Method for preparing formamidine hydriodate by using spray drying process

Abstract

The invention discloses a method for preparing formamidine hydriodate by using a spray drying process, which is characterized in that a reaction solution formed by formamidine acetate and hydriodic acid is input into a spray drying system through a peristaltic pump to directly prepare high-purity formamidine hydriodate. According to the method, the problem that residual acidic impurities cannot be completely removed by a traditional rotary evaporation process is solved, the uniformity of the granularity of formamidine hydroiodate can be ensured, large-scale continuous industrial production of products can be realized, and sufficient high-quality raw material guarantee is provided for rapid expansion of the perovskite photovoltaic cell industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite photovoltaic cell precursor materials, and specifically relates to a method for preparing formamidinium hydroiodide by a spray drying process. Background Art

[0002] Perovskite photovoltaic cells are a photovoltaic technology with great development potential and are currently in the golden period of booming industrial expansion. Formamidinium iodide-based perovskites with high conversion efficiency and high stability are currently widely used composition systems in the perovskite industry. As an indispensable raw material, the demand for formamidinium hydroiodide is increasing day by day. At present, the preparation of formamidinium hydroiodide follows a relatively mature laboratory process route. Small-batch preparation basically meets the current demand for perovskite photovoltaics, but it is extremely difficult to achieve large-scale production. First, the laboratory process uses rotary evaporation to obtain formamidinium hydroiodide, but this method has limited equipment productivity and low operability of large-scale equipment, and continuous production cannot be carried out, so it is difficult to achieve industrialization. Second, the formamidinium hydroiodide prepared by the rotary evaporation method has a high water content and serious residual acidic impurities, and a recrystallization process must be added for purification, which increases the complexity of the process. Finally, it is difficult to control the particle size of formamidinium hydroiodide by relying on the recrystallization process, the process cost is high, and it is difficult to achieve the uniformity of product particle size, and thus it is difficult to ensure the batch stability of the product. Therefore, developing a process route for large-scale production of high-purity formamidinium hydroiodide to replace the traditional laboratory process is a key step in promoting the rapid development of perovskite photovoltaic technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a simple and efficient method for preparing formamidinium hydroiodide to replace the traditional rotary evaporation process, solve the problems of low yield, large residual acidic impurities, and poor product uniformity of the rotary evaporation process, and provide a solution for the industrial production of high-quality formamidinium hydroiodide.

[0004] To achieve the above purpose, the present invention uses a spray drying method to directly dry the reaction solution to obtain formamidinium hydroiodide. By atomizing the reaction solution, the contact area between the solution and the high-temperature gas flow is increased, so as to fully remove by-products acetic acid and excessive hydroiodic acid, and at the same time completely evaporate water to prepare a formamidinium hydroiodide product with high purity, low water content, and uniform particle size. Specifically, the present invention includes the following steps:

[0005] (1) Mix two raw materials, formamidinium acetate and hydroiodic acid, and stir and react at 30-40 °C for 4-8 h;

[0006] (2) Add an appropriate amount of solvent to the reaction solution obtained in step (1) at room temperature to adjust the solid content of the reaction solution;

[0007] (3) Filter the reaction solution obtained in step (2);

[0008] (4) Feed the solution obtained in step (3) into a spray dryer through a peristaltic pump under the condition of a rotation speed of 50 - 100 rpm to achieve complete evaporation of the reaction solution and prepare near-spherical particles of formamidine hydroiodide with a low water content.

[0009] Preferably, the molar ratio of the two raw materials, formamidine acetate and hydroiodic acid, in step (1) is 1.04 - 1.06 to ensure that hydroiodic acid is in excess, enabling the reaction to proceed fully and rapidly. The chemical equation of this reaction is as follows:

[0010] [NH 2 CH=NH 2 + CH 3 COOˉ + HI → [NH 2 CH=NH 2 + Iˉ + CH 3 COOH

[0011] Preferably, the solvent used to adjust the solid content of the reaction solution in step (2) includes one or more of deionized water, absolute ethanol, methanol, isopropanol, and acetonitrile, achieving the effect of reducing the boiling point of the reaction solution.

[0012] Preferably, the solid content of the reaction solution in step (2) is 0.3 - 0.6 g / mL to ensure a better spray drying effect. The inventor found that the solid content is the key factor controlling the particle size of the formamidine hydroiodide product. When the solid content is too high, the product agglomerates severely after spray drying, and the particle size uniformity of the product is poor; when the solid content is too low, the particle size of the product after spray drying is small and is easily carried away by the air flow, resulting in a decrease in yield. In addition, the solid content also affects the spray drying equipment. Too high a solid content increases the solution viscosity, causing the product to precipitate directly on the atomizer and blocking the atomizer; too low a solid content increases the equipment energy consumption and raises the cost.

[0013] Preferably, the inlet air temperature of the spray drying in step (4) is 130 - 150 °C, and the outlet air temperature is 120 - 140 °C. The inventor found that the inlet air temperature and the outlet air temperature during spray drying are the key factors for removing the reaction by-products acetic acid and residual hydroiodic acid. A suitable inlet air temperature is conducive to removing a large amount of acetic acid and hydroiodic acid, and then a suitable outlet air temperature ensures the complete removal of a small amount of acidic impurities while completely evaporating the water. However, too high an inlet air temperature and outlet air temperature are extremely likely to cause the decomposition of formamidine hydroiodide, and too low a temperature results in incomplete removal of acidic impurities and even a high water content, deteriorating the product quality.

[0014] Compared with the existing rotary evaporation method, the technical effects achieved by the present invention are as follows:

[0015] ​​(1) The formamidine hydroiodide prepared by the present invention is in the form of nearly spherical particles, with low product moisture content, few residual acetic acid and acidic impurities of hydroiodic acid, and high particle size uniformity.

[0016] (2) The present invention does not require additional steps such as recrystallization, washing, and drying, is simple and easy to operate, has a short process time, and low process cost, and is suitable for the industrial production of formamidine hydroiodide. Brief Description of the Drawings

[0017] Figure 1 is a schematic process flow diagram of spray drying of the present invention;

[0018] Figure 2 is a morphology diagram of the formamidine hydroiodide product in Example 1 under 500 times magnification of a scanning electron microscope;

[0019] Figure 3 is a morphology diagram of the formamidine hydroiodide product in Comparative Example 1 under 500 times magnification of a scanning electron microscope. Detailed Description of the Invention

[0020] The present invention will be further described in detail below with reference to the drawings, examples, and comparative examples. It can be understood that the specific examples described herein are only for explaining the present invention and not for limiting the present invention.

[0021] Example 1:

[0022] (1) Add 520.5 g of formamidine acetate to a small reaction kettle, and add 715.6 mL of 55% wt concentration hydroiodic acid to the reaction kettle according to the molar ratio of formamidine acetate to hydroiodic acid of 1.04. Stir and react at 30 °C for 4 h to obtain a reaction solution.

[0023] (2) Add 800 mL of deionized water, 600 mL of absolute ethanol, and 380 mL of isopropanol to the reaction solution, for a total of 1780 mL of solvent, and control the solid content of the reaction solution at 0.3 g / mL.

[0024] (3) Drain the reaction solution from the reaction kettle, filter it, and transfer it to a storage tank.

[0025] (4) Start the stirring paddle in the storage tank and continuously stir the reaction solution at a rate of 100 rpm / min.

[0026] (5) Set the inlet air temperature and outlet air temperature of the spray dryer to 130 °C and 120 °C respectively. After the temperature reaches the preset value, start the peristaltic pump to input the solution in the storage tank into the spray dryer, and set the peristaltic pump speed to 50 rpm.

[0027] (6) Collect the formamidine hydroiodide product after spray drying.

[0028] The appearance diagram of the prepared formamidine hydroiodide product under 500 - fold magnification of a scanning electron microscope is as Figure 2 shown.

[0029] Comparative Example 1:

[0030] (1) Add 520.5 g of formamidine acetate to a beaker, and add 715.6 mL of 55% wt hydroiodic acid to the beaker according to the molar ratio of formamidine acetate to hydroiodic acid of 1.04. Stir and react at 30 °C for 4 h to obtain a reaction solution.

[0031] (2) Filter the reaction solution and pour it into a flask, then place it on a rotary evaporator to evaporate the solvent. Set the rotary evaporation temperature to 100 °C and the vacuum pump pressure to 0.095 MPa.

[0032] (3) After waiting for the solvent to completely evaporate, remove the flask to collect the formamidine hydroiodide product.

[0033] The morphology diagram of the prepared formamidine hydroiodide product under 500 - fold magnification of a scanning electron microscope is as Figure 3 shown.

[0034] It can be seen from Example 1 and Comparative Example 1 that the formamidine hydroiodide prepared by the traditional rotary evaporation method has irregular shapes, serious agglomeration, and poor particle size uniformity; while the formamidine hydroiodide prepared by spray drying is nearly spherical, with small and uniform particle sizes.

[0035] Example 2:

[0036] (1) Add 832.8 g of formamidine acetate to a small reaction kettle, and add 1155.9 mL of 55% wt hydroiodic acid to the reaction kettle according to the molar ratio of formamidine acetate to hydroiodic acid of 1.05. Stir and react at 35 °C for 6 h to obtain a reaction solution.

[0037] (2) Add 500 mL of deionized water, 400 mL of absolute ethanol, and 136 mL of methanol, a total of 1036 mL of solvent, to control the solid content of the reaction solution at 0.5 g / mL.

[0038] (3) Release the reaction solution from the reaction kettle, filter it, and transfer it to a storage tank.

[0039] (4) Start the stirring paddle in the storage tank and continuously stir the reaction solution at a rate of 100 rpm / min.

[0040] (5) Set the inlet air temperature and outlet air temperature of the spray dryer to 140 °C and 130 °C respectively. After the temperature reaches the preset value, start the peristaltic pump to input the solution in the storage tank into the spray dryer, and set the peristaltic pump speed to 80 rpm.

[0041] (6) Collect the formamidine hydroiodide product after spray drying.

[0042] Comparative Example 2:

[0043] The difference between this comparative example and Comparative Example 1 is that the feeding amount of raw materials in a single batch is increased and the product yield is increased. The specific operation steps are as follows:

[0044] (1) Add 832.8 g of formamidine acetate to a beaker, and add 1144.9 mL of 55% wt hydroiodic acid to the beaker according to the molar ratio of formamidine acetate to hydroiodic acid of 1.04. Stir and react at 30 °C for 4 h to obtain a reaction solution.

[0045] (2) Filter the reaction solution and pour it into a flask, then place it on a rotary evaporator to evaporate the solvent. Set the rotary evaporation temperature to 100 °C and the vacuum pump pressure to 0.095 MPa.

[0046] (3) After waiting for the solvent to be completely evaporated, remove the flask and collect the formamidine hydroiodide product.

[0047] Example 3:

[0048] (1) Add 1041 g of formamidine acetate to a small reaction kettle, and add 1458.7 mL of 55% wt hydroiodic acid to the reaction kettle according to the molar ratio of formamidine acetate to hydroiodic acid of 1.06. Stir and react at 40 °C for 8 h to obtain a reaction solution.

[0049] (2) Add 200 mL of deionized water, 400 mL of absolute ethanol and 120 mL of acetonitrile to the reaction solution, for a total of 720 mL of solvent, and control the solid content of the reaction solution to 0.6 g / mL.

[0050] (3) Drain the reaction solution from the reaction kettle, filter it and transfer it to a storage tank.

[0051] (4) Start the stirrer in the storage tank and continuously stir the reaction solution at a rate of 100 rpm / min.

[0052] (5) Set the inlet air temperature and outlet air temperature of the spray dryer to 150 °C and 140 °C respectively. After the temperature reaches the preset value, start the peristaltic pump to input the solution in the storage tank into the spray dryer, and set the peristaltic pump speed to 80 rpm.

[0053] (6) Collect the formamidine hydroiodide product after spray drying.

[0054] The crystal purity, moisture content and pH of the aqueous solution of the formamidine hydroiodide prepared in the examples and comparative examples are shown in Table 1:

[0055] Table 1

[0056] sample Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Purity (%) 99.9 99.9 99.7 92.5 90.2 Moisture content (%) 0.0082 0.0074 0.0093 3.44 5.22 pH 7.2 7.3 6.9 4.3 3.5

[0057] It can be seen that the formamidine hydroiodide prepared in the embodiments of the present invention has high purity, the water content is lower than 100 ppm, the pH of the aqueous solution is about 7, showing neutrality; while the product prepared in the comparative example has low purity, too high water content, the pH of the aqueous solution is acidic, and as the single-batch production increases, the water content of the product shows an upward trend and the pH of its aqueous solution shows a downward trend. This indicates that the residual amount of acidic impurities in the formamidine hydroiodide prepared in the examples is minimal and the product quality is high; while the residual amount of acidic impurities in the product prepared in the comparative example is too high, and as the single-batch production increases, the rotary evaporation effect is greatly reduced and the product quality deteriorates.

Claims

1. A method for preparing formamidine hydroiodide by spray drying process, characterized in that: The following steps are involved: (1) fully mixing two raw materials, formamidine acetate and hydroiodic acid, to react; (2) adding an appropriate amount of solvent to the reaction solution obtained in step (1) at room temperature to reduce the boiling point of the reaction solution, and adjusting the solid content of the reaction solution to 0.3 to 0.6 g / mL; (3) filtering the reaction solution obtained in step (2); (4) The solution obtained in step (3) is input into a spray drying system by a peristaltic pump for spray drying to achieve complete evaporation of the reaction solution and prepare formamidine hydroiodide with low water content and nearly spherical particles, wherein the spray dryer has an air inlet temperature of 130 to 150° C. and an air outlet temperature of 120 to 140° C.

2. The method according to claim 1, characterized in that The molar ratio of formamidine acetate to hydroiodic acid is 1.04 to 1.

06.

3. The method according to claim 1, characterized in that The temperature of the mixed reaction of formamidine acetate and hydroiodic acid is 30-40°C and the time is 4-8 hours.

4. The method according to claim 1, characterized in that: The solvent for adjusting the solid content of the reaction solution includes one or more of deionized water, anhydrous ethanol, methanol, isopropanol, and acetonitrile.

5. The method according to claim 1, characterized in that The rotation speed of the peristaltic pump is 50-100 rpm.

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