COMPOSITION MADE FROM UREA FOR TREATING EXHAUST GASES

Abstract

An aqueous composition including an NOx reducing agent or a precursor of such an agent, in particular urea, and at least one paraffin dispersed in the aqueous phase. Such a composition can be used for reducing the formation of deposits in an SCR exhaust system while preventing foaming during the handling of same.

Claims

1-23. (canceled)

24. An aqueous composition comprising at least one reducing agent for NOx or one precursor of a reducing agent for NOx, and at least one paraffin dispersed in the aqueous phase, said paraffin representing from 50 to 10 000 ppm by weight, with respect to the weight of reducing agent for NOx or with respect to the weight of precursor of reducing agent for NOx.

25. The composition as claimed in claim 24, wherein the precursor of the reducing agent for NOx is urea.

26. The composition as claimed in claim 24, wherein the C.sub.20-C.sub.36 paraffins represent at least 90% by weight, with respect to the total weight of paraffins in the composition.

27. The composition as claimed in claim 24, which comprises at least one surfactant.

28. The composition as claimed in claim 27, which comprises at least one nonionic surfactant.

29. The composition as claimed in claim 28, which comprises at least one nonionic surfactant chosen from oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups, at least one of the hydroxyl groups being substituted by a mono- or polyalkoxylated group.

30. The composition as claimed in claim 29, wherein the nonionic surfactant is chosen from polyethoxylated sorbitans and polyethoxylated isosorbides.

31. The composition as claimed in claim 29, wherein the oxygen-comprising C.sub.4-C.sub.20 hydrocarbon surfactants comprising one or two furanose or pyranose rings, and one or more mono- or polyalkoxylated hydroxyl groups, are present in amounts ranging from 1% to 70% by weight, with respect to the total weight of paraffins in the composition.

32. The composition as claimed in claim 27, which comprises at least one stabilizing agent for the emulsions.

33. The composition as claimed in claim 32, which additionally comprises at least one stabilizing agent for emulsions chosen from fatty acids.

34. The composition as claimed in claim 33, wherein the fatty acid is present in amounts ranging from 1% to 50% by weight, with respect to the total weight of paraffins in the composition.

35. The composition as claimed in claim 28, which comprises at least one nonionic surfactant chosen from esters of fatty acids and of oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups, at least one of the hydroxyl groups being substituted by a mono- or polyalkoxylated group.

36. The composition as claimed in claim 35, wherein the nonionic surfactant or surfactants are chosen from esters of fatty acids and of mono- or polyethoxylated sorbitans and esters of fatty acids and of mono- or polyethoxylated isosorbides.

37. The composition as claimed in claim 35, wherein the esters of fatty acids and of oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more mono- or polyalkoxylated hydroxyl groups, are present in amounts ranging from 1% to 70% by weight, with respect to the total weight of paraffins in the composition.

38. The composition as claimed in claim 27, which comprises at least: a nonionic surfactant chosen from oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups, at least one of the hydroxyl groups being substituted by a mono- or polyalkoxylated group, an emulsion stabilizer chosen from C.sub.8-C.sub.30 fatty acids, and a nonionic surfactant chosen from esters of fatty acids and of oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups, at least one of the hydroxyl groups being substituted by a mono- or polyalkoxylated group.

39. The composition as claimed in claim 27, which comprises at least: a nonionic surfactant chosen from oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups, at least one of the hydroxyl groups being substituted by a mono- or polyalkoxylated group, an emulsion stabilizer chosen from C.sub.8-C.sub.30 fatty acids, and a nonionic surfactant chosen from esters of fatty acids and of oxygen-comprising C.sub.4-C.sub.20 hydrocarbon molecules comprising one or two furanose or pyranose rings, and one or more hydroxyl groups.

40. The composition as claimed in claim 27, wherein the combined surfactants and emulsion stabilizers represent from 1% to 100% by weight, with respect to the total weight of paraffin(s) in the composition.

41. A process for the treatment of exhaust gases in an internal combustion engine equipped with an SCR system, said process comprising at least one stage of introduction of a composition as claimed in claim 24 into the SCR line, upstream of the SCR system.

42. The process as claimed in claim 41, for averting, limiting or preventing the formation of deposits in an SCR exhaust line.

43. The process as claimed in claim 41, for reducing the deposits in the SCR line.

Description

FIGURES

[0193] FIG. 1: diagrammatic representation of an SCR test bed.

[0194] FIG. 2: diagrammatic representation of a device for evaluation of the foaming.

[0195] The examples below are given for the purpose of illustrating the characteristics of the invention but not of limiting the scope thereof.

[0196] Experimental Part:

[0197] In the experimental part, all the percentages are expressed by weight, with respect to the total weight of the composition.

[0198] IMaterials and Methods:

[0199] Preparation of the Compositions:

[0200] Use was made, as basis for the composition, of a commercial 32.5% by weight aqueous urea solution: AdBlue.

[0201] This composition was additivated with different compositions in the amounts shown in table 2: on the one hand with an emulsion of paraffins (Emulsion P) and on the other hand with surfactant compositions of the prior art. [0202] Emulsion P: aqueous emulsion comprising (as % by weight, with respect to the total weight of the emulsion) [0203] 50% of water, [0204] 42% of C.sub.22-C.sub.32 paraffins, [0205] approximately 8% of a mixture of polyoxyethylenated sorbitans and isosorbides, the distribution of the polyoxyethylenated chains being centered respectively on C.sub.13 and C.sub.16, of fatty acids consisting of stearic acid (C18:0), palmitic acid (C16:0) and myristic acid (C14:0) and stearic ester (C18:0) and palmitic ester (C16:0) of sorbitan. [0206] Polyaldo TMSH KFG (3-1-SH): product of the reaction of a triglycerol with saturated C.sub.16-C.sub.18 and unsaturated C.sub.18 fatty acids, sold by Lonza [0207] Marlipal O13/30: C.sub.13-oxo alcohol (isotridecanol+3 EO/mol), sold by Sasol [0208] Mixture of 70% Marlipal O13/120+30% Marlipal O13/30 (sold by Sasol): 30% C.sub.13-oxo alcohol (isotridecanol+3 EO/mol)+70% C.sub.13-oxo alcohol (isotridecanol+12 EO/mol)

[0209] Radiasurf 7157: ethoxylated (20 EO) sorbitan monostearate, HLB=15, sold by Oleon

[0210] Radiasurf 7137: ethoxylated (20 EO) sorbitan monolaurate, sold by Oleon

[0211] Proppabort: alkoxylated fatty alcohol, sold by Proppabort AB

[0212] Observation and Measurement of the Deposits:

[0213] The tests were carried out on an SCR test bed 1, the configuration of which is represented in FIG. 1. The composition C is sprayed via an injector 2 located slightly set back with respect to the stream 3 of the exhaust gases. The droplets of solution 4 will subsequently be impacted on the mixer 5, in order to facilitate the homogenization thereof and the hydrolysis reaction of the urea in the stream of hot gases. The exhaust line is fed with air by a hot air gun (not represented); the temperature of the gases and their flow rate are controlled. Thermocouples (not represented) placed at the injector, in the line outlet and close to the line make it possible to monitor the thermal conditions during the test.

[0214] The operating conditions of the test are summarized in table 1 below:

TABLE-US-00001 TABLE 1 Operating conditions selected for the SCR test bed Duration [h] 2.5 Airflow rate [L/min] 500 AdBlue flow rate [g/h] 60 Injector temperature [ C.] 250

[0215] In order to evaluate the performance of a product, the weight of deposits collected over the following two regions: the injector (nose/injection nozzle holder) region and the mixing (upstream/mixer/downstream) region, was compared.

[0216] The deposits were thus collected and weighed over the injector and mixing regions of the SCR line. The total of the deposits collected for each test was calculated.

[0217] Evaluation of the Foaming:

[0218] The method is based on the use of a device 10 comprising a tank 11 (injection column) in which the product 12 is stored under pressure, a 250-ml graduated glass measuring cylinder 13, a detection cell 14 of photoelectric type, a solenoid valve 15, which controls the opening and the closing of the tank, and a stopwatch (not represented). The method consists in injecting an amount of product 12 (100 ml) at a pressure of 400 millibar into the graduated measuring cylinder 13. The detection cell 14 detects the moment when the 100 ml of product 12 initially present in the injection column 11 have emptied into the measuring cylinder 13. The solenoid valve 15 is closed and the stopwatch is started. The volume of foam formed is located visually using the graduations 16 present on the measuring cylinder 13. The time at the end of which the foam has completely disappeared is also noted. The test is halted after 300 seconds if foam is still present.

[0219] IITests:

[0220] The tests carried out are reported in table 2 below. The reference example was carried out with a commercial 32.5% aqueous urea solution AdBlue. The other examples were carried out with the same commercial 32.5% aqueous urea solution AdBlue to which the various additives mentioned were added.

[0221] Tests C1 and C2 are according to the invention. Tests D1 to D6 are comparative.

TABLE-US-00002 TABLE 2 Formulations produced Amount of additive as active Amount of Test material additive No. Additive (ppm) (ppm) Observations Ref. (*) Light and clear C1 Emulsion P 250 500 Opalescent C2 Emulsion P 500 1000 Opalescent D1 Polyaldo TMSH 500 500 Cloudy KFG (3-1-SH) D2 Marlipal O13/30 500 500 Light and clear D3 Marlipal 500 500 Light and clear (70% O13/120 + 30% O13/30) D4 Radiasurf 7157 500 500 Light and clear D5 Radiasurf 7137 500 500 Light and clear D6 Proppabort 1000 1000 Slightly cloudy (*) Adblue 32.5% aqueous urea solution

[0222] IIIResults:

[0223] The results of the tests are reported in table 3 below:

TABLE-US-00003 TABLE 3 Results of the tests Total Foam amount Amount Amount Test Time for foam volume of deposits deposits No. disappearance (s) [mL] deposits mixing injector Ref. (*) 0 0 884 803 81 C1 14 30 221 136 85 C2 198 30 204 127 77 D1 >300 40 222 174 48 D2 150 40 367 251 116 D3 >300 68 228 77 151 D4 >300 92 342 241 101 D5 >300 90 463 356 107 D6 >300 30 537 379 158

[0224] It is found that the examples according to the invention C1 and C2 exhibit a reduced amount of deposits with respect to the reference and with respect to the majority of the comparative examples (D2 to D6). In addition, the examples according to the invention exhibit little foaming, and this rapidly disappears, in contrast to the compositions of the prior art.