Temperature-stable emulsified fuel

Details Temperature-stable emulsified fuel Temperature-stable emulsified fuel

2003-07-18

2004-09-21

Toomer, Cephia D. (Department: 1714)

Fuel and related compositions

Liquid fuels

Emulsion fuel

C044S302000

Reexamination Certificate

active

06793694

ABSTRACT:

The present invention relates to emulsified fuels which are temperature stable up to above 70° C. and down to less than −10° C., in particular automobile fuels intended for use in internal combustion engines. More precisely, the fuels envisaged here contain a major part of a liquid hydrocarbon, and notably:
those of inorganic origin such as petroleum derivatives of the gasoline, gas-oil, kerosene, fuel-oil type and/or such as derivatives of coal or gas (synthetic fuels).
those of vegetable origin such as vegetable oils and esters thereof,
and their mixtures, to which optionally oxygenated compounds such as the mono-and poly-alcohols have been added.
The present invention more specifically covers the composition of the fuels constituted by water/liquid hydrocarbon emulsions, preferably water/Diesel fuel emulsions, that are economically valuable and which limit problems of environmental pollution. Below, we shall discuss stabilised water/hydrocarbon emulsions, comprising surfactants suitable for favoring and maintaining the emulsions stable for temperature variations between −10° C. and greater than 70° C.
Water very quickly appeared to be a valuable additive or partial substitutuent for gasoline or Diesel fuel, as it is inexpensive and non-toxic, allowing reduction of specific fuel consumption and emission of poluants whether visible or not.
Despite all these presumed advantages, very few water/hydrocarbon fuels have been produced industrially and distributed on a wide scale to fuel consumers.
Among all the tests carried out, it has been envisaged to provide for separate storage of water and automobile fuel on the vehicle, for mixing prior to injection into the running engine. This approach required a complex and sophisticated device for mixing and metering out each component of the mixture to be implemented on board the vehicle. It became clear that the cost, bulk and fragility of such devices made development of this approach completely dissuasive.
A second approach consisted in storing the pre-metered mixture of water and fuel, but the distributor soon encountered problems of stability during storage of such mixtures in the temperature ranges varying from −20° C. to 70° C., and the automobile owner met with the problems of stability of this mixture in the gasoline tank.
Consequently, numerous fruitless technical propositions exist which in vain set out to provide emulsified fuels comprising water and, more generally, new and non-polluting fuels, leading to a low specific consumption.
As illustration of this state-of-the-art, we can cite French Patent application 2,470,153 which discloses an emulsified fuel, comprising hydrocarbons, and water, and alcohol (methanol, ethanol) and an emulsifying system formed by sorbitan mono-oleate and by ethoxylated nonylphenol. The concentration of the emulsifying system in the emulsion is comprised between 3 and 10% by volume. The indispensable presence of alcohol in this emulsion, constitutes an extremely penalizing element, notably in view of the economies and engine performance obtainable with this emulsion. Additionally, it should be noted that the stability of this water-alcohol/hydrocarbon emulsion has not demonstrated its effectiveness. Indeed, after 72 hours storage of the emulsion, corresponding to a realistic period of non-use of a vehicle operating with this fuel, signs of phase separation (dephasing/demixing) can be seen between the hydrocarbons and the hydro-alcoholic mixture. The de-phased (separated) hydrocarbons at the end of this period can make up up to 3 percent by volume of the emulsion. One can readily imagine that after a few days storage, phase separation of the emulsions in French patent application 2,470,153 will be sufficiently great to make them unsuitable for use, under normal conditions of application.
Additionally, from U.S. Pat. No. 4,877,414, an emulsified fuel is known that includes a certain number of additives, including an emulsifying system formed by a sorbitan sesquioleate, sorbitan mono-oleate, and polyoxyethylene (6 EO) ether of dodecylalcohol. Preferably, according to that patent, total concentration of all additives is around 2.1 percent. Apart from the emulsifying system, the other additives able to be employed can be: a mono-&agr;-olefin (decene-1), methoxymethanol, toluene, and alkyl benzene and calcium hydroxides. This formula is extremely complex, if only in view of the number of additives employed. It is additionally relatively expensive. Finally, the emulsified fuel according to that patent also itself suffers from a lack of stability, particularly at low temperatures. Applicant has further clearly brought this to light by reproducing the preferred example of implementation of the emulsified fuel according to this U.S. patent. It was found that the emulsion separated (suffered phase separation) in one hour. The phenomenon is further accentuated at low temperature, below 5° C. One could hardly dare imagine what could happen in an automobile gasoline tank containing this emulsion under strong winter conditions.
The abstract of Japanese Patent 77-69909 given in Chemical Abstracts 87: 138513 x, relates to an emulsified fuel (kerosene:water) comprising sorbitan sesquiolate and polyethylene glycol ether of nonylphenol as emulsifiers. The size of the dispersed aqueous phase is ≦20 &mgr;m and, on average, is of the order of 10 &mgr;m. This technical proposition also does not provide a suitable way of satisfying the objectives of physico-chemical stability, limitation of pollution, economy and reduction of fuel consumption. That technical teaching consequently in no way helps the skilled person in his investigative work on this invention.
A further Chemical Abstract No. 101: 57568 z, summarizing Brazilian Patent 82 4 947 covers an emulsified fuel comprising hydrocarbons constituted by extremely viscose and heavy petroleum derivatives, water, ethanol and an emulsifier constituted by ethoxylated nonylphenol. This emulsified fuel is intended for use in ovens, conventional fuel oil burners. This fuel could not meet the expected performance specifications for combustion, pollution limitation and low consumption in light or heavy vehicle internal combustion engines. Additionally, this emulsion has poor physico-chemical stability.
International application WO 97/34969, in the name of the applicant, discloses emulsified fuels which the present invention sets out to improve.
These emulsified fuels, which can be automobile fuels, comprise specific amounts of hydrocarbon and a minor amount of a set of additives including, notably, an emulsifying system comprising at least one sorbitol ester, at least one polyalcoxylated fatty acid ester of HLB greater than or equal to 9, and at least one polyalcoxylated alkylphenol of HLB comprised between 10 and 15, the respective concentration ratios of these components varying from 2.5-3.5; 1.5-2.5; 0.5-1.9. The dispersed phase of these emulsified fuels is constituted by water present in an amount of 5-35% by weight while the additives are present in amount of 0.1 to 2% by weight. These fuels are particularly stable over storage times of at least three months. Nevertheless, it has been noted that when used in vehicles in which the fuel gets heated up prior or during the injection phase, before introduction into the carburettor, and when a portion is sent back to the gasoline tank after passage through a filter reaching temperatures close to 75° C., the emulsified fuel separated out into two water and hydrocarbon phases. Thus, a bus which had been stopped over the weekend could not start again on the Monday morning, all of the fuel having decanted. This decantation phenomenon of the emulsified fuels is accentuated when a high-pressure supply system is used, favoring temperature increase. In particular, in all the new direct injection diesel engine technologies equipping all new heavy goods vehicles and an increasingly large percentage of new light vehicles, fuels are heated to a temperature greater than 70° C.
The performance of these known emulsified fue

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