A process for the production of lithium dihydrogen phosphate and its coproduction of inositol

Abstract

The application discloses a production method of lithium dihydrogen phosphate and its co-production of inositol, and belongs to the field of chemical technology. The method uses a plant source phytic acid solution as raw material, and uses chloroethanol quaternary amine anion exchange resin for adsorption, then sequentially carries out desorption treatment and hydrolysis treatment, and then carries out continuous separation through a simulated moving full bed device. The method can not only significantly improve production efficiency and reduce unit product energy consumption, but also can realize full-component conversion of phytate to lithium dihydrogen phosphate and inositol, and finally obtain battery-grade lithium dihydrogen phosphate (LiH2PO4) and food and drug-grade inositol (C6H 12 O6), so that the problems of high dependence of preparation of battery-grade lithium dihydrogen phosphate on high-purity lithium salt raw material, high preparation cost, great influence of inositol production on environment and low raw material utilization rate in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical industry, and particularly relates to a production method of lithium dihydrogen phosphate and co-production of inositol. BACKGROUND

[0002] As an important raw material in the field of new energy lithium battery, lithium dihydrogen phosphate is mainly used for preparing lithium iron phosphate positive electrode material. Under the background of rapid development of lithium ion battery industry, lithium dihydrogen phosphate can provide phosphorus source and lithium source at the same time. When lithium dihydrogen phosphate is used as the main raw material to synthesize lithium iron phosphate together with iron oxalate, the compaction density and energy density are superior to those of other process paths, and lithium dihydrogen phosphate has become the main process scheme and raw material of the third generation and the fourth generation of lithium iron phosphate. In addition, lithium dihydrogen phosphate can also be used for preparing electrolyte additives such as lithium manganese iron phosphate and lithium difluorophosphate.

[0003] Inositol is an important component of vitamin B family and is widely used in many fields such as medicine, food, cosmetics and feed. In the field of medicine, inositol can be used for treating diseases such as cirrhosis, fatty liver and diabetes, and can be used as an intermediate for synthesizing nicotinic acid inositol ester and inositol selenium acid ester. In the feed industry, inositol can promote animal growth and improve feed utilization efficiency.

[0004] In the prior art, the preparation of battery-grade lithium dihydrogen phosphate highly depends on high-purity lithium salt raw materials, so that the preparation cost is high. The production of inositol has a greater impact on the environment and the utilization rate of raw materials is low. Therefore, how to reduce the preparation cost of lithium dihydrogen phosphate, reduce the impact of inositol production on the environment and improve the utilization rate of inositol production raw materials is a technical problem to be solved. SUMMARY

[0005] The main purpose of the present application is to provide a production method of lithium dihydrogen phosphate and co-production of inositol, which aims to solve the problems in the prior art that the preparation of battery-grade lithium dihydrogen phosphate highly depends on high-purity lithium salt raw materials, so that the preparation cost is high, and the production of inositol has a greater impact on the environment and the utilization rate of raw materials is low.

[0006] To achieve the above-mentioned purpose, the present application provides a production method of lithium dihydrogen phosphate and co-production of inositol, which comprises the following steps:

[0007] Using chloroethanol quaternary amine anion exchange resin to adsorb phytic acid solution of plant source, anion exchange resin adsorbed with phytate ions is obtained;

[0008] Injecting mixed desorption solution containing lithium chloride and inorganic acid into the anion exchange resin adsorbed with phytate ions to perform desorption treatment, and obtaining a lithium phytate solution;

[0009] Performing hydrolysis treatment on the lithium phytate solution to obtain a mixed aqueous solution of lithium dihydrogen phosphate and inositol;

[0010] The mixed aqueous solution of lithium dihydrogen phosphate and inositol is continuously separated by using a simulated moving full-bed device to obtain a lithium dihydrogen phosphate solution and an inositol solution, respectively.

[0011] The lithium dihydrogen phosphate solution and the inositol solution are sequentially purified, concentrated and crystallized to obtain lithium dihydrogen phosphate and inositol, respectively.

[0012] Alternatively, the chloroethanol quaternary amine anion exchange resin is prepared by the following method:

[0013] The white ball resin is obtained by polymerization of styrene-divinylbenzene with methyl acrylate, methyl methacrylate or ethyl acrylate.

[0014] The white ball resin is subjected to chloromethylation catalytic reaction, and then amine reaction and quaternary amine reaction are sequentially performed by using ethylenediamine and chloroethanol to obtain the chloroethanol quaternary amine anion exchange resin.

[0015] Alternatively, the amount of the mixed desorption solution is 2bv~4bv, and the injection flow rate is 0.5bv / h~1.5bv / h.

[0016] Alternatively, the concentration of the lithium chloride is 1mol / L~5mol / L, and the concentration of the inorganic acid is 0.5mol / L~2.0mol / L.

[0017] Alternatively, the temperature of the desorption treatment is 25℃~60℃.

[0018] Alternatively, the hydrolysis treatment is realized based on the following steps:

[0019] After the phytate lithium salt solution is subjected to membrane filtration, it is placed in a high-pressure reactor, heated to a preset temperature, and then incubated at a preset pressure for a preset time period, and then cooled to room temperature to complete the hydrolysis treatment.

[0020] Alternatively, in the above hydrolysis treatment, the preset temperature is 120℃~200℃, the preset pressure is 0.6MPa~0.8MPa, and the preset time period is 2h~8h.

[0021] Alternatively, in the process of continuously separating the mixed aqueous solution of lithium dihydrogen phosphate and inositol by using a simulated moving full-bed device, the feed flow rate is 1.5mL / min~2.5mL / min, the switching time is 4.5min~5.5min, and the continuous separation time is 3.5h~4.5h.

[0022] To achieve the above purpose, the application further provides a lithium dihydrogen phosphate prepared by the above production method.

[0023] Optionally, the purity of the lithium dihydrogen phosphate is > 99.9%, and the content of metal impurities is less than 10 ppm.

[0024] Compared with the prior art, the beneficial effects that can be achieved by the present application are as follows:

[0025] 1. In the technical solution of the present application, the phytic acid solution of plant origin is used as raw material, and after adsorption by chloroethanol quaternary amine anion exchange resin, desorption treatment and hydrolysis treatment are carried out in turn, and continuous separation is carried out through a simulated moving full bed device. Not only can the production efficiency be significantly improved and the energy consumption per unit product be reduced, but also the full component conversion of phytate to lithium dihydrogen phosphate and inositol can be realized, and finally battery-grade lithium dihydrogen phosphate (LiH2PO4) and food-grade inositol (C6H 12 O6) are obtained, which has strong industrial adaptability and high economic value, and solves the problems in the prior art that the preparation of battery-grade lithium dihydrogen phosphate highly depends on high-purity lithium salt raw materials, the production cost is high, the production of inositol has a greater impact on the environment, and the raw material utilization rate is low.

[0026] 2. In the co-production process of lithium dihydrogen phosphate and inositol, the process conditions are mild, no greenhouse gases such as carbon dioxide are produced, and no pressure is caused to the environment, which meets the requirements of green chemical development.

[0027] 3. The purity of lithium dihydrogen phosphate obtained by the production method of the present application is > 99.9%, and the content of metal impurities is less than 10 ppm, which is battery-grade lithium dihydrogen phosphate, and the purity of co-produced inositol is > 98.5%, which is suitable for medical or food grade applications. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the production method for co-producing lithium dihydrogen phosphate and inositol;

[0029] Figure 2 The resin column structure front view of the simulated moving full bed device.

[0030] BRIEF DESCRIPTION OF DRAWINGS: Figure 2 In the figure, 1 is a lower discharge port, 2 is a lower manhole, 3 is a resin column, 4 is an upper manhole, 5 is an upper feed port, 6 is an upper water distributor, 7 is an upper agent loading port, 8 is a lower agent discharge port, 9 is a fixed support, and 10 is a lower water distributor. DETAILED DESCRIPTION

[0031] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0032] In order to solve the problems in the prior art that the preparation of battery-grade lithium dihydrogen phosphate is highly dependent on high-purity lithium salt raw materials, the production cost is high, the production of inositol has a greater impact on the environment, and the utilization rate of raw materials is low, the present application provides a production method for co-producing lithium dihydrogen phosphate and inositol, as shown in Figure 1 The production method comprises the following steps:

[0033] S10. Using chloroethanol quaternary amine anion exchange resin to adsorb a phytic acid solution of plant origin, to obtain an anion exchange resin adsorbed with phytate ions;

[0034] S20. Injecting a mixed desorption solution containing lithium chloride and inorganic acid into the anion exchange resin adsorbed with phytate ions, to perform desorption treatment, to obtain a lithium phytate solution;

[0035] S30. Performing hydrolysis treatment on the lithium phytate solution, to obtain a mixed aqueous solution of lithium dihydrogen phosphate and inositol;

[0036] S40. Using a simulated moving full-bed device to continuously separate the mixed aqueous solution of lithium dihydrogen phosphate and inositol, to obtain a lithium dihydrogen phosphate solution and an inositol solution, respectively;

[0037] S50. Sequentially performing purification, concentration and crystallization on the lithium dihydrogen phosphate solution and the inositol solution, respectively, to obtain lithium dihydrogen phosphate and inositol.

[0038] Optionally, in the phytic acid solution of plant origin, the plant origin can be selected from plant raw materials containing phytic acid.

[0039] Optionally, the plant raw material containing phytic acid can be corn leaching solution, rice bran leaching solution, or leaching solution mixed by corn leaching solution and rice bran leaching solution in any proportion.

[0040] Optionally, taking the rice bran leaching solution as an example, the leaching method of the phytic acid solution of plant origin can be as follows: commercially available rice bran powder is mixed with deionized water at a mass ratio of 1:10, and stirred and leached at 70°C for 2 hours; then 0.45 μm filter membrane is used for filtration, to obtain a clear phytic acid solution, and the pH value of the phytic acid solution is about 4.5.

[0041] Optionally, the method for adsorbing phytate ions on anion exchange resin by using chloroethanol quaternary amine anion exchange resin to adsorb phytic acid solution from plant sources can be as follows:

[0042] The chloroethanol quaternary amine anion exchange resin is packed in a column, and the particle size of the resin is about 0.60±50 mm; then the above-mentioned clear phytic acid solution is injected into the resin column at a flow rate of 1 bv / h until the resin is saturated, which is indicated by the fact that the concentration of phytic acid in the effluent at the outlet of the resin column is less than 2%.

[0043] Optionally, after the adsorption is completed, the impurities in the anion exchange resin adsorbed with phytate ions can be eluted with deionized water until the content of impurity ions such as sodium and potassium in the eluent is less than 5 ppm.

[0044] Optionally, the inorganic acid in the mixed desorption solution can be hydrochloric acid (HCl).

[0045] Optionally, the method for desorbing the anion exchange resin adsorbed with phytate ions by injecting a mixed desorption solution containing lithium chloride and an inorganic acid into the resin to obtain a lithium phytate solution can be as follows:

[0046] The lithium chloride and the inorganic acid are mixed in a volume ratio of 1:1 to obtain a mixed desorption solution, which is injected into the anion exchange resin adsorbed with phytate ions; when the content of lithium (Li) in the effluent at the outlet of the resin column reaches 0.5%, the desorption solution is collected, which is the lithium phytate solution, and the concentration of lithium salt in the solution is about 12%.

[0047] Optionally, in the continuous separation of the mixed aqueous solution of lithium dihydrogen phosphate and inositol by using the simulated moving packed bed device, the resin used can be a cation exchange resin or a macroporous adsorption resin, and the particle size of the resin can be 300 μm~800 μm; the mobile phase can be deionized water.

[0048] In the technical scheme of the present application, the front view of the single resin column structure of the simulated moving packed bed device can be as shown in Figure 2 The front view of the single resin column structure of the simulated moving packed bed device can be as shown in

[0049] Optionally, the separation system of the simulated moving packed bed device can be composed of 6 independent resin columns, which can be divided into four zones Z1 (1 column), Z2 (2 columns), Z3 (2 columns) and Z4 (1 column), to realize the functional division of the adsorption zone, the elution zone, the refining zone and the regeneration zone, and to achieve the purpose of continuous separation.

[0050] In the technical solution of the present application, in the process of continuously separating the mixed aqueous solution of lithium dihydrogen phosphate and inositol by using the simulated moving full-bed device, the position of the material inlet and outlet is periodically switched by the valve to move relative to the resin column, so as to simulate the movement of the resin in the opposite direction, realize continuous separation, that is, the resin is stationary, and the material flow direction is changed by the valve array switching, which is equivalent to the movement of the resin.

[0051] Further, when the mixed aqueous solution of lithium dihydrogen phosphate and inositol is continuously separated by using the simulated moving full-bed device, the mixed aqueous solution is first immersed in the Z1 zone, Li + is adsorbed by the resin, and part of the mobile phase flows out quickly; secondly, the mobile phase enters the Z2 zone, and Li + adsorbed by the resin is eluted, and a high-concentration lithium dihydrogen phosphate solution is obtained; thirdly, a small amount of mobile phase is used to flush the Z3 zone, so as to remove the residual inositol in the resin layer, and further purify the lithium dihydrogen phosphate solution; finally, the Z4 zone is flushed with the mobile phase or the regeneration liquid, and at the same time, the regenerated resin column enters the Z1 zone by switching the valve array, so as to realize circulation.

[0052] Further, when the mixed aqueous solution of lithium dihydrogen phosphate and inositol is continuously separated by using the simulated moving full-bed device, the mixed aqueous solution is first immersed in the Z1 zone, Li + is adsorbed by the resin, and part of the mobile phase flows out quickly; secondly, the mobile phase enters the Z2 zone, and Li + adsorbed by the resin is eluted, and a high-concentration lithium dihydrogen phosphate solution is obtained; thirdly, a small amount of mobile phase is used to flush the Z3 zone, so as to remove the residual inositol in the resin layer, and further purify the lithium dihydrogen phosphate solution; finally, the Z4 zone is flushed with the mobile phase or the regeneration liquid, and at the same time, the regenerated resin column enters the Z1 zone by switching the valve array, so as to realize circulation.

[0053] Alternatively, the method of sequentially purifying, concentrating and crystallizing the lithium dihydrogen phosphate solution and the inositol solution can be as follows:

[0054] The lithium dihydrogen phosphate solution is sequentially treated by nanofiltration membrane and reverse osmosis membrane to remove multivalent metal ions and part of organic small molecules, and the solution concentration is increased to 1.2 mol / L, so that the total content of impurity ions is less than 5 ppm; then, under vacuum condition, evaporation, concentration and crystallization are carried out at 60°C, the crystals are collected and dried for 12 h, and finally, the battery-grade lithium dihydrogen phosphate product with purity > 99.9% and metal impurity content less than 10 ppm is obtained;

[0055] The inositol solution is subjected to activated carbon adsorption decolorization, and the pH value is adjusted to 7.0; pre-cooled ethanol is added in a volume ratio of 1:2 for precipitation, and after standing at 0°C for 2 h, filtration, washing and drying are carried out, so as to obtain inositol crystals with purity > 98.5%, which are suitable for pharmaceutical or food grade applications.

[0056] In a possible implementation method, the preparation method of the chloroethanol quaternary amine anion exchange resin is as follows:

[0057] The white ball resin is obtained by performing a polymerization reaction on styrene-divinyl benzene and methyl acrylate, methyl methacrylate or ethyl acrylate.

[0058] The white ball resin is subjected to chloromethylation catalytic reaction, and then amine reaction and quaternary amine reaction are performed on the white ball resin by using ethylenediamine and chloroethanol in sequence, so as to obtain the chloroethanol quaternary amine anion exchange resin.

[0059] Optionally, the mass ratio of the monomers of the styrene-divinyl benzene is 90-93:7-10, in which styrene is a main monomer and divinyl benzene is a crosslinking agent. When the mass ratio of styrene to divinyl benzene is 90-93:7-10, the performance of the obtained styrene-divinyl benzene copolymer can be ensured to be mainly based on styrene, and the copolymer skeleton is prevented from being too brittle due to too high content of divinyl benzene.

[0060] Optionally, the mass ratio of the styrene-divinyl benzene to methyl acrylate, methyl methacrylate or ethyl acrylate can be 10-20:100.

[0061] Optionally, when the styrene-divinyl benzene is subjected to the copolymerization reaction with methyl acrylate, methyl methacrylate or ethyl acrylate, the implementation method can be as follows: the reaction is performed at a temperature of 75-85℃ for 6-8h, then the temperature is increased to 90-95℃, and the reaction is continuously performed for 2-4h, so as to finally obtain the white ball resin.

[0062] It should be noted that, in the preparation process of the white ball resin, in the first stage, if the temperature is higher than 85℃, the reactant material will be rapidly decomposed, the free radical concentration will be suddenly increased, the polymerization exothermic will be instantaneously generated, and the problem of “explosive polymerization” is easily caused. The temperature range of 75-85℃ is matched with the reaction monomers, the free radicals can be slowly released within 6-8h, the polymerization reaction can be uniformly performed, and the problems of bubbles, cavities or surface charring of the resin particles are avoided. After the first stage is completed, the monomer concentration in the system is reduced, and the reaction rate is slowed down. In particular, divinyl benzene and the ester monomers that are not completely reacted are easily left. At this time, the temperature is increased to 90-95℃, the diffusion rate of the free radicals is increased, the undecomposed initiators in the system are activated, the residual monomers are caused to participate in the reaction, and the influence of the residual monomers on subsequent chloromethylation and amination steps is avoided.

[0063] Optionally, the temperature of the amine reaction and quaternary amine reaction performed by using ethylenediamine and chloroethanol in sequence can be 70-80℃, and the reaction time can be 2-3h.

[0064] Optionally, in the above catalytic reaction of chloromethylation, the catalyst can be ZnCl2. When ZnCl2 is used as the catalyst, the -CH2Cl active group can be introduced.

[0065] Optionally, in the above catalytic reaction of chloromethylation, the reaction temperature can be 65-75℃, and the reaction time can be 5-6h. If the reaction temperature is lower than 65℃, the catalytic activity is insufficient, the chloromethylation efficiency is low, and the reaction period is long. If the temperature is higher than 75℃, the acrylic ester segment in the resin is thermally degraded, and the backbone structure is destroyed. Within the range of 65-75℃, the catalytic activity of ZnCl2 can be met, and the reaction efficiency and the stability of the backbone structure can be considered.

[0066] It should be noted that in the above process of preparing the chloroethanol quaternary amination anion exchange resin, the optional parameters of each step have a synergistic effect. Specifically, the monomer ratio of styrene to divinylbenzene can ensure a low to medium crosslinking degree. During the copolymerization reaction, the slow polymerization at a low temperature of 75-85℃ can form uniform initial pores. The crosslinking of the residual divinylbenzene at a high temperature of 90-95℃ can promote the stability of the pore structure. The reaction parameters under the catalysis of ZnCl2 and the backbone structure in the copolymerization stage can form a precise match. The active sites of chloromethyl (-CH2Cl) can be introduced efficiently without destroying the ester group and the pores. The parameters of ethylenediamine amination and chloroethanol quaternization can be coordinated with the density of active sites formed by chloromethylation and the pore structure, so that the specific adsorption capacity of the final resin for phytate is enhanced.

[0067] It should be noted that in the process of preparing the chloroethanol quaternary amination anion exchange resin using the above method, styrene-divinylbenzene is the crosslinked backbone of the ion exchange resin. The amount of divinylbenzene as the crosslinking agent can control the crosslinking degree of the resin to be 8-10%. Within this range of crosslinking degree, the resin will not be easily broken due to low crosslinking degree, nor will it have high mass transfer resistance due to high crosslinking degree. Secondly, in this crosslinking system, the introduction of methyl acrylate, methyl methacrylate or ethyl acrylate can further optimize the toughness of the crosslinked backbone, reduce the volume shrinkage or expansion of the resin in the "adsorption-desorption" cycle, make the swelling degree less than 15%, and thus prolong the service life of the resin.

[0068] Further, the acrylic ester monomers will be partially hydrolyzed or removed during the polymerization reaction, forming a mixed pore structure of mesopores and macropores; and phytate is myo-inositol hexakisphosphate (C6H6O 24 P6 6- ), which is a macromolecular anion. The mesopore-macropore structure of the resin can allow phytate to rapidly diffuse to the functional group sites, and the adsorption rate is increased by more than 60%, and the saturated adsorption capacity is higher.

[0069] Further, in the above preparation method, through the three-step reaction of “chloromethylation -> ethylenediamine amination -> chloroethanol quaternary amination”, a chloroethanol quaternary ammonium group (-N + (CH2CH2OH)3Cl - ) can be introduced in a targeted manner, and the structural characteristics of the group make it have high selectivity and strong binding force for the adsorption of phytate, which is specifically manifested as follows: the quaternary ammonium group is a strong alkaline anion exchange group, and has high positive charge density, can form multi-point electrostatic combination with the six-membered negative charge (C6H6O 24 P6 6- ) of phytate, compared with weak alkaline anion resins (such as primary amine and secondary amine groups), the strong alkaline resin can still maintain strong positive charge under acidic conditions, and will not cause the adsorption capacity to decrease due to acid protonation, and can stably adsorb phytate; and the weak alkaline resin is easy to be protonated in an acidic environment, and the adsorption capacity for anions is significantly weakened; secondly, the chloroethanol chain (-CH2CH2OH) on the quaternary ammonium group has a hydroxyl group (-OH), and the group can form a hydrogen bond with the hydroxyl group in the phytate molecule, and the action mode of “electrostatic combination + hydrogen bond coordination” makes the resin have much higher adsorption selectivity for phytate than other small molecule anions; in addition, in a plant source phytate solution, a small amount of Cl - , PO4 3- is usually contained, the resin can preferentially adsorb phytate, reduce the interference of impurity anions, and the purity of the obtained lithium phytate solution is higher.

[0070] Further, when ZnCl2 is selected as the catalyst, the -CH2Cl active group can be efficiently introduced on the benzene ring of the styrene-divinylbenzene skeleton, so that the exchange capacity of the resin is stable, and the instability of the phytate adsorption efficiency caused by the fluctuation of the exchange capacity is avoided.

[0071] Further, in the above preparation method, after the chloromethylation catalytic reaction, amination is first carried out by using ethylenediamine, then the amino group (-NH2) of the ethylenediamine can react with -CH2Cl to introduce a secondary amine or tertiary amine group (-N (CH2CH2NH2)-) on the crosslinked skeleton, so as to provide a reaction site for subsequent quaternary amination; and then quaternary amination is carried out by using chloroethanol, and the -Cl of the chloroethanol can react with the nitrogen atom on the amine group to form a quaternary ammonium salt (-N + (CH2CH2OH)3Cl - ), and this step has no small molecule by-product, and the amount of chloroethanol used is controllable, so that the generation of tertiary amine residues is avoided.

[0072] Therefore, in the technical scheme of the present application, when the mixed desorption solution containing lithium chloride and inorganic acid is used to desorb the anion exchange resin adsorbed with phytate ions, Li +Can compete with the positive charge of quaternary ammonium group for binding sites, destroy electrostatic interaction; inorganic acid, such as hydrochloric acid, provides H + Can combine with the hydroxyl group of phytate, destroy hydrogen bond interaction; both through the synergistic effect of "reversible electrostatic + hydrogen bond binding", the desorption rate of phytate reaches more than 98%, and the resin after desorption can restore the positive charge state of quaternary ammonium group by water washing, the recycling times are significantly improved, and the production cost can be reduced. In addition, the chloroethanol quaternary amine anion exchange resin of the application contains strong alkaline quaternary ammonium group (-N + R3) will not be protonated under acidic conditions, while the weak alkaline amine group will be protonated and deactivated, still maintaining a positive charge, and normally adsorbing phytate; compared with weak alkaline anion resin, the resin does not need to adjust the pH value of the raw material liquid, and can be directly fed and adsorbed, simplifying the process steps; and the cross-linked structure of the resin skeleton contained therein is stable, and will not be excessively swollen in high-concentration salt solution, so that the resin can be avoided from being compressed and the column pressure from being increased due to swelling; at the same time, the binding force of quaternary ammonium group and Cl - is weaker than that with phytate, and high-concentration Cl - Will not cause the resin to be deactivated in advance.

[0073] In a possible implementation, the amount of the mixed desorption liquid is 2bv ~4bv, and the flow rate of injection is 0.5bv / h ~1.5bv / h.

[0074] It should be noted that when the amount of the mixed desorption liquid is 2bv ~4bv, the total amount of phytate adsorbed by the resin + the excess driving force can be covered, so that more than 95% of the phytate in the resin can be eluted, the desorption rate is further improved to more than 98%, and the concentration of phytate in the desorption liquid is too low due to excessive amount, which increases the energy consumption of subsequent concentration.

[0075] Further, when the flow rate of injection is 0.5bv / h ~1.5bv / h, Li + (competes for electrostatic sites) and H + (breaks hydrogen bonds) in the desorption liquid can fully act, if the flow rate is lower than 0.5bv / h, the treatment efficiency will be reduced; if the flow rate is higher than 1.5bv / h, the contact time is too short, the desorption liquid and the resin do not fully contact, and part of the phytate is not fully eluted and flows out with the desorption liquid, which causes the concentration of phytate in the desorption liquid to fluctuate, and the residual phytate in the resin increases.

[0076] In a possible implementation, the concentration of lithium chloride is 1mol / L ~5mol / L, and the concentration of inorganic acid is 0.5mol / L ~2mol / L.

[0077] It should be noted that when the concentration of the lithium chloride is 1 mol / L to 5 mol / L, the Li + can compete with the phytate for the positive charge sites of the quaternary ammonium groups on the resin; while the Li + has a small radius and a high charge density, and can effectively replace the phytate to bind with the quaternary ammonium groups, thereby destroying the electrostatic binding force between the phytate and the resin, and making the phytate fall off from the resin into the desorption solution; when the concentration of the inorganic acid is 0.5 mol / L to 2 mol / L, the H + can bind with the hydroxyl groups in the phytate molecules, interfere with the hydrogen bond interaction between the phytate and the resin, and promote the desorption of the phytate from the resin.

[0078] Further, the lithium chloride can be synergized with the inorganic acid through the concentration to make the desorption rate of the phytate reach more than 98%; if the concentration of the lithium chloride is lower than 1 mol / L, the Li + has insufficient competition ability; if it is higher than 5 mol / L, the cost of the desorption solution and the subsequent processing difficulty will be increased; if the concentration of the inorganic acid is lower than 0.5 mol / L, the destruction ability to the hydrogen bond is limited; if it is higher than 2 mol / L, the resin structure may be damaged to a certain extent, and the burden of the subsequent processing such as neutralization is increased.

[0079] In a possible implementation, the temperature of the desorption treatment is 25°C to 60°C.

[0080] It should be noted that in the desorption treatment, when the temperature of the desorption treatment is 25°C to 60°C, the molecular motion efficiency can be improved, the action of the desorption solution and the phytate can be strengthened, the desorption time can be shortened, and the desorption rate can be improved. Specifically, in this temperature range, the Li + diffusion coefficient can be significantly improved, thereby accelerating the H + reaction rate with the hydroxyl groups, shortening the desorption time, and stabilizing the desorption rate to be more than 95%. If the temperature is too high, for example, higher than 60°C, the volatilization of the desorption solution will be intensified, and the phytate may be hydrolyzed, which in turn reduces the purity of the desorption solution; if the temperature is lower than 25°C, the molecular motion is slow, the Li + diffusion rate in the resin pore channel is low, and the H + reactivity with the hydroxyl groups of the phytate is insufficient.

[0081] In a possible implementation, the hydrolysis treatment is implemented based on the following steps:

[0082] After the lithium phytate solution is subjected to membrane filtration, it is placed in a high-pressure reactor, heated to a preset temperature, and then kept at a preset pressure for a preset time length, and then cooled to room temperature, to complete the hydrolysis treatment.

[0083] Optionally, the high-pressure reactor can be a high-pressure reaction kettle.

[0084] Optionally, the membrane filtration can be performed by first using a ceramic membrane with a pore size of 0.45 μm to 0.5 μm, and then using a nanofiltration membrane with a molecular weight cut-off of 1000 D for concentration.

[0085] In one possible implementation, in the hydrolysis process, the preset temperature is 120°C to 200°C, the preset pressure is 0.6 MPa to 0.8 MPa, and the preset time length is 2 h to 8 h.

[0086] It should be noted that the preset pressure is the autogenous pressure in the high-pressure reactor during the hydrolysis process, that is, as the reaction temperature increases and the reaction time extends, the pressure in the reactor gradually increases and can finally be maintained at 0.6 MPa to 0.8 MPa.

[0087] It should be noted that in the hydrolysis process, the membrane filtration can improve the concentration of the lithium phytate solution and enhance the efficiency of the hydrolysis reaction. During the hydrolysis reaction in the high-pressure reactor, the conversion of “lithium phytate → lithium dihydrogen phosphate + inositol” occurs. In the phytate molecular structure, the phosphate group is connected to the inositol skeleton through a “C-O-P” bond, which has a high bond energy. When the temperature is 120°C to 200°C, enough energy can be provided to break the C-O-P bond, so that each phytate molecule is completely hydrolyzed into 6 lithium dihydrogen phosphate molecules (LiH2PO4) and 1 inositol molecule (C6H 12 O6), without any partial hydrolysis product remaining. Secondly, when the preset pressure is 0.6 MPa to 0.8 MPa, the solution can be prevented from boiling vigorously at high temperatures, ensuring that the reaction is carried out in a homogeneous liquid environment and reducing local concentration unevenness caused by boiling. Within the preset time length of 2 h to 8 h, a high hydrolysis conversion rate can be achieved for high-concentration lithium phytate at a high temperature of 200°C, meeting the demand for efficient production, while for low-concentration lithium phytate, the hydrolysis is ensured to be complete at 120°C, and degradation of inositol caused by excessive reaction time is avoided.

[0088] In the hydrolysis process described above, the synergistic effect of each step can achieve efficient conversion of “lithium phytate → mixed hydrolysis solution”.

[0089] In one possible implementation, in the process of continuously separating the mixed aqueous solution of lithium dihydrogen phosphate and inositol using the simulated moving packed bed device, the feed flow rate is 1.5 mL / min to 2.5 mL / min, the switching time is 4.5 min to 5.5 min, and the continuous separation time is 3.5 h to 4.5 h.

[0090] It should be noted that the switching time refers to the time interval for periodically switching the connection relationship of the resin column "feed port, mobile phase inlet, product outlet, and waste liquid outlet" in the SMB system according to the preset program.

[0091] Optionally, in the process of continuously separating the mixed aqueous solution of lithium dihydrogen phosphate and inositol by using the simulated moving bed chromatography device, the cation exchange resin can be selected as the stationary phase, and deionized water can be used as the mobile phase, and the system partition is greater than or equal to 4.

[0092] It should be noted that when the SMB is used to continuously separate the mixed aqueous solution of lithium dihydrogen phosphate and inositol, compared with the traditional fixed bed chromatography, the SMB system feeds and produces synchronously, and when the continuous separation time is 3.5h-4.5h, the Li+ recovery rate is greater than or equal to 98%, and the inositol recovery rate is greater than or equal to 95%, which is much higher than that of the traditional extraction process; secondly, when the feed flow rate is 1.5mL / min-2.5mL / min, different total amounts of mixed solution can be adapted without replacing the resin column or adjusting the distribution of the functional area, thereby reducing the operation difficulty.

[0093] In order to achieve the above-mentioned purpose, the application further provides a lithium dihydrogen phosphate prepared by the above production method.

[0094] Optionally, the purity of the lithium dihydrogen phosphate is greater than 99.9%, and the content of metal impurities is less than 10ppm, which is a battery-grade lithium dihydrogen phosphate.

[0095] By the production method of lithium dihydrogen phosphate and inositol according to the application, the prepared lithium dihydrogen phosphate completely meets the "high-end power battery" index requirements in "Battery-grade lithium dihydrogen phosphate" (YS / T 1563.1-2022). The purity of the inositol produced by coproduction is greater than 98.5%, which meets the "premium product" standard in "Food additives-inositol" (GB 1886.237-2016).

[0096] In the technical scheme of the application, the separation of lithium dihydrogen phosphate and inositol is completed synchronously relying on the SMB system, and the subsequent purification is respectively carried out by "membrane separation-crystallization" and "adsorption-precipitation", which are both based on aqueous solution system, without switching solvents to reduce material transfer loss, and the ethanol waste liquid produced in the inositol purification can be used for washing the crystal after the lithium dihydrogen phosphate crystallization, realizing "waste resource", and reducing the material consumption of the whole process. The production of lithium dihydrogen phosphate and inositol is coordinated, the resources are recycled, and the cost is optimized, realizing the transformation of agricultural waste into treasure, and promoting the integration development of circular economy and green manufacturing.

[0097] Example 1

[0098] A production method of lithium dihydrogen phosphate and inositol, comprising the following steps:

[0099] S10. Based on the implementation of S101 and S102, specifically as follows:

[0100] S101. Mix commercially available rice bran powder with deionized water at a mass ratio of 1:10, stir and extract at 70°C for 2h. After the extraction is completed, filter with a 0.45μm filter membrane to obtain a clear phytic acid solution with a pH of about 4.5;

[0101] S102. Mix styrene-divinylbenzene and methyl acrylate at a mass ratio of 10-100, react at 75°C for 8h, then increase the temperature to 90°C and continue to react for 4h to obtain white spherical resin. Perform chloromethylation catalytic reaction on the white spherical resin using ZnCl2 at 65°C for 6h, then perform amine and quaternary amine reactions on the chloromethylation resin using ethylenediamine and chloroethanol at 70°C, respectively, for 3h to obtain chloroethanol quaternary amine anion exchange resin. Pack the chloroethanol quaternary amine anion exchange resin in a column, then inject the phytic acid solution obtained in S10 into the column at a flow rate of 1.0bv / h until the resin is saturated, which is indicated by the phytic acid concentration in the outlet stream of the resin column being less than 2%. After the adsorption is completed, wash the impurities in the resin with deionized water until the content of sodium, potassium and other impurity ions in the eluate is less than 5ppm to obtain anion exchange resin adsorbed with phytate ions.

[0102] S20. Mix 1.5mol / L lithium chloride (LiCl) solution and 1.0mol / L hydrochloric acid (HCl) solution at a volume ratio of 1:1 to obtain a mixed desorption solution, then inject the mixed desorption solution into the anion exchange resin adsorbed with phytate ions obtained in S20 at a flow rate of 1.0BV / h at 40°C, and the amount is 3bv. When the lithium content in the outlet of the resin column reaches 0.5%, start collecting the desorption solution, i.e. the lithium phytate salt solution, and its concentration is about 12.0%.

[0103] S30. Remove the suspended solids in the lithium phytate salt solution obtained in S20 by passing it through a ceramic membrane with a pore size of 0.45-0.5μm, then concentrate it using a nanofiltration membrane with a molecular weight cutoff of 1000D, and the potassium phytate concentration can reach 35%. Then place the concentrated lithium phytate salt solution in a high-pressure reaction kettle, heat it to 160°C, maintain the pressure at 0.8MPa, and react for 2h. After the reaction is completed, cool it to room temperature, remove a small amount of precipitate by filtration, and obtain a mixed hydrolysate containing lithium dihydrogen phosphate and inositol.

[0104] S40. A four-zone simulated moving bed is set up with cation exchange resin as the stationary phase and deionized water as the mobile phase. The four zones are Z1 (1 column), Z2 (2 columns), Z3 (2 columns), and Z4 (1 column). The six resin columns in the four zones are 100% filled with cation exchange resin. The sealing of all pipelines and solenoid valve interfaces is checked. Then the mobile phase pump is turned on to flush the system and remove air bubbles from the resin columns and pipelines. The system is set to a feed flow rate of 2.0 mL / min. The mixed hydrolysate of lithium dihydrogen phosphate and inositol obtained in S30 is injected, and periodic switching is performed by the solenoid valve array to make the six columns circulate through the functional zones in the order of "Z1→Z2→Z3→Z4→Z1" with a switching time of 5 min. After continuous separation for 4.0 h, lithium dihydrogen phosphate solution and inositol solution are obtained, respectively. The purity of the lithium dihydrogen phosphate solution is ≥99.5%, the lithium concentration is about 0.75 mol / L, and the purity of the inositol solution is ≥98%, the concentration is about 0.05 mol / L.

[0105] S50. Based on S501~S502, the implementation is as follows:

[0106] S501. The lithium dihydrogen phosphate solution obtained in S40 is treated by nanofiltration membrane and reverse osmosis membrane in sequence. The nanofiltration membrane can remove multivalent metal ions and part of small organic molecules, and the reverse osmosis membrane is used to concentrate the lithium dihydrogen phosphate solution. After treatment, the concentration of lithium dihydrogen phosphate is increased to 1.2 mol / L, and the total content of impurity ions is less than 5 ppm.

[0107] S501. The lithium dihydrogen phosphate solution obtained in S501 is evaporated, concentrated and crystallized at 60°C under vacuum conditions. The crystals are collected and dried for 12 h to obtain a battery-grade lithium dihydrogen phosphate product with a purity of not less than 99.9% and a metal impurity content of less than 10 ppm.

[0108] S503. The inositol solution obtained in S501 is subjected to activated carbon adsorption decolorization, the pH is adjusted to 7.0, pre-cooled ethanol is added in a volume ratio of 1:2 for precipitation, and the mixture is filtered after standing at 0°C for 2 h, washed and dried to obtain inositol crystals with a purity of about 98.5%, which are suitable for pharmaceutical or food grade applications.

[0109] In Example 1, set up Comparative Example 1

[0110] Comparative Example 1 differs from Example 1 in that in S10, a styrene-based anion exchange resin is used instead of chloroethanol quaternary amine anion exchange resin to adsorb the phytic acid solution from plant sources. The remaining steps are the same as those of Example 1.

[0111] In Example 1, set up Comparative Example 2

[0112] The difference between Comparative Example 2 and Example 1 is that, in S10, an acrylic anion exchange resin is used instead of the chloroethanol quaternized anion exchange resin for adsorbing the plant-derived phytic acid solution. The remaining steps are the same as in Example 1.

[0113] The adsorption capacity and adsorption rate of the anion exchange resin, the concentration of lithium phytate solution, and the purity and yield of lithium dihydrogen phosphate and inositol were determined in Examples 1, 2, and 2, respectively. The results are shown in Table 1.

[0114] Table 1

[0115]

[0116] Analysis of the data in Table 1 shows that, firstly, in terms of the adsorption capacity and adsorption rate of the anion exchange resin for phytic acid solutions from plant sources, Example 1 is significantly superior to Comparative Examples 1 and 2. This is because the chloroethanol quaternized anion exchange resin used in Example 1 can bind phytate ions through a combination of electrostatic attraction and hydrogen bonding, and its macroporous structure allows for free diffusion of phytate ions, resulting in high internal surface utilization. Therefore, its adsorption capacity and efficiency are optimal. In contrast, the styrene-based resin used in Comparative Example 1 has a trimethylamine quaternary ammonium group (-N) as its functional group. + Phytate (CH3)3 is bound by a single electrostatic attraction, and the hydrophobic effect of its methyl group repels the hydrophilic group of phytate, weakening the binding force. Furthermore, its small-pore structure and rigid benzene ring skeleton result in significant steric hindrance, making it difficult for phytate to enter the pores and forcing it to adsorb only on the surface, thus significantly reducing capacity and efficiency. The acrylic resin in Comparative Example 2 has mostly dimethylamino (-N+(CH3)2H) functional groups, with a lower charge density than quaternary ammonium groups, resulting in weaker electrostatic interactions with phytate. Moreover, its gel structure can hardly accommodate large phytate molecules, allowing adsorption only through a few groups on its outer surface, thus exhibiting the worst performance.

[0117] Secondly, regarding the concentration of the lithium phytate solution obtained through S20, the reduced adsorption capacity and adsorption rate of the anion exchange resins in Comparative Examples 1 and 2 lead to a significant decrease in the concentration of the lithium phytate solution obtained after desorption treatment. Consequently, the content of lithium dihydrogen phosphate and inositol in the resulting mixed aqueous solution after subsequent hydrolysis treatment decreases substantially. In contrast, the concentration of the lithium phytate solution obtained in Example 1 can be maintained at a higher value, thus having a positive effect on subsequent treatment and significantly increasing the content of lithium dihydrogen phosphate and inositol.

[0118] In addition, the styrene and acrylic anion exchange resins used in Comparative Examples 1 and 2 have poor selectivity for small molecular impurities in terms of the purity of lithium dihydrogen phosphate and inositol, which can cause impurity ions to enter the solution with the phytate after desorption treatment, the total content of impurities still exceeds the standard, and the final lithium dihydrogen phosphate product cannot meet the purity requirements of battery grade; and the ethylene and acrylic anion exchange resins have weak adsorption capacity for plant-derived pigments, which can cause the color of the inositol solution to deepen, which is lower than the required standard; at the same time, the acrylic resin has insufficient interception of sugar impurities, which can cause the purity of the final inositol product to decrease, which does not meet the application requirements of food and drug grade. In terms of yield, the double decline of the adsorption rate and the hydrolysis conversion rate of Comparative Examples 1 and 2 superimposes the loss of concentration, which can cause the yield of lithium dihydrogen phosphate and inositol to decrease and the production cost to increase. Compared with this, the purity and yield of lithium dihydrogen phosphate and inositol obtained in Example 1 are both higher, which meet the required standard.

[0119] According to the analysis of Table 1, in the technical scheme of the present application, the dual action force (electrostatic + hydrogen bond) and macroporous structure adaptability of the chloroethanol quaternary amine anion exchange resin are excellent in phytate adsorption performance, and have a synergistic effect with the subsequent process, which is the core material to ensure the efficient operation of the co-production process and cannot be replaced.

[0120] Example 2

[0121] A production method of lithium dihydrogen phosphate co-produced with inositol, comprising the following steps:

[0122] S101 in S10 is the same as that in Example 1;

[0123] S102. The white ball resin is obtained by mixing styrene-divinylbenzene and methyl methacrylate at a mass ratio of 20-100, reacting at 85°C for 6h, then increasing the temperature to 95°C and continuing to react for 2h; the white ball resin is subjected to chloromethylation catalytic reaction with ZnCl2 at 75°C for 5h, and then subjected to amine reaction with ethylenediamine and quaternary amination reaction with chloroethanol at 80°C, respectively, for 2h to obtain the chloroethanol quaternary amine anion exchange resin; the chloroethanol quaternary amine anion exchange resin is packed in a column, and then the phytate solution obtained in S10 is injected into the column at a flow rate of 1.0 bv / h until the resin is saturated, which is marked by the phytate concentration of the outlet effluent of the resin column being less than 2%; after the adsorption is completed, the impurities in the resin are eluted with deionized water until the content of sodium, potassium and other impurity ions in the eluate is less than 5 ppm, to obtain the anion exchange resin adsorbed with phytate ions.

[0124] S20. A 1.0 mol / L lithium chloride (LiCl) solution is mixed with a 0.5 mol / L hydrochloric acid (HCl) solution at a volume ratio of 1:1 to obtain a mixed desorption solution. Then, the mixed desorption solution is injected into the anion exchange resin in S20, which has adsorbed phytate ions, at a flow rate of 0.5 BV / h at 60°C, and the amount is 4 BV. When the lithium content at the outlet of the resin column reaches 0.5%, the desorption solution, i.e., lithium phytate solution, is collected, and the concentration is about 12.0%.

[0125] S30. The lithium phytate solution obtained in S20 is passed through a ceramic membrane with a pore size of 0.45-0.5 μm to remove suspended matter, and then concentrated using a nanofiltration membrane with a molecular weight cutoff of 1000 D, and the potassium phytate concentration can reach 35%. Then, the concentrated lithium phytate solution is placed in a high-pressure reaction kettle, heated to 120°C, and maintained at a pressure of 0.6 MPa for 8 h. After the reaction is completed, it is cooled to room temperature, and a small amount of precipitate is removed by filtration to obtain a mixed hydrolysate containing lithium dihydrogen phosphate and inositol.

[0126] S40. A four-zone simulated moving bed apparatus is set up using cation exchange resin as the stationary phase and deionized water as the mobile phase. The four zones are Z1 (1 column), Z2 (2 columns), Z3 (2 columns), and Z4 (1 column). The six resin columns in the four zones are 100% filled with cation exchange resin, and the sealing of all pipelines and solenoid valve interfaces is checked. Then, the mobile phase pump is turned on to flush the system and remove air bubbles in the resin columns and pipelines. The system is set to a feed flow rate of 2.5 mL / min, and the mixed hydrolysate containing lithium dihydrogen phosphate and inositol obtained in S30 is injected. Periodic switching is performed by the solenoid valve array to make the six columns circulate through the functional zones in the order of "Z1→Z2→Z3→Z4→Z1" with a switching time of 4.5 min. After continuous separation for 4.5 h, lithium dihydrogen phosphate solution and inositol solution are obtained, respectively. The purity of the lithium dihydrogen phosphate solution is ≥99.5%, and the lithium concentration is about 0.75 mol / L. The purity of the inositol solution is ≥98%, and the concentration is about 0.05 mol / L.

[0127] S50 is the same as in Example 1.

[0128] Through S10-S50, a battery-grade lithium dihydrogen phosphate product with a purity of not less than 99.9% and a metal impurity content of less than 10 ppm is obtained. At the same time, an inositol crystal with a purity of about 98.5% is obtained, which is suitable for pharmaceutical or food grade applications.

[0129] In Example 2, Comparative Example 3 is set up.

[0130] Comparative Example 3 differs from Example 2 in that in S40, a fixed bed chromatographic column is used to separate the mixed aqueous solution of lithium dihydrogen phosphate and inositol. The rest is the same as in Example 2.

[0131] The technical solutions of Example 2 and Comparative Example 3 are analyzed from the aspects of product concentration, purity and resin utilization rate.

[0132] Specifically, first, in terms of separating the mixed aqueous solution of lithium dihydrogen phosphate and inositol, the SMB device of Example 2 realizes continuous separation by making each column sequentially undergo “adsorption → elution → refinement → regeneration” through 6 fixed bed columns in series + periodic valve switching, so that the feed is not stopped and the product is continuously produced. During continuous operation, the mixed solution can be stably treated without production interruption. In contrast, in the technical solution of Comparative Example 3, a fixed bed chromatographic column is used to separate the mixed aqueous solution of lithium dihydrogen phosphate and inositol, which needs to stop the feed during the switching stage, and the separation process cannot be continuous, which is time-consuming and labor-intensive, and cannot meet the needs of industrial large-scale production. Secondly, in terms of product concentration and purity, the SMB device of Example 2 can precisely control the material flow direction through “multi-column zoning”, ensuring that the lithium dihydrogen phosphate and inositol production fluids are not cross-contaminated and the purity is stable. The fixed bed chromatographic column used in Comparative Example 3 is prone to cross-contamination of lithium dihydrogen phosphate and inositol production fluids, resulting in significant fluctuations in purity, which can cause some batches to fail to meet the standards and reduce production, thereby increasing unit cost.

[0133] Therefore, in the technical solution of the present application, the SMB device realizes the co-production of lithium dihydrogen phosphate and inositol through continuous, high utilization rate and high precision separation, which can not only meet the stringent purity requirements of battery-grade lithium dihydrogen phosphate, but also realize the high-value recovery of inositol. The fixed bed chromatographic column cannot achieve this purpose.

[0134] Example 3

[0135] A production method for co-producing lithium dihydrogen phosphate and inositol, comprising the following steps:

[0136] S101 in S10 is the same as that in Example 1;

[0137] S102. The white ball resin is obtained by mixing styrene-divinylbenzene with ethyl acrylate at a mass ratio of 15-100, reacting at 80°C for 7h, then increasing the temperature to 95°C and continuing to react for 3h; the white ball resin is subjected to chloromethylation catalytic reaction with ZnCl2 at 70°C for 5h, and then subjected to amination and quaternary amination reaction with ethylenediamine and chloroethanol at 75°C in sequence for 2h to obtain a chloroethanol quaternary amine anion exchange resin; the chloroethanol quaternary amine anion exchange resin is packed in a column, and the phytic acid solution obtained in S10 is injected into the column at a flow rate of 1.0 bv / h until the resin is saturated, which is indicated by the phytic acid concentration in the effluent from the outlet of the resin column being less than 2%; after the adsorption is completed, the impurities in the resin are eluted with deionized water until the content of sodium, potassium and other impurity ions in the eluate is less than 5 ppm, and an anion exchange resin adsorbed with phytate ions is obtained.

[0138] S20. A mixed desorption solution is obtained by mixing 5.0 mol / L lithium chloride (LiCl) solution with 2.0 mol / L hydrochloric acid (HCl) solution at a volume ratio of 1:1, and then the mixed desorption solution is injected into the anion exchange resin adsorbed with phytate ions obtained in S20 at a flow rate of 1.5 BV / h at 25°C, and the amount of the mixed desorption solution is 2bv; when the lithium content in the outlet of the resin column reaches 0.5%, the desorption solution, i.e. lithium phytate solution, is collected, and the concentration thereof is about 12.0%.

[0139] S30. The lithium phytate solution obtained in S20 is subjected to ceramic membrane filtration with a pore size of 0.45-0.5 μm to remove the suspended matter, and then concentrated by using a nanofiltration membrane with a molecular weight cut-off of 1000D, so that the concentration of the lithium phytate solution can reach 35%; the concentrated lithium phytate solution is placed in a high-pressure reaction kettle, heated to 200°C, and kept at a pressure of 0.7 MPa for 2h; after the reaction is completed, the solution is cooled to room temperature, and a small amount of precipitate is removed by filtration to obtain a mixed hydrolysate containing lithium dihydrogen phosphate and inositol.

[0140] S40. A four-zone simulated moving bed device is set up with cation exchange resin as the stationary phase and deionized water as the mobile phase. The four zones are Z1 (1 column), Z2 (2 columns), Z3 (2 columns), and Z4 (1 column). The six resin columns in the four zones are 100% filled with cation exchange resin. The sealing of all pipelines and solenoid valve interfaces is checked. Then the mobile phase pump is turned on to flush the system and remove air bubbles from the resin columns and pipelines. The system is set to a feed flow rate of 1.5 mL / min. The mixed hydrolysate containing lithium dihydrogen phosphate and inositol obtained in S30 is injected, and periodic switching is performed by the solenoid valve array to make the six columns circulate through the functional zones in the order of “Z1→Z2→Z3→Z4→Z1” with a switching time of 3.5 min. After continuous separation for 3.5 h, lithium dihydrogen phosphate solution and inositol solution are obtained, respectively. The purity of the lithium dihydrogen phosphate solution is ≥99.5%, the lithium concentration is about 0.75 mol / L, and the purity of the inositol solution is ≥98%, and the concentration is about 0.05 mol / L.

[0141] S50 is the same as in Example 1.

[0142] Through S10-S50, a battery-grade lithium dihydrogen phosphate product with a purity of not less than 99.9% and a metal impurity content of less than 10 ppm is obtained. At the same time, an inositol crystal with a purity of about 98.5% is obtained, which is suitable for pharmaceutical or food grade applications.

[0143] In Example 3, set up Comparative Example 4

[0144] Comparative Example 4 differs from Example 3 in that in S20, the concentration of LiCl is 6.5 mol / L, the concentration of HCl is 3 mol / L, and LiCl and HCl are mixed in a volume ratio of 2:1 to obtain a mixed desorption solution. Then, the mixed desorption solution is injected into the anion exchange resin in S20 at a flow rate of 2.5 BV / h at 70°C, and the amount used is 5 bv. In S30, the concentrated lithium phytate solution is placed in a high-pressure reaction kettle, heated to 300°C, and maintained at a self-pressure of 1.0 MPa for 5 h. In S40, the system is set to a feed flow rate of 3.5 mL / min, the switching time is 6.5 min, and the continuous separation time is 7 h. The rest is the same as in Example 3.

[0145] The purity of lithium dihydrogen phosphate and inositol obtained in Example 3 and Comparative Example 4, respectively, is determined.

[0146] The purity of lithium dihydrogen phosphate of Example 3 is greater than 99.9%, and the content of metal impurities is less than 8 ppm, which is a battery-grade lithium dihydrogen phosphate; the purity of inositol is greater than 98.5%, which is a pharmaceutical-grade and food-grade inositol. In contrast, the purity of lithium dihydrogen phosphate obtained in Comparative Example 4 is less than 90%, and the content of metal impurities is 20 ppm to 30 ppm, which cannot meet the requirements of battery grade; and the purity of inositol is less than 90%, which cannot meet the requirements of pharmaceutical grade or food grade. The reasons for this phenomenon are as follows:

[0147] In the technical scheme of Comparative Example 4, HCl is 3 mol / L, which will produce a strong acid environment, accelerate the "de-crosslinking" reaction of the styrene-divinylbenzene crosslinked skeleton of the resin, cause the collapse of the resin pore channel, and the high temperature of 70°C will further intensify the "de-alkylation" of the functional groups of the resin, causing the quaternary ammonium group to decompose into a tertiary amine, losing the positive charge site; at the same time, LiCl 6.5 mol / L is an oversaturated concentration, and the ionic strength is too high, which will cause the resin to swell excessively, release trace amounts of metal impurities, and enter the desorption solution with phytate, ultimately causing the concentration of lithium phytate salt solution to decrease significantly and the impurity content to increase. During the hydrolysis treatment process, when the temperature is 300°C, the inositol in the solution will undergo a dehydration and carbonization reaction, and the hydroxyl groups (-OH) will successively dehydrate to form double bonds, and finally generate black carbon residue, and the high pressure of 1.0 MPa will intensify the reaction rate, and after 5 h, the carbonization degree will be further intensified; and part of the lithium dihydrogen phosphate in the solution will undergo a thermal decomposition reaction at 300°C to generate lithium diphosphate, which has low solubility in water and will precipitate; ultimately, the conversion rate of lithium dihydrogen phosphate and inositol will be reduced, and the impurity content will increase. In the continuous separation process, the feed flow rate of 3.5 mL / min will exceed the "resin adsorption-elution equilibrium" capacity, which will cause the inositol content in the lithium dihydrogen phosphate product to increase, and the Li + content in the inositol product will not meet the standard; at the same time, the switching of 6.5 min will cause the resin in the adsorption zone to be completely saturated, and the residence time of the resin in the regeneration zone will be too long, which will cause H + to be excessively adsorbed, and after the SMB is continuously operated for 7 h, the resin capacity will be significantly reduced, and the concentrations of lithium dihydrogen phosphate and inositol will be significantly reduced. In summary, the purity of the lithium dihydrogen phosphate product and the inositol product will be significantly reduced, and the impurity content will increase, which cannot meet the requirements.

[0148] In the technical scheme of Example 3, the "LiCl concentration + HCl concentration + temperature + flow rate" in the desorption treatment has a synergistic effect, in which the Li + provides a high concentration of Li +By using hydrogen bonding interference to assist desorption, the two work synergistically to achieve a desorption rate of over 95%, while avoiding the problems of excessive resin swelling and resin skeleton corrosion caused by excessive concentration of a single component; and at 25℃, it can enhance Li + With H + The diffusion rate, matched to a flow rate of 1.5 BV / h, ensures complete desorption of phytate. During hydrolysis, 200℃ provides sufficient energy to break the COP bonds of phytate, and a pressure of 0.7 MPa maintains the solution in a liquid state. This temperature is below the inositol carbonization threshold and lithium dihydrogen phosphate decomposition threshold, ensuring no side reactions occur with the two products. In continuous separation, a feed flow rate of 1.5 mL / min and a turnover time of 3.5 min ensure that each column sequentially completes "adsorption-elution-purification-regeneration," avoiding insufficient adsorption due to excessively high flow rates or insufficient throughput due to excessively low flow rates. Simultaneously, the turnover time matched to the mobile phase flow rate satisfies the flow balance of "mobile phase = feed + dual product collection," preventing waste liquid waste. Furthermore, the 3.5-hour operation time avoids both low equipment utilization due to short-term operation and resin overload and impurity accumulation due to long-term operation, ensuring product purity fluctuations of <0.5% during continuous operation. Therefore, in Example 3, through the synergistic effect of the processes in each step, high-purity lithium dihydrogen phosphate and inositol are finally obtained, realizing the co-production of lithium dihydrogen phosphate and inositol.

[0149] Comparative analysis of Examples 1-3 and Comparative Examples 1-4 reveals that, in the technical solution of this invention, the various process conditions and parameters of the lithium dihydrogen phosphate co-production method for inositol are interconnected and mutually supportive, forming an organic whole with significant synergistic effects. By precisely controlling the desorption intensity, hydrolysis conditions, and separation rhythm, a balance between resin protection, product purity, and process economy is achieved. However, replacing process conditions or parameters disrupts this synergistic relationship, leading to resin damage, product side reactions, and separation failure. This results in reduced purity and increased impurity content in the final lithium dihydrogen phosphate and inositol, rendering them unsuitable for industrial application. This demonstrates that the parameter design of the co-production technology of this invention is highly correlated; no single parameter can be adjusted independently, and optimization based on a balanced overall process is necessary.

[0150] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for producing lithium dihydrogen phosphate co-produced with inositol, characterized by, The production method includes the following steps: An anion exchange resin adsorbing phytic acid solution from plant sources was obtained by using chloroethanol quaternized anion exchange resin. A mixed desorption solution containing 1 mol / L to 5 mol / L lithium chloride and 0.5 mol / L to 2 mol / L inorganic acid is injected into the anion exchange resin adsorbed with phytate ions for desorption treatment to obtain a lithium phytate salt solution; the volume of the mixed desorption solution is 2 bv to 4 bv, and the injection flow rate is 0.5 bv / h to 1.5 bv / h; The lithium phytate solution is hydrolyzed to obtain a mixed aqueous solution of lithium dihydrogen phosphate and inositol; the desorption treatment temperature is 25℃~60℃. The mixed aqueous solution of lithium dihydrogen phosphate and inositol was continuously separated using a simulated moving full-chamber bed device to obtain lithium dihydrogen phosphate solution and inositol solution, respectively. The lithium dihydrogen phosphate solution and the inositol solution were purified, concentrated, and crystallized sequentially to obtain lithium dihydrogen phosphate and inositol; The preparation method of the chloroethanol quaternized anion exchange resin is as follows: At a temperature of 75℃~85℃, styrene-divinylbenzene is polymerized with methyl acrylate, methyl methacrylate or ethyl acrylate for 6h~8h, and then the temperature is raised to 90℃~95℃ and the reaction is continued for 2h~4h to obtain white ball resin. Using ZnCl2 as a catalyst, the white sphere resin was subjected to a chloromethylation catalytic reaction at a temperature of 65℃~75℃ for 5h~6h. Then, ethylenediamine and chloroethanol were used sequentially for amination and quaternization reactions at a temperature of 70℃~80℃ for 2h~3h to obtain a chloroethanol quaternized anion exchange resin.

2. The production method according to claim 1, characterized by, The hydrolysis treatment is achieved based on the following steps: After membrane filtration, the lithium phytate solution is placed in a high-pressure reactor, heated to a preset temperature, reacted at a preset pressure for a preset time, and then cooled to room temperature to complete the hydrolysis process.

3. The production method according to claim 2, characterized by, The preset temperature is 120℃~200℃, the preset pressure is 0.6MPa~0.8MPa, and the preset duration is 2h~8h.

4. The production method according to claim 1, characterized by, During the continuous separation of the mixed aqueous solution of lithium dihydrogen phosphate and inositol using a simulated moving full-chamber bed device, the feed flow rate is 1.5 mL / min to 2.5 mL / min, the turnover time is 4.5 min to 5.5 min, and the continuous separation time is 3.5 h to 4.5 h.

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