High-efficiency energy-saving process and device for preparing 1,2-propanediol by hydrating propylene oxide
By combining a novel tubular reactor with multi-effect distillation technology, the problems of high energy consumption and low product quality in propylene oxide hydration have been solved, enabling efficient production of high-purity 1,2-propanediol and dipropylene glycol, suitable for production units ranging from 5,000 tons/year to 200,000 tons/year.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANJIN UNIV
- Filing Date
- 2026-04-14
- Publication Date
- 2026-06-16
AI Technical Summary
The existing direct hydration process for propylene oxide is energy-intensive and produces low-quality products, making it difficult to meet the demand for high-end 1,2-propanediol in industries such as food and pharmaceuticals.
By employing a novel tubular reactor, coupled with multi-effect distillation and indirect wall column technology, and through pressurized water heat extraction, multi-effect countercurrent distillation, and heat coupling, the reaction efficiency and selectivity are improved, energy consumption is reduced, and product purity is increased.
The purity of 1,2-propanediol product exceeded 99.9 wt%, the yield of dipropylene glycol exceeded 95%, and the steam consumption was reduced to 1.60 t/t, meeting the quality and energy efficiency requirements of high-end 1,2-propanediol.
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Figure CN122212892A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a process for producing 1,2-propanediol, and more particularly to a highly efficient and energy-saving process and apparatus for producing 1,2-propanediol from propylene oxide hydration, which yields high-quality products and consumes little energy. Background Technology
[0002] 1,2-Propanediol (PG) is a colorless, odorless, viscous liquid at room temperature and pressure. It is stable and hygroscopic. Its chemical formula is C3H8O2. It belongs to the diol family and is miscible with water, ethanol, and many organic solvents. 1,2-Propanediol is an important chemical intermediate with wide applications in industrial plastics, synthetic resins, cosmetics, pharmaceuticals, food, lubricants, antifreeze, and many other fields.
[0003] The main production methods for 1,2-propanediol include direct hydration of propylene oxide, transesterification, glycerol hydrogenolysis, and propylene hydrogen peroxide method. Industrially, the first two methods are widely used, while the latter two are not industrialized due to technological immaturity. The direct hydration of propylene oxide is characterized by its simple process flow, high product quality, and absence of byproducts. The main process involves the reaction of propylene oxide and water in a reactor to produce 1,2-propanediol and small amounts of byproducts, dipropylene glycol (DPG) and tripropylene glycol (TPG). Unreacted water is first separated from the reaction products and recycled back to the reactor inlet as a feedstock to maintain the water-to-propylene oxide ratio. The material after water separation enters the distillation section for purification, yielding PG, DPG, and heavy impurities. The key to this process lies in efficiently generating PG, reducing energy consumption during water separation, and achieving high-purity PG purification.
[0004] Main reaction:
[0005]
[0006] Side reactions:
[0007]
[0008]
[0009] CN 117486676 A reports a method and apparatus for producing 1,2-propanediol from propylene oxide via hydration. The patent utilizes the exothermic reaction to exchange heat between the reactor feed and the reactor outlet product, reducing the energy consumption for feedstock preheating. However, it employs a single-stage distillation dehydration process, resulting in high energy consumption for the separation of propylene glycol and water. Furthermore, its 1,2-propanediol purification process is inadequate, leading to low purity of the 1,2-propanediol product. The recombinant fraction is not separated, and dipropylene glycol cannot be obtained.
[0010] CN 1304384 C reports a continuous process for the preparation of propylene glycol. First, propylene reacts with hydrogen peroxide to produce propylene oxide. The reaction product then reacts with water to produce 1,2-propanediol, dipropylene glycol, and tripropylene glycol. The process uses a separate wall column to purify and separate the reactants, obtaining 1,2-propanediol and dipropylene glycol in different regions of the column. Although the process is simple, the equipment is complex, and the purity of the obtained 1,2-propanediol and dipropylene glycol products is only between 95% and 99%, which is insufficient to meet the demand for high-end 1,2-propanediol in the food and pharmaceutical industries.
[0011] CN 1026102C reports a method for preparing propylene glycol using a tubular reactor. This method adds a static mixer before the material reactor to increase the mixing degree of propylene oxide and water, reducing the reaction time and reactor volume. However, it does not solve the problem of high energy consumption for water recovery, resulting in high steam consumption of 4.98 t steam / t 1,2-propanediol. Furthermore, its separation process is relatively simple, leading to low product purity; the 1,2-propanediol purity is only 99%, which is insufficient to meet the demand for high-end 1,2-propanediol in the food and pharmaceutical industries.
[0012] To address the issues of high energy consumption and low product quality in the current direct hydration process of propylene oxide, this method employs a novel tubular reactor, coupled multi-effect distillation technology, and indirect wall column technology to improve reaction efficiency and selectivity, minimize process energy consumption, enhance product quality, and meet the demand for high-end 1,2-propanediol in industries such as food and pharmaceuticals. Summary of the Invention
[0013] To address the shortcomings of existing technologies, this invention proposes a highly efficient and energy-saving process and apparatus for the hydration of propylene oxide to produce 1,2-propanediol. Taking full account of the characteristics of the hydration reaction and the features of the equipment, the reaction apparatus and process route are rationally designed to minimize energy consumption while obtaining high-quality products.
[0014] To achieve the above objectives, the technical solution of the present invention is as follows:
[0015] (1) The raw material propylene oxide, fresh water and recycled water are mixed and then fed into the 1,2-propanediol synthesis reactor to generate 1,2-propanediol, dipropylenediol and a small amount of tripropylenediol; the reactor shell side is heated by pressurized water, and the pressurized water after vaporization on the reactor shell side enters the steam drum in a gas-liquid two-phase manner. The steam generated by the steam drum heats the product tower and the reboiler of the de-weighting tower.
[0016] (2) The material from the reactor outlet enters multiple dehydration towers connected in series, with a number of 2 to 4. The water distilled from the dehydration towers is recycled back to the reactor. The dehydration towers are thermally coupled, and the top gas of the next dehydration tower heats the reboiler of the previous dehydration tower.
[0017] (3) The bottom of the last dehydration tower is fed into the product tower, and 1,2-propanediol is obtained from the side of the product tower. The product tower distillate is sent to the light component removal tower, the light component removal tower distillate is returned to the reactor inlet, and the light component removal tower bottom is returned to the product tower. The product tower bottom is sent to the heavy component removal tower, the heavy component removal tower distillate is dipropylene glycol, and the bottom is heavy component impurities.
[0018] The reactor is a tubular reactor, with pressurized water introduced into the reactor shell to remove the heat of reaction. The reactor can be horizontal or vertical.
[0019] The temperature of the pressurized water on the reactor shell side is 160~224℃, and the pressurized water pressure is 0.618 MPaA~2.500 MPaA.
[0020] The pressurized water flow mode on the reactor shell side is a thermosiphon natural circulation. After the gas-liquid two-phase pressurized water enters the steam drum, it generates medium-pressure steam, which provides a heat source for the product tower and the deweighting tower.
[0021] The reactor outlet stream is dehydrated by multi-effect countercurrent distillation, and there are 2 to 4 dehydration towers. The dehydration towers of this invention are described in the order of A, B, C, and D.
[0022] When there are two dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 10~30kPaA, Dehydration tower B: 80~200kPaA;
[0023] When there are 3 dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 5~15kPaA, Dehydration tower B: 20~50kPaA, Dehydration tower C: 80~200kPaA;
[0024] When there are 4 dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 1~8kPaA, Dehydration tower B: 10~20kPaA, Dehydration tower C: 30~50kPaA, Dehydration tower D: 80~200kPaA.
[0025] The theoretical number of plates for each dehydration tower is 5 to 15.
[0026] The product column is a partitioned column with interconnected top and bottom sections, and the partitions are only located in the middle of the column. The total number of theoretical plates is 20-50, with 5-20 theoretical plates above the partitions and 5-20 theoretical plates below the partitions. The side inlet is located on the discharge side of the partition, and the distance between the side inlet and the upper part of the partition is 2-15 theoretical plates. The product column is a vacuum distillation column with a top pressure of 1-10 kPa.
[0027] The aforementioned deweight removal column is a vacuum distillation column with a theoretical plate number of 5 to 20; the pressure at the top of the column is 1 to 10 kPaA.
[0028] This invention relates to a highly efficient and energy-saving device for the production of 1,2-propanediol from propylene oxide hydration, comprising a reactor 1, a steam drum 2, a series-connected dehydration tower 3, a product tower 4, and a de-heavy phase tower 5. Fresh water, recycled water, and PO are mixed and fed into the reactor 1 via a pipe-side inlet. The reactor 1's pipe-side outlet is connected to the feed inlet of the series-connected dehydration tower 3. The series-connected dehydration towers 3 are thermally coupled; the overhead gas from the subsequent dehydration tower heats the reboiler of the preceding dehydration tower, and the bottom distillate from the last dehydration tower is sent to the product tower 4. The top discharge from the first tower of the series-connected dehydration tower 3 is divided into two streams. One stream of water is recycled back to the inlet of reactor 1 and connected to the fresh water feed; another stream is collected as light components; the remaining water distilled from the tops of the various dehydration towers is recycled back to the reactor. The bottom discharge of the last tower in series dehydration tower 3 is connected to the feed of product tower 4. The top discharge of product tower 4 is divided into two streams: one stream is recycled back to the inlet of reactor 1 and connected to the fresh water feed; the other stream is collected as wastewater. The bottom discharge of product tower 4 is connected to the feed of heavy components tower 5. 1,2-Propanediol is collected from the side of product tower 4. The bottom discharge of heavy components tower 5 is heavy component impurities. The top discharge of heavy components tower 5 is dipropylene glycol. The shell-side outlet of reactor 1 is connected to the inlet of steam drum 2. The liquid phase outlet of steam drum 2 is connected to the shell-side inlet of reactor 1. The gas phase outlet of steam drum 2 is connected to the reboilers of product tower 4 and heavy components tower 5, respectively.
[0029] The specific explanation is as follows:
[0030] For a double-effect dehydration process with two dehydration towers in series: fresh water, recycled water, and PO are mixed and fed into the reactor tube-side inlet; the reactor tube-side outlet is connected to the feed of dehydration tower A; the reactor shell-side outlet is connected to the steam drum inlet; the steam drum liquid phase outlet is connected to the reactor shell-side inlet; the steam drum gas phase outlet is connected to the product tower and the reboiler of the heavy weight removal tower, respectively; the bottom discharge of dehydration tower A is connected to the feed of dehydration tower B; the top discharge of dehydration tower A is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is used as... Light components are collected; the bottom discharge of dehydration tower B is connected to the feed of the product tower; the gas phase at the top of dehydration tower B is connected to the reboiler of dehydration tower A; the condensate from the reboiler of dehydration tower A is divided into two streams, which are connected to the fresh water feed and the reflux of dehydration tower B, respectively; the top discharge of the product tower is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is collected as wastewater; the bottom discharge of the product tower is connected to the feed of the heavy components removal tower; 1,2-propanediol is collected from the side of the product tower; the bottom discharge of the heavy components removal tower is heavy component impurities; the top discharge of the heavy components removal tower is dipropylene glycol.
[0031] For a triple-effect dehydration process with three dehydration towers in series: Fresh water, recycled water, and PO are mixed and fed into the reactor tube-side inlet; the reactor tube-side outlet is connected to the feed of dehydration tower A; the reactor shell-side outlet is connected to the steam drum inlet; the steam drum liquid phase outlet is connected to the reactor shell-side inlet; the steam drum gas phase outlet is connected to the product tower and the reboiler of the heavy component removal tower, respectively; the bottom discharge of dehydration tower A is connected to the feed of dehydration tower B; the top discharge of dehydration tower A is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is collected as a light component; the bottom discharge of dehydration tower B is connected to the feed of dehydration tower C; the top gas phase of dehydration tower B is mixed with the dehydrated water... Water tower A is connected to the reboiler; the condensate from the reboiler of dehydration tower A is divided into two streams, which are connected to the fresh water feed and the reflux of dehydration tower B, respectively; the bottom discharge of dehydration tower C is connected to the feed of the product tower; the gas phase at the top of dehydration tower C is connected to the reboiler of dehydration tower B; the condensate from the reboiler of dehydration tower B is divided into two streams, which are connected to the fresh water feed and the reflux of dehydration tower C, respectively; the top discharge of the product tower is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is collected as wastewater; the bottom discharge of the product tower is connected to the feed of the heavy components removal tower; 1,2-propanediol is collected from the side of the product tower; the bottom discharge of the heavy components removal tower is heavy impurities; the top discharge of the heavy components removal tower is dipropylene glycol.
[0032] For a four-effect dehydration process with four dehydration towers connected in series: Fresh water, recycled water, and PO are mixed and fed into the reactor tube-side inlet; the reactor tube-side outlet is connected to the feed of dehydration tower A; the reactor shell-side outlet is connected to the steam drum inlet; the steam drum liquid phase outlet is connected to the reactor shell-side inlet; the steam drum gas phase outlet is connected to the product tower and the reboiler of the heavy weight removal tower, respectively; the bottom discharge of dehydration tower A is connected to the feed of dehydration tower B; the top discharge of dehydration tower A is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is collected as a light component; the bottom discharge of dehydration tower B is connected to the feed of dehydration tower C; the top gas phase of dehydration tower B is connected to the reboiler of dehydration tower A; the condensate from the reboiler of dehydration tower A is divided into two streams, connected to the fresh water feed and the dehydration tower, respectively. B is connected to the reflux; the bottom discharge of dehydration tower C is connected to the feed of dehydration tower D; the top gas phase of dehydration tower C is connected to the reboiler of dehydration tower B; the condensate from the reboiler of dehydration tower B is divided into two streams, which are connected to the fresh water feed and the reflux of dehydration tower C respectively; the bottom discharge of dehydration tower D is connected to the feed of the product tower; the top gas phase of dehydration tower D is connected to the reboiler of dehydration tower C; the condensate from the reboiler of dehydration tower C is divided into two streams, which are connected to the fresh water feed and the reflux of dehydration tower D respectively; the top discharge of the product tower is divided into two streams, one of which is recycled back to the reactor inlet and connected to the fresh water feed, and the other is collected as wastewater; the bottom discharge of the product tower is connected to the feed of the heavy components tower; 1,2-propanediol product is collected from the side of the product tower; the bottom discharge of the heavy components tower is heavy component impurities; the top discharge of the heavy components tower is dipropylene glycol product.
[0033] The raw material propylene oxide, fresh water, and recycled water are mixed and fed into reactor 1. The material from reactor 1 is sequentially fed into multiple dehydration towers 3 connected in series. The water distilled from the series dehydration towers 3 is recycled back to the reactor. Thermal coupling occurs between the dehydration towers. The top gas from the next dehydration tower heats the reboiler of the previous dehydration tower. The bottom distillate from the last dehydration tower is sent to product tower 4. The top distillate from product tower 4 is recycled back to the inlet of reactor 1. 1,2-propanediol is collected from the side of the tower. The bottom distillate is sent to heavy component dehydration tower 5. Dipropylenediol is obtained from the top of heavy component dehydration tower 5. Heavy component dehydration tower 5 contains heavy component impurities. The pressurized water generated on the shell side of reactor 1 enters steam drum 2. The steam generated in the steam drum provides a heat source for the reboilers of product tower 4 and heavy component dehydration tower 5.
[0034] The specific explanation is as follows:
[0035] The raw materials, propylene oxide, fresh water, and water recovered from the dehydration tower 3 (connected in series), are mixed and pressurized to 2.5–6 MPaA before entering reactor 1. The reactants are reacted at a pressure of 2.5–6 MPaA and a temperature of 180–240°C to produce 1,2-propanediol, dipropylene glycol, and a small amount of tripropylene glycol. The reactor is a tubular reactor. On the shell side, pressurized water removes heat. After vaporization, the pressurized water enters the steam drum for gas-liquid separation. The vapor phase is fed to product tower 4 and deweighting tower 5 for reboiler heating. The aqueous phase, along with the steam drum makeup water, is circulated back to the reactor shell side. The pressurized water circulation between the reactor shell side and the steam drum is a thermosiphon natural circulation. The reactor tube side pressure is 2.5–6 MPaA, and the temperature is 180–240°C; the pressurized water temperature on the reactor shell side is 160–224°C, and the pressurized water pressure is 0.618 MPaA–2.500 MPaA. The preferred reactor tube pressure is 3~5 MPaA, and the reaction temperature is 180~220℃. The preferred reactor shell-side pressure is 0.8 MPaA~2.0 MPaA, and the shell-side temperature is 170~210℃.
[0036] The reactor outlet material sequentially enters multiple dehydration towers 3 connected in series, numbering 2 to 4. The water distilled from the top of each dehydration tower is recycled back to the reactor. Thermal coupling occurs between the dehydration towers; the top gas from the next dehydration tower heats the reboiler of the previous dehydration tower, and the bottom distillate from the last dehydration tower is sent to the product tower 4. The dehydration towers of this invention are described in the order A, B, C, and D. When there are two dehydration towers, the pressure configuration for each tower is as follows: Dehydration Tower A: 10~30 kPaA, Dehydration Tower B: 80~200 kPaA; When there are three dehydration towers, the pressure configuration for each tower is as follows: Dehydration Tower A: 5~15 kPaA, Dehydration Tower B: 20~50 kPaA, Dehydration Tower C: 80~200 kPaA; When there are four dehydration towers, the pressure configuration for each tower is as follows: Dehydration Tower A: 1~8 kPaA, Dehydration Tower B: 10~20 kPaA, Dehydration Tower C: 30~50 kPaA, Dehydration Tower D: 80~200 kPaA. The theoretical number of plates in each dehydration tower is 5~15. The preferred number of dehydration towers is 3, and the preferred dehydration tower pressure configuration is: dehydration tower A: 8~15kPaA, dehydration tower B: 30~45kPaA, dehydration tower C: 90~120kPaA. The preferred theoretical number of dehydration tower plates is 5~10.
[0037] Product column 4 is a partitioned-wall column that receives material from the bottom of the last dehydration column 3 connected in series. Its main components are 1,2-propanediol, dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of water. The product column is a partitioned-wall column with interconnected top and bottom sections; the partition is only located in the middle of the column. 1,2-propanediol is collected from the discharge side of the partition. The water distilled from the top is recycled back to the reactor, and the bottom material is sent to the de-heavy distillation column 5. The total number of theoretical plates is 20-50, with 5-20 theoretical plates above the partition and 5-20 theoretical plates below the partition. The side sampling port is located on the discharge side of the partition, and the distance from the side sampling port to the top of the partition is 2-15 theoretical plates. The product column is a vacuum distillation column with a top pressure of 1-10 kPa. The preferred product tower 4 has a total of 30-40 theoretical plates, with 5-10 theoretical plates above the partition and 5-10 theoretical plates below the partition; the side sampling port is preferably 2-10 theoretical plates from the top of the partition. The preferred tower top pressure is 1-5 kPaA.
[0038] The heavy component removal column 5 receives material from product column 4. The main components are dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of heavy components. The distillate at the top of the column is dipropylene glycol, while the bottom product is the heavy components. The heavy component removal column is a vacuum distillation column with 5-20 theoretical plates and a top pressure of 1-10 kPaA. Preferably, the number of theoretical plates is 5-15, and the preferred top pressure is 1-5 kPaA.
[0039] The beneficial effects of this invention are as follows:
[0040] To address the issues of high energy consumption and low product quality in the current direct hydration process of propylene oxide, this method employs a novel tubular reactor, coupled multi-effect distillation technology, and indirect wall column technology to improve reaction efficiency and selectivity, minimize process energy consumption, enhance product quality, and meet the demand for high-end 1,2-propanediol in industries such as food and pharmaceuticals.
[0041] The 1,2-propanediol produced by this invention has a purity >99.9 wt%, a yield of 1,2-propanediol and dipropylene glycol >95%, and a propylene oxide consumption of <0.8 t propylene oxide / t (total of 1,2-propanediol and dipropylene glycol); the steam consumption is 1.60 t steam / t (total of 1,2-propanediol and dipropylene glycol, triple-effect dehydration scheme). This significantly surpasses existing specifications: 1,2-propanediol purity 98.5 wt%, 1,2-propanediol and dipropylene glycol yield ~92%; steam consumption <4.98 t steam / t (total of 1,2-propanediol and dipropylene glycol). Furthermore, this scheme does not have a bottleneck in scaling up the processing capacity and is suitable for 1,2-propanediol production plants ranging from 5,000 tons / year to 200,000 tons / year. Attached Figure Description
[0042] Figure 1 : Simplified process flow diagram of PO hydration to 1,2-PG based on dual-effect dehydration
[0043] Figure 2 Simplified process flow diagram of PO hydration to 1,2-PG based on triple-effect dehydration
[0044] Figure 3 Simplified process flow diagram of PO hydration to 1,2-PG based on four-effect dehydration
[0045] The components include: reactor 1, steam drum 2, dehydration tower 3 connected in series, product tower 4, and heavy weight removal tower 5. Detailed Implementation
[0046] Specific embodiments of the present invention Figure 1 and Figure 2Further description, but the scope of the invention is not limited thereto. The raw material propylene oxide, fresh water, and recycled water are mixed and fed into a 1,2-propanediol synthesis reactor to produce 1,2-propanediol, dipropylene glycol, and a small amount of tripropylene glycol. Pressurized water on the reactor shell side is vaporized and enters a steam drum; the generated steam heats the product tower and the reboiler of the heavy components removal tower. The reactor outlet material sequentially enters multiple dehydration towers connected in series, numbering 2 to 4. Water distilled from the dehydration towers is recycled back to the reactor; thermal coupling occurs between the dehydration towers, with the overhead gas from the next dehydration tower heating the reboiler of the previous one. The bottom distillate from the last dehydration tower is sent to the product tower, where 1,2-propanediol is collected. The product tower distillate is sent to the light components removal tower, where the distillate returns to the reactor inlet, and the bottom product from the light components removal tower returns to the product tower. The bottom product from the product tower is sent to the heavy components removal tower, where the distillate is dipropylene glycol, and the bottom product is heavy impurities.
[0047] Example 1:
[0048] In this embodiment, the propylene oxide feed rate is 2171 kg / h, and the water feed rate is 652 kg / h. Both are mixed with recovered water and pressurized to 4 MPaA before entering the vertical tubular reactor 1. Pressurized water is introduced through the shell side of reactor 1 to remove the heat of reaction, maintaining the temperature inside the reaction tubes at 180~185℃. The temperature of the pressurized water on the shell side of reactor 1 is 175℃, and the pressure is 0.89 MPaA. The pressurized water enters the steam drum 2 in a gas-liquid two-phase form via thermosiphon circulation. The steam drum 2 produces 1.42 t / h of steam, which is sent to the product tower 4 and the deweighting tower 5 to provide a heat source for the reboiler.
[0049] The reactor outlet material sequentially enters two dehydration towers: dehydration tower 3A and dehydration tower 3B. The bottom material of dehydration tower 3B is sent to product tower 4. The vapor phase from the top of dehydration tower 3B heats the reboiler of dehydration tower 3A, and the reboiler of dehydration tower 3B is heated by steam. Dehydration tower 3A has a theoretical number of 15 plates, and dehydration tower 3B has a theoretical number of 15 plates. The top pressure of dehydration tower 3A is 40 kPaA, and the top pressure of dehydration tower 3B is 120 kPaA.
[0050] Product column 4 is a partitioned-wall column that receives material from the bottom of dehydration column 3B. Its main components are 1,2-propanediol, dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of water. The column is a partitioned-wall column with interconnected top and bottom sections; the partition is only located in the middle of the column. 1,2-propanediol is collected from the side of the partition outlet, with a yield of 2500 kg / h and a purity >99.9 wt%. The water distilled from the top is recycled back to the reactor, and the bottom material is sent to the de-heavyweight column 5. Product column 4 has a total of 40 theoretical plates: 20 above the partition and 10 below. The side outlet is located 4 theoretical plates above the partition. The pressure at the top of the column is 5 kPa.
[0051] Product column 5 receives material from product column 4. The main components are dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of heavy components. The distillate at the top of the column is dipropylene glycol, with a yield of 228.4 kg / h and a purity >99.9 wt%. The bottom product is heavy components. The column has 15 theoretical plates and a top pressure of 3 kPa.
[0052] In this example, the 1,2-propanediol production capacity is 20,000 tons / year, and the steam consumption is 2.12 t steam / t (total of 1,2-propanediol and dipropylene glycol). The purity of 1,2-propanediol is >99.9 wt%, and the purity of dipropylene glycol is >99.9 wt%.
[0053] Example 2:
[0054] In this embodiment, the propylene oxide feed rate is 1088 kg / h, and the water feed rate is 328 kg / h. Both are mixed with recovered water and pressurized to 2.5 MPaA before entering the vertical tubular reactor 1. Pressurized water is introduced through the shell side of reactor 1 to remove the heat of reaction, maintaining the temperature inside the reaction tubes at 230~240℃. The temperature of the pressurized water on the shell side of reactor 1 is 224℃, and the pressurized water pressure is 2.500 MPaA. The pressurized water enters the steam drum 2 in a gas-liquid two-phase form via thermosiphon circulation. The steam drum 2 produces 0.68 t / h of steam, which is sent to the product tower 4 and the deweighting tower 5 to provide a heat source for the reboiler.
[0055] The reactor outlet material sequentially enters three dehydration towers: dehydration tower 3A, dehydration tower 3B, and dehydration tower 3C. The bottom material of dehydration tower 3C is sent to product tower 4. The vapor phase from the top of dehydration tower 3C heats the reboiler of dehydration tower 3B, the vapor phase from the top of dehydration tower 3B heats the reboiler of dehydration tower 3A, and the reboiler of dehydration tower 3C is heated by steam. Dehydration tower 3A has 10 theoretical plates, dehydration tower 3B has 10 theoretical plates, and dehydration tower 3C has 10 theoretical plates. The top pressure of dehydration tower 3A is 10 kPaA, the top pressure of dehydration tower 3B is 45 kPaA, and the top pressure of dehydration tower 3C is 100 kPaA.
[0056] Product column 4 is a partitioned-wall column that receives material from the bottom of dehydration column 3C. Its main components are 1,2-propanediol, dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of water. The column is partitioned, with both the top and bottom connected, and the baffle plate is only located in the middle. 1,2-propanediol is collected from the baffle outlet side, with a yield of 1250 kg / h and a purity >99.9 wt%. The water distilled from the top is recycled back to the reactor, and the bottom material is sent to de-heavyweight column 5. Product column 4 has a total of 20 theoretical plates: 5 above the baffle plate and 5 below the baffle plate; the side collection port is located 2 theoretical plates above the baffle plate. The pressure at the top of the column is 10 kPa.
[0057] Product column 5 receives material from product column 4. The main components are dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of heavy components. The distillate from the top of the column is dipropylene glycol, with a yield of 114.2 kg / h and a purity >99.9 wt%. The bottom product is heavy components. The column has 20 theoretical plates and a top pressure of 10 kPa.
[0058] In this example, the 1,2-propanediol production capacity is 10,000 tons / year, and the steam consumption is 1.60 t steam / t (total of 1,2-propanediol and dipropylene glycol). The purity of 1,2-propanediol is >99.9 wt%, and the purity of dipropylene glycol is >99.9 wt%.
[0059] Example 3:
[0060] In this embodiment, the propylene oxide feed rate is 5425 kg / h, and the water feed rate is 1628 kg / h. Both are mixed with recovered water and pressurized to 6 MPaA before entering the vertical tubular reactor 1. Pressurized water is introduced through the shell side of reactor 1 to remove the heat of reaction, maintaining the temperature inside the reaction tubes at 180~185℃. The temperature of the pressurized water on the shell side of reactor 1 is 160℃, and the pressurized water pressure is 0.618 MPaA. The pressurized water enters the steam drum 2 in a gas-liquid two-phase form via thermosiphon circulation. The steam drum 2 produces 3.55 t / h of steam, which is sent to the product tower 4 and the deweighting tower 5 to provide a heat source for the reboiler.
[0061] The reactor outlet material sequentially enters four dehydration towers: dehydration tower 3A, dehydration tower 3B, dehydration tower 3C, dehydration tower 3D, and dehydration tower 3D. The bottom material of dehydration tower 3D is sent to product tower 4. The vapor phase from the top of dehydration tower 3D heats the reboiler of dehydration tower 3C; the vapor phase from the top of dehydration tower 3C heats the reboiler of dehydration tower 3AB; the vapor phase from the top of dehydration tower 3B heats the reboiler of dehydration tower 3A; and the reboiler of dehydration tower 3D is heated by steam. Dehydration tower 3A has 5 theoretical plates, dehydration tower 3B has 5 theoretical plates, dehydration tower 3C has 5 theoretical plates, and dehydration tower 3D has 5 theoretical plates. The pressure at the top of dehydration tower 3A is 8 kPaA, the pressure at the top of dehydration tower 3B is 20 kPaA, the pressure at the top of dehydration tower 3C is 50 kPaA, and the pressure at the top of dehydration tower 3D is 120 kPaA.
[0062] Product column 4 is a partitioned-wall column that receives material from the bottom of dehydration column 3D. Its main components are 1,2-propanediol, dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of water. The column is a partitioned-wall column with interconnected top and bottom sections; the partition is only located in the middle of the column. 1,2-propanediol is collected from the side of the partition outlet, with a yield of 6250 kg / h and a purity >99.9 wt%. The water distilled from the top is recycled back to the reactor, and the bottom material is sent to de-heavyweight column 5. Product column 4 has a total of 50 theoretical plates: 10 above the partition and 20 below. The side outlet is located 15 theoretical plates above the partition. The pressure at the top of the column is 1 kPa.
[0063] Product column 5 receives material from product column 4. The main components are dipropylene glycol, a small amount of tripropylene glycol, and trace amounts of heavy components. The distillate from the top of the column is dipropylene glycol, with a yield of 571.1 kg / h and a purity >99.9 wt%. The bottom product is heavy components. There are 5 theoretical plates, and the top pressure is 1 kPa.
[0064] In this example, the 1,2-propanediol production capacity is 50,000 tons / year, and the steam consumption is 1.50 t steam / t (total of 1,2-propanediol and dipropylene glycol). The purity of 1,2-propanediol is >99.9 wt%, and the purity of dipropylene glycol is >99.9 wt%.
[0065] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. The present invention is not limited to the above description, and various changes can be made according to the purpose of the invention. All modifications, combinations, simplifications, equivalent substitutions, etc., made in accordance with the spirit and principle of the implementation of the technical solution of the present invention should be considered equivalent substitution modes. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they should be included within the protection scope of the present invention.
Claims
1. A highly efficient and energy-saving process for the hydration of propylene oxide to produce 1,2-propanediol; characterized by, Includes the following steps: (1) The raw material propylene oxide, fresh water and recycled water are mixed and then fed into the 1,2-propanediol synthesis reactor to generate 1,2-propanediol, dipropylenediol and a small amount of tripropylenediol; the reactor shell side is heated by pressurized water, and the pressurized water after vaporization on the reactor shell side enters the steam drum in a gas-liquid two-phase manner. The steam generated by the steam drum heats the product tower and the reboiler of the de-weighting tower. (2) The material at the reactor outlet enters multiple dehydration towers connected in series in sequence. The water distilled from the dehydration towers is recycled back to the reactor. The dehydration towers are thermally coupled. The top gas of the next dehydration tower heats the reboiler of the previous dehydration tower. (3) The bottom of the last dehydration tower is fed into the product tower, and 1,2-propanediol is obtained from the side of the product tower. The product tower distillate is sent to the light component removal tower, the light component removal tower distillate is returned to the reactor inlet, and the light component removal tower bottom is returned to the product tower. The product tower bottom is sent to the heavy component removal tower, the heavy component removal tower distillate is dipropylene glycol, and the bottom is heavy component impurities.
2. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The reactor is a tubular reactor, with pressurized water introduced into the reactor shell to remove the heat of reaction. The reactor can be horizontal or vertical.
3. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The temperature of the pressurized water on the reactor shell side is 160~224℃, and the pressurized water pressure is 0.618 MPaA~2.500 MPaA.
4. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The pressurized water flow mode on the reactor shell side is a thermosiphon natural circulation. After the gas-liquid two-phase pressurized water enters the steam drum, it generates medium-pressure steam, which provides a heat source for the product tower and the deweight tower.
5. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The reactor outlet stream uses multi-effect countercurrent distillation to remove moisture, with 2-4 dehydration towers connected in series. The dehydration towers are described in the order A, B, C, and D. When there are two dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 10~30kPaA, Dehydration tower B: 80~200kPaA; When there are 3 dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 5~15kPaA, Dehydration tower B: 20~50kPaA, Dehydration tower C: 80~200kPaA; When there are 4 dehydration towers, the pressure configuration of each dehydration tower is as follows: Dehydration tower A: 1~8kPaA, Dehydration tower B: 10~20kPaA, Dehydration tower C: 30~50kPaA, Dehydration tower D: 80~200kPaA.
6. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The theoretical number of plates for each dehydration tower is 5 to 15.
7. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The product column is a partitioned column with interconnected top and bottom sections. The partitions are only located in the middle of the column. The total number of theoretical plates is 20-50, with 5-20 theoretical plates above the partitions and 5-20 theoretical plates below the partitions. The side inlet is located on the discharge side of the partitions, and the distance between the side inlet and the upper part of the partitions is 2-15 theoretical plates. The product column is a vacuum distillation column with a top pressure of 1-10 kPa.
8. The high-efficiency and energy-saving process for the hydration of propylene oxide to 1,2-propanediol as described in claim 1; characterized in that, The deweight removal column is a vacuum distillation column with 5 to 20 theoretical plates and a top pressure of 1 to 10 kPaA.
9. The apparatus for the highly efficient and energy-saving process of hydrating propylene oxide to produce 1,2-propanediol according to claim 1, characterized in that, The system includes reactor 1, steam drum 2, dehydration tower 3, product tower 4, and heavy component removal tower 5 connected in series. Fresh water, recycled water, and PO are mixed and fed into the inlet of reactor 1. The outlet of reactor 1 is connected to the inlet of dehydration tower 3. The dehydration towers 3 are thermally coupled; the overhead gas from the next dehydration tower heats the reboiler of the previous tower, and the bottom distillate from the last dehydration tower is sent to product tower 4. The top product from the first tower of dehydration tower 3 is divided into two streams: one stream is recycled back to the inlet of reactor 1 and connected to the fresh water feed, and the other stream is collected as a light component. The water distilled from the tops of the remaining dehydration towers is recycled... The reactor is a recirculating reactor; the bottom of the last column of the series dehydration tower 3 is connected to the feed of the product tower 4; the top output of the product tower 4 is divided into two streams, one of which is recycled back to the inlet of reactor 1 and connected to the fresh water feed, and the other is collected as wastewater; the bottom output of the product tower 4 is connected to the feed of the heavy removal tower 5; 1,2-propanediol product is collected from the side of the product tower 4; the bottom output of the heavy removal tower 5 is heavy component impurities; the top output of the heavy removal tower 5 is dipropylene glycol product; the shell-side outlet of reactor 1 is connected to the inlet of steam drum 2; the liquid phase outlet of steam drum 2 is connected to the shell-side inlet of reactor 1; the gas phase outlet of steam drum 2 is connected to the reboilers of product tower 4 and heavy removal tower 5, respectively.