WO2024201367A1

WO2024201367A1 - Process for sulfoalkylation of k-humates

Info

Publication number: WO2024201367A1
Application number: PCT/IB2024/053025
Authority: WO
Inventors: George KLEINHANS; Barend Frederik STANDER; Johannes Jacobus Huyser
Original assignee: Omnia Group Pty Ltd
Current assignee: Omnia Group Pty Ltd
Priority date: 2023-03-30
Filing date: 2024-03-28
Publication date: 2024-10-03
Anticipated expiration: 2025-09-30

Abstract

The invention relates to a process for the preparation of a potassium humate ("K- humate") that is stable at pH of from at least 0.5, optionally including in the presence of divalent and trivalent cations, without aggregation occurring, comprising an initial step of synthesis of a formaldehyde-sodium/potassium bisulphite adduct, prepared via the addition of formaldehyde to a solution of sodium/potassium sulphite, followed by subsequent addition of the formaldehyde-sodium bisulphite adduct to an aqueous solution of K-humate and reacting the mixture at elevated temperatures to obtain the stable K-humate. The invention further relates to methods for stimulating plant growth with the use of the stable K-humate produced by the process of the invention.

Description

PROCESS FOR SULFOALKYLATION OF K-HUMATES

FIELD OF THE INVENTION

The current invention relates to a process for the preparation of a potassium humate (“K-humate”) that is stable at pH of from at least 0.5, optionally including in the presence of divalent and trivalent cations, without aggregation occurring, comprising an initial step of synthesis of a formaldehyde-sodium/potassium bisulphite adduct, prepared via the addition of formaldehyde to a solution of sodium/potassium sulphite, followed by subsequent addition of the formaldehyde-sodium bisulphite adduct to an aqueous solution of K-humate and reacting the mixture at elevated temperatures to obtain the stable K-humate. The invention further relates to methods for stimulating plant growth with the use of the stable K-humate produced by the process of the invention.

BACKGROUND OF THE INVENTION

The ever-increasing population, global warming and availability of arable land, burdens the agricultural sector to produce more food, which fosters a decrease in soil fertility. In addition, unsustainable farming practices further decreases soil fertility and also results to soil degradation. In order to keep up with the high food demand, whilst at the same time overcoming the above-mentioned disadvantages and appropriately managing arable lands, fertilizers fulfilling multiple roles must be developed. Organic products, such as biostimulants, have already been documented as attractive alternatives to the classically used fertilizers, fulfilling multiple roles. It has been reported that these biostimulants promote plant growth, increases plant resistance towards biotic and abiotic stress, improves fruit quality, etc. Additionally, biostimulants improves plant nutrient use efficiency, which decreases the required amount of nutrients that must be applied to crops. This decrease in the amount of classical fertilizers used, results to a decrease in soil degradation and pollution, whilst increasing crop yield, ultimately leading to sustainable farming practices.

A biostimulant that is well-known, especially for its controlled nutrient release properties, is humic substances. Humic substances are macromolecular organic compounds generally comprised of various aromatic motifs such as quinones and catechols, that are decorated with alcohol and carboxylate functional groups. Additionally, humates contain various aliphatic functionalities such as acyclic sugars, and even amino acid-like structures forming part of the humate complex. These humic substances result from the chemical and/or biological degradation of plant and animal matter, and constitutes an extensive portion of the pool of organic carbon in the soil. It is generally accepted that humic substances regulate vital environmental and ecological processes such as; supporting the growth of plants and microorganisms, stabilizing the soil structure, modulating both soil carbon and nitrogen, all the while ensuring efficient transport of various cationic elements to the plants when required (Canellas, et al. , 2015; Jardin, 2015). This ultimately results to increased plant health and plant growth, and an increase in crop yield. Humic acid is extracted from the appropriate raw material under alkaline conditions. This allows for the solubilisation of humic substances, usually as sodium or potassium humate, due to the use of sodium or potassium hydroxide as base for extraction. Furthermore, insoluble components such as humin, can be separated from the liquid potassium humate, yielding a higher purity humate fraction that is made commercially available. The solubilisation is a result of the deprotonation of the acidic humate hydrogens, yielding an organic salt that is much more soluble in water compared to the neutral organic humate fraction. The liquid humate is much easier to handle, and can be applied to various crops using different methods of application, such as foliar spray, drip irrigation, etc. The easy to handle K-humates can be readily applied to the plants, whilst fulfilling its various functions as a humic substance, as was mentioned above.

However, K-humates precipitate under acidic conditions. This is a result of the protonation of the anionic oxygen functional groups, yielding a neutral organic compound that is insoluble in water. To circumvent this, the K-humates can be chemically modified, to yield humates that are acid compatible. A common method to increase the solubility of organic compounds towards acidic solutions, is through substitution of the organic fragment with sulfonic functional groups. This can be achieved through reacting an organic compound with a sulphur containing reagent, such as SO₂, SO₃, H₂SO₄, SO3 H2SO4, HSO3CI, H3NSO3, NaHSO₃, Na₂SO₃, Na₂S₂O₅, etc. The process of synthesizing an organic compound containing a sulfonic functional group, is commonly referred to as a sulfonation or sulfation reaction. These two industrial processes are used to prepare a range of products, including dyes, pigments, medicinal compounds, pesticides, surfactants, etc. (Foster, 1997; Ortega, 2012). Sulfonation and/or sulfation processes can also be used to prepare sulfonic acid substituted humate products, which have improved solubility in acidic solutions, compared to the humate acid or K-humates.

Various reports describe the sulfonation of humic acids, employing a sulphur containing reagent such as SO₂, SO₃, H₂SO₄, etc. However sulfonation of humic substances with concentrated H₂SO₄ yielded a targeted sulfonated humate product that had low solubility in acidic solutions, and was therefore incompatible with low pH fertilizers (Zhamba, 1991 ). U.S. Patent No. 3700728 describes the extraction of humates from the appropriate raw material using an alkali reagent, followed by treatment of the corresponding solubilized humates with sulphite, bisulphite or sulphur dioxide, under basic conditions. The reaction mixture was then heated to the desired temperature for several minutes to several hours, depending on the reaction temperature. However, as with the use of concentrated H₂SO₄ above, the isolated sulfonic acid containing humate product was reported to be insoluble in low pH solutions, a result of insufficient sulfonation of the starting humates.

A slightly different approach towards acid soluble humates involves sulfoalkylation of humates, instead of sulfonation, as described by U.S. Patent No. 3352902 which discloses sulfoalkylation of humate bearing ores, which yielded the corresponding humates substituted with alkyl-sulfonic functional groups, rendering the humates acid compatible. This method entailed the addition of a sodium hydroxymethanesulfonate solution to sodium humates, obtained by treatment of humic acid with an aqueous sodium hydroxide solution. The final product was obtained after refluxing the reaction mixture for one hour. It was further reported that the humate products were soluble in an acidic solution with a pH of between 2- 3. However, the compatibility of the prepared humates in acidic solutions with a pH lower than 2, or in low pH fertilizer formulations where there are divalent and trivalent cations present, was not reported.

Following a different procedure towards acid compatible humates, EP patent application no. 0786490A2 also disclosed the sulfoalkylation of humates with sodium hydroxymethanesulfonate (in this case, prepared in one-pot reaction), but at higher temperature and pressure than the reflux temperature. This method entailed the addition of formaldehyde and sodium meta-bisulphite to the humate containing ore (in this example, the ore was Leonardite). This was followed by increasing the pH of the mixture to between 9 to 12 with sodium hydroxide. Finally, the reaction temperature was increased to 160 °C in a high-pressure reactor, and the mixture was allowed to react for 90 minutes, yielding the targeted compound after filtration. It was determined that the sulfoalkylated humates were soluble in acidic solution with a pH as low as 0.5, likely due to the higher reaction temperature, that resulted to increased sulfoalkylation of the humate reagent. However, the method has a high capital cost together with high operational risk due to the high temperature and pressure reaction required. Furthermore, there is no evidence that such acid soluble humates are also stable without aggregation when used with pH fertilizer formulations where there are divalent and trivalent cations present.

There is therefore a need for an improved, simplified and/or more cost effective procedure for preparation of acid compatible humates from potassium humates that are insoluble in low pH solutions for use in fertilizer compositions. Furthermore, it would be an added advantage if such acid compatible humates were also stable in the presence of divalent and trivalent cations without aggregation occurring.

SUMMARY OF THE INVENTION According to a first aspect of the invention, there is provided a method for sulfoalkylation of a humate, particularly potassium humate (K-humate), comprising: a) an initial step of preparation of a formaldehyde-sodium/potassium bisulphite adduct; b) subsequently adding the formaldehyde-sodium/potassium bisulphite adduct to the humate, particularly K-humate, followed by heating from between about 96 °C to reflux temperature or about 98 °C, at atmospheric pressure to form a sulfoalkylated humate; and c) optionally cooling the sulfoalkylated humate to ambient temperature including about 25 °C, wherein the initial preparation step a) comprises or consists of: i. adding from about 25 to about 35 wt. %, or from about 28 to about 34 wt. %, water of the total amount of formaldehyde-sodium/potassium bisulphite adduct to a reaction vessel and stirring the water in the reaction vessel with an agitator; ii. adding from about 20 to about 35 wt. %, or from about 22 to about 34 wt. % of the total amount of formaldehyde-sodium/potassium bisulphite adduct, sodium meta-bisulphite (SMBS) to the water and stirring to yield an aqueous solution comprising sodium sulphite and SO2; iii. adding from about 20 to about 30 wt. %, or about 21 to about 26 wt. %, potassium hydroxide (KOH) or sodium hydroxide (NaOH) of the total amount of formaldehyde-sodium/potassium bisulphite adduct, preferably in a liquid solution of (50 wt. % in H₂O) to the aqueous solution with stirring to yield a sodium and potassium sulphite solution; and iv. adding from about 15 to about 20 wt. %, or about 16 to about 19 wt. % of the total amount of formaldehyde-sodium/potassium bisulphite adduct, formaldehyde to the sodium and potassium sulphite solution with stirring to yield the formaldehyde-sodium/potassium bisulphite adduct.

In a particular embodiment, the amount of water added in step i. above is about 33.4 wt. %; the amount of SMBS added in step ii. above is about 22.0 wt. %; the amount of liquid KOH (50 wt. % in H₂O) added in step iii. above is about 21 .4 wt. %; and the total amount of formaldehyde added in step iv. above is about 18.7 wt. % of the total amount of formaldehyde-sodium/potassium bisulphite adduct. Optionally, the formaldehyde may be added as a solution of 37 wt. % formaldehyde in H₂O.

The initial step a) of preparation of the formaldehyde-sodium/potassium bisulphite adduct may be performed immediately subsequent to the step b) of adding the formaldehyde-sodium/potassium bisulphite adduct to the humate, including K- humate in the method. Alternatively, the initial step a) may be performed and the formaldehyde-sodium/potassium bisulphite adduct may be stored at about 0 °C for later use in step b) of the method, if desired.

The humate may be liquid humate, in particular liquid K-humate, including at a concentration of up to about 30%, or up to about 26 wt. % in H₂O. The humate may be initially heated to a temperature of between about 65 to about 80 °C, more preferably between about 70 to about 78 °C, even more preferably between about 70 to about 75 °C prior to adding the formaldehyde-sodium/potassium bisulphite adduct in step b).

Where the heating in step b) above is between about 96 °C to the reflux temperature or about 98 °C at an atmospheric pressure, typically at a residence time upon reaching said temperature of between about 2 hours and about 6 hours, or between about 3 hours and about 6 hours, or between about 4 hours and about 6 hours preferably about 5 hours, the total quantity of humate, in particular K-humate, added to the formaldehyde-sodium/potassium bisulphite adduct in step b) may be between about 50 to about 60 wt. %, or about 52 to about 58 wt. %, preferably about 55 wt. % and the total quantity of mixed formaldehyde-sodium/potassium bisulphite adduct formed by steps i. to iv. above may be between about 40 to about 50 wt. %, or from about 42 to about 48 wt. %, preferably about 45 wt. % of the total amount of mixed K-humate and formaldehyde-sodium/potassium bisulphite adduct.

It should be noted that the residence time may be longer than that set out above, and would be selected by a person skilled in the art taking into consideration technoeconomic factors balancing the cost of the residence time at high temperature with the quantity of sulfoalkylated humate generated by the process.

In one embodiment of the invention, the humate, in particular K-humate and in particular liquid humate, further particularly, liquid K-humate, may be initially heated prior to adding the formaldehyde-sodium/potassium bisulphite adduct to a temperature of between about 70 to about 78 °C, more preferably at about 75 °C.

The sulfoalkylated humate produced by the method of the invention may be stored or packaged for inclusion in a fertilizer or plant biostimulant solution having a pH of from at least 0.50, 0.70, 0.75, 0.80, 8.50, 9.00, 9.50, 1.00, 1.50, or 2.00 or above, optionally including where the fertilizer or plant biostimulant solution comprises divalent and trivalent cations.

In one embodiment of the invention, the ratio of dry formaldehyde-sodium/potassium bisulphite adduct to K-humate reacted at reflux temperature or about 98 °C and atmospheric pressure may be at least 0.4 for compatibility of the sulfoalkylated humate product with the fertilizer or plant biostimulant solution, including fertilizer formulations 11 :7:4(22), 6:2:1 or 7:3:0.

Alternatively, in another embodiment of the invention, the ratio of dry formaldehyde- sodium/potassium bisulphite adduct to K-humate reacted at reflux temperature or about 98 °C and atmospheric pressure may be at least 1 .32 for compatibility of the sulfoalkylated humate product with the fertilizer or plant biostimulant solution, including where such fertilizer or plant biostimulant solution also contains divalent and trivalent cations.

The sulfoalkylated humate products may be diluted to between 3 wt. % to 15 wt. %, or between about 3 wt. % to 10 wt. % or between about 3 wt. % to 6 wt. % prior to formulation with a pH fertilizer and/or plant biostimulant solution either with or without divalent and trivalent cations, including fertilizer formulations 11 :7:4(22), 6:2:1 or 7:3:0. According to a second aspect of the invention, there is provided a fertilizer or plant biostimulant solution having a pH of at least 0.50, 0.70, 0.75, 0.80, 8.50, 9.00, 9.50, 1.00, 1.50, or 2.00 or above, optionally including where the fertilizer or plant biostimulant solution comprises divalent and trivalent cations, formulated to comprise a sulfoalkylated humate, in particular K-humate, produced according to the method of the invention.

According to a third aspect of the invention, there is provided a method of feeding a plant or stimulating plant growth with the use of a fertilizer and/or plant biostimulant solution comprising the sulfoalkylated humate, in particular K-humate, produced according to the method of the invention.

DETAILED DESCRIPTION OF DRAWINGS

FIGURE 1 : shows the compatibility of the sulfoalkylated humates produced by the methods of the invention in various low pH fertilizers;

FIGURE 2: shows the compatibility of various humate derivatives in low pH fertilizer 11 :7:4(22); and

FIGURE 3: shows refluxed sulfoalkylated humate compatibility in different low pH fertilizer formulations, 11 :7:4(22), 6:2:1 and 7:3:0.

DETAILED DESCRIPTION OF THE INVENTION

The following description of the invention is provided as an enabling teaching of the invention, is illustrative of the principles of the invention and is not intended to limit the scope of the invention. It will be understood that changes can be made to the embodiment/s depicted and described, while still attaining beneficial results of the present invention. Furthermore, it will be understood that some benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances, and are a part of the present invention. The applicant has developed a novel method for the preparation of an acid compatible humate, stable in the presence of divalent and trivalent cations, without aggregation occurring. The acid compatible humate of the invention can therefore be used in a low pH environment of pH 0.5 or less, and furthermore can be added to a low pH fertilizer where there are divalent and trivalent cations, without aggregation occurring.

The novel method involves the initial synthesis of a formaldehyde-sodium/potassium bisulphite adduct, before adding this to K-humate. The applicant has determined that there are advantages to the abovementioned step-wise process developed, compared with the processes described in EP 0786490A2 and U.S. Patent No. 3352902. Firstly, the step-wise approach was found by the applicant to lead to a ‘cleaner’ reaction, as compared to the one-pot process described by EP 0786490A2. The step-wise approach was also found to decrease the possibility for side reactions to take place, as compared to the one-pot synthetic methodology. The sidereactions include the commonly encountered formaldehyde oligomerization reaction, occurring at room or elevated temperatures, yielding the paraformaldehyde polymer that is typically less reactive during the sulfoalkylation reaction. Similarly, excess base would lead to a Cannizzaro type reaction, in which the base would catalyse the formation of formic acid and methanol from formaldehyde (Martin, 1954). The unwanted Cannizzaro and formaldehyde oligomerization side reactions, would result in a decrease in the concentration of formaldehyde that can react with the sulphur containing reagent, to yield the targeted formaldehyde- sodium/potassium bisulphite adduct.

In addition, the release of SO₂, a common occurrence when dissolving sulphites in water, was found to be managed more effectively when preparing the adduct in this step-wise manner. Furthermore, the use of the initially synthesised formaldehyde- sodium/potassium bisulphite adduct in the sulfoalkylation of a K-humate solution by addition of the adduct to a K-humate solution, followed by reacting the mixture at a elevated temperatures for a given period, was found by the applicant to yield the desired sulfoalkyl-containing K-humate product that is not only acid soluble down to a lower limit of pH 0.8, but is also stable in low pH fertilizer formulations where there are divalent and trivalent cations present.

Initially, different sets of reaction conditions were investigated by the applicant for comparison. The first method entailed the preparation of the sulfoalkylated humate product at a high temperature and pressure of 150 °C and 4 bar (G) pressure, with a residence time of one hour. The reaction was carried out in a pressure vessel rated to safely operate under the above-mentioned reaction conditions. The product obtained was found to be compatible in various liquid fertilizers at low pH, when diluted with water to a specified dilution (Figure 1 ). However, the above-mentioned procedure is not technoeconomically feasible due to the high capital cost together with high operational risk, similar to the method of EP 0786490A2, and was not considered further.

The second method investigated, utilised reflux reaction conditions, typically at 98 - 100 °C and under atmospheric pressure, to prepare the sulfoalkylated humate product. Increased residence time of five hours compare to one hour in the abovementioned reaction, was required for this reaction, but due to the lower temperature and pressure conditions, was still found to be a technoeconomically feasible possibility. A third set of processing conditions involved decreasing the reaction temperature. Specifically, the reaction temperature was decreased to below the reflux point, typically at a temperature of between 96 - 98 °C.

The second and third methods reduced the capital costs and operational risks significantly to the point where these were technoeconomically viable. The applicant has also developed a quick and easy, yet quantitative method to determine the amount of sulfoalkylated humates remaining in a specified low pH nutrient solution. The method developed can be used for quality control purposes, as well as determining the compatibility of the humate product in a given nutrient solution. The method was used to determine the sulfoalkylated humate compatibility in nitric, phosphoric and sulphuric acid solutions at pH values ranging from 0.9 to as low as 0.5. Consequently, a pH of 0.8 was selected as the lower pH limit in the experiments performed. It was found that the compatibility of the sulfoalkylated humates produced in the second and third methods developed by the applicant, in solutions containing different macro- and/or micronutrients, indicated that the sulfoalkylated humates were readily soluble in different nutrient solutions, resulting to little or no precipitation/agglomeration at selected concentrations. Furthermore, it was determined that the sulfoalkylated humate product prepared under reflux conditions and atmospheric pressure, as well as below the reflux point, was compatible in liquid fertilizers 11 :7:4(22), 6:2:1 and in 7:3:0 (Figure 1 ), after diluting the prepared humate analogue with water to a specified concentration.

EXAMPLE 1

The sulfoalkylation reaction conditions in Example 1 were adapted from the method provided in EP 0786490A2.

The following experimental procedure was followed:

1 . Weigh off a specified amount of formaldehyde (37 wt. % in H₂O) solution, as well as sodium meta-bisulphite (SMBS) as set out in the batch card in Table 1.

2. Place the formaldehyde solution on a magnetic stirrer and added a magnet. Switch the unit on.

3. Slowly add SMBS to the formaldehyde solution.

4. Weigh off the specified amount of potassium hydroxide (KOH) (50 wt. % in H₂O) and add slowly to the formaldehyde and SMBS mixture to form the formaldehyde-sodium/potassium bisulphite adduct.

5. Weigh off the specified amount of liquid K-Humate (26 wt. % in H₂O) and add to the pressure reactor.

6. Initiate heating of the K-humate mixture to a temperature of 70 °C.

7. Add the formaldehyde-sodium/potassium bisulphite adduct (prepared in step 4) to the K-humate mixture in the pressure reactor, once the K-humate temperature reached 70 °C.

8. Close the valve and increase the temperature set point of the oil bath to the specified temperature for the experiment. 9. The residence time starts as soon as the local temperature gauge indicates that the set point was reached.

10. After the specified residence time is completed, the heat source is switched off.

11 . Once ambient temperature is reached, the vent valve is slowly opened to decrease the pressure inside the reactor.

12. Once ambient conditions inside the reactor is reached, the drain valve is slowly opened and the sulfoalkylated humate product emptied into a container for testing.

Results and Discussion

The experiments conducted included variations in residence time as well as temperature. The following variations were investigated at 4 bar (G) pressure:

• Temperature range: 125 °C, 135 °C and 150 °C

• Residence time: 1 hour, 2 hours and 3 hours.

Table 1 : Batch card for high temperature reaction

Raw Materials Unit Value

Formaldehyde (37 wt. % in H₂O) wt. % 11.6 (4.3% F in 7.3% H₂O)

Sodium meta-bisulphite wt. % 8.6

KOH (50 wt. % in H₂O) wt. % 5.5

K-Humate (26 wt. % humate in H₂O) wt. % 74.3

Total wt. % 100

All reaction products were evaluated by adding the synthesized product to a liquid fertilizer with a low pH of between about 0.5 to about 2. Evaluation of product compatibility in the liquid fertilizer was based on a visual test of the precipitate, or lack thereof, that formed. Table 2 provides a summary of the visual test results, of the compatibility of the different products prepared, including a pure K-humate sample as well as a commercially available product (CAP), in the low pH fertilizer.

Table 2: Experimental results obtained from high pressure reactor Material Temperature (°C) Residence time Precipitation

(h)

Liquid K-Humate* N/A N/A Complete precipitation

Reaction 1 125 1, 2, 3 Precipitate

Reaction 2 135 1, 2, 3 Precipitate

Reaction s 150 1, 2, 3 Precipitate

Commercial product* N/A N/A No precipitate

★Liquid K-Humate and commercially available product were selected as the reference samples

The visual tests indicated that the low pH fertilizer compatibility of the prepared sulfoalkylated humate products were not comparable to a commercially available product. However, with regards to the compatibility of humic substances in a fertilizer formulation, a significant improvement of the sulfoalkylated humates compared against a pure K-humate reference was noted. Furthermore, less precipitate was visually detected for the sulfoalkylated humate product prepared at 150 °C, as compared to the product prepared at 125 °C.

The results obtained in this initial experiment indicated that the low pH fertilizer compatibility of K-humates can be improved via the sulfoalkylation of humates in a pressure reactor. The qualitative evaluation of the data obtained indicated that an increased residence time does not have a significant influence on the outcome of the reaction. Instead, an increase in temperature significantly increased the fertilizer compatibility of the sulfoalkylated humates, as there were less precipitate formed when testing the product obtained from the reaction at 150 °C, as compared to the product synthesized at 125 °C. However, the commercially available acid compatible humate product did not precipitate when added to the low pH fertilizer. Furthermore, at temperatures of 150 °C, the pressure in the system can reach 4 bar (g) due to the amount of water in the reactor that forms steam. This significantly increases the operational risk, in addition to the cost of the reaction. To decrease the operational risk and the production cost, reflux reaction conditions were selected as the next set of processing conditions to evaluate. However, the formaldehyde- sodium/potassium bisulphite adduct synthesis first had to be optimized. EXAMPLE 2

The applicant developed a two-step metod of preparation of the formaldehyde- sodium/potassium bisulphite adduct. The first step (1 ) is the preparation of an intermediate bisulphite anion, that is subsequently reacted with a formaldehyde in the second step of the process (2).

The step-wise synthesis of the formaldehyde-sodium/potassium bisulphite adduct was based on the following procedure:

1 . In separate beakers weigh off the specified amount of water and SMBS.

2. Place a magnetic stirring bar in the beaker containing the water, and initiate stirring on a stirring plate.

3. Add the SMBS to the water. Stir mixture for 40 minutes.

4. Weigh off and add the specified amount of KOH (50 wt. % in H₂O) to the SMBS aqueous solution to yield a sulphite solution.

5. Stir the mixture for 10 minutes.

6. Weigh off the specified amount of formaldehyde and add to the sulphite solution of step 4.

8. Stir the mixture for 20 minutes.

Table 3 below indicates the batch card used during the adduct preparation. The preprepared adduct was found to be stable for several weeks at 0 °C with no precipitation occurring. Resultantly, a large amount of adduct can be prepared in one batch, and several sulfoalkylation reactions can be completed from the one preprepared adduct batch.

Reagent Unit Value wt. %

%H₂O (for dissolving SMBS) g 196.0 33.4

Sodium meta-bisulphite (SMBS) g 129.0 22.0

KOH (50 wt. % in H₂O) g 152.0 25.9

Formaldehyde (37 wt. % in H₂O) g 110.0 18.7

Total batch size g 587.0 100

The pH of the reaction mixture during the various stages of the reaction was also monitored. The pH of the aqueous sodium meta-bisulphite solution was determined to be 4.30. This is slightly acidic, which could result to decomposition of the sodium bisulphite yielding SO₂. However, after the addition of KOH, the pH of the reaction mixture increased to 7.7. At that neutral pH, the probability of SO₂ formation was significantly reduced. The addition of formaldehyde resulted to a further increase of the pH of the reaction mixture. The pH of the solution after formaldehyde addition was determined to be 11.5. The sharp increase of the pH of the reaction mixture after formaldehyde addition, suggested that the sulphite derivative with which the formaldehyde reacts, was the sulphite anion (see equation b, (2) above). The release of hydroxide ions would significantly increase the pH of the reaction mixture, as was noted during the reaction.

EXAMPLE 3

Sulfoalkylated Humates Prepared Under Reflux Conditions

The applicant developed an alternative variation towards acid compatible humic substances. The procedure is milder, when compared against the method of Example 1 . Accordingly, the preparation of the sulfoalkylated humates, using the pre-prepared adduct of Example 2 above under reflux reaction conditions was investigated.

The following experimental procedure was used: 1 . Weigh off specified amount of K-humate.

2. Add the K-humate to a 2L round bottom flask, equipped with a condenser

3. Heat up the K-humate solution until the temperature is at 75 °C.

4. Weigh off specified amount of the formaldehyde-sodium/potassium bisulphite adduct solution in a separate beaker.

5. Add the formaldehyde-sodium/potassium bisulphite adduct solution to the K-humate.

6. The temperature of the reaction mixture is increased until the reaction mixture starts to reflux.

7. The residence time starts as soon as the reaction mixture starts to reflux.

8. After the residence time is completed, the heat source is turned off and the reaction mixture allowed to reach ambient conditions.

Acid Compatibility Test

A qualitative method was used to evaluate the acid compatibility of the product, and therefore the efficiency of the method employed to prepare the sulfoalkylated humates. The method used was based on the following procedure:

1. Prepare an equimolar acid solution containing nitric acid and phosphoric acid with pH values ranging between 0.4 and 1 .5.

2. Weigh off pre-determined amount of acid solution.

3. Add sulfoalkylated humates, in a ratio of 27.5:1 (acid solution:sulfoalkylated humates), to the acid solution.

4. Visually scrutinize the formation of precipitate. Product fails the test if humate agglomeration occurs.

The acid compatibility test is simple and quick, and allows for evaluation of the method used to prepare the adduct. It is important to note that the method used was only a qualitative method, and not a quantitative one, which resulted to different outcomes. Furthermore, the final concentration of sulfoalkylated humates in solution was roughly 1 %. Finally, the qualitative method allowed for scrutinizing the product’s acid compatibility. It did not account for the compatibility of the sulfoalkylated humate product in a fertilizer formulation, and more specifically, the stability of the product towards aggregation in the presence of divalent and trivalent cations.

Ratio of Formaldehyde-sodium/potassium Bisulphite Adduct to K-Humate

The ratio of adduct to liquid K-Humate was also investigated, during the optimization of the batch card used towards the preparation of the sulfoalkylated humates. During these experiments, the residence time was kept constant at four hours, refluxing the reaction mixture at atmospheric pressure. The screening method used to evaluate the efficiency of the reaction and therefore the extent of sulfoalkylation of the humates, was the qualitative acid compatibility test described above. Table 4 below provides the batch cards used for the variations of formaldehyde-sodium/potassium bisulphite adduct: K-Humate ratio.

Table 5: Variation of adduct: K-Humate ratio under reflux conditions

The temperature remained constant for the duration of the 4 hours for the reaction where the adduct: K-Humate ratio was 0.53. The advantage to the round bottom flask heater used as the heat source, is that it has a high heat flux per area and as such, there is ample energy for the process. Based on the qualitative acid compatibility test, the lowest pH limit for different adduct: K-humate ratios which did not precipitate indicates that, at an adduct to K-humate ratio of 0.4 and higher, the sulfoalkylated humates prepared under reflux reaction conditions were compatible in the acidic solution, based on the visual inspection of the solution. However, increasing the ratio of adduct to K-humates, above the ratio of 0.4, did not result in an improvement of the acid compatibility of the sulfoalkylated humate product. The cut-off pH at which the humate derivatives remained in solution and did not agglomerate, was therefore 0.4. The results were very promising, and allowed for the preparation of sulfoalkylated humates at reduced pressure and temperatures compared with the procedure of Example 1 , but that are still compatible in acidic solutions. However, the low pH solutions used to complete the compatibility studies did not contain divalent and trivalent cations.

The next step involved testing the sulfoalkylated humates produed according to the method of Example 3, for compatibility in pH fertilizer formulations having a pH of from at least 0.5. The same amounts of product and ratios were used as in the test described above. The only difference was the replacement of the acidic solution with a low pH fertilizer formulation containing various salts, and more specifically, divalent and trivalent cationic salts. In all cases, with the use of the undiluted sulfoalkylated humates prepared at various adduct: K-humate ratios, immediate precipitation of the sulfoalkylated humate products was observed. However, upon diluting the sulfoalkylated humate products to specified dilutions, the products were indeed found to be compatible with low pH fertilizers, including fertilizer formulations 11 :7:4(22), 6:2:1 and 7:3:0. It was further determined that the sulfoalkylated humate products prepared at higher adduct: K-humate ratios performed better in the low pH fertilizer formulations. This could be a result of increased sulfoalkylation of the humic substances. The dry adduct: K-humate ratio of 1.32 was selected as the most optimal ratio towards the synthesis of the targeted sulfoalkylated humate product, under reflux reaction conditions.

The next parameter that was investigated, and subsequently optimized, was the residence time of the reaction under reflux conditions.

Residence Time Optimization

It was previously determined in Example 1 that an increased residence time does not result in a significant increase in the reaction efficiency and the compatibility of the sulfoalkylated humate products in various low pH solutions were found to be similar at different residence times. However, the high reaction temperature used in Example 1 significantly increased the rate of the reaction, decreasing the time required for the reaction to occur. Contrary to this, a lower reaction temperature associated with reflux reaction conditions, might require an increased residence time for efficient sulfoalkylation of K-humates. As such, the residence time was optimized, based on the reflux reaction conditions and the optimised dry adduct: K- humate ratio above. The residence time variations were as follows:

• Residence time: 0.5 hours ,1 hour, 2 hours, 3 hours, 4 hours, 5 hours, & 24 hours

Optimum Residence Time for Reflux Reaction

Residence time variations were completed and the products thereof evaluated based on the qualitative quick acid compatibility test described above. The visual test indicated that a residence time of at least two hours is required to ensure sufficient sulfoalkylation of K-humates, rendering the targeted product acid compatible. The results are provided in Table 6 below.

Table 6: Evaluation of sulfoalkylated humate compatibility in a low pH solution

Residence time (h) Precipitation³

0.5 Precipitate

1 Precipitate

2 No precipitate

3 No precipitate

4 No precipitate

5 No precipitate

24 No precipitate ^aSulfoalkylated humate product was evaluated as isolated after the reaction (i.e. not diluted)

It should be reiterated that, the quick acid compatibility test does not take into account the compatibility of the sulfoalkylated humates in a low pH fertilizer formulation, containing divalent and trivalent cations, in addition to being only a qualitative method for analysis. Nonetheless, it was confirmed that an increase in residence time is required, to allow for sufficient sulfoalkylation of the K-humates, especially when compared against the product prepared in a high-pressure reactor of Example 1 . As such, the optimal residence time was determined to be from about 2 to about five hours, most optimally about 5 hours. A residence time of five hours is adequate to allow for efficient sulfoalkylation of the K-humates, in addition to being short enough for the batch to be completed in one shift. EXAMPLE 4

Sulfoalkylated Humate- Synthesized below the Reflux Point

The third set of processing conditions that were considered was a reduction in the temperature of the reaction below the reflux temperature of Example 3. Specifically, the temperature of the reaction was set to a temperature of either 85 °C or 96 to 98 °C. A significant amount of energy is required to evaporate the solvent (in this case water) at reflux conditions, which results to a higher cost of production, and therefore a reduction in the technoeconomic feasibility of the process. Below the reflux point, the amount of energy required for the reaction is substantially reduced, decreasing the cost of production.

The experimental procedure used to prepare the sulfoalkylated humate product is described below. The previously optimized parameters from Example 3, such as the residence time and the adduct: K-humate ratio, was kept constant during the temperature optimization experiments. Accordingly, a residence time of 5 hours and a dry adduct: K-humate ratio of 1.32 was used during the temperature variation experiments. The subsequent procedure was followed during the temperature variation experiments:

1 . Weigh off specified amount of K-humate.

2. Add the K-humate to a 1 L round bottom flask, equipped with a magnetic stirring bar and a condenser.

3. Heat up the K-humate solution until the temperature is at 75 °C.

4. Weigh off specified amount of the pre-prepared formaldehyde- sodium/potassium bisulphite adduct in a separate beaker.

6. Increase the temperature of the reaction mixture to the specified temperature.

7. The residence time starts as soon as the reaction mixture reaches the temperature set point. 8. After the residence time is completed, the heat source is turned off and the reaction mixture is allowed to reach ambient conditions.

The following table, Table 7, indicates the amount of reagents used during the temperature optimisation reactions.

Table 7: Batch card used for sulfoalkylation reactions below boiling point

Reagent Unit Value

Adduct solution g 293.5

K-Humate g 358.0

Total batch size g 651.5

As could be expected, the energy requirements at the lower temperatures decreased, as compared to the requirements for reflux reaction conditions of Example 3. The qualitative quick acid compatibility test indicated that the sulfoalkylated humate product prepared at 96 - 98 °C, was compatible in the acidic solution, as no agglomerates were visually detected. In addition, the sulfoalkylated humate product prepared at 96 °C, was determined to be compatible in low pH fertilizer formulations at specified concentrations. With regards to the sulfoalkylated humate product prepared at 85 °C, it was determined that the temperature of the reaction was too low. The product isolated, after five hours at 85 °C, agglomerated in the acidic solution during the quick acid compatibility test. Acid compatibility could be achieved, only when increasing the residence time to 24 hours. The decreased reaction temperature of 85 °C does not compensate for the increased residence time with regards to the cost of production, therefore this low temperature is no technoeconomically feasible. As such, preparation of the product at 85 °C was not considered during the rest of the study.

Quantification of Sulfoalkylated Humate Compatibility

The compatibility of the prepared sulfoalkylated humate products in various low pH solutions, had been evaluated with the quick acid compatibility test which does not allow for the quantitative evaluation of the prepared products in low pH formulations. For this reason, the applicant developed a method which would allow for the quantitative evaluation of the sulfoalkylated humate products in various low pH solutions.

The following experimental procedure was developed for the quantification of the compatibility of the sulfoalkylated humate product in low pH fertilizer formulations containing divalent and trivalent cations:

1 . Prepar a series of specified dilutions of the humate product to be analysed.

2. Weigh off specified amounts of the concentrated or diluted humate product.

3. In a separate beaker, weigh off a specified amount of low pH fertilizer having a pH of between 0.5 and 2.

4. Add the aqueous sulfoalkylated humate to the low pH fertilizer.

5. Stir the mixture for 5 minutes.

6. Filter the mixture via vacuum filtration through filter paper with a diameter of 125 mm and a pore size of 20-25 pm, of which the mass is known.

7. Wash the filter paper with two portions (1 x 100 gram portion and 1 x 50 gram portion) of aqueous nitric acid solution, with a pH of 0.15.

8. Dry the filter paper containing the residue at 65 °C for 20 - 24 hours.

9. Determine the mass of the dried filter paper with the precipitated residue.

This method allows for the quick and easy evaluation of the compatibility of the humate analogues in various low pH fertilizer formulations. Moreover, the method was determined to be repeatable, yielding consistent quantitative data. Through applying this method, the prepared humate derivative could also be compared against a commercially available product.

Sulfoalkylated Humate Compatibility in Low pH Fertilizer Formulations

The sulfoalkylated humate products that were prepared under various processing conditions, were evaluated based on the quantification method described above. Specifically, low pH fertilizer compatibility of five different humate derivatives were evaluated. The five humate derivatives that were tested, were: • Sulfoalkylated humate prepared according to Example 4 - i.e. below the reflux (96 - 98 °C) point (humate product referred to as ‘below reflux point’)

• Sulfoalkylated humate prepared according to Example 3 - i.e. at reflux conditions (humate product referred to as ‘Refluxed’)

• Sulfoalkylated humate prepared according to Example 3 - i.e. at reflux conditions, but using an adduct that was pre-prepared and stored at room temperature for 6 days (humate product referred to as ‘Refluxed_6d adduct’)

• Sulfoalkylated humate prepared according to Example 1 - i.e. at high temperature and pressure (150 °C and 385 kPa) (humate product referred to as ‘High T/P’)

• Commercially available acid compatible humate product (referred to as ‘commercial product’)

The various humate analogues above were tested as a concentrated humate solution (which was a 30% humate solution), as well as the corresponding diluted humate solutions. Table 8 below indicates the dilutions tested, the amount of diluted solution used as well as the amount of fertilizer used during the tests, following the quantification method described above.

Table 8: Batch card used during the quantitative evaluation of the modified humate products in acidic fertilizers

Humate Mass Humate Low pH Total batch size Final ‘active’ concentration solution (g) Fertilizer (g) (g) humate

(%) concentration

(%)

30 2.0 98.0 100.0 0.60

15 4.0 98.0 102.0 0.59

6 10.0 98.0 108.0 0.56

3 20.0 98.0 118.0 0.51

As can be deduced from the table above, the mass of ‘active’ humate substance was kept constant throughout the various tests. If the humate solution was diluted, more of the solution would then be added in order to end-up with roughly the same amount of humate in the final mixture. The mass of fertilizer used, was also kept constant. This would ensure that the differences in compatibility would be a result of the dilution for a certain product tested, as well as a difference in the product compatibility between the various products tested.

Figure 2 illustrates the comparative display of the various prepared humate derivatives’ compatibility in the low pH fertilizer 11 :7:4(22). As is clear from the figure, the commercially available product was compatible with the fertilizer at all humate concentrations tested. Furthermore, upon diluting the various prepared sulfoalkylated humate products formed according to Examples 1 , 3 and 4, to a 15% humate solution, it was determined that the products were almost completely compatible in the fertilizer, with more than 95% of the sulfoalkylated humates remaining in solution. Further dilutions to both 6% and 3% sulfoalkylated humate solutions did not result in any precipitate formed during the quantitative test. Therefore, at a 3% or 6% sulfoalkylated humate solution, the prepared products are optimally compatible with the low pH fertilizer 11 :7:4(22).

The refluxed prepared sulfoalkylated humates compatibility in two other low pH fertilizer formulations, 6:2:1 and 7:3:0, were also evaluated. Figure 3 represents the compatibility of the refluxed prepared sulfoalkylated humates in the various fertilizers mentioned, in addition to the 11 :7:4(22) formulation for comparative purposes. As is evident from the figure, the refluxed prepared sulfoalkylated humates are compatible with different low pH fertilizer formulations, albeit at specified sulfoalkylated humate concentrations, as was noted above. In addition, even with a 15% diluted sulfoalkylated humate solution, more than 90% of the humic analogue remained in solution, demonstrating sufficient fertilizer compatibility.

It should be noted that the humate precipitation that occurs is a result of the presence of divalent and trivalent cations in the fertilizer, and not the acidic environment. It was previously determined in Example 1 that the prepared sulfoalkylated humates were visually compatible in acidic solutions with a pH of 0.5. The agglomerates/precipitate are therefore a result of the various cations that coordinate and form cross-links between different humate molecules, leading to humate aggregation and finally precipitation. However, when diluted, no humate aggregation occurs in the fertilizer formulation. Therefore, the prepared sulfoalkylated humates can be used in solutions that contain various divalent and trivalent cations as a concentrated solution. However, if the sulfoalkylated humates are to be used in low pH fertilizer formulations containing divalent and trivalent cations, the sulfonic containing humates must to be diluted to a specified concentration of from about 3% to about 15%, more preferably from about 3% to about 6% sulfoalkylated humate solution.

Conclusion

The formaldehyde-sodium/potassium bisulphite adduct synthesis was optimized. The step-wise method towards adduct preparation allows for increased control of the reaction. The possible release of SO₂ was decreased, due to the addition of potassium hydroxide, which shifted the reaction equilibrium to favour the formation of the targeted bisulphite/sulphite reagents. The addition of formaldehyde to the sulphite solution, yielded the corresponding formaldehyde-sodium/potassium bisulphite adduct, which was determined to be stable at low temperatures for several weeks.

As was mentioned above, three sets of processing conditions for the sulfoalkylation of K-humates, were investigated. The sulfoalkylation reaction at 96 - 98 °C, for five hours under atmospheric pressure, was selected as the most optimal set of processing conditions for the preparation of the sulfoalkylated humates. The method is accompanied with a decrease in both the operational risk and cost of production, as compared to the methods at reflux conditions, or at high temperature and pressures, which required the use of a high-pressure reactor. The sulfoalkylated humate product was determined to be compatible in low pH fertilizers, at specified sulfoalkylated humate concentration. At the specific concentrations, it was determined that the sulfoalkylated humate was comparable to a commercially available product.

EXAMPLE 5 The following set out a possible commercial production process for an optimsed sulfoalkylated humate following the sulfoalkylation reaction at 96 - 98 °C, for five hours under atmospheric pressure.

Adduct preparation starting point: Adduct will be prepared in large enough quantities to be used for multiple batches. a) Water - Potable water is transferred to a reaction vessel in which an agitator is provided and the agitator is turned on. b) Sodium Meta-bisulphite - Sodium meta-bisulphite (SMBS) is added to a hopper having a scrubber extraction to ensure control of dust emissions, after which a desired mass of SMBS is fed into the reaction vessel containing the water by a screw feeder where it decomposes into sodium sulphite and sulphur dioxide (SO2). c) Liquid KOH - Liquid KOH (50 wt. %) at the desired mass is added to the mixture of step b) above and reacted with the SO2 to form potassium sulphite. Liquid KOH is preferred to solid KOH due to the hygroscopic nature of KOH which causes difficulties in handling. The addition of liquid KOH to the mixture will generate heat, which will reach temperatures of 65 °C if the starting temperature was 25 °C (i.e. ambient). The heat released is not severe enough to install a cooling system in the reactor. d) Formaldehyde - Formaldehyde stored in flowbins having an extraction system for safe disposal of any vapor release is transferred to the sodium sulphite and potassium sulphite mixture in the reaction vessel by way of a flexible suction pipe until the desired mass set point is reached thereby yielding the formaldehyde-sodium/potassium bisulphite adduct (“the Adduct”).

Sulphoalkylation Reaction: e) K-humate and the Adduct - K-Humates at the desired mass set point are transferred from a storage vessel into a second reaction vessel provided with an agitator and a heating means (preferably a steam circuit) and the agitator is turned on. The second reaction vessel containing K-Humates is heated to 65 °C and then the desired mass set point of the Adduct is transferred from the reaction vessel of d) above into the second reaction vessel. The temperature is increased to the temperature set point of 96 °C and the mixture is reacted for a residence time of 5 hours to yield the sulfoalkylated acid-soluble humate. After 5 hours, the heating is turned off and the sulfoalkylated acid-soluble humate is cooled overnight to ambient temperature and is ready for storage or packaging.

Sulfoalkylated Humate Compatibility Chart

The experimental data obtained gives an overview of the sulfoalkylated humate compatibility in different low pH nutrient solutions. Table 10 below summarizes the acid compatibility of the sulfoalkylated humates in different acid solutions, at different pH values.

Table 10: Sulfoalkylated humate (SAPHAC) compatibility in various acidic solutions at different pH values

Acid Solution SAPHAC (30%)^a Compatability

HNOs (pH = 0.52) FP Compatable

HNOs (pH = 0.65) VFP Compatable

H₂SO₄ (pH = 0.65) PA Partially Compatable

H₂SO₄ (pH = 0.78) VFP Compatable

H₃PO₄ (pH = 0.68) PA Partially Compatable

H₃PO₄ (pH = 0.85) FP Compatable ^aConcentrated acid compatible humates added to acidic solution (final acid compatible humate concentration in acidic solution is 3% w/w)

VFP = Very fine precipitate

FP = Fine precipitate

PA = Precipitate (agglomerates)

The prepared sulfoalkylated humates are soluble in nitric acid, sulphuric acid or phosphoric acid solutions. Sulfoalkylated humates are compatible in mono-protic nitric acid at a pH of 0.52. The compatibility decreases, at this pH value, for di- and tri-protic acids. However, at a pH of 0.85, the sulfoalkylated humates are still fully compatible with the triprotic phosphoric acid. This pH value is still well-below the pH value commonly encountered for low pH fertilizers. This confirms that the acidity of a formulation will not cause humate aggregation and therefore precipitation. Resultantly, sulfoalkylated humate compatibility is dependent on the nutrients/salts in solution, and not the pH of that solution.

Table 11 below summarizes the sulfoalkylated humate compatibility in various macro/micro-nutrient solutions. The data evidence towards the full compatibility of the sulfoalkylated humates in various macronutrient containing solutions, such as urea-ammonium nitrate (UAN) fertilizer having a pH of about 6 to about 7, monoammonium phosphate (MAP) fertilizer having a pH of about 4 and potassium sulphate fertilizer having a pH of about 2.5 (such as Vita-K™). The data further indicates that the sulfoalkylated humates are also compatible in the presence of various micronutrients, albeit with certain limitations. Specifically, the concentration of the micronutrient or the sulfoalkylated humates solution should not exceed the concentrations used and outlined in Table 11 .

Table 11 : SAPHAC Compatibility in various macro/micronutrient solutions Macro/micro nutrient (%)^a SAPHAC (30%)^b Compatability

Urea (43%) Compatible

ANO (60%) Compatible

UAN (32) VFP Partially compatable

CN (1%) Compatible

CN (3.12%) FP Partially compatable

CN (6.25%) PA Incompatable

KNO₃ (25%) Compatible

AS (40%) Compatible

KCI (15%) Compatible

MAP (20%) Compatible

Vita-K (7%) Compatible

MgSO₄ 7H₂O (40%) Compatible

Micronutrient mixture⁰ PA Incompatable

Concentration expressed as w/w percentage of nutrient in water

Concentrated acid compatible humates added to nutrient solution (final acid compatible humate concentration in nutrient solution is 3%)

VFP = Very fine precipitate

FP = Fine precipitate

PA = Precipitate (agglomerates) ^cMicro nutrient mixture: solution at pH 1 .5, containing FeSO₄7H₂O, ZnSO₄ H₂O, MnSO₄ H₂O and CuSO₄ 5H₂O (final concentration of the respective metal ion is 1 % w/w each)

REFERENCES

Canellas, L. P. et al., 2015. Humic and fulvic acids as biostimulants in horticulture. Scientia Horticulturae, Issue 196, pp. 15-27.

Detroit, W. J., Lebo, S. E. & Bushar, L. L., 1997. Production of acid soluble humates. Europe, Patent No. 0786490A2.

Foster, N. C., 1997. Sulfonation and sulfation processes. The Chemithon Corporation. [Online] Available at: www. chemithon. com/Resources/pdfs/Technical.../Sulfo%20and%20Sulfa%201. pdf [Accessed 4 June 2019],

Jardin, P. d., 2015. Plant biostimulants: Definition, concept, main categories and regulation. Scientia Horticulturae, Issue 196, pp. 3-14.

Martin, R., 1954. The mechanism of the Cannizzaro reaction of Formaldehyde. Australian Journal of Chemistry, Issue 7, pp. 335-347.

Moschopedis, S. E., 1967. Sulfomethylation of humic acids, lignites and coals and products thereof. United States of America, Patent No. 3352902.

Moschopedis, S. E., Czakert, E. & Creighton, S. M., 1972. Solubilization of humic acids, lignites and coals. United States of America, Patent No. 3700728.

Ortega, J. A. T., 2012. Sulfonation/Sulfation Processing Technology for Anionic Surfactant Manufacture. In: Z. Nawaz & S. Naveed, eds. Advances in Chemical Engineering. Rijeka: InTech, pp. 269-294.

Zhamba, D., 1991. Composition and structural features of sulphonated humic acids. Khimiya tverdogo topliva, Issue 2, pp. 70-72.

Claims

1 . A method for sulfoalkylation of a humate comprising the steps of: a) preparing a formaldehyde-sodium/potassium bisulphite adduct; and b) subsequently adding the formaldehyde-sodium/potassium bisulphite adduct to the humate, followed by heating from between about 96 °C to a reflux temperature at atmospheric pressure to form a sulfoalkylated humate; wherein the initial preparation step a) comprises the steps of: i. adding between 25 and 35 wt. % water of the total amount of the formaldehyde-sodium/potassium bisulphite adduct, to a reaction vessel and stirring the water in the reaction vessel with an agitator; ii. adding between 20 and 35 wt. % sodium meta-bisulphite (SMBS) of the total amount of formaldehyde-sodium/potassium bisulphite adduct, to the water and stirring to yield an aqueous solution comprising sodium sulphite and SO2; iii. adding between 20 to about 30 wt. % potassium hydroxide (KOH) or sodium hydroxide (NaOH) of the total amount of formaldehyde- sodium/potassium bisulphite adduct, to the aqueous solution with stirring to yield a sodium and potassium sulphite solution; and iv. adding between 15 to about 20 wt. % formaldehyde of the total amount of formaldehyde-sodium/potassium bisulphite adduct, to the sodium and potassium sulphite solution with stirring to yield the formaldehyde- sodium/potassium bisulphite adduct.

2. The method according to claim 1 wherein the humate is potassium humate (K- humate).

3. The method according to claim 1 wherein the reflux temperature is 98 °C.

4. The method according to claim 1 further comprising a step after step b) of cooling the sulfoalkylated humate to ambient temperature.

5. The method according to claim 4 wherein the ambient temperature is 25 °C.

6. The method according to claim 1 wherein the wt. % value in step i) is between 28 to about 34.

7. The method according to claim 1 wherein the wt. % value in step ii) is between 22 to about 34.

8. The method according to claim 1 wherein the wt. % value in step iii) is between 21 to about 26.

9. The method according to claim 1 wherein the potassium hydroxide (KOH) or sodium hydroxide (NaOH) is a liquid solution of 50 wt. % in H₂O.

10. The method according to claim 1 wherein the wt. % in step iv) is between 16 to about 19.

11 . The method according to claim 1 wherein the amount of water added in step i. above is 33.4 wt. %; the amount of SMBS added in step ii. is 22.0 wt. %; the amount of liquid KOH (50 wt. % in H₂O) added in step iii. is 21 .4 wt. %; and the total amount of formaldehyde added in step iv. is 18.7 wt. % of the total amount of formaldehyde-sodium/potassium bisulphite adduct.

12. The method according to claim 1 wherein the formaldehyde is added as a solution of 37 wt. % formaldehyde in H₂O.

13. The method according to claim 1 wherein the step a) is performed immediately subsequent to step b) of adding the formaldehyde-sodium/potassium bisulphite adduct to the humate

14. The method according to claim 1 wherein step a) is performed and the formaldehyde-sodium/potassium bisulphite adduct is stored at a temperature between 0 °C and 25 °C until use in step b) of the method.

15. The method according to claim 1 wherein the humate is a liquid humate having a concentration value lower than 30% wt. % in H₂O.

16. The method according to claim 1 wherein the humate is a liquid humate having a concentration value lower than 26% wt. % in H₂O.

17. The method according to claim 1 wherein the humate is initially heated to a temperature of between 65 to 80 °C, prior to adding the formaldehyde- sodium/potassium bisulphite adduct in step b).

18. The method according to claim 17 the humate is initially heated to a temperature of between 70 to 78 °C.

19. The method according to claim 17 the humate is initially heated to a temperature of between 70 to 75 °C.

20. The method according to claim 1 wherein the heating in step b) is between 96 °C to the reflux temperature at an atmospheric pressure, at a residence time upon reaching the temperature of between 2 hours and 6 hours.

21. The method according to claim 20 wherein the residence time is selected by consideration technoeconomic factors balancing the cost of the residence time at high temperature with the quantity of sulfoalkylated humate generated by the process.

22. The method according to claim 1 wherein the total quantity of humate added to the formaldehyde-sodium/potassium bisulphite adduct in step b) is between 50 to about 60 wt %.

23. The method according to claim 1 wherein the total quantity of mixed formaldehyde-sodium/potassium bisulphite adduct formed by steps i. to iv. Is between 40 to about 50 wt. % of the total amount of mixed humate and formaldehyde-sodium/potassium bisulphite adduct.

24. The method according to claim 1 wherein the humate is initially heated prior to adding the formaldehyde-sodium/potassium bisulphite adduct to a temperature of between 70 to 78 °C.

25. The method according to claim 1 wherein the sulfoalkylated humate is stored or packaged for inclusion in a fertilizer or plant biostimulant solution having a pH of from at least 0.50 or above,

26. The method according to claim 25 wherein the pH value is selected from the group consisting of 0.70, 0.75, 0.80, 8.50, 9.00, 9.50, 1.00, 1.50, or 2.00.

27. The method according to claim 1 wherein the fertilizer or plant biostimulant solution comprises divalent and trivalent cations.

28. The method according to claim 1 wherein the ratio of dry formaldehyde- sodium/potassium bisulphite adduct to humate reacted at reflux temperature or and atmospheric pressure is at least 0.4 for compatibility of the sulfoalkylated humate product with the fertilizer or plant biostimulant solution.

29. The method according to claim 1 wherein the sulfoalkylated humate is a fertilizer formulation comprising a N:P:K ration selected from the group consisting of 11 :7:4(22), 6:2:1 , 7:3:0, and combinations thereof.

30. The method according to claim 1 wherein the ratio of dry formaldehyde- sodium/potassium bisulphite adduct to humate reacted at reflux temperature and atmospheric pressure is at least 1 .32 for compatibility of the sulfoalkylated humate product with the fertilizer or plant biostimulant solution, and wherein the fertilizer or plant biostimulant solution also comprises divalent and trivalent cations.

31. The method according to claim 1 comprising a further step of diluting the sulfoalkylated humate to between 3 wt. % to 15 wt. % prior to formulation with a fertilizer or plant biostimulant solution, or fertilizer and plant biostimulant solution in combination.

32. The method according to claim 31 wherein the fertilizer or plant biostimulant solution, or fertilizer and plant biostimulant solution in combination comprise divalent and trivalent cations

33. A method according to any of the preceding claims for preparing a fertilizer or plant biostimulant solution having a pH of at least 0.50 where fertilizer or plant biostimulant solution comprises divalent and trivalent cations, formulated to comprise a sulfoalkylated humate prepared according to the method.

34. The method according to claim 33 wherein the pH value is selected from the group consisting of 0.70, 0.75, 0.80, 8.50, 9.00, 9.50, 1.00, 1.50, or 2.00.

35. A method according to any of the preceding claims for feeding a plant or stimulating plant growth with the use of a fertilizer or plant biostimulant solution, or fertilizer and plant biostimulant solution in combination comprising the sulfoalkylated humate prepared according to the method.