SYNTHETIC FUELS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to fuel additives, and more particularly to fuel additives to enhance engine performance.

BACKGROUND OF THE INVENTION

It is known in the art of engine performance that blending certain additives into natural and synthetic fuels can provide measureable advantages. For example, it has been demonstrated that some metal-based additives can improve engine performance, e.g., increasing power and fuel economy. However, metal-based additives are commonly associated with disadvantages such as the toxicity related to use of the materials in a combustion operating environment.

Recently, academic work has been undertaken to assess the potential use of carbon nanomaterials such as graphene oxide, graphene quantum dot materials, graphene nanoplatelets and carbon nanotubes as a fuel additive, to address the identified toxicity issue while maintaining engine performance advantages. While various researchers have confirmed the utility of carbon nanomaterials in a laboratory setting in terms of performance advantages and reduced emissions, a few have noted that the carbon nanomaterials agglomerate and fall out of solution - a significant challenge for commercial application of the fuel additive technology. Some techniques have been proposed to address the dispersion stability issue, such as using butanol as a mediator or blending in surfactants, but the limited proposals have primarily been directed to the requirements of the bench-scale experimentation rather than commercial application in vehicles, and it has been noted that use of surfactants in particular could negatively impact combustion performance.

What is needed, therefore, is a fuel additive that manifests the advantages of carbon nanomaterials while maintaining a state of dispersion in the fuel.

SUMMARY OF THE INVENTION

According to a first broad aspect of the present invention, there is provided a fuel additive for use in natural and synthetic fuels, the fuel additive comprising a carbon nanomaterial functionalized with a multi-carbon amine chain. The natural and synthetic fuels may include diesel, biodiesel, synthetic diesel, and jet fuel.

In some exemplary embodiments of the first aspect, an amine group of the multi-carbon amine chain replaces an oxygen-containing functional group on the carbon nanomaterial. The oxygen-containing functional group may be selected from the group consisting of epoxide, hydroxyl and carboxyl. The carbon nanomaterial may be selected from the group consisting of graphene oxide and graphene quantum dots.

In some embodiments the multi-carbon amine chain comprises a hydrocarbon chain. In some preferred embodiments the multi-carbon amine chain with the hydrocarbon chain is octadecylamine.

An amine group of the multi-carbon amine chain preferably reduces the carbon nanomaterial. Where the multi-carbon amine chain is a branched (Y-shaped) chain it may be capable of reducing more than one location on the carbon nanomaterial.

The chemical similarity of the hydrocarbon chain and the natural and synthetic fuels may enhance dispersion stability of the fuel additive in the natural and synthetic fuels.

The multi-carbon amine chain comprises an amine group that replaces an oxygen group of the carbon nanomaterial, changing the surface chemistry so that it is more hydrophobic and thereby sustaining dispersion of the carbon nanomaterial in suspension in the fuel.

Carbon nanomaterials contain different types of oxygen-containing functional groups such as hydroxide, carboxyl, and epoxide. These functional groups make the surface of the carbon nanomaterials superhydrophilic. Grafting of multi-carbon amine chains on the surface of the carbon nanomaterials and replacement of oxygen-containing groups with multi-carbon amine chains makes the carbon nanomaterials both hydrophobic - assisting in dispersion stability - and compatible with fuels. Also, some molecular and intermolecular interactions such as chains entanglement occur between multi-carbon chains of fuels and modified carbon nanomaterials, helping the carbon nanomaterials achieve greater stability in the fuels.

Also, carbon nanomaterials with a specific surface chemistry which is similar to the chemistry of media (matrix) are more compatible with the matrix. Thus, the final suspension is more stable. Moreover, carbon nanomaterials modified with multi-carbon amine chains have a similar chemistry to the fuel chains. Consequently, the zeta potentials are very close to each other. The formed repulsive forces or electrostatic repulsive forces between the functionalized carbon nanomaterials and fuel chains make the final suspension more stable.

According to a second broad aspect of the present invention, there is provided a use of a fuel additive in a natural or synthetic fuel for improving engine performance, the fuel additive comprising a carbon nanomaterial functionalized with a multi-carbon amine chain. The natural or synthetic fuels may include diesel, biodiesel, synthetic diesel, and jet fuel.

In some exemplary embodiments an amine group of the multi-carbon amine chain replaces an oxygen-containing functional group on the carbon nanomaterial. The oxygen-containing functional group may be selected from the group consisting of epoxide, hydroxyl and carboxyl. The carbon nanomaterial may be selected from the group consisting of graphene oxide and graphene quantum dots.

In some embodiments the multi-carbon amine chain comprises a hydrocarbon chain. In some preferred embodiments the multi-carbon amine chain with the hydrocarbon chain is octadecylamine.

An amine group of the multi-carbon amine chain preferably reduces the carbon nanomaterial. Where the multi-carbon amine chain is a branched (Y-shaped) chain it may be capable of reducing more than one location on the carbon nanomaterial.

The chemical similarity of the hydrocarbon chain and the natural and synthetic fuels may enhance dispersion stability of the fuel additive in the natural and synthetic fuels.

According to a third broad aspect of the present invention, there is provided a method of modifying a fuel additive for a natural or synthetic fuel, comprising the steps of: providing a carbon nanomaterial; functionalizing the carbon nanomaterial with a multi-carbon amine chain to form a functionalized carbon nanomaterial; and blending the functionalized carbon nanomaterial into the natural or synthetic fuel. The natural or synthetic fuels may include diesel, biodiesel, synthetic diesel, and jet fuel.

In some exemplary embodiments the carbon nanomaterial is selected from the group consisting of graphene oxide and graphene quantum dots. The multi-carbon amine chain may be octadecylamine.

In some embodiments the step of providing the carbon nanomaterial comprises dispersing the carbon nanomaterial in water to form a suspension.

The step of functionalizing the carbon nanomaterial with the multi-carbon amine chain may comprise dissolving the multi-carbon amine chain in ethanol to form a solution, boiling the solution, and adding the solution to the suspension. In some such cases the step of blending the functionalized carbon nanomaterial into the natural or synthetic fuel may comprise removing any excess ethanol and water before introducing the functionalized carbon nanomaterial to the natural or synthetic fuel.

In some embodiments the step of functionalizing the carbon nanomaterial with the multi-carbon amine chain comprises an amine group of the multi-carbon amine chain replacing an oxygen- containing functional group on the carbon nanomaterial.

In some embodiments the multi-carbon amine chain comprises a hydrocarbon chain. In some such cases chemical similarity of the hydrocarbon chain and the natural or synthetic fuels may enhance dispersion stability of the fuel additive in the natural or synthetic fuels.

In some embodiments the step of functionalizing the carbon nanomaterial with the multi-carbon amine chain comprises an amine group of the multi-carbon amine chain reducing the carbon nanomaterial. In some such cases the multi-carbon amine chain is a branched (Y-shaped) chain such that the multi-carbon amine chain may reduce more than one location on the carbon nanomaterial.

A detailed description of exemplary embodiments of the present invention is given in the following. It is to be understood, however, that the invention is not to be construed as being limited to these embodiments. The exemplary embodiments are directed to particular applications of the present invention, while it will be clear to those skilled in the art that the present invention has applicability beyond the exemplary embodiments set forth herein. BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate exemplary embodiments of the present invention:

FIG. 1a is an illustration of a graphene oxide and an image of a test vessel showing the graphene oxide settling out of suspension in diesel; and

FIG. 1b is an illustration of a graphene oxide functionalized with multi-carbon amine chains and an image of a test vessel showing the functionalized graphene oxide remaining in suspension in diesel.

FIG. 2 is an image of a sample biodiesel stabilized by an additive in accordance with an embodiment of the present invention.

Exemplary embodiments will now be described with reference to the accompanying drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. The following description of examples of the invention is not intended to be exhaustive or to limit the invention to the precise form of any exemplary embodiment. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

The present invention is directed to fuel additives for improving engine performance while reducing harmful emissions. Specifically, the present invention is directed to a novel fuel additive comprising a carbon nanomaterial functionalized with a multi-carbon amine chain, and the use and application of same. In the exemplary embodiment described below for illustrative purposes only, the carbon nanomaterial is graphene oxide and the multi-carbon amine chain is octadecylamine, while the fuel is diesel or biodiesel.

Graphene oxide is a polar compound that includes a number of oxygen groups like epoxy and hydroxyl. Other compounds can attach to the oxygen groups or replace the groups to functionalize the graphene oxide so that the surface chemistry is changed allowing for a stable dispersion to be formed. Octadecylamine consists of an 18 group hydrocarbon chain that is attached to an amine group. The amine group can reduce the graphene oxide by replacing the oxygen with the nitrogen. The 18-group hydrocarbon chain (the octadecyl) is compatible with the composition of diesel fuel and creates a stable interaction with the diesel fuel. As noted above, carbon nanomaterials such as graphene oxide modified with multi-carbon amine chains such as octadecylamine have a similar chemistry to the fuel chains, such that the zeta potentials are very close to each other, and the formed repulsive forces or electrostatic repulsive forces between the functionalized graphene oxide and fuel chains make the final suspension more stable. The amine groups in multi-carbon amine chains such as octadecylamine are aggressive groups that can attach to oxygen-containing groups of graphene oxide and form C-N bonds. The length of carbon chains or number of carbon atoms in the chain is responsible for the hydrophobicity of the chain, with more carbon atoms resulting in greater hydrophobicity.

A multi-carbon amine chain comprises an amine group and multiple carbon chains. The amine group replaces an oxygen group on the graphene oxide. Where the carbon chains are hydrocarbon chains, the hydrocarbon chains provide the same chemistry (surface energy) as the surrounding fuel.

In the exemplary embodiment, the multi-carbon amine chain is a hydrocarbon amine, although there are other forms of multi-carbon amine chains that may have utility with the present invention, such as for one non-limiting example branched (Y-shaped) chains that can reduce more than one location on the graphene oxide.

Turning now to FIG. 1a, a formula for a graphene oxide is illustrated. In addition, a test vessel is shown in which a graphene oxide has been mixed in a diesel fuel without functionalizing with octadecylamine. As can be seen, the graphene oxide agglomerates and falls out of suspension, thus losing the advantages the graphene oxide might provide as a fuel additive.

FIG. 1b illustrates a formula for a graphene oxide that has been functionalized with octadecylamine. Another test vessel is presented, this time showing that the functionalized graphene oxide remains in solution in the diesel fuel, thus maintaining the advantages the graphene oxide might provide as a fuel additive.

FIG. 2 is an image of a biodiesel sample that was mixed with an additive in accordance with an embodiment of the present invention. The biodiesel was BioStable® 501 of Innospec, and the image shows the biodiesel 24 hours after the functionalized graphene oxide was mixed with the biodiesel. As can be seen, the functionalized graphene oxide remains in solution in the biodiesel fuel.

While the exemplary embodiment is directed to diesel fuels (commonly defined as 14-20 carbon chain lengths), it is believed that the octadecylamine-modified graphene oxide additive may be advantageous in other fuels such as jet fuel (commonly defined as 8-16 carbon chain lengths). The present invention is believed to have utility in medium-weight fuels (commonly defined as 10-25 carbon chain lengths).

EXAMPLE

In a laboratory-scale experiment, 1 g of graphene oxide nanosheets was dispersed in water using sonication in a first vessel, and the pH of the suspension was adjusted to around 4-5.

The suspension was kept subject to stirring and heated to reach at least 75 C. In a second vessel, 1.7 g of octadecylamine was dissolved in ethanol and the mixture was boiled (around 73-78 C). The boiling ethanol/octadecylamine solution was added drop-by-drop into the graphene oxide suspension, the temperature of the final suspension maintained around 90 C. The suspension was subjected to stirring for at least 12 hours, and the now-functionalized graphene oxide was collected by filtration and washed three times with ethanol to remove unreacted octadecylamine and water molecules. In order to disperse the functionalized graphene oxide in diesel, the excess amount of ethanol was removed by evaporation or washed again with jet fuel or diesel. Preferably a solvent exchange method is used to remove water from the functionalized graphene oxide. Washing with ethanol and then jet fuel is recommended. For any fuel, the time of sonication (both bath and probe sonication) should be optimized.

In the unmodified graphene oxide, as shown in the vessel in FIG. 1a, it was observed that the graphene oxide began to agglomerate and fall out of solution in the diesel fuel in less than one hour after sonication. In the modified graphene oxide, however, as shown in the vessel in FIG. 1b, it was observed that the graphene oxide remained stable in the diesel fuel for over three months.

While the above experimentation was conducted with natural diesel fuel, the similarity in chemistry indicates that similar results should be evident with biodiesel and syndiesel fuels. Further, graphene oxide was used as the carbon nanomaterial in the experimentation, but based on chemical similarities it is believed that other carbon nanomaterials such as graphene quantum dots may be useful in other embodiments of the present invention.

EXAMPLE

Preliminary testing in a diesel engine has demonstrated utility of a fuel additive in accordance with the present invention, although in some contexts and at very high RPM the engine may need to be tuned to the fuel specifications to optimize performance (pressure, timing, etc.), as would be clear to those skilled in the art.

A functionalized graphene oxide as described above was tested to determine the effect of the fuel additive using a GUNT CT159 single piston diesel engine. The engine was run from 700 to 2500 rpm with measurements of rpm, torque and fuel rate at 100rpm intervals. The test was repeated three times on each fuel and four different fuels were used: neat diesel, and three diesel and graphene oxide blends at the following loadings: 50 mg/L graphene oxide and two different formulas at 75 mg/L graphene oxide. The results for the three diesel and graphene oxide blends up to 2300 rpm are shown in Table 1.

Fuel Fuel Fuel rpm 1 2 3 700 33% -23% 73%

800 -11% -25% -20% 900 -2% -12% -7%

1000 23% 11% 31%

1100 -14% -2% -21%

1200 -43% 1% -9%

1300 -11% -22% -8%

1400 -15% -8% -18%

1500 -13% -17% -10%

1600 -6% -7% -17% 1700 -6% -3% -9%

1800 -13% -2% -4%

1900 -13% -9% -4%

2000 2% -2% -5%

2100 -3% 8% 5%

2200 17% 34% 10%

2300 18% 29% 8%

Average improvement from 1200-1600 rpm

Fuel 1 18%

Fuel 2 10%

Fuel 3 12%

Average improvement from 1000-2000 rpm

Fuel 1 10%

Fuel 2 5%

Fuel 3 7%

Table 1: Percent Change for Fuel Economy between doped fuels and neat fuel at various rpm

There were no apparent changes in engine operation with the different blends of fuels, with no changes in sound, temperature or discharge from the engine.

Graphene oxide enhanced fuel demonstrated an average improvement in fuel economy of 10- 20% within the 1200-1600 rpm range. The fuel economy had an average improvement of 5- 15% within the 1000-2000 rpm range. There was a measured reduction in the overall fuel economy when the engine was operated above 2200 with the graphene oxide enhanced fuel, however this may be due to the combustion dynamics.

The foregoing is considered as illustrative only of the principles of the present invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the foregoing, but should be given the broadest interpretation consistent with the specification as a whole.