Fertilizer mixture containing nitrification inhibitor

Abstract

The invention features a fertilizer mixture containing (i) a calcium ammonium nitrate mineral fertilizer and (ii) 2-(N-3,4-dimethylpyrazole)succinic acid, or a salt thereof.

Claims

1. A process for preparing 2-(N-3,4-dimethylpyrazole)succinic acid or a salt thereof by: (i) reaction in water of 3,4-dimethylpyrazole with maleic acid and/or maleic anhydride in the absence of organic solvents or diluents at a temperature from 70° C. to 105° C. to produce a reaction mixture, and (ii) following step (i), in the absence of organic solvents or diluents cooling the reaction mixture to induce crystallization of 2-(N-3,4-dimethylpyrazole)succinic acid or salt thereof having a purity of at least 99.7%.

2. The process of claim 1, characterized in that aqueous solutions or pastes of 3,4,-dimethylpyrazole and/or maleic acid and/or maleic anhydride are reacted.

3. The process of claim 1, characterized in that the crystallization takes place with accompanying use of seed crystals.

4. The process of claim 1, characterized in that the 2-(N-3,4-dimethylpyrazole)succinic acid or salt thereof obtained after the crystallization has a purity of at least 99.9%.

Description

EXAMPLES

A. Preparation Examples

Example 1

(1) 9.6 g of 3,4-dimethylpyrazole (0.1 mol) and 9.8 g of maleic anhydride (0.1 mol) were heated to 100° C. in 50 ml of 50% strength acetic acid. After 16 hours the reaction mixture was evaporated to dryness. When the residue is taken up in diethyl ether, the product (2-(N-3,4-dimethylpyrazole)succinic acid) is precipitated in pure form and is isolated by filtration: white crystals in a yield of 92%. In the NMR spectrum there are a number of methyl signals apparent, this being in agreement with the elimination of the 3,5-tautomerism as a result of the substitution on nitrogen.

Example 2: Preparation on the 200 kg Scale

(2) Starting materials used for the experiments were maleic anhydride from CVM with a purity of more than 99.5%, and an 80% strength aqueous solution of 3,4-dimethylpyrazole (3,4-DMP) from BASF SE. According to NMR spectrum, the solution of 3,4-DMP used contained about 2% of otherwise uncharacterized impurities.

(3) The experiments were first conducted in a 20 L reaction vessel, which in further experiments was replaced by a 25 L reaction vessel.

(4) In the first experiment, 41.608 mol of maleic anhydride were introduced and dissolved in 11 liters of distilled water. The temperature rose here by 10° C. Then 41.608 mol of 80% strength aqueous 3,4-dimethylpyrazole solution were added, the temperature rising by a further 12° C. After the end of the addition, the reaction mixture was heated to an internal temperature of 100° C. When this temperature was reached, the reaction mixture was stirred at 100° C. for 24 hours and then cooled. When the reaction mixture had cooled to 90° C., a sample was taken for NMR-spectroscopic reaction monitoring, and the reaction mixture was subsequently seeded with 1 g of product (crystals of 2-(N-3,4-dimethylpyrazole)succinic acid). At this temperature, crystallization did not yet begin, but the added crystals also no longer dissolved. On further cooling, crystallization began slowly from around 85° C. The major quantity of the product only crystallized at just below 80° C., with an increase in temperature. For complete crystallization, the reaction mixture was left to cool overnight with stirring. The precipitated solid was filtered off on three 8 L G3 glass suction filters, using a suction flask and membrane pump, under reduced pressure, and the solid product was washed with a total of 8 liters of distilled water and then dried under reduced pressure at a bath temperature of 60° C. The dry product thus obtained was placed into a container and mixed thoroughly, and a sample thereof was analyzed by NMR spectroscopy. In the subsequent experiments, instead of the distilled water, a corresponding amount of the combined filtrates was employed as the reaction medium. The excess amount of the combined the bifiltrates was discarded.

(5) NMR-spectroscopic reaction monitoring after 24 hours showed a relatively constant conversion of around 92%, with a relatively constant P1/P2 (2-(3,4-dimethyl-1H-pyrazol-1-yl)succinic acid/2-(2,3-dimethyl-1H-pyrazol-1-yl)succinic acid) isomer ratio of around 3.3. Only at the start of the serial experiment was the ratio slightly higher. That, however, was also anticipated, since the use of the filtrate instead of the distilled water as reaction medium introduced a greater amount of P2 (P1/P2 ratio in the filtrates is around 1.0) into the subsequent experiments.

(6) After just a few experiments, the composition of the reaction mixture after a reaction time of 24 hours reached constant levels. By the same token, the compositions of the isolated products from the individual experiments differ only slightly from one another.

(7) The solids, obtained on average with a yield of 90.22%, possessed a purity of 99.9% and on average an isomer ratio of 4.0 (2-(3,4-dimethyl-1H-pyrazol-1-yl)succinic acid to 2-(2,3-dimethyl-1H-pyrazol-1-yl)succinic acid). Impurities of 3,4-DMP, maleic acid, and rac-malic acid were detectable in the 1H NMR spectra not at all or only in traces (<0.1%).

Example 3

(8) The carrier fertilizer used was calcium ammonium nitrate with 27% N and 10% Ca. 2 g of 2-(N-3,4-dimethylpyrazole)succinic acid and 46 g of KOH were dissolved in 133 g of water. 20 kg of the carrier fertilizer in the form of granules were slowly sprayed in a drum with 85 g of the formulation of the pyrazole compound.

Example 4

(9) Example 3 was repeated, using 111 g of water and 22 g of diammonium phosphate instead of 133 g of water.

Comparative Example

(10) In analogy to example 3, 3,4-dimethylpyrazole phosphate (DMPP) was used instead of 2-(N-3,4-dimethylpyrazole)succinic acid.

B. Application Examples

Example 1

(11) Investigation of Storage Stability

(12) Calcium ammonium nitrate (CAN) mineral fertilizer additized with 2-(N-3,4-dimethylpyrazole)succinic acid (DMPSA) or with DMPP, in accordance with example 3 or comparative example, respectively, was investigated for storage stability in an accelerated test, in which the nitrification-inhibited mineral fertilizers were stored in an open glass beaker (which, as a mini-heap, mimics the storage situation in a large heap) for 40 days at 30° C., 40% to 50% relative humidity and approximately 1.2 m/s air speed in an aerated heating cabinet. The concentration of nitrification inhibitor on the mineral fertilizer was determined before, during and after storage at two different depths in the bed, and the loss of nitrification inhibitor was ascertained. In each case about 10 to 30 g of treated mineral fertilizer were stored. The concentration of DMPP at the start was 1.028 g/kg fertilizer; for 2-(N-3,4-dimethylpyrazole)succinic acid, the figure was 1.244 g/kg fertilizer.

(13) After 20 and 40 days, samples were taken from a surface region of the fertilizer bed (0 to 5 cm sampling depth and >5 cm sampling depth).

(14) The results are shown in table 1 below, where DMPSA denotes 2-(N-3,4-dimethylpyrazole)succinic acid.

(15) TABLE-US-00001 TABLE 1 Storage stability of DMPP and DMPSA on CAN Analytical value [g/kg] DMPP on CAN Value at start 1.028 d20, 0-5 cm 0.86 d20, >-5 cm 0.91 d40, 0-5 cm 0.45 d40, >-5 cm 0.68 DMPSA on CAN Value at start 1.244 d20, 0-5 cm 1.15 d20, >-5 cm 1.18 d40, 0-5 cm 1.21 d40, >-5 cm 1.26 d = day 0-5 cm sampling depth

(16) From the table it is clear that the loss is much lower for 2-(N-3,4-dimethylpyrazole)succinic acid than for DMPP on storage over 20 to 40 days.

(17) This is evidence of the advantages of the fertilizer of the invention.

Example 2

(18) Verification of the biological (nitrification-inhibiting) effect of the 2-(N-3,4-dimethylpyrazole)succinic acid

(19) The biological activity of 2-(N-3,4-dimethylpyrazole)succinic acid was tested in a number of field trials in different environments.

(20) The field trials were set up, sampled, harvested, and evaluated in accordance with the processes customary in agricultural trialing.

(21) The plant and soil samples were analyzed by standard methods. The other production-related measures, such as the crop protection, were in line with good agricultural practice and were carried out uniformly.

(22) Preferably, a distinguishing feature of a biologically active nitrification inhibitor is that it exhibits higher levels of NH.sub.4 nitrogen relative to the control (here, unadditized CAN carrier fertilizer) within a period of up to 4 weeks and longer after application. As a consequence of these conditions, the yield is increased and the nitrate content of the plants is reduced.

(23) The active ingredient was applied in analogy to example 3 to solid CAN fertilizers with an application rate of 0.73% based on the reduced nitrogen. The active ingredient exhibits a strong nitrification-inhibiting action in the soil after application of the fertilizers. In the CAN (calcium ammonium nitrate)+DMPSA, given by way of example in table 2, there are still considerable amounts of reduced nitrogen both after 14 days and after 28 days, in comparison to untreated products; without nitrification inhibitor, the entire reduced nitrogen has undergone nitrification and conversion to nitrate N after no later than 28 days.

(24) TABLE-US-00002 TABLE 2 Inhibition of nitrification by DMPSA % NH.sub.4N (or NH.sub.2 N) of the fertilized N after Fertilizer 0 days 14 days 28 days CAN 100 9.1 0.0 CAN + DMPSA 100 79.3 61.9

Example 3

(25) Reduction in Greenhouse Gas Emissions (N.sub.2O)

(26) In addition to the protection of the hydrosphere, the maximum avoidance of release of climate-relevant gases as a consequence of the agricultural exploitation of soils is also a great challenge for agriculture.

(27) The compilation of the measurements of nitrous oxide (N.sub.2O), an extremely active climate gas (around 300 times stronger than CO.sub.2), both during the vegetation period of winter wheat after fertilization, and after harvesting into the winter, gave a reduction by 28% (table 3) in comparison to conventional CAN when using CAN+DMPSA in accordance with example 3.

(28) TABLE-US-00003 TABLE 3 Effect of fertilization with CAN with and without DMPSA on release of climate gas during winter wheat culture Without fertilization CAN CAN + DMPSA g N.sub.2O N/ha cumulative March to December 1149 2690 1953 43% 100% 72%

Example 4

(29) Effect on Yield and Quality of Agricultural and Horticultural Crops Yields

(30) In addition to possible consequences for the gentle treatment of soil, water, and air, the effect on yield and quality is particularly important to the farmer. The compilation of the weighed yields of various crops shows a consistently improved yield boost by the fertilizers with DMPSA in accordance with example 3 than by the use of the respective conventional fertilizers (table 4). Here there are virtually no differences between agricultural crops and vegetable crops, or in terms of the respective climate environments and different soils. The reasons for the extra yields are firstly the reduced losses as a result of leaching and the gaseous losses through denitrification, and secondly in the partial ammonium nutrition of the plants, which is beneficial for the plant metabolism by comparison with the customary nitrate nutrition with conventional fertilizers.

(31) TABLE-US-00004 TABLE 4 Effect of fertilization with CAN with and without DMPSA on the yield of various garden and agricultural crops Yield Yield Extra Region/ Fertilizer dt/ha dt/ha yield Crop Country used without with [%] Potato Hanover/D CAN 464 609 31 Potato Jutland/DK CAN 390 405 32 Potato Picardy/F CAN 642 667 4 Potato Orgiano/I CAN 531 582 9 Potato Galicia/E CAN 644 728 13 Celery* Palatinate/D CAN 563 595 5 Celery* Palatinate/D CAN 756 781 3 Chinese Palatinate/D CAN 757 842 11 cabbage** Chinese Palatinate/D CAN 817 930 13 cabbage** *weight/100 plants **weight per head, g