Preparation method of nano zinc oxide

Abstract

The invention discloses a preparation method of nano zinc oxide. The preparation method comprises the following steps: mixing an alkali solution with a mixed solution containing zinc salt and polyvinylpyrrolidone in a microreactor, and reacting at 120-180 DEG C to obtain the nano zinc oxide. The preparation method of the nano-zinc oxide meets one or more of the following effects and advantages: (1) the prepared nano-zinc oxide is low in size and uniform in particle size distribution; (2) the reaction time is short; (3) the efficiency is high; and (4) the method is safe and can be industrially amplified.

Description

Technical Field

[0001] The invention belongs to the technical field of nano materials, and in particular relates to a method for synthesizing nano zinc oxide by adopting micro-reaction technology. Background Art

[0002] Nanoparticles generally refer to particles with a diameter of 1 to 100 nm, which have special properties that traditional bulk materials do not have, such as surface effect, volume effect, quantum size effect and macroscopic tunneling effect. Among them, nano ZnO, as a new multifunctional inorganic material, has a stable hexagonal wurtzite structure at room temperature, has the advantages of high surface activity, large specific surface area, good thermal stability and chemical stability, and exhibits good photocatalytic performance, UV resistance, antibacterial and anticorrosive properties, making it occupy an important position in the field of functional materials.

[0003] There are many methods for synthesizing nano zinc oxide, among which the most common ones are hydrothermal method and precipitation method. The hydrothermal method is currently the most commonly used method for preparing ZnO nanomaterials. It was first used to prepare ultrafine powders. It mainly refers to the use of water as a solvent in a sealed pressure vessel, under high temperature and high pressure conditions, to dissolve and recrystallize insoluble or insoluble substances to obtain nanomaterials. This method has low raw material costs, and the prepared products have high purity, good monodispersity, easy control of material shape and size, and good crystallinity; but it has high requirements for equipment technology, and the reaction time is long and the energy consumption is large. The precipitation method for preparing nano ZnO is usually to add a precipitant to a soluble zinc salt solution to generate a zinc salt, and then precipitate, dry, and calcine to obtain ZnO particles. The precipitation method has low requirements for equipment and technology, low cost, and simple and easy operation, but the resulting product has the disadvantages of large particle size, severe agglomeration, poor dispersibility, and uneven particle size.

[0004] Microreactors, also known as microchannel reactors, are three-dimensional structural elements that contain microchannels with characteristic dimensions ranging from several micrometers to hundreds of micrometers, and reactants undergo chemical reactions in the microchannels. The microreaction process is a homogeneous or multiphase mixing or reaction process carried out at a microscale. By regulating key parameters such as reactant concentration, reaction flow rate, reaction temperature, type and amount of additives, the reaction process is precisely controlled to successfully prepare nanoparticles with uniform particle size. Summary of the invention

[0005] In order to overcome the problems of large size of nano zinc oxide prepared by precipitation method and long time of preparation of nano zinc oxide by hydrothermal method in the prior art, a method for preparing nano zinc oxide is provided. Compared with the traditional precipitation method and hydrothermal method, the method for preparing nano zinc oxide of the present invention satisfies one or more of the following advantages: (1) the size of the prepared nano zinc oxide is small and the particle size distribution is uniform; (2) the reaction time is short; (3) the efficiency is high; (4) it is safe and can be industrially scaled up.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a method for preparing nano zinc oxide, which comprises the following steps: mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor, reacting at 120-180° C. to prepare nano zinc oxide;

[0008] Wherein, in the mixed solution containing zinc salt and polyvinyl pyrrolidone, the concentration of zinc salt is 0.3-1 mol / L;

[0009] The mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1wt%-8wt%; and when the concentration of the zinc salt is 1 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 8wt%.

[0010] In some embodiments, the alkaline solution is an aqueous solution of an alkaline substance. The alkaline substance is an inorganic base and / or a strong base weak acid salt. The inorganic base is preferably sodium hydroxide and / or potassium hydroxide; more preferably sodium hydroxide. The strong base weak acid salt is preferably sodium carbonate and / or ammonium carbonate. The alkaline solution is more preferably an aqueous solution of sodium hydroxide.

[0011] In some embodiments, the concentration of the alkaline solution is 2.7-9.8 mol / L; for example, 2.7 mol / L, 4.7 mol / L, 7.6 mol / L or 9.8 mol / L.

[0012] In some embodiments, the mixed solution containing zinc salt and polyvinyl pyrrolidone is an aqueous solution of zinc salt and polyvinyl pyrrolidone.

[0013] In some embodiments, the zinc salt is one or more of zinc sulfate, zinc chloride, zinc acetate and zinc nitrate; preferably zinc nitrate; more preferably zinc nitrate hexahydrate.

[0014] In some embodiments, the concentration of the zinc salt is 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.

[0015] In some embodiments, the K value of the polyvinyl pyrrolidone is 25-34, such as 27.0-32.4.

[0016] In some embodiments, the total nitrogen content of the polyvinyl pyrrolidone is 9%-14%, such as 11.5%-12.8%.

[0017] In some embodiments, the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30 purchased from Sinopharm Chemical Reagent.

[0018] In some embodiments, the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1 wt%, 2 wt%, 4 wt% or 8 wt%.

[0019] In some embodiments, the flow rate of the alkaline solution in the microreactor is 10-100 mL / min; preferably 22-82 mL / min; for example 22 mL / min, 43 mL / min, 63 mL / min or 82 mL / min.

[0020] In some embodiments, the flow rate of the mixed solution containing zinc salt and polyvinyl pyrrolidone in the microreactor is 5-60 mL / min; for example, 10 mL / min, 20 mL / min, 30 mL / min or 40 mL / min.

[0021] In some embodiments, the flow rate ratio of the mixed solution containing zinc salt and polyvinyl pyrrolidone to the alkaline solution in the microreactor is 1:(2-3); for example, 1:2.05, 1:2.1, 1:2.15 or 1:2.2.

[0022] In some embodiments, the reaction temperature is 120°C, 140°C, 160°C or 180°C.

[0023] In some embodiments, the reaction is preferably performed in a microcoil.

[0024] In some embodiments, the reaction time is generally related to the reaction scale and is not specifically limited, but is preferably 1-20 min; more preferably 2.5 min-10 min; for example, 2.5 min, 3.3 min, 5 min or 10 min.

[0025] In some embodiments, the particle size of the nano zinc oxide is less than 10 nm, preferably 5-8 nm, for example 5.4 nm, 6.5 nm, 7.2 nm or 7.6 nm.

[0026] In some embodiments, the crystallinity of the nano zinc oxide is 70%-99%, for example, 79.6%, 87.3%, 96.4% or 98.7%.

[0027] In some embodiments, the specific surface area of ​​the nano zinc oxide is 70-90 m2 / g; for example 86.4m 2 / g, 79.2m 2 / g, 76.7m 2 / g or 73.5m 2 / g.

[0028] In some embodiments, the preparation method is any of the following schemes:

[0029] Scheme 1: An alkaline solution is mixed with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacted at 120° C. to obtain nano zinc oxide;

[0030] The concentration of the alkaline solution is 2.7 mol / L; the flow rate of the alkaline solution is 22 mL / min;

[0031] The concentration of the zinc salt is 0.3 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1 wt %; the flow rate of the mixed solution containing the zinc salt and polyvinyl pyrrolidone is 10 mL / min;

[0032] Scheme 2: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacting at 140° C. to obtain nano zinc oxide;

[0033] The concentration of the alkaline solution is 4.7 mol / L; the flow rate of the alkaline solution is 43 mL / min;

[0034] The concentration of the zinc salt is 0.5 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 2 wt %; the flow rate of the mixed solution containing the zinc salt and the polyvinyl pyrrolidone is 20 mL / min;

[0035] Scheme 3: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacting at 160° C. to obtain nano zinc oxide;

[0036] The concentration of the alkaline solution is 7.6 mol / L; the flow rate of the alkaline solution is 63 mL / min;

[0037] The concentration of the zinc salt is 0.8 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 4 wt %; the flow rate of the mixed solution containing the zinc salt and the polyvinyl pyrrolidone is 30 mL / min;

[0038] Scheme 4: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor, reacting at 180° C. to obtain nano zinc oxide;

[0039] The concentration of the alkaline solution is 9.8 mol / L; the flow rate of the alkaline solution is 82 mL / min;

[0040] The concentration of the zinc salt is 1 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 8 wt %; and the flow rate of the mixed solution containing the zinc salt and polyvinyl pyrrolidone is 40 mL / min.

[0041] In some embodiments, the preparation method may further include the following post-processing steps: collecting the reaction solution, separating, washing, drying, and grinding. The separation may be centrifugal separation or filtration separation, preferably centrifugal separation. The washing may be rinsed with anhydrous ethanol; the amount of anhydrous ethanol used is preferably 100 mL. The drying temperature may be 60°C.

[0042] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0043] The reagents and raw materials used in the present invention are commercially available.

[0044] The positive and progressive effects of the present invention are that the method for preparing nano zinc oxide of the present invention satisfies one or more of the following advantages: (1) the prepared nano zinc oxide has one or more of the advantages of small size, uniform particle size distribution, high crystallinity and large specific surface area; (2) short reaction time; (3) high efficiency; (4) safety and industrial scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the TEM image of ZnO nanoparticles synthesized using microreaction technology in Example 2.

[0046] Figure 2 This is the XRD pattern of ZnO nanoparticles synthesized using microreaction technology in Example 2. DETAILED DESCRIPTION

[0047] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0048] Polyvinylpyrrolidone K30 (PVP) was purchased from Sinopharm Chemical Reagents. The specific information is as follows:

[0049] Table 1

[0050]

[0051] Example

[0052] 1) Prepare a zinc nitrate solution containing a dispersant: refer to the feeding ratio in Example 2 in Tables 2 to 4, weigh 0.30 g of PVP and disperse it in 100 mL of deionized water, then add 14.87 g of zinc nitrate hexahydrate, dissolve and disperse, and obtain a dispersed phase solution;

[0053] 2) Prepare alkali solution: refer to the feeding ratio in Example 2 in Table 2-Table 4, weigh 40g of sodium hydroxide and add it into 215mL of deionized water to dissolve and disperse evenly to obtain a mobile phase solution;

[0054] 3) Microreactor: Referring to the parameters in Example 2 in Tables 2-4, the flow rates of the dispersed phase and the mobile phase were set to 20 ml / min and 43 ml / min respectively, and the oil bath temperature of the microreactor coil was set to 140° C. When the actual temperature rises to the same as the set temperature, the pumps of the dispersed phase and the mobile phase are turned on to mix and disperse the dispersed phase and the mobile phase in the microreactor, and then a high-temperature reaction is carried out in the coil;

[0055] 4) Centrifugation: Collect the reaction solution after passing through the microcoil, centrifuge it, then add deionized water to wash and centrifuge it until the conductivity of the deionized water in the supernatant after centrifugation is lower than 50us / cm; then rinse it with 100ml of anhydrous ethanol to obtain the target product;

[0056] 6) Drying: The centrifuged product was dried at 60°C and ground to obtain the target product, nano zinc oxide. Its TEM and XRD were as follows: Figure 1 and Figure 2 shown.

[0057] Table 2

[0058]

[0059] Table 3

[0060]

[0061] Table 4

[0062]

[0063] The size and crystallinity of zinc oxide are based on the test data of zinc oxide XRD, and the specific values ​​are calculated by JADE software.

[0064] The specific surface area of ​​zinc oxide was tested using a fully automatic specific surface and porosity analyzer (BET).

[0065] Compared with Example 2, Comparative Example 1 mainly has a lower concentration of zinc source, and the supersaturation is low in the micro-reaction process, resulting in a large crystal size;

[0066] Compared with Example 2, Comparative Example 2 is mainly due to the increase in the concentration of the zinc source. At this time, when the dispersed phase and the mobile phase are mixed during the micro-reaction process, a large number of crystal nuclei are generated instantly, resulting in clogging of the coil of the micro-reaction, causing the pressure of the microreactor pump to exceed the upper limit of the pump and stop, and no target product is obtained;

[0067] Compared with Example 2, in Comparative Example 3, the concentration of the dispersant is lower, and the dispersing effect is not achieved, resulting in agglomeration of the synthesized nano zinc oxide and an increase in size;

[0068] Compared with Example 2, in Comparative Example 4, the concentration of the dispersant is higher, and too much PVP will wrap on the surface of zinc oxide, which will increase the size of the product.

[0069] Compared with Example 2, in Comparative Example 5, the reaction temperature is lower, zinc oxide crystals cannot be formed, the degree of crystallization is low, and mainly an amorphous zinc oxide precursor is generated;

[0070] Compared with Example 2, the reaction temperature of Comparative Example 6 is higher and the crystals grow too fast, resulting in an increase in the size of the product.

[0071] Compared with Example 2, Comparative Example 7 mainly adopts the hydrothermal method to prepare nano zinc oxide, the hydrothermal temperature is 180° C., the hydrothermal time is relatively long at 480 min, and the size of the target product is relatively large.

Claims

1. A method for preparing nano zinc oxide, comprising the following steps: mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor, reacting at 120-180° C. to obtain nano zinc oxide; in, In the mixed solution containing zinc salt and polyvinyl pyrrolidone, the concentration of zinc salt is 0.3-1 mol / L; The mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1wt%-8wt%; and when the concentration of the zinc salt is 1 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 8wt%.

2. The method for preparing nano zinc oxide according to claim 1, wherein It meets one or more of the following conditions: (1) The alkaline solution is an aqueous solution of an alkaline substance; (2) The concentration of the alkaline solution is 2.7-9.8 mol / L; (3) The mixed solution containing zinc salt and polyvinyl pyrrolidone is an aqueous solution of zinc salt and polyvinyl pyrrolidone; (4) The zinc salt is one or more of zinc sulfate, zinc chloride, zinc acetate and zinc nitrate; (5) The concentration of the zinc salt is 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L; (6) The K value of the polyvinyl pyrrolidone is 25-34; (7) The total nitrogen content of the polyvinyl pyrrolidone is 9%-14%; (8) The mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1wt%, 2wt%, 4wt% or 8wt%; (9) The flow rate of the alkaline solution in the microreactor is 10-100 mL / min; (10) The flow rate of the mixed solution containing zinc salt and polyvinyl pyrrolidone in the microreactor is 5-60 mL / min; (11) The flow rate ratio of the mixed solution containing zinc salt and polyvinyl pyrrolidone to the alkaline solution in the microreactor is 1:(2-3); (12) The reaction temperature is 120°C, 140°C, 160°C or 180°C; (13) The reaction is carried out in a microcoil; (14) The reaction time is 1-20 min; (15) The particle size of the nano zinc oxide is less than 10 nm; (16) The crystallinity of the nano zinc oxide is 70%-99%; The specific surface area of ​​the nano zinc oxide described in (17) is 70-90m 2 / g.

3. The method for preparing nano zinc oxide according to claim 2, characterized in that: It meets one or more of the following conditions: (1) The alkaline substance is an inorganic base and / or a salt of a strong base or a weak base; (2) The concentration of the alkaline solution is 2.7 mol / L, 4.7 mol / L, 7.6 mol / L or 9.8 mol / L; (3) The zinc salt is zinc nitrate; (4) The K value of the polyvinyl pyrrolidone is 27.0-32.4; (5) The total nitrogen content of the polyvinyl pyrrolidone is 11.5%-12.8%; (6) The flow rate of the alkaline solution in the microreactor is 22-82 mL / min; (7) The flow rate of the mixed solution containing zinc salt and polyvinyl pyrrolidone in the microreactor is 10 mL / min, 20 mL / min, 30 mL / min or 40 mL / min; (8) The flow rate ratio of the mixed solution containing zinc salt and polyvinyl pyrrolidone to the alkaline solution in the microreactor is 1:2.05, 1:2.1, 1:2.15 or 1:2.2; (9) The reaction time is 2.5 min to 10 min; (10) The particle size of the nano zinc oxide is 5-8 nm; (11) The crystallinity of the nano zinc oxide is 79.6%, 87.3%, 96.4% or 98.7%; The specific surface area of ​​the nano zinc oxide described in (12) is 86.4 m 2 / g, 79.2m 2 / g, 76.7m 2 / g or 73.5m 2 / g.

4. The method for preparing nano zinc oxide according to claim 3, characterized in that: It meets one or more of the following conditions: (1) The inorganic base is sodium hydroxide and / or potassium hydroxide; (2) The strong base and weak acid salt is sodium carbonate and / or ammonium carbonate; (3) The zinc salt is zinc nitrate hexahydrate; (4) The flow rate of the alkaline solution in the microreactor is 22 mL / min, 43 mL / min, 63 mL / min or 82 mL / min; (5) The reaction time is 2.5 min, 3.3 min, 5 min or 10 min; And (6) the particle size of the nano zinc oxide is 5.4 nm, 6.5 nm, 7.2 nm or 7.6 nm.

5. The method for preparing nano zinc oxide according to claim 4, characterized in that: The inorganic base is sodium hydroxide.

6. The method for preparing nano zinc oxide according to claim 2, characterized in that: The alkaline solution is an aqueous solution of sodium hydroxide.

7. The method for preparing nano zinc oxide according to claim 1, characterized in that: The preparation method is any of the following: Scheme 1: An alkaline solution is mixed with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacted at 120° C. to obtain nano zinc oxide; The concentration of the alkaline solution is 2.7 mol / L; the flow rate of the alkaline solution is 22 mL / min; The concentration of the zinc salt is 0.3 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 1 wt %; the flow rate of the mixed solution containing the zinc salt and polyvinyl pyrrolidone is 10 mL / min; Scheme 2: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacting at 140° C. to obtain nano zinc oxide; The concentration of the alkaline solution is 4.7 mol / L; the flow rate of the alkaline solution is 43 mL / min; The concentration of the zinc salt is 0.5 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 2 wt %; the flow rate of the mixed solution containing the zinc salt and the polyvinyl pyrrolidone is 20 mL / min; Scheme 3: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor and reacting at 160° C. to obtain nano zinc oxide; The concentration of the alkaline solution is 7.6 mol / L; the flow rate of the alkaline solution is 63 mL / min; The concentration of the zinc salt is 0.8 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 4 wt %; the flow rate of the mixed solution containing the zinc salt and the polyvinyl pyrrolidone is 30 mL / min; Scheme 4: Mixing an alkaline solution with a mixed solution containing zinc salt and polyvinyl pyrrolidone in a microreactor, reacting at 180° C. to obtain nano zinc oxide; The concentration of the alkaline solution is 9.8 mol / L; the flow rate of the alkaline solution is 82 mL / min; The concentration of the zinc salt is 1 mol / L; the mass ratio of the polyvinyl pyrrolidone to the zinc salt is 8 wt %; and the flow rate of the mixed solution containing the zinc salt and polyvinyl pyrrolidone is 40 mL / min.

8. The method for preparing nano zinc oxide according to any one of claims 1 to 7, characterized in that: The preparation method may further comprise the following post-processing steps: collecting the reaction solution, separating, washing, drying and grinding.

9. The method for preparing nano zinc oxide according to claim 8, characterized in that: It meets one or more of the following conditions: (1) The separation is centrifugal separation or filtration separation; (2) The washing is performed by rinsing with anhydrous ethanol; and (3) the drying temperature is 60°C.

10. The method for preparing nano zinc oxide according to claim 9, characterized in that: The dosage of the anhydrous ethanol is 100 mL.

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