WO2002059236A2

WO2002059236A2 - Stabilizer blends for alcohol in hydrocarbon fuel

Info

Publication number: WO2002059236A2
Application number: PCT/US2001/049267
Authority: WO
Inventors: Paul R. Hart; Ellen M. Meyer; Nancy R. Calvert
Original assignee: Ge Betz, Inc.
Priority date: 2000-12-29
Filing date: 2001-12-18
Publication date: 2002-08-01
Also published as: US20040093789A1; WO2002059236A3; AU2002246715B2

Abstract

The present invention relates to compositions to stabilize hydrocarbon fuel, over a range of alcohol and water concentrations, against phase separation, containing a blend of two or more wide or one or more wide and one or more tall gaint hydrophobe nonionic surfactants. It also relates to fuel compositions stable toward such phase separation, which include (a) a major portion of a hydrocarbon fuel; (b) a minor amount of a low-alkyl (C1-C3) alcohol; (c) a minor portion of water; and (d) a minor portion of a stabilizer comprising a blend of wide or wide and tall giant hydrphobe nonionic surfactants. Optionally, the fuel compositions also include (e) a minor amount of a combustion aid, such as a cetane improver and (f) a minor amount of a solvent, such as a water solubilizing higher (C4 to C16) alcohol.

Description

STABILIZER BLENDS FOR ALCOHOL IN HYDROCARBON FUEL

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to stabilizer blend compositions and hydrocarbon fuel compositions for combustible use and a method of forming the fuel compositions, and more particularly to a fuel composition comprised of a stabilized blend of hydrocarbon fuel, alcohol and water.

2. Background of the Invention and Related Art

Conventional hydrocarbon fuels, due to their cost and availability, are used globally for combustion, to heat and power a wide variety of stationary structures and machines and moving vehicles such as, for example, buildings, power generators, farm equipment, passenger cars, buses, trucks, construction equipment, aircraft and ships. In an effort to reduce dependence on fossil hydrocarbon fuels, recent research has been done in the alternative fuel and hybrid fuel sector. In particular, in the hydrocarbon fuel sector hybrid compositions have been proposed containing an alcoholic fraction, especially one of low-alkyl alcohols like methanol and ethanol, these being in principle obtainable from renewable resources. The problems associated with these hybrid compositions are of various kinds.

One problem is that, while low-alkyl alcohols have superior combustion characteristics in some applications (e.g. Octane No. in gasoline engines) their combustion properties are inferior in other applications (e.g. Cetane No. in diesel engines). To compensate for this problem, a combustion aid, such as a Cetane Improver, can be added to the alcohol. Known cetane improvers include alkyl nitrates, such as 2-ethylhexylnitrate (2EHN), and organic peroxides. Combustion aids for other applications include various organometallic compounds, containing lead, manganese, or iron.

The most important and difficult problems with these hybrid formulations derive from the water tolerance and phase separation characteristics of such compositions. For example, ethanol, which is considered the most interesting from the point of view of economics, availability, toxicology and combustion characteristics, is miscible with most hydrocarbon fuels in all proportions when anhydrous; but even a small quantity of water is sufficient to induce phase separation. This separated hydrous alcoholic layer is undesirable as it leads to erratic combustion or poor combustion emissions, and can lead to the corrosion of components of the fuel delivery system, combustion furnace or engine. The heavier and more hydrogen-saturated the hydrocarbon, and the lower the temperature, the

less the fuel's ability to solubilize water. At 0°C, a water concentration of only 0.05% in a typical low sulfur diesel will cause phase separation. Since low-alkyl alcohols such as ethanol are highly hygroscopic, the fuel will typically pick up this amount during transport and storage. For this reason, alcohol-hydrocarbon fuel blends tend to be impractical.

On one hand, the limited miscibility of hydrous alcohol fractions means that surface-active additives are required in order to stabilize the blends as emulsions. On the other hand, the fact that the anhydrous alcohols are soluble to a large extent in the hydrocarbon liquids in question, and vice versa, means they are significantly less polar than water, so that conventional surfactants effective for stabilizing water emulsions are not very effective for this purpose. Consequently, extensive research has been directed towards alcoholic hydrocarbon fuel compositions possessing greater water tolerance.

Hybrid hydrocarbon fuel compositions have been developed to improve the tolerance toward water-induced phase separation of alcoholic hydrocarbon fuels, as well as the ease of formation and/or the stabiliy of any resultant emulsion. The following patents describe the state-of-the-art relating to fuel compositions comprised of several components including hydrocarbon fuel, water, various alcohols, and surfactants, the relevant parts are incorporated herein by reference.

USP 4,203,877, A. S. Baker, covers a block or graft copolymer (A-COO)_m-B in which one polymeric component (A) is the residue of an oil-soluble complex monocarboxylic acid and another polymeric component (B) is the residue of a water-soluble polyalkylene glycol or polyalkyleneoxy polyol. The most preferred example comprising A = ρoly(12-hydroxystearic acid) [PHS] MW 1500-2000, B = poly(ethylene glycol) [PEG] MW 1500, and m = 2. The reaction may be carried out by either of two procedures: polymerize the 12-hydroxystearic acid and then react it with PEG, or perform the 12-hydroxystearic acid polymerization simultaneously with PEG addition. Baker states that procedures 1 and 2 yield products similar in composition and characteristics. British patent GB 2,002,400, and USP 4,509,950; 4,504,276; and 4,504,275 (below), all cover the use of this surfactant blended with other surfactants.

GB 2,002,400, A. S. Baker, covers a water-in-hydrocarbon fuel oil emulsion containing up to 25% by weight of water. This is stabilized with the reaction product of 12-hydroxystearic acid and PEG- 1500 (PHS-PEG) in combination with nonylphenol tetraethoxylate (NPE), or a fatty alcohol tetraethoxylate, and/or a co- solvent. One of the examples describes a blend of 3.75 part methanol, 11.25 parts demineralized water, 85 parts diesel fuel, 0.24 parts NPE and 0.24 parts of PHS- PEG. The methanol was added to increase the stability of the emulsion towards low temperatures. For all of the examples, high shear mixing was required to form the emulsion.

USP 4,509,950, Alan S. Baker, covers ethanol/diesel blends stabilized with a blend of surfactants:

1. Block or graft copolymer in which one polymeric component is the residue of an oil-soluble complex monocarboxylic acid and another polymeric component is the residue of a water-soluble polyalkylene glycol or polyalkyleneoxy polyol (10-90%, poly(12-hydroxystearic acid) MW > 500 + PEG MW > 500)

2. Polyester obtained by condensation of poly(isobutenyl) succinic acid or anhydride with a water-soluble poly(alkylene glycol) (10-90%, PIBSA MW 500-5000 + PEG MW 400-4000)

All of the blends used in the ethanol examples also contained significant amounts of tall oil fatty acid (TOF A) in the PIBSA reaction.

In this and the following '276 and '275 patents, diesel blends may contain 1-75% by weight ethanol or methanol, the methanol or ethanol containing at least 1% by weight of water. The patent does not state how long the emulsions were stable, or which emulsions required high speed mixing. Different blends are used for different ethanol and water concentrations. USP 4,504,276, Alan S. Baker, covers ethanol/diesel blends stabilized with a blend of surfactants:

Block or graft copolymer in which one polymeric component is the residue of an oil-soluble complex monocarboxylic acid and another polymeric component is the residue of a water-soluble polyalkylene glycol or polyalkyleneoxy polyol (10-90%>, poly(12-hydroxystearic acid) MW > 500 + PEG MW > 500) Aliphatic amino compound with a long-chain aliphatic carboxylic acid (90-10, poly(isobutenyl) succinic acid + triethanolamine)

USP 4,504,275, Alan S. Baker, covers ethanol/diesel blends stabilized with a blend of surfactants:

2. A conventional non-ionic surfactant in which the oil-soluble component has a MW < 500, and the HLB is between 11 and 18.

EP 156,572, Alan Stuart Baker, covers the surfactant composition containing a hydrophobic component of C₃₀-₅₀₀ covalently bound to a hydrophilic component containing phosphate, phosphonate, sulphate, sulphonate or carboxymethyl. It also claims any emulsion system comprising an aqueous phase and a water-immiscible phase that includes these surfactants.

U.S. Pat. No. 4,451,265 describes a microemulsion containing hydrocarbon fuel, water, water-miscible alcohols, and a surfactant system using N,N-dimethyl ethanolamine and a long-chain fatty acid substance.

U.S. Pat. No. 6,017,369 describes a fuel composition containing hydrocarbon fuel, ethanol, an alkyl ester of a fatty acid, and a stabilizer. The stabilizer is either a mixture of fatty acid alcohols, a polymeric material, or a combination of the two .

U.S. Pat. No. 4,509,950 discloses the emulsions of methanol or ethanol in the heavier fuel fractions using a blend of block or graft polymer and a polyester.

U.S. Pat. No. 4,083,698 describes fuel compositions which are water-in-oil emulsions and which comprise a hydrocarbon fuel such as gasoline of hydrocarbon fuel, water, a water-soluble alcohol and certain combinations of surface-active agents. U.S. Pat. No. 4,406,519 teaches a microemulsion fuel comprised of gasoline, methanol, water, and a surfactant blend having a hydrophilic-lipophilic balance value of 3 to about 4.5.

U.S. Pat. No. 4,451,267 teaches microemulsions prepared from vegetable oil, a Cl -C3 alcohol, water and a lower trialkyl amine surfactant. This patent teaches the optional addition of 1-butanol as a co-surfactant for the purpose of lowering both the viscosity and the solidification temperature of the microemulsion.

U.S. Pat. No. 3,876,391, McCoy et al., teaches microemulsions prepared from hydrocarbon fuels and water by means of a multicomponent surfactant system. The petroleum-soluble component is an aliphatic ester of a polyol or a polyoxyalkylated alkyl phenol, while the water-soluble component is selected from a variety of known surfactants such as the fatty acid salts of polyalkanolamines, quaternary ammonium salts, and polyoxylated alkyl phenols. McCoy does not disclose the use of an alcohol in the fuel composition.

In U.S. Pat. No.3,346,494, Robbins et al. teaches the preparation of a hydrocarbon microemulsion with either water or methanol and a tri-component microemulsifier system including a long-chain fatty acid or fatty acid mixture, an amino alcohol, and an alkyl polyoxylated phenol. Exemplary amino alcohols include ethanolamine, diethanolamine, and 2-amino-2-methyl-l-propanol.

International Application WO 95/02654 discloses a hydrocarbon fuel composition containing up to 20% ethanol and/or n-propanol and up to 15% of a fatty acid and/or organic ester.

U.S. Patent No. 4,477,258 discloses a hydrocarbon fuel emulsion of the water-in-oil type containing a mixture of hydrocarbon fuel, an aqueous solution of methanol, ethanol or a mixture thereof and an emulsifying blend of sorbitan monooleate with a water soluble, ethoxylated, non-ionic surfactant.

U.S. Pat. No. 5,104,418 describes a hybrid hydrocarbon fuel composition containing hydrocarbon fuel, water, a glycolipid surfactant and an aliphatic alcohol co-surfactant.

U.S. Pat. No. 4,744,796 teaches a microemulsion fuel composition containing a hydrocarbon fuel, water and/or methanol and a co-surfactant combination.

A major disadvantage of prior formulations, however, is the relative lack of emulsion stability with respect to time and temperature at an affordable dosage under the type of conditions which the fuel formulations can be expected to encounter.

In general, where prior cosolvent compositions tend to increase the amount of water needed to precipitate a separate phase, they do so only to an impractical extent compared to the amount of water to which the fuel would likely be exposed. They tend to fail at only very low levels of water which fuels are most likely to encounter. Moreover, once the phase precipitates, it demulsifies too rapidly and requires more agitation to re-emulsify than is generally available in the manufacture, transport, and use of the fuels.

Prior surfactant compositions, which keep the phases emulsified, are found to be too sensitive to particular ratios of alcohol, water, and hydrocarbon. For a given level of alcohol, a given stabilizer composition will work for a relatively high level of water or low level of water, but not both. Or for a given level of water, a given stabilizer composition will work for a relatively high level of alcohol or low level of alcohol, but not both. To be commercially viable, a single stabilizer composition must maintain fuel stability across the full range of compositions, contaminations, and conditions it is likely to encounter.

Accordingly, it would be desirable to provide a single emulsifying stabilizer composition for use in alcohol-hydrocarbon fuel blends that is more effective at a lower addition rate and across a wider range of alcohol compositions and variations in water content and contamination. Still further, it would be desirable to provide a "splash blendable" fuel stabilizer composition that can be mixed into fuel readily by simply feeding into the same tank, without the need for energy and capital intensive blending procedures. It is also desirable, for environmental and regulatory reasons, that this fuel stabilizer contain only chemical elements "substantially similar" to that of standard fuel: essentially C, H, O, N, and S, preferably just C, H, and O.

It is an object of this invention to provide alcohol-hydrocarbon fuel stabilizer compositions that overcome these drawbacks. It is also an object of this invention to provide a method for producing alcohol-hydrocarbon fuel compositions employing these stabilizer compositions.

3. Summary Of The Invention

It has now been found that the use of blends of a selected class of surfactants termed "wide", or a combination of "wide" and a class of surfactants termed "tall hydrophobe" nonionic surfactants of the present invention produces stable emulsions of wet low-alkyl alcohols in hydrocarbon fuel across a wide range of alcohol and water concentrations. The present invention accordingly provides for a stabilizer composition and an alcoholic hydrocarbon fuel composition suitable for use in combustion, specifically, internal combustion engines. The fuel composition is a blend of hydrocarbon fuel, low-alkyl alcohol, water and a blend of wide or wide and tall hydrophobe nonionic surfactant stabilizer. Optionally, the composition of the stabilizer or of the fuel containing it includes an alcohol compensating combustion aid, such as an alkyl nitrate cetane improver, and a water solubilizing higher alcohol solvent.

Stabilizers of the present invention are blends of wide or wide and tall hydrophobe nonionic surfactants. Surfactants are organic molecules that contain both hydrophilic and hydrophobic groups. The hydrophobic groups may be aliphatic, olefinic, aromatic, or alicyclic. If aliphatic, they are preferably branched, or if linear, preferably have < 24 sequential hydrophobic carbons. (Excessive straight chain sequences cause the hydrophobe to precipitate above the cloud point of the fuel.) "Nonionic" surfactants are those in which the hydrophile is dipolar or hydrogen bonding ("hydric") but not ionized into positive and/or negative charge centers.

The "wide" surfactants, so-called because they are thought to lay down flat at the alcohol / hydrocarbon interface, have hydrophobes comprising heteroatom punctuated hydrocarbon polymers, and extended hydrophiles spread out over > 5, preferably >10, individual polar groups or monomers. These surfactants have a molecular weight of about 10³ to 10⁶ in which C₅.₃₀, preferably C₁₀-₂₀, alkyl or alkenyl hydrocarbon groups are separated in some way ("punctuated") by heteroatom (non-C, non-H) containing groups which are smaller in size than the fatty groups. Such heteroatom containing groups can include ethers, esters, amides, amines, and the like. The hydrophile may also include polar polymers, larger than the fatty groups, punctuated by non-polar hydrophobic carbons.

One stabilizer of the present invention is a blend of wide surfactants of two different hydrophilicities. A "low" hydrophilicity surfactant is one in which non- hydric hydrophilic groups comprise < 25% by weight, or hydric hydrophilic groups comprise < 14%, by weight of the molecule. A "high" hydrophilicity surfactant is one in which non-hydric hydrophilic groups comprise > 25% by weight, or hydric hydrophilic groups comprise > 14%, by weight of the molecule. Surprisingly, blends of low and high hydrophilicity hydrophiles are far more robust across a wide range of water and alcohol concentrations than a single, intermediate type alone. Hydric hydrophiles are those with hydrogen bonding hydrogens, i.e. those attached to nitrogens or oxygens.

The "tall" surfactants, so-called because they are thought to protrude more from the alcohol / hydrocarbon interface, have long hydrophobes in which > 24, preferably > 36, of the hydrophobic carbons are in a row; and compact, that is having a molecular weight less than 400, polyhydric hydrophiles. A "compact, polyhydric" hydrophile has > 1 , preferably > 2, hydrogen bonding hydrogens < 11 atoms apart. A preferred stabilizer of the present invention is one where the hydrophilicity of the tall surfactants in the blend complements that of the wide surfactants. That is, a high hydrophilic tall surfactant would complement a low hydrophilic wide surfactant and a low hydrophilic tall surfactant would complement a high hydrophilic wide surfactant. If, preferably, a blend of low and high hydrophilicity wide surfactants is used, the tall surfactant hydrophilicity is preferably medium, having hydric hydrophilic groups comprising 10-20% by weight of the molecule. A specific example of a medium hydrophilicity tall surfactant is Lubrizol 5948, a 1300 MW PIBSA pentaerithritol diester.

Preferably, the stabilizer compositions also include a combustion aid, such as a cetane improver and a solvent, such as an inexpensive naphtha or a water- solubilizing higher (C .₁₆) alcohol.

The fuel compositions of the present invention include (a) a major portion of a hydrocarbon fuel; (b) a minor amount of a low-alkyl (C^) alcohol; (c) a minor portion of water; and, (d) a minor portion of a stabilizer comprising a blend of wide or wide and tall hydrophobe nonionic surfactants. Optionally, the fuel compositions also include (e) a minor amount of a combustion aid, such as a cetane improver and (f) a minor amount of a solvent, such as a water solubilizing higher (C₄-₁₆) alcohol. In another aspect of the invention, a method for forming a fuel composition includes providing a mixture of hydrocarbon fuel and 0.01% to 10.0% of a blend of wide or wide and tall hydrophobe nonionic surfactant stabilizer (optionally including up to 5% of a combustion aid and up to 30% of a water solubilizing solvent) to form a first composition and mixing the first composition with a low- alkyl alcohol (optionally containing up to 1.0% of a combustion aid and up to 20% of a water solubilizing solvent) in a ratio of 100 : 1 to 1 : 1. Another method for forming a fuel composition comprises adding from about 0.1 % to about 10.0% of a blend of wide or wide and tall hydrophobe nonionic surfactant stabilizer (optionally including up to 99.9% of a combustion aid or a water solubilizing solvent) to a 100:1 to 1:1 blend of hydrocarbon and alcohol, respectively (optionally including up to 5% of a combustion aid and up to 30% of a water solubilizing solvent).

4. Detailed Description Of The Inventioin

Conventional hydrocarbon fuels, due to their cost and availability, are used globally for combustion, to heat and power a wide variety of stationary structures and machines and moving vehicles such as, for example, buildings, power generators, farm equipment, passenger cars, buses, trucks, construction equipment, aircraft and ships. It has now been found that blends of wide nonionic surfactants or blends of wide and tall hydrophobe nonionic surfactants are capable of stabilizing hydrocarbon fuel compositions containing low-alkyl alcohols and water against phase separation. The present invention relates to stabilizer blend compositions and a fuel composition comprising a hydrocarbon fuel, a low-alkyl alcohol, water, a blend of wide or wide and tall hydrophobe nonionic surfactant stabilizer, and, optionally, a combustion aid and a solvent.

Hydrocarbon fuels are generally obtained from the distillation of petroleum hydrocarbon feedstocks. The hydrocarbon fuel used in the composition of the present invention may be any petroleum fraction meeting the local standards for hydrocarbon fuel use. Such fuels include gasoline, diesel, jet, kerosene, marine and furnace oils. Generally, the hydrocarbon fuel is present in the composition in an amount in the range of about 50 volume % to about 99 volume % based on the total volume of the fuel composition.

Regardless of the fuel used in this invention, the key aspect is the desire to improve the stability of the alcoholic hydrocarbon fuel composition against phase separation. The invented fuel composition also includes a low-alkyl alcohol component, generally in the C ι-₃ range per hydroxyl. This includes methanol, ethanol, isopropanol, hexylene glycol, etc. Ethanol is generally preferred due to its ready availability, low toxicity, and renewable origins. Ethanol typically is produced by fermentation or enzymatic digestion of sugars derived from grains or other biomass materials. Ethanol suitable for use in accordance with the invention preferably includes fuel grade ethanol, typically containing 0.1% to 0.5% water, as well as more hydrous, less expensive grades containing as much as 50% water.

As indicated above, use of a hydrous ethanol in combination with a hydrocarbon fuel poses problems wherein the ethanol/hydrocarbon fuel mixture separates into two separate bodies of liquid. This renders the resultant mixture unsuitable for use as a combustible fuel. However, in combination with the stabilization stabilizer of the present invention, hydrous ethanol may be blended satisfactorily with conventional hydrocarbon fuel without separating into two separate bodies of liquid.

Generally, the amount of ethanol blended to form the invented fuel composition is in a range of about 1 volume % to about 50 volume %, inclusive, based on the total volume of the fuel composition. Preferably, the amount of ethanol is present in the solution in a range of about 5 volume % to about 15 volume %, and more preferably about 7 volume % to about 15 volume %, and most preferably about 10 volume % to about 15 volume % based on the total volume of the fuel composition.

Water may be present in the fuel composition from about 0.004 % to about 25 %, though more typically from about 0.04 % to about 2.5 %, most typically from about 0.1 % to about 1.0 %, based on the total volume of the fuel composition. The water is not intentionally added but inevitably comes with the alcohol and therefore tends to be present in proportion to the alcohol content.

The fuel composition also includes a stabilizer comprising a blend of wide nonionic surfactants, or wide and tall hydrophobe nonionic surfactants.

The tall hydrophobe nonionic surfactants are composed of the combination of a and b described below.

a) a hydrocarbyl moiety of molecular weight 600-4000 that has a terminal functional group capable of condensing with hydroxyl and amine groups. The hydrocarbyl moiety can be aliphatic, olefinic, aromatic or alkyl ether. Examples include polypropylene or polybutenyl groups. A more specific example is polyisobutylene. The terminal functional group is typically a carboxylic acid or anhydride functionality bound to the hydrocarbyl substituent. b) A compact polyhydric moiety capable of condensing with a) above, and results after condensation with more than one site still capable of hydrogen bonding (hydridic). Such sites capable of hydrogen bonding include hydroxyl groups and primary and secondary amines. The compact polyhydridic moiety includes polyols and polyamines with molecular weights of no more than 400. Examples include glycerol, penterythratol, diethylenetriamine, trietliylenepentaamine, and tetraethylenpentaamine.

The combination of a) and b) above can be in the ratio of 1 : 1 to 1 :3 of a to b.

Examples of tall surfactants include poly(isobutenyl)succinic esters, amides, and imides of polyhydroxyls and polyamines. Commercially available sources of the above-preferred embodiment include Lubrizol 5948 and 8065, which feature approximately two C₇₀-₁₂₀ polyisobutylene succinate (PIBSA) groups adducted to pentaerithritol, or tetraethylene pentaamines, to form combinations of the mono-, di-, or tri-succinates or succinimides.

In one embodiment, the wide surfactants are composed of the condensation product of c) and d) below.

c) is a copolymer of formula (1) below that contains repeat ester units and the total molecular weight is at least 500. R-CO-[O-CR₃H-(R₂)_x-CO]_y-OH (1) in which

R is a hydrogen or Cl to C24 hydrocarbon group; R₃ is a hydrogen of a monovalent d to C₂ hydrocarbon group; R₂ is a divalent C toC₂₄ hydrocarbon group x is zero or 1; y is an integer form zero to 200;

d) is a water soluble polyalkylene glycol moiety represented by the general formula (2) below.

H-[O-CR₄H-CH₂]z-R₅ (2) in which

R4 is a hydrogen or a Cl to C4 alkyl group; Z is an integer from 10 to 400; and R₅ is -OH or a C₁-C₂₃ acyl group.

Specific materials include Uniqema's Hypermer B246 and B261, which feature polyhydroxystearate (PHS) [12-hydroxystearic acid condensed with itself and stearic acid into a polyester of degree of polymerization (dp) 4-5] esterified on the terminal acid with 200-2000 MW polyethylene glycol)s (PEG), [ethylene glycol reacted with 4-40 moles of ethylene oxide (oxirane)]. Another wide type surfactant is represented by formula (3) below and is the condensation product of fatty amines and reactive oxygenates, such as epichlorohydrin.

R₅-NH-[CH₂-CHOH-CH₂-NR₅]_q-H (3)

In which R₅ is a Cl to C24 hydrocarbon group; q is an integer from 5 to 50.

A specific example of the second type is an epichlorohydrin / fatty amine copolymer, featuring C₁₂-₂₄ alkyl amines copolymerized with an equimolar amount of epichlorohydrin to form a poly(hydroxypropyl fatty amine) with a degree of polymerization 12, then alkaline washed to form the free amine.

One synergistic blend of the present invention combines two or more wide surfactants, one of which has non-hydric hydrophilic groups comprising < 25%, or hydric hydrophilic groups comprising < 14%, by weight of the molecule and another of which has non-hydric hydrophilic groups comprising > 25%, or hydric hydrophilic groups comprising > 14%, by weight of the molecule. Blend ratios can be from 90:10 to 10:90.

A specific example of a low hydrophilicity wide surfactant is Hypermer

B246, a PHS diester with 200-700 MW PEG (10-25% non-hydric hydrophile). Specific examples of high hydrophilicity wide surfactants include Hypermer B261 , a PHS diester with 700-2000 MW PEG (25-50% non-hydric hydrophile) and an alkaline washed epichlorohydrin / fatty amine 1:1 copolymer (20-35% hydric hydrophile)

Another synergistic blend of the present invention combines one or more wide surfactants with one or more tall surfactants. Blend ratios can be anywhere

firom 99:1 to 1:99.

A preferred synergistic blend of wide and tall surfactants is one where the hydrophilicity of the tall surfactants in the blend complements that of the wide surfactants. That is, a tall surfactant with a hydric hydrophilic group comprising > 14% by weight of the molecule is blended with a wide surfactant having non- hydric hydrophilic groups comprising < 25%, or hydric hydrophilic groups comprising < 14%, by weight of the molecule; or a tall surfactant with a hydric hydrophilic group comprising < 14% by weight of the molecule is blended with a wide surfactant having non-hydric hydrophilic groups comprising > 25%, or hydric hydrophilic groups comprising > 14%, by weight of the molecule. If, preferably, a blend of low and high hydrophilicity wide surfactants is used, the tall surfactant hydrophilicity is preferably medium, having hydric hydrophilic groups comprising 10-20% by weight of the molecule. A specific example of a medium hydrophilicity tall surfactant is Lubrizol 5948, a 1300 MW PIBSA pentaerithritol diester. These blends of wide or wide and tall giant hydrophobe nonionic surfactant stabilizers are generally not liquid at ambient temperatures when neat. They are preferably diluted to the range of about 4% to about 40% active in a low polarity organic solvent. This lowers the viscosity enough that they readily pour and "splash blend" into the fuel.

Appropriate low polarity solvents include saturated and unsaturated hydrocarbons, ethers, esters, N-alkylated amides, and C8 or higher alcohols. Added combustion aids, such as alkyl nitrates, organic peroxides, and bio-diesels can also perform the added function of solvents. Bio-diesels are typically methyl esters of naturally occurring fatty acids, for example methyl soyate. Particularly cost- effective are low-grade, discolored, aromatic naphthas.

The higher alkyl alcohols, though more expensive than naphtha, were found to have the extra value of improving the solubility of the lower alkyl alcohols in the hydrocarbon fuel. This delays the onset of alcohol precipitation until higher levels of water inclusion or intrusion are reached. The most cost- effective solvents in this regard were found to be those derived from the "Oxo" hydrocarbonylation process, n-butanol and 2-ethylhexanol, of which the latter was found to be the better solvent for the stabilizers. The stabilizer composition or the present invention, using the above embodiments, can generally contain the constituents in the following percentage ranges (by weight or volume):

a) First wide stabilizer component (active): from about 0.3% to about 30.0%, preferably from about 3.0% to about 30%.

b) Second or more wide and/or one or more tall stabilizer components (active): from about 0.3% to about 30%, preferably from about 3% to about 30%.

c) Stabilizer solvent: from about 40% to about 95%, preferably from 70% to about 90%.

d) Optionally, combustion aid: up to about 95%, typically from about 5% to about 30%.

The fuel composition of the present invention, when using the above embodiments, can generally contain the constituents in the following percentage ranges (by weight or volume):

e) Hydrocarbon fuel: from about 50 to about 99%, preferably from about 75 to about 95%; f) Low-alkyl alcohol (as anhydrous): from about 1 to about 50%, preferably from about 2 to about 20%;

g) Water: from about 0.004 to about 25%, typically from about 0.2 to about 2%;

h) First wide stabilizer component (active): from about 0.01 to about 2.0%, preferably from about 0.04 to about .4%;

i) Second or more wide and/or one or more tall stabilizer component (active): from about 0.01 to about 2.0%, preferably from about 0.04 to about .4%;

j) Optionally, stabilizer solvent: up to about 15 %, preferably from 0.3 to about 3%; and,

k) Optionally, combustion aid: up to about 1.5 %, typically from 0.05 to about

0.5%.

The fuel compositions according to this invention may also include numerous other additives. Among these are flow improvers, wax anti-settling aids, cloud point depressants, antistatic additives, antioxidants, biocides, odor masks, metal deactivators, antifoams, antifoulants, corrosion inhibitors, dyes, de-icers, and lubricity improvers. The fuel compositions of the present invention may be produced by incorporation of either the stabilizer alone or a stabilizer composition which includes other additive compounds as described above, provided that they do not adversely affect the stabilizing effectiveness of the blend of giant hydrophobe nonionic surfactant stabilizers described in this invention and that the components of such mixtures are compatible. Moreover, the stabilizers or stabilizer compositions may be incorporated into either the alcohol or hydrocarbon fuel portions prior to combining the portions to form the final composition.

The stabilizer compositions may be used as liquid solutions. The amount used of each of these solutions will be such as to insure the incorporation into the hydrocarbon fuel composition of the requisite amount of the blend of wide or wide and tall giant hydrophobe nonionic surfactant stabilizer. For example, regardless of whether the stabilizer composition is added neat or in solution, the amount of active ingredient of each type of stabilizer will be in the range of about 0.01 % to about 2.0 % of the base hydrocarbon fuel.

The present invention provides for a method for improving the phase stability of a hydrocarbon fuel composition including a hydrocarbon fuel, a low- alkyl alcohol and water. This method includes the step of combining with the hydrocarbon fuel, alcohol and water composition a sufficient amount of a liquid solution containing a blend of two or more wide or one or more wide and one or more tall giant hydrophobe nonionic surfactants, as described above, to stabilize the composition against separation into distinct bodies of liquid.

The following components may be combined in the following amounts:

a) Hydrocarbon fuel: from about 50 to about 99%, preferably from about 75 to about 95% of the blended fuel;

b) Hydrous low-alkyl alcohol containing:

i) Low-alkyl alcohol (as anhydrous): from about 1 to about 50%, preferably from about 2 to about 20%, of the blended fuel;

ii) Water: from about 0.004 to about 25%, typically from about 0.2 to about 2%>, of the blended fuel;

c) Stabilizer solution containing:

i) First wide stabilizer component (active): from about 0.01 to about

2.0%, preferably from about 0.04 to about 0.4%, of the blended fuel;

ii) Second or more wide and/or one or more tall stabilizer components (active): from about 0.01 to about 2.0%, preferably from about 0.04 to about 0.4%, of the blended fuel; iii) Stabilizer solvent: from 0.04 to about 15 %, preferably from 0.3 to about 3%>, of the blended fuel; and

d) Optionally, combustion aid: up to about 1.5 %, typically from 0.05 to about 0.5%, of the blended fuel.

Conventional blending equipment, techniques and ambient temperatures may be used at in preparing the fuel compositions of the present invention. Most conveniently, blending is carried out simply by pouring the liquid ingredients together into the same tank. Because the stabilizer solution is generally not miscible with the low-alkyl alcohol, they combine most readily when poured into a tank ("splash blended") in the following order: stabilizer solution, hydrocarbon fuel, low-alkyl alcohol. The combustion aid can be added at any time but is generally added with the alcohol.

The present invention further provides for an internal combustion engine system wherein the engine system includes hydrocarbon fuel compositions herein described which have improved phase separation stability.

As will become readily apparent from the following examples, phase separation tests reveal that the invented hydrocarbon fuel compositions, containing the blends of wide or wide and tall giant hydrophobe nonionic surfactants herein described, produce time and temperature stable fuel compositions of hydrocarbon, alcohol and water.

5. Examples

The following examples are intended to demonstrate the efficacy of the present invention and should not be construed as limiting the scope thereof. Equipment

1) 40 mL borosilicate glass vials

2) Refrigerator, set to 0 or -30 °F Reagents

1) Stock solution of 1 part anhydrous ethanol (a low Cetane No. alternate diesel fuel) and 0.25 parts 2-ethylhexylnitrate (2EHN), a Cetane No. improver. This stock solution is hygroscopic and was dispensed with the aid of a drying tube on the dispenser. 2) Water (distilled or deionized)

3) Low sulfur diesel fuel, commercial grade, from local filling station

4) Stabilizer treatments listed in Table I. If not liquid, these were liquefied for volumetric dispensing by diluting in appropriate solvent. Table I: Stabilizer Treatments Tested

Test Procedure

Tests were performed by adding the appropriate ratios of ethanol/2EHN stock solution and diesel fuel to vials followed by addition of about 10,000 ppm (actives) of the stabilizers and shaking lightly by hand ten times. (For low

temperature tests, winter specification fuel was placed in a refrigerator at -30 °F

and summer specification fuel was placed a refrigerator at 0 °F for 24 hours before

recording the appearance). Water was then added and the vial again shaken lightly by hand ten times. The samples were then left to stand for 1 hour and the appearance was recorded. (For low temperature tests, the samples were placed in a

refrigerator at approximately -30 or 0 °F for the standing portions of tests.) Finally,

the samples were left to stand overnight and the appearance was again recorded. The ease with which the sample redispersed was also noted.

Better stability is indicated by: 1) preventing phase separation completely (a "0" % Separation reading),

2) reducing the amount that separated (separating less clear liquid), or

3) restricting separation to a form a) more compositionally similar to the diesel (completely opaque white emulsion rather than partially clear liquid) or b) more easily remixed (by merely twirling rather than vigorously shaking).

Tests

20-mL samples were prepared and tested with the equipment, reagents, and test procedure described above. Samples were prepared and tested at the following ratios:

0.061 95 5 1

95 5 2

95 5 3

90 10 1

90 10 2

90 10 3

85 15 1

85 15 2

85 15 3

These were referred to as the 5-1, 5-2, 5-3, 10-1, 10-2, 10-3, 15-1, 15-2, and 15-3 conditions, respectively. Stabilizer samples that were solid or too thick to

pipette were diluted in Aromatic 150, a 150°F flash point aromatic naphtha solvent

(e.g. available from Unisourse as Unarom 150). An attempt was made to adjust the amount pipetted to take into account the effect of all dilution (even that from production). Solvent in the stabilizer as received, however, was not always taken into account until the amount of it was later measured.

The minimum stability needed for commercial use is believed to be that in which visual inspection after one hour of standing reveals no separation (a homogeneous emulsion) and visual inspection after one day of standing reveals no clear or merely hazy liquid layer, nor any emulsion layer which does not readily mix back into solution with gentle twirling of the sample bottle. Stratification of an opaque white, waxy emulsion, still dispersed in the hydrocarbon phase and easily rehomogenized, is considered acceptable. Commercial use, especially as a transport fuel, would require a product to pass this test under all likely conditions.

Table II lists the results of testing blends of low and high hydrophile wide surfactants.

Table II: Blends of Low and High Hydrophile Wide Surfactants

The data in Table II show that while both low and high hydrophobe wide surfactants were acceptable under certain conditions, they failed at others. Combining them resulted in improved robustness across the full range of conditions. For example, the 3:1 formulation was acceptable under all conditions.

Table III lists the results of testing a blend of low and high non-hydric hydrophile wide surfactants with low and medium hydric hydrophile tall surfactants on the four corners of the screening grid above.

Table III: Phase Separation Test Results for 40:60 Blend of Wide 1 and 2 plus Tall 1 or 2

The data in Table III show that the addition of a tall surfactant even to a blend of low and high hydrophile wide surfactants provided better stability at much lower dosages. Moreover the blend employing the more complementary, medium hydrophile, tall surfactant was better than the one employing the less complementary, low hydrophile, tall surfactant.

Adding to the complexity of commercial development is the discovery that while the value of adding alcohol fuel is generally proportional to the amount of alcohol added (up to about 15% for ethanol in diesel), the amount of stabilizer needed is non-linear with respect to alcohol and water content. The least stable emulsion could be that formed with just 0.1-0.4 % water, the minimum amount needed to precipitate the alcohol, or that formed with the highest amount of water. Emulsions with 10 % alcohol were could be less stable than those with 5 or 15 % alcohol. Moreover, different types of giant hydrophobe surfactants have significantly different economic costs. To find the highest value stabilizer, tests on an even wider range of water alcohol ratios, including those down to the precipitaton onset levels, using surfactact solutions diluted to equal economic costs, were added in an amount proportional to the amount of alcohol in the fuel. The most valuable benefit of blending the wide and tall surfactants together was found to be a radical lowering of the minimum dose required needed for adequate stability under all conditions. Table IN lists the results of testing a blend of low and high non-hydric hydrophile wide surfactants with a medium hydric hydrophile tall surfactant in various 3 -way ratios. The minimum dose requirement is listed as a percentage of the amount of alcohol in the fuel sample.

The data in Table IN show that certain critical blend ratios in the vicinity of

7-13 % (13-24 % of 54%) Wide 1, 0-11 % (0-21% of 54%) Wide 2, and 2-20 % (2-21% of 96%) Tall 1 have several times better cost effectiveness than single components or any blend of wide surfactants alone.

In all cases, the 0°F low temperature tests yielded equivalent results. At -

30°F, equivalent stability could be attained at about twice the ambient dose requirement. In addition, without water added, these treatments did not freeze or precipitate from the fuel at low temperature and passed standard lubricity, corrosion, cold flow, and other compatibility harms tests.

While the present invention has been described with respect to particular embodiments thereof, it is apparent that other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

Claims

WE CLAIM:

1. A surfactant combination suitable for emulsification of Cι_₃ alkyl alcohol in a hydrocarbon liquid comprising a blend of at least two nonionic surfactants selected from the group consisting of:

(i) a nonionic surfactant having less than about 25% by weight non- hydric hydrophile groups;

(ii) a nonionic surfactant having greater than about 25% by weight non- hydric hydrophile groups; and

(iii) a nonionic surfactant comprising the condensation product of a) a hydrophobe having greater than 24 carbons in a row and b) polyhydric hydrophiles having a molecular weight less than about 400 and more than 1 hydrogen bonding hydrogens 11 or less atoms apart.

2. The surfactant combination of claim 1 wherein said nonionic surfactant having greater than about 25% non-hydric hydrophile groups comprises the condensation product of:

c) a copolymer of the formula

R-CO-[O-CR₃ H-R₂)_x-CO]_y -OH

wherein R is hydrogen or Ci-C₂₄ hydrocarbon;

R₃ is hydrogen or a monovalent Cι-C₂ hydrocarbon group; R is a divalent C₂-C₂₄ hydrocarbon group; x is 0 or 1; and y is an integer from 0 to 200 and

d) a water soluble polyalkylene glycol moiety represented by the formula:

H-[O-CR₄H-CH₂]_z-R₅

wherein R-j is hydrogen or Cι-C alkyl; and z is an integer from about 10 to 400 and R₅ is -OH or a C1-C2₃ acyl group.

3. The surfactant combination of claim 1 wherein said nonionic surfactant having greater then about 25% non-hydric hydrophile groups comprises the condensation product of:

d) fatty amine of the general formula

R₅-NH-[CH₂-CHOH-CH₂-NR₅]_q-H

wherein R₅ is a C1-C₂₄ hydrocarbon group and q is an integer from about 5 to 50; and

f) epichlorohydrin.

4. The surfactant combination of claim 1 wherein said nonionic surfactant having less than about 25% non-hydric hydrophile groups comprises the condensation product of: c) a copolymer of the formula

R-CO-[O-CR₃ H-(R₂)_x-CO]_y -OH

wherein R is hydrogen or C:L-C hydrocarbon; R₃ is hydrogen or a monovalent Ci-C₂₄ hydrocarbon group; R₂ is a divalent C₂-C ₄ hydrocarbon group; x is 0 or 1 ; and y is an integer from 0 to 200 and

d) a water soluble polyalkylene glycol moiety represented by the formula:

wherein R is hydrogen or Ci-C₄ alkyl; and z is an integer from about 10 to 400 and R₅ is -OH or a Ci-C^ acyl group.

5. The surfactant combination of claim 1 wherein the ratio of said at least two nonionic surfactants ranges from 99:1 to 1:99 by weight.

6. The surfactant combination of claim 1 wherein when said at least two nonionic surfactants comprises (i) and (iii), nonionic surfactant (iii) comprises a nonionic surfactant having more than 14% by weight hydric hydrophilic groups.

7. The surfactant combination of claim 1 wherein when said at least two nonionic surfactants comprises (ii) and (iii), nonionic surfactant (iii), comprises a nonionic surfactant having less than 14% by weight hydric hydrophilic groups.

8. The surfactant combination of claim 1 wherein said at least two nonionic surfactants comprise (I) and (ii) and (iii) wherein nonionic surfactant (iii) comprises a nonionic surfactant having about 14% by weight hydric hydrophilic groups.

9. The surfactant combination of claim 1 diluted to from about 1% to about 40% by weight in a low polarity organic solvent.

10. The surfactant combination of claim 9 wherein said low polarity solvent is selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, ethers, esters, N-alkylated amides, C₈ or higher alcohols or mixture thereof.

11. The surfactant combination of claim 9 wherein said low polarity organic solvent comprises a combination aid selected from the group consisting of alkyl nitrates, organic peroxides, aromatic naphthas, and bio-diesels.

12. The surfactant combination of claim 11 wherein said bio-diesel comprises a methyl ether of naturally occurring fatty acids.

13. The surfactant combination of claim 11 wherein said bio-diesel comprises methyl soyate.

14. The surfactant combination of claim 1 wherein said nonionic surfactant component (i) has a molecular weight ranging from about 1,000 to 1,000,000.

15. The surfactant combination of claim 1 wherein said nonionic surfactant component (ii) has a molecular weight ranging from about'1,000 to 1,000,000.

16. The surfactant combination of claim 1 wherein said nonionic surfactant component (i) comprises hydrophobes comprising heteroatom, punctuated hydrocarbon polymers comprising hydrophiles spread out over more than 5 individual polar groups.

17. The surfactant combination of claim 16 wherein nonionic surfactant component (i) comprises C₅-₃o alkyl, or alkenyl hydrocarbon groups punctuated by non-C and non-H heteroatom groups.

18. The surfactant combination of claim 17 wherein said heteroatom groups are selected from the group consisting of ethers, esters, amides, amines and mixtures thereof.

19. The surfactant combination of claim 1 wherein said nonionic surfactant component (ii) comprises hydrophobes comprising heteroatom, punctuated hydrocarbon polymers comprising hydrophiles spread out over more than 5 individual polar groups.

20. The surfactant combination of claim 19 wherein nonionic surfactant component (i) comprises C₅-₃₀ alkyl, or alkenyl hydrocarbon groups punctuated by non-C and non-H heteroatom groups.

21. The surfactant combination of claim 20 wherein said heteroatom groups are selected from the group consisting of ethers, esters, amides, amines and mixtures thereof.

22. The surfactant combination of claim 1 wherein said nonionic surfactant (iii) comprises the condensation product of a hydrophile having a molecular weight less than 400 selected from the group consisting of polyols and polyamines and said polyhydric hydrophile comprises polybutylene.

23. An emulsion of .3 alkyl alcohol in a liquid hydrocarbon, the emulsion containing 1% to 50% by weight of Cι-₃ alkyl alcohol as the disperse phase and from 50% to 99% by weight of the hydrocarbon fuel as the continuous phase, from about 0.004% to about 25% by weight water and in addition as emulsifying agent, a surfactant composition as claimed in claim 1.