Use of a lubricating composition in an ammonia combustion engine

Abstract

Use of a lubricating composition in an ammonia combustion engine The present invention relates to the use of a lubricating composition comprising at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt, in an ammonia combustion engine. It also relates to the use of said hydroxybenzoate salt as a corrosion retardant in an ammonia combustion engine. It also relates to a method for lubricating an ammonia combustion engine, comprising a step of bringing at least one mechanical part of said engine into contact with a lubricating composition comprising at least said hydroxybenzoate salt. Figure for abstract: None

Description

Title of the invention: Use of a lubricating composition in an ammonia combustion engine Technical field

[0001] The present invention relates to the field of lubricating compositions, and more particularly to lubricating compositions intended for the lubrication of ammonia combustion engines.

[0002] More particularly, the present invention proposes the use of specific detergents making it possible to reduce and / or slow down the corrosion of metal parts, such as parts comprising copper, under engine lubrication conditions in the presence of ammonia. Prior art

[0003] Ammonia is increasingly considered an alternative to conventional fuels because it has an improved environmental impact, including a reduced carbon footprint. For example, ammonia can be produced from hydrogen without requiring fossil resources. In addition, the combustion of ammonia does not emit CO2. Thus, ammonia combustion engines are being developed for various industries, such as maritime transport, mining vehicles, agricultural vehicles and even rail transport.

[0004] In order to lubricate ammonia combustion engines, conventional lubricating compositions such as those used in gasoline or diesel combustion engines have been used until now. These lubricating compositions, more simply called "lubricants", are commonly used in mechanical systems for the main purposes of reducing friction forces between the various moving metal parts and to prevent premature wear or even damage to these parts, in particular their surface. They are conventionally composed of a base oil with which several additives are generally associated, designed to boost the lubricating performance of the base oil, but also to provide additional performance.

[0005] Unfortunately, ammonia has degreasing properties which can lead to the removal of lubricant from mechanical parts, and therefore to premature wear of the engine. In addition, it has been observed that ammonia causes accelerated corrosion of mechanical parts, particularly copper, which can lead to engine reliability problems.

[0006] Consequently, conventional lubricating compositions do not prove to be truly satisfactory with regard to ammonia combustion engines.

[0007] Certainly, more specific lubricating compositions have already been developed for ammonia compressors. However, these mechanical systems implement lubrication conditions distinct from those of an ammonia combustion engine. In addition, they do not usually include copper parts, which are precisely subject to corrosion problems in ammonia combustion engines.

[0008] Thus, the present invention aims to propose a lubricating composition adapted to the conditions of use in an ammonia combustion engine, and in particular making it possible to delay the corrosion of the mechanical parts of an ammonia combustion engine. Statement of the invention

[0009] The present invention relates to the use of a lubricating composition comprising at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt, in an ammonia combustion engine.

[0010] Hereinafter, the term “lubricating composition according to the invention” or “lubricant according to the invention” is more simply understood to mean a lubricating composition as defined above, incorporating at least one hydroxybenzoate salt.

[0011] According to a particular embodiment, the lubricating composition according to the invention comprises, in addition to said hydroxybenzoate salt(s), at least one phosphosulfur additive such as a metal alkyldithiophosphate.

[0012] It is already known to use hydroxybenzoate salts as detergents for the lubrication of conventional engines such as gasoline or diesel engines. However, to the inventors' knowledge, these salts have never been used for ammonia combustion engines.

[0013] The inventors have found, surprisingly, that the presence of hydroxybenzoate salts in a lubricating composition advantageously makes it possible to reduce and / or delay the corrosion of parts containing copper, observed specifically in the case of an ammonia combustion engine.

[0014] Indeed, as is apparent from the examples below, the use of a lubricating composition comprising a hydroxybenzoate salt makes it possible to significantly delay the corrosion of parts containing copper which are subjected to a flow of ammonia. In addition, it makes it possible to slow down the wear of parts, in particular those containing copper, during the operation of an ammonia combustion engine.

[0015] Thus, the hydroxybenzoate salt(s) can be used in the lubricating composition as a corrosion retarding agent, in particular for copper corrosion.

[0016] The present invention also relates to the use of at least one alkali salt or alkaline earth hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt, as a corrosion retardant in an ammonia combustion engine, preferably as a corrosion retardant for existing copper, in particular as such or in the form of a copper alloy, at the engine level.

[0017] Preferably, the hydroxybenzoate salt(s) can be used in association with at least one phosphosulfur additive.

[0018] Thus, according to a preferred embodiment, the present invention relates to the use of at least one hydroxybenzoate salt in association with at least one phosphosulfur additive as a corrosion retardant in an ammonia combustion engine, preferably as a corrosion retardant for the copper existing in said engine.

[0019] According to a particular embodiment, the hydroxybenzoate salt(s) are used in a lubricating composition according to the invention.

[0020] The corrosion retardant properties of the lubricant with respect to ammonia can be assessed by measuring the corrosion initiation time (CIT). The corrosion initiation time can be measured by monitoring, over time, the internal capacitance of a sensor coated with a layer of copper, at a surface in contact with a lubricant in which ammonia is bubbled, as described in the examples. The corrosion initiation time corresponds to the time when a drop of at least 25% of the electrical signal is observed.

[0021] The present invention also relates to a method for lubricating an ammonia combustion engine, comprising a step of bringing at least one mechanical part of said engine into contact with a lubricating composition comprising at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, the lubricating composition being in particular a lubricating composition according to the invention.

[0022] Preferably, in the uses and the method according to the invention, the ammonia combustion engine is an internal combustion engine, preferably a marine engine, in particular a two-stroke or four-stroke marine engine.

[0023] Other characteristics, variants and advantages of the implementation of a hydroxybenzoate salt according to the invention will emerge more clearly on reading the description and examples which follow, given by way of illustration and not limitation of the invention.

[0024] The expressions “between ... and ...”, “ranging from ... to ...”, “formed from ... to ...”, and “varying from ... to ...”, must be understood inclusively, unless otherwise stated.

[0025] In the description and examples, unless otherwise indicated, the percentages are weight percentages.

[0026] In the context of the invention, the following terms are understood to mean: - “hydrocarbon group”, a saturated or unsaturated, linear, branched or cyclic, aromatic or not, radical comprising carbon and hydrogen; - “aliphatic chain” means a hydrocarbon group consisting exclusively of carbon and hydrogen atoms, linear or branched, saturated or unsaturated, non-aromatic. Preferably, an aliphatic chain is an alkyl chain; - “alkyl” means a saturated, linear or branched aliphatic group; for example, a Cx to Cz alkyl represents a saturated carbon chain of x to z carbon atoms, linear or branched; - “alkenyl”, a mono- or polyunsaturated, linear or branched aliphatic group; - “aryl”, a mono- or polycyclic aromatic group, in particular comprising between 6 and 10 carbon atoms. Examples of aryl groups include phenyl or naphthyl groups; - “aralkyl”, an aryl group as defined above, substituted by at least one alkyl group as defined above. Detailed description Hydroxybenzoate salt

[0027] As mentioned previously, the uses and the method according to the invention implement at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt.

[0028] They can use a single hydroxybenzoate salt or a mixture of at least two hydroxybenzoate salts.

[0029] Hereinafter, the term "hydroxybenzoate ion" is intended to denote the hydroxybenzoate ion of said hydroxybenzoate salt. These hydroxybenzoate ions are formed from an aromatic ring carrying, in addition to a carboxylate function, at least one hydroxyl function, and optionally one or more hydrocarbon substituents, in particular alkyl, alkenyl, aryl or aralkyl. The hydrocarbon substituent may comprise from 1 to 50 carbon atoms.

[0030] By way of illustration and without limitation of these hydroxybenzoate ions, mention may in particular be made of mono-substituted alkyl or alkenyl salicylate ions, di-substituted alkyl and / or alkenyl salicylate ions, calixarenes functionalized by one or more carboxylate functions, in particular salicylate calixarenes, and mixtures thereof.

[0031] A calixarene is a macrocycle consisting of several phenolic units which can be substituted in the para position and connected to each other by a methylene bridge. The macrocycle, which can also be called a cyclic oligomer, can comprise a sequence of 4 to 16 phenols forming a ring and connected by methylene bridges -(CH2)- or similar bridges.

[0032] In particular, the hydroxybenzoate ions suitable for the invention are of the following formula (I):

[0033] [Chem 1] OH in which a is an integer equal to 0, 1 or 2; and R represents a hydrocarbon group comprising from 1 to 50 carbon atoms, R possibly comprising one or more heteroatoms.

[0034] According to a particular embodiment, a is equal to 0.

[0035] According to another particular embodiment, a is equal to 1 or 2.

[0036] When a is 2, the R groups may be identical or different. In particular, they are identical.

[0037] Preferably, a is an integer equal to 1.

[0038] In particular, R represents a hydrocarbon group comprising from 12 to 40 carbon atoms, more particularly from 18 to 30 carbon atoms, R possibly comprising one or more heteroatoms.

[0039] The group(s) R may be linear, branched or cyclic.

[0040] The group(s) R may in particular be alkyl, alkenyl, aryls or aralkyls, optionally comprising one or more heteroatoms, preferably alkyl or alkenyl groups, in particular linear or branched.

[0041] The optional heteroatom(s) in R may be chosen from oxygen, nitrogen and sulfur. For example, they may be present in the form of a bridge chosen from -O-, -NH-, -N= and / or -S-, in particular -O- or -NH-; and / or optionally a substituent chosen from the groups -OH, -NH2 and / or -SH, in particular -OH or -NH2.

[0042] Preferably, R does not comprise a heteroatom.

[0043] In particular, the R group(s) represent a linear or branched aliphatic chain comprising from 1 to 50 carbon atoms, in particular from 12 to 40 carbon atoms, more particularly from 18 to 30 carbon atoms.

[0044] Preferably, the group(s) R represent a linear or branched alkyl or alkenyl group, C1 to C50, in particular C12 to C40, more particularly C18 to C30.

[0045] Preferably, the group(s) R represent an alkyl group, in particular linear, in Ci to C50, in particular in Ci2 to C40, more particularly in C[8 to C30.

[0046] When present, the R group and the hydroxyl function may be in the ortho, meta or para position relative to the carboxylic acid function, and relative to each other. In particular, the hydroxyl and carboxylate functions are in the ortho position relative to each other.

[0047] In particular, the optionally substituted hydroxybenzoate ion may be chosen from the salicylate ion (2-hydroxybenzoate), the 3-hydroxybenzoate ion and the 4-hydroxybenzoate ion, preferably is the salicylate ion.

[0048] According to a preferred embodiment, the hydroxybenzoate ion is chosen from the salicylate ion and its derivatives, in particular of the following formula (Ia):

[0049] [Chem 2] OH O in which a and R are as defined previously.

[0050] The hydroxybenzoate ion may also be chosen from 2-hydroxy-5-octadecylbenzoate and its isomers, for example 2-hydroxy-4-(2-methylheptadecyl)benzoate, 2-hydroxy-5-(2-methylheptadecyl)benzoate and 2-hydroxy-6-(2-methylheptadecyl)benzoate, or is a mixture of isomers of 2-hydroxy-5-octadecylbenzoate.

[0051] Thus, in a particular embodiment, the hydroxybenzoate salt used according to the invention is chosen from salicylate salts, for example a calcium salicylate, in particular as described as detergent additives for two-stroke and four-stroke marine engines, for example in documents EP 3 112 447 and EP 2 735 603.

[0052] According to another particular embodiment, the hydroxybenzoate ion can be chosen from calixarene structures.

[0053] The calixarene structures considered in the present invention more particularly designate cyclic structures comprising m units of hydroxybenzoate ion of formula (II) and n units of a phenol of formula (III) which are linked together to form a cycle:

[0054] [Chem.3]

[0055] in which

[0056] Gi represents a linear, branched or cyclic hydrocarbon group, comprising from 1 to 50 carbon atoms, and Gi may optionally comprise one or more heteroatoms,

[0057] b is an integer equal to 0, 1 or 2,

[0058] Q represent independently of each other a bivalent linking group,

[0059] G2, G3, G4 and G5 are chosen, independently of each other, from OH, H or a hydrocarbon group comprising from 1 to 50 carbon atoms and optionally comprising one or more heteroatoms, provided that one or two of G2, G3, G4 and G5 represent OH,

[0060] m and n are integers such that:

[0061] m is between 1 and 8,

[0062] n is at least 3, and

[0063] m+n is between 4 and 20.

[0064] According to a particular embodiment, b is equal to 0.

[0065] According to another particular embodiment, b is equal to 1 or 2.

[0066] Advantageously, m+n can be between 5 and 12.

[0067] When b is 2, the two Gi ​​groups may be identical or different. In particular, they are identical.

[0068] The hydrocarbon group(s) in formulae (II) or (III) may be alkyl, alkenyl, aryl or aralkyl groups, optionally comprising one or more heteroatoms.

[0069] The hydrocarbon group(s) in formulas (II) or (III) may be linear, branched or cyclic.

[0070] The optional heteroatom(s) in Gb G2, G3, G4 and G5 may be chosen from oxygen, nitrogen and sulfur atoms. For example, they may be present in the form of a bridge chosen from -O-, -NH-, -N= and / or -S-, in particular -O- or -NH-; and / or optionally a substituent chosen from the groups -OH, -NH2 and / or -SH, in particular -OH or -NH2.

[0071] In particular, the hydrocarbon group(s) in formulae (II) or (III) may comprise one or more heteroatoms.

[0072] Preferably, Gi is chosen from alkyl and alkenyl groups, preferably alkyl, in particular linear.

[0073] Preferably, Gi represents a hydrocarbon group, in particular a linear alkyl group, comprising from 1 to 50 carbon atoms, in particular from 12 to 40 carbon atoms, more particularly from 18 to 30 carbon atoms.

[0074] Preferably, the units (II) are chosen from those which correspond to the following formula (IIa):

[0075] [Chem.4]

[0076] in which Gi, Q and b are as defined previously.

[0077] Preferably, G5 represents in formula (III) a hydroxyl group.

[0078] Preferably, G2, G3 and G4 represent, independently of each other, H or an alkyl or alkenyl group comprising from 1 to 50 carbon atoms, more preferably H or a linear alkyl group comprising from 1 to 40 carbon atoms.

[0079] Preferably, G2, G3 and G4 are chosen independently of one another from H and linear alkyl groups comprising from 1 to 30 carbon atoms, in particular from 4 to 25 carbon atoms.

[0080] When more than one unit of formula (II) is present, these may be the same or different.

[0081] The units of formula (III) may be the same or different in a calixarene molecule.

[0082] When more than one unit of formula (II) is present in the cycle, i.e. when m>l, the units of formula (II) and (III) are distributed randomly.

[0083] The groups Q may be chosen independently of each other from -S- and the groups of formula -(CHG6)c- in which G6 is chosen from a hydrogen atom and a hydrocarbon group comprising from 1 to 10 carbon atoms and c is an integer between 1 and 4. Preferably G6 is H or a hydrocarbon group comprising from 1 to 6 carbon atoms, more preferably G6 is H.

[0084] Preferably, at least 50% of the linking groups Q are represented independently of each other by the formula -(CHG6)c-, with G6 and c being as defined above. Preferably, c is an integer between 1 and 4, and G6 is H or a hydrocarbon group comprising from 1 to 6 carbon atoms, more preferably G6 is H.

[0085] Advantageously, all the groups Q can be chosen from those of formula -(CHG6)c, with c being 1 and G6 being H or a hydrocarbon group comprising from 1 to 6 carbon atoms, more preferably G6 being H.

[0086] The hydroxybenzoate salt(s) may or may not be overbased. A hydroxybenzoate salt is said to be non-overbased if it contains the alkali or alkaline earth metal in a stoichiometric quantity relative to the number of negative charges provided by the hydroxybenzoate ion. It is said to be overbased if it contains the alkali or alkaline earth metal in excess, i.e. in a quantity greater than the stoichiometric quantity, relative to the number of negative charges provided by the hydroxybenzoate ion.

[0087] In particular, the hydroxybenzoate salt(s) may be chosen from calcium salts, magnesium salts, sodium salts, lithium salts, potassium salts, barium salts and mixtures thereof, in particular from calcium salts, magnesium salts, sodium salts, barium salts and mixtures thereof, preferably from calcium salts.

[0088] According to a particular embodiment, the hydroxybenzoate salt is chosen from the salts of the following formula (IV):

[0089] [Chem.5] OH P (IV)

[0090] in which R and a are as defined previously for formula (I),

[0091] M is chosen from Na, Mg, Ca, Li, K and Ba, preferably represents Ca,

[0092] p, q and r are integers,

[0093] p is 1 or 2,

[0094] r is 1 or 2, and

[0095] p = qr or p < qr

[0096] Preferably, the hydroxybenzoate salt is an alkali or alkaline earth salt of acid salicylic, optionally substituted by at least one hydrocarbon group, in particular of the following formula (IVa):

[0097] [Chem.6] OH O P (IVa)

[0098] in which R, a, M, p, q and r are as defined above.

[0099] Alternatively, the hydroxybenzoate salt may be a sodium, magnesium, barium, lithium, potassium or calcium salt of calixarene functionalized by one or more carboxylate functions, in particular comprising m units of formula (II) and n units of formula (III) as defined above, in particular overbased or not. Preferably, the hydroxybenzoate salt may be a sodium, magnesium, barium, lithium, potassium or calcium salt of calixarene of salicylate, in particular comprising m units of formula (IIa) and n units of formula (III) as defined above, in particular overbased or not.

[0100] In a particular embodiment, the hydroxybenzoate salt is a salicylate salt, in particular a calcium salicylate salt, and in particular an overbased calcium salicylate.

[0101] The optionally substituted hydroxybenzoate salts, in particular the salicylate salts and its derivatives of formula (Ia) above, can be synthesized by methods known to those skilled in the art, or else be commercially available.

[0102] The said hydroxybenzoate salt(s) considered according to the invention, in particular as defined above, may be used in an amount of at least 0.1% by mass, in particular from 1% to 30% by mass, more particularly from 2% to 20% by mass, in particular from 8% to 18% by mass, or even from 9% to 16% by mass, relative to the total mass of the lubricating composition. Phosphosulfur additive

[0103] As mentioned previously, the uses and the method according to the invention can further implement at least one phosphosulfur additive in association with the hydroxybenzoate salt.

[0104] In particular, the phosphosulfur additive may be chosen from dithiophosphates, thiophosphates, and mixtures thereof.

[0105] According to a preferred embodiment, the phosphosulfur additive is chosen from metal alkyldithiophosphates, in particular metal dialkyldithiophosphates, more particularly zinc dialkyldithiophosphates or DTPZn. For example, zinc dialkyldithiophosphates may be of formula Zn((SP(S)(OR1)(OR2))2, in which R1 and R2, identical or different, independently represent an alkyl chain, in particular C1 to C18.

[0106] According to a particular embodiment, the zinc dialkyldithiophosphate of formula Zn((SP(S)(OR')(OR2))2 is obtained from secondary alcohols of formulas R'OH and R20H, in which R1 represents a C4 alkyl group and R2 represents a C6 alkyl group.

[0107] According to another embodiment, the zinc dialkyldithiophosphate of formula Zn((SP(S)(OR')(OR2))2 is obtained from the primary alcohols of the formulas R'OH and R20H, in which R1 represents a C4 alkyl group and Represents a C5 alkyl group.

[0108] According to a particular embodiment, the phosphosulfur additive is chosen from non-metallic dithiophosphates and non-metallic thiophosphates, or mixtures thereof, for example as defined in document US8404624.

[0109] According to a particular embodiment, the non-metallic dithiophosphates are chosen from compounds derived from 3-dithiophosphorylpropionic acid of the following formula (V):

[0110] [Chem.7]

[0111] in which R3 and R4, identical or different, independently represent a C3 to C18 alkyl group, a (C5-C12)cycloalkyl group, in particular a (Cg-C10)cycloalkyl group, a (Cg-C10)bicycloalkylmethyl group, a (Cg-C10Xricycloalkylethyl) group, a phenyl group or a (C7-C24)alkylphenyl group, or

[0112] R3 and R4 together form a group:

[0113] [Chem. 8] H3C^ / CH2 h3c ch2— , And

[0114] R5 represents a hydrogen atom or a methyl group.

[0115] According to a particular embodiment, R3 and R4 independently represent a C3 to C[8] alkyl group, more particularly an isopropyl, isobutyl or 2-ethylhexyl group.R3 and R4 may also represent other groups including an n-propyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, an isoamyl group, a neopentyl group, a 2-ethylbutyl group, an n-hexyl group, a 1-methylpentyl group, a 1,3-dimethylbutyl group, an n-heptyl group, an isoheptyl group, an n-octyl group, a 1,4,4-trimethyl-2-pentyl group, a 3,4-dimethyl-1-hexyl group, a 3,5-dimethyl-1-hexyl group, a 4,5-dimethyl-1-hexyl group, a 3-methyl-heptyl group, a 5-methyl-heptyl group, a 1,1,3,3-tetramethylbutyl group, a branched octyl as obtained from an isobutylene dimer, an n-nonyl group, a 1,1,3-trimethylhexyl group, a branched nonyl group as obtained from a tripropylene trimer.

[0116] More particularly, the non-metallic dithiophosphates correspond to compounds derived from 3-dithiophosphorylpropionic acid of formula (V) as defined above, in which R3 and R4 represent a C 3 to C 8 alkyl group, for example a 2-methylpropyl group, and R5 represents a methyl group.

[0117] For example, a non-metallic dithiophosphate corresponds to a derivative of 3-dithiophosphorylpropionic acid corresponding to 3-bis(2-methylpropoxy)phosphinothioylthio-2-methyl-propanoic acid.

[0118] According to another particular embodiment, the phosphosulfur additive is chosen from non-metallic thiophosphates, in particular thiophosphoric acid esters of the following formula (VI):

[0119] [Chem.9]

[0120] in which R6, R7 and R8, identical or different, represent hydrocarbon groups comprising from 3 to 20 carbon atoms. In particular, R6, R7 and R8 independently represent a C3 to C2o aliphatic or aromatic group, in in particular a phenyl group optionally substituted by a linear or branched C7 to C24 alkyl chain.

[0121] According to a particular embodiment, R6, R7 and R8 independently represent a phenyl group or a (C7-C2o)alkylphenyl group.

[0122] According to a particular embodiment, R6, R7 and R8 independently represent a phenyl group or a (Ci-C9alkyl)i_3phenyl group.

[0123] According to a particular embodiment, R6, R7 and R8 represent a phenyl group; or one of R6, R7 and R8 represents a phenyl group and two of R6, R7 and R8 represent a (Ci-C9alkyl)i_3phenyl group; or two of R6, R7 and R represent a phenyl group and one of R6, R7 and R8 represents a (Ci-C9alkyl)i_3phenyl group; or R6, R7 and R8 represent a (CrC9 alkyl)i_3phenyl group.

[0124] According to a particular embodiment, R6, R7 and R8, identical or different, represent a C3 to C20 alkyl group, a (C5-C12)cycloalkyl group, a phenyl group, a (C7-C20)alkylphenyl group, a (C7-C20)alkoxyphenyl, naphthyl and (C7-C9)phenylalkyl group.

[0125] In particular, a C3 to C20 alkyl group is, for example, an isopropyl group, n-nonyl group, a 1,1,3-trimethylhexyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a 1-methylundecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-neptadecyl group or an n-octadecyl group.

[0126] In particular, a (C5-Ci2)cycloalkyl group is for example a cyclopentyl group or a cyclohexyl group.

[0127] In particular, a (C5-Ci2)cycloalkyl-(Ci-C4)alkyl group is, for example, a cyclopentylmethyl group, a 2-cyclopentylethyl group, a cyclohexylmethyl group or a 2-cyclohexylethyl group.

[0128] In particular, a (C7-C20)alkylphenyl group is a phenyl group which is substituted, for example, by one, two or three C1-C4 alkyl groups, or by one, two or three C1-C6 alkyl groups, or one, two or three C1-C12 alkyl groups.

[0129] In particular, a (C7-C2)alkoxyphenyl group is a phenyl group which is substituted, for example, by one, two or three C1-C4 alkoxy groups, in particular a methoxy or ethoxy group, or by one, two or three C1-C6 alkoxy groups, or by one, two or three C1-C12 alkoxy groups, these groups being analogous to the aforementioned alkyl groups.

[0130] In particular, a (C7-C9)phenylalkyl group is, for example, a benzyl group, a 1-phenyl-1-ethyl group or a 2-phenyl-1-ethyl group.

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] According to a particular embodiment, the phosphosulfur additive is a mixture of thiophosphoric acid esters of the following formula (Via) [Chem. 10] in which x is between 0 and 2.5, y is equal to 3-(x+z), z is between 0 and 3-(x+y), and x+y+z=3, and Ar represents a phenyl group, a (C7-Ci8)alkylphenyl group, a (C7-Ci8)alkoxyphenyl group, a naphthyl group or a (C7-C9)phenylalkyl group mentioned above. The preparation of thiophosphoric acid esters of formula (Via) is for example described in document EP368803. According to one embodiment, the thiophosphoric acid esters of formula (Via) are mixtures of triarylthiophosphate, such as mixtures of n-decylphenyl-n-nonylphenyl-phenylthiophosphate, o-tert-butylphenyl-o-isopropylphenyl-phenylthiophosphate, and / or n-hexylphenyl-phenylthiophosphate. According to another embodiment, the phosphosulfur additive is a thiophosphoric acid ester of the triphenylthiophosphate type such as 0,0,0-tris(2(or4)-C9-10-isoalkylphenyl)phosphorothioate. According to a particular embodiment, the non-metallic dithiophosphates correspond to ammonium salts of dithiophosphoric acid of formula (VII): [Chem. 11] in which R3 and R4 are as defined above, Ra, Rb, Rc and Rd, identical or different, represent a hydrogen atom or a C to C20 hydrocarbon group. According to a particular embodiment, R3 and R4 of formula (VII) independently represent a phenyl group or a (C3-C8)alkyl group, and in particular an isopropyl group. According to a particular embodiment, Ra, Rb, Rc and Rd independently represent a hydrogen atom or a (Ci2-C2o)alkyl group.

[0141] According to another embodiment, the phosphosulfur additive is chosen from compounds derived from 3-dithiophosphorylpropionic acid of formula (V) as described above, thiophosphoric acid esters of formula (VI) as described above, ammonium salts of dithiophosphoric acid of formula (VII) as described above, and mixtures thereof.

[0142] The phosphosulfur additive(s), in particular as defined above, may be used in an amount of at least 0.05% by mass, in particular from 0.1% to 1% by mass, more particularly from 0.2% to 0.6% by mass, relative to the total mass of the lubricating composition.

[0143] In particular, the phosphosulfur additive(s) provide a quantity of phosphorus atoms of between 50 and 1000 ppm by mass, more particularly of between 100 and 800 ppm by mass, in particular between 200 and 600 ppm by mass, relative to the total mass of the lubricating composition.

[0144] Generally speaking, the phosphosulfur additive(s) and the hydroxybenzoate salt(s) may be used according to the invention in a mass ratio of phosphosulfur additive(s) / hydroxybenzoate salt(s) ranging from 0.005 to 0.1, in particular from 0.01 to 0.08, more particularly from 0.02 to 0.05. LUBRICATING COMPOSITION

[0145] A lubricating composition according to the invention may comprise, in addition to the hydroxybenzoate salt, at least one phosphosulfur additive.

[0146] In particular, a lubricating composition according to the invention may comprise, in addition to the hydroxybenzoate salt and optionally a phosphosulfur additive, one or more base oils and, optionally, other additives conventionally considered in lubricating compositions.

[0147] It is understood that the nature and quantity of the other additives are adapted with regard to the intended use of the lubricant, and more particularly with regard to the type of ammonia combustion engine for which it is intended, for example depending on whether it is intended for use in a light vehicle, a heavy goods vehicle, an all-terrain vehicle, a railway vehicle, a marine vehicle, etc. Base oil

[0148] Conventionally, a lubricating composition comprises one or more base oils.

[0149] These base oils can be chosen from base oils conventionally used in the field of lubricating oils for engines, in particular for internal combustion engines, such as mineral, synthetic or natural, animal or vegetable oils or their mixtures.

[0150] It may be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0151] The base oils of the lubricating compositions considered according to the invention may in particular be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in the table below or their mixtures.

[0152] [Tables 1] Saturates content Sulphur content Viscosity index (VI) Group I Mineral oils <90% >0.03% 80 <VI < 120 Groupement II Huiles hydrocraquées >90% <0.03% 80 <Vl < 120 Groupement III Hu il es hydrocraquées ou hydro-isomérisées >90% <0.03% >120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0153] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0154] Synthetic base oils may be esters of carboxylic acids and alcohols, polyalphaolefins or polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms. The polyalphaolefins used as base oils are for example obtained from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and whose viscosity at 100°C is between 1.5 and 15 mm2.s 1 according to the ASTM D445 standard. Their average molecular mass is generally between 250 and 3000 according to the ASTM D5296 standard.

[0155] Mixtures of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0156] There is generally no limitation on the use of different base oils in the lubricating composition, except that they must have properties, in particular viscosity, viscosity index, sulfur content or oxidation resistance, suitable for use in ammonia combustion engines, in particular for vehicle engines, for example light vehicles, heavy goods vehicles, off-road vehicles, engines used in marine, aeronautical or train applications.

[0157] Preferably, a lubricating composition considered according to the invention comprises at least one base oil chosen from oils of group I, II and III of the API classification, and their mixtures.

[0158] In particular, such a lubricating composition may comprise at least one group II base oil, in particular a mixture of at least two group II base oils.

[0159] The base oils suitable for the invention may have a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard ranging from 10 to 550 mm2 / s.

[0160] They can have a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard ranging from 1 to 35 mm2 / s.

[0161] In a particular embodiment, the base oils suitable for the invention may have a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard ranging from 12 to 100 mm2 / s, more particularly from 15 to 40 mm2 / s.

[0162] In a particular embodiment, the base oils suitable for the invention may have a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard ranging from 2 to 10 mm2 / s, in particular from 4 to 8 mm2 / s.

[0163] Other base oils of more viscous grade can be used, in particular in combination with more fluid base oils as described previously, for example group I base oils of BBS type (distillation residue), with a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard of the order of 450 to 550 mm2 / s and / or a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard of the order of 30 to 35 mm2 / s. These base oils are conventionally used for cylinder lubricants for marine engines.

[0164] The base oil(s) may be present in a lubricating composition according to the invention in a content of at least 50% by mass, relative to its total mass, in particular at least 60% by mass, more particularly ranging from 60 to 99% by mass and preferably from 70 to 90% by mass.

[0165] Preferably, the group II oil or oils represent(s) at least 50% by mass, in particular at least 60% by mass, more particularly between 60 and 99 % by mass, for example between 70 and 90% by mass, of the total mass of the base oils in the composition.

[0166] In particular, the group II oil or oils may represent at least 50% by mass, in particular at least 60% by mass, more particularly between 60 and 99% by mass, for example between 70 and 90% by mass, of the total mass of the composition.

[0167] According to a particular embodiment, a lubricating composition according to the invention may comprise: - at least 50% by mass, in particular 60 to 99% by mass, in particular 70 to 90% by mass, of one or more base oils; and - at least 0.1% by mass, in particular from 1 to 30% by mass, in particular from 8 to 18% by mass, of one or more hydroxybenzoate salts, in particular as defined above; the contents being expressed relative to the total mass of said lubricating composition.

[0168] More particularly, a lubricating composition according to the invention may comprise: - at least 50% by mass, in particular 60 to 99% by mass, in particular 70 to 90% by mass, of one or more base oils; - at least 0.1% by mass, in particular from 1 to 30% by mass, in particular from 8 to 18% by mass, of one or more hydroxybenzoate salts, in particular as defined above; and - at least 0.05% by mass, in particular from 0.1 to 1% by mass, in particular from 0.2 to 0.6% by mass, of one or more phosphosulfur additives, in particular one or more metal alkyldithiophosphates; the contents being expressed relative to the total mass of said lubricating composition. Additives

[0169] A lubricating composition according to the invention may further comprise one or more additives, distinct from said hydroxybenzoate salt(s) and said phosphosulfur additive(s), called additional additives. These additional additives may in particular be chosen from detergent additives, in particular metallic detergent additives, friction modifying additives, anti-wear additives, extreme pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, seal swelling agents, and mixtures thereof.

[0170] Advantageously, a lubricating composition according to the invention comprises one or several additional additives chosen from detergent additives, in particular chosen from metallic detergent additives, viscosity index improvers, pour point lowering additives, anti-wear additives, antioxidants, dispersants, and mixtures thereof.

[0171] The lubricating composition considered according to the invention, optionally containing one or more phosphosulfur additives, in particular as defined above, may further comprise one or more detergent additives, in particular one or more metallic detergent additives.

[0172] They are generally chosen from alkali or alkaline-earth salts of carboxylic acid distinct from the hydroxybenzoate salt(s), also called alkali or alkaline-earth metal carboxylates, alkali or alkaline-earth metal naphthenates, alkali or alkaline-earth metal phenates, alkali or alkaline-earth metal sulfonates and mixtures thereof. The alkali and alkaline-earth metals are preferably calcium, magnesium, sodium or barium, more preferably calcium.

[0173] These metal salts may or may not be overbased. When the detergent additive is overbased, it is then generally in the form of a metal salt insoluble in the base oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0174] In a particular embodiment, the lubricating composition according to the invention may comprise less than 5% by mass, in particular less than 1% by mass, more particularly less than 0.5% by mass, in particular less than 0.1% by mass, of metallic detergent additive(s) distinct from the hydroxybenzoate salts according to the invention, in particular chosen from alkali or alkaline-earth metal phenates, alkali or alkaline-earth metal sulfonates and mixtures thereof, relative to the total mass of said composition. For example, the lubricating composition may be devoid of metallic detergent additive(s) distinct from the hydroxybenzoate salts according to the invention, in particular alkali or alkaline-earth metal phenates and / or alkali or alkaline-earth metal sulfonates.

[0175] According to a particular embodiment, a lubricating composition according to the invention may comprise: - at least 50% by mass, in particular 60 to 99% by mass, in particular 70 to 90% by mass, of one or more base oils; and - at least 0.1% by mass, in particular from 1 to 30% by mass, in particular from 8 to 18% by mass, of one or more hydroxybenzoate salts, in particular as defined above; - optionally at least 0.05% by mass, in particular 0.1 to 1% by mass, in particular 0.2 to 0.6% by mass, of one or more phosphosulfur additives, in particular one or more metal alkyldithiophosphates; and - less than 5% by mass, in particular less than 1% by mass, in particular less than 0.1% by mass, of one or more metallic detergent additives, distinct from the hydroxybenzoate salts according to the invention, in particular as defined above; the contents being expressed relative to the total mass of said lubricating composition.

[0176] In particular, the additional additive(s) may represent from 1% to 30% by mass relative to the total mass of the composition, in particular from 1 to 20% by mass, in particular from 3% to 15% by mass and more particularly from 5 to 15% by mass, relative to the total mass of the lubricating composition.

[0177] According to a particular embodiment, a lubricating composition according to the invention may comprise, or even consist of: - a base oil or a mixture of base oils; - one or more hydroxybenzoate salts, in particular as defined above; - optionally one or more phosphosulfur additives, in particular one or more metal alkyldithiophosphates; and - optionally one or more additional additives, distinct from said hydroxybenzoate salt(s) and said phosphosulfur additive(s), chosen from detergent additives, friction modifiers, anti-wear additives, extreme pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, seal swelling agents, and mixtures thereof.

[0178] Preferably, a lubricating composition formulated according to the invention comprises, or even consists of: - at least 50% by mass, in particular 60 to 99% by mass, in particular 70 to 90% by mass, of one or more base oils; and - at least 0.1% by mass, in particular from 1 to 30% by mass, in particular from 8 to 18% by mass, of one or more hydroxybenzoate salts, in particular as defined above; - optionally at least 0.05% by mass, in particular from 0.1 to 1% by mass, in particular from 0.2 to 0.6% by mass, of one or more phosphosulfur additives, in particular one or more metal alkyldithiophosphates; and - optionally from 1% to 30% by mass, preferably from 3% to 20% by mass, of one or more additional additive(s), distinct from said hydroxybenzoate salt(s) and said phosphosulfur additive(s), in particular chosen from detergent additives, friction modifiers, anti-wear additives, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, antifoam agents, corrosion inhibitors, and mixtures thereof; the contents being expressed relative to the total mass of said lubricating composition.

[0179] In particular, a lubricating composition formulated according to the invention may comprise, or even consist of: - at least 50% by mass, in particular 60 to 99% by mass, in particular 70 to 90% by mass, of one or more base oils; - at least 0.1% by mass, in particular from 1 to 30% by mass, in particular from 8 to 18% by mass, of one or more hydroxybenzoate salts, in particular as defined above; - optionally at least 0.05% by mass, in particular from 0.1 to 1% by mass, in particular from 0.2 to 0.6% by mass, of one or more phosphosulfur additives, in particular one or more metal alkyldithiophosphates; - less than 5% by mass, in particular less than 1% by mass, in particular less than 0.1% by mass, of one or more metallic detergent additives, distinct from the hydroxybenzoate salts according to the invention, in particular as defined above; and - optionally from 1% to 30% by mass, preferably from 3% to 20% by mass, of one or more additional additive(s), distinct from said hydroxybenzoate salt(s) and said phosphosulfur additive(s), in particular chosen from friction modifiers, anti-wear additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, corrosion inhibitors, and mixtures thereof; the contents being expressed relative to the total mass of said lubricating composition.

[0180] According to a particular embodiment, a lubricating composition according to the invention may have a kinematic viscosity, measured at 40°C according to the ASTM D445 standard, of between 20 mm2 / s and 300 mm2 / s, preferably between 60 mm2 / s and 250 mm2 / s.

[0181] In particular, a lubricating composition according to the invention may have a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, of between 6.9 mm2 / s and 26.1 mm2 / s, preferably between 9.3 mm2 / s and 21.9 mm2 / s. APPLICATIONS

[0182] As mentioned previously, the alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, considered according to the invention is advantageously used in an ammonia combustion engine, in particular to delay corrosion and / or wear.

[0183] For example, the hydroxybenzoate salt may be used in an ammonia combustion engine to retard corrosion of copper, iron or nickel. Preferably, the hydroxybenzoate salt may be used in an ammonia combustion engine to retard corrosion of copper, especially present as such or in the form of a copper alloy such as bronze or brass, for example present in the form of a copper part.

[0184] In particular, the hydroxybenzoate salt is used in the lubrication of an ammonia combustion engine, preferably in a lubricating composition according to the invention.

[0185] For the purposes of the invention, the term “ammonia combustion engine” is understood to mean an engine using a fuel comprising ammonia, called “ammonia-based fuel”, in particular comprising at least 50% by mass of ammonia, more particularly at least 75% by mass of ammonia, in particular at least 85% by mass of ammonia, or even consisting of ammonia. The ammonia may be introduced in the form of an air / ammonia mixture.

[0186] An ammonia combustion engine may operate solely on ammonia-based fuel, or may be a dual-fuel engine, i.e., one using a mixture of two separate fuels, one of the two fuels being ammonia-based. For example, a dual-fuel engine considered according to the present invention may be an engine operating on an ammonia-based fuel and gasoline (ammonia / gasoline dual-fuel engine), an engine operating on an ammonia-based fuel and diesel (ammonia / diesel dual-fuel engine), an engine operating on an ammonia-based fuel and ethanol (ammonia / ethanol dual-fuel engine), or an engine operating on an ammonia-based fuel and hydrogen (ammonia / hydrogen dual-fuel engine).

[0187] Preferably, ammonia is synthesized from non-fossil resources and / or from renewable resources.

[0188] The ammonia combustion engine may be a mobile or stationary, preferably mobile, ammonia combustion engine.

[0189] A “mobile” engine is more particularly an engine used in vehicles, including light vehicles, heavy goods vehicles, all-terrain vehicles (known as “off road” in English terminology), in particular mining vehicles and agricultural vehicles, railway vehicles, air transport vehicles or even marine vehicles.

[0190] A “stationary” motor can find applications, for example, in electrical energy production devices.

[0191] In particular, the ammonia combustion engine may be a combustion engine internal, such as a piston engine or a combustion turbine. For example, the ammonia combustion engine can be a two-stroke or four-stroke engine.

[0192] Advantageously, the hydroxybenzoate salt can make it possible to delay the corrosion and / or wear of parts comprising copper, in particular copper parts, of an internal combustion engine, for example parts chosen from rotating shaft bearings, bushings or heat exchanger pipes.

[0193] In particular, the ammonia combustion engine may be an off-road vehicle engine, in particular a mining vehicle engine, or a marine vehicle engine.

[0194] More particularly, the ammonia combustion engine may be an off-road vehicle engine, in particular an internal combustion engine, in particular a mining or agricultural vehicle engine, preferably a mining vehicle engine.

[0195] Preferably, the ammonia combustion engine is a marine vehicle engine, called a marine engine, in particular a boat or submarine engine. The marine engines may be slow, semi-fast or fast marine engines. In particular, it may be a two-stroke or four-stroke ammonia marine engine.

[0196] In particular, a lubricating composition according to the invention can be used for the lubrication of moving parts in an ammonia combustion engine, in particular as defined above, in particular in the fields of automobiles, naval, off-road transport, rail transport, aeronautics, or electricity production. Preferably, it is used for the lubrication of moving parts in an ammonia marine or off-road engine, in particular in an ammonia marine engine.

[0197] Advantageously, a lubricating composition according to the invention can make it possible to delay the wear of an ammonia combustion engine.

[0198] In particular, when a lubricating composition according to the invention is used in a piston engine, it can be used as cylinder oil, in other words for the lubrication of at least the piston-cylinder zone or the piston-ring-liner zone of the engine, and / or as system oil, for the lubrication of the moving parts of the engine outside the piston-cylinder assembly or outside the piston-ring-liner assembly.

[0199] The invention will now be described by means of the following examples given of course by way of illustration and not limitation of the invention. Examples Corrosion measurement a) Measurement of corrosion initiation time

[0200] The lubricating composition to be tested is placed in a 2L reactor and maintained at 170°C. A gas of known composition is bubbled into the lubricating composition. at a flow rate of 0.85 L / min and homogenized using a mechanical stirrer placed in the reactor.

[0201] The surface of a capacitive sensor, rectangular in shape and with a surface area of ​​240 mm2, is coated with a thickness of copper of a few hundred nanometers and is then immersed in the composition to be tested where the gas bubbling occurs. During the test, an electrical device measures the capacitance existing between the electrodes of the sensor and the coated copper surface.

[0202] As the copper coating corrosion occurs, its volume decreases and its capacitance decreases. Monitoring the change in capacitance over time therefore makes it possible to determine the state of corrosion of the copper part. A measurement of the capacitance of the copper-coated sensor at the start of the test corresponds to a signal of 100% while the measurement of the capacitance of the sensor in the absence of copper coating corresponds to a signal of 0%. The time required for the signal to decrease from 100% to 75% is called the corrosion induction time (CIT). Comparing the CIT values ​​for different lubricant compositions makes it possible to evaluate the performance of the lubricant compositions in protecting against copper corrosion.

[0203] b) Measurement of corrosion during an engine test

[0204] The engine test uses a Renault K9K 4-cylinder ammonia combustion engine with a displacement of 1.5 L. The ammonia is injected indirectly into the intake manifold and mixed with air in stoichiometric proportions. The air / ammonia mixture thus introduced into the combustion chamber is ignited by a pilot injection of diesel.

[0205] Each tested lubricating composition is implemented in the ammonia combustion engine described above to lubricate the parts in contact during operation of the engine.

[0206] The conditions of the test are as follows:

[0207] Engine rotation speed: 2000 rpm;

[0208] Average Effective Pressure: 21 bar.

[0209] The oil is sampled after 100 hours of operation. The dissolved wear metal contents in the sampled oil are measured by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) according to ASTM D5185 method. Example 1

[0210] Corrosion initiation time for compositions according to the invention and outside the invention

[0211] A CL1 formulation according to the invention was prepared by mixing a calcium salicylate and additives in group II base oils, according to the composition indicated in the following table.

[0212] This formulation was compared to a CCI formulation, not in accordance with the invention, in which the calcium salicylate is replaced by a mixture of calcium sulfonate, calcium phenate and calcium carboxylate (non-benzoate).

[0213] A CC2 formulation, not in accordance with the invention, was also prepared by replacing the calcium salicylate with a mixture of calcium sulfonate and calcium phenate.

[0214] The contents in Table 2 are expressed as a percentage by mass relative to the total mass of the composition.

[0215] [Tables2] CLI CCT CC2 Calcium Salicylate 15 1 " - Calcium Sulfonate 0.49 17.19 Calcium Phenate - | 3.56 1j îo LA Calcium Carboxylate 8.26 - Zinc DiThioPhosphate 0.5 0.49 - Silicone Antifoam 0.02 0.03 0.06 PIB Succinimide - i * 1.4 Group II Base Oils 84.48 87.17 69.1

[0216] The kinematic viscosity of the three compositions is measured at 100°C according to the ASTM D445 standard, and reported in Table 3.

[0217] The basicity of the three compositions, characterized by the Total Base Number (TBN), is measured according to the ASTM D2896 standard, and reported in Table 3.

[0218] The corrosion initiation time is measured as detailed previously by bubbling a mixture of air and ammonia in air / ammonia volume proportions 78.3 / 21.7 and reported in Table 3.

[0219] [Tables3] CL1 CCI CC2 Kinematic viscosity at 100-C (mmvs) 13.7 13.4 19.5 TBN (mgKOH / g) 18 30 94 CIT (h) 71 29 25

[0220] As can be seen from Table 3, corrosion is significantly delayed for the composition CL1 according to the invention comprising a calcium salicylate, compared to the compositions CCI and CC2 comprising detergents distinct from hydroxybenzoate salts considered according to the invention. Thus, a composition according to the invention has improved effectiveness in delaying corrosion due to the presence of ammonia. Example 2

[0221] Evaluation of corrosion during an engine test

[0222] The additives of formulation CL1 were blended with Group II base oils to form a formulation CL2 according to the invention

[0223] The additives of the CCI formulation were blended with Group II base oils to form a CC3 formulation.

[0224] A common lubricating oil formulation, named CC4 formulation, was also evaluated for comparison.

[0225] The compositions CL2, CC3 and CC4 are detailed in the following table 4, the contents being expressed as a mass percentage relative to the total mass of the composition.

[0226] [Tables4] CT2 CC3 CC4 Calcium Salicylate 15 - - Calcium Sulfonate - 0.49 1.45 Calcium Phenate - 3.56 - Calcium Carboxylate - 8.26 1.6 Zinc DiThioPhosphate 0.5 0.49 1 Silicone Antifoam 0.02 0.03 0.01 PIB Succinimide - - 4 Primary Antioxidant - 1.85 Group II Base Oils 84.48 87.17 90.09

[0227] These three lubricating compositions are evaluated during an engine test as described previously.

[0228] The kinematic viscosity of the three compositions is measured at 100°C according to the ASTM D445 standard, and reported in Table 5.

[0229] The basicity of the three compositions, characterized by the Total Base Number (TBN), is measured according to the ASTM D2896 standard, and reported in Table 5.

[0230] The copper and nickel contents in the lubricating compositions after 100 hours of engine operation are reported in Table 5.

[0231] [Tables5] CL2 CC3 CC4 Kinematic viscosity at 100°C (inmVs) 11.8 12.1 12.0 TBN (mgKOH / g) 19 30 6.4 Copper content (ppm) 91 137 405 Nickel content (ppm) 1 28

[0232] As can be seen from Table 5, the dissolved copper content and the dissolved nickel content in the CL2 oil according to the invention following 100 hours of operation in an ammonia combustion engine are significantly reduced compared to the CC3 and CC4 oils outside the invention, which shows a reduction in corrosion and engine wear.

Claims

1.

2. Claims Use of a lubricating composition comprising at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt, in an ammonia combustion engine. Use according to the preceding claim, the hydroxybenzoate anion of said hydroxybenzoate salt being of the following formula (I): OH

3. in which a is an integer equal to 0, 1 or 2, in particular equal to 1; and R represents a hydrocarbon group comprising from 1 to 50 carbon atoms, in particular from 12 to 40 carbon atoms, more particularly from 18 to 30 carbon atoms, R possibly possibly comprising one or more heteroatoms, preferably R represents an alkyl group, in particular linear, C1 to C50, in particular C12 to C40, more particularly C18 to C30. Use according to any one of the preceding claims, the hydroxybenzoate anion of said hydroxybenzoate salt being chosen from the salicylate ion and its derivatives, in particular of formula (Ia) below:

4.

5. wherein a and R are as defined in claim 2. Use according to any one of the preceding claims, the hydroxybenzoate salt(s) being overbased or not, in particular chosen from calcium salts, magnesium salts, sodium salts, lithium salts, potassium salts, barium salts and mixtures thereof, preferably from calcium salts. Use according to any one of the preceding claims, said lubricating composition comprising at least 0.1% by mass, in par- in particular from 1% to 30% by mass, more particularly from 2% to 20% by mass, in particular from 8% to 18% by mass, or even from 9% to 16% by mass of hydroxybenzoate salt(s), relative to the total mass of the lubricating composition.

6. Use according to any one of the preceding claims, said lubricating composition further comprising at least one phosphorus-phosphorus additive, in particular chosen from dithiophosphates, thiophosphates, and mixtures thereof.

7. Use according to the preceding claim, the phosphorus-phosphorus additive(s) being chosen from metal alkyldithiophosphates, in particular metal dialkyldithiophosphates, more particularly zinc dialkyldithiophosphates (DTPZn) of formula Zn((SP(S)(OR*)(OR2))2, in which R1 and R2, identical or different, independently represent an alkyl chain, in particular C1 to C18.

8. Use according to claim 6 or 7, said lubricating composition comprising at least 0.05% by mass, in particular from 0.1% to 1% by mass, more particularly from 0.2% to 0.6% by mass of phosphosulfur additive(s), in particular of metallic alkyldithiophosphate(s), relative to the total mass of the lubricating composition.

9. Use according to any one of the preceding claims, said composition further comprising one or more base oils, in particular in a content of at least 50% by mass, more particularly at least 60% by mass, in particular ranging from 60% to 99% by mass, or even from 70% to 90% by mass, relative to the total mass of the lubricating composition.

10. Use according to any one of the preceding claims, said composition further comprising one or more additional additives, distinct from said hydroxybenzoate salt(s) and said phosphosulfur additive(s), chosen from friction modifying additives, anti-wear additives, extreme pressure additives, antioxidants, viscosity index improvers, pour point lowering additives, dispersants, detergent additives, antifoaming agents, thickeners, corrosion inhibitors, seal swelling agents, and mixtures thereof.

11. Use according to any one of the preceding claims, the ammonia combustion engine being an internal combustion engine, preferably a marine engine, in particular a two-stroke or four-stroke marine engine.

12. Use according to any one of the preceding claims, the hydroxybenzoate salt(s) being used as a corrosion retarding agent, in particular the corrosion of copper.

13. Use of at least one alkali or alkaline earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, called hydroxybenzoate salt, as a corrosion retardant in an ammonia combustion engine.

14. Use according to the preceding claim of said hydroxybenzoate salt as a corrosion retardant for the copper existing in said engine.

15. Use according to claim 13 or 14, the hydroxybenzoate salt(s) being as defined in any one of claims 2 to 4.

16. Use according to any one of claims 13 to 15, the hydroxybenzoate salt(s) being used in association with at least one phosphosulfur additive, in particular as defined in claim 6 or 7.

17. uu / . Use according to any one of claims 13 to 16, said hydroxybenzoate salt(s) being used in a lubricating composition according to any one of claims 1 to 10.

18. A method of lubricating an ammonia combustion engine, comprising a step of bringing at least one mechanical part of said engine into contact with a lubricating composition comprising at least one alkali or alkaline-earth salt of hydroxybenzoic acid, optionally substituted by at least one hydrocarbon group, the lubricating composition being in particular according to any one of claims 1 to 10.