Boron aqueous solution

Abstract

There is provided an aqueous boron solution and a method of making same. The aqueous boron solution contains at least 8 wt. % boron, an alkanolamine and an alkaline sodium salt. The aqueous boron solution has a boron to alkanolamine molar ratio of more than 3.0. Moreover, the aqueous boron solution obtained is clear and stable. The boron present in the solution is solubilized in the form of B(OH)3 or anions thereof and does not precipitate even in long term storage of the aqueous boron solution.

Description

BORON AQUEOUS SOLUTIONTECHNICAL FIELD

[0001] This disclosure relates to the field of boron aqueous solutions, in particular to boron aqueous solutions with a reduced proportion of alkanolamine.BACKGROUND OF THE ART

[0002] Concentrated boron solutions are generally obtained by reacting boric acid to an alkanolamine such as monoethanolamine. The level of concentration of boron can be measured in relation to monoethanolamine by the molar ratio of boron to monoethanolamine (MEA) (B / MEA). Traditional compositions and processes allow to obtain a B / MEA molar ratio of up to 3.0. MEA is an expensive chemical but is traditionally what allows to obtain sufficiently concentrated boron solutions. It would be desirable to maintain or increase the concentration of boron while reducing the concentration of MEA by replacing it with less expensive chemicals. Accordingly, improvements in boron aqueous solutions are desired, particularly to reduce their price by reducing the content of MEA without reducing the boron concentration. It is also desirable to maintain the MEA concentration and be able to increase the boron content and thus increasing the B / MEA molar ratio to more than 3.SUMMARY

[0003] In one aspect, there is provided an aqueous boron solution comprising: at least 8 wt. % boron; an alkanolamine; and an alkaline sodium salt; wherein a molar ratio of boron to alkanolamine is of more than 3.0, and wherein the at least 8 wt. % boron are solubilized in the aqueous solution in the form of B(OH)3or anions thereof.

[0004] In some embodiments, the boron is in a concentration of at least 10 wt. %.

[0005] In some embodiments, the ratio is of up to 4.0.

[0006] In some embodiments, the alkanolamine is a C2-C5 alkyl terminated by an OH group on one side of the C2-C5 alkyl chain and by a NH2group on the other end of the C2-C5 alkyl chain. The C2-C5 alkyl chain may be substituted with methyl, ethyl, a halogen, an amine and / or a hydroxyl.

[0007] In some embodiments, the alkanolamine is monoethanolamine.

[0008] In some embodiments, the anions are one or more of B(OH)4_, B3O3(OH)4_, B5O6(OH)4, B4O5(OH)42- or B3O3(OH)52-.

[0009] In some embodiments, the dissolved alkaline sodium salt is dissolved NaOH, or a hydrate of Na2(B2O3)s, Na2B4O?, Na2CO3, NaHCO3, CH3COONa.

[0010] In some embodiments, the dissolved alkaline sodium salt is dissolved NaOH, or Na2(B2O3)2, Na2B4O? or hydrates thereof.

[0011] In some embodiments, the boron concentration is at least 100 g / L.

[0012] In some embodiments, the alkanolamine is present in a concentration of from 1 to 150 g / L.

[0013] In a further aspect, there is provided a method of producing an aqueous boron solution, the method comprising mixing boric acid, alkanolamine, and alkaline sodium salt in water, wherein a molar ratio of boron to alkanolamine is of more than 3.0, and wherein the aqueous boron solution comprises at least 8 wt. % boron that is solubilized in the form of B(OH)3or anions thereof.

[0014] In some embodiments, the method comprises first mixing a portion of the boric acid and the alkaline sodium salt in the water, and then mixing the remaining boric acid and alkanolamine.

[0015] In some embodiments, the mixing is performed at a temperature under 80 °C.

[0016] In some embodiments, the method further comprises adding a nitrogenated compound in the aqueous boron solution.

[0017] Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure.DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 A is a1H nuclear magnetic resonance spectrum of two samples solutions.

[0019] FIG. 1 B is a11B nuclear magnetic resonance spectrum of two samples solutions.

[0020] FIG. 1C is a11B nuclear magnetic resonance spectrum of different controls in comparison to a formulation obtained according to the present disclosure.

[0021] FIG. 2A is an infrared spectrum for two sample solutions.

[0022] FIG. 2B is a closer look at the peaks of the spectra of Fig. 2A.DETAILED DESCRIPTION

[0023] To reduce the concentration of alkanolamines in boron solutions, it was surprisingly found that alkaline sodium salts can replace a portion of the alkanolamines while maintaining or even increasing the concentration of boron. A boron solution as used herein is considered sufficiently concentrated in boron if it contains at least 8 wt. %, at least 9 wt. %, 10 wt. % of boron. In some embodiments, the boron concentration is at least 11 wt. %, at least 12 wt. %, at least 13 wt. % or at least 14 wt . %. In some embodiments, the concentration of boron is from 10 to 25 wt. %, from 10 to 20 wt. %, from 8 to 15 wt. % or from 10 to 15 wt. %. In some embodiments, the boron concentration is at least 100 g / L, at least 125 g / L or at least 140 g / L, for example from 100 to 250 g / L. The boron aqueous solution of the present disclosure achieves the aforementioned boron concentrations while maintaining a molar ratio B / MEA of more than 3.0, at least 3.1 , at least 3.2, at least 3.3, at least 3.4, more than 3.5, at least 3.6, at least 3.7, at least 3.8 or at least 3.9. Moreover, when referring to the boron concentration, what is referred to is boron in its solubilized form which is B(OH)3or anions thereof. The anions include but are not limited to one or more of B(OH)4-, B3O3(OH)4-, B5O6(OH)4-, B4O5(OH)42- or B3O3(OH)52'.

[0024] Accordingly, the present disclosure provides alkaline sodium salts to reduce the concentration of alkanolamines in boron solution and / or to increase the boron concentration while maintaining or even reducing the concentration of alkanolamines. In some embodiments, alkanolamines are defined as 02-05 alkyls terminated by an OH group on one side of the 02-05 alkyl chain and by a NH2 group on the other end of the 02-05 alkyl chain. The 02-05 alkyl chain is optionally substituted with methyl, ethyl, a halogen such as F, Br, or Cl, an amine or a hydroxyl. In one example, the alkanolamine is monoethanolamine (2-aminoethanol). Alkanolamines react as a base with boric acid to make aminium cation, forming themselves aminium salts with polyborate anions to improve the solubility of boron.

[0025] Examples of alkaline sodium salts include but are not limited to sodium tetraborate, sodium pentaborate, sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium acetate. In some embodiments, the alkaline sodium salts contain an oxygen atom. In preferred embodiments, the alkali sodium salt is NaOH, Na2O(B2O3)5, Na2B4O?, hydrates thereof and / or combinations thereof. Na2B4O? is a salt that has the advantage of providing further boron in thecomposition. As demonstrated in the Example section below, it was surprisingly found that sodium salts increase the solubility of boron in the aqueous solution. This was not the case for potassium or ammonium salts. Accordingly, the present compositions contain alkaline sodium salts to increase the concentration of boron and / or to reduce the concentration of alkanolamines in the solution. As explained above, the alkaline sodium salts can replace alkanolamines such as MEA, they allow to maintain the pH in the solution and to generate polyborate anions therefore improving boron solubility. Sodium salts also react as a base with boric acid to produce a sodium (poly)borate salt. The alkaline sodium salts are provided in a concentration of 1 to 150 g / L, from 5 to 100 g / L, from 10 to 100 g / L, or from 10 to 85 g / L.

[0026] Concentrated boron aqueous solutions are useful in agriculture as fertilizers. Nitrogen is an important element for the growth of many crops. Accordingly, in some cases, the aqueous boron solution of the present disclosure contains an addition of a nitrogenated compound to compensate for the reduced alkanolamine content (if the alkanolamine is reduced). Nitrogenated compounds are for example urea. The nitrogenated compound should be inert with regards to the formation of a stable solution according to the present method. The nitrogenated compound is preferably an organic compound that is not a salt (for example only has C, O, N, and H as atoms). Other sources of nitrogenated compounds can also be provided. In the case of agriculture, it is an advantage of urea and other organic aminated compounds that their nitrogen is not free and is released slowly into the soil over a period of time.

[0027] It should be noted that the solubility of boron in aqueous solutions depends on the temperature of the solution. The present aqueous solution contains solubilized boron and is stable at room temperature (i.e. no precipitation of boron in a timespan of more than 3 days). Room temperature can be defined as from 15 to 25 °C. It is even stable in freezing temperature to a minimum of - 20 °C. This is an advantage for outdoors storage of the solution. The solution is therefore a clear solution.

[0028] There is also provided a method of producing a boron aqueous solution. The method is performed at under 80 °C, under 70 °C or under 65 °C to limit evaporation of the solution. To obtain the boron aqueous solution, the alkaline sodium salt, the alkanolamine and boric acid are mixed in water. The amounts of boric acid and alkanolamine are such that the B / MEA ratio in the solution are more than 3.0, at least 3.1 , at least 3.2, at least 3.3, at least 3.4, more than 3.5, at least 3.6, at least 3.7, at least 3.8 or at least 3.9 and such that the obtained solution contains at least 8 wt. % of boron. In some embodiments, the mixing is performed without heating. In otherembodiments, the mixing is performed at a temperature of 40 - 80 °C or 60 - 75 °C. The boric acid can be provided all at once or can be provided in two steps. For example, a first portion of the boric acid and the alkaline sodium salt are first mixed in water until a solution is obtained. Then, the alkanolamine and the second portion of the boric acid dose is mixed is mixed into the solution. Optionally, additional alkanolamine or alkaline sodium salt can be provided after obtaining the solution to further improve the shelf life and stability of the solution. The optional addition of a nitrogenated compound is performed after obtaining the solution.EXAMPLE

[0029] A boron aqueous solution was produced with a concentration of 150 g / L of boron. The goal was to reduce the content of MEA from a B / MEA molar ratio of 3.0 to a 3.9 while maintaining the concentration of boron at 150 g / L. To prepare the solution, based on a total mass of 1 kg, the following was included: 198.3 g of water; 94.2 g of H3BO3 as a first dose; 74.0 g of Na2O(B2O3)s, 5H2O (borax pentahydrate, Neobor™); 160 g of MEA, and 473.4 g of H3BO3 as a second dose.

[0030] First, under a chemical hood, the water was heated to a temperature of between 50 and 60 °C to limit evaporation. The first dose of H3BO3 is added to the heated water and then the Na2O(B2O3)5, 5H2O was added. The resulting mixture was mixed until a solution is obtained. The temperature can be increased to 63 °C if necessary. The MEA is then added to the solution and then the second dose of H3BO3 is added while maintaining the temperature in the range of 45 to 63 °C. The solution was mixed until it became mostly clear.

[0031] More specifically, the temperature of the water is first brought to 50 °C. After the addition of the first dose of H3BO3 and the Na2O(B2O3)5, 5H2O the temperature reaches 59 - 60 °C. MEA is added slowly during 5 mins in which the temperature rises to 73 °C. After the addition of the second dose of H3BO3 the temperature drops to 52 °C. Mixing is then performed during 60 mins at 60 °C to obtain a clear solution.

[0032] A second boron aqueous solution was produced in which the goal was to increase the boron content of a 150 g / L boron solution to 165 g / L boron solution while maintaining the same amount of MEA (20.9 wt. %). To prepare the solution, based on a total mass of 1 kg, the following was included: 90.4 g of water; 41 .2 g of H3BO3 as a first dose; 32.4 g of Na2O(B2C>3)5, 5H2O (borax pentahydrate, Neobor™); 209 g of MEA, and 627 g of H3BO3 as a second dose.

[0033] First, under a chemical hood, the water was heated to 60 °C to limit evaporation. The first dose of H3BO3 was added and then the Na2O(B2O3)s, 5H2O was added while maintaining the temperature at 60 °C. The resulting mixture was mixed until a solution was obtained. The heating was then stopped. MEA was added and then the second dose of H3BO3 was added. Vigorous mixing was performed for 1 h and a clear solution was obtained.

[0034] A boron content of 171 .6 g / L was attempted while maintaining the same concentration of MEA (20.9 wt. %) and excluding Neobor™. In other words, it was attempted to compensate the absence of Neobor™ with additional H3BO3. To prepare the solution, based on a total mass of 1 kg, the following was included: 95.6 g of water, 209 g of MEA and 695.4 g of H3BO3. It was not possible to obtain a solution as precipitation happened despite vigorous mixing resulting in insoluble boron crystals.

[0035] It was evaluated whether the polyol mannitol can improve the solubility of Na2O(B2O3)s, 10H2O. In a beaker, the following was added 173 mL of water, 52.4 g of H3BO3 and 24.7 g of Na2O(B2O3)5, 5H2O. The resulting concentration of Na2O(B2O3)s, 10H2O is 20% (50 g). After a few minutes, the solution was found to be cloudy and have a pH of 6.9. A total of 7.7 g of mannitol was added progressively to the solution to determine whether this addition helps reduce the crystals. The pH was reduced to 6.6 but no change in solubility was observed.

[0036] The possibility of not heating and not including the H3BO3 in two separate doses was evaluated. The following were mixed without any heating: 292.6 g of water, 627.0 g of MEA, 1992.7 g of H3BO3 and 87.7 g of Na2O(B2O3)s, 5H2O. The solution obtained was separated into three different flasks. The first flask was placed in a fridge (temperature of 5 - 10 °C), a second flask was left at room temperature (around 20 °C) and the third flask was placed at 30 °C. The three flasks were left overnight. The viscosity was found to still be acceptable. The solution was successfully prepared and it was therefore determined that heating and a two dose addition of H3BO3 is not necessary.

[0037] A second solution was prepared in the absence of heating but with two doses of H3BO3. Accordingly, the following contents were used: 97.5 g of water, 209.0 g of MEA, 332.1 g for the first dose of H3BO3, 87.7 g of Na2O(B2O3)s, 5H2O and 332.1 g for the second dose of H3BO3. A clear solution was also obtained. In some cases, an addition of 2 g of Na2O(B2Os)5, 5H2O at the end can help reduce the cloudiness of the solution.

[0038] Another solution was produced at 30 °C with the following contents: 160 g MEA, 283.8 g for the first dose of H3BO3, 283.8 g for the second dose of H3BO3, 74 g of Na2O(B2O3)s, 5H2O and 198.3 g of water. The mixture was agitated for 1 h and then was divided to test stability in four different conditions (freezer, fridge, room temperature and 40 °C heat). After 72 h in each condition, the viscosity for the freezer solution was 750 Cp at 9 °C, the viscosity for the fridge condition was 632 CP at 14.1 °C, the viscosity for the ambient condition was 288 Cp at 23 °C and the viscosity for the heat condition was 170 Cp at 31 .3 °C.

[0039] The addition of urea was tested as a means to compensate for the reduction of nitrogen content. Depending on the application for the boron solution, the nitrogen content can be important (for example in agriculture). To 174.2 g of water, 94.2 g of H3BO3 and then 74 g of Na2O(B2O3)s, 5H2O were added and mixed. Then, 160 g of MEA was added and then 473.4 g of H3BO3 was added and mixed until a solution was obtained. To that solution, 24.1 g of urea were added. The resulting composition has a ratio of B / MEA of 3.9 while maintaining the nitrogen content that a traditional B / MEA solution of 3.0 (i.e. both 150 g / L of boron) would have.

[0040] The use of other sodium salts was tested. NaOH was first tested. To prepare the solution, based on a total mass of 1 kg, the following was included: 193 g of water, 160 g of MEA, 633 g of H3BO3 (separated in two doses of 316.5 g) and 14.0 g of NaOH. The initial temperature was 20 °C and about 2 g of water were added during the process to compensate for evaporation. Under a chemical hood, the first dose of H3BO3 and MEA were added which raised the temperature to 40 °C. The NaOH was added which further raised the temperature to 43 °C. The remaining H3BO3 was added and the temperature reached 25 °C. Then vigorous mixing was performed. Additional NaOH can be included to accelerate obtaining a clear solution (for example an addition of up to 6.3 g of NaOH). Ultrasonication can also be performed to clarify the solution by removing air bubbles.

[0041] A second NaOH solution was produced while further increasing the ratio from 3.9 to 4.0. To prepare the solution, based on a total mass of 1 kg, the following was included: 194.2 g of water, 156.4 g of MEA, 633.0 g of H3BO3 (separated in two doses of 316.5 g), and 16.4 g of NaOH. The same protocol as for the above NaOH solution was performed except with an addition of 3.9 g of NaOH at the end.

[0042] Other non-sodium salts were surprisingly found to fail at producing a boron solution. KOH was first tested. To prepare the solution, based on a total mass of 1 kg, the following wasincluded: 185.1 g of water, 156.4 g of MEA, 633 g of H3BO3 (separated in two doses of 316.5 g) and 25.5 g of KOH. The initial temperature was 21 °C and about 2 g of water were added during the process to compensate for evaporation. Under a chemical hood, the first dose of H3BO3 was added which raised the temperature to 41 °C. The KOH was added which further raised the temperature to 47 °C. The remaining H3BO3 was added and the temperature reached 29 °C. Then vigorous mixing was performed. Despite the mixing it was not possible to solubilize the boron and it was not possible to obtain a boron solution as many crystals in suspension remained and the suspension was very cloudy.

[0043] Another non-sodium salt was tested, namely ammonium. To prepare the solution, based on a total mass of 1 kg, the following was included: 225.7 g of water, 156.4 g of MEA, 506.4 g of H3BO3 (separated in two doses of 253.2 g) and 1 11.5 g of ammonium pentaborate. By following the same protocol as for NaOH and KOH it was not possible to obtain a solution using ammonium pentaborate.

[0044] It was attempted again to obtain a KOH solution with heating during the process. To prepare the solution, based on a total mass of 1 kg, the following was included: 142.1 g of water, 160.4 g of MEA, a first dose of 127.87 g of H3BO3, a second dose of 505.1 g of H3BO3 and 64.48 g of KOH. An addition of 5 g of water was performed during the process to compensate for evaporation. The first dose of H3BO3 was added to the water at room temperature of 19 °C. Then, KOH was added to the water which was heated to 66 °C. Mixing was performed, then MEA was added and further heating and mixing was performed at 74 °C. A white precipitate was observed and despite the addition of the second dose of H3BO3 it was not possible to obtain a solution since a milky and viscous suspension was obtained due to precipitation of boron crystals.

[0045] Using heat also failed with ammonium pentaborate. To prepare the solution, based on a total mass of 1 kg, the following was included: 219.6 g of water, 160.4 g of MEA, 524.0 g of H3BO3, and 96 g of ammonium pentaborate. The same protocol as for KOH was attempted (with heating to up to 82 °C) however when the ammonium was added a white suspension was obtained and it was not possible to obtain a solution. In fact, a solid block of precipitates formed at the bottom of the flask.

[0046] It should be noted that although KOH produced suspensions that appeared stable, they were found to lack stability and form precipitates within 2 days of storage.

[0047] On the other hand, the same heating protocol with NaOH worked. To prepare the solution, based on a total mass of 1 kg, the following was included: 194.2 g of water, 156.4 g of MEA, 633 g of H3BO3 (separated in two doses of 316.5 g) and 16.4 g of NaOH. A clear solution was successfully obtained even without heating.

[0048] Two samples were subjected to nuclear magnetic resonance imaging (NMR) (1H and11B) and to infrared (IR) spectroscopy analysis. Sample 1 was a control formulation with a ratio of B / MEA of 3.0 without any sodium salts. Sample 2 is a sample obtained as per paragraph

[0023] and having a B / MEA ratio of 3.9. The samples were labeled sample 1 and sample 2. The NMR calibration was performed at 0 ppm with sodium salt in D2O for1H spectra. The NMR calibration of11B was performed at 19.42 ppm with the H3BO3 peak. The resulting NMR spectra are shown in Figs. 1 A-1 C. The IR spectra are shown in Figs. 2A and 2B. As can be seen from the spectra, in particular Fig. 1 C, sample 2 was shown to contain no boric acid in the final formulation. This is a desirable outcome it is toxic and may limit the ease and applicability of use of the formulation.

Claims

WHAT IS CLAIMED IS:1 . An aqueous boron solution comprising: at least 8 wt. % boron; an alkanolamine; and an alkaline sodium salt; wherein a molar ratio of boron to alkanolamine is of more than 3.0, and wherein the at least 8 wt. % boron are solubilized in the aqueous solution in the form of B(OH)3or anions thereof.

2. The aqueous boron solution of claim 1 , comprising boron in a concentration of at least 10 wt. %.

3. The aqueous boron solution of claim 1 or 2, wherein the ratio is of up to 4.0.

4. The aqueous boron solution of any one of claims 1 to 3, wherein the alkanolamine is a C2-C5 alkyl terminated by an OH group on one side of the C2-C5 alkyl chain and by a NH2group on the other end of the C2-C5 alkyl chain.

5. The aqueous boron solution of claim 4, wherein the C2-C5 alkyl chain is substituted with methyl, ethyl, a halogen, an amine and / or a hydroxyl.

6. The aqueous boron solution of any one of claims 1 to 4, wherein the alkanolamine is monoethanolamine.

7. The aqueous boron solution of any one of claims 1 to 6, wherein the anions are one or more of B(OH)4, B3O3(OH)4-, B5O6(OH)4-, B4O5(OH)42- or B3O3(OH)52-.

8. The aqueous boron solution of any one of claims 1 to 7, wherein the dissolved alkaline sodium salt is dissolved NaOH, or a hydrate of Na2(B2O3)s, Na2B4O7, Na2CO3, NaHCO3, CHsCOONa.

9. The aqueous boron solution of any one of claims 1 to 8, wherein the dissolved alkaline sodium salt is dissolved NaOH, or Na2(B2O3)2, Na2B4O? or hydrates thereof.

10. The aqueous boron solution of any one of claims 1 to 9, wherein the boron concentration is at least 100 g / L.11 . The aqueous boron solution of any one of claims 1 to 10, wherein the alkanolamine is present in a concentration of from 1 to 150 g / L.

12. A method of producing an aqueous boron solution, the method comprising mixing boric acid, alkanolamine, and alkaline sodium salt in water, wherein a molar ratio of boron to alkanolamine is of more than 3.0, and wherein the aqueous boron solution comprises at least 8 wt. % boron that is solubilized in the form of B(OH)3or anions thereof.

13. The method of claim 12, wherein the method comprises first mixing a portion of the boric acid and the alkaline sodium salt in the water, and then mixing the remaining boric acid and alkanolamine.

14. The method of claim 12 or 13, wherein the mixing is performed at a temperature under 80 °C.

15. The method of any one of claims 12 to 14, further comprising adding a nitrogenated compound in the aqueous boron solution.

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