Process for manufacturing phosphoryl or thiophosphoryl triamide, and use of the compound in nitrogen fertilizer formulations

Abstract

A process for manufacturing phosphoryl triamide OP(NH2)3 or thiophosphoryl triamide SP(NH2)3, wherein a) phosphoryl trichloride OPCl3 or thiophosphoryl trichloride SPCl3, respectively, are reacted with gaseous ammonia in a nonpolar liquid phase to obtain a first precipitate comprising phosphoryl triamide or thiophosphoryl triamide and ammonium chloride, respectively; b) said first precipitate is treated with sodium carbonate or potassium carbonate, preferably with sodium carbonate, in a polar organic liquid phase, to obtain a second precipitate comprising NaCl and the phosphoryl triamide or thiophosphoryl triamide remaining in said polar organic liquid phase, and said second precipitate is separated from said polar organic liquid phase.The latter may undergo a further concentration step to increase its concentration of phosphoryl triamide or thiophosphoryl triamide.

Description

Title of the invention: Process for the manufacture of phosphoryl or thiophosphoryl triamide, and use of the compound in nitrogen fertilizer formulations Technical field of the invention

[0001] The invention relates to the field of synthetic organic chemistry, and more particularly to the synthesis of phosphoryl triamide (abbreviated PTA, Phosphoryl Tri Amide) or its thio homologue (abbreviated TPTA, Thio Phosphoryl Tri Amide). It presents a new, simple and ecological process for obtaining this compound in a highly enriched form, and in particular in the form of a mixture enriched in phosphoryl triamide and depleted in chlorides.

[0002] The invention also relates to the field of agrochemistry, and more particularly to the use of such a mixture enriched in PTA or TPTA and depleted in chlorides in nitrogen fertilizer formulations, and in particular in solid urea-based fertilizer formulations, with the aim of inhibiting urease in order to limit ammonia losses by volatilization and thus increase the actual coefficient of use of the nitrogen fertilizer. State of the art

[0003] A method for synthesizing PTA from OPC13 and NH3 in cold chloroform is known, described in Inorganic Syntheses, Vol VI, ed. EG Rochow, 1960, p. 108. This synthesis generates NH4C1 as a side product. Different methods have been proposed to separate it from PTA. The method described in Rochow's work uses diethylamine NH(C2H5)2; this reaction generates NH3 which is reused. However, diethylamine is a flammable and quite toxic compound which one would like to avoid.

[0004] It is also possible to proceed by washing with cold or hot water which dissolves the NH4C1 (see Comprehensive Treatise on Inorganic and Theoretical Chemistry, ed. Mellor, vol. 8, p. 713, published in 1947); this is not an industrial method either because it produces an aqueous liquid effluent which carries with it some of the PTA. US 2,661,264 (Monsanto) proposes a methanol wash which dissolves the NH4C1; even if methanol can be easily distilled, its toxicity makes it undesirable for an industrial process.

[0005] US 2,596,935 describes the use of the partially polymerized product from the reaction OPC13 + NH3 as a fertilizer. The NH4C1, a by-product of the reaction, was removed by leaching with water.

[0006] Certain derivatives of phosphoric and thiophosphoric triamides and their oligomers or polymers have been explored for use in the field of agriculture, and more specifically as fertilizers and urease inhibitors.

[0007] Worldwide, urea-based nitrogen fertilizers are the main nitrogen fertilizer with an overall annual volume of around 180 million tons; only in some countries do ammonium nitrate products containing either 33.5% ammonium nitrate (which present an explosion hazard) or 27% ammonium nitrate in the form of calcium ammonium nitrate (inert) exceed urea. Urea is commonly used in the form of granules with a diameter of between about 2 mm and about 4 mm, typically containing about 46% by mass of nitrogen, or in the form of a nitrogen solution which may contain, in addition to urea, ammonium nitrate.

[0008] The major disadvantage of urea is the volatilization of ammonia, which results from the action of the urease enzyme, and which leads to significant nitrogen losses, ammonia-related air pollution, and eutrophication of natural environments. The European Union, like other countries in the world, is seeking to reduce ammonia emissions into the atmosphere. In Europe, the use of mineral fertilizers represents approximately 22% of ammonia emissions, 80% of which come from mineral fertilizers, knowing that 75% of ammonia emissions come from livestock farming.

[0009] To mitigate the emission of ammonia from nitrogen fertilizers, the use of urease inhibitors is one way among others (such as burying the fertilizer, coating the grains for delayed release, and irrigation following the application of nitrogen fertilizer). With regard to urease inhibitors, however, their ecotoxicological balance must be taken into account since they are synthetic products.

[0010] WO 2009 / 079994 (Fertiva) describes urea-based fertilizers comprising thiophosphoryl triamine derivatives, such as N-(n-butyl)thiophosphoric triamide (abbreviated nNBPT or simply NBPT) and N-(n-propyl)thiophosphoric triamide (abbreviated nNMP). WO 00 / 58317 and EP 1 163 245 (SKW Stickstoffwerke Piesteritz) describe the inhibition of urease by OP(NH2)2(NHR2) type compounds with a complex R2 residue. Urease is an enzyme that catalyzes the transformation of urea into carbon dioxide and ammonia (which can react to form ammonium, a highly water-soluble cation); it is present in a large number of bacteria, yeasts and plants. In soil fertilized with a urea-based fertilizer, urease hydrolyzes urea, which transforms it into NH4+. During this transition, some of the nitrogen is released in the form of gaseous ammonia.The NH4+ molecule is then transformed by Nitrosomonas and Nitrobacter (two soil bacteria) into nitrate (NO3) which can be easily leached, and which will therefore be lost for soil fertilization: this natural process reduces the amount of nitrogen available as fertilizer. The two patent documents mentioned describe a urea-based fertilizer to which these molecules are added as a urease inhibitor to prevent the loss of part of the urea. US . 4,676,822 (Tennessee Valley Authority) describes a urease inhibitory effect for the triophosphoryl triamide SP(NH2)3 (abbreviated TPTA).

[0011] CB Christianson, BH Byrnes & G. Carmona, in a publication entitled "A comparison of the sulfur and oxygen analogs of phosphoric triamide urease inhibitors in reducing urea hydrolysis and ammonia volatilization", published in the journal Fertilizer Research 26, 21-27, 1990, compare different complex molecules derived from phosphoryl triamide or thiophosphoryl triamide, namely the thio derivatives nBTPT and its cyclohexyl analog (abbreviated CHTPT), and the oxygen analog derivatives (nBPT and CHPT). They postulate that in the soil, thiophosphoryl molecules are transformed into their phosphoryl analog form, i.e. by replacement of sulfur by oxygen. This process depends on the nature and chemistry of the soil and takes time, during which urease is not sufficiently inhibited.The authors raise the problem of the stability of these molecules in the soil, as well as the problems of the cost of these molecules, and the way to incorporate them into a solid nitrogen fertilizer.

[0012] The hypothesis of Christianson et al. on the transformation of the thio form into its oxo form in soils was demonstrated by Danièle Pro, for molecules similar to those used by these authors, in her doctoral thesis entitled "Development of new urease inhibitors and nitrification for phytosanitary purposes" (Ecole Nationale Supérieure de Chimie de Rennes, November 4, 2011); this work also postulates a reaction mechanism for the acid hydrolysis of these molecules, a phenomenon which limits their effectiveness in humid environments, and which must be taken into account when storing solid fertilizer containing urease inhibitors, as well as when spreading it on a field.

[0013] Among the practical problems that have been described in connection with urease inhibitors are in particular the coating of fertilizer grains with the urease inhibitor additive from a liquid, by spraying or impregnation, or from a solid powder by dusting, as described in WO 2009 / 079994; in any case, this is an additional industrial process that can present a certain complexity if it is desired to achieve a homogeneous distribution of the additive in the mass of fertilizer to be treated. When impregnating a solid fertilizer with a liquid comprising a urease inhibitor additive, this fertilizer must however not lose its properties as a dry granular solid: the liquid phase must be as concentrated as possible, while allowing its easy and homogeneous spreading on the fertilizer stock.This also makes it possible to minimize the quantity of additive to be supplied and handled, which is desirable in order to simplify the use of this additive, and to minimize its environmental impact.

[0014] Another problem related to urease inhibitors is their ecotoxicity. As For example, in some countries such as France, urease inhibitors are not approved, and in particular the above-mentioned NBPT is not currently considered a satisfactory product from an ecotoxicological point of view. Its use can only be achieved through an expansion of the EC fertilizer standard. These complex derivatives of TPA are also quite expensive, and their synthesis results in a mixture of products, among which dimers and oligomers are often found.

[0015] Since the problem of urea volatilization by urease still does not have a solution that would be completely satisfactory from a technical, economic and ecological point of view, the present invention aims to provide new preparations of urease inhibitors, which are low in toxicity, can be incorporated in a simple and practical manner into a solid nitrogen fertilizer, and which are not expensive. And finally, it is desired that the process for manufacturing the urease inhibitor preparation has as low an ecological impact as possible, which prohibits the use of toxic auxiliary products, as well as processes that discourage the use of processes that generate secondary products that must be treated in a specific manner. Objects of the invention

[0016] Thus, a first object of the invention is a process for manufacturing phosphoryl triamide OP(NH2)3 or thiophosphoryl triamide SP(NH2)3 in which

[0017] a) phosphoryl trichloride OPC13 or thiophosphoryl trichloride SPC13 is reacted, respectively, with gaseous ammonia in an apolar liquid phase to obtain a first precipitate comprising phosphoryl triamide and ammonium chloride,

[0018] b) treating said first precipitate with sodium carbonate or potassium carbonate, preferably with sodium carbonate, in a polar organic liquid phase, to obtain a second precipitate comprising NaCl and phosphoryl triamide or thiophosphoryl triamide, respectively, remaining in said polar organic liquid phase, and separating said second precipitate from said polar organic liquid phase.

[0019] The latter can further undergo a concentration step to increase its phosphoryl triamide concentration, for example by partial evaporation of said polar organic liquid phase.

[0020] In a variant, a step c) is added in which said organic liquid phase obtained at the end of step b) is evaporated to obtain a third precipitate comprising, respectively, phosphoryl triamide or thiophosphoryl triamide.

[0021] Said carbonate, of sodium or potassium, is preferably anhydrous.

[0022] Said first precipitate typically has a mass fraction of phosphoryl triamide or thiophosphoryl triamide of at least 15%, preferably at least less than 22%, and even more preferably at least 28%; this simplifies the purification step (step b).

[0023] Another subject of the invention is the product obtainable by the process described above and comprising steps a) and b), said product being said third precipitate. This precipitate has a high concentration of PTA or TPTA, with a specific spectrum of impurities. Advantageously, said third precipitate has a mass fraction of PTA or TPTA of at least 70%, preferably at least 80%, and even more preferably at least 90%; depending on the reaction conditions, said concentration of PTA or TPTA may exceed 90% by mass, and may reach 92%, 94% or even 96%.

[0024] Yet another object of the invention is the use of said polar organic liquid phase obtained at the end of step b), possibly diluted, for coating or impregnating granules of nitrogen fertilizer, preferably based on urea, for inhibiting and / or regulating the loss of nitrogen from a nitrogen fertilizer, in particular for inhibiting and / or regulating the enzymatic hydrolysis of urea, and / or for inhibiting and / or regulating the microbiological oxidation of ammonium.

[0025] Yet another object of the invention is a process for preparing a so-called stabilized solid nitrogen fertilizer formulation, in which a solid nitrogen fertilizer is supplied, and it is impregnated with a liquid phase comprising which is said polar organic liquid phase obtained at the end of step b), possibly diluted, or which is obtained by complete dissolution of said third precipitate in water.

[0026] Advantageously, said liquid phase is used in an amount which does not exceed 3 L of liquid per tonne of fertilizer, preferably does not exceed 2.5 L per tonne of fertilizer, and even more preferably does not exceed 2 L per tonne of fertilizer. This does not alter the properties of the granular solid of the fertilizer, and does not harm its storage stability. Detailed description

[0027] The abbreviation "PTA" here designates the phosphoryl triamide (CAS No. 13597-72-3) of formula O=P(NH2)3. Here we prefer the simplified writing OP(NH2)3 to the more common writing PO(NH2)3 because it better represents the structure of the molecule. The same remark applies to the writing of the formula of the molecule O=PCl3 and to the thio homologues of these two molecules. The abbreviation "TPTA" here designates the thiophosphoryl triamide of formula S=P(NH2)3.

[0028] Unless otherwise stated, all values ​​given as a percentage in a composition or formulation are mass percentages.

[0029] The PTA manufacturing process according to the invention comprises two stages.

[0030] The first step is known as such: oxychloride is reacted with phosphorus POCl3 with gaseous ammonia in a non-polar liquid phase to obtain a first precipitate comprising PTA and ammonium chloride. This reaction typically takes place at a temperature below 20°C, preferably between -20°C and 20°C, and even more preferably between -10°C and 5°C. Said non-polar liquid phase advantageously comprises anhydrous chloroform as solvent. Any trace of water in the reaction medium risks promoting the hydrolysis of phosphoryl chloride into phosphoric acid.

[0031] In an advantageous embodiment, said apolar liquid phase is chloroform, preferably anhydrous. It can be easily recycled, and can in particular be reused in this first step of the process.

[0032] The separation of said first precipitate can be carried out using known methods, in particular by filtration. The product represented by the first precipitate advantageously comprises at least 15% by mass of PTA; this assumes in particular the use of an anhydrous apolar solvent and working at a temperature not exceeding 20°C. Advantageously, the mass fraction of PTA is at least 22% or even at least 28%; it can typically reach approximately 35%.

[0033] It is not advantageous to use this first precipitate as such as a urease inhibitor preparation in a nitrogen fertilizer, because it contains a large quantity of ammonium chloride, which is highly soluble, the anion of which is undesirable in agricultural soil, and the cation, which carries nitrogen, is difficult for certain plants to assimilate. Furthermore, to dissolve this first precipitate which contains a high concentration of ammonium chloride, it is necessary to use a fairly large quantity of water, which will lead to the need to impregnate the fertilizer with a quantity of liquid greater than 3 liters per ton of fertilizer treated, which is not desirable.

[0034] The process according to the invention comprises a second step which aims to separate the PTA from the ammonium chloride. In this step, herein referred to as "step b)", said first precipitate is first treated with a polar organic liquid phase, to dissolve it. This is advantageously done with stirring, until a homogeneous mixture is obtained. Then sodium carbonate, preferably anhydrous, is added to this liquid phase, still with stirring. This operation can take place at room temperature. A second precipitate is thus obtained. The latter mainly comprises NaCl; the PTA remaining in said polar organic liquid phase. Said second precipitate is separated from said polar organic liquid phase using known separation methods, which may be filtration.

[0035] The polar organic liquid phase containing the PTA may further undergo a concentration step to increase its PTA concentration, for example by partial evaporation of said polar organic liquid phase.

[0036] In a variant, a step c) is added in which said phase is evaporated organic liquid obtained at the end of step b) until a third precipitate containing PTA is obtained.

[0037] Advantageously, said polar liquid phase is ethanol, which is a common solvent, not very toxic, not too volatile, easy to recover and purify. Preferably, it is used in the process according to the invention in its anhydrous form.

[0038] The PTA obtained from the second step has good purity. The main impurities are the hydrolysis products of PTA, in particular OP(NH2)2 OH (which can be easily identified on an NMR spectrum centered on the 31P isotope), the dimers or oligomers of PTA, and other PTA derivatives. These typical impurities also partly exhibit an inhibitory activity on urease. However, it is preferable to minimize the level of impurities in such a product, because the behavior of the impurities is not necessarily the same as that of the target product.

[0039] Typically, said third precipitate has a mass fraction of phosphoryl triamide of at least 70%, preferably at least 80%, and even more preferably at least 90%; a content exceeding 94% and even 96% can be achieved.

[0040] The third precipitate resulting from the process according to the invention can be used, as such or diluted in a solid material, in a solid formulation of nitrogen fertilizer, preferably based on urea, to inhibit and / or regulate the loss of nitrogen from a nitrogen fertilizer, in particular to inhibit and / or regulate the enzymatic hydrolysis of urea, and / or to inhibit and / or regulate the microbiological oxidation of ammonium.

[0041] The product according to the invention is preferably in the form of said third precipitate or in the form of said apolar liquid phase. As indicated above, it is enriched in PTA and depleted in chloride. This has various advantages. The introduction of chloride into a soil for agricultural use is generally not desirable.

[0042] The applicant has found that a quantity of PTA of the order of 0.05% to 0.3%, preferably between 0.05% and 0.2%, incorporated into a urea-based fertilizer, significantly reduces the production of ammonia.

[0043] The addition of the urease inhibitor to a solid nitrogen fertilizer formulation can be done with an inhibitor that is in the form of a solid phase (preferably powdered) or liquid (generally in the form of a solution).

[0044] The addition of the solid inhibitor requires particularly efficient mechanical mixing means. The powdered inhibitor can be diluted in another solid additive, or in a certain quantity of granular fertilizer, before adding it to the volume of fertilizer to be treated.

[0045] The addition of the inhibitor in the liquid phase can be done by directly using the polar organic liquid phase from the second stage of the process, after separation of the NaCl; it is also possible to dilute the polar organic liquid phase from the second step of the process according to the invention, if this is desired for any reason. Even if the solubility of PTA in ethanol is good, this approach of using an alcoholic solution is not preferred because it requires managing in the workshop in which this impregnation is carried out a risk of explosion linked to the gas, something which the fertilizer industry is not accustomed to.

[0046] Alternatively, a liquid phase loaded with PTA can be obtained by dissolving said third precipitate, which comprises a high proportion of solid PTA, in a suitable solvent, which is preferably aqueous.

[0047] The addition of a liquid phase comprising a urease inhibitor to a solid nitrogen fertilizer is usually done by impregnating said solid fertilizer, which is typically in a granular form, with said liquid phase; said liquid phase is preferably applied by spraying. The quantity of this liquid phase is critical: generally speaking, it is not desired to impregnate a solid formulation of nitrogen fertilizer with more than 3 L of liquid per ton of fertilizer, so that said solid formulation does not lose its character as a dry granular solid. It is preferred that this quantity does not exceed 2.5 L per ton, and even more preferably it does not exceed 2 L per ton. This objective can only be achieved if the urease inhibitor is initially present in the liquid phase in a fairly concentrated form.This is impossible to achieve if we use the first precipitate, which typically only contains about twenty or thirty percent of PTA alongside the majority product which is ammonium chloride: it would be necessary to apply 5 or 10 liters of solution per ton to obtain a target PTA concentration of about 0.1% compared to the total quantity of fertilizer.

[0048] The problem of the quantity of liquid is exacerbated in the case of water, because urea-based fertilizers are sensitive to humidity. Standards generally tolerate a maximum of 0.5% humidity. Adding five or ten liters of liquid risks exceeding this standard. And finally, to process 180 million tons of nitrogen fertilizers per year worldwide, it would be necessary to provide approximately 10 to 20 million liters of diluate (PTA + water), which poses a definite logistical problem.

[0049] However, the solubility of PTA in water is better than in a polar organic solvent such as ethanol. It is for this reason that the process for manufacturing PTA according to the invention is very advantageous, because it results in a product that is fairly concentrated in PTA, which makes it possible to minimize the quantity of solvent necessary to put it into solution and apply it to the fertilizer, since the solvation of the PTA is not disturbed by the solvation of secondary products.

[0050] By way of example, it is possible to advantageously use an aqueous solution obtained by complete dissolution of the third precipitate, comprising a higher PTA content at 85% and preferably greater than 88%, and even more preferably at least 90%, at a rate of at most 3 L of liquid per tonne of fertilizer, and preferably at most 2.5 L of liquid per tonne, and even more preferably at most 2 L of liquid per tonne. In this embodiment, the concentration of PTA in the fertilizer is preferably between 0.05% and 0.3%, more preferably between 0.05% and 0.2%; a concentration of approximately 0.1% gives good results.

[0051] The addition of a liquid phase comprising a urease inhibitor to a liquid nitrogen fertilizer does not raise any particular problem.

[0052] Alternatively, the third precipitate may be added in solid form to a solid or liquid nitrogen fertilizer. The addition of the third precipitate to a solid nitrogen fertilizer may be done by any suitable means, for example using a mixing screw.

[0053] The invention can also be carried out with thiophosphoryl triamide SP(NH2 )3 (abbreviated TPTA), synthesized from thiophosphoryl trichloride SPC13 (CAS No. 3982-91-0) by following the same reaction as that described for PTA, and by following the same purification route; for each of these steps, operating conditions very similar to those described for PTA can be used. TPTA can be used in the same way as PTA. It has two major disadvantages compared to PTA: its very unpleasant odor, and thiophosphoryl trichloride is more expensive than phosphoryl trichloride. Examples

[0054] Example 1: Synthesis and purification of phosphoryl triamide (PTA).

[0055] The first step is the synthesis according to the formula 6 NH3 (g) + OPC13 (g) 3 NH4C1 (s) + OP(NH2)3 (s). In a three-necked 1-liter flask (two necks being fitted with a septum, and the third neck being fitted with a balloon) previously purged with argon, approximately 300 ml of anhydrous chloroform (CAS No.: 67-66-3, molar mass 119.38 g / mol, supplier: Sigma Aldrich (ref: 372978)) were introduced with a stirring olive. Then 10 g of phosphoryl trichloride (POC13, CAS No. 10025-87-3, molar mass 153.33 g / mol, supplier Sigma Aldrich (ref: 201170)) were added using a syringe through a septum. The flask was placed in an ice bath with stirring. When the contents were well cooled, gaseous ammonia (CAS No. 7664-41-7, molar mass 17.03 g / mol, supplier Sigma Aldrich (ref: 294993)) was introduced very slowly using a cannula through the septum. A white precipitate appeared in the chloroform phase. The reaction is complete when the balloon remains inflated.

[0056] The white precipitate was recovered by filtration on a frit. The white precipitate is a mixture of NH4C1 and PTA. After drying the white precipitate, the yield of the reaction was approximately 96% to 98% relative to the POC13 consumed.

[0057] The second step is the purification of the white precipitate obtained in the first step according to the reaction NH4C1 + Na2CO3 NH3 (g) + NaCl (s) + NaHCO3 (s). The white precipitate obtained in the first step was solubilized in anhydrous ethanol (CAS No. 64-17-5) at room temperature. Anhydrous Na2CO3 (CAS No. 497-19-8) was added with a molar ratio of 1 / 1 to NH4C1. The mixture was left stirring for 12 hours, then the mixture was filtered to separate the NaCl and NaHCO3 from the solution. The filtrate is a solution of ethanol with PTA. After evaporation of the ethanol from the filtrate, a white solid with a PTA concentration of approximately 96% to 98% remains.

[0058] PTA was identified by 31P-NMR. The main impurity was O=P(NH2)2OH.

[0059] It should be noted that in an industrial process, the gaseous NH3 released during the second stage can be reused. Similarly, the two organic solvents, namely that of the first stage and that of the second stage, can be collected, distilled, freed from their traces of water and reused.

[0060] Example 2: Efficacy of PTA as a urea inhibitor

[0061] Three 1500 g samples of garden soil were prepared, placed in airtight enclosures. One sample was treated with urea containing no PTA, and two samples with urea containing 0.1% by mass of PTA. The amount of urea was the same for each sample. The PTA was the "second precipitate" within the meaning of the subject of the present invention. It contained at least 75% by mass of PTA; the indication "0.1% by mass of PTA" refers here to the total mass of the second precipitate and not to the pure PTA it contains.

[0062] Each soil sample was treated with 250 g of water before placing the PTA-treated or non-PTA-treated urea samples on the surface. The volatilization of the urea after four days, expressed as a mass percentage, was determined. To do this, a stream of air was sent over each sample using a membrane pump, and this air was passed through a citric acid solution which fixes the ammonia by transforming it into ammonium. The citric acid solution was then titrated with a sodium hydroxide solution to calculate the quantity of ammonia reacting with the citric acid solution. From the quantity of ammonia, the quantity of urea generating it is calculated.

[0063] The following results were obtained:

[0064] Control sample (without PTA): 15.4%

[0065] Samples 2 and 3 (0.1% PTA): 1.5% and 3.05%

[0066] In this test, the soil was taken from a single location, and the enclosures were stored side by side in the same room. It can therefore be assumed that each batch was exposed to the same experimental conditions. Since the temperature of the room was not controlled (urea volatilization is known to increase with temperature), and since the bacterial activity of a batch of soil can change depending on the sampling location, the results of this test are not necessarily quantitatively comparable to those published in other studies on urease inhibitors. However, this test clearly demonstrates the effect of PTA contained in the "second precipitate" on urea volatilization.

[0067] It should be noted that a volatilization of 15.4% without the addition of PTA corresponds to an unusually low value compared to what is encountered outdoors, especially at temperatures above 20°C: in real sites, volatilization can reach 50%.

[0068] Example 3: Use of PTA as an adjuvant in nitrogen fertilizers

[0069] PTA can be applied directly to urea-based fertilizers using a nozzle system that allows a precise amount of PTA to be applied by spraying per tonne of fertilizer. A conveyor is used to determine the flow of fertilizer in tonnes and, depending on this flow, a quantity of PTA is applied, which can typically range from 2 to 3 L / tonne, to the urea fertilizer granules. This application is carried out in a mixing screw using several nozzles allowing the application of PTA.

Claims

Claims

1. A process for the production of phosphoryl triamide OP(NH2)3 or thiophosphoryl triamide SP(NH2)3, in which a) phosphoryl trichloride OPCl3 or thiophosphoryl trichloride SPCl3, respectively, is reacted with gaseous ammonia in a non-polar liquid phase to obtain a first precipitate comprising, respectively, phosphoryl triamide or thiophosphoryl triamide, and ammonium chloride, b) said first precipitate is treated with sodium carbonate or potassium carbonate, preferably with sodium carbonate, in a polar organic liquid phase, to obtain a second precipitate comprising NaCl and the phosphoryl triamide or thiophosphoryl triamide remaining in said polar organic liquid phase, and said second precipitate is separated from said polar organic liquid phase,the latter being able to undergo a further concentration step to increase its concentration of phosphoryl triamide or thiophosphoryl triamide.,

2. Method according to claim 1, characterized in that in a step c) said organic liquid phase obtained at the end of step b) is evaporated to obtain a third precipitate comprising phosphoryl triamide or thiophosphoryl triamide.

3. Method according to claim 1 or 2, characterized in that said first precipitate has a mass fraction of phosphoryl triamide or thiophosphoryl triamide of at least 15%, preferably at least 22%, and even more preferably at least 28%.

4. Method according to claim 2 or 3, characterized in that said third precipitate has a mass fraction of phosphoryl triamide or thiophosphoryl triamide of at least 70%, preferably at least 80%, and even more preferably at least 90%.

5. Method according to any one of claims 1 to 4, characterized in that said apolar liquid phase is chloroform, preferably anhydrous, and / or said polar liquid phase is ethanol, preferably anhydrous.

6. Product obtainable by the process according to any one of claims 2 to 5, characterized in that said product is said third precipitate.

7. Use of the third precipitate according to any one of claims 2 to 6, possibly diluted in a solid material, in a solid formulation of nitrogen fertilizer, preferably based on urea, for inhibiting and / or regulating the loss of nitrogen from a nitrogen fertilizer, in particular for inhibiting and / or regulating the enzymatic hydrolysis of urea, and / or for inhibiting and / or regulating the microbiological oxidation of ammonium.

8. Use of said polar organic liquid phase obtained at the end of step b) according to any one of claims 1 or 2 to 5, possibly diluted, for coating or impregnating granules of nitrogen fertilizer, preferably based on urea, for inhibiting and / or regulating the loss of nitrogen from a nitrogen fertilizer, in particular for inhibiting and / or regulating the enzymatic hydrolysis of urea, and / or for inhibiting and / or regulating the microbiological oxidation of ammonium.

9. Process for preparing a so-called stabilized solid nitrogen fertilizer formulation, in which a solid nitrogen fertilizer is supplied, and mixed with a liquid phase, or impregnated with a liquid phase, said liquid phase comprising or being said polar organic liquid phase obtained at the end of step b) according to any one of claims 1 or 2 to 5, possibly diluted, or being obtained by complete dissolution of said third precipitate in water.

10. Preparation process according to claim 9, or use according to claim 8, characterized in that said liquid phase is used in an amount which does not exceed 3 L of liquid per tonne of fertilizer, preferably does not exceed 2.5 L per tonne of fertilizer, and even more preferably does not exceed 2 L per tonne of fertilizer.