A segmented distillation system for tert-butyl benzyl chloride

Abstract

The application discloses a segmented distillation system for tert-butyl benzyl chloride, which comprises a front fraction distillation tower, a flash vaporization tower and a segmented rectification tower which are independently operated; the front fraction distillation tower is used for removing light components under high vacuum conditions; the flash vaporization tower and the segmented rectification tower are operated in series; an independent heater is additionally arranged in the flash vaporization tower so that materials are rapidly vaporized within 5-10 seconds; the height of the segmented rectification tower is controlled within 10-12 meters and is provided with a finished product recovery system; through the three-stage cooperative design, the whole process is operated under high vacuum, low temperature and short residence time, the polymerization reaction of the tert-butyl benzyl chloride is greatly inhibited, the product yield is increased by 10-25%, the purity reaches 99.0-99.8%, the tower height is reduced by more than 40% than that of the traditional process, the equipment operation cycle is prolonged by 3-5 times, and the segmented distillation system is especially suitable for low-space plant installation and old plant transformation.

Description

Technical Field

[0001] This invention relates to the field of organic chemical equipment technology, and in particular to a fractional distillation system for p-tert-butylbenzyl chloride. Background Technology

[0002] p-tert-butylbenzyl chloride is an important organic synthesis intermediate used in the production of fine chemical products such as pesticides, pharmaceuticals, and fragrances. In industrial production, p-tert-butylbenzyl chloride is usually purified by distillation to obtain high-purity products that meet downstream requirements. Currently, the industry mainly uses traditional single-tower distillation systems for separation and purification. Gas-liquid mass transfer is achieved through packing or trays in the tower, and the fore-distillate, product, and heavy components are separated one by one by utilizing the difference in volatility of the components. This type of equipment is relatively mature in conventional chemical separation processes, with a relatively simple operation process and controllable investment costs. Therefore, it is still widely used in small and medium-scale production.

[0003] p-tert-butylbenzyl chloride readily polymerizes at high temperatures, forming high-boiling-point polymers, leading to decreased product yield and severe scaling in the distillation column. Traditional single-column distillation typically requires tall columns (generally 15-25 meters) to achieve high separation efficiency and increase the number of theoretical plates. In such tall columns, the material requires a long residence time from the bottom to the top, especially in the high-temperature region of the reboiler, where prolonged heating significantly increases the risk of polymerization. Furthermore, traditional single-column distillation often involves continuous feed and discharge, with the material undergoing multiple vaporization and condensation processes within the column, making localized overheating unavoidable and further exacerbating the polymerization reaction.

[0004] Therefore, in response to the problems mentioned above, the present invention proposes a fractional distillation system for tert-butylbenzyl chloride. Summary of the Invention

[0005] To overcome the problems of easy polymerization of p-tert-butylbenzyl chloride at high temperatures and the excessive height of traditional single-tower distillation columns leading to long residence times and high polymerization risks in existing technologies, this invention proposes a segmented distillation system for p-tert-butylbenzyl chloride. By operating the distillation process in segments, setting up an independent pre-fraction distillation system to remove light components in advance, adding a rapid vaporization system to shorten the material heating time, and combining a low-tower, high-segmentation distillation system to reduce installation space requirements, the entire process adopts a high-vacuum, low-temperature, and short-residence-time operation mode, which effectively inhibits the occurrence of polymerization reactions, improves product yield and purity, reduces energy consumption, and extends the equipment operating cycle.

[0006] The technical solution of the present invention is: a fractional distillation system for tert-butylbenzyl chloride, comprising: System 1 is an independently operating fore-distillation column used to distill the fore-distillate from the feedstock under high vacuum conditions, thereby reducing the polymerization risk of subsequent systems. It specifically includes a column body, packing layer, top condenser, fore-distillate collection tank, and vacuum system; the height of the column body is 4-8 meters. System 2 is a rapid vaporization tower connected in series with System 3. It is used to rapidly vaporize the material after the removal of the pre-distillate within 5-10 seconds. The vaporization process is enhanced by heat transfer through an independent heater. Specifically, it includes a tower body, a thin-layer evaporator or a falling film evaporator, an independent heater, and a vacuum system. The tower body is 4-6 meters high, and the independent heater is one of a jacketed heater, a coil heater, or an electric heater. System three is a segmented distillation column with a height of 10-12 meters, used to distill and separate the vaporized material to obtain high-purity p-tert-butylbenzyl chloride. Specifically, it includes a column body, an upper packing layer, a lower packing layer, a finished product recovery system, and a vacuum system; the column body is 10 meters high. 12 meters, with the upper filler layer height being 4 meters. 6 meters, the lower section of the filler layer is 6 meters high. The 8-meter-long finished product recycling system includes a condenser, a finished product buffer tank, a finished product transfer pump, and a return distributor. System 2 and System 3 operate in series, while System 1 operates independently. The entire process is carried out under high vacuum, with a vacuum level of 1-20 kPa and an operating temperature lower than the polymerization temperature of p-tert-butylbenzyl chloride. A first buffer tank and a magnetic pump are installed between System 1 and System 2, and a second buffer tank and a metering pump are installed between System 2 and System 3 to stabilize material transport. The pre-distillate from System 1 is condensed and returned to the raw material tank for recycling.

[0007] Preferably, the packing layer uses one or more of θ rings, BX packing, CY packing, or Mellapak 250Y packing.

[0008] Preferably, the upper packing layer uses one or more of BX packing, CY packing, or Mellapak 250Y packing; the lower packing layer uses one or more of Mellapak 250Y or 500Y packing.

[0009] As a preferred option, the high-purity p-tert-butylbenzyl chloride obtained at the top of the column in System 3 can reach a purity of 99.0%. 99.8% of the bottom heavy components are returned to the raw material system or processed separately.

[0010] The beneficial effects of this invention are: 1. This invention sets up an independently operating pre-distillation tower as System 1 to remove low-boiling-point pre-distillate from the raw material under high vacuum conditions. This not only effectively reduces the processing load of subsequent Systems 2 and 3, but also reduces the risk of induced polymerization of low-boiling substances at high temperatures, laying a good material foundation for the entire distillation process. At the same time, the pre-distillate can be returned to the raw material tank for recycling, improving the comprehensive utilization rate of the raw material.

[0011] 2. By adding an independent heater to System 2 and combining it with a thin-layer evaporator or a falling film evaporator, the present invention enables the material to achieve rapid vaporization in a very short time of 5-10 seconds, which greatly shortens the residence time of the material in the high-temperature region and effectively avoids the serious polymerization and coking problems caused by prolonged heating of the material under the traditional tower reboiler heating method, thereby inhibiting the polymerization reaction of tert-butylbenzyl chloride.

[0012] 3. This invention controls the height of the segmented distillation column of System 3 to 10-12 meters, which is about 40%-50% lower than the height of the traditional distillation column of 15-25 meters. This significantly reduces the requirements for plant space, making it easy to apply to ordinary plant installations or old plant renovation projects with limited floor height. At the same time, through the optimized combination of different packing materials in the upper and lower sections, a highly efficient separation effect is achieved within the limited column height.

[0013] 4. The entire process of this invention adopts a high vacuum operation of 1-20 kPa, which significantly reduces the operating temperature of each system. This allows the entire distillation process to be carried out under conditions far below the polymerization temperature of p-tert-butylbenzyl chloride. Combined with the pretreatment function of System 1 and the rapid vaporization design of System 2, the polymerization reaction is suppressed from the aspects of temperature, time and materials.

[0014] 5. Through the synergistic effect of System 1, System 2 and System 3, this invention increases the product yield by 10-25% compared to the traditional single-tower distillation process. Data from the examples show that the yield can reach 94.5%-95.8%, while the yield of the traditional single-tower process is only 78.5%. At the same time, the product purity is consistently maintained at 99.0-99.8%, which fully meets the quality requirements of high-purity p-tert-butylbenzyl chloride in high-end applications.

[0015] 6. By effectively inhibiting the polymerization reaction, this invention significantly reduces scaling in the tower bottom and extends the continuous operation cycle of the equipment by 3-5 times. In the example, the expected operation cycle can reach more than 5-6 months, while the traditional single-tower process requires shutdown and cleaning after about 1 month of operation. This greatly reduces unplanned downtime and equipment maintenance costs, and improves production efficiency. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic representation of the overall structure of the present invention. Figure 2The diagram shown is a structural schematic of System 1 of the present invention; Figure 3 The diagram shown is a structural schematic of system two of the present invention; Figure 4 The diagram shown is a structural schematic of System Three of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides an embodiment of a fractional distillation system for tert-butylbenzyl chloride: Please see Figure 1 The fractional distillation system includes a feed tank, System 1, System 2, System 3, a fore-fraction collection tank, a finished product buffer tank, and a finished product storage tank.

[0019] The crude p-tert-butylbenzyl chloride to be separated, stored in the feed tank, is first fed into System 1 via a feed pump. System 1 operates independently. Under high vacuum conditions, the low-boiling-point fore-distillate (light components) in the feed is preferentially distilled off, condensed in a condenser, and flows into the fore-distillate collection tank. The intermediate material, from which the fore-distillate has been removed, is discharged from the bottom of System 1 and enters the first buffer tank located between System 1 and System 2, and is then stably transported to System 2 via a magnetic pump.

[0020] System 2 is a rapid vaporization tower equipped with an independent heater. After entering System 2, the material is rapidly vaporized within a very short time (5-10 seconds) under the strong heat of the heater. The vaporized material is discharged from System 2 and enters a second buffer tank located between System 2 and System 3, and is then precisely fed into System 3 by a metering pump.

[0021] System Three is a segmented distillation column with a height controlled at 10-12 meters, filled with highly efficient structured packing. The materials undergo precise mass and heat transfer separation within System Three. The high-purity p-tert-butylbenzyl chloride vapor phase distilled from the top of the column is condensed in the top condenser and then enters the finished product recovery system. This system includes a reflux distributor, a finished product buffer tank, and a finished product transfer pump. Under the action of the reflux distributor, part of the condensate is returned to the top of the column as reflux, and part is collected as product and sent to the finished product buffer tank, and finally sent to the finished product storage tank by the finished product transfer pump. Heavy components enriched in the bottom of the column can be either returned to the feed tank for further processing or discharged from the system as waste, depending on their composition.

[0022] The entire system effectively isolates pressure fluctuations and flow disturbances between different systems through the setting of multi-stage buffer tanks and pumps (magnetic pumps and metering pumps), ensuring the entire distillation process.

[0023] System 1 is a pretreatment unit independent of the main distillation sequence. Its function is to remove low-boiling-point components from the material before it enters the high-temperature, high-separation-requirement rectification section, thereby reducing the processing load of subsequent Systems 2 and 3, and reducing the risk of induced polymerization that low-boiling-point substances may cause at high temperatures.

[0024] Please see Figure 2 The system mainly includes the tower body, packing layer, top condenser, front fraction collection tank and supporting vacuum system.

[0025] The tower height of System 1 is designed to be 4-8 meters. This height range is determined based on the difference in boiling points between the fore-distillate and the main component p-tert-butylbenzyl chloride, as well as the high vacuum operating conditions. At this height, with the help of efficient packing, it is sufficient to achieve clear separation between the fore-distillate and the main product, while avoiding material retention and space occupation caused by excessive tower height.

[0026] The packing layer fills the interior of the tower and can employ various high-efficiency structured packings or random packings, specifically including one or more of θ-ring packings, BX wire mesh corrugated packings, CY wire mesh corrugated packings, or Mellapak 250Y plate corrugated packings. BX and CY packings are high-efficiency packings with high theoretical plate numbers, suitable for applications with complex separation requirements; Mellapak 250Y packing combines high efficiency with high throughput and low pressure drop. The specific choice depends on the content of the foredistillate in the feed and the separation requirements. For example, when the foredistillate content is high or the composition is complex, BX or CY packings with higher theoretical plate numbers can be selected; for larger throughput, Mellapak 250Y packing can be used.

[0027] The vacuum system of System 1 is independent of Systems 2 and 3, and is used to maintain the absolute pressure inside the column within the range of 1-20 kPa. By precisely controlling the vacuum level and the reboiler heating temperature, the operating temperature is kept far below the boiling point of p-tert-butylbenzyl chloride at atmospheric pressure, thereby distilling off the pre-distillate under mild conditions and minimizing polymerization losses of the main component during the pretreatment stage. The pre-distillate vapor distilled from the top of the column is condensed by a condenser and collected in a pre-distillate collection tank. This pre-distillate can be recycled back to the feed tank according to its purity, or processed separately as a by-product, thereby improving the overall utilization rate of the raw materials.

[0028] System 2's function is to achieve rapid and efficient transformation of materials from the liquid phase to the gas phase, and to minimize the residence time of materials in the high-temperature region.

[0029] Please see Figure 3 System 2 mainly includes a tower body, a thin-film evaporator or a falling film evaporator, an independent heater and a matching vacuum system.

[0030] The tower height of System 2 is designed to be 4-6 meters. This height is relatively low, and its main function is to provide enough space to install evaporation elements and perform preliminary gas-liquid separation, rather than to achieve a precise number of separation stages.

[0031] Thin-film evaporators or falling film evaporators are the core evaporation elements of System 2. Their design principle is to use gravity or mechanical force to form an extremely thin liquid film on the heating surface of the material, thereby greatly increasing the evaporation surface area of ​​the material and facilitating the rapid escape of the gas phase.

[0032] The independent heater, which can be a jacketed heater, a coil heater, or an electric heater, provides a centralized and controllable heat source for the evaporation process. The heater is tightly integrated with the evaporator, ensuring rapid heat transfer to the flowing liquid film. Combined with a high vacuum environment, the total residence time of the material within the system can be controlled within 5-10 seconds. The material is heated to its boiling point and rapidly vaporizes in such a short time, avoiding the severe polymerization and coking problems caused by prolonged exposure to high temperatures in traditional reboiler heating methods.

[0033] The vacuum system of System 2 also maintains an operating pressure of 1-20 kPa. The vaporized material, mainly in the gas phase with a small amount of incompletely vaporized liquid phase, is discharged from the outlet of System 2 and enters the next-stage buffer tank.

[0034] System 3 is the final separation unit of the entire system. Its function is to perform high-precision separation of the vaporized material from System 2 to obtain high-purity p-tert-butylbenzyl chloride product. This system adopts a low tower height design of 10-12 meters and a segmented packing structure to adapt to the installation requirements of low-space plants while ensuring separation efficiency.

[0035] Please see Figure 4 The system mainly includes the tower body, the upper packing layer, the lower packing layer, the finished product recovery system, and the supporting vacuum system.

[0036] The total height of the tower in System 3 is strictly limited to 10-12 meters. Compared with the height of traditional distillation towers of 15-25 meters, the tower height of this invention is reduced by about 40%-50%, which makes the system easy to install in ordinary factory buildings with limited floor height, and is particularly suitable for old factory renovation projects.

[0037] To achieve efficient separation within a limited column height, a segmented packing design is employed inside the column, dividing the interior into upper and lower packing layers along the height. The upper packing layer is 4-6 meters high, while the lower packing layer is 6-8 meters high. This design, with the lower layer higher than the upper layer, is based on the actual needs of the separation process. The lower packing layer needs to handle the steam rising from the column bottom and ensure it fully contacts the reflux liquid, drawing the heavy components back to the column bottom; therefore, a higher packing layer is required to guarantee the separation effect. The upper packing layer primarily purifies the steam rising from the top of the column, thereby ensuring product purity.

[0038] The selection of packing material was optimized based on the function of each section. The lower packing layer, needing to handle larger gas-liquid loads, typically uses packing with high throughput and low pressure drop, such as Mellapak 250Y or Mellapak 500Y plate corrugated packing. This type of packing effectively reduces the pressure drop at the bottom of the column, thereby lowering the operating temperature at the bottom, which is particularly beneficial for heat-sensitive materials. The upper packing layer requires even higher separation efficiency; therefore, BX or CY packing with high theoretical plate counts can be used to maintain low pressure drop while ensuring separation accuracy.

[0039] The finished product recovery system is a crucial component for ensuring product yield and operational stability. It includes a condenser, a finished product buffer tank, a finished product transfer pump, and a reflux distributor. The rising vapor from the top of the column enters the condenser and condenses into liquid, all of which enters the reflux distributor. Based on a set reflux ratio, the reflux distributor returns a portion of the condensate to the top of the column as reflux, while the remainder is collected as product and enters the finished product buffer tank. The buffer tank buffers and stabilizes the flow rate, and the product within is ultimately transferred to the finished product storage tank by the finished product transfer pump.

[0040] The vacuum system of System 3 is independently controlled, maintaining the pressure inside the column at 1-20 kPa. Temperature, pressure, and other parameters at the top and bottom of the column are precisely regulated by an automated control system to ensure product quality and system stability.

[0041] To ensure the stable operation of the entire fractional distillation system, this invention incorporates material conveying and buffering units between the various systems. Specifically, a first buffer tank and a magnetic pump are installed between System 1 and System 2. The first buffer tank receives the material from the bottom of System 1 after the foremilk has been removed, buffering the discontinuity of the feed from System 1 and the fluctuations in the feed from System 2. The magnetic pump, due to its leak-free characteristics, is suitable for conveying heat-sensitive materials under vacuum conditions, ensuring a stable and safe transfer of material from the low-pressure System 1 to System 2.

[0042] A second buffer tank and a metering pump are installed between System 2 and System 3. The second buffer tank receives the vaporized mixture from System 2, serving to separate the gas and liquid and stabilize the pressure, while the metering pump is used to accurately and quantitatively deliver the material from System 2 to the feed inlet of the distillation column in System 3.

[0043] This invention provides Embodiment 1: In this embodiment, the raw material is crude p-tert-butylbenzyl chloride, wherein the p-tert-butylbenzyl chloride content is 90.5 wt%, the fore fraction content is 5.2 wt%, and the heavy fraction content is 4.3 wt%.

[0044] System 1 has a tower height of 6 meters and uses BX packing. The operating vacuum is 5 kPa, and the reboiler temperature is 95℃. The feedstock is fed into System 1 at a flow rate of 500 kg / h. The fore-distillate is distilled off at the top of the tower, condensed, and collected at a flow rate of 26 kg / h. The intermediate material, after the fore-distillate has been removed, is collected from the reboiler at a flow rate of 474 kg / h and fed into System 2 via a first buffer tank and a magnetic pump.

[0045] System 2 has a tower height of 5 meters and is equipped with a falling film evaporator and a jacketed heater. The operating vacuum is 5 kPa, and the heater temperature is controlled at 115℃. The residence time of the material in System 2 is approximately 7 seconds, achieving rapid vaporization. The vaporized material is then fed into System 3 via a second buffer tank and a metering pump at a flow rate of 474 kg / h.

[0046] System 3 has a tower height of 11 meters, with an upper packing layer height of 5 meters using CY packing and a lower packing layer height of 6 meters using Mellapak 500Y packing. The operating vacuum is 5 kPa, the tower top temperature is controlled at 98℃, the reflux ratio is 3:1, the product is continuously collected from the top of the tower and then collected by the finished product recovery system, while the heavy components in the tower bottom are discharged intermittently.

[0047] After 72 hours of continuous and stable operation, samples were taken for analysis. The purity of p-tert-butylbenzyl chloride in the top product was 99.5 wt%, and the product yield (based on the total amount of p-tert-butylbenzyl chloride in the feed) was 95.2%. The total energy consumption of the system, converted to unit product energy consumption, was reduced by about 30% compared with the traditional single-tower process. After shutdown, the three towers showed almost no scaling. The equipment is expected to have a continuous operating cycle of more than 6 months.

[0048] This invention provides Embodiment 2: In this embodiment, the raw material is crude p-tert-butylbenzyl chloride, with a p-tert-butylbenzyl chloride content of 90.5 wt%, a fore-distillate (mainly low-boiling-point impurities) content of 5.2 wt%, and a heavy component content of 4.3 wt%. The raw material is stored in a raw material tank and is pumped into system one via a raw material transfer pump.

[0049] System 1 is an independently operating pre-distillation column with a height of 6 meters and BX packing. System 1 is equipped with an independent vacuum system, with the operating vacuum level adjusted to 10 kPa and the reboiler temperature controlled at 102℃. The feed enters System 1 at a flow rate of 500 kg / h. Under high vacuum conditions, the low-boiling-point pre-distillate is preferentially distilled off. After condensation in the top condenser, it enters the pre-distillate collection tank at a flow rate of 26 kg / h. The intermediate material after removing the pre-distillate is discharged from the reboiler of System 1 and enters the first buffer tank located between System 1 and System 2. It is then stably transported to System 2 by a magnetic pump.

[0050] System 2 is a rapid vaporization tower with a height of 5 meters, equipped with a falling film evaporator and a jacketed heater. System 2 has an independent vacuum system with an operating vacuum level adjusted to 10 kPa and a heater temperature controlled at 125°C. Intermediate materials from System 1 enter System 2 and are rapidly vaporized under the strong heat of the heater. The residence time of the material in System 2 is controlled to be approximately 7 seconds. The vaporized material is discharged from System 2 and enters a second buffer tank located between System 2 and System 3, and is then precisely fed into System 3 via a metering pump.

[0051] System 3 is a segmented distillation column with a total height of 11 meters. The column interior employs a segmented packing design: the upper packing layer is 5 meters high and uses CY packing; the lower packing layer is 6 meters high and uses Mellapak 500Y packing. System 3 is equipped with an independent vacuum system, with the operating vacuum adjusted to 10 kPa, the top temperature controlled at 108℃, and the reflux ratio adjusted to 5:1. After the material from System 2 enters System 3, it undergoes distillation separation within the column. The high-purity p-tert-butylbenzyl chloride vapor phase distilled from the top of the column is condensed by the top condenser and enters the product recovery system. Under the action of the reflux distributor, part of the condensate is returned to the top of the column as reflux, and part is collected as product and sent to the product buffer tank. Finally, it is pumped into the product storage tank via a product transfer pump. The heavy components enriched in the bottom of the column are intermittently discharged and returned to the feed tank for further processing.

[0052] After the system ran continuously and stably for 72 hours, samples were taken for analysis, and the product purity was determined by gas chromatography area normalization. The purity of p-tert-butylbenzyl chloride in the top product was 99.7 wt%. The product purity was slightly improved, but the yield was slightly decreased. This is because the higher reflux ratio increased the circulation volume in the column, resulting in a longer residence time of some products in the column, a slight increase in polymerization loss, and a corresponding increase in energy consumption. The condition of the column bottom was good, with only slight traces.

[0053] This invention provides embodiment 3: In this embodiment, the raw material is crude p-tert-butylbenzyl chloride, wherein the p-tert-butylbenzyl chloride content is 90.5 wt%, the fore fraction content is 5.2 wt%, and the heavy fraction content is 4.3 wt%.

[0054] System 1 has a column height of 6 meters and uses Mellapak 250Y packing. The operating vacuum is 5 kPa, and the reboiler temperature is 95℃. The feedstock is fed into System 1 at a flow rate of 500 kg / h. The fore-distillate is distilled off at the top of the column, condensed, and collected at a flow rate of 26 kg / h. The intermediate material, after the fore-distillate has been removed, is collected from the reboiler and fed into System 2 via a first buffer tank and a magnetic pump.

[0055] System 2 has a tower height of 5 meters and is equipped with a falling film evaporator and a jacketed heater. The operating vacuum is 5 kPa, and the heater temperature is controlled at 115°C. The material residence time in System 2 is approximately 7 seconds, achieving rapid vaporization. The vaporized material is then sent to System 3 via a second buffer tank and a metering pump.

[0056] System 3 has a tower height of 11 meters, with an upper packing layer height of 5 meters using Mellapak 250Y packing and a lower packing layer height of 6 meters using Mellapak 250Y packing. The operating vacuum is 5 kPa, the tower top temperature is controlled at 98℃, the reflux ratio is 3:1, the product is continuously collected from the top of the tower and then collected by the finished product recovery system, while the heavy components in the tower bottom are discharged intermittently.

[0057] After 72 hours of continuous and stable operation, samples were taken for analysis. The purity of the top product was 99.2 wt%, and the yield was 95.8%. Compared to Example 1, the product purity was slightly lower because the theoretical plate number of the upper section packing (Mellapak 250Y) was lower than that of the CY packing, resulting in slightly weaker separation ability. However, the yield was slightly higher, mainly because the pressure drop of the Mellapak 250Y packing was lower, resulting in a slightly lower reboiler operating temperature and reduced polymerization loss. This indicates that, while ensuring purity requirements, higher yields and lower energy consumption can be achieved through packing combination optimization.

[0058] This invention is illustrated by Comparative Example 1: This example uses a traditional single-tower distillation system as a comparative example. The distillation column is 22 meters high and filled with Mellapak 500Y packing. The same feedstock as in Example 1 is used, with a feed rate of 500 kg / h. The operating vacuum is 5 kPa, the top temperature is 98°C, and the reflux ratio is 5:1. The product is collected at the top of the column, and the heavy components are discharged from the bottom.

[0059] After 48 hours of continuous operation, the purity of the product at the top of the column reached a maximum of 99.3 wt%, but the yield was only 78.5%. After 72 hours of operation, the product purity began to decline, and the pressure difference at the bottom of the column increased significantly. A shutdown inspection revealed severe scaling in the bottom of the column and the reboiler. Polymer accumulation led to reduced heat transfer efficiency and uneven gas-liquid distribution within the column. Analysis concluded that the material's long residence time in the 22-meter-high column, especially the repeated heating in the high-temperature bottom region, resulted in significant polymerization, which not only reduced the product yield but also severely impacted the continuous operation cycle of the equipment.

[0060]

[0061] First, by removing the pre-distillate that could potentially trigger polymerization in System 1, and by achieving rapid vaporization of the material through a "flash evaporation" process in System 2, combined with high-vacuum operation throughout the entire process, the residence time of the material in the high-temperature region is significantly shortened. The yield of Example 1 reached 95.2%, far exceeding the 78.5% of Comparative Example 1 and 78.5% of Comparative Example 2. Second, this invention, through functional segmentation, breaks down the traditional single tower exceeding 20 meters into three towers, each less than 12 meters in height. This significantly reduces the total floor space and height requirements, making it easily applicable to existing factory renovation projects with limited floor height, greatly expanding its application scenarios. Third, the system of this invention can stably obtain high-purity p-tert-butylbenzyl chloride with a purity between 99.2% and 99.7%, fully meeting the requirements of high-end applications. By adjusting operating parameters (such as vacuum degree and reflux ratio) and packing combinations, the purity and yield can be optimized and adjusted within a certain range to adapt to different production goals.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A fractional distillation system for tert-butylbenzyl chloride, characterized in that, include: System 1 is an independently operating fore-distillation tower used to distill the fore-distillate from the feedstock under high vacuum conditions; System 2 is a rapid vaporization tower connected in series with System 3. It is used to rapidly vaporize the material after the removal of the pre-distillate. The vaporization process is enhanced by heat transfer through an independent heater. System 3 is a segmented distillation column with a height of 10-12 meters, used to distill and separate the vaporized material to obtain high-purity p-tert-butylbenzyl chloride; System 2 and System 3 operate in series, while System 1 operates independently. The entire process is carried out under high vacuum, with a vacuum level of 1-20 kPa and an operating temperature lower than the polymerization temperature of p-tert-butylbenzyl chloride.

2. The fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The system includes a tower body, a packing layer, a top condenser, a pre-fraction collection tank, and a vacuum system; the tower body is 4-8 meters high, and the packing layer uses one or more of the following: θ rings, BX packing, CY packing, or Mellapak 250Y packing.

3. The fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The second system includes a tower body, a thin-layer evaporator or a falling film evaporator, an independent heater, and a vacuum system; the tower body is 4-6 meters high, and the independent heater is used to heat and vaporize the material within 5-10 seconds.

4. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The system includes a tower body, an upper packing layer, a lower packing layer, a finished product recovery system, and a vacuum system; the tower body is 10-12 meters high, the upper packing layer is 4-6 meters high, and the lower packing layer is 6-8 meters high; the finished product recovery system includes a condenser, a finished product buffer tank, a finished product transfer pump, and a reflux distributor.

5. A fractional distillation system for tert-butylbenzyl chloride according to claim 4, characterized in that: The upper packing layer uses one or more of BX packing, CY packing, or Mellapak250Y packing, and the lower packing layer uses one or more of Mellapak250Y or 500Y packing.

6. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: A first buffer tank and a magnetic pump are installed between System 1 and System 2 to stabilize material transport.

7. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: A second buffer tank and metering pump are installed between System 2 and System 3 to stabilize the feed.

8. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The high-purity p-tert-butylbenzyl chloride obtained at the top of System 3 has a purity of 99.0-99.8%, while the heavy components at the bottom of the tower are returned to the raw material system or processed separately.

9. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The fore-distillate from the first distillation of the system is condensed and returned to the feed tank for recycling.

10. A fractional distillation system for tert-butylbenzyl chloride according to claim 1, characterized in that: The independent heater is one of a jacketed heater, a coil heater, or an electric heater.

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