WO2011131008A1

WO2011131008A1 - Method for preparing nano-nickel powder with microchannel reactor

Info

Publication number: WO2011131008A1
Application number: PCT/CN2010/079476
Authority: WO
Inventors: 张利雄; 张钰; 王重庆; 董利; 徐南平
Original assignee: 南京工业大学
Priority date: 2010-04-19
Filing date: 2010-12-06
Publication date: 2011-10-27
Also published as: CN101804459A; CN101804459B

Abstract

A method for preparing nano-nickel powder with microchannel reactor is provided. The method comprises the following steps: preparing the alcoholic solution of soluble nickel salt and the alcoholic solution of alkaliferous hydrazine hydrate; injecting the two solutions into a heated micromixer according to a certain molar ratio of hydrazine hydrate/nickel; directly injecting the mixed solution into the heated microchannel reactor; separating and washing the products and then storing them without air. During the preparation process, solvents partially vaporize to form a flowing form of gas phase and liquid phase section flows, which can eliminate the blockage in the microchannel reactor during the process of synthesizing the nano granules, and thereby the nano-nickel granules can be continuously synthesized. Furthermore, the preparation process has the advantages of no addition of any surfactants such as dispersing agents, low cost of raw materials, simple operation, uniform nano-nickel granule size, good dispersibility and the like.

Description

Method for preparing nano nickel powder by using microchannel reactor

Technical field

The invention relates to a preparation method of preparing nano metal nickel powder, in particular to a method for continuously preparing nano nickel powder through a microchannel reactor. Background technique

Nanomaterials are one of the most active areas of current research. Due to their unique physical and chemical properties, nano-nickel has been widely used in many fields such as catalysts, battery materials, magnetic materials and nano-coating materials.

At present, the preparation methods of nano nickel mainly include a carboxyl group thermal decomposition method, an evaporation condensation method, a physical preparation method, a hydrothermal method, an electrolysis method, a mechanical pulverization method, a microemulsion method, and a chemical reduction method. Among these preparation methods, the liquid phase chemical reduction method has become a focus of researchers due to its advantages such as simple process, easy operation, and uniform product particles. Patent CN200510121349.1 discloses a preparation method of nano nickel powder, which uses water-soluble polymer monomer as surface dispersant, hydrazine hydrate or sodium borohydride as reducing agent, and uses a batch reactor to liquid phase under alkaline conditions. Nano nickel powder having a particle diameter of 10 to 50 nm was prepared by reducing nickel chloride or nickel sulfate. Patent CN200810123127.7 uses sodium disulfite as reducing agent, polyvinylpyrrolidone as dispersant, propylene glycol-water mixed solution as reaction medium, and nano-nickel powder with particle size of 30-60 nm synthesized by liquid phase chemical reduction in batch reactor. . The method has simple process, low production cost and good industrial application prospect. Patent CN200910051160.8 In the preparation of nano-nickel powder, the nickel salt and the dispersing agent are thoroughly mixed, and then the alkali solution is added dropwise, and after stirring for 30-60 minutes, the reducing agent is added dropwise to carry out the reduction reaction. The nano nickel powder is uniformly dispersed and the preparation process is simple.

The liquid nickel chemical powder prepared by the above liquid phase chemical reduction method is synthesized in a batch manner, and the dispersing agent is added in the preparation process to prevent the agglomeration of the nano nickel, which brings inconvenience to the subsequent treatment. Patent CN03113326.6 discloses a process and a special equipment for continuously preparing ultrafine nano powder by a precipitation method, which first mixes a nickel salt and a reducing agent in a tank reactor, and then mixes the materials. The reaction is carried out in a tubular reactor equipped with a static mixer, and finally a nano-nickel powder having a good dispersibility and a narrow particle size distribution can be obtained. The whole process is continuous and simple to operate, but conventional reactors have different degrees of "magnification effect" during the amplification process. In recent years, microchannel reactors have achieved remarkable results in the continuous preparation of nano metal particles due to their excellent properties in heat transfer, mass transfer, size control and absence of "amplification effect". Microchannels have been successfully utilized. The reactor continuously synthesizes a variety of nano metal particles, including Au (Nano Lett. 2005, 5, 685), Ag (Nano Lett. 2004, 4, 2227), Pt (J. Nanosci. Nanotechnol. 2004, 4, 788), Cu (J. Phys. Chem. B. 2005, 109, 9330) and Co (Chem. Mater. 2006, 18, 2817), etc., but using microchannels to prepare nano-nickel and Rarely, the main reason may be that nano metal particles will deposit in the channel during the synthesis process and block the microchannel, making the reaction impossible. We have successfully solved the problem of clogging of nanoparticles in microchannels by using the flow pattern of liquid-liquid two-phase block flow. However, this method requires two-phase separation after the reaction, which will increase the subsequent processing steps. Therefore, it is necessary to develop a preparation method that can continuously synthesize nano-nickel particles while being easy to operate. Summary of the invention

The object of the present invention is to overcome the disadvantages of low batch production efficiency, and to utilize the flow form of the gas-liquid two-phase block flow formed by partial vaporization of the solvent to solve the problem of clogging of the microchannel during the synthesis of the particles, and to provide a A method for preparing nano-nickel powder using a microchannel reactor.

The technical scheme of the invention is: A method for preparing nano nickel powder by using a microchannel reactor, the specific steps are:

1) separately preparing a soluble nickel salt alcohol solution A and a base containing hydrated sterol solution B;

2) The liquid A and the liquid B are mixed according to the molar ratio of hydrazine hydrate/nickel ion 2~10:1 by pump into the heated micro-mixer, and the mixed liquid is directly injected into the heated microchannel reactor to collect and collect. Discharge product;

3) The product is separated by centrifugation, washed to pH=6~7, and stored in isolation air; nano-nickel powder is obtained.

Preferably, the soluble nickel salt is nickel chloride, nickel sulfate, nickel nitrate, nickel acetate, more preferably nickel chloride or nickel acetate; and the concentration of the alcohol solution of the soluble nickel salt is 0.05 to 1.0 mol/L. Step 1) The concentration of the alkali-containing hydrazine hydrate solution in the B solution is 0.15-2 mol/L, and the molar ratio of the alkali/hydrated hydrazine is 0.8 to 1.2:1.

Preferably, the base in the alkali-containing hydrazine hydrate solution in the step 1) is NaOH or KOH; preferably the alcohol in the solution A and the solution B in the step 1) is methanol, ethanol, isopropanol or ethylene glycol, more preferably methanol, Ethanol.

The above steps 2) the micro-mixer and the micro-channel reactor are heated at a temperature of 50 to 90 V. Preferably, the micromixer has a channel diameter of 25 to 200 μm, the material stays in the micromixer for 10 to 100 ms, the microchannel reactor has an inner diameter of 0.5 to 3 mm, and the residence time of the material in the microchannel reactor is 2 ~30 min.

The flow chart of the reaction apparatus of the present invention is shown in Fig. 1.

Beneficial effect

1. The invention adopts a microchannel reactor for nano nickel synthesis, which can realize continuous and controllable reaction process, and is simple and easy to operate, has no "amplification effect", and the production process can be industrialized;

2. The invention does not add any other dispersing agent or initiator in the synthesis process, and the raw material cost is low, and the synthesized nano nickel particles have the advantages of narrow particle size distribution and good dispersibility;

3. The invention adopts a partial vaporization of a solvent to form a gas-liquid two-phase block flow, which can avoid the nano-particles in the micro-pass Blockage in the channel and facilitate subsequent separation of the product. DRAWINGS

1 is a schematic flow chart of a device for preparing a nano-nickel powder in a microchannel reactor, wherein a: a nickel salt alcohol solution; b: a hydration sterol solution containing a base; 1-1 and 1-2: a feed pump; 2: a micromixer 3: water bath heating constant temperature zone; 4: microchannel reactor; 5: product collection tank;

2 is an X-ray diffraction pattern (XRD) of the sample of Example 1;

Figure 3 is a transmission electron micrograph (TEM) of the sample of Example 1;

Figure 4 is a field emission scanning electron micrograph (FESEM) of the sample of Example 2. detailed description

Example 1

Dissolve 4.75 g of nickel chloride in 50 ml of ethanol and configure liquid A. Add 4.71 g of hydrazine hydrate and 3.2 g of sodium hydroxide to 50 ml of ethanol to configure liquid B. The liquids of liquid A and liquid B are pumped through the pump at a temperature of 70 ° C. The micro-mixer with a diameter of 100 μm (purchased from IMM, Germany) was mixed. After 60 ms, the solution was directly injected into a microchannel reactor with a reaction temperature of 70 V and an inner diameter of 2 mm (purchased from Nanjing Qingqing Industrial Co., Ltd.). The reaction was carried out for 3.5 min, and the product was collected. The product was separated by centrifugation, washed to pH=7, and stored in an isolated atmosphere. XRD showed that the product was nickel metal, and the average nano-nickel particle size was 73 nm. The X-ray diffraction pattern (XRD) of the sample was shown in Figure 2, and the TEM image is shown in Figure 3. Example 2

Dissolve 9.51 g of nickel chloride in 100 ml of ethanol to configure liquid A. Add 8.83 g of hydrazine hydrate and 6 g of sodium hydroxide to 100 ml of ethanol to configure liquid B. The liquids of liquid A and liquid B are pumped at a temperature of 70 °C. A micro-mixer with a channel diameter of 100 μm (purchased from IMM, Germany) was mixed. After 80 ms, the solution was directly injected into a microchannel reactor with a reaction temperature of 70 ° C and an inner diameter of 2 mm (purchased from Nanjing Qingqing). In the industrial company, the reaction was carried out for 5 min, and the product was collected. The product was separately centrifuged, washed to pH=6.5, and the obtained sample was stored in air. The XRD shows that the sample is nickel metal, and the obtained nano nickel has an average particle diameter of 65 nm. The FESEM image of the sample is shown in Fig. 4. Example 3

Dissolve 2.08 g of nickel chloride in 50 ml of ethanol to configure solution A, and add 4.12 g of hydrazine hydrate and 2.8 g of sodium hydroxide. The liquid B was placed in 50 ml of ethanol, and the liquids A and B were mixed by a pump into a micro-mixer (purchased from IMM, Germany) with a channel diameter of 50 μm, and the solution was kept for 50 ms. The reaction was carried out by directly injecting a microchannel reactor (purchased from Nanjing Nianqing Industrial Co., Ltd.) with a reaction temperature of 68 ° C and an internal diameter of 2 mm for 4 min to collect the product. The product was separately centrifuged and washed to pH=6.5. The resulting sample was stored in air. The sample was characterized by XRD as nickel metal, and the obtained nano-nickel had an average particle diameter of 45 nm. Example 4

Dissolve 5.67 g of nickel acetate in 60 ml of ethanol to configure liquid A. Add 8.06 g of hydrazine hydrate and 6.02 g of sodium hydroxide to 60 ml of ethanol to configure liquid B. The liquids of liquid A and liquid B are pumped through a pump at a temperature of 72 ° C. The micromixer with a diameter of 50 μm (purchased from IMM, Germany) was mixed and the solution was directly injected into the reaction temperature for 72 ms. C, a microchannel reactor with an inner diameter of l mm (purchased from Nanjing Qingqing Industrial Co., Ltd.) was allowed to react for 8 min, and the product was collected. The product was separated by centrifugation and washed to pH=6.5 to isolate the sample. It was stored in air and characterized by XRD to show that the sample was nickel metal. The obtained nano nickel has an average particle diameter of 50 nm. Example 5

Dissolve 8.32 g of nickel chloride in 100 ml of methanol to configure liquid A, add 9.28 g of hydrazine hydrate and 5.67 g of sodium hydroxide to 100 m of methanol to configure liquid B. The liquids of liquid A and liquid B are pumped at a temperature of 62 °C. Micro-mixer with a channel diameter of 25 μm

(purchased from IMM, Germany), after 40 ms, the feed was directly injected into the microchannel reactor (purchased from Nanjing Nianqing Industrial Co., Ltd.) with a reaction temperature of 62 °C and an internal diameter of 1 mm for 7 min to carry out the reaction. The product was discharged, and the product was separately centrifuged, washed to pH = 6.5, and the obtained sample was stored in air. XRD analysis showed that the sample was nickel metal, and the average nano-nickel particle size was 55 nm.

Claims

Claim

A method for preparing nano nickel powder by using a microchannel reactor, the specific steps of which are:

2. The method according to claim 1, wherein the soluble nickel salt in the step 1) is nickel chloride, nickel sulfate, nickel nitrate, nickel acetate; and the concentration thereof is 0.05 to 1.0 mol/L.

3. A method according to claim 1, characterized in that the concentration of the alkali-containing hydrazine hydrate solution in step 1) is 0.15-2 mol/L, wherein the molar ratio of alkali/hydrated hydrazine is 0.8 to 1.2:1.

4. The method according to claim 1, wherein the base in the alkali-containing hydration sterol solution in step 1) is NaOH or KOHo

5. Process according to claim 1, characterized in that the alcohol in solution A and solution B in step 1) is methanol, ethanol, isopropanol or ethylene glycol.

6. The method of claim 1 wherein the step 2) the micromixer and the microchannel reactor are heated to a temperature of 50 to 90 volts.

7. The method according to claim 1, wherein the micro-mixer has a channel diameter of 25 to 200 μm and the material stays in the micro-mixer for 10 to 100 ms; the inner diameter of the microchannel reactor is 0.5~3 mm, the residence time of the material in the microchannel reactor is 2~30 min.