Fuel and related compositions – Liquid fuels – Emulsion fuel
Reexamination Certificate
2000-02-04
2002-04-09
Medley, Margaret (Department: 1714)
Fuel and related compositions
Liquid fuels
Emulsion fuel
C044S302000
Reexamination Certificate
active
06368368
ABSTRACT:
TECHNICAL FIELD
The present invention relates to emulsions containing alcohol and/or water in a dispersed phase and a hydrocarbon liquid in the continuous phase. More particularly the present invention relates to such emulsions that are resistant to stratification on relatively long term undisturbed storage at ambient temperature.
BACKGROUND ART
It is known from the applicant's Australian patent specification 544.728 that emulsions containing alcohol and/or water in one phase and a hydrocarbon liquid in the other may be formed using an emulsifier that is a block copolymer of ethylene oxide and styrene type monomers. These emulsions are of particular utility as liquid transport fuel in which hydrated methanol or hydrated ethanol is dispersed in diesel oil or gasoline. Hydrated alcohol in diesel oil (termed AW/D) emulsions represent a new and potentially cost effective option for significantly reducing particulate and NOx emissions from diesel engines. Emulsions of hydrated alcohol in gasoline exhibit reduced vapour pressure, increased water tolerance and reduced NOx emission on combustion as compared with anhydrous alcohol solutions in gasoline. When the alcohol is ethanol produced from biomass there can be a reduction in the net emission of carbon dioxide (“greenhouse gas”) as compared with the use of unblended petroleum fuel.
The arrangement described in the above mentioned specification utilised not only a block copolymer as the emulsifier but also a block copolymer as a coupling agent. The coupling agent typically comprised a block copolymer of butadiene and styrene type monomers and was described as containing butadiene and styrene in weight ratios of at least 2:1, preferably at least 3:1. The emulsifier and the coupling agent are described in that specification as being present in the emulsion in a ratio of from 1:3 to 3:1. In these ratios solutions of the two copolymers are compatible.
It has been found that while the AW/D emulsions described in the aforementioned Australian patent specification produce generally stable emulsions they do suffer from a problem of stratification, i.e., a tendency for the dispersed or discontinuous phase droplets to rise if they are less dense than the continuous phase of the emulsion, called ‘creaming’, or to fall if they are more dense than the continuous phase, called ‘settling’. While this stratification may take a relatively long time and may be readily reversed by gentle agitation it is a major commercial disadvantage as there is the possibility that any given aliquot of emulsion may, after a period of relatively long-term undisturbed storage, contain more or less of the dispersed phase component than is intended. In the case of an emulsion used as a fuel such stratification makes the starting and/or running of an engine difficult, if not impossible.
DISCLOSURE OF INVENTION
The present invention relates to emulsions containing in a continuous phase a hydrocarbon liquid and in a dispersed phase alcohol and/or water in the presence of:
(a) an emulsifier being a copolymer containing at least one relatively hydrophobic polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes, and at least one relatively hydrophilic polymeric block of at least one monomer selected from the group having the formula H(O—R)
n
OH where R is an aliphatic radical containing from 1 to 4 carbon atoms and n is a number between 20 and 300, and
(b) a coupling agent being a copolymer containing at least one polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes, and at least one block being a saturated or unsaturated aliphatic hydrocarbon moiety, the emulsifier being present in an amount sufficient to form micelles of the relatively hydrophilic polymer block sufficient to contain the dispersed phase and the coupling agent being present in an amount that is sufficient to substantially prevent the dispersed phase droplets from coalescing while not being present in a sufficiently high amount that micelles of the styrene containing polymeric blocks of the coupling agent form in the continuous phase of the emulsion.
The absolute amounts of the emulsifier and the coupling agent can be determined for any given emulsifier and coupling agent by quantitative testing. It is apparent to the present inventor that the amount of the coupling agent in the emulsion is important and typically approaches the solubility limit of the coupling agent in the continuous phase. If the amount of the coupling agent is lower than the critical amount it will not couple effectively with the micelles of the emulsifier and therefore stratification of the dispersed phase of the emulsion will not be inhibited. If the amount of the coupling agent is higher than the critical amount it will form micelles of the styrene containing polymeric blocks of the coupling agent which will in turn cause flocculation of the dispersed phase to occur. The solubility of the coupling agent in the continuous phase can be adjusted by an alteration of the amount of the styrene moiety relative to the hydrocarbon moiety in the coupling agent. The solubility will also depend to some extent upon the aromaticity of the hydrocarbon liquid comprising the continuous phase. The more aromatic is the hydrocarbon liquid the higher will be the solubility of any given coupling agent.
The maximum amount of emulsifier is not as critical as the maximum amount of the coupling agent as, within reasonable limits, the presence of an excess of emulsifier has only an economic disadvantage and not a technical one. The emulsifier should be present in an amount greater than 3 times the amount of the coupling agent as is described in more detail later in this specification. Preferred amounts of the coupling agent in the emulsion are in the range of from 0.75 to 1.5 gm/l. When the dispersed phase is hydrated methanol it is preferred that the coupling agent is present in the emulsion in the range of from 0.75 to 1.0 gm/l whereas in the case of the dispersed phase comprising hydrated ethanol the preferred range is from 1.0 to 1.5 gm/l.
In total the copolymer content of the emulsion, i.e. the combined amount of the emulsifier and of the coupling agent, is preferably in the range of from 4 to 10 gm/l. In the case of emulsions containing hydrated methanol in an amount of 12% by volume in the dispersed phase the preferred amount of copolymers is 4 to 6 gm/l, more preferably 5 gm/l, and in the case of emulsions containing hydrated ethanol in an amount of 15% by volume in the dispersed phase the preferred concentration of copolymers is 5 to 8 gm/l, more preferably 6 gm/l. In the case of emulsions that contain greater amounts of alcohol and/or water in the dispersed phase the preferred amount of the copolymers will typically remain less than 10 gm/l, however in this case the ratio of the emulsifier to the coupling agent will rise. This is because, as the amount of the dispersed phase increases so the quantity of emulsifier required increases in proportion to the increase in the surface area of the dispersed phase of the emulsion; by contrast, the quantity of coupling agent stays substantially constant as the amount of the dispersed phase increases.
As used in this specification the following terms have the meanings indicated:
Alcohol:
This term means methanol or ethanol or
mixtures thereof and
Hydrocarbon liquid:
This term includes all liquid fractions
obtained from petroleum crude oil and
synthetic liquid hydrocarbons obtained
from the processing of gaseous or solid
hydrocarbons.
The hydrocarbon liquid is preferably selected from the group comprising gasolines, kerosenes, diesel oils, gas oils and fuel oils. The gasolines are liquid hydrocarbons boiling below 190° C. The kerosenes, diesel oils and gas oils boil between 170° and 480° C., while the fuel oils boil above 450° C.
The hydrocarbon liquid is preferably selected from the gasolines, the kerosenes which boil between 170 and 230° C., the diesel oils which boil from 170 to 315° C. and t
Apace Research Limited
Christie Parker & Hale LLP
Medley Margaret
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