High-purity nickel powder, system and method for field flow control preparation of plant polyphenol

Abstract

The invention discloses high-purity nickel powder prepared from plant polyphenol through field flow control, a system and a method, a sulfonated tannic acid-gallic acid bio-based system is used as a reduction-stabilizer, and green and efficient preparation of nickel nano powder is realized through a multi-physical field synergistic effect of a three-stage gradient continuous flow reactor and double-frequency ultrasonic-pulse microwave-nitrogen bubbling. The total residence time of the reaction is 25.1-37.7 min, mother liquor is reused after being subjected to salt separation treatment (nanofiltration desalination of a NiSO4 system and ion exchange Cl removal of a NiCl2 system), and the wastewater discharge amount is greatly reduced compared with that of a traditional process; the surface oxygen content of the product is smaller than or equal to 0.9 wt%, the PDI is smaller than or equal to 0.15, the tap density is larger than or equal to 4.0 g / cm < 3 >, the GB / T 33828-2017 standard is met, the method can be used for the high-end field of lithium ion batteries and the like, and green industrial production of the nanometer nickel powder is achieved from the source.

Description

Technical Field

[0001] This invention relates to the field of green manufacturing technology for nanomaterials, and in particular to a system and method for preparing high-purity nickel powder, which is prepared by field-controlled flow of plant polyphenols. Background Technology

[0002] Nickel nanoparticles are metallic nickel powders with particle sizes between 1 and 100 nanometers. Due to their unique small size effect, surface effect, and quantum effect, they have been widely used in fields such as batteries, magnetic recording materials, microelectronic materials and devices, chemical industry, and national defense.

[0003] Existing nickel nanopowder preparation technologies suffer from the following bottlenecks: 1. Chemical safety defects: Traditional reducing agents (such as hydrazine hydrate and sodium borohydride) are highly toxic, and each ton of product generates 3-5 tons of high COD wastewater (chemical oxygen demand COD value is usually >5000mg / L), which puts significant pressure on the environment.

[0004] 2. Inadequate product quality: Traditional products have surface oxygen content > 2wt%, polydispersity index (PDI) > 0.25, and tap density < 3.8 g / cm³. 3 This does not meet the requirements for high-purity nickel powder in the GB / T 33828-2017 standard.

[0005] 3. Low production efficiency: Batch reaction time > 3h, gas phase method energy consumption > 4.5kWh / kg, liquid phase method energy consumption > 2.8kWh / kg, laboratory yield < 50g / h, making it difficult to achieve industrial mass production. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a system and method for preparing high-purity nickel nanopowders through a continuous flow reactor and multi-physics field coupling, using a "sulfonated tannic acid-gallic acid" bio-based synergistic system as a reducing-stabilizing agent. This aims to solve the problems of high toxicity, high pollution, insufficient product quality, and low production efficiency in traditional processes.

[0007] The purpose of this invention is to provide a high-purity nickel powder, which is prepared by the combined use of four functional modules and methods, forming a closed-loop continuous flow system through a polytetrafluoroethylene (PTFE) flexible tube and a high-purity quartz tube, as detailed below: 1. The raw material preparation module is used to prepare the reaction solution. Core equipment: 200L double-walled glass mixing tank (with external constant temperature water bath, temperature fluctuation ±0.5℃), equipped with pH online monitoring instrument (accuracy ±0.05), 0.2μm nitrogen deoxygenation distributor, and 20kHz ultrasonic disperser (50-80W).

[0008] Composition of raw material solution: nickel salt (0.05-0.30 mol / L, NiSO4・6H2O / NiCl2・6H2O, purity ≥99.9%); sulfonated tannic acid (0.8-1.2 g / L, sulfonation degree 25-35%, also used as Y2O3 dispersant), gallic acid (0.20-0.35 g / L, purity ≥99%); Y2O3 (0.03-0.06 wt%, particle size ≤100 nm after ultrasonic dispersion); citric acid-sodium citrate buffer (0.05 mol / L each, pH 5.2-5.8, buffer capacity ≥0.03 mol / (L・pH)).

[0009] Nitrogen microbubbling: Nitrogen is filtered through a 0.01μm filter (purity ≥99.999%), with a flow rate of 0.5-1.2L / min, a gas-liquid ratio of 0.04-0.06v / v, and a bubble diameter of 0.6mm; it serves as an ultrasonic cavitation nucleus (improving cavitation efficiency by 35%) and isolates oxygen (ensuring DO ≤0.5mg / L).

[0010] Key indicators: Dissolved oxygen (DO) in raw material solution ≤ 0.5 mg / L, PDI of Y2O3 dispersion ≤ 0.2 (detected by dynamic light scattering DLS).

[0011] The three-level gradient continuous flow reaction module and the multiphysics coupling module realize continuous reaction. Three-stage gradient continuous flow reaction module Core equipment: A 6.0m long, 8.0±0.1mm inner diameter high-purity quartz spiral coil (temperature resistance ≥200℃, conforming to GB / T 18943-2018), with three independent temperature control sections (PID controller + infrared closed-loop, temperature fluctuation ±0.3℃). Real-time monitoring of the reaction process and Ni... 2 ⁺→Ni 0 Conversion (correlated with Raman probe), particle size / PDI (correlated with DLS), system temperature (correlated with infrared thermometer), and dissolved oxygen (correlated with online DO meter) are used to ensure process stability.

[0012] Temperature zone Set temperature (°C) Dwell time (s) Level 1 65±1 125-188 Level 2 75±1 502-753 Level 3 85±1 879-1319 total - 1506-2260 Multiphysics coupling module Dual-frequency ultrasound: 28kHz (100W / L, to break up initial agglomerates), 100kHz (200W / L, to suppress secondary agglomerates).

[0013] Pulsed microwave: 2.45GHz gallium nitride (GaN) power devices (efficiency ≥92%), duty cycle 30-50%.

[0014] After the end-of-life reaction, the material is filtered through an Al2O3 ceramic membrane in a cross-flow manner to retain nano-nickel powder, which is then dried and passivated. The process is carried out in a φ100mm fluidized bed dryer (60℃ nitrogen flow, moisture ≤0.3wt%). Online two-fluid atomization passivation is performed (0.3wt% oleic acid / ethanol + 0.05wt% epigallocatechin gallate (EGCG) solution, atomized particle size 10-20μm, spray angle 60°).

[0015] The mother liquor recycling module is used to recycle mother liquor. Mother liquor treatment (applicable to NiSO4): After being concentrated by evaporation using a mechanical vapor recompression (MVR) system (evaporation rate 15L / h, compression ratio 1.8, condensate COD < 150mg / L), every 3 batches are desalted by a 0.5μm membrane (Na2SO4 removal rate > 60%) before reuse.

[0016] Mother liquor treatment (NiCl2): Cl⁻ is removed by cation exchange resin (removal rate 96%), then it enters MVR for evaporation. After being reused 3 times, the Cl⁻ concentration is ≤0.03mol / L.

[0017] The present invention has the following advantages: 1. Bio-based reduction-stabilized synergistic system Synergistic mechanism: The "sulfonated tannic acid-gallic acid" complex system enhances Ni through chelation. 2 The reduction efficiency is improved by forming a protective film on the nickel powder surface through "π-d coordination bonds + hydrogen bonds", which inhibits agglomeration and makes PDI ≤ 0.15.

[0018] Antioxidant design: Y2O3 uses oxygen vacancies to capture oxygen and combines with a bio-based protective film to form a double barrier, controlling the oxygen content on the product surface to ≤0.9wt%.

[0019] 2. Multiphysics Collaborative Enhancement Technology Energy matching: Dual-frequency ultrasound (28kHz + 100kHz, power ratio 1:1.8) + pulsed microwave (150-200W / L), optimized by online DLS, which improves efficiency by 2 times compared with a single physical field and has no local overheating.

[0020] Multi-stage synergy: Nitrogen microbubbles combine the functions of "cavitation nucleus (improving cavitation efficiency by 35%), heat transfer medium (radial temperature difference ≤1.5℃), and oxygen barrier" to solve the temperature gradient problem of traditional reactors.

[0021] 3. Green circular process system Raw material reuse: The mother liquor is desalinated according to the nickel salt type (NiSO4 nanofiltration / NiCl2 ion exchange), and the nickel utilization rate is ≥82% after 3 reuses.

[0022] Environmental control: The citric acid buffer system (pH 5.5-6.5) inhibits Ni (OH)2 byproducts; wastewater discharge and COD content are greatly reduced. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of a plant polyphenol field-controlled flow preparation system for high-purity nickel powder; Figure 2 TEM images and particle size distribution statistics of nano-nickel powder (Example 1); Figure 3 This is an XPS analysis chromatogram of the oxygen content on the product surface.

[0024] In the diagram: 1-1: Raw material preparation module: double-layered glass mixing tank, equipped with constant temperature water bath, online pH monitoring, nitrogen bubbling deoxygenator distributor, and ultrasonic disperser; 1-2: Three-stage gradient continuous flow reaction module: high-purity quartz spiral coil, three-stage independent temperature control. Real-time measurement of temperature, particle size, dissolved oxygen, and Raman spectroscopy; 1-3: Multi-physics coupling module: dual-frequency ultrasound and pulsed microwave; 1-4: End-of-pipe treatment and mother liquor recycling module; 3-1: Ni 2p-XPS; 3-2: O 1s-XPS. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the four functional modules are connected to form a closed-loop continuous flow system through polytetrafluoroethylene (PTFE) hoses and high-purity quartz tubes.

[0027] Example 1 40nm high-purity nickel powder (NiSO4 system) was prepared according to the following steps. 1. Raw material preparation The reaction solution composition is as follows: 0.12 mol / L NiSO4・6H2O, 1.0 g / L sulfonated tannic acid, 0.30 g / L gallic acid, and 0.05 wt% Y2O3; Preparation process: First, mix Y2O3 with sulfonated tannic acid solution and disperse by ultrasonication at 20kHz for 15min (DLS detection particle size 85nm, PDI=0.18). Then add the remaining components, adjust the pH to 5.5 with citrate-sodium citrate buffer, and purge with nitrogen to remove oxygen until DO=0.4mg / L.

[0028] 2. Continuous reaction Equipment parameters: Three-stage gradient coil reactor flow rate 10 mL / min, total residence time 28.5 min; dual-frequency ultrasonic power 28 kHz 100 W / L + 100 kHz 180 W / L; pulsed microwave power 180 W / L, duty cycle 40% (reaction liquid center temperature 86℃); nitrogen flow rate 0.8 L / min; Online monitoring: Raman detection Ni 2 ⁺ Conversion rate reaches 99.8% (210cm⁻) 1 (Peak intensity stable), average particle size monitored by DLS was 39±2nm, PDI=0.12, and DO was stable at 0.38-0.42mg / L.

[0029] 3. End-of-pipe processing Solid-liquid separation: 0.2μm ceramic membrane filtration, nickel powder rejection rate 99.6%; Mother liquor reuse: After evaporation and concentration by MVR, it is desalted by nanofiltration membrane (Na2SO4 removal rate 92%) and reused in the preparation of raw materials; Drying and passivation: fluidized bed drying (0.25wt% moisture), after atomization passivation, the oxygen content on the product surface is 0.83wt%.

[0030] 4. Product performance testing Testing items Detection methods Test results GB / T 33828-2017 Standard Average particle size TEM (n=300) 38±1.5nm 20-100nm Surface oxygen content XPS (Peak Segmentation Fitting) 0.83wt% ≤1.0wt% Multidispersion Index (PDI) DLS 0.12 ≤0.20 Tap density GB / T 5162-2006 <![CDATA[4.25g / cm 3 ]]> <![CDATA[≥3.8g / cm 3 ]]> purity ICP-OES 99.93wt% ≥99.90wt% Total impurities ICP-OES 680ppm <1000ppm Storage stability (6 months) XPS after being placed at room temperature Oxygen content 0.92wt% Increase ≤ 0.2wt% Example 2 60nm high-purity nickel powder (NiCl2 system) was prepared according to the following steps. 1. Raw material preparation The reaction solution composition is as follows: 0.10 mol / L NiCl2・6H2O, 0.9 g / L sulfonated tannic acid, 0.25 g / L gallic acid, and 0.04 wt% Y2O3; Preparation process: Y2O3 was ultrasonically dispersed to a particle size of 92nm (PDI=0.19), pH was adjusted to 5.6, and DO was controlled at 0.38mg / L.

[0031] 2. Continuous reaction Equipment parameters: flow rate 8 mL / min, total residence time 37.7 min; dual-frequency ultrasonic power 28 kHz 80 W / L + 100 kHz 150 W / L; microwave power 200 W / L, duty cycle 38% (center temperature 88℃); nitrogen flow rate 1.0 L / min; Online monitoring: Ni 2 ⁺ Conversion rate 99.7%, DLS average particle size 58±3nm, PDI=0.13.

[0032] 3. End-of-pipe processing Mother liquor treatment: Cl⁻ is removed by cation exchange resin (removal rate 96%), then it enters MVR for evaporation. After being reused 3 times, the Cl⁻ concentration is ≤0.03mol / L; Drying and passivation: Same as in Example 1, product moisture content 0.28wt%.

[0033] 4. Product performance testing Average particle size: 58±3 nm (TEM); Surface oxygen content: 0.79wt% (XPS, of which NiO oxygen content is 0.28wt% and passivation layer oxygen content is 0.51wt%). Tap density: 4.31 g / cm³ 3 ; Purity: 99.91 wt%, total impurities: 720 ppm; Nickel ion utilization rate: 82% (after 3 reuses) Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity nickel powder from plant polyphenols under controlled flow conditions, characterized in that, Includes the following steps, S1. Preparation of reaction solution: Mix nickel salt, sulfonated tannic acid, gallic acid, Y2O3 and citrate-sodium citrate buffer solution; S2. Continuous reaction: The reaction solution is introduced into a three-stage gradient coil reactor, and dual-frequency ultrasound, pulsed microwave and nitrogen bubbling are applied simultaneously; S3. End-of-line treatment: The reacted material is filtered through an Al2O3 ceramic membrane to retain nano-nickel powder. The nickel powder is dried by a nitrogen-fluidized bed and then passivated by online atomization with oleic acid / ethanol and EGCG solution to obtain nano-nickel powder.

2. The system and method for preparing high-purity nickel powder from plant polyphenols under controlled flow conditions according to claim 1, characterized in that: The nickel salt is selected from NiSO4・6H2O or NiCl2・6H2O; if the raw material is NiSO4, the mother liquor generated in step S3 is evaporated and then desalted and reused through a nanofiltration membrane; if the raw material is NiCl2, the mother liquor generated in step S3 is first dechlorinated by a cation exchange resin and then evaporated and reused.

3. The method for preparing high-purity nickel powder from plant polyphenols under controlled flow according to claim 1, characterized in that: The degree of sulfonation of sulfonated tannic acid is 25-35%; the purity of gallic acid is ≥99%; the amount of Y2O3 added is 0.03-0.06wt%, and the particle size is ≤100nm after ultrasonic dispersion at 20kHz; the pH of the buffer solution is 5.2-5.8, and the buffer capacity is ≥0.03mol / (L・pH).

4. The method for preparing high-purity nickel powder from plant polyphenols under controlled flow according to any one of claims 1-3, characterized in that: The nickel salt concentration is 0.05-0.30 mol / L, the sulfonated tannic acid concentration is 0.8-1.2 g / L, and the gallic acid concentration is 0.20-0.35 g / L.

5. The method for preparing high-purity nickel powder from plant polyphenols under controlled flow according to claim 1, characterized in that: Nitrogen gas is introduced during the preparation of the reaction solution to ensure that the dissolved oxygen (DO) in the reaction solution is ≤0.5mg / L.

6. The method for preparing high-purity nickel powder from plant polyphenols under controlled flow according to claim 1, characterized in that: The three-stage gradient reaction temperature zones are 65℃, 75℃, and 85℃, respectively.

7. The method for preparing high-purity nickel powder from plant polyphenols under controlled flow according to claim 1, characterized in that: The dual-frequency ultrasound is 28kHz 80-120W / L and 100kHz 150-180W / L, with a power ratio of 1:1.8; the pulsed microwave is a 2.45GHz GaN solid-state source with a power density of 150-200W / L and a duty cycle of 35-45%; nitrogen bubbling is used with a gas-liquid ratio of 0.04-0.06v / v.

8. The plant polyphenol field-controlled flow high-purity nickel powder prepared according to any one of claims 1-7, characterized in that: The average particle size is 20-80 nm, the surface oxygen content is ≤0.9 wt%, of which the NiO oxygen content is ≤0.35 wt%, the polydispersity index (PDI) is ≤0.15, and the tap density is ≥4.0 g / cm³. 3 Purity ≥ 99.9 wt%, total impurities < 1000 ppm, oxygen content increase ≤ 0.1 wt% after 6 months of storage at room temperature.

9. A plant polyphenol field-controlled flow system for obtaining the high-purity nickel powder of claim 8, characterized in that, It includes four functional modules, which form a closed-loop continuous flow system through polytetrafluoroethylene (PTFE) hoses and high-purity quartz tubes. Raw material preparation module: includes a double-layered glass mixing tank, an online pH monitor, a nitrogen deoxygenation distributor, and an ultrasonic disperser; the outer layer of the mixing tank is equipped with a constant temperature water bath. Three-stage gradient coil reactor and online monitoring module: total length 6.0m, inner diameter 8.0±0.1mm, segmented tube lengths 0.5m / 2.0m / 3.5m, each segment equipped with an independent PID + infrared closed-loop temperature control system; includes Raman probe, dynamic light scattering instrument, infrared thermometer and online dissolved oxygen meter; Multiphysics module: includes a dual-frequency ultrasonic system (28kHz + 100kHz piezoelectric transducer), a 2.45GHz GaN pulsed microwave source, an optical fiber temperature probe, and a nitrogen microbubble device. End-of-line processing module: includes an Al2O3 ceramic membrane filtration system, an MVR evaporator, a nanofiltration membrane / cation exchange resin, a nitrogen flow bed dryer, and a two-fluid atomization passivation device.

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