Preparation method of 1, 2-octylene glycol

Abstract

The invention relates to the technical field of chemical production, in particular to a preparation method of 1, 2-octylene glycol, the preparation method comprises the steps of oxidation ring-opening esterification reaction, saponification hydrolysis reaction and post-treatment and refining, and an air flotation synergistic layering device comprises a tank body, a central shaft, a pre-filtering unit, an air flotation unit and a driving mechanism; the central shaft is vertically mounted in the tank body, and the top end and the bottom end of the central shaft both penetrate and extend to the outside of the tank body; the center shaft is rotationally connected with the top of the tank body, and a rotating seat fixedly sleeves the bottom end of the center shaft and is rotationally connected with the bottom of the tank body; the driving mechanism is arranged at the top of the tank and used for driving the center shaft to rotate. By accurately controlling the dripping rate of hydrogen peroxide, the reaction temperature and the effective oxygen molar ratio, side reactions such as violent decomposition and over-oxidation of peroxyformic acid are inhibited, and the selectivity and safety of the reaction are improved; and rectification is carried out under the conditions of high vacuum degree and specific tower kettle temperature, so that high-boiling-point impurities can be efficiently separated out, and a high-purity target product can be obtained.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically a method for preparing 1,2-octanediol. Background Technology

[0002] 1,2-Octanediol is an important fine chemical intermediate and functional raw material, which is a white solid or colorless to pale yellow liquid at room temperature. Its molecule contains two adjacent hydroxyl groups, giving it excellent moisturizing, antibacterial, and surface-active properties. It is widely used in high-end cosmetics, personal care products, and detergents, and also has potential applications in pharmaceuticals, pesticides, and polymer materials.

[0003] The industrial production of 1,2-octanediol currently mainly adopts the epoxidation-hydrolysis route using octene as a raw material. This route first epoxidizes octene with peroxyacid (such as peroxyformic acid), and then hydrolyzes it to obtain the glycol. Among these methods, the in-situ peroxyformic acid method (which involves the reaction of hydrogen peroxide with formic acid to produce peroxyformic acid) has become the mainstream due to its high reactivity and mild conditions.

[0004] The above process has several drawbacks in actual production: peroxyformic acid is highly reactive and the reaction is exothermic, requiring strict control of the hydrogen peroxide droplet acceleration and temperature to avoid side reactions and safety risks; the post-reaction system contains unreacted formic acid, water, and byproducts, making separation, recovery, and purification steps complex; the generated byproducts are wasted significantly, increasing production costs; in addition, the saponification and hydrolysis section relies on traditional separators for static stratification, depending on gravity for natural separation, which is slow and requires a standing time of 2-3 hours, severely restricting production batch turnover and equipment utilization, becoming a key bottleneck in improving overall process efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 1,2-octanediol to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] A method for preparing 1,2-octanediol includes the following steps: S1. Oxidative ring-opening esterification reaction: 1-Octenene and formic acid are mixed at a mass ratio of 1:1.5-1:2.0, a catalyst is added, and hydrogen peroxide with an effective oxygen molar ratio of 1.0:1 to 1.2:1 to 1-octene is slowly added dropwise over 4-6 hours at 55-70℃. After the addition is completed, the reaction is maintained at this temperature for 0.5-1 hours. After the reaction is completed, the formic acid is recovered under reduced pressure to obtain a reaction mixture containing octyl formate. The recovered formic acid can be recycled. S2, Saponification and Hydrolysis Reaction: Add 25%-30% sodium hydroxide solution to the mixture obtained in step S1, wherein the molar ratio of sodium hydroxide to formic acid added in step S1 is 1.0:1 to 1.1:1, and saponify at 55-65℃ for 0.5-1 hours. After the reaction, use an air flotation enhanced separator to assist in separation. The separated aqueous phase is neutralized with formic acid, distilled, centrifuged and dried to obtain sodium formate as a byproduct. The organic phase is washed with water to obtain an organic layer containing 1,2-octanediol. The washing liquid is used to prepare alkali solution. S3. Post-processing and purification: The organic layer is dehydrated by vacuum distillation at 80-90℃. The distillate is used to prepare alkali. The remaining crude product is subjected to high-vacuum distillation at a vacuum degree of not less than -0.095MPa, and the temperature of the column bottom is controlled at 134-150℃. The fraction is collected to obtain high-purity 1,2-octanediol product. The distillation residue is treated as solid waste.

[0008] Preferably, the flotation-enhanced stratifier includes a tank, a central shaft, a pre-filtration unit, a flotation unit, and a drive mechanism. The central shaft is vertically installed inside the tank, with both its top and bottom ends extending through to the outside of the tank. The central shaft is rotatably connected to the top of the tank, and a rotating seat is fixedly fitted at the bottom of the central shaft, which is rotatably connected to the bottom of the tank. The drive mechanism is located at the top of the tank and is used to drive the central shaft to rotate. The pre-filtration unit is fitted outside the drive mechanism and near the top wall of the tank, and is used to filter out large organic droplets. The flotation unit is divided into two parts: one part is located at the bottom of the tank, and the other part is integrated on the rotating seat, which is used to assist in the rapid stratification of water and small organic droplets.

[0009] Preferably, the pre-filtration unit includes a corrugated filter disc and a cover plate; the corrugated filter disc is formed by alternating fixed connections of annular plates and annular filter bodies, the annular filter bodies have a U-shaped cross-section, and the annular plates are connected between the tops of two adjacent annular filter bodies, and both the annular plates and annular filter bodies are arranged in a pattern where the diameter increases towards the outer edge, with the innermost annular plate fixed to the outer wall of the central shaft; the annular filter bodies are made of superhydrophobic calcium carbonate granular membranes; the cover plate is positioned above the corrugated filter disc and is configured to reciprocate and move up and down during the rotation of the central shaft; when the cover plate moves to its extreme position, a guide gap is formed between the lower surface of the cover plate and the annular plate to allow large droplets of organic phase to pass through; when the cover plate moves to its extreme position, the lower surface of the cover plate is tightly fitted to the annular plate, and a closed cavity is formed within each annular filter body; the drive mechanism is configured to drive the central shaft to rotate at low speed when the cover plate moves to its extreme position and to drive the central shaft to rotate at high speed when the cover plate moves to its extreme position; there is a discharge gap between the outermost annular plate and the inner wall of the tank.

[0010] Preferably, a feeding system is provided on the central shaft for guiding the mixture from the saponification reaction in step S2 to the corrugated filter disc; the feeding system includes a feeding channel opened at the top of the central shaft, a plurality of first guide holes arranged in an annular array on the outer wall of the central shaft, and a feeding pipe rotatably connected to the top of the central shaft via an adapter; the feeding pipe is connected to the feeding channel, each of the first guide holes is connected to the feeding channel, and the first guide holes are used to guide the mixture in the feeding channel to the annular filter body closest to the central shaft when the central shaft rotates.

[0011] Preferably, the cover plate has guide holes evenly distributed, and the outermost annular plate has guide rods fixed in a ring array. The cover plate slides onto the guide rods through the guide holes, and the outer edge of the cover plate is in movable contact with the inner wall of the tank. Each guide rod has an end cap fixed at its top, and each guide rod is fitted with a spring. One end of the spring is fixed to the lower surface of the end cap, and the other end is fixed to the upper surface of the cover plate. The upper surface of the cover plate has several mounting seats in a ring array, and each mounting seat has a ball embedded in its top. The top wall of the tank has several arc-shaped extrusion blocks in a ring array, and the lower end of each arc-shaped extrusion block is an arc-shaped slope that cooperates with the extrusion of the ball.

[0012] Preferably, the rotating seat has several mixing channels extending radially around the central axis, and each mixing channel penetrates the outer peripheral surface of the rotating seat; a guide channel is provided below the feed channel in the central axis, and several second guide holes are provided on the central axis and the rotating seat. One end of the second guide hole is connected to the guide channel, and the other end is connected to the mixing channel; a collection cover is fixed to the bottom of the corrugated filter disc, and the collection cover is fixedly fitted on the central axis. A collection cavity is formed between the corrugated filter disc and the collection cover for collecting the aqueous phase and small droplet organic phase passing through the annular filter body; a pump body is installed on the collection cover, and the pump body is connected to the guide channel through a pipe.

[0013] Preferably, the air flotation unit includes an air inlet channel located below the material guide channel within the central shaft, a first air inlet pipe rotatably connected to the bottom end of the central shaft via an adapter, and an annular cavity located below the mixing channel within the rotating seat. The annular cavity is distributed around the central shaft, and the central shaft and the rotating seat are provided with a plurality of annularly arrayed air guide holes. One end of each air guide hole is connected to the air inlet channel, and the other end is connected to the annular cavity. The first air inlet pipe is connected to the air inlet channel. The inner wall of the mixing channel is provided with a plurality of vertically downward extending unidirectional air outlet microholes, and the bottom of each unidirectional air outlet microhole is connected to the annular cavity.

[0014] Preferably, the air flotation unit further includes an annular shell, microbubble nozzles, and a second air inlet pipe; an annular shell is fixed on the inner side wall of the tank and near its bottom wall, and a plurality of microbubble nozzles extending toward the mixing channels are evenly distributed on the inner edge wall of the annular shell, and each microbubble nozzle is connected to the inside of the annular shell; one end of the second air inlet pipe is connected to the annular shell, and the other end extends to the outside of the tank.

[0015] Preferably, a conical cover plate is fixed on the inner wall of the tank and above the annular shell, and there is an annular gap between the conical cover plate and the outer wall of the central axis; the conical cover plate gradually expands downward; and a receiving area is formed between the upper surface of the conical cover plate and the inner wall of the tank.

[0016] Preferably, the drive mechanism includes a drive motor, a main gear, and a driven gear; the drive motor is fixed to the top of the tank via a motor mount, the main gear is fixed to the output shaft of the drive motor, and the driven gear is fixedly mounted on the outer wall of the central shaft and meshes with the main gear.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0018] This invention suppresses side reactions such as violent decomposition and excessive oxidation of peroxyformic acid by precisely controlling the dropping rate of hydrogen peroxide, reaction temperature, and effective oxygen molar ratio, thereby improving the selectivity and safety of the reaction. Distillation under high vacuum and specific column bottom temperature can efficiently separate high-boiling-point impurities, ensuring that the final product contains ≥98% 1,2-octanediol and ≤0.1% moisture, thus obtaining a high-purity target product.

[0019] This invention recovers 50%-65% of formic acid under reduced pressure and recycles it, and uses the washing liquid to prepare alkali solution and the distilled water to be reused for alkali preparation, forming an internal circulation system of reaction solvent and process water, which reduces the consumption of fresh raw materials and process water. At the same time, the aqueous phase generated by saponification is converted into sodium formate by-product through neutralization, distillation and other treatments, realizing the resource utilization of waste liquid and reducing the discharge of waste gas, wastewater, and solid waste.

[0020] This invention utilizes an air flotation-enhanced phase separator after the saponification reaction, along with dehydration under reduced pressure followed by high-vacuum distillation. This avoids multiple transfers and complex processing of intermediate products, reduces material exposure and loss, enables standardized solid waste treatment of distillation residues, and lowers safety risks such as high-temperature decomposition and material leakage. This makes the process easier to implement and control industrially.

[0021] The stratifier used in this method achieves pre-separation of large and small organic droplets through a pre-filtration unit, reducing the impact of the slow floating speed of large organic droplets on the stratification speed. Subsequently, the aqueous phase and small organic droplets enter the air flotation unit, where they are fully mixed with microbubbles, allowing the small organic droplets to be quickly adsorbed by the bubbles and float to the surface. This shortens the traditional stratification process, which relies on gravity settling for 2-3 hours, to less than 1 hour, thus improving production efficiency.

[0022] The present invention uses a cone-shaped cover plate with a cone-shaped gradually expanding design, which can guide and temporarily store the pre-separated large droplets of organic phase in the receiving area at the beginning of feeding, avoiding secondary mixing with the bottom bubble swirling area. At the same time, it promotes the small bubbles rising to merge and grow larger as they converge toward the central axis, further accelerating the floating rate, achieving two goals at once. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation method. Figure 2 This is a schematic diagram of the air flotation-enhanced stratifier used in this preparation method. Figure 3 This is a schematic diagram of a partial structure on the surface of the tank. Figure 4 This is a schematic diagram of a partial internal structure of the tank. Figure 5 for Figure 3 A cross-sectional schematic diagram of the structure shown; Figure 6 for Figure 5 Enlarged schematic diagram of the structure at point A in the middle; Figure 7 This is a schematic diagram of the cover plate structure installation in this invention; Figure 8 for Figure 7 Enlarged schematic diagram of the structure at point B; Figure 9 for Figure 2 One of the schematic diagrams of a partial structural cross-section shown; Figure 10 for Figure 9 Enlarged schematic diagram of the structure at point C; Figure 11 This is a schematic diagram illustrating the structure of a closed cavity; Figure 12 This is a schematic diagram showing the structure of the material guide gap; Figure 13 For Figure 2 The second schematic diagram of the partial structural cross-section shown; Figure 14 for Figure 13 Enlarged schematic diagram of the structure at point D; Figure 15 for Figure 13 Enlarged schematic diagram of the structure at point E in the middle; Figure 16 The flowchart and material balance diagram are for Example 1.

[0024] In the diagram: 1. Tank body; 101. Viewing window; 11. First heavy phase outlet; 12. Second heavy phase outlet; 13. Light phase outlet; 131. Slide bar; 132. Annular float; 133. Blocking component; 134. Annular pipe; 135. Suction port; 136. Suction pipe; 14. Exhaust port; 2. Central shaft; 21. Feed channel; 211. Feed pipe; 212. First guide hole; 22. Guide channel; 221. Pump body; 23. Air inlet channel; 231. First air inlet pipe; 3. Drive mechanism; 31. Drive motor; 32. Main gear; 33. From... 4. Moving gear; 5. Corrugated filter disc; 6. Annular plate; 7. Annular filter body; 8. Material guide gap; 9. Closed cavity; 10. Collection hood; 11. Collection cavity; 12. Cover plate; 13. Guide hole; 14. Guide rod; 15. End cap; 16. Spring; 17. Mounting base; 18. Roller ball; 19. Arc-shaped extrusion block; 20. Conical cover plate; 10. Receiving area; 11. Annular shell; 12. Microbubble nozzle; 13. Second air inlet pipe; 14. Rotating seat; 15. Annular cavity; 16. Air guide hole; 17. One-way air outlet micropore; 18. Mixing channel; 19. Second material guide hole. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments: This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0028] Please see Figures 1-15 This invention provides an example of 1,2-octanediol preparation. The process flow and material balance diagram of this example are shown in the attached specification. Figure 16 As shown, the specific steps include: S1, Oxidative ring-opening esterification reaction: Add approximately 700 kg of formic acid and approximately 400 kg of 1-octene sequentially to the glass-lined reactor, start stirring to mix the materials evenly, add the specified amount of catalyst to the system, turn on the steam heating of the reactor jacket to raise the temperature of the materials to about 60°C and maintain it stable. Approximately 243 kg of 50% hydrogen peroxide was slowly and uniformly added to the reactor using a metering pump over a period of about 5 hours. The reaction was exothermic during the addition. The reactor temperature was controlled between 60-65°C by adjusting the jacket cooling water flow rate, and the temperature was not to exceed 65°C. The adding pipe should extend below the liquid surface to prevent localized overheating or gas-phase reactions. After the hydrogen peroxide addition was complete, the reaction temperature was maintained at 60-65°C, and the reaction was stirred for 0.5 hours to ensure complete reaction and full conversion of 1-octene to octyl formate. After the reaction is complete, the reactor is switched to reduced pressure mode. At a reactor temperature of approximately 85°C and an appropriate vacuum level, the unreacted formic acid in the system is distilled off and recovered. The recovered formic acid collected in the receiving tank is pale yellow with a concentration of approximately 50-65%. After metering, it is pumped to the formic acid recovery storage tank for reuse in the next batch of reaction. Approximately 550 kg of formic acid is distilled off during the recovery process. The remaining material in the reactor is a concentrated formic acid ester mixture, ready for the next reaction.

[0029] S2, Saponification and hydrolysis reaction: Slowly add a pre-prepared 28% sodium hydroxide aqueous solution to the above-mentioned reaction vessel containing formate esters, and control the appropriate temperature. Stir continuously at 60°C for 0.5 hours to carry out the saponification and hydrolysis reaction. Sodium hydroxide reacts with residual formic acid and formate esters to generate 1,2-octanediol and sodium formate. Stop stirring and turn off heating. Use an air flotation-enhanced stratifier to assist in stratification. The mixture is clearly divided into two layers. The upper layer is an orange-yellow to light yellow oily organic layer, the main components of which are crude 1,2-octanediol, a small amount of water and a small amount of dissolved organic matter. The lower layer is a colorless or light yellow water layer containing a high concentration of sodium formate, excess sodium hydroxide and other water-soluble impurities. Open the bottom valve of the separator to completely discharge the lower aqueous phase and collect it in the intermediate aqueous phase tank for further processing to recover sodium formate. The remaining organic layer is left in the reactor or transferred to the washing tank. Add a certain amount of process water (or the previous washing solution) to the organic layer and wash it once with gentle stirring to remove the small amount of inorganic salts entrained in the organic phase. Then separate the washing solution, which contains a certain alkalinity. It can be pumped to the alkali preparation tank to dissolve fresh sodium hydroxide to prepare a 28% alkali solution, thus realizing the recycling of water. The washed organic layer is the crude 1,2-octanediol. The collected aqueous phase is neutralized to near-neutral or weakly acidic pH with formic acid (which can be recycled). The neutralized solution is then sent to an evaporation and concentration unit to evaporate most of the water. The concentrated solution is cooled and crystallized, and then the solid wet material is separated by a centrifuge. The wet material is dried by a dryer to obtain white or light yellow sodium formate solid, which is packaged and sold as a by-product. The centrifugation mother liquor can be returned to the concentration process or used for subsequent wastewater treatment.

[0030] S3. Post-processing and refining: The obtained crude 1,2-octanediol is pumped to a vacuum distillation kettle and distilled under a suitable vacuum and a heating temperature of 80-90°C. The main purpose is to remove the dissolved and carried water from the crude product. The distilled water is collected after condensation (this part of the process water is relatively clean and can also be sent to the alkali preparation tank for reuse). Distillation continues until no water is distilled off. The dehydrated crude product is transferred to the reboiler of the high-vacuum distillation system. The high-vacuum unit is started to raise the system vacuum to above -0.095 MPa, preferably -0.098 MPa or higher. The reboiler is gradually heated, and the bottom temperature is controlled. The process is as follows: Initially, a small amount of foredistillate is collected separately. When the temperature at the top of the column stabilizes within the range corresponding to the boiling point of 1,2-octanediol, the main fraction is collected. According to the process data, at this vacuum level, the fraction at approximately 134°C to 150°C is collected. Product quality is ensured by observing the appearance of the fraction and by online detection or periodic sampling and analysis. The fraction that meets the specifications is collected in the product receiving tank. After cooling, it becomes the finished product 1,2-octanediol, with a single batch yielding approximately 380 kg of product. After distillation, the small amount of viscous or coke-like residue remaining in the reboiler, mainly consisting of high-boiling-point impurities such as polymers and carbides, is discharged after heating is stopped and the residue is collected as hazardous solid waste and regularly entrusted to a qualified environmental protection unit for safe disposal.

[0031] The products manufactured according to the process of Example 1 have the following test indicators: Appearance: White or pale yellow transparent liquid; Content (1,2-octanediol) ≥98%; Moisture ≤0.1%; Other indicators meet industry standards or customer requirements.

[0032] This invention also provides an air flotation-enhanced separator, which is mainly used in the saponification and hydrolysis reaction section to efficiently and rapidly separate the organic phase (oil phase) and the aqueous phase. The specific structure and operating principle of this separator are as follows: Example 2

[0033] Please see Figures 2-15 The air flotation-enhanced stratifier includes a tank 1, a central shaft 2, a pre-filtration unit, and a drive mechanism 3. The side of the tank 1 is provided with a viewing window 101 for observing the stratification inside the tank 1. The bottom of the tank 1 is provided with a first heavy phase outlet 11 for discharging the stratified water phase (heavy phase). In addition, the side of the tank 1 is also provided with an exhaust port 14, which is equipped with a pressure relief valve for releasing pressure when there is high pressure inside the tank 1 to ensure operational safety.

[0034] The central shaft 2 is vertically installed inside the tank 1, and both the top and bottom ends of the central shaft 2 extend through to the outside of the tank 1. The central shaft 2 is rotatably connected to the top of the tank 1, and a rotating seat 9 is fixedly fitted at the bottom of the central shaft 2. The rotating seat 9 is rotatably and sealed to the bottom of the tank 1 to ensure that the central shaft 2 can rotate stably. The drive mechanism 3 is set at the top of the tank 1 to drive the central shaft 2 to rotate. The pre-filtration unit is fitted outside the drive mechanism 3 and close to the inner top wall of the tank 1 to filter out large droplets of organic phase.

[0035] like Figure 5 and Figures 9-12 As shown, the pre-filtration unit includes a corrugated filter disc 4 and a cover plate 6. The corrugated filter disc 4 is formed by alternating fixed connections of annular plates 41 and annular filter bodies 42. Specifically, an annular filter body 42 is fixed between two adjacent annular plates 41, and an annular plate 41 is between two adjacent annular filter bodies 42. The innermost and outermost annular plates 41 are both annular plates 41. The annular plates 41 and annular filter bodies 42 are arranged in a pattern where the diameter increases towards the outermost edge. The innermost annular plate 41 is fixed to the outer wall of the central shaft 2, and there is a discharge gap between the outermost annular plate 41 and the inner wall of the tank 1.

[0036] The annular filter body 42 has a U-shaped cross-section, and the annular plate 41 is connected between the tops of two adjacent annular filter bodies 42. The annular filter body 42 uses a superhydrophobic calcium carbonate granular membrane to filter large droplets of organic phase (large droplets of oil phase). The cover plate 6 is set above the corrugated filter disc 4. The cover plate 6 is configured to reciprocate and move up and down during the rotation of the central shaft 2. When the cover plate 6 moves to the limit position, a guide gap 43 is formed between the lower surface of the cover plate 6 and the annular plate 41 to allow the large droplets of organic phase to pass through. When the cover plate 6 moves to the limit position, the lower surface of the cover plate 6 is tightly fitted with the annular plate 41. Each annular filter body 42 forms a closed cavity 44 due to being blocked by the cover plate 6. The drive mechanism 3 is configured to drive the central shaft 2 to rotate at low speed when the cover plate 6 moves to the limit position and drive the central shaft 2 to rotate at high speed when the cover plate 6 moves to the limit position.

[0037] Among them, such as Figure 3 As shown, the drive mechanism 3 includes a drive motor 31, a main gear 32, and a driven gear 33. The drive motor 31 is fixed to the top of the tank 1 via a motor mount. The main gear 32 is fixed to the output shaft of the drive motor 31. The driven gear 33 is fixedly mounted on the outer wall of the central shaft 2 and meshes with the main gear 32. The drive motor 31 drives the main gear 32 to rotate. Under the meshing transmission action of the main gear 32 and the driven gear 33, the rotating main gear 32 can drive the central shaft 2 to rotate. The drive motor 31 is controlled by a controller.

[0038] A feeding system is installed on the central shaft 2 to guide the mixture from the saponification reaction in step S2 onto the corrugated filter disc 4, such as... Figure 5 , Figure 9 and Figure 10 As shown, the feeding system includes a feeding channel 21 opened at the top of the central shaft 2, a plurality of first guide holes 212 arranged in an annular array on the outer wall of the central shaft 2, and a feeding pipe 211 rotatably connected to the top of the central shaft 2 via an adapter (using prior art, not shown in the figure). The feeding pipe 211 is connected to the feeding channel 21, and each of the first guide holes 212 is connected to the feeding channel 21. The first guide holes 212 are used to guide the mixture in the feeding channel 21 to the annular filter body 42 closest to the central shaft 2 when the central shaft 2 rotates. The use of the adapter allows the feeding pipe 211 to maintain a rotatable connection with the top of the central shaft 2, preventing the feeding pipe 211 from rotating synchronously with the central shaft 2.

[0039] like Figure 7 and Figure 8As shown, guide holes 61 are evenly distributed on the cover plate 6. Guide rods 62 are fixed in a ring array on the outermost annular plate 41. The cover plate 6 slides onto the guide rods 62 through the guide holes 61, and the outer edge of the cover plate 6 is in contact with the inner wall of the tank 1, so that the cover plate 6 has the ability to be raised and lowered. An end cap 63 is fixed to the top of each guide rod 62, and a spring 64 is sleeved on the outside of each guide rod 62. One end of the spring 64 is fixed to the lower surface of the end cap 63, and the other end is fixed to the upper surface of the cover plate 6. Several guide rods 62 are fixed in a ring array on the upper surface of the cover plate 6. The mounting base 65 has a ball 66 embedded in its top. The inner top wall of the tank body 1 has a number of arc-shaped extrusion blocks 67 arranged in a ring. The lower end of each arc-shaped extrusion block 67 is an arc-shaped slope that cooperates with the ball 66 in extrusion, ensuring that the extrusion process between the ball 66 and the lower end of the arc-shaped extrusion block 67 is smooth enough. The middle part of the arc-shaped slope is flat, ensuring that the closed cavity 44 is maintained for a certain period of time. The ball 66 and the arc-shaped extrusion block 67 are arranged at intervals, ensuring that the material guide gap 43 is maintained for a certain period of time.

[0040] As the cover plate 6 rotates with the central shaft 2, the rolling ball 66 on it moves synchronously around the central shaft 2. When the rolling ball 66 contacts the arc-shaped slope of the arc-shaped extrusion block 67, it creates a downward pressure effect. The cover plate 6 is pressed and moves downward along the guide rod 62. At this time, the spring 64 is stretched and stores force. When the rolling ball 66 contacts and presses against the flat part in the middle of the arc-shaped slope of the arc-shaped extrusion block 67, as... Figure 11 As shown, when the cover plate 6 descends to its limit position, a closed cavity 44 is formed between the annular filter body 42 and the cover plate 6. After the rolling ball 66 completely separates from the arc-shaped slope of the arc-shaped extrusion block 67, the cover plate 6 is driven to move upward and reset to its limit position under the elastic force of the spring 64. At this time, as shown... Figure 13 As shown, a material guiding gap 43 is formed between the cover plate 6 and the annular plate 41.

[0041] The working principle of this embodiment is as follows: The mixture from the saponification reaction is fed into the feed pipe 211. At the same time, the drive mechanism 3 drives the central shaft 2 to rotate. After the mixture flows into the feed channel 21, it flows out through the first guide hole 212 into the annular filter body 42 closest to the central shaft 2. The corrugated filter disc 4 and the cover plate 6 rotate synchronously with the central shaft 2. During the rotation, the cover plate 6 moves up and down repeatedly. When the cover plate 6 descends to the limit position, a closed cavity 44 is formed in the annular filter body 42. At the same time, the controller controls the drive motor 31 to rotate at high speed. Under the action of centrifugal force of high speed rotation, the aqueous phase and small droplet organic phase in the closed cavity 44 can be forcibly thrown out to the outside of the annular filter body 42, while the large droplet organic phase remains in the closed cavity 44. When the cover plate 6 moves upward to form a material guiding gap 43, the controller controls the drive motor 31 to rotate at a low speed. The large droplets of organic phase, as well as a small amount of water phase and small droplets of organic phase retained in the closed cavity 44, flow into the outer annular filter body 42 under the action of centrifugal force through the material guiding gap 43. When the cover plate 6 moves downward again, the mixture is forced to be separated by centrifugation again. The above corresponding process is repeated. The large droplets of organic phase gradually transfer into the outer annular filter body 42 and continue to be forced to be separated. Finally, it is discharged outward from the discharge gap between the outer annular plate 41 and the inner wall of the tank 1 into the tank 1.

[0042] Because large organic droplets are heavier, they float slowly during stratification, prolonging the stratification time. The above mechanism uses a pre-filtration unit to pre-separate the large organic droplets from the aqueous phase and the small organic droplets, reducing the stratification time of the large organic droplets and accelerating the stratification process.

[0043] When the cover plate 6 moves downward to its limit position to form a closed cavity 44, it rotates at high speed, resulting in a large centrifugal force. This process allows the aqueous phase and small droplet organic phase to pass through the annular filter body 42 quickly for forced separation. When the cover plate 6 moves upward to its limit position to form a guide gap 43, in order to prevent the large droplet organic phase and a small amount of aqueous phase and small droplet organic phase from being thrown directly into the discharge gap without complete separation, the rotation speed is reduced to decrease the centrifugal force, thereby slowing down the speed of the large droplet organic phase and the small amount of aqueous phase and small droplet organic phase. This ensures that the mixture can pass through each annular filter body 42 in sequence for multiple forced separations, ensuring that the separation of the large droplet organic phase is more thorough.

[0044] It is worth noting that in this application, a sensing device is installed inside the tank 1 to monitor the height of the cover plate 6. The specific model and sensing principle of the sensing device are based on existing technology and will not be elaborated here. By monitoring the height of the cover plate 6, the position of the cover plate 6 is analyzed and determined. Then, combined with the controller to control the speed of the drive motor 31, the speed of the central shaft 2 is precisely controlled. The specific speed is selected and controlled according to actual needs. Example 3

[0045] Please see Figures 2-15 Based on Example 2, the air flotation-enhanced stratifier also includes an air flotation unit. The air flotation unit is divided into two parts: one part is located at the bottom of the tank 1, and the other part is integrated on the rotating seat 9. It is used to assist in the rapid stratification of water and small organic droplets. The specific configuration is as follows: like Figure 5As shown, a plurality of mixing channels 94 extending radially along the central shaft 2 are provided inside the rotating seat 9. Each mixing channel 94 penetrates the outer peripheral surface of the rotating seat 9. A guide channel 22 is provided inside the central shaft 2 below the feed channel 21. A plurality of second guide holes 95 are provided on the central shaft 2 and the rotating seat 9. One end of the second guide hole 95 is connected to the guide channel 22, and the other end is connected to the mixing channel 94. A collection cover 5 is fixed to the bottom of the corrugated filter disc 4. The collection cover 5 is fixedly fitted on the central shaft 2. A collection cavity 51 is formed between the corrugated filter disc 4 and the collection cover 5 for collecting the aqueous phase and small droplet organic phase passing through the annular filter body 42. A pump body 221 is installed on the collection cover 5. The pump body 221 is connected to the guide channel 22 through a pipe.

[0046] The aqueous phase and small organic droplets forced out of the annular filter 42 fall onto the collection hood 5 and converge in the collection chamber 51. The aqueous phase and small organic droplets in the collection chamber 51 can be pumped through the pipeline to the feed channel 22 by the pump body 221. The mixture in the feed channel 22 flows into 54 through the second feed hole 95 and is finally thrown out into the tank 1 under the action of centrifugal force, forming a swirling effect of multiple fluids.

[0047] like Figure 13 and Figure 14 As shown, the air flotation unit includes an air inlet channel 23 located below the material guide channel 22 within the central shaft 2, a first air inlet pipe 231 rotatably connected to the bottom end of the central shaft 2 via an adapter, and an annular cavity 91 located below the mixing channel 94 within the rotating seat 9. Similarly, the bottom end of the central shaft 2 and the first air inlet pipe 231 are rotatably connected via the adapter to prevent the first air inlet pipe 231 from rotating synchronously with the central shaft 2. The annular cavity 91 is distributed around the central shaft 2. Several air guide holes 92 are arranged in annular array on the central shaft 2 and the rotating seat 9. One end of each air guide hole 92 is connected to the air inlet channel 23, and the other end is connected to the annular cavity 91. The first air inlet pipe 231 is connected to the air inlet channel 23. Several vertically downward extending one-way air outlet micro-holes 93 are provided on the inner wall of the mixing channel 94 along its axial direction. The bottom of each one-way air outlet micro-hole 93 is connected to the annular cavity 91.

[0048] The first air inlet pipe 231 is connected to an external inert gas supply device. The inert gas is supplied into the air inlet channel 23 through the first air inlet pipe 231, and finally flows into the mixing channel 94 through the air guide hole 92, the annular cavity 91 and the one-way air outlet micro hole 93 in sequence. The uniformly distributed micro bubbles are formed in the mixing channel 94, which can be forcibly mixed with the aqueous phase and the small droplet organic phase mixture, so that the small droplet organic phase is uniformly adsorbed in the small bubbles, and finally discharged into the tank 1 to form a bubble vortex.

[0049] like Figure 13 and Figure 15As shown, the air flotation unit also includes an annular shell 8, microbubble nozzles 81, and a second air inlet pipe 82. An annular shell 8 is fixed on the inner side wall of the tank 1 near its bottom wall. Several microbubble nozzles 81 extending toward the mixing channel 94 are evenly distributed on the inner edge wall of the annular shell 8. Each microbubble nozzle 81 is connected to the inside of the annular shell 8. One end of the second air inlet pipe 82 is connected to the annular shell 8, and the other end extends to the outside of the tank 1 and is connected to an external inert gas supply device.

[0050] Inert gas is introduced into the annular shell 8 through the second air inlet pipe 82, and finally sprayed out towards the mixing channel 94 through the microbubble nozzle 81 to form a bubble flow. This bubble flow is mixed with the bubble vortex formed above, which further strengthens the mutual adsorption between the droplet organic phase and the bubbles, and effectively increases the floating speed of the droplet organic phase. Example 4

[0051] Please see Figure 4 , Figure 5 and Figure 13 Based on the aforementioned embodiments, this embodiment incorporates the following design: A conical cover plate 7 is fixed on the inner wall of the tank body 1 and above the annular shell 8. There is an annular gap between the conical cover plate 7 and the outer wall of the central shaft 2. The conical cover plate 7 gradually expands downward. A receiving area 71 is formed between the upper surface of the conical cover plate 7 and the inner wall of the tank body 1.

[0052] The pre-separated large droplets of organic phase are thrown onto the inner wall of the tank 1 and flow downward through the discharge gap between the annular plate 41 and the inner wall of the tank 1. The large droplets of organic phase flow down the inner wall of the tank 1 and eventually fall into the receiving area 71. In the initial stage of feeding into the tank 1, the conical cover plate 7 is used to block and collect the large droplets of organic phase in the receiving area 71, so as to prevent the large droplets of organic phase from mixing with the bubble swirling below the conical cover plate 7 again.

[0053] The bubbles below the conical cover plate 7 carry small droplets of organic phase to the surface. As the feed continues, the liquid level in the tank 1 rises. Because the diameter of the conical cover plate 7 decreases as it rises, the bubbles carrying small droplets of organic phase gradually converge toward the central axis 2, causing the small bubbles to merge into large bubbles, which further increases the subsequent rising speed. Furthermore, due to centrifugal force and gravity differences, the water phase, as the heavier phase, is distributed in the outer and lower regions of the bubble swirling flow, while the organic phase, as the lighter phase, is distributed in the inner and upper regions. Combined with the guiding effect of the conical cover plate 7 (smaller at the top and larger at the bottom) on the bubbles and organic phase, the bubbles and organic phase can further collide and mix violently when they converge at the central axis 2, thereby increasing the adsorption rate of the organic phase by the bubbles.

[0054] When the liquid level in tank 1 is higher than the top of the conical cover plate 7, the liquid will slowly flow into the receiving area 71. Because the conical cover plate 7 separates the area above it from the turbulent area formed by the bubble swirling, the large droplets of organic phase can float stably to the upper layer and gradually rise.

[0055] After the feeding was stopped, the liquid level in tank 1 remained stable. The air flotation unit continued to operate for ten minutes, continuously generating tiny bubbles at the bottom of tank 1 to adsorb the residual organic phase in the aqueous phase. After that, it was left to stand for another ten minutes, and the organic phase and aqueous phase were completely separated. The entire separation process took less than 1 hour. It can be seen that this method is more efficient when using an air flotation-enhanced separator to separate the mixture.

[0056] like Figure 5 and Figure 6 As shown, at least two sliding rods 131 are vertically fixed above the conical cover plate 7. An annular float 132 is slidably mounted on the sliding rods 131. An annular tube 134 is embedded below the annular float 132. Several downward-facing suction ports 135 are opened on the blocking member 133. A light phase outlet 13 is provided on the side of the tank 1. One end of the light phase outlet 13 is connected to a suction tube 136. The other end of the suction tube 136 is connected to the annular tube 134. The blocking member 133 is fixed on the sliding rods 131 to block and restrict the annular float 132 to the position above the conical cover plate 7. The suction tube 136 is a flexible tube to adapt to the height changes of the annular float 132 and the annular tube 134.

[0057] After the organic phase and aqueous phase are completely separated, a clear boundary line between the two phases can be seen through the viewing window 101. The other end of the light phase outlet 13 is connected to the suction equipment, and the annular float 132 floats to the liquid surface in the tank 1. The suction equipment generates a negative pressure suction effect, and the upper organic phase is successively sucked out through the suction port 135, the annular pipe 134, the suction pipe 136 and the light phase outlet 13, which is convenient for transfer to the next process. As the organic phase is continuously sucked, the liquid level in the tank 1 decreases, and the annular float 132 descends synchronously with the liquid level to ensure continuous suction of the organic phase.

[0058] The staff can judge the stratification of the tank 1 through the viewing window 101. After the organic phase layer is completely sucked out, the external suction equipment stops working. The remaining water phase in the tank 1 is discharged through the first heavy phase outlet 11. In addition, a second heavy phase outlet 12 is provided on the side of the tank 1, which is connected to the bottom of the receiving area 71, to discharge the remaining water phase in the receiving area 71 to the outside of the tank 1. The extreme position of the annular float 132 is lower than the boundary height between the organic phase layer and the water phase layer.

[0059] It is worth noting that the method of using this air flotation enhanced stratifier (stratification principle) is part of the 1,2-octanediol preparation method provided by this invention and is included within the protection scope of this invention.

[0060] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Therefore, the present invention will not explain the control method and circuit connection in detail.

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. A method for preparing 1,2-octanediol, characterized in that, Includes the following steps: S1. Oxidative ring-opening esterification reaction: 1-Octenene and formic acid are mixed at a mass ratio of 1:1.5-1:2.0, a catalyst is added, and hydrogen peroxide with an effective oxygen molar ratio of 1.0:1 to 1.2:1 to 1-octene is slowly added dropwise over 4-6 hours at 55-70℃. After the addition is completed, the reaction is maintained at this temperature for 0.5-1 hours. After the reaction is completed, the formic acid is recovered under reduced pressure to obtain a reaction mixture containing octyl formate. The recovered formic acid can be recycled. S2, Saponification and Hydrolysis Reaction: Add 25%-30% sodium hydroxide solution to the mixture obtained in step S1, wherein the molar ratio of sodium hydroxide to formic acid added in step S1 is 1.0:1 to 1.1:1, and saponify at 55-65℃ for 0.5-1 hours. After the reaction, use an air flotation enhanced separator to assist in separation. The separated aqueous phase is neutralized with formic acid, distilled, centrifuged and dried to obtain sodium formate as a byproduct. The organic phase is washed with water to obtain an organic layer containing 1,2-octanediol. The washing liquid is used to prepare alkali solution. S3. Post-processing and purification: The organic layer is dehydrated by vacuum distillation at 80-90℃. The distillate is used to prepare alkali. The remaining crude product is subjected to high-vacuum distillation at a vacuum degree of not less than -0.095MPa, and the temperature of the column bottom is controlled at 134-150℃. The fraction is collected to obtain high-purity 1,2-octanediol product. The distillation residue is treated as solid waste.

2. The method for preparing 1,2-octanediol according to claim 1, characterized in that: The air flotation-enhanced stratifier includes a tank (1), a central shaft (2), a pre-filtration unit, an air flotation unit, and a drive mechanism (3); The central shaft (2) is vertically installed inside the tank (1), and the top and bottom ends of the central shaft (2) extend through to the outside of the tank (1); The central shaft (2) is rotatably connected to the top of the tank (1), and a rotating seat (9) is fixedly fitted at the bottom of the central shaft (2), and the rotating seat (9) is rotatably connected to the bottom of the tank (1); The drive mechanism (3) is located on the top of the tank (1) and is used to drive the central shaft (2) to rotate; The pre-filtration unit is installed outside the drive mechanism (3) and close to the top wall inside the tank (1) to filter out large droplets of organic phase; The air flotation unit is divided into two parts. One part is set at the bottom of the tank (1), and the other part is integrated on the rotating seat (9) to assist water and small droplet organic phases in rapid stratification.

3. The method for preparing 1,2-octanediol according to claim 2, characterized in that: The pre-filtration unit includes a corrugated filter disc (4) and a cover plate (6); The corrugated filter disc (4) is formed by alternating fixed connections of annular plates (41) and annular filter bodies (42). The annular filter body (42) has a U-shaped cross section, and the annular plates (41) are connected between the tops of two adjacent annular filter bodies (42). The annular plates (41) and the annular filter bodies (42) are arranged in a pattern where the diameter increases towards the outer edge. The innermost annular plate (41) is fixed to the outer wall of the central axis (2). The annular filter (42) is made of superhydrophobic calcium carbonate granular membrane; The cover plate (6) is disposed above the corrugated filter disc (4), and the cover plate (6) is configured to reciprocate and move up and down during the rotation of the central shaft (2); When the cover plate (6) moves upward to the limit position, a guide gap (43) is formed between the lower surface of the cover plate (6) and the annular plate (41) to allow the large droplets of organic phase to pass through. When the cover plate (6) moves downward to the limit position, the lower surface of the cover plate (6) and the annular plate (41) are tightly fitted together, and a closed cavity (44) is formed in each annular filter body (42). The drive mechanism (3) is configured to drive the central shaft (2) to rotate at low speed when the cover plate (6) moves upward to the limit position, and to drive the central shaft (2) to rotate at high speed when the cover plate (6) moves downward to the limit position. There is a discharge gap between the outermost annular plate (41) and the inner wall of the tank (1).

4. The method for preparing 1,2-octanediol according to claim 3, characterized in that: A feeding system is provided on the central shaft (2) for guiding the mixture of saponification reaction in step S2 to the corrugated filter plate (4); The feeding system includes a feeding channel (21) opened at the top of the central shaft (2), a number of first guide holes (212) opened in a ring array on the outer wall of the central shaft (2), and a feeding pipe (211) rotatably connected to the top of the central shaft (2) via an adapter. The feed pipe (211) is connected to the feed channel (21), and each of the first guide holes (212) is connected to the feed channel (21). The first guide hole (212) is used to guide the mixture in the feed channel (21) to the annular filter body (42) closest to the central shaft (2) when the central shaft (2) rotates.

5. The method for preparing 1,2-octanediol according to claim 3, characterized in that: The cover plate (6) has guide holes (61) evenly distributed on it. The outermost annular plate (41) has guide rods (62) fixed in an annular array. The cover plate (6) slides on the guide rods (62) through the guide holes (61) on it, and the outer edge wall of the cover plate (6) is in contact with the inner wall of the tank (1). Each of the guide rods (62) has an end cap (63) fixed at its top end, and each guide rod (62) has a spring (64) sleeved on its outside. One end of the spring (64) is fixed to the lower surface of the end cap (63), and the other end is fixed to the upper surface of the cover plate (6). The cover plate (6) has a number of mounting seats (65) arranged in a ring on its upper surface, and each mounting seat (65) has a ball (66) embedded on its top. The inner top wall of the tank (1) has a ring array of several arc-shaped extrusion blocks (67), and the lower end of each arc-shaped extrusion block (67) is an arc-shaped slope that is extruded and cooperates with the rolling ball (66).

6. The method for preparing 1,2-octanediol according to claim 3, characterized in that: The rotating seat (9) has several mixing channels (94) that extend radially around the central axis (2) and each mixing channel (94) penetrates the outer peripheral surface of the rotating seat (9). The central shaft (2) is provided with a guide channel (22) below the feed channel (21). The central shaft (2) and the rotating seat (9) are provided with a plurality of second guide holes (95). One end of the second guide hole (95) is connected to the guide channel (22), and the other end is connected to the mixing channel (94). The bottom of the corrugated filter disc (4) is fixed with a collection cover (5), which is fixedly fitted on the central shaft (2). A collection cavity (51) is formed between the corrugated filter disc (4) and the collection cover (5) for collecting the aqueous phase and droplet organic phase passing through the annular filter body (42). A pump body (221) is installed on the collection cover (5), and the pump body (221) is connected to the material guide channel (22) through a pipe.

7. The method for preparing 1,2-octanediol according to claim 6, characterized in that: The air flotation unit includes an air inlet channel (23) located below the material guide channel (22) in the central shaft (2), a first air inlet pipe (231) rotatably connected to the bottom end of the central shaft (2) via an adapter, and an annular cavity (91) located below the mixing channel (94) in the rotating seat (9). The annular cavity (91) is distributed around the central axis (2). The central axis (2) and the rotating seat (9) are provided with a number of annular array air guide holes (92). One end of each air guide hole (92) is connected to the air inlet channel (23), and the other end is connected to the annular cavity (91). The first air intake pipe (231) is connected to the air intake channel (23); The inner wall of the mixing channel (94) is provided with several vertically downward extending one-way air outlet microholes (93), and the bottom of each one-way air outlet microhole (93) is connected to the annular cavity (91).

8. The method for preparing 1,2-octanediol according to claim 7, characterized in that: The air flotation unit also includes an annular shell (8), a microbubble nozzle (81), and a second air inlet pipe (82). The annular shell (8) is fixed on the inner side wall of the tank (1) and near its bottom wall. A number of microbubble nozzles (81) extending toward the mixing channel (94) are evenly distributed on the inner edge wall of the annular shell (8). Each microbubble nozzle (81) is connected to the inside of the annular shell (8). One end of the second air inlet pipe (82) is connected to the annular shell (8), and the other end extends to the outside of the tank (1).

9. A method for preparing 1,2-octanediol according to claim 8, characterized in that: A conical cover plate (7) is fixed on the inner wall of the tank (1) and above the annular shell (8), and there is an annular gap between the conical cover plate (7) and the outer wall of the central shaft (2); The conical cover plate (7) gradually expands downwards; The upper surface of the conical cover (7) forms a receiving area (71) between the inner wall of the tank (1).

10. A method for preparing 1,2-octanediol according to claim 2, characterized in that: The drive mechanism (3) includes a drive motor (31), a main gear (32), and a driven gear (33). The drive motor (31) is fixed to the top of the tank (1) by a motor mount, and the main gear (32) is fixed to the output shaft of the drive motor (31); The driven gear (33) is fixedly mounted on the outer wall of the central shaft (2) and meshes with the main gear (32).

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