METHANOL-BASED ENGINE FUEL CONTAINING A COMBUSTION IMPROVER ADDITIVE

Abstract

A compression ignition engine fuel includes 98.0% to 99.9% by weight of methanol and 0.01% to 2.0% by weight of an alkyl nitrate or mixture of alkyl nitrates.

Claims

1. A compression ignition engine fuel comprising from about 98.0% to about 99.9% by weight methanol and from about 0.01% to about 2.0% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

2. The fuel of claim 1, comprising from about 0.05% to about 1.5% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

3. The fuel according to claim 1, which consists of methanol and an alkyl nitrate or a mixture of alkyl nitrates.

4. The fuel of claim 1, wherein the alkyl nitrate is a nitrate of a linear alkyl having from 4 to 36 carbon atoms, a nitrate of a branched alkyl having from 4 to 36 carbon atoms, a nitrate of a cyclic alkyl having from 4 to 18 carbon atoms, or a mixture of these nitrates.

5. The fuel of claim 1, wherein the alkyl nitrate is selected from the group consisting of: 2 ethyl hexyl nitrate, cyclohexyl nitrate, dodecyl nitrate, n-nonyl nitrate, 2-tetradecyl-1-octadecyl nitrate, hexyl nitrate, 2-octyl nitrate, isononyl nitrate, 2-propylheptyl nitrate, a mixture of C.sub.9 to C.sub.13 branched alkyl nitrates, and mixtures thereof.

6. The fuel of claim 1, wherein the alkyl nitrate is 2-ethylhexyl nitrate.

7. A method of obtaining a fuel according to claim 1, which comprises mixing, in a liquid state, an alkyl nitrate or a mixture of alkyl nitrates with methanol.

8. The method of claim 7, wherein methanol and the alkyl nitrate or the mixture of alkyl nitrates are mixed in an engine tank.

9. The method of claim 7, wherein methanol and the alkyl nitrate or the mixture of alkyl nitrates are mixed in an injector.

10. The method of claim 7, wherein the methanol and the alkyl nitrate or the mixture of alkyl nitrates are mixed in a premix chamber of an engine.

11. (canceled)

12. (canceled)

13. (canceled)

14. (canceled)

15. The method of claim 21, wherein the alkyl nitrate or mixture of alkyl nitrates and methanol are mixed in an injector.

16. The method of claim 21, wherein the alkyl nitrate or mixture of alkyl nitrates and methanol are mixed in a premix chamber of the combustion engine.

17. An engine containing a fuel as defined in claim 1.

18. A vehicle or vessel comprising an engine as defined in claim 17.

19. The fuel of claim 1, comprising from about 0.1% to about 1.0% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

20. The fuel according to claim 1, which consists of methanol and an alkyl nitrate.

21. A method for igniting a fuel in a combustion engine, the fuel comprising from about 98.0% to about 99.9% by weight of methanol, the improvement comprising adding to the fuel from about 0.01% to about 2.0% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

22. The method of claim 21, comprising adding to the fuel from about 0.05% to about 1.5% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

23. The method of claim 21, comprising adding to the fuel from about 0.1% to about 1.0% by weight of an alkyl nitrate or of a mixture of alkyl nitrates.

24. The method of claim 21, wherein the alkyl nitrate is 2-ethylhexyl nitrate.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0015] FIG. 1 shows the effect of alkyl nitrates on the cetane number of a standard diesel fuel.

[0016] FIG. 2 shows the effect of EHN on the ignition delay of methanol for a richness (air/fuel) of 0.5 at a compression pressure Pc of 30 bars: left curve=fuel consisting of 100% methanol, right curve=fuel consisting of 99.8% methanol and 0.2% EHN.

[0017] FIG. 3 shows the effect of EHN on the ignition delay of methanol for a richness (air/fuel) of 1 at a compression pressure Pc of 30 bars: left curve=fuel made of 100% methanol; right curve=fuel made of 99.8% methanol and 0.2% EHN.

[0018] FIG. 4 shows the effect of EHN on the ignition delay of methanol for a richness (air/fuel) of 1.5 at a compression pressure Pc of 30 bars: left curve=fuel made of 100% methanol; right curve=fuel made of 99.8% methanol and 0.2% EHN.

[0019] FIG. 5 shows the ignition delay of a methanol-based fuel containing different amounts of EHN as a function of temperature, for a richness (air/fuel) of 1 at a compression pressure Pc of 30 bars: curves from left to right=fuel consisting of 100% methanol; fuel consisting of 99.8% methanol and 0.2% EHN; fuel consisting of 99.5% methanol and 0.5% EHN; fuel consisting of 99.0% methanol and 1.0% EHN.

[0020] FIG. 6 shows the ignition delay of a methanol-based fuel containing different amounts of EHN, for a richness (air/fuel) of 1, at a compression pressure Pc of 30 bar, over a temperature range from 850K to 1000K.

[0021] FIG. 7 is an expanded view of FIG. 6 over the temperature range of 900K to 1000K.

DESCRIPTION OF THE INVENTION

[0022] The present disclosure relates to a compression ignition or spark ignition engine fuel which comprises about 98.0% to about 99.9% by weight of methanol and about 0.01% to about 2.0% by weight of a compound consisting of an alkyl nitrate or a mixture of alkyl nitrates.

[0023] In one embodiment, the fuel comprises about 0.05% to about 1.5% by weight of said compound. In another embodiment, the fuel comprises about 0.1% to about 1.0% by weight of said compound. In another embodiment, the fuel comprises about 0.1% to less than 1.0% (<0.1%) by weight of said compound.

[0024] In one embodiment, the fuel of the invention consists of methanol and said compound (and in this case, the amount of compound in the fuel is at least 0.1% by mass).

[0025] In another embodiment, when the sum of the amount of methanol and the amount of compound is not equal to 100% by weight, the fuel may contain one or more other additives to make the fuel 100% complete, such as additives with preservative, anti-corrosion or detergent functions.

[0026] Said compound added to the methanol is selected from one or more linear, branched or cyclic alkyl nitrates.

[0027] Said compound is more particularly selected from linear alkyl nitrates having 4 to 36, advantageously 4 to 24 carbon atoms, branched alkyl nitrates having 4 to 36, advantageously 4 to 24 carbon atoms, cyclic alkyl nitrates (or cycloalkyl nitrate) having 5 to 18 carbon atoms, and mixtures thereof. In one embodiment, said compound is selected from 2-ethylhexyl nitrate, cyclohexyl nitrate, dodecyl nitrate, n-nonyl nitrate, 2-tetradecyl-1-octadecyl nitrate, hexyl nitrate, 2-octyl nitrate, isononyl nitrate, 2-propylheptyl nitrate, a mixture of C.sub.9 to C.sub.13 branched alkyl nitrates, and mixtures thereof. In one embodiment, the alkyl nitrate is 2-ethylhexyl nitrate alone or in admixture with one or more other alkyl nitrates as defined above, advantageously the alkyl nitrate is 2-ethylhexyl nitrate.

[0028] Mixtures of C.sub.9 to C.sub.13 branched alkyl nitrates can be synthesized from the corresponding mixtures of branched C.sub.9 to C.sub.13 alcohols, for example the alcohols available under the tradename Exxal from Exxon. As an example, a mixture of at least two branched alcohols selected from a C.sub.9 branched alcohol, a C.sub.10 branched alcohol, a Cu branched alcohol, a C.sub.12 branched alcohol and a C.sub.13 branched alcohol can be prepared and then the corresponding mixture of alkyl nitrates can be synthesized.

[0029] According to an embodiment, the methanol ignition enhancement compound, consisting of an alkyl nitrate or a mixture of alkyl nitrates, is mixed with the methanol in the tank supplying the engine, to obtain the fuel according to the invention.

[0030] According to one embodiment, said compound and methanol are stored separately, and brought together in an injector, thereby forming the fuel according to the invention before it is fed into the combustion chamber of the engine.

[0031] According to one embodiment, said compound is stored separately from the methanol and is co-injected with the methanol to form the fuel according to the invention in a premix chamber of the engine.

[0032] The present disclosure also relates to the use of an alkyl nitrate or mixture of alkyl nitrates (as defined above), in the proportions defined above, as an ignition improver for a fuel based on (or consisting of) methanol.

[0033] The present disclosure also relates to a method for improving the ignition of a fuel based on (or consisting of) methanol in a combustion engine, the method comprising adding to the methanol an alkyl nitrate or a mixture of alkyl nitrates (as defined above), in the proportions defined above. In one embodiment, the alkyl nitrate or mixture of alkyl nitrates and methanol are mixed in an injector. In one embodiment, the alkyl nitrate or mixture of alkyl nitrates and methanol are mixed in a premix chamber of the engine.

[0034] The present disclosure also relates to an engine of a motorized vehicle (such as a car, truck, tractor, etc.), or motorized vessel (such as a tanker, container ship, etc.) containing a fuel as defined above. The present disclosure also relates to a motorized vehicle or vessel comprising a combustion engine comprising a fuel as defined above.

[0035] The present disclosure is illustrated by the following examples given for information purposes.

EXAMPLES

[0036] The ignition delay improvement of methanol was measured under test conditions equivalent to those described in the scientific paper Ignition delay times of NH.sub.3/DME blends at high pressure and low DME fraction: RCM experiments and simulations (Combustion and Flame Volume 227, May 2021, Pages 120-134). The test laboratory engine is a fast compression machine equivalent to the one described in this scientific paper. This is a fast compression machine for measuring the auto-ignition time of a mixture. This machine allows compressing in a very short time the mixture in order to obtain preset pressure and temperature conditions. The liquids are admitted into the tank through a different orifice than the gas inlet. The liquid quantities are measured with a syringe and a precision balance.

[0037] The ignition delay dAI is defined according to the following formula in which Pc is the pressure applied to the injected fuel:

[00001]$\mathrm{dAI}=t\left({\frac{\mathrm{dP}}{\mathrm{dt}}}_{\max }\right)-t\left(P_c\right)$

Example 1

[0038] The ignition delays were determined as a function of the injection temperature (between 800K and 1000K), at a pressure Pc of 30 bar, of a fuel according to the invention consisting of 99.8% by mass of methanol and 0.2% by mass of EHN and for a richness of 0.5, 1 and 1.5 of mixture with air respectively. The results are shown in FIGS. 2, 3 and 4 with the ignition delay benchmarks of methanol alone. There is a significant reduction, approximately by a factor of 5 to 10, in fuel ignition delay when the fuel contains EHN, compared to methanol alone. This reduction in ignition delay compared to methanol alone is all the more important that the temperature is low.

Example 2

[0039] The ignition delays of different fuels containing either methanol alone or a mixture of methanol and EHN at 0.2%, 0.5% or 1% by weight, at different injection temperatures (temperature range 790K to 1000K), at a pressure Pc of 30 bar and a mixture richness of 1 with air, were determined. As can be seen in FIGS. 5 to 7, the addition of EHN to a methanol fuel results in a significant decrease in ignition delay compared to methanol alone.

[0040] These examples show that the use of alkyl nitrate(s) in a very low weight percentage can significantly improve the ignition delay of a methanol-based fuel. There was no reason to believe 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 like methanol.

[0041] Although the presently disclosed subject matter and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the presently disclosed subject matter, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized according to the presently disclosed subject matter.

[0042] Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0043] In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having any other possible combination of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. Thus, the foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

[0044] It will be apparent to those skilled in the art that various modifications and variations can be made in the composition, device, and method of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.

[0045] For any patents, patent applications, publications, product descriptions, and protocols are cited throughout this application, the disclosures of all of which are incorporated herein by reference in their entireties for all purposes.