USE OF A COMPOSITION OF ADDITIVES FOR REDUCING DIESEL VEHICLE EMISSIONS

Abstract

The present invention relates to the use of a composition of additives for reducing emissions of nitrogen oxides and of at least one type of pollutant selected from carbon monoxide and hydrocarbons which are unburnt during the combustion of a liquid fuel in a compression-ignition internal combustion engine, said composition comprising: (i) one or more additive(s) selected from compounds having at least one alkylphenol group in their structure; and (ii) one or more additives which improve the cetane number, selected from alkyl nitrates, aryl peroxides and alkyl peroxides; wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is within the range from 1:3 to 3:1. The present invention also relates to a method for reducing emissions of nitrogen oxides and of at least one type of pollutant selected from carbon monoxide and hydrocarbons which are unburnt during the combustion of a liquid fuel in a compression-ignition internal combustion engine which employs this composition of additives.

Claims

1. A method for reducing emissions of nitrogen oxides and at least one type of pollutant selected from carbon monoxide and unburnt hydrocarbons during combustion of a liquid fuel in a compression-ignition internal combustion engine, the method comprising adding a composition of additives to the liquid fuel, wherein the composition comprises: (i) one or more additives selected from compounds having at least one alkyl phenol group in their structure; and (ii) one or more cetane number improving additives selected from alkyl nitrates, aryl peroxides and alkyl peroxides; wherein the ratio by weight of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:3 to 3:1, and; subjecting the liquid fuel to combustion in the compression-ignition internal combustion engine; whereby emissions of nitrogen oxides and at least one type of pollutant selected from carbon monoxide and unburnt hydrocarbons are reduced compared to emissions from a combustion of the liquid fuel without the composition of additives in the compression-ignition internal combustion engine.

2. The method according to claim 1, wherein the additive(s) (i) are selected from compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl groups, and preferably from methyl-t-butyl phenols, dimethyl-t-butyl phenols, ethyl-t-butyl phenols, t-butyl phenols, di-t-butyl phenols, tri-t-butyl phenols, di-t-butyl-di-methyl phenols, and mixtures thereof.

3. The method according to claim 2, wherein the compound(s) (i)a) are selected from (di)tert-butylphenols, methyl-tert-butylphenols and di-methyl-tert-butylphenols, mixtures thereof, and two-by-two condensation products thereof, such as in particular 2,6-di-t-butyl-4-methyl phenol (BHT), 2,4-dimethyl-6-t-butyl phenol, 2,5-dimethyl-4-t-butyl phenol, 2,6 and 2,4 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, mixtures thereof, and two-by-two condensation products thereof.

4. The method according to claim 1, wherein the additive or additives (i) are selected from modified alkylphenol-aldehyde resins (i)b) obtainable by Mannich reaction of an alkylphenol-aldehyde condensation resin: with at least one aldehyde, ketone or combination of aldehyde and ketone, having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms; and at least one hydrocarbon compound having at least one alkyl polyamine group, having between 1 and 30 carbon atoms, preferably between 4 and 30 carbon atoms, said alkylphenol-aldehyde condensation resin itself being obtainable by condensation of: at least one alkylphenol substituted with at least one linear or branched alkyl group having from 1 to 30 carbon atoms, preferably a monoalkylphenol, with at least one aldehyde and/or ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.

5. The method according to claim 4, wherein the modified alkylphenol-aldehyde resins are obtainable from p-nonylphenol, formaldehyde and at least one hydrocarbon compound comprising at least one alkyl polyamine group.

6. The method according to claim 4, wherein the modified alkylphenol-aldehyde resins are obtainable from at least one alkyl polyamine having at least two primary amine groups, and at least one fatty chain having from 12 to 24 carbon atoms, preferably from 12 to 22 carbon atoms.

7. The method according to claim 1, wherein the composition of additives comprises one or more compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl groups, and one or more modified alkylphenol-aldehyde resins (i)b).

8. The method according to claim 1, wherein the additive or additives (ii) are selected from alkyl nitrates of the formula RNO.sub.3 with R an alkyl radical comprising from 2 to 12 carbon atoms, more preferably from 4 to 8 carbon atoms, and still better the additive (ii) is ethyl hexyl nitrate.

9. The method according to claim 1, wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:2.5 to 2.5:1.

10. The method according to claim 1, wherein the composition of additives additionally comprises one or more deposit control additive(s) (iii) selected from the group consisting of amines, succinimides, alkenyl succinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts and triazole derivatives; more preferably from polyisobutylene succinimides functionalised with a quaternary ammonium group, fatty acid amides functionalised with a quaternary ammonium group and dimers thereof such as di-(quaternary alkylamido-propyl-ammonium) compounds, fatty chain alkylamidoalkyl betaines and triazole derivatives; and even more preferably from polyisobutylene succinimides functionalised with a quaternary ammonium group and polyisobutylene succinimides functionalised with a triazole group.

11. The method according to claim 1, wherein the ratio of the total content by weight of compounds (i) having at least one alkyl phenol group in their structure, to the total content by weight of deposit control additive(s) (iii), ranges from 1:60 to 1:2.

12. The method according to claim 1, wherein the liquid fuel is selected from gas oils, biodiesels, B.sub.x-type gas oils containing x % (v/v) of vegetable or animal oil esters with x a number greater than zero and less than or equal to 100, hydrotreated vegetable oils (HVO), and mixtures thereof; and preferably from B.sub.x type gas oils containing x % (v/v) vegetable or animal oil esters with x a number greater than zero and less than or equal to 100, the vegetable oil esters preferably being selected from fatty acid methyl esters and fatty acid ethyl esters.

13. The method according to claim 1, wherein the emissions of nitrogen oxides, carbon monoxide and unburnt hydrocarbons are reduced simultaneously.

14. The method according to claim 1, whereby emissions of solid particles are reduced compared to emissions of solid particles from a combustion of the liquid fuel without the composition of additives in the compression-ignition internal combustion engine.

15. The method according to claim 1, wherein the compression-ignition internal combustion engine is a hybrid diesel engine or a direct-injection diesel engine.

16. The method according to claim 1, wherein the compression-ignition internal combustion engine is a marine engine.

17. (canceled)

18. The method according to claim 9, wherein the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:2 to 2:1 or from 1:1 to 1.5:1.

19. The method according to claim 11, wherein the ratio of the total content by weight of compounds (i) having at least one alkyl phenol group in their structure to the total content by weight of deposit control additive(s) (iii) ranges from 1:20 to 1:3.

20. The method according to claim 15, wherein the direct-injection diesel engine is a diesel engine with a common-rail injection system.

Description

DETAILED DESCRIPTION

Alkyl Phenol Compounds:

[0031] The invention uses as additive (i) one or more compound(s) having at least one alkyl phenol group in their structure.

[0032] This means that this compound or these compounds have in their formula at least one phenolic ring (that is a benzene ring substituted with one or more hydroxy-OH groups) substituted with one or more alkyl groups.

[0033] According to a first embodiment, the additive(s) (i) is/are selected from compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl (or tert-butyl) groups.

[0034] These compounds (i)a) may more particularly be selected from methyl-t-butyl phenols, dimethyl-t-butyl phenols, ethyl-t-butyl phenols, t-butyl phenols, di-t-butyl phenols, tri-t-butyl phenols, di-t-butyl-di-methyl phenols, and mixtures thereof.

[0035] Preferred compounds are selected from 2,6-di-t-butyl-4-methyl phenol (BHT), 4,6-di-tert-butyl-2-methylphenol, t-butyl hydroquinone (TBHQ), 2,6 and 2,4 di-t-butyl phenol, 2,4-dimethyl-6-t-butyl phenol, 2,4,6-tri-t-butyl phenol, 2,3,6-trimethyl phenol, 2,4,6-trimethyl phenol, 4,4-methylene bis (2,6-di-t-butyl phenol) (CAS No. 1 18-82-1), alone or as a mixture.

[0036] Particularly preferred compounds are selected from (di)tert-butyl phenols, methyl-tert-butylphenols and di-methyl-tert-butylphenols, mixtures thereof, and two-by-two condensation products thereof, such as in particular 2, 6-di-t-butyl-4-methyl phenol (BHT), 2,4-dimethyl-6-t-butyl phenol, 2,5-dimethyl-4-t-butyl phenol, 2,6 and 2,4 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, mixtures thereof, and two-by-two condensation products thereof.

[0037] According to a second embodiment, the additive or additives (i) are selected from modified alkylphenol-aldehyde resins (i)b) obtainable by Mannich reaction of an alkylphenol-aldehyde condensation resin: [0038] with at least one aldehyde and/or ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms; [0039] and at least one hydrocarbon compound having at least one alkyl polyamine group, having between 1 and 30 carbon atoms, preferably between 4 and 30 carbon atoms,
said alkylphenol-aldehyde condensation resin itself being obtainable by condensation of: [0040] of at least one alkylphenol substituted with at least one linear or branched alkyl group having from 1 to 30 carbon atoms, preferably a monoalkylphenol, [0041] with at least one aldehyde and/or ketone having from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.

[0042] The alkylphenol-aldehyde condensation resin may be selected from any resin of this type already known and especially those described in documents EP857776 and EP1584673.

[0043] Modified alkylphenol-aldehyde resins according to the invention are advantageously obtained from at least one para-substituted alkylphenol. Nonylphenol is preferably used.

[0044] The average number of phenolic rings per molecule of nonylphenol-aldehyde resin is advantageously in the range from 6 to 25, preferably from 8 to 17, and more preferably from 9 to 16.

[0045] The number of phenolic rings can be determined by Nuclear Magnetic Resonance (NMR) or Gel Permeation Chromatography (GPC).

[0046] Advantageously, the modified alkylphenol-aldehyde resins are obtained by implementing a same aldehyde or ketone at both steps of preparation thereof.

[0047] The modified alkylphenol-aldehyde resins can be obtained from at least one aldehyde and/or ketone selected from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, 2-ethyl-hexanal, benzaldehyde and/or acetone. Preferably, the modified alkylphenol-aldehyde resin is obtained from at least one aldehyde, preferably at least formaldehyde (or methanal).

[0048] Preferably, modified alkylphenol-aldehyde resins are obtainable from p-nonylphenol, formaldehyde and at least one hydrocarbon compound comprising at least one alkyl polyamine group.

[0049] Said hydrocarbon compound may be an alkyl polyamine having at least two primary and/or secondary amine groups. In particular, the alkyl polyamine is advantageously selected from primary or secondary polyamines substituted with, respectively, one or two alkyl groups comprising, preferably, from 12 to 24 carbon atoms, more preferably from 12 to 22 carbon atoms.

[0050] Preferably, the modified alkylphenol-aldehyde resin is obtained from at least one alkyl polyamine having at least two primary amine groups, preferably three primary amine groups.

[0051] In particular, the modified alkylphenol-aldehyde resin can advantageously be obtained from at least one alkyl polyamine in which all the amine groups are primary amines.

[0052] Preferably, the modified alkylphenol-aldehyde resin is obtained from at least one alkyl polyamine comprising at least one fatty chain having from 12 to 24 carbon atoms, preferably from 12 to 22 carbon atoms.

[0053] A particularly preferred alkyl polyamine is tallow dipropylene triamine.

[0054] Commercial alkyl polyamines are generally not pure compounds but mixtures. Suitable commercial alkyl polyamines include fatty chain alkyl polyamines marketed under the names Trinoram?, Duomeen?, Dinoram?, Triameen?, Armeen?, Polyram?, Lilamin? and Cemulcat?.

[0055] One preferred example is Trinoram? S, which is a tallow dipropylene triamine, also known as N-(Tallowalkyl)dipropylene triamine (CAS 61791-57-9).

[0056] It is of course possible to combine both embodiments and to use a combination of compounds (i)a) and (i)b) as described above.

[0057] Thus, according to one preferred embodiment, the composition of additives comprises one or more compounds (i)a) comprising one or two phenolic ring(s) substituted with one or more alkyl groups selected from methyl and t-butyl groups, and one or more modified alkylphenol-aldehyde resins (i)b).

Cetane Number Improving Additives:

[0058] The invention implements as additives (ii) one or more cetane number improving additives, also known as procetane additives or cetane booster additives.

[0059] The additive or additives (ii) are selected from alkyl nitrates and aryl or alkyl peroxides.

[0060] Among aryl peroxides, particular mention may be made of benzyl peroxide. One example of an alkyl peroxide is tert-butyl peroxide.

[0061] The additive or additives (ii) are preferably selected from alkyl nitrates, and more preferably those of the formula RNO.sub.3 with R an alkyl radical comprising from 2 to 12 carbon atoms, preferably from 4 to 8 carbon atoms.

[0062] A particularly preferred additive (ii) is ethyl hexyl nitrate.

The Composition of Additives

[0063] The composition of additives used in accordance with the present invention is characterised in that the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:3 to 3:1.

[0064] Preferably, the weight ratio of the amount of additive(s) (i) to the amount of additive(s) (ii) is in the range from 1:2.5 to 2.5:1, preferably from 1:2 to 2:1 and more preferably from 1:1 to 1.5:1.

Deposit Control Additives

[0065] According to one preferred embodiment, the composition of additives used in accordance with the present invention additionally comprises one or more detergency additive(s) (iii), also called deposit control additive(s), other than the compounds (i) having in their structure at least one alkyl phenol group and the additives (ii) improving the cetane number described above, and which may be selected from the detergency additives for diesel fuels usually employed. The latter are compounds well known to those skilled in the art.

[0066] The deposit control additives may especially (but not limited to) be selected from the group consisting of amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts, and triazole derivatives, and more preferably from quaternary ammonium salts, and polyisobutylene mono- or poly-amines (or PIB-amines), even more preferably from among polyisobutylene succinimides (substituted or not with a triazole group), or quaternary ammonium salts and even more preferably from among polyisobutylene succinimides functionalised with a quaternary ammonium group, fatty acid amides functionalised with a quaternary ammonium group and dimers thereof such as the di-(quaternary alkylamido-propyl-ammonium) compounds described for example in European patent application No 18306589.5, fatty-chain alkylamidoalkyl betaines and triazole derivatives. Polyisobutylene succinimides functionalised with a quaternary ammonium group and polyisobutylene succinimides functionalised with a triazole group are particularly preferred.

[0067] Examples of deposit control additives are given in the following documents: EP0938535, US2012/010112, WO2012/004300, U.S. Pat. No. 4,171,959 and WO2006/135881.

[0068] Block copolymers formed by at least one polar unit and one apolar unit, such as, for example, those described in patent application FR 1761700 on behalf of the Applicant, may also be used.

[0069] According to one embodiment, the composition of additives comprises at least one deposit control additive consisting of a quaternary ammonium salt obtained by reaction with a quaternisation agent of a nitrogen compound comprising a tertiary amine function, this nitrogen compound being the product of the reaction of an acylation agent substituted with a hydrocarbon group and a compound comprising at least one tertiary amine group and at least one group selected from primary amines, secondary amines and alcohols. Preferably, said nitrogen compound is the reaction product of a succinic acid derivative substituted with a hydrocarbon group, preferably a polyisobutenyl succinic anhydride, and an alcohol or a primary or secondary amine also comprising a tertiary amine group. Such deposit control additives, as well as preferred combinations of deposit control additives comprising them, are especially described in patent application WO 2015/124584 on behalf of the applicant.

[0070] When the composition of additives contains one or more deposit control additive(s), preferably the ratio of the total weight content of compounds (i) having in their structure at least one alkyl phenol group on the one hand to the total weight content of deposit control additive(s) (iii) on the other hand ranges from 1:60 to 1:2, preferably from 1:20 to 1:3.

[0071] Preferably, the total content of deposit control additive(s) (iii) in the fuel ranges from 5 to 5000 ppm by weight, preferably from 10 to 1000 ppm by weight, and even more preferably from 20 to 500 ppm by weight, relative to the total weight of the fuel.

Other Additives

[0072] The composition of additives may also comprise other additives, in addition to the compound(s) (i) having at least one alkyl phenol group in their structure, additives (ii) improving the cetane number described above and deposit control additive(s) (iii) described above.

[0073] These other additive(s) may be chosen, for example, but not limited to, from anti-corrosion additives, dispersant additives, demulsifier additives, anti-foaming agents, biocides, reodorants, friction modifiers, lubricity additives, combustion aids (catalytic combustion and soot promoters), cold-stability additives and in particular agents improving the cloud point, the pour point, the CFPP (Colder Filter Plugging Point), anti-settling agents, anti-wear agents, tracers, solvents/carrier oils and conductivity modifiers.

[0074] Examples of these additives include: [0075] a) anti-foaming additives, especially (but not limited to) selected from polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides derived from vegetable or animal oils. Examples of such additives are given in EP861882, EP663000, EP736590; [0076] b) Cold Flow Improver (CFI) additives selected from ethylene-unsaturated ester copolymers, such as ethylene/vinyl acetate (EVA), ethylene/vinyl propionate (EVP), ethylene/vinyl ethanoate (EVA) and ethylene/vinyl propionate (EVP) copolymers, ethylene/vinyl ethanoate (EVE), ethylene/methyl methacrylate (EMMA), and ethylene/alkyl fumarate copolymers described, for example, in documents U.S. Pat. Nos. 3,048,479, 3,627,838, 3,790,359, 3,961,961 and EP261957; [0077] c) lubricity additives or anti-wear agents, especially (but not limited to) selected from the group consisting of fatty acids and ester or amide derivatives thereof, especially glycerol monooleate, and mono- and polycyclic carboxylic acid derivatives. Examples of such additives are given in the following documents: EP680506, EP860494, WO98/04656, EP915944, FR2772783, FR2772784; [0078] d) cloud point additives, especially (but not limited to) selected from the group consisting of long-chain olefin/(meth)acrylic ester/maleimide terpolymers and fumaric/maleic acid ester polymers. Examples of such additives are given in FR2528051, FR2528423, EP112195, EP172758, EP271385, EP291367; [0079] e) polyfunctional cold workability additives selected from the group consisting of olefin and alkenyl nitrate based polymers as described in EP573490; [0080] f) anti-corrosion additives such as, for example, fatty acid ester dimers and aminotriazoles.

[0081] These additional additives may be present in amounts ranging from 5 to 1000 ppm (each), preferably from 50 to 500 ppm by weight, based on the total weight of fuel.

[0082] The composition of additives may advantageously comprise an organic solvent, which may for example be selected from aromatic hydrocarbon solvents such as the solvent marketed under the name SOLVESSO, alcohols, ethers and other oxygenated compounds, and paraffinic solvents such as hexane, pentane or isoparaffins, including hydrotreated vegetable oils known as HVO, alone or in a mixture.

[0083] According to one preferred embodiment, the composition of additives comprises at least one solvent selected from alcohols. Particularly advantageously, the composition of additives contains at least one C1 to C8 monohydric alcohol, preferably selected from ethanol and 2-ethylhexanol.

Liquid Fuel

[0084] The use of the composition of additives according to the invention applies to a fuel in liquid form at ambient temperature (20? C.) and atmospheric pressure (1.013?10.sup.5 Pa). This fuel is intended to supply a diesel engine.

[0085] Such a fuel typically comprises at least one fraction of liquid hydrocarbons from one or more sources selected from the group consisting of mineral sources, animal sources, vegetable sources and synthetic sources.

[0086] The fuel is advantageously selected from hydrocarbon fuels and non-essentially hydrocarbon fuels, and mixtures thereof.

[0087] By hydrocarbon fuel, it is meant a fuel consisting of one or more compounds consisting solely of carbon and hydrogen.

[0088] By non-essentially hydrocarbon fuel, it is meant a fuel consisting of one or more compounds not essentially consisting of carbon and hydrogen, that is which also contain other atoms, in particular oxygen atoms.

[0089] Hydrocarbon fuels include middle distillates with boiling temperatures ranging from 100 to 500? C. These distillates may, for example, be selected from distillates obtained by direct distillation of crude hydrocarbons, vacuum distillates, hydrotreated distillates, distillates from catalytic cracking and/or hydrocracking of vacuum distillates, distillates resulting from conversion processes such as ARDS (atmospheric residue desulphurisation) and/or visbreaking, distillates resulting from the reclaiming of Fischer Tropsch fractions, biodiesels such as distillates resulting from BTL (biomass to liquid) conversion of plant and/or animal biomass and Hydrotreated Vegetable Oils known to those skilled in the art as HVO or HDRD (hydrogenation-derived renewable diesel). Hydrocarbon fuels are typically gas oils (also called diesel fuels).

[0090] Gas oils include, in particular, all commercially available diesel engine fuel compositions. A representative example is gas oils complying with standard NF EN 590.

[0091] Non-essentially hydrocarbon fuels include, in particular, vegetable and/or animal oils and/or oil esters.

[0092] Blends of hydrocarbon fuel and non-essentially hydrocarbon fuel are typically type Bx gas oils.

[0093] Type Bx gas oil for a diesel engine is a gas oil which contains x % (v/v) vegetable or animal oil esters (including used cooking oils) transformed by a chemical process called transesterification, obtained by reacting this oil with an alcohol in order to obtain fatty acid esters (FAE). Methanol and ethanol are used to obtain fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE) respectively. The letter B is followed by a number x greater than zero and less than or equal to 100, which indicates the percentage of FAE contained in the gas oil. Thus, B99 contains 99% FAE and 1% middle distillates of fossil origin (mineral source), while B20 contains 20% FAE and 80% middle distillates of fossil origin, etc. . . . A distinction is therefore made between type B.sub.0 gas oils, which contain no oxygenated compounds, and type B.sub.x gas oils, which contain x % (v/v) vegetable oil or fatty acid esters, usually methyl esters (VOME or FAME), where x is a number ranging from 0 to 100. When FAE is used alone in engines, the fuel is referred to as B.sub.100.

[0094] According to one preferred embodiment, the fuel is selected from gas oils, biodiesels, B.sub.x type gas oils containing x % (v/v) vegetable or animal oil esters with x a number greater than zero and less than or equal to 100, hydrotreated vegetable oils (HVO), and mixtures thereof.

[0095] According to one particularly preferred embodiment, the fuel is selected from type Bx gas oils containing x % (v/v) vegetable or animal oil esters with x a number greater than zero and less than or equal to 100. The vegetable oil esters are highly particularly selected from fatty acid methyl esters (FAME) and fatty acid ethyl esters (FAEE).

[0096] The sulphur content of the fuel is preferably less than or equal to 1000 ppm, preferably less than or equal to 500 ppm, and more preferably less than or equal to 50 ppm, or even less than 10 ppm, and advantageously sulphur-free.

Use

[0097] The composition of additives according to the invention is used to reduce emissions of nitrogen oxides as well as carbon monoxide and/or unburnt hydrocarbons during combustion of a liquid fuel in a compression-ignition internal combustion engine. Preferably, the use is to also reduce particulate emissions.

[0098] By this, it is meant that incorporation of the composition of additives according to the invention into the liquid fuel produces an effect of reducing emissions of nitrogen oxides as well as carbon monoxide and/or unburnt hydrocarbons output from compression-ignition engines supplied with said fuel, with respect to the same fuel not comprising the composition according to the invention. Preferably, the reduction effect is produced for all three types of emissions, namely nitrogen oxides, carbon monoxide and unburnt hydrocarbons. Preferably, the reduction effect is also produced for particulate emissions.

[0099] According to a first preferred embodiment, the compression ignition engine or diesel engine is a hybrid diesel engine or a direct injection diesel engine, preferably a direct injection diesel engine and in particular a diesel engine with a Common Rail Direct Injection (CRDI) system.

[0100] According to a second preferred embodiment, the compression ignition or diesel engine is a marine engine.

[0101] Emission levels of nitrogen oxides, carbon monoxide, unburnt hydrocarbons and particulates are measured in accordance with the methods defined in European regulation ECE-R83.05.

[0102] These regulations define a harmonised test procedure for the type approval of vehicles in Europe and the measurement of different types of emissions. These regulations are defined with reference to a standardised test known as the WLTP (World harmonised Light duty Test Procedure), which is a globally harmonised test procedure. This test involves measuring the emissions of a standardised vehicle (Euro 6) during a defined test cycle known as the WLTC (World harmonised Light duty Test Cycle), using high-precision emissions analysers.

[0103] The composition of additives is advantageously used in an amount such that: [0104] the total amount by weight of additives (i) ranges from 10 to 2000 ppm by weight, preferably from 20 to 1000 ppm by weight, more preferably from 50 to 500 ppm by weight and still more preferably from 200 to 400 ppm by weight, relative to the total weight of the fuel; [0105] the total amount by weight of additives (ii) ranges from 10 to 1500 ppm by weight, preferably from 20 to 1000 ppm by weight, more preferably from 50 to 500 ppm by weight and better still from 150 to 400 ppm by weight, relative to the total weight of the fuel.

[0106] The use according to the invention is compatible with existing exhaust gas post-treatment devices, and makes it possible to further reduce the levels of pollutants emitted by vehicles equipped with such devices and/or to extend the life time of this equipment and/or to space out maintenance operations on this equipment.

[0107] Thus, according to a particularly advantageous embodiment, the compression ignition engine is equipped with one or more exhaust gas post-treatment devices, preferably selected from among the selective catalytic reduction devices known as SCR, exhaust gas recirculation devices known as EGR, particle filter type devices commonly known as DPF, and devices known as SCRoF (SCR on Filter) or SCRF or SDPF which combine, within a same device, functions of selective catalytic reduction and particle filtration.

Process or Method

[0108] The process or method for decreasing emissions of nitrogen oxides and of at least one type of polluting agent selected from carbon monoxide and unburnt hydrocarbons during the combustion of a liquid fuel in a compression-ignition internal combustion engine, consists in adding a composition of additives as described above to said fuel composition.

[0109] Preferably, the method is a method for decreasing emissions of nitrogen oxides, carbon monoxide and unburnt hydrocarbons. According to a particularly preferred embodiment, it also reduces emissions of solid particles.

[0110] The additives making up the composition of additives can be incorporated into the liquid fuel within a refinery and/or incorporated downstream of the refinery, either separately or as a mixture, in this case possibly as a dispersion in an organic solvent, particularly in the form of an additive package.

[0111] Combustion of thus additivated fuel in the internal combustion engine produces an effect on the reduction in emissions of nitrogen oxides, carbon monoxide and particulates measured according to the methods previously described in the scope of the use. A simultaneous reduction in the various types of pollutants is thus achieved.

[0112] The above description of the composition of additives, fuels and its use in fuels supplying a compression ignition engine fully applies to the process or method according to the invention.

[0113] The following examples are given by way of illustration of the invention, and should not be construed in such a way as to limit the scope thereof.

EXAMPLES

[0114] The tests below have been carried out using a B7 type Austrian gas oil, meeting the specifications of standard EN590.

[0115] This virgin fuel is referred to as G0.

[0116] A first fuel composition G1 has been prepared by adding to the fuel G0 an additive package A1 containing the following compounds: [0117] Procetane additive: ethyl hexyl nitrate at a content of 300 ppm by weight in the fuel G1, [0118] Deposit control additive: polyisobutylene succinimide functionalised with a quaternary ammonium group at a content of 42 ppm by weight in fuel G1, [0119] Deposit control additive: polyisobutylene succinimide functionalised with a triazole group at a content of 30 ppm by weight in fuel G1.

[0120] A second fuel composition G2 has been prepared by adding to fuel composition G1 a mixture of compounds of the alkyl phenol type (consisting of 15% by weight of 2,6-di-t-butyl-4-methyl phenol, and 85% by weight of the condensation product of 2,4-dimethyl-6-t-butyl phenol and 2,5-dimethyl-4-t-butyl phenol) at a content of 350 ppm by weight in fuel G2.

[0121] Three identical tests have been carried out in accordance with the standardised WLTP test protocol, using an Opel Crossland X equipped with a diesel engine with a displacement of 1560 cm3 and 88 kW. This vehicle complies with the Euro 6b standard.

[0122] The driving cycle associated with the WLTP protocol consists in driving the vehicle on a chassis dynamometer over a defined distance of 23 kilometres over a period of 1,800 seconds (30 minutes), with an initial cold start. The driving profile alternates variable driving speeds over four main phases, separated by stops (zero speed).

[0123] The three tests differ only in the type of fuel supplying the engine (G0, G1 and G2 respectively).

[0124] For each test, five cycles have been carried out (each fuel has been evaluated 5 times, in order to ensure robustness and statistical validity of the results).

[0125] The levels of pollutants emitted during each test have been measured in accordance with the methods defined in European regulation ECE-R83.05.

[0126] The results obtained (average over the five cycles) are shown in Table I below:

TABLE-US-00001 TABLE I Polluants G0 G1 G2 NOx (mg/km) 82.1 94.1 68 CO (mg/km) 94.7 58 50 Unburnt hydrocarbons + 84.4 97 70.9 NO.sub.x (mg/km) Total gaseous emissions 179.1 155 120.9 (NO.sub.x + CO + unburnt hydrocarbons, in mg/km) calculation Solid particulates (value by 0.006 0.014 0.0007 number, in mg/km)

[0127] The above results demonstrate that adding the additive package A1 to virgin gas oil G0 results in a significant increase in nitrogen oxide (NOx) and particulate emissions. The diesel composition G2, further comprising alkylphenol additives in accordance with the invention, enables NOx emissions to be reduced very significantly, by 28% with respect to the comparative gas oil G1 and by 17% with respect to the virgin reference gas oil G0. With regard to particles, composition G2 enables emissions to be reduced by 95% with respect to the comparative gas oil G1 and by 88% with respect to the virgin reference gas oil G0.

[0128] In addition, the total level of gaseous emissions is very strongly decreased with fuel G2, with respect to the comparative fuels G1 and G0.