USE OF A UREA COMPOSITION TO PRODUCE DIESEL EXHAUST FLUID (AUS 32)

Abstract

A process for producing a NOx reductant AUS 32 solution (diesel exhaust fluid), including at least the mixing of water and a particulate composition including (i) urea and an additive comprising component (ii). The additive component is a combination of at least one polymer or oligomer containing amino groups and at least one functionalized polyvinyl compound, wherein the proportion by weight of component (i) in the particulate composition is >60% by weight and the proportion by weight of component (ii) in the particulate composition is <1% by weight and wherein a urea solution is obtained and the proportion by weight of component (i) in the urea solution obtained is between 31% by weight and 34% by weight.

Claims

1.-10. (canceled)

11. A process for producing a NO.sub.x reductant AUS 32 solution (diesel exhaust fluid), comprising at least the mixing of water and a particulate composition comprising: (i) urea; and an additive comprising component (ii): (ii) a combination of at least one polymer or oligomer containing amino groups and at least one functionalized polyvinyl compound; wherein the proportion by weight of component (i) in the particulate composition is >60% by weight and the proportion by weight of component (ii) in the particulate composition is <1% by weight, and wherein a urea solution is obtained and the proportion by weight of component (i) in the urea solution obtained is not less than 31% by weight and not more than 34% by weight.

12. The process of claim 11, wherein the additive comprises component (iii): (iii) at least one compound selected from the group of the aliphatic dicarboxylic acids, and anhydrides, the aliphatic tricarboxylic acids, and anhydrides, the aromatic dicarboxylic acids, and anhydrides, wherein the proportion by weight of component (i) in the particulate composition is >60% by weight and the proportion by weight of the sum total of components (ii) and (iii) in the particulate composition is <1% by weight.

13. The process of claim 11, wherein the particulate composition comprises: (i) urea; and an additive comprising component (ii) and component (iii): (ii) a combination of polyethyleneimine and polyvinyl alcohol or a combination of polyethyleneimine and polyvinylamine; (iii) at least one compound selected from the group of the aliphatic dicarboxylic acids, and anhydrides, the aliphatic tricarboxylic acids, and anhydrides, the aromatic dicarboxylic acids, and anhydrides; wherein the proportion by weight of component (i) in the particulate composition is >97% by weight and the proportion by weight of the sum total of components (ii) and (iii) in the particulate composition is <1% by weight.

14. The process of claim 11, wherein the particulate composition comprises: (i) urea; and an additive comprising component (ii) and component (iii): (ii) a combination of polyethyleneimine and polyvinylamine; (iii) at least one compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid, phthalic anhydride, wherein the proportion by weight of component (i) in the particulate composition is >97% by weight and the proportion by weight of the sum total of components (ii) and (iii) in the particulate composition is <1% by weight.

15. The process of claim 14, wherein the polyethyleneimine in component (ii) has a molecular weight in the range of 500-2,000,000 Da.

16. The process of claim 15, wherein the polyvinylamine in component (ii) has a molecular weight in the range of 500-1,000,000 Da.

17. The process of claim 11, wherein the proportion by weight of component (i) in the composition is >98% by weight

18. The process of claim 17, wherein the proportion by weight of component (i) in the composition is >98.5% by weight.

19. The process of claim 11, wherein the proportion by weight of the sum total of components (ii) and (iii) in the composition is <0.5% by weight.

20. The process of claim 11, wherein the proportion by weight of the sum total of components (ii) and (iii) in the composition is <0.4% by weight.

21. The process of claim 11, wherein the proportion by weight of the sum total of components (ii) and (iii) in the composition is <0.3% by weight.

22. The process of claim 11, wherein the proportion by weight of the sum total of components (ii) and (iii) in the composition is <0.25% by weight.

23. A NO.sub.x reductant AUS 32 solution (diesel exhaust fluid) obtained by the process of claim 11.

Description

EXAMPLES

Example 1

[0108] In a test plant, urea was granulated in a fluidized bed granulator having a cylindrical fluidized bed of diameter 40 cm at a temperature of about 108 C. The fluidized bed was concluded at its lower end by a perforated plate, the holes of which had a diameter of 2.0 mm. The fluidization air flowed at a superficial flow rate of about 2 m/s into the fluidized bed. An overflow was mounted 10 cm above the baseplate at the side wall of the bed. A defined amount (about 45 kg) of urea particles or urea granules having a narrow size distribution was then introduced into the granulator column as seeds for the granulation. The bed with the seeds (about 50 cm deep) was fluidized with hot air at a temperature of about 100 C., and the addition of 96 to 97% by weight urea solution at a temperature of about 135 C. was commenced as soon as the bed had reached the temperature of about 108 C. that was envisaged for the run. From a reservoir tank, the urea solution having a water content of 3-4% by weight was then introduced into the fluidized bed granulator at a rate of 350 kg/h via a spray nozzle that was operated at a temperature of about 140 C. with air, supplied at a rate of 240 kg/h. The additives used according to table 1 below for the granulation were then mixed with the urea solution at about 135. Solids were discharged from the fluidized bed via an outlet at regular intervals of 5 minutes in order to achieve a largely constant height of the bed. The samples of the solids thus removed were then each sieved in order to determine the size distribution thereof. No solids were recycled into the fluidized bed granulator. The duration per batch was about 30 minutes in each case. After this time had elapsed, the feed was stopped, the granular material was cooled down to about 100 C. and removed from the fluidized bed granulator, and it was separated by sieving it into the different fractions. The fraction having the desired size distribution was then cooled down to about 60 C. in order to analyze the product properties thereof. All fractions were weighed in order to ascertain the growth rate of the granular material. In addition, the dust from the bag filters of the waste air apparatus was also collected and weighed.

[0109] In accordance with the procedure described above, comparative tests for granulation were also conducted without addition of additive and with polyvinylamine (PVA), a polyvinylamine/polyethyleneimine mixture or a standard additive (urea-formaldehyde additive UF80), and the granular material obtained in each case was correspondingly worked up and analyzed.

[0110] Table 1a below shows the corresponding assessment of the granular materials with regard to dust formation, compressive strength, density and clumping. The sensitivity to dust formation which is likewise stated is the result of a visual assessment of collected dust from a small fluidized bed cooler. The scale used for the assessment of the granular materials obtained is shown in table 1 b.

TABLE-US-00001 TABLE 1a PEI/PVA/oxalic PEI/PVA acid 95/5% by 5/90/5% Additive UF80 PVA weight.sup.1) by wt..sup.2) Inventive (I)/ C C C I I comparative (C) Dosage 0 5500 500 800 500 mg/kg Parameters Dust in the 5 2 5 3 2 granulator filter Dust formation on 5 2 4 2 3 cooling Clumping % 2 1 3 1 2 Clump hardness 3 1 3 1 1 Compressive 4 2 3 3 2 strength Bulk density (loose) 3 1 3 1 1 Assessment 22 9 21 11 11 (not weighted) PVA: polyvinylamine PEI: polyethyleneimine .sup.1)based in each case on the mixture of PVA and PEI .sup.2)based in each case on the mixture of PVA, PEI and oxalic acid

TABLE-US-00002 TABLE 1b Compressive Dust in the Dust on strength Bulk density Clumping Hardness _Scale filter (%) cooling kg (g/l) (%) (kg) 1 0-4 0 >3.5 >675 0 zero 2 >4-6 1 >3.0-3.5 675-665 0-10 low 3 >6-8 2 >2.5-3.0 <665-655 11-20 moderate 4 >8-10 2-3 >2.0-2.5 <655-645 21-30 hard 5 >10 3 <2.0 <645 >30

Example 2

[0111] In accordance with the procedure described in example 1, the effect of an inventive granulation additive composed of oxalic acid in various dosages and of a mixture of 500 mg/kg of polyethyleneimine and polyvinylamine (40% by weight/60% by weight, based in each case on the mixture of polyethyleneimine and polyvinylamine) was determined. This was done by introducing the oxalic acid into the reservoir tank for the urea solution and feeding the polyethyleneimine/polyvinylamine mixture into the urea stream fed to the nozzle prior to spraying. The urea solution thus obtained, with a water content of 3% by weight, was then supplied at a temperature of 132 C. at a rate of 350 kg/h, and the workup was effected as described in example 1. A corresponding comparative test with formaldehyde was likewise conducted.

[0112] Table 2 below shows the respective proportion of dust in the fluidized bed granulator:

TABLE-US-00003 TABLE 2 Inventive (I)/ Dosage Dust content/ comparative (C) in mg/kg granulator in % Oxalic acid I 0 5.19 I 250 4.44 I 500 4.05 I 1000 2.81 Formaldehyde C 4500 3.9

[0113] The studies of the granular materials obtained according to examples 1-2 showed that both dust formation and the properties of the granular material (compressive strength, tendency to clumping) improved on addition of the additives of the invention. The result was comparable with or even better than the results obtained when formaldehyde was used, and significantly smaller amounts of additive were required.

Example 3

[0114] Example 3 shows, in table 3, a comparison between a comparative urea solution with typical fertilizer grade urea, i.e. typical urea used as fertilizer, and a urea solution of the invention.

TABLE-US-00004 TABLE 3 Specification Comparative AUS32 from DIN urea solution Urea 70070:2005-08, with typical solution Table 1 fertilizer grade of the Min. Max. urea invention Urea content 31.8 33.2 32.5 32.5 % by wt. Density at 20 C. 1.087 1.093 n.s. 1.0903 g/cm.sup.3 Refraction at 20 C. 1.3814 1.3843 n.s. 1.3828 Alkalinity as NH.sub.3 0.2 n.s. 0.2 % Biuret 0.3 0.276-0.333 <0.3 % Aldehydes 5 1138-1788 <5 mg/kg Insoluble constituents 20 n.s. <20 mg/kg Phosphates (PO.sub.4) 0.5 n.s. <0.5 mg/kg Ca, Fe (each) 0.5 n.s. <0.5 mg/kg Cu, Zn, Cr, Ni, Al (each) 0.2 n.s. <0.2 mg/kg Mg, Na, K (each) 0.5 n.s. <0.5 mg/kg

[0115] As can be seen in table 3, the urea solution of the invention with 32.5% by weight of urea satisfies the limits given in the specification (table 1 of DIN 70070:2005-08). In the case of a typical commercial urea solution (fertilizer grade urea), likewise with 32.5% by weight of urea, the values for aldehydes are well above the limits. The content of biuret is in the region of the limit. The other proportions in the typical commercial urea solution (fertilizer grade urea) are not stated (n.s.).

[0116] Owing to the known very high aldehyde content of the comparable typical commercial urea solution, the possible use of the particulate urea composition of the invention, which has likewise been developed for the fertilizer sector, in the field of the AUS 32 solution (diesel exhaust fluid) is surprising. Same time, the particulate composition of the invention can be better dry and transported by comparison with urea of technical grade purity. The particulate composition of the invention shows higher particle stability, storability (higher tendency to caking in the technical grade urea), lower dust formation and lower water absorption than straight technical grade urea. These aforementioned disadvantages make it difficult to reproducibly make up an AUS 32 solution (diesel exhaust fluid) from technical grade urea.