Fluid for purifying heat engines and methods for preparing said fluids by emulsification

Abstract

The present invention describes a fluid which is suitable for the decontamination of heat engines which can carry out, at the same time, both the catalytic reduction of oxides of nitrogen (NOx) contained in exhaust gases and assist in the regeneration of the particulate filter (PF). The invention also describes several embodiments of said fluid consisting of producing an oil-in-water type emulsion.

Claims

1. A fluid for the decontamination of heat engines in order to be able to carry out, at the same time, both the selective catalytic reduction of oxides of nitrogen contained in exhaust gases as well as assisting in the regeneration of the particulate filter (PF) by catalytic combustion of particles of soot deposited in the particulate filter, the fluid comprising: an oil-in-water emulsion comprising: an aqueous solution of at least one reducing compound or precursor of a reducing compound, the aqueous solution of at least one reducing compound or precursor of a reducing compound being a solution of urea, 32.50.7% by weight in solution in demineralized water or being a solution of at least one of ammonium formate, ammonium carbamate, and guanidine salts in water, a dispersion of metal oxides in a hydrocarbon or a mixture of hydrocarbons, and a surfactant or a mixture of surfactants enabling the production and stabilization of a stable oil-in-water type emulsion, the surfactant or mixture of surfactants comprising a nonionic surfactant soluble in water and having an HLB (hydrophilic/lipophilic balance) in the range 7 to 16 selected from any mixture produced from the chemical families sorbitan esters, ethoxylated sorbitan esters, ethylene oxide (EO)/propylene oxide (PO) block copolymers, ethoxylated fatty acids or alcohols, ethoxylated fatty acid esters, ethoxylated octylphenols, alkylpolyglucosides or APG, alone or as a mixture.

2. The fluid for the decontamination of heat engines, as claimed in claim 1, in which the metal oxides, used alone or in combination, are selected from the following list of metals: Fe, Cu, Ni, Co, Zn, Mn, Ti, V, Sr, Pt, Ce, Ca, Li, Na, Nb.

3. The fluid for the decontamination of heat engines as claimed in claim 1, in which the dispersion of metal oxides is in the form of a dispersion of an oxide of iron or a mixture of oxides of iron in a mixture of hydrocarbons of the Eolys Powerflex type.

4. The fluid for the decontamination of heat engines as claimed in claim 1, in which the reducing compound or precursor of a reducing agent in aqueous solution is selected from urea, ammonia, formamide, and ammonium salts.

5. The fluid for the decontamination of heat engines as claimed in claim 1, in which the concentration of metal ion in the emulsion produced using the surfactant or surfactants with the reducing compound or precursor of a reducing agent is in the range 10 to 10000 ppm.

6. The fluid for the decontamination of heat engines as claimed in claim 1, in which the aqueous solution of at least one reducing compound or precursor of a reducing compound is urea, 32.50.7% by weight in solution in demineralized water.

7. The fluid for the decontamination of heat engines as claimed in claim 1, in which the solution of the reducing compound is prepared from the commercially available product AdBlue.

8. The fluid for the decontamination of heat engines as claimed in claim 1, in which the fluid remains stable at a temperature in the range 11 C. to +60 C.

9. A process for the preparation of fluid for the decontamination of heat engines as claimed in claim 1, in which a surfactant is added to an aqueous solution of at least one reducing compound or precursor of a reducing agent, followed by addition of the dispersion of metal oxides which is emulsified by means of a mixing system, then diluting by adding the aqueous solution of at least one reducing compound or precursor of a reducing agent in order to obtain the desired metal oxides content.

10. Use of the fluid for the decontamination of heat engines as claimed in claim 1, in an internal combustion engine of the diesel type, the injection of said fluid being carried out upstream of the SCR and PF systems for the treatment of exhaust gases and being operated as a function of the operational conditions of the heat engine.

11. The fluid for the decontamination of heat engines, as claimed in claim 1, in which the metal oxides, used alone or in combination, are selected from the following list of metals: Fe, Ce, Cu, Sr.

12. The fluid for the decontamination of heat engines as claimed in claim 1, in which the aqueous solution of at least one reducing compound or precursor of a compound is a solution of at least one of ammonium formate, ammonium carbamate, and guanidine salts in water.

13. The fluid for the decontamination of heat engines as claimed in claim 1, in which the concentration of metal ion in the emulsion produced using the surfactant or surfactants with the reducing compound or precursor of a reducing agent is in the range 10 to 5000 ppm.

14. The fluid for the decontamination of heat engines as claimed in claim 1, in which the concentration of metal ion in the emulsion produced using the surfactant or surfactants with the reducing compound or precursor of a reducing agent is in the range 10 to 2000 ppm.

15. A process for the decontamination of heat engines, comprising injecting the fluid for the decontamination of heat engines as claimed in claim 1 directly into an exhaust system of an internal combustion engine of the diesel type upstream of the SCR and PF systems for the treatment of exhaust gases and being operated as a function of the operational conditions of the heat engine.

16. The fluid for the decontamination of heat engines as claimed in claim 1, in which the aqueous solution of at least one reducing compound or precursor of a compound is a solution of guanidinium formate in water.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention consists of a multi-functional fluid for the decontamination of exhaust gases emitted by an internal combustion engine. The multi-functional fluid in accordance with the invention promotes either the continuous regeneration of the particulate filter or the combustion of soot during the active regeneration phases of the PF, or can be used to combine these two advantages.

(2) This fluid is essentially composed of an emulsion between a dispersion of one or more metal oxides in a hydrocarbon or a mixture of hydrocarbons on the one hand, and an aqueous solution containing at least one reducing agent or at least one precursor of a reducing agent for NOx on the other hand.

(3) Said emulsion is made possible by the presence of one or more surfactants.

(4) The fluid obtained in this manner can be used to concomitantly carry out two of the functions necessary to the decontamination of heat engines, more particularly the diesel engine, namely the selective catalytic reduction of NOx and assistance with the oxidation of particles trapped in the PF by catalytic combustion.

(5) Producing the fluid in accordance with the invention results in an emulsion which has the characteristics of stability over time, with this being up to a temperature of 60 C.

(6) The fluid in accordance with the invention may be produced from a commercially available solution of AdBlue which complies with the ISO 22241 specifications.

(7) One important advantage of the fluid in accordance with the invention resides in the fact that it combines the two functions of engine emission decontamination in a single fluid.

(8) One of the other advantages of the invention is that it does not substantially modify the properties of density, viscosity and storage of the solution of AdBlue, which in practice means that it is not necessary to modify the system for injecting AdBlue into the engine in order to benefit from the advantages of the invention.

(9) The principle of the invention is to combine, in a single fluid, on the one hand a reducing compound or precursor of a reducing agent such as urea, which will act as a reducing agent or as a precursor of a reducing agent such as ammonia, and on the other hand a dispersion of metal oxides which, in the exhaust line under the effect of temperature and the residual oxygen of the exhaust gases, will bring the soot into contact with a compound which reduces its oxidation temperature, which has the effect of assisting continuous oxidation of the filtered soot and reducing the energy cost of active regeneration of the filter when this is necessary. Another effect of the metal oxides is to increase the rate of oxidation of the soot by a catalytic process and thus to regenerate the PF in a shorter time.

(10) Various ways of producing the fluid in accordance with the invention exist, corresponding to several variations.

(11) The simplest consists of modifying a commercial solution of AdBlue or of producing a solution of urea which complies with ISO 22241 specifications, or in fact of using another reducing compound such as ammonia, for example.

(12) It is possible to produce stable emulsions with different nonionic surfactants and dispersions which are capable of providing a sufficient concentration of at least one metal oxide promoting the oxidation of soot. The remainder of the description details several embodiments of the fluid in accordance with the invention.

(13) The chemistry of surfactants is very rich and has many applications in fields as disparate as the cosmetics industry, pharmaceuticals industry, road industry and detergent industry, for example.

(14) There are many surfactants. They may be divided into cationic, anionic and nonionic surfactants.

(15) Emulsification (i.e. the process of dispersion of oil in water) may be carried out using any appropriate means which is known to the person skilled in the art with the aid of any dynamic mixer, batchwise or continuously.

(16) Examples of equipment of this type are rotor-stator mixers (for example those sold by VMI Rayneri under the trademark Ultramix), colloidal mills, high pressure homogenizers or in fact ultrasound devices.

(17) Equipment constituted by a rotary agitator comprising one or more movable parts fixed on a shaft which has a power density of the order of 10.sup.3 to 10.sup.9W/m.sup.3 is particularly suitable.

(18) The metal oxides content in the final composition of the fluid in accordance with the invention may be in the range 1 to 10000 ppm, preferably in the range 1 to 5000 ppm, and more preferably in the range 10 to 2000 ppm.

(19) Reducing the metal content can prevent the accumulation of metallic ash in the PF.

(20) The fluid as described in the present invention is stable over time. The action of light does not modify the stability of the solution and the crystallization conditions and the stability of the urea are not affected.

(21) Prolonged exposure to temperatures of +60 C. also do not affect this stability.

(22) Thawing of the solution after freezing to the core can recover the properties of the solution before freezing (no decanting or coalescence). Finally, in the case in which the fluid is prepared from a solution of urea or AdBlue, the quantity of the agents added to the solution remains low and can comply with the normalized concentration of urea of 32.50.7%.

(23) The inventive merit of the invention resides in the judicious selection of the components of the formulation. It is not obvious to produce a stable emulsion between a dispersion of metal oxides in one or more hydrocarbons on the one hand and an aqueous solution of urea on the other hand. In fact, naturally, these two phases, one aqueous and the other oily, are not miscible.

EXAMPLES IN ACCORDANCE WITH THE INVENTION

(24) The examples below describe four embodiments for the preparation of the fluid in accordance with the invention. These examples do not limit the possibilities of the invention, but are provided by way of illustration.

(25) The fluids may be prepared at ambient temperature or at a temperature of less than 60 C.

(26) When the fluid has two distinct phases, it does not comply with the specifications.

(27) These few cases demonstrate that obtaining a fluid in accordance with the invention is not a systematic occurrence. All of the examples described were produced with a commercially available solution of AdBlue for the urea solution, and with commercially available Eolys Powerflex for the dispersion of metal oxides in hydrocarbons.

Examples in Accordance with Embodiment 1

(28) The fluid was produced as follows: 51 g of AdBlue was introduced into a 150 cm.sup.3 glass flask; a mass of 1.5 grams of surfactant was added which was dispersed with the aid of a manual stirrer. Next, 3 g of Eolys Powerflex was introduced which was dispersed with the aid of a laboratory mixer provided with a blade adapted to forming an emulsion. After stirring for 5 minutes at ambient temperature, the appearance of the fluid was evaluated.

(29) TABLE-US-00001 TABLE 1 Process embodiment 1 Eolys Surfactant Appearance of Example AdBlue Powerflex (1.5 g) fluid 1 51 g 3 g Laurylglucoside Heterogeneous appearance - two distinct phases 2 51 g 3 g Decylglucoside Homogeneous appearance 3 51 g 3 g Cocoglucoside Heterogeneous appearance - two distinct phases

(30) It can be seen that fluid compositions exist which provide emulsions with a homogeneous appearance without any solid deposits, which are then diluted with the necessary quantity of AdBlue in order to obtain the target concentration of metal oxides in the range 300 to 400 ppm in the example. The appearance of the fluid was evaluated once more. It can be seen that the fluid compositions were still emulsions with a homogeneous appearance with no solid deposits or phase separation.

(31) In Table 1, Examples 1 and 3 are not in accordance with the invention because they resulted in a heterogeneous fluid. Example 2 satisfied the criteria of the invention.

Examples in Accordance with Embodiment 2

(32) The fluid was produced as follows: 100 g of AdBlue was introduced into a 250 cm.sup.3 glass flask; a mass of 1 gram of surfactant was added which was dispersed with the aid of a manual stirrer. Next, 2 g of Eolys Powerflex was introduced which was dispersed with the aid of a laboratory mixer provided with a blade adapted to the formation of an emulsion. After stirring for 15 minutes at ambient temperature, the appearance of the fluid was evaluated.

(33) TABLE-US-00002 TABLE 2 Process embodiment 2 Eolys Appearance of Example AdBlue Powerflex Surfactant (1 g) fluid 4 100 g 2 g Laurylglucoside Heterogeneous (BASF plantacare appearance - two 1200 UP) distinct phases 5 100 g 2 g Decylglucoside Homogeneous (BASF plantacare appearance 2000 UP) 6 100 g 2 g Cocoglucoside Heterogeneous (BASF plantacare appearance - two 818 UP) distinct phases

(34) It can be seen that fluid compositions exist which provide emulsions with a homogeneous appearance without any solid deposits.

(35) In Table 2, Examples 4 and 6 are not in accordance with the invention because they resulted in a heterogeneous fluid. Example 5 satisfied the criteria of the invention.

(36) Examples Illustrating the Stability of the Fluid as a Function of Temperature

(37) In order to verify that the examples of fluid in accordance with the invention did not modify the crystallization temperature, we placed test tubes containing the fluid compositions in accordance with the invention in a cold bath maintained at 10 C.1 C. for two hours. We observed that at this temperature, the fluid remained homogeneous in appearance.

(38) TABLE-US-00003 TABLE 3 Evaluation of characteristics of different fluids in accordance with the invention at a temperature close to that for the crystallization of AdBlue Example Example tested Appearance of fluid at 10 C. 7 Example 2 Homogeneous appearance, liquid 8 Example 5 Homogeneous appearance, liquid

(39) In order to verify that the fluid examples in accordance with the invention remained stable after crystallization due to freezing then thawing, we placed test tubes containing the various fluids in accordance with the invention for two hours in a cold bath maintained at 18 C.1 C., then we removed them after confirming that the fluids had solidified, in order to return them to ambient temperature over two hours. We observed that the various fluids regained their homogeneous, liquid appearance.

(40) TABLE-US-00004 TABLE 4 Influence of freezing/thawing on the stability of various fluids in accordance with the invention Appearance of fluid after Example freezing to the core at 18 C. then Example tested thawing 9 Example 2 Homogeneous appearance, liquid 10 Example 5 Homogeneous appearance, liquid