Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
  • C10L1/328—Oil emulsions containing water or any other hydrophilic phase

Definitions

• the present invention relates to the use of an emulsion fuel in a gasoline direct injection engine, usually referred to as a GDi engine.
• Gasoline direct injection engine technology can provide improved gasoline engine efficiency compared to conventional multi-point fuel injection.
• GDi engines ultra-lean burn operation is employed to give lower fuel consumption and CO 2 emissions than conventional multi-point injection engines.
• GDi engines Despite providing improved (lower) fuel consumption, however, GDi engines also suffer from a number of drawbacks when compared to conventional multi-point injection engines.
• NOx nitrogen oxides
• the NOx produced may be reduced by use of after-treatment systems that utilise unburned hydrocarbons to selectively reduce the NOx to nitrogen in the presence of excess molecular oxygen.
• after-treatment systems that utilise unburned hydrocarbons to selectively reduce the NOx to nitrogen in the presence of excess molecular oxygen.
• post treatment exhaust NOx emissions can still be a problem.
• GDi engines also suffer from fuel injector nozzle deposit formation, which is attributed to pyrolysis of certain species, especially olefins and aromatics, in the fuel and/or lubricating oil. This occurs because the fuel is subjected to much higher injection pressures e.g. 5-20 atmospheres, than in conventional engines and very much higher temperatures at the injection nozzle than in conventional engines because the nozzles are in the combustion zone. These extreme conditions promote thermal cracking of the fuel and deposition of soot on and around the injection nozzle. The presence of the soot tends to produce uneven combustion.
• the GDi engine manufacturers have tried to overcome the problem by treating the nozzle to resist solids deposition.
• water may be injected directly into an engine
• use of a homogeneous emulsion containing very finely dispersed water-in-fuel is considered to have advantages over direct water injection to the engine, including reduced fuel flammability, due to higher vaporisation temperature; elimination of the need for a separate water tank; reduced air pollution through lower hydrocarbon vapour losses from the tank; improved atomisation; providing greater and more uniform cooling; and safer transportation and storage, due to low volatility.
• a microemulsion is a transparent, thermodynamically stable system wherein the water droplets are nanometres in size. The droplets are too small to scatter light; giving the micro-emulsion a similar appearance to conventional homogeneous hydrocarbon fuel. The extremely low surface tension of the very finely dispersed water droplets makes such microemulsions inherently stable.
• Water-gasoline microemulsions are known, and are described, for example, in US 6,068,670 , US 4,599,088 , US 4,465,494 , US 4,158,551 , US 4,046,519 and US 3,876,391 .
• US 6,068,670 relates to water-fuel microemulsions comprising water, at least one hydrocarbon and an emulsifying system comprising at least one sorbitol ester, at least one fatty acid ester and at least one polyalkoxylated alkylphenol.
• the fuel is said to offer an advantage of two different types of carrier for additives: a lipophilic continuous hydrocarbon phase and a hydrophilic aqueous phase.
• the additives which are said to be useful are those that improve octane, inhibit soot, confer biocidal or bactericidal properties, provide detergency, inhibit NOx formation and/or provide antifreeze properties.
• US 3,876,391 relates to a process for preparing water-petroleum microemulsions comprising water, gasoline, at least one gasoline-soluble surfactant, at least one water-soluble surfactant, and a selected water-soluble insufficiently gasoline-soluble additive.
• the process is said to increase the quantity of water soluble additives that can be incorporated into petroleum fractions.
• water-gasoline microemulsions can advantageously be used with GDi engines to provide improved performance compared to use of non-emulsion gasoline fuels.
• the present invention provides for use of a water-gasoline microemulsion fuel composition to fuel a gasoline direct injection engine.
• the present invention also provides for use of a water-gasoline microemulsion fuel composition to reduce engine deposit formation in a gasoline direct injection engine, especially when compared to the use of the fuel without water.
• a water-gasoline microemulsion fuel composition to reduce engine deposit formation in a gasoline direct injection engine, especially when compared to the use of the fuel without water.
• such use may reduce fuel injector nozzle deposit formation and/or piston crown deposit formation.
• the present invention also provides a gasoline direct injection engined vehicle which comprises a water-gasoline microemulsion fuel composition in its fuel tank.
• the water-gasoline microemulsion fuels have also been found to have higher octane numbers than the base gasolines, even without the addition of octane improving additives.
• the water-gasoline microemulsion fuels preferably comprise 0.5% by weight to 20% by weight water, for example, 2 to 10% by weight water.
• the water-gasoline microemulsion fuels preferably comprise 75 to 98% by weight of a gasoline base fuel, for example, 80 to 95% by weight gasoline base fuel.
• a surfactant is present to facilitate the dispersion of water in gasoline.
• the water-gasoline microemulsion fuels preferably comprise 2 to 15 % by weight of a surfactant, for example, 5 to 9 % by weight surfactant.
• the water-gasoline microemulsion fuels may also comprise other additives typically found in the gasoline fuels. Such additives may be present in the gasoline base fuel before formulation of the water-gasoline microemulsion fuel, or may be added separately to the microemulsion fuel.
• water soluble additives to the microemulsion fuel which are not soluble in the gasoline alone.
• Typical motor gasoline additives are described, for example, in " Gasoline and Diesel Fuel Additives Ed. K Owen, Publ. J Wiley 1989 or as listed in ASTM D-4814, and include antioxidants, corrosion inhibitors, stabilisers, pour point depressants, demulsifiers, antifoams, cetane improvers, lubricity additives, anti-static additives, dehazers, lubricity additives package compatibilisers and dispersant/detergent additives. Such additives may typically each be present in the water-gasoline microemulsion fuel in amounts of 1-1000ppm, for example, 20-200ppm by weight.
• the gasoline base fuel may comprise a mixture of liquid saturated hydrocarbons, for example, a distillation product e.g. naphtha or straight run gasoline, or a reaction product from a refinery reaction e.g. an alkylate including aviation alkylate (bp 30-190°C), an isomerate (bp 25-80°C), a light reformate (bp 20-79°C) or a light hydrocrackate.
• a distillation product e.g. naphtha or straight run gasoline
• a reaction product from a refinery reaction e.g. an alkylate including aviation alkylate (bp 30-190°C), an isomerate (bp 25-80°C), a light reformate (bp 20-79°C) or a light hydrocrackate.
• the gasoline base fuel typically contains at least 60% by weight, for example, 70-90% by weight liquid saturated aliphatic hydrocarbon.
• the gasoline base fuel also preferably contains at least one olefin, in particular which is a liquid alkene of 5-10 carbons, for example, pentene, isopentene, hexene, isohexene or heptene or 2 methyl 2 pentene, or a mixture comprising alkenes which may be made by cracking.
• the mixture may be made by catalytically or thermally cracking a residue from crude oil, e.g. atmospheric or vacuum residue.
• the mixture may be heavy or light catalytically cracked spirit (or a mixture there of).
• the volume amount of olefin(s) in total in the gasoline base fuel is typically 0-30% by weight, for example, 5-30% by weight.
• the gasoline base fuel preferably also contains at least one aromatic compound, preferably an alkyl aromatic compound such as toluene or o-, m-, or p-xylene or a mixture thereof or a trimethyl benzene.
• the aromatics may have been added as single compounds or may be added as an aromatics mixture containing at least 30% by weight aromatic compounds.
• Such mixtures may be made from catalytically reformed or cracked gasoline obtained from heavy naphtha. Examples of such mixtures are catalytic reformate and heavy reformate.
• the volume amount of aromatic(s) in total in the gasoline base fuel is typically 5-40% by weight, for example, 10-35% by weight.
• the gasoline base fuel compositions may also contain at least one oxygenate octane booster, usually an ether, usually of Motor Octane Number of at least 96-105 e.g. 98-103.
• the ether octane booster is usually a dialkyl ether.
• oxygenates include methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether and methyl tertiary amyl ether.
• the oxygenate may also be an alcohol of 1-6 carbons e.g. ethanol and/or butanol.
• the volume amount of the oxygenate in the base fuel composition may be 0-25% by weight, for example, 1-5% by weight.
• the gasoline base fuel compositions usually have a Motor Octane Number (MON) value of at least 80 e.g. 80 to 98.
• the gasoline base fuel compositions usually have a Research Octane Number (RON) of 90-120 e.g. 90-100.
• the gasoline base fuel usually has a boiling range (ASTM D86) of 20-225°C.
• the water-gasoline microemulsion fuel compositions usually have a Motor Octane Number (MON) value of at least 85 e.g. 85 to 105.
• the water-gasoline microemulsion fuel compositions usually have a Research Octane Number (RON) of 95-125 e.g. 95-105.
• the surfactant is preferably a non-ionic surfactant with a C 8 -C 20 backbone.
• Preferred surfactants are selected from one or more non-ionic ethoxylates, especially alkyl phenol ethoxylates, linear alcohol ethoxylates, sorbitan ester ethoxylates and mixtures thereof.
• Suitable alkyl phenol ethoxylates include nonyl phenol ethoxylates.
• the microemulsions employed in the present invention are stable dispersions of water droplets in a continuous gasoline phase.
• the water droplets of the water-gasoline microemulsion fuels are generally too small to scatter light, and hence the microemulsions usually appear transparent.
• the water droplets have a droplet size of the order of nanometres, for example less than 1000nm.
• the surfactants in the water-gasoline microemulsion fuels preferably have a hydrophilic : lipophilic balance (HLB) of 8 to 14, preferably 10 to 13.
• HLB hydrophilic : lipophilic balance
• hydrophilic : lipophilic balance is a classification of the relative simultaneous attraction that a surfactant possesses for water and hydrocarbon, and for non-ionic surfactants, is normally calculated from its ratio of ethoxylated : hydrocarbon molecular weights.
• Surfactants having a high HLB of above 12 are highly hydrophilic (and predominantly water soluble) whilst substances having a low HLB below 8 are lipophilic and predominantly oil-soluble. Those with HLB values between 8 and 12 have intermediate properties.
• microemulsions for use in the present invention may be made by blending together water, gasoline and a suitable surfactant.
• microemulsions for use in the present invention may be formed as the "middle phase" of a three-phase system.
• phase-behaviour of microemulsions is described, for example, in " Microemulsions in Technical Processes", Chemical Reviews, 1995, Vol. 95, No.4, p.849-864 .
• a ternary water, gasoline and surfactant mixture will form three-phases with a surfactant-rich middle phase.
• the water-gasoline microemulsion fuels can be prepared by mixing the required components at ambient temperature and pressure, typically in the percent weight ratio range of 1 - 20 : 75 - 98 : 2 -15 of water : gasoline base fuel : surfactant, respectively.
• the mixture will separate into three phases, and the middle phase of the three phases, which is the desired water-gasoline microemulsion phase, may be separated, for example by decantation.
• the base fuel comprised 26% by weight aromatics, less than 1% by weight benzene, less than 20ppm sulphur, and had a density of 0.74 g/ml.
• the base fuel has a research octane number (RON) of 96.0, and a motor octane number (MON) of 85.6.
• Emulsion A Emulsion A
• Emulsion A was prepared by mixing the base fuel with 8.8% by weight of a nonyl phenol ethoxylate surfactant and subsequently adding 6.9% by weight of water.
• the density was 0.78 g/ml.
• Emulsion A was found to have a RON of 98.7 and a MON of 92.0.
• the vehicle was run on a EURO Stage 2 test cycle, with 40 second idle, and at an ambient temperature of 25°C +/-2°C.
• Emulsion A under steady-state conditions.
• the NOx emissions were observed to be reduced by 85%, and under steady-state conditions at 120kph, the fuel consumption was increased by 6.6% compared to the base fuel, consistent with the water content of the emulsion (6.9% by weight water).

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Citations (8)

• 2008
  • 2008-07-15 EP EP08252407A patent/EP2145940A1/fr not_active Withdrawn

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