Fuel compositions with hydrogen

Abstract

A fuel composition for an internal combustion engine comprising hydrogen gas and a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. Use of the gaseous additives in the present invention provides protection against friction loss and wear of moving parts of a hydrogen-fuelled internal combustion engine.

Description

[0001]SP3113 - 1 - FUEL COMPOSITIONS Field of the Invention The present invention relates to fuel compositions suitable for an internal combustion engine, wherein the fuel compositions comprise hydrogen. In particular, the 5 fuel compositions of the present invention have improved friction and wear properties. Background of the Invention Hydrogen (H2) as fuel for an Internal Combustion Engine (ICE) has been considered as carbon free fuel for 10 transportation powertrains, due to its carbon free emissions and high energy efficiency (Berry, G.D.; Pasternak, A.D.; Smith, J.R.; Schock, R.N.; ‘Hydrogen as a future transportation fuel’, Energy 1996, 21, 289-303). The Hydrogen Council, a global initiative composed of 15 various energy and transportation companies, estimated that approximately 25% of passenger car vehicles and 20% of non-electrified rail transportation would be fuelled with hydrogen by 2050, reducing daily oil consumption for transportation use by up to 20% (Hydrogen Scaling Up: A 20 Sustainable Pathway for the Global Energy Transition; Hydrogen Council: Belgium, 2017 and Oil Market Report; International Energy Agency: Paris, France, 2019.). Although hydrogen as fuel can be used in both fuel cells and internal combustion engines (ICEs), the 25 hydrogen ICE can leverage the current production infrastructure for vehicle manufacture and existing powertrains, with some modifications enabling hydrogen as fuel, and therefore, presents a near term opportunity to reduce Greenhouse Gas (GHG) emissions. 30 Both Port Fuel Injection (PFI) and Direct Injection SP3113 - 2 - (DI) technologies have been used in Hydrogen ICEs. A hydrogen DI system with up to 300 bar injection pressure has been developed and integrated into a spark ignition (SI) engine, achieving a maximum efficiency of 42%, 5 paralleling diesel engine with turbo charging (‘BMW Hydrogen Engine Reaches Top Level Efficiency, BMW: Munich, Germany, 2009). The hydrogen gas must be pumped and injected into a combustion chamber, and both pump and injector require 10 effective lubrication to limit friction, wear and seizure of rubbing surfaces. Unfortunately, hydrogen gas is a poor lubricant for most engineering metals, so additional lubrication must be provided, for example an oil or grease, or by employing coatings on rubbing parts. 15 CN116478760A discloses an engine oil for a hydrogen- fuelled internal combustion engines comprising 89% to 92% of a synthetic base oil. CN115125053 discloses a lubricating oil composition for a hydrogen-fuelled internal combustion engine wherein 20 the lubricating oil composition comprises a base oil. It would be desirable to find alternative ways of improving the friction and wear properties of hydrogen containing fuel compositions. Summary of the Invention 25 According to the present invention there is provided a fuel composition for an internal combustion engine comprising hydrogen gas and a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and 30 mixtures thereof. According to the present invention there is further provided a process for preparing a fuel composition for an internal combustion engine comprising blending SP3113 - 3 - hydrogen gas with a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. According to the present invention there is further 5 provided a method for operating an internal combustion engine comprising fuelling the internal combustion engine with a fuel composition, and combusting the fuel composition within a combustion chamber of the internal combustion engine, wherein the fuel composition comprises 10 hydrogen gas and a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. According to the present invention there is further provided a method for reducing friction within an 15 internal combustion engine fuelled with a fuel composition comprising hydrogen gas, wherein the method comprises adding to the fuel composition a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon 20 compound, and mixtures thereof, and combusting the fuel composition in a combustion chamber of the internal combustion engine. According to the present invention there is further provided the use of a gaseous additive in a fuel 25 composition comprising hydrogen gas for reducing the friction coefficient of the fuel composition, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. 30 According to the present invention there is further provided a method for reducing engine wear within an internal combustion engine fuelled with a fuel composition comprising hydrogen gas, wherein the method SP3113 - 4 - comprises a step of adding to the fuel composition a gaseous additive and combusting the fuel composition in a combustion chamber of the internal combustion engine, wherein the gaseous additive is selected from an 5 oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. According to the present invention there is further provided the use of a gaseous additive in a fuel composition comprising hydrogen gas for reducing the wear 10 scar of the fuel composition, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. It has been surprisingly found that by adding a very small amounts, (i.e. additive amounts) of a chemically- 15 active, lubricious gas or vapour species to the hydrogen gas flow, the required pump and injector lubrication is provided and the friction and wear properties of the fuel system are improved. It has been found that the present invention is 20 analogous to using dissolved lubricity additives in liquid hydrocarbon fuels but based in the gas rather than a liquid phase. It has been found by the present inventors that this approach can provide excellent friction and wear control of hydrogen supply systems. 25 The reduction in friction and wear control provided by the present invention could be achieved by co- injecting a lubricant oil with a hydrogen fuel or a co- injecting diesel fuel along with gaseous hydrogen fuel. However, the single fuel solution for hydrogen ICEs 30 provided by the present invention is preferable because it reduces carbon-based emissions and handling and storage is easier. Further, the powertrain system design is simplified. With the single fuel solution of the SP3113 - 5 - present invention, there is no need for separate injection systems for co-injecting lubricating oil or diesel fuel. Brief Description of the Drawings 5 Figure 1 shows the friction coefficient plotted against the Rubbing Time in seconds for Examples 1 and 2 (containing 1000 ppmw and 5000 ppmw, respectively, of carbon monoxide) and Comparative Example 1. Figure 2 shows the average friction coefficient for 10 Examples 1 and 2 (containing 1000 ppmw carbon monoxide and 5000 ppmw carbon monoxide, respectively) and Comparative Example 1. Figure 3 shows the wear scar diameter for Examples 1 and 2 (containing 1000 ppmw carbon monoxide and 5000 ppmw 15 carbon monoxide, respectively) and Comparative Example 1. Figure 4 shows the friction coefficient plotted against the Rubbing Time in seconds for Examples 3 and 4 (containing 1000 ppmw dimethylether and 5000 ppmw dimethylether, respectively) and Comparative Example 1. 20 Figure 5 shows the average friction coefficient for Examples 3 and 4 (containing 1000 ppmw dimethylether and 5000 ppmw dimethylether, respectively) and Comparative Example 1. Figure 6 shows the wear scar diameter for Examples 3 25 and 4 (containing 1000 ppmw dimethylether and 5000 ppmw dimethylether, respectively) and Comparative Example Detailed Description of the Invention The fuel composition of the present invention comprises hydrogen gas and a gaseous additive. 30 The hydrogen gas used in the fuel composition of the present invention can be any hydrogen gas suitable for use in an internal combustion engine. The internal combustion engine here is preferably a hydrogen-fuelled internal SP3113 - 6 - combustion engine. The gaseous additive is selected from a gaseous oxygenated carbon compound, a gaseous oxygenated hydrocarbon compound, and mixtures thereof. 5 As used herein, the term ‘oxygenated hydrocarbon’ means a compound which consists of hydrogen, carbon and oxygen. As used herein, the term ‘oxygenated carbon compound’ means a compound which consist of carbon and oxygen. The oxygenated hydrocarbon is preferably 10 selected from dimethyl ether, formaldehyde, acetaldehyde, vinylmethylether, and mixtures thereof. The oxygenated carbon compound is preferably carbon monoxide. In a preferred embodiment herein, the gaseous additive is an oxygenated hydrocarbon, preferably dimethyl ether. 15 The gaseous oxygenated hydrocarbon is preferably present in the fuel composition in an amount from 1 ppmw to 10,000 ppmw, more preferably from 150 ppmw to 5000 ppmw, even more preferably from 500 to 5000 ppmw, and especially from 1000 ppmw to 5000 ppmw. In one 20 embodiment, the gaseous oxygenated hydrocarbon is present in an amount from 1000 ppmw to 2000 ppmw. The fuel compositions are prepared by mixing the additive with the hydrogen. The fuel compositions of the present invention 25 provide reduced friction and wear. In the context of this aspect of the invention, the term “reducing the friction’ and ‘reducing the friction coefficient’ embraces any degree of reduction in the friction and friction coefficient achieved by the fuel 30 composition. The reduction in the coefficient of friction of the fuel composition may be of the order of 1% or more, preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, and SP3113 - 7 - especially 35% or more compared to the coefficient of friction of an analogous fuel composition comprising hydrogen gas alone and which does not contain the specified gaseous additive. Even a 1% reduction in 5 friction coefficient is worthwhile, as such a reduction can bring a material within prevailing fuel specifications, which it would not otherwise meet. In the context of this aspect of the invention, the term “reducing engine wear’ and ‘reducing the wear scar 10 diameter’ embraces any degree of reduction in the engine wear and wear scar diameter achieved by the fuel composition. The reduction in the wear scar diameter may be of the order of 1% or more, preferably 5% or more, more preferably 10% or more, even more preferably 20% or 15 more, and especially 35% or more compared to the wear scar diameter of an analogous fuel composition comprising hydrogen gas alone and which does not contain the specified gaseous additive. Even a 1% reduction in wear scar diameter is worthwhile, as such a reduction can 20 bring a material within prevailing fuel specifications, which it would not otherwise meet. While the fuel compositions of the present invention are particularly advantageous for reducing friction and wear in a hydrogen-fuelled internal combustion engine, 25 the fuel compositions of the present invention can also be used as fuel in a Proton-exchange membrane (PEM) fuel cell application. The invention is illustrated by the following non- limiting examples. 30 Examples Examples 1-4 and Comparative Example 1 Hydrogen fuel was blended with a series of gaseous hydrocarbon additives and the resulting fuel compositions SP3113 - 8 - were tested for friction and wear properties in a sealed HFR rig experiment. Example 1 consisted of hydrogen gas and an additive amount (1000 ppmw) of carbon monoxide gas. 5 Example 2 consisted of hydrogen gas and an additive amount (5000 ppmw) of carbon monoxide. Example 3 consisted of hydrogen gas and an additive amount (1000 ppmw) of dimethylether. Example 4 consisted of hydrogen gas and an additive 10 amount (5000 ppmw) of dimethylether. Comparative Example 1 consisted of hydrogen gas without any gaseous additives. The fuel compositions were subjected HFR tests as described in Zhang,J.,Bolle,B., Wong,J.S.S., Spikes,H.S. 15 ‘Influence of Atmosphere on Carbonaceous Film Formation in Rubbing, Metallic Contacts’, Tribol Lett 72, 4(2024), in order to determine friction coefficients and wear scar diameter. A sealed HFR (HPR) from PCS Instruments was used. This is a fully automated ball-on-plate 20 reciprocating system for the measurement of friction and wear under fully sealed, pressurised, and controlled conditions. It has a fully sealed pressure chamber which is able to run under high pressure or vacuum. It comprises a removable chamber design which maintains 25 pressure or vacuum even when off the system, which allows test blends to be made in situ. The small volume of the chamber allows test fluids to be changed in situ and / or during a test. This instrument has the same contact configuration as the conventional HFR and uses the same 30 ball and disc specimen. The entire unit is enclosed in a stainless steel casing with a small internal volume of 60ml. Sealing of reciprocating shaft is via two flexible bellows, while an external transducer monitors friction SP3113 - 9 - by displacement of the disc holder. The latter differs from the conventional HFR only in that the shaft to transducer is attached to and passes through a flexible, metal membrane to enable complete sealing. The test rig 5 can operate up to 10 bar pressure and 150°C. The HPR test conditions are shown below in Table 1. Table 1 Applied load 1.96N (200g), Pmax = 0.82 GPa Stroke length Isooctane 1mm, hexadecane 2mm Stroke frequency Isooctane 50Hz, Hexadecane 20Hz Test fluid volume 6cm3(when fluid used) Test Temperature Isooctane 25°C, hexadecane 60°C Disc roughness, Rq 4.8 ± 1.2 nm Ball roughness, Rq 9.9 ± 1.2 nm Ball hardness 790 HV Ball hardness Hard disc = 775 HV Table 2 below shows the average friction coefficient0 (µ) and the average ball wear scar diameter (WSD) for Examples 1-4 and Comparative Example 1. Table 2 Example Average ball wear Average friction scar diameter coefficient (µm) Comparative 496.2 0.901 Example 1 (hydrogen, no additive) Example 1 (H2, 418.1 0.905 1000 ppmw CO) Example 2 (H2, 436.3 0.806 5000 ppmw CO) Example 3 (H2, 399.9 0.862 1000 ppmw dimethylether) Example 4 (H2, 389.6 0.568 5000 ppmw dimethylether) SP3113 - 10 - Figure 1 shows the friction coefficient as a function of Rubbing time (Seconds) for Examples 1 and 2 and shows that carbon monoxide did not show instantaneous friction reduction for either treat rate. Despite that, 5 carbon monoxide showed a significant reduction in average friction coefficient at a treat rate of 5000 ppmw (see Figure 2 and discussion below). Figure 2 shows the average friction coefficient for Examples 1 and 2 and Comparative Example 1, as well as 10 the %reduction in friction coefficient for each of Examples 1 and 2 and Comparative Example 1. Example 2 (containing 5000 ppmw carbon monoxide) showed a significant reduction in friction coefficient compared with hydrogen gas alone. In particular, Figure 2 shows 15 that addition of 5000 ppmw carbon monoxide to hydrogen gas (Example 2) provided over 10% reduction in friction coefficient compared with hydrogen gas alone (Comparative Example 1). However, at a treat rate of 1000 ppmw carbon monoxide (Example 1), a reduction in friction coefficient 20 was not observed compared with hydrogen gas alone. Figure 3 shows the average wear scar diameter for Examples 1 and 2 and Comparative Example 1, as well as the %reduction in wear scar diameter for each of Examples 1 and 2 and Comparative Example 1. Examples 1 and 2 25 (containing 1000 ppmw carbon monoxide and 5000 ppmw carbon monoxide, respectively) showed a significant reduction in wear scar diameter compared with hydrogen gas alone. In particular, Figure 3 shows that addition of 1000 ppmw carbon monoxide to hydrogen gas (Example 1) 30 provided over 15% reduction in wear scar diameter compared with hydrogen gas alone (Comparative Example 1). Further, Figure 3 shows that addition of 5000 ppmw of carbon monoxide to hydrogen gas (Example 2) provided over 12% reduction in wear scar diameter compared with hydrogen gas alone. Figure 4 shows the friction coefficient as a function of Rubbing time (Seconds) for Examples 3 and 4 5 and shows that dimethylether showed instantaneous friction reduction when used at both treat rates. Figure 5 shows the average friction coefficient for Examples 3 and 4 and Comparative Example 1, as well as the %reduction in average friction coefficient for each 10 of Examples 1 and 2 compared with hydrogen alone. Examples 3 and 4 (containing 1000 ppmw dimethylether and 5000 ppmw dimethylether, respectively) showed a significant reduction in friction coefficient compared with hydrogen gas alone. In particular, Figure 5 shows 15 that addition of 1000 ppmw dimethylether to hydrogen gas (Example 3) provided over 4% reduction in average friction coefficient compared with hydrogen gas alone. Further, Figure 5 shows that addition of 5000 ppmw dimethyl ether to hydrogen gas (Example 4) provided over 20 36% reduction in average friction coefficient compared with hydrogen gas alone. Figure 6 shows the average wear scar diameter for Examples 3 and 4 and Comparative Example 1, as well as the %reduction in average wear scar diameter for each of 25 Examples 3 and 4 compared with hydrogen alone. Examples 3 and 4 (containing 1000 ppmw dimethylether and 5000 ppmw dimethylether, respectively) showed a significant reduction in average wear scar diameter compared with hydrogen gas alone. In particular, Figure 5 shows that 30 addition of 1000 ppmw dimethylether to hydrogen gas (Example 3) provided over 19% reduction in average wear scar diameter compared with hydrogen gas alone. Further, Figure 5 shows that addition of 5000 ppmw dimethyl ether - 12 - to hydrogen gas (Example 4) provided over 21% reduction in average wear scar diameter compared with hydrogen gas alone. 5

Claims

C L A I M S 1. A fuel composition for an internal combustion engine comprising hydrogen gas and a gaseous additive, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon 5 compound, and mixtures thereof.

2. A fuel composition according to Claim 1 wherein the gaseous additive is an oxygenated hydrocarbon compound.

3. A fuel composition according to Claim 1 or 2 wherein the oxygenated hydrocarbon is selected from 10 dimethyl ether, formaldehyde, acetaldehyde, vinylmethylether, and mixtures thereof.

4. A fuel composition according to Claim 3 wherein the oxygenated hydrocarbon is dimethyl ether.

5. A fuel composition according to Claim 1 wherein the 15 gaseous additive is an oxygenated carbon compound.

6. A fuel composition according to Claim 5 wherein the oxygenated carbon compound is carbon monoxide.

7. A fuel composition according to any of Claims 1 to 6 wherein the gaseous additive is present in an amount of 1 20 ppmw to 10000 ppmw, based on the fuel composition.

8. A process for preparing the fuel composition of any of Claims 1 to 7 comprising blending hydrogen gas with a gaseous additive.

9. Method for operating an internal combustion engine 25 comprising fuelling the internal combustion engine with a fuel composition, and combusting the fuel composition within a combustion chamber of the internal combustion engine, wherein the fuel composition comprises hydrogen gas and a gaseous additive, wherein the gaseous additive 30 is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof.- 14 - 10. Method for reducing the friction within an internal combustion engine fuelled with a fuel composition comprising hydrogen gas, wherein the method comprises adding to the fuel composition a gaseous additive, 5 wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon, and mixtures thereof, and combusting the fuel composition in a combustion chamber of the internal combustion engine. 10 11. Use of a gaseous additive in a fuel composition comprising hydrogen gas for reducing the friction coefficient of the fuel composition, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof. 15 12. Method for reducing engine wear within an internal combustion engine fuelled with a fuel composition comprising hydrogen gas, wherein the method comprises a step of adding to the fuel composition a gaseous additive and combusting the fuel composition in a combustion 20 chamber of the internal combustion engine, wherein the gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof.

13. Use of a gaseous additive in a fuel composition 25 comprising hydrogen gas for reducing the wear scar of the fuel composition, wherein gaseous additive is selected from an oxygenated carbon compound, an oxygenated hydrocarbon compound, and mixtures thereof.

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