Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M1/00—Liquid compositions essentially based on mineral lubricating oils or fatty oils; Their use as lubricants
  • C10M1/08—Liquid compositions essentially based on mineral lubricating oils or fatty oils; Their use as lubricants with additives

Definitions

• the field of the invention is that of fuels for combustion engines.
• the fuel of the invention is one of the new fuels with reduced environmental impact, for example those commonly called “e-fuels” when they are produced from low-carbon electricity, low-carbon hydrogen, and/or from CO 2 . They are considered as a solution for the decarbonization of transport.
• the fuel of the invention is essentially composed of a mixture of alcohol and water, and is thus one of the ecological alternatives for the replacement of fossil fuels. Water represents up to 15% by mass of said mixture. The function of water is to reduce the production of nitrogen oxides in the combustion products of the engine. Alcohol is therefore the major component of the fuel.
• the invention relates to an additive which, incorporated into the mixture of alcohol and water, ensures better ignition and faster combustion of the fuel in the engine.
• Methanol of the "e-fuels" type represents a credible low-impact alternative to replace fossil fuels and biofuels in combustion engines in the near future.
• the combustion of this methanol thus produced leads to a neutral CO 2 balance.
• Methanol as a fuel has a usable energy density in combustion engines but has a low cetane number. Its ignition in compression-ignition engines, such as diesel, is problematic, especially at low engine speeds.
• compression-ignition engines such as diesel
• the first method is the co-injection into the engine of a pilot fuel or an additive with methanol.
• patent application CN 214944586 describes the co-injection of a diesel-type pilot fuel with methanol as the main fuel.
• the scientific article “Effect of Cetane Improvers on Gasoline, Ethanol, and Methanol Reactivity and the Implications for RCCI Combustion” (SAE International Journal of Fuels and Lubricants Vol. 6, No. 1 (April 2013), pp. 170-187) describes the co-injection of 2-ethylhexyl nitrate (NEH) with a fuel composed mainly of gaseous methanol.
• NHE 2-ethylhexyl nitrate
• a fuel and a low reactivity oxidant well mixed are compressed to the gaseous state but do not reach auto-ignition.
• high reactivity fuel here NEH
• NEH high reactivity fuel
• a mass rate of NEH of 7% co-injected in the presence of gaseous methanol is likely to lead to an acceptable combustion efficiency in comparison with a reference fuel consisting of a mixture of isooctane and n-heptane.
• This type of process has the major disadvantage of requiring co-injection control according to the engine operating conditions, structural arrangements such as separate tanks and injection systems. Also, the use of a fuel as a pilot fuel generates CO 2 emissions with a negative impact on the environment.
• the second method is a mixture of fuels with methanol. It is known to mix alcohols, such as methanol or ethanol, in minority or majority proportions with fossil or synthetic diesel fuels such as dimethyl ether (DME) or with gasoline. In this case, the CO2 emissions balance also has a negative impact on the environment.
• alcohols such as methanol or ethanol
• DME dimethyl ether
• the third method is the incorporation of an ignition-enhancing additive mixed with methanol, possibly also mixed with diesel fuel.
• Many patent applications such as patent applications CN 103865592 and CN 104232180, describe the incorporation of a cocktail of multifunctional additives mixed with methanol, possibly also mixed with fuel. These additives have, for example, preservation, anti-corrosion, combustion-improving, and detergency functions. These additives generally represent at least 10% of the mass of the fuel. The proportion of methanol in the fuel is between 30% and 90% by mass depending on the mass percentages of additives and diesel fuel present in the fuel. The combined effects of these additives are only observed globally without precisely measuring the necessary quantities. It is therefore not a fuel essentially composed of methanol.
• 2-ethylhexyl nitrate has long been known as a cetane improver for diesel fuel.
• a higher cetane value ensures lower fuel consumption, reduced particulate matter and NOx emissions, faster cold engine starting, reduced engine knocking and noise, and reduced engine wear.
• the reaction mechanism of NEH in the presence of a hydrocarbon diesel fuel has been studied, for example, in the scientific publication "The Autoignition Behavior of Surrogate Diesel Fuel Mixtures and the Chemical Effects of 2-Ethylhexyl Nitrate (2-EHN) Cetane Improver" (vol. 108, section 4: Journal of fuels and lubricants (1999), pp. 1029-1045).
• the said compound at these low levels in the presence of the alcohol/water mixture, is therefore conventionally considered a fuel additive.
• liquid compound to the alcohol/water mixture is carried out in the liquid state to form the fuel according to the invention in a tank. It can also be stored separately and mixed with the alcohol/water mixture to form the fuel according to the invention prior to its injection into the engine, or co-injected to form the fuel according to the invention in a premixing chamber of the engine.
• Figure 1 shows the effect of NEH on the ignition delay of a methanol/water mixture, with water representing 5% by mass of the mixture, with a single main injection (circular dots in the figure) or a micro-injection followed by a main injection (square dots in the figure) in the engine cylinder.
• the present disclosure relates to a combustion engine fuel, whether compression-ignited or spark-ignited, which comprises about 95.0% to 99.9% by mass of a mixture of alcohol and water, the water comprising from 1% to 15% by mass of the mixture, and about 0.01% to about 5.0% by mass of an alkyl nitrate.
• the fuel comprises about 0.1% to about 3% by weight of alkyl nitrate.
• the fuel may contain one or more other additives to make up the fuel to 100%, such as additives with preservative, anti-corrosion or detergency functions.
• the fuel according to the invention does not comprise an unsaturated fatty acid dimer and/or a phosphorous acid ester. In another embodiment, which can be combined with the previous one, the fuel according to the invention does not comprise a C 8 -C 2 o- aliphatic monocarboxylic acid. In another embodiment, which can be combined with the two previous ones, the fuel according to the invention does not comprise a mixture of C 4 and/or C 5 /C 6 and/or C 5 - C 7 hydrocarbons, nor a mixture of gasoline with at least one of said hydrocarbons.
• the alkyl nitrate, added to the alcohol/water mixture is more particularly chosen from linear alkyl nitrates comprising 4 to 36, advantageously 4 to 24 carbon atoms, branched alkyl nitrates comprising 4 to 36, advantageously 4 to 24 carbon atoms, cyclic alkyl nitrates (or cycloalkyl nitrate) comprising 5 to 18 carbon atoms, and mixtures thereof.
• the compound for improving fuel ignition i.e. the alkyl nitrate
• the alkyl nitrate is mixed in the liquid state with the alcohol/water mixture in the tank which supplies the engine, to obtain the fuel according to the invention.
• said alkyl nitrate on the one hand, and the alcohol/water mixture on the other hand are stored separately, and brought into contact with each other in the liquid state in an injector, thus forming the fuel according to the invention before it is conveyed into the combustion chamber of the engine.
• said alkyl nitrate is stored separately from the alcohol/water mixture and is co-injected with the methanol/water mixture to form the liquid fuel according to the invention in a premixing chamber of the engine.
• the present disclosure also relates to the use of an alkyl nitrate e, in the proportions defined above, as an agent for improving the ignition of a fuel based on (consisting of) alcohol and water.
• the present disclosure also relates to a method for improving the ignition of a fuel based on (consisting of) a mixture of alcohol and water in an engine (in particular a combustion engine), the method comprising adding to said mixture an alkyl nitrate (as defined above), in the proportions defined above.
• the alkyl nitrate and the alcohol/water mixture are mixed in an injector.
• the alkyl nitrate and the alcohol/water mixture are mixed in a premixing chamber of the engine.
• the present disclosure also relates to an engine (in particular a combustion engine) of a vehicle (such as a car, heavy goods vehicle, tractor, etc.) or a ship (such as an oil tanker, container ship, etc.) containing a fuel as defined above.
• a vehicle or ship comprising an engine as defined above.
• the performance of the fuel according to the invention compared to a fuel composed solely of methanol and water was measured with an experimental laboratory engine with compression ignition, single cylinder with a volume of 0.499 L with direct injection, targeting an average indicated pressure (PMI) of 3 Bars at 1500 rpm. After having passed 100 cycles (necessary for the calculations to come to have a consistent average of the values), the values of the operating parameters of the engine are measured. In At the same time, it is possible to record 20 pollutant measurement cycles, each spaced 5 seconds apart to obtain a representative average of the emissions from different cycles. From the values previously collected, the following quantities characterizing fuel combustion and engine operation are extracted:
• the addition of said compound with the methanol/water mixture improves all the combustion and operating parameters of the engine compared to a fuel consisting solely of a methanol/water mixture.
• the performance of the fuel of the invention can be further improved by controlling the injection of the fuel with multiple injections at each engine cycle, for example with one or more micro-injections called pilot injections then a main injection.
• the ignition delay as a function of the fuel inlet temperature is the resulting value of the tests which is presented below to illustrate in the following examples the advantages of the invention.
• the ignition delay dAI is defined according to the following formula in which Pc is the pressure applied to the injected fuel:
• This example concerns the improvement by addition of the NEH compound of the combustion performance in an engine of a mixture consisting of 95% by mass of methanol and 5% by mass of water.
• the ignition times were determined as a function of the intake temperature (from 313 K to 473 K), at a pressure Pc of 300 bars, of a fuel according to the invention consisting of 99% by mass of methanol/water mixture, the water representing 5% by mass of the mixture, and 1% by mass of NEH and for a richness of 0.25 of mixture with air.
• the results are shown in Figure 1 with the reference points of the ignition delay of the methanol/water mixture (in mass ratio 95%/5%) alone.
• a significant reduction in the ignition delays of the fuel containing NEH is observed, compared to the methanol/water fuel. This reduction in the ignition delay compared to that of the methanol/water fuel alone is all the more significant as the temperature is low.
• the ignition delay of the fuel of the invention according to the present example is approximately 3 times lower than that of the reference fuel comprising methanol and water.
• the fuel of the invention ignites even at low intake temperatures below 403 K, up to 373 K with an ignition delay of 2 ms, for which the methanol/water mixture does not ignite.
• This example concerns the improvement of performance by adding NEH to the combustion in an engine of a mixture consisting of 90% by mass of methanol and 10% by mass of water.
• the ignition delays were determined as a function of the intake temperature (between 313 K and 463 K), at a pressure Pc of 300 bars, of a fuel according to the invention consisting of 98% by mass of methanol/water mixture, the water representing 10% by mass of the mixture, and 2% by mass of NEH and for a richness of 0.25 of mixture with air.
• the results are shown in Figure 2 with the reference points of the ignition delay of the methanol/water mixture alone.
• a fuel according to the invention consisting of 98% by mass of methanol/water mixture, the water representing 10% by mass of the mixture, and 2% by mass of NEH and for a richness of 0.25 of mixture with air.
• the results are shown in Figure 2 with the reference points of the ignition delay of the methanol/water mixture alone.
• a fuel according to the invention consisting of 98% by mass of methanol/water mixture, the water representing 10% by mass of the mixture, and 2% by mass of NEH and for a richness of 0.25 of mixture
• the ignition delay at this temperature is 2 times lower than that of the methanol/water mixture.
• the methanol/water mixture does not ignite, whereas fuels containing 1% by mass of NEH and 2% by mass of NEH ignite with a delay of approximately 4 ms and 2.2 ms respectively.
• Table 1 These examples show that the use of alkyl nitrate in low mass percentages makes it possible to significantly improve the ignition delay of an alcohol and water-based fuel. More generally, the addition of an alkyl nitrate compound to an alcohol/water mixture improves the overall performance of the fuel in a combustion engine, while maintaining limited nitrogen oxide emissions, up to intake temperatures close to ambient temperature. None could have suggested that additives known to increase the cetane number of a diesel or biodiesel hydrocarbon could be used so effectively, in very small quantities, to improve the ignition of an alcohol mixed with water.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
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• 2023
  • 2023-11-22 FR FR2312850A patent/FR3155536A1/fr active Pending
• 2024
  • 2024-11-21 EP EP24821488.4A patent/EP4615939A1/de active Pending
  • 2024-11-21 WO PCT/FR2024/051542 patent/WO2025109286A1/fr active Pending

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