Post-treatment process and device for producing polyol

Abstract

The invention provides a post-treatment process and device for producing polyol, and belongs to the technical field of fine chemical engineering. According to the post-treatment process for producing the polyhydric alcohol, disclosed by the invention, through coupling of rectification and crystallization, the precipitated inorganic salt cannot cause equipment blockage, and water extracted from a rectification tower and fusel with a boiling point lower than that of water are prevented from entraining the polyhydric alcohol through rectification, so that the loss amount of the polyhydric alcohol is reduced; meanwhile, two-stage separation treatment is adopted, so that the purpose of simultaneously separating water, salt, fusel and reaction product polyhydric alcohol is achieved; the device for the post-treatment process for producing the polyhydric alcohol is formed by coupling the rectifying tower at the upper part and the crystallizer at the lower part, the equipment can be continuously and stably operated and can also be switched to intermittent operation at any time, and the treatment capacity is large and flexible; the equipment quantity is reduced, the occupied area is small, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, and in particular to a post-processing process and device for producing polyols. Background Art

[0002] Polyols are alcohol compounds containing two or more hydroxyl groups. Low-level polyols are viscous liquids with a much higher boiling point than monohydric alcohols with the same number of carbon atoms. As the number of hydroxyl groups increases, the water solubility increases. At present, emerging and widely used polyols include 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,3-butanediol, etc. Among them, 1,3-butanediol has a wide range of uses. It can be used to produce plasticizers, unsaturated polyester resins, industrial dehydrating agents, etc.; it can also be used as a humidifier and softener for textiles, tobacco and paper, an antibacterial agent for cheese or meat, etc.; it can also be used in cosmetics as a moisturizer.

[0003] 1,3-Butanediol (1,3-BDO) is a compound with good hygroscopicity and water solubility, and is odorless and low in toxicity. At present, the acetaldehyde condensation method is the mainstream method for preparing 1,3-butanediol. Its production process is as follows: acetaldehyde undergoes condensation reaction in an alkaline aqueous solution to generate 3-hydroxybutyraldehyde, and after adding acid to neutralize the reaction liquid, 1,3-butanediol is generated by hydrogenation.

[0004] If an inorganic base (such as NaOH, KOH aqueous solution, etc.) is used in the condensation reaction of the 1,3-butanediol preparation process, and an inorganic acid (such as sulfuric acid, hydrochloric acid aqueous solution, etc.) is used for neutralization, although the raw material cost is low, inorganic salts (Na2SO4, K2SO4) will be generated. Inorganic salts are soluble in water, and the product 1,3-butanediol and by-product fusel alcohols, light and heavy component impurities are also soluble in water, resulting in the above-mentioned multi-components being homogeneously miscible and unable to be separated by simple liquid-liquid phase separation. In addition, the boiling point of 1,3-butanediol is greater than that of water, and it does not azeotrope with water, so that the target product 1,3-butanediol cannot be obtained from the top of the tower before the water evaporates. See the table below for specific substances:

[0005]

[0006] If only a distillation tower is used for separation, while water is separated from the top of the distillation tower, the inorganic salts dissolved in the water will also precipitate crystals in the tower kettle in proportion. The crystals will quickly block the distillation tower packing, the tower kettle and the reboiler, and continuous operation is impossible. If only a crystallizer is used to evaporate water for desalination, the evaporated condensed water will carry 1,3-butanediol products, resulting in product losses and excessive COD of discharged wastewater. In addition, the crystallizer is operated continuously, and one crystallizer is only equivalent to one theoretical plate, and fusel alcohol cannot be completely removed from the 1,3-butanediol product. In addition, when a large amount of water is evaporated and the water content in the remaining 1,3-butanediol aqueous solution is low, the boiling point of 1,3-butanediol will increase, which will cause the operating temperature of evaporation crystallization to be too high, the residence time of the crystallization operation to be long, and the product 1,3-butanediol is heat-sensitive and easy to deteriorate if it stays too long at high temperature. The suspension of 1,3-butanediol and salt crystals that does not contain water will cool down after leaving the crystallizer. When it drops below 20°C, the viscosity of the suspension will increase sharply to more than 200cp. Too high a viscosity is not conducive to centrifugal or filtration separation of solids.

[0007] Therefore, based on the salt-containing alcohol-water mixed solution produced in the production process of polyols such as 1,3-butanediol, the main research direction of polyol production separation technology is to continuously separate and remove water, salt and fusel alcohol components to avoid equipment blockage, reduce separation energy consumption and reduce operating intensity. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention discloses a post-treatment process and device for producing polyols.

[0009] On the one hand, the present invention proposes a post-treatment process for producing polyols, including a primary separation process and a secondary separation process, wherein the primary separation process and the secondary separation process are both carried out in a device consisting of a distillation tower at the top and a crystallizer at the bottom; a salt-containing alcohol-water mixture is extracted from a portion of water and fusel alcohols having a boiling point lower than that of water through the distillation tower of the primary separation process, and a primary extraction from the crystallizer of the primary separation process enters a secondary separation process, and the remaining water is extracted from the distillation tower of the secondary separation process, and a secondary extraction is obtained from the crystallizer of the secondary separation process.

[0010] In the post-treatment process for producing polyols of the present invention, the primary separation process and the secondary separation process are carried out in a device composed of a distillation tower at the upper part and a crystallizer at the lower part, so as to achieve the effect of simultaneous distillation and crystallization. During separation, since the distillation tower separates part of the water, the water content in the primary produced product and the secondary produced product is lower than the amount of water that can be dissolved by both the inorganic salt and the polyol, and the inorganic salt will reach supersaturation first. Since the lower part of the separation process of the present invention is a crystallizer, the precipitated inorganic salt will not cause equipment blockage, and the distillation tower of the separation process prevents part of the water produced by the primary separation process and the secondary separation process and fusel alcohols with a boiling point lower than that of water from entraining the polyol.

[0011] The present invention achieves the purpose of separating water, salt and polyols at the same time by arranging a primary separation process and a secondary separation process. First, the salty alcohol water enters the primary separation process for rough separation, and after being rectified by the rectifying tower of the primary separation process, a portion of water and byproducts and impurities (such as various fusel alcohols) with boiling points lower than water are extracted. The primary extraction product extracted by the crystallizer of the primary separation process includes polyols, another portion of water, inorganic salts, and light component impurities and heavy component impurities with higher boiling points than water. Secondly, since the primary separation process cannot completely separate the water in the salty alcohol water, the primary extraction product of the crystallizer of the primary separation process is input into the secondary separation process for further dehydration treatment, and the residual water is extracted by the rectifying tower of the secondary separation process. The crystallizer of the secondary separation process obtains the slurry of the secondary extraction product (including inorganic salt crystalline solid, polyols, light component impurities and heavy component impurities with higher boiling points of water) and removes solid salts through centrifugation or filtration separation, completing the desalination and initial separation process. The crude polyol obtained by desalination does not contain inorganic salts and can be sent to other subsequent processes for further refining to obtain a final high-purity product. The post-treatment process for producing polyols of the present invention is at least two-stage, otherwise under continuous operation, the crystallizer is a fully mixed flow container, and water and salt cannot be completely removed.

[0012] Optionally, a two-stage or more separation process can be used under the following working conditions. For example, (1) when the salt content in the salt-containing alcohol aqueous solution to be separated is high and the solid content needs to be controlled at each stage to avoid clogging the pipeline, or when the solid-liquid separation equipment is frequently shut down for cleaning due to excessive solid content, the number of stages can be increased to facilitate the control of the solid content of the slurry discharged from the bottom of each stage, so as to facilitate long-term continuous operation; (2) when the density difference between the inorganic salt crystalline solid and the liquid phase is large, when the amount of water evaporated in a single stage is too large, the solid content in the bottom discharge slurry is too high, and it is difficult for the slurry to carry the solids. It is necessary to reduce the solid content of the discharge at each stage, so that a multi-stage separation process is required; (3) when the amount of water evaporated in a single stage is too large, the solid content is too high, and the crystal content per unit volume is high, the crystals are easy to agglomerate, and it is necessary to reduce the solid content of the discharge at each stage, so that a multi-stage separation process is required.

[0013] The polyol in the salt-containing alcohol-water mixture of the present invention is miscible with water and has a higher boiling point than water, preferably a diol with 3-8 carbon atoms and 2-4 hydroxyl groups; the inorganic salt is soluble in water and can form a solid crystalline compound as the solvent water is removed.

[0014] For example, taking 1,3-butanediol as an example, the salt-containing alcohol-water mixture is 1,3-butanediol, fusel alcohols (ethanol, butanol), water, inorganic salts, light component impurities (1-hexanol), and heavy component impurities (2,2,4,4-tetramethyl-cyclobutanediol).

[0015] Optionally, the primary output of the crystallizer of the primary separation process can be separated from the solid by centrifugation or filtration and then sent to the secondary separation process, or it can be sent to the secondary separation process directly together with the crystal particles without separation, and the crystal particles can be used as seeds for the secondary separation process.

[0016] Optionally, if the polyol has an anti-solvent effect (or salting-out effect) on inorganic salts dissolved in water, when 0-20wt% of water remains in the polyol in the crystallizer of the secondary separation process, the content of inorganic salts extracted from the crystallizer of the secondary separation process can be reduced to 0-500ppm, and it can be considered that the inorganic salts in the product have been basically removed and will not block the subsequent distillation equipment. And retaining a certain amount of water in the polyol of the crystallizer of the secondary separation process is conducive to reducing the viscosity of the liquid to be centrifuged or filtered, so that the separation operation can be carried out smoothly and continuously, and energy consumption is saved. Therefore, it is also possible to choose to retain 20wt% of water in the crystallizer of the secondary separation process, and it is considered that desalination has also been completed. The water content of the secondary extraction of the crystallizer of the secondary separation process can be selected according to actual production needs.

[0017] Further, the salt-containing alcohol-water mixture is fed from the rectifying tower of the primary separation process, and enters the rectifying tower of the secondary separation process after being discharged from the crystallizer; or the salt-containing alcohol-water mixture is fed from the crystallizer of the primary separation process, and enters the crystallizer of the secondary separation process after being discharged from the crystallizer. According to the different requirements of the feed composition of the separated material and the content of the fusel alcohol in the discharged material, the feed position of the primary separation process and the secondary separation process can be selected. If the fusel alcohol content in the salt-containing alcohol-water mixture is high, and it is necessary to control the fusel alcohol content of the discharged material from the rectifying tower and the amount of fusel alcohol in the subsequently separated material flow, for example, the amount of fusel alcohol in the feed is greater than 1wt%, and the fusel alcohol content of the discharged material is required to be less than 100ppm, it is suitable to feed from the rectifying tower of the separation process, and optionally, it can be fed from the middle of the rectifying tower. If the fusel alcohol content in the salt-containing alcohol-water mixture is not high, for example, the fusel alcohol content in the feed composition is ≤1wt%, or the fusel alcohol in the discharged polyol is ≥100ppm, it can be fed from the crystallizer of the separation process.

[0018] Furthermore, the number of theoretical plates of the distillation tower of the primary separation process and / or the secondary separation process is 3 to 30, and the reflux ratio is 0.25 to 9. Within this range, the number of theoretical plates and the reflux ratio can reduce the amount of polyols entrained in the distillation tower extract of the primary separation process and the secondary separation process to less than 200 ppm, effectively reducing the loss of polyols and improving the recovery rate of polyols. Optionally, if the feed is fed from the distillation tower of the separation process, the stripping section below the feed port uses an anti-clogging tray, preferably a flow-through tray, and the number of theoretical plates of the stripping section is 1 to 5 theoretical plates. The opening of the flow-through tray is large, with an aperture of 20 to 30 mm, and the structure is simple, without internal parts such as downcomers and overflow weirs, and inorganic salt crystals are easy to pass through and are not easy to cause blockage.

[0019] Further, the pressure of the primary separation process and / or the secondary separation process is -80 to 200 kPaG, and the embodiment of the present invention shows the specific pressure parameters.

[0020] Furthermore, the distillation tower temperature of the primary separation process and / or the secondary separation process is 40-130° C., and the crystallizer temperature of the primary separation process and / or the secondary separation process is 75-140° C. The embodiments of the present invention show specific temperature parameters.

[0021] Furthermore, the distillation tower of the secondary separation process is an azeotropic distillation, and the azeotropic agent of the azeotropic distillation is one or more of acetone, lower chain alkanes, cycloalkanes, aromatic hydrocarbons, and ethers. Optionally, the lower chain alkanes are n-pentane, hexane, cyclohexane, n-heptane, isooctane, etc., the aromatic hydrocarbons are benzene, toluene, p-xylene, etc., and the ethers are isopropyl ether, etc.

[0022] The distillation tower of the secondary separation process of the present invention can utilize the principle of azeotropic distillation, and water can be vaporized and removed by adding an entrainer, and inorganic salts soluble in water can also be completely precipitated. The distillation tower of the secondary separation process utilizes azeotropic distillation to reduce the operating temperature, avoid the decomposition and deterioration of heat-sensitive polyols at high temperatures, and improve product purity and separation yield. Optionally, the entrainer is added to the phase separation tank at the top of the distillation tower of the secondary separation process, and then pumped to the reflux pipe port of the distillation tower of the secondary separation process and the crystallizer circulation pipeline of the secondary separation process. After azeotropic distillation, water and the entrainer are steamed from the top of the distillation tower of the secondary separation process, and after condensation, they are left to stand in the phase separation tank for phase separation, and the entrainer is recycled, and the water is recycled after treatment.

[0023] Furthermore, the steam at the top of the distillation tower of the primary separation process is input into the crystallizer of the secondary separation process, or the steam at the top of the distillation tower of the secondary separation process is input into the crystallizer of the primary separation process; or the steam at the top of the distillation tower of the primary separation process is input into the crystallizer of the primary separation process through steam mechanical recompression or heat pump distillation, or the steam at the top of the distillation tower of the secondary separation process is input into the crystallizer of the secondary separation process through steam mechanical recompression or heat pump distillation. The primary separation process and the secondary separation process can adopt one or more of heat coupling, mechanical vapor recompression technology (MVR) or heat pump distillation (TVR). The above technologies can achieve the effect of saving the amount of heating steam and cooling medium, and save energy by 40 to 90%.

[0024] Optionally, the steam at the top of the distillation tower of the primary separation process is input into the circulation heater of the crystallizer of the secondary separation process, or the steam at the top of the distillation tower of the secondary separation process is input into the circulation heater of the crystallizer of the primary separation process, that is, through thermal coupling, the steam generated by the primary separation process is used as the heat source of the secondary separation process, or the heat source generated by the secondary separation process is used as the heat source of the primary separation process.

[0025] Optionally, the steam at the top of the distillation tower of the primary separation process and / or the secondary separation process is input into the circulation heater of the crystallizer of the primary separation process and / or the secondary separation process through steam mechanical recompression or heat pump distillation. That is, the steam generated by the distillation tower is used as the heat source of the crystallizer through the mechanical steam recompression technology.

[0026] Optionally, the steam at the top of the distillation tower of the primary separation process and / or the secondary separation process is input into the circulation heater of the crystallizer of the primary separation process and / or the secondary separation process through a distillation heat pump. That is, the steam generated by the distillation tower is used as the heat source of the crystallizer through heat pump distillation.

[0027] On the other hand, the present invention also provides a post-treatment process device for producing polyols, comprising a primary separation device and a secondary separation device, wherein both the primary separation device and the secondary separation device are provided with an upper distillation tower and a lower crystallizer coupled;

[0028] One end of the primary separation device is connected to the feed pipeline, and the other end is connected to the secondary separation device. The crystallizer of the secondary separation device is connected to the solid-liquid separation equipment. The distillation tower of the primary separation device is provided with a primary gas phase outlet, and the distillation tower of the secondary separation device is provided with a secondary gas phase outlet.

[0029] The primary separation device and the secondary separation device of the present invention both include an upper distillation tower and a lower crystallizer coupled to achieve the effect of simultaneous distillation and crystallization. The equipment can operate continuously and smoothly, and can also be switched to intermittent operation at any time, with a large and flexible processing capacity. The post-processing device for producing polyols of the present invention is a two-stage process, and each stage uses one of the above-mentioned distillation and crystallization coupling devices; it is actually equivalent to using only two devices to perform two-stage distillation on the mixed solution and complete two-stage crystallization at the same time, which reduces the number of equipment, occupies a small area, and saves costs.

[0030] Optionally, the primary separation device and the secondary separation device of the present invention are formed by coupling a device with a distillation tower at the top and a crystallizer at the bottom. The two are connected by flanges or directly welded, and the top of the crystallizer is directly connected to the bottom of the distillation tower; preferably, the distillation tower is located directly above the gas phase space of the crystallizer. The position directly above can make the distillation tower and the crystallizer coaxial up and down, with the same center of gravity and uniform force, which is easier to manufacture and install. The distillation section is directly integrated with the crystallizer and is directly connected to the top. According to the diameter of the distillation tower, the top of the crystallizer is a conical reducer, or has the same diameter as the distillation tower. The structure is simple without dead angles, the gas phase resistance drop is small, and the liquid phase is not easy to be blocked or scarred.

[0031] Optionally, the solid-liquid separation equipment of the present invention is a filtering device such as a centrifuge, a candle filter or a filter press, which separates the crystalline solid from the liquid, and the liquid is a crude polyol free of water and salt obtained by pre-separation, which is sent to a downstream refining device for further separation to obtain the final product.

[0032] Further, the distillation tower of the primary separation device is connected to the feed pipeline, and the crystallizer of the primary separation device is connected to the distillation tower of the secondary separation device;

[0033] Or one end of the crystallizer of the primary separation device is connected to the feed pipeline, and the other end is connected to the crystallizer of the secondary separation device.

[0034] According to different requirements on the feed composition of the separated materials and the fusel content of the discharged materials, the feed position of the primary separation device and the secondary separation device can be fed from the distillation tower of the primary separation device and the secondary separation device, or from the crystallizer of the primary separation device and the secondary separation device; if the fusel content in the saline alcohol water is relatively high, and it is necessary to control the fusel content of the discharged material at the bottom of the primary separation device and the amount of fusel in the subsequently separated stream, it is suitable to feed from the distillation tower, preferably the middle part of the distillation tower of the primary separation device and the secondary separation device.

[0035] Furthermore, the crystallizer of the primary separation device is any one of FC, DT, and DTB crystallizers; and / or, the crystallizer of the secondary separation device is an FC crystallizer. No agitator is provided in the crystallizer, and stirring is achieved through the circulation of an internal guide tube and an external axial flow pump. The DTB and DT crystallizers of the primary grading device provide control over the uniformity of the maximum supersaturation, and can also separate fine crystals and control the density of crystal nuclei. Because the FC crystallizer has the widest range of uses and the simplest structure, it can prevent the secondary separation slurry with high solid content from scarring in the crystallizer. The secondary separation process is mainly azeotropic dehydration, and the resulting crystal particles are smaller, which is more suitable for FC crystallizers. The internal structure of the crystallization equipment used in the present invention is simple and has no dead corners; the bottom is conical, the inclination is greater than the angle of repose, and no material is stored; the inner wall is polished to prevent scaling.

[0036] Further, the post-processing device for producing polyols further comprises a primary condenser and a secondary condenser, wherein one end of the primary condenser is connected to the primary gas phase outlet, and the other end is connected to the primary liquid outlet of the primary condenser; one end of the secondary condenser is connected to the secondary gas phase outlet, and the other end is connected to the secondary liquid outlet of the secondary condenser; preferably, the post-processing device for producing polyols further comprises a phase separation tank, and the secondary liquid outlet of the secondary condenser is connected to the phase separation tank;

[0037] And / or, the post-processing device for producing polyols also includes a primary circulation heater and a secondary circulation heater, the primary circulation heater is arranged at the lower part of the crystallizer of the primary separation device; the secondary circulation heater is arranged at the lower part of the crystallizer of the secondary separation device.

[0038] A phase separation tank is arranged on the basis of the condenser, so that the outlet of the secondary condenser is connected to the inlet of the phase separation tank. When the secondary separation device adopts azeotropic distillation, the entrainer is added to the phase separation tank at the upper part of the distillation tower of the secondary separation process, and then pumped to the reflux pipe port of the distillation tower of the secondary separation process and the crystallizer circulation pipeline of the secondary separation process. After azeotropic distillation, water and the entrainer are evaporated from the top of the distillation tower of the secondary separation device, and after condensation, they are left to stand in the phase separation tank for phase separation, the entrainer is recycled, and the water is recycled after treatment.

[0039] The first-stage circulation heater and the second-stage circulation heater are located lower than the liquid level in the crystallizer. The static liquid level is used to press the heated solution in the heat exchanger so that the solution does not vaporize inside the heater. It vaporizes when it rises into the crystallizer to precipitate crystals, thus preventing scaling on the heating surface. A high flow rate is maintained in the heat exchange tubes of the heater to prevent scaling of the heat exchange tubes.

[0040] Optionally, the primary circulation heater and the secondary circulation heater are external circulation heaters, preferably one or more of a plate heat exchanger, a vertical or horizontal shell and tube heat exchanger, a spiral plate heat exchanger, a coil or a shell and tube heat exchanger.

[0041] Furthermore, the primary gas phase outlet is connected to the secondary circulation heater, or the secondary gas phase outlet is connected to the primary circulation heater; or the primary gas phase outlet is connected to the primary circulation heater through a distillation heat pump or a steam mechanical recompression device, or the secondary gas phase outlet is connected to the secondary circulation heater through a distillation heat pump or a steam mechanical recompression device. The primary separation device and the secondary separation device are also provided with one or more of a heat coupling device, a heat pump distillation device, and a mechanical steam recompression device. By providing the above devices, the effect of saving the amount of heating steam and cooling medium can be achieved, and energy saving can be achieved by 40 to 90%.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The post-treatment process for producing polyols of the present invention is carried out in a device consisting of a distillation tower at the top and a crystallizer at the bottom. Through the coupling of distillation and crystallization, the precipitated inorganic salts will not cause equipment blockage, and the distillation prevents part of the water and fusel alcohols with a boiling point lower than that of water extracted from the distillation tower from entraining the polyols, thereby reducing the loss of the polyols. At the same time, a two-stage treatment is adopted to achieve the purpose of simultaneously separating water, salts, fusel alcohols and the reaction product polyols.

[0044] 2. The post-processing device for producing polyols of the present invention is composed of an upper distillation tower and a lower crystallizer coupled together. The equipment can be operated continuously and smoothly, and can also be switched to intermittent operation at any time. The processing capacity is large and flexible; the number of equipment is reduced, the footprint is small, and the cost is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0046] Figure 1 A diagram showing a post-processing device for producing polyols according to the present invention.

[0047] Among them, the above-mentioned drawings include the following drawing marks: T-1, primary separation device, T-2, secondary separation device, S-3, solid-liquid separation equipment, E-1D, primary condenser, E-2D, secondary condenser, E-1W, primary circulation heater, E-2W, secondary circulation heater, V-2, phase separation tank, 1, feed pipeline, 2, primary gas phase outlet, 3, primary liquid outlet, 4, secondary gas phase outlet, 5, secondary liquid outlet. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, not limiting the scope of protection of the present invention.

[0050] The raw materials and equipment used in this application, unless otherwise specified, are all commonly used raw materials and equipment in this field, and are all commercially available products. The methods used in this application, unless otherwise specified, are all conventional methods in this field.

[0051] The specific implementation of this application uses 1,3-butanediol as an example to illustrate the post-treatment process and device for producing polyols. However, the salt-containing alcohol-water mixture of the present invention is not limited to 1,3-butanediol. The polyol in the salt-containing alcohol-water mixture of the present invention is miscible with water and has a higher boiling point than water, preferably a diol with 3-8 carbon atoms and 2-4 hydroxyl groups; the inorganic salt is soluble in water, and can form a solid crystalline compound as the solvent water is removed.

[0052] The salt-containing alcohol-water mixture in the specific embodiment of the present application comes from the product obtained by the condensation hydrogenation reaction of 1,3-butanediol pilot plant. The pilot plant adopts the preparation method of CN111574325A. The composition of the salt-containing alcohol-water mixture is 76.5-78wt% of water, 18.5-20.5wt% of 1,3-butanediol, ~2wt% of inorganic salt, 0.5-0.6wt% of fusel alcohol, and the rest are light components and heavy component impurities.

[0053] Example 1

[0054] A post-processing process for producing polyols, such as Figure 1As shown, a salt-containing alcohol-water mixture (76.34wt% water, 2.01wt% inorganic salt, 20.41wt% 1,3-butanediol, 1.01wt% fusel alcohol, 0.22wt% light components and heavy components) is input into the lower crystallizer of the primary separation device T-1; the upper distillation tower of the primary separation device T-1 has a theoretical plate number of 10, a reflux ratio of 1, a feed flow rate of 115L / h, a top pressure of the primary separation device T-1 of 0barg, and a bottom pressure of the primary separation device T-1 of 0.1barg. g, the top temperature of the first-stage separation device T-1 is 96.1°C, the bottom temperature of the first-stage separation device T-1 is 104.2°C, and after rectification and crystallization, 97.72wt% water and 2.28wt% fusel alcohol are produced from the top of the first-stage separation device T-1, and 35.35wt% 1,3-butanediol, 3.48wt% inorganic salts, 60.70wt% water, 0.39wt% light components and heavy components impurities, and 0.09wt% fusel alcohol are produced from the bottom of the first-stage separation device T-1; the bottom of the first-stage separation device T-1 is used to produce The effluent is input into the lower crystallizer of the secondary separation device T-2. The theoretical number of plates of the upper distillation tower of the secondary separation device T-2 is 10, the reflux ratio is 1, the feed flow rate is 66.4L / h, the top pressure of the secondary separation device T-2 is 0barg, the bottom pressure of the secondary separation device T-2 is 0.1barg, the top temperature of the secondary separation device T-2 is 99.5℃, and the bottom temperature of the secondary separation device T-2 is 122.5℃. After distillation and crystallization, 99.35wt% water and 0.34wt% of fusel alcohol, 78.37wt% of 1,3-butanediol, 0.05wt% of inorganic salt, 19.02wt% of water, 2.54wt% of light components and heavy components, and 0.0215wt% of fusel alcohol are extracted from the bottom of the T-2 tower of the secondary separation device; the extracted product of the bottom of the T-2 tower of the secondary separation device is separated by solid-liquid filtration to obtain crude polyol (78.37wt% of 1,3-butanediol, 19.02wt% of water, 2.54wt% of light components and heavy components, and 0.0215wt% of fusel alcohol). If pure 1,3-butanediol is to be obtained, the post-treatment process for producing polyols in this application needs to be followed by light removal, heavy removal and other steps to remove other light and heavy impurities. After the subsequent steps of light removal tower and heavy removal tower to separate the light components and heavy components, the composition of 1,3-butanediol is 99.5-99.9%, which meets the purity requirements of downstream products.

[0055] In the actual production process, the packing and lower crystallizer of the primary separation device T-1 and the secondary separation device T-2 were not blocked after continuous and stable operation for more than one month. The components and contents of each part of the primary separation device T-1 and the secondary separation device T-2 are shown in Table 1.

[0056] Table 1 Composition and content of each part of the primary separation device and the secondary separation device of Example 1

[0057]

[0058] Example 2

[0059] A post-processing process for producing polyols, such as Figure 1 As shown, a salt alcohol-water mixture (75.26wt% water, 2.11wt% inorganic salt, 20.39wt% 1,3-butanediol, 2.11wt% fusel alcohol, 0.13wt% light components and heavy components) is input into the upper distillation tower of the primary separation device T-1; the theoretical number of plates of the upper distillation tower of the primary separation device T-1 is 10, the feed position is above the 8# plate, the reflux ratio is 1, the feed flow rate is 115L / h, and the top pressure of the primary separation device T-1 is 0barg The bottom pressure of the first-stage separation device T-1 is 0.1 barg, the top temperature of the first-stage separation device T-1 is 91.8°C, and the bottom temperature of the first-stage separation device T-1 is 104.2°C. After distillation and crystallization, 94.94wt% water and 4.99wt% fusel alcohol are produced from the top of the first-stage separation device T-1, and 35.33wt% 1,3-butanediol, 3.65wt% inorganic salts, 60.82wt% water, 0.2wt% light components and heavy component impurities, 0.00173wt% of fusel alcohol; the output from the bottom of the first separation device T-1 is input into the lower crystallizer of the second separation device T-2, the theoretical number of plates of the upper distillation tower of the second separation device T-2 is 10, the reflux ratio is 1, the feed flow rate is 66.17L / h, the top pressure of the second separation device T-2 is 0barg, the bottom pressure of the second separation device T-2 is 0.1barg, the top temperature of the second separation device T-2 is 71.2℃, and the second separation device T-2 The bottom temperature of the tower is 107.3°C. After distillation and crystallization, 99.33wt% water, 0.0033wt% fusel alcohol, 0.10wt% light components and heavy impurities are extracted from the top of the secondary separation device T-2 tower. The extract from the bottom of the secondary separation device T-2 tower is separated by solid-liquid filtration to obtain crude polyols (81.2wt% 1,3-butanediol, 0.02wt% inorganic salts, 18.49wt% water, 0.31wt% light components and heavy impurities, 0.00wt% fusel alcohol).

[0060] In the actual production process, the primary separation device T-1 and the secondary separation device T-2 have been running stably for more than one month, and there is no blockage in the packing and lower crystallizer of the primary separation device T-1 and the secondary separation device T-2. The components and contents of each part of the primary separation device T-1 and the secondary separation device T-2 are shown in Table 2.

[0061] Table 2 Composition and content of each part of the primary separation device and the secondary separation device of Example 2

[0062]

[0063]

[0064] It can be seen from Examples 1 and 2 that feeding from the distillation tower at the top of the primary separation device T-1 and the secondary separation device T-2 can effectively reduce the content of fusel alcohol in the bottom extract of the primary separation device T-1 and the secondary separation device T-2. If the fusel alcohol content in the salt-containing alcohol water is high and it is necessary to control the fusel alcohol content of the bottom discharge of the primary separation device T-1 and the amount of fusel alcohol in the subsequently separated stream, it is suitable to feed from the middle of the distillation tower.

[0065] Example 3

[0066] Based on the post-treatment process for producing polyols described in Example 1, in this example, entrainer cyclohexane is added to the secondary separation device T-2, and water and fusel alcohols are distilled out from the top of the secondary separation device T-2 together with the entrainer cyclohexane, the entrainer and the water phase, the entrainer is completely refluxed (0.01wt% water, 0.07wt% fusel alcohol, 0.03wt% light and heavy impurities, 99.89wt% cyclohexane), and the water phase is discharged (99.33wt% water, 0.0022wt% 1 ,3-butanediol, 0.66wt% fusel alcohol, 0.01wt% light and heavy impurities) are reused after treatment; the output from the bottom of the secondary separation unit T-2 is 78.44wt% 1,3-butanediol, 19.76wt% water, 1.59wt% light components and heavy components, 0.08wt% fusel alcohol, 0.02wt% inorganic salts, 0.11wt% cyclohexane. The components and contents of each part of the primary separation unit T-1 and the secondary separation unit T-2 are shown in Table 3.

[0067] Table 3 Composition and content of each part of the primary separation device and the secondary separation device of Example 3

[0068]

[0069] It can be seen from Examples 1 and 3 that adding an azeotropic agent to the secondary separation device T-2 can significantly reduce the operating temperature of the tower bottom, avoid decomposition and deterioration of heat-sensitive 1,3-butanediol at high temperatures, and improve the purity and separation yield of 1,3-butanediol.

[0070] Example 4

[0071] Based on a post-treatment process for producing polyols shown in Example 3, the primary separation device T-1 and the secondary separation device T-2 are two-effect distillation, the operating pressure of the primary separation device T-1 tower is increased to 1 barg, the steam at the top of the primary separation device T-1 tower is used as the heat source of the secondary circulation heater E-2W, or the steam at the top of the secondary separation device T-2 tower is used as the heat source of the primary circulation heater E-1W, and the operating parameters and utility consumption are shown in Table 4:

[0072] Table 4 Two-effect distillation operating conditions

[0073]

[0074]

[0075] The operating parameters and utility consumption of Example 3 are shown in Table 5;

[0076] Table 5 Operating parameters and utility consumption of Example 1

[0077]

[0078] It can be seen from the operating parameters and utility consumption of Examples 4 and 3 that the thermal coupling method used in the primary separation device T-1 and the secondary separation device T-2 of Example 4 can greatly reduce the steam and circulating water consumption. In Example 3, the total steam consumption of the two towers is reduced from 340kg / h to 191kg / h, saving 43.8%.

[0079] Comparative Example 1

[0080] Use 1000mm high and 30mm diameter The ring-filled column is used to distill the salt-containing alcohol-water mixture. The material is continuously added from the top of the packed column at a flow rate of 10 ml / min. After distillation, water and fusel alcohol are distilled out from the top of the packed column. While the water is distilled out, the salt is precipitated from the solution and is filtered and intercepted by the packing in the packed column. The continuous feeding time is less than 1 hour. The packed column below the feeding position is basically blocked and distillation cannot continue.

[0081] By comparing Example 1 with Comparative Example 1, it can be seen that the crystallizer structure helps prevent the precipitated salt from clogging the tower packing, thereby ensuring continuous operation.

[0082] Comparative Example 2

[0083] Based on a post-treatment process for producing polyols shown in Example 1, the material is discharged from the pipe opening of the gas phase space at the top of the crystallizer below the distillation filler of the primary separation device T-1, and no material is discharged from the top of the distillation tower, which is equivalent to no distillation tower at the top of the crystallizer. The components and contents of each part of the primary separation device T-1 are shown in Table 6.

[0084] Table 6 Components and contents of each part of the primary separation device of Comparative Example 2

[0085]

[0086] By comparing Example 1 with Comparative Example 2, it can be seen that compared with Comparative Example 2 which only has a crystallizer, the primary separation device T-1 and the secondary separation device T-2 of Example 1 are both coupled by a device with a distillation tower at the top and a crystallizer at the bottom, which can avoid the alcohol-water solution discharged from the top of the tower from carrying 1,3-butanediol product and improve the recovery rate of 1,3-butanediol.

[0087] Example 5

[0088] A device for a post-processing process for producing polyols, such as Figure 1 As shown, it includes a primary separation device T-1 and a secondary separation device T-2. Both the primary separation device T-1 and the secondary separation device T-2 are provided with an upper distillation tower and a lower crystallizer coupled; one end of the primary separation device T-1 is connected to the feed pipeline 1, and the other end is connected to the secondary separation device T-2. The crystallizer of the secondary separation device T-2 is connected to the solid-liquid separation equipment S-3. The distillation tower of the primary separation device T-1 is provided with a primary gas phase outlet 2, and the distillation tower of the secondary separation device T-2 is provided with a secondary gas phase outlet 4.

[0089] Optionally, the distillation tower of the primary separation device T-1 is connected to the feed pipeline 1, and the crystallizer of the primary separation device T-1 is connected to the distillation tower of the secondary separation device T-2.

[0090] Optionally, the crystallizer of the primary separation device T-1 is connected to the feed pipeline 1, and the other end is connected to the crystallizer of the secondary separation device T-2.

[0091] The optional crystallizer of the primary separation device T-1 is any one of FC, DT, and DTB type crystallizers, and the crystallizer of the secondary separation device T-2 is a FC type crystallizer.

[0092] Example 6

[0093] Based on the device for post-treatment process of producing polyols shown in Example 5, this embodiment is a preferred embodiment. Figure 1 As shown, the post-processing device for producing polyols also includes a primary condenser E-1D and a secondary condenser E-2D. One end of the primary condenser E-1D is connected to the primary gas phase outlet 2, and the other end is connected to the primary liquid outlet 3 of the primary condenser E-1D; one end of the secondary condenser E-2D is connected to the secondary gas phase outlet 4, and the other end is connected to the second liquid outlet 5 of the secondary condenser E-2D.

[0094] Optionally, the post-processing device for producing polyols also includes a primary circulation heater E-1W and a secondary circulation heater E-2W. The bottom of the crystallizer of the primary separation device T-1 is connected to the bottom inlet of the primary circulation heater E-1W, and the top outlet of the primary circulation heater E-1W is connected to the crystallizer of the primary separation device T-1. The feed pipeline 1 is connected to the top outlet pipeline of the primary circulation heater E-1W, so that the material passing through the feed pipeline 1 is mixed with the circulating material heated by the primary circulation heater E-1W and then enters the bottom of the crystallizer of the primary separation device T-1; the bottom of the crystallizer of the secondary separation device T-2 is connected to the bottom inlet of the secondary circulation heater E-2W, and the top outlet of the secondary circulation heater E-2W is connected to the crystallizer of the primary separation device T-1. The bottom discharge port of the crystallizer of the primary separation device T-1 is connected to the top outlet pipeline of the heater 1E-1W through the feed pipeline of the secondary separation device.

[0095] Optionally, the secondary liquid outlet 5 is connected to the phase separation tank V-2. The phase separation tank V-2 is used only for adding an azeotropic agent for azeotropic distillation. A portion of the oil phase azeotropic agent obtained by phase separation in the phase separation tank V-2 is transported to the secondary separation device T-2 as reflux, and the rest is transported to the heater E-2W as an azeotropic agent.

[0096] Example 7

[0097] Based on the device for post-treatment process of producing polyols shown in Example 5, this embodiment is a preferred embodiment. Figure 1 As shown, the primary gas phase outlet 2 is connected to the secondary circulation heater E-2W, or the secondary gas phase outlet 4 is connected to the primary circulation heater E-1W.

[0098] Optionally, the primary gas phase outlet 2 is connected to the primary circulation heater E-1W via a primary distillation heat pump or a primary steam mechanical recompression device.

[0099] Optionally, the secondary gas phase outlet 4 is connected to the secondary circulation heater E-2W via a secondary distillation heat pump or a secondary steam mechanical recompression device.

[0100] Optionally, the first-stage steam mechanical recompression equipment is a Roots blower or a centrifugal steam compressor, and the second-stage steam mechanical recompression equipment is a screw compressor.

[0101] The above is only a preferred embodiment of the invention, and is not intended to limit the invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the invention, which all belong to the protection scope of the invention. Therefore, the protection scope of the patent of the invention shall be based on the attached claims.

Claims

1. A post-treatment process for producing polyols, characterized in that: The invention comprises a primary separation process and a secondary separation process, wherein both the primary separation process and the secondary separation process are carried out in a device which is composed of a distillation tower at the top and a crystallizer at the bottom. The salt-containing alcohol-water mixture is subjected to the distillation tower of the primary separation process to extract part of water and fusel alcohol with a boiling point lower than that of water, and the primary extraction product of the crystallizer of the primary separation process enters the secondary separation process, the remaining water is extracted by the distillation tower of the secondary separation process, and the crystallizer of the secondary separation process obtains the secondary extraction product.

2. A post-treatment process for producing polyols according to claim 1, characterized in that: The salt-containing alcohol-water mixture is fed from the distillation tower of the primary separation process, and enters the distillation tower of the secondary separation process after being discharged from the crystallizer; Alternatively, the salt-containing alcohol-water mixture is fed into the crystallizer of the primary separation process, and discharged from the crystallizer before entering the crystallizer of the secondary separation process.

3. A post-treatment process for producing polyols according to any one of claims 1 to 2, characterized in that: The number of theoretical plates of the distillation tower of the primary separation process and / or the secondary separation process is 3 to 30, and the reflux ratio is 0.25 to 9; and / or, the pressure of the primary separation process and / or the secondary separation process is -80 to 200 kPaG; And / or, the distillation tower temperature of the primary separation process and / or the secondary separation process is 40-130°C, and the crystallizer temperature of the primary separation process and / or the secondary separation process is 75-140°C.

4. A post-treatment process for producing polyols according to any one of claims 1 to 2, characterized in that: The distillation tower of the secondary separation process is azeotropic distillation, and the azeotropic agent of the azeotropic distillation is one or more of acetone, lower chain alkanes, cyclic alkanes, aromatic hydrocarbons, and ethers.

5. A post-treatment process for producing polyols according to any one of claims 1 to 2, characterized in that: The steam at the top of the distillation tower of the primary separation process is input into the crystallizer of the secondary separation process, or the steam at the top of the distillation tower of the secondary separation process is input into the crystallizer of the primary separation process; Alternatively, the steam at the top of the distillation tower of the primary separation process is input into the crystallizer of the primary separation process through steam mechanical recompression or heat pump distillation, or the steam at the top of the distillation tower of the secondary separation process is input into the crystallizer of the secondary separation process through steam mechanical recompression or heat pump distillation.

6. A device for the post-treatment process for producing polyols according to any one of claims 1 to 5, characterized in that: It comprises a primary separation device (T-1) and a secondary separation device (T-2), wherein both the primary separation device (T-1) and the secondary separation device (T-2) are provided with an upper distillation tower and a lower crystallizer coupled; One end of the primary separation device (T-1) is connected to the feed pipeline (1), and the other end is connected to the secondary separation device (T-2); the crystallizer of the secondary separation device (T-2) is connected to the solid-liquid separation equipment (S-3); the distillation tower of the primary separation device (T-1) is provided with a primary gas phase outlet (2), and the distillation tower of the secondary separation device (T-2) is provided with a secondary gas phase outlet (4).

7. The device according to claim 6, characterized in that The distillation tower of the primary separation device (T-1) is connected to the feed pipeline (1), and the crystallizer of the primary separation device (T-1) is connected to the distillation tower of the secondary separation device (T-2); Or one end of the crystallizer of the primary separation device (T-1) is connected to the feed pipeline (1), and the other end is connected to the crystallizer of the secondary separation device (T-2).

8. The device according to any one of claims 6 to 7, characterized in that: The crystallizer of the primary separation device (T-1) is any one of FC, DT, and DTB type crystallizers; And / or, the crystallizer of the secondary separation device (T-2) is a FC crystallizer.

9. The device according to any one of claims 6 to 7, characterized in that: The post-processing device for producing polyols further comprises a primary condenser (E-1D) and a secondary condenser (E-2D), one end of the primary condenser (E-1D) is connected to the primary gas phase outlet (2), and the other end is connected to the primary liquid outlet (3) of the primary condenser (E-1D); one end of the secondary condenser (E-2D) is connected to the secondary gas phase outlet (4), and the other end is connected to the secondary liquid outlet (5) of the secondary condenser (E-2D); preferably, the post-processing device for producing polyols further comprises a phase separation tank (V-2), and the secondary liquid outlet (5) of the secondary condenser (E-2D) is connected to the phase separation tank (V-2); And / or, the post-processing device for producing polyols also includes a primary circulation heater (E-1W) and a secondary circulation heater (E-2W), wherein the primary circulation heater (E-1W) is arranged at the lower part of the crystallizer of the primary separation device (T-1); and the secondary circulation heater (E-2W) is arranged at the lower part of the crystallizer of the secondary separation device (T-2).

10. The device according to claim 9, characterized in that The primary gas phase outlet (2) is connected to the secondary circulation heater (E-2W), or the secondary gas phase outlet (4) is connected to the primary circulation heater (E-1W); Alternatively, the primary gas phase outlet (2) is connected to the primary circulation heater (E-1W) via a distillation heat pump or a steam mechanical recompression device, or the secondary gas phase outlet (4) is connected to the secondary circulation heater (E-2W) via a distillation heat pump or a steam mechanical recompression device.

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