WO2024256785A1 - Use of an aqueous composition for lubricating the internal parts of a hydrogen or ammonia engine - Google Patents

Abstract

The present invention relates to the use, for lubricating a drive system comprising an internal combustion engine supplied with a non-hydrocarbon fuel selected from hydrogen and/or ammonia, of a composition comprising water, at least 10% by mass of one or more polyalkylene glycols with a weight-average molar mass of at least 1500 g.mol-1, said composition comprising a content of antifreeze additive(s), selected from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, of strictly less than 1% by mass. The invention also relates to a method for lubricating moving components in a drive system including an internal combustion engine supplied with at least one non-hydrocarbon fuel selected from hydrogen and ammonia, comprising a step of bringing at least said components into contact with such a composition.

Description

DESCRIPTION

TITLE: Use of an aqueous composition for lubricating the internal parts of a hydrogen or ammonia engine

The present invention relates to the use of a particular aqueous lubricating composition for lubricating a powertrain system comprising an internal combustion engine powered by a non-hydrocarbon fuel chosen from hydrogen and/or ammonia.

The present invention also relates to a method of lubricating an internal combustion engine powered by at least one non-hydrocarbon fuel chosen from hydrogen and ammonia, comprising a step of bringing at least one internal part of the engine into contact with a composition, as described below.

STATE OF THE PRIOR ART

In order to reduce greenhouse gas emissions generated by the combustion of hydrocarbon fuels, the international community is studying the use of alternative fuels with low carbon dioxide emissions. In this perspective, hydrogen and ammonia are considered promising solutions, particularly for the transport sectors (especially maritime transport) and the production of electricity in gas turbines.

Hydrogen and ammonia have multiple benefits, including but not limited to:

- These are fully decarbonized fuels that can be produced using different technologies, including from renewable electricity;

- Their combustion does not generate emissions of carbon dioxide CO2, sulfur gases (SOx), unburned hydrocarbons or particles;

- They can be used in existing engines and heating devices, with some adaptations.

However, internal combustion engines are generally lubricated by lubricating compositions which are essentially formulated from hydrocarbon base oils and additives. Hydrocarbon base oils are derived from refining processes (for Group I to III bases according to the API classification - "American Petroleum Institute") or from synthetic chemistry such as polyalphaolefins (PAO, or Group IV base oils according to the API classification). Group V base oils represent all other sources of unconventional base oils and are generally represented by oxygenated hydrocarbons such as esters and polyglycols.

During engine operation, a phenomenon of combustion of part of the lubricant present on the internal parts of the engine occurs. Even if this combustion is not desired, it is practically impossible to avoid. In the case of engines powered by hydrogen or ammonia, this partial combustion of the engine lubricant leads to emissions of carbon dioxide CO2, unburned hydrocarbons and particles, which are precisely the emissions that we seek to avoid with the use of these alternative fuels. These unwanted emissions from the lubricant have a negative impact on the environmental balance of engines running on hydrogen or ammonia.

It is therefore desirable to further improve the environmental impact of engines powered by hydrogen and/or ammonia, and in particular to reduce undesirable emissions including CO2, unburned hydrocarbons and particles.

Lubricant compositions formulated with more or less variable amounts of water are also known, including emulsions of water and hydrocarbon oils. These compositions are primarily intended for use in metalworking applications or as transmission fluids.

However, such compositions have not until now been used to lubricate the internal parts of combustion engines, in particular because of the risks of evaporation of water under the thermal flow of combustion, which causes accelerated consumption of the lubricant incompatible with conventional oil change intervals. Furthermore, it has generally been considered that the level of lubrication provided by these aqueous compositions could be insufficient in an engine in which the frictional constraints are extremely high, which could lead to an increased risk of failure of the engine lubricated with such compositions.

The present invention aims to remedy the problems described above and in particular to reduce the emissions of internal combustion engines powered by hydrogen and/or ammonia.

The Applicant has now discovered that particular aqueous compositions, as defined below, make it possible to effectively lubricate the internal parts of these specific engines while significantly reducing undesirable emissions compared to the use of conventional lubricants formulated with one or more hydrocarbon bases.

The present invention thus relates to the use, for lubricating a motorization system comprising an internal combustion engine powered by at least one non-hydrocarbon fuel chosen from hydrogen and/or ammonia, of a composition comprising:

- water;

- at least 10% by mass, relative to the total mass of said composition, of one or more polyalkylene glycol(s) with a weight-average molar mass, Mw, of at least 1500 g. mol ¹ ; said composition having a content of antifreeze additive(s) chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, relative to the total mass of the composition.

In the remainder of the text, the term “aqueous lubricating composition” will refer to a composition used according to the invention as defined above.

The aqueous lubricating composition according to the invention makes it possible to very effectively lubricate the various moving parts in a motorization system, mobile or stationary, including a internal combustion engine fueled by hydrogen and/or ammonia, hereinafter referred to as "hydrogen and/or ammonia engine".

For the purposes of the present invention, the term "engine system" is understood to mean a system comprising all the mechanical parts necessary for the intended mobile or stationary application and including at least one hydrogen and/or ammonia engine. The term "hydrogen and/or ammonia engine" means a combustion engine powered by a hydrogen and/or ammonia-based fuel. In particular, it may be an engine operating solely on hydrogen (hydrogen engine), an engine operating solely on ammonia (ammonia engine), an engine operating with a hydrogen, ammonia mixture or an engine operating on ammonia and diesel (dual fuel ammonia/diesel engine).

A “stationary” motorization system within the meaning of the invention is a motorization system including a stationary engine, in particular a hydrogen engine. It can find applications, for example, in electrical energy production devices.

A “mobile” motorization system is more particularly a motorization system implemented in vehicles, including light vehicles, heavy-duty vehicles, so-called “off-road” mobile machines, competition vehicles, railway vehicles, or even marine vehicles.

A mobile motorization system can thus be a propulsion system for a vehicle.

For the purposes of the present invention, the term “propulsion system” means a system comprising the mechanical parts necessary for the propulsion of a vehicle. The propulsion system more particularly includes at least one hydrogen and/or ammonia engine.

The implementation of the aqueous lubricating compositions according to the invention proves to be particularly advantageous in several respects.

First of all, hydrogen and/or ammonia engines have the particularity of emitting significant quantities of water vapor during combustion which, when the engine contains a hydrocarbon-based lubricating composition, can lead to problems of emulsification of the lubricating composition, leading to a degradation of its properties and in particular its lubricating power. The use of a composition as defined above, with an aqueous base, makes it possible to avoid this phenomenon of emulsification of the lubricant.

In addition, in hydrogen and/or ammonia engines lubricated by a traditional hydrocarbon-based lubricating composition, the lubricant droplets in the lubricant chamber can locally create hot spots, which can lead to premature ignition of the air/fuel mixture, and therefore to an abnormal combustion phenomenon known as pre-ignition. However, it is preferable to reduce or even eliminate this abnormal combustion phenomenon, in particular pre-ignition, because it generally results in the presence of a sharp increase in temperatures and pressures in the combustion chamber, and thus have a significant negative impact on the overall efficiency and performance of the engine, or even damage it.

Advantageously, these abnormal combustion phenomena do not occur with the use of the lubricating composition according to the invention, with an aqueous base.

Furthermore, the composition as defined above has unexpectedly proven to have excellent lubricating power under the operating conditions of combustion engines fueled by hydrogen and/or ammonia, superior to their lubricating power in combustion engines fueled by hydrocarbon fuels.

Finally, compared to the use of a traditional hydrocarbon-based lubricating composition, the lubrication of hydrogen and/or ammonia engine systems with a composition as defined above makes it possible to further reduce emissions of CO2, unburned hydrocarbons and particles, which further improves the environmental impact of these engine systems.

The present invention also relates to a method or process for lubricating moving parts in a powertrain system including an internal combustion engine powered by at least one at least one non-hydrocarbon fuel chosen from hydrogen and/or ammonia, comprising a step of bringing at least one part of said engine system into contact with a composition as defined above.

The invention also relates to a method of operating a mobile or stationary motorization system, including an internal combustion engine, consisting of supplying said engine with at least one non-hydrocarbon fuel chosen from hydrogen and ammonia and lubricating at least one part of said motorization system with an aqueous lubricating composition as defined above.

The present invention also relates to a method of operating a motorization system, mobile or stationary, including an internal combustion engine powered by at least one fuel chosen from hydrogen and/or ammonia, consisting of lubricating at least one part of said motorization system with a composition as defined above.

Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the description which follows.

In what follows, and unless otherwise indicated, the limits of a domain of values are included in this domain, in particular in the expressions “between” and “ranging from ... to . . ”.

Furthermore, the expressions “at least one” and “at least” used in this description are respectively equivalent to the expressions “one or more” and “greater than or equal”.

Finally, in a manner known per se, a compound or group in CN is a compound or group containing N carbon atoms in its chemical structure.

DETAILED DESCRIPTION

The aqueous lubricating composition

The aqueous lubricating composition according to the present invention includes water. In particular, water is present as the major solvent, in other words in greater quantity than any other solvent possibly present in the composition.

The lubricating composition used in the present invention advantageously comprises at least 15% by mass of water, in particular from 15 to 85% by mass of water, relative to the total mass of the composition.

Preferably, the water content ranges from 20 to 80% by mass, more preferably from 30 to 70% by mass, and better still from 40 to 60% by mass, relative to the total mass of the composition.

According to a particular embodiment, the water used in said composition is osmosis or demineralized water, more preferably deionized water.

The term "osmosed water" denotes water that has undergone purification, in particular by a reverse osmosis process, which makes it possible to reduce the content of organic and/or mineral compounds, for example to a content of less than 5.0% by weight, preferably less than 1.0% by weight. In the present description, the expressions "demineralized water" or "ultrapure water" are considered equivalent or synonymous with the expression "osmosed water". In particular, the osmosed water may be "deionized water", in other words water that has undergone purification in order to reduce the content of ions, such as the Ca ²⁺ and HCOs' ions generally present in water. Preferably, deionized water does not comprise ions.

According to a preferred embodiment, the composition used in the invention is single-phase, that is to say it consists of a single aqueous phase. In particular in this embodiment, the composition is not an emulsion such as an oil-in-water emulsion or a water-in-oil emulsion.

In this embodiment, the composition does not comprise any water-insoluble compounds, and in particular no water-insoluble hydrocarbons including non-water-soluble base oils.

"Water-insoluble oil" means, in particular, an oil which does not dissolve substantially in water at room temperature. ambient (25°C). In particular, an oil that is not soluble in water has a solubility in water of less than 0.2 g/L at 25°C.

Advantageously, in this embodiment the composition does not comprise a lubricating base oil belonging to groups I to IV according to the classes defined in the API classification (or their equivalents according to the ATIEL classification).

The presence of water-insoluble hydrocarbons, even if not desired, is nevertheless tolerated within the framework of the invention because it can come from a migration of residual compounds onto the engine parts coming for example from a previous hydrocarbon lubricant used in the engine.

Preferably, the composition used in the present invention comprises less than 2% by mass of water-insoluble hydrocarbons, more preferably less than 1% by mass, relative to the total mass of the composition.

More preferably, the composition comprises less than 2% by mass of water-insoluble lubricating base oil and better still less than 1% by mass, relative to the total mass of the composition.

Advantageously, said composition is completely free of oil not soluble in water.

The composition used in the present invention advantageously has a kinematic viscosity, measured at 40°C according to standard ASTM D445, of between 20 mm ² /s and 1000 mm ² /s, preferably between 25 mm ² /s and 100 mm ² /s.

Advantageously, said composition has a viscosity index in the range from 100 to 350, preferably from 150 to 300.

Polyalkylene glycols

The composition used in the present invention contains one or more polyalkylene glycols. Polyalkylene glycols (denoted “PAG”) are more particularly chosen from water-soluble or water-soluble polyalkylene glycols.

By “water soluble” is meant a polyalkylene glycol having a water solubility of at least 10 g/L, preferably at least 500 g/L, in water at room temperature (about 25°C).

Preferably, said polyalkylene glycol(s) used according to the invention are chosen from polyalkylene glycols having a cloud point, in other words having the property of inverse demixing (or “inverse solubility” in English).

The reverse demixing property characterizes the property of certain polyalkylene glycols to be soluble in water up to a temperature beyond which they become insoluble. This turbidity or "cloudiness" indicates a phase separation with water, which results in a deposit of said polyalkylene glycol on the surfaces in contact with the lubricant.

The temperature at which turbidity and insolubility occur is called the cloud point of the polyalkylene glycol. The cloud point can be determined, for example, according to ASTM D 2024 or DIN EN 1890, typically for a mixture of 1% by mass of polyalkylene glycol in water.

Preferably, said polyalkylene glycol(s) used according to the invention have a cloud point greater than or equal to 70°C.

The water solubility and reverse demixing properties of said polyalkylene glycol(s) used according to the invention advantageously make it possible to increase the lubrication properties.

Advantageously, a polyalkylene glycol used according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass, or even at least 95% by mass of propylene oxide and/or ethylene oxide units. In particular, the polyalkylene glycols used according to the invention consist of propylene oxide and/or ethylene oxide units.

Preferably, the polyalkylene glycol used according to the invention may be a copolymer, in particular a statistical copolymer, of oxide ethylene (EO) and propylene oxide (PO). In particular, the ethylene oxide (EO) and propylene oxide (PO) units are present in the copolymer in an EO/PO mass ratio of between 50/50 and 90/10, in particular between 60/40 and 85/15, and more particularly between 70/30 and 80/20.

Preferably, the polyalkylene glycol used according to the invention is obtained by polymerization from one or more alkylene oxide monomers, in particular ethylene oxide and/or propylene oxide, initiated by a compound of alcohol type, in particular of polyol type, preferably by a diol compound.

In particular, the polyalkylene glycol used according to the invention comprises hydroxyl terminal functions. By “terminal functions”, within the meaning of the invention, is meant the functions located at the ends of the polymer chains.

As indicated above, said polyalkylene glycol(s) used according to the invention have a weight-average molar mass (Mw) greater than or equal to 1500 g/mol.

In particular, a polyalkylene glycol is distinguished from alkylene glycol oligomers having a number of monomeric units less than or equal to ten.

Preferably, a polyalkylene glycol used according to the invention has a weight-average molar mass (Mw) of at least 2000 g. mol ¹ , in particular of at least 2500 g. mol ¹ , in particular of at least 3000 g. mol ¹ , and more particularly between 3000 and 50 000 g. mol ¹ , in particular between 5000 and 25 000 g. mol ¹ , preferably between 5 000 and 15 000 g. mol ¹ .

The weight average molar mass can be measured by gel permeation chromatography (GPC).

Preferably, a polyalkylene glycol used according to the invention has a kinematic viscosity measured at 100°C (KV 100), according to standard ASTM D445, of between 100 and 25,000 mm ² /s, in particular between 150 and 15,000 mm ² /s.

Preferably, a polyalkylene glycol used according to the invention has a kinematic viscosity measured at 40°C (KV40), according to ASTM D445, between 500 and 100,000 ^mm2 /s, more particularly between 1,000 and 70,000 ^mm2 /s.

The flash point of a polyalkylene glycol used according to the invention is preferably greater than or equal to 160°C, in particular greater than or equal to 220°C. The flash point can be measured by the ISO 2592 or ASTM D92 standard.

Preferably, a polyalkylene glycol used according to the invention has a viscosity index measured according to standard ASTM D2270, between 100 and 800, preferably between 250 and 550.

It is understood that a single polyalkylene glycol or a mixture of several different polyalkylene glycols, in particular as described above, can be used according to the invention.

In particular, an aqueous lubricating composition according to the invention may comprise a mixture of at least two distinct polyalkylene glycols, more particularly of at least one polyalkylene glycol of low weight average molar mass and of at least one polyalkylene glycol of high weight average molar mass.

It is within the general skills of a person skilled in the art to adjust the nature and content of low and high weight-average molar mass polyalkylene glycols in the polyalkylene glycol mixture, particularly with regard to the viscosity targeted for the final lubricating composition.

According to a particularly advantageous embodiment, said polyalkylene glycol(s) used according to the invention are biosourced.

For the purposes of the invention, a “bio-sourced” compound means a compound derived, partially or totally, from biomass, or obtained from renewable raw materials derived from biomass, in particular from plants.

Advantageously, the implementation according to the invention of one or more bio-sourced PAGs thus makes it possible to further reduce the carbon footprint of the lubricating composition according to the invention. The aqueous lubricating composition contains at least 10% by weight and preferably at least 15% by weight of said polyalkylene glycol(s). Preferably, it contains from 15 to 50% by weight of said polyalkylene glycol(s), more preferably from 15 to 30% by weight and even more preferably from 16 to 20% by weight, relative to the total weight of the composition.

In a particular embodiment, said polyalkylene glycol(s) are present in an aqueous lubricating composition according to the invention in a mass ratio of the total quantity of polyalkylene glycol(s) to the quantity of water less than or equal to 0.30, in particular between 0.10 and 0.30, more particularly between 0.15 and 0.25, and in particular between 0.15 and 0.20.

According to a particular embodiment, the assembly consisting of water and said polyalkylene glycol(s) represents more than 80% of the total mass of said aqueous lubricating composition.

Antifreeze additives

The aqueous lubricating composition used in the present invention advantageously comprises a reduced content of antifreeze additives also called antifreeze compounds, chosen from glycols, in particular alkylene glycols having from 2 to 6 carbon atoms such as monoethylene glycol and/or monopropylene glycol and oxyalkylene glycols having from 4 to 14 carbon atoms such as diethylene glycol; aliphatic monoethers of said glycols and polyhydric aliphatic alcohols such as glycerol. This content is strictly less than 1% by mass, relative to the total mass of said composition.

Glycols are diols in which the two hydroxyl groups are carried by different carbon atoms, preferably by vicinal carbon atoms. Glycol-type antifreeze additives are more particularly alkylene glycols having from 2 to 6, preferably from 2 to 4, carbon atoms, such as monoethylene glycol, monopropylene glycol and monobutylene glycol, and oxyalkylene glycols, preferably oxyethylene and oxypropylene glycols, having from 4 to 14 carbon atoms, preferably from 4 to 10 carbon atoms, such as diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol and tripropylene glycol.

Preferably, the content of glycol-type antifreeze compound(s), for example monoethylene glycol, diethylene glycol, and/or monopropylene glycol, if present in an aqueous lubricating composition according to the invention, is strictly less than 1.0% by mass, preferably less than or equal to 0.5% by mass, in particular less than or equal to 0.1% by mass, relative to the total mass of the composition.

Advantageously, an aqueous lubricating composition according to the invention is completely free of glycol-type antifreeze compounds, and thus makes it possible to avoid the toxicity effects associated with these compounds. An aqueous lubricating composition according to the invention thus advantageously has reduced toxicity.

Advantageously, by comprising a reduced quantity, or even being free of glycol-type antifreeze additives, the aqueous lubricating composition used according to the invention has reduced toxicity and environmental footprint.

The environmental footprint associated with the production of a lubricant can be assessed according to different indicators defined by the European Union, including in particular the “climate change” indicator which is a figure for the global warming potential associated with greenhouse gas emissions, expressed in kilograms of carbon dioxide equivalent (kg CO2 eq).

Known antifreeze additives for aqueous lubricants may still be aliphatic monoethers of glycols as mentioned above, for example monomethyl, monoethyl, monopropyl and monobutyl ethers.

These may also be polyhydric aliphatic alcohols, in particular glycerol, diglycerol, triglycerol, erythritol and pentaerythritol.

In particular, the aqueous lubricating composition according to the invention comprises a content of antifreeze additives chosen from: glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, in particular less than or equal to 0.5% by mass and more particularly less than or equal to 0.1% by mass, relative to the total mass of the composition.

According to one embodiment, an aqueous lubricating composition according to the invention is free of such antifreeze additives.

In a particular embodiment, an aqueous lubricating composition according to the invention comprises:

- at least 15% by mass, in particular at least 30% by mass and more particularly from 30% to 85% by mass, of water, preferably deionized water;

- at least 15% by mass, in particular from 15% to 50% by mass, more particularly from 15% to 30% by mass, of one or more polyalkylene glycol(s) (PAG(s)) with an average molar mass, Mw, of at least 1500 g. mol ¹ ; the mass ratio of the total quantity of polyalkylene glycol(s) to the quantity of water being less than or equal to 0.30, in particular between 0.10 and 0.30, more particularly between 0.15 and 0.25, and in particular between 0.15 and 0.20; said aqueous lubricating composition comprising a content of antifreeze additive(s) chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, preferably less than or equal to 0.5% by mass, or even less than or equal to 0.1% by mass; the contents being indicated relative to the total mass of said lubricating composition.

Additional additives

The composition used in the present invention may further contain one or more additional additives, other than the polyalkylene glycols as described above and the antifreeze additives defined above.

It is understood that the said additional additive(s) are compatible with their implementation in an aqueous environment. Advantageously, the additives are implemented in a form soluble or emulsifiable in water, for example in the form of salts or ionic liquids.

Such additives may be more particularly chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, anti-wear and/or extreme pressure additives, sequestering agents, metal passivating agents, dyes, dispersants, and mixtures thereof.

Advantageously, the composition used in the invention may comprise one or more additives chosen from anti-foaming agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, and mixtures thereof.

The composition may more particularly comprise from 0.1 to 20% by mass of additives, in particular from 2.0 to 15% by mass of additives, in particular from 5.0 to 13% by mass, relative to the total mass of the composition.

pH regulators

The composition used in the present invention may comprise at least one pH regulating additive, in particular an alkaline buffer. The pH regulator advantageously makes it possible to maintain the desired pH of the lubricating composition, in particular in order to preserve an alkaline pH, advantageously between 8 and 15.

The said pH regulator(s), by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, makes it possible in particular to prevent corrosion of metal surfaces, but also to promote the solubilization of the various compounds in the lubricating composition, in particular of the polyalkylene glycol(s).

The pH regulator can be chosen from the amine family, in particular alkanolamines and amino alcohols.

This may include in particular a pH regulating additive chosen from alkanolamines, such as dimethylethanolamine (DMEA), ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), isopropanolamines, such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA), and triisopropanolamine (TIPA); diglycolamine (DGA); ethylene amines, such as ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetramine (TETA), and tetraethylene pentamine (TEPA); cyclamines, such as cyclohexylamine; 2-amino-2-ethyl-1,3-propanediol; 2-amino-2-methyl-1-propanol; and mixtures thereof.

The composition may in particular comprise from 0.1% to 10% by mass of pH regulating additive(s), preferably from 0.5% to 5% by mass, relative to the total mass of the composition.

Advantageously, the composition used in the invention comprises at least one pH regulating additive making it possible to maintain the pH of said lubricating composition between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, said pH regulating additive being chosen in particular from alkanolamines, preferably ethanolamines, and more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA), diglycolamine (DGA) and their mixtures.

Corrosion inhibitors

The composition used in the present invention may comprise at least one corrosion inhibiting agent. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of the corrosion inhibitor(s) may be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass.

Among the inorganic corrosion inhibitors, nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, zinc, magnesium or nickel sulfates may be mentioned.

Among the organic corrosion inhibitors that may be mentioned are alkanolamines, such as triethanolamine, aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized by triethanolamine, such as 1,3,5-triazine-2,4,6-tri-(6-aminocaproic) acid, alkanoyl-carboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borated amides, products of the reaction of amines or amino alcohols with boric acid, may also be used.

Preferably, the corrosion inhibitor(s) are distinct from the pH regulating additive(s), in particular making it possible to maintain the pH of the composition between 8 and 15 defined above.

The composition may in particular comprise from 0.1% to 5% by mass of corrosion inhibitor(s), in particular as defined above, preferably from 0.5% to 4% by mass, more preferably from 1% to 2.5% by mass, relative to the total mass of the composition.

Anti-wear/extreme pressure additive

The composition used in the present invention may comprise at least one anti-wear and/or extreme pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-metal contact by forming a protective film adsorbed on these surfaces.

There are a wide variety of anti-wear additives, among which can be mentioned those chosen from phosphosulfur additives such as metal alkylthiophosphates or their salts.

Additives that do not provide phosphorus may also be suitable, such as, for example, polysulfides, in particular sulfur olefins.

According to a particular embodiment, an aqueous lubricating composition according to the invention may comprise at least one extreme pressure additive chosen from sulfur-containing fatty acids and dimercaptothiadiazoles, preferably implemented in their neutralized form, in particular by inorganic alkalizing agents or alkanolamines, emulsifiable or soluble in water. The composition may comprise less than 0.1% by mass of extreme pressure additive of the sulfur-containing fatty acid type, in particular in a neutralized form, preferably less than 0.01% by mass, more particularly less than 0.001% by mass, relative to the total mass of the composition, or even is completely free of extreme pressure additive of the sulfur-containing fatty acid type.

Sulfur-containing fatty acids can contain from 8 to 22 carbon atoms, particularly from 12 to 18 carbon atoms.

The amount of sulfur according to ASTM D2622 provided by said sulfur-containing fatty acid(s) may be between 5% and 30% by mass, in particular between 10% and 20% by mass, relative to the total mass of the composition.

Preferably, the amount of active sulfur at 150°C according to the ASTM D 1662 standard provided by said sulfur-containing fatty acid(s) in the aqueous lubricating composition according to the invention is less than or equal to 2% by mass, in particular less than or equal to 1% by mass, more particularly less than 0.1% by mass, relative to the total mass of the lubricating composition.

For the purposes of the present invention, the term "active sulfur" means the sulfur that a chemical compound is capable of yielding or releasing when this compound is placed under the conditions of ASTM D 1662. ASTM D-1662 defines an active sulfur level of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reaction of a sample of this sulfur compound with a given quantity of copper for a fixed time.

As indicated above, said sulfur-containing fatty acid(s) are generally implemented in an aqueous lubricating composition in their form neutralized by an alkalizing agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

The composition may in particular comprise between 0.01% and 10% by mass of anti-wear and/or extreme pressure additive(s), preferably between 0.2% and 5% by mass, relative to the total mass of the composition.

Anti-foam

The composition used in the present invention may comprise at least one anti-foam additive. Anti-foams make it possible to prevent foaming of the lubricating fluid.

It may be, for example, an anti-foaming agent based on polysiloxanes or acrylate polymers. Preferably, the anti-foaming agent is chosen from three-dimensional siloxanes.

Antifoaming agents can also be polar polymers such as polymethylsiloxanes or polyacrylates.

The composition may comprise from 0.001% to 3.0% by weight of anti-foam additive(s), preferably from 0.005% to 1.5% by weight, more preferably from 0.01% to 1.0% by weight, relative to the total weight of the lubricating composition.

Metal passivating agents

The composition used in the present invention may comprise at least one metal passivating agent. Metal passivating agents make it possible to protect metal parts by promoting the formation of metal oxide on their surface.

The metal passivating agents may be selected, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted with a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-yl methanamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazol-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazol-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazol-1-methanamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazol-1-methanamine, N,N-bis(undecyl)-ar-methyl- l H-benzotriazole- 1 -methanamine, N,N-bis(dodecyl)-ar-methyl- 1 H-benzotriazole- 1 -methanamine, N, -bis(2-ethylhexyl)-ar-methyl- l H-benzotriazole- 1 -methanamine, 1, !,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, -alkyldithiobenzothiazoles, 2- (N, N-dialkyldithiocarbamoyl)benzothiazoles, 2,5 -bis(alkyldithio)-

1.3.4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2 ,5- bis (tert- decyl dithio) - 1,3,4-thiadiazole, the 2,5-bis(tert-undecyldithio)-

1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole,

2.5 -bis(tert-tridecyldithio) - 1,3,4-thiadiazole, 2,5-bis(tert-tetradecyldithio) - 1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)- 1 ,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole,

2.5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-1 ,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole,

2.5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

Preferably, the metal passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures.

The composition may in particular comprise from 0.01% to 2.0% by mass of metal passivating agent(s), preferably from 0.1% to 1.0% by mass, more preferably from 0.2% to 0.8% by mass, relative to the total mass of the composition.

Dyes

The composition used in the present invention may comprise one or more dyes. The dyes may be natural or synthetic, generally organic.

The dyes that can be used in an aqueous lubricant composition can be more particularly chosen from natural or synthetic water-soluble dyes, for example the dyes FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beetroot), carmine, a chlorophyllin, methylene blue, anthocyanins (enocyanin, black carrot and hibiscus), caramel and riboflavin.

An aqueous lubricating composition used according to the invention may comprise between 0.01% and 2.0% by mass of colorant(s), preferably between 0.01% and 1.5% by mass, more preferably between 0.02% and 1.0% by mass, relative to the total mass of the composition.

Sequestering agents

The composition used in the present invention may comprise at least one sequestering agent. Sequestering agents, also called chelating agents, make it possible to limit the encrustation of metal ions in the composition.

Examples of sequestering agents include those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic acid) (ATMP), hydroxyethanediphosphonic acid (HEDP), 1,1-hydroxyethylidene-1-diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic acid) (HEAMBP), diethylenetriaminopenta(methylenephosphonic acid) (DTMP), multifunctional organic acids and hydroxy acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), polyorganic acids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

The composition may comprise from 0.001% to 2.0% by weight of sequestering agent(s), preferably from 0.01% to 1.0% by weight, relative to the total weight of the composition.

Biocides and fungicides

The composition used in the present invention may comprise at least one biocidal and/or fungicidal agent. The biocides and fungicides may be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

Such biocides may be selected from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and their mixtures.

Preferably, the biocides may be selected from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT/CMIT), orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably from orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chlorocresol, benzisothiazolinones and N,N-methyleneisomorpholine.

The composition may in particular comprise between 0.01% and 10% by mass of biocide(s) and/or fungicide(s), preferably between 0.5% and 5.0% by mass, relative to the total mass of the composition.

The use

According to the present invention, the composition as described above is used to lubricate the various moving parts in a motorization system, mobile or stationary, including an internal combustion engine powered by a fuel based on at least hydrogen and/or ammonia.

Advantageously, said composition is used to reduce friction between moving parts inside a hydrogen and/or ammonia internal combustion engine. It is also used to reduce wear of said parts. The part(s) of the internal combustion engine lubricated by means of the aqueous lubricating composition are advantageously chosen from: pistons, segments, cylinders, connecting rods, piston pins, bearings, crankshafts, oil pumps, turbochargers, camshafts, distribution systems (including in particular cams, tappets, levers, rocker arms, oil pump).

The engine can be any internal combustion engine operating by combustion of hydrogen and/or ammonia. It can be a piston engine or a gas turbine. As is known per se, a gas turbine, also called a combustion turbine, is a thermodynamic rotating machine from the internal combustion engine family and which can be used for propulsion purposes, electricity production, or as a stationary engine (for example to drive pumps, compressors, etc.).

Preferably, the internal combustion engine is a piston engine.

The present invention applies to any known piston engine, including on-board engines and stationary engines. The invention applies in particular to marine engines, heavy goods vehicles, construction machinery or agricultural machinery such as, for example, tractors, public transport vehicles (buses, trains, etc.) as well as to engines of light vehicles such as cars, engines used in air or space propulsion (airplanes, rockets), as well as to engines used in stationary industrial applications.

The piston engine can be chosen in particular from compression ignition engines or diesel engines, spark ignition engines, mixed fuel engines (in English “dual fuel”).

According to a first preferred embodiment, the engine is a spark-ignition engine powered by hydrogen, or hydrogen engine.

According to a second embodiment, the engine is a compression ignition engine or diesel engine fueled by ammonia, or ammonia engine. Use in a marine engine (i.e. a compression ignition engine used for the propulsion of a ship) is particularly preferred.

According to an advantageous variant of this embodiment, the compression ignition engine is a mixed fuel engine (also commonly called a "dual fuel" engine). In this use, ammonia supplies the engine in combination with a second fuel different from ammonia, such as for example hydrogen and/or a hydrocarbon fuel, preferably a hydrocarbon fuel. The hydrocarbon fuel can be chosen among fuels of petroleum origin and in particular diesel and more or less heavy fuel oils, bio-sourced fuels (in particular derived from biomass), and mixtures of these two types of fuels. According to a preferred embodiment, the hydrocarbon fuel is chosen from fuels based on heavy fuel oils (such as marine fuels), bio-sourced fuels and mixtures thereof.

Ammonia and the second fuel are injected in different proportions depending on the power required from the engine. The second fuel is advantageously injected into the engine to initiate combustion, by auto-ignition of a mixture of air and a small quantity of fuel called pilot injection. Ammonia is injected in a mixture with air to fuel the combustion. The pilot injection generally represents less than 10% by mass of the total mass of fuel (ammonia and second fuel) consumed, typically of the order of 5% by mass of the total mass of fuel consumed.

Particularly preferably, the mixed-fuel compression-ignition engine is a marine engine, i.e. a mixed-fuel diesel engine fitted to a ship.

The methods

The present invention also relates to a method for lubricating moving parts in a motorization system including an internal combustion engine powered by at least one non-hydrocarbon fuel chosen from hydrogen and ammonia, comprising a step of bringing at least one of said parts into contact with a composition as defined above.

The invention also relates to a method of operating a mobile or stationary motorization system, including an internal combustion engine, consisting of supplying said engine with at least one non-hydrocarbon fuel chosen from hydrogen and ammonia and lubricating at least one part of said motorization system by means of an aqueous lubricating composition as defined above. The engine part(s) are advantageously chosen from pistons, segments, cylinders, connecting rods, piston pins, bearings, crankshafts, oil pumps, turbochargers, camshafts, distribution systems (including in particular cams, tappets, levers, rocker arms, oil pump).

The engine may be any internal combustion engine, including but not limited to those described above.

Preferably, the internal combustion engine is selected from piston engines and gas turbines (or combustion turbines).

According to a first preferred embodiment, the engine is a spark-ignition engine powered by hydrogen.

According to a second preferred embodiment, the engine is a compression ignition engine fueled by ammonia, preferably a dual fuel compression ignition engine. In this embodiment, the method of operating the engine according to the invention comprises supplying the compression ignition engine with ammonia and with another fuel other than ammonia, preferably a hydrocarbon fuel as described above.

The example presented below is intended only to illustrate in a non-limiting manner the advantages of the present invention.

EXAMPLE

Two lubricating compositions were prepared: a comparative composition C and a composition I in accordance with the invention.

The ingredients of each of the compositions and their contents are detailed in Table 1 below, in which the quantities are indicated as a percentage by mass of active material, relative to the total mass of the composition. Table 1

The lubricity of these two compositions was determined under the conditions of the HFRR (“High Frequency Reciprocating Rig”) test as described in ISO 12156-1 (CEC-F-06-A-96). This test consists of measuring the lubricity by measuring the wear mark produced by the contact of an oscillating ball on a fixed plate immersed in the tested composition under closely controlled conditions. The lubricity is expressed by the average value of the diameter of the wear mark of the ball on the plate. The smaller the wear diameter, the higher the lubricity.

The results obtained are shown in Table 2 below: Table 2

These results show that composition I according to the invention has excellent lubricating properties, at least equivalent to those of comparative composition C.

Claims

1. Use for lubricating a motorization system comprising an internal combustion engine powered by at least one non-hydrocarbon fuel chosen from hydrogen and/or ammonia, of a composition comprising: - water; - at least 10% by mass, relative to the total mass of said composition, of one or more polyalkylene glycol(s) with a weight-average molar mass, Mw, of at least 1500 g. mol ¹ ; said composition having a content of antifreeze additive(s) chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols, strictly less than 1% by mass, relative to the total mass of the composition. 2. Use according to the preceding claim, characterized in that the water content of the composition ranges from 15 to 85% by mass, preferably from 20 to 80% by mass, more preferably from 30 to 70% by mass, and better still from 40 to 60% by mass, relative to the total mass of the composition. 3. Use according to any one of the preceding claims, characterized in that the polyalkylene glycol(s) have a weight-average molar mass of at least 2000 g.mol', in particular of at least 2500 g.mol ¹ , in particular of at least 3000 g.mol ¹ , and more particularly of between 3000 and 50,000 g.mol ¹ , in particular between 5000 and 25,000 g.mol ¹ , preferably between 5,000 and 15,000 g.mol ¹ . 4. Use according to any one of the preceding claims, characterized in that the polyalkylene glycol(s) comprise at least 50% by mass, preferably at least 80% by mass, more preferably at least 90% by mass of propylene oxide and/or ethylene oxide units, and preferably the polyalkylene glycol(s) consist of propylene oxide and/or ethylene oxide units. 5. Use according to any one of the preceding claims, characterized in that the composition contains from 15 to 50% by mass of said polyalkylene glycol(s), preferably from 15 to 30% by mass and more preferably from 16 to 20% by mass, relative to the total mass of the composition. 6. Use according to any one of the preceding claims, characterized in that the assembly consisting of water and said polyalkylene glycol(s) represents more than 80% of the total mass of the composition. 7. Use according to any one of the preceding claims, characterized in that the content of the composition in antifreeze additives chosen from glycols, aliphatic monoethers of said glycols and polyhydric aliphatic alcohols is less than or equal to 0.5% by mass, preferably less than or equal to 0.1% by mass, relative to the total mass of the composition. 8. Use according to any one of the preceding claims, characterized in that the composition contains one or more additional additives, chosen from anti-foam agents, biocides, pH regulators, corrosion inhibitors, anti-wear and/or extreme pressure additives, sequestering agents, metal passivating agents, dyes, dispersants, and mixtures thereof. 9. Use according to any one of the preceding claims, for reducing friction between moving parts inside the internal combustion engine and/or for reducing wear of said parts. 10. Use according to any one of the preceding claims, characterized in that the internal combustion engine is a piston engine or a gas turbine, preferably a piston engine. 1 1. Use according to the preceding claim, characterized in that the engine is a spark-ignition engine powered by hydrogen. 12. Use according to claim 10, characterized in that the engine is a compression ignition engine fueled by ammonia. 13. Use according to the preceding claim, characterized in that the compression ignition engine is a mixed carburetion engine. 14. Method for lubricating moving parts in a powertrain system including an internal combustion engine powered by at least one non-hydrocarbon fuel chosen from hydrogen and ammonia, comprising a step of bringing at least one of said parts into contact with a composition as defined in any one of claims 1 to 8. 15. Method of operating a motorization system, mobile or stationary, including an internal combustion engine, consisting of supplying said engine with at least one non-hydrocarbon fuel chosen from hydrogen and ammonia and lubricating at least one part of said motorization system by means of a composition as defined in any one of claims 1 to 8.