Lemniscate microchannel reactor and method for preparing nanoparticles

Abstract

Spiral structures on the left side and the right side are circular arcs, the spiral diameters of the two ends are equal, the spiral diameter ranges from 1 cm to 10 cm, the arc radian ranges from Pi to 1.8 Pi, the distance between vertexes on the left side and the right side is 2-3 times of the spiral diameter, the inner diameter of a micro-channel ranges from 0.5 mm to 2 mm, the outer diameter of the micro-channel ranges from 1 mm to 5 mm, the pitch ranges from 2 times to 5 times of the inner diameter of the micro-channel, and the total length of the reactor ranges from 0.2 m to 5 m. Regulating and controlling the size of the nano-particles by changing the process parameters of the micro-channel reaction or / and the design parameters of the lemniscate type micro-channel reactor; the process parameters comprise the flow of reaction materials; the design parameters comprise the length, the inner diameter and the spiral diameter of the micro-channel reactor; the spiral structure of the lemniscate microchannel reactor enables fluid to form secondary flow, the direction of the secondary flow is changed for multiple times by changing the flowing angle at the cross position, the mixing degree is enhanced, the heat and mass transfer performance is good, the controllability is high, blockage is not prone to occurring, and the lemniscate microchannel reactor is particularly suitable for synthesizing nano particles through a liquid phase precipitation reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to a microchannel reactor and a method for preparing nanoparticles. Background Art

[0002] The traditional method of synthesizing nanoparticles by liquid phase precipitation reaction faces many challenges. In the classic precipitation method, the reactants are mixed in a macroscopic reaction vessel. Due to uneven mixing and difficulty in controlling local supersaturation, the nucleation and growth process are prone to randomness, resulting in a wide particle size distribution.

[0003] A microchannel reactor is a device that uses tiny channels (usually 10 to 1000 μm in diameter) to carry out chemical reactions. It has a compact structure, efficient heat and mass transfer performance, and can achieve precise control of reaction conditions. The fluid in the microchannel reactor flows evenly and has a good mixing effect, which helps to improve the selectivity and conversion rate of the reaction. At the same time, the reactor has a flexible modular design and is easy to scale up and down, suitable for various scales from laboratory research and development to industrial production. In addition, the microchannel reactor also has the advantages of high safety and environmental friendliness, and is an important innovative technology in the modern chemical industry.

[0004] Microchannel reactors have significant advantages in synthesizing nanoparticle materials. Their microscale design helps to shorten the diffusion distance of reactants in the channel, improve the reaction rate and mixing efficiency, and can achieve precise control of reaction conditions, thereby optimizing the generation process of solid particles, making the product particle size smaller and more evenly distributed. However, due to the small size of the channel, reactant precipitation, crystallization or particle aggregation may cause channel blockage, affecting the normal operation of the reactor. In addition, in order to improve the mixing efficiency, the currently designed microchannel reactors will have a more complex structure design. These complex structures will cause a large number of dead zones in the system, making the microchannels more prone to blockage than reactors of general structure, greatly limiting the use scenarios.

[0005] Therefore, how to design microchannel reactors to improve mixing efficiency, synthesize nanoparticles with small particle size and narrow distribution, and at the same time reduce blockage to ensure stable operation of the reactor and reduce maintenance costs has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] One of the purposes of the present invention is to provide a microchannel reactor suitable for synthesizing nanoparticles by liquid phase precipitation reaction, which ensures the speed and uniformity of nanoparticle synthesis while keeping the microchannel unobstructed and stable.

[0007] A lemniscate type microchannel reactor, wherein the spiral shape of the lemniscate type microchannel reactor satisfies the characteristics of the Bernoulli lemniscate.

[0008] According to the above scheme, the spiral structures on the left and right sides of the double-twist microchannel reactor are both arcs, the spiral diameters at both ends are equal, the spiral diameter is 1-10 cm, the arc angle is π-1.8π, the distance between the vertices on the left and right sides is 2-3 times the spiral diameter, the inner diameter of the microchannel is 0.5-2 mm, the outer diameter of the microchannel is 1-5 mm, the pitch is 2-5 times the inner diameter of the microchannel, and the total length of the reactor is 0.2-5 m.

[0009] According to the above scheme, the double-twist microchannel reactor is made of metal, glass or high molecular polymer material.

[0010] The second object of the present invention is to provide a method for synthesizing nanoparticles by regulating the size of a liquid phase precipitation reaction using the above-mentioned microchannel reactor.

[0011] The method for synthesizing nanoparticles by regulating the size of liquid phase precipitation reaction using the above-mentioned lemniscate microchannel reactor comprises the following steps: regulating the size of nanoparticles by changing the process parameters of the microchannel reaction or / and the design parameters of the lemniscate microchannel reactor; The process parameters of the microchannel reaction include the flow rate of the reaction materials; The design parameters of the lemniscate microchannel reactor include the length, inner diameter and spiral diameter of the microchannel reactor.

[0012] According to the above scheme, by increasing the flow rate of the reaction materials, the size of the nanoparticles synthesized by the liquid phase precipitation reaction is regulated to decrease, and vice versa.

[0013] According to the above scheme, by increasing the inner diameter of the double-twist microchannel reactor, the size of the nanoparticles synthesized by the liquid phase precipitation reaction is regulated to increase, and vice versa.

[0014] According to the above scheme, by increasing the spiral diameter of the double-twist microchannel reactor, the size of the nanoparticles synthesized by the liquid phase precipitation reaction is regulated to increase, and vice versa.

[0015] According to the above scheme, the size of the nanoparticles is between 10nm and 1500nm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The spiral structure of the double-twist microchannel reactor will cause the fluid to form a secondary flow. By changing the flow angle at the intersection, the direction of the secondary flow is changed multiple times, which enhances the degree of mixing, has good heat and mass transfer performance, strong controllability, and is not prone to clogging. It is particularly suitable for the synthesis of nanoparticles by liquid phase precipitation reaction.

[0017] (2) The reaction device is small in size and occupies little area, which reduces investment costs.

[0018] (3) It has a wide range of applications and is applicable to the synthesis of nanoparticles by liquid phase precipitation reactions. The geometric parameters of the reactor can also be adjusted to control the particle size and distribution of the product.

[0019] (4) The reactor device has a simple structure and low manufacturing and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : Schematic diagram of the synthesis of barium sulfate nanoparticles using a microchannel reactor.

[0021] Figure 2 : Schematic diagram of the structure of the double-zigzag microchannel reactor of the present invention.

[0022] Figure 3 : Example 1: The particle size distribution diagram of nano-barium sulfate obtained.

[0023] Figure 4 : The particle size distribution diagram of nano barium sulfate obtained in Comparative Example 1.

[0024] Figure 5 : The particle size distribution diagram of nano barium sulfate obtained in Comparative Example 2.

[0025] Figure 6 : Comparative Example 3 obtained the particle size distribution diagram of nano barium sulfate.

[0026] Figure 7 : The particle size distribution diagram of nano barium sulfate obtained in Comparative Example 4.

[0027] Figure 8 : Comparative Example 5 obtained the particle size distribution diagram of nano barium sulfate.

[0028] Fig. 9 : The particle size distribution diagram of nano barium sulfate obtained in Comparative Example 6. DETAILED DESCRIPTION

[0029] The following examples further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0030] Example 1 A method for preparing barium sulfate nanoparticles using a microchannel reactor, referring to the attached Figure 1 As shown: 1) At 25°C, use an electronic balance to weigh 14.20 g of sodium sulfate and 20.80 g of barium chloride and dissolve them in 100 mL of deionized water to obtain a barium chloride and sodium sulfate solution with a concentration of 0.1 mol / L.

[0031] 2) The double-twist microchannel reactor is made of PFA material. The structural diagram is shown in the attached Figure 2As shown in the figure, the tube length is 1 m, the microchannel outer diameter is 2 mm, the microchannel inner diameter is 1 mm, the spiral diameter is 1 cm, the distance between the two ends is 3 cm, and the pitch is 4 mm.

[0032] 3) The reactant solutions were pumped into the microchannel reactor at the same flow rate through the plunger pump. After the reaction system was stable, the sample was collected from the reactor outlet. The volume flow rate of the feed pump was 10 mL / min. The system pressure was stabilized at 0 bar and no blockage occurred.

[0033] 4) The reaction solution was centrifuged at 3000 r / min for 3 min, and the obtained white precipitate was washed twice with deionized water and twice with ethanol, and then dried in an oven at 80°C for 24 h to obtain nano-barium sulfate powder.

[0034] The average particle size of the precipitated particle sample was analyzed using a laser particle size analyzer. First, a stable dispersion of the sample in a solvent was prepared by mixing 3 mg of BaSO 4 The powder was dispersed in 10 mL of 1 g / L NaHMP solution to prepare the sample for size analysis, and was ultrasonically treated for 5 min before particle size determination to help the particles disperse properly. The average particle size and PDI of the product were analyzed, and the results were: 218 nm, 0.11, respectively. The particle size distribution of nano barium sulfate prepared in this example is shown in the attached figure. Figure 3 shown.

[0035] Comparative Example 1 Example 1 was repeated, the volume flow rate of the feed pump was increased to 40 mL / min, the reactant flow ratio was 1:1, the analysis conditions were the same as in Example 1, and the average particle size and PDI of the product were analyzed, and the results were 110 nm and 0.12, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Figure 4 shown.

[0036] Comparative Example 2 Repeat Example 1, shorten the length of the microchannel reactor to 0.25 m, the reactant flow ratio is 1:1, and the analysis conditions are the same as in Example 1. The average particle size and PDI of the product are analyzed, and the results are 208 nm and 0.12, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Figure 5 shown.

[0037] Comparative Example 3 Example 1 was repeated, and the size of the double-twist microchannel reactor was changed. The spiral diameter was increased from 1 cm to 5 cm, the distance between the two ends was 12 cm, the pitch was unchanged, the reactant flow ratio was 1:1, and the analysis conditions were the same as in Example 1. The average particle size and PDI of the product were analyzed, and the results were 272 nm and 0.19, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Figure 6 shown.

[0038] Comparative Example 4 Example 1 was repeated, the inner diameter of the lemniscate microchannel reactor was changed to 0.5 mm, the reactant flow ratio was 1:1, and the analysis conditions were the same as in Example 1. The average particle size and PDI of the product were analyzed, and the results were 153 nm and 0.11, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Figure 7 shown.

[0039] Comparative Example 5 Example 1 was repeated using a single spiral microchannel reactor, wherein the microchannel length was 1 m, the microchannel outer diameter was 2 mm, the microchannel inner diameter was 1 mm, the spiral diameter was 1 cm, and the pitch was 4 mm. The average particle size and PDI of the product were analyzed, and the results were 252 nm and 0.21, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Figure 8 shown.

[0040] Comparative Example 6 Example 1 was repeated using a straight tube microchannel reactor, wherein the microchannel length was 1 m, the microchannel outer diameter was 2 mm, and the microchannel inner diameter was 1 mm. The average particle size and PDI of the product were analyzed, and the results were 308 nm and 0.18, respectively. The particle size distribution of nano-barium sulfate prepared in this comparative example is shown in the attached figure. Fig. 9 shown.

[0041] By comparing the results of Example 1 and Comparative Examples 1-4, it can be seen that increasing the volume flow rate of the reactants can reduce the average particle size of the nanoparticles, but there is no obvious regularity in the effect on PDI.

[0042] The microchannel length was varied to adjust the residence time, and for the range of residence times used here, the results showed no significant correlation with the residence time of the reactants in the reactor. This means that for the range of residence times used, the residence time has minimal effect on particle size and distribution for the same volume flow rate. This suggests that the time scale associated with the growth of the barium sulfate particles is smaller than the residence time used in the experiments.

[0043] By comparing Example 1 with Comparative Examples 5 and 6, the double-twist tube reactor shows a smaller particle size and a narrower size distribution than the straight tube reactor and the spiral tube reactor. This shows that the double-twist reactor has a better mixing effect and a narrower residence time distribution. Its good micro-mixing can ensure the uniform distribution of reactants around the crystal nucleus, avoid abnormal growth of the crystal nucleus caused by excessive local concentration, and thus obtain nanoparticles with uniform particle size distribution.

[0044] Dean flow in the lemniscate microchannel reactor pipe is a key parameter affecting the average particle size and PDI. The particle size can be controlled by adjusting the curvature: reducing the spiral diameter of the lemniscate pipe can increase the Dean number and obtain a smaller particle size. A narrower microchannel inner diameter can produce a smaller particle size under the same conditions.

Claims

1. A lemniscate microchannel reactor, characterized in that The spiral shape of the lemniscate type microchannel reactor meets the characteristics of the Bernoulli lemniscate.

2. The lemniscate microchannel reactor according to claim 1, characterized in that The spiral structures on the left and right sides of the double-twist microchannel reactor are both arcs, the spiral diameters at both ends are equal, the spiral diameter is 1-10 cm, the arc radian is π-1.8π, the distance between the left and right vertices is 2-3 times the spiral diameter, the inner diameter of the microchannel is 0.5-2 mm, the outer diameter of the microchannel is 1-5 mm, the pitch is 2-5 times the inner diameter of the microchannel, and the total length of the reactor is 0.2-5 m.

3. The lemniscate microchannel reactor according to claim 1, characterized in that The lemniscate microchannel reactor is made of metal, glass or high molecular polymer.

4. A method for synthesizing nanoparticles by regulating the size of a liquid phase precipitation reaction using the lemniscate microchannel reactor of claim 1, characterized in that The following steps are involved: The size of the nanoparticles is regulated by changing the process parameters of the microchannel reaction or / and the design parameters of the lemniscate microchannel reactor; The process parameters of the microchannel reaction include the flow rate of the reaction materials; The design parameters of the lemniscate microchannel reactor include the length, inner diameter and spiral diameter of the microchannel reactor.

5. The method for regulating the size of nanoparticles synthesized by liquid phase precipitation reaction as claimed in claim 4, characterized in that By increasing the flow rate of the reaction materials, the size of the nanoparticles synthesized by the liquid phase precipitation reaction can be reduced, and vice versa.

6. The method for regulating the size of nanoparticles synthesized by liquid phase precipitation reaction as claimed in claim 4, characterized in that By increasing the inner diameter of the double-twist microchannel reactor, the size of the nanoparticles synthesized by the liquid phase precipitation reaction can be increased, and vice versa.

7. The method for regulating the size of nanoparticles synthesized by liquid phase precipitation reaction as claimed in claim 4, characterized in that By increasing the spiral diameter of the double-twist microchannel reactor, the size of nanoparticles synthesized by liquid phase precipitation reaction can be increased, and vice versa.

8. The method for regulating the size of nanoparticles synthesized by liquid phase precipitation reaction as claimed in claim 4, characterized in that The size of the nanoparticles is between 10nm and 1500nm.

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