Urea-based composition comprising elemental sulphur and method for the manufacture thereof

Abstract

The invention relates to a particulate urea-based composition comprising elemental sulphur and a urease inhibitor of the type phosphoric triamide, wherein the urea-based composition comprising elemental sulphur is further characterized in that it comprises a magnesium sulphate. The composition according to the invention has improved properties for reducing ammonia loss by urease activity in the soil and is in particular suitable as a fertilizer. The invention further relates to a method for the manufacture of a particulate urea-based composition comprising urea, elemental sulphur and a urease inhibitor of the type phosphoric triamide, in particular N-(n-butyl) thiophosphoric triamide (nBTPT), as well as to a composition of kit of parts comprising a magnesium sulphate.

Claims

1. A particulate, urea-based composition comprising: at least 75 weight % of a particulate urea base material based on the total weight of the urea-based composition, the particulate urea base material comprising at least 1 weight % elemental sulphur, based on the total weight of the urea base material; 0.02 to 0.2 weight % of a phosphoric triamide urease inhibitor based on the total weight of the urea-based composition; and 0.05 to 5 weight % of magnesium sulphate based on the total weight of the urea-based composition, wherein a ratio of the urease inhibitor to the magnesium sulphate is 1:20 to 1:10.

2. The urea-based composition according to claim 1, wherein the urea-based composition further comprises an alkaline or alkaline-forming compound selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof.

3. The urea-based composition according to claim 2, wherein the weight ratio of alkaline or alkaline-forming compound to magnesium sulphate ranges from 1:20 to 1:2.

4. The urea-based composition of claim 3, wherein the weight ratio of alkaline or alkaline-forming compound to magnesium sulphate is from 1:15 to 1:2.

5. The urea-based composition according to claim 1, wherein the urea-based composition further comprises anti-caking and/or moisture-repellent and/or anti-dust material.

6. The urea-based composition according to claim 5, wherein the anticaking and/or moisture-repellent coating comprising at least a non-polar material, present in the composition at a level of 0.0001 to 1 weight %.

7. The urea-based composition of claim 6, wherein the non-polar material is selected from the group consisting of oil, wax, resin and mixtures thereof.

8. The urea-based composition according to claim 1, wherein the urease inhibitor is N-(n-butyl) thiophosphoric triamide (nBTPT).

9. The urea-based composition according to claim 8, wherein the urea-based composition comprises 90 to 99.9 weight % of a urea base material comprising 0.03 to 0.06 weight % of nBTPT, 0.05 to 0.1 weight % of magnesium sulphate, and 0.015 to 0.03 weight % of magnesium oxide, adding up to 100 weight %, being the total weight of the composition.

10. The urea-based composition according to claim 1, wherein the magnesium sulphate is selected from the group consisting of anhydrous, mono-, di-, tri-, tetra-, penta-, hexa-, heptahydrate, and mixtures thereof.

11. The urea-based composition according to claim 1, wherein the phosphoric triamide urease inhibitor is a compound of formula I: ##STR00004## wherein: X is oxygen or sulphur; R.sub.1 is alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl, or cycloalkyl; R.sub.2 is hydrogen, alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl, or cycloalkyl, or R.sub.1 and R.sub.2 together may form an alkylene or alkenylene chain which may optionally include one or more heteroatoms of divalent oxygen, nitrogen or sulphur completing a 4, 5, 6, 7, or 8 membered ring system; and R.sub.3, R.sub.a, R.sub.5 and R.sub.6 are individually hydrogen or alkyl having 1 to 6 carbon atoms; and alkyl, cycloalkenyl, aralkyl, aryl, alkenyl, alkynyl, and cycloalkyl refer to compounds having from 1 to 10 carbon atoms.

12. The urea-based composition according to claim 1, wherein the urease inhibitor of the type phosphoric triamide is present onto the urea base material in liquid or in particulate form, is present as a melt-mixed component within the particles of the urea base material, or a combination thereof.

13. The urea-based composition according to claim 1, wherein the urea base material comprises finely divided sulphur particles in a urea base material, or a urea base material coated with elemental sulphur.

14. The urea-based composition according claim 1, wherein, the urea base material is selected from the group consisting of urea, urea-ammonium sulphate, urea-ammonium phosphate, and combinations thereof.

15. The urea-based composition according to claim 1, wherein the average particle size (dp50) of the urea base material in particulate form is between 1 mm and 5 cm, as determined by mesh sieve screening.

16. A method comprising fertilizing a soil with the particulate urea-based composition as claimed in claim 1.

17. A method for the manufacture of a particulate urea-based composition according to claim 1, the method comprising the steps of: 1) providing at least 75 weight % of a particulate urea base material based on the total weight of the urea-based composition, the particulate urea base material comprising at least 1 weight % elemental sulfur; 2) providing 0.05 to 5 weight %, relative to the total weight of the composition, of magnesium sulphate; 3) providing 0.02 to 0.2 weight %, relative to the total weight of the composition, of a phosphoric triamide urease inhibitor wherein a ratio of the urease inhibitor to the magnesium sulphate is 1:20 to 1:10; 4) optionally, providing 0.0001 to 1% weight %, relative to the total weight of the composition, of an alkaline or alkaline-forming compound, selected from the group consisting of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof, and 5) optionally, providing coating material, wherein the coating material increases the anticaking and/or moisture repellence and/or anti-dust properties of said urea-based composition; and 6) adding the components provided in steps 2), 3), 4) and 5) in any order to the component, provided in step 1).

18. The urea-based composition of claim 17, wherein the urease inhibitor is N-(n-butyl) thiophosphoric triamide.

19. A method for improving the stability of a phosphoric triamide urease inhibitor in a urea-based composition comprising a urea base material comprising 0.1 to 20 weight % of elemental sulphur and said urease inhibitor, the method comprising adding to said composition 0.05 to 5 weight % of magnesium sulphate, relative to the total weight of the composition, wherein a ratio of the urease inhibitor to the magnesium sulphate is 1:20 to 1:10.

20. The urea-based composition of claim 19, wherein the urease inhibitor is N-(n-butyl) thiophosphoric triamide.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1. Ammonia release of a YaraVera® Amidas product comprising 462 ppm nBTPT, treated with several stabilizers (see Table 1).

(2) FIG. 2A. Stability of nBTPT on a YaraVera® Amidas product comprising 462 ppm nBTPT in plastic containers open to air at room temperature after 40 days [A=no stabilizer; B=CaO (2541 ppm); C=MgSO.sub.4 99.5% purity (4957 ppm)].

(3) FIG. 2B. Stability of nBTPT on a YaraVera® Amidas product comprising 462 ppm nBTPT, in bags at 40° C. [A=no stabilizer; B=CaO (2541 ppm); C=MgSO.sub.4 99.5% purity (4957 ppm)] after 8 days.

(4) FIG. 3. Stability of nBTPT on a YaraVera® Amidas product comprising 462 ppm nBTPT using different grades and forms of MgSO.sub.4 and Na.sub.2SO.sub.4, stored in open plastic containers at room temperature for 21 days. [A=no stabilizer; B=CaO (2541 ppm); C=MgSO.sub.4 99.5% purity (4957 ppm); D=MgSO.sub.4 99.999% purity (4957 ppm); E=MgSO.sub.4.7H.sub.2O (10163 ppm; F=Na.sub.2SO.sub.4 (5849 ppm]

(5) FIG. 4. Stability of nBTPT on a YaraVera® Amidas product comprising 462 ppm nBTPT using different MgSO.sub.4/MgO combinations [A=no stabilizer; B=CaO (2310 ppm); C=MgO (212 ppm); D=MgSO.sub.4>98% grade (4620 ppm); E=MgSO.sub.4>98% grade (924 ppm)/MgO (212 ppm)]

EXPERIMENTAL

(6) All examples shown were carried out with a YaraVera® Amidas product, which is a urea-based composition comprising urea ammonium sulfate material.

(7) 1. Volatilization Measurements (Ammonia Release 2 L Diffusion Kit)

(8) 200 g of UAS product, treated with nBTPT/stabilizer are put in a 2 L plastic container. Through the lid, a Draeger tube is placed for the measurement of vol % ammonia. The Draeger tube turns from yellow to bleu/purple when ammonia is absorbed by the tube. The amount of vol % ammonia released can be followed in time.

(9) 2. nBTPT Measurements

(10) For lab scale experiments, 1.2 kg of solid fertilizer material was added to a lab scale drum. In a next step, the nBTPT/stabilizer material was slowly added. A residence time of 10 minutes was applied and the rotating speed of the drum was consequently the same in each experiment. In case a moisture-repellent coating was added, a nebulizer was used and depending on the order of addition, the moisture-repellent coating was added before or after addition of the nBTPT material. Before use, the moisture-repellent coating was preheated to 80° C. Larger scale experiments with amounts up to 40 kg of fertilizer material were performed in a concrete mixer.

(11) The samples were stored under several conditions, dependent on the type of samples: Bagged at room temperature (18-25° C.) Bagged at 40° C. Open to air at room temperature (18-25° C.)

(12) 3. HPLC Analysis of nBTPT-Content

(13) HPLC analysis of nBTPT is done as described in the procedure CEN 15688-2007.

(14) 4. Products

(15) UAS was obtained from Yara as granules YaraVera® Amidas 40-0-0 (product code PA421X).

(16) Solid N-(n-butyl)thiophosphoric triamide was obtained from Sunfit Chemical Co. (China) (CAS-Nr. 94317-64-3), as a white crystalline solid with a melting point of 58-60° C.

(17) MgO technical grade was obtained from Mannekus & Co B.V., Schiedam, The Netherlands (dp(50)=27 μm, +/−90% purity, 2-2.9% CaO, 1.1% SiO2).

(18) CaO technical grade was obtained from VWR International, Oud-Heverlee, Belgium (91.3% pure, 2.7% CaCO.sub.3 and 6% Ca(OH).sub.2), dp(50)=22 μm).

(19) CaCO.sub.3 (limestone powder) was obtained from Nordkalk AB, Finland (98.5% pure, dp(50)=7 μm).

(20) CaSO.sub.4 anhydrous was obtained from Alfa Aesar, Haverhill, USA.

(21) MgSO.sub.4 anhydrous, 99.999%, was obtained from Alfa Aesar, Haverhill, USA.

(22) MgSO.sub.4 anhydrous, >99.5%, was obtained from Alfa Aesar, Haverhill, USA.

(23) MgSO.sub.4 anhydrous, >98%, was obtained from Ekmekciogullari, Turkey.

(24) MgSO.sub.4.7H.sub.2O, >99.5%, was obtained from Merck KGaA, Darmstadt, Germany.

(25) Coating: Moisture-repellent (MR) coating was made according to EP 0768993 A1 (Norsk Hydro ASA) by mixing about 28 weight % of wax, about 68 weight % of oil and about 4 weight % of a resin, applied in an amount of about 0.1-0.5 weight % to the fertilizer. It will be referred herein as NH-coating.

(26) Experiment 1 (Ammonia Release)

(27) Experiment 1 defines the problem. FIG. 1 shows the ammonia release of a YaraVera® Amidas product comprising 462 ppm nBTPT, treated with several stabilizers. The numbers between brackets represent, for each stabilizer compound, the weight ratio of the said stabilizer compound compared to nBTPT.

(28) TABLE-US-00001 TABLE 1 Ammonia release with different stabilizers Example Stabilizer composition A (prior art) MgO (4.3) B (prior art) CaO-G-0554 (5.5) C (prior art) MgO (0.86) D (prior art) none E (prior art) CaCO.sub.3 (9.98) F (prior art) CaSO.sub.4 (12.1) G MgSO.sub.4 (10.7)

(29) Although compounds such as MgO and CaO are mentioned in the prior art document WO2018/069486 (Yara International, 2018) as most effective stabilizers for nBTPT in the presence of a urea base material comprising elemental sulphur, these compounds are observed as producing ammonia in the presence of said material, which is an unwanted effect of these stabilizers. Only without stabilizer, and with MgSO.sub.4 and with CaSO.sub.4, there is no ammonia release.

(30) Experiment 2

(31) This experiment was conducted to show the difference between the beneficial effect of the addition of an alkaline or alkaline-forming inorganic or organic compound (CaO—prior art) and MgSO.sub.4 (VWR grade 99.5%) to UAS on the stability of nBTPT in the presence of UAS open to the air at room temperature (FIG. 2A) and in bags at elevated temperature (FIG. 2B). As can be seen, the stabilizing effect of MgSO.sub.4 is comparable with the effect of the prior art compound (CaO), but no ammonia is generated (as shown in FIG. 1).

(32) Experiment 3 (Different Grades)

(33) This experiment shows the effect of the addition of different grades and forms of MgSO.sub.4 and also another sulfate, Na.sub.2SO.sub.4, compared to the prior art compound CaO for open to air storage conditions at room temperature (FIG. 3). All MgSO.sub.4 grades give a comparable nBTPT stability on the YaraVera® Amidas product. This experiment shows that the stabilizing effect of MgSO.sub.4 on nBTPT on UAS is not 100% based on a pH effect (alkaline pH 8.5 for MgSO.sub.4 99.5% versus acidic pH 6.1 for MgSO.sub.4 99.999%) and also not 100% based on the waterbinding effect of anhydrous MgSO.sub.4 as MgSO.sub.4.7H.sub.2O delivers similar nBTPT stability. Na.sub.2SO.sub.4 actually has a negative effect on the stability of nBTPT. This shows the unique stabilizing effect of magnesium sulphate.

(34) Experiment 4 (Effect of Addition of Oxides and Synergetic Effect of MgSO.sub.4 and MgO)

(35) This experiment shows the effect of the addition of a small amount of oxide to the stabilizer. Small amounts of MgSO.sub.4, which have little effect, become very effective in a combination with MgO (see D versus E). The effect is synergetic (see C+D versus E) and not additive. There is almost no difference in stability depending on the method of combining the components of the stabilizer composition (i.e. adding the components one by one in any order/making a pre-mix of the components and adding the pre-mix to UAS). MgO was found more effective than CaO, but it is assumed that any alkaline or alkaline-forming compound, selected from the group of calcium oxide, zinc oxide, magnesium oxide, calcium carbonate, and mixtures thereof, is effective.