Use of urea compositions to produce diesel exhaust fluid (AUS 32)

Abstract

The present invention relates to the use of a urea composition to produce a diesel exhaust treatment fluid (AUS 32), said method comprising mixing at least water and a particulate composition comprising: (i) urea; and an additive comprising component (ii): (ii) a combination of at least one polymer or oligomer comprising an amino group and at least one functionalized polyvinyl compound; wherein the percentage by weight of component (i) in the particulate composition is greater than 60% by weight, the percentage by weight of component (ii) in the particulate composition is less than 1% by weight, and wherein a urea solution is obtained and the percentage by weight of component (i) in the obtained urea solution is from 31% by weight to 34% by weight.

Description

[0001] The present application is a divisional application of the Chinese patent application entitled "Use of urea composition in producing diesel exhaust treatment fluid (AUS 32)" and application number 201780043369.2. Patent application 201780043369.2 is a national application that entered the Chinese national phase based on the international application (PCT / EP2017 / 067657) filed on July 13, 2017 under the Patent Cooperation Treaty. Technical Field

[0002] The present invention relates to the production of NO from a granular urea-containing composition x A method for preparing a reducing agent AUS 32 solution (diesel exhaust fluid), its use in diesel vehicles and NO obtainable by the method of the invention x Reductant AUS 32 solution (diesel exhaust fluid). Background Art

[0003] Various methods for producing particulate urea-containing compositions are known in the prior art. In the past, urea granules were usually produced by spray crystallization, by spraying a substantially anhydrous urea melt (water content of 0.1% to 0.3% by weight) from the upper part of a spray crystallization tower into a rising air stream at ambient temperature and solidifying the droplets to obtain crystals (granules). The granules thus obtained have a relatively small diameter and low mechanical strength.

[0004] At present, urea granules with larger particle sizes and better mechanical properties are usually produced by granulating a substantially anhydrous urea melt or aqueous urea solution in a fluidized bed, as described, for example, in US 4,219,589. In these granulation processes, an aqueous urea solution having a urea concentration of 70% to 99.9% by weight is introduced into a fluidized bed of urea particles in the form of very finely divided droplets having an average diameter of 20 μm to 120 μm, and the temperature is selected so that the water in the solution sprayed onto the urea particles evaporates and the urea is deposited on the particles, resulting in a granular material having the desired particle size of 2.5 mm or more.

[0005] Since relatively large amounts of fine dust are obtained in this process, in particular when the water content of the urea solution used is greater than 5% by weight, granulation additives are usually used which reduce the formation of this dust. The effect of adding these additives is that the granular particles and in particular their surface remain plastic, so that due to their rolling motion and collisions, round particles with a smooth surface and good mechanical stability are obtained. The granulated material thus obtained therefore has a high compressive strength and impact resistance, a low tendency to form dust due to abrasion and, moreover, only a low tendency to agglomerate even during long-term storage. However, corresponding granulation additives find use not only in fluidized bed granulation, but also in other processes, such as spray crystallization or drum granulation.

[0006] The granulation additives used are usually formaldehyde or water-soluble adducts and / or condensation products of formaldehyde and urea, but these have to be added in relatively large amounts and are not without problems in terms of handling due to their toxic properties. Formaldehyde leaks constitute a serious risk to health and the environment, although the introduction of urea-formaldehyde prepolymers (e.g. UF80 or UF85) has reduced such risks. In addition, the question of health risks associated with long-term exposure to formaldehyde vapors also arises, according to the classification of "carcinogen" by IARC (International Agency for Research on Cancer, part of WHO), which cannot be completely avoided even by using such prepolymers.

[0007] Another problem in the granulation of urea is the formation of dust, which is understood to mean particles with a diameter of less than 0.5 mm. Dust formation is essentially due to three sources. First of all, the abrasion of the granulated material due to the movement and collision between the particles, for example in a fluidized bed, should be mentioned, wherein the amount of dust obtained depends essentially on the mechanical properties of the granulated material. In addition, the nozzles each produce droplets with a certain diameter distribution, in which case the finest droplets solidify before they encounter the urea particles, so that the dust formed thereby again leaves the granulator with the exhaust gas. Finally, a third source that should be mentioned is the dust obtained by crushing the oversized granulated particles, which in the methods and plants according to the prior art is usually transferred directly back to the granulator. 10% to 20% by weight of the crushed particles have a diameter of less than 1 mm, and a high proportion of them are dust. Therefore, 1% to 1.5% of the dust per ton of final product is returned to the granulator by this proportion of the crushed particles, and 3% to 5% of the total dust per ton of final product from the industrial plant is attributed to the granulator.

[0008] In order to avoid or reduce the above disadvantages, various substitutes for formaldehyde and its water-soluble addition and / or condensation products have been investigated, but each substitute is also subject to limitations or disadvantages.

[0009] As an example, reference is made to the use of alkali metal lignin sulfonates as described in US 5,766,302, or to the use of glyoxal or carbohydrates. However, in the urea product obtained, these result in a yellowish or brownish color, depending on the production process, which is undesirable in many cases (e.g. in the production of melamine). On the other hand, the use of surface-active substances (e.g. mixtures of polyvinyl acetate and polyvinyl alcohol) as granulation additives also leads to problems, since these have a tendency to foam, for example when the additive is mixed with the melt or in a scrubber, where the treated urea dust dissolves and impairs the efficiency of the scrubber. The tendency of these substances to form foam also has an impact on the final product, which has a lower density and is not accepted by the market. Therefore, in general, the tendency to form foam in the industrial use of urea granules is unacceptable.

[0010] In view of the concerns about nitrogen oxides (NO X ) emissions, the use of technical-grade purity urea solutions is becoming increasingly important. Here, the urea solution is introduced into the exhaust gas and converts the nitrogen oxides present in the exhaust gas into nitrogen (N2) and water (H2O) in a selective catalytic reduction (SCR). The urea injected into the exhaust gas is thermally decomposed into ammonia (NH3). The ammonia thus released reduces the nitrogen oxides present in the exhaust gas. This technical-grade purity urea solution (also known as diesel exhaust fluid, AUS 32 (aqueous urea solution) or The composition of urea is specified very precisely according to ISO 22241. A urea solution of technical purity contains 32.5% by weight of urea. A list of quality characteristics and impurities can also be found in DIN 7007: 2005-08. This standard specifies, in particular, a limit of 5 mg / kg for aldehydes.

[0011] Due to strict regulations regarding urea purity, it is not possible to use any desired urea source. Therefore, usually, the urea obtained directly in the preparation is mixed with demineralized water (distilled water) in a determined concentration and transported to the place of use. In this way, up to 2 / 3 of the water is transported in addition to the urea. In addition, these aqueous solutions cannot be transported and stored for a long time as required; on the contrary, biological degradation may occur. The alternative (i.e., transporting granular urea to the place of use) is usually ineffective due to the aldehydes present in the granular material, which prevents the use as NO x Reducing agent AUS 32 solution. Summary of the invention

[0012] Therefore, it is an object of the present invention to provide a method for producing NO from a particulate urea-containing composition and water. x A method of reducing agent AUS 32 solution (diesel exhaust fluid) which, if used, brings the disadvantages of the prior art into at least a reduced form.

[0013] This object is achieved by the subject matter of the description and the claims.

[0014] It has surprisingly been found that by the process of the present invention, without the use of formaldehyde and urea-formaldehyde condensates, a granular composition having satisfactory properties can be obtained by mixing water with a urea-containing medium and said granular composition can be used together with demineralized water to produce NO x Reductant AUS 32 solution (diesel exhaust fluid), preferably according to ISO 22241. More particularly, in this way,

[0015] Urea-containing granules can be provided which meet the purity specifications for the production of AUS 32 solution (diesel exhaust fluid). Furthermore, the production of AUS 32 solution (diesel exhaust fluid) can be separated from the urea synthesis, so that the amount to be transported can be reduced by up to 2 / 3. This not only reduces the necessary fuel consumption, but also reduces the emissions released during transportation. In addition, NO x The cost and inconvenience of packaging the reducing agent AUS 32 solution is significantly reduced. Compared to packaging and transporting smaller quantities of granular urea, it involves weighing up to 2 / 3 of the NO at the urea synthesis site. x The cost and inconvenience of transporting and packaging the reducing agent AUS 32 solution to the point of use is much higher;

[0016] The health and environmental risks associated with the use of formaldehyde and urea-formaldehyde condensates can be avoided; and / or

[0017] Compared to compositions produced using formaldehyde and urea-formaldehyde condensates, a less expensive alternative for producing the composition can be provided. The urea composition of the invention allows the use of granular urea optimized for the fertilizer sector. The urea composition of the invention in aqueous solution unexpectedly meets the limits specified in Table 1 of the standard DIN 70070:2005-08 for AUS 32 solutions (diesel exhaust fluid). In contrast, conventional urea compositions used in the fertilizer sector often fail to meet this standard, in particular due to the high formaldehyde content; and / or

[0018] The formation of dust during the production of the composition can be reduced or even completely avoided, and / or

[0019] Granular compositions can be obtained whose granules exhibit at least comparable or even better properties than compositions produced using formaldehyde and urea-formaldehyde condensates, in particular with regard to mechanical properties, such as compressive strength, impact resistance, low tendency to wear or agglomeration, in particular during long-term storage.

[0020] The present invention relates to a method for producing NO xA method for preparing a reducing agent AUS 32 solution (diesel exhaust fluid), the method comprising mixing at least water and a particulate composition, the particulate composition comprising:

[0021] (i) Urea;

[0022] and an additive comprising component (ii):

[0023] (ii) a combination of at least one polymer or oligomer comprising amino groups and at least one functionalized polyvinyl compound;

[0024] wherein the proportion of component (i) in the granular composition is >60% by weight, the proportion of component (ii) in the granular composition is <1% by weight, and

[0025] A urea solution is obtained, and the proportion of component (i) in the obtained urea solution is 30 wt % to 35 wt % (including endpoints), in particular 31 wt % to 34 wt %, in particular 31.8 wt % to 33.2 wt %. The obtained urea solution having a concentration range within the concentration range specified in ISO 22241 corresponds to NO x Reductant AUS 32 solution (diesel exhaust fluid).

[0026] The granular composition of the present invention preferably contains only small amounts (if any) of aldehydes and / or sulfur, less than 20 ppm. In the context of the present invention, this means that the available NO x The components mentioned in the reducing agent AUS 32 solution are present in concentrations lower than those specified in ISO 22241 and / or DIN 70070:2005-08.

[0027] The polymers and oligomers containing amino groups used according to the invention include in particular polymers and oligomers having a molecular weight (MW) of 250 to 2,000,000 Daltons, 300 to 2,000,000 Daltons, 350 to 2,000,000 Daltons, 400 to 2,000,000 Daltons, 450 to 2,000,000 Daltons, 500 to 2,000,000 Daltons, 550 to 2,000,000 Daltons, 600 to 2,000,000 Daltons, 650 to 2,000,000 Daltons, Daltons, 700 to 2,000,000 Daltons, 750 to 2,000,000 Daltons, 800 to 2,000,000 Daltons, 850 to 2,000,000 Daltons, 900 to 2,000,000 Daltons, 950 to 2,000,000 Daltons, 1000 to 2,000,000 Daltons, 1050 to 2,000,000 Daltons, 1100 to 2,000,000 Daltons, 1150 to 2,000,000 Daltons and 1200 to 2,000,000 Daltons.

[0028] For example, the molecular weight (MW) of the polymers and oligomers containing amino groups used in accordance with the present invention may be 500 Daltons to 1000000 Daltons, 550 Daltons to 1000000 Daltons, 600 Daltons to 1000000 Daltons, 650 Daltons to 1000000 Daltons, 700 Daltons to 1000000 Daltons, 750 Daltons to 1000000 Daltons, 800 Daltons to 1000000 Daltons, 850 Daltons to 1000000 Daltons, 900 Daltons to 1000000 Daltons, 950 Daltons to 1000000 Daltons, 1000 Daltons to 1000000 Daltons, 1050 Daltons to 1000000 Daltons, 1100 Daltons to 1000000 Daltons, 1150 Daltons to 1000000 Daltons, Daltons to 10,000 Daltons, 1,000,000 and 1,200 to 1,000,000 Daltons or can be within the range of 500 to 10,000, 550 to 10,000 Daltons, 600 to 10,000 Daltons, 650 to 10,000 Daltons, 700 to 10,000 Daltons, 750 to 10,000 Daltons, 800 to 10,000 Daltons, 850 to 10,000 Daltons, 900 to 10,000 Daltons, 950 to 10,000 Daltons, 1000 to 10,000 Daltons, 1050 to 10,000 Daltons, 1100 to 10,000 Daltons, 1150 to 10,000 and 1200 to 10,000 Daltons.

[0029] Preferably, the polymers and oligomers containing amino groups may have a nitrogen content of 10% to 50% by weight based on the weight of the polymer or oligomer and contain primary, secondary or tertiary amino groups which independently contain alkyl or arylalkyl groups, such as C 1-6 Alkyl or aryl-C 1-3 alkyl, wherein aryl may be phenyl or pyridyl in particular, which may be unsubstituted or optionally independently selected from F, Cl, Br, CF3, C 1-6 Alkyl, C 1-6 Alkoxy, NH2, C 1-6 Alkylamino and di(C 1-6 The amino group is substituted with 1, 2, 3, 4 or 5 substituents.

[0030] For example, useful polymers and oligomers containing amino groups include polyamines, polymeric polyamines, nitrogen-substituted vinyl polymers, polyoxazolines, polypropylene imine and its dendrimers, polyethylene imine and its dendrimers, polyamidoamine and its dendrimers, and copolymers and derivatives and combinations of two or more of the mentioned substances.

[0031] Preferred polymers and oligomers containing amino groups include polyamines and polymeric polyamines, polyalkyleneimines (such as polyethyleneimines and polypropyleneimines), polyethyleneamines, polyalkoxylated polyamines, ethoxylated polyamines, propoxylated polyamines, alkylated and benzylated polyamines, and combinations of two or more of the foregoing.

[0032] Particularly preferably used polymers and oligomers containing amino groups are polyethyleneimine, polyethyleneimine dendrimers, and copolymers and derivatives thereof, and mixtures of at least two of these components.

[0033] Suitable polyethyleneimine may include linear or branched polyethyleneimine polymers or oligomers having, for example, 10 or more monomer units, and derivatives, analogs, copolymers thereof, and mixtures of at least two of these components.

[0034] Polyethyleneimine can be obtained by polymerization of ethyleneimine and is commercially available as e.g. and The products are commercially available in the form of a family of products, in particular G20, FG, G35, P and 1595 products( Products are available from BASF (Florham Park, NJ, USA), and SP-003, SP-006, SP-012, SP-018, SP-200, SP-1000 and SP-1050( The product is available from Nippon Shokubai (Osaka, Japan).

[0035] According to the invention, useful functionalized polyvinyl compounds include in particular those based on repeating (CHXCHY) n A compound of the invention wherein X is selected from H, NH2, OH, COOH, COR, CONH2, CH2NH2, CH2NHR, CH2OH and CH2OR, and Y is selected from NH2, OH, COOH, COR, CONH2, CH2NH2, CH2NHR, CH2OH and CH2OR, and wherein R is independently in each case alkyl, in particular C 1-6 Alkyl, or aryl, in particular phenyl or pyridyl, which may be unsubstituted or optionally independently selected from F, Cl, Br, CF3, C 1-6 Alkyl, C 1-6 Alkoxy, NH2, C 1-6 Alkylamino and di(C 1-6 The amino group is substituted with 1, 2, 3, 4 or 5 substituents.

[0036] For example, the molecular weight (MW) of the functionalized polyvinyl compound used in accordance with the present invention can be 250 Daltons to 2,000,000 Daltons, 300 Daltons to 2,000,000 Daltons, 350 Daltons to 2,000,000 Daltons, 400 Daltons to 2,000,000 Daltons, 450 Daltons to 2,000,000 Daltons, 500 Daltons to 2,000,000 Daltons, 550 Daltons to 2,000,000 Daltons, 600 Daltons to 2,000,000 Daltons, 650 Daltons to 2,000,000 Daltons, 700 Daltons to 2,000,000 Daltons, 8 ... Daltons to 2,000,000 Daltons, 750 Daltons to 2,000,000 Daltons, 800 Daltons to 2,000,000 Daltons, 850 Daltons to 2,000,000 Daltons, 900 Daltons to 2,000,000 Daltons, 950 Daltons to 2,000,000 Daltons, 1000 Daltons to 2,000,000 Daltons, 1050 Daltons to 2,000,000 Daltons, 1100 Daltons to 2,000,000 Daltons, 1150 Daltons to 2,000,000 Daltons and 1200 Daltons to 2,000,000 Daltons.

[0037] Useful functionalized polyvinyl compounds preferably include polyvinyl alcohol or polyvinyl amine or a mixture thereof. The functionalized polyvinyl compound is more preferably polyvinyl amine.

[0038] The molecular weight (MW) of each of the polyvinylamine and the polyvinyl alcohol may preferably be 500 Dalton to 1000000 Dalton, 550 Dalton to 1000000 Dalton, 600 Dalton to 1000000 Dalton, 650 Dalton to 1000000 Dalton, 700 Dalton to 1000000 Dalton, 750 Dalton to 1000000 Dalton, 800 Dalton to 1000000 Dalton, 850 Dalton to 1000000 Dalton, 900 Dalton to 1000000 Dalton, 950 Dalton to 1000000 Dalton, 1000 Dalton to 1000000 Dalton, 1050 Dalton to 1000000 Dalton, 1100 Dalton to 1000000 Dalton, 1150 Dalton to 1000 and 1200 to 10,000 Daltons. Or, in the range of 500 to 10,000 Daltons, 550 to 10,000 Daltons, 600 to 10,000 Daltons, 650 to 10,000 Daltons, 700 to 10,000 Daltons, 750 to 10,000 Daltons, 800 to 10,000 Daltons, 850 to 10,000 Daltons, 900 to 10,000 Daltons, 950 to 10,000 Daltons, 1000 to 10,000 Daltons, 1050 to 10,000 Daltons, 1100 to 10,000 Daltons, 1150 to 10,000 and 1200 to 10,000 Daltons.

[0039] Suitable polyvinylamines include in particular linear polymers and copolymers derived from vinylformamide monomers and may comprise cationic and anionic polyvinylamine copolymers as well as charged and protonated polyvinylamines.

[0040] Suitable polyvinylamines are commercially available, for example from Those of the product family, and in this case especially 1595, 4500, 5095, 9030, 9050 and 9095 product. Examples of cationic and anionic polyvinylamine copolymers are those derived from Those of the product family, and in this case especially Am na, AV, VH, VI. VM, PR8094, PR8261 and PR8349 product. Examples of charged or protonated polyvinylamines are those derived from Products of the product range, and in this case especially products GM, PL, PR8236, VCB, VFH, VLW, VMP and VSH. and The product is available from BASF (Florham Park, NJ, USA).

[0041] Unless otherwise stated, the weight figures (wt%) given in connection with the granule composition always relate in each case to the total weight of the granule composition. The person skilled in the art will recognize that the given components and weight figures do not need to relate to any arbitrarily small fraction of the granule, but rather to average values ​​representing a representative amount of the granules produced.

[0042] Unless otherwise stated, the combination of NO x The weight figures (wt %) given for reducing agent AUS 32 solution or urea solution always relate in each case to NO x Total weight of reducing agent AUS 32 solution or urea solution.

[0043] The granular composition according to the invention may optionally contain other ingredients as well as the ingredients mentioned. The nature of the ingredients and their amounts depend, for example, on the component (i) used. For example, the granular composition according to the invention may contain: water in an amount of, for example, 0.05% to 0.5% by weight, in particular 0.1% to 0.3% by weight, and by-products from the urea synthesis, such as biuret or NH3. Typically, the proportion of by-products is not more than 1.5% by weight, in particular not more than 1.25% by weight.

[0044] In a preferred embodiment of the process, the granular composition comprises as additive component (iii) at least one compound selected from the group consisting of aliphatic dicarboxylic acids, their salts and anhydrides, aliphatic tricarboxylic acids, their anhydrides, aromatic dicarboxylic acids, their salts and anhydrides, and anhydrides, wherein, preferably, the proportion by weight of component (i) is >60% by weight and the proportion by weight of the sum of component (ii) and component (iii) in the composition is <1% by weight.

[0045] It will be apparent to those skilled in the art that the components (ii) and (iii) used to produce the granular composition may partially or completely interact with one another and may also interact with the urea component (i). For example, it is known that aldehydes or carboxylic anhydrides crosslink with urea to form covalent bonds, or to form complexes of urea and carboxylic acids. Components such as polyvinyl alcohol and polyvinyl amine, for example, tend to form hydrogen bonds. Therefore, it is possible that the components used to produce the granular composition are in partially or completely modified forms in the resulting final product. The present invention also includes such modified components.

[0046] In a particularly preferred embodiment of the method, the granular composition according to the invention comprises:

[0047] (i) Urea;

[0048] and an additive comprising component (ii) and component (iii):

[0049] (ii) a combination of polyethyleneimine and polyvinyl alcohol or a combination of polyethyleneimine and polyvinylamine;

[0050] (iii) at least one compound selected from aliphatic dicarboxylic acids, salts and anhydrides thereof, aliphatic tricarboxylic acids, salts and anhydrides thereof, and aromatic dicarboxylic acids and anhydrides;

[0051] Preferably, the proportion of component (i) in the granular composition is >97 wt %, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1 wt %.

[0052] If the composition according to the invention comprises an aliphatic dicarboxylic acid as component (iii), it may preferably be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, and the respective anhydrides. More preferably, the dicarboxylic acid of component (iii) present is oxalic acid, succinic acid or a mixture of these two acids.

[0053] If the composition according to the invention comprises an aliphatic tricarboxylic acid as component (iii), it may preferably be selected from citric acid, isocitric acid, and the respective anhydrides. The tricarboxylic acid of component (iii) present is more preferably citric acid.

[0054] If the composition of the present invention comprises an aromatic dicarboxylic acid or an anhydride thereof as component (iii), it may preferably be selected from phthalic acid, phthalic anhydride, isophthalic acid and terephthalic acid. The aromatic dicarboxylic acid or anhydride thereof present in component (iii) is more preferably phthalic acid, phthalic anhydride or a mixture thereof.

[0055] In another preferred embodiment of the method, the granular composition comprises:

[0056] (i) Urea;

[0057] and an additive comprising component (ii) and component (iii):

[0058] (ii) a combination of polyethyleneimine and polyethyleneamine;

[0059] (iii) at least one compound selected from the group consisting of oxalic acid, succinic acid, citric acid, phthalic acid and phthalic anhydride;

[0060] The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

[0061] A particularly preferred embodiment of the granular composition in the method comprises:

[0062] (i) Urea;

[0063] and an additive selected from the groups (a) to (g):

[0064] (a) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine;

[0065] (c) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine and (iii) oxalic acid;

[0066] (d) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine and (iii) citric acid;

[0067] (e) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine and (iii) succinic acid;

[0068] (f) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine and (iii) phthalic acid;

[0069] (g) an additive comprising (ii) a combination of polyethyleneimine and polyethyleneamine and (iii) phthalic anhydride;

[0070] The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

[0071] The proportion by weight of component (i) in the granular composition is preferably >97% by weight, more preferably >98% by weight, most preferably >98.5% by weight.

[0072] The proportions by weight of the additive components may vary, for example, depending on the components (ii) and (iii) used. Preferably, the proportion by weight of the sum of components (ii) and (iii) in the granular composition is <0.5 wt.-%, more preferably <0.4 wt.-%, even more preferably <0.3 wt.-%, even more preferably <0.25 wt.-%.

[0073] If the additive component comprises two or more components, the relative proportions thereof may also vary. For example, the component weight ratio of component (ii) to component (iii) may be in the range of 1:20 to 20:1, preferably 1:15 to 15:1, more preferably 1:10 to 10:1, and including incremental values ​​therebetween.

[0074] Particularly preferred embodiments of the granular composition of the method include a combination of polyethyleneimine and polyvinylamine. The weight ratio of polyethyleneimine to polyvinylamine in the combination of these two components may vary, for example in the range of 1:20 to 20:1, preferably 1:15 to 15:1, more preferably 1:10 to 10:1, and including incremental values ​​therebetween.

[0075] Furthermore, the weight ratio of the combination of the two components polyethyleneimine and polyvinylamine to component (iii) may also vary and in each case may be, for example, in the range from 1:20 to 20:1, preferably from 1:15 to 15:1, more preferably from 1:10 to 10:1, and including incremental values ​​therebetween.

[0076] In a preferred embodiment of the method, the granular composition according to the invention is substantially free of formaldehyde. In the context of the present invention, the expression "substantially free of formaldehyde" means that the composition comprises <0.1 wt.-%, preferably <0.05 wt.-%, more preferably <0.005 wt.-%, even more preferably <0.0005 wt.-% formaldehyde.

[0077] The present invention also includes NO obtainable by the method of the present invention x Reductant AUS 32 solution (diesel exhaust fluid). x The impurities of the reducing agent AUS 32 solution (defined by the particulate additive) are different from those of a pure urea solution in water. In particular, the polymer additives are difficult to characterize in any other way than by this method.

[0078] All preferred embodiments which have been described above in conjunction with the granular composition according to the invention also apply correspondingly to the inventive use of the additive for producing a granular composition comprising urea and are therefore not repeated here.

[0079] For reasons of completeness, another possible method for producing a granular composition comprising urea according to WO 2015 / 193377 A1 is disclosed below, comprising the following steps:

[0080] (A) providing a urea-containing solution;

[0081] (B) The urea-containing solution is granulated while adding the additive having the composition described above.

[0082] All preferred embodiments which have been described above in connection with the granular composition of the invention also apply correspondingly to the disclosed method for producing a granular composition comprising urea and are therefore not repeated here.

[0083] In a preferred embodiment of the process for producing a granular composition, the urea content of the solution used in step (A) is >60 wt.-%, preferably >95 wt.-%, more preferably >97 wt.-%, even more preferably >98 wt.-%, even more preferably >98.5 wt.-%.

[0084] In step (B), the granulation of the urea-containing solution to which the additive is added can be carried out by customary methods known to the person skilled in the art, for example by means of spray crystallization (granulation), drum granulation or fluidized bed granulation.

[0085] In one disclosed embodiment of the method for producing a granular composition, the granulation in step (B) is carried out by means of fluidized bed granulation, which comprises the following steps:

[0086] (B1) providing a urea-containing seed crystal;

[0087] (B2) fluidizing the urea-containing seed crystals;

[0088] (B3) A urea-containing solution is spray-applied using an additive having the composition described above.

[0089] If the additive comprises two or more components, these can be used individually or together in the method of the present invention, or in the form of a premix. The timing and addition of the components can vary. For example, one or more components can be added to the provided urea solution, or one or more components can be added to the urea-containing solution just before it is sprayed. Depending on the characteristics of the components, it may be advantageous to use the components in the form of solutions, suspensions, emulsions, etc. Suitable liquids for solutions or other formulations include in particular water, but also organic solvents, such as alcohols, ethers, etc.

[0090] The temperature of the urea-containing solution is preferably >130°C.

[0091] In one embodiment for producing a granular composition, the method comprises step (C):

[0092] (C) After the granular urea composition is produced, it is divided into three fractions, wherein

[0093] One fraction (F1) contains particles having a desired target size,

[0094] One fraction (F2) contains particles larger than the desired target size, and

[0095] One fraction (F3) contains particles smaller than the desired target size, and

[0096] Therein, preferably, fraction F2 is recycled back into the process after particle comminution and fraction F3 is recycled back into the process.

[0097] In the equipment for producing urea and for further processing thereof to produce granular compositions, ammonia is usually also obtained. This can be converted into the corresponding ammonium salts, such as ammonium nitrate or ammonium sulfate, by washing operations with suitable acids (e.g. nitric acid or sulfuric acid), and these can be transported for further use, for example in fertilizers. Suitable methods and procedures for acid washing are described, for example, in WO 2010 / 060535.

[0098] In another embodiment for producing a granular composition, the disclosed method comprises step (D):

[0099] (D) Pickling.

[0100] Acid washing can also advantageously be carried out using the acid of component (iii) above.

[0101] Another disclosed aspect of the present invention relates to an apparatus for producing a granular composition comprising urea, comprising:

[0102] (a) granulator;

[0103] (b) at least one device for adding an additive as described above;

[0104] (c) at least one device for separating the particulate composition into different particle size fractions;

[0105] (d) optionally at least one device for performing pickling.

[0106] In a preferred embodiment of the apparatus according to the invention, the granulator (a) is a fluidized bed granulator.

[0107] The disclosed apparatus is particularly suitable for carrying out the disclosed method.

[0108] Another aspect of the invention relates to the use of the AUS 32 solution of urea in water obtained according to the invention in diesel vehicles, furnaces, waste incinerators, gas turbines, ship engines or industrial plants for reducing nitrogen oxides. For this purpose, the solution of the invention is injected into the exhaust gas stream, for example from a vehicle, and the nitrogen oxides are reduced to N2 and H2O on an SCR catalyst (for example composed of titanium). This mechanism is carried out, for example, by thermally decomposing urea to isocyanic acid and then hydrolyzing it to ammonia. The ammonia finally reacts with the nitrogen oxides on the catalyst. DETAILED DESCRIPTION

[0109] The present invention is described below by way of examples. These examples are intended to be illustrative only and are not intended to limit the general scope of the present invention.

[0110] Example:

[0111] Example 1

[0112] In the test plant, urea was granulated in a fluidized bed granulator with a cylindrical fluidized bed of 40 cm in diameter at a temperature of about 108° C. The fluidized bed was terminated at its lower end by a perforated plate with a hole diameter of 2.0 mm. Fluidizing air was caused to flow into the fluidized bed at a superficial velocity of about 2 m / s. An overflow was installed at the side walls of the bed 10 cm above the base plate. A determined amount (about 45 kg) of urea particles or urea granules with a narrow size distribution was then introduced into the granulator column as seed crystals for granulation. The bed with seed crystals (about 50 cm deep) was fluidized with hot air at a temperature of about 100° C., and once the bed had reached a temperature of about 108° C. envisaged for operation, the addition of a 96% to 97% by weight urea solution at a temperature of about 135° C. was started. Then a urea solution with a water content of 3% to 4% by weight is introduced into the fluidized bed granulator from a storage tank at a rate of 350 kg / hour through a nozzle, which is operated at a temperature of about 140°C and supplies air at a rate of 240 kg / hour. Then the additives used for granulation according to Table 1 below are mixed with the urea solution at about 135°. Solids are discharged from the fluidized bed via an outlet at regular intervals of 5 minutes to achieve a substantially constant height of the bed. Then the solid samples thus removed are sieved to determine their size distribution. No solids are recycled into the fluidized bed granulator. The duration of each batch in each case is about 30 minutes. After this period of time, the feed is stopped, the granulated material is cooled to about 100°C and removed from the fluidized bed granulator, and separated by sieving it into different fractions. The fraction with the desired size distribution is then cooled to about 60°C to analyze its product characteristics. All fractions are weighed to determine the growth rate of the granulated material. In addition, dust from the bag filter of the exhaust device is collected and weighed.

[0113] Comparative granulation tests were also carried out according to the above procedure without additives and with polyvinylamine (PVA), polyvinylamine / polyethyleneimine mixtures or standard additives (urea-formaldehyde additive UF80), and the granulated material obtained in each case was worked up and analyzed accordingly.

[0114] Table 1a below shows the corresponding evaluation of the granular materials with respect to dust formation, compressive strength, density and agglomeration. Also illustrated is the sensitivity to dust formation as a result of a visual evaluation of the dust collected by a small fluidized bed cooler. The grades used to evaluate the granular materials obtained are shown in Table 1b.

[0115] Table 1a

[0116]

[0117] PVA: Polyvinylamine PEI: Polyethyleneimine 1) In each case based on a mixture of PVA and PEI 2) In each case based on a mixture of PVA, PEI and oxalic acid

[0118] Table 1b

[0119]

[0120] Example 2

[0121] The effect of an inventive granulation additive consisting of different doses of oxalic acid and 500 mg / kg of a mixture of polyethyleneimine and polyvinylamine (in each case 40% by weight / 60% by weight, based on the mixture of polyethyleneimine and polyvinylamine) was determined according to the procedure described in Example 1. This was carried out by introducing the oxalic acid into a storage tank for the urea solution before spraying and feeding the polyethyleneimine / polyvinylamine mixture into the urea stream supplied to the nozzle. 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 / hour and worked up as described in Example 1. A corresponding comparative test with formaldehyde was carried out in the same manner.

[0122] Table 2 below shows the respective proportions of dust in a fluidized bed granulator:

[0123] Table 2:

[0124]

[0125] Studies of the granular materials obtained according to Examples 1 to 2 show that when the additive according to the invention is added, both dust formation and the properties of the granular materials (compressive strength, caking tendency) are improved. The results are comparable to or even better than those obtained when formaldehyde is used, and significantly smaller amounts of additive are required.

[0126] Embodiment 3:

[0127] Example 3 A comparison between a comparative urea solution having a typical fertilizer grade of urea (ie, typical urea used as a fertilizer) and a urea solution of the present invention is shown in Table 3.

[0128] Table 3

[0129]

[0130] As can be seen from Table 3, the urea solution of the invention with 32.5% by weight of urea meets 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) also with 32.5% by weight of urea, the values ​​for aldehydes are far above the limits. The content of biuret is within the limit region. The other proportions in a typical commercial urea solution (fertilizer grade urea) are not specified (ns).

[0131] The possible use of the granular urea compositions of the invention, which were also developed for the fertilizer sector, in the field of AUS 32 solutions (diesel exhaust fluid) was unexpected due to the known very high aldehyde content of comparable typical commercial urea solutions. At the same time, the granular compositions of the invention can be dried and transported better than urea of ​​technical purity. The granular compositions of the invention show higher granule stability, storability (higher caking tendency in technical urea), lower dust formation and lower water absorption than pure technical urea. These above-mentioned disadvantages make it difficult to reproducibly prepare AUS 32 solutions (diesel exhaust fluid) from technical urea.

[0132] The present invention provides the following technical solutions:

[0133] Scheme 1. A method for producing NO x A method of preparing a reducing agent AUS 32 solution (diesel exhaust fluid) comprising mixing at least water and a particulate composition comprising:

[0134] (i) Urea;

[0135] and an additive comprising component (ii):

[0136] (ii) a combination of at least one polymer or oligomer comprising amino groups and at least one functionalized polyvinyl compound;

[0137] wherein the proportion of component (i) in the granular composition is >60% by weight, the proportion of component (ii) in the granular composition is <1% by weight, and

[0138] A urea solution is obtained, and the proportion of component (i) in the obtained urea solution is not less than 31% by weight and not more than 34% by weight.

[0139] Scheme 2. The method according to Scheme 1, wherein the additive comprises component (iii):

[0140] (iii) at least one compound selected from aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, and aromatic dicarboxylic acids and anhydrides,

[0141] The proportion of component (i) in the granular composition is >60% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

[0142] Option 3. The method according to Option 1 or 2, wherein the granular composition comprises:

[0143] (i) Urea;

[0144] and an additive comprising component (ii) and component (iii):

[0145] (ii) a combination of polyethyleneimine and polyvinyl alcohol or a combination of polyethyleneimine and polyvinylamine;

[0146] (iii) at least one compound selected from aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, and aromatic dicarboxylic acids and anhydrides;

[0147] The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

[0148] Embodiment 4. The method according to any one of embodiments 1 to 3, wherein the particle composition comprises:

[0149] (i) Urea;

[0150] and an additive comprising component (ii) and component (iii):

[0151] (ii) a combination of polyethyleneimine and polyethyleneamine;

[0152] (iii) at least one compound selected from oxalic acid, succinic acid, citric acid, phthalic acid and phthalic anhydride;

[0153] The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

[0154] Scheme 5. The method according to any one of schemes 1 to 4, wherein the molecular weight of the polyethyleneimine in component (ii) is in the range of 500 Da to 2,000,000 Da.

[0155] Scheme 6. The method according to any one of schemes 1 to 5, wherein the molecular weight of the polyvinylamine in component (ii) is in the range of 500 Da to 1,000,000 Da.

[0156] Option 7. The method according to any one of Option 1 to Option 6, wherein the proportion of component (i) in the composition is >98 wt%, preferably >98.5 wt%.

[0157] Scheme 8. A method according to any one of schemes 1 to 7, characterized in that the proportion of the sum of component (ii) and component (iii) in the composition is <0.5% by weight, preferably <0.4% by weight, more preferably <0.3% by weight, and most preferably <0.25% by weight.

[0158] Scheme 9. NO of urea in water obtained according to any one of Schemes 1 to 8 x Use of reducing agent AUS 32 solution in diesel vehicles, furnaces, waste incinerators, gas turbines, ship engines or industrial equipment for reducing nitrogen oxides.

[0159] Scheme 10. A NO x A reducing agent AUS 32 solution (diesel exhaust fluid), which can be obtained by the method according to any one of Schemes 1 to 8.

Claims

1. A method for producing NO x A method for preparing a reductant diesel exhaust fluid (AUS 32) solution comprises mixing at least water and a particulate composition comprising: (i) Urea; and an additive comprising component (ii): (ii) a combination of at least one polymer or oligomer comprising amino groups and at least one functionalized polyvinyl compound; wherein the proportion of component (i) in the granular composition is >60% by weight, the proportion of component (ii) in the granular composition is <1% by weight, and wherein a urea solution is obtained, and the proportion of component (i) in the obtained urea solution is not less than 31 wt % and not more than 34 wt % by weight; The method allows the urea solution thus obtained to be used for the production of the NO x The reducing agent is AUS 32 solution, and the limit of aldehyde in the AUS 32 solution is 5 mg / kg.

2. The method of claim 1, wherein the granular composition comprises less than 20 ppm of aldehydes and / or sulfur.

3. The method of claim 1, wherein the granular composition comprises <0.0005 wt% formaldehyde.

4. The method according to any one of claims 1 to 3, wherein the additive comprises component (iii): (iii) at least one compound selected from aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, and aromatic dicarboxylic acids and anhydrides, The proportion of component (i) in the granular composition is >60% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

5. The method according to any one of claims 1 to 3, wherein the granular 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 aliphatic dicarboxylic acids and anhydrides, aliphatic tricarboxylic acids and anhydrides, and aromatic dicarboxylic acids and anhydrides; The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

6. The method according to any one of claims 1 to 3, wherein the granular composition comprises: (i) Urea; and an additive comprising component (ii) and component (iii): (ii) a combination of polyethyleneimine and polyethyleneamine; (iii) at least one compound selected from oxalic acid, succinic acid, citric acid, phthalic acid and phthalic anhydride; The proportion of component (i) in the granular composition is >97% by weight, and the proportion of the sum of component (ii) and component (iii) in the granular composition is <1% by weight.

7. The method according to claim 6, wherein the molecular weight of the polyethyleneimine in component (ii) is in the range of 500 Da to 2,000,000 Da.

8. The method according to claim 6, wherein the molecular weight of the polyvinylamine in component (ii) is in the range of 500 Da to 1,000,000 Da.

9. The method according to any one of claims 1 to 3, wherein the proportion by weight of component (i) in the composition is >98% by weight.

10. The method according to claim 9, wherein the proportion of component (i) in the composition is >98.5% by weight.

11. The process according to any one of claims 1 to 3, characterized in that the proportion by weight of the sum of component (ii) and component (iii) in the composition is <0.5% by weight.

12. The process according to claim 11, characterized in that the proportion by weight of the sum of components (ii) and (iii) in the composition is <0.4% by weight.

13. The method according to claim 12, characterized in that the proportion by weight of the sum of components (ii) and (iii) in the composition is <0.3% by weight.

14. The process according to claim 13, characterized in that the proportion by weight of the sum of components (ii) and (iii) in the composition is <0.25% by weight.

15. NO of urea in water obtained according to any one of claims 1 to 14 x Use of reducing agent AUS32 solution in diesel vehicles, furnaces, waste incinerators, gas turbines, ship engines or industrial equipment for reducing nitrogen oxides.

16. A NO x A reducing agent diesel exhaust fluid AUS 32 solution, which can be obtained by the method according to any one of claims 1 to 14.

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