A method for the continuous production of ethephon

Abstract

This application discloses a method for the continuous preparation of ethephon, belonging to the field of ethephon preparation. The method includes the following steps: pre-dispersing bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon, and hydrogen chloride gas to obtain a gas-liquid dispersion with a dispersed phase size ≤1 mm; conveying the gas-liquid dispersion to a micro-packed bed reactor for reaction to obtain reaction products; and separating the reaction products to obtain a liquid-phase crude ethephon product. This application, by pre-introducing ethephon into the reaction feedstock system and enhancing the dispersibility of the feedstock system, can accelerate the heat and mass transfer process of the reaction system, significantly improve reaction efficiency, and avoid the generation of by-products. It features high feedstock conversion rate, high product purity, high product space-time yield, and short reaction time, enabling efficient, safe, and continuous production of ethephon with broad application prospects.

Description

Technical Field

[0001] This application belongs to the field of ethephon preparation, specifically relating to a method for the continuous preparation of ethephon. Background Technology

[0002] Ethephon, as an important plant growth regulator, plays a crucial role in agricultural production. It releases ethylene, which regulates plant growth and development processes, such as promoting fruit ripening, regulating flowering and sex differentiation, and enhancing plant resistance to adverse conditions. Due to these significant effects, ethephon is widely used in the cultivation of various fruits, vegetables, flowers, and other crops, effectively improving the yield and quality of agricultural products and providing a strong guarantee for increased agricultural production and income.

[0003] In the field of ethephon preparation, traditional methods mostly employ batch production processes. This process typically involves reacting bis(2-chloroethyl)-(2-chloroethyl)phosphonate with hydrogen chloride gas under suitable reaction conditions to produce ethephon. In addition, there have been some reports in recent years of continuous batch reactor synthesis of ethephon. However, the aforementioned existing methods for preparing ethephon generally suffer from drawbacks such as low feed conversion rates and poor product purity, requiring further improvement. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to propose a method for the continuous preparation of ethephon. By introducing ethephon into the reaction feedstock system beforehand and enhancing the dispersibility of the reaction feedstock system, this application can accelerate the heat and mass transfer process of the reaction system, significantly improve reaction efficiency, and avoid the formation of by-products. It features high feedstock conversion rate, high product purity, high product space-time yield, and short reaction time, enabling efficient, safe, and continuous production of ethephon with broad application prospects.

[0005] This application discloses a method for the continuous preparation of ethephon. According to embodiments of this application, the method includes the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon and hydrogen chloride gas were pre-dispersed to obtain a gas-liquid dispersion fluid with a dispersed phase size ≤1 mm. The gas-liquid dispersion fluid is transported to a micro-packed bed reactor for reaction to obtain reaction products; The reaction products were separated to obtain crude ethephon in liquid phase; The mass M1 of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the mass M2 of ethephon in the gas-liquid dispersion fluid satisfy the following relationship: M1 < M2.

[0006] The method for continuous preparation of ethephon according to the above embodiments of this application can accelerate the heat and mass transfer process of the reaction system by introducing ethephon into the reaction raw material system in advance and enhancing the dispersibility of the reaction raw material system, which significantly improves the reaction efficiency and avoids the generation of by-products. It has the characteristics of high raw material conversion rate, high product purity, high product space-time yield and short reaction time, and can realize efficient, safe and continuous production of ethephon, with broad application prospects.

[0007] In addition, the continuous preparation method of ethephon according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the step of pre-dispersing bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon, and hydrogen chloride gas to obtain a gas-liquid dispersion includes the following processes: The bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the ethephon are mixed to obtain a liquid-phase feedstock at a temperature of 80~120℃; The liquid raw material and the hydrogen chloride gas are dispersed to obtain the gas-liquid dispersion fluid with a dispersed phase size ≤1mm.

[0008] In some embodiments of this application, the ratio of M1 to M2 is 1:(4~10).

[0009] In some embodiments of this application, the molar ratio of the bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the hydrogen chloride gas is 1:(3~10).

[0010] In some embodiments of this application, the packing material in the micro-packed bed reactor has a size of 500-700 μm, and the packing material includes glass packing.

[0011] In some embodiments of this application, the operating temperature of the micro-filled bed reactor is 100~150℃; And / or, the operating pressure of the micro-packed bed reactor is 0.1~0.8 MPa; And / or, the operating time of the micro-filled bed reactor is 5 to 60 minutes.

[0012] In some embodiments of this application, the crude liquid-phase ethephon product is divided into a first liquid-phase ethephon and a second liquid-phase ethephon. The first liquid-phase ethephon is used to prepare the gas-liquid dispersion fluid, and the second liquid-phase ethephon is purified to obtain pure ethephon.

[0013] In some embodiments of this application, the ethephon content in the crude liquid ethephon product is ≥73.2% by mass. And / or, by mass percentage, the content of 2-chloroethyl(2-chloroethyl)phosphonate in the crude ethephon product is ≤13.5%.

[0014] In some embodiments of this application, the conversion rate of the bis(2-chloroethyl)-(2-chloroethyl)phosphonate is ≥86.7%.

[0015] In some embodiments of this application, the space-time yield of the crude ethephon product in the liquid phase is >4000 kg / (m²). 3 ·d).

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic flowchart of a method for the continuous preparation of ethephon in this application embodiment.

[0018] Explanation of reference numerals in the attached figures: 1- Hydrogen chloride gas feed, 2- Liquid phase feed, 3- Micro-dispersion, 4- Micro-packed bed reactor, 5- Gas-liquid separation. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] This application discloses a method for the continuous preparation of ethephon. According to embodiments of this application, the method includes the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon and hydrogen chloride gas were pre-dispersed to obtain a gas-liquid dispersion fluid with a dispersed phase size ≤1 mm. The gas-liquid dispersion fluid is transported to a micro-packed bed reactor for reaction to obtain reaction products; The reaction products were separated to obtain crude ethephon in liquid phase; The mass M1 of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the mass M2 of ethephon in the gas-liquid dispersion fluid satisfy the following relationship: M1 < M2.

[0021] The continuous ethephon preparation method described in the above embodiments of this application, by introducing ethephon into the reaction feedstock system beforehand and enhancing the dispersibility of the reaction feedstock system, can accelerate the heat and mass transfer process of the reaction system, significantly improve reaction efficiency, and avoid the formation of by-products. It features high feedstock conversion rate, high product purity, high product space-time yield, and short reaction time, enabling efficient, safe, and continuous ethephon production with broad application prospects. Specifically: On the one hand, by introducing ethephon into the reaction raw material system beforehand, this application can act as a solvent, which is beneficial for the subsequent formation of a gas-liquid dispersion between the liquid raw material (i.e., bis(2-chloroethyl)-(2-chloroethyl)phosphonate, or simply phosphonate diester) and hydrogen chloride gas; at the same time, it can also increase the solubility of the gaseous reactants in the reaction solution, promoting liquid-phase conversion. In addition, by further controlling the mass of ethephon in the gas-liquid dispersion to be greater than the mass of bis(2-chloroethyl)-(2-chloroethyl)phosphonate, it is beneficial to improve the raw material conversion rate and product purity.

[0022] On the other hand, this application enhances the dispersibility of the reaction raw material system. For example, bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon, and hydrogen chloride gas can be introduced together into existing micro-dispersion equipment such as microchannels, microporous membranes, microsieves, and micromixers to obtain a gas-liquid dispersion fluid with a dispersed phase size ≤1mm. This achieves continuous enhancement of heat and mass transfer within the system, thereby improving reaction efficiency and avoiding the generation of by-products.

[0023] In the embodiments of this application, the aforementioned gas-liquid dispersion fluid with a dispersed phase size ≤1 mm specifically refers to a gas-liquid dispersion fluid in which the dispersed phase achieves a dispersion at the millimeter level or below; if the dispersed phase is a gas, then the bubble diameter is ≤1 mm, and if the dispersed phase is a liquid, then the droplet diameter is ≤1 mm. Furthermore, the aforementioned dispersed phase particle size can be determined using existing detection methods such as laser diffraction (or a laser particle size analyzer, which uses laser light to irradiate the dispersed phase and calculates the dispersed phase particle size by measuring the intensity distribution of scattered light).

[0024] It should be noted that the above reaction products are separated (mainly gas-liquid separation) to obtain not only the crude ethephon product in liquid phase, but also tail gas containing unreacted hydrogen chloride, etc. The gas phase is pressurized and recycled or sent to tail gas treatment.

[0025] According to some specific embodiments of this application, the method for continuous preparation of ethephon according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the step of pre-dispersing bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon, and hydrogen chloride gas to obtain a gas-liquid dispersion fluid includes the following process: mixing bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon to obtain a liquid phase raw material at a temperature of 80~120°C (e.g., 90°C, 95°C, 100°C, 110°C, etc.); dispersing the liquid phase raw material and hydrogen chloride gas to obtain the gas-liquid dispersion fluid with a dispersed phase size ≤1mm. This application obtains a liquid-phase raw material with a temperature of 80~120℃ by preheating and mixing bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon, thereby increasing the heat sink of the system and improving temperature uniformity and fluid stability. Furthermore, the above-mentioned liquid-phase raw material and hydrogen chloride gas are introduced together into existing micro-dispersion equipment such as microchannels, microporous membranes, microsieves, and micromixers. By utilizing the microchannel structure (micrometer level) of the micro-dispersion equipment, the gas-liquid contact area is greatly increased, promoting the rapid dissolution of hydrogen chloride gas and heat and mass transfer (such as increased diffusion rate), forming a gas-liquid dispersion fluid with a dispersed phase size ≤1mm, thereby enhancing the dispersibility of the reaction raw material system and the heat and mass transfer process of the reaction system.

[0026] According to some specific embodiments of this application, the ratio of M1 to M2 is 1:(4~10), for example, it can be 1:4, 1:5, 1:6, 1:7, 1:8, etc., preferably 1:5. This application controls the bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon in the gas-liquid dispersion fluid to be within the above-mentioned mass ratio range, which is beneficial to improving the raw material conversion rate and product purity, etc.

[0027] According to some specific embodiments of this application, the molar ratio of bis(2-chloroethyl)-(2-chloroethyl)phosphonate to hydrogen chloride gas is 1:(3~10), for example, it can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc., preferably 1:5. This application ensures that excess acid catalysis promotes the complete conversion of the intermediate phosphonate monoester to ethephon, which is beneficial to improving the raw material conversion rate and product purity, and reducing the generation of by-products.

[0028] In some embodiments of this application, the packing material in the micro-packed bed reactor has a size of 100-700 μm, for example, 500-700 μm, 105-125 μm, etc.; the packing material includes glass packing.

[0029] In some embodiments of this application, the operating temperature of the micro-packed bed reactor is 100~150℃, for example, 100℃, 110℃, 120℃, etc.; and / or, the operating pressure of the micro-packed bed reactor is 0.1~0.8 MPa (or referred to as the back pressure of the micro-packed bed reactor), for example, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.6 MPa, etc.; and / or, the operating time of the micro-packed bed reactor is 5~60 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 45 min, 50 min, etc. The reaction time for preparing ethephon in this application is short, achieving efficient ethephon preparation within 5~60 min. Compared to existing batch reactor processes (where residence time may exceed several hours), the micro-packed bed reactor utilizes its high specific surface area to achieve rapid reaction kinetics.

[0030] According to some specific embodiments of this application, the crude ethephon product is divided into a first liquid-phase ethephon and a second liquid-phase ethephon. The first liquid-phase ethephon is used to prepare the gas-liquid dispersion fluid, and the second liquid-phase ethephon is purified to obtain pure ethephon. This application increases the heat sink of the system by partially refluxing the crude ethephon product (i.e., refluxing the first liquid-phase ethephon as a raw material for the gas-liquid dispersion fluid), improving temperature uniformity and fluid stability, and avoiding side reactions caused by hot spot formation. The remaining crude ethephon product (i.e., the second liquid-phase ethephon) is purified by existing conventional purification methods such as distillation and rectification to obtain a high-purity ethephon product, so as to better meet the needs of different fields.

[0031] According to some specific embodiments of this application, the ethephon content in the crude liquid-phase ethephon product is ≥80.7% by mass, and can reach up to 99.3%. It is evident that the continuous ethephon preparation method provided in this application has the characteristic of high product purity.

[0032] According to some specific embodiments of this application, the content of 2-chloroethyl(2-chloroethyl)phosphonate (hereinafter referred to as phosphonic acid monoester, CAS No. 17378-30-2) in the crude ethephon product by mass is ≤13.5%, and can be as low as 0.3%. It is evident that the continuous preparation method of ethephon provided in this application has the characteristic of low by-product content, effectively avoiding the formation of by-products.

[0033] In some embodiments of this application, the conversion rate of bis(2-chloroethyl)-(2-chloroethyl)phosphonate is ≥86.7%, and can reach up to 99.6%. Therefore, the continuous preparation method for ethephon provided in this application has the characteristic of high feedstock conversion rate.

[0034] In some embodiments of this application, the space-time yield of crude ethephon in the liquid phase is >4000 kg / (m²). 3·d), up to 6550 kg / (m 3 ·d). As can be seen, the method for continuous preparation of ethephon provided in this application has the characteristic of high product space-time yield.

[0035] It should be noted that the ethephon content and phosphonic acid monoester content mentioned above can be determined using existing detection methods such as liquid chromatography and liquid chromatography-mass spectrometry; the conversion rate of the bis(2-chloroethyl)-(2-chloroethyl)phosphonate can be determined using existing detection methods such as liquid chromatography; and the space-time yield of the crude ethephon product in liquid phase can be determined using existing detection methods such as recording the yield of crude ethephon product per unit time by weighing or using a flow meter.

[0036] Furthermore, the flowchart of the improved continuous preparation method of ethephon in this application is shown below. Figure 1 ( Figure 1 As shown in the diagram (1-hydrogen chloride gas feed, 2-liquid feed, 3-micro-dispersion, 4-micro-packed bed reactor, 5-gas-liquid separation), hydrogen chloride gas feed 1 and liquid feed 2 react in a micro-packed bed reactor 4 via micro-dispersion 3. The resulting reaction products are separated by gas-liquid separation 5 to obtain gaseous tail gas and liquid-phase ethephon crude product. A portion of the liquid-phase ethephon crude product is recycled to liquid feed 2, and another portion is further purified to obtain ethephon product, thus completing the entire reaction.

[0037] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0038] Example 1 This embodiment provides a method for the continuous preparation of ethephon, including the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon were prepared into a liquid-phase mixed solution at 100℃ with a mass ratio of 1:8. The feed rate of the liquid-phase mixed solution was 1.26 mL / min, the gaseous feed flow rate of hydrogen chloride was 32 sccm, and the molar ratio of hydrogen chloride gas to bis(2-chloroethyl)-(2-chloroethyl)phosphonate was 1:4. The liquid-phase mixed solution and the hydrogen chloride gas phase are fed into a microchannel mixer to form a gas-liquid micro-dispersion fluid with a dispersed phase size ≤1mm. The gas-liquid micro-dispersion fluid then enters a micro-packed bed reactor packed with 500-700μm spherical glass packing to complete the reaction. The temperature of the micro-packed bed reactor is 100℃, the back pressure is 0.1 MPa, and the liquid phase residence time is 8 min. After the reactants flow out of the micro-packed bed reactor, they are heated to 130℃ by a heat exchanger and then enter the separation unit for gas-liquid separation. The gas phase is compressed and recycled or sent to the tail gas treatment. The liquid phase is the crude ethephon product. The crude ethephon product is split into two streams. The first stream is used to mix with bis(2-chloroethyl)-(2-chloroethyl)phosphonate to form a liquid-phase mixed solution. The second stream is sent to the separation and purification unit to obtain the ethephon product.

[0039] Example 2 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The mass ratio of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon in the liquid-phase mixed solution is 1:5.

[0040] Example 3 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The mass ratio of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon in the liquid-phase mixed solution is 1:10.

[0041] Example 4 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The temperature of the micro-filled bed reactor is 120℃.

[0042] Example 5 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The temperature of the micro-filled bed reactor is 150℃.

[0043] Example 6 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The back pressure of the micro-packed bed reactor is 0.5 MPa.

[0044] Example 7 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The back pressure of the micro-filled bed reactor is 0.8 MPa.

[0045] Example 8 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The residence time of the liquid phase in the micro-packed bed reactor is 15 min.

[0046] Example 9 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The residence time of the liquid phase in the micro-packed bed reactor is 30 min.

[0047] Example 10 This embodiment provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The residence time of the liquid phase in the micro-packed bed reactor is 60 min.

[0048] Example 11 This embodiment provides a method for the continuous preparation of ethephon, including the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon were prepared into a liquid-phase mixed solution at 120°C with a mass ratio of 1:6. The feed rate of the liquid-phase mixed solution was 1.12 mL / min, the gaseous feed flow rate of hydrogen chloride was 48 sccm, and the molar ratio of hydrogen chloride gas to bis(2-chloroethyl)-(2-chloroethyl)phosphonate was 1:5. The liquid-phase mixed solution and the hydrogen chloride gas phase are fed into a microchannel mixer to form a gas-liquid micro-dispersed fluid with a dispersed phase particle size ≤1mm. The gas-liquid micro-dispersed fluid then enters a micro-packed bed reactor packed with 105-125μm spherical glass packing to complete the reaction. The temperature of the micro-packed bed reactor is 120℃, the back pressure is 0.5MPa, and the liquid phase residence time is 5 min. After the reactants flow out of the micro-packed bed reactor, they are heated to 130℃ by a heat exchanger and enter the separation unit for gas-liquid separation. The gas phase is compressed and recycled or sent to the tail gas treatment. The liquid phase is the crude ethephon product. The crude ethephon product is split into two streams. The first stream is used to mix with bis(2-chloroethyl)-(2-chloroethyl)phosphonate to form a liquid-phase mixed solution. The second stream is sent to the separation and purification unit to obtain the ethephon product.

[0049] Example 12 This embodiment provides a method for the continuous preparation of ethephon, including the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon were prepared into a liquid-phase mixed solution at 120°C with a mass ratio of 1:10. The feed rate of the liquid-phase mixed solution was 1.8 mL / min, the gaseous feed flow rate of hydrogen chloride was 64 sccm, and the molar ratio of hydrogen chloride gas to bis(2-chloroethyl)-(2-chloroethyl)phosphonate was 1:6. The liquid-phase mixed solution and the hydrogen chloride gas phase are fed into a microchannel mixer to form a gas-liquid micro-dispersed fluid with a dispersed phase particle size ≤1mm. The gas-liquid micro-dispersed fluid then enters a micro-packed bed reactor packed with 350-500μm spherical glass packing to complete the reaction. The temperature of the micro-packed bed reactor is 150℃, the back pressure is 0.2 MPa, and the liquid phase residence time is 12 min. After the reactants flow out of the micro-packed bed reactor, they are heated to 130℃ by a heat exchanger and enter the separation unit for gas-liquid separation. The gas phase is compressed and recycled or sent to the tail gas treatment. The liquid phase is the crude ethephon product. The crude ethephon product is split into two streams. The first stream is used to mix with bis(2-chloroethyl)-(2-chloroethyl)phosphonate to form a liquid-phase mixed solution. The second stream is sent to the separation and purification unit to obtain the ethephon product.

[0050] Example 13 This embodiment provides a method for the continuous preparation of ethephon, including the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon were prepared into a liquid-phase mixed solution at 120°C with a mass ratio of 1:9. The feed rate of the liquid-phase mixed solution was 1.6 mL / min, the gaseous feed flow rate of hydrogen chloride was 32 sccm, and the molar ratio of hydrogen chloride gas to bis(2-chloroethyl)-(2-chloroethyl)phosphonate was 1:3. The liquid-phase mixed solution and the hydrogen chloride gas phase material enter a microchannel mixer to form a gas-liquid micro-dispersed fluid with a dispersed phase particle size ≤1mm. Subsequently, the gas-liquid micro-dispersed fluid enters a micro-packed bed reactor packed with 177-250μm spherical glass packing to complete the reaction. The temperature of the micro-packed bed reactor is 150℃, the back pressure is 0.5 MPa, and the liquid phase residence time is 9 min. After the reactants flow out of the micro-packed bed reactor, they are heated to 130℃ by a heat exchanger and enter the separation unit for gas-liquid separation. The gas phase is compressed and recycled or sent to the tail gas treatment. The liquid phase is the crude ethephon product. The crude ethephon product is split into two streams. The first stream is used to mix with bis(2-chloroethyl)-(2-chloroethyl)phosphonate to form a liquid-phase mixed solution. The second stream is sent to the separation and purification unit to obtain the ethephon product.

[0051] Comparative Example 1 This comparative example provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The mass ratio of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon in the liquid-phase mixed solution is 1:0.5.

[0052] Comparative Example 2 This comparative example provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The liquid-phase mixed solution and the hydrogen chloride gas phase two-phase material are conventionally mixed and dispersed by a gas distributor to form a gas-liquid micro-dispersed fluid with a dispersion phase particle size >1mm.

[0053] Comparative Example 3 This comparative example provides a method for the continuous preparation of ethephon, which differs from Example 1 only in that: (1) The mass ratio of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and ethephon in the liquid-phase mixed solution is 1:2.

[0054] Test case This test case examines the reaction effects of the continuous ethephon preparation methods provided in Examples 1 to 13 and Comparative Examples 1 to 3.

[0055] The testing method is as follows: 1) Detection of ethephon content in crude ethephon product in liquid phase: Using tributyl phosphate as an internal standard, the ethephon content in the sample was quantitatively measured by nuclear magnetic resonance phosphorus spectroscopy.

[0056] 2) Detection of phosphonic acid monoester content in crude ethephon product in liquid phase: Tributyl phosphate was used as an internal standard, and the content of phosphonic acid monoester in the sample was quantitatively measured by nuclear magnetic resonance phosphorus spectroscopy.

[0057] 3) Conversion rate detection of bis(2-chloroethyl)-(2-chloroethyl)phosphonate: Using tributyl phosphate as an internal standard, the content of bis(2-chloroethyl)-(2-chloroethyl)phosphonate in the sample was quantitatively measured by nuclear magnetic resonance phosphorus spectroscopy.

[0058] 4) Space-time yield detection of crude ethephon in liquid phase: The space-time yield is calculated based on the quantitative measurement results of NMR phosphorus spectrum, residence time and reactor volume.

[0059] The test results are shown in Table 1.

[0060] Table 1

[0061] Table 1 shows that the micro-reaction system formed by the micro-dispersion device and the micro-packed bed reactor can effectively improve the efficiency of ethephon flow synthesis, reducing the reaction time from hours in batch processes to minutes. The key factor promoting the reaction is the formation of microbubbles with a size ≤1 mm in the micro-reaction system. The specific surface area of ​​microbubbles is much higher than that of conventionally sized bubbles; therefore, the mass transfer flux on the surface of microbubbles is typically 1-2 orders of magnitude greater than that of conventionally sized bubbles. Due to the reduction in reactor volume and time, the micro-reaction system can effectively improve equipment safety while increasing space-time yield, enabling the controlled synthesis of ethephon.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for continuous preparation of ethephon, characterized in that, Includes the following steps: Bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon and hydrogen chloride gas were pre-dispersed to obtain a gas-liquid dispersion fluid with a dispersed phase size ≤1 mm. The gas-liquid dispersion fluid is transported to a micro-packed bed reactor for reaction to obtain reaction products; The reaction products were separated to obtain crude ethephon in liquid phase; The mass M1 of bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the mass M2 of ethephon in the gas-liquid dispersion fluid satisfy the following relationship: M1 < M2.

2. The method for continuous preparation of ethephon according to claim 1, characterized in that, The steps of pre-dispersing bis(2-chloroethyl)-(2-chloroethyl)phosphonate, ethephon, and hydrogen chloride gas to obtain a gas-liquid dispersion include the following processes: The bis(2-chloroethyl)-(2-chloroethyl)phosphonate and the ethephon are mixed to obtain a liquid-phase feedstock at a temperature of 80~120℃; The liquid raw material and the hydrogen chloride gas are dispersed to obtain the gas-liquid dispersion fluid with a dispersed phase size ≤1mm.

3. The method for continuous preparation of ethephon according to claim 1, characterized in that, The ratio of M1 to M2 is 1:(4~10).

4. The method for continuous preparation of ethephon according to claim 1, characterized in that, The molar ratio of the bis(2-chloroethyl)-(2-chloroethyl)phosphonate to the hydrogen chloride gas is 1:(3~10).

5. The method for continuous preparation of ethephon according to claim 1, characterized in that, The packing material in the micro-packed bed reactor has a size of 100-700 μm, and the packing material includes glass packing.

6. The method for continuous preparation of ethephon according to claim 5, characterized in that, The operating temperature of the micro-filled bed reactor is 100~150℃; And / or, the operating pressure of the micro-packed bed reactor is 0.1~0.8 MPa; And / or, the operating time of the micro-filled bed reactor is 5 to 60 minutes.

7. The method for continuous preparation of ethephon according to claim 1, characterized in that, The crude ethephon product is divided into a first liquid ethephon and a second liquid ethephon. The first liquid ethephon is used to prepare the gas-liquid dispersion fluid, and the second liquid ethephon is purified to obtain pure ethephon.

8. The method for continuous preparation of ethephon according to any one of claims 1 to 7, characterized in that, The ethephon content in the crude liquid ethephon product is ≥73.2% by mass. And / or, by mass percentage, the content of 2-chloroethyl(2-chloroethyl)phosphonate in the crude ethephon product is ≤13.5%.

9. The method for continuous preparation of ethephon according to any one of claims 1 to 7, characterized in that, The conversion rate of the bis(2-chloroethyl)-(2-chloroethyl)phosphonate is ≥86.7%.

10. The method for continuous preparation of ethephon according to any one of claims 1 to 7, characterized in that, The space-time yield of the crude ethephon in the liquid phase is >4000 kg / (m²). 3 ·d).

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