Preparation method of electronic-grade polybasic sugar alcohol

Abstract

The invention discloses a preparation method of electronic-grade polybasic sugar alcohol, and aims to construct a continuous refining route formed by coupling multiple units in order to solve the technical problems that metal ions in a polybasic sugar alcohol system coexist in a free state, a complex state and a colloid state and three-state metals cannot be simultaneously reduced to an electronic-grade level by a traditional food-grade process. The method sequentially comprises the following steps: pre-filtering and decolorizing with activated carbon to remove a metal complex precursor, removing free inorganic ions by using macroporous cation / anion exchange resin, carrying out MWCO 800-1500 Da ultrafiltration to remove colloidal impurities, deeply removing weak binding ions by using electrodialysis, and separating the reducing sugar and part of metal complexes by using Ca < 2 + > type ion exchange chromatography through coordination exchange. And carrying out electronic-grade mixed bed polishing and vacuum concentration to obtain a finished product. Multiple units form synergy in a specific sequence, metal ions, anions and organic impurities can be reduced step by step, and finally the electronic-grade polyhydric sugar alcohol with the total metal being smaller than or equal to 0.1 ppm, the conductivity being smaller than or equal to 1 microsecond / cm and the reducing sugar being smaller than or equal to 0.01 wt% is obtained. The process is water-based in the whole process, high in stability and suitable for industrial continuous production.

Description

Technical Field

[0001] This invention belongs to the field of preparation of electronic-grade ultra-clean high-purity reagents, specifically relating to a method for preparing electronic-grade polyols. Background Technology

[0002] Plant-based polyols are a class of polyhydroxy compounds produced from plant polysaccharides through liquefaction, saccharification, and hydrogenation reactions. Depending on the process, they can contain different proportions of monohydric, dihydric, and higher sugar alcohols. Due to their excellent hygroscopicity, reducing properties, and chemical stability, they are widely used in food, pharmaceuticals, daily chemicals, resins, and coatings. However, with the rapid development of the electronic chemicals and semiconductor industries, the demand for polyols as novel electronic-grade organic solvents, components of wet electronic materials, and photoresist additives is increasing, placing much higher technical requirements on their purity, metal ion content, conductivity, and reducing impurity levels than those for food-grade and pharmaceutical-grade products.

[0003] Currently, the common industrial production route for polyols mainly involves using corn starch or cassava starch as raw material, followed by liquefaction, saccharification, filtration, and hydrogenation to obtain a crude sugar alcohol mixture (containing sorbitol, maltitol, mannitol, and higher sugar alcohols in varying proportions). This mixture, in addition to the target product, still contains various impurities, such as unreacted monosaccharides and disaccharides, carboxylic acid byproducts, and residual catalyst metal ions (Ni). 2+ Fe 3+ etc.), inorganic ions (Na+, etc.) + K + Ca 2 + Mg 2+ Cl - SO4 2- (etc.), as well as pigments, caramelization products, colloidal substances and microbial debris, etc.

[0004] These impurities significantly affect the electrical conductivity, thermal stability, and optical purity of polyols, making them unable to meet the standards for electronic-grade products, which require "extremely low ion content, colorless and transparent, free of particles, and free of reducing impurities." Existing polyol refining processes are typically geared towards food or pharmaceutical applications, often employing unit operations such as activated carbon decolorization, single-stage ion exchange, and evaporation concentration. While these traditional processes can reduce color and some ion content, they still present the following problems:

[0005] (1) Limited desalination capacity. Due to the high viscosity of the raw material system, single-stage ion exchange can often only remove 90% to 95% of the ions, leaving residual metal ions at the ppm level, which is difficult to meet the requirements of electronic chemical grade. More importantly, the metal ions in the polyol system do not exist in a single form, but coexist in three states: free state, carboxylic acid / aldehyde / ketone complex state, and colloidal state coated by polymers or caramel. Traditional ion exchange can only remove free metals and is basically ineffective against complexed and colloidal metals.

[0006] (2) Insufficient removal efficiency of organic impurities. Activated carbon mainly removes pigments, but it is almost ineffective against organic pollutants such as reducing sugars, low-molecular-weight organic acids, and aldehyde and ketone byproducts. These impurities can cause oxidation and discoloration or form complex metal ions during storage, which seriously affects product stability. In addition, in polyol mixed systems, weak coordination can occur between different components, making the stability of metal-sugar alcohol complexes higher than that of monomeric sugar alcohol systems, further increasing the difficulty of demetallization.

[0007] (3) Weak control of particulate matter and microorganisms. Traditional production lines lack electronic-grade hygienic design, with filtration accuracy limited to 1-5 μm, making it difficult to ensure that particle count and colony count meet electronic-grade standards. Metals and inorganic salts in particulate matter often act as "carriers," further making it difficult to remove colloidal metals from the system.

[0008] (4) The process system has high energy consumption and frequent regeneration. Conventional resin systems have low mass transfer efficiency under high viscosity conditions, short regeneration cycles, and high acid and alkali consumption, resulting in high production costs.

[0009] (5) Conductivity and metal ion indicators are difficult to meet simultaneously. Even if the conductivity is reduced to below 10 μS / cm, trace amounts of heavy metal ions or reducing impurities may still exist, which cannot meet the stringent standards in fields such as semiconductors, display panels, and new energy electrolytes. In particular, complexed metals do not significantly affect conductivity, so relying solely on conductivity control cannot truly reflect the metal purification effect.

[0010] In recent years, Shin-Etsu Chemicals of Japan proposed a representative improved route in its patent CN107540491B, "Metal Reduction Method for Sugar Alcohol Compounds." This method employs a three-step process: chemical protection, metal removal, and deprotection. First, the hydroxyl groups of the sugar alcohol are temporarily blocked with protecting groups such as acetone groups to prevent them from complexing with metal ions. Then, metal impurities are removed in an anhydrous organic system through extraction, separation, and vacuum distillation. Finally, hydrolysis removes the protecting groups to obtain high-purity sugar alcohol. The metal content of the product can be reduced to 100 ppb or even lower, successfully breaking through the ion removal limit of traditional physical methods. This approach has significant advantages in metal control and is particularly suitable for the high-purity refining of monomeric sugar alcohols (such as sorbitol). However, this process involves numerous steps, requiring multiple solvent phase inversion and deprotection reactions, and demands a strict operating environment, making continuous and low-energy production difficult. Furthermore, this route primarily targets monosaccharide alcohol systems, neglecting the complexities of complexed metals, colloidal impurities, and interactions between different sugar alcohol components in polysaccharide alcohol mixtures. Therefore, its technical solution cannot be directly applied to the electronic-grade purification of polysaccharide alcohols. The purity requirements for electronic-grade polysaccharide alcohols are far higher than those for food or pharmaceutical-grade products. According to industry standards for electronic chemicals, typical indicators are: total metal ion content ≤ 0.1 ppm, single metal ion content ≤ 0.05 ppm, and anion content (Cl... - SO4 2- ≤0.2 ppm, conductivity (25℃) ≤1 μS / cm, reducing sugar content ≤0.01wt%, particle number (≥0.2 μm) ≤10 4 Currently, no systematic process for simultaneously removing free, colloidal, and complexed metals has been reported in domestic and international literature, nor is there a continuous, low-energy electronic-grade purification route suitable for multi-component sugar alcohol mixtures.

[0011] Therefore, developing an electronic-grade refining process suitable for polyol mixed systems, through the rational design of units such as filtration, decolorization, ion exchange, mixed bed, membrane separation and concentration degassing, to achieve efficient removal of multidimensional impurities such as metal ions, anions, reducing sugars and particles, especially solving the problem of the coexistence of the three states of metal ions in polyol systems, and realizing continuous coupling and low-energy operation of the process, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0012] This invention aims to solve the technical problems in existing sugar alcohol production processes, such as the inability to reduce metal ions to the ppb level, the difficulty in removing metal complexes / colloidal states, low ion exchange efficiency, excessive mixed bed load, and difficulty in stabilizing conductivity below 1 μS / cm. It provides a multi-stage coupled deep purification process suitable for preparing electronic-grade polysaccharides.

[0013] This invention, through in-depth analysis of the characteristics of polyol systems—high viscosity, high complexing ability, and the presence of metal ions in multiple forms (free, complexed, and colloidal)—proposes a clean, refined, and industrially scalable electronic-grade purification route specifically designed for polyol systems. This route follows the principles of front-end diversion, mid-stage ion disassembly, and rear-stage deep polishing, with differentiated designs for the removal mechanisms of impurities in different forms. The final polyol contains ≤0.1 ppm total metal ions and ≤1.0 μS / cm conductivity, meeting the application requirements of wet electronic chemicals and semiconductor chemicals.

[0014] The technical solution adopted in this invention is:

[0015] A method for preparing electronic-grade polysaccharide alcohols, using crude polysaccharide alcohols as raw materials, involves the following steps in sequence: pre-filtration, decolorization, macroporous ion exchange desalination, ultrafiltration to remove colloidal and macromolecular impurities, electrodialysis for deep deionization, and Ca2+. 2+ Electronic-grade polysaccharide alcohol solutions are prepared through steps such as ion exchange chromatography separation, mixed-bed deep polishing, and vacuum concentration.

[0016] Includes the following steps:

[0017] (1) Raw material pretreatment and decolorization: The crude polysaccharide solution was filtered to remove particulate impurities, and activated carbon was added for decolorization treatment. The decolorized solution was then filtered to obtain the decolorized solution.

[0018] (2) Macroporous ion exchange desalination: The decolorized solution obtained in step (1) is sequentially passed through a cation exchange column and an anion exchange column to remove free metal ions and anions and reduce conductivity.

[0019] (3) Ultrafiltration to remove colloidal and macromolecular impurities: The solution obtained in step (2) is subjected to ultrafiltration to remove colloidal and macromolecular impurities from the solution;

[0020] (4) Electrodialysis for deep deionization: The ultrafiltration permeate from step (3) is subjected to electrodialysis to further remove weakly bound metal ions and small molecule inorganic ions;

[0021] (5) Ca 2+ Type Ion Exchange Chromatography Separation: The solution obtained in step (4) is passed through Ca... 2+ Type III weakly acidic ion exchange resin columns utilize sugar alcohols, reducing sugars, and metal complexes with Ca... 2+ The resins are separated based on their affinity differences, and the main distillation section is collected.

[0022] (6) Mixed bed deep polishing: The main distillation section obtained in step (5) is sent into a mixed bed column composed of strong acid cation resin and strong base anion resin for deep desalination;

[0023] (7) Vacuum concentration and degassing: The mixed bed effluent from step (6) is concentrated to the target concentration and then subjected to fine filtration and degassing to obtain electronic grade polysaccharide products.

[0024] In step (1), the crude polyol solution has a solid content of 55-70 wt%. The crude polyol solution is heated to 40-50°C and filtered through a 5-10 μm filter to remove catalyst residue and solid impurities. Then activated carbon is added for decolorization.

[0025] The decolorization temperature is 50-60℃, the decolorization time is 30-45 min, and the stirring rate is 100-200 rpm. After decolorization, plate and frame filtration is used for solid-liquid separation to obtain a decolorized liquid with a transmittance of ≥97%.

[0026] After decolorization, the COD value in the liquid decreases by 40-60%, and the color (APHA) is less than 10;

[0027] The activated carbon addition amount is 0.2-0.5 wt%; the activated carbon is powdered activated carbon with a BET specific surface area of ​​900-1200 m². 2 / g.

[0028] In step (2), the cation exchange column (cation bed) uses a macroporous strong acid cation exchange resin (SAC), preferably D001-H or 001×7 type resin (H). + (Type), with a pore size of 20-50 nm, a crosslinking degree of 6-10%, and a total wet-base exchange capacity ≥4.5 mmol / mL;

[0029] The anion exchange column (anion bed) uses type II macroporous strong base anion exchange resin (SBA), preferably D201-OH or D301 type resin (OH- type), with a pore size of 10-30 nm, a wet-phase exchange capacity ≥1.3 mmol / mL, and a functional group of dimethylethanolamine type;

[0030] The cation exchange column and anion exchange column are operated in series, with the effluent conductivity controlled at 5-10 μS / cm; the resin regeneration cycle is 20-30 BV, the acid-base regeneration concentration is 4-6%, and the total acid-base consumption is less than 5 kg / m³. 3 Solution; Na in the liquid after ion exchange + K + Ca 2+ Mg 2+ The total amount of metal ions is less than 1.5 ppm.

[0031] The resin particle size is controlled at 0.3-0.6 mm, and the bed height is 1.0-1.5 m;

[0032] Operating conditions are: inlet temperature 35-45℃, flow rate 3-6 BV / h, and empty bed contact time (EBCT) 10-15 min.

[0033] The macroporous strong acid cation exchange resin is selected from D001-H or 001×7 type resin (H+ type), and the type II macroporous strong base anion exchange resin is selected from D201-OH or D301 type resin (OH- type).

[0034] In step (3), the ultrafiltration process uses spiral wound membrane or hollow fiber membrane modules with a molecular weight cutoff of 800-1500 Da. The membrane material is polyethersulfone (PES) or polyvinylidene fluoride (PVDF), and the membrane shell is 316L stainless steel or food-grade FRP.

[0035] The system operates in a continuous circulating cross-flow mode, with the circulating flow rate of the spiral wound membrane being 2-4 m³ / s. 3 / h·m 2 The cross-flow velocity of the hollow fiber membrane is 1.5-3.0 m / s.

[0036] The operating pressure range is 0.4-1.0 MPa at the inlet and 0.2-0.6 MPa at the outlet; the operating temperature is maintained at 25-40℃; and the membrane flux is 20-45 L / m³. 2 •h, the recovery rate is controlled at 80-90% (preferably 85-90%).

[0037] To protect the membrane assembly, a 50-100 μm pre-filter is installed before entering the ultrafiltration unit. After ultrafiltration, the turbidity of the permeate is no higher than 1 NTU, and the amount of macromolecular or colloidal impurities in the retentate is reduced by 80-95% compared to the feed solution.

[0038] The membrane module of the ultrafiltration device has an effective filtration area of ​​2-20 m². 2 The transmembrane pressure difference (TMP) is maintained stably at 0.15-0.35 MPa during operation, and the fluctuation range of the permeate conductivity is controlled within ±10% of the feed conductivity. The system can restore flux through online or offline cleaning after an 8-12 hour operating cycle, and the membrane flux decay rate is no higher than 10%.

[0039] In step (4), the electrodialysis stack is composed of alternating layers of anion exchange membranes (AEM) and cation exchange membranes (CEM), with each membrane having an effective membrane area of ​​0.05-0.2 m². 2 The membrane stack consists of 5-15 membrane pairs, and the channel thickness is controlled at 0.4-0.8 mm to ensure that the liquid forms a stable laminar flow in the membrane channel.

[0040] During operation, the dilution chamber uses the ultrafiltration permeate as feed, while the concentration chamber is pre-filled with deionized water and forms an independent circulation system. Operating conditions are: DC voltage 20-40 V, current density 3-6 mA / cm². 2 The temperature is 20-40℃, the dilute solution flow rate is 0.5-1.5 L / min, and the electrode water circulation uses 18.2 MΩ·cm ultrapure water with a circulation flow rate of 0.2-0.5 L / min. When the conductivity of the electrodialysis dilute chamber drops to 2-3 μS / cm, the process switches to the next stage.

[0041] The total dissolved ion content at the dilute chamber outlet of the electrodialysis system is reduced by 70-90% compared to the influent, the ion concentration factor in the concentrated chamber reaches 4-8 times, the voltage utilization rate of the membrane stack is higher than 85%, and the energy consumption per unit treated liquid is no higher than 0.5-0.8 kWh / m³. 3 The electrodialysis can operate continuously and stably for 12-16 hours; the total exchange capacity of the membrane maintains a linear decay relationship with the conductivity of the treatment solution, and its periodic recovery can be achieved by rinsing with 0.1-0.5wt% dilute acid and dilute alkali.

[0042] In step (5), the solution treated by electrodialysis in step (4) is diluted to 25-35 wt% and then introduced into the Ca2+ system at 70-80℃. 2+ Separation was performed using a type of ion-exchange chromatography column.

[0043] The chromatographic column packing material is Ca 2+ Type weakly acidic resin, wherein Ca 2+ The weakly acidic ion exchange resin is selected from Ca-Dowex 50WX8 resin or Ca-type 001×7 resin; the resin particle size is 0.3-0.5 mm, the degree of crosslinking is 8%, the column height is controlled at 0.8-1.5 m, and the column inner diameter is 0.4-1.2 m depending on the processing capacity.

[0044] The chromatographic operation used deionized water as the eluent, and was run at 70-80℃ with a flow rate of 0.5-1.0 BV / h. The injection volume was 20-30% (v / v) of the resin volume.

[0045] The cutting point of the fraction is controlled by an online conductivity detector (3-5 μS / cm), and the main distillate section is used as a high-purity sugar alcohol fraction for subsequent processes.

[0046] The main distillate was collected at a cut-off point with an online conductivity of 3-5 μS / cm.

[0047] The Ca 2+The mass fraction of polyols in the main distillation section of the chromatogram should not be less than 95%, and the mass fraction of reducing sugars in the side distillation section should not exceed 0.01 wt%. The column's unit resin volume processing capacity should be 0.8-1.5 kg (dry basis) / L·cycle, the conductivity fluctuation of the fraction should not exceed ±0.5 μS / cm, and the column should be able to run continuously for 30-50 cycles without significant exchange capacity decay. The residual Ca in the chromatographic effluent should be... 2+ Not exceeding 0.05 ppm, and can be further removed to undetectable levels through subsequent mixed bed treatment.

[0048] In step (6), via Ca 2+ The sugar alcohol fraction separated by chromatographic chromatography enters a mixed-bed deep deionization system. The mixed-bed column is filled with a strong acid cation exchange resin and a strong base anion exchange resin, which are uniformly mixed at a volume ratio of 1:1.

[0049] The cation exchange resin is H + The macroporous strong acid resin of type OH, the anion resin is OH - It is a macroporous strong base resin with a particle size of 0.3-0.6 mm and a total bed height of 1.0-1.5 m.

[0050] The operating temperature of the mixed bed is controlled at 20-40℃, and the operating flow rate is 2-4 BV / h. The feed conductivity is generally 1-3 μS / cm, and the effluent conductivity of the mixed bed is stable within the range of ≤1.0 μS / cm.

[0051] The mixed bed system employs cation and anion exchange resins with core-shell structures or electronic-grade application-level resins. The total wet-balance exchange capacity of the resins is not less than 4.5 mmol / mL (cation resin) and 1.2 mmol / mL (anion resin), respectively. During mixed bed operation, the cation and anion resins maintain a uniform distribution in the bed, and the mixing uniformity between resin particles is not less than 90%. The Na+ concentration in the solution after mixed bed treatment is... + K + Ca 2+ Mg 2+ The total amount of metal cations is not higher than 0.1 ppm, Cl - SO4 2- NO3 - The anion content is not higher than 0.2 ppm, and the sugar alcohol retention rate is not lower than 99.8%. The mixed bed can run continuously for 40-60 BV before entering the regeneration cycle. The regeneration process includes acid and alkali staged countercurrent regeneration operations, and is rinsed with deionized water until the conductivity of the effluent returns to the initial value.

[0052] This mixed-bed unit features high ion removal capability, low penetration rate, and stable conductivity control performance, making it suitable for the final deep polishing treatment of electronic-grade polysaccharides.

[0053] In step (7), the sugar alcohol solution treated with mixed bed is concentrated under vacuum conditions using a falling film or scraped evaporator at a concentration temperature of 60-80℃ and a vacuum degree of approximately -0.09 MPa to a concentration of 70-75 wt%. Before concentration, it is preferable to pre-filter the solution at a concentration of 40-50 wt% using 0.45 μm and 0.2 μm filter units. The concentrated product is then degassed by an online degassing system and then directly filled at high temperature or stored under nitrogen sealing conditions.

[0054] The concentrated liquid has a transparency of >98% and dissolved oxygen of <0.5 ppm; the storage tank is made of 316L electropolished stainless steel or clean HDPE container, with a nitrogen sealing pressure of 0.02-0.05 MPa and a storage temperature of 20-25℃.

[0055] This invention addresses the challenges of electron-grade purification posed by the high viscosity, strong complexing properties, and coexistence of free, complexed, and colloidal states of metal ions in polyol systems. It constructs a purification process consisting of pre-filtration and decolorization, macroporous ion exchange, ultrafiltration, electrodialysis, and Ca2+ purification. 2+ This involves a continuous coupled purification route consisting of "type chromatography, electronic-grade mixed bed, vacuum concentration, and degassing." This route is not a simple superposition of traditional food-grade processes, but rather a functional differentiation based on the removal mechanisms of different impurity forms. It enables deep ion removal, metal removal, and organic removal to be completed synergistically, thereby solving the industry bottleneck of "difficulty in simultaneously meeting standards for conductivity and metal content" that is prevalent in existing technologies.

[0056] At the front end, high-surface-area activated carbon is used in conjunction with pre-filtration to dismantle caramelized polymers and colloidal metal coatings in the sugar alcohol system, significantly reducing the risk of subsequent resin clogging and metal leakage. In the middle stage, macroporous SAC / SBA resin with pore size, cross-linking degree, and exchange capacity optimized for high-viscosity systems operates at 35-45℃ and 3-6 BV / h, efficiently removing free metals and reducing metal content to the ppm level, while providing a suitable ionic strength window for ultrafiltration and electrodialysis. The ultrafiltration unit further removes colloidal metals, polymeric organic matter, and particulates, eliminating common irreversible sources of contamination in electrodialysis and mixed-bed systems.

[0057] Electrodialysis operates under the conditions of low colloidal, low organic, and low metal content in the ultrafiltration permeate. This allows for the selective migration of weakly complexed metal ions and residual inorganic anions, reducing the dilute chamber conductivity to 2-3 μS / cm and creating an extremely low background ion environment for chromatographic separation. More importantly, this invention identifies that the main source of excessive electronic-grade metals is not free ions, but rather reducing sugar-metal chelates and weakly complexed metal-sugar alcohol complexes. These species are typically insensitive to ion exchange resins. By introducing Ca... 2+ Type Ion exchange chromatography, utilizing metal chelates and sugar alcohols in Ca... 2+The significant differences in retention behavior in the coordination environment enable the selective separation of the aforementioned difficult-to-remove impurities, further reducing the total metal content to the ppb level.

[0058] The end-stage mixed bed uses electronic-grade core-shell resin, operates with low-conductivity feed, exhibits extremely low penetration, and has a regeneration cycle of 40-60 BV. It can stably obtain polishing products with conductivity ≤1 μS / cm, metal content ≤0.1 ppm, and anion content ≤0.2 ppm, without resin staining or rapid decay of exchange capacity. Combined with vacuum concentration, fine filtration, and degassing, the generation of oxidative impurities can be suppressed, ensuring that the final product meets or exceeds electronic-grade specifications in terms of color, turbidity, particle number, and reducing sugar content.

[0059] Beneficial effects:

[0060] This invention utilizes an aqueous system throughout the entire process, requiring no protecting group reactions, solvent-free phase inversion, or heavy metal catalysts. It boasts high safety, low energy consumption, and minimal environmental impact, enabling continuous and modular industrial operation. This process is not only applicable to multi-component mixed sugar alcohol systems but can also be extended to the electronic-grade purification of other polyhydroxy compounds such as glycerol and polyethylene glycol, providing a reliable technical pathway for the domestic production of high-end electronic chemicals and semiconductor wet electronic materials. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the electronic-grade polysaccharide alcohol refining process of the present invention. Detailed Implementation

[0062] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0063] Example 1: Preparation of electronic-grade polyols

[0064] (1) Raw materials and pretreatment

[0065] A crude polyol solution, prepared from corn starch through liquefaction, saccharification, and high-pressure hydrogenation, was selected as the raw material. The stock solution had a solids content of 62 wt%, with the main components being sorbitol (52.3 wt%), mannitol (2.5 wt%), maltitol (36.7 wt%), and higher sugar alcohols (8.5 wt%), the remainder being trace amounts of reducing sugars and inorganic ions. The initial conductivity of the stock solution was 185 μS / cm, and the total metal ion content was approximately 13.64 ppm (all concentrations are calculated based on a 70 wt% solids content, including Na). + 4.92ppm, K + 3.70 ppm, Ca 2+ 2.81 ppm, Mg 2+ 1.12 ppm, Ni 2+The content of reducing sugar is about 0.38 ppm, the COD is about 4800 mg / L, the color (APHA) is 68, the transmittance (420 nm) is 85.1%, the dissolved oxygen is about 2.8 ppm, and the pH is 6.6.

[0066] The stock solution was added to a 316L stainless steel pretreatment tank and heated to 45°C. It was then filtered through a 10 μm filter to remove catalyst residue and particulate impurities, reducing the suspended particulate content to <10 mg / L and the turbidity from 8.5 NTU to 1.2 NTU. A solution with a specific surface area of ​​approximately 1050 m² was added at 0.35 wt% of the solution mass. 2 / g of powdered activated carbon was stirred at 55℃ for 40 min for decolorization at a stirring rate of 150 rpm. After decolorization, plate and frame filtration was used to remove the activated carbon filter cake and obtain a clear decolorized solution. The transmittance of the decolorized solution was ≥97.0%, COD decreased from 4800 mg / L to approximately 2200 mg / L, color (APHA) decreased from 68 to 9, and total metal ion content decreased to approximately 5.82 ppm (all concentrations are calculated based on 70wt% solids content, including Na). + 2.05 ppm, K + 1.61 ppm, Ca 2+ 1.02 ppm, Mg 2+ 0.61 ppm, Ni 2+ The concentration of reducing sugars decreased slightly to 0.31 wt%, and the solids content of the solution was approximately 60 wt%. The activated carbon consumption per unit of treated solution (1000 L) was approximately 3.2 kg, which is about 25% lower than that of the traditional process.

[0067] (2) Macroporous ion exchange desalination

[0068] In step (1) above, the clarified and decolorized liquid is adjusted to 40°C via a heat exchanger and then sequentially passed through a cation exchange column and an anion exchange column. The cation exchange bed packing material is D001×7 (H + (Type) Macroporous strong acid macroporous resin, pore size 20-50 nm, wet-balance exchange capacity approximately 4.7 mmol / mL; anion exchange bed packing material is D201 (OH-). - Type II macroporous strong-base resin (type II) with a pore size of 10-30 nm and a wet-balance exchange capacity of approximately 1.4 mmol / mL. The operating flow rate was 4 BV / h, and the empty bed contact time (EBCT) was approximately 12 min. The conductivity of the ion-exchange solution stabilized at around 7.8 μS / cm (fluctuating within the range of 7-9 μS / cm), and the total metal ion content decreased from approximately 5.82 ppm after decolorization to approximately 1.35 ppm (both concentrations are calculated based on 70 wt% solids content, including Na). + 0.45 ppm, K +0.37 ppm, Ca 2+ 0.20 ppm, Mg 2+ 0.11 ppm, Ni 2+ The COD was further reduced to approximately 1600 mg / L, the reducing sugar content was approximately 0.22 wt%, the color (APHA) was approximately 8, and the transmittance (420 nm) was approximately 98.6%. After ion exchange, the solid content of the solution was approximately 55 wt%, with virtually no significant loss due to evaporation or dilution.

[0069] (3) Ultrafiltration to remove colloidal impurities

[0070] In step (2), the ion exchange effluent is pumped into the ultrafiltration system, using a MWCO 1000 Da spiral wound membrane module (PES material) with an effective membrane area of ​​12 m². 2 The system inlet pressure is 0.7 MPa, the outlet pressure is 0.4 MPa, and the total pressure per unit volume (TMP) is maintained between 0.22 and 0.30 MPa. The transmembrane flow rate is 3.2 m³ / s. 3 / h·m 2 The operating temperature is controlled at 32℃.

[0071] After approximately 3 hours of continuous operation, the turbidity of the ultrafiltration permeate decreased to approximately 0.4 NTU, and the high molecular weight impurities characterized by UV254 decreased by approximately 87%, while the number of colloidal particles decreased from 1.2 × 10⁻⁶. 6 Counts / mL decreased to approximately 8.5 × 10⁻⁶ 3 Counts / mL. The permeate conductivity remained essentially the same as the feed conductivity (approximately 7.8 μS / cm), indicating that ultrafiltration had minimal impact on ion content. COD decreased to approximately 1000 mg / L after ultrafiltration. To facilitate subsequent electrodialysis, the permeate was adjusted to approximately 45 wt% solids by adding an appropriate amount of deionized water.

[0072] (4) Electrodialysis for deep desalination

[0073] In step (3) above, the ultrafiltration permeate is used as the feed to the dilute chamber of the electrodialysis stack. The effective membrane area of ​​each membrane in the electrodialysis stack is 0.1 m². 2 The membrane has 10 membrane pairs and a flow channel thickness of approximately 0.6 mm. The feed flow rate to the dilute chamber is 1.0 L / min; the concentrate chamber is initially injected with deionized water and circulated at a flow rate of 0.3 L / min. The operating voltage is 30 V, the current density is approximately 4 mA / cm², and the operating temperature is approximately 30 °C. After approximately 2.5 h of operation, the conductivity of the dilute chamber decreased from 7.8 μS / cm to approximately 2.4-2.6 μS / cm, and the total metal ion content decreased from approximately 1.35 ppm to approximately 0.40 ppm (all concentration values ​​are calculated based on 70 wt% solids content, where Na...). + Approximately 0.11 ppm, K +Approximately 0.10 ppm, Ca 2+ Approximately 0.07 ppm, Mg 2+ Approximately 0.04 ppm, Ni 2+ (Approximately 0.02 ppm). Sugar alcohol retention was ≥99.7%, and no sugar alcohol migration to the concentration chamber was observed. After electrodialysis, the solids content of the dilute solution remained at approximately 45 wt%. At this stage, the COD was approximately 1000 mg / L, and the reducing sugar content was approximately 0.15 wt%.

[0074] (5) Ca 2+ Type Ion Exchange Chromatography Separation

[0075] In step (4), the electrodialysis solution is diluted to approximately 30 wt% solids and preheated to 75°C. It is then introduced into the Ca-filled substrate at a flow rate of 0.8 BV / h. 2+ A Dowex 50WX8 resin column was used. The injection volume was 25% (v / v) of the resin volume. Deionized water was used as the eluent. The conductivity of the fraction was monitored using an online conductivity detector at the chromatographic operating temperature (75℃). The main fraction was collected when the column outlet conductivity signal dropped to 4 μS / cm. Analysis showed that the polyol purity in the main fraction reached 96.8%, the reducing sugar content decreased to ≤0.008-0.012wt%, and the total metal ion content remained at approximately 0.17 ppm (all concentrations are calculated based on 70wt% solids content, including Na). + 0.04 ppm, K + 0.04 ppm, Ca 2+ 0.02 ppm, Mg 2+ 0.02 ppm, Ni 2+ The concentration of chlorine is 0.01 ppm, the conductivity is approximately 1.1 μS / cm, and the COD is approximately 400 mg / L. The color is maintained at 8 APHA, and the transmittance is approximately 99.2%. The side fraction (mainly the high-conductivity, high-reducing-sugar portion) is discharged to the waste tank. At this point, the solids content of the main fraction solution is approximately 28 wt%.

[0076] (6) Electronic-grade mixed bed deep polishing

[0077] In step (5), Ca 2+The main distillation section of the chromatography column is fed into a mixed-bed column. The volume ratio of cation exchange resin to anion exchange resin in the mixed bed is 1:1, and the total bed height is approximately 1.2 m. In this embodiment, the preferred cation exchange resin is Amberlite IR-120H (electronic grade), and the preferred anion exchange resin is Amberlite IRA-400OH (electronic grade). Both resins possess low metal leaching, high exchange capacity, and pore structures suitable for high-viscosity sugar alcohol systems. They undergo electronic-grade pretreatment before use to ensure sub-ppb polishing capability. The operating flow rate is approximately 3 BV / h, and the operating temperature is 25-30℃. The feed conductivity is approximately 1.1-1.3 μS / cm, and the discharge conductivity is stable at 0.6-0.8 μS / cm.

[0078] The metal ion content of the mixed bed effluent, after analysis by ICP-MS and other methods, was approximately 0.09 ppm (all concentrations are calculated based on 70 wt% solids content, including Na). + Approximately 0.03 ppm, K + Approximately 0.03 ppm, Ca 2+ Approximately 0.02 ppm, Mg 2+ Approximately 0.02 ppm, Ni 2+ <0.01ppm); Cl - SO4 2- The anion content of each component is no higher than 0.2 ppm. The reducing sugar content in the mixed bed effluent is maintained at approximately 0.008 wt%, COD at approximately 280 mg / L, color at 8 APHA, transmittance at approximately 99.3%, dissolved oxygen at approximately 0.4 ppm, and pH at approximately 6.8. Sugar alcohol retention is ≥99.8%. Under the operating conditions of this embodiment, the mixed bed can operate continuously for 50 BV without significant breakthrough, and the resin condition is good. At this point, the solution solids content is approximately 26 wt%.

[0079] (7) Vacuum concentration and online degassing

[0080] In step (6), the effluent from the mixed bed was fed into a falling film evaporator and concentrated to approximately 70 wt% solids under a vacuum of -0.09 MPa and a temperature of approximately 70°C. To control the pressure difference and prevent clogging of the high-viscosity system, two-stage pre-filtration (0.45 μm and 0.2 μm) was performed before concentration (when the solids were approximately 45 wt%). During concentration, the viscosity increased from approximately 280 mPa·s (45 wt%) to approximately 1650 mPa·s (70 wt%). After concentration, the solution was deoxygenated by circulating it through an online degassing device for approximately 30 min, reducing the dissolved oxygen from approximately 0.4 ppm to approximately 0.3 ppm, the COD to approximately 270 mg / L, and the conductivity at 25°C to approximately 0.72 μS / cm. The final product was filled into a 316L electropolished stainless steel storage tank while still hot, and stored under nitrogen sealing (nitrogen sealing pressure of about 0.03 MPa) at a storage temperature of about 25°C. After being stored under nitrogen sealing conditions at room temperature for 30 days, no significant deterioration was observed in color, conductivity, or metal ion indicators.

[0081] Product testing results

[0082] Table 1 shows the changes in solids, conductivity, total metal ion content, main organic impurities (reducing sugar, COD), optical properties (color, transmittance), dissolved oxygen, pH, and inorganic anions and particle counts at each key process stage from crude polysaccharide alcohol solution to electronic-grade product. As can be seen from Table 1, the multi-stage coupled purification system of this invention can achieve a reduction of over 99.4% in ionic impurities, a reduction of approximately 97.7% in reducing sugars, a decrease in total conductivity of over 250 times, and control of total metal ions in the finished product below 0.1 ppm (100 ppb). - SO4 2- Each is no higher than 0.2 ppm, and the particle number (≥0.2 μm) is approximately 3 × 10⁻⁶. 3 The concentration of particles per L is significantly better than the typical requirements for electronic chemicals (total metals ≤0.1 ppm, anions ≤0.5 ppm, particle number ≤10). 4 (pcs / L), demonstrating the effectiveness and stability of the process of the present invention in the preparation of electronic-grade polysaccharides.

[0083] Table 1. Changes in key indicators at each critical process stage from crude polysaccharide alcohol solution to electronic-grade product.

[0084] project crude sugar alcohol solution Bleaching Ion exchange Ultrafiltration + Electrodialysis <![CDATA[Ca 2+ Chromatography Mixed bed Final product Solids (wt%) 62 60 55 45 28 26 70 Reducing sugar (wt%) 0.35 0.31 0.22 0.15 0.008 0.008 0.008 COD (mg / L) 4800 2200 1600 1000 400 280 270 Chromaticity (APHA) 68 9 8 8 8 8 8 Transmittance (420nm, %) 85.1 97 98.6 99 99.2 99.3 99.3 Dissolved oxygen (ppm) 2.8 2.5 1.9 1.3 0.6 0.4 0.3 pH (25℃) 6.6 6.7 6.8 6.8 6.8 6.8 6.8 Electrical conductivity (μS / cm) 185 65 7.8 2.4 1.1 0.7 0.72 Total metal ions (ppb) 13643.27 5821.60 1347.54 400.66 166.57 <90 <90 7Li 0.44 0.17 0.04 <0.01 0.00 0.00 0.00 9Be 0.23 0.08 0.02 <0.01 0.00 0.00 0.00 11B 13.54 5.25 1.14 0.33 0.11 0.09 0.08 23Na 4927.86 2051.2 450.26 114.1 43.25 34.84 34.92 24Mg 1120.56 605.82 114.96 40.30 17.52 1.01 1.19 27Al 189.94 136.78 57.54 22.21 10.76 0.71 0.81 28Si <0.01 <0.01 0.00 0.00 0.00 0.00 0.00 39K 3703.2 1610.52 371.2 102.71 41.17 27.52 27.61 44Ca 2816.98 1018.83 195.18 67.8 23.05 15.54 16.26 48Ti 61.93 25.9 5.63 1.65 0.57 0.38 0.38 51V 0.00 0.00 0.00 0.00 0.00 0.00 0.00 53Cr 0.97 0.41 0.09 0.03 <0.01 <0.01 <0.01 55Mn 5.39 2.25 0.49 0.14 0.04 0.03 0.03 56Fe 168.31 129.57 56.21 21.82 12.63 1.51 1.64 59Co 3.08 1.29 0.28 0.08 0.03 0.02 0.02 60Ni 375.11 131.05 71.01 22.65 15.18 4.46 4.51 65Cu 3.36 1.32 0.30 0.09 0.03 0.02 0.02 66Zn 154.88 60.77 14.08 4.15 1.43 0.95 0.95 71Ga 0.88 0.37 0.08 0.02 <0.01 <0.01 <0.01 73Ge 0.22 0.04 0.02 <0.01 0.00 0.00 0.00 75As 0.99 0.42 0.09 0.03 <0.01 <0.01 <0.01 87Rb 0.5 0.23 0.05 <0.01 <0.01 0.00 0.00 88Sr 4.29 1.78 0.39 0.12 0.03 0.03 0.03 90Zr 0.75 0.23 0.05 <0.01 <0.01 0.00 0.00 93Nb 1.43 0.59 0.13 0.04 <0.01 <0.01 <0.01 95Mo 2.31 0.97 0.21 0.06 0.02 <0.01 <0.01 107Ag 1.49 0.6 0.13 0.04 <0.01 <0.01 <0.01 111Cd 0.84 0.32 0.08 0.02 <0.01 <0.01 <0.01 115In 0.44 0.15 0.04 <0.01 0.00 0.00 0.00 118Sn 11.22 4.60 1.02 0.32 0.10 0.07 0.07 121Sb 0.22 0.06 0.02 <0.01 0.00 0.00 0.00 133Cs 0.43 0.13 0.03 <0.01 0.00 0.00 0.00 137Ba 9.56 4.41 0.96 0.28 0.09 0.06 0.06 181Ta 0.67 0.27 0.06 0.02 <0.01 0.00 0.00 182W 7.14 2.40 0.74 0.21 0.07 0.05 0.05 195Pt 35.42 14.61 3.22 0.94 0.33 0.22 0.22 197Au 0.44 0.17 0.04 <0.01 0.00 0.00 0.00 202Hg <0.01 <0.01 0.00 0.00 0.00 0.00 0.00 205Tl 0.21 0.08 0.02 <0.01 0.00 0.00 0.00 207Pb 0.78 0.32 0.07 0.02 <0.01 0.00 0.00 209Bi 17.26 7.64 1.66 0.48 0.16 0.11 0.11 <![CDATA[Cl - (ppm)]]> 3.50 2.00 0.80 0.30 0.18 0.10 0.10 <![CDATA[SO4 2- (ppm)]]> 2.80 1.60 0.60 0.25 0.14 0.08 0.08 Particle number (≥0.2 μm, particles / L) <![CDATA[5.0×10 6 ]]> <![CDATA[8.0×10 5 ]]> <![CDATA[1.5×10 5 ]]> <![CDATA[1.0×10 4 ]]> <![CDATA[8.0×10 3 ]]> <![CDATA[5.0×10 3 ]]> <![CDATA[3×10 3 ]]>

[0085] Note: The data in the table are representative results under typical process conditions. The content of solids and reducing sugars was determined according to GB1886.187-2016; COD was determined according to GB / T 11914-2020 potassium dichromate method; metal ion content was determined by Agilent 7900 ICP-MS and uniformly converted to the concentration value at 70wt% solids content. Total metal ions are expressed in ppb (1 ppm = 1000 ppb); Cl - SO4 2- The particle count (≥0.2 μm) was determined by ion chromatography and expressed as particles / L by an online particle counter. The final product met the quality standards for electronic-grade polyols (conductivity ≤1 μS / cm, total metal ion content ≤0.1 ppm, each anion ≤0.2 ppm, particle count ≤10). 4 (pieces / L).

[0086] Example 2: Key Parameter Impact Analysis

[0087] In this embodiment, to evaluate the impact of key operating parameters on the final electronic-grade quality, while strictly maintaining the raw material composition and all operating conditions except for this parameter as described in Example 1, the ultrafiltration membrane MWCO, electrodialysis voltage, and Ca were varied. 2+ Chromatographic temperature was used to systematically test the downstream purification effect.

[0088] When the MWCO of the ultrafiltration membrane in Example 1 was increased to 2000 Da, although the transmembrane pressure difference (TMP) decreased slightly and the unit energy consumption decreased by about 15%, the reduced retention capacity led to an increase in the penetration rate of colloidal and some oligosaccharide impurities, resulting in an increase in the organic load entering the electrodialysis unit. The results showed that the conductivity of the electrodialysis effluent increased from about 2.4-2.6 μS / cm in Example 1 to 2.9 μS / cm, the total metal ion residue increased to about 0.53 ppm, and further increased the exchange load of the mixed bed resin. The continuous operating cycle was shortened from about 50 BV in Example 1 to 20-25 BV, the regeneration frequency increased significantly, and the resin lifespan was also adversely affected.

[0089] When the electrodialysis operating voltage is reduced to 15 V, the system current density decreases significantly, resulting in insufficient driving force for migratable ions. This leads to the inability of weakly complexed metal ions in the dilute effluent of the electrodialysis chamber to migrate sufficiently, manifested as a significant increase in both total conductivity and metal ion residue. Under these conditions, even if Ca is subsequently used... 2+ Chromatography and mixed-bed treatment still struggle to consistently meet electronic-grade standards.

[0090] On the other hand, when Ca 2+When the column operating temperature is increased to 85℃, the equilibrium adsorption capacity between the resin and sugar alcohol decreases slightly, which improves the separation efficiency. However, the high temperature also causes irreversible relaxation of the resin structure, resulting in a decrease in sugar alcohol retention rate of about 3.2%. At the same time, the column pressure drop increases, the mechanical strength of the resin decreases, and the long-term cycling stability is significantly reduced.

[0091] The above results show that: ultrafiltration MWCO, electrodialysis voltage, and Ca 2+ Chromatographic temperature has a crucial impact on the "multi-impurity synergistic control mechanism" of the entire system. If any parameter deviates from the optimal range, it will cause a sharp increase in the load on the downstream purification unit or even its failure, making it impossible to obtain electronic-grade quality. The preferred conditions determined after system optimization in this invention are: ultrafiltration MWCO of 800-1500 Da, electrodialysis voltage of 30±10 V, and Ca... 2+ The chromatographic column temperature is 70-80℃, which can achieve the best balance between purity, energy consumption, resin life and economy, so that the entire process chain can stably produce polyol products that meet electronic grade requirements.

[0092] Example 3: The Influence of Ion Exchange Resin Selection and Configuration

[0093] To verify the necessity of the combination of macroporous strong acid cation exchange resin and type II macroporous strong base anion exchange resin used in step (2) of this invention, a resin comparison experiment completely parallel to Example 1 was designed in this embodiment. The comparison group used gel-type resins commonly used in the production of food-grade polyols: the cation bed used 001×4 (H+ type) gel-type strong acid resin (wet-based exchange capacity of about 4.0 mmol / mL, pore size less than 10 nm), and the anion bed used 201 (OH- type) gel-type strong base resin (wet-based exchange capacity of about 1.0 mmol / mL). The remaining process conditions were completely consistent with those in Example 1, including feed solids of about 60 wt%, feed conductivity of about 65 μS / cm, temperature of 40℃, flow rate of 4 BV / h, and EBCT of about 12 min.

[0094] Under the above conditions, the desalination performance of the gel resin system is shown in Table 2. The results show that, due to the small pore size, short mass transfer channels, and susceptibility to blockage by colloids and caramelization byproducts in the high-viscosity polysaccharide alcohol system, the ion exchange efficiency of the gel resin system is significantly lower than that of the system described in this invention. The effluent conductivity of the gel resin system only decreased to 18.6 μS / cm, while the macroporous 001×7 / D201 system used in this invention can stably reach 7.8 μS / cm; the total metal ion residue is still as high as 3.12 ppm, while the system of this invention is only 1.35 ppm. Furthermore, the bed pressure drop of the gel resin system increased to 28 kPa (compared to only 12 kPa in this invention), and significant metal penetration occurred after 20 BV of operation, while no metal penetration was detected in the system of this invention under the same conditions, demonstrating a significant advantage in exchange capacity and operational stability.

[0095] Table 2 Comparison of ion exchange effects between the two resin systems

[0096] project Comparative gel type 001×4 / 201 The large hole 001×7 / D201 of this invention Electrical conductivity (μS / cm) 18.6 7.8 Total metal ions (ppm) 3.12 1.35 COD (mg / L) 2100 1600 Resin pressure drop (kPa) 28 12 20 BV after metal penetration obvious Not detected

[0097] Subsequently, the ion exchange effluents from the two resin systems were fed into the ultrafiltration, electrodialysis, and mixed-bed units of this invention for testing. The comparative results are shown in Table 3. It can be observed that the gel resin system, due to the high levels of residual metal ions, organic matter, and weak complexes in its effluent, significantly accelerated the fouling rate of the ultrafiltration membrane (TMP rapidly increased from 0.30 MPa to 0.45 MPa), reduced the desalination capacity of the electrodialysis unit (effluent conductivity increased to 3.8-4.1 μS / cm), and further led to unstable polishing of the mixed bed, maintaining an effluent conductivity of only 1.3-1.5 μS / cm within a 15-20 BV operating cycle. Subsequently, the mixed bed rapidly failed, with significant metal ion penetration, and the total metal residue increased to 0.19-0.23 ppm, failing to meet electronic grade requirements. In contrast, the macroporous resin system used in this invention exhibited significant advantages throughout the entire downstream treatment chain. The ultrafiltration membrane fouling rate was significantly reduced (TMP stabilized at 0.22-0.30 MPa), the electrodialysis effluent was stably maintained at 2.4-2.6 μS / cm, the mixed bed polishing effluent was consistently controlled at 0.6-0.8 μS / cm, the total metal ion content was consistently below 0.1 ppm, and the mixed bed could operate continuously for more than 50 BV without significant breakthrough, demonstrating significantly higher operational reliability than the gel resin system.

[0098] Table 3 Performance Comparison of Downstream Processes

[0099] Process Gel-type resin system Macroporous resin systems Ultrafiltration TMP rise 0.30→0.45 MPa (rapid increase) 0.22→0.30 MPa (stable) Electrodialysis solution conductivity (μS / cm) 3.8-4.1 2.4-2.6 Electrodialysis energy consumption +22% - Initial effluent conductivity of mixed bed (μS / cm) 1.3-1.5 0.6-0.8 After the mixed bed has been running for 20 BV Conductivity >2 μS / cm, significant metal penetration Conductivity <1 μS / cm, no penetration Final total metals (ppm) 0.19-0.23 (Not up to standard) <0.10 (Meets the standard)

[0100] In summary, this embodiment confirms that gel-type resins, due to their small pore size, slow mass transfer rate, and susceptibility to fouling by colloids and caramel compounds in sugar alcohol systems, have insufficient desalination and antifouling capabilities to meet the pretreatment requirements for electronic-grade polysaccharides. Their high metal residue and organic load also have a cascading adverse effect on downstream membrane processes and mixed-bed processes, ultimately preventing the production of electronic-grade products. In contrast, the macroporous SAC / SBA resin system used in this invention possesses larger pore sizes, superior mass transfer kinetics, and stronger antifouling capabilities. It can effectively dismantle free metals and weakly complexed metals, and significantly reduce the load on subsequent processes. It is a crucial and irreplaceable foundation for realizing the electronic-grade refining process of this invention.

[0101] Example 4: Missing Ca 2+ Effect of chromatographic separation steps

[0102] To verify Ca in step (5) 2+ The crucial role of type Ion exchange chromatography in electronic-grade purification systems is illustrated in this embodiment, which uses the exact same raw material composition and all process conditions as Example 1, except for the removal of Ca. 2+ Chromatographic procedure: The electrodialysis eluent (conductivity approximately 2.4 μS / cm, reducing sugar approximately 0.15 wt%) was appropriately diluted and directly fed into an electronic-grade mixed bed for deionization and polishing. Initially, the conductivity of the mixed bed eluent remained at 0.7-0.8 μS / cm, but rapid failure occurred after less than 15 BV of continuous operation, with the eluent conductivity jumping to over 1.5 μS / cm, and significant metal penetration was detected, including Fe. 3+ With Al 3+ The levels of each metal ion reached 0.02 ppm, and the total metal ion level exceeded 0.1 ppm, which failed to meet the electronic grade standard.

[0103] Further analysis showed that the 0.15 wt% reducing sugar remaining in the electrodialysis solution could react with polyvalent metals (such as Fe). 3+ Al 3+ This forms stable, weakly electrochemical complexes, which are difficult for mixed-bed resins to effectively capture and disassemble. Without Ca... 2+ Chromatography utilizes coordination differences for separation. These complexes will rapidly occupy resin exchange sites during mixed-bed operation, causing a decrease in resin selectivity and premature breakthrough, resulting in the effluent losing its electronic quality. This example demonstrates that Ca... 2+ Chromatography is an indispensable key unit in the technical route of this invention. Its unique complex separation and selective retention functions cannot be replaced by electrodialysis or mixed bed chromatography.

[0104] Example 5: The impact of process sequence adjustment

[0105] To verify the scientific validity of the "ultrafiltration first, then electrodialysis" process sequence proposed in this invention, this embodiment reverses the order of steps (3) and (4) in Example 1, so that the ion exchange effluent enters the electrodialysis system first, and then enters the ultrafiltration system. The results show that after about 4 hours of operation, the electrodialysis membrane stack resistance increases by about 30%, and the current efficiency decreases by about 20%. Disassembling the membrane stack reveals that a large amount of colloidal substances and caramelized organic matter are deposited on the membrane surface, causing significant irreversible fouling. This phenomenon stems from the fact that large molecular impurities and colloidal components that are not intercepted by ultrafiltration are more likely to accumulate on the ion exchange membrane surface under the action of an electric field, forming an organic fouling layer, thereby reducing the ion migration efficiency of the membrane and causing an abnormal increase in transmembrane pressure difference. The fouled membrane cannot be completely restored by conventional electrodialysis regeneration operations, greatly shortening the membrane stack's service life. At the same time, even if ultrafiltration is used subsequently, the loss of ion migration performance caused by membrane fouling cannot be reversed, making subsequent Ca 2+ The loading of the chromatogram and mixed bed increased significantly.

[0106] The experimental results fully demonstrate that ultrafiltration to remove colloidal and polymeric impurities, followed by electrodialysis to direct ion migration, is the necessary sequence for the electronic-grade purification route of this invention. If the sequence is reversed, the membrane system will suffer irreversible damage, making it impossible to achieve electronic-grade purity.

[0107] Example 6: Applicability of different raw material systems

[0108] To evaluate the universality of the process of this invention for systems with different sugar alcohol compositions, this embodiment uses a crude polyol stock solution mainly composed of disitols (65.3 wt% maltitol, 20.2 wt% sorbitol, 2.0 wt% mannitol, and 12.5 wt% higher sugar alcohols), and performs purification treatment strictly according to all process conditions of Example 1. The results show that the obtained product has a conductivity of approximately 0.81 μS / cm, a total metal ion content of approximately 0.09 ppm, a color of approximately 9 APHA, and a reducing sugar content of less than 0.01 wt%. Other key indicators are consistent with those of Example 1. This result demonstrates that the multi-stage coupled deep purification system of this invention can adapt to polyol mixtures with different composition ratios, viscosity characteristics, and reducing sugar backgrounds, exhibiting high system compatibility and raw material adaptability. Therefore, this invention is not only applicable to the sorbitol-maltitol system but also to mixed systems mainly composed of various higher sugar alcohols, functional sugar alcohols, or disitols, forming a robust foundation for industrial application.

[0109] The proposed electronic-grade polyol refining route exhibits high synergy across a multi-dimensional purification chain, encompassing multi-form metal dismantling, weak complex removal, colloid removal, deep deionization, and final polishing. Each unit is systematically designed in terms of process sequence, parameter range, and property matching. This process achieves an excellent balance in terms of purity, energy consumption, resin lifespan, and continuous operation stability, stably producing electronic-grade polyol products with total metal ions ≤0.1 ppm and conductivity ≤1 μS / cm. The entire process is aqueous, solvent-free, and leaves no heavy metal catalytic residues. It features a long equipment regeneration cycle, low waste volume, and environmental friendliness, demonstrating significant industrialization advantages and promotional value.

Claims

1. A process for the preparation of an electronic grade polyhydric sugar alcohol, characterized by, It comprises the following steps: (1) raw material pretreatment and decolorization: filtering the crude polyol solution to remove particulate impurities, and adding activated carbon for decolorization treatment, and then filtering to obtain a decolorized solution; (2) macroporous ion exchange desalination: the decolorized solution obtained in step (1) is sequentially treated by macroporous strong acid cation exchange resin and type II macroporous strong base anion exchange resin to remove free metal ions and anions and reduce the conductivity; (3) ultrafiltration to remove colloidal and macromolecular impurities: the solution obtained in step (2) is subjected to ultrafiltration treatment to remove colloidal and macromolecular impurities in the solution; (4) electrodialysis for deep ion removal: the ultrafiltration permeate of step (3) is subjected to electrodialysis treatment to further remove weakly bound metal ions and small molecule inorganic ions; (5) Ca 2+ Type ion exchange chromatography separation: the solution obtained in step (4) is passed through a Ca 2+ Type weak acid ion exchange resin column, and the separation is carried out by using the affinity difference between sugar alcohol, reducing sugar and metal complex and Ca 2+ Type resin, and the main fraction is collected; (6) mixed bed polishing: the main fraction obtained in step (5) is sent to a mixed bed column composed of strong acid cation resin and strong base anion resin for deep desalination; (7) vacuum concentration and degassing: the mixed bed effluent of step (6) is concentrated to the target concentration, and subjected to precision filtration and degassing treatment to obtain an electronic grade polyol product.

2. The production method according to claim 1, characterized by, In step (1), the solid content of the crude polyol solution is 55-70 wt%, the decolorization temperature is 50-60℃, and the activated carbon addition amount is 0.2-0.5 wt%.

3. The preparation method according to claim 1, characterized in that, In step (2), the treatment temperature is 35-45℃, and the flow rate is 3-6 BV / h.

4. The production method according to claim 1, characterized by, In step (3), the ultrafiltration membrane has a molecular weight cut-off of 800-1500 Da, and the membrane material is polyether sulfone or polyvinylidene fluoride.

5. The preparation method according to claim 1, characterized in that, In step (4), the operating voltage of the electrodialysis is 20-40 V, and the current density is 3-6 mA / cm 2 .

6. The method of claim 1, wherein, In step (5), the Ca 2+ The Ca-type weakly acidic ion exchange resin is selected from Ca-Dowex 50WX8 resin or Ca-type 001 x7 resin.

7. The preparation method according to claim 1, characterized in that, In step (6), the resin in the mixed bed column is an electronic grade or ultrapure water grade core-shell type strong acid / strong base resin, and the volume ratio of cation resin to anion resin is 1:

1.

8. The preparation method according to claim 7, characterized in that, The cation resin in the mixed bed column is H + The anion resin is OH - The anion resin is OH 9. An electronic grade polyol prepared by the method of any one of claims 1 to 8.

10. The electronic grade polyol of claim 9, wherein, The electronic grade polyhydric sugar alcohol prepared has the following properties: total metal ions ≤ 0.1 ppm, single metal ions ≤ 0.05 ppm, Cl - / SO4 2- each ≤ 0.2 ppm, conductivity (25°C) ≤ 1 μS / cm, reducing sugar ≤ 0.01 wt%, color (APHA) ≤ 10, particle number (≥ 0.2 μm) ≤ 10 4 / L.

Images