Method for preparing superfine barium sulfate

Abstract

The present application provides a method for preparing superfine barium sulfate, comprising the following steps: at room temperature, weighing industrial-grade barium chloride and industrial-grade sodium sulfate solids, adding water to prepare solutions having equal molar concentrations, and filtering out impurities and then respectively loading the solutions into storage tanks; and adjusting the flow rates of diaphragm metering pumps to 2.25-500 L / h, then adjusting the two solutions to have the same stable flow rate, so that the two solutions flow out of the storage tanks at the set flow rate, enabling the two solutions flowing out of the storage tanks to simultaneously enter a spherical suction pipe to experience a rapid precipitation reaction to generate an emulsion containing superfine barium sulfate particles, enabling the emulsion to enter a product storage tank for placement, and finally sequentially carrying out centrifugal filtration, water washing, and second centrifugal filtration on the emulsion to obtain an ultrafine barium sulfate filter cake, to complete the preparation. In the present application, by means of a small size effect, a barium chloride solution and a sodium sulfate solution are quickly and fully mixed in a spherical suction pipe, thereby enhancing the mixing and mass transfer between the fluids and facilitating industrial preparation of superfine barium sulfate.

Description

A method for preparing ultrafine barium sulfate

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on February 4, 2024, with application number CN202410157017.1 and invention name “A Method for Preparing Ultrafine Barium Sulfate”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application belongs to the technical field of barium sulfate preparation methods, and specifically relates to a method for preparing ultrafine barium sulfate. Background Art

[0003] BaSO4, an important inorganic chemical product, is widely used in industries such as paints, pigments, coatings, inks, batteries, papermaking, rubber, ceramics, enamel, and fragrances due to its low price, wide availability of raw materials, and non-toxicity. BaSO4 includes traditional barium sulfate and ultrafine barium sulfate. In terms of application, the latter is more effective than the former because traditional barium sulfate has disadvantages such as a wide particle size distribution and poor dispersion in solvents.

[0004] The market demands high uniformity and fineness of ultrafine barium sulfate, and demand for high-quality products exceeds supply. Producing ultrafine barium sulfate with a small particle size and narrow particle size distribution is a top priority. Furthermore, ultrafine barium sulfate is significantly more valuable than conventional barium sulfate.

[0005] Existing methods for preparing ultrafine barium sulfate utilize impinging stream microreactors. These reactors, with characteristic sizes of 0.1 to 1 mm, offer advantages such as rapid and uniform mixing and a narrow product particle size. However, these reactors also suffer from drawbacks such as susceptibility to clogging, low throughput, cumbersome operation, and the need for high-pressure nitrogen, making large-scale industrial production of ultrafine barium sulfate impractical. Therefore, it is imperative to vigorously promote industrialization and produce ultrafine barium sulfate with small particle size and high quality without increasing production costs.

[0006] Based on this, a preparation method of ultrafine barium sulfate was proposed. Summary of the Invention

[0007] The technical problem to be solved by the present application is to provide a method for preparing ultrafine barium sulfate in view of the deficiencies of the above-mentioned prior art, so as to solve the problems raised in the above-mentioned background technology.

[0008] To solve the above technical problems, the technical solution adopted in this application is: a method for preparing ultrafine barium sulfate, comprising the following steps:

[0009] S1. At room temperature, weigh industrial-grade barium chloride and industrial-grade sodium sulfate solids, add water to prepare barium chloride and sodium sulfate solutions with equimolar concentrations, filter impurities, and load them into barium chloride and sodium sulfate storage tanks, respectively;

[0010] S2, then adjusting the flow rate of the diaphragm metering pump connected to the barium chloride liquid storage tank and the sodium sulfate liquid storage tank to 2.25-500 L / h respectively to provide a stable pressure environment, and then turning the opening of the knob of the diaphragm metering pump to adjust the two liquids to the same stable flow rate so that the two liquids flow out of the storage tank at the set flow rate;

[0011] S3, the two liquids flowing out of the storage tank enter the spherical exhaust pipe at the same time, and a rapid precipitation reaction is performed to form an emulsion containing ultrafine barium sulfate particles, which is then placed in a product storage tank;

[0012] S4. Finally, the emulsion is centrifuged, filtered, washed, and centrifuged again to obtain an ultrafine barium sulfate filter cake, thereby completing the preparation.

[0013] As a further illustration of the present application, the molar concentrations of the barium chloride solution and the sodium sulfate solution are 0.1 to 2.4 mol / L.

[0014] As a further illustration of this application, the feed cross-sectional area of ​​the spherical exhaust pipe is 10.17 mm 2 .

[0015] As a further illustration of the present application, the flow rate is 3.47 to 20.83 m / s.

[0016] Compared with the prior art, this application has the following advantages:

[0017] The present application replaces the impinging stream microreactor with a characteristic size of 0.1 to 1 mm with a spherical exhaust tube, and utilizes the small size effect to quickly and fully mix the barium chloride solution and the sodium sulfate solution in the spherical exhaust tube, thereby enhancing the mixing and mass transfer between the fluids and facilitating the industrial preparation of ultrafine barium sulfate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a SEM comparison of barium sulfate prepared in different reactors in Example 1 of the present application; (a) is a SEM image of barium sulfate produced in a spherical exhaust tube; (b) is a SEM image of barium sulfate produced in a microreactor with a characteristic size of 0.1 to 1 mm;

[0019] FIG2 is a SEM comparison of barium sulfate manufactured by Foshan Anyi Ultrafine Materials Co., Ltd. and barium sulfate produced by Xinji Yudong Chemical Plant in Example 4 of the present application; wherein (a) is a SEM image of barium sulfate manufactured by Foshan Anyi Ultrafine Materials Co., Ltd.; (b) is a SEM image of barium sulfate produced by Xinji Yudong Chemical Plant;

[0020] FIG3 is a SEM image of barium sulfate produced by Hebei University of Science and Technology in Example 4 of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] Example 1

[0023] A method for preparing ultrafine barium sulfate comprises the following steps:

[0024] S1. At room temperature, weigh an appropriate amount of industrial-grade barium chloride and an appropriate amount of industrial-grade sodium sulfate solid, add water to prepare equimolar concentrations of barium chloride solution and sodium sulfate solution, filter out impurities and load them into barium chloride solution storage tank and sodium sulfate solution storage tank respectively;

[0025] S2. Then, the flow rates of the diaphragm metering pumps connected to the barium chloride liquid storage tank and the sodium sulfate liquid storage tank are adjusted to 2.25-500 L / h respectively to provide a stable pressure environment. Then, the opening of the diaphragm metering pump knob is turned to adjust the two liquids to have the same stable flow rate so that the two liquids flow out of the storage tank at the set flow rate (10.42 m / s);

[0026] S3, the two liquids flowing out of the storage tank enter the spherical exhaust pipe at the same time (the feed cross-sectional area is 10.17mm 2 ), a rapid precipitation reaction generates an emulsion containing ultrafine barium sulfate particles, and the emulsion enters a product storage tank for storage;

[0027] S4. Finally, the emulsion is centrifuged and filtered, washed with water, and centrifuged again to obtain an ultrafine barium sulfate filter cake, thereby completing the preparation.

[0028] Then, a portion of the filter cake was added to a water-carrying agent with a mass 13 times that of barium sulfate (converted to dry barium) for emulsification, and the powder was obtained by azeotropic evaporation. The specific surface area of ​​the BaSO4 powder was measured.

[0029] Another part of the filter cake was used to characterize the particle size and morphology of BaSO4.

[0030] 1) Specific surface area tester (BET) analysis:

[0031] The specific surface area of ​​the product was analyzed using a TristarⅡ3020 fully automatic physical adsorption instrument produced by the American company Micromeritics. Its performance indicators are as follows: Specific surface area: 0.01m 2 / g~no upper limit; pressure measurement: 0~1000mmHg; minimum pore volume detection: 0.0001cc / g.

[0032] The testing process is as follows: First, the powdered sample is pressed into a pellet. The processed sample is then vacuum desorbed at an appropriate temperature. Then, nitrogen is introduced while maintaining liquid nitrogen at -197°C to measure the sample's adsorption-desorption curve. The resulting adsorption-desorption curve is then used in conjunction with the BET equation to calculate the specific surface area of ​​BaSO₄.

[0033] 2) Scanning electron microscopy analysis:

[0034] A Hitachi S4800-I scanning electron microscope (SEM) was used to characterize the ultrafine barium sulfate particles. Operating voltage: 3 kV; minimum resolution: 1 nm (at 15 kV) and 1.4 nm (at 1 kV); elemental analysis range: Be₄4-U₄9₂; magnification: 20x to 800,000x. SEM observations and comparisons of BaSO₄ particle size, morphology, and dispersion were performed. The resulting SEM images are shown in Figure 1.

[0035] Compared with the microreactor with a characteristic size of 0.1-1 mm (the conditions for preparing barium sulfate in the microreactor are: reactant concentration 0.8 mol / L, feed flow rate 10.42 m / s, room temperature, feed cross-sectional area 0.32 mm 2 ), the barium sulfate prepared in this application has a narrow particle size distribution, and its average particle size is 30nm.

[0036] This embodiment uses a spherical exhaust pipe as a reactor and a diaphragm metering pump as a power delivery device. The flow rate is adjustable in the range of 2.25 to 500 L / h. By utilizing the small size effect, that is, under the conditions of the same reactant concentration and feed flow rate, only the feed cross-sectional area is changed, and ultrafine barium sulfate with a narrow particle size distribution is prepared, the average particle size of which is 33.18 nm.

[0037] The surface area and morphology of the prepared products were analyzed, and the results are shown in Table 1.

[0038] Table 1 Effect of amplification effect on the specific surface area of ​​ultrafine barium sulfate

[0039] As shown in Table 1 and Figure 1, compared with the microreactor with a characteristic size of 0.1 to 1 mm, the feed cross-sectional area is 10.17 mm. 2 The particle size of the ultrafine barium sulfate particles prepared in the spherical exhaust tube is still about 30 nm, and the particle size distribution is uniform, which indicates that there is no amplification effect for the microreactor.

[0040] Since the ultrafine barium sulfate particles are spherical, the formula for the definition of specific surface area is as follows: d = 6000 / (4.5×S 表 ).

[0041] The particle size can be calculated according to the formula.

[0042] The calculated results are close to the size of the ultrafine barium sulfate particles observed in the electron microscope photos, which shows that the results of the specific surface area meter are consistent with those obtained by SEM.

[0043] In the spherical exhaust tube, ultrafine barium sulfate with small particle size and narrow distribution can be prepared. This is because the small channel size greatly shortens the diffusion time. Compared with the microreactor, the fluid can be repeatedly divided and merged, which shortens the molecular diffusion distance. The reactants can achieve complete radial mixing within milliseconds, and the mixing distance is at the micron level.

[0044] Under the premise of ensuring the feed cross-sectional area, if you want to increase the feed flow rate of the microreactor, you need to increase the feed flow rate to increase the nitrogen pressure, the total pressure is 15MPa, and the partial pressure is 1MPa. This will lead to high energy consumption and potential safety hazards. Under the premise of ensuring that the feed flow rate remains unchanged, if you want to increase the feed flow rate, you must reduce the feed cross-sectional area, which will accelerate the blockage of the microreactor.

[0045] Compared with the maximum feed flow rate of 12 L / h in the microreactor under nitrogen power transport, it can also be seen that the feed cross-sectional area is 10.17 mm 2 The spherical exhaust pipe has a very large processing capacity of 381L / h, which is 30 times higher than the processing capacity of the microreactor and can be used for industrial production.

[0046] Example 2

[0047] A method for preparing ultrafine barium sulfate, using a spherical exhaust pipe and a diaphragm metering pump as the power delivery equipment, with a flow rate of 381L / h and a reactant concentration of 0.8mol / L. The fixed feed flow rate at room temperature is 10.42m / s, and the feed cross-sectional area is selected to be 10.17mm 2The concentrations of the barium chloride solution and sodium sulfate solution were varied to 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1.2 mol / L, and 2.4 mol / L, respectively. The specific surface area and morphology of the obtained product were measured, and the results are shown in Table 2.

[0048] Table 2 Effect of reactant concentration on specific surface area of ​​ultrafine barium sulfate

[0049] It can be seen from Table 2 that the particle size and morphology of the ultrafine barium sulfate particles show a trend of first decreasing and then increasing with the increase of the reactant concentration. When the concentration of the reactant is 1.2 mol / L, the minimum particle size of the prepared ultrafine barium sulfate is 28.17 nm.

[0050] This is because the initial concentration of the reaction solution not only affects the reaction rate, but also the quality of the reaction product. In the rapid precipitation reaction process, the solute forms crystals from the solution, which needs to go through the following two steps:

[0051] ① First, microscopic grains must be produced as the core of crystallization, which are called crystal nuclei;

[0052] ②Then they grow and become called macroscopic crystals.

[0053] Crystal nuclei can only form or grow in the presence of a driving force. This driving force is the supersaturation of the solution, or the concentration difference between the solutions. The process of generating crystal nuclei is called nucleation, and the process of their growth is called crystal growth. As the concentration of the reactants increases, the supersaturation of the solution increases. This increase in supersaturation increases both the nucleation rate and the growth rate of ultrafine barium sulfate, but the growth rate is far lower than the nucleation rate, thus producing ultrafine barium sulfate. However, when the concentration reaches a certain limit, the viscosity of the reaction solution increases, forming a certain adhesion effect, increasing the mixing contact resistance, and in turn hindering the formation of crystal nuclei.

[0054] Furthermore, industry desires high yields of ultrafine barium sulfate, and as the concentration of the reactants increases, the concentration of the byproduct sodium chloride also increases. If the concentration of sodium chloride in the wastewater is high, it can be recovered by evaporation, a process that saves energy. Therefore, to ensure that the spherical ultrafine barium sulfate produced has a small particle size, a narrow particle size distribution, and a high yield, the concentration of the reactants is selected to be 1.2 mol / L.

[0055] Experiment C Na2SO4 =1.2mol / L, C BaCl2 =1.2mol / L Substitute into the supersaturation formula:

[0056] The ion concentration constant K sp 1.1×10-10 mol 2 dm -6 .

[0057] Calculation shows that the supersaturation S is 1109, which means a homogeneous nucleation reaction occurs. Substituting the supersaturation S into the nucleation rate formula:

[0058] The nucleation rate was calculated to be 4.28xl0 26 m -3 s -1 .

[0059] Example 3

[0060] A method for preparing ultrafine barium sulfate using a spherical exhaust tube and a microreactor with a feed cross-sectional area of ​​10.17 mm 2 Ultrafine barium sulfate was prepared under the condition of feed flow rate range of 3.47~20.83m / s. On this basis, the feed flow rate was increased. Under the maximum nitrogen pressure of 1MPa, the feed flow rate was 20.83m / s, the reaction temperature was room temperature, the reactant concentration was fixed at 1.2mol / L, and the reactor was selected with a feed cross-sectional area of ​​10.17mm 2 The spherical exhaust pipe device was used to adjust the flow rate of the pump, and only the reactant feed flow rate was changed, which were 3.47m / s, 6.94m / s, 10.42m / s, and 20.83m / s respectively. The specific surface area and morphology of the obtained product were measured, and the results are shown in Table 3:

[0061] Table 3 Effect of reactant feed flow rate on specific surface area of ​​ultrafine barium sulfate

[0062] As can be seen from Table 3, with the increase of the reactant flow rate, the particle size and morphology of the ultrafine barium sulfate particles decrease. When the reactant flow rate is 20.83 m / s, the particle size of the ultrafine barium sulfate particles has reached 27.94 nm.

[0063] The reaction process is as follows: Under external power, two liquid feeds form a certain flow rate, where they collide and react to produce ultrafine barium sulfate particles. When the velocity is high, the rapid collision generates a large shear force, and the barium chloride and sodium sulfate achieve highly uniform mixing under the action of the mutual shear force, which is conducive to the rapid precipitated product particle size reduction and homogenization, thereby obtaining ultrafine barium sulfate particles with good uniformity. A reactant flow rate of 10.42 m / s achieves excellent microscopic mixing effect, and the particle size of ultrafine barium sulfate particles is not much different from that at a reactant flow rate of 20.83 m / s. To save consumption and avoid equipment explosion under high pressure, the reactant flow rate of 10.42 m / s is selected.

[0064] Example 4

[0065] A method for preparing ultrafine barium sulfate, using a spherical exhaust pipe, a reaction temperature of room temperature, a reactant concentration of 1.2 mol / L, a reactant feed flow rate of 10.42 m / s, and a comparative feed cross-sectional area of ​​10.17 mm 2 The annual output of ultrafine barium sulfate produced by the spherical vacuum tube device is shown in Table 4:

[0066] Table 4 Effect of reactor on annual output of ultrafine barium sulfate

[0067] Compared with the microreactor, the feed cross-sectional area is 10.17mm 2 The processing capacity of the spherical exhaust pipe has been expanded by 30 times, and the annual output of ultrafine barium sulfate produced is 30 times that of before.

[0068] And the feed cross-sectional area is 10.17mm 2 The BaSO4 particles prepared by the spherical vacuum tube are compared with the barium sulfate produced by the existing Foshan Anyi Ultrafine Materials Co., Ltd. and Xinji Yudong Chemical Plant. The ultrafine barium sulfate has a smaller particle size and a narrower particle size distribution. The specific results are shown in Figure 2 (a) and (b);

[0069] The ultrafine BaSO4 particles obtained under the optimal conditions in this embodiment are compared with the ultrafine BaSO4 particles produced by research at Hebei University of Science and Technology, as shown in Figure 3. It can be seen that the particles in this embodiment are of better quality, with a small particle size, good particle uniformity, and a narrow particle size distribution.

[0070] In summary, the feed cross-sectional area is 10.17mm 2 spherical exhaust tube, when the concentration of the reaction material is 1.2 mol / L and the reactant feed flow rate is 10.42 m / s, ultrafine barium sulfate with a minimum particle size of 28.17 nm can be produced.

[0071] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0072] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing ultrafine barium sulfate, characterized in that: The following steps are involved: S1. At room temperature, weigh industrial-grade barium chloride and industrial-grade sodium sulfate solids, add water to prepare barium chloride and sodium sulfate solutions with equimolar concentrations, filter impurities, and load them into barium chloride and sodium sulfate storage tanks, respectively; S2, then adjusting the flow rate of the diaphragm metering pump connected to the barium chloride liquid storage tank and the sodium sulfate liquid storage tank to 2.25-500 L / h respectively to provide a stable pressure environment, and then turning the opening of the knob of the diaphragm metering pump to adjust the two liquids to the same stable flow rate so that the two liquids flow out of the storage tank at the set flow rate; S3, the two liquids flowing out of the storage tank enter the spherical exhaust pipe at the same time, and quickly precipitate and react to form an emulsion containing ultrafine barium sulfate particles; S4. Finally, the emulsion is centrifuged, filtered, washed with water, and centrifuged again to obtain an ultrafine barium sulfate filter cake, thereby completing the preparation.

2. The method for preparing ultrafine barium sulfate according to claim 1, wherein: The molar concentrations of the barium chloride solution and the sodium sulfate solution are 0.1-2.4 mol / L.

3. The method for preparing ultrafine barium sulfate according to claim 2, wherein: The molar concentrations of the barium chloride solution and the sodium sulfate solution are 1.2-2.4 mol / L.

4. The method for preparing ultrafine barium sulfate according to claim 1, wherein: The feed cross-sectional area of the spherical exhaust pipe is 10.17 mm 2 .

5. The method for preparing ultrafine barium sulfate according to claim 1, wherein: The set flow rate is 3.47 to 20.83 m / s.

6. The method for preparing ultrafine barium sulfate according to claim 5, characterized in that: The set flow rate is 10.42-20.83 m / s 7. The method for preparing ultrafine barium sulfate according to claim 1, wherein: The flow rate of the diaphragm metering pump is 381-500 L / h.

8. The method for preparing ultrafine barium sulfate according to claim 1, wherein: The emulsion is placed in a product storage tank.

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