Process for preparing a dipotassium hydrogen phosphate composition

Abstract

The present invention concerns an easy and simple process for preparing a DKP composition with low level of chlorates or without chlorates comprising the steps of: providing one solution (A) comprising based on the total weight of said solution (A), at least 45 wt.% of H3PO4; contacting with at least one alkaline composition comprising at least one potassic compound with said one solution (A), thereby forming one composition (C); contacting one material able to reduce said chlorate with either the solution (A), or said one alkaline composition, or said composition (C) drying step of said composition (C), thereby forming a DKP composition; said DKP composition comprising, at least 90.0 wt.% of DKP.

Description

[0001] “PROCESS FOR PREPARING A DIPOTASSIUM HYDROGEN PHOSPHATE COMPOSITION”

[0002] FIELD OF THE INVENTION

[0003] The present invention belongs to the field of dipotassium hydrogen phosphate compositions, more particularly the field of processes for preparing a dipotassium hydrogen phosphate composition, even more particularly the field of processes for preparing a food grade a dipotassium hydrogen phosphate composition.

[0004] STATE OF THE ART

[0005] Dipotassium hydrogen phosphate (DKP) can be prepared by various wet processes that generally start with an acid attack of a phosphate ore in order to produce phosphoric acid. The acid attack can be carried out with mineral acids such as hydrochloric acid or sulfuric acid. Such processes usually involve many different steps such as, for example, the production of DKP from a solution of phosphoric acid with a potassium base such as potassium hydroxide (KOH). Other potassium bases may be used as well.

[0006] Therefore, these processes require the use of many different reactants which can contain impurities. This is particularly the case of KOH which is often synthetized through electrolysis of an aqueous solution of potassium chloride (KCI) in diaphragm-type cell. Indeed, it is common general knowledge that these processes result in KOH comprising significant amounts of chlorates. As a consequence, DKP can be contaminated by significant amounts of impurities such as chlorates. In theory, chlorate impurities may also come from other sources such as the phosphoric acid or additives.

[0007] DKP is also known as E340ii, a food additive often used as a stabilizer, emulsifier or texturizer. However, around the word, legislators are seeking to compel companies to reduce the presence of chlorates in products destined to the food market. For example, the “COMMISSION REGULATION (EU) 2020 / 749 of 4 June 2020 amending Annex III to Regulation (EC) No 396 / 2005 of the European Parliament and of the Council as regards maximum residue levels for chlorate in or on certain products” defines maximum level of chlorates for various products such as fruits, vegetables, milk and honey. Another piece of legislation which relevant is “COMMISSION DELEGATED REGULATION (EU) 2016 / 127 of 25 September 2015 supplementing Regulation (EU) No 609 / 2013 of the European Parliament and of the Council as regards the specific compositional and information requirements for infant formula and follow-on formula and as regards requirements on information relating to infant and young child feeding”.

[0008] There is thus a continuous need to reduce the concentration of chlorates in DKP, especially in DKP which is intended to be used as food additive (food grade DKP), more specifically DKP intended for use in infant food formulations.

[0009] CN110817823A discloses a method for manufacturing food-grade dipotassium hydrogen phosphate by using wet dilute phosphoric acid. The method involves several steps including a membrane filtration, a neutralization reaction and simultaneous defluorination and desulfurization, an oxidative dearsenization via addition of an oxidant such as hydrogen peroxide, pH adjustment and concentration, and a crystallization step.

[0010] However, this document does not disclose the removal of chlorate. Moreover, the method requires many steps and the use of additives such as hydrogen peroxide which are known to be very corrosive and relatively uneasy to handle at the industrial scale because of their instability.

[0011] There is thus a continuous need to provide easy and simple processes for preparing DKP compositions with low level of chlorates or without chlorates. Moreover, for economic reasons the process should enable the use of additives and / or raw materials contaminated with chlorates such as KOH synthetized through the electrolysis processes. Furthermore, another requirement that must be fulfilled is that the obtained DKP has to be suitable for use in food applications such as baby food applications.

[0012] INVENTION SUMMARY

[0013] The inventors have surprisingly found that the present invention solves the above identified problems.

[0014] The present invention concerns a process for preparing a dipotassium hydrogen phosphate composition [hereafter, DKP composition] comprising at least the following steps of:

[0015] (i). providing at least one solution [hereafter, solution (A)] comprising based on the total weight of said solution (A), at least 45 wt.% of H3PO4;

[0016] (ii). contacting at least one alkaline composition comprising at least one potassic compound with said at least one solution (A), thereby forming at least one composition [hereafter, composition (C)]; said composition (C) having a molar ratio K2O / P2O5 of at least 1 .90 and at most 2.10; said alkaline composition or said solution (A) further comprising at least 0.50 ppm of chlorate;

[0017] (iii). contacting at least one material able to reduce said chlorate

[0018] [hereafter, material (R)] with either:

[0019] • the solution (A), or

[0020] • said at least one alkaline composition, or

[0021] • said composition (C);

[0022] (iv). drying said composition (C), thereby forming a DKP composition; said DKP composition comprising, based on the total weight of said DKP composition, at least 90.0 wt.% of DKP; wherein said material (R) is contacted in step (iii) in an amount sufficient to transfer at least 0.0090 mmol of electrons from said material (R) to said chlorate per kg of said DKP composition formed in step (iv). The present invention also concerns a DKP composition and a DKP composition obtained by the process according to the present invention.

[0023] DETAILED DESCRIPTION

[0024] In the context of the present invention, the term “comprising” should not be interpreted as excluding features or elements other than those explicitly mentioned. It should be construed as specifying the presence of the features or elements indicated, but does not exclude the presence or addition of one or more other features or elements. Thus, the scope of the expression "a method comprising steps A and B" should not be limited to methods consisting only of steps A and B. Similarly, a composition comprising components A and B should not be limited to compositions consisting only of components A and B. Accordingly, the terms "comprising" and "including" encompass the terms more restrictive “consisting essentially of” and “consisting of”.

[0025] In the context of the present invention, if an element or component is said to be selected from a list of recited elements or components, it should be understood that the element or component can also be any one of the individual recited elements or components in said list, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components.

[0026] Unless stated otherwise, all the percentages and ppm concentrations are respectively percentages by weight (= wt.%) and ppm in weight (= ppm).

[0027] The use of roman numerals such as (i), (ii), (iii) for designating steps in a process does not necessarily impart an order to said steps, unless specified otherwise. Thus, for example, a step (iii) can be carried out before a step (ii). If one of the step is optional that means that it can sometimes be omitted. For example if step (iii) is optional, the skilled in the art understands that step (iv) can be carried out after step (ii). In the context of the present invention, the terms “DKP”, and “dipotassium hydrogen phosphate” are intended to refer to a compound having the formula K2HPO4.

[0028] Step (i) and solution (A)

[0029] The process according to the present invention comprise a step (i) of providing at least one solution (A) comprising based on the total weight of said solution (A), at least 45 wt.%, preferably at least 60 wt.%, more preferably at least 70 wt.% of H3PO4.

[0030] It is understood that said solution (A) preferably comprises based on the total weight of said solution (A), at most 90 wt.%, more preferably at most 85 wt.% of H3PO4.

[0031] Preferably, said solution (A) comprises based on the total weight of said solution (A), at least 60 wt.% and at most 90 wt.%, more preferably at least 70 wt.% and at most 85 wt.%, even more preferably 75 wt.%, of H3PO4.

[0032] Within the context of the present invention, the “wt.% of H3PO4” represents the total amount of phosphorus atoms expressed as wt.% of H3PO4 equivalent, and may also be expressed in weight percentages of P2O5 equivalents, denoted wt.% of P2O5. The correspondence between the two concentration units is defined by the relation: 1 wt.% of P2O5 = 0.7245 wt.% of H3PO4.

[0033] Preferably, said solution (A) has a weight ratio WSO4 / WP2OS below 0.030, preferably below 0.010; more preferably below 0.0050, even more preferably below 0.0010, wherein Wso4 represents the wt.% of SO4 in said solution (A) and WP205 represents the wt.% P2O5 in said solution (A). Both Wso4 and WP205 are based on the total weight of said solution (A).

[0034] In the context of the present invention, the “wt.% of SO4” represents the total weight of sulfur atoms in said solution (A) expressed as wt. % SO4 equivalent. Preferably, said solution (A) has a weight ratio WF / WP2O5 below 0.01 , preferably below 0.005; wherein WF represents the percentage by weight of fluor in said solution (A). WF and WP205 are based on the total weight of said solution (A). Thus, it means that said solution (A) may comprise fluor based compounds such as for example but not limited to fluorides.

[0035] In the context of the present invention, all the percentage by weight of fluor may be measured by any suitable method known in the art. All the WF may be determined by direct potentiometry.

[0036] In particular, said solution (A) may originally come from a phosphoric acid solution which is itself the result of a sulfuric acid attack of a phosphate source (ore or equivalent). The phosphoric acid solutions which are directly obtained after a sulfuric acid attack of a phosphate ore usually contain high amounts of impurities such as sulfates which need to be lowered, especially if the phosphoric acid is to be used in the production of food grade DKP.

[0037] The weight ratio WS04 / WP205 as defined above for solution (A) indicates that the solution (A) comprises a relatively low amount of sulfur in comparison to the amount of P2O5. This characteristic of solution (A) may for example be the result of various purification processes known by the skilled in the art which has reduced the amounts of sulfates in solution (A) such as desulfatation by adding a calcium source or by specific process such as the one described in for example described in WO 2012163425 A1 which is hereby incorporated by reference.

[0038] Within the context of the present invention, all the Wso4 may be measured by any suitable method known in the art. All the Wso4 may be measured by Inductively Coupled Plasma (ICP) spectrometry , more particularly by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES).

[0039] If desired, said solution (A) may be a phosphoric acid solution obtained by the process disclosed in WO 2021 / 254944 A1 which is hereby incorporated by reference. In particular, said solution (A) may be the result of a purification process which includes ion exchange and desulfatation. In other words, said solution (A) may be obtained from a sulfuric acid attack of a phosphate ore followed by purification by ion exchange and / or desulfatation.

[0040] Alternatively, said solution (A) may also come from polyphosphoric acid which is hydrolyzed or not. The obtained polyphosphoric acid may be the result of processes known by the skilled in the art such as dissolution of polyphosphate salt or such as production processes as described in WO 2010 / 108991 A1 which is hereby incorporated by reference.

[0041] If desired, the process according to the present invention may comprise at least one addition of phosphoric acid salts such as potassium salts, into said solution (A). This enables the recycling of the phosphoric acid salts.

[0042] In particular, said solution (A) may also come from the dissolution of phosphoric or polyphosphoric acid salts in water or in phosphoric acid. Non limiting examples of salts include but are not limited to: monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, hemipotassium phosphate, potassium pyrophosphate, tetrapotassium pyrophosphate or mixtures thereof.

[0043] Said solution (A) may comprise at least 0.50 ppm of chlorate, based on the total weight of said solution (A). Preferably, said solution (A) can comprise based on the total weight of said solution (A) at least 1 ppm or at least 2 ppm or at least 3 ppm, or at least 4 ppm of chlorate. It is understood that said solution (A) can comprise, based on the total weight of said solution (A) at most 15 ppm or at most 10 ppm or at most 5 ppm of chlorate.

[0044] In certain embodiments, said solution (A) can comprise based on the total weight of said solution (A) at least 1 ppm and at most 15 ppm or at least 2 ppm and at most 10 ppm or at least 3 ppm and at most 5 ppm, at least 4 ppm and at most 5 ppm of chlorate. Said solution (A) of step (i) may be provided in any suitable container known by the skilled in the art such as a reactor or a tank. In certain cases, depending on the set-up and the origin of said solution (A), agitation may be needed, for example for the step(s) (i) and / or (ii). In this case, the reactor or the tank will be equipped with devices enabling agitation to occur during the step(s) (i) and / or (ii). If desired, said step (i) may be carried out in batch or continuously.

[0045] Step (ii) and composition (C)

[0046] The process according to the present invention further comprises a step (ii) of contacting said solution (A) with at least one alkaline composition comprising at least one potassic compound thereby forming at least one composition (C) having a molar ratio K2O / P2O5 of at least 1 .90 and at most 2.10. Said alkaline composition or said solution (A) further comprises at least 0.50 ppm of chlorate, based on the total weight of said alkaline composition or said solution (A).

[0047] Since, either the alkaline composition or the solution (A) comprises said chlorate, it is clear that the composition (C) comprises said chlorate if in step (iii), the material (R) is not contacted with the alkaline composition or solution (A) but with the composition (C) after its formation in step (ii).

[0048] Within the context of the present invention, an alkaline composition is given its normal meaning in the art. Particularly, an alkaline composition can be defined as a composition which, when added into an aqueous solution, will increase the pH of said aqueous solution, more particularly a pH over 7.

[0049] Within the context of the present invention, a potassic compound is intended to denote a compound comprising at least one potassium cation.

[0050] Within the context of the present invention said at least one alkaline composition comprising at least one potassic compound is sometimes referred to said / the at least one alkaline composition or said / the alkaline composition.

[0051] Within the context of the present invention, the molar ratio K2O / P2O5 refers to the ratio of mol.% of K2O comprised in said composition (C) over the mol.% of P2O5 comprised in said composition (C).

[0052] In the context of the present invention, all the molar ratio K2O / P2O5 may be directly determined by potentiometric titration.

[0053] It was advantageously found that the specific molar ratio K2O / P2O5 of at least 1 .90 and at most 2.10 enables to obtain DKP, in particular in the drying step (iv). Thus, said composition (C) preferably comprises DKP. Preferably, said DKP comprised in said composition (C) may be at least partially or totally dissolved in said composition (C). Preferably, said DKP comprised in said composition (C) may be at least partially or totally dissociated or undissociated form.

[0054] Preferably, said molar ratio K20 / P20s of said composition (C) is of at least 1.95, more preferably at least 1.98, even more preferably at least 1 .99. It is understood that said molar ratio K2O / P2O5 of said composition (C) is of at most 2.05, more preferably at most 2.02, even more preferably at most 2.01.

[0055] In a preferred embodiment, said molar ratio K2O / P2O5 of said composition (C) is of at least 1 .95 and at most 2.05, more preferably at least 1 .98 and at most 2.02, even more preferably at least 1 .99 and at most 2.01.

[0056] The contacting in step (ii) may be done in any suitable manner known by the skilled in the art with the proviso that said composition (C) has a molar ratio K2O / P2O5 as specified above. For example, the alkaline composition comprising at least one potassic compound may be added to said solution (A) which is already contained in a tank or a reactor. Alternatively, said solution (A) and said alkaline composition comprising at least one potassic compound may be added simultaneously into a tank or a reactor. In another alternative embodiment, said solution (A) is added to said alkaline composition comprising at least one potassic compound which is already contained in a tank or a reactor.

[0057] The contacting step (ii) preferably comprises a step (iia) of adding said alkaline composition comprising at least one potassic compound to said solution (A). More preferably, said alkaline composition comprising at least one potassic compound is added to said solution (A) in step (iia) until said solution (A) reaches a molar ratio K2O / P2O5 of at least 1.90 and at most 2.10.

[0058] If desired, said step (ii) may be carried out in batch or continuously.

[0059] The process according to the present invention preferably comprises a step (iib) of mixing said solution (A) and said alkaline composition comprising at least one potassic compound together. Said mixing step (iib) may be carried out simultaneously or after said step (iia), preferably said mixing step (iib) is an agitation step.

[0060] The skilled in the art may use any suitable alkaline composition comprising at least one potassic compound. Examples of suitable potassic compounds suitable for all the embodiments of the present invention include but are not limited to: KOH (in a solid form such as prills or flakes or as a solution), K2CO3, KHCO3, KH2PO4, K2HPO4, K3PO4, K4P2O7, K2H2P2O7, KPO3, K5P3O10, HKP and mixtures thereof. Preferably, said potassic compound is KOH.

[0061] In step (ii), the alkaline composition comprising at least one potassic compound may be in any suitable form such as in solid form or in solution or as a slurry.

[0062] Preferably, said alkaline composition is in solid form and comprises based on the total weight of said alkaline composition at least 10 wt.%, preferably at least 20 wt.% of K2O. It is understood that said alkaline composition in solid form may comprise preferably at most 80 wt.%, more preferably at most 75 wt.%, even more preferably at most 70 wt.% of K2O.

[0063] In a preferred embodiment, said alkaline composition is in solid form and comprises based on the total weight of said alkaline composition at least 10 wt.% and at most 80 wt.%, preferably at least 15 wt.% and at most 75 wt.%, even more preferably at least 20 wt.% and at most 70 wt.% of K2O.

[0064] Within the context of the present invention the mol.% of K2O in said composition (C) refers to the total mol.% of potassium (K) comprised in said composition (C) expressed as K2O equivalent.

[0065] Within the context of the present invention, the wt.% of K2O in said composition (C) refers to the total wt.% of potassium (K) comprised in said composition (C) expressed as K2O equivalent.

[0066] Within the context of the present invention, all the wt.% of K2O may be measured by any suitable method known in the art. All the wt.% of K2O may be measured by potentiometric titration or by Inductively Coupled Plasma (ICP) spectrometry , more particularly by Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES).

[0067] Preferably, said alkaline composition is in solid form and comprises based on the total weight of said alkaline composition at least 10 wt.%, preferably at least 20 wt.%, more preferably at least 30 wt., even more preferably at most 40 wt.%, even more preferably at most 50 wt.%, even more preferably at most 60 wt.%, even more preferably at most 80 wt.%, even more preferably at most 90 wt.%, even more preferably at most 99 wt.% of potassic compound.

[0068] Preferably, the alkaline composition is a solution [hereafter, solution (B)]. Said potassic compound may be at least partially or totally dissolved in said solution (B). Preferably, said solution (B) comprises based on the total weight of said solution (B), at last 20 wt.%, more preferably at least 30 wt.%, more even preferably at least 40 wt.%, even more preferably at least 45 wt.% of K2O and / or of potassic compound.

[0069] It is understood that said solution (B) preferably comprises based on the total weight of said solution (B), at most 60 wt.%, more preferably at most 55 wt.% of K2O and / or of potassic compound.

[0070] In a preferred embodiment, said solution (B) preferably comprises based on the total weight of said solution (B), at least 30 wt.% and at most 60 wt.%, preferably at least 40 wt.% and at most 60 wt.% more preferably at least 45 wt.% and at most 55 wt.% of K2O and / or of potassic compound.

[0071] In a more preferred embodiment, the alkaline composition comprises at least one potassic compound selected from the group consisting of KOH, K2CO3, KHCO3, KH2PO4, K2HPO4, K3PO4, K4P2O7, K2H2P2O7, KPO3, K5P3O10, HKP and mixtures thereof; wherein said alkaline composition is a solution (B) comprising based on the total weight of said solution (B), at least 40 wt.% and at most 55 wt.% of said potassic compound.

[0072] It is understood that at least part or the totality of the potassic compound comprised in the alkaline composition may advantageously react with at least part or the totality of the phosphoric acid comprised in solution (A).

[0073] Preferably, said composition (C) has a pH of at least 8.5 and at most 9.5, more preferably a pH of at least 8.7 and at most 9.2.

[0074] If said material (R) is added after step (ii) and the formation of composition (C), said composition (C) may preferably comprises based on the total weight of said composition (C), before step (iii), at least 0.050 ppm of chlorate.

[0075] In certain embodiments, if said material (R) is added after step (ii) and the formation of composition (C), said composition (C) may comprise at least 1 ppm or at least 2 ppm or at least 3 ppm, or at least 4 ppm of chlorate. It is understood that if said material (R) is added after step (ii) and the formation of composition (C), said composition (C) may comprise at most 15 ppm or at most 10 ppm or at most 5 ppm of chlorate, based on the total weight of said composition (C).

[0076] In certain embodiments, if said material (R) is added after step (ii) and the formation of composition (C), said composition (C) may comprise based on the total weight of said composition (C) at least 1 ppm and at most 15 ppm or at least 2 ppm and at most 10 ppm or at least 3 ppm and at most 5 ppm or at least 4 ppm and at most 5 ppm of chlorate.

[0077] The term “chlorate” is intended to denote a CIOs’ anion. Thus, the ppm’s of chlorate are calculated with regards to the CIOs’ anion. Of course, the chlorate may be present in the composition (C) in associated form with cations such as for example potassium or sodium in order to form KCIOs or NaCIOs. When in solution, chlorates such as KCIOs and NaCIOs may be at least partially or totally dissociated. Therefore, said chlorate may be KCIOs or NaCIOs or other chlorates.

[0078] The chlorate comprised in said composition (C) may come from different sources. For example, the chlorate may be comprised in said solution (A) and / or it may be comprised in said alkaline composition comprising at least one potassic compound. The skilled in the art knows that alkaline compositions comprising at least one potassic compound such as KOH may comprise significant amounts of chlorate because KOH is generally synthetized through electrolysis of an aqueous solution of potassium chloride (KCI) in diaphragm-type cell. The chlorate may also come from other additives which were added to said composition (C) or from the solution (A) provided in step (i).

[0079] Therefore, preferably, said alkaline composition or said solution (B), comprises based on the total weight of said alkaline composition or said solution (B), at least 1 ppm of chlorate, more preferably at least 2 ppm of chlorate, even more preferably at least 3 ppm of chlorate. It is understood that said alkaline composition or said solution (B) comprises at most 15 ppm of chlorate, more preferably at most 10 ppm of chlorate, of chlorate based on the total weight of said alkaline composition or said solution (B).

[0080] In a preferred embodiment, the alkaline composition comprises at least one potassic compound selected from the group consisting of KOH, K2CO3, KHCO3, KH2PO4, K2HPO4, K3PO4, K4P2O7, K2H2P2O7, KPO3, K5P3O10 , HKP and mixtures thereof; and said alkaline composition is a solution (B) comprising based on the total weight of said solution (B), at least 40 wt.% and at most 55 wt.% of said potassic compound and at least 45 wt.% and at most 55 wt.%, preferably 50 wt.% of KOH and at least 2 ppm and at most 15 ppm of chlorate preferably 5 ppm of chlorate.

[0081] Said contacting step (ii) may be carried out in batches or continuously.

[0082] Said contacting step (ii) may preferably be carried out for at least 30 minutes, more preferably at least 1 hour, even more preferably at least 2 hours. It is understood that said contacting step (ii) may preferably be carried out for at most 8 hours, more preferably at least 6 hours. In a preferred embodiment, said contacting step (ii) may preferably be carried out for at least 1 hour and at most 8 hours, more preferably at least 2 hours and at most 6 hours.

[0083] Step (iii) and the material (R)

[0084] The process according to the present invention further comprises a step (iii) of contacting at least one material able to reduce said chlorate [hereafter, material (R)] with:

[0085] • said solution (A), or

[0086] • said at least one alkaline composition, or

[0087] • said composition (C).

[0088] In a first embodiment, said at least one material (R) is contacted with said solution (A) provided in step (i). As a result, in step (ii), said at least solution (A) which has been contacted with the material (R), is contacted with said at least one alkaline composition.

[0089] In a second embodiment, said at least one material (R) is contacted with said at least one alkaline composition before step (ii). As a result, in step (ii), said at least one alkaline composition which has been contacted with the material (R), is contacted with said solution (A).

[0090] In a third embodiment, said alkaline composition is contacted with said solution (A) in step (ii). As a result, said material (R) is contacted with said composition (C) in step (iii).

[0091] If desired, in the process according to the invention, said at least one material (R), said solution (A) and said at least one alkaline composition may also be contacted simultaneously.

[0092] Thus, said material (R) is able to reduce chlorate present in said composition (C) and / or said solution (A) and / or said alkaline compositions. Preferably, the material (R) is contacted with said composition (C) and said material (R) must be able to reduce chlorate in said composition (C).

[0093] By the terms “reduce said chlorate”, it is understood that the material (R) must be able to reduce the Cl atom from the chlorate to a lower oxidation stage. Thus, the chlorate anion (CIO3 ) may for example be converted to CI2 and / or Ch

[0094] Said material (R) may be contacted with said solution (A) or said at least one alkaline composition or said composition (C) in any suitable form such as solid form or at least partially or totally dissolved in a solution. Preferably, said material (R) may be added in an apart agitating reactor or in the same reactor as in step (ii) or in the 2 reactors.

[0095] Non-limiting examples of material (R) are: Fe(ll) salts, Fe(0), Cu(l) salts, Cu(0), Zn(0), hydroquinone, oxalic acid, acetic acid, formic acid, phosphorous acid, H2O2, other suitable reducing agents and mixtures thereof. The roman number between parenthesis or the 0 indicates the oxidation state.

[0096] Preferably, said material (R) comprises at least one metal selected from the group consisting of Fe(ll), Cu(l), Fe(0), Cu(0), Zn(0) and mixtures therefore. Each metal may for example be in metallic form or in the form of a salt of sulfate, of chloride, of carbonate, or an organic salt such as for instance acetate, oxalate or gluconate.

[0097] Preferably, suitable materials (R) include but are not limited to iron (II) sulfate, iron (II) chloride, metallic iron, iron (II) nitrate, iron (II) hydroxide, iron (II) carbonate, iron (II) gluconate, iron (II) acetate, iron (II) oxalate, metallic copper, metallic zinc, copper (I) sulfate, copper (I) chloride, metallic iron, copper (I) nitrate, copper (I) hydroxide, copper (I) carbonate, copper (I) gluconate, copper (I) acetate, copper (I) oxalate and hydroquinone and oxalic acid and acetic acid and formic acid and phosphorous acid, sulfurous acid and H2O2 and mixtures thereof. When the material (R) is a metal salt, it may be hydrated or not.

[0098] The inventors surprisingly found that the use of material (R) enables to simplify the production of a food grade DKP composition. Indeed, the material (R) is not only able to reduce the chlorate and thus to lower the amount of chlorate in the final DKP composition obtained in step (iv) but it also does not require to be removed from the final DKP composition obtained in step (iv). As a consequence, the DKP composition does not require further purification steps when used for food applications such as baby food applications.

[0099] Optional heating and / or concentrating step

[0100] The process according to the present invention preferably further comprise a step of concentrating and / or heating said composition (C). The concentration step and / or heating step of said composition (C) is / are preferably carried out after step (iii) and before step (iv). It was surprisingly found by the inventors that heating and / or concentration said composition (C) after contacting said material (R) diminishes the time needed to reduce the chlorate in the final DKP composition obtained at step (iv).

[0101] Preferably, said concentration and / or heating step comprises heating the composition (C) obtained after step (iii) to a temperature of at least 90°C, preferably at least 100 °C, more preferably at least 105°C, even more preferably at least 110°C. It is understood that in said concentration step and / or heating step, the composition (C) may be heated to a temperature of at most 140°C, preferably at most 135 °C, more preferably at most 130°C.

[0102] In a preferred embodiment, said concentration and / or heating step comprises heating the composition (C) obtained after step (iii) to a temperature of at least 90°C and at most 140°C, preferably at least 100 °C and at most 135°C, more preferably at least 105°C and at most 135°C, even more preferably at least 110°C and at most 130°C.

[0103] Preferably, in said concentration or heating step, the composition (C) is heated for at least 30 minutes, preferably at least 1 hour, more preferably at least 1.5 hour, even more preferably at least 2 hours, even more preferably at least 3 hours. It is understood that in said concentration or heating step, the composition (C) may be heated for at most 10 hours, preferably at most 8 hours, more preferably at most 6 hours, even more preferably at most 5 hours, even more preferably at most 4 hours.

[0104] In a preferred embodiment, in said concentration or heating step, the composition (C) is heated for at least 30 minutes and at most 10 hours, preferably at least 1 hour and at most 8 hours, more preferably at least 1 .5 hour and at most 6 hours, even more preferably at least 2 hours and at most 5 hours, even more preferably at least 3 hours and at most 4 hours.

[0105] In a more preferred embodiment, said concentration or heating step comprises heating the composition (C) obtained after step (iii) to a temperature of at least 110°C and at most 130°C for at least 30 minutes and at most 10 hours, preferably at least 1 hour and at most 8hours, more preferably at least 1 .5 hour and at most 6 hours, even more preferably at least 2 hours and at most 5 hours, even more preferably at least 3 hours and at most 4 hours.

[0106] Step (iv)

[0107] The process according to the present invention further comprises a drying step (iv) of said composition (C) obtained in step (iii) or optionally after said concentration or heating step, thereby forming said DKP composition.

[0108] The drying step (iv) may be performed by any suitable means known by the skilled in the art. Preferably, said drying step (iv) may comprise drying said composition (C) using a direct or indirect contact with a fluid (preferably hot fluid, preferably hot gases). The drying step (iv) may be carried out with a drying device such as (but not limited to) a fluidized bed, an atomizer, a flash dryer, a drum dryer, a spray dryer or by a combination thereof.

[0109] The inventors have also surprisingly found that the chlorate is at least partially degrading during said drying step (iv).

[0110] Preferably said drying step (iv) is carried out until said DKP composition obtained in step (iv) comprises at most 10 wt.%, preferably at most 5 wt.%, more preferably at most 2 wt.%, even more preferably at most 1 wt.% of water, based on the total weight of said DKP composition.

[0111] Preferably, said drying step (iv) is carried out by heating said composition (C) until a temperature of at least 150 °C, more preferably at least 180°C, even more preferably at least 200°C, even more preferably at least 220°C is reached. It is understood that in said drying step said composition (C) may be dried in step (iv) at a temperature of at most 250°C. In a preferred embodiment, said drying step (iv) is carried out by heating said composition (C) to a temperature of at least 150 °C and at most 250°C, more preferably at least 180°C and at most 250°C, even more preferably at least 220°C and at most 250°C.

[0112] Said composition (C) is preferably dried in step (iv) for at least 2 hours, more preferably at least 3 hours, even more preferably at least 4 hours. Said composition (C) is preferably dried in step (iv) for at most 8 hours, more preferably at most 7 hours, even more preferably at most 6 hours. Alternatively, said composition (C) may be dried in step (iv) substantially instantaneously, preferably for at least 15 seconds, more preferably at least 1 minute, even more preferably at least 3 minutes, even more preferably at least 5 minutes, even more preferably at least 10 minutes, even more preferably at least 15 minutes, even more preferably at least 30 minutes, even more preferably at least 1 hour. Said composition (C) may be dried in step (iv) for at most 2 hours, more preferably at most 1 hour, even more preferably at most 45 minutes, even more preferably at most 20 minutes, even more preferably at most 10 minutes, even more preferably at most 5 minutes, even more preferably at most 1 minute.

[0113] In a preferred embodiment, said composition (C) may be dried in step (iv) during at least 10 seconds and at most 15 seconds, or at least 45 seconds and at most 90 seconds, or at least 4 minutes and at most 6 minutes or at least 10 minutes and at most 20 minutes, or at least 20 minutes and at most 40 minutes, or at least 1 hour and at most 2 hours.

[0114] According to the present invention, said material (R) is contacted in step (iii) in an amount sufficient to transfer at least 0.009 mmol, preferably at least 0.020 mmol, more preferably at least 0.050 mmol, even more preferably at least 0.100 mmol of electrons from said material (R) to said chlorate, per kg of said DKP composition formed in step (iv).

[0115] The material (R) advantageously transfers electrons to the chlorate in said composition (C), thereby reducing the oxidation stage of the Cl atom of the chlorate, in other words, the chlorate is for example reduced to Cl- and / or CI2.

[0116] The amount of chlorate may regularly or continually be measured in said DKP composition obtained in step (iv). Thus, the quantity of material (R) contacted in step (iii) may be adjusted if needed. For example, if the amount of chlorate in said DKP composition obtained in step (iv) is too high, more material (R) may be contacted in step (iii) in order to reduce more chlorate.

[0117] It is understood that said material (R) may preferably be contacted in step (iii) in an amount sufficient to transfer at most 1.250 mmol, preferably at most 1.000 mmol, more preferably at most 0.500 mmol, even more preferably at most 0.7500 mol, even more preferably at most 0.200 mmol of electrons from said material (R) to said chlorate, per kg of said DKP composition formed in step (iv).

[0118] In a particular embodiment, it is understood that said material (R) may preferably be contacted in step (iii) in an amount sufficient to transfer at least 0.009 mmol and at most 1 .000 mmol, preferably at least 0.020 mmol and at most 0.500 mmol, more preferably at least 0.100 mmol and at most 0.200 mmol of electrons from said material (R) to said chlorate, per kg of said DKP composition formed in step (iv).

[0119] In particular, if said material (R) comprises at least one metal element selected in the group of Fe(ll), Cu(l), Fe(0), Cu(0), Zn(0) and mixtures therefore, the said material (R) may preferably be contacted in an amount of at least 0.3. mg, more preferably 0.5 mg, more preferably at least 1 mg, more preferably at least 5 mg, more preferably at least 7 mg, even more preferably at least 10 mg of metal element per kg of said DKP composition formed in step (iv). The said material (R) may preferably be contacted in an amount of at most 60 mg, more preferably at most 50 mg, even more preferably at most 40 mg, even more preferably at most 35 mg, even more preferably at most 30 mg, even more preferably at most 25 mg of metal element per kg of said DKP composition formed in step (iv).

[0120] Thus, the said material (R) may preferably be contacted in an amount between 0.5 and 60 mg, preferably between 5 and 50 mg, more preferably between 10 and 40 mg of metal element per kg of said DKP composition formed in step (iv).

[0121] Preferably, the process according to the present invention may comprise after step (iv), a milling step or a granulometry section (sieving).

[0122] DKP composition

[0123] Each of the features and embodiments disclosed hereafter for the DKP composition applies to the DKP composition according to the present invention and to the DKP composition obtained in step (iv) of the process according to the present invention.

[0124] The DKP composition comprises based on the total weight of said DKP composition at least 90.00 wt.%, more preferably at least 95.00 wt.%, even more preferably at least 98.00 wt.%, even more preferably at least 99.00 wt.% of DKP.

[0125] The DKP composition may comprise based on the total weight of said DKP composition at most 100.00 wt.%.

[0126] Preferably, the DKP composition essentially consists of DKP. The expression “essentially consisting of” is intended to denote that any additional ingredient in said DKP composition, different from DKP such as impurities, including for example pyrophosphate, sulfates and / or fluorides are only present in a minor amount, typically, less than 1 wt.%; being understood that said additional ingredients do not substantially modify the properties of said DKP composition, i.e. do not materially affect the essential characteristics of said DKP composition.

[0127] The DKP composition comprises based on the total weight of said DKP composition, at most 4.00 ppm of chlorate, preferably at most 2.00 ppm of chlorate, more preferably at most 1 .00 ppm of chlorate, even more preferably at most 0.50 ppm of chlorate, even more preferably at most 0.10 ppm, even more preferably at most 0.05 ppm, even more preferably at most 0.03 ppm, even more preferably at most 0.02 ppm, even more preferably at most 0.01 ppm.

[0128] The DKP composition may comprise, based on the total weight of said DKP composition, at least 0.0006 wt.%, preferably at least 0.0010 wt.%, more preferably at least 0.0015 wt.%, even more preferably at least 0.0020 wt.%, even more preferably at least 0.0030 wt.%, even more preferably at least 0.0050 wt.%, even more preferably at least 0.0080 wt.% of at least one metal element selected from the group consisting of Cu, Fe, Zn and mixtures thereof.

[0129] The DKP composition may comprise based on the total weight of said DKP composition, at most 0.0150 wt.%, preferably at most 0.0100 wt.%, more preferably at most 0.0095 wt.%, even more preferably at most 0.0090 wt.%, even more preferably at most 0.0085 wt.%, even more preferably at most 0.0080 wt.%, of at least one metal element selected from the group consisting of Cu, Fe, Zn and mixtures thereof.

[0130] The DKP composition may comprise based on the total weight of said DKP composition, at least 0.0006 wt.%, preferably at least 0.0010 wt.% and at most 0.0150 wt.%, more preferably at least 0.0015 wt.% and at most 0.0100 wt.%, even more preferably at least 0.0020 wt.% and at most

[0131] 0.0095 wt.%, even more preferably at least 0.0030 wt.% and at most

[0132] 0.0090 wt.%, even more preferably at least 0.0040 wt.% and at most

[0133] 0.0090 wt.%, even more preferably at least 0.0050 wt.% and at most

[0134] 0.0090 wt.%, even more preferably at least 0.0060 wt.% and at most

[0135] 0.0090 wt.%, even more preferably at least 0.0070 wt.% and at most

[0136] 0.0090 wt.%, even more preferably 0.0080 wt.%, of at least one metal element selected from the group consisting of Cu, Fe, Zn and mixtures thereof. The metal element comprised in said DKP composition may be present at any oxidation stage, preferably the at least one metal element is present at its maximum oxidation stage. Within the context of the present invention, the maximum oxidation stage for Cu is (II), the maximum oxidation stage for Fe is (III), the maximum oxidation stage for Zn is (II).

[0137] The DKP composition preferably comprises based on the total weight of said DKP composition, at most than 0.060 wt.%, preferably at most 0.050 wt.%, more preferably at most 0.040 wt.%, even more preferably at most 0.030 wt.% of sulfate, even more preferably at most 0.020 wt.%, even more preferably at most 0.016 wt.% of SC .

[0138] The DKP composition preferably comprises at least 40 wt.%, more preferably at least 40.5 wt.%, of P2O5 based on the total weight of said DKP composition. The DKP composition according to the present invention preferably comprises at most 42 wt.%, more preferably at most 41 .5 wt.%, even more preferably 41 wt.%, of P2O5 based on the total weight of said DKP composition.

[0139] The DKP composition has preferably a D10 of at least 15 pm, more preferably at least 17 pm, even more preferably at least 19 pm, even more preferably at least 20 pm, even more preferably at least 25 pm, even more preferably at least 30 pm, even more preferably at least 35 pm, even more preferably at least 40 pm. The DKP composition according to the present invention has preferably a D10 of at most 70, even more preferably at most 65 pm, even more preferably at most 60 pm, even more preferably at most 55 pm, even more preferably at most 50 pm, more preferably at most 45 pm, even more preferably at most 40 pm.

[0140] Preferably, said DKP composition has a D10 of at least 10 pm and at most 70 pm, more preferably, at least 15 pm and at most 65 pm, even more preferably at least 20 pm and at most 65 pm, even more preferably at least 25 pm and at most 65 pm, even more preferably at least 30 pm and at most 65 pm, even more preferably at least 35 pm and at most 65 pm, even more preferably at least 40 pm and at most 65 pm.

[0141] Within the context of the present invention, a D10 is defined as a diameter expressed in pm for which 10 % by volume with regards to the total volume of particles, have smaller diameter than the D10 value. Thus, for example, a DKP composition having a D10 of 30 pm means that 10 vol.% of the total volume of DKP composition has a particle diameter smaller than 30 pm.

[0142] Given the definitions of D10, D50 and D90, for a given composition the D10 is intrinsically always lower than the D50 and the D50 is always lower than D90.

[0143] In a preferred embodiment, said DKP composition has preferably a D10 of at least 15 pm and at most 50 pm, more preferably at least 17 pm and at most 45 pm, even more preferably at least 19 pm and at most 40 pm.

[0144] The DKP composition has preferably a D50 of at least 70 pm, more preferably at least 75 pm, even more preferably at least 80 pm. The DKP composition has preferably a D50 of at most 150 pm, more preferably at most 140 pm, even more preferably at most 130 pm.

[0145] Within the context of the present invention, a D50 is defined as a diameter expressed in pm for which 50 % by volume with regards to the total volume of particles, have smaller diameter than said D50 value. Thus, for example, a DKP composition having a D50 of 120 pm means that 50 vol.% of the total volume of DKP composition has a particle diameter smaller than 120 pm.

[0146] In a preferred embodiment, said DKP composition has preferably a D50 of at least 70 pm and at most 150 pm, more preferably at least 75 pm and at most 140 pm, even more preferably at least 80 pm and at most 130 pm. The DKP composition has preferably a D90 of at least 155 pm, more preferably at least 180 pm, even more preferably at least 200 pm. The DKP composition according to the present invention has preferably a D90 of at most 700 pm, more preferably at most 650 pm, even more preferably at most 600 pm.

[0147] Within the context of the present invention, a D90 is defined as a diameter expressed in pm for which 90 % by volume with regards to the total volume of particles, have smaller diameter than said D90 value. Thus, for example, a DKP composition having a D90 of 400 pm means that 90 vol.% of the total volume of said DKP composition has a particle diameter smaller than 400 pm.

[0148] In a preferred embodiment, said DKP composition has preferably a D90 of at least 155 pm and at most 700 pm, more preferably at least 180 pm and at most 650 pm, even more preferably at least 200 pm and at most 600 pm.

[0149] In a more preferred embodiment, said DKP composition has preferably a D50 of at least 80 pm and at most 130 pm and a D10 of at least 19 pm and at most 40 pm and has preferably a D90 of at least 155 pm and at most 700 pm, more preferably at least 180 pm and at most 650 pm, even more preferably at least 200 pm and at most 600 pm.

[0150] The DKP composition has preferably a bulk density of at least 0.90, preferably at least 0.92, more preferably at least 0.94. Preferably, said DKP composition has a bulk density of at most 1 .3, preferably at most 1 .2.

[0151] In the context of the present invention, the bulk density is determined according to the method defined in DIN ISO 697.

[0152] Preferably said DKP composition is obtained by the process according to the present invention.

[0153] Preferably, said DKP composition is suitable for use in food such as baby food. Preferably said DKP composition comprises at most 5 wt.%, more preferably at most 2 wt.%, even more preferably at most 1 wt.% of water.

[0154] Each feature described above for any given embodiment may be combined with any other feature of any other embodiments of the present invention.

[0155] Method for measuring D10, D50 and D90

[0156] Within the context of the present invention, all the D10, D50 and D90 values are measured by laser granulometry (Mastersizer Hydro 200S of Malvern) with 3 minutes ultrasonication in methanol.

[0157] Method for measuring P2O5 content

[0158] Within the context of the present invention all the P2O5 wt.% may be measured by any suitable method known in the art. Preferably all the P2O5 wt.% can be measured by colorimetry of phospho-vanado-molybdate at 436 nm (yellow) (Light absorption spectrophotometry).

[0159] Method for measuring chlorate content

[0160] Whitin the context of the present invention all the mentioned chlorate contents may be measured according to the Quick Polar Pesticides Method (QuPPe). This method involves extraction with acidified methanol and LC- MS / MS measurement. Isotope labelled analogues of the compounds are used as internal standards (ILISs) to correct for volumetric variations, matrix effects and other biases. The separation of the species and the subsequent quantification is performed by a LC-MS / MS method. In particular, all the chlorate amounts measured in the context of the present patent application can be measured by application of the method M2 disclosed in the document : M. Anastassiades; A.-K. Wachtler; D. I. Kolberg; E. Eichhorn; H. Marks; A. Benkenstein; S. Zechmann; D. Mack; C. Wildgrube; A. Barth; I. Sigalov; S. Gbrlich; D. Dork; G. Cerchia, Quick Method for the Analysis of Highly Polar Pesticides in Food Involving Extraction with Acidified Methanol and LC- or IC-MS / MS Measurement, EU Reference Laboratory for pesticides requiring Single Residue Methods, European Commission, (EURL-SRM) Version 12 of the 22.07.2021 , page 52.

[0161] EXAMPLE 1

[0162] A solution of phosphoric acid (solution A) having the characteristics shown in table 1 was provided (step (i)).

[0163] A solution of KOH (alkaline composition) in water was prepared (solution (B)). The solution comprised 50 wt.% based on the total weight of solution of KOH and 2 ppm of chlorates.

[0164] The solution of KOH and the phosphoric acid solution were added simultaneously into a 20L tank (step (iia)). The content of the tank was mixed during the whole addition (step (iib)). The amount of KOH solution added was such that the final pH of the resulting mixture (the composition (C)) had a pH of 8.5-9.5 and a K2O / P2O5 molar ratio comprised between 1 .98 and 2.01 (step (ii)). The temperature of the content of the tank during addition of the KOH solution to the tank was of 112°C. The obtained composition (C) comprised DKP which was at least partially or totally dissolved in said composition (C). During the whole step (ii), the solution of KOH (solution (B)) and the solution (A) of phosphoric acid were contacted for at least 1 hour and at most 6 hours

[0165] Then, FeSO4 (material (R)) was added in the mixture already contained in the tank (step (iii)). The added amounts of FeSO4, and the addition conditions are summarized in table 1 . The addition of FeSO4 was done under stirring. The content of chlorate in ppm were measured in the DKP composition after step (ii) and after step (iii), thus before and after the addition of FeSC to the DKP composition. The % of chlorate removal is also shown in table 1 .

[0166] The obtained mixture in the tank after the addition of the FeSC was concentrated by heating the obtained mixture up to 124 °C during a time specified in table 1. Then, the mixture was dried by heating until a temperature of above 220°C is reached. The total drying step lasted for 3 hours.

[0167] The obtained dried solid DKP had very low amounts of chlorate which are shown in table 1 .

[0168] Table 1

[0169] All the DKP compositions obtained in step (iv) comprised over 99.00 wt.% of DKP and between 8 and 55 ppm of Fe and at most 1 wt.% of water and at most 0.016 wt.% of SC , based on the total weight of said DKP compositions.

Claims

CLAIMS1. A process for preparing a dipotassium hydrogen phosphate composition [hereafter, DKP composition] comprising at least the following steps of:(i). providing at least one solution [hereafter, solution (A)] comprising based on the total weight of said solution (A), at least 45 wt.% of H3PO4;(ii). contacting at least one alkaline composition comprising at least one potassic compound with said at least one solution (A), thereby forming at least one composition [hereafter, composition (C)]; said composition (C) having a molar ratio K2O / P2O5 of at least 1 .90 and at most 2.10; said alkaline composition or said solution (A) further comprising at least 0.50 ppm of chlorate;(iii). contacting at least one material able to reduce said chlorate[hereafter, material (R)] with either:• the solution (A), or• said at least one alkaline composition, or• said composition (C);(iv). drying said composition (C), thereby forming a DKP composition; said DKP composition comprising, based on the total weight of said DKP composition, at least 90.0 wt.% of DKP; wherein said material (R) is contacted in step (iii) in an amount sufficient to transfer at least 0.0090 mmol of electrons from said material (R) to said chlorate per kg of said DKP composition formed in step (iv).

2. A process according to claim 1 , wherein said material (R) is selected from the group consisting of Fe(ll) salts, Fe(0), Cu(l) salts, Cu(0), Zn(0), hydroquinone, oxalic acid, acetic acid, formic acid, phosphorous acid, H2O2 and mixtures thereof.

3. A process according to claim 1 or claim 2, wherein said material (R) comprises at least one metal selected from the group consisting ofFe(ll), Cu(l), Fe(O), Cu(O), Zn(O) and mixtures therefore, wherein said at least one metal is in metallic form or in the form of sulfate, chloride, carbonate, or an organic salt such as for instance acetate, oxalate or gluconate.

4. A process according to any of the preceding claims, wherein said material (R) is selected from the group consisting of iron (II) sulfate, iron (II) chloride, metallic iron, iron (II) nitrate, iron (II) hydroxide, iron (II) carbonate, iron (II) gluconate, iron (II) acetate, iron (II) oxalate, metallic copper, metallic zinc, copper (I) sulfate, copper (I) chloride, metallic iron, copper (I) nitrate, copper (I) hydroxide, copper (I) carbonate, copper (I) gluconate, copper (I) acetate, copper (I) oxalate and hydroquinone and oxalic acid and acetic acid and formic acid and phosphorous acid, sulfurous acid and H2O2 and mixtures thereof.

5. A process according to any of the preceding claims, wherein said material (R) is contacted in step (iii) in an amount sufficient to transfer at least 0.009 mmol, preferably at least 0.020 mmol, more preferably at least 0.050 mmol, even more preferably at least 0.100 mmol of electrons from said material (R) to said chlorate, per kg of said DKP composition formed in step (iv).

6. A process according to any of the preceding claims, wherein said material (R) is contacted in step (iii) in an amount sufficient to transfer at most 1.250 mmol, preferably at most 1.000 mmol, more preferably at most 0.500 mmol, even more preferably at most 0.7500 mol, even more preferably at most 0.200 mmol of electrons from said material (R) to said chlorate, per kg of said DKP composition formed in step (iv).

7. A process according to any of the preceding claims, wherein said material (R) comprises at least one metal element selected in the group of Fe(ll), Cu(l), Fe(0), Cu(0), Zn(0) and mixtures therefore, said material (R) being contacted in step (iii) in an amount of at least 0.5 mg, morepreferably at least 5 mg, even more preferably at least 10 mg of metal element per kg of said DKP composition formed in step (iv).

8. A process according to claim 7, wherein said material (R) is contacted in step (iii) in an amount of at most 60 mg, more preferably at most 50 mg, even more preferably at most 40 mg of metal element per kg of said DKP composition formed in step (iv).

9. A process according to any of the preceding claims, wherein said solution (A) comprise based on the total weight of said solution (A), at least 45 wt.%, preferably at least 60 wt.%, more preferably at least 70 wt.% of H3PO4.

10. A process according to any of the preceding claims, wherein said solution (A) has a weight ratio WSO4 / WP2OS below 0.030, preferably below 0.010; more preferably below 0.0050, even more preferably below 0.0010, wherein Wso4 represents the wt.% of SO4 in said solution (A) and WP205 represents the wt.% P2O5 in said solution (A).1 1 . A process according to any of the preceding claims, wherein said solution (A) has a weight ratio WF / WP2OS below 0.01 , preferably below 0.005; wherein WF represents the percentage by weight of fluor in said solution (A). WF and WP205 are based on the total weight of said solution (A).

12. A process according to any of the preceding claims, wherein said molar ratio K2O / P2O5 of said composition (C) is of at least 1 .95, more preferably at least 1 .98, even more preferably at least 1 .99.

13. A process according to any of the preceding claims, wherein the alkaline composition comprises at least one potassic compound selected from the group consisting of KOH, K2CO3, KHCO3, KH2PO4, K2HPO4, K3PO4, K4P2O7, K2H2P2O7, KPO3, K5P3O10, HKP and mixtures thereof; and wherein said alkaline composition is a solution (B) comprising based on the total weight of said solution (B), at least 40 wt.% and at most 55 wt.% of said potassic compound.

14. A DKP composition comprising based on the total weight of said DKP composition, at least 90.00 wt.%, more preferably at least 95.00 wt.%, even more preferably at least 98.00 wt.%, even more preferably at least 99.00 wt.% of DKP and at most than 4.00 ppm of chlorate, preferably at most 2.00 ppm of chlorate, more preferably at most 1 .00 ppm of chlorate, even more preferably at most 0.50 ppm of chlorate, even more preferably at most 0.10 ppm, even more preferably at most 0.05 ppm, even more preferably at most 0.03 ppm, even more preferably at most 0.02 ppm, even more preferably at most 0.01 ppm.

15. A DKP composition according to claim 14, comprising based on the total weight of said DKP composition, at most than 0.060 wt.%, preferably at most 0.050 wt.%, more preferably at most 0.040 wt.%, even more preferably at most 0.030 wt.% of sulfate, even more preferably at most 0.020 wt.%, even more preferably at most 0.016 wt.% of SC .

Images