Aqueous composition having improved properties for treating exhaust gas

Abstract

The present invention relates to a paraffin-free aqueous composition comprising 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 polyoxyethylenated monoesters of fatty acids and sorbitan containing 12 to 22 carbon atoms in a total content of 10 to 1,500 weight ppm based on the total weight of the composition. The present invention also relates to the use of such a composition for treating exhaust gases at the outlet of an internal combustion engine, and to a method for treating exhaust gases of an internal combustion engine using said composition.

Description

Technical Field

[0001] The present invention relates to a composition for treating exhaust gases at the outlet of a mounted (embarques) or stationary (stationnaires) heat engine, the engine being a large vehicle, such as a heavy goods vehicle, a transport vehicle, a so-called "off-road" vehicle, such as an agricultural machine, an engine for a boat, or an engine for a small vehicle and / or a multi-purpose vehicle, or an engine for stationary industrial use, regardless of which. The present invention also relates to the use of such a composition in any device for treating exhaust gases, and to a method for treating exhaust gases by implementing this composition.

Background Art

[0002] Due to European standards regarding pollutants emitted by heat engines, particularly those supplied with diesel fuel, and in particular the standards applicable to heavy goods vehicles, engine manufacturers have been required to place after-treatment systems for exhaust gases. These systems include SCR (Selective Catalytic Reduction), EGR (Exhaust Gas Recirculation), DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter), and SCRF (registered trademark) (a combination of SCR and DPF) technologies. These various after-treatment systems can be installed alone or in combination, provided that they do not necessarily act on the same pollutants present in the exhaust gases.

[0003] To comply with standards, particularly European standards (Euro IV and later for heavy goods vehicles and Euro 6 for small vehicles), most European vehicle manufacturers have adopted SCR after-treatment at the exhaust outlet of vehicle engines. This after-treatment acts exclusively on the reduction of nitrogen oxides present in the gas. Another advantage of this technology is that by optimizing the engine settings, it is possible to substantially reduce fuel consumption, particularly compared to other after-treatment systems such as NOx traps.

[0004] SCR post-treatment is a catalytic device that can bring nitrogen oxides NO and NO2 (generally referred to as NOx) into contact with a reducing agent, and aims to reduce these nitrogen oxides. This device contains a catalyst that generally has a carrier based on zeolite exchanged with iron or copper. This catalyst promotes the reduction of NOx to nitrogen by reaction with the reducing agent. For example, a conventional reducing agent is ammonia (NH3). In order to introduce gaseous ammonia into the exhaust gas treatment system, it is known to directly generate gaseous ammonia by vaporizing an aqueous solution of a precursor of this reducing agent, such as urea, in a pipe that transports these gases to the SCR system. Urea solution injected at an average exhaust temperature generally of 150 to 400 °C releases ammonia by continuous thermal decomposition and hydrolysis reactions. Under similar conditions, other ammonia precursor compounds can also be used. The injection device is usually used to introduce an aqueous urea solution into the pipe that transports the exhaust gas upstream of the SCR catalyst. A mixer or blender installed between this injection device and the SCR catalyst can be used to improve the vaporization of the aqueous urea solution spray in 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 non-limiting conventional examples of the configuration of the SCR aftertreatment line are described below. The first configuration is the so-called "underfloor" or "underfloor type" configuration, which places the SCR aftertreatment device downstream of the engine and under the vehicle floor (generally more than 50 cm at 1 m from the outlet of the combustion chamber). This configuration has the advantage that the aftertreatment device can be installed in an area where sufficient space is available, and thus can be arranged under more favorable geometric conditions for the vaporization of the aqueous urea solution. Another so-called "close-coupled" configuration places the SCR aftertreatment device very close to the engine (generally less than 50 cm from the outlet of the combustion chamber). This configuration has the advantage that the temperature of the SCR catalyst is higher compared to the so-called "underfloor" configuration, resulting in improved priming and its efficiency. On the other hand, its disadvantage is that the available space is smaller than that of the "underfloor" configuration, which implies that the injection device for the aqueous urea solution is placed closer to the mixer and the SCR catalyst. In this configuration, the vaporization of the aqueous urea solution may be reduced. Documents SAE2014-01-1522 ("Control of a Combined SCR on Filter and Under-Floor SCR System for Low Emission Passenger Cars", Balloon J. et al.) and SAE2015-01-0994 ("Next Generation All in One Close-Coupled Urea-SCR System", Kojima H. et al.), or WO2014060987A1 describe these two configuration types.

[0006] In some configurations of the installation of SCR devices and the injection of ammonia precursors, especially in the case of urea injection, manufacturers have noticed that deposits form in the exhaust pipe located between the injection device and the SCR device. These deposits can grow large enough to cause partial or even complete blockage of the exhaust duct in relation to the backpressure at the exhaust outlet, and thus the engine output may be lost. In certain injection configurations, the amount of deposits formed is greater at lower temperatures than at higher temperatures. According to the analysis carried out in the SAE2016 - 01 - 2327 technical publication, these deposits have properties that vary according to the temperature at which they are formed. Thus, these deposits consist mainly of crystallized urea at temperatures below 250 - 300 °C and mainly of cyanuric acid above 300 °C. Cyanuric acid can sublime and potentially form gaseous ammonia again. However, this reaction can only occur at very high temperatures above 450 °C. At this location in the exhaust pipe, it is very unlikely to reach such temperatures.

[0007] In particular, due to the lack of space within the vehicle and when the distance between urea injection and the first elbow is too short, as in the aforementioned "proximity" configuration, it has been noticed that these deposits are present in the pipe with the elbow. It has been hypothesized that in this type of configuration, there is not enough time for some of the urea droplets to vaporize and completely decompose into gaseous ammonia. The urea droplets deposit on the pipe walls, where the temperature is too low for complete decomposition into gaseous ammonia, and are only partially decomposed, forming cyanuric acid deposits adhering to the walls. Furthermore, it has also been noticed that depending on the configuration and temperature of the SCR line, urea can crystallize within the line, resulting in blockage of the line (see document 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 WO2008 / 125745 describes an aqueous solution containing a compound that is likely to release gaseous ammonia above 200 °C and at least one polyfunctional additive, and its HEB varies from 7 to 17, particularly limiting the formation of cyanuric acid-based deposits in SCR-type exhaust gas aftertreatment devices. In particular, the polyfunctional additives practiced are ethers of polyalkoxylated fatty alcohols and esters of polyalkoxylated fatty alcohols.

[0009] Application EP2337625 describes a mixture of surfactants that reduces the diameter of the droplets of the aqueous urea solution, thus promoting the vaporization of urea and enabling the conversion of urea to gaseous ammonia in an SCR system. The proposed solution consists of a mixture of polyalkoxylated fatty alcohols with a controlled degree of alkoxylation.

[0010] Patent application EP2488283 describes additives of a specific polyalkoxylated fatty alcohol type for urea solutions. These additives are also intended to promote the reduction of the formation of deposits resulting from the decomposition of urea in an SCR system.

[0011] Patent US5,453,257 teaches reducing the nitrogen oxide content in the combustion exhaust of a carbonaceous fuel by introducing an emulsion of a nitrogen oxide reducing compound and a hydrocarbon compound having a lower boiling point than the nitrogen oxide reducing agent into the exhaust.

[0012] In addition, it has been pointed out that an aqueous ammonia precursor solution containing a surfactant is prone to foaming. In particular, this foaming occurs during the transportation and handling of the solution, for example, when discharging into a storage tank and then when introducing the composition from the storage tank into the vehicle tank, thereby complicating the tank filling operation and potentially causing tank overflow. The current use of guns during the dispensing of the composition also promotes foaming of the composition. Furthermore, when the composition is injected into the vehicle's gas treatment system, foaming of the composition may introduce more or less a large amount of air into the system. This phenomenon hinders the control of the amount of solution to be injected and affects the efficiency of the treatment system.

[0013] One solution to this problem is to add one or more defoamers to the aqueous solution. However, such additives often have reduced efficiency during the storage period of the composition before use, especially when the composition is stored at relatively high temperatures above 30 °C or 35 °C or 40 °C. Under such storage conditions, the composition generally cannot be held for more than several months (average 5 months), which can be seen to be very restrictive.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0015]

Non-Patent Document 1

[0016] Therefore, there is a need to formulate a composition having optimized properties for exhaust gas treatment in the form of a NOx reducing agent, such as ammonia, or a precursor of such a reducing agent, such as an aqueous solution based on urea. This composition is expected to avoid or reduce deposits during use in the SCR line, while reducing and preferably avoiding the foaming phenomenon as much as possible. This composition is also expected to be stable over time, i.e., to retain its properties over a long storage period including high temperatures. [Means for Solving the Problems]

[0017] The Applicant has found that these objectives are achieved by adding to the aqueous composition at least one specific additive selected from certain polyoxyethylenated esters of fatty acids and sorbitan as defined below.

[0018] Accordingly, one object of the present invention is (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 polyoxyethylenated monoesters of fatty acids and sorbitan containing 12 to 22 carbon atoms, in a total content of 10 to 1,500 weight ppm relative to the total weight of the composition in an aqueous composition.

[0019] This composition does not contain paraffin.

[0020] Another object of the present invention is the use of such a composition for the treatment of exhaust gases at the outlet of a vehicle-mounted or stationary internal combustion engine, more specifically for the treatment of exhaust gases in a device for the selective catalytic reduction of nitrogen oxides.

[0021] In particular, the engine can be selected from diesel engines, spark ignition engines (including gasoline engines and vehicle NGVs or natural gas engines), and hybrid fuel engines, particularly gas oil gas engines. Preferably, the engine is a diesel engine.

[0022] The present invention applies to any type of engine capable of emitting nitrogen oxides, including vehicle-mounted engines and stationary engines. The present invention applies in particular to marine engines, heavy goods vehicles, transport vehicles, work machines or agricultural machines, such as the engines of tractors, etc., the engines of small vehicles and multi-purpose vehicles, and the engines used in stationary industrial applications.

[0023] The "device for selective catalytic reduction of nitrogen oxides" should be understood to be a device known per se as an SCR device representing "Selective Catalytic Reduction" in English. Such a device includes a selective catalytic reduction catalyst (so-called SCR catalyst).

[0024] The present invention also relates to a method for treating exhaust gas generated from an internal combustion engine, preferably a diesel engine, provided with a device for selective catalytic reduction of nitrogen oxides, which comprises at least one step of introducing the composition defined above into a pipe that carries the exhaust gas from the engine outlet towards the selective catalytic reduction device.

[0025] Next, the SCR exhaust line or SCR line should be understood to be a pipe that carries the exhaust gas from the engine outlet towards a selective catalytic reduction device (SCR device) in a manner known per se.

[0026] The composition according to the present invention has numerous advantages and can be used in the same way and with the same equipment as prior art solutions. It is at least as effective as prior art solutions, especially urea-based solutions, and even more effective in reducing or preventing the formation of deposits in SCR systems, particularly in so-called "close" configurations. The composition according to the present invention causes little or no foaming during its handling, use, movement, and / or transport, for example, during transfer or filling operations into containers such as cans, vehicle tanks, storage tanks, or transport tanks. In particular, the composition according to the present invention can avoid overflow during filling of a vehicle's storage tank. Also, the composition according to the present invention can fill storage tanks and vehicle tanks more quickly, and in the latter case, can limit the impact of the filling gun simultaneously.

[0027] This composition can also accurately control the amount of the composition to be injected, and in particular, can avoid errors related to sensor failures due to foam.

[0028] The composition according to the present invention is stable during storage. Further, the composition according to the present invention maintains its defoaming performance over a wide range of storage temperatures in the range of 5°C to 40°C for a long period of time, particularly for a period up to 1 year.

[0029] Other objects, features, aspects and advantages of the present invention will become more apparent upon reading the following description and examples.

[0030] Next, unless otherwise specified, the boundaries of a range of values are included in this range, particularly in the expressions "included between" and "ranging from... to...".

[0031] Furthermore, the expressions "at least one" and "at least" used in this description are equivalent to the expressions "one or more" and "equal to or more than", respectively.

[0032] Finally, a CN compound or group should be understood to be a compound or group having N carbon atoms in its chemical structure in a manner known per se.

Mode for Carrying Out the Invention

[0033] Reducing agent and / or precursor of such an agent The composition used in the present invention contains at least one nitrogen oxide reducing agent and / or at least one precursor (1) of a nitrogen oxide reducing agent.

[0034] The "nitrogen oxide reducing agent" should be understood to be a compound that can at least partially or otherwise completely reduce nitrogen oxides (also called NOx, which represents the compounds NO and NO2) to nitrogen at a temperature in the range of 150 to 400°C under the conventional operating conditions of the SCR line, i.e., in the presence of an SCR catalyst. Among the NOx reducing agents, ammonia (NH3) can be particularly mentioned.

[0035] The term "precursor of the NOx reducing agent" should be understood as a compound that can release the NOx reducing agent under the effect of temperature and / or by a catalytic reaction.

[0036] Among the ammonia precursors, urea can be mentioned, which produces ammonia according to a well-known process by continuous thermal decomposition and hydrolysis reactions. The SCR exhaust line may include a catalyst having a function of converting the precursor of the NOx reducing agent into the NOx reducing agent, particularly gaseous ammonia, upstream of the SCR catalyst system.

[0037] Preferably, the reducing agent or the precursor of the reducing agent is selected from the list consisting of urea, ammonia, formamide, ammonium salts, particularly ammonium formate, ammonium carbamate, and guanidine salts, particularly guanidine formate, preferably from the list consisting of urea and ammonia.

[0038] According to a preferred embodiment, urea as the precursor of the reducing agent is used. In fact, urea has the advantages of being stable, non-volatile, non-explosive, and non-flammable. Even an operator with no special training can transport, store, and handle it without risk.

[0039] In this embodiment, the composition has a urea content in the range of preferably 25% to 42% by weight, more preferably 30% to 40% by weight, even more preferably 31% to 35% by weight, and even better 32% to 33% by weight, based on the total weight of the composition. In a particularly preferred manner, the composition contains urea with a content of 32.5 ± 0.7% by weight in accordance with the specifications of ISO22241-1 standard.

[0040] According to a particularly preferred variant of this embodiment, the aqueous solution according to the invention is prepared from a product commercialized under the brand name AdBlue® which is an aqueous solution of urea at 32.5 ± 0.7% by weight. In this description, the term AdBlue® is used to denote without distinction the commercial products well known under the names AdBlue®, DEF, AUS32, ARLA32. "Extended" should be understood to mean all urea-based aqueous solution products, which corresponds to an aqueous solution of urea of approximately 40% by weight and includes in particular the product commercialized under the name AUS40 which is essentially intended for marine engines.

[0041] Nevertheless, it is also within the scope of the invention to use aqueous compositions containing urea having a concentration higher than 32.5%, which compositions can then be diluted immediately before use. This variant makes it possible to achieve savings in the transport costs of these urea-based compositions.

[0042] Polyoxyethylenated monoesters of fatty acids and sorbitan The composition according to the invention contains at least one additive (2) selected from polyoxyethylenated monoesters of fatty acids and sorbitan containing from 12 to 22 carbon atoms.

[0043] Advantageously, these esters are selected from those having an HLB in the range from 12 to 17, more preferably from 12.5 to 16.5. The HLB should be understood to be the hydrophilic / lipophilic balance of said compounds, determined according to a method defined by Griffin in a manner known per se.

[0044] Preferably, the fatty acids of the monoester (2) are linear saturated or monounsaturated monocarboxylic acids. As indicated above, these fatty acids contain from 12 to 22 carbon atoms. More preferably, they contain from 12 to 20 carbon atoms, even more preferably from 12 to 18 carbon atoms. Lauric acid, myristic acid, palmitic acid and oleic acid are preferred. Lauric acid and oleic acid are particularly preferred.

[0045] Advantageously, the monoester (2) contains from 10 to 30, preferably from 15 to 25, more preferably an average of 20 oxyethylene units (referred to as OE units of the formula -CH2-CH2-O-).

[0046] Particularly preferred monoester (2) is selected from polyoxyethylenated sorbitan monolaurate having 20 OEs, polyoxyethylenated sorbitan monooleate having 20 OEs, and mixtures thereof. Polyoxyethylenated sorbitan monolaurate having 20 OEs is particularly preferred.

[0047] These compounds are generally available on the market.

[0048] The monoester (2) is present in a total content of from 10 to 1,500 ppm by weight, preferably from 50 to 1,000 ppm by weight, more preferably from 200 to 800 ppm by weight, based on the total weight of the composition.

[0049] Defoaming additive According to a preferred embodiment, the composition according to the invention further comprises one or more defoaming additives preferably selected from grafted polydimethylsiloxane polymers.

[0050] Preferably, the defoaming additive(s) is 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.

[0051] Thus, these copolymers are graft polymers having a polydimethylsiloxane backbone and polyoxyalkylene side chains (or grafts) grafted to the backbone.

[0052] The backbone of these polymers is a polydimethylsiloxane chain (commonly also referred to as PDMS), i.e. the formula -[Si(CH3)2-O]n It consists of a chain of - and n is a number included in the range of 150 to 300.

[0053] Preferably, the polydimethylsiloxane backbone contains an average number of dimethylsiloxane units in the range of 180 to 250. This corresponds to the value of the number n included in the range of 180 to 250.

[0054] Advantageously, the polyoxyalkylene chain is of the formula -(RO) m -(where R represents one or more branched or straight-chain C1 - C4, preferably C2 or C3 alkylene groups, and m is a number included in the range of 10 to 55).

[0055] Preferably, the average number m of oxyalkylene units is included in the range of 20 to 50, more preferably 30 to 50.

[0056] Also preferably, R represents one or more C2 and / or C3 alkylene groups, and more preferably, the polyoxyalkylene chain is of the formula -(CH2 - CH2 - O) m - of polyoxyethylene (EO), of the formula -(CH2 - CH(CH2)-O) m - of polyoxypropylene (PO), and is selected from chains formed from oxyethylene units and oxypropylene units (EO / PO).

[0057] According to a particularly preferred embodiment, the polyoxyalkylene chain is formed from oxyethylene (EO) units and oxypropylene (PO) units. Preferably, the ratio of the average number of EO units to the average number of PO units is included in the range of 0.2 to 2, preferably 0.3 to 1.3. Preferably, these chains are formed from polyoxyethylene blocks and polyoxypropylene blocks.

[0058] The grafting rate of the copolymer (i.e., the number-average ratio of dimethylsiloxane units having polyoxyalkylene side chains) is advantageously in the range of 0.5% to 5%, preferably 1% to 2%.

[0059] Unless otherwise specified, all averages mentioned in this description are number averages.

[0060] According to a preferred embodiment, the copolymer forming the antifoaming additive is crosslinked. Such crosslinking imparts a three-dimensional structure to the antifoaming additive.

[0061] Advantageously, the antifoaming additive(s) may be present in a total content in the range of 1 to 200 weight ppm, preferably 2 to 100 weight ppm, more preferably 3 to 50 weight ppm, still better 5 to 25 weight ppm, even better 10 to 15 weight ppm, based on the total weight of the composition.

[0062] The above copolymers are known per se and are commercially available.

[0063] In commercial products, these copolymers may be in a particularly diluted form or in a mixture containing them.

[0064] In this case, the content of the copolymer(s) in such a mixture is generally included in the range of 10% to 80% by weight, preferably 20% to 60% by weight, more preferably 30% to 50% by weight, even better 35% to 45% by weight.

[0065] Thus, according to one embodiment, the antifoaming additive(s) is used as a mixture with an inorganic oxide such as solid hydrophobic silica.

[0066] According to another embodiment, the antifoaming additive(s) is used as a mixture with one or more emulsifiers that can be selected particularly from the polyoxyalkylene polymers described above, more preferably EO / PO copolymers. Generally, these polymers correspond to the proportion of polyoxyalkylene chains that are not grafted to the polydimethylsiloxane backbone and are derived from the synthesis of the copolymer.

[0067] According to a particularly preferred embodiment, the antifoaming additive(s) is used as a mixture with an inorganic oxide and an emulsifier, for example, especially a hydrophobic silica and one or more of the polyoxyalkylene polymers described above.

[0068] Commercially available products containing the antifoaming additive(s) may be in the form of anhydrous (i.e., water-free) solid products, or in the form of solutions in solvents that can consist of water or organic solvents.

[0069] Additional surfactant The composition according to the invention may further comprise one or more additional surfactants different from the polyoxyethylenated monoesters of fatty acids and sorbitan containing 12 to 22 carbon atoms described above. In particular, these surfactants can be selected from water-soluble ionic, non-ionic, or amphoteric surfactants.

[0070] The ionic surfactant can be selected from cationic surfactants and anionic surfactants, preferably from cationic surfactants. Generally, these contain a cationic or ionizable nitrogen group in cationic form. In particular, they can be selected from linear alkylamines and alkylammonium, linear diamines, aromatic or saturated heterocycles containing one or more nitrogen atoms, imidazole-type cyclic compounds, etheramines and etheramides, oxyamines and ethoxyamines, which can be considered separately or as mixtures.

[0071] In particular, the amphoteric surfactant can be selected from amino acids and their imide or amide derivatives, which can be considered separately or as mixtures.

[0072] Preferably, the non-ionic surfactant is selected from the following compounds: a) Hydrocarbyl and mono- or polyalkylene glycol ethers, b) Hydrocarbyl and polyol ethers, c) esters of fatty acids and mono- or polyalkylene glycols, d) esters of fatty acids and mono- or polyglycerols, e) and mixtures of these compounds.

[0073] "Hydrocarbyl" should be understood to be a group selected from alkyl, alkenyl, alkynyl, aryl, arylalkyl or "aralkyl" groups, and preferably, the hydrocarbyl is a C1-C 50 group.

[0074] "C i ~C j alkyl" should be understood to be a saturated straight-chain, branched or cyclic hydrocarbon chain containing i to j carbon atoms.

[0075] "C x ~C y " alkenyl should be understood to be a straight-chain, branched or cyclic hydrocarbon chain containing at least one carbon-carbon double bond and containing x to y carbon atoms.

[0076] "C x ~C y " alkynyl should be understood to be a straight-chain, branched or cyclic hydrocarbon chain containing at least one carbon-carbon triple bond and containing x to y carbon atoms.

[0077] "C x ~C y aryl" should be understood to be a functional group derived from an aromatic hydrocarbon compound containing x to y carbon atoms. This functional group can be monocyclic or polycyclic. By way of example, C6-C 18 aryl can be phenyl, naphthalene, anthracene, phenanthrene and tetracene.

[0078] "C x ~C yAn aralkyl is to be understood as a preferably monocyclic aromatic hydrocarbon compound which is substituted by at least one linear or branched alkyl chain and in which the total number of carbon atoms of the aromatic ring and its substituents ranges from x to y carbon atoms. As an example, C7~C 18 Aralkyl can be selected from the group formed by benzyl, tolyl and xylyl.

[0079] In the context of the present invention, a "polyol" is to be understood as an oxygenated hydrocarbon compound containing at least two alcohol functional groups. The polyol may contain one or more other oxygenated functional groups such as, for example, an acetal functional group, an ether bridge, an ester group.

[0080] A fatty acid is a carboxylic acid containing a linear or branched alkyl or alkenyl chain of C4~C 30 , preferably C8~C 30 as is known per se.

[0081] a) Hydrocarbyl and mono- or polyalkylene glycol ethers Hydrocarbyl and mono- or polyalkylene glycol ethers may be monoethers or diethers depending on whether the polyalkylene glycol chain is substituted by a hydrocarbyl group at one or both ends.

[0082] Advantageously, the hydrocarbyl and mono- or polyalkylene glycol ethers contain a C1~C 50 hydrocarbyl group and are selected from those having 1 to 60 alkylene glycol units.

[0083] More preferably, the hydrocarbyl and mono- or polyalkylene glycol ethers are selected from the following compounds: · Formula (I): R-(Y) n -OH mono- or poly-alkoxylated hydrocarbyl monoethers, · Formula (II): R-(Y)m -OR’ mono- or poly-alkoxylated hydrocarbyl diether, · Formula (III): HO-(Y) n -R’’-(Y’) m -OH mono- or poly-alkoxylated hydrocarbyl diether, · and mixtures of these compounds.

[0084] In the above formulas (I)-(III), R and R’ independently represent a C3-C 40 alkyl or alkenyl or alkynyl or aryl or aralkyl group, and R’’ represents a C3-C 40 diylalkane or diylalkene or diylalkyne group or aryldiradical or aralkyldiradical.

[0085] For ease of explanation, the same designations of alkyl or alkenyl or alkynyl or aryl or aralkyl radicals are later used for the monoradicals (R, R’) and diradicals (R’’).

[0086] In the above formulas (I)-(III), Y and Y’ independently of each other are groups selected from the following group: -(O-CH2-CH2)-, -(O-CH(CH3)-CH2)- and -(O-CH2-CH2-CH2)-.

[0087] In the same compound of formula (I), (II), or (III), the Y groups and Y’ groups may all be the same or different from each other. For example, -(Y) n - can represent a copolymer having ethylene oxide and propylene oxide units, such as a block copolymer and the like.

[0088] Preferably, in formulas (I)-(III), all of the Y groups and Y’ groups are the same respectively.

[0089] Even more preferably, in formulas (I) to (III), all of the Y groups and Y' groups are ethylene oxides of the formula -(O-CH2-CH2)-.

[0090] In the above formulas (I) to (III), n and m represent the degree of alkoxylation of the molecule and, independently of each other, represent integers in the range of 1 to 60, preferably 1 to 30, even more preferably 1 to 20. More preferably, n and m vary from 3 to 15, even more preferably from 5 to 12.

[0091] Advantageously, in formula (III), the Y group and the Y' group represent -(O-CH2-CH2)- and n = m.

[0092] According to the first embodiment, in formulas (I), (II) and (III), preferably, R, R' and R'' are selected from linear or branched, preferably linear alkyl and alkenyl groups.

[0093] Even more advantageously, R, R' and R'' are C5-C 32 , more preferably C8-C 30 alkyl groups selected.

[0094] The compound of formula (I) can be selected in particular from linear or branched polyalkoxylated fatty alcohols containing 4 to 30 carbon atoms, preferably 8 to 30 carbon atoms, even more preferably 10 to 24 carbon atoms, and 5 to 12 ethylene oxide and / or propylene oxide units, preferably ethylene oxide units.

[0095] Among the commercially available compounds of formula (I), mention may be made of products in the range of Marlipal® and products in the range of Surfaline®.

[0096] According to the second embodiment, in formulas (I), (II) and (III), R, R' and R'' are selected from C4-C 50 alkynyl.

[0097] Advantageously, this embodiment relates to formula (III) wherein R’’ is C4-C 50 alkynyl.

[0098] For example, according to this embodiment, the compound of formula (III) can be represented by the following formula (IV)

[0099] [Chemical formula] [wherein, R1, R2, R3, and R4 are each independently H or a C1-C 20 alkyl group, and x and y each independently represent an integer in the range of 1 to 60, preferably 1 to 30].

[0100] An example of a commercially available product corresponding to this formula is Surfynol 104 (registered trademark) commercialized by Air Products.

[0101] According to the third embodiment, in formulas (I), (II) and (III), R, R’ and R’’ are selected from aralkyl groups containing 9 to 30 carbon atoms.

[0102] Preferably, this embodiment relates to formula (I) wherein R represents a group selected from aralkyl containing 9 to 30 carbon atoms.

[0103] More preferably, R is selected from para-alkylphenyl containing a C1-C 24 , more preferably C3-C 20 , even more preferably C5-C 18 alkyl group.

[0104] According to this embodiment, the compound of formula (I) can be represented by the following formula (V)

[0105] [Chemical formula] [wherein, R5 is a C1-C 24 , preferably C3-C20 , more preferably C5 - C 18 represents an alkyl group, and x represents an integer in the range of 1 to 50, preferably 1 to 30].

[0106] An example of such a compound is the product Dynol 800 (registered trademark) commercialized by Air Products, which corresponds to the following formula.

[0107] [Chemical formula]

[0108] Advantageously, the compound of formula (I) can be a mixture obtained by the reaction of an R - OH alcohol with n ethylene oxide and / or propylene oxide units. n represents the number of moles of alkylene oxide reacted with 1 mole of R - OH alcohol.

[0109] Advantageously, the compound of formula (II) can be a mixture obtained by the reaction of an R - OH alcohol compound with m units of ethylene oxide and / or propylene oxide, followed by an etherification reaction with the alcohol compound R - OH. m represents the number of moles of alkylene oxide reacted with 1 mole of R - OH alcohol.

[0110] Advantageously, the compound of formula (III) can be obtained by the reaction of a diol HO - R’’ - OH with (n + m) ethylene oxide and / or propylene oxide units. Advantageously, in formula (III), n = m. (m + n) represents the number of moles of alkylene oxide reacted with 1 mole of the diol HO - R’’ - OH.

[0111] Generally, the compounds of formula (I), (II) and (III) are in the form of a mixture of compounds having various degrees of alkoxylation.

[0112] b) Ethers of Hydrocarbyl and Polyol Advantageously, the ethers of hydrocarbyl and polyol are C1 - C50 - Preferably C3 - C 40 - More preferably C5 - C 32 - Even more preferably C8 - C 30 selected from alcohols and ethers derived from polyols containing an alkyl or alkenyl group.

[0113] The polyols referred to in this specification are different from mono - and polyalkylene glycols.

[0114] Advantageously, according to a first variant form, the polyol is selected from compounds belonging to the carbohydrate family and their oligomers. In particular, the polyol is selected from cyclic carbohydrate compounds such as, for example, glucopyranose oligomers. In particular, the present invention relates to hydrocarbyl ethers and cyclic polyglucosides.

[0115] Among hydrocarbyl and cyclic polyglucoside ethers, alkyl polyglucosides can be mentioned, for example, products commercialized under the name Triton CG650 (registered trademark) by Dow Chemical.

[0116] Advantageously, according to a second variant form, the polyol is glycerol or a glycerol oligomer, for example an oligomer containing 2 - 30 glycerol units, preferably 3 - 20 glycerol units.

[0117] c) esters of fatty acids and mono - or polyalkylene glycols The esters of fatty acids and mono - or polyalkylene glycols are molecules resulting from the condensation of at least one fatty acid with 1 - 60 alkylene glycol units, preferably 1 - 50 alkylene glycol units. Advantageously, this ester is derived from the reaction of a fatty acid with 1 - 50 ethylene glycol units.

[0118] Generally, a fatty acid contains an alkyl or alkenyl chain and bears a carboxylic acid functional group at its end, and is a molecule containing 4 to 30 carbon atoms, preferably 8 to 30 carbon atoms, more preferably 8 to 24 carbon atoms.

[0119] The fatty acid group may be a single molecule or a mixture corresponding to the fatty acid distribution of animal or vegetable oils.

[0120] Among fatty acids, non-limiting examples include 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.

[0121] Advantageously, the ester of a fatty acid and a mono- or polyalkylene glycol contains 3 to 50, even better 5 to 40 alkylene oxide units. Even better, the ester of a fatty acid and a mono- or polyalkylene glycol contains 3 to 50, preferably 5 to 40 ethylene oxide units.

[0122] An example of an ester of a fatty acid and a polyalkylene glycol is product DUB S PEG 30S (PEG-30 stearate) commercialized by Stearinerie Dubois.

[0123] d) Esters of fatty acids and mono- or polyglycerol The esters of fatty acids and mono- or polyglycerol 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.

[0124] The fatty acids are the same as those described in point c) above.

[0125] Advantageously, the esters of fatty acids and mono- or polyglycerol contain from 3 to 50, more preferably from 5 to 40, glycerol units.

[0126] Examples of fatty acid and polyglycerol esters include the product Polyaldo 10-1-0 KFG® (polyglyceryl laurate) commercialized by LONZA.

[0127] According to a preferred embodiment, the surfactant(s) is / are selected from non-ionic surfactants. In particular, it is preferred to use one or more surfactants selected from ethers of hydrocarbyl and mono- or polyalkylene glycols, more preferably mono- or poly-alkoxylated hydrocarbyl monoethers of formula (I): R-(Y) n -OH [wherein, R is a C3-C 40 , preferably C8-C 30 , even more preferably C 10 ~C 24 alkyl, alkenyl or alkynyl group, Y is selected from -(O-CH2-CH2)-, -(O-CH(CH3)-CH2)- and -(O-CH2-CH2-CH2)-, preferably Y represents -(O-CH2-CH2)-, 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 most preferably 5 to 12].

[0128] When additional surfactant(s) is / are present, the total content thereof can be in the range of 5 to 10,000 weight ppm, preferably 50 to 5,000 weight ppm, more preferably 100 to 2,500 weight ppm, even more preferably 200 to 1,000 weight ppm, based on the total weight of the composition.

[0129] Other components Optionally, the aqueous composition can contain one or more other compounds different from nitrogen oxide reducing agents and their precursors, mono-esters of fatty acids and sorbitan, defoaming additives, and the additional surfactants described above.

[0130] Thus, the composition may include, without limitation, one or more preferably water-miscible organic fluids, such as alcohols, polyols, and / or one or more metal compounds, etc.

[0131] According to a preferred embodiment, the composition according to the invention contains no metal compounds.

[0132] "Metal compound" should be understood to be any organic or inorganic compound containing one or more metals. These compounds may be ionic or non-ionic. In particular, the composition contains no organometallic or inorganic metal compounds, whether ionic or non-ionic.

[0133] Examples of ionic compounds excluded according to this embodiment include, 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.

[0134] "Containing no metal compounds" should be understood to mean that the composition does not contain such compounds added intentionally. Thus, if such compounds are present in the composition, they are regarded as impurities, and the content of each metal element provided by the metal compound(s) is less than 1 weight ppm, particularly less than 0.5 weight ppm, based on the total weight of the composition.

[0135] The composition according to the invention does not contain paraffin. Paraffin is of the formula C n H 2n+2It should be understood that it is an alkane, and n is an integer in the range of 2 to 50, preferably 6 to 40, more preferably 18 to 35. "Not containing paraffin" should be understood to mean that the composition does not contain intentionally added paraffin. Therefore, if such paraffin is present in the composition, they are regarded as impurities, and their content is less than 80 weight ppm, preferably less than 50 weight ppm, more preferably less than 20 weight ppm, and even more preferably less than 10 weight ppm based on the total weight of the composition.

[0136] According to a preferred embodiment, the composition according to the present invention does not contain a hydrocarbon liquid phase. In particular, the composition does not contain a water-insoluble hydrocarbon liquid phase in a dispersed form (oil-in-water emulsion).

[0137] The "liquid phase" should be understood to be a phase in a liquid state at 25 °C and atmospheric pressure (1.013×10 5 Pa).

[0138] "Water-insoluble" should be understood to be a phase with a solubility in water at 25 °C and atmospheric pressure (1.013×10 5 Pa) of less than 2% by weight, preferably less than 1% by weight, and even more preferably less than 0.5% by weight.

[0139] In particular, the composition according to the present invention is not in the form of an emulsion. An "emulsion" should be understood to be a composition that contains at least two liquid phases in a manner known per se, and one of the liquid phases is dispersed in the form of droplets in the other liquid phase.

[0140] Composition and its embodiments The composition used in the present invention is an aqueous composition, that is, its main component is water. Preferably, the water content of the composition is in the range of 50% to 90% by weight, preferably 60% to 80% by weight, and even more preferably 65% to 70% by weight based on the total weight of the composition.

[0141] The composition can be prepared in a conventional manner by mixing its components, preferably at room temperature and typically in a temperature range generally from 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 a commercially available composition known as AdBlue® which contains, for example, 32.5% by weight of urea.

[0143] The first embodiment consists in adding to this pre-formulated aqueous solution of urea a polyoxyethylenated monoester (2) of fatty acid and sorbitan, and optionally an antifoaming additive(s), in an amount necessary to reach the content defined above.

[0144] The second embodiment consists in adding to this pre-formulated aqueous solution of urea a urea-concentrated aqueous composition containing additives. According to this embodiment, the urea-concentrated aqueous composition containing additives contains a polyoxyethylenated monoester (2) of fatty acid and sorbitan, and optionally an antifoaming additive(s), preferably in a content much higher than that of the final aqueous composition introduced into the SCR line, in an aqueous urea solution having a urea content of 32.5% by weight. Mixing the two compositions in a suitable ratio to obtain the desired final content is carried out immediately before injection into the SCR line.

[0145] The same embodiment may be practiced starting from a pre-formulated aqueous solution of a precursor other than urea.

[0146] Use The aqueous composition according to the invention is used for treating the exhaust gases of an internal combustion engine in a device for selective catalytic reduction of nitrogen oxides or SCR device.

[0147] To achieve this purpose, the aqueous composition according to the present invention is introduced into the SCR exhaust line downstream of the engine and upstream of the SCR device. This introduction is typically carried out by pumping the composition from one or more tanks and injecting it using one or more injection devices capable of spraying the composition into the exhaust gas stream. These devices are known per se.

[0148] The use according to the present invention can also prevent or reduce deposits in the pipe carrying the exhaust gas from the outlet of the internal combustion engine towards the selective catalytic reduction device.

[0149] These deposits are typically deposits of nitrogen compounds containing a reducing agent(s) for nitrogen oxides and / or their precursor(s), and / or decomposition products of said precursor(s). In particular, the present invention can prevent and / or reduce deposits in the SCR exhaust pipe, in particular deposits of urea and / or cyanuric acid, more specifically deposits of cyanuric acid.

[0150] As indicated above, the present invention can reduce or avoid these deposits regardless of the configuration of the SCR line. The present invention is particularly suitable, but not limited to, so-called "close" and "underfloor" SCR exhaust lines as described above.

[0151] In particular, the present invention can reduce such deposits while avoiding the foaming phenomenon of the composition.

[0152] As described 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 the components of the composition according to the invention, in particular the nitrogen oxide reducing agent(s) and / or their precursor(s) (1), the monoester of polyoxyethylene sorbitan fatty acid (2), and optionally the antifoaming additive(s), are incorporated into the same aqueous composition in the desired amounts, and this composition is introduced into one tank.

[0154] According to a second variant, a first intermediate aqueous composition containing the nitrogen oxide reducing agent(s) and / or their precursor(s) (1) is incorporated in the desired amount into the final composition resulting from the mixing of two intermediate compositions. This first intermediate composition is introduced into a first tank. A second concentrated intermediate aqueous composition containing additives is also presented, this composition containing the nitrogen oxide reducing agent(s) and / or their precursor(s) (1) in the desired amount in the final composition resulting from the mixing of the two intermediate compositions, and containing the monoester of polyoxyethylene sorbitan fatty acid (2) and optionally the antifoaming additive(s) in a concentration higher than the desired amount in said final composition.

[0155] This second composition is introduced into a second tank separate from the first tank. The two tanks are supplied to the same injection system to enable the mixing of the two intermediate compositions. A vehicle equipped with two tanks for practicing such a variant is described in particular in EP2541012.

[0156] Process The process (or method) according to the invention can treat the exhaust gases generated by an internal combustion engine, preferably a diesel engine, equipped with an SCR system.

[0157] This process includes the step of introducing the above-described aqueous composition into the pipe carrying the exhaust gases from the engine outlet towards the device for selective catalytic reduction of nitrogen oxides. This introduction is typically carried out by pumping the composition from one or more tanks and injecting the composition into the pipe using one or more injection devices, as described above.

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

Example

[0159] Tested compositions A commercially available aqueous AdBlue (registered trademark) solution containing 32.5% by weight of urea was used as the base composition in accordance with the ISO22241 standard. This base composition is referred to as C0.

[0160] The following additives were added: - A1: Polyoxyethylene sorbitan monolaurate having 20 OEs - A2: Polyoxyethylene sorbitan monooleate having 20 EOs - A3: A crosslinked copolymer containing a PDMS backbone having 200 average dimethylsiloxane units grafted at a grafting rate of 1.57% by a chain formed from a polyoxyethylene block and a polyoxypropylene block having an average number of OE units = 16 and an average number of OP units = 30. This copolymer further contains hydrophobic silica and an EO / OP copolymer and is in the form of a mixture containing 40% by weight of the copolymer.

[0161] The additive compositions C1 to C4 were prepared by adding the additives defined above to the composition C0, and their contents are detailed in Table 1 below (the contents are shown by the weight ppm of the active substance with respect to the total weight of the composition).

[0162]

Table 1

[0163] Test for determining the amount of deposits The deposition reduction ability of the additive compositions C1 - C4 was evaluated using the ECTO-Lab™ system (Exhaust Composition Transient Operation Laboratory™) in comparison to the reference composition C0. These tests were conducted in the laboratory of South West Research Institute (SwRI, San Antonio, Texas, USA). This system further has an oxidation catalyst device and a particulate filter (a so-called "DOC / DPF" device representing "Diesel Oxidation Catalyst / Diesel Particulate Filter") upstream of the injection device to remove soot generated from the exhaust gas. A Bosch Denoxtronix 2.2 injection device was used. A static mixer is incorporated 5 cm after the injection device. At the end of the test, the amount by weight of the deposits in the mixer and in the local elbow after the mixer is quantified.

[0164] The test conditions are as follows: - Pressure of the injection device: 8 bar, - Flow rate of the injection composition: 920 g / h, - Air flow rate: 660 kg / h, - Test duration: 1 hour, - Exhaust gas temperature at the injection device: 180 - 215 °C.

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

[0166]

Table 2

[0167] These results indicate that the compositions according to the present invention can substantially reduce the deposits generated by crystallization and / or poor decomposition of urea in the SCR system.

[0168] Foaming test The foaming levels of these various compositions were measured by using a DFA100 foaming bench commercialized by Kruss.

[0169] In this system, foaming is generated by supplying rising air that is introduced through the entire sintered glass at the bottom of the column containing the composition to be tested. This device enables direct reading of the volume of the bubbles formed over time.

[0170] Measurements were carried out at room temperature (25 °C) with a flow rate of 0.3 L / min after a 30 - second air injection duration each time. The volume of the composition introduced into the column for each test was 40 ml. The volume of the bubbles was measured 60 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 indicate that Compositions C3 and C4 can also substantially reduce foaming.

Claims

1. (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 polyoxyethylenated monoesters of fatty acids and sorbitan containing 12 to 22 carbon atoms, with a total content of 10 to 1,500 ppm by weight based on the total weight of the composition An aqueous composition containing, and not containing paraffin.

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

3. The composition contains urea in an amount in the range of 25% to 42% by weight, preferably 30% to 40% by weight, more preferably 31% to 35% by weight, and even more preferably 32% to 33% by weight, based on the total weight of the composition. Even more preferably, the composition contains 32.5 ± 0.7% by weight of urea based on the total weight of the composition. The composition according to any one of the preceding claims.

4. The fatty acid of the monoester (2) contains 12 to 20 carbon atoms, preferably 12 to 18 carbon atoms. The composition according to any one of the preceding claims.

5. The monoester (2) contains 10 to 30, preferably 15 to 25, more preferably an average number of 20 oxyethylene units (OE units). The composition according to any one of the preceding claims.

6. The monoester (2) is selected from polyoxyethylene sorbitan monolaurate having 20 OEs, polyoxyethylene sorbitan monooleate having 20 OEs, and mixtures thereof, and preferably the ester (2) is polyoxyethylene sorbitan monolaurate having 20 OEs. The composition according to the preceding claim.

7. The monoester (2) is present in a total content of 50 to 1,000 ppm by weight, preferably 200 to 800 ppm by weight, based on the total weight of the composition. The composition according to any one of the preceding claims.

8. Preferably selected from grafted polydimethylsiloxane polymers, more preferably copolymers containing a polydimethylsiloxane backbone having an average number of dimethylsiloxane units in the range of 150 to 300 grafted by polyoxyalkylene chains, the composition according to any one of the preceding claims, further comprising one or more defoaming additives.

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

10. The polyoxyalkylene chain of the copolymer is represented by the formula -(RO) ｍ -(wherein R represents one or more C １ to C ４ alkylene group, and m is a number in the range of 10 to 55), preferably the polyoxyalkylene chain is selected from a chain formed from polyoxyethylene (EO), polyoxypropylene (PO), and a chain formed from oxyethylene units and oxypropylene units (EO / PO), and more preferably the ratio of the average number of EO units to the average number of PO units is preferably in the range of 0.2 to 2, more preferably in the range of 0.3 to 1.

3. The composition according to any one of claims 8 and 9, characterized in that it is selected from a chain formed from oxyethylene (EO) units and oxypropylene (PO) units.

11. The composition according to any one of claims 8 to 10, wherein the copolymer is crosslinked.

12. The defoaming additive(s) is / are present in a total content in the range of 1 to 200 ppm by weight, preferably 2 to 100 ppm by weight, more preferably 3 to 50 ppm by weight, even better 5 to 25 ppm by weight, still better 10 to 15 ppm by weight, based on the total weight of the composition, the composition according to any one of claims 8 to 11.

13. The composition according to any one of claims 8 to 11, characterized by containing no metal compound at all.

14. Use of the composition according to any one of the preceding claims for the treatment of exhaust gases from a vehicle-mounted or stationary internal combustion engine.

15. Use of the composition according to any one of claims 1 to 13 for preventing or reducing deposits in a pipe carrying exhaust gas from the outlet of an internal combustion engine towards a device for selective catalytic reduction of nitrogen oxides.

16. A method for treating exhaust gas generated from an internal combustion engine equipped with a device for selective catalytic reduction of nitrogen oxides, comprising at least one step of introducing the composition according to any one of claims 1 to 13 into a pipe carrying exhaust gas from the outlet of the engine to the selective catalytic reduction device.

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