Method and system for deep dealdehyding of epoxypropane

Abstract

The invention discloses a method and a system for deep dealdehyding of epoxypropane, and belongs to the technical field of chemical engineering. The method for deep dealdehyding of epoxypropane comprises the following steps: an epoxypropane liquid containing aldehyde impurities is taken as a raw material liquid and passes through an adsorption tower filled with an adsorbent, the aldehyde impurities are adsorbed by the adsorbent, and a refined epoxypropane product is obtained from the top of the adsorption tower; the raw material liquid is epoxypropane liquid containing aldehyde impurities; after the adsorbent is saturated by adsorption, stopping feeding and discharging residual liquid in the tower from the bottom of the adsorption tower; and introducing nitrogen into the adsorption tower, and carrying out high-temperature purging regeneration on the adsorption bed layer. The invention also discloses a system for deep dealdehyding of epoxypropane, which is used in the method. According to the method disclosed by the invention, aldehydes impurities in the epoxypropane can be reduced to 10 ppm or below through an adsorption effect; and meanwhile, the method has technical feasibility, economic benefit and environmental friendliness, and provides a reliable solution for realizing high-efficiency, low-carbon and low-cost deep dealdehyding of the epoxypropane liquid.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method and system for deep dealdehyde removal from propylene oxide. Background Technology

[0002] Propylene oxide (PO) is an important intermediate in the petrochemical industry and a basic raw material for organic chemical synthesis. It is the third largest propylene derivative after polypropylene and acrylonitrile. Propylene oxide is mainly used to produce polyether polyols, propylene glycol, and various nonionic surfactants, with nearly a hundred downstream products widely used in industries such as furniture, home appliances, automobiles, construction, food, tobacco, pharmaceuticals, and cosmetics. Among these, polyether polyols are the most important downstream product of propylene oxide, serving as a core raw material for the synthesis of polyurethane, and are further used in the manufacture of sponges, fire-retardant materials, and thermal insulation materials.

[0003] Propylene oxide products often contain aldehyde impurities, primarily acetaldehyde. These impurities have boiling points close to propylene oxide, making them difficult to separate effectively using conventional distillation methods, thus severely impacting product quality. Aldehydes not only inhibit propylene oxide polymerization but also interfere with the chain growth of polyether polyol molecules, leading to abnormally high pressure during polymerization and increasing production safety risks. Furthermore, high aldehyde content in propylene oxide can affect the color of downstream polyether polyols, limiting their application in high-end sectors. Therefore, developing a dealdehyde removal process that can reduce aldehyde impurity content in propylene oxide to below 10 ppm, while minimizing propylene oxide loss, reducing energy consumption, and ensuring a clean process, is of significant economic and environmental importance for enhancing product added value and expanding high-end applications.

[0004] Currently, industrial methods for removing aldehyde impurities from propylene oxide mainly include extractive distillation and adsorption. Regarding extractive distillation, for example, patent CN100500659C discloses a method using compounds containing unsubstituted amine groups for extractive distillation. However, this method struggles to stably reduce aldehyde impurities to below 10 ppm, and the hydrazone derivatives formed by the reaction of amine compounds with aldehydes easily lead to high-nitrogen wastewater, posing challenges for subsequent treatment. Patent CN112209904A achieved aldehyde content reduction to below 10 ppm by preparing modified adsorbents and controlling the acidity of the formaldehyde removal agent; however, this process has high energy consumption, complex procedures, and significant equipment investment.

[0005] Regarding adsorption methods, patent CN106117165A uses alkaline substances to modify zeolite molecular sieves for adsorption and formaldehyde removal. Although it can reduce the formaldehyde content from 20-200 ppm to below 10 ppm, the modified molecular sieve exhibits poor formaldehyde removal stability and a low volume hourly space velocity, making it unsuitable for large-scale industrial applications. Patent CN110041292A proposes using modified resins to remove aldehyde and ketone impurities. While this method boasts high removal rates and low propylene oxide loss, the short resin lifespan limits its long-term economic viability. Patent CN114749160A reports a highly efficient formaldehyde removal adsorption material and its preparation method, which can rapidly reduce the formaldehyde content to below 10 ppm. However, the preparation process of this adsorbent is complex and costly, making large-scale industrial applications difficult.

[0006] Therefore, providing a dealdehyde removal method that can efficiently and stably reduce the aldehyde impurity content in propylene oxide to below 10 ppm, while having low propylene oxide loss, low energy consumption, clean process, and applicability to industrial production, in order to solve the defects of existing technologies such as insufficient dealdehyde removal depth, high process energy consumption, poor adsorbent stability, short lifespan, complex preparation, or secondary pollution, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] One objective of this invention is to address the problem of excessively high aldehyde impurities in propylene oxide in existing technologies, which fail to meet downstream application requirements, by providing a deep aldehyde removal method for propylene oxide. This method reduces aldehyde impurities in propylene oxide from 10-200 ppm to below 10 ppm through adsorption.

[0008] A second objective of this invention is to provide a deep propylene oxide dealdehyde removal system for use in the above-described method.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention discloses a method for deep dealdehyde removal from propylene oxide, comprising the following steps: S1. Adsorption step: The raw material liquid is passed through an adsorption tower containing adsorbent, where aldehyde impurities are adsorbed by the adsorbent, and refined propylene oxide product is obtained from the top of the adsorption tower; the raw material liquid is propylene oxide liquid containing aldehyde impurities; S2. Drainage procedure: Once the adsorbent is saturated, stop feeding and drain the residual liquid from the bottom of the adsorption tower. S3. Regeneration step: Nitrogen gas is introduced into the adsorption tower to regenerate the adsorption bed by high-temperature purging.

[0010] In some embodiments of the present invention, the aldehyde impurity content in the raw material liquid is 10-200 ppm, and the aldehyde substances include at least one of formaldehyde, acetaldehyde, and propionaldehyde; the aldehyde impurity content in the refined propylene oxide product is less than 10 ppm.

[0011] In some embodiments of the present invention, at least two adsorption towers are operated in parallel, wherein when one or more adsorption towers perform the adsorption step, another one or more adsorption towers perform the drainage step or the regeneration step; Preferably, the adsorbent comprises activated alumina and at least one of 5A, ZSM-5 or 13X molecular sieves.

[0012] In some embodiments of the present invention, when the raw material liquid is adsorbed in the adsorption tower, the pressure is 0.1~10 MPa and the temperature is 5~40℃; Volumetric hourly space velocity (VHSV) is 0.5–24 h⁻¹. -1 Preferably 4~16 h -1 ; The adsorption time is 0.5~16h.

[0013] In some embodiments of the present invention, in the regeneration step, the high-temperature purging temperature is the regeneration temperature at which the adsorbed impurities are desorbed, and the room-temperature purging temperature is the temperature at which the adsorption tower is restored to room temperature. Preferably, the nitrogen high-temperature purging temperature is 100~250℃, more preferably 150~190℃, and the purging time is 0.5~24h.

[0014] In the regeneration step, the gas generated by high-temperature purging is condensed and separated into condensate and non-condensable gas; most of the non-condensable gas is returned to the regeneration step for recycling, and a small portion is sent to the flare system for processing. Preferably, nitrogen is used for room temperature purging after high-temperature purging; More preferably, the high-temperature purging temperature is the regeneration temperature at which the adsorbed impurities are desorbed, and the room-temperature purging temperature is the temperature at which the adsorption tower is restored to room temperature. More preferably, the nitrogen high-temperature purging temperature is 100~250℃, more preferably 150~190℃, and the purging time is 0.5~24h.

[0015] In some embodiments of the present invention, the feed liquid comes from the crude distillation unit, and the separated condensate is sent back to the crude distillation unit for recovery treatment; Alternatively, the feed liquid may be crude propylene oxide produced from the methanol removal tower in propylene oxide production; the separated condensate may be sent to the acetaldehyde removal process in propylene oxide production.

[0016] A second aspect of the present invention discloses a system for deep propylene oxide dealdehyde removal using the above method, comprising an adsorption purification unit and a regeneration gas supply unit; the adsorption purification unit is used to adsorb impurities in the raw material liquid by adsorbing an adsorbent to obtain a purified product; The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0017] In some embodiments of the present invention, the adsorption purification unit includes one or more adsorption towers arranged in parallel, and each adsorption tower is connected to a feed liquid conveying line at its bottom; preferably, the feed liquid conveying line is connected from the crude distillation unit in the propylene oxide production system, or from the methanol removal tower in the propylene oxide production. Preferably, the number of adsorption towers arranged in parallel is 3 to 5.

[0018] In some embodiments of the present invention, the system further includes a condensation recovery unit, which includes a condenser and a gas-liquid separator connected in sequence. The condenser inlet is connected to the bottom of the adsorption tower via a pipeline; The gas outlet of the gas-liquid separator is connected to the regeneration gas supply unit and the flare system via pipelines, while the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in propylene oxide production.

[0019] In some embodiments of the present invention, the regenerated gas supply unit includes a nitrogen subsystem and a heater, wherein the nitrogen subsystem is connected to a nitrogen source to provide fresh nitrogen; the heater is disposed on the pipeline connecting the nitrogen subsystem and the adsorption purification unit to heat the gas; the gas outlet of the gas-liquid separator is connected to the pipeline between the heater and the nitrogen subsystem via a pipeline to enable the non-condensable gas to be recycled.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention is scientifically designed and ingeniously conceived. The method of this invention can reduce aldehyde impurities in propylene oxide from 10~200ppm to below 10ppm through adsorption. At the same time, it is technically feasible, economically efficient and environmentally friendly, providing a reliable solution for achieving efficient, low-carbon and low-cost deep aldehyde removal from propylene oxide liquid.

[0021] The process route of this invention is concise, the equipment configuration is reasonable, and the system operating energy consumption is significantly reduced. By effectively recovering and comprehensively utilizing the residual liquid and condensate in the regeneration tower, not only is the overall recovery rate of propylene oxide liquid containing aldehyde impurities greatly improved, but also near-zero discharge of waste liquid is achieved. The overall process is clean and environmentally friendly, improving resource utilization efficiency while reducing environmental treatment costs, resulting in significant economic benefits.

[0022] This invention features a highly modular system that can be directly integrated with existing production facilities, achieving deep desulfurization without requiring large-scale modifications to the original process. This integration method simplifies the process, effectively reducing new investment and implementation difficulty. It facilitates rapid deployment and application in existing facilities, is easy to operate and maintain, and possesses excellent engineering applicability and promotional value.

[0023] During the regeneration stage, this invention achieves efficient recovery and recycling of nitrogen, with most of the nitrogen being returned for reuse, significantly reducing the consumption of fresh nitrogen. This design not only reduces material operating costs but also effectively improves the economics of the desulfurization process, substantially reducing the overall unit desulfurization cost and enhancing the technology's market competitiveness. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of one embodiment of the deep propylene oxide dealdehyde removal method and system provided by the present invention.

[0025] Figure 2 This is a schematic diagram of the device process in Example 1.

[0026] Figure 3 This is a schematic diagram of the device process in Example 2.

[0027] The names corresponding to the reference numerals in the attached figures are: 1-Adsorption tower, 2-Condenser, 3-Gas-liquid separator, 4-Heater, 5-Nitrogen subsystem. Detailed Implementation

[0028] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0029] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0030] The method for deep dealdehyde removal from propylene oxide according to the present invention will be described in detail below.

[0031] The method for deep dealdehyde removal from propylene oxide according to the present invention includes the following steps: S1. Adsorption step The raw material liquid is passed through an adsorption tower containing an adsorbent, where aldehyde impurities are adsorbed by the adsorbent, and refined propylene oxide product is obtained from the top of the adsorption tower; the raw material liquid is propylene oxide liquid containing aldehyde impurities. At least two adsorption towers are operated in parallel, with one or more adsorption towers performing the adsorption step while the other one or more adsorption towers perform the drainage step or the regeneration step. The adsorbent includes activated alumina and at least one of 5A, ZSM-5 or 13X molecular sieves; When the feed liquid undergoes adsorption in the adsorption tower, the pressure is 0.1~10 MPa, the temperature is 5~40℃, and the volume hourly space velocity is 0.5~24 h⁻¹. -1 Preferably 4~16 h -1 The adsorption time is 0.5~16h. The aldehyde impurity content in the feed liquid is 10~200ppm, and the aldehyde substances include at least one of formaldehyde, acetaldehyde, and propionaldehyde; the aldehyde impurity content in the refined propylene oxide product obtained from the top of the adsorption tower is less than 10ppm.

[0032] S2. Drainage procedure Once the adsorbent is saturated, stop feeding and discharge the residual liquid from the bottom of the adsorption tower. S3. Regeneration Steps Nitrogen gas is introduced into the adsorption tower for purging, followed by high-temperature purging and room-temperature purging. The gas generated by high-temperature purging is condensed and separated into condensate and non-condensable gas. The high-temperature purging temperature is the regeneration temperature at which the adsorbed impurities are desorbed, while the room-temperature purging temperature is the temperature at which the adsorption tower is restored to room temperature. Preferably, the nitrogen high-temperature purging temperature is 100~250℃, more preferably 150~190℃, and the purging time is 0.5~24h.

[0033] S4. Gas Circulation Steps Most of the non-condensable gas is returned to the regeneration step for recycling, while a small portion is sent to the flare system for processing.

[0034] In some embodiments of the present invention, the feed liquid comes from the crude distillation unit, and the condensate obtained in step S5 is sent to the crude distillation unit for recovery treatment.

[0035] In other embodiments of the present invention, the feed liquid is crude propylene oxide produced from the methanol removal tower in propylene oxide production; the separated condensate is sent to the acetaldehyde removal process in propylene oxide production.

[0036] Meanwhile, the present invention also provides a system for deep aldehyde removal from propylene oxide, which includes an adsorption purification unit, a regeneration gas supply unit, and a condensation recovery unit. The adsorption purification unit is used to adsorb impurities in the feed liquid using an adsorbent to obtain a purified product. The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0037] The adsorption purification unit includes one or more adsorption towers 1 connected in parallel, and each adsorption tower 1 is connected to a feed liquid conveying line at its bottom. In some embodiments of the present invention, the feed liquid conveying line is connected from the crude distillation unit in the propylene oxide production system, or from the methanol removal tower in the propylene oxide production process.

[0038] The number of adsorption towers set in parallel is 3 to 5.

[0039] The condensation recovery unit includes a condenser 2 and a gas-liquid separator 3 connected in sequence; the inlet of the condenser 2 is connected to the bottom of the adsorption tower 1 via a pipeline; the gas outlet of the gas-liquid separator 3 is connected to the regeneration gas supply unit and the flare system via pipelines, and the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in propylene oxide production.

[0040] The regenerated gas supply unit includes a nitrogen subsystem 5 and a heater 4. The nitrogen subsystem 5 is connected to a nitrogen source to provide fresh nitrogen. The heater 4 is installed on the pipeline connecting the nitrogen subsystem 5 and the adsorption purification unit to heat the gas. The gas outlet of the gas-liquid separator 3 is connected to the pipeline between the heater 4 and the nitrogen subsystem 5 through a pipeline to allow the non-condensable gas to be recycled.

[0041] Example 1 As attached Figure 1 As shown, this embodiment discloses a system for deep propylene oxide dealdehyde removal of the present invention, which includes an adsorption purification unit and a regeneration gas supply unit. The adsorption purification unit is used to adsorb impurities in the feed liquid through an adsorbent to obtain a purified product; it includes an adsorption tower 1, the bottom of which is connected to a feed liquid conveying line; the feed liquid conveying line is connected from the crude distillation unit in the propylene oxide production system, or from the methanol removal tower in the propylene oxide production.

[0042] The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0043] This invention features a highly modular system that can be directly integrated with existing production facilities, achieving deep desulfurization without requiring large-scale modifications to the original process. This integration method simplifies the process, effectively reducing new investment and implementation difficulty. It facilitates rapid deployment and application in existing facilities, is easy to operate and maintain, and possesses excellent engineering applicability and promotional value.

[0044] Example 2 As attached Figure 1 As shown, this embodiment discloses a system for deep propylene oxide dealdehyde removal of the present invention, which includes an adsorption purification unit and a regeneration gas supply unit. The adsorption purification unit is used to adsorb impurities in the feed liquid using an adsorbent to obtain a purified product. It includes one or more adsorption towers 1 connected in parallel, with a feed liquid conveying line connected to the bottom of each tower. This feed liquid conveying line originates from the crude distillation unit in the propylene oxide production system or from the methanol removal tower in propylene oxide production. Preferably, the number of adsorption towers connected in parallel is 3 to 5.

[0045] The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0046] This embodiment 2 provides a more preferred technical solution based on embodiment 1. Specifically, the number of adsorption towers 1 is limited to one or more; when there are multiple towers, they are connected in parallel; and the bottom of each adsorption tower 1 is connected to a feed liquid conveying line; this feed liquid conveying line is connected from the crude distillation unit in the propylene oxide production system, or from the methanol removal tower in the propylene oxide production process. This embodiment improves the adaptability and reliability of the adsorption separation process through the synergistic effect of parallel connection, flexible access of multiple feedstocks, and precise temperature control, thereby optimizing the overall separation efficiency and operational stability.

[0047] Example 3 As attached Figure 1 As shown, this embodiment discloses a system for deep propylene oxide dealdehyde removal of the present invention, which includes an adsorption purification unit and a regeneration gas supply unit. The adsorption purification unit is used to adsorb impurities in the feed liquid using an adsorbent to obtain a purified product. It includes one or more adsorption towers 1 connected in parallel, with a feed liquid conveying line connected to the bottom of each tower. This feed liquid conveying line originates from the crude distillation unit in the propylene oxide production system or from the methanol removal tower in propylene oxide production. Preferably, the number of adsorption towers connected in parallel is 3 to 5.

[0048] The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0049] The system also includes a condensation recovery unit, which includes a condenser 2 and a gas-liquid separator 3 connected in sequence; the inlet of the condenser 2 is connected to the bottom of the adsorption tower 1 via a pipeline. The gas outlet of the gas-liquid separator 3 is connected to the regeneration gas supply unit and the flare system via pipelines, while the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in propylene oxide production.

[0050] This embodiment 3 provides a more preferred technical solution based on embodiment 2. Specifically, the system further includes a condensation recovery unit, which comprises a condenser 2 and a gas-liquid separator 3 connected in sequence; the inlet of the condenser 2 is connected to the bottom of the adsorption tower 1 via a pipeline; the gas outlet of the gas-liquid separator 3 is connected via pipelines to the regeneration gas supply unit and the flare system, respectively, and the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in propylene oxide production. This embodiment, by setting up a condensation recovery unit, condenses and separates the components in the gas discharged from the adsorption tower, realizing the recovery of valuable liquid components and their introduction into subsequent distillation or production units. Simultaneously, the separated gas is reused for regeneration or safe incineration, thereby improving resource utilization efficiency, reducing waste emissions, and enhancing the system's environmental friendliness and economy.

[0051] Example 4 As attached Figure 1 As shown, this embodiment discloses a system for deep propylene oxide dealdehyde removal of the present invention, which includes an adsorption purification unit and a regeneration gas supply unit. The adsorption purification unit is used to adsorb impurities in the feed liquid using an adsorbent to obtain a purified product. It includes one or more adsorption towers 1 connected in parallel, with a feed liquid conveying line connected to the bottom of each tower. This feed liquid conveying line originates from the crude distillation unit in the propylene oxide production system or from the methanol removal tower in propylene oxide production. Preferably, the number of adsorption towers connected in parallel is 3 to 5.

[0052] The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

[0053] The system also includes a condensation recovery unit, which includes a condenser 2 and a gas-liquid separator 3 connected in sequence; the inlet of the condenser 2 is connected to the bottom of the adsorption tower 1 via a pipeline. The gas outlet of the gas-liquid separator 3 is connected to the regeneration gas supply unit and the flare system via pipelines, while the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in propylene oxide production.

[0054] The regenerated gas supply unit includes a heater 4 and a nitrogen subsystem 5, wherein the nitrogen subsystem 5 is connected to a nitrogen source to provide fresh nitrogen; the heater 4 is installed on the pipeline connecting the nitrogen subsystem 5 and the adsorption purification unit to heat the gas; the gas outlet of the gas-liquid separator 3 is connected to the pipeline between the heater 4 and the nitrogen subsystem 5 through a pipeline to enable the non-condensable gas to be recycled.

[0055] This embodiment 4 provides a more preferred technical solution based on embodiment 3. Specifically: the regenerated gas supply unit includes a heater 4 and a nitrogen subsystem 5, wherein the nitrogen subsystem 5 is connected to a nitrogen source to provide fresh nitrogen; the heater 4 is installed on the pipeline connecting the nitrogen subsystem 5 and the adsorption purification unit to heat the gas; the gas outlet of the gas-liquid separator 3 is connected to the pipeline between the heater 4 and the nitrogen subsystem 5 via a pipeline to allow the non-condensable gas to be recycled. This embodiment achieves the recycling of non-condensable gas by recovering the non-condensable gas from the gas-liquid separator and mixing it into the regenerated gas supply pipeline, thereby significantly reducing the consumption of fresh nitrogen and improving system energy efficiency.

[0056] Example 5 This embodiment discloses a method for deep dealdehyde removal from propylene oxide, the process flow of which is attached. Figure 2 As shown. The propylene oxide liquid used as feedstock comes from the crude propylene oxide distillation unit of a petrochemical plant, and its aldehyde impurity content is about 20 ppm and its water content is about 50 ppm.

[0057] The feed liquid was pressurized to 0.1 MPa using a liquid metering pump and then fed into the adsorption purification unit for formaldehyde removal in adsorption tower 1, which was filled with adsorbent. The adsorbent was a composite system of activated alumina and 5A molecular sieve at a mass ratio of 2:1. The adsorption operation was carried out at 20°C with a volume hourly space velocity (VHSV) of 9 h⁻¹. -1 The continuous injection time was 3 hours.

[0058] After adsorption treatment, propylene oxide product after aldehyde removal was obtained from the top of adsorption tower 1. Gas chromatography analysis showed that its aldehyde content was 4.4 ppm, meeting the technical requirement of less than 10 ppm.

[0059] Once the adsorbent is saturated, feeding is stopped and liquid is drained. Subsequently, nitrogen is used as the regeneration gas to purge and regenerate the adsorption bed at a high temperature of 185°C for 1.5 hours to achieve impurity desorption.

[0060] The regenerated gas flowing from the bottom of adsorption tower 1 is sent to the condensation and recovery unit. After being cooled by condenser 2, it enters gas-liquid separator 3, where condensate and non-condensable gas are separated. The condensate is returned to the propylene oxide crude distillation unit of the petrochemical plant to recover the propylene oxide.

[0061] After the non-condensable gas is pressurized by the blower, most of it, about 80%, is returned to the regenerated nitrogen inlet for reuse, while about 1 / 5 of the regenerated gas is discharged to the flare. At the same time, pure nitrogen is added from the nitrogen subsystem 5 to replenish the discharged gas volume into the regenerated nitrogen cycle.

[0062] The regenerated adsorption tower 1 can be reused for adsorption operations. Multiple runs have shown that the aldehyde content in the propylene oxide product can be stably maintained below 5 ppm. Calculations show that the single-pass acetaldehyde removal rate in this embodiment reaches 86.3%, and the propylene oxide yield is 97.8%.

[0063] Example 6 This embodiment discloses a method for deep dealdehyde removal from propylene oxide, the process flow of which is attached. Figure 3 As shown, crude propylene oxide produced by the methanol removal tower of a propylene oxide production plant is used as the feed liquid. The temperature is approximately 32°C, the pressure is approximately 0.8 MPa, and its aldehyde content is 116 ppm and water content is 42 ppm. This feed liquid is directly introduced into adsorption tower 1 for aldehyde removal treatment.

[0064] The adsorption system consists of three adsorption towers operating in parallel. The feed liquid enters from the bottom of the tower, and after adsorption, the product propylene oxide is obtained from the top of the tower. Testing revealed that the aldehyde content in the propylene oxide product is 5.1–6.6 ppm.

[0065] The volumetric space velocity (VHSV) of the feed liquid entering the tower is 10.5 h⁻¹. -1 The adsorption time for a single tower is 8 hours. The adsorbent is a composite system of activated alumina, 5A, and ZSM-5 molecular sieves, with a mass ratio of 2:2:1. After adsorption, feeding is stopped, and the residual liquid is discharged from the bottom of adsorption tower 1 and temporarily stored in gas-liquid separator 3.

[0066] Once adsorption tower 1 is saturated, it enters the regeneration stage. Nitrogen gas, supplied by the regeneration gas supply unit, enters from the top of adsorption tower 1 to regenerate the adsorbent. The regeneration process consists of two stages: first, a high-temperature purging process is performed at 190 °C to desorb the adsorbed aldehyde impurities; then, a room-temperature purging process is initiated to cool adsorption tower 1 to room temperature. The total regeneration time is approximately 16 hours. During the regeneration period, the remaining adsorption towers in adsorption tower 1 are sequentially switched to the adsorption step to ensure continuous production.

[0067] During the regeneration process, the regeneration gas flowing out from the bottom of adsorption tower 1 is cooled by condenser 2 and then enters gas-liquid separator 3, where condensate and non-condensable gas are separated. The resulting condensate is pumped back to the inlet of the acetaldehyde removal tower by a liquid transfer pump to recover propylene oxide.

[0068] After the non-condensable gas is pressurized by the blower, most of it, about 80%, is returned to the regenerated nitrogen inlet for reuse, while about 1 / 5 of the regenerated gas is discharged to the flare. At the same time, pure nitrogen is added from the nitrogen subsystem 5 to replenish the discharged gas volume into the regenerated nitrogen cycle. After the above process, the aldehyde removal rate in this embodiment is 94.7%, and the propylene oxide yield is 98.9%.

[0069] The above description is merely a preferred embodiment of the invention and does not constitute any limitation on the invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the invention and within the spirit and principles of the invention shall still fall within the protection scope of the invention's technical solution.

Claims

1. A method for deep dealdehyde removal from propylene oxide, characterized in that, Includes the following steps: S1. Adsorption step: The raw material liquid is passed through an adsorption tower containing adsorbent, where aldehyde impurities are adsorbed by the adsorbent, and refined propylene oxide product is obtained from the top of the adsorption tower; the raw material liquid is propylene oxide liquid containing aldehyde impurities; S2. Drainage procedure: Once the adsorbent is saturated, stop feeding and drain the residual liquid from the bottom of the adsorption tower. S3. Regeneration step: Nitrogen gas is introduced into the adsorption tower to regenerate the adsorption bed by high-temperature purging.

2. The method for deep dealdehyde removal from propylene oxide according to claim 1, characterized in that, The aldehyde impurity content in the raw material liquid is 10~200ppm, and the aldehyde substances include at least one of formaldehyde, acetaldehyde, and propionaldehyde; the aldehyde impurity content in the refined propylene oxide product is less than 10ppm.

3. The method for deep dealdehyde removal from propylene oxide according to claim 1, characterized in that, At least two adsorption towers are operated in parallel, with one or more adsorption towers performing the adsorption step while the other one or more adsorption towers perform the drainage step or the regeneration step. Preferably, the adsorbent comprises activated alumina and at least one of 5A, ZSM-5 or 13X molecular sieves.

4. A method for deep dealdehyde removal from propylene oxide according to any one of claims 1-3, characterized in that, When the feed liquid is adsorbed in the adsorption tower, the pressure is 0.1~10 MPa and the temperature is 5~40℃; Volumetric hourly space velocity (VHSV) is 0.5–24 h⁻¹. -1 Preferably 4~16 h -1 ; The adsorption time is 0.5~16h.

5. The method for deep dealdehyde removal from propylene oxide according to claim 1, characterized in that, In the regeneration step, the gas generated by high-temperature purging is condensed and separated into condensate and non-condensable gas; most of the non-condensable gas is returned to the regeneration step for recycling, and a small portion is sent to the flare system for processing. Preferably, nitrogen is used for room temperature purging after high-temperature purging; More preferably, the high-temperature purging temperature is the regeneration temperature at which the adsorbed impurities are desorbed, and the room-temperature purging temperature is the temperature at which the adsorption tower is restored to room temperature. More preferably, the nitrogen high-temperature purging temperature is 100~250℃, more preferably 150~190℃, and the purging time is 0.5~24h.

6. The method for deep dealdehyde removal from propylene oxide according to claim 5, characterized in that, The feed liquid comes from the crude distillation unit, and the condensate obtained from the separation is sent back to the crude distillation unit for recycling. Alternatively, the feed liquid may be crude propylene oxide produced from the methanol removal tower in propylene oxide production; the separated condensate may be sent to the acetaldehyde removal process in propylene oxide production.

7. A system for deep dealdehyde removal from propylene oxide using the method according to any one of claims 1-6, characterized in that, Includes an adsorption purification unit and a regenerated gas supply unit; The adsorption purification unit is used to adsorb impurities in the feed liquid using an adsorbent to obtain a purified product. The regeneration gas supply unit is connected to the adsorption purification unit and is used to supply nitrogen gas for regeneration to the adsorption purification unit.

8. A propylene oxide deep dealdehyde removal system according to claim 7, characterized in that, The adsorption purification unit includes one or more adsorption towers (1) arranged in parallel, and each adsorption tower (1) is connected to a raw material liquid conveying line at its bottom; preferably, the raw material liquid conveying line is connected from the crude distillation unit in the propylene oxide production system, or from the methanol removal tower in the propylene oxide production. Preferably, the number of adsorption towers arranged in parallel is 3 to 5.

9. A propylene oxide deep dealdehyde removal system according to claim 7, characterized in that, The system also includes a condensation recovery unit, which includes a condenser (2) and a gas-liquid separator (3) connected in sequence. The inlet of the condenser (2) is connected to the bottom of the adsorption tower (1) via a pipe; The gas outlet of the gas-liquid separator (3) is connected to the regeneration gas supply unit and the flare system via pipelines, and the liquid outlet is connected to the crude distillation unit or the acetaldehyde removal tower in the production of propylene oxide.

10. A deep propylene oxide dealdehyde removal system according to claim 9, characterized in that, The regenerated gas supply unit includes a heater (4) and a nitrogen subsystem (5), wherein the nitrogen subsystem (5) is connected to a nitrogen source to provide fresh nitrogen; the heater (4) is installed on the pipeline connecting the nitrogen subsystem (5) and the adsorption purification unit to heat the gas; the gas outlet of the gas-liquid separator (3) is connected to the pipeline between the heater (4) and the nitrogen subsystem (5) through a pipeline to enable the non-condensable gas to be recycled.

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