A method and system for refining a polyether

Abstract

The application discloses a refining method and system of polyether, and the refining method comprises the following steps: (1) polyether crude and stripping steam I are reversely contacted in a stripping tower I to perform primary stripping; and (2) the tower bottom material of the stripping tower I is introduced into a stripping tower II and reversely contacted with stripping steam II to perform secondary stripping. The method and system mainly solve the problems of high refining cost, complex process, ineffective separation of components, poor product quality, poor stability between product batches and the like in the high-molecular polyether polyol industry.

Description

Technical Field

[0001] This invention belongs to the field of polyethers, and particularly relates to the purification of polyethers. Background Technology

[0002] Polymer polyols are important high-molecular materials and a major raw material for the production of polyurethane products, which are widely used in coatings, elastomers, polyurethane foams, and other fields. Currently, with global economic development and industrial progress, the demand for high-performance materials continues to grow. Industries such as automotive, construction, and electronics have an increasingly urgent need for high-strength, wear-resistant, and corrosion-resistant materials, and polyether polyols and high-molecular-weight polymer polyols, as important precursor materials, have huge market demand. Therefore, improving product quality, stability, and controllability to meet market demand for high-quality products is crucial for companies to gain market share and maintain a competitive advantage.

[0003] However, monomer or oligomer residues often remain during the preparation of polymer polyols. These residues can reduce the performance and stability of the final product, limiting its application range. Therefore, developing an efficient and environmentally friendly polyether refining process to improve the purity and stability of polyols is of great significance for improving product quality, reducing production costs, and enhancing market competitiveness. In recent years, many researchers have studied the refining process of polymer polyols and proposed various methods and technologies. However, in general, polyether refining processes still suffer from problems such as complex operation, low efficiency, high energy consumption, and certain environmental impacts.

[0004] CN108239277B discloses a method for purifying polyether polyols. Through crystallization, drying, filtration, and adsorption, this method can effectively remove monomers and oligomers at relatively low temperatures, thus obtaining a low-odor polyether polyol product. However, due to drawbacks such as complex process flow and high operational complexity, this method cannot strictly guarantee the stability of the product in practical applications, thereby limiting its application to some extent.

[0005] CN101775132A discloses an adsorption purification method for polyether polyols. This method involves using 1.0-1.5% water (by mass fraction of the crude product) and two other adsorbents for 2-3 adsorption cycles, resulting in the filtration of low-odor polyether polyols. The adsorbents used are magnesium silicate and diatomaceous earth. However, due to the excessive number of adsorption cycles, the purification cost is high, thus limiting the practical application value of this method.

[0006] CN106589345B discloses a method for refining polyether to reduce VOC content and odor. The method uses an adsorbent accounting for 1.0-1.5% of the crude product by mass to remove moisture and low-boiling substances from the polyether polyol under vacuum conditions and heating. This method can ensure that potassium and sodium ions are adsorbed and removed while reducing the odor and VOC content of the polyether polyol. However, the vacuum equipment used has high technical requirements, which increases production costs and operational difficulty.

[0007] CN109851769B discloses a method for treating polyether polyols using a composition of ion exchange resin and adsorbent, which can obtain high-quality polyether polyols with total Na and K content below 5 ppm and aldehyde content below 5 ppm. At the same time, it can also achieve 95% recycling of polyether polyols in filter residue, greatly reducing solid waste generation.

[0008] CN113908834B discloses a method for preparing an aldehyde removal catalyst and a corresponding polyether polyol refining technology. By using a catalyst with titanium salt and iron salt as active components, impurities such as formaldehyde, acetaldehyde, acrolein, acetone, and propionaldehyde can be effectively removed during the polyether polyol refining process to prepare low-aldehyde, low-color polyether polyols.

[0009] CN116640359A discloses a method for separating and recovering byproducts from the purification of polyether polyols. The method uses water as a separation solvent and achieves the separation and recovery of polyether polyol products, solid salts, and solid adsorbents by adjusting the temperature of the mixture of byproducts and water. This method has certain advantages in improving the economic efficiency and operational stability of byproduct separation. However, due to the different solubilities of various polyether polyols in water, the components cannot be well separated in water. Summary of the Invention

[0010] In order to overcome the problems existing in the prior art, the present invention provides a method and system for refining polyethers, which mainly solves the problems of high cost, complex process, ineffective separation of components, poor product quality and poor batch-to-batch stability in the polyether polyol industry.

[0011] One of the objectives of this invention is to provide a method for refining polyether, comprising: (1) stripping crude polyether in a stripping tower I by counter-current contact with stripping steam I; and (2) stripping the bottom material of stripping tower I into stripping tower II by counter-current contact with stripping steam II.

[0012] In a preferred embodiment, in step (1), the stripping steam I is selected from at least one of water vapor and organic alcohol vapor, preferably organic alcohol vapor.

[0013] In a further preferred embodiment, the organic alcohol vapor is selected from C1 to C6 organic alcohol vapors, preferably from methanol vapor and / or ethanol vapor.

[0014] In a further preferred embodiment, the weight ratio of the crude polyether to the stripping steam I is 10 to 50, preferably 30 to 35, for example 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0015] In this invention, it is not necessary to remove aldehydes from the high-viscosity crude polyether. Instead, a large amount of stripping steam I is used to directly strip the crude polyether to remove impurities (such as aldehydes). This method of aldehyde removal is highly efficient and causes very little loss of the crude polyether.

[0016] In a preferred embodiment, the crude polyether enters the stripping tower I from the top or top, and the stripping steam I enters the stripping tower I from the middle or lower middle.

[0017] In a further preferred embodiment, the overhead gas of the stripping tower I is cooled and then subjected to formaldehyde removal treatment to obtain formaldehyde-removed condensate. The formaldehyde-removed condensate is evaporated to form stripping steam I, which enters the stripping tower I.

[0018] Although a relatively large amount of stripping steam I is used in the primary stripping process of this invention, it does not result in material consumption because the steam after the primary stripping is recovered and recycled back to the first stripping tower. The overhead gas of the first stripping tower is recycled back to the first stripping tower after aldehyde removal treatment. The inventors have found through extensive experiments that cooling the overhead gas of the first stripping tower before aldehyde removal treatment can significantly improve the aldehyde removal efficiency.

[0019] In a further preferred embodiment, the overhead gas of the stripping tower I is cooled by exchanging heat with the crude polyether product and the stripping steam II.

[0020] The method of exchanging heat with the crude polyether and the stripping steam II not only cools the overhead gas of stripping tower I, but also heats the crude polyether and the stripping steam II, thereby further improving the efficiency of primary and secondary stripping.

[0021] In a preferred embodiment, the formaldehyde removal treatment is carried out by adsorption, membrane separation, or catalysis by a formaldehyde removal agent.

[0022] The methods used for formaldehyde removal, such as adsorption, membrane separation, or catalysis with formaldehyde-removing agents, are not particularly limited and can be any method disclosed in the prior art. For example, when using a formaldehyde-removing agent for catalysis, the formaldehyde-removing agent can be selected from any catalyst disclosed in the prior art that can be used to remove or eliminate aldehydes, preferably a manganese oxide molecular sieve of the hydrated manganese oxide type, such as a solid-phase Ce-δ-MnO2 molecular sieve catalyst.

[0023] In a preferred embodiment, in step (2), the stripping steam II is selected from at least one of compressed air and protective gas, preferably, the protective gas is selected from one or more of nitrogen and inert gas.

[0024] In a further preferred embodiment, in step (2), the weight ratio of the crude polyether to the stripping steam II is 8 to 20, preferably 12 to 15, for example 8, 10, 12, 14, 16, 18 or 20.

[0025] In this process, a large amount of stripping steam II is used for secondary stripping.

[0026] In a preferred embodiment, the bottom material I of the stripping tower I enters the stripping tower II from the top or top, and the stripping steam II enters the stripping tower II from the middle or lower middle.

[0027] In a preferred embodiment, the overhead material II of the stripping tower II is cooled and separated into the overhead gas phase and the overhead condensate of the stripping tower II, and the refined polyether product is collected from the bottom of the stripping tower II.

[0028] In a further preferred embodiment, the gas phase at the top of the stripping tower II is mixed with compressed air and / or a protective gas to form a mixture II, which is then heated II to form stripping steam II, and the stripping steam II is recycled back to the middle or lower middle part of the stripping tower II.

[0029] In a further preferred embodiment, the heating II is carried out by heat exchange with the top material I of the stripping tower I.

[0030] In a preferred embodiment, the top material I of the stripping tower I is cooled and then mixed with the condensate from the top of the stripping tower II and optionally water and / or organic alcohol to form a mixture I. The mixture I is then heated and treated by a steam generator to obtain stripping steam I, which is then recycled back to the middle or lower middle section of the stripping tower I.

[0031] In a further preferred embodiment, the top material I of the stripping tower I is cooled by heat exchange treatment with the crude polyether product before entering the stripping tower I and the mixture II before entering the stripping tower II.

[0032] In a preferred embodiment, stripper I and stripper II are packed towers or plate towers.

[0033] In a further preferred embodiment, an open material distributor (connected to the liquid inlet of each of stripper tower I and stripper tower II) is provided on the first section of packing or the first plate from top to bottom.

[0034] In a further preferred embodiment, an open-ended material distributor is optionally provided between each section of packing or adjacent plates. In a preferred embodiment, the refining method includes:

[0035] (a) After being heated by I, the crude polyether enters the stripping tower I from the top or top, and the stripping steam I enters the stripping tower I from the middle or lower middle part; the crude polyether after heating I (preferably uniformly distributed in the stripping tower I by the material distributor in the stripping tower I) comes into counter-current contact with the stripping steam I.

[0036] (b) The bottom material I of stripping tower I enters stripping tower II from the top or top, and the stripping steam II enters stripping tower II from the middle or lower middle part; the bottom material I of stripping tower I (preferably uniformly distributed in stripping tower II via a material distributor in stripping tower II) is in counter-current contact with stripping steam II.

[0037] (c) The overhead material II of stripper II is cooled and separated into overhead gas phase and overhead condensate of stripper II in sequence. Refined polyether is collected from the bottom of stripper II. The overhead gas phase of stripper II is mixed with compressed air and / or protective gas to form mixture II. The mixture II is heated to form stripping steam II (entering stripper II from the middle or lower part).

[0038] (d) The top material I of the stripping tower I is cooled and then mixed with the condensate at the top of the stripping tower II and optionally water and / or organic alcohol to form a mixture I. The mixture I is then subjected to a formaldehyde removal process and a steam generator to form the stripping steam I (which enters the stripping tower I from the middle or lower part).

[0039] In a further preferred embodiment, the crude polyether product and the mixture II each independently exchange heat with the overhead material I of the stripping tower I, thereby achieving the heating I of the crude polyether product, the heating II of the mixture II, and the cooling of the overhead material I of the stripping tower I.

[0040] In a preferred embodiment, the operating pressure of the stripping tower I is 0.1–20 kPaA, and the operating temperature of the stripping tower I is 65–120°C.

[0041] For example, the operating pressure of the stripping tower I is 0.1 kPaA, 0.5 kPaA, 0.8 kPaA, 1 kPaA, 2 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, 12 kPaA, 15 kPaA, 18 kPaA, or 20 kPaA, and the operating temperature of the stripping tower I is 65°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C.

[0042] In a further preferred embodiment, the operating pressure of the stripping tower I is 0.5–16 kPaA, and the operating temperature of the stripping tower I is 83–116 °C.

[0043] In a preferred embodiment, the operating pressure of the stripping tower II is 0.1–18 kPaA, and the operating temperature of the stripping tower II is 79–111°C.

[0044] For example, the operating pressure of the stripping tower II is 0.1 kPaA, 0.5 kPaA, 0.8 kPaA, 1 kPaA, 2 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, 12 kPaA, 15 kPaA, or 18 kPaA, and the operating temperature of the stripping tower II is 79, 80, 90, 100, 110, or 111°C.

[0045] In a further preferred embodiment, the operating pressure of the stripping tower II is 0.4–15 kPaA, and the operating temperature of the stripping tower II is 83–109°C.

[0046] In a preferred embodiment, the temperature of stripping tower I is controlled to be higher than the temperature of stripping tower II.

[0047] A second objective of this invention is to provide a polyether refining system, preferably used for the method described in one objective of this invention. The refining system includes a stripping tower I and a stripping tower II. A crude polyether inlet is provided at the upper part or top of the stripping tower I, and a stripping steam inlet I is provided at the middle or lower part of the stripping tower I. The bottom of the stripping tower I is connected to the upper part or top of the stripping tower II via a pipeline. A stripping steam inlet II is provided at the middle or lower part of the stripping tower II, and a refined polyether product external sampling pipeline is provided at the bottom of the stripping tower II.

[0048] In a preferred embodiment, a cooler and a condensate tank are sequentially arranged at the top of the stripping tower II.

[0049] In a further preferred embodiment, the system further includes compressed air and / or protective gas delivery pipelines, and a stripping tower II overhead gas phase delivery pipeline and a stripping tower II overhead condensate delivery pipeline are provided on the condensate tank. The stripping tower II overhead gas phase delivery pipeline and the compressed air and / or protective gas delivery pipeline are combined to form a mixture II delivery pipeline.

[0050] In a further preferred embodiment, the mixture II conveying pipeline is connected to the stripping steam II inlet on the stripping tower II.

[0051] In a preferred embodiment, a crude polyether feed line is provided at the crude polyether feed inlet of the stripping tower I.

[0052] In a preferred embodiment, the top of the stripping tower I is provided with a stripping tower I top material I conveying pipeline, and the system further includes water and / or organic alcohol feed pipelines.

[0053] In a further preferred embodiment, the overhead material I conveying pipeline of the stripping tower I is combined with the water and / or organic alcohol feed pipeline and the overhead condensate conveying pipeline of the stripping tower II to form the mixed material I conveying pipeline.

[0054] In a further preferred embodiment, a formaldehyde removal device and a steam generator are sequentially arranged on the pipeline for conveying the mixture I, and a formaldehyde removal catalyst is packed inside the formaldehyde removal device.

[0055] In a preferred embodiment, the system further includes heat exchanger one and heat exchanger two, each independently including a cold medium passage and a hot medium passage.

[0056] In a further preferred embodiment, the crude polyether feed line is connected to the cold medium channel of heat exchanger one, and the overhead material I conveying line of stripping tower I is connected to the hot medium channel of heat exchanger one; and / or, the mixed material II conveying line is connected to the cold medium channel of heat exchanger two, and the overhead material I conveying line of stripping tower I is connected to the hot medium channel of heat exchanger two.

[0057] In this process, the crude polyether product and the overhead material I of stripping tower I exchange heat in heat exchanger one, while the mixed material II and the overhead material I of stripping tower I exchange heat in heat exchanger two.

[0058] In a preferred embodiment, stripper I and stripper II are packed towers or plate towers.

[0059] In a further preferred embodiment, an open material distributor (connected to the liquid inlet of each of stripper tower I and stripper tower II) is provided on the first section of packing or the first plate from top to bottom.

[0060] In a further preferred embodiment, an open material distributor is optionally provided between each section of packing or adjacent plates.

[0061] In a preferred embodiment, each of the stripping tower I and stripping tower II has an independent discharge pump installed on its respective discharge pipeline.

[0062] In a further preferred embodiment, a residual content detector is independently installed at the outlet of each discharge pump of the stripping tower I and the stripping tower II.

[0063] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) Compared with other processes, the present invention uses a secondary stripping refining process, which does not require the introduction of adsorbents and adsorption equipment in the process, thereby solving the problems of high adsorbent cost, difficult technical requirements of adsorption equipment, and ineffective separation of adsorbent and product in the refining process of polyether polyol industry.

[0066] (2) The system and process described in this invention can achieve continuous refining of crude polyether products, and use steam and nitrogen as two-stage stripping steam, which is inexpensive, highly automated, time-saving and efficient.

[0067] (3) The device and process described in this invention can realize the recycling of two stages of stripping steam in the process, thereby saving the consumption of steam materials. At the same time, through the heat exchange network design between steam and polyether products, the energy utilization efficiency of the overall process system can be effectively improved.

[0068] (4) The polyether polyols obtained by the method and system described in this invention have the advantages of high purity and high yield, wherein aldehyde impurities can reach the PPM level;

[0069] (5) When the method and system described in this invention are used for continuous operation, the batch quality of the product is highly stable, and the purity deviation of each batch of polyether is ±1%. Attached Figure Description

[0070] Figure 1 A schematic diagram of the system described in this invention is shown.

[0071] 101 Polyether crude product feed, 102 Heated crude product feed, 103 Stripping tower I bottom material I, 104 Stripping tower I top material I, 105 Stripping tower I top material I primary condensate, 106 Stripping tower I top material I secondary condensate, 107 Mixed material I, 108 Formaldehyde-removed mixed material I, 109 Stripping steam I, 110 Stripping tower II feed, 201 Stripping tower II bottom product, 202 Refined polyether, 203 Stripping tower II top material II, 204 Stripping tower II top material II coolant, 205 Stripping tower II top condensate, 206 Stripping tower II top vapor, 207 Mixed material II, 208 Stripping steam II.

[0072] E1 Heat Exchanger I, E2 Heat Exchanger II, E3 Steam Generator, E4 Cooler, P3 Stripping Tower II Top Vapor Pump, T1 Stripping Tower I, T2 Stripping Tower II, V1 Dealdehyde Removal Unit, V2 Condensate Tank.

[0073] In this invention, the crude polyether product feed 101 is heated by heat exchanger E1 and then fed into stripping tower I T1, where it undergoes stripping purification with stripping steam I 109. The bottom material I 103 of stripping tower I is fed into stripping tower II for secondary stripping; the top material I 104 of stripping tower I is cooled by heat exchanger E1 and heat exchanger E2 and then mixed with the top condensate 205 of stripping tower II, optional water and / or organic alcohol to form a mixture I 107, which is then sequentially fed into the formaldehyde removal unit V1 and the steam generator E3 to generate stripping steam I 109.

[0074] The feed 110 from stripper II undergoes secondary stripping purification with stripping steam II 208. The overhead material II 203 from stripper II is cooled by the overhead cooler E4 and then enters the condensate tank V2 for gas-liquid separation. The overhead gas phase 206 from stripper II is sent to heat exchanger II E2 via overhead gas phase pump P3 with compressed air and / or protective gas (e.g., nitrogen) to form stripping steam II 208 after heating. The overhead condensate 205 from stripper II is mixed with the secondary condensate 106 from the overhead material I of stripper I after water replenishment. Detailed Implementation

[0075] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0076] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0077] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0078] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0079] The following embodiments use Figure 1 The system shown performs:

[0080] The crude polyether product enters the stripping tower I from the top, and the stripping steam I enters the stripping tower I from the middle and lower parts. The crude polyether product feed 101 exchanges heat with the top material I 104 of the stripping tower I through heat exchanger E1 and is then sent to the stripping tower IT1, where it undergoes stripping purification with the stripping steam I 109. The bottom material I 103 of the stripping tower I is sent to the stripping tower II for secondary stripping via the bottom discharge pump P1. The top material I 104 of the stripping tower I passes through heat exchanger E1 and heat exchanger E2 in sequence, exchanging heat with the crude polyether product feed 101 and mixture II 207, and then mixes with the top condensate 205 of the stripping tower II, optional water and / or organic alcohol to form mixture I 107. The mixture I 107 is then sent to the formaldehyde removal unit V1 and the steam generator E3 in sequence, thereby generating stripping steam I 109.

[0081] The bottom material I of stripper I enters stripper II from the top, and the stripping steam II enters stripper II from the middle and lower parts. The feed 110 of stripper II undergoes secondary stripping purification with the stripping steam II 208. The bottom product 201 of stripper II is discharged via bottom product pump P2; the top material II 203 of stripper II is cooled by the top cooler E4 and then enters the condensate tank V2 for gas-liquid separation. The top gas phase 206 of stripper II and nitrogen are sent to heat exchanger E2 via the top gas phase pump P3, where they are heated to form stripping steam II 208 (which enters stripper II). The top condensate 205 of stripper II is supplemented with optional water and / or organic alcohol and then mixed with the secondary condensate 106 of the top material I of stripper I.

[0082] The formaldehyde removal device V1 is filled with a formaldehyde removal agent, which is a solid-phase Ce-δ-MnO2 molecular sieve catalyst (see Example 1 of CN115364850A for the preparation process).

[0083] Both stripping tower I and stripping tower II are packed towers. An open-ended annular material distributor is installed above the first section of packing. The annular material distributor is connected to the liquid phase feed of stripping tower I and stripping tower II respectively (i.e., the inlet of the crude polyether product in stripping tower I and the inlet of the bottom material I of stripping tower I in stripping tower II).

[0084]

Example 1

[0085] Inside stripping tower I: the stripping steam I is water, the weight ratio of crude polyether to stripping steam I is 35, the operating pressure of stripping tower I is 2 kPaA, and the operating temperature of stripping tower I is 89°C.

[0086] Inside stripper II: the stripping steam II is nitrogen, the weight ratio of crude polyether to stripping steam II is 13, the operating pressure of stripper II is 2 kPaA, and the operating temperature of stripper II is 83°C.

[0087] After continuous operation, this embodiment yielded polyether polyols with an average purity of 99.999%, and aldehyde impurities reached the PPM level. The product quality exhibited high batch-to-batch stability, with polyether purity deviations between batches within ±1%. The average yield of refined polyether polyols was 97%.

[0088]

Example 2

[0089] Inside stripping tower I: the stripping steam I is water, the weight ratio of crude polyether to stripping steam I is 50, the operating pressure of stripping tower I is 8 kPaA, and the operating temperature of stripping tower I is 96°C.

[0090] Inside stripper II: the stripping steam II is nitrogen, the weight ratio of crude polyether to stripping steam II is 20, the operating pressure of stripper II is 8 kPaA, and the operating temperature of stripper II is 80°C.

[0091] After continuous operation, this embodiment yielded polyether polyols with an average purity of 99.62%, and aldehyde impurities reached the PPM level. The product quality exhibited high batch-to-batch stability, with a polyether purity deviation of ±1.5% between batches. The average yield of refined polyether polyols was 97%.

[0092]

Example 3

[0093] Inside stripping tower I: the stripping steam I is water, the weight ratio of crude polyether to stripping steam I is 10, the operating pressure of stripping tower I is 12 kPaA, and the operating temperature of stripping tower I is 90°C.

[0094] Inside stripper II: the stripping steam II is nitrogen, the weight ratio of crude polyether to stripping steam II is 20, the operating pressure of stripper II is 12 kPaA, and the operating temperature of stripper II is 82°C.

[0095] After continuous operation, this embodiment yielded polyether polyols with an average purity of 99.84%, and aldehyde impurities reached the PPM level. The product exhibited high batch-to-batch stability, with a polyether purity deviation of ±1.5% between batches. The average yield of refined polyether polyols was 96.5%.

[0096]

Example 4

[0097] The process of Example 2 is repeated, except that in stripping tower I, the stripping steam I is ethanol, and other conditions remain unchanged.

[0098] After continuous operation, this embodiment yielded polyether polyols with an average purity of 99.999%, and aldehyde impurities reached the PPM level. The product quality exhibited high batch-to-batch stability, with a polyether purity deviation of ±0.5% between batches. The average yield of refined polyether polyols was 97%.

[0099]

Example 5

[0100] The process of Example 3 is repeated, except that in stripping tower I, the stripping steam I is ethanol, and other conditions remain unchanged.

[0101] After continuous operation, this embodiment yielded polyether polyols with an average purity of 99.997%, and aldehyde impurities reached the PPM level. The product exhibited high batch-to-batch stability, with a polyether purity deviation of ±0.5% between batches. The average yield of refined polyether polyols was 97%.

[0102] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for purifying polyether, comprising: (1) The crude polyether product is stripped once by counter-current contact with stripping steam I in stripping tower I. (2) The bottom material of stripping tower I enters stripping tower II and is stripped twice by counter-current contact with stripping steam II.

2. The refining method according to claim 1, characterized in that, In step (1), the stripping steam I is selected from at least one of water vapor and organic alcohol vapor; preferably, the organic alcohol vapor is selected from C1 to C6 organic alcohol vapor, and more preferably from methanol vapor and / or ethanol vapor; And / or, In step (1), the weight ratio of the crude polyether to the stripping steam I is 10 to 50, preferably 30 to 35.

3. The refining method according to claim 1, characterized in that, The crude polyether product enters the stripping tower I from the top or top, and the stripping steam I enters the stripping tower I from the middle or lower middle. Preferably, the overhead gas of the stripping tower I is cooled and then subjected to formaldehyde removal treatment to obtain formaldehyde-removed condensate, which is then evaporated to form stripping steam I, which enters the stripping tower I; more preferably, the overhead gas of the stripping tower I is cooled by exchanging heat with the crude polyether product and the stripping steam II.

4. The refining method according to claim 1, characterized in that, In step (2), the stripping steam II is selected from at least one of compressed air and protective gas, preferably, the protective gas is selected from one or more of nitrogen and inert gas; And / or, In step (2), the weight ratio of the crude polyether to the stripping steam II is 8 to 20, preferably 12 to 15.

5. The refining method according to claim 1, characterized in that, The bottom material I of stripping tower I enters stripping tower II from the top or top, and the stripping steam II enters stripping tower II from the middle or lower middle; and / or, The overhead material II of the stripping tower II is cooled and separated into overhead gas phase and overhead condensate of the stripping tower II after cooling. The refined polyether product is collected from the bottom of the stripping tower II. Preferably, the overhead gas phase of the stripping tower II is mixed with compressed air and / or protective gas to form mixture II. The mixture II is heated by heating II to form stripping steam II. The stripping steam II is recycled back to the middle or lower middle part of the stripping tower II. More preferably, the heating II is carried out by heat exchange with the overhead material I of the stripping tower I.

6. The refining method according to claim 5, characterized in that, The top material I of stripping tower I is cooled and then mixed with the condensate from the top of stripping tower II and optionally water and / or organic alcohol to form mixture I. The mixture I is heated and processed by a steam generator to obtain stripping steam I. The stripping steam I is recycled back to the middle or lower middle part of stripping tower I. Preferably, the top material I of the stripping tower I is cooled by heat exchange with the crude polyether product before entering the stripping tower I and the mixture II before entering the stripping tower II.

7. The refining method according to any one of claims 1 to 6, characterized in that, The operating pressure of stripping tower I is 0.1–20 kPaA, and the operating temperature of stripping tower I is 65–120°C; preferably, the operating pressure of stripping tower I is 0.5–16 kPaA, and the operating temperature of stripping tower I is 83–116°C. And / or, the operating pressure of the stripping tower II is 0.1 to 18 kPaA, and the operating temperature of the stripping tower II is 79 to 111°C; preferably, the operating pressure of the stripping tower II is 0.4 to 15 kPaA, and the operating temperature of the stripping tower II is 83 to 109°C.

8. A polyether refining system, preferably used for the method described in any one of claims 1 to 7, the refining system comprising a stripping tower I and a stripping tower II, wherein a crude polyether inlet is provided at the upper part or top of the stripping tower I, and a stripping steam inlet I is provided at the middle or lower middle part of the stripping tower I; the bottom of the stripping tower I is connected to the upper part or top of the stripping tower II by a pipeline, a stripping steam inlet II is provided at the middle or lower middle part of the stripping tower II, and a refined polyether product external sampling pipeline is provided at the bottom of the stripping tower II; preferably, a crude polyether inlet pipeline is provided at the crude polyether inlet of the stripping tower I; more preferably, the system further comprises compressed air and / or protective gas delivery pipelines, and water and / or organic alcohol inlet pipelines.

9. The refining system according to claim 8, characterized in that, A cooler and a condensate tank are sequentially installed at the top of the stripping tower II; Preferably, a stripping tower II overhead vapor phase conveying pipeline and a stripping tower II overhead condensate conveying pipeline are provided on the condensate tank. The stripping tower II overhead vapor phase conveying pipeline is combined with the compressed air and / or protective gas conveying pipeline to form a mixture II conveying pipeline. More preferably, the mixture II conveying pipeline is connected to the stripping steam II inlet on the stripping tower II.

10. The refining system according to claim 9, characterized in that, The top of the stripping tower I is provided with a top material conveying pipeline of the stripping tower I. Preferably, the overhead material I conveying pipeline of stripping tower I is combined with the water and / or organic alcohol feed pipeline and the overhead condensate conveying pipeline of stripping tower II to form the mixed material I conveying pipeline; More preferably, a formaldehyde removal device and a steam generator are sequentially arranged on the conveying pipeline of the mixture I, and a formaldehyde removal catalyst is filled in the formaldehyde removal device.

11. The refining system according to claim 9 or 10, characterized in that, The system further includes heat exchanger one and heat exchanger two, each of which independently includes a cold medium passage and a hot medium passage; Preferably, the crude polyether feed line is connected to the cold medium channel of heat exchanger one, and the overhead material I conveying line of stripping tower I is connected to the hot medium channel of heat exchanger one; and / or, the mixed material II conveying line is connected to the cold medium channel of heat exchanger two, and the overhead material I conveying line of stripping tower I is connected to the hot medium channel of heat exchanger two.

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