WO2021105321A1

WO2021105321A1 - Use of diols as detergent additives

Info

Publication number: WO2021105321A1
Application number: PCT/EP2020/083574
Authority: WO
Inventors: Hélène Rodeschini; Géraldine DELORME
Original assignee: Total Marketing Services
Priority date: 2019-11-29
Filing date: 2020-11-27
Publication date: 2021-06-03
Also published as: US20230357656A1; FR3103815B1; FR3103815A1; CN115175975B; PL4065672T3; EP4065672B1; EP4065672A1; CN115175975A

Abstract

The present invention relates to the use, for improving the detergency properties of a liquid fuel composition comprising one or more detergent additives, of an additive consisting of one or more hydrocarbon compound(s) comprising from 2 to 10 carbon atoms and two hydroxyl functions. The present invention also relates to a method for improving the cleanliness of and/or for cleaning at least one inner portion of an internal combustion engine supplied with a liquid fuel comprising one or more detergent additives, the method consisting of a step of adding such a hydrocarbon compound to the fuel composition.

Description

DESCRIPTION

TITLE: Use of Diols as Detergency Additives The present invention relates to the use of particular compounds of the diol family as detergency additives in fuel compositions.

The present invention also relates to a process or method for improving the cleanliness and / or cleaning at least an internal part of an internal combustion engine using these particular compounds.

STATE OF THE PRIOR ART Liquid fuels for internal combustion engines contain components which can be degraded during engine operation. The problem of deposits in the internal parts of combustion engines is well known to engine manufacturers. It has been shown that the formation of these deposits has consequences on engine performance and in particular has a negative impact on fuel consumption and particle emissions. Advances in fuel additive technology have made it possible to tackle this problem. So-called detergent additives used in fuels have already been proposed to maintain engine cleanliness by limiting deposits ("keep-clean" effect) or by reducing deposits already present in the internal parts of the combustion engine ("effect" clean-up ”in English). Mention may be made, by way of example, of document US Pat. No. 4,171959 which describes a detergent additive for gasoline fuel containing a quaternary ammonium function. Document WO2006135881 describes a detergent additive containing a quaternary ammonium salt used to reduce or clean deposits, in particular on the intake valves. Nevertheless, engine technology is constantly evolving and fuel requirements must evolve to cope with these technological advances in combustion engines. In particular, the new direct injection systems petrol or Diesel expose the injectors to more severe pressure and temperature conditions, which favors the formation of deposits. In addition, these new injection systems have more complex geometries to optimize the spraying, in particular, more numerous holes having smaller diameters but which, on the other hand, induce greater sensitivity to deposits. The presence of deposits can alter combustion performance, and in particular increase pollutant emissions and particulate emissions. Other consequences of the excessive presence of deposits have been reported in the literature, such as increased fuel consumption and drivability problems.

The prevention and reduction of deposits in these new engines is essential for the optimal functioning of today's engines. There is therefore a need to provide detergent additives for fuels which promote optimal operation of combustion engines, in particular but not limited to new engine technologies.

There also remains a need for universal detergency solutions which make it possible to prevent or reduce deposits on the internal parts of internal combustion engines, whatever the technology of the engine and / or the nature of the fuel.

OBJECT OF THE INVENTION The Applicant has discovered that particular compounds of the diol type, as defined below, have remarkable and unexpected properties, in that they improve the effectiveness of the detergent additives used in fuel compositions. .

These compounds exhibit an effect of the “booster” type of the detergent properties of conventional detergency additives, that is to say that their addition even in very small quantities (for example less than 50 ppm by weight) makes it possible to increase in such a way. remarkable detergency performance of said additives. In other words, the addition of the compounds according to the invention in a fuel composition, whether of diesel or gasoline type, comprising at least one detergency additive, has the effect of increasing the detergent properties of said fuel. composition. They make it possible to maintain the cleanliness of the engine, in particular by limiting or avoiding the formation of deposits ("keep-clean" effect in English) or by reducing the deposits already present in the internal parts of the combustion engine ("clean-clean" effect). up ”in English).

The additional advantages associated with the use as fuel additives of the compounds according to the invention are:

- optimal engine operation,

- reduced fuel consumption,

- reduced pollutant emissions, and

- savings due to less engine maintenance. A subject of the present invention is thus the use, to improve the detergency properties of a liquid fuel composition comprising one or more detergency additives, of an additive consisting of one or more hydrocarbon compound (s). comprising from 2 to 10 carbon atoms and two hydroxyl functions. The subject of the invention is also a process or method for improving the cleanliness and / or cleaning of at least one internal part of an internal combustion engine supplied with a liquid fuel comprising one or more detergency additives, consisting of in adding to said fuel composition an additive consisting of at least one hydrocarbon compound comprising from 2 to 10 carbon atoms and two hydroxyl functions.

Preferably, the compound according to the invention is incorporated into the fuel composition at a minimum content of 5 ppm by weight, and at a content which may range up to 500 ppm by weight. Preferably, the liquid fuel composition is chosen from hydrocarbon fuels, non-essentially hydrocarbon fuels, and mixtures thereof. Advantageously, the hydrocarbon fuel is chosen from gasolines and gas oils, also called diesel fuel. According to a preferred embodiment, the compound according to the invention is used in the liquid fuel to maintain cleanliness and / or to clean at least one of the internal parts of said internal combustion engine. In particular, said compound is used in liquid fuel to limit or prevent the formation of deposits in at least one of the internal parts of said engine and / or reduce the deposits existing in at least one of the internal parts of said engine.

Advantageously, the deposits are localized in at least one of the internal parts chosen from the engine intake system, the combustion chamber and the fuel injection system.

In particular, the compound according to the invention is used to prevent and / or reduce the formation of deposits associated with the phenomenon of coking (or "coking") and / or deposits of the soap and / or varnish type. The compound according to the invention also makes it possible to reduce the fuel consumption of the internal combustion engine.

It also reduces pollutant emissions, in particular particulate emissions from the internal combustion engine.

According to a first embodiment, the internal combustion engine is a spark ignition engine, also known as a gasoline engine.

According to a second embodiment, the internal combustion engine is a compression ignition engine, also known as a diesel engine. Other objects, characteristics, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples which follow.

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

Moreover, the expressions “at least one” and “at least” used in the present description are respectively equivalent to the expressions “one or more” and “greater than or equal”. Finally, in a manner known per se, the term “C _N compound or group” denotes a compound or a group containing in its chemical structure N carbon atoms. DETAILED DESCRIPTION

The additive according to the invention:

The invention uses as an additive a hydrocarbon compound comprising from 2 to 10 carbon atoms and two hydroxyl functions.

Preferably, this compound has the formula C _n H _{2n + 2} 0 ₂ , with n an integer ranging from 2 to 10.

According to a preferred embodiment, n ranges from 3 to 8, more preferably from 4 to 8; better still n denotes 5 or 6, and even more preferably n denotes 6.

According to a particularly preferred embodiment, said compound is hexylene glycol. Use

The compound according to the invention is used as an additive to improve the detergency performance of a fuel composition. This is understood to mean that the incorporation, including in a very small amount, of the compound according to the invention into the liquid fuel comprising a detergent additive other than the compound according to the invention, produces an effect on the cleanliness of the engines supplied by said fuel, compared to the same fuel not comprising the compound according to the invention. Advantageously, the use of said compound in the fuel composition makes it possible, compared with the liquid fuel not comprising such a compound, to limit or avoid the formation of at least one type of deposits as described below, and / or reduce at least one type of existing deposits. In particular, the use of the compounds according to the invention in a liquid fuel makes it possible to maintain the cleanliness of at least one of the internal parts of the internal combustion engine and / or to clean at least one of the internal parts of the internal combustion engine. . The use of said compound as an additive in liquid fuel makes it possible in particular to limit or avoid the formation of deposits in at least one of the internal parts of said engine (“keep-clean” effect in English) and / or to reduce existing deposits. in at least one of the internal parts of said engine (“clean-up” effect). Advantageously, the use of said compound as an additive in the liquid fuel makes it possible to observe both the two effects, of limitation (or prevention) and reduction of deposits (“keep-clean” and “clean-up” effects). .

Deposits are distinguished according to the type of internal combustion engine and the location of the deposits in the internal parts of said engine.

According to a first embodiment, the internal combustion engine is a spark ignition engine or gasoline engine, preferably with direct injection (DISI in English “Direct Injection Spark Ignition engine”). The targeted deposits are located in at least one of the internal parts of said spark-ignition engine. The internal part of the spark-ignition engine kept clean (keep-clean) and / or cleaned (clean-up) is advantageously chosen from the engine intake system, in particular the intake valves (IVD in English " Intake Valve Deposit ”), the combustion chamber (CCD in English“ Combustion Chamber Deposit ”or TCD in English“ Total Chamber Deposit ”) and the fuel injection system, in particular the injectors of an indirect injection system (PLI in English “Port Luel Injector”) or the injectors of a direct injection system (DISI).

According to a second embodiment, the internal combustion engine is a compression ignition engine or diesel engine, preferably a direct injection diesel engine, in particular a Diesel engine with a Common-Rail injection system (CRDI in English " Common Rail Direct Injection ”). The targeted deposits are located in at least one of the internal parts of said diesel engine.

Advantageously, the targeted deposits are located in the injection system of the diesel engine, preferably, located on an external part of an injector of said injection system, for example the nose of the injector and / or on an internal part. an injector of said injection system (IDID in English “Internai Diesel Injector Deposits”), for example on the surface of an injector needle.

The deposits may consist of deposits associated with the phenomenon of coking (“coking” in English) and / or deposits of the soap and / or varnish type (in English “lacquering”).

The compound (s) according to the invention as described above can advantageously be used in fuel to reduce and / or avoid the loss of power due to the formation of deposits in the internal parts of a direct injection diesel engine. , said power loss being able to be determined according to the standard engine test method CEC F-98-08.

Said compound (s) according to the invention can advantageously be used in the fuel to reduce and / or avoid the restriction of the flow of fuel emitted by the injector of a direct injection diesel engine during its operation. , said flow restriction being able to be determined according to the standardized engine test method CEC F-23-1 -01.

More generally, there are several well-known methods for evaluating the detergency performance of a fuel composition, among which there may be mentioned, in addition to the standard test methods CEC F-98-08 and CEC F- 23-1-01 mentioned above which are carried out on diesel engines, the standard test methods CEC F-05-A-93 and CEC F-20-A-98 which are carried out on positive-ignition engines.

According to an advantageous embodiment, the use of the compounds according to the invention also makes it possible to reduce the fuel consumption of the internal combustion engine. According to another advantageous embodiment, the use of the compounds according to the invention also makes it possible to reduce the emissions of pollutants, in particular the emissions of particles from the internal combustion engine. The compounds according to the invention can be added to the liquid fuel within a refinery and / or be incorporated downstream of the refinery, optionally mixed with other additives in the form of an additive package.

The compound (s) according to the invention are advantageously used in the fuel composition at a total content of at least 5 ppm by weight, relative to the total weight of said composition.

Preferably, the hydrocarbon compound (s) according to the invention are used at a total content ranging from 5 to 500 ppm by weight, preferably from 10 to 200 ppm by weight, preferably from 10 to 100 ppm. by weight, more preferably from 10 to 50 ppm by weight, more preferably from 20 to 50 ppm by weight, and better still from 20 to 40 ppm by weight, relative to the total weight of the fuel composition.

Fuel composition

The fuel composition in which the compound (s) according to the invention are used as additives typically comprises at least one liquid hydrocarbon cut obtained from one or more sources chosen from the group consisting of mineral sources, animal sources, vegetable and synthetic.

Oil will preferably be chosen as the mineral source.

The fuel composition is advantageously chosen from hydrocarbon fuels and non-essentially hydrocarbon fuels, and mixtures thereof. The term "hydrocarbon fuel" means a fuel consisting of one or more compounds consisting solely of carbon and hydrogen.

The term “non-essentially hydrocarbon-based fuel” is understood to mean a fuel consisting of one or more compounds consisting of not essentially carbon and hydrogen, that is to say which also contain other atoms, in particular oxygen atoms.

Hydrocarbon fuels include in particular middle distillates with a boiling point ranging from 100 to 500 ° C or lighter distillates having a boiling point in the range of gasolines. These distillates can for example be chosen from the distillates obtained by direct distillation of crude hydrocarbons, the vacuum distillates, the hydrotreated distillates, the distillates resulting from the catalytic cracking and / or the hydrocracking of vacuum distillates, the distillates resulting from ARDS (atmospheric residue desulfurization) and / or visbreaking type conversion processes, distillates resulting from the upgrading of Fischer Tropsch cuts. Hydrocarbon fuels are typically gasoline and diesel fuel (also called diesel fuel). Advantageously, the fuel composition is chosen from gasolines and gas oils.

Gasolines include, in particular, any commercially available spark ignition engine fuel compositions. By way of representative example, gasolines meeting the NF EN 228 standard may be cited. The gasolines generally have sufficiently high octane numbers to avoid the knocking phenomenon. Typically, gasoline type fuels marketed in Europe, conforming to standard NF EN 228 have an engine octane number (MON in English "Motor Octane Number") greater than 85 and a research octane number (RON in English " Research Octane Number ”) of a minimum of 95. Gasoline-type fuels generally have a RON ranging from 90 to 100 and an MON ranging from 80 to 90, the RON and MON being measured according to the standard ASTM D 2699- 86 or D 2700-86. Gas oils (diesel fuels) include, in particular, all commercially available diesel engine fuel compositions. By way of representative example, we can cite gas oils meeting standard NF EN 590.

Non-primarily hydrocarbon fuels include in particular oxygenates, for example distillates resulting from the BTL (“biomass to liquid”) conversion of plant and / or animal biomass, taken alone or in combination; biofuels, for example oils and / or esters of vegetable and / or animal oils; biodiesels of animal and / or plant origin and bioethanols.

The mixtures of hydrocarbon fuel and non-essentially hydrocarbon fuel are typically gas oils of type B _x or gasolines of type E _x .

By type B _x diesel fuel for Diesel engines is meant a diesel fuel which contains x% (v / v) of esters of vegetable or animal oils (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 (EAG). With methanol and ethanol, methyl esters of fatty acids (FAME) and ethyl esters of fatty acids (EEAG) are obtained, respectively. The letter "B" followed by a number indicates the percentage of EAG contained in the diesel fuel. Thus, a B99 contains 99% of EAG and 1% of middle distillates of fossil origin (mineral source), B20, 20% of EAG and 80% of middle distillates of fossil origin etc. Bo type gas oils which do not contain oxygenated compounds, Bx type gas oils which contain x% (v / v) of vegetable oil esters or fatty acids, most often methyl esters (VME or FAME), x denoting a number ranging from 0 to 100. When the EAG is used alone in the engines, the fuel is denoted by the term B ioo.

By gasoline of type E _x for a spark ignition engine is meant a gasoline fuel which contains x% (v / v) of oxygenates, generally ethanol, bioethanol and / or ethyl-tertio-butyl-ether. (ETBE), x denoting a number ranging from 0 to 100. The sulfur content of the fuel composition 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 at 50 ppm, or even less than 10 ppm and advantageously without sulfur. Detergent additives

The fuel composition according to the invention comprises one or more detergent additive (s), which can be chosen from the detergency additives for fuels usually used. The latter are compounds well known to those skilled in the art.

The detergent additives can be in particular (but not limited to) chosen from the group consisting of amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts, triazole derivatives, and Mannich bases, and more preferably among Mannich bases, quaternary ammonium salts, and polyisobutylene mono- or poly-amines (or PIB-amines), more preferably still among quaternary ammonium salts and better still among polyisobutylene succinimides functionalized with a quaternary ammonium group, fatty acid amides functionalized with a quaternary ammonium group and their dimers such as the di- (alkylamido-propyl-quaternary ammonium) compounds described for example in patent application WO2020 / 109568 , and fatty chain alkylamidoalkyl betaines.

Examples of detergent additives are given in the following documents: EP0938535, US2012 / 0010112, WO2012 / 004300, US4171959 and WO2006135881.

One can also advantageously use block copolymers formed of at least one polar unit and one non-polar unit, such as for example those described in patent application FR 1761700 in the name of the Applicant.

According to a preferred embodiment, the fuel composition comprises at least one detergent additive consisting of a quaternary ammonium salt, obtained by reaction with a quaternization agent of a nitrogen compound comprising a tertiary amine function, this nitrogen compound being the reaction product of an acylating agent substituted with a hydrocarbon group and of a compound comprising at least one tertiary amine group and at least one group chosen from primary amines, secondary amines and alcohols.

According to a particularly preferred embodiment, said nitrogen compound is the reaction product of a derivative of succinic acid substituted with a hydrocarbon group, preferably a polyisobutenyl succinic anhydride, and of an alcohol or of a primary amine or secondary also comprising a tertiary amine group.

Such detergent additives, as well as preferred combinations of detergent additives comprising them, are in particular described in patent application WO 2015/124584 in the name of the applicant.

Preferably, the total content of detergent additive (s) in the fuel composition (without including the hydrocarbon compounds according to the invention) ranges from 5 to 5000 ppm by weight, preferably from 10 to 1000 ppm by weight , and more preferably from 20 to 250 ppm by weight, relative to the total weight of the fuel composition.

Preferably, the ratio between the total weight content of hydrocarbon compound (s) according to the invention on the one hand and the total weight content of detergent additive (s) on the other hand ranges from 1: 50 to 1: 1, preferably from 1:20 to 1: 1, more preferably from 1:20 to 1: 2, and more preferably from 1:20 to 1: 3.

Other additives

The fuel composition according to the invention may also include other additives, in addition to the detergent additive (s) and the hydrocarbon compound (s) according to the invention.

This or these other additives can be chosen, for example, in a nonlimiting manner, from anti-corrosion / antioxidant additives, dispersant additives, demulsifying additives, anti-foam agents, biocides, reodorants, procetane additives, friction modifiers, lubricity additives or lubricity additives, combustion aid agents (catalytic combustion and soot promoters), cold resistance additives and in particular agents improving the cloud point, the point flow, the TLF ("Limit filterability temperature"), anti-sedimentation agents, anti-wear agents, tracers, solvents / carrier oils, and conductivity modifiers.

Among these additives, there may be mentioned in particular: a) procetane additives, in particular (but not limited to) chosen from alkyl nitrates, preferably 2-ethylhexyl nitrate, aryl peroxides, preferably peroxide benzyl, and alkyl peroxides, preferably tert-butyl peroxide; b) anti-foam additives, in particular (but not limited to) chosen from polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides obtained from vegetable or animal oils. Examples of such additives are given in EP861882, EP663000, EP736590; c) Cold flow improving additives (CFI) chosen from copolymers of ethylene and unsaturated ester, such as ethylene / vinyl acetate (EVA), ethylene / vinyl propionate (EVP) copolymers , ethylene / vinyl ethanoate (EVE), ethylene / methyl methacrylate (EMMA), and ethylene / alkyl fumarate described, for example, in documents US3048479, US3627838, US3790359, US3961961 and EP261957; d) lubricity additives or anti-wear agents, in particular (but not limited to) chosen from the group consisting of fatty acids and their ester or amide derivatives, in particular glycerol monooleate, and mono- and carboxylic acid derivatives. polycyclic. Examples of such additives are given in the following documents: EP680506, EP860494, WO98 / 04656, EP915944, FR2772783,

FR2772784; e) cloud point additives, in particular (but not limited to) chosen from the group consisting of long-chain olefin / (meth) acrylic ester / maleimide terpolymers, and polymers of fumaric / maleic acid esters. Examples of such additives are given in FR2528051, FR2528051, FR2528423,

EPI 12195, EP 172758, EP271385, EP291367; f) polyfunctional cold operability additives chosen from the group consisting of polymers based on olefin and on alkenyl nitrate as described in EP573490; g) anti-corrosion additives such as, for example, fatty acid ester dimers and aminotriazoles. These additional additives may be present in an amount ranging, for each, from 10 to 1000 ppm (each), preferably from 50 to 500 ppm by weight, relative to the total weight of the fuel composition. The process or method

The process or method for improving the cleanliness and / or cleaning at least an internal part of an internal combustion engine supplied with a liquid fuel comprising one or more detergency additives, consists in adding to said fuel composition. an additive consisting of at least one hydrocarbon compound as described above.

The combustion of this fuel composition thus additivated in an internal combustion engine produces an effect on the cleanliness of the engine, compared to a fuel composition containing the same ingredients except for said hydrocarbon compound (s). .

The combustion of this fuel composition makes it possible, in particular, to prevent and / or reduce the fouling of the internal parts of the engine. These effects on engine cleanliness are as previously described in use.

According to a preferred embodiment, a method of maintaining the cleanliness (“keep-clean”) and / or cleaning (“clean-up”) of at least one of the internal parts of an internal combustion engine comprises: a) adding, to a fuel composition comprising at least one detergency additive, one or more hydrocarbon compounds as described above; then b) combustion of the fuel composition resulting from step a) in the internal combustion engine.

According to a first embodiment, the internal combustion engine is a controlled ignition engine, preferably with direct injection (DISI). The internal part kept clean and / or cleaned of the spark ignition engine is preferably chosen from the engine intake system, in particular the intake valves (IVD), the combustion chamber (CCD or TCD) and the fuel injection system, in particular the injectors of an indirect injection system (PFI) or the injectors of a direct injection system (DISI).

According to a second embodiment, the internal combustion engine is a diesel engine, preferably a direct injection diesel engine, in particular a diesel engine with a common rail injection system (CRDI). The internal part kept clean (keep-clean) and / or cleaned

(clean-up) of the Diesel engine is preferably the injection system of the Diesel engine, preferably an external part of an injector of said injection system, for example the nose of the injector and / or one of the internal parts of an injector of said injection system, for example the surface of an injector needle.

According to a preferred variant, step (a) above is preceded by a preliminary step of determining the content of hydrocarbon compound (s) to be incorporated into said fuel composition in order to achieve a given specification relating to the properties. detergency of the fuel composition.

This preliminary step comes within common practice in the field of fuel additivation and involves defining at least one characteristic representative of the detergency properties of the fuel composition as well as a target value. The characteristic representative of the detergency properties of the fuel will depend on the type of internal combustion engine, for example Diesel or spark ignition, the direct or indirect injection system and the location in the engine of the deposits targeted for cleaning and / or maintaining cleanliness. For direct injection diesel engines, the characteristic representative of the detergency properties of the fuel may, for example, correspond to the loss of power due to the formation of deposits in the injectors or the restriction of the flow of fuel emitted by the injector to the fuel. during the operation of said engine.

The representative characteristic of the detergency properties may also correspond to the appearance of lacquering-type deposits at the level of the injector needle (IDID).

Methods for evaluating the detergent properties of fuels have been widely described in the literature and are within the general knowledge of those skilled in the art. Mention will be made, by way of nonlimiting example, of the tests standardized or recognized by the profession or the methods described in the following literature:

For direct injection Diesel engines: - the DW10 method, CEC F-98 standardized engine test method -

08, to measure the power loss of direct injection Diesel engines

- the XUD9 method, standard engine test method CEC F-23- 1-01 Issue 5, to measure the fuel flow restriction emitted by the injector

- the method described by the applicant in application WO2014 / 029770 page 17 to 20, for the evaluation of lacquering deposits (IDID).

For indirect injection spark ignition engines: - the Mercedes Benz M 102E method, standardized test method

CEC F-05-A-93, and

- the Mercedes Benz M l 11 method, CEC F-20-A-98 standardized test method.

These methods make it possible to measure deposits on the intake valves (IVD), the tests generally being carried out on Eurosuper gasoline meeting the EN228 standard.

For direct injection positive-ignition engines:

- the method described by the applicant in the article "Evaluating Injector Fouling in Direct Injection Spark Ignition Engines ”, Mathieu Arondel, Philippe China, Julien Gueit; Conventional and future energy for automobiles; 10th international colloquium; January 20-22, 2015, p.375-386 (Technische Akademie Esslingen by Techn. Akad. Esslingen, Ostfildern), for the evaluation of coking type deposits on the injector,

- the method described in document US20130104826, for the evaluation of coking type deposits on the injector.

The determination of the amount of compound (s) according to the invention to be added to the fuel composition to achieve a given specification is typically carried out by comparison with the fuel composition but without the compound (s) according to the invention

The process of maintaining cleanliness (keep-clean) and / or cleaning (clean-up) can also include an additional step c) after step b), of checking the target reached and / or of adjusting the level. additivation rate with the compound (s) according to the invention.

The hydrocarbon compounds according to the invention exhibit remarkable properties as efficiency boosters for detergent additives in a liquid fuel, in particular in a gas oil or gasoline fuel. These compounds are particularly remarkable in particular because they are effective for a wide range of liquid fuels, for several types of engines and against various types of deposits which form in the internal parts of internal combustion engines. The examples below are given by way of illustration of the invention, and should not be interpreted in such a way as to limit its scope. EXAMPLES

Example 1: “Keep clean” type detergency tests in diesel fuel

The performance in terms of detergency was evaluated using the XUD9 engine test, consisting in determining the flow loss defined as corresponding to the restriction of the flow of a diesel fuel emitted by the injector of a pre-chamber Diesel engine during its operation, according to the standardized engine test method CEC F-23-1-01.

The objective of the XUD9 test is to assess the ability of the additive and / or the composition of additives tested to maintain the cleanliness, a so-called "keep clean" effect, of the injectors of a Peugeot XUD9 engine. A / L with four cylinders and pre-chamber Diesel injection, in particular to assess its ability to limit the formation of deposits on the injectors.

The test was carried out on a virgin diesel fuel of type B7 meeting the EN590 standard, additivated with a known detergency additive consisting of a quaternary ammonium salt obtained by reaction of propylene oxide with the product of the reaction of '' a polyisobutenyl succinic anhydride in which the polyisobutylene group (PIB) has a number-average molecular mass (Mn) of 1000 g / mol and dimethyl-aminopropylamine, at a treatment rate of 37.5 ppm by weight (37, 5 mg / kg). The diesel fuel thus supplemented is called G.

The test was carried out with gas oil G on the one hand, and with gas oil G supplemented with 20 ppm by weight of hexylene glycol on the other hand.

The test is started with a Peugeot XUD9 A / L four-cylinder diesel pre-chamber injection engine fitted with clean injectors, the flow rate of which has been determined beforehand. The engine follows a determined test cycle for 10 hours and 3 minutes (repeating the same cycle 134 times). At the end of the test, the flow rate of the injectors is evaluated again. The quantity of fuel required for the test is 60L. The flow loss is measured on the four injectors. The results are expressed as a percentage loss of flow for different needle lifts. Usually, the fouling values are compared with 0.1 mm needle lift because they are more discriminating and more precise and repeatable (repeatability <5%). The evolution of the loss of flow before / after the test makes it possible to deduce the loss of flow as a percentage. Taking into account the repeatability of the test, a significant detergent effect is affirmable for a reduction in flow loss, ie a gain in flow greater than 10 points (> 10%).

The results obtained are shown in Table 1 below: [Table 11

The above results show that the addition of hexylene glycol leads to significantly better detergency performance in terms of preventing clogging of engine injectors ("keep-clean" effect).

Example 2: "Clean up" type detergency tests in diesel fuel The following two consecutive phases were carried out, by reproducing for each phase the test method described in Example 1 above:

- Phase 1 of fouling (or "dirty up") with conventional diesel fuel type B7, compliant with standard EN 590 and containing no detergent additives. The loss of flow evaluated after this first phase is 80%.

- Phase 2 of cleaning (or "clean up") with the candidate fuel.

The test was carried out using gas oil G as a candidate fuel in phase 2 on the one hand, and gas oil G with an additive of 20 ppm in weight of hexylene glycol on the other hand, as described in Example 1 above.

The results obtained are shown in Table 2 below: [Table 21

The above results show that the addition of hexylene glycol leads to significantly better detergency performance in terms of reducing engine injector fouling ("clean up" effect).

Claims

1. Use, for improving the detergency properties of a liquid fuel composition comprising one or more detergency additives, of an additive consisting of one or more hydrocarbon compound (s) comprising from 2 to 10 carbon atoms. carbon and two hydroxyl functions.

2. Use according to the preceding claim, characterized in that said hydrocarbon compound has the formula C _n Hm _{+ i} Ch, with n an integer ranging from 2 to 10.

3. Use according to the preceding claim, characterized in that n ranges from 3 to 8, more preferably from 4 to 8; better still n denotes 5 or 6, and even more preferably n denotes 6.

4. Use according to the preceding claim, characterized in that said hydrocarbon compound is hexylene glycol.

5. Use according to any one of the preceding claims, characterized in that the hydrocarbon compound (s) are used at a total content ranging from 5 to 500 ppm by weight, preferably from 10 to 200 ppm by weight. weight, preferably from 10 to 100 ppm by weight, more preferably from 10 to 50 ppm by weight, more preferably from 20 to 50 ppm by weight, and better still from 20 to 40 ppm by weight, relative to the total weight of the fuel composition.

6. Use according to any one of the preceding claims, characterized in that the fuel composition is chosen from hydrocarbon fuels, non-essentially hydrocarbon fuels, and mixtures thereof.

7. Use according to any one of the preceding claims, characterized in that the fuel composition is chosen from gasolines and gas oils.

8. Use according to any one of the preceding claims, characterized in that the detergent additive (s) are chosen from the group consisting of amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines, polyetheramines, quaternary ammonium salts, triazole derivatives, and Mannich bases, preferably from Mannich bases, quaternary ammonium salts, and mono- polyisobutylene. or poly-amines (or PIB-amines), more preferably still from quaternary ammonium salts and better still from polyisobutylene succinimides functionalized with a quaternary ammonium group, amides of fatty acids functionalized with a quaternary ammonium group and their dimers such as di- (alkylamido-propyl-quaternary ammonium) compounds, and fatty-chain alkylamidoalkyl betaines.

9. Use according to any one of the preceding claims, characterized in that the total content of detergent additive (s) different from said hydrocarbon compounds in the fuel composition ranges from 5 to 5000 ppm by weight, preferably of 10 to 1000 ppm by weight, and more preferably 20 to 250 ppm by weight, relative to the total weight of the fuel composition.

10. Use according to any one of the preceding claims, characterized in that the ratio between the total weight content of hydrocarbon compound (s) on the one hand and the total weight content of detergent additive (s) on the other hand ranges from 1:50 to 1: 1, preferably from 1:20 to 1: 1, more preferably from 1:20 to 1: 2, and more preferably from 1:20 to 1: 3.

11. Use according to any one of the preceding claims, for limiting or preventing the formation of deposits in at least one of the internal parts of an internal combustion engine and / or for reducing the deposits existing in at least one of the internal parts of an internal combustion engine. internal combustion engine.

12. Use according to the preceding claim, characterized in that the internal combustion engine is a spark ignition engine or gasoline engine.

13. Use according to claim 1 1, characterized in that the internal combustion engine is a compression ignition engine or diesel engine.

14. A method of improving the cleanliness and / or cleaning of at least an internal part of an internal combustion engine supplied with a liquid fuel comprising one or more detergency additives, comprising adding to said fuel composition a additive consisting of at least one hydrocarbon compound as defined in any one of claims 1 to 4.