WO2000063322A1 - Fuel compositions - Google Patents

Abstract

Fuel compositions, and methods of forming and using such fuel compositions and components thereof. The fuel compositions may include a hydrocarbon fuel, a polar fluid, and an emulsifier present in an amount effective for the hydrocarbon fuel, polar fluid, and emulsifier to form an emulsion. The methods may include methods of forming noncyclic polyol fatty acid esters and noncyclic polyol fatty alcohol ethers.

Description

FUEL COMPOSITIONS

Cross-References

This application is based upon and claims priority under 35 U.S.C. § 119 from

U.S. Provisional Application Serial No. 60/130,534, filed April 21, 1999, which is

incoφorated herein by reference.

Field of the Invention

The invention relates to fuel compositions, and more particularly to diesel fuel

compositions comprising diesel fuel, a polar fluid such as alcohol and/or water, and an

emulsifier.

Background of the Invention

"Fossil fuels" are hydrocarbon deposits, such as petroleum, coal, and natural

gas, that are derived from the remains of prehistoric plants and animals and that are

used today for fuel. Fossil fuels are the primary source of manmade energy, being

used for heat, electricity, and propulsion, among others. Unfortunately, despite their

widespread use, fossil fuels, and particularly diesel fuels, suffer from a number of

shortcomings.

One shortcoming of fossil fuels is that they are a nonrenewable resource.

Already, countries such as the U.S. must import oil to meet demand. Fossil fuel

supplies may be extended and imports reduced by creating fuel compositions in which

a portion of the fossil fuel is displaced with renewable fuel components, such as

fermentation ethanol and vegetable oils. However, renewable fuels also have serious

shortcomings. For example, ethanol can be blended with gasoline only up to a certain

point (around 20% maximum), and ethanol cannot be blended with diesel at all if either component contains the slightest moisture. Similarly, triglycerides such as

degummed soybean oil or fatty acid methyl esters can be substituted for diesel fuel,

but such substitution can cause a deposition of carbon in engines, an increase in the

viscosity of lubricating oil in the engine's crankcase, and adverse effects on engine

emissions.

Another shortcoming of fossil fuels is that their combustion, and especially the

combustion of diesel fuel, results in large releases of harmful emissions into the

atmosphere. These harmful emissions include nitrogen oxides (NO_x), particulates

(unburned carbon with adsorbed hydrocarbons), and excess carbon dioxide (C0₂).

Nitrogen oxide emissions contribute to ozone formation, resulting in smog associated

with many respiratory diseases. Particulate emissions contribute to an increased risk of

cancer. Carbon dioxide emissions contribute to global warming by acting as a

greenhouse gas.

Harmful emissions from internal-combustion engines can be reduced using

emission controls. Indeed, emission controls such as catalytic converters have been

quite successful in reducing emissions from gasoline engines. Unfortunately, emission

controls have been much less successful in reducing emissions from diesel engines, in

part because diesel engines produce higher levels of NO_x and particulates than

gasoline engines. Moreover, emission controls may not reduce emissions enough to

meet tough new emissions standards now being promulgated. In particular, recent

action by the State of California declaring diesel fumes toxic presents a formidable

challenge to the trucking industry and other diesel users in that state. Harmful emissions from internal-combustion engines also can be reduced

through changes in fuel formulation. For example, emulsions incorporating water in

fuel may reduce NO_x and particulate emissions. NO_x formation is reduced because

water lowers the combustion temperature. Particulate formation is reduced because

water in such microemulsions is distributed in micelles, or "microbubbles," that

explode during combustion to better atomize the fuel, thereby causing more complete

combustion and reducing particulate formation. These mechanisms have been

thoroughly reviewed in the report, "Water and Alcohol Use in Automotive Diesel

Engines" in the U.S. Department of Energy report # DOE/CS/50286-4, published

September 1983 by J. J. Donnelly, Jr. and H.M. White.

The desirability of mixing fuel with renewable fuel components and/or water

has spurred interest in developing surfactants for stabilizing microemulsions of

nonpolar diesel fuel and polar additives. However, development of suitable surfactants

has proven difficult, because surfactant performance often is highly dependent on the

type of fuel (e.g., gasoline, diesel, etc.) and additive.

Various combinations of surfactants have been used to form microemulsions of

gasoline, alcohol, and water. For example, U.S. Patent No. 4,046,519 to Piotrowski

discloses a surfactant blend consisting of a 9: 1 mixture of diglycerides of oleic acid

and bis (hydroxyethyl) stearyl amine oxide for blending of 2-19 vol% aqueous

methanol with gasoline. However, these surfactants may not work for diesel fuel,

which behaves much differently than gasoline in fuel compositions.

Various combinations of surfactants also have been used to form

microemulsions of diesel fuel, alcohol, and/or water. For example, U.S. Patent No. 4,297,107 to Boehmke et al. discloses microemulsions of diesel fuel with water and/or

alcohol, wherein the surfactant is an addition product of ethylene oxide or propylene

oxide and a carboxylic acid amide with 9-21 carbon atoms. U.S. Patent No. 4,451,265

to Schwab discloses similar microemulsions, wherein the surfactant is a combination

of N,N-dimethylethanolamine and a long chain fatty acid. U.S. Patent Nos. 4,744,796

and 4,770,670 to Hazbun et al. disclose similar microemulsions, wherein the

surfactant is a mixture of nitrogenous cationic surfactants, non-ionic surfactants, and

alcohols such as t-butyl alcohol and phenyl alcohol. These surfactant blends all

combine ionic and non-ionic water-soluble surfactants. These surfactant blends all

consist of complex mixtures of ingredients, many of which are expensive, effective

only at high concentrations, and nitrogen containing leading to increased NO_x

emissions.

Polyether-based surfactants also have been used to form microemulsions of

hydrocarbon fuel, alcohol, and/or water. U.S. Patent Nos. 4,002,435 and 4,083,698 to

Wenzel et al. disclose surfactants consisting of complex mixtures of ammonium or

sodium salts of fatty acids, free fatty acids, and non-ionic surfactants, mostly for use

with gasoline. The patents identified a wide range of suitable non-ionic surfactants,

including ethylene oxide condensation products and the cyclic polyol ester Span 80

(sorbitan monooleate), although the latter formed unstable microemulsions. The

required levels of surfactants were very high. Moreover, the sodium-salt surfactants

may lead to the formation of corrosive ash. U.S. Patent No. 4,477,258 to Lepain

discloses a surfactant consisting of sorbitan monooleate in combination with an

ethoxylated water-soluble non-ionic surfactant. This surfactant had to be mixed in a special fashion with the fuel and other components to form stable mixtures, the

thermal stability of which was not addressed.

Previous fuel compositions suffer from additional shortcomings. Most of the

compositions employ petrochemical-based alcohols and surfactants, even though the

associated patents often cite displacement of petroleum-derived resources as an

objective. Most also use nitrogenous compounds that would tend to increase rather

than decrease NO_x emissions, even though the associated patents often cite achieving

emissions reductions as an objective. Finally, many of the compositions include

surfactants containing unwanted aromatics and sodium, or surfactants that are so

expensive that their high cost precludes commercial viability.

Summary of the Invention

The invention provides fuel compositions for use in internal-combustion

engines, and methods of forming and using such compositions, including components

thereof. The fuel compositions may include a hydrocarbon fuel, a polar fluid, and an

emulsifier present in an amount effective for the hydrocarbon fuel, polar fluid, and

emulsifier to form an emulsion. The methods may include methods of forming

noncyclic polyol fatty acid esters and noncyclic polyol fatty alcohol ethers.

The nature of the invention will be understood more readily after consideration of

the drawings and detailed description of the invention that follow. Brief Description of the Drawings

Figure 1 is a flowchart showing a method for forming polyol fatty acid esters

and polyol fatty alcohol ethers in accordance with aspects of the invention.

Figure 2 is a synthetic pathway showing how the method of Figure 1 can be

used to synthesize glyceryl-α-monooleate (α-GMO).

Figure 3 is a schematic view of an apparatus for performing the methods of

Figures 1 and 2.

Figure 4 is a schematic view of a mechanism for retrofitting an existing

industrial glyceryl monooleate (GMOI) plant to produce high purity GMO.

Figure 5 is a schematic view of the fine structure of microemulsion micelles

thought to be formed using high purity GMO.

Figure 6 is a diagram showing the range of stable emulsions formed of hydrous

ethanol/diesel fuel and 90% GMO.

Detailed Description of the Invention

The invention provides fuel compositions for use in internal-combustion

engines, and methods of forming and using such compositions.

The fuel compositions generally comprise (1) a hydrocarbon fuel, such as

diesel, (2) a polar fluid, such as alcohol, water, and/or other oxygen rich fluids, and (3)

an emulsifier present in an amount effective for the hydrocarbon fuel, polar fluid, and

emulsifier to form an emulsion. The emulsifier may be selected from a group

consisting of noncyclic polyol fatty acid esters and noncyclic polyol fatty alcohol

ethers. In some embodiments, at least about half of the emulsifier is selected from this

group. In other embodiments, at least about half of this group is mono-substituted. The emulsifier also may consist essentially of a single molecular species having both polar

and nonpolar portions.

The methods generally comprise methods of forming and using the fuel

compositions, including components thereof. For example, the invention provides

methods of forming the emulsifier, by synthesizing and/or purifying components of

the emulsifier. These components may include noncyclic polyol fatty acid esters and

noncyclic polyol fatty alcohol ethers.

These and other aspects of the invention are described in the following four

sections: (1) synthesis of noncyclic polyol fatty acid esters and noncyclic polyol fatty

alcohol ethers, (2) purification of noncyclic polyol fatty acid esters and noncyclic

polyol fatty alcohol ethers, (3) fuel compositions, and (4) examples.

Synthesis

Monoglycerides of fatty acids have been used for years as surfactants in a

variety of food, cosmetic, and other formulated products. In most applications,

industrial-grade monoglyceride compositions having 40-55% monoglyceride content

have proven suitable. However, the present application in fuel formulations requires

high-purity monoglycerides to yield optimal performance, and inexpensive

monoglycerides to be economically practical.

Monoglycerides have been synthesized by a variety of methods. Unfortunately,

these methods generally yield products that must be further distilled or extracted to

obtain high-purity monoglycerides. Moreover, these methods generally are unsuitable

for forming monoglycerides of unsaturated fatty acids, such as oleic acid, because of

oxidative decomposition at the point of unsaturation. U.S. Patent No. 2,022,493 to Christensen et al. discloses the conventional method for synthesizing monoglycerides,

which involves the transesterification of triglycerides with glycerol and sodium

hydroxide to form the monoglycerides. However, the product of this method is a

mixture of 40-55% monoglyceride, 20-30% diglyceride, and a remainder of unreacted

triglyceride. U.S. Patent Nos. 2,132,437 to Richardson et al. and 2,073,797 to Hilditch

et al. disclose two methods of increasing monoglyceride selectivity by converting the

triglyceride to free fatty acid before esterification. However, the products of these

methods are still contaminated with at least 20% di- and triglyceride, and the methods

are considerably more complex than the conventional method. U.S. Patent No.

5,153,126 to Schroder et al. discloses a method for making additional gains in

selectivity by using a lipase enzyme as the transesterification catalyst. However, this

method is very costly and difficult to scale up.

Figure 1 shows a new method 100 for synthesizing monoglycerides, as well as

other polyol fatty acid esters and polyol fatty alcohol ethers. Here, polyols are

polyhydric alcohols, or alcohols having three or more hydroxyl (OH) groups.

Examples of polyols include glycerol, which has three hydroxyl groups, and sugar

alcohols, which generally have four to seven hydroxyl groups. A first step 102 in the

method involves providing a polyol having at least three reactive alcohol groups. A

second step 104 involves selecting a fatty acid or fatty chloride to react with the

polyol. A third step 106 involves protecting all but a preselected one of the reactive

alcohol groups on the polyol by reacting all but the preselected one of the reactive

alcohol groups with protecting groups. A fourth step 108 involves linking the fatty

acid to the polyol through an ester linkage or linking the fatty chloride to the polyol through an ether linkage by reacting the fatty acid or fatty chloride with the

preselected one of the reactive alcohol groups. A fifth step 110 involves forming the

polyol fatty acid ester or forming the fatty alcohol ether by removing the protecting

groups. The first, second, and third steps may be performed in any order, as long as

the third step follows the first step.

These steps may be performed under conditions that would tend not to

substantially reduce an unsaturated fatty acid or fatty chloride. Such conditions may

include performing one or more of the steps in an inert atmosphere, such as a nitrogen

atmosphere, or performing one or more of the steps in the absence of light.

Figure 2 shows how the method of Figure 1 can be used to synthesize glyceryl-

α-monooleate (α-GMO). Here, the polyol is glycerol, the fatty acid is oleic acid, and

the protecting group is derived from acetone. In a first step 150, the glycerol is reacted

with the acetone in the presence of an acid catalyst to form an intermediate acetonide,

1 ,2-/5O-propylidene glycerol. The preferred acid catalyst is p-toluenesulfonic acid, but

any concentrated mineral acid will suffice. Suitable solvents include any solvent that

(1) does not react with the reactants, (2) is easily separated from acetone in a

fractionating column, and (3) will carry water over by vapor condensation. Such

solvents include benzene and solvents having 1-2 parts of chlorocarbons, such as

chloroform. In a second step 152, the 1,2-tsO-propylidene glycerol is reacted with

oleic acid to form the corresponding 1,2-tsO-propylidene glyceryl ester. In a third step

154, the 1 ,2-wo-propylidene glyceryl ester is reacted with aqueous acetic acid to

remove the protecting group and give the corresponding α-monoglyceride. Acetic acid

acts as both solvent and acid catalyst. Water is added at a rate that sustains hydrolysis without rendering reactants insoluble. Hydrolysis also can be effected by formation of

intermediate borate esters, which are then hydrolyzed with water.

The methods in Figures 1 and 2 can be employed with a wide range of organic

acids, requiring only slight modifications in product work-up. Generally, end-

substituted α-polyols can be synthesized from odd-numbered polyols of the formula

CH₂OH(CHOH)_nCH₂OH (n=l,3,5...) by forming the protecting group using acetone,

among others, as described above. Alternatively, inside-substituted β-polyols can be

synthesized by forming the protecting group using benzaldehyde, among others. In

Figure 2, the glycerol would react with benzaldehyde to form 1 ,3-benzylidene

glycerol, which would yield a corresponding β-glyceryl ester upon esterification and

removal of the benzylidene group by catalytic hydrogenation.

Figure 3 shows an apparatus 200 for performing the methods shown in Figures

1 and 2. A solution 202 of acetone, glycerol, and acid catalyst in chloroform is placed

in a flask 204 such as a 3-neck round-bottom flask fitted with a fractionating column

206, light-oil separating trap 208, and condenser 210. The flask may be placed in a

heating mantle 212 and further fitted with a dropping funnel 214 and a stirrer motor

216 configured to drive a stir rod 217 and paddle 218. The reaction mixture is

refluxed, and water is collected in the trap until no more water forms. The desired

organic acid is then added to the reaction mixture, and reflux is continued until no

additional water collects in the trap. The solvent is distilled off the reaction mixture,

and the residue is dissolved in glacial acetic acid and heated at 60°C for several hours

as water is gradually added. The reaction product precipitates upon cooling and

dilution with additional water. The apparatus is a simple and efficient means of driving the reaction to

completion. During reflux, chloroform and water vapors are separated from reactants

by the use of fractionating column 206, which is packed with glass beads 220. The

chloroform/water vapors are then condensed by means of condenser 210, such as a

Friedrichs condenser, with the condensate flowing down into light oil-type separation

trap 208, where the water and chloroform phases separate. The denser chloroform

phase continuously returns to the reaction vessel via a sidearm 222, while water

accumulates in a receiver trap 224. Water can be periodically removed from the

receiver trap via a stopcock 226 if the production scale exceeds the volume capacity of

the trap. Upon completion of step 1, the desired organic acid can be added and step 2

then carried out without interruption of reflux. The system works smoothly with little

operator attention up to semi-pilot (22-liter reaction volume) scale. Although reaction

times for steps 1 and 2 were fairly long (24-26 h) with the equipment used, reaction

times can be shortened greatly by increasing the capacity of the fractionating column

and condenser. Chloroform solvent can be replaced with other less harmful solvents,

as long as the substitute has a density greater than water and an appropriate boiling

point.

The final acid hydrolysis step using glacial acetic acid represents an

improvement over other acetonide hydrolysis reagents previously employed, such as

mineral acids or boric acid/2 -methoxyethanol. The process takes advantage of the

product's limited solubility in aqueous acetic acid. By adding water only gradually

during hydrolysis, all reactants are kept in solution throughout the step. Once

hydrolysis is complete, the addition of a small amount of water to the cooled product solution causes the product to precipitate. The acetic acid/water mixture, containing

less than 20% water, is then decanted and can be purified and recycled. The combined

attributes of selectivity, simplicity, and recyclability of materials all make the process

amenable for use at an industrial scale. In contrast, in the past, the acetonide

protecting group was removed using a two-step process. The acetonide was first

converted into the borate ester using boric acid and 2 -methoxyethanol, and the borate

ester was then extracted into ether and washed with water to hydrolyze the ether back

to the original diol functionality. This procedure is cumbersome, and some of the

reagents are too costly to use on an industrial scale.

There are many attributes of the present process that render it a practical means

for monoglyceride production. All three steps of the reaction sequence are

accomplished in the same reaction vessel. By using a co-solvent such as chloroform in

combination with a separation trap, water is continuously removed from the reaction

mixture, thereby driving both the acetonide and ester formation steps to completion. In

the past, acetonide formation steps were driven to completion by mechanisms only

suitable at very small scales, such as using water carrier solvents such as chloroform

or benzene, and either a collection tube or Soxhlet extractor filled with drying agent to

remove water from the reaction mixture as it is formed. The solvent mixture obtained

by distillation of the wo-propylidene glyceryl ester product mixture can be recycled

for use in the next batch. The final acetonide hydrolysis step is mild and fast, and the

acetic acid recovered can be purified and recycled.

The product yield from each step is virtually quantitative, and the overall yields

range from 94-98%. Thin layer chromatography (TLC) reveals only traces of residual reactants and no di- or triglyceride contaminants. The product work-up is easy;

involving neutralization of residual acid with sodium bicarbonate, followed by three

water washes. This crude product can be used in microemulsion formulations without

further purification. However, partitioning of the crude product between aqueous

ethanol and hexane removes residual reactants; concentration of the aqueous ethanol

phase affords a pure α-monoglyceride product that readily crystallizes. In

microemulsion formulations using glyceryl-α-monooleate (α-GMO) as the surfactant,

only one-sixth the amount of this α-monoglyceride is needed versus the amount of

industrial grade glyceryl monooleate (GMOI) needed otherwise to emulsify an

equivalent amount of aqueous ethanol in diesel fuel.

The method also may be used to synthesize glyceryl fatty alcohol ethers from

the corresponding fatty alcohol chloride. For example, the method may be used to

synthesize 1,2-iso-propylidene glyceryl R, where R is a hydrocarbon chain, from RC1

and 1 ,2-iso-propylidene glycerol.

Purification

The monoglyceride product may be purified by a variety of methods. U.S.

Patent No. 3,826,720 to Lowrey discloses a monoglyceride purification method based

on the partitioning of crude glyceride mixtures between aqueous methanol and

hexane. Monoglycerides preferentially migrate to the aqueous methanol phase.

However evaporation of the aqueous methanol proves difficult because of excessive

foaming. Since the present application uses the monoglyceride in combination with

aqueous ethanol, it would be advantageous if aqueous ethanol could be substituted for

aqueous methanol in an analogous procedure. Working with product solutions would

reduce the materials handling problems associated with such products, which are

typically very tacky and viscous in the liquid state. Such a method might also be

useful for upgrading industrial grade monoglycerides.

The solvent partitioning purification method for removing residual

contaminants from the crude product is also effective for upgrading the purity of

industrial grade GMOI. It is based on a commonly employed method using a counter-

current separatory column with aqueous methanol as the descending phase and hexane

as the ascending phase to separate monoglycerides from di- and triglyceride

contaminants. The monoglycerides migrate to the aqueous methanol phase, while the

di- and triglycerides migrate to the hexane phase. In the present application, 5%

aqueous ethanol was substituted for the aqueous methanol. The crude GMO sample is

dissolved in 10 parts of hexane and 15 parts of 5% ethanol to afford a homogeneous

solution. Upon addition of 1 part of water, the solution separates into two phases.

Concentration of the aqueous ethanol phase affords a viscous oil that crystallizes on standing and contains very little residual di- and triglyceride by TLC. Concentration

of the hexane phase affords an oil that is primarily di- and triglyceride by TLC.

In formulation experiments with diesel fuel, the GMO thus purified performs as

well as crude α-GMO. If either this product or crude α-GMO is again partitioned by

the same procedure, the requirement for either surfactant is further reduced by 50%,

which represents an overall six fold reduction in GMO requirement compared to

industrial GMOI. Further partitioning does not afford significant additional

performance improvements. This method therefore appears to be effective in

removing both residual reactants and di- and triglycerides from monoglyceride

products.

Figure 4 shows how the partitioning method may be used to obtain high purity

GMO industrially. Existing GMOI plants could be retrofitted with such an extraction

purification system to enable them to produce high purity GMO without greatly

increasing manufacturing costs. The di- and triglyceride mixture isolated from the

hexane fraction could be recycled to the original transesterification reactor. Also,

since the GMO product is used in combination with aqueous ethanol in diesel

microemulsions, the aqueous ethanol does not have to be completely removed for use

in fuel formulations. This would greatly simplify materials handling.

Fuel compositions

One purpose of the synthesis and purification research is to provide options for

the low cost manufacture of purified GMO. The ability to accomplish this has proven

critical to the feasibility of using GMO and other polyol fatty acid esters as surfactants for stabilizing water/ethanol/diesel microemulsions. Previous investigations have

demonstrated that such microemulsions can be made using industrial grade GMOI but

have serious drawbacks. Nearly three parts of GMOI are needed to create a 10%

microemulsion of 5% aqueous ethanol with diesel fuel that is stable at room

temperature. At current prices, the cost of a 30 wt% GMOI: 10 wt% aqueous ethanol:

60 wt% diesel is more than $2.50/gallon which is more than twice the current price of

diesel. Such emulsions also are temperature sensitive, and prolonged storage at

temperatures below the freezing point of water results in the precipitation of solids

and/or phase separation depending upon the particular source of GMOI. The

composition of GMOI varies considerably from supplier to supplier, making it

difficult to predict the behavior of a particular source of GMOI.

These microemulsions are considered to be extremely fine colloidal dispersions

consisting of micelles, or "bubbles," of water and alcohol coated with a layer of

surfactant. As depicted in Figure 5, the surfactant molecules are oriented so that their

hydrophilic, or "water-loving," ends point inward, mixing with the water/ethanol

phase, and their hydrophobic, or "water-hating," ends point outward, mixing with the

similarly hydrophobic constituents of the diesel fuel. This is how the surfactant draws

these two incompatible phases together into stable microsuspensions of tiny

water/ethanol bubbles dispersed throughout a diesel oil phase. There is an excellent

mechanistic role for GMO and other fatty acid monoglycerides to disperse and form a

uniform coating around these bubbles, thereby rendering the emulsion stable.

However, the industrial grade product, GMOI, is only 40-55% monooleate with

the balance being di- and trioleate. Neither the di- or trioleate fits well into the model; the dioleate has little hydrophilic character and the trioleate none. Their presence only

serves to interfere with the action of the monooleate. The need for higher purity

material drove the investigations into synthesis and purification options. It was

subsequently discovered that a higher purity grade of GMO, which analyzed as 90%

monooleate, is commercially available for specialized uses in cosmetics. Formulation

tests using either the α-GMO obtained by direct synthesis or the 90% GMO available

commercially demonstrated a six- fold reduction in the amount of GMO needed. The

30: 10: 60 GMOI: aqueous ethanol: diesel fuel formulation possible with the industrial

grade product could be achieved using a 5: 10: 85 α-GMO (or 90% GMO): aqueous

ethanol: diesel fuel formulation with high purity GMO (α-GMO and 90% GMO). The

fact that a six-fold increase in effect was achieved with only a two-fold increase in

purity has important implications. The disproportionate increase suggests that the

relationship between the constituents is, indeed, quite specific. The dilution effects of

the contaminants are compounded by another effect, which is most likely their

interference in the efficient ordering of the monooleate molecules. Microemulsions

made with high purity GMO exhibit the positive Tyndall effect expected of colloidal

dispersions. All indications support a well-ordered micelle with an ethanol/water core

and a monomolecular layer of monooleate molecules.

It also was found that the formulations using high purity GMO had much more

thermal stability. In addition to the known antifreeze action of the ethanol, it is

reasonable that the hydrophilic ends of the monooleate molecule duplicate the

antifreeze ethylene glycol and thereby cause an analogous effect. The addition of a

small amount of high purity GMO considerably enhances the microemulsion 's thermal stability. Whereas microemulsions using industrial GMOI were only stable

for a period of hours at -10°C, microemulsions using high purity GMO could be stored

at -10°C for months without phase separation or the formation of any precipitate. The

additional stabilizing benefits of adding small portions of ethylene glycol, iso-

propanol, or a 6: 1 mixture of cyclohexanol and cyclohexanone also were noted, with

small portions of either (less than 0.5%) further stabilizing the emulsions down to -

20°C. For practical purposes, the high purity GMO enables use of the fuel without

concern in most of the coastal and southern United States. Fuel system heaters that

might be needed in cold climates are already in use for diesel trucks operating in these

regions.

It is possible that there may be some cold starting difficulties, because

formulations with diesel incorporating high levels of alcohol have exhibited such

problems in the past. Also, engine timing in diesel engines varies with engine type and

model year, and this can affect the emissions reductions achieved. Although water has

a beneficial effect by lowering combustion temperature, it also can retard ignition,

which can have a counter-productive effect depending upon engine timing. If either of

these problems arises with particular formulations, the addition of cetane enhancing

organic nitrates such as 2-ethyl hexyl nitrate or organic peroxides such as ditertiary

butyl peroxide should alleviate either problem. Although the presence of nitrogenous

components in emulsion formulations may contribute to NO_x formation, there is

strong evidence that the nitro groups in alkyl nitrate cetane enhancers are converted to

harmless nitrogen gas in the combustion process. However, the surfactant has a good

cetane value itself, so the levels of cetane enhancer that may be required would not be high (0.5-3.0 wt%) in any event. 2-Ethylhexyl nitrate also was found to have a modest

stabilizing effect in emulsion formulations.

The microemulsions using high purity GMO also tolerate the presence of more

water than that present in just the 5% aqueous ethanol phase, as long as the ethanol

content is relatively high. Formulations using a 5: 10:85 ratio can tolerate up to two

percent added water. Stable formulations with water contents exceeding 5% have been

made using only 2 parts high purity GMO per part of water. Thermal stability is

compromised as the water content is increased, but this, too, can be compensated for

by increasing the ethanol or GMO content or by using the stabilizing additives

previously noted. The presence of water accounts for NO_x-reducing effects of

microemulsions by reducing combustion temperature and results in smoother running

by broadening the temperature-time profile. The particulate reduction effects also are

accounted for by the "steam explosion" of the microbubbles upon combustion, which

better atomizes the fuel and thereby results in more complete combustion. The ability

to control the level of water is important in efforts to find the maximum emissions-

reducing effects. Ethanol also burns very cleanly in diesel engines, producing no

smoke, so its presence can dramatically reduce particulate emissions. Ethanol also

contributes to the moderation of combustion temperature and can, thereby, reduce

NO_x emissions by 10% or more even in the absence of any water.

Another constituent, ammonia, shows a dramatic NO_x -reducing effect. Stable

emulsions also can be made using GMO in combination with the ammonium salt of

oleic acid or other suitable carboxylicacids. Ammonia is used to reduce NO_x in

exhaust gas in both high- temperature and catalytic low- temperature systems. It reacts with NO_x to produce harmless nitrogen gas and water. It was reasoned that

introducing ammonia in the form of ammonium oleate might neutralize N0_X formed

during the combustion process, and the emissions data presented at the end of the

example section show a large N0_X reduction when ammonia is present in this form.

Ammonia reduces NO_x emissions in formulations both with and without cetane

enhancer. In formulations with cetane enhancer, ammonia also appears to reduce

particulate emissions. Calculations show that 12-59% of the ammonia present is

consumed in neutralizing NO_x. Ammonia and oleic acid also are inexpensive and

reduce the requirement for the more expensive GMO.

It is possible to combine almost any proportions of ingredients by using the

appropriate amount of high-purity GMO surfactant. However, significant emissions

reductions have been noted at a level of only 10% aqueous ethanol (overall water

content of 0.5 wt%). Since the GMO costs more than diesel fuel, the quantity used

should be kept to the minimum needed to obtain the desired effect. The estimated cost

of a microemulsion containing 10 wt% aqueous ethanol is about 20% greater than

diesel fuel alone at current diesel, ethanol, and high-purity GMO prices. Reasonable

reductions in manufacturing costs could reduce the price differential to as little as 10%

at the current, very low price for diesel. Only a modest increase in diesel price is

needed to offset this disadvantage.

All constituents in the subject formulations come from renewable resources,

the aqueous ethanol being produced by fermentation and the GMO being derived from

corn oil. The microemulsion formulations that are the object of the present invention

are fully renewable fuels, the 5: 10: 85 formulation having a renewable content of 15%o. Users not only qualify for consideration as a renewable fuel but also may qualify

for C0₂ reduction credits should programs to curb global warming be put into effect.

Although the GMO: aqueous ethanol: diesel fuel formulations have been

identified as one preferred embodiment, the method has considerable generality.

Stable emulsions can be formed with any of the C C₄ alcohols. The level of

monoglyceride required can be reduced through the use of the ammonium salts of

fatty acids, preferably unsaturated fatty acids such as oleic acid. Monoglycerides

incorporating other unsaturated fatty acids such as elaidic, erucic, or linoleic acid also

are effective in amounts comparable to those of GMO and exhibit reasonable thermal

stability. Monoglycerides incorporating saturated fatty acids such as lauric, myristic,

or stearic acid also form microemulsions, but most are thermally unstable. To those

skilled in the art, it is evident that both the synthesis and the application can be

generalized to a wide range of polyol fatty acid esters and polyol fatty alcohol ethers.

The corresponding glyceryl fatty alcohol ethers exercise effects comparable to their

ester analogues. This is to be expected from the model because the position of the

oxygen absent in the ethers has no bearing on the key structural features of the

monoglycerides as surfactants.

It also should be noted that the use of these emissions-reducing microemulsions

will enable the use of additional control methods such as catalytic conversion and

exhaust gas recycle that are currently impractical because of the high level of

particulate soot in diesel exhaust.

The following examples illustrate without limitation these and other aspects of

the invention. Examples

EXAMPLE 1

Direct Synthesis of α-GMO with Hydrolysis via the Borate Ester

50.0 g (0.543 moles) of glycerol, technical grade was added to a 500 mL round

bottom flask fitted with a magnetic stir bar, heating mantle, and 400 mm fractionation

column packed two-thirds full with glass beads connected to a light oil separation trap

and Liebig condenser, as shown in Figure 3. 75 mL (59.1 g, 1.02 moles) of acetone,

reagent grade and 100 mL chloroform, reagent grade and methanol-free, and 0.5 g

(0.0029 moles) of p-toluenesulfonic acid, reagent grade were then added to the flask.

The reaction mixture was heated to reflux, and condensate was collected in the trap

with periodic removal of accumulated water from the trap via the stopcock. Reflux

was maintained until no more water accumulated (approximately 4 hours with the

water recovery rate being 4 mL/h and total water recovered being 10 mL). Reflux was

interrupted, and the reaction mixture was allowed to cool 30 minutes, and then 50.0 g

(0.177 moles) of oleic acid, technical grade was added. A nitrogen inlet/outlet was

placed on top of the condenser, slow nitrogen flow was initiated, and reflux was

resumed for four hours, collecting an additional 3.1 mL of reaction water. The

reaction flask was shielded from light. The reaction mixture was allowed to cool, then

0.55 g (0.0067 moles) of anhydrous sodium acetate, technical grade was added, and

the flask was capped and shaken vigorously. The product solution was transferred to a

500 mL separatory funnel and washed 4 times with 100 mL portions of distilled water.

Solvent was removed from the product mixture with warming under mild vacuum to give 68.5 g (0.173 moles, 97.7% yield) of l,2-«ø-propylidene glyceryl oleate as a

light amber liquid.

The crude ester product was placed in a 500 mL Erlenmeyer flask, and 200 mL

2-ethoxyethanol and 60.0 g (0.97 moles) of ground powdered boric acid, technical

grade were added. The mixture was heated on a hot plate at 100°C for 45 minutes then

allowed to cool. The boric acid gradually dissolved upon heating but white solids,

presumably unreacted boric acid, precipitated on cooling. The mixture was transferred

to a 1 L separatory funnel and extracted with 500 mL of diethyl ether. The ethereal

solution was washed 4 times with 500 mL portions of distilled water. The third and

fourth water washes formed strong emulsions that took 45 minutes to break and

partition. The ethereal solution was dried over anhydrous sodium sulfate, technical

grade, filtered into a 1 L beaker, and gently warmed until all the ether was evaporated.

The oil was placed in a vacuum desiccator and subjected to high vacuum overnight to

give 44.6 g (0.125 moles, 72.3% yield) of light amber viscous oil that crystallized on

standing. The product melting point was 32-37°C. Chromatographic analysis by

comparison with known standards using silica gel plates in 10% methanol in benzene

confirmed that the product was glyceryl- 1 -monooleate uncontaminated with any di- or

trioleate with trace amounts of intermediate 1 ,2-tsO-propylidene glycerol and 1,2-iso-

propylidene glyceryl oleate impurities. EXAMPLE 2

Scaled-up Direct Synthesis of α-GMO Using Hydrolysis in Acetic Acid

To a 22 L 3 -neck flask fitted with mechanical stirrer, heating mantle, 900 mm

fractionating column two-thirds full of glass beads and fitted with a light oil-type

liquid-liquid separator and Friedricks condenser and nitrogen inlet and outlet were

added: 3,000 g (2,372 mL, 32.6 moles) glycerol, technical grade, 4,500 mL (3,546 g,

61.1 moles) acetone, reagent grade, 4,800 mL chloroform, Unisolv methanol-free

grade, and 12.0 g (0.07 moles) p-toluenesulfonic acid, reagent grade. The reaction

mixture was carefully heated to a state of reflux, producing an appropriate rate of

condensation into the separator. Reflux was continued until no more water

accumulated in the separator (approximately 24 h at a collection rate of 25 mL/h with

580 mL of water collected). The separator was designed with sufficient capacity (1 1)

to eliminate any need to remove reaction water during reflux. Nitrogen gas flow was

initiated, and the reaction vessel was protected from light. 3,070 g (3,431 mL, 10.87

moles) of oleic acid, technical grade were added to the still hot reaction mixture via a

dropping funnel, and reflux was continued until no more water accumulated in the

separator (approximately 20 h at a collection rate of 10 mL/h with 195 mL collected).

Heat was discontinued, and 26.4 g (0.32 moles) of anhydrous sodium acetate,

technical grade was added with vigorous stirring. After cooling, 4 L of distilled water

was added and thoroughly mixed. Mixing was stopped, the phases were allowed to

separate, and the aqueous phase was removed by siphon. This step was repeated twice

with 8 L portions of distilled water. The dense organic phase was separated from residual water in a separatory

funnel and charged into a clean 22 L flask for distillation and hydrolysis. The flask

was fitted with a distilling head and 900 mm Liebig condenser, heating mantle, and

mechanical stirrer. Chloroform and residual acetone were distilled off. The distillation

temperature went from 57°C to 72°C, at which point 4,500 mL of distillate had been

collected. The distillation system was put under mild vacuum, and another 300 mL of

distillate were collected. In subsequent runs, the chloroform/acetone solvents were

distilled entirely under mild vacuum, such that the head temperature was kept between

40-45°C. This reduced the distillation time to 2 h. 4,083 mL of glacial acetic acid,

technical grade was added, and the reaction mixture was warmed to 60°C. 600 mL of

distilled water was added until the reaction mixture just became cloudy. An additional

1,800 mL of distilled water were added in 100 mL portions via a dropping funnel

whenever the reaction mixture completely cleared, and the temperature was

maintained between 60-70°C. After 5 h, the reaction mixture was allowed to cool

overnight. In subsequent runs, the distilled water was added as fast as the cloudiness

dissipated, which reduced the reaction time to 2 h. The reaction mixture was poured

into 12 L of rapidly stirring distilled water. Subsequent trials showed that the added

water volume could be reduced to as little as 2 L without significantly affecting

product purity or handling as long as the crude product mass was washed well. After

the precipitated product mass had time to set on standing (going from a viscous liquid

to a semi-solid state), the aqueous acetic acid was decanted off. The mass was washed

3 times with 6 L of distilled water with maceration to penetrate the product mass. The

mass was transferred to a glass reactor and treated with 5 L of saturated aqueous sodium bicarbonate with warming and maceration. When effervescence subsided, the

bicarbonate solution was decanted, and the mass was washed twice with 4 L of

distilled water and then heated just to the boiling point in 6 L of fresh distilled water

and allowed to cool gradually to give an amber gel which formed at the surface as the

α-GMO melted and then re-solidified. This process effectively expresses most of the

water from the mass. The gel was dried overnight under a strong vacuum with gentle

warming at 45-50°C to give 3,717 g (10.42 moles, 96% yield) of viscous amber oil

that crystallized on cooling. The product melting point was 33-36°C. TLC analysis

showed a single spot corresponding to glyceryl- 1 -monooleate (α-GMO) with no di- or

trioleate contamination and only faint traces of acetonide intermediates.

EXAMPLE 3

Purification of Industrial GMOI bv Solvent Partitioning

5.0 g of GMOI (Canamex Glicepol 182 Lot G-20Z7) was weighed into a flask.

75 mL (50 g) hexane, technical grade and 94 mL (75 g) 5% aqueous ethanol, technical

grade were added and the contents mixed until a uniform solution was obtained. An

additional 7.0 g of distilled water was added to the flask and mixed and decanted into

a 250 mL separatory funnel. The funnel was capped, thoroughly shaken, then allowed

to stand so the phases could separate. The phases were separated into two 125 mL

Erlenmeyer flasks, and the solvent was removed by gentle heating. The hexane

fraction weighing 45.6 g with solvent afforded 2.96 g of light tan oil. The ethanolic

phase weighing 86.39 g with solvent was evaporated, then 100 mL anhydrous ethanol

was added and evaporated to remove any residual water to give 1.92 g of light tan oil that spontaneously crystallized on cooling. TLC analysis using silica gel plates in 10%

methanol in benzene showed the hexane-derived oil to be primarily di- and trioleate

with some residual monooleate and the ethanol-derived solid to be primarily

monooleate with only traces of di- and trioleate evident.

EXAMPLE 4

Hvdrous Ethanol with Refined GMOI in Diesel Fuel

In formulation experiments using either unrefined or refined GMOI, 10 parts

diesel fuel were mixed with 1 part hydrous ethanol in a flask, and then the GMOI

sample was added in portions until a clear homogeneous mixture was obtained. The

final proportions are compared in the following:

The formulation using the refined GMOI also appeared particularly stable to

temperature, remaining completely clear on prolonged storage at -9°C. Refining

reduced the amount of GMOI needed by 50%. This method when applied to crude α-

GMO obtained by direct synthesis also afforded substantial performance

improvements, which indicated that it also is effective in removing intermediate

acetonide contaminants as well. EXAMPLE 5

Hydrous Ethanol with Industrial GMOI in Diesel Fuel

40.0 g of industrial grade glyceryl monooleate (GMOI) of 40%+ monooleate

content (PPG Industries) was blended with 60 g of diesel fuel until a homogeneous

mixture was achieved. Hydrous ethanol (190 proof) was then added in portions and

mixed until homogeneous. The mixture remained homogeneous over the following

range of proportions:

The mixtures with the above ranges were clear and stable at room temperature.

The phases did not separate after refrigeration for 24 h at -12°C until the ethanol

concentration exceeded 25%. At room temperature up to 2.0 wt% water could be

added before phase separation was noted.

To determine the minimum amount of GMOI needed to effect a stable

emulsion of hydrous ethanol (190 proof) with diesel fuel, GMOI (PPG Industries),

hydrous ethanol, and diesel fuel were mixed in the following proportions with the

indicated results:

The mixture containing 30 g GMOI became cloudy upon cooling below 7°C, but the

mixture containing 35 g GMOI remained clear to 0°C. The 60:30:10

diesel:GMOI:hydrous ethanol mixture, which contained 0.5 wt% of added water was

subjected to water analysis by Karl-Fischer titration (Coffey Laboratories, Inc.) to

determine the exact total amount of water present, and a mean result of 1.0 wt% ± 0.2

wt% was obtained. This indicates that another 0.5 wt% of water was inadvertently

introduced by way of water contamination of the GMOI and, to a much lesser extent,

of the diesel. This means that the maximum water holding capacity of the 60:30:10

mixture at room temperature is 3.0 wt%. This means that there is considerable

flexibility to add water to formulations to enhance NO_x reduction effects. Further

experiments using high purity GMO (90%+) demonstrate that as much as 4% water

can be formulated while retaining diesel as the main component.

Experiments to test the sensitivity of emulsions to chemical contaminants were

conducted by adding a small amount (10 drops) of concentrated base (50% sodium

hydroxide) or concentrated acid ( 37% hydrochloric acid) to a 60:30:10 emulsion and

observing the effects with time. Results showed that the emulsion was quite stable to

base, being unchanged after 30 days, but rapidly darkened and separated into two

phases after only 4 days upon exposure to acid. It was found that GMOI samples from different suppliers varied in terms of the

minimum amount needed. The cold stability of the emulsions appeared more variable

from supplier to supplier. Specifications varied in terms of monooleate content from

40-55%, residual glycerol from 1-3%, and residual triglyceride from 2-5%, but no

particular variable clearly correlated with cold stability. In another experiment, a

60:30:10 emulsion with GMOI was stored for 4 days at -15°C, at which point a

substantial amount of white flocculent solid had precipitated out. This solid was

isolated by vacuum filtration in the cold to give a white waxy solid upon vacuum

drying that appeared to be a mixture of trioleate and dioleate by chromatographic

analysis. The filtrate obtained, which was now devoid of these solids, remained clear

and homogeneous upon prolonged storage at -15°C. It, therefore, appears that the di-

and triglyceride contaminants present in formulations using GMOI are a leading cause

of solids precipitation in the cold and contribute nothing to the stability of the

emulsion because their removal stabilizes rather than destabilizes the emulsion. This

evidence provided a strong impetus to seek a means of synthesizing glyceryl

monooleate free of di- and trioleate contaminants.

The foregoing formulations are advantageous because they employ only a

single surfactant compared to the use of a minimum of two surfactants in prior art

examples. The absence of any nitrogen containing substances should help to minimize

NO_x emissions. However, there is considerable product variability depending upon

supplier, and the fairly large amounts of GMOI needed rendered the formulation cost

about twice that of diesel alone. EXAMPLE 6

Hydrous Ethanol with Glyceryl Monostearate in Diesel Fuel

30.0 g of Glyceryl monostearate flake was placed in a 250 mL Erlenmeyer

flask. 10.0 g of hydrous ethanol (190 proof) was added and stirred. At room

temperature, the two did not form a homogeneous solution. Upon gentle warming

until the glyceryl monostearate melted (56°C), the two components mixed to give a

homogeneous solution that remained clear upon addition of 60.0 g of diesel fuel while

warm. The still warm clear homogeneous emulsion formed a dense white solid

precipitate of glyceryl monostearate upon standing at room temperature. Additional

experiments using purified GMO having a significant concentration of saturated fats

such as stearic acid showed a similar tendency to precipitate solids upon cooling.

EXAMPLE 7

Hvdrous Methanol with Industrial GMOI in Diesel Fuel

30.0 g of Industrial GMOI (PPG Industries) was mixed with 10.0 g of

anhydrous methanol. 60.0 g of diesel fuel was then added, and the mixture was stirred

until clear and homogeneous. 0.5 g of distilled water was added dropwise and stirred

until fully dispersed to give a clear homogeneous emulsion of the following final

proportions:

The mixture was clear and stable at room temperature. The phases did not separate

after refrigeration for 24 h at 0°C. At room temperature, up to 1 wt% water could be

added before phase separation was noted.

Methanol is currently the least expensive of the C C₄ alcohols. Although it is

currently manufactured by the reforming of natural gas, it can be produced from

synthesic gas obtained by biomass gasification so it has future potential as a

renewable energy source.

EXAMPLE 8

C₂ and C_£ Alcohols with GMOI in Diesel Fuel

30.0 g of GMOI (Kemester 2000, 50-60% monoester content) was weighed

into each of three flasks. 10.0 g was then added of one of (a) /t-propyl alcohol, (b) iso-

propyl alcohol, or (c) n-butyl alcohol, and each flask was stirred until a homogeneous

mixture was obtained. 60.0 g diesel fuel was then added and thoroughly mixed. In all

three cases, homogeneous mixtures were obtained. 0.5 wt% distilled water was then

added dropwise to each and mixed until fully dispersed. Again, all three cases gave

clear homogeneous mixtures, although it appeared to take longer for the water to

disperse in case (c) using n-butyl alcohol. All of the emulsions were stable down to a

temperature of 10°C, but a gel-like solid formed upon prolonged storage of samples

(a) and (c) at 7°C. The sample using wo-propyl alcohol was stable down to 0°C. EXAMPLE 9

Hydrous Ethanol with Crude α-GMO in Diesel Fuel

10.0 g of crude α-GMO was placed in a flask. 10.0 g of hydrous ethanol (190

proof) was then added and mixed until homogeneous. 80.0 g of diesel fuel was then

added and mixed to give a cloudy suspension. Additional warm liquid α-GMO was

added dropwise with stirring until a clear homogeneous mixture was obtained,

requiring the addition of 2.7 g. The emulsion was then chilled to 1°C, which resulted

in a cloudy emulsion. Addition of a further 0.5 g of α-GMO while still cold rendered a

clear emulsion. Further chilling to -13°C resulted in solids formation and a small

amount of a dense liquid phase. Further addition of 1.5 g of α-GMO while in the cold

afforded a clear emulsion that was stable to prolonged storage at -13°C. The final

proportions needed to achieve stable emulsions over the temperature range are:

The α-GMO used represents a crude synthesis product that was not subjected

to any purification. Although the α-GMO was devoid of di- and triglyceride

contaminants, there were trace amounts of residual reactants present. Some variability

was observed from batch to batch, with the wt% of α-GMO needed to effect a stable

emulsion of 10 wt% hydrous2 23°C:

The emulsion having the maximum ethanol concentration was stable at room

temperature, but phase separation occurred upon cooling to 12°C. Upon addition of

another 1.7 wt% α-GMO, the emulsion was stable to 0°C. Emulsions having a

hydrous ethanol concentration of 10 wt% and 10 wt% crude α-GMO were thermally

stable to prolonged storage at -12°C. Note that the α-GMO lot used in this test proved

more thermally stable than the lot used in Example 9. There are a number of subtle

factors that affect thermal stability. This variability underscores the importance of

cleaning up crude α-GMO by solvent partitioning before use.

EXAMPLE 11

Hvdrous Ethanol with Commercial 90% GMO in Diesel Fuel

5.0 g of hydrous ethanol and 50.0 g of diesel fuel were added to a flask and

mixed. Portions of GMO (Germany, 90% monooleate, M.P. 33-38°C) were added and

mixed until a clear homogeneous mixture was obtained at room temperature. The

sample was then chilled to -9°C, at which point a fine white solid and dense liquid

phase had formed. Portions of GMO were again added until a mixture was achieved

that remained clear and homogeneous at -9°C. The final proportions were:

This result shows that higher purity GMO grades available commercially are

quite suitable as is for producing stable emulsions and can reduce the amount of GMO

required by four to six fold over emulsions using industrial GMOI. Although the price

for the 90% purity grade is $1.50/lb in bulk versus $0.83/lb for GMOI in bulk , the

cost of the emulsion fuel (at a 10% hydrous ethanol level) is $1.66/gallon using high

purity GMO versus $2.45/gallon using GMOI. This is quite favorable when compared

to the current diesel price of $1.19/gallon. The synthesis and purification methods that

are the object of the present invention should enable a reduction in high purity GMO

prices by 25-30%, which would render emulsion formulations competitive with diesel.

EXAMPLE 12

Hvdrous Ethanol/Diesel Fuel Solubility Over a 0-100% Range

Using Commercial 90% GMO

50.00 g of certified diesel (Phillips, Lot D-538) was weighed into a flask, and

5.00 g of hydrous ethanol (190 proof) was added and mixed. GMO (German, 90%)

was added in portions and mixed until a clear, homogeneous emulsion was obtained.

Another portion of ethanol was added and then more GMO was added to render the

mixture clear. These sequential additions were continued until the ethanol

concentration exceeded 36 wt%. In a separate experiment, 50.00 g of hydrous ethanol and 5.00 g of certified diesel were weighed into a flask, and GMO was added until

clear and homogeneous. This cycle of diesel and GMO additions was continued until

the diesel concentration exceeded 36 wt%. Thus, the GMO requirement for blending

hydrous ethanol and diesel was determined over the entire range of possible

concentrations. These results are tabulated on the following page.

EXAMPLE 13

90% GMO Requirements for Emulsions with High Water

And Ethanol Concentrations

40.00 g of certified diesel (Phillips, Lot D-538) and 24.00 g of anhydrous

ethanol were weighed into a flask. A portion of water was then added, followed by

portions of GMO (German, 90%) until a clear, homogeneous emulsion was obtained.

This cycle of water and GMO additions was continued until the water concentration

exceeded 5 wt% with the following results:

EXAMPLE 14

90% GMO Requirements for Emulsions with High Water

And Low Ethanol Concentrations

25.00 g of No. 2 diesel fuel and 0.51 g of distilled water were measured into a

flask, and portions of GMO (German, 90%) were added and mixed until dispersed.

After addition of 1.72 g GMO, it was evident that the water and GMO were not going

to mix to give a clear emulsion, although the water was well-dispersed. Upon addition

of 1.00 g of anhydrous ethanol, the mixture formed a clear emulsion, which became cloudy upon further addition of 0.72 g of anhydrous ethanol. Addition of a 0.28 g

portion of GMO again afforded a clear emulsion. Portions of water were then added

followed by portions of GMO until clear emulsions were obtained. The proportions

affording clear, stable emulsions at room temperature are summarized in the following

table:

EXAMPLE 15

Hvdrous Ethanol with the Ammonium Salt of Oleic Acid and

Crude α-GMO in Diesel Fuel

5.0 g of oleic acid was first mixed with 6.0 g of hydrous ethanol (190 proof) in

a flask. 0.55 g of 28% aqueous ammonium hydroxide was then added and mixed until

a clear homogeneous solution was obtained. 22.5 g of diesel fuel was then added in

portions and mixed to the following final proportions:

The resulting emulsion was clear and homogeneous at 23°C.

Upon addition of 27.5 g more diesel fuel, phase separation occurred. Crude α-

GMO obtained by direct synthesis was then added in portions until a clear

homogeneous emulsion was obtained with the following final proportions:

The emulsion was stable at 23°C. Upon cooling to 12°C, phase separation occurred.

Upon addition of 0.5 wt% α-GMO, the emulsion cleared and remained stable to 0°C.

Results of emissions tests shown in the table following Example 16 show a dramatic

drop in NO_x emissions using the formulation with ammonia even though cetane

enhancer is absent. The same formulation without ammonia showed no reduction in

emissions. This is strong evidence that ammonia is exerting a "neutralizing" effect on

NO_x, presumably by reacting with NO_x to give nitrogen and water. EXAMPLE 16

Formulations Including Cetane Enhancers

Two emulsions were formulated by successive mixing of ingredients in a flask

to the following final compositions:

The cetane enhancer, 2-ethylhexyl nitrate, was added in proportions of 1.5 and

3 wt% to compositions 1 and 2, respectively. The properties of the resulting emulsions

were compared to the original emulsions lacking cetane enhancer. All compositions

remained stable to temperatures down to -8°C, although those having cetane enhancer

appeared to be somewhat more stable to colder temperatures. The cetane number of

composition 1 was raised from 37.8 to 51.1 by the addition of 1.5 wt% of 2-ethylhexyl

nitrate.

Selected formulations were tested for cetane number, exhaust emissions, and

mileage at California Environmental Engineering using a 1995 Dodge Ram and

certified testing procedures. The results are presented in the following table:

HC = Hydrocarbons NOx = Nitrogen Oxides NH3 = Ammonia

CO = Carbon Monoxide C02 = Carbon Dioxide

The test vehicle employed represents a late model vehicle that produces

inherently lower emissions than earlier model or heavy-duty engines. Although a

number of formulations afforded emissions reductions when tested in an earlier model

engine (1989 Cummins), the same formulations afforded little or no emissions

reductions when re-tested in the 1995 vehicle. Both compositions referenced in

Example 16 afforded dramatic reductions in NO_x and particulate, while fuel economy

was maintained. Examination of particulate filters used in these tests shows very low

soot levels. The cetane enhancer proved important in realizing emissions reduction by

reducing the ignition time of the fuel which would otherwise be retarded by the

presence of water and ethanol. As noted, Example 15 containing ammonia also

showed a dramatic reduction in NO_x emissions, even though one would predict no

emissions reduction because cetane enhancer was absent. Indeed, there was no

reduction in particulate emissions as expected. This powerful NO_x reducing effect of

ammonia is in addition to the emissions reducing effects of water and ethanol in the

presence of cetane enhancer. Thus, formulations having both water, ethanol,

ammonia, and cetane enhancer are predicted to give twice the NO_x emissions

reduction shown for either separately. EXAMPLE 17

Formulations of 90% GMO With Ethylene Glvcol

10.0 g of certified diesel and 1.0 g of ethylene glycol were added to a flask and

mixed. GMO (German, 90%) was added in portions and mixed until a clear,

homogeneous emulsion was obtained with the following final composition:

Although stable at room temperature, chilling quickly induced the precipitation of

white solids.

EXAMPLE 18

Formulations with Ammonia and Cetane Enhancer

71.35 g of certified diesel fuel (lot D-538) was weighed into a flask. 12.63 g of

hydrous ethanol (190 proof, USP grade) was added and mixed to give two immiscible

phases. 10.62 g of oleic acid (USP grade) was added and mixed to give a very hazy

unstable suspension. 190 g of 28% ammonium hydroxide solution (technical grade)

was added and mixed to give a clear homogeneous emulsion. 1.50 g of 2-ethyl hexyl

nitrate was added and mixed. The emulsion was stable at room temperature but

became very cloudy upon cooling to 0°C. Portions of high purity GMO (German)

were added and mixed until the resulting emulsion was stable overnight at -14°C. 2.00

g of GMO was required. The final proportions required to produce stable emulsions at

various temperatures are shown in the following table:

Results of emissions tests shown in the table following Example 16 show a dramatic

drop in NO_x emissions using the formulation with ammonia. The same formulation

without ammonia showed a smaller reduction in NO_x and particulate emissions. This

provides additional confirmation that ammonia is exerting a "neutralizing" effect on

NO_x. Although the invention has been disclosed in preferred forms, the specific

embodiments thereof as disclosed and illustrated herein are not to be considered in a

limiting sense, because numerous variations are possible. For example, although the

description of the synthesis and purification focused on GMO, it will be obvious to

those skilled in the art that the methods can be generalized to synthesize and purify

other polyol fatty acid esters and polyol fatty alcohol ethers. Applicant regards the

subject matter of his invention to include all novel and nonobvious combinations and

subcombinations of the various elements, features, functions, and/or properties

disclosed herein. No single feature, function, element or property of the disclosed

embodiments is essential. The following claims define certain combinations and

subcombinations of features, functions, elements, and/or properties that are regarded

as novel and nonobvious. Other combinations and subcombinations may be claimed

through amendment of the present claims or presentation of new claims in this or a

related application. Such claims, whether they are broader, narrower, or equal in scope

to the original claims, also are regarded as included within the subject matter of

applicants' invention.

Claims

I CLAIM:

1. A diesel composition for use in internal-combustion engines, the diesel

composition comprising:

diesel fuel;

an alcohol;

water; and

an emulsifier, the emulsifier being present in an amount effective for the diesel

fuel, alcohol, water, and emulsifier to form an emulsion, wherein at least about half of

the emulsifier is selected from the group consisting of noncyclic polyol fatty acid

esters and noncyclic polyol fatty alcohol ethers.

2. The diesel composition of claim 1 , wherein the alcohol has one to four

carbons.

3. The diesel composition of claim 2, wherein the alcohol is selected from

the group consisting of methanol and ethanol.

4. The diesel composition of claim 1, wherein the alcohol is aqueous

alcohol.

5. The diesel composition of claim 1, wherein the diesel fuel, alcohol,

water, and emulsifier are present in amounts effective to reduce emissions of nitrogen

oxides by a threshold amount upon combustion of the diesel composition, relative to

diesel fuel alone.

6. The diesel composition of claim 1, wherein the diesel fuel, alcohol,

water, and emulsifier are present in amounts effective to reduce emissions of

particulates by a threshold amount upon combustion of the diesel composition,

relative to diesel fuel alone.

7. The diesel composition of claim 6, wherein the diesel fuel, alcohol,

water, and emulsifier also are present in amounts effective to reduce emissions of

nitrogen oxides by a threshold amount upon combustion of the diesel composition,

relative to diesel fuel alone.

8. The diesel composition of claim 1, wherein the polyol fatty acid esters

and polyol fatty alcohol ethers include monoglycerides of unsaturated fatty acids.

9. The diesel composition of claim 8, wherein the unsaturated fatty acids

are selected from the group consisting of arachidic, elaidic acid, erucic acid, gadoleic

acid, margaroleic acid, myristoleic acid, linoleic acid, linolenic acid, palmitoleic acid

and oleic acid.

10. The diesel composition of claim 9, wherein the unsaturated fatty acid is

oleic acid.

11. The diesel composition of claim 10, wherein at least about half of the

monoglycerides are end substituted.

12. The diesel composition of claim 8, wherein at least about half of the

monoglycerides are end substituted.

13. The diesel composition of claim 1, wherein the diesel fuel, alcohol,

water, and emulsifier are present in amounts effective to form an emulsion containing

no more than about 90% diesel fuel.

14. The diesel composition of claim 1, wherein the diesel fuel, alcohol,

water, and emulsifier are present in amounts effective to form micelles in which a

substantially monomolecular layer of emulsifier surrounds a substantially

alcohol/water core.

15. The diesel composition of claim 1, wherein the diesel composition is

fluid at room temperature.

16. The diesel composition of claim 1, wherein the diesel composition is

suspended in air to form an aerosol.

17. The diesel composition of claim 1, wherein the diesel composition has a

viscosity of less than about 10 millipascals.

18. The fuel composition of claim 1, further comprising a small amount of

one or more additives selected from the following group: cetane enhancers, thermal

stabilizers, NO_x neutralizers, and combustion modifiers.

19. The fuel composition of claim 1, wherein the emulsifier consists

essentially of a single species selected from the group consisting of noncyclic polyol

fatty acid esters and noncyclic polyol fatty alcohol ethers.

20. A fuel composition for use in internal-combustion engines, the fuel

composition comprising:

a hydrocarbon fuel suitable for use in internal-combustion engines;

an alcohol;

water; and

an emulsifier, the emulsifier being present in an amount effective for the

hydrocarbon fuel, alcohol, water, and emulsifier to form an emulsion, wherein at least

a portion of the emulsifier is selected from the group consisting of noncyclic polyol

fatty acid esters and noncyclic polyol fatty alcohol ethers, at least about half of that

portion being mono-substituted.

21. The fuel composition of claim 20, wherein the hydrocarbon fuel is diesel

fuel.

22. The fuel composition of claim 20, wherein at least about half of the

portion is end-substituted.

23. The fuel composition of claim 20, wherein at least about half of the

portion is a single species.

24. A fuel composition for use in internal-combustion engines, the fuel

composition comprising:

a hydrocarbon fuel suitable for use in internal-combustion engines;

a polar fluid; and

an emulsifier, the emulsifier being present in an amount effective for the

hydrocarbon fuel, polar fluid, and emulsifier to form an emulsion,

wherein the emulsifier consists essentially of noncyclic polyol fatty acid esters

and noncyclic polyol fatty alcohol ethers.

25. The diesel composition of claim 24, wherein the polar fluid includes

oxygen.

26. The diesel composition of claim 24, wherein the polar fluid is selected

from the group consisting of water and alcohol.

27. A fuel composition for use in internal-combustion engines, the fuel

composition comprising:

a hydrocarbon fuel suitable for use in internal-combustion engines;

an alcohol;

water; and

an emulsifier consisting essentially of a single molecular species having a polar

portion and a nonpolar portion, the emulsifier being present in an amount effective for

the hydrocarbon fuel, alcohol, water, and emulsifier to form micelles containing the

alcohol, water, and emulsifier.

28. The fuel composition of claim 27, wherein the emulsifier comprises a

combination of a polyol fatty acid ester or polyol fatty alcohol ether with the

ammonium salt of a carboxylic acid.

29. The fuel composition of claim 28, wherein the carboxylic acid is oleic

acid.

30. A diesel composition for use in internal-combustion engines, the diesel

composition consisting essentially of:

diesel fuel;

a polar fluid; and

an emulsifier, the emulsifier being present in an amount effective for the

hydrocarbon fuel, polar fluid, and emulsifier to form an emulsion,

wherein at least a portion of the emulsifier is selected from the group consisting

essentially of noncyclic polyol fatty acid esters and noncyclic polyol fatty alcohol

ethers, at least about half of that portion being mono-substituted.

31. The diesel composition of claim 30, wherein the polar fluid includes

oxygen.

32. The diesel composition of claim 30, wherein the polar fluid is selected

from the group consisting of water and alcohol.

33. A diesel composition for use in internal-combustion engines, the diesel

composition comprising:

diesel fuel; and

an oxygen-containing fluid;

wherein the oxygen-containing fluid is substantially homogeneously dispersed

in the diesel to form the diesel composition.

34. The diesel composition of claim 33, further comprising an emulsifier,

the emulsifier being present in an amount effective for the diesel fuel, oxygen-

containing fluid, and emulsifier to form an emulsion.

35. A method of formulating a hydrocarbon fuel composition for use in

internal-combustion engines, the method comprising:

providing a hydrocarbon fuel; and

forming the hydrocarbon fuel composition by adding to the hydrocarbon fuel a

polar fluid and an emulsifier, the emulsifier being present in an amount effective for

the diesel fuel, alcohol, water, and emulsifier to form an emulsion, wherein at least

about half of the emulsifier is selected from the group consisting of noncyclic polyol

fatty acid esters and noncyclic polyol fatty alcohol ethers.

36. The method of claim 35, further comprising mixing the hydrocarbon

fuel composition with air to form an aerosol.

37. The method of claim 35, further comprising combusting the

hydrocarbon fuel composition.

38. The method of claim 35, wherein the emulsifier includes purified GMO.

39. A method involving forming a polyol fatty acid ester, the method

comprising:

providing a polyol having at least three reactive alcohol groups;

selecting a fatty acid;

protecting all but a preselected one of the reactive alcohol groups on the polyol

by reacting all but the preselected one of the reactive alcohol groups with protecting

groups, wherein a single protecting group may protect one or more reactive alcohol

groups;

linking the fatty acid to the polyol through an ester linkage by reacting the fatty

acid with the preselected one of the reactive alcohol groups; and

forming the polyol fatty acid ester by removing the protecting groups;

wherein each of the steps is performed under conditions that would tend not to

substantially reduce an unsaturated fatty acid.

40. The method of claim 39, wherein the fatty acid is unsaturated.

41. The method of claim 40, wherein the fatty acid is selected from the

group consisting of arachidic, elaidic acid, erucic acid, gadoleic acid, margaroleic

acid, myristoleic acid, linoleic acid, linolenic acid, palmitoleic acid and oleic acid.

42. The method of claim 39, wherein the polyol is a noncyclic polyol.

43. The method of claim 39, wherein the polyol is glycerol.

44. The method of claim 39, wherein the protecting group is acetone.

45. The method of claim 39, wherein the protecting group is benzaldehyde.

46. The method of claim 39, wherein the step of removing the protecting

group includes acid hydrolysis.

47. The method of claim 39, wherein the step of removing the protecting

group includes formation and subsequent hydrolysis of a borate ester.

48. The method of claim 46, wherein the acid hydrolysis is performed using

acetic acid.

49. The method of claim 39, wherein each of the steps is performed under

an inert atmosphere.

50. The method of claim 49, wherein the inert atmosphere consists

essentially of nitrogen.

51. The method of claim 39, wherein each of the steps is performed in the

same reaction vessel.

52. The method of claim 39, further comprising purifying the fatty acid

ester.

53. The method of claim 39, further comprising combining the fatty acid

ester with a hydrocarbon fuel and a polar fluid to form an emulsion suitable for use as

a fuel composition in an internal-combustion engine.

54. The method of claim 39, further comprising linking an additional moiety

to a second reactive alcohol group different than the preselected one of the reactive

alcohol groups.

55. The method of claim 54, wherein the additional moiety nitrates one or

both hydroxyl groups on the polyol fatty acid ester to produce a nitro polyol fatty acid

ester.

56. The method of claim 55, wherein the nitro polyol fatty acid ester is a

cetane enhancer.

57. The method of claim 56, wherein the cetane enhancer retains at least a

portion of its surfactant properties.

58. The method of claim 54, wherein the additional moiety is ammonia and

the polyol fatty acid ester is glyceryl monooleate

59. A method involving forming a polyol fatty acid ester, the method

comprising:

providing a polyol having at least three reactive alcohol groups;

selecting a fatty acid chloride;

protecting all but a preselected one of the reactive alcohol groups on the polyol

by reacting all but the preselected one of the reactive alcohol groups with protecting

groups, wherein a single protecting group may protect one or more reactive alcohol

groups;

linking the fatty acid chloride to the polyol through an ester linkage by reacting

the fatty acid with the preselected one of the reactive alcohol groups in the presence of

an acid scavenger; and

forming the polyol fatty acid ester by removing the protecting groups;

wherein each of the steps is performed under conditions that would tend not to

substantially reduce an unsaturated fatty acid.

60. The method of claim 59, wherein the acid scavenger is pyridine.

61. A method involving separating monoglycerides from a mixture

containing monoglycerides and multiglycerides, the method comprising:

providing a mixture of monoglycerides and multiglycerides;

selecting an extraction fluid having a nonpolar component and a polar

component that includes aqueous ethanol;

preferentially associating the monoglycerides with the polar component and the

multiglycerides with the nonpolar component by contacting the mixture with the

extraction fluid; and

at least partially separating the monoglycerides from the multiglycerides by

separating the polar component from the nonpolar component.

62. The method of claim 61, wherein the monoglycerides and

multiglycerides primarily include esters of oleic acid.

63. The method of claim 61, wherein the polar component consists

essentially of aqueous ethanol.

64. The method of claim 63, wherein the aqueous ethanol includes about

five percent water.

65. The method of claim 61, wherein the nonpolar component includes

hexane.

66. The method of claim 65, wherein the polar component consists

essentially of aqueous ethanol.

67. The method of claim 66, wherein the extraction fluid includes about

fifteen parts of the polar component for every ten parts of the nonpolar component.

68. The method of claim 61, wherein the polar component is separated from

the nonpolar component by contacting the two components with water.

69. The method of claim 61, further comprising concentrating the polar

component to concentrate the monoglycerides.

70. The method of claim 69, further comprising combining the concentrated

polar component with a hydrocarbon fuel and a polar fluid to form an emulsion

suitable for use as a fuel composition in an internal-combustion engine.

71. The method of claim 61, further comprising repeating the steps of

preferentially associating the monoglycerides and separating the monoglycerides,

using the ethanol component as the mixture.

72. The method of claim 61, wherein the step of contacting the mixture with

an extraction fluid includes using a counter-current process.

73. The method of claim 72, wherein the counter-current process includes

using the polar component in a descending phase and the nonpolar component in an

ascending phase.

74. The method of claim 61, further comprising using the monoglycerides as

an emulsifier in a fuel composition for an internal-combustion engine.

75. The method of claim 61, wherein the polar component and the nonpolar

component form distinct phases.

76. A method involving separating polyol monoesters from a mixture of

polyol monoesters and polyol multi-esters, the polyol including at least a four-carbon

chain, the method comprising:

providing a mixture of polyol monoesters and polyol multi-esters;

selecting an extraction fluid having a nonpolar component and a polar

component;

preferentially associating the polyol monoesters with the polar component and

the polyol multi-esters with the nonpolar component by contacting the mixture with

the extraction fluid; and

at least partially separating the polyol monoesters from the polyol multi-esters

by separating the polar component from the nonpolar component.