Aqueous compositions for treating exhaust gases having improved properties

Abstract

The present invention relates to a composition comprising a single aqueous liquid phase, which comprises at least one nitrogen oxide (NOx) reducing agent and / or at least one precursor of such an agent, and at least one additive selected from block copolymers consisting of one or more poly(ethylene oxide) blocks and one or more poly(propylene oxide) blocks, in a total content of 100 to 1500 ppm by weight, relative to the total weight of the composition. The present invention also relates to the use of such a composition for treating exhaust gases from an internal combustion engine, and to a method for treating exhaust gases from an internal combustion engine using this composition.

Description

[Technical Field]

[0001] The present invention relates to compositions for treating exhaust gases from the outlet of on-board or stationary combustion engines, whether the engines are engines for heavy vehicles such as trucks, transport vehicles, off-road vehicles, e.g. agricultural machinery, boats, etc., or engines for light vehicles and / or work vehicles, or even engines for stationary industrial use. The invention also relates to the use of such compositions in any exhaust treatment device, and to methods for treating exhaust gases using the compositions. [Background technology]

[0002] European standards regarding pollutants emitted by combustion engines, especially those powered by diesel-based fuels, especially those applicable to heavy vehicles, have led engine manufacturers to introduce exhaust gas aftertreatment systems. These systems include selective catalytic reduction (SCR), exhaust gas recirculation (EGR), diesel oxidation catalysts (DOC) or particulate filters (FAP), and SCRF® (SCR combined with FAP) technology. These different aftertreatment systems may be installed alone or in combination, since they do not necessarily act on the same pollutants present in the exhaust gases.

[0003] To meet standards, especially European standards (Euro IV and above for heavy vehicles and Euro 6 for light vehicles), the majority of European car manufacturers have opted for SCR exhaust aftertreatment for their engines. This aftertreatment is primarily effective in reducing the levels of nitrogen oxides in the gases. Another advantage of this technology is that with optimized engine tuning, it is possible to achieve a substantial reduction in fuel consumption, especially compared to other aftertreatment systems such as NOx traps.

[0004] SCR aftertreatment consists of reducing nitrogen oxides (NO and NO2) (referred to as NOx) in a catalytic device that contacts them with a reducing agent. This device typically includes a catalytic converter containing a support based on iron or copper-exchanged zeolite. This catalytic converter promotes the reduction of NOx to nitrogen by reaction with the reducing agent. A typical reducing agent is ammonia (NH3). To introduce gaseous ammonia into an exhaust gas treatment system, it is known to generate it directly in the duct that transports these gases to the SCR system by spraying an aqueous solution of a precursor of this reducing agent, such as urea. The urea solution, typically injected at average exhaust temperatures between 150 and 400 °C, releases ammonia as a result of successive thermal decomposition and hydrolysis reactions. Other ammonia precursor compounds may be used under similar conditions. An injector is typically used to introduce the urea solution into the upstream duct that transports the exhaust gas to the SCR catalytic converter. A mixer installed between the injector and the SCR catalytic converter can be used to improve the vaporization of the urea solution spray into the exhaust gas stream. An example of a mixer is described in the document SAE2015-01-1020 ("Advanced Close Coupled SCR Compact Mixer Architecture", Michelin J. et al.).

[0005] Two typical, but non-limiting, examples of SCR aftertreatment line configurations are described below. The first example, referred to as the "underfloor" configuration, involves placing the SCR aftertreatment device downstream of the engine under the vehicle floor (typically more than 50 cm to 1 m from the combustion chamber outlet). This has the advantage of placing the aftertreatment device in an area with a lot of available space, thus allowing for a more favorable geometric configuration for vaporizing the urea / water solution. Another configuration, referred to as the "direct-coupled" configuration, involves placing the SCR aftertreatment device very close to the engine (typically less than 50 cm from the combustion chamber outlet). Compared to the "underfloor" configuration, this configuration has the advantage of providing a higher temperature at the SCR catalytic converter, improving its priming and efficiency. However, the disadvantage is that the available space is smaller than in the "underfloor" configuration, which means that the injector for the urea / water solution must be positioned closer to the mixer and the SCR catalytic converter. This configuration may result in less effective vaporization of the urea / water solution. The documents SAE2014-01-1522 ("Control of a Combined SCR on Filter and Under-Floor SCR System for Low Emission Passenger Cars", Balland J. et al.) and SAE2015-01-0994 ("Next Generation All in One Close-Coupled Urea-SCR System", Kojima H. ​​et al.) or WO2014060987A1 also describe these two types of configurations.

[0006] In certain configurations of SCR device installation and ammonia precursor injection, particularly in the case of urea injection, manufacturers have noticed the appearance of deposits in the exhaust duct between the injector and the SCR device. These deposits can become large enough to cause partial or even complete blockage of the exhaust duct due to exhaust backpressure, resulting in a loss of engine power. In a constant injection configuration, the amount of deposits formed is greater at lower temperatures than at higher temperatures. According to an analysis conducted in technical publication SAE 2016-01-2327, these deposits actually vary depending on the temperature at which they form. Thus, at temperatures below 250-300°C, they consist primarily of crystallized urea, while above 300°C they consist primarily of cyanuric acid. Cyanuric acid can sublimate and regenerate ammonia gas. However, this reaction can only occur at extremely high temperatures above 450°C, temperatures rarely reached in exhaust ducts at present.

[0007] These deposits have been noted to be particularly prevalent in ducts with bends due to a lack of space in the vehicle, and when the distance between the urea injection and the first bend is too short, as in the "direct-coupled" configuration described above. The hypothesis is that in this type of configuration, some of the urea droplets do not have time to vaporize and completely decompose into gaseous ammonia. The urea droplets remain on the duct walls, which are too cold to allow complete decomposition into gaseous ammonia, so they only partially decompose, forming cyanuric acid deposits that adhere to the walls. It has also been found that, depending on the configuration and temperature of the SCR line, urea is prone to crystallization within the line, leading to line blockage (see SAE2017-26-0132 ("A Study on the Factors Affecting the Formation of Urea Crystals and Its Mitigation for SCR After-Treatment Systems"), Jain A. et al.).

[0008] Application WO 2008 / 125745 describes an aqueous solution comprising a compound capable of releasing gaseous ammonia above 200°C and at least one polyfunctional additive with an HLB in the range of 7 to 17, for limiting the formation of cyanuric acid-based deposits, in particular in exhaust gas aftertreatment devices of the SCR type. The polyfunctional additives used include, in particular, polyalkoxylated fatty alcohol ethers and polyalkoxylated fatty alcohol esters.

[0009] Application EP 2337625 describes a mixture of surfactants that can reduce the droplet size of aqueous urea solutions, thereby facilitating their evaporation and conversion to gaseous ammonia in SCR systems. The proposed solution consists of a mixture of polyalkoxylated fatty alcohols with a controlled degree of alkoxylation.

[0010] Application EP 2488283 describes additives for urea solutions of certain types of polyalkoxylated fatty alcohols. These additives are also intended to reduce the formation of deposits resulting from the decomposition of urea in SCR systems.

[0011] No. 5,453,257 teaches the reduction of nitrogen oxides in carbonaceous fuel combustion effluents by introducing into said effluent an emulsion of a nitrogen oxide reducing compound and a hydrocarbon compound having a boiling point lower than that of the nitrogen oxide reducing agent.

[0012] Furthermore, it has been found that the aqueous ammonia precursor solution containing surfactants tends to foam. This foaming occurs especially during the transportation and handling of the solution, for example, when it is lowered into a storage tank, and then when the composition is introduced from the storage tank into the tank of a vehicle, which can complicate the tank filling operation and cause overflow. The common use of a spray gun when dispensing the composition also promotes foaming. Furthermore, the foaming of the composition when sprayed into the exhaust gas treatment system of a vehicle can result in the introduction of more or less air into the system. This phenomenon disrupts the control of the amount of solution sprayed and affects the efficiency of the treatment system.

[0013] One solution to this problem is to add another antifoaming agent to the aqueous solution. However, such additives often become less effective the longer the composition is stored before use, especially if the composition is stored at relatively high temperatures above 30° C., or even above 35° C. or 40° C. Under such storage conditions, the composition generally cannot be maintained for more than a few months (5 months on average), which is very limiting. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] WO2014 / 060987 [Patent Document 2] WO2008 / 125745 [Patent Document 3] EP2337625 [Patent Document 4] EP2488283 [Patent Document 5] US5,453,257 [Non-patent literature]

[0015] [Non-Patent Document 1] SAE2015-01-1020 (“Advanced Close Coupled SCR Compact Mixer Architecture” Michelin J. et al.) [Non-patent document 2] SAE2014-01-1522 (“Control of a Combined SCR on Filter and Under-Floor SCR System for Low Emission Passenger Cars” Balland J. et al.) [Non-patent document 3] SAE2015-01-0994 (“Next Generation All in One Close-Coupled Urea-SCR System” Kojima H. ​​et al.) [Non-patent document 4] SAE2017-26-0132 (“A Study on the Factors Affecting the Formation of Urea Crystals and Its Mitigation for SCR After-Treatment Systems” Jain A. et al.) Summary of the Invention [Means for solving the problem]

[0016] Therefore, it is necessary to formulate a composition for treating exhaust gases in the form of an aqueous solution of a NOx reducing agent, such as ammonia, or a precursor of such a reducing agent, such as urea, with optimized properties. It is expected that this composition will minimize foaming while avoiding or reducing deposits when used in an SCR system. It is also expected that this composition will be stable over time, i.e., retain its properties over long storage periods, even at high temperatures.

[0017] Applicants have discovered that these objectives are achieved by adding to the aqueous composition at least one specific additive selected from poly(ethylene oxide) and poly(propylene oxide) block copolymers, as defined below.

[0018] An object of the present invention is therefore a composition comprising a single aqueous liquid phase, (1) at least one nitrogen oxide NOx reducing agent, and / or at least one precursor of such an agent; and (2) at least one additive selected from block copolymers formed by one or more poly(ethylene oxide) blocks and one or more poly(propylene oxide) blocks, in a total content of 100 to 1500 ppm by weight relative to the total weight of the composition; A composition comprising:

[0019] A further object of the present invention is the use of such a composition for treating exhaust gases from built-in or stationary internal combustion engines, more particularly for treating exhaust gases in devices for the selective catalytic reduction of nitrogen oxides.

[0020] The engine may in particular be selected from diesel engines, spark ignition engines (including gasoline engines for vehicles and CNG or natural gas engines), and engines with mixed carburetion, in particular gazole-gas. Preferably, the engine is a diesel engine.

[0021] The invention applies to any type of engine that emits nitrogen oxides, including self-contained and stationary engines, but also to marine engines, engines for heavy goods vehicles, transport vehicles, building site or agricultural machines, such as tractors, and engines for light vehicles and work vehicles, as well as engines used in stationary industrial applications.

[0022] Selective catalytic reduction systems for nitrogen oxides are known per se as selective catalytic reduction (SCR) systems. Such devices include a selective catalytic reduction (SCR) catalyst.

[0023] The present invention also relates to a method for treating exhaust gases from an internal combustion engine, preferably a diesel engine, equipped with a device for selective catalytic reduction of nitrogen oxides, characterized in that it comprises at least one step of introducing a composition as defined above into a duct that transfers the exhaust gases from the engine outlet to said selective catalytic reduction device.

[0024] In the following, the term "SCR exhaust line" or "SCR line", as known per se, is also used to refer to a duct that conveys exhaust gases from the engine outlet to a selective catalytic reduction device (SCR device).

[0025] The composition according to the present invention has many advantages. It can be used in the same manner and with the same equipment as prior art solutions. It is at least as effective, if not more effective, than prior art solutions, particularly urea-based solutions, for reducing or preventing deposit formation in SCR systems, particularly in so-called "direct-coupled" configurations. It causes little or no foaming during handling, use, movement, and / or transportation, such as decanting or filling operations into containers such as cans, vehicle tanks, storage tanks, or transport tanks. In particular, it prevents overflowing when filling vehicle storage tanks. It also allows for faster filling of storage tanks and vehicle tanks, with less shaking of the filling gun in the latter case.

[0026] This composition also allows for precise control of the amount of composition sprayed, avoiding false triggering, particularly related to foaming of the sensor.

[0027] The compositions according to the invention are stable during storage and maintain their anti-foaming properties over a wide storage temperature range of 5°C to 40°C and over time, particularly for periods of up to one year.

[0028] Further objects, features, aspects and advantages of the present invention will become more apparent from the following description and examples.

[0029] Secondly, and unless otherwise stated, particularly in the phrases "included between" and "ranging from... to...", the boundaries of a range of values ​​are included within that range.

[0030] Furthermore, as used herein, the terms "at least one" and "at least" are equivalent to the terms "one or more" and "more than," respectively.

[0031] Finally, as is known per se, C N A compound or group refers to a compound or group that contains N carbon atoms in its chemical structure. DETAILED DESCRIPTION OF THE INVENTION

[0032] Reducing agents and / or precursors of such agents The compositions used in the present invention include (1) at least one agent that reduces nitrogen oxides and / or at least one precursor of a nitrogen oxide reducing agent.

[0033] A "nitrogen oxide reducing agent" is defined as a compound that is capable of at least partially, if not completely, reducing nitrogen oxides (also called NOx to denote the compounds NO and NO2) to nitrogen under typical SCR line operating conditions, i.e., in the presence of an SCR catalytic converter, and at temperatures in the range of 150-400°C. Ammonia (NH3) is a particularly suitable NOx reducing agent.

[0034] A "NOx reducing agent precursor" is defined as a compound that is capable of releasing a NOx reducing agent under the influence of temperature and / or catalytic reaction.

[0035] Ammonia precursors include urea, which undergo successive pyrolysis and hydrolysis reactions to produce ammonia in a well-known process. The SCR exhaust line may include a catalytic converter upstream of the SCR catalyst system that converts the NOx reductant precursors into the NOx reductant, specifically gaseous ammonia.

[0036] Preferably, the reducing agent or precursor of the reducing agent is selected from the list consisting of urea, ammonia, formamide, ammonium salts, in particular ammonium formate, ammonium carbamate, and guanidine salts, in particular guanidine formate, preferably from the list consisting of urea and ammonia.

[0037] According to a preferred embodiment, urea, which is a precursor of the reducing agent, is used. Indeed, urea has the advantages of being stable, non-volatile, non-explosive, and non-flammable. Urea can be safely transported, stored, and handled by operators without any specific training.

[0038] In this embodiment, the composition preferably has a urea content ranging from 25% to 42% by weight, more preferably from 30% to 40% by weight, even more preferably from 31 to 35% by weight, and even better from 32% to 33% by weight, relative to the total weight of the composition. In a particularly preferred manner, the composition contains urea in a content of 32.5±0.7% by weight, in accordance with the ISO 22241-1 specification.

[0039] According to a particularly preferred variant of this embodiment, the aqueous solution according to the invention is prepared from the commercial product AdBlue®, which is a 32.5±0.7% by weight urea solution in water. The term AdBlue® is used in this specification to refer indistinguishably to the well-known commercial products with the following names: AdBlue®, DEF, AUS32, ARLA32. By extension, the term is also used to refer to all products within the AdBlue® range, including the product marketed as AUS40, which corresponds to an aqueous solution of approximately 40% by weight urea and is essentially intended for marine engines.

[0040] However, the present invention also encompasses the use of aqueous compositions containing urea at concentrations greater than 32.5%, which can then be diluted immediately prior to use. This variation can reduce the shipping costs of these urea-based compositions.

[0041] PEG and PPG block copolymers The composition according to the invention contains at least one additive (2) selected from block copolymers formed by at least one poly(ethylene oxide) block or EO block or PEG block in the case of polyethylene glycol, and at least one poly(propylene oxide) block or PO block or PPG block in the case of polypropylene glycol.

[0042] Preferably, the one or more copolymers (2) are triblock polymers poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) or poloxamers. These triblock polymers have the following formula (I): H(OCH2CH2) a (OCH(CH3)CH2) b (OCH2CH2) c OH (I) where a, b and c are integers strictly greater than 1.

[0043] Preferably, the triblock polymer is selected from the triblock polymers of the above formula (I) in which a is in the range of 2 to 15, b is in the range of 15 to 60, and c is in the range of 2 to 15. In a more preferred manner, a is in the range of 4 to 10, b is in the range of 20 to 40, and c is in the range of 4 to 10.

[0044] According to a preferred embodiment, said copolymer (2) is chosen from Poloxamer 182, ie a copolymer comprising 20% ​​by weight of ethylene oxide and 80% by weight of propylene oxide.

[0045] The copolymer (2) advantageously has a molar mass M ranging from 500 to 5000. N They also advantageously have a molar mass M between 1000 and 5000. W It has.

[0046] These compounds are now commercially available.

[0047] The copolymer (2) is present in a total amount of 100 to 1500 ppm by mass, preferably 200 to 1000 ppm by mass, more preferably 350 to 750 ppm by mass, based on the total mass of the composition.

[0048] Antifoaming Additives According to a preferred embodiment, the composition according to the invention further comprises one or more antifoam additives, preferably chosen from grafted polydimethylsiloxane polymers.

[0049] In a preferred manner, the one or more antifoam additives are selected from copolymers comprising a polydimethylsiloxane backbone having an average number of dimethylsiloxane units in the range of 150 to 300 grafted with polyoxyalkylene chains.

[0050] These copolymers are therefore graft polymers having a polydimethylsiloxane backbone and side chain (or graft) polyoxyalkylenes grafted onto the backbone.

[0051] The backbone of these polymers is a polydimethylsiloxane chain (also commonly referred to as PDMS), i.e., a polymer with the formula -[Si(CH3)2-O] n - (n is a number in the range of 150 to 300) chains.

[0052] Preferably, the polydimethylsiloxane backbone comprises an average number of dimethylsiloxane units in the range of 180 to 250. This corresponds to a value of the number n in the range of 180 to 250.

[0053] The polyoxyalkylene chains grafted onto the polydimethylsiloxane backbone are advantageously of formula -(RO) m - (wherein R represents one or more branched or linear C1-C4 alkylene groups, preferably C2 or C3, and m is a number ranging from 10 to 55).

[0054] Preferably, the average number m of oxyalkylene units is in the range of 20-50, more preferably 30-50.

[0055] Also in a preferred manner, R represents one or more C2 and / or C3 alkylene groups, and in a more preferred manner the polyoxyalkylene chain has the formula -(CH2-CH2-O) m -polyoxyethylene (EO), of the formula -(CH2-CH(CH2)-O) m - polyoxypropopylenes (PO), and chains formed from oxyethylene and oxypropylene units (EO / PO).

[0056] According to a particularly preferred embodiment, the polyoxyalkylene chains are formed by oxyethylene units (EO) and oxypropylene units (PO). Preferably, the ratio of the average number of EO units to the average number of PO units is in the range of 0.2 to 2, preferably 0.3 to 1.3. Preferably, these chains are formed by polyoxyethylene blocks and polyoxypropylene blocks.

[0057] The graft ratio of the copolymer (ie the number-average proportion of dimethylsiloxane units carrying polyoxyalkylene side chains) is advantageously in the range of 0.5% to 5%, preferably 1% to 2%.

[0058] Unless otherwise stated, all averages referred to herein are number averages.

[0059] According to a preferred embodiment, the copolymers that make up the antifoam additive are crosslinked, such crosslinking giving them a three-dimensional structure.

[0060] The antifoam additive(s) may advantageously be present in a total content ranging from 1 to 200 ppm by weight relative to the total weight of the composition, preferably from 2 to 100 ppm by weight, more preferably from 5 to 50 ppm by weight, even more preferably from 5 to 25 ppm by weight and most preferably from 5 to 15 ppm by weight.

[0061] The copolymers mentioned above are known per se and commercially available.

[0062] In commercial products, these copolymers may be present in diluted form, especially in mixtures containing them.

[0063] In this case, the copolymer content of such a mixture is generally in the range of 10 to 80% by weight, preferably 20 to 60% by weight, more preferably 30 to 50% by weight, even more preferably 35 to 45% by weight.

[0064] Thus, according to one embodiment, one or more antifoam additives are used in a mixture with an inorganic oxide, such as solid hydrophobic silica.

[0065] According to another embodiment, one or more antifoam additives are used in a mixture with one or more emulsifiers, which may in particular be chosen from the above-mentioned polyoxyalkylene polymers, more preferably from EO / PO copolymers, which generally come from copolymer synthesis and correspond to the proportion of polyoxyalkylene chains not grafted onto the polydimethylsiloxane backbone.

[0066] According to a particularly preferred embodiment, one or more antifoam additives are used in a mixture with an inorganic oxide and an emulsifier, such as in particular hydrophobic silica, and one or more polyoxyalkylene polymers as described above.

[0067] Commercially available products containing one or more antifoam additives may in particular be in the form of an anhydrous (i.e. water-free) solid product or in the form of a solution in a solvent, which may be water or an organic solvent.

[0068] Additional surfactants The composition according to the invention may also comprise one or more surfactants different from the above-mentioned PEG and PPG block copolymers, which may in particular be chosen from water-soluble ionic, non-ionic or amphoteric surfactants.

[0069] Ionic surfactants can be selected from cationic surfactants and anionic surfactants, preferably cationic surfactants. The latter generally contain ionizable nitrogen-containing groups in cationic or cationic form. In particular, they can be selected from linear alkylamines and alkylammoniums, linear diamines, aromatic or saturated heterocycles containing one or more nitrogen atoms, imidazole-type cyclic compounds, etheramines and etheramides, oxyamines, and ethoxyamines, either alone or in mixtures.

[0070] The amphoteric surfactants may in particular be chosen from amino acids and their imide or amide derivatives, alone or in mixtures.

[0071] The nonionic surfactant is preferably chosen from the following compounds: a) hydrocarbyl and monopolyalkylene glycol ethers; b) hydrocarbyl and polyol ethers; c) mono- or polyalkylene glycol fatty acid esters; d) mono- or polyglycerol fatty acid esters, and e) Mixtures of these compounds.

[0072] "Hydrocarbyl" refers to a group selected from alkyl, alkenyl, alkynyl, aryl, aryl-alkyl or "aralkyl", advantageously the hydrocarbyl is C1-C 50 It is the base.

[0073] "C i ~C j "Alkyl" refers to a saturated, straight, branched, or cyclic hydrocarbon chain containing i to j carbon atoms.

[0074] "C x ~C y "Alkenyl" refers to a straight, branched or cyclic hydrocarbon chain containing at least one carbon-carbon double bond and x to y carbon atoms.

[0075] "C x ~C y "Alkynyl" refers to a straight, branched or cyclic hydrocarbon chain containing at least one carbon-carbon triple bond and x to y carbon atoms.

[0076] "C x ~C y "Aryl" refers to a functional group derived from an aromatic hydrocarbon compound containing x to y carbon atoms. The functional group may be monocyclic or polycyclic. Examples include C6 to C 18 Aryl can be phenyl, naphthalene, anthracene, phenanthrene and tetracene.

[0077] "C x ~C y "Aralkyl" refers to an aromatic hydrocarbon compound, preferably monocyclic, substituted with at least one linear or branched alkyl chain, wherein the total number of carbon atoms in the aromatic ring and its substituents ranges from x to y carbon atoms. Illustrative examples include C7 to C8. 18 Aralkyl may be selected from the group formed by benzyl, tolyl and xylyl.

[0078] For the purposes of the present invention, polyol is understood to mean an oxygenated hydrocarbon compound containing at least two alcohol functional groups, which may optionally contain one or more other oxygenated functional groups, such as acetal functional groups, ether bridges or ester groups.

[0079] The term "fatty acid" refers to any straight-chain or branched C4-C 30 , preferably C8 to C30 alkyl or alkenyl chains.

[0080] a) Hydrocarbyl and mono- or polyalkylene glycol ethers The hydrocarbyl and mono- or polyalkylene glycol ethers may be mono- or diethers, depending on whether the polyalkylene glycol chain is substituted at one or both ends with a hydrocarbyl group.

[0081] The hydrocarbyl mono- or polyalkylene glycol ether is advantageously a C1-C 50 It is selected from those containing a hydrocarbyl group and 1 to 60 alkylene glycol units.

[0082] The hydrocarbyl and mono- or polyalkylene glycol ethers are more preferably chosen from the following compounds: Formula (I): R-(Y) n -OH mono- or polyalkoxylated hydrocarbyl monoethers; Formula (II): R-(Y) m -OR' mono- or polyalkoxylated hydrocarbyl diethers; Formula (III): HO-(Y) n -R”-(Y’) m -OH mono- or polyalkoxylated hydrocarbyl diethers; - and mixtures of these compounds.

[0083] In the above formulas (I) to (III), R and R' are independently C3 to C 40 R" represents an alkyl, alkenyl, alkynyl, aryl or aralkyl group, and R" is a C3-C 40 Represents an alkanediyl or alkenediyl or alkynediyl or diradical aryl or diradical aralkyl group.

[0084] For ease of explanation, the same designations of alkyl or alkenyl or alkynyl or aryl or aralkyl groups are used for the monoradicals (R, R') and the diradical (R").

[0085] In the above formulas (I) to (III), Y and Y' are groups independently selected from the following groups: -(O-CH2-CH2)-, -(O-CH(CH3)-CH2)-, and -(O-CH2-CH2-CH2)-.

[0086] In the same compound of formula (I), (II) or (III), the groups Y, Y' may each be all the same or different. For example, -(Y) n - may represent a copolymer having ethylene oxide and propylene oxide units, such as a block copolymer.

[0087] Preferably, in formulas (I) to (III), the groups Y and Y' are all the same.

[0088] In a more preferred manner, in formulae (I) to (III), the groups Y, Y' are each all ethylene oxide of formula -(O-CH2-CH2)-.

[0089] In the above formulas (I) to (III), n and m represent the degree of alkoxylation of the molecule and independently represent integers ranging from 1 to 60, advantageously from 1 to 30, and more advantageously from 1 to 20. More preferably, n and m range from 3 to 15, more preferably from 5 to 12.

[0090] Advantageously, in formula (III), the groups Y and Y' represent -(O-CH2-CH2)-, with n=m.

[0091] According to a first embodiment, in formulae (I), (II) and (III), R, R' and R" are advantageously chosen from linear or branched, preferably linear, alkyl and alkenyl groups.

[0092] Even more advantageously, R, R' and R" are C5 to C 32 Alkyl groups, more preferably C8 to C 30 The alkyl group is selected from the group consisting of:

[0093] The compounds of formula (I) may in particular be chosen from linear or branched polyalkoxylated fatty alcohols containing 4 to 30 carbon atoms, preferably 8 to 30 carbon atoms, more preferably 10 to 24 carbon atoms; and 5 to 12 ethylene oxide and / or propylene oxide units, preferably ethylene oxide units.

[0094] Commercially available compounds of formula (I) include products within the Marlipal® range and products within the Surfaline® range.

[0095] According to a second embodiment, in formulas (I), (II) and (III), R, R' and R" are C4 to C 50 alkynyl.

[0096] Advantageously, this embodiment is such that R″ is C4 to C 50 With respect to formula (III) which is alkynyl.

[0097] For example, according to this embodiment, the compound of formula (III) may be represented by the following formula (IV):

[0098] [ka] (In the formula, R1, R2, R3, and R4 are each independently H or C1 to C 20represents an alkyl group, and x and y each independently represent an integer ranging from 1 to 60, preferably from 1 to 30).

[0099] An example of a commercially available product corresponding to this formula is Surfynol 104® marketed by Air Products.

[0100] According to a third embodiment, in formulae (I), (II) and (III), R, R' and R" are selected from aralkyl groups containing from 9 to 30 carbon atoms.

[0101] Preferably, this embodiment relates to formula (I) in which R represents a group selected from aralkyl containing from 9 to 30 carbon atoms.

[0102] In a more preferred embodiment, R is C1 to C 24 , more preferably C3 to C 20 , and even more preferably C5 to C 18 The alkyl group is selected from para-alkylphenyl.

[0103] According to this embodiment, the compound of formula (I) has the following formula (V):

[0104] [ka] (Wherein R5 is C1 to C 24 , preferably C3 to C 20 , more preferably C5 to C 18 represents an alkyl group, and x represents an integer ranging from 1 to 50, preferably from 1 to 30).

[0105] An example of such a compound is the product Dynol 800® sold by Air Products, which corresponds to the following formula:

[0106] [ka]

[0107] The compound of formula (I) may advantageously be a mixture obtained by reacting an alcohol R—OH with n units of ethylene oxide and / or propylene oxide, n representing the number of moles of alkylene oxide reacted with one mole of alcohol R—OH.

[0108] The compound of formula (II) may advantageously be a mixture obtained by reacting an alcohol compound R—OH with m units of ethylene oxide and / or propylene oxide, followed by an etherification reaction with an alcohol compound R′—OH, m representing the number of moles of alkylene oxide reacted with one mole of alcohol R—OH.

[0109] The compounds of formula (III) can advantageously be obtained by reacting a diol HO-R"OH with (n+m) units of ethylene oxide and / or propylene oxide. Advantageously, in formula (III), n=m. (m+n) represents the number of moles of alkylene oxide reacted with one mole of diol HO-R"-OH.

[0110] The compounds of formulae (I), (II) and (III) are generally in the form of mixtures of compounds with different degrees of alkoxylation.

[0111] b) Hydrocarbyl and Polyol Ethers The hydrocarbyl and polyol ethers are advantageously C1-C 50 , preferably C3 to C 40 , more advantageously C5~C 32 , and even more advantageously C8 to C 30 It is selected from alcohols containing alkyl or alkenyl groups and ethers obtained from polyols.

[0112] The polyols referred to herein are distinct from mono- and polyalkylene glycols.

[0113] Advantageously, according to a first variant, the polyol is chosen from compounds belonging to the carbohydrate family and their oligomers. In particular, the polyol is chosen from cyclic carbohydrate compounds, such as glucopyranose oligomers. The invention particularly relates to hydrocarbyl ethers and cyclic polyglucoside ethers.

[0114] Examples of hydrocarbyl and cyclic polyglucoside ethers include alkyl polyglucosides, such as the product sold under the name Triton CG650® by Dow Chemical Company.

[0115] Advantageously, according to a second variant, the polyol is glycerol or a glycerol oligomer, for example an oligomer comprising between 2 and 30 glycerol units, preferably between 3 and 20 glycerol units.

[0116] c) mono- or polyalkylene glycol fatty acid ester Mono- or polyalkylene glycol fatty acid esters are molecules resulting from the condensation of at least one fatty acid with 1 to 60 units of alkylene glycol, preferably 1 to 50 units of alkylene glycol. Advantageously, they are obtained from the reaction of a fatty acid with 1 to 50 units of ethylene glycol.

[0117] Fatty acids are generally molecules containing an alkyl or alkenyl chain terminated in a carboxylic acid functionality and containing from 4 to 30 carbon atoms, preferably from 8 to 30 carbon atoms, and more advantageously from 8 to 24 carbon atoms.

[0118] The fatty acid group may be a single molecule or a mixture corresponding to the distribution of fatty acids in animal or vegetable oils.

[0119] Fatty acids include, but are not limited to, saturated fatty acids such as n-caproic acid, caprylic acid, n-capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, arachidic acid, or unsaturated fatty acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, or docosahexaenoic acid.

[0120] The fatty acid mono- or polyalkylene glycol ester advantageously comprises from 3 to 50, even more preferably from 5 to 40, alkylene oxide units. Preferably, the ester of fatty acid and mono- or polyalkylene glycol comprises from 3 to 50, advantageously from 5 to 40, ethylene oxide units.

[0121] Examples of esters of fatty acids and polyalkylene glycols include DUB S PEG 30S (PEG-30 stearate) sold by Stearinerie Dubois.

[0122] d) Mono- or polyglycerol fatty acid esters Mono- or polyglycerol fatty acid esters are molecules resulting from the condensation of at least one fatty acid with 1 to 60 alkylene glycol units, preferably 1 to 50 glycerol units.

[0123] The fatty acids are the same as those described in point c) above.

[0124] The fatty acid mono- or polyglycerol ester advantageously comprises between 3 and 50, more preferably between 5 and 40, glycerol units.

[0125] Examples of polyglycerol fatty acid esters include Polyaldo 10-1-0 KFG® (polyglycerol laurate) sold by the company LONZA.

[0126] According to a preferred embodiment, the surfactant or surfactants are selected from non-ionic surfactants, in particular from hydrocarbyl mono- or polyalkylene glycol ethers, more preferably those of formula (I): R-(Y) n -OH (Wherein, R is C3 to C 40 , preferably C8 to C 30 , and even more preferably C 10 ~C 24 represents an alkyl, alkenyl or alkynyl group, Y is selected from —(O—CH—CH)—, —(O—CH(CH)—CH)— and —(O—CH—CH—CH)—, preferably Y represents —(O—CH—CH)—, It is preferred to use one or more surfactants selected from mono- or polyalkoxylated hydrocarbyl monoethers (where n is an integer in the range of 1 to 60, preferably 1 to 30, more preferably 1 to 20, even more preferably 3 to 15, and even more preferably 5 to 12).

[0127] According to a preferred embodiment, the composition further comprises at least one additional surfactant selected from polyalkoxylated linear or branched fatty alcohols containing 4 to 30 carbon atoms, preferably 8 to 30 carbon atoms, preferably 10 to 24 carbon atoms; and 5 to 12 ethylene oxide and / or propylene oxide units, preferably ethylene oxide.

[0128] When present, the total content of additional surfactants may range from 5 to 1000 ppm by weight, preferably from 10 to 500 ppm by weight, more preferably from 50 to 150 ppm by weight, relative to the total weight of the composition.

[0129] Other constituents The aqueous composition may optionally contain one or more other compounds in addition to the nitrogen oxide reducing agent and its precursor, the PEG and PPG block copolymer, the antifoam additive, and the additional surfactants described above.

[0130] The composition may also include, but is not limited to, one or more water-miscible organic fluids, such as alcohols, polyols, and / or one or more metal compounds.

[0131] According to a preferred embodiment, the composition according to the invention does not contain paraffins. n H 2n+2 where n is an integer ranging from 2 to 50, preferably from 6 to 40, and more preferably from 18 to 35. Free from paraffins means that the composition does not contain intentionally added paraffins. Thus, if such paraffins are present in the composition, they are considered as impurities, and their content is less than 80 ppm by mass, preferably less than 50 ppm by mass, advantageously less than 20 ppm by mass, and more advantageously less than 10 ppm by mass, relative to the total mass of the composition.

[0132] According to a preferred embodiment, the composition according to the invention does not comprise one or more metal compounds.

[0133] A metal compound is defined as any organic or inorganic compound containing one or more metals. These compounds may be ionic or non-ionic. Specifically, the composition does not contain any organometallic or inorganic metal compounds, whether ionic or non-ionic.

[0134] Examples of ionic compounds excluded by this embodiment are, in particular, compounds containing one or more metals selected from the following metals: Fe, Cu, Ni, Co, Zn, Mn, Mg, Ti, V, Sr, Pt, Ce, Ca, Li, Na, and Nb.

[0135] "Free of metal compounds" means that the composition does not contain any such intentionally added compounds. Thus, if such compounds are present in the composition, they are considered as impurities, and the content of each metal element contributed by said one or more metal compounds is less than 1 ppm by weight, in particular less than 0.5 ppm by weight, relative to the total weight of the composition.

[0136] Compositions and embodiments thereof The composition used in the present invention is a composition containing a single liquid phase having aqueous properties. In other words, this composition contains a single liquid phase whose main component is water. The content of water in the composition is preferably within the range of 50 to 90% by mass, preferably 60 to 80% by mass, more preferably 65 to 70% by mass, based on the total mass of the composition.

[0137] The composition according to the invention does not contain any liquid phase other than the aqueous phase mentioned above, in particular the composition does not contain any hydrocarbon liquid phase, including in dispersed form (oil-in-water emulsion).

[0138] The liquid phase is at 25°C and atmospheric pressure (1.013 × 10 5 It is a phase that is in a liquid state at temperatures below 100 Pa.

[0139] Water insoluble means that the water content is less than 1.013 × 10 5 This indicates that the amount of phase that is water soluble at 2% by weight, preferably less than 1% by weight, and even more preferably less than 0.5% by weight (at 250°C / Pa) is water soluble.

[0140] In particular, the composition according to the invention is not in the form of an emulsion, which, as is known, is defined as a composition comprising at least two liquid phases, one of the phases dispersed in the other in the form of droplets.

[0141] The composition may be prepared in the usual manner by mixing its constituents, preferably at ambient temperature, typically within the temperature range of 10 to 60°C.

[0142] According to a preferred embodiment, the aqueous composition is prepared from a pre-formulated aqueous solution of urea, such as the commercially available composition known as AdBlue®, which contains 32.5% urea by weight.

[0143] A first embodiment consists in adding one or more block copolymers (2) and, optionally, one or more antifoam additives to this pre-formulated aqueous urea solution in the amount necessary to achieve the content defined above.

[0144] A second embodiment consists in adding a concentrated aqueous urea composition to this pre-prepared aqueous urea solution. According to this embodiment, the concentrated aqueous urea additive composition comprises one or more block copolymers (2)(2) and optionally one or more antifoam additives in an aqueous solution of urea at a content much higher than that of the final aqueous composition introduced into the SCR line, preferably at a content of 32.5% by mass urea. The two compositions are mixed in a suitable ratio to obtain the desired final content just before injection into the SCR line.

[0145] The same embodiment can be carried out using pre-prepared aqueous solutions of precursors other than urea.

[0146] use The aqueous composition according to the present invention is used to treat exhaust gases emitted from an internal combustion engine in a selective catalytic reduction (SCR) system of nitrogen oxides.

[0147] For this purpose, the aqueous composition is introduced into the SCT exhaust line downstream of the engine and upstream of the SCR device. This introduction is typically achieved by pumping the composition from one or more tanks and injecting it through one or more injectors that spray the composition into the exhaust gas stream. These devices are known per se.

[0148] The use according to the invention may also prevent or reduce deposits in the ducts transporting exhaust gases from the outlet of the internal combustion engine towards said selective catalytic reduction device.

[0149] These deposits are typically deposits of nitrogen compounds containing one or more nitrogen oxide reducing agents and / or one or more precursors thereof, and / or decomposition products of said precursors. In particular, the present invention can prevent and / or reduce the deposits of urea and / or cyanuric acid, more preferably the deposits of cyanuric acid, in the SCR exhaust duct.

[0150] As indicated above, the present invention can reduce or avoid these deposits regardless of the SCR line, and is particularly well suited to, but not limited to, the aforementioned "direct-coupled" and "underfloor" SCR exhaust lines.

[0151] In particular, the present invention makes it possible to reduce such deposits while avoiding foaming of the composition.

[0152] As mentioned above, the composition injected into the SCR line is pumped from one or more conventional storage tanks known per se.

[0153] According to a first variant, all of the components of the composition according to the invention, in particular the one or more nitrogen oxide reducing agents and / or one or more precursors thereof (1), the one or more block copolymers (2) and optionally the one or more antifoam additives, are formulated in the same aqueous composition in the desired contents and this composition is introduced into a single tank.

[0154] According to a second variant, a first intermediate aqueous composition containing one or more nitrogen oxide reducing agents and / or one or more precursors thereof (1) is prepared in the amount desired in the final composition resulting from the mixing of the two intermediate compositions. This first intermediate composition is introduced into the first tank. A second additive-enriched aqueous intermediate composition is also prepared, containing one or more nitrogen oxide reducing agents and / or one or more precursors thereof (1) in the amount desired in the final composition resulting from the mixing of the two intermediate compositions, and containing the block copolymer (2) and optional one or more antifoam additives in a more concentrated amount than the amount desired in the final composition.

[0155] This second composition is introduced into a second tank separate from the first tank. The two tanks feed a single injection system, allowing mixing of the two intermediate compositions. A vehicle equipped with two tanks for implementing this variant is described, inter alia, in EP 2541012.

[0156] method The method according to the invention allows the treatment of exhaust gases of an internal combustion engine, preferably a diesel engine, equipped with an SCR system.

[0157] The method includes introducing the aqueous composition described above into a duct that transports exhaust gases emitted from an engine to a device for selective catalytic reduction of nitrogen oxides, which introduction is typically accomplished by pumping the composition from one or more tanks and injecting it into the duct using one or more injectors, as described above.

[0158] The following examples are provided for the purpose of illustrating the present invention and should not be construed as limiting its scope. [Example]

[0159] Compositions tested: A commercially available 32.5% by weight urea solution in water of AdBlue® according to standard ISO 22241 was used as the base composition. This base composition is called C0.

[0160] The following additives were added: - A1: Poloxamer 182; - A2: Polyethoxylated fatty alcohol (trideceth-8); A3: crosslinked copolymer comprising a PDMS backbone with an average number of 200 dimethylsiloxane units, grafted with chains formed by polyoxyethylene and polyoxypropylene blocks, with an average number of OE units=16 and an average number of OP units=30; grafting rate 1.57%; this copolymer is in the form of a mixture that also contains hydrophobic silica and an OE / OP copolymer, and comprises 40% by weight of said copolymer.

[0161] Additive compositions C1 to C3 were prepared by adding to composition C0 the additives defined above in the amounts detailed in Table 1 below (the amounts being expressed as the mass of active material relative to the total mass of the composition).

[0162] [Table 1]

[0163] Tests to determine the amount of sediment The deposit reduction capabilities of additive compositions C1-C3 were evaluated in comparison with reference composition C0 using an ECTO-Lab™ system (Exhaust Composition Transient Operation Laboratory™). These tests were performed in the laboratory of the Southwest Research Institute (SwRI, San Antonio, Texas, USA). The system also contained a diesel oxidation catalyst / diesel particulate filter (DOC / DPF) upstream of the injector to remove soot from the exhaust gas. Bosch Denoxtronix 2.2 injectors were used. A static mixer was installed 5 cm after the injector. At the end of the test, the mass of deposits in the mixer and in the bend located after the mixer were quantified.

[0164] The test conditions were as follows: - Injector pressure: 8 bar; - injection flow rate of the composition: 920 g / h; - air flow rate 660 kg / h; - Exam duration: 1 hour; - Exhaust gas temperature at the injector: 180-215°C.

[0165] The results obtained are detailed in Table 2 below.

[0166] [Table 2]

[0167] These results demonstrate that compositions according to the present invention can provide a substantial reduction in deposits formed by crystallization and / or incomplete decomposition of urea in SCR systems.

[0168] Foaming test: The foaming levels of these different compositions were determined using a DFA100 foaming bench marketed by Kruss.

[0169] In this system, foaming is generated by an upward flow of air introduced through a sintered glass column located at the bottom of the column containing the composition to be tested. The device allows direct reading of the volume of foam formed as a function of time.

[0170] Measurements were taken at ambient temperature (25°C) at each time point after a 30-second injection of air at a flow rate of 0.3 L / min. The volume of composition introduced into the column for each test was 40 ml. The foam volume was measured 50 seconds after the start of the test.

[0171] Each composition was tested immediately after its preparation.

[0172] The results obtained are detailed in Table 3 below.

[0173] [Table 3]

[0174] The above results show that compositions C2 and C3 can also substantially reduce foaming.

Claims

1. 1. A composition comprising a single aqueous liquid phase, (1) at least one nitrogen oxide reducing agent, and / or at least one precursor of such an agent; and (2) at least one additive selected from block copolymers consisting of one or more poly(ethylene oxide) blocks and one or more poly(propylene oxide) blocks, in a total content of 100 to 1500 ppm by weight relative to the total weight of the composition; A composition comprising:

2. 2. The composition according to claim 1, characterized in that the reducing agent or precursor of the reducing agent (1) is selected from the list comprising urea, ammonia, formamide, ammonium salts and guanidine salts, preferably from the list comprising urea and ammonia, more preferably the precursor of the reducing agent is urea.

3. 3. Composition according to claim 1 or 2, characterized in that it contains urea in a content ranging from 25% to 42% by weight, preferably from 30% to 40% by weight, more preferably from 31 to 35% by weight, even better still from 32% to 33% by weight, and even more preferably 32.5±0.7% by weight relative to the total weight of the composition.

4. 4. The composition according to claim 1, wherein the copolymer(s) (2) are poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock polymers or poloxamers.

5. The one or more copolymers (2) are represented by the following formula (I): H(OCH) ２ CH ２ ) ａ (OCH(CH ３ )CH ２ ) ｂ (OCH) ２ CH ２ ) ｃ OH (I) (In the formula, a is in the range from 2 to 15, b is in the range from 15 to 60 and c is in the range from 2 to 15; preferably, a is in the range of 4 to 10, b is in the range of 20 to 40, and c is in the range of 4 to 10.

5. The composition according to claim 1, wherein the polymer is a triblock polymer corresponding to:

6. 6. The composition according to claim 5, characterized in that the copolymer(s) (2) are / are chosen from Poloxamer 182.

7. 7. Composition according to any one of claims 1 to 6, characterized in that the copolymer(s) (2) are present in a total content of from 200 to 1000 ppm by weight, preferably from 350 to 750 ppm by weight, relative to the total weight of the composition.

8. 8. The composition according to claim 1, further comprising one or more antifoam additives, preferably chosen from grafted polydimethylsiloxane polymers, more preferably from copolymers comprising a polydimethylsiloxane backbone having an average number of dimethylsiloxane units in the range of 150 to 300, grafted with polyoxyalkylene chains.

9. 9. The composition of claim 8, wherein the polydimethylsiloxane backbone of the copolymer contains an average number of dimethylsiloxane units in the range of 180 to 250.

10. The polyoxyalkylene chains grafted onto the polydimethylsiloxane backbone of the copolymer have the formula -(RO) ｍ 10. Composition according to claim 8 or 9, which corresponds to the formula: wherein R represents one or more C1-C4 alkylene groups and m represents a number in the range from 10 to 55, and preferably the polyoxyalkylene chain is chosen from polyoxyethylene (EO), polyoxypropylene (PO) and chains formed from oxyethylene and oxypropylene units (EO / PO), even more preferably from chains formed by oxyethylene (EO) and oxypropylene units (PO), preferably with a ratio of the average number of EO units to the average number of PO units in the range from 0.2 to 2, more preferably from 0.3 to 1.

3.

11. 11. The composition according to any one of claims 8 to 10, characterized in that the one or more antifoam additives are provided in a total content ranging from 1 to 200 ppm by weight, preferably from 2 to 100 ppm by weight, more preferably from 5 to 50 ppm by weight, even more preferably from 5 to 25 ppm by weight, and most preferably from 5 to 15 ppm by weight relative to the total weight of the composition.

12. 12. Composition according to any one of claims 1 to 11, characterized in that it is free of paraffin.

13. 13. Use of a composition according to any one of claims 1 to 12 for treating exhaust gases from on-board or stationary internal combustion engines.

14. 13. Use of a composition according to any one of claims 1 to 12 for preventing or reducing deposits in a duct transporting exhaust gases from the outlet of an internal combustion engine to a device for selective catalytic reduction of nitrogen oxides.

15. 13. A method for treating exhaust gases from an internal combustion engine equipped with a device for selective catalytic reduction of nitrogen oxides, characterized in that it comprises at least one step of introducing a composition according to any one of claims 1 to 12 into a duct which transports the exhaust gases from the outlet of the engine to said device for selective catalytic reduction.

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