WO2021198095A1

WO2021198095A1 - Copper-based homogeneous fluid for pollutant removal from heat engines

Info

Publication number: WO2021198095A1
Application number: PCT/EP2021/057983
Authority: WO
Inventors: Annabelle COLLIN; Jérôme OBIOLS; Michel Maraval; Patrick FOUR; David Pasquier; Emmanuelle TRELA-BAUDOT; Stéphane ZINOLA
Original assignee: IFP Energies Nouvelles; Total Marketing Services
Priority date: 2020-03-30
Filing date: 2021-03-26
Publication date: 2021-10-07
Also published as: FR3108531A1; FR3108531B1

Abstract

The invention relates to a fluid for removing pollutants from heat engines, which allows both optimised selective catalytic reduction of the nitrogen oxides contained in the exhaust gases, and optimised aid of the regeneration of the particle filter by catalytic combustion of the soot particles deposited in the particle filter, said fluid consisting of a homogeneous solution of at least one organometallic copper complex comprising at least one complexing agent and copper of valency II, in an aqueous solution of at least one reducing compound or reducing agent precursor selected from urea, formamide, ammonium salts and guanidine salts, alone or as a mixture, wherein at least one complexing agent is a polyaminocarboxylic acid, and the complexing agent(s) are optionally in molar excess with respect to the copper. The invention also relates to the method for preparing said fluid and to the use thereof for removing pollutants from heat engines.

Description

Homogeneous copper-based fluid for depollution of heat engines

Technical area

The present invention describes a fluid for automotive pollution control, making it possible to perform in an optimized manner two distinct operations: the selective catalytic reduction of NOx using the Selective Catalytic Reduction technology, commonly referred to by its English name Selective Catalytic Reduction, or by the selective catalytic reduction technology. The acronym SCR, as well as the aid for the regeneration of the particulate filter (F AP), this aid for regeneration which can be manifested either by the promotion of the continuous regeneration of the particulate filter, or by the acceleration of the combustion of soot during the active regeneration phases of the DPF, or by a combination of these two advantages.

The fluid according to the invention is a homogeneous fluid which makes it possible to promote the release of ammonia and therefore the Selective Catalytic Reduction (SCR) reaction. The present invention also describes the preparation of said fluid as well as the uses of said fluid.

Prior art

Different technologies are used to reduce harmful emissions of exhaust gases from heat engines, including nitrogen oxides (NOx) and particulates.

With the evolution of regulatory standards, and more particularly the regulations on NOx emissions on diesel engines, SCR (Selective Catalytic Reduction) technology has developed considerably. This involves the injection of a reducing agent into the flow of exhaust gases and a catalyst allowing the reduction of nitrogen oxides. The use of SCR catalysts in diesel engine exhaust lines effectively reduces nitrogen oxides (NOx) produced during the combustion phase. This process requires the injection of a reducing agent precursor in solution to the exhaust. In the case where this reducing agent precursor is urea, in particular in the form of an aqueous solution of urea, for example a solution of urea at 32.5% by mass in pure water of the Adblue type ®, this is thermally and chemically decomposed in order to release the reducing agent - in this case ammonia (NH ₃ ) - which is then involved in the process of reducing nitrogen oxides (NOx).

The urea thermolysis reaction is incomplete at low temperature and does not start until around 150 ° C. This process therefore requires a minimum temperature level (of the order of 180 to 200 ° C), otherwise undesirable species may form more or less reversible nitro deposits in the exhaust line.

For these reasons, manufacturers limit or even eliminate the injection of urea at low temperature (<180 ° C). The treatment of NOx in cold conditions and / or in urban operating conditions is therefore difficult to achieve.

An example of an exhaust line integrating the NOx treatment system by selective catalytic reduction (denoted SCR abbreviation of Selective Catalytic Reduction in English terminology) and the particulate filter (abbreviated FAP), is given in patent FR 2947004. These two pollution control systems can also be grouped together in a single module, this module being known by the term of SCR on filter or SCRF or SDPF or SCRoF. An example of a homogeneous fluid used for the pollution control of heat engines is presented in patent FR 3043569, said fluid making it possible to carry out both the selective catalytic reduction of the nitrogen oxides contained in the exhaust gases, as well as the helps regenerate the particulate filter by catalytic combustion of particulate matter soot deposited in the particulate filter (so-called DPF regeneration aid function).

There remains, however, the need to optimize the treatment of NOx by producing more ammonia NH ₃ at low temperature. Tests carried out in a closed cell with monitoring of the decomposition of urea by FTIR measurement have surprisingly shown that a specific formulation of fluid was able to promote the decomposition of the urea contained, for example, in the solution. Adblue® and promote the release of ammonia. This has the particular effect of increasing the quantity of NH ₃ available for the NOx reduction reaction in the SCR catalyst, and of reducing the temperature necessary for this decomposition process.

The homogeneous fluid according to the invention comprising specific organometallic compounds can also make it possible to accelerate the reaction of thermolysis of urea to ammonia.

The fluid composition according to the invention which makes it possible to demonstrate these favorable effects on the decomposition of urea into ammonia NH ₃ is described below.

Summary of the invention The invention relates to a fluid for the pollution control of heat engines, making it possible to perform in an optimized manner both the selective catalytic reduction of nitrogen oxides contained in the exhaust gases, as well as the aid to the regeneration of the particulate filter by catalytic combustion of the soot particles deposited in the particulate filter, said fluid consisting of a homogeneous solution of at least one organometallic complex of copper comprising at least one complexing agent and valence II copper , in an aqueous solution of at least one reducing compound or reducing agent precursor chosen from urea, formamide, ammonium salts, in particular ammonium formate and ammonium carbamate, guanidine salts, in particular guanidinium formate, alone or as a mixture, in which at least one complexing agent is a polyaminocarboxylic acid, said complexing agent (s) (s) being optionally in molar excess relative to the copper.

Preferably, at least one complexing agent is selected from the following compounds: DETPA or DTPA (diethylenetriamine penta acetic acid), EDTA (ethylenediamine tetra acetic acid), HEDTA or HEEDTA (N- (2-hydroxyethyl) ethylenediamine-triacetic acid), MGDA (methylglycine diacetic acid), EDDHA (N, N '-Ethylenebis (2- [2- hydroxyphenylglycine), NTA (nitrilotriacetic acid), GLDA (N, N- bis (carboxymethyl) -L-glutamic acid), ODS (oxy acid -disuccinic), EDDS (ethylenediamine-N-N'-disuccinic acid), IDA (iminodiacetic acid), EGDTA (ethylene glycol tetraacetic acid), Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid), and their salts .

Preferably, at least one complexing agent is in the form of ammonium salts.

The copper concentration in the aqueous solution of the precursor compound of a reducing agent may be between 10 and 10,000 ppm, preferably between 10 and 5,000 ppm, preferably between 10 and 2,000 ppm, very preferably between 10. and 500 ppm, even more preferably between 10 and 100 ppm, very advantageously between 50 and 100 ppm relative to the total mass of fluid.

The fluid according to the invention can comprise between 30 and 42% by weight of urea, limits included, preferably between 30 and 40% by weight, limits included, very preferably between 31 and 35% by weight, limits included, moreover. preferably between 31 and 34% by mass, limits included, even more preferably between 32 and 33% by mass, limits included, relative to the total mass of fluid. The aqueous solution of at least one reducing compound or reducing agent precursor can comprise a mixture of urea and ammonium formate.

Advantageously, the molar excess of complexing agent (s) relative to the copper is between 2 and 200%, preferably between 4 and 100%, very preferably between 10% and 100%.

The invention also relates to a process for preparing said fluid for the depollution of heat engines, according to which at least one organometallic copper complex comprising at least one complexing agent and valence II copper in said aqueous solution of at least one reducing compound is added. or precursor of a reducing agent.

Copper can also be introduced in the form of at least one organic or inorganic salt chosen from carbonates, formates, acetates, 2 ethyl hexanoates, citrates, fumarates, gluconates, nitrates and tartrates in an aqueous solution of at least one reducing compound. or precursor of a reducing agent into which at least one complexing agent is introduced beforehand.

It is also possible to add at least one organometallic copper complex comprising at least one complexing agent and valence II copper and at least one basic copper carbonate in said aqueous solution of at least one reducing compound or precursor of a reducing agent.

The invention finally relates to the use of said fluid for the depollution of heat engines to carry out the selective catalytic reduction of nitrogen oxides contained in the exhaust gases, as well as to aid in the regeneration of the particulate filter by catalytic combustion. soot particles deposited in the particulate filter.

Said fluid can be used in an internal combustion engine of the Diesel type, the injection of said fluid being carried out upstream of the SCR and FAP exhaust gas treatment systems, and preferably being carried out. regularly depending on the operating conditions of the heat engine.

Said fluid can also be used in a thermal engine with spark ignition, running on gasoline or gas, or powered by two different fuels.

List of Figures

Other characteristics and advantages of the fluid according to the invention will become apparent on reading the following description of non-limiting examples of embodiments, with reference to the appended figures and described below.

Figure 1 shows the change in absorbance at 930 cm ¹ at 175 ° C in the kinetic monitoring tests of the degradation of urea to ammonia NH ₃ carried out in an infrared IR cell in Example 2, for fluids 1 and 2 according to the invention compared to the reference fluid (Adblue®).

Figure 2 shows the change in the amount of NH ₃ released as a function of time for fluids 1 and 2 according to the invention, compared to the reference fluid, in the thermodegradation tests at 175 ° C carried out by furnace-spectrometry coupling mass of Example 3.

Description of the embodiments

Throughout the description, the expressions "between ... and ..." and "from ... to ..." used in the present description must be understood as including each of the limits mentioned, unless otherwise specified. contrary.

By “reducing compound of nitrogen oxides or NOx” is meant a compound capable of reducing at least partially, if not entirely, nitrogen oxides (also called NOx to denote the compounds NO and NO2) into nitrogen, in the conventional operating conditions of an SCR line, i.e. in the presence of an SCR catalyst and at a temperature ranging from 150 to 400 ° C. Among the NOx reducing compounds, mention may be made very particularly of ammonia (NH ₃ ).

By "precursor compound of a NOx reducing agent" is meant a compound capable of releasing a NOx reducing agent under the effect of temperature and / or by catalytic reaction.

The present invention describes a fluid for the pollution control of heat engines, in particular diesel engines, making it possible to carry out both the selective catalytic reduction of the nitrogen oxides contained in the exhaust gases (so-called SCR function), as well as the aid in the regeneration of the particulate filter (F AP) by catalytic combustion of the soot particles deposited in the particulate filter (function known as aid to the regeneration of the F AP), this regeneration aid being able to be manifested either by the promotion of continuous regeneration of the particulate filter, either by accelerating the combustion of soot during the active regeneration phases of the DPF, or by a combination of these two advantages.

Furthermore, the specific composition of the fluid according to the invention makes it possible to decompose urea more easily and to promote the release of ammonia in situ, which makes it possible in particular to increase the quantity of ammonia NH ₃ available for the reaction of reducing NOx in the SCR catalyst, and reducing the temperature required for this decomposition process.

The fluid composition according to the invention is an aqueous composition, that is to say that its major component is water, in particular the percentage of water is greater than 50% by mass, preferably greater than 58% by mass, very preferably greater than 67% by mass.

The fluid according to the invention consists of a homogeneous solution comprising at least one organometallic complex of copper based on at least one complexing agent and of valence II copper in an aqueous solution of at least one reducing compound or precursor of an agent. reducer. According to the invention, the fluid comprises at least one complexing agent, acting in particular as a ligand for the copper ion, optionally in an overstoichiometric amount relative to the copper. In said fluid for the depollution of heat engines according to the invention, at least one complexing agent belongs to the family of polyaminocarboxylic acids and their salts, and preferably is a tetra- or penta-aminocarboxylic acid.

In the fluid for the pollution control of heat engines, in particular diesel, according to the invention, at least one complexing agent can thus be selected from the following compounds: DETPA or DTPA (diethylene triamine penta acetic acid), EDTA (ethylene diamine tetra acetic acid) ), HEDTA or HEEDTA (N- (2-hydroxyethyl) ethylenediaminetriacetic acid), MGDA (methylglycine diacetic acid), EDDHA (N, N'- Ethylenebis (2- [2-hydroxyphenyl] glycine), NTA (nitrilotriacetic acid ), GLDA (N, N-bis (carboxymethyl) -L-glutamic acid), ODS (oxy-disuccinic acid), EDDS (ethylenediamine-N-N '-disuccinic acid), IDA (iminodiacetic acid), EGDTA ( ethylene glycol tetraacetic), iron (4,5-dihydroxy-1,3-benzenedisulfonic acid), and their salts, in particular ammonium.

Very preferably, the complexing agent is chosen from DETPA or DTPA (diethylene triamine penta acetic acid) and EDTA (ethylene diamine tetra acetic acid), taken alone or as a mixture.

A preferred variant of the invention consists in using, in the fluid according to the invention, metal complexes based on complexing agents of the polyaminocarboxylic acid or polycarboxylic acid salt type, and for which, are associated (in addition to the metal center to copper base) ammonium NH4 ⁺ cations in a preferred manner. An organometallic complex which is advantageous for the fluid according to the invention is in particular an organometallic complex using said complexing agent, copper and ammonium cations, with CAS number 67989-88-2. In fact, in contrast, salts of alkaline cations (Na ⁺ , K ^+, etc.) induce, during the degradation of fluids in the SCR system, a deposit which could reduce the long-term performance of the SCR, for example a gradual increase in the pressure drop. On the contrary, the thermal degradation of the same metal complexes associated with ammonium cations generates a flow of gaseous ammonia, which can also contribute to the catalytic reduction of NOx.

Another preferred variant is to use in the fluid formulation according to the invention at least one organometallic copper complex which is an ethylenediamine complex of formula (I): bis (ethylenediamine) copper (II) hydroxide ) (CAS n ° 14552-35-3)

According to another variant of the fluid for the depollution of heat engines according to the invention, the metal ion (Cu) is introduced in the form of organic or inorganic copper salts chosen from carbonates, formates, acetates, 2 ethyl hexanoates, citrates, fumarates, gluconates, nitrates and tartrates. Preferably, the copper carbonate is a basic copper carbonate. Very preferably, basic copper carbonate is chosen from the list consisting of basic copper carbonate of chemical formula Cu ₃ (C0 _{3) 2} (0H) ₂ , basic copper carbonate of chemical formula Cu ₂ (C0 ₃ ) (0H) ₂ , basic copper carbonate of formula

CU ₂ (C0 ₃ ) (0H) ₂ .

Even more preferably, the copper carbonate is Cu ₂ C0 ₃ (0H) _{2 malachite.}

The concentration of copper, in ionic or complexed form, in the solution of the reducing compound or precursor of a reducing agent can be between 10 and 10,000 ppm, preferably between 10 and 5,000 ppm, and very preferably between 10. and 2000 ppm, more preferably between 10 and 500 ppm, even more preferably between 10 and 100 ppm, very advantageously between 50 and 100 ppm, relative to the total mass of the fluid composition according to the invention.

According to a preferred variant of the fluid for the pollution control of heat engines according to the invention, the reducing compound or precursor of a reducing agent is urea. The urea concentration in the aqueous phase is advantageously between 30 and 42% by weight, preferably between 30 and 40% by weight, very preferably between 31 and 35% by weight, even more preferably between 31 and 34% by weight, of most preferably between 32 and 33% by mass relative to the total mass of fluid. Very advantageously, it is possible to use a urea concentration equal to 32.5 +/- 0.7% by mass in solution and which meets the specifications of the ISO 22241 standard.

The solution containing the reducing compound (s) or the precursor (s) of a reducing agent can be prepared from a product meeting the specifications of ISO 22241, for example the commercial products AdBlue®, DEF, AUS32 or ARLA32.

The solution containing the reducing compound (s) or the precursor (s) of a reducing agent may contain commercial additives known to those skilled in the art. The inventive nature of the fluid according to the invention lies in the judicious selection of the components of the formulation. According to a variant of the invention, the use of at least one complexing agent in the composition, optionally in an overstoichiometric amount relative to the copper according to the invention, makes it possible, among other things, to stabilize the formulation. This is all the more important since the pH of aqueous urea solutions naturally tends to increase over time, which gradually induces a change in equilibrium in the complexation of metal salts and the possible sedimentation of metal hydroxides. The molar excess relative to copper (ie overstoichiometry) by complexing according to the invention is preferably between 2 and 200%, very preferably between 4 and 100%, even more preferably between 10% and 100%, to guarantee the stability in solution of the metal cations in complexed form.

Preferred fluid formulations are in particular compositions comprising organo-copper complexes based on DTPA, EDTA, HEDTA, optionally exhibiting an overstoichiometric amount of complexing agent relative to copper, advantageously in molar excess ranging from 2 to 200%, of preferably from 4 to 100%, very preferably ranging from 10 to 100%, in an aqueous solution of urea or an aqueous solution of ammonium formate or an aqueous solution comprising a mixture of urea and formate ammonium, the copper content advantageously being between 10 and 500 ppm. Preferably, the DTPA, EDTA and HEDTA complexing agents are used in the form of ammonium salts, alone or as a mixture. Examples of engine depollution fluid formulations leading to stable formulations that can be used in the applications targeted by the invention are typically:

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

The fluid for the depollution of heat engines according to the invention preferably remains stable in a temperature range going from -11 to + 60 ° C.

Finally, the fluid for the depollution of heat engines has good stability with respect to light.

The production of the fluid according to the invention leads to a perfectly clear and homogeneous solution, which has characteristics of stability over time, and in a pH range going from 7 to 12, and this up to a temperature of 60 ° C. . The fluid according to the invention can be made from an aqueous solution of commercial urea of AdBlue® type according to ISO 22241 specifications.

One of the advantages of the fluid according to the invention lies in the fact that the composition of this fluid combines the two engine pollution control functions in a single fluid, in an optimized manner, by promoting an increased release of ammonia.

One of the other advantages of the invention is not to significantly modify the density, viscosity and retention properties of the aqueous urea solution, which in practice means that no modification of the system for injecting the fluid into the engine. is necessary in order to benefit from the advantages of the invention.

The principle of the fluid according to the invention is to bring together in the solution a compound, such as urea, which will act as a reducing agent or precursor of a reducing agent such as ammonia, in the presence of at least one complexing agent, and a copper metal ion which, in the exhaust line under the effect of the temperature and the residual oxygen of the exhaust gases, will transform into a compound capable of lowering the oxidation temperature soot, or even to increase the rate of oxidation by a catalytic process, and thus help the regeneration of the DPF.

Preparation methods

There are different ways of making the fluid according to the invention. The fluid according to the invention can be prepared by mixing its constituents, preferably at room temperature, typically in a temperature range generally ranging from 10 to 60 ° C.

The valence II copper and said complexing agent (s) can be introduced into said aqueous solution of at least one reducing compound or precursor of a reducing agent according to different modes and variants described below or a combination of the modes described below according to any of their variants.

According to a first embodiment, an organometallic copper complex comprising at least one complexing agent and valence II copper is added to said aqueous solution of at least one reducing compound or precursor of a reducing agent, said at least one complexing agent being introduced in an amount greater than the stoichiometry relative to copper.

According to a second embodiment, the copper can be introduced in the form of salts chosen from carbonates, formates, acetates, 2 ethyl hexanoates, citrates, fumarates, gluconates, nitrates and tartrates, and dissolves in an aqueous solution of at least a reducing compound or precursor of a reducing agent, and into which at least one complexing agent is introduced beforehand, optionally in an amount greater than the stoichiometry relative to the copper. Preferably, it is also possible to introduce copper into the aqueous solution of at least one reducing compound or precursor of a reducing agent in the form of a mixture of at least one organometallic complex of copper comprising at least one complexing agent and copper of valence II and of at least one basic copper carbonate, optionally in the presence of at least one other complexing agent, optionally in an overstoichiometric amount. Preferably, said basic copper carbonate is chosen from the list consisting of basic copper carbonate of chemical formula Cu ₃ (C0 _{3) 2} (OH) ₂ , basic copper carbonate of chemical formula Cu ₂ (C0 ₃ ) ( 0H) ₂ , basic copper carbonate of formula

CU ₂ (C0 ₃ ) (0H) ₂ .

Very preferably, the copper carbonate is malachite

CU ₂ C0 ₃ (0H) ₂ . According to a preferred embodiment, the aqueous composition is prepared from a preformulated aqueous urea solution, such as for example a commercial composition known under the name of AdBlue® comprising 32.5% by weight of urea.

It is thus possible to add said at least one organometallic complex of copper, said at least one complexing agent, said copper in the form of an organic or inorganic salt, alone or as a mixture with this preformulated aqueous urea solution, in the required quantity. to achieve the levels defined above.

Another variant consists in adding to this preformulated aqueous urea solution a concentrated aqueous urea composition with additives. According to this embodiment, the concentrated aqueous urea composition with additives comprises the organometallic complex at levels much greater than that of the final aqueous composition introduced into the SCR line, in an aqueous urea solution, preferably at a content of 32.5% by mass of urea. The mixture of the two compositions in an appropriate ratio to obtain the desired final contents is carried out just before the injection into the SCR line. The same embodiments can be implemented from a preformulated aqueous solution of another reducing compound precursor than urea.

According to the first embodiment, it is for example possible to add an organometallic complex of copper in the aqueous solution of reducing agent or precursor of a reducing compound, in particular an aqueous solution of urea at a content of between 30 and 42% by weight, for example an aqueous solution of urea at 32.5% by mass such as AdBlue®. Optionally, at least one basic copper carbonate as described above is also added.

Different organometallic copper complexes, for example, are marketed, and can be added to the aqueous solution of reducing agent or precursor of a reducing compound, for example a solution of urea of the AdBlue® type in order to obtain a clear solution and homogeneous. It is also possible, when there are no commercially available complexes, to carry out the synthesis of the desired metal complex, to isolate it and add it to the aqueous solution of reducing agent or precursor of a reducing compound, for example an aqueous solution. of Adblue®-type urea.

In the fluid according to the invention, said complexing agent (s) may be present in a substoichiometric, stoichiometric or even overstoichiometric manner with respect to copper.

Complexing agents are numerous, they belong to various chemical families, and can be natural or synthetic compounds. The article by Robert D. Hancock and Arthur E. Martell (Ligand Design for Selective Complexation of Metal Ions in Aqueous Solution (Chem. Rev. 1989, pp 1875-1914) describes a detailed approach to the design and choice of complexing agents. Reference may also be made to the book by J. Kragten: Atlas of Metal- Ligand Equilibria in Aqueous Solution (Kragten / Ellis Horwood Ltd., 1978) in order to have a clearer view of the solubility conditions of species, and to the article by L. Lattuada et al. on the synthesis and applications of bifunctional polyamino polycarboxylic chelating agents {Chem. Rev. 40, pp 3019-3049 - 2011)

The metal content (copper) in solution in ionic or complexed form is adjusted to be between 1 and 10,000 ppm in the final composition of the fluid, preferably between 1 and 5,000 ppm, very preferably between 10 and 2000 ppm, more preferably between 10 and 500 ppm, even more preferably between 10 and 100 ppm, and very advantageously between 50 and 100 ppm relative to the total mass of fluid.

Reducing the metal content is preferred because it helps prevent the build-up of metal ash in the particulate filter (F AP).

The fluid as described in the present invention is stable over time in a pH range of between 7 and 12. The action of light does not modify the stability of the solution, and the conditions of crystallization and stability of the fluid. urea are not affected. Prolonged exposure to temperatures of +60 ° C also does not affect this stability.

Thawing of the solution after freezing through the core makes it possible to recover the properties of the solution before freezing (no precipitation). Finally, in the case where the fluid is prepared from a solution of urea or AdBlue®, the quantity of the agent (s) added to the solution remains low and makes it possible to satisfy the standardized urea concentration of 32 , 5% by mass. Characterization techniques

In order to precisely quantify the gains that can be obtained by using the fluids according to the invention, it is necessary to have an analytical method, representative of the operating conditions implemented in the exhaust line, making it possible to characterize the gain in terms of the temperature difference over the urea decomposition reaction and / or the gain in terms of the amount of ammonia made available at a given temperature.

Crystallization and the various chemical reactions resulting from the decomposition of urea are widely studied in the literature. To do this, different analytical techniques can be used such as thermogravimetric analysis coupled to infrared (ATG-IR) and differential scanning calorimetry (DSC). These techniques make it possible to monitor the consumption of urea and the degradation products formed as a function of temperature over time. In the publications listed below, in particular references (7), (8), (9), and (10) below, experimental conditions have been defined in order to reproduce the evaporation of the urea solution and the associated decomposition reactions occurring in the exhaust lines of vehicles equipped with an SCR system. Comparative analyzes with the conditions encountered on an engine test bench or in real life were carried out, validating the experimental and analytical approach.

Other analytical techniques more relevant than ATG or DSC were used because they are more representative of the behavior of the sample in the exhaust line. Bibliographical references:

The experimental conditions in ATG-IR and DSC known to those skilled in the art are detailed in the following bibliographical references:

(1) W. Muller, D. Heilig, S. Meyer, G. Porten, Combust. Sci. Technol. 153 (2000) 313. (2) L. Xu, RW McCabe, RH Hammerle, Appl. Catal. B: 39 (2002) 51-63.

(3) C.S. Sluder, J.M.E. Storey, S.A. Lewis, L.A. Lewis, SAE 2005-01-1858.

(4) "Urea Décomposition and SCR Performance at LowTemperature", project summary by Oak Ridge National Laboratory, Engine and Emission Control Technology, FreedomCAR and Vehicle Technologies Progam, DOE, 2005.

(5) H.L. Fang, H.F.M. DaCosta, Appl. Catal. B: 46 (2003) 17-34.

(6) P.M. Schaber, J. Colson, S. Higgens, E. Dietz, D. Theilen, B. Anspach, J. Brauer, American Laboratory, 14, Aug. 1999, 13-21.

(7) W. Brack, B. Heine, F. Birkhold, M. Kruse, G. Schoch, S. Tischer, O; Deutschmann, Chemical Engineering Science 106 (2014) 1 -8

(8) L. Xu, W. Watkins, R. Snow, G. Graham, R. McCabe, C. Lambert, R. O. Carter III, SAE 2007-01-1582

(9) T. Tang, J. Zhang, S. Shuai, D. Cao, SAE 2014-01-2808

(10) H. Dong, S. Shuai, J. Wang, SAE 2008-01-1544. Uses of the fluid according to the invention

The fluid according to the invention is a multifunctional fluid for the depollution of exhaust gases from a heat engine. Said multifunctional fluid according to the invention promotes either the continuous regeneration of the particulate filter, or the combustion of soot during the active regeneration phases of the DPF, or allows a combination of these two advantages. Furthermore, it appears that the nature of the fluid allows an increased release of ammonia in situ.

The engine depollution fluid according to the invention can be used in an internal combustion engine, preferably of the diesel type, the injection of said fluid being carried out upstream of the SCR and FAP exhaust gas treatment systems, and being carried out. regularly depending on the operating conditions of the heat engine.

The engine depollution fluid according to the invention can also be used in a thermal engine with spark ignition, operating at gasoline or gas, or according to another variant in an engine supplied by two fuels (liquid-liquid, gaseous-gaseous, or gaseous liquid).

The fluid according to the invention makes it possible to carry out the selective catalytic reduction of the nitrogen oxides contained in the exhaust gases, as well as to aid in the regeneration of the particulate filter by catalytic combustion of the soot particles deposited in the filter. with particles.

The fluid according to the invention in fact incorporates a catalytic additive for regenerating the particulate filter in the form of an organometallic complex of copper in an aqueous solution containing at least one reducing agent or at least one precursor of a NOx reducing agent.

The soot oxidation catalyst is injected directly to the exhaust, bypassing the engine's combustion chamber. The injection of the fluid according to the invention is triggered by the engine computer to meet a need to have the necessary quantity of ammonia on the SCR catalyst to effect the effective reduction of NOx.

The injections are carried out regularly, over a period typically between a few milliseconds and a few tens of seconds depending on the operating conditions of the engine, which makes it possible to promote a homogeneous mixture of the catalyst with the soot and to ensure intimate contact between soot and catalyst.

Ultimately, the fact of injecting the fluid according to the invention makes it possible either to promote the phenomenon of continuous regeneration of the particulate filter and thus to space out the periods of active regeneration of the particulate filter, or to accelerate the combustion of the particulate filter. soot during the active regeneration phases of the particulate filter, making it possible to limit the fuel consumption relating to this phase and / or to maximize the chances of burning a large mass of soot when the temperature and composition conditions exhaust gases are favorable to this active regeneration, a combination of these two advantages.

The use of the multifunctional fluid according to the invention thus makes it possible to reduce CO2 emissions by slowing down the loading of the particulate filters (continuous regeneration effect, which allows the spacing of active regenerations) and makes it possible to reduce the duration of the phases of active regeneration of these filters by accelerating the soot oxidation reaction. The intended users are both manufacturers of diesel passenger cars (PCs) and light commercial vehicles (LCVs) as well as manufacturers of heavy goods vehicles and non-road machinery such as construction machinery or agricultural tractors.

Examples

Two analytical techniques have been implemented in order to evaluate the efficiency of the depollution fluids according to the invention: - Infra-red cell;

- Four-FTICRMS coupling.

Example 1: Fluid compositions

For each of the methods identified, the evaluation of two organometallic additives was carried out by comparison with a reference composition consisting solely of a commercial aqueous solution at 32.5% by mass of urea, of the AdBlue® type, in accordance with the standard. ISO 22241.

The organometallic and complexing complexes of the fluids according to the invention were introduced at a concentration making it possible to lead to a copper mass content of 80 ppm relative to the total mass of the fluid in all cases. Fluid composition 1 is prepared as follows:

In 1 kg of a commercial solution of urea at 32.5% by mass in pure water, 244 mg of basic copper carbonate are dissolved in the form of malachite (Cu ₂ C0 ₃ (0H) ₂ ) (i.e. 70 ppm by mass of Cu) and 61 mg of an [EDTA.Cu] (NH) ₂ complex (i.e. 10 ppm by mass of Cu), the latter being introduced from an aqueous solution concentrated at 55% by mass of complex in water. The total concentration of copper in solution is therefore 80 ppm by mass.

The composition of fluid 1 is as follows: Table 11

Fluid composition 2 is prepared as follows:

In 1 kg of a commercial solution of urea at 32.5% by mass in pure water, 488 mg of [EDTA.Cu] (NH ₄ ) ₂ complex, in powder or dissolved in an aqueous solution, are dissolved. concentrated.

The composition of fluid 2 is as follows:

Table 12

Example 2: Kinetic monitoring of degradation of urea into ammonia by infrared cell (IR-cell)

Gas phase measurements at a fixed temperature were performed on fluid samples injected into an infrared cell. An infrared signal passing through the cell is collected and provides access to the degradation kinetics of urea to ammonia.

The parameters are listed below:

- Fixed temperature: 175 ° C;

- FT-IR spectrometer Each sample is analyzed at 175 ° C, a temperature at which car manufacturers limit or even stop the injection of urea into the exhaust, because the rate of conversion of urea into NH ₃ then becomes too low . Between each sample, the cell is returned to ambient temperature as well as its cleaning. A comparison between the samples of fluid according to the invention compared to the reference not comprising any additive was carried out at 175 ° C. The spectra obtained are presented below.

The various plots obtained at 175 ° C. are reproduced in FIG. 1. They show that the fluids according to the invention allow a faster production of ammonia than for the reference composition comprising only AdBlue®. Indeed, the ammonia band at 930 cm ¹ gains in intensity more quickly and reaches the plateau value sooner.

Example 3: Monitoring of the quantity of ammonia (NH3) released by measurements in mass spectrometry (Four-FTICRMS coupling) Measurements were also carried out by mass spectrometry, in order to obtain quantitative data on the quantity of NH ₃ released depending on the nature of the formulations used. The measurement was carried out with an FTICR (Fourier Transform Ion Cyclotron Resonance) mass spectrometer, incorporating a permanent magnet. The experimental set-up consists of the following elements:

- an oven: allowing the heating up to 1000 ° C, in isothermal or in a temperature ramp, of the samples;

- a nacelle pusher system (in quartz): allowing the sample to be introduced into the oven;

- a system allowing the generation of a carrier gas at a controlled rate;

- the gas mixture at the furnace outlet (carrier gas + compounds) is entrained towards a vent. Only a small part of this flow is removed by suction for analysis in the mass spectrometer.

The following experimental conditions were selected for these tests:

- The thermodegradation tests were carried out under nitrogen N2.

- Oven temperature control to maintain a stable temperature at the sample level at 175 ° C ± 5 ° C (isothermal).

- For each of the tests carried out, 2 μl (test sample) of a "daughter" solution (initial solution diluted 20 times in distilled water) were used.

The results obtained are shown in Figure 2. The tests were carried out at 175 ° C. The integrals of the peak emissions (in ppm mol / mol) shown in Figure 2 are listed in Table 13 below and represent, quantitatively, the amounts of ammonia released.

Table 13

The compositions of fluids 1 and 2 according to the invention lead to an average area and therefore a _{greater release of ammonia NH 3} at 175 ° C than for the reference composition containing only Adblue®, the gain ranging from + 9% to + 10%. These results obtained using the four-FTICRMS coupling are therefore consistent with the data coming from the IR cell.

Claims

1. Fluid for the depollution of heat engines, making it possible to perform in an optimized manner both the selective catalytic reduction of nitrogen oxides contained in the exhaust gases, as well as aid in the regeneration of the particulate filter by catalytic combustion of the soot particles deposited in the particulate filter, said fluid consisting of a homogeneous solution of at least one organometallic copper complex comprising at least one complexing agent and valence II copper, in an aqueous solution of at least at least one reducing compound or reducing agent precursor chosen from urea, formamide, ammonium salts, in particular ammonium formate and ammonium carbamate, guanidine salts, in particular guanidinium formate, alone or as a mixture, in which at least one complexing agent is a polyaminocarboxylic acid, said at least one complexing agent being in molar excess of between 2 and 200% relative to the copper.

2. Fluid for the depollution of heat engines, according to claim 1, wherein at least one complexing agent is selected from the following compounds DETPA or DTPA (diethylenetriamine penta acetic acid), EDTA (ethylenediamine tetra acetic acid), HEDTA or HEEDTA (acid). N- (2-hydroxyethyl) ethylenediamine-triacetic), MGDA (methylglycine diacetic acid), EDDHA (N, N '-Ethylenebis (2- [2- hydroxyphenyljglycine), NTA (nitrilotriacetic acid), GLDA (N, N- bis acid) (carboxymethyl) -L-glutamic), ODS (oxy-disuccinic acid), EDDS (ethylenediamine-N-N'-disuccinic acid), IDA (iminodiacetic acid), EGDTA (ethylene glycol tetra acetic acid), Tiron (acid 4,5 -dihydroxy-1,3-benzenedisulfonique), and their salts.

3. Fluid for the pollution control of heat engines, according to one of claims 1 or 2, wherein at least one complexing agent is in the form of ammonium salts.

4. Fluid for the depollution of heat engines, according to any one of claims 1 to 3, wherein the copper concentration in the aqueous solution of the precursor compound of a reducing agent is between 10 and 10,000 ppm, preferably between 10 and 5000 ppm, preferably between 10 and 2000 ppm, very preferably between 10 and 500 ppm, even more preferably between 10 and 100 ppm, very advantageously between 50 and 100 ppm relative to the total mass of fluid.

5. Fluid for the depollution of heat engines, according to any one of claims 1 to 4, comprising between 30 and 42% by mass of urea, limits included, preferably between 30 and 40% by mass, limits included, very preferably between 31 and 35% by weight, limits included, more preferably between 31 and 34% by weight, limits included, even more preferably between 32 and 33% by weight, limits included, relative to the total mass of fluid.

6. Fluid for the depollution of heat engines, according to any one of claims 1 to 5, wherein the aqueous solution of at least one reducing compound or reducing agent precursor comprises a mixture of urea and formate. ammonium.

7. Fluid for the depollution of heat engines, according to any one of claims 1 to 6 wherein the molar excess of said at least one complexing agent relative to the copper is between 4 and 100%, very preferably between 10. % and 100%.

8. Process for preparing the fluid for the depollution of heat engines according to any one of claims 1 to 7, according to which at least one organometallic copper complex comprising at least one complexing agent and valence II copper in said aqueous solution is added. at least one reducing compound or precursor of a reducing agent.

9. A method of preparing the fluid for the depollution of heat engines according to any one of claims 1 to 7 wherein the copper is introduced in the form of at least one organic or inorganic salt chosen from carbonates, formates, acetates, 2 -ethyl-hexanoates, citrates, fumarates, gluconates, nitrates and tartrates in an aqueous solution of at least one reducing compound or precursor of a reducing agent into which said at least one complexing agent is introduced beforehand.

10. Process for preparing the fluid for the depollution of heat engines according to any one of claims 1 to 7, in which at least one organometallic copper complex is added comprising at least one complexing agent and valence II copper and at least one carbonate. of basic copper in said aqueous solution of at least one reducing compound or precursor of a reducing agent.

11. Use of the fluid for the depollution of heat engines according to any one of claims 1 to 7 for carrying out the selective catalytic reduction of the nitrogen oxides contained in the exhaust gases, as well as aid in the regeneration of the filter. particulate matter by catalytic combustion of soot particles deposited in the particulate filter.

12. Use of the fluid for the depollution of heat engines according to claim 11, in an internal combustion engine of Diesel type, the injection of said fluid being carried out upstream of the SCR and FAP exhaust gas treatment systems, and being preferably operated regularly depending on the operating conditions of the heat engine.

13. Use of the fluid for the depollution of heat engines according to claim 11 in a heat engine with spark ignition, running on gasoline or gas, or supplied by two different fuels.