 0 or 1.
In a preferred embodiment of the present invention, A is an ethylene radical. Ethoxylated polyisobutene is thus preferably used. It is furthermore preferred if, in the polyisobutene alkoxylates or ethoxylates used, the proportion of polymers in which n is 1 is from 75 to 95%.
These alkoxylated polyisobutenes are prepared from the corresponding polyisobutenes. If such a polyisobutene has a terminal double bond, it is converted into the corresponding primary alcohol by hydroformylation and then reacted with the corresponding alkylene oxide, preferably ethylene oxide, in a manner known per se. Polyisobutenes having a geminal double bond are converted, prior to the alkoxylation, into the corresponding alcohol in another manner known per se, for example by epoxidation and subsequent reduction.
The polyisobutene alkoxylates used in the present invention are disclosed in the German Application having the title Polyalkenalkohol-Polyalkoxylate und deren Verwendung in Schmier- und Kunststoffen [Polyalkenyl alcohol polyalkoxylates and their use in lubricants and fuels] of BASF AG of Feb. 25, 1999. That part of this Application which relates to these alkoxylated polyisobutenes and their preparation is an integral part of the present invention and is hereby incorporated by reference into the present Application.
The alkoxylated polyisobutenes used according to the invention have an HLB of from 2 to 6, preferably from 3 to 5. HLB is hydrophilic-lipophilic balance and is a well known parameter for characterizing surfactants. An exact definition of this parameter appears in: Emulsions: Theory and Practice, Paul Becher, Reinhold Publishing Corporation, ACF Monograph, Ed. 1965, Chapter entitled The Chemistry of Emulsifying Agents, page 232 et seq.
The alkoxylated polyisobutene is used in the novel fuel-water emulsions in amounts of from 0.2 to 10, preferably from 0.5 to 5, % by weight. These emulsions furthermore have a fuel content of from 60 to 95, preferably from 70 to 90, % by weight and a water content of from 3 to 35, preferably from 10 to 25, % by weight.
In one embodiment of the invention, the water used in the novel emulsions may contain a certain amount of one o
Eisenbeis Ansgar
Hüffer Stephan
Klingelhöfer Paul
Stang Michael
BASF - Aktiengesellschaft
Meldey Margaret B.
Oblon, Spivak, McClelland, Maier & Neustad, P.C.
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