Aqueous composition with improved properties for treating exhaust gases

Abstract

The invention relates to a composition comprising a single aqueous liquid phase containing:-at least one nitrogen oxide (NOx)-reducing agent and / or at least one precursor of such 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 invention also relates to the use of such a composition for treating exhaust gases from an internal combustion engine and to a process for treating exhaust gases from an internal combustion engine using the composition.

Description

Technical Field

[0001] The present invention relates to a composition for treating the exhaust gas (waste gas, tail gas, exhaust gas) at the outlet of an onboard or stationary combustion engine, whether the engine is an engine for a heavy vehicle such as a truck, a transport vehicle, an off-road vehicle such as an agricultural machine, a boat, an engine for a light vehicle and / or a utility vehicle, or even an engine for stationary industrial applications. The invention also relates to the use of such a composition in any exhaust gas treatment device, and a method for treating exhaust gas using the composition. Background Art

[0002] European standards concerning pollution emitted by combustion engines, in particular those powered by diesel type fuels, and in particular those applicable to heavy vehicles, have led engine manufacturers to introduce aftertreatment systems for the exhaust gas. These systems include selective catalytic reduction (SCR), exhaust gas recirculation (EGR), diesel oxidation catalysts (DOC), or particulate filters (FAP) and (SCR and FAP combined) technology. These different aftertreatment systems can be installed individually or in combination, as they do not always act on the same pollutants present in the exhaust gas.

[0003] In order to comply with standards, in particular European standards (Euro IV and higher for heavy vehicles, and Euro 6 for light vehicles), most European car manufacturers have chosen SCR exhaust aftertreatment for their engines. This aftertreatment technology is specifically designed to reduce the level of nitrogen oxides in the gas. Another advantage of this technology is that it enables a significant reduction in fuel consumption through optimized engine tuning, especially when compared with other aftertreatment systems such as NOx traps.

[0004] The SCR post-treatment consists in reducing the nitrogen oxides NO and NO2 (called NOx) in a catalytic device which makes it possible to contact them with a reducing agent. The device contains a catalytic converter which comprises a support generally based on an iron or copper exchanged zeolite. The catalytic converter promotes the reduction of NOx to nitrogen by reacting with the reducing agent. Typical reducing agents are, for example, ammonia ( ). In order to introduce gaseous ammonia into the exhaust gas treatment system, it is known, for example, to produce gaseous ammonia directly in the pipe that conveys these gases to the SCR system by spraying an aqueous solution of a precursor of the reducing agent, such as urea. The urea solution injected at an average exhaust gas temperature of generally 150 to 400° C. releases ammonia as a result of successive thermal decomposition and hydrolysis reactions. Other ammonia precursor compounds can be used under similar conditions. An injector is generally used to introduce the urea-water solution into a pipe that conveys the exhaust gas to an SCR catalytic converter upstream thereof. A mixer installed between the injector and the SCR catalytic converter can be used to improve the vaporization of the spray of the urea-water solution in the exhaust gas flow. An example of a mixer is described in the document SAE 2015-01-1020 (“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, known as the "underfloor" configuration, includes placing the SCR aftertreatment device downstream of the engine, under the vehicle board (generally greater than 50 cm to 1 m from the outlet of the combustion chamber). It has the following advantages: it allows the aftertreatment device to be installed in an area with a large amount of available space, and thus places it under geometric conditions that are more conducive to the vaporization of the urea-water solution. Another configuration, known as the "close-coupled" configuration, includes placing the SCR aftertreatment device in the immediate vicinity of the engine (generally less than 50 cm from the outlet of the combustion chamber). Compared with the "underfloor" configuration, this configuration has the following advantages: it provides a higher temperature in 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 of the urea-water solution must be positioned closer to the mixer and the SCR catalytic converter. This configuration can lead to a less efficient vaporization of the urea-water solution. The documents SAE 2014-01-1522 (“Control of a Combined SCR on Filter and Under-Floor SCR System for Low Emission Passenger Cars”, Balland J. et al.) and SAE 2015-01-0994 (“Next Generation All in One Close-Coupled Urea-SCR System”, Kojima H. ​​et al.), or also WO 2014060987 A1 describe these two types of configurations.

[0006] In some configurations of the installation of the SCR device and the injection of the ammonia precursor, in particular in the case of urea injection, manufacturers have noticed the appearance of deposits in the exhaust pipe between the injector and the SCR device. These deposits can be large enough to cause partial or even complete blockage of the exhaust pipe due to the back pressure of the exhaust gas, resulting in a loss of engine power. In a constant injection configuration, the amount of deposits formed at low temperatures is greater than at high temperatures. According to the analysis carried out in the technical publication SAE2016-01-2327, these deposits vary in nature depending on the temperature at which they are formed. Thus, at temperatures below 250-300°C, they consist mainly of crystallized urea and above 300°C mainly of cyanuric acid. Cyanuric acid can sublime and produce ammonia again. However, this reaction can only occur at very high temperatures, above 450°C. Such temperatures are rarely reached at this point in the exhaust pipe.

[0007] In particular, it has been noted that these deposits are present in pipes with bends, due to the lack of space in the vehicle and when the distance between the urea injection and the first bend is too short, as in the "closely coupled" configuration described above. The hypothesis proposed is that in this type of configuration, some urea droplets do not have time to vaporize and completely decompose into gaseous ammonia. The urea droplets are deposited on the walls of the pipe, the temperature of which is too low to allow complete decomposition into gaseous ammonia, and they only partially decompose, forming cyanuric acid deposits that stick to the walls. It has also been found that, depending on the configuration and temperature of the SCR line, urea has the potential to crystallize in the line, leading to obstruction of the line (see document SAE 2017-26-0132 ("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 containing a compound capable of releasing gaseous ammonia at above 200° C. and at least one polyfunctional additive having an HLB ranging from 7 to 17, for limiting the formation of deposits based on cyanuric acid in exhaust gas aftertreatment devices, in particular 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 which makes it possible to reduce the diameter of the droplets of aqueous urea solutions, thereby promoting their vaporization and the conversion of urea into 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 2 488 283 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] US Pat. No. 5,453,257 teaches reducing the nitrogen oxide content in the combustion effluent of a carbon fuel by introducing into the effluent an emulsion of a nitrogen oxide reducing compound and a hydrocarbon compound having a boiling point lower than that of a nitrogen oxide reducing agent (nitrogen oxide reducing agent).

[0012] Furthermore, it has been found that aqueous solutions of ammonia precursors containing surfactants have a tendency to foam. This foaming occurs in particular during the transport and handling of the solution, for example when unloading it into a storage tank, and then when introducing the composition from the storage tank into the tank of the vehicle, which complicates the tank filling operation and may cause it to overflow. The use of a spray gun, which is usually used when dispensing the composition, also promotes foaming. In addition, when injecting the composition into the exhaust gas treatment system of the vehicle, the foaming of the composition may cause a greater or lesser amount of air to be introduced into the system. This phenomenon interferes with the control of the amount of solution injected and affects the efficiency of the treatment system.

[0013] One solution to this problem is to add a further defoaming agent to the aqueous solution. However, such additives are generally less effective the longer the composition is stored before use, and this is even more true when the composition is stored at relatively higher temperatures, above 30° C., or even at 35 or 40° C. Under such storage conditions, the composition generally cannot be kept for more than a few months (5 months on average), which is very restrictive.

[0014] Therefore, there is a need to be able to formulate a composition for treating exhaust gases in the form of an aqueous solution based on a NOx-reducing agent such as ammonia or a precursor of such a reducing agent such as urea with optimized properties. Such a composition is expected to be able to avoid or reduce deposits when used on SCR lines, while minimizing foaming phenomena. It is also expected that the composition is stable over time, i.e. it retains its properties over long storage periods, even at elevated temperatures.

[0015] The Applicant has found that these objects are achieved by adding to the aqueous composition at least one specific additive chosen from poly(ethylene oxide) and poly(propylene oxide) block copolymers as defined below.

[0016] The object of the present invention is therefore a composition comprising a single aqueous liquid phase, containing:

[0017] (1) at least one nitrogen oxide NOx reducing agent and / or at least one precursor of such an agent, and

[0018] (2) at least one additive selected from block copolymers formed from 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 mass relative to the total mass of the composition.

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

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

[0021] The invention is applicable to any type of engine emitting nitrogen oxides, including built-in engines and stationary engines. The invention is also applicable to marine engines, engines for heavy freight vehicles, transport vehicles, construction site machinery or agricultural machinery such as tractors, engines for light and utility vehicles, and engines for stationary industrial applications.

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

[0023] The invention also relates to a method for treating exhaust gases from an internal combustion engine, preferably a diesel engine, equipped with a device for the 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 conveying the exhaust gases from the engine outlet to said selective catalytic reduction device.

[0024] In the following, the term “SCR exhaust gas line” or “SCR line” is also used in a manner known per se to refer to a pipe which carries exhaust gas from the engine outlet to a selective catalytic reduction device (SCR device).

[0025] The composition according to the invention has many advantages: it can be used in the same manner and in the same equipment as the solutions of the prior art. It is at least as effective, if not more effective, than the solutions of the prior art, in particular urea-based solutions, for reducing or preventing the formation of deposits in SCR systems, in particular in the so-called "closely coupled" configuration. It causes no or almost no foaming when handled, used, transferred, and / or transported, for example during pouring or filling operations into containers such as cans, vehicle tanks, storage tanks, or transport tanks. In particular, it prevents overflow when filling storage tanks of vehicles. It also enables storage tanks and vehicle tanks to be filled faster and, in the latter case, with less shaking of the filling gun.

[0026] This composition also makes it possible to precisely control the amount of composition injected and in particular to avoid errors related to foaming of the sensor.

[0027] The composition according to the invention is stable on storage. It also has defoaming properties that are retained over time, in particular over a period of up to one year, within a wide range of storage temperatures ranging from 5°C to 40°C.

[0028] Further objects, features, aspects and advantages of the present invention will appear more clearly after reading the following description and examples.

[0029] Next, and unless otherwise indicated, the limits of the range of values ​​are included in the range, particularly in the expressions "comprising... and "ranging from... to... ".

[0030] In addition, "at least one" and "at least" used in the present specification are equivalent to "one or more" and "higher than or equal to", respectively.

[0031] Finally, in a manner known per se, C N The compound or group means a compound or group containing N carbon atoms in its chemical structure. DETAILED DESCRIPTION

[0032] Reducing agents and / or precursors of such agents

[0033] The composition used in the present invention comprises (1) at least one agent for reducing nitrogen oxides and / or at least one precursor of a nitrogen oxide reducing agent.

[0034] A "nitrogen oxide reducing agent" is defined as a nitrogen oxide reducing agent capable of reducing nitrogen oxides (also referred to as NOx to denote the compounds NO and ), if not completely, at least partially reduced to nitrogen. Ammonia ( ) are particularly suitable NOx-reducing agents.

[0035] "Precursor of a NOx reducing agent" is defined as a compound that is capable of releasing a NOx reducing agent under the action of temperature and / or catalytic reaction.

[0036] Ammonia precursors include urea, which produces ammonia in a well-known process by successive thermal decomposition and hydrolysis reactions. The SCR exhaust line may include a catalytic converter upstream of the SCR catalytic system, the function of which is to convert a precursor of the NOx reducing agent into a NOx reducing agent, in particular gaseous ammonia.

[0037] Preferably, the reducing agent or the 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; and preferably from the list consisting of urea and ammonia.

[0038] According to a preferred embodiment, urea is used, which is a reducing agent precursor. In fact, urea has the advantages of being stable, non-volatile, non-explosive and non-flammable. It can be safely transported, stored and handled by operators without any specific training.

[0039] In this embodiment, the composition has a content of urea preferably ranging from 25% to 42% by mass, more preferably from 30% to 40% by mass, even more preferably from 31% to 35% by mass, and even better from 32% to 33% by mass, relative to the total mass of the composition. In a particularly preferred manner, the composition contains urea in a content of 32.5±0.7% by mass, complying with the specifications of standard ISO 22241-1.

[0040] According to a particularly preferred variant of this embodiment, the aqueous solution according to the invention consists of a commercial product Preparation, which is a 32.5±0.7 mass % urea aqueous solution. In this specification, the following commercial products are used indiscriminately: , DEF, AUS32, ARLA32. By extension, the term is used to refer to All products in the range, including the product sold as AUS 40, which corresponds to an aqueous solution of about 40% by mass of urea and is essentially intended for use in marine engines.

[0041] However, the invention also covers the use of aqueous compositions containing urea in concentrations greater than 32.5%, which compositions can then be diluted just before use. This variant makes it possible to save on transport costs for these urea-based compositions.

[0042] PEG and PPG block copolymers

[0043] The composition according to the invention contains at least one additive (2) chosen from block copolymers formed by at least one poly(ethylene oxide) block or EO block or PEG block of polyethylene glycol and at least one poly(propylene oxide) block or PO block or PPG block of polypropylene glycol.

[0044] Preferably, one or more of the copolymers (2) are triblock polymers of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) or poloxamer. These triblock polymers correspond to the following formula (I):

[0045]

[0046] Wherein, a, b and c are integers strictly greater than 1.

[0047] Preferably, the triblock polymer is selected from those of formula (I) above, wherein 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.

[0048] According to a preferred embodiment, the copolymer (2) is selected from Poloxamer 182, ie a copolymer containing 20% ​​by mass of ethylene oxide and 80% by mass of propylene oxide.

[0049] Advantageously, the copolymer (2) has a number average molar mass (molar mass number) M ranging from 500 to 5000. N Advantageously, they also have a weight-average molar mass (molar mass by weight) M of 1000 to 5000. W .

[0050] These compounds are currently commercially available.

[0051] The copolymer (2) is present in a total amount of 100 to 1500 mass ppm, preferably 200 to 1000 mass ppm, and more preferably 350 to 750 mass ppm, relative to the total mass of the composition.

[0052] Defoaming Additives

[0053] According to a preferred embodiment, the composition according to the invention further comprises one or more antifoam additives, preferably chosen from grafted polydimethylsiloxane polymers.

[0054] In a preferred manner, the one or more defoaming 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.

[0055] These copolymers are therefore grafted polymers having a polydimethylsiloxane backbone and polyoxyalkylene side chains (or grafts) grafted onto the backbone.

[0056] The backbone of these polymers is composed of polydimethylsiloxane chains (also commonly referred to as PDMS), i.e., A chain of , wherein n is a number in the range of 150 to 300.

[0057] Preferably, the polydimethylsiloxane backbone comprises an average number of dimethylsiloxane units ranging from 180 to 250. This corresponds to a value for the number n ranging from 180 to 250.

[0058] Advantageously, the polyoxyalkylene chains grafted onto the polydimethylsiloxane backbone correspond to the formula , wherein R represents one or more branched or linear C1 to C4, preferably C2 or C3 alkylene groups, and m is a number ranging from 10 to 55.

[0059] Preferably, the average number m of oxyalkylene units is in the range of 20-50, more preferably 30-50.

[0060] In a further preferred embodiment, R represents one or more C2 and / or C3 alkylene groups, and in a more preferred embodiment, the polyoxyalkylene chain is selected from the formula Polyoxyethylene (EO), formula Polyoxypropylene (PO), and a chain formed of oxyethylene units and oxypropylene units (EO / PO).

[0061] According to a particularly preferred embodiment, the polyoxyalkylene chains are formed from 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 from polyoxyethylene blocks and polyoxypropylene blocks.

[0062] The grafting rate of the copolymer (ie, the number average proportion of dimethylsiloxane units having polyoxyalkylene side chains) is advantageously in the range of 0.5% to 5%, preferably 1% to 2%.

[0063] Unless otherwise stated, all average values ​​mentioned in this description are number average values.

[0064] According to a preferred embodiment, the copolymers constituting the antifoam additive are crosslinked. Such crosslinking imparts them a three-dimensional structure.

[0065] Advantageously, the one or more antifoam additives may be present in a total content ranging from 1 to 200 ppm by mass, preferably from 2 to 100 ppm by mass, more preferably from 5 to 50 ppm by mass, even more preferably from 5 to 25 ppm by mass, and most preferably from 5 to 15 ppm by mass, relative to the total mass of the composition.

[0066] The abovementioned copolymers are known per se and are commercially available.

[0067] In commercial products, these copolymers may be present in particular in diluted form in the mixtures containing them.

[0068] In this case, the content of the copolymer of such a mixture is generally in the range of 10 to 80% by mass, preferably 20 to 60% by mass, more preferably 30 to 50% by mass, and even more preferably 35 to 45% by mass.

[0069] Thus, according to one embodiment, the one or more antifoam additives are used in the form of a mixture with an inorganic oxide, such as solid hydrophobic silica.

[0070] According to another embodiment, the one or more defoaming additives are used in admixture with one or more emulsifiers, which may be chosen in particular from polyoxyalkylene polymers as described above, and more preferably from EO / PO copolymers. These polymers generally come from copolymer synthesis and correspond to the proportion of polyoxyalkylene chains not grafted onto the polydimethylsiloxane backbone.

[0071] According to a particularly preferred embodiment, the one or more antifoam additives are used in the form of a mixture with an inorganic oxide and an emulsifier, such as in particular with a hydrophobic silica as described above and one or more polyoxyalkylene polymers.

[0072] Commercial products containing one or more antifoam additives may be in the form of a solid product, in particular anhydrous (ie free of water), or in the form of a solution in a solvent which may be water or an organic solvent.

[0073] Additional surfactants

[0074] The composition according to the invention may also comprise one or more surfactants, which are different from the above-mentioned PEG and PPG block copolymers. These surfactants may be chosen in particular from water-soluble ionic, nonionic or amphoteric surfactants.

[0075] Ionic surfactants may be selected from cationic surfactants and anionic surfactants and are preferably selected from cationic surfactants. The latter generally contain nitrogen-containing groups which are cationic or ionizable in cationic form. In particular, they may 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, selected individually or in the form of a mixture.

[0076] Amphoteric surfactants may be chosen in particular from amino acids and their imide or amide derivatives, either alone or in mixtures.

[0077] The nonionic surfactant is preferably selected from the following compounds:

[0078] a) hydrocarbon and monopolyalkylene glycol ethers,

[0079] b) hydrocarbon and polyol ethers,

[0080] c) mono- or polyalkylene glycol fatty acid esters,

[0081] d) mono- or poly-glycerol fatty acid esters, and

[0082] e) and mixtures of these compounds.

[0083] "Hydrocarbyl" refers to a group selected from alkyl, alkenyl, alkynyl, aryl, aryl-alkyl or "aralkyl"; advantageously, the hydrocarbyl group is Group.

[0084] “ "Alkyl" refers to a saturated, linear, branched or cyclic hydrocarbon chain containing i to j carbon atoms.

[0085] “ "Alkenyl" refers to a linear, branched or cyclic hydrocarbon chain containing at least one carbon-carbon double bond and comprising x to y carbon atoms.

[0086] “ "Alkynyl" refers to a linear, branched or cyclic hydrocarbon chain containing at least one carbon-carbon triple bond and comprising x to y carbon atoms.

[0087] “ "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. As an example, The aryl group may be phenyl, naphthalene, anthracene, phenanthrene and tetracene.

[0088] “ "Aralkyl" means an aromatic hydrocarbon compound, preferably monocyclic, substituted by at least one linear or branched alkyl chain, and the total number of carbon atoms in its aromatic ring and its substituents ranges from x to y carbon atoms. As an example, The aralkyl group may be selected from the group consisting of benzyl, tolyl and xylyl.

[0089] For the purposes of the present invention, a polyol shall mean an oxygen-containing hydrocarbon compound comprising at least two alcohol functions. The polyol may optionally contain one or more further oxygen-containing functions, such as acetal functions, ether bridges or ester groups.

[0090] The term "fatty acids" is known per se to mean linear or branched , preferably a carboxylic acid with a C8-C30 alkyl or alkenyl chain.

[0091] a) Hydrocarbyl and mono- or polyalkylene glycol ethers

[0092] The hydrocarbyl group and the mono- or polyalkylene glycol ether may be a monoether or a diether, depending on whether the polyalkylene glycol chain is substituted at one or both ends with a hydrocarbyl group.

[0093] Hydrocarbyl mono- or polyalkylene glycol ethers are advantageously selected from the group consisting of Those of a hydrocarbon group and 1 to 60 alkylene glycol units.

[0094] More preferably, the hydrocarbyl and mono- or polyalkylene glycol ethers are selected from the following compounds:

[0095] Mono- or poly-alkoxylated hydrocarbyl monoethers of formula (I): ;

[0096] Mono- or poly-alkoxylated hydrocarbyl diethers of formula (II): ;

[0097] Mono- or poly-alkoxylated hydrocarbyl diethers of formula (III): ;

[0098] and mixtures of these compounds.

[0099] In the above formulae (I) to (III), R and R' independently represent Alkyl or alkenyl or alkynyl or aryl or aralkyl; R'' represents Alkane diyl or alkene diyl or alkyne diyl or aryl diyl (di-radical aryl) or aralkyl diyl (di-radical aralkyl).

[0100] To simplify the description, the same representation of alkyl or alkenyl or alkynyl or aryl or aralkyl will be used for the monoradical ( ) and for diradicals (R'').

[0101] In the above formulae (I) to (III), Y and Y' are groups independently selected from the following groups: , ,and .

[0102] In the same compound of formula (I), (II) or (III), the groups Y, respectively Y', may all be the same or may be different. For example, It may be intended to mean a copolymer having ethylene oxide and propylene oxide units, for example a block copolymer.

[0103] Preferably, in formulae (I) to (III), the radicals Y, respectively Y′, are all identical.

[0104] In a more preferred embodiment, in formula (I) to (III), the groups Y and corresponding Y' are all of the formula of ethylene oxide.

[0105] In the above formulae (I) to (III), n, m represent the degree of alkoxylation of the molecule and independently represent integers ranging from 1 to 60, advantageously from 1 to 30, more advantageously from 1 to 20. More preferably, n and m vary from 3 to 15, more preferably from 5 to 12.

[0106] Advantageously, in formula (III), the groups Y and Y' represent And n=m.

[0107] 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.

[0108] Even more advantageously, R, R' and R'' are selected from Alkyl, more preferably alkyl.

[0109] The compound of formula (I) may be chosen in particular from: linear or branched poly(alkoxylated) fatty alcohols comprising 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.

[0110] Commercially available compounds of formula (I) include Products in the series and Those in the series.

[0111] According to a second embodiment, in formula (I), (II) and (III), R, R' and '' are selected from alkyl.

[0112] Advantageously, this embodiment relates to formula (III) wherein R'' is Alkynyl.

[0113] For example, according to this embodiment, the compound of formula (III) can be represented by the following formula (IV):

[0114] (IV)

[0115] Wherein R1, R2, R3, and R4 are independently H or An alkyl group, and x and y independently represent an integer ranging from 1 to 60, preferably 1 to 30.

[0116] Sold by Air Products is an example of a commercial product corresponding to this formulation.

[0117] According to a third embodiment, in formulae (I), (II) and (III), R, R' and R" are chosen from aralkyl groups containing from 9 to 30 carbon atoms.

[0118] Preferably, this embodiment relates to formula (I) in which R represents a group chosen from aralkyl groups containing from 9 to 30 carbon atoms.

[0119] In a more preferred embodiment, R is selected from the group consisting of C1-C 24 , more preferably C3-C 20 , and even more preferably C5-C 18 Alkyl-p-alkylphenyl.

[0120] According to this embodiment, the compound of formula (I) may be represented by the following formula (V):

[0121] (V)

[0122] Where R5 represents C1-C 24 , preferably C3-C 20 , more preferably C5-C 18 An alkyl group, and x represents an integer ranging from 1 to 50, preferably 1 to 30.

[0123] An example of such a compound is the product sold by the company Air Products , which corresponds to the following formula:

[0124]

[0125] Advantageously, the compound of formula (I) may be a mixture obtained by reacting an alcohol R-OH with n units of ethylene oxide and / or propylene oxide. n represents the number of units of ethylene oxide and / or propylene oxide to which one mole of the alcohol is added. The number of moles of alkylene oxide reacted.

[0126] 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 etherification with the alcohol compound R'-OH. m represents the number of moles of alkylene oxide reacted with one mole of alcohol R-OH.

[0127] The compound 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.

[0128] In general, the compounds of the formulae (I), (II) and (III) are in the form of mixtures of compounds having different degrees of alkoxylation.

[0129] b) Hydrocarbon and polyol ethers

[0130] The hydrocarbon radical and the polyol ether are advantageously selected from the group consisting of C1-C 50 , preferably C3-C 40 , more advantageously C5-C 32 , even more advantageously C8-C 30 Alkyl or alkenyl alcohols and ethers of polyols.

[0131] The polyols referred to herein are distinct from mono- and polyalkylene glycols.

[0132] Advantageously, according to a first variant, the polyol is chosen from compounds belonging to the carbohydrate family and oligomers thereof. In particular, the polyol is chosen from cyclic carbohydrates, such as pyranose oligomers. In particular, the invention relates to hydrocarbyl ethers and cyclic polyglucosidoside ethers.

[0133] Examples of hydrocarbon and cyclic polyglucosides include alkyl polyglucosides such as those marketed by Dow Chemical under the name Products for sale.

[0134] Advantageously, according to a second variant, the polyol is glycerol or is selected from glycerol oligomers, for example oligomers comprising from 2 to 30 glycerol units, preferably from 3 to 20 glycerol units.

[0135] c) Mono- or poly-alkylene glycol fatty acid esters

[0136] Mono- or polyalkylene glycol 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 alkylene glycol units. Advantageously, they are derived from the reaction of fatty acids with 1 to 50 ethylene glycol units.

[0137] In general, fatty acids are molecules comprising an alkyl or alkenyl chain, with a carboxylic acid function at its terminal end, and containing from 4 to 30 carbon atoms, preferably from 8 to 30 carbon atoms, more advantageously from 8 to 24 carbon atoms.

[0138] The fatty acid radical may be a single molecule or a mixture corresponding to the fatty acid distribution of an animal or vegetable oil.

[0139] Fatty acids include, but are not limited to, saturated fatty acids such as hexanoic acid, caprylic acid, 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.

[0140] The fatty acid mono- or polyalkylene glycol esters advantageously comprise from 3 to 50, even more preferably from 5 to 40, ethylene oxide units.Preferably, the esters of fatty acids and mono- or polyalkylene glycols comprise from 3 to 50, advantageously from 5 to 40, ethylene oxide units.

[0141] Examples of esters of fatty acids and polyalkylene glycols include DUB S PEG 30S (PEG-30 stearate) sold by the company Stéarinerie Dubois.

[0142] d) Mono- or poly-glycerol fatty acid esters

[0143] Mono- or polyglycerol fatty acid esters are molecules resulting from the condensation of at least one fatty acid with 1 to 60 glycerol units, preferably 1 to 50 glycerol units.

[0144] The fatty acids are the same as those described above in point c).

[0145] The mono- or polyglycerol fatty acid esters advantageously comprise from 3 to 50, more preferably from 5 to 40, glycerol units.

[0146] Examples of polyglycerol fatty acid esters include those sold by LONZA Corporation. (Polyglyceryl laurate).

[0147] According to a preferred embodiment, the one or more surfactants are selected from nonionic surfactants. In particular, preferably one or more surfactants selected from the following: hydrocarbon mono- or polyalkylene glycol ethers, and more preferably selected from mono- or poly-alkoxylated hydrocarbon monoethers of formula (I):

[0148] ,in:

[0149] R stands for C3-C 40 , preferably C8-C 30 , even more preferably C 10 -C 24 alkyl, alkenyl or alkynyl;

[0150] Y is selected from: , and ; and preferably Y represents ;

[0151] n is an integer ranging from 1 to 60, preferably 1 to 30, more preferably 1 to 20, even more preferably 3 to 15, even more preferably 5 to 12.

[0152] According to a preferred embodiment, the composition further comprises at least one additional surfactant selected from poly(poly)alkoxylated 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.

[0153] When present, the total content of the additional surfactant may range from 5 to 1,000 mass ppm, preferably from 10 to 500 mass ppm, and more preferably from 50 to 150 mass ppm, relative to the total mass of the composition.

[0154] Other Ingredients

[0155] In addition to the nitrogen oxide reducing agents and their precursors, PEG and PPG block copolymers, antifoam additives and additional surfactants described above, the aqueous composition may optionally contain one or more other compounds.

[0156] 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.

[0157] According to a preferred embodiment, the composition according to the invention does not contain paraffin. Paraffin is of the formula alkane, wherein n is an integer ranging from 2 to 50, preferably from 6 to 40, more preferably from 18 to 35. The fact that it does not contain paraffins means that the composition does not contain paraffins added intentionally. Therefore, if such paraffins are present in the composition, they are considered as impurities and their content is less than 80 mass ppm, preferably less than 50 mass ppm, preferably less than 20 mass ppm and more advantageously less than 10 mass ppm relative to the total mass of the composition.

[0158] According to a preferred embodiment, the composition according to the invention does not contain one or more metal compounds.

[0159] A metal compound is defined as any organic or inorganic compound containing one or more metals. These compounds may be ionic or non-ionic. In particular, the composition does not contain an organometallic compound or an inorganic metal compound, whether ionic or non-ionic.

[0160] Examples of ionic compounds excluded according to this embodiment include in particular compounds of one or more metals selected from the group consisting of Fe, Cu, Ni, Co, Zn, Mn, Mg, Ti, V, Sr, Pt, Ce, Ca, Li, Na, and Nb.

[0161] "Free of metal compounds" means that the composition does not contain any such intentionally added metal compounds. Therefore, if such compounds are present in the composition, they are considered impurities, and the content of each metal element contributed by the one or more metal compounds is less than 1 mass ppm, in particular less than 0.5 mass ppm, relative to the total mass of the composition.

[0162] Composition and its embodiment

[0163] The composition used in the present invention is an aqueous composition containing a single liquid phase. In other words, the composition contains a single liquid phase, the main component of which is water. The content of water in the composition is preferably in the range of 50 to 90 mass %, preferably 60 to 80 mass %, and more preferably 65 to 70 mass % relative to the total mass of the composition.

[0164] The composition according to the invention does not comprise other liquid phases than the aqueous phase described above. In particular, the composition does not comprise any hydrocarbon liquid phase, including a hydrocarbon liquid phase in dispersed form (oil-in-water emulsion).

[0165] Liquid phase refers to the phase at 25°C and atmospheric pressure ( Pa) is a liquid phase.

[0166] Water insoluble means the amount of water insoluble at 25°C and atmospheric pressure ( A phase having a water-soluble content (water soluble) of less than 2% by mass, preferably less than 1% by mass, and even more preferably less than 0.5% by mass at 1.5% Pa.

[0167] In particular, the composition according to the invention is not in the form of an emulsion. An emulsion is defined in a known manner as a composition comprising at least two liquid phases, one of the phases being dispersed in the form of droplets in the other phase.

[0168] The composition may be prepared in the usual manner by mixing its ingredients, preferably at ambient temperature, typically in the temperature range of 10 to 60°C.

[0169] According to a preferred embodiment, the aqueous composition is prepared from a pre-formulated aqueous solution of urea, for example, a pre-formulated aqueous solution of urea containing 32.5% by mass of urea. Commercial composition.

[0170] A first embodiment comprises adding to the preformulated aqueous urea solution one or more block copolymers (2) and optionally one or more defoaming agents in the amounts required to achieve the contents defined above.

[0171] A second embodiment comprises adding a concentrated aqueous urea composition to the preformulated aqueous urea solution. According to this embodiment, the concentrated aqueous urea additive composition comprises one or more block copolymers (2) and optionally one or more antifoam additives in an aqueous solution of urea at contents much higher than those of the final aqueous composition introduced into the SCR line, preferably at a urea content of 32.5% by mass. Just before injection into the SCR line, the two compositions are mixed in a suitable ratio to obtain the desired final content.

[0172] The same embodiment can be practiced using preformulated aqueous solutions of precursors other than urea.

[0173] use

[0174] The aqueous composition according to the invention is used for treating exhaust gas from the outlet of an internal combustion engine in a selective catalytic reduction (SCR) system for nitrogen oxides.

[0175] For this purpose, it 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, which spray the composition into the exhaust gas flow. These devices are known per se.

[0176] The use according to the invention also makes it possible to prevent or reduce deposits in the duct that conveys the exhaust gas from the outlet of the internal combustion engine towards the selective catalytic reduction device.

[0177] These deposits are typically deposits of nitrogen compounds containing one or more reducing agents for nitrogen oxides and / or one or more precursors thereof, and / or decomposition products of said precursors. In particular, the invention makes it possible to prevent and / or reduce deposits of urea and / or cyanuric acid, and more particularly deposits of cyanuric acid, in the SCR exhaust line.

[0178] As indicated above, the invention makes it possible to reduce or avoid these deposits, independently of the SCR line.The invention is particularly, but not exclusively, suitable for use in what are known as "close-coupled" and "under-the-plate" SCR exhaust lines as described above.

[0179] In particular, the invention makes it possible to reduce such deposits while avoiding foaming phenomena of the composition.

[0180] As mentioned above, the composition injected into the SCR line is pumped from one or more conventional storage tanks known per se.

[0181] According to a first variant, all the components of the composition according to the invention, in particular the reducing agent(s) for nitrogen oxides and / or the precursor(s) thereof (1), the block copolymer(s) (2) and optionally the antifoam additive(s), are formulated in the same aqueous composition in the desired contents and this composition is introduced into a single tank.

[0182] According to a second variant, a first intermediate aqueous composition comprising a reducing agent or agent for nitrogen oxides and / or one or more of their precursors (1) is formulated in the desired content in the final composition obtained by mixing the two intermediate compositions. This first intermediate composition is introduced into a first tank. A second additive-concentrated aqueous intermediate composition is also formulated, which comprises a reducing agent or agent for nitrogen oxides and / or one or more of their precursors (1) in the desired content in the final composition obtained by mixing the two intermediate compositions, and a block copolymer (2) and optionally one or more defoaming additives in a content more concentrated than the content desired in the final composition.

[0183] This second composition is introduced into a second tank separate from the first. The two tanks feed a single injection system making it possible to mix the two intermediate compositions. A vehicle comprising two tanks for implementing this variant is notably described in EP2541012.

[0184] method

[0185] The method according to the invention makes it possible to treat exhaust gas problems from an internal combustion engine, preferably a diesel engine, provided with an SCR system.

[0186] The method comprises the step of introducing an aqueous composition as described above into a conduit conveying exhaust gas from an engine outlet to a device for selective catalytic reduction of nitrogen oxides. The introduction is typically achieved by pumping the composition from one or more tanks and injecting it into the conduit by means of one or more injectors, as described above.

[0187] The following examples are given by way of illustration of the present invention and should not be construed in such a way as to limit the scope thereof.

[0188] Example

[0189] Compositions tested:

[0190] According to ISO 22241, a commercially available 32.5 mass % urea aqueous solution was used. As the base composition. This base composition is called C0.

[0191] Add the following additives:

[0192] -A1: Poloxamer 182;

[0193] -A2: polyethoxylated fatty alcohol (Trideceth-8);

[0194] -A3: a cross-linked copolymer comprising a PDMS backbone having an average number of dimethylsiloxane units of 200, grafted with chains formed by polyoxyethylene blocks and polyoxypropylene blocks having an average number of OE units = 16 and an average number of OP units = 30; grafting rate 1.57%; the copolymer is in the form of a mixture also containing hydrophobic silica and an OE / OP copolymer, containing 40% by mass of the copolymer.

[0195] Additive compositions C1 to C3 are prepared by adding the additives defined above to composition C0 in the amounts detailed in Table 1 below (the amounts are expressed by mass of active material relative to the total mass of the composition):

[0196] [Table 1]

[0197]

[0198] Tests used to determine the amount of sediment:

[0199] use system( ) evaluates the deposit reduction capability of additive compositions C1 to C3 compared to reference composition C0. These tests were conducted in the laboratory of Southwest Research Institute (SwRI, San Antonio, Texas, USA). The system also has a diesel oxidation catalyst / diesel particulate filter (DOC / DPF) upstream of the injector to remove soot from the exhaust. A Bosch Denoxtronix 2.2 injector was used. A static mixer was incorporated 5 cm after the injector. At the end of the test, the amount of deposits by mass in the mixer and in the bend positioned after the mixer was quantified.

[0200] The test conditions are as follows:

[0201] - Injector pressure: 8 bar;

[0202] - Injection composition flow rate: 920 g / h;

[0203] - Air flow rate: 660 kg / h;

[0204] - Duration of the test: 1h;

[0205] - Temperature of the exhaust gas at the injector: 180-215°C.

[0206] The results obtained are detailed in Table 2 below.

[0207] [Table 2]

[0208]

[0209] These results show that the composition according to the invention makes it possible to obtain a significant reduction in the deposits generated by crystallization and / or poor decomposition of urea in SCR systems.

[0210] Foaming test :

[0211] The foaming level of these different compositions was determined using a DFA100 foaming station sold by the company Krüss.

[0212] In this system, foaming is produced by an upward air flow introduced through a fritted glass located at the bottom of the column containing the composition to be tested. This device allows direct reading of the volume of foam formed as a function of time.

[0213] The measurements were carried out at ambient temperature (25°C), each time after 30 s of air injection, at a flow rate of 0.3 L / min. For each test, the volume of composition introduced into the column was 40 mL. The volume of the foam was measured 50 s after starting the test.

[0214] Each composition was tested immediately after its preparation.

[0215] The results obtained are detailed in Table 3 below.

[0216] [Table 3]

[0217]

[0218] The above results show that compositions C2 and C3 also make it possible to significantly reduce foaming.

Claims

1. A composition comprising a single aqueous liquid phase, comprising: (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 mass relative to the total mass of the composition.

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

3. A composition according to any one of the preceding claims, characterized in that The composition contains urea in a content ranging from 25% to 42% by mass, preferably from 30% to 40% by mass, more preferably from 31% to 35% by mass, and even better from 32% to 33% by mass relative to the total mass of the composition; and even more preferably in a content of 32.5±0.7% by mass relative to the total mass of the composition.

4. A composition according to any one of the preceding claims, characterised in that One or more of the copolymers (2) are poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock polymers or poloxamers.

5. Composition according to the preceding claim, characterized in that One or more of the copolymers (2) are triblock polymers corresponding to the following formula (I): ， in: - 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; and 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.

6. Composition according to the preceding claim, characterized in that The one or more copolymers (2) are selected from Poloxamer 182.

7. A composition according to any one of the preceding claims, characterised in that The copolymer(s) (2) are present in a total content of 200 to 1000 ppm by mass, preferably 350 to 750 ppm by mass, relative to the total mass of the composition.

8. A composition according to any one of the preceding claims, characterised in that It further comprises one or more antifoaming additives, preferably selected from grafted polydimethylsiloxane polymers, and more preferably 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.

9. Composition according to the preceding claim, characterized in that The polydimethylsiloxane backbone of the copolymer comprises an average number of dimethylsiloxane units in the range of 180 to 250.

10. The composition according to any one of claims 8 and 9, characterized in that The polyoxyalkylene chain grafted onto the polydimethylsiloxane backbone of the copolymer corresponds to the formula , wherein R represents one or more C1 to C4 alkylene groups, and m is a number in the range of 10 to 55, preferably the polyoxyalkylene chain is selected from polyoxyethylene (EO), polyoxypropylene (PO), and a chain formed of oxyethylene units and oxypropylene units (EO / PO), and is even more preferably selected from the following chains formed of oxyethylene (EO) units and oxypropylene (PO) units: wherein 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 0.3 to 1.

3.

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 mass ppm, preferably 2 to 100 mass ppm, more preferably 5 to 50 mass ppm, even more preferably 5 to 25 mass ppm, and most preferably 5 to 15 mass ppm, relative to the total mass of the composition.

12. A composition according to any one of the preceding claims, characterised in that The composition does not contain paraffin.

13. Use of a composition as defined in any one of the preceding claims for treating exhaust gases from a board-mounted or stationary internal combustion engine.

14. Use of a composition as defined in any one of claims 1 to 12 for preventing or reducing deposits in a line conveying exhaust gas from the outlet of an internal combustion engine to a device for the selective catalytic reduction of nitrogen oxides.

15. Method for treating exhaust gas from an internal combustion engine provided with a device for the selective catalytic reduction of nitrogen oxides, characterized in that Said method comprises at least one step of introducing a composition as defined in any one of claims 1 to 12 into a conduit conveying the exhaust gas from the outlet of the engine to said device for selective catalytic reduction.

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