FR3053049A1 - REDUCTION OF NITROGEN OXIDES - Google Patents

Abstract

The present application relates to the use of at least one ammonia source compound in a lubricating composition for reducing nitrogen oxides (NOx), with the exception of ammonia source compounds by hydrolysis.

Description

REDUCTION OF NITROGEN OXIDES

The present invention relates to the use of ammonia source compounds in lubricating compositions for reducing NOx, especially in automotive engine lubricating compositions.

Current automotive engines are responsible for particulate emissions and nitrogen oxides (NOx). These pollutants are found especially in the exhaust. The introduction of new European standards will strongly modify exhaust aftertreatment strategies. One of the objectives is in particular to reduce the oxides to the exhaust. This has led to the emergence of various technical devices such as the introduction of selective catalytic reduction systems (SCR) capable of treating NOx. With these new systems, the manufacturers have modified the combustion timing, for example by shifting the NOx emission / particle emission compromise to the increased NOx production that will be processed by the SCR systems. The direct consequence is the significant increase of the NOx concentration in the blow-by gases (corresponding to the gas flows from the combustion chamber to the casing) which will flow through the lubricating composition film and thus solubilize the NOx in the lubricating composition. It is therefore to be feared that the phenomenon of nitroxidation of the lubricant compositions will be increased, which is a much more aggressive phenomenon than the simple oxidation of the lubricating composition. This would be responsible for a decrease in the quality of the lubricating composition and would necessitate a change in the more frequent lubricating composition.

There is therefore an interest in providing a means of reducing NOx especially in lubricating compositions.

An object of the present invention is to provide compounds which, when introduced into a lubricating composition, reduce NOx.

Another object of the present invention is to provide such a compound which is simple to implement and which does not degrade the properties of the lubricant composition.

Another object of the present invention is also to provide a method of reducing NOx in an engine. Still other objects will appear on reading the description of the invention which follows.

The present invention provides the use of at least one ammonia source compound in a lubricating composition for reducing nitrogen oxides (NOx) with the exception of ammonia source compounds by hydrolysis.

In the context of the present invention, the term "ammonia source compound" means any compound capable of generating or releasing ammonia. The term "compound capable of generating ammonia" means any compound capable of generating ammonia by chemical reaction, for example by decomposition at temperature. The term "compound capable of releasing ammonia" means any compound that releases ammonia in response to a stress, for example temperature and / or shear stress. In the context of the present invention, ammonia source compound by hydrolysis means any compound generating ammonia following a hydrolysis reaction.

Preferably, the ammonia source compounds by reaction with water are not included in the present invention.

The ammonia source compounds according to the invention may in particular be any compound capable of generating or releasing ammonia under a certain shear stress and / or at a temperature corresponding to the operating temperature of the engine. For example at a temperature between 20 and 250 ° C, preferably between 40 and 200 ° C, for example between 40 and 150 ° C. In particular, for a release or generation of ammonia in the crankcase, the ammonia source compounds used are the compounds capable of generating or releasing ammonia at a temperature of between 20 and 100 ° C., preferably between 40 and 100 ° C. and 100 ° C. For an ammonia release or generation in the SPC zone (Piston Segment segment), the ammonia source compounds used are the compounds capable of generating or releasing ammonia at a temperature of between 100 and 250 ° C. .

Advantageously, several different ammonia source compounds can be used in the context of the present invention thus allowing, for example, releases or generations of ammonia under different conditions, in particular at different temperatures, different shear stresses, etc. thus possibly allowing a release / generation of ammonia at different locations of the engine, for example in the crankcase and in the SPC zone.

Preferably, in the context of the invention, the ammonia source compounds are chosen in particular from ammonium-based compounds, that is to say compounds comprising an ammonium cation, encapsulated ammonia and the compounds organic compounds comprising at least one NH 2 group, these compounds being especially capable of being encapsulated in an optionally functionalized polymer.

Preferably, the ammonium-based compounds are chosen from: - ammonium salts chosen in particular from: • acetates of formula R1-COO NH4 +, [(R1CO2) 2H] NH4 +, [(R1CO2) 3H2] 'NH4 + with R 1 is a linear, branched or cyclic alkyl group comprising from 10 to 20 carbon atoms, optionally comprising at least one unsaturation and optionally comprising at least one substituent of the alkylaryl or arylalkyl type, the alkyl being linear or branched and comprising 1 to 10 carbon atoms and aryl comprising 6 to 10 carbon atoms; or • ammonium salicylate optionally comprising one or more substituents chosen from an alkyl group comprising from 1 to 20 carbon atoms and / or a saturated, partially or totally unsaturated or aromatic hydrocarbon-based ring comprising from 3 to 10 carbon atoms; or • ammonium sulphonates of formula R1-S03 "NH4 +" or • ammonium phenolates optionally substituted by one or more alkyl group comprising from 1 to 20 carbon atoms, optionally two phenolates can be connected by a sulfur bridge ( a sulfur atom), these ammonium salts also being able to be encapsulated, in particular in an optionally functionalized polymer, or ammonium ions, or - ammonium ions complexed in cyclic or polycyclic ligands, in particular in ether-crown compounds, for example 18-C-6, aza-crowns, cryptands, or a polymer comprising a main hydrocarbon chain, in particular linear or branched, and at least one pendant group comprising an anionic group, for example O ", COO, SO 3", P03 ", and a counterion ammonium (NH4 +) or a pendant group comprising an ammonium group (NH4 +) and anionic counterion for example O", COO ", SO3", PO3 "; said polymer possibly being encapsulated, in particular in an optionally functionalized polymer.

Preferably, the encapsulated ammonia is ammonia encapsulated in an optionally functionalized polymer.

Preferably, the organic compounds comprising at least one NH 2 group are chosen from: ammonium carbamate; or - amino acids, for example phenylalanine, leucine, tyrosine, preferably phenylalanine; or - fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) - R2-NH2, wherein R2 is a linear or branched alkyl group having 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2; or - the compounds of formula R 3 -NH 2 in which R 3 is a saturated, partially or completely unsaturated or aromatic carbocyclic group, comprising from 6 to 10 members, optionally substituted with an alkyl group comprising from 1 to 10 carbon atoms, carbon; or guanidine NH 2 C (NH) NH 2 or its derivatives comprising at least one NH 2 group, the other hydrogen atoms possibly being substituted, for example by an alkyl group; or benzhydrazide, optionally substituted with one or more alkyl groups; or - the compounds of formula (I)

wherein R4 represents a linear or branched alkyl group comprising from 5 to 20 carbon atoms, preferably from 7 to 17 carbon atoms, and optionally at least one unsaturation; or these organic compounds comprising at least one NH 2 group that can also be encapsulated, in particular in an optionally functionalized polymer.

Advantageously, when the source compound of ammonia is encapsulated, the encapsulation is carried out in an optionally functionalized polymer capsule which can in particular break with an external stimulus such as temperature, shear stresses and / or the action of a chemical compound.

Preferably, the ammonium source compounds are chosen from organic compounds comprising at least one NH 2 group and in particular: ammonium carbamate; or - amino acids, for example phenylalanine, leucine, tyrosine, preferably phenylalanine; or - guanidine; or - the compounds of formula (I)

wherein R4 represents a linear or branched alkyl group comprising from 5 to 20 carbon atoms, preferably from 7 to 17 carbon atoms, and optionally at least one unsaturation; or - fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) - R2-NH2, in which R2 is a linear or branched alkyl group comprising from 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2.

In a particularly preferred manner, the ammonium source compounds are chosen from organic compounds comprising at least one NH 2 group and in particular: ammonium carbamate; or - amino acids, for example phenylalanine; or fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) -R2 -NH2, wherein R2 is a linear or branched alkyl group comprising from 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2.

Preferably, the ammonia source compound is used in a proportion of 0.1 to 10% by weight relative to the weight of the lubricant composition.

Particularly advantageously, the use of at least one ammonia source compound according to the invention makes it possible to reduce NOx in the lubricant composition since the ammonia released or generated will reduce NOx. Particularly advantageously, the ammonia released or generated will also be able to circulate especially via the blow-by gases and allow the reduction of NOx in other parts of the engine, for example in the combustion chamber.

The lubricant composition according to the invention may be any lubricating composition, in particular that used in engines, in particular in automobile engines. More particularly, the lubricating composition according to the invention comprises at least one base oil.

In general, the lubricating composition according to the invention may comprise any type of mineral lubricating base oil, synthetic or natural, animal or vegetable, known to those skilled in the art.

The base oils used in the lubricant compositions according to the invention may be oils of mineral or synthetic origins belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) (Table A) or their mixtures.

Table A

The mineral base oils according to the invention include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, desalphating, solvent dewaxing, hydrotreatment, hydrocracking. , hydroisomerization and hydrofinition.

Mixtures of synthetic and mineral oils can also be used.

There is generally no limitation on the use of different lubricating bases to make the lubricating compositions according to the invention, except that they must have properties, in particular viscosity, viscosity index, sulfur content. , oxidation resistance, suitable for use for engines or for vehicle transmissions.

The base oils of the lubricant compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols or certain polyalkylene glycols (PAGs), and from polyalphaolefins. The polyalphaolefins used as base oils are, for example, obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene, and whose viscosity at 100 ° C. is between 1.5 and 15 mm 2. .s'1 according to ASTM D445. Their average molecular weight is generally between 250 and 3000 according to ASTM D5296.

Preferably, the base oils of the present invention are chosen from the above base oils whose aromatic content is between 0 and 45%, preferably between 0 and 30%. The aromatic content of the oils is measured according to UV Burdett method. Without wishing to be bound by any theory, the aromaticity of the base oil is a character that makes it possible to optimize the operation of the polymer as a function of temperature. The choice of a low aromatic oil allows an optimum at a higher temperature.

Advantageously, the lubricant composition according to the invention comprises at least 50% by weight of base oils relative to the total mass of the composition.

More advantageously, the lubricating composition according to the invention comprises at least 60% by weight, or even at least 70% by weight, of base oils relative to the total mass of the composition.

More particularly advantageously, the lubricant composition according to the invention comprises from 60 to 99.5% by weight of base oils, preferably from 70 to 99.5% by weight of base oils, relative to the total weight of the composition.

Advantageously, the lubricating composition may comprise a main base oil, especially chosen from Group I to IV base oils, and a proportion of base oil V (co-base), preferably ester and PAG, allowing to improve the solubility of the ammonia source compound in the lubricating composition.

Many additives can be used for this lubricant composition according to the invention.

The additives for the lubricating composition according to the invention are in particular chosen from detergent additives, anti-wear additives, friction modifying additives, extreme pressure additives, dispersants, pour point improvers, anti-wear agents and anti-wear agents. foam, thickeners, viscosity index improvers and mixtures thereof.

Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces.

There is a wide variety of anti-wear additives. In a preferred manner for the lubricating composition according to the invention, the anti-wear additives are chosen from phosphosulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTPs. The preferred compounds have the formula Zn ((SP (S) (OR 5) (OR 6)) 2, in which R 5 and R 6, which may be identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms. .

Phosphorus-based compounds are also anti-wear additives that can be used in the lubricating composition according to the invention. However, the phosphorus provided by these additives can act as a poison of the catalytic systems of automobiles because these additives are ash generators. These effects can be minimized by substituting phosphorus-based compounds with non-phosphorus additives, such as, for example, polysulfides, especially sulfur-containing olefins.

Advantageously, the lubricant composition according to the invention may comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% by weight relative to the mass. total lubricating composition, anti-wear additives and extreme pressure additives.

Advantageously, the lubricant composition according to the invention may comprise at least one friction-modifying additive. The friction modifying additive may be chosen from a compound providing metal elements and an ash-free compound. Among the compounds providing metal elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu and Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus. The ashless friction modifier additives are generally of organic origin and may be selected from monoesters of fatty acids and polyols, fatty epoxides, borate fatty epoxides; or glycerol esters of fatty acid. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

Advantageously, the lubricating composition according to the invention may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or 0.1 at 2% by weight relative to the total mass of the lubricant composition, friction modifier additive.

Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive. The antioxidant additive generally serves to retard the degradation of the lubricating composition in service. This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the lubricant composition.

Antioxidant additives act in particular as radical inhibitors or destroyers of hydroperoxides. Among the antioxidant additives commonly used, mention may be made of antioxidant additives of phenolic type and phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can be ash generators. Phenolic antioxidant additives may be ash-free or may be in the form of neutral or basic metal salts. The antioxidant additives may especially be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge.

Preferably, according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon carrying the alcohol function is substituted with at least one C 1 -C alkyl group, preferably an alkyl group. Ci-C6, preferably a C4 alkyl group, preferably by the ter-butyl group.

Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

Another class of antioxidant additives is copper compounds, for example copper thio- or dithio-phosphates, copper and carboxylic acid salts, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper salts I and II, succinic acid or anhydride salts can also be used.

The lubricant composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

Advantageously, the lubricating composition comprises at least one ash-free antioxidant additive.

Also advantageously, the lubricating composition according to the invention comprises from 0.5 to 2% by weight relative to the total weight of the composition, of at least one antioxidant additive.

The lubricant composition according to the invention may also comprise at least one detergent additive.

The detergent additives generally make it possible to reduce the formation of deposits on the surface of the metal parts by dissolving the secondary oxidation and combustion products.

The detergent additives that can be used in the lubricant composition according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali metal or alkaline earth metal.

The detergent additives are preferably chosen from the alkali metal or alkaline earth metal salts of carboxylic acids, the sulphonates, the salicylates, the naphthenates and the phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally comprise the metal in stoichiometric quantity or in excess, therefore in an amount greater than the stoichiometric amount. It is then overbased detergent additives; the excess metal bringing the overbased character to the detergent additive is then generally in the form of an oil insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate .

Advantageously, the lubricant composition according to the invention may comprise from 2 to 4% by weight of detergent additive relative to the total mass of the lubricating composition.

Also advantageously, the lubricant composition according to the invention may also comprise at least one pour point depressant additive.

By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the lubricant composition according to the invention.

As examples of pour point depressant additives, mention may be made of alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

Advantageously, the lubricant composition according to the invention may also comprise at least one dispersing agent. The dispersing agent may be chosen from Mannich bases, succinimides and their derivatives.

Also advantageously, the lubricating composition according to the invention may comprise from 0.2 to 10% by weight of dispersing agent relative to the total mass of the lubricating composition.

The lubricating composition of the present invention may also comprise at least one viscosity index improver. Examples of viscosity index improvers include polymeric esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene, butadiene and isoprene, polymethacrylates (PMA) or alternatively olefin copolymers, such as, for example, ethylene / propylene copolymers.

The lubricating composition according to the invention can be in various forms. The lubricant composition according to the invention may in particular be an anhydrous composition.

Preferably, this lubricating composition is not an emulsion. The subject of the invention is also a process for reducing NOx in an engine, in particular a vehicle engine, comprising the use of a lubricating composition comprising at least one source compound of ammonia, with the exception of the source compounds. ammonia by hydrolysis. The set of characteristics and preferences for the ammonia source compound described above also apply to the above process.

The term "vehicle engine" according to the invention is more particularly intended to mean vehicle engines such as: motor vehicle engines, and more specifically engines operating on diesel and gasoline; - the engines of heavy goods vehicles, and more specifically the engines of heavy goods vehicles running on diesel fuel; - gas engines.

Example

The thermal degradation of the following compounds, under an air flow at 100 ml / min, was monitored and the amount of NH3 generated / released was measured. The compounds are placed in a furnace for heating up to 1000 ° C. This is set to have a temperature ramp of 5 ° C / min. The furnace is also equipped with a system for recovering the gases emitted by the thermal degradation and sent to a Fourier transform ion cyclotron resonance mass spectrophotometer (FTICR) coupled to chemical ionization methods (IMR). This makes it possible to detect and measure the amount of NH3 produced during the thermal degradation.

Phenylalanine: For an 18 mg sample, a release of 1205 ppm NH3 / mg was measured over a temperature range of 180 to 350 ° C, with a peak of release at about 210 ° C.

Armeen T®: For a 17.6 mg sample, a release of 457.2 ppm NHs / mg was measured over a temperature range of 180 to 350 ° C, with a peak of release at about 210 ° C .

Triameen YT®: For a 20.5 mg sample, a release of 1169.9 ppm NH3 / mg was measured over a temperature range of 180 to 350 ° C, with a peak of release at approximately 220 ° C and about 260 ° C.

Duomeen T®: For a 24 mg sample, a release of 1096.6 ppm NHs / mg was measured over a temperature range of 180 to 350 ° C, with a peak of release at about 280 ° C.

Ammonium carbamate: For a 0.8 mg sample, a release of 9676.8 ppm NHa / mg was measured over a temperature range of 20 to 150 ° C, with a peak of release at about 75 ° vs.

Claims (10)

1. - Use of at least one source compound of ammonia in a lubricating composition for reducing nitrogen oxides (NOx), with the exception of ammonia source compounds by hydrolysis. 2. - Use according to claim 1 wherein the ammonia source compounds are any compound capable of generating or releasing ammonia at a temperature between 20 and 250 ° C, preferably between 40 and 200 ° C, by example between 40 and 150 ° C. 3. - Use according to any one of claims 1 or 2, wherein the ammonia source compounds are chosen in particular from ammonium-based compounds, that is to say compounds comprising an ammonium cation, encapsulated ammonia and organic compounds comprising at least one NH 2 group. 4. - Use according to claim 3, wherein the ammonium salts are chosen from: • acetates of formula R1-COONH4 +, [(R1CO2) 2H] NH4 +, [(R1CO2) 3H2] NH4 + with R1 is an alkyl group , linear, branched or cyclic, comprising from 10 to 20 carbon atoms, optionally comprising at least one unsaturation and optionally comprising at least one substituent of the alkylaryl or arylalkyl type, the alkyl being linear or branched and comprising from 1 to 10 carbon atoms, carbon and aryl comprising from 6 to 10 carbon atoms; or • ammonium salicylate optionally comprising one or more substituents chosen from an alkyl group comprising from 1 to 20 carbon atoms and / or a saturated, partially or totally unsaturated or aromatic hydrocarbon-based ring comprising from 3 to 10 carbon atoms; or • ammonium sulphonates of formula R1-SO3 'NH4 +; or • ammonium phenolates optionally substituted by one or more alkyl group comprising from 1 to 20 carbon atoms, optionally two phenolates may be connected by a sulfur bridge (a sulfur atom); these ammonium salts may also be encapsulated, especially in an optionally functionalized polymer; or - ammonium ions; or - ammonium ions complexed in cyclic or polycyclic ligands, especially in ether-crown compounds, for example 18-C-6; aza-crowns; cryptands; or a polymer comprising a hydrocarbon-based main chain, in particular a linear or branched chain, and at least one pendant group comprising an anionic group, for example O, COO, SO 3, PO 3, and an ammonium counterion (NH 4 +) or a pendant group comprising a ammonium group (NH4 +) and anionic counterion for example O, COO, SO3, PO3 '; said polymer possibly being encapsulated, in particular in an optionally functionalized polymer. 5. Use according to claim 3, in which the organic compounds comprising at least one NH 2 group are chosen from: ammonium carbamate; or - amino acids, for example phenylalanine, leucine, tyrosine, preferably phenylalanine; or - fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) - R2-NH2, wherein R2 is a linear or branched alkyl group having 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2; or - the compounds of formula R 3 -NH 2 in which R 3 is a saturated, partially or completely unsaturated or aromatic carbocyclic group, comprising from 6 to 10 members, optionally substituted with an alkyl group comprising from 1 to 10 carbon atoms, carbon; or guanidine NH 2 C (NH) NH 2 or its derivatives comprising at least one NH 2 group, the other hydrogen atoms possibly being substituted, for example by an alkyl group; or benzhydrazide, optionally substituted with one or more alkyl groups; or - the compounds of formula (I) in which R4 represents a linear or branched alkyl group comprising from 5 to 20 carbon atoms, preferably from 7 to 17 carbon atoms, and optionally at least one unsaturation; these organic compounds comprising at least one NH 2 group which may also be encapsulated, in particular in an optionally functionalized polymer. 6. The use according to claim 3, wherein the organic compounds comprising at least one NH 2 group are chosen from: ammonium carbamate; or - amino acids, for example phenylalanine, leucine, tyrosine, preferably phenylalanine; or - guanidine; or - the compounds of formula (I) wherein R4 represents a linear or branched alkyl group comprising from 5 to 20 carbon atoms, preferably from 7 to 17 carbon atoms, and optionally at least one unsaturation; or - fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) - R2-NH2, wherein R2 is a linear or branched alkyl group having 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2; these organic compounds comprising at least one NH 2 group which may also be encapsulated, in particular in an optionally functionalized polymer. 7. - Use according to claim 3, wherein the organic compounds comprising at least one NH 2 group, are chosen from: - ammonium carbamate; or - amino acids, for example phenylalanine; or - fatty amines, for example compounds of formula RNH2 in which R is a linear or branched alkyl group comprising from 10 to 20 carbon atoms and optionally comprising at least one unsaturation or compounds of formula R- (NH) - R2-NH2, wherein R2 is a linear or branched alkyl group having 1 to 10 carbon atoms, the compounds of formula NH2-R2-N (R) -R2-NH2; these organic compounds comprising at least one NH 2 group which may also be encapsulated, in particular in an optionally functionalized polymer. 8. - Use according to any one of claims 3 to 7, wherein when the ammonia source compound is encapsulated, the encapsulation is carried out in an optionally functionalized polymer capsule which breaks by an external stimulus such as temperature, shear stresses and / or the action of a chemical compound. 9. - Use according to any one of claims 1 to 8, wherein the ammonia source compound is used in a proportion of 0.1 to 10% by weight relative to the weight of the lubricant composition. 10. A method for reducing NOx in an engine, especially a vehicle engine, comprising the use of a lubricating composition comprising at least one ammonia source compound as described in any one of claims 1 to 9, with the exception of ammonia source compounds by hydrolysis.