A continuous separation system and process for a glycerol-glycerol carbonate mixture

Abstract

The application provides a continuous separation system and process for a glycerol-glycerol carbonate mixture, which comprises an extraction column, an extract phase extractant recovery rectifying column and a raffinate phase extractant recovery rectifying column; a first inlet, a second inlet and a third inlet are respectively arranged at the bottom, the top and the middle of the extraction column, the third inlet of the extraction column is used for receiving the glycerol-glycerol carbonate mixture, the first inlet of the extraction column is used for receiving a first extractant, and the second inlet of the extraction column is used for receiving a second extractant; the first extractant is methyl isobutyl ketone, cyclohexanone or 2-pentanone, and the second extractant is water; the top outlet of the extraction column is connected with the feed inlet of the extract phase extractant recovery rectifying column, and the bottom outlet is connected with the feed inlet of the raffinate phase extractant recovery rectifying column. The system and the process thereof have a simple separation process, a wide applicable concentration range and can realize efficient separation of the glycerol-glycerol carbonate mixture.

Description

Technical Field

[0001] This invention belongs to the field of homogeneous liquid mixture separation technology, specifically relating to a continuous separation system and process for a glycerol-glycerol carbonate mixture. Background Technology

[0002] Glycerol (C3H8O3), also known as glycerol, is widely used in the food, cosmetics, pharmaceutical, and petrochemical industries due to its low toxicity, hygroscopicity, and biodegradability. Glyceryl carbonate (C4H6O4) is a high-value product synthesized from glycerol and carbonic acid derivatives. Glyceryl carbonate can replace traditional volatile organic solvents in coatings, inks, and adhesives. Due to its low toxicity and high biodegradability, it can be used as a solvent and surfactant in cosmetics and skincare products. Simultaneously, as a polyol component, glyceryl carbonate can serve as a monomer for polymer materials such as foams, elastomers, coatings, and environmentally friendly materials. Furthermore, glyceryl carbonate can also be used as an electrolyte in lithium batteries and a reactant in the synthesis of polymers such as polyesters, polyurethanes, and polycarbonates.

[0003] Glyceryl carbonate is mainly synthesized from glycerol. This process primarily involves the reaction of glycerol with dimethyl carbonate, diethyl carbonate, urea, carbon dioxide, or phosgene. Currently, the mainstream method for synthesizing glyceryl carbonate is the reaction of glycerol with dimethyl carbonate. However, this method cannot completely convert glycerol; therefore, it is necessary to separate and concentrate glycerol and glyceryl carbonate to obtain high-concentration glyceryl carbonate.

[0004] Among the reported methods for separating glycerol and glycerol carbonate, the commonly used methods are vacuum distillation, molecular distillation, and liquid-liquid extraction.

[0005] Chinese invention patent application CN104926781A discloses a method for synthesizing glycerol carbonate from glycerol. The concentration method involves vacuum distillation at a vacuum level of 0.2 kPa and a temperature of 180–190 °C to concentrate the crude glycerol carbonate. However, vacuum distillation makes it difficult to completely separate the mixture, resulting in a low concentration of glycerol carbonate and a yield of only 75%.

[0006] In contrast, molecular distillation can increase the concentration of glycerol carbonate. Chinese invention patent application CN106582661A discloses a metal-supported catalyst and its application in the synthesis of glycerol carbonate. This catalyst concentrates the product using molecular distillation under vacuum conditions of 1–15 Pa and evaporator temperature of 100–1200 °C, ultimately achieving a glycerol carbonate yield greater than 95% and a concentration of not less than 99%. Vacuum distillation and molecular distillation require low-pressure operation, necessitating vacuum pumps and extremely high sealing to maintain this environment. This places extremely high demands on equipment sealing performance and results in lower separation efficiency, significantly increasing operating and equipment costs. In contrast, extraction methods offer advantages such as lower operating temperatures, suitability for heat-sensitive substances, relatively lower energy consumption, and higher separation concentrations. However, current extractants generally have a narrow applicable concentration range for separating glycerol and glycerol carbonate. Chinese invention patent application CN115677501A discloses a liquid-liquid extraction method for separating glycerol and glyceryl carbonate. The extractant consists of acetone and a hydrocarbon compound, specifically one selected from dichloromethane, dichloroethane, cyclohexane, and chloroform. The yield of the separated glyceryl carbonate reaches 87%–91.7%, with a concentration of 91%–96.5%. These extraction separation methods use an extractant to extract glyceryl carbonate from glycerol. However, glyceryl carbonate is amphiphilic, promoting miscibility between glycerol and the extractant. When the concentration of glyceryl carbonate is too high, the extractant-glycerol-glyceryl carbonate phase easily forms a homogeneous phase (as described in Chinese invention patent application CN114456032A), making stratification impossible. Therefore, these methods are unsuitable for separating high-concentration glyceryl carbonate from glycerol. Furthermore, existing extraction separation methods employ batch and intermittent operations, resulting in low production efficiency and limited processing scale, making it difficult to meet the needs of large-scale continuous production. Summary of the Invention

[0007] The purpose of this invention is to provide a continuous separation system and process for a glycerol-glyceryl carbonate mixture. This process has a simple separation flow, a wide applicable concentration range, and can achieve efficient separation of the glycerol-glyceryl carbonate mixture.

[0008] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a continuous separation system for a glycerol-glyceryl carbonate mixture, comprising: an extraction tower, an extractant recovery distillation tower for the extract phase, and a raffinate extractant recovery distillation tower; The extraction tower has a first inlet, a second inlet, and a third inlet at its bottom, top, and middle sections, respectively. The third inlet of the extraction tower is used to receive a glycerol-glyceryl carbonate mixture, the first inlet of the extraction tower is used to receive a first extractant, and the second inlet of the extraction tower is used to receive a second extractant. The first extractant is methyl isobutyl ketone, cyclohexanone, or 2-pentanone, and the second extractant is water. The top outlet of the extraction column is connected to the inlet of the extractant recovery distillation column, and the bottom outlet is connected to the inlet of the raffinate extractant recovery distillation column.

[0009] Preferably, the top outlet of the extractant recovery distillation column is connected to the first inlet of the extraction column; the top outlet of the raffinate extractant recovery distillation column is connected to the second inlet of the extraction column.

[0010] Furthermore, the continuous separation system for the glycerol-glyceryl carbonate mixture further includes a first extractant mixer and a second extractant mixer; the first extractant mixer has a first inlet and a second inlet, the first inlet of the first extractant mixer is used to receive supplemental first extractant, the second inlet of the first extractant mixer is connected to the top outlet of the extractant recovery distillation column, and the outlet of the first extractant mixer is connected to the first inlet of the extraction column; the second extractant mixer has a first inlet and a second inlet, the first inlet of the second extractant mixer is used to receive supplemental second extractant, the second inlet of the second extractant mixer is connected to the top outlet of the raffinate extractant recovery distillation column, and the outlet of the second extractant mixer is connected to the second inlet of the extraction column.

[0011] Furthermore, the continuous separation system for the glycerol-glyceryl carbonate mixture also includes a splitter, the inlet of which is connected to the top outlet of the extractant recovery distillation column, the first outlet of which is connected to the first inlet of the extraction column, and the second outlet of which is connected to the second inlet of the extraction column.

[0012] Preferably, the extraction column has 8 to 30 trays, the extractant recovery distillation column has 10 to 30 trays, and the raffinate extractant recovery distillation column has 20 to 70 trays. The tray order of the extraction column, the extractant recovery distillation column, and the raffinate extractant recovery distillation column is defined as increasing sequentially from the top to the bottom of the column. The third inlet of the extraction column is located at trays 2 to 20; the feed inlet of the extractant recovery distillation column is located at trays 3 to 20; and the feed inlet of the raffinate extractant recovery distillation column is located at trays 10 to 65.

[0013] Secondly, the present invention provides a continuous separation process for a glycerol-glyceryl carbonate mixture, based on the continuous separation system described above, comprising: The glycerol-glyceryl carbonate mixture is fed into the third inlet of the extraction tower. The first extractant and the second extractant enter the extraction tower from the first inlet and the second inlet, respectively. The glycerol-glyceryl carbonate mixture is subjected to multi-stage countercurrent extraction using the first extractant and the second extractant. The extract phase is collected at the top outlet of the extraction tower, and the raffinate phase is collected at the bottom outlet of the extraction tower. The extractant phase is separated by an extractant recovery distillation column, and the heavy distillate is glycerol carbonate, while the light distillate is an extractant mixture rich in the first extractant. The raffinate is separated by a raffinate extractant recovery distillation column, and the heavy distillate is glycerol, while the light distillate is an extractant mixture rich in a second extractant.

[0014] Preferably, the extractant mixture rich in the first extractant is mixed with a supplement of the first extractant and then enters the extraction tower through the first inlet; the extractant mixture rich in the second extractant is mixed with a supplement of the second extractant and then enters the extraction tower through the second inlet.

[0015] Furthermore, the extractant mixture rich in the first extractant is divided into two parts by a splitter. One part is mixed with the supplemented first extractant and enters the extraction tower from the first inlet, while the other part is mixed with the supplemented second extractant and enters the extraction tower from the second inlet.

[0016] Furthermore, the mass flow ratio of the first extractant to the glycerol-glyceryl carbonate mixture fed into the extraction tower is 1 to 6; the mass flow ratio of the second extractant to the glycerol-glyceryl carbonate mixture fed into the extraction tower is 0.5 to 2.

[0017] Furthermore, the multi-stage extraction pressure of the extraction column is 0.5~3.5 atm, and the extraction temperature is 20~80 ℃; the pressure of the extractant recovery distillation column is 0.1~2 atm, the bottom temperature is 150~300 ℃, the top temperature is 30~80 ℃, and the reflux ratio is 0.1~5; the pressure of the raffinate recovery distillation column is 0.1~2 atm, the bottom temperature is 150~300 ℃, the top temperature is 30~100 ℃, and the reflux ratio is 0.1~3.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The extractant of this invention comprises two immiscible extractants. The first extractant can be a weakly polar methyl isobutyl ketone, cyclohexanone, or 2-pentanone, and the second extractant is water. Unlike conventional extraction columns that use only a single extractant inlet, the first and second extractants of this invention enter from the top and bottom of the extraction column, respectively. Under the influence of gravity and due to density differences, the two extractants come into countercurrent contact within the extraction column, forming a countercurrent liquid-liquid two-phase flow. This allows for the selective distribution of the glycerol-glyceryl carbonate mixture entering from the middle of the extraction column within the two phases. The countercurrent contact of the liquid-liquid two phases within the column creates a mass transfer concentration gradient, enabling multi-stage continuous countercurrent extraction and separation. In the upper part of the extraction column (above the third inlet), the second extractant, entering through the second inlet (top of the column), flows downwards, carrying away glycerol from the mixture to form the raffinate phase. In the lower part of the extraction column (below the third inlet), the first extractant, entering through the first inlet (bottom of the column), flows upwards, enriching the glyceryl carbonate in the mixture to form the extract phase. Thus, through multi-stage extraction in a single extraction tower, glycerol and glyceryl carbonate can be completely separated, yielding high-purity glycerol and glyceryl carbonate (excluding the extractant) at the two outlets of the extraction tower, without the need to recycle the glycerol-glyceryl carbonate mixture. Simultaneously, the mixed extractant used in this invention spontaneously forms a liquid-liquid two-phase system, solving the problem of miscibility between high-concentration glyceryl ester mixtures and the extractant. Therefore, it is applicable to a wider range of glycerol-glyceryl carbonate concentrations, from 1% to 99%, and can particularly separate mixtures with high glyceryl carbonate concentrations (>60%); the yield of the separated glyceryl carbonate reaches 99.99%, and the concentration reaches 99.6%. Therefore, this invention can efficiently and continuously separate mixtures of glycerol and glyceryl carbonate of different concentrations. Furthermore, the process of this invention includes separate extractant recovery distillation towers for the extractant phase and raffinate phase at the two outlets of the extraction tower for extractant recovery and reuse, resulting in a simple process, high yield, and flexible operating conditions.

[0019] Furthermore, in this invention, the top outlet of the extractant recovery distillation column is connected to the first inlet of the extraction column, and the top outlet of the raffinate extractant recovery distillation column is connected to the second inlet of the extraction column. This allows the extractant mixture rich in the first extractant collected at the top of the column after distillation of the extractant phase, as well as the extractant mixture rich in the second extractant collected at the top of the column after distillation of the raffinate phase, to be recycled back to the extraction column for reuse, thereby improving the utilization rate of the extractant and reducing costs.

[0020] Furthermore, within the extraction tower, a significant amount of the second extractant dissolves into the first extractant and subsequently enters the extraction phase. Therefore, in this invention, the extractant mixture rich in the first extractant is divided into two parts via a distributor. One part is mixed with the supplemented second extractant and enters the extraction tower through the second inlet to replenish the second extractant that entered the extraction phase during the extraction process, thus maintaining a good extraction effect. The other part is mixed with the supplemented first extractant and enters the extraction tower through the first inlet. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a process flow diagram of Example 1; Figure 2 This is a process flow diagram for Example 2.

[0023] In the diagram: 1 is the extraction column, 2 is the extractant recovery distillation column, 3 is the raffinate extractant recovery distillation column, 4 is the second extractant mixer, 5 is the first extractant mixer, and 6 is the splitter. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0026] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0027] Furthermore, it should be noted that the terms "first," "second," etc., used in this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In addition, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements.

[0028] The continuous separation system for the glycerol-glyceryl carbonate mixture of the present invention includes: an extraction tower 1, an extractant recovery distillation tower 2 for the extract phase, and an extractant recovery distillation tower 3 for the raffinate phase; The extraction tower 1 has a first inlet, a second inlet, and a third inlet at its bottom, top, and middle sections, respectively. The third inlet of the extraction tower 1 is used to receive a glycerol-glyceryl carbonate mixture, the first inlet of the extraction tower 1 is used to receive a first extractant, and the second inlet of the extraction tower 1 is used to receive a second extractant. The first extractant is methyl isobutyl ketone, cyclohexanone, or 2-pentanone (MPK), and the second extractant is water. The top outlet of the extraction tower 1 is connected to the inlet of the extraction phase extractant recovery distillation tower 2, and the bottom outlet is connected to the inlet of the raffinate phase extractant recovery distillation tower 3.

[0029] Compared with other existing glycerol-glyceryl carbonate extraction and separation methods, this invention uses a weakly polar first extractant and a strongly polar second extractant to perform multi-stage extraction on the mixture of glycerol and glyceryl carbonate, thereby achieving the extraction and separation of high-concentration glyceryl carbonate. In addition, the separated glyceryl carbonate has a high yield and concentration, with a yield of 99.9% and a concentration of 99.6%.

[0030] In some preferred embodiments, the top outlet of the extractant recovery distillation column 2 is connected to the first inlet of the extraction column 1; the top outlet of the raffinate extractant recovery distillation column 3 is connected to the second inlet of the extraction column 1. This allows the extractant mixture rich in the first extractant collected at the top of the column after distillation of the extractant phase, and the extractant mixture rich in the second extractant collected at the top of the column after distillation of the raffinate phase, to be recycled back to the extraction column 1 for reuse, improving extractant utilization and reducing costs.

[0031] In some preferred embodiments, the separation system further includes a first extractant mixer 5 and a second extractant mixer 4. The first extractant mixer 5 has a first inlet and a second inlet. The first inlet of the first extractant mixer 5 receives supplemental first extractant, and the second inlet of the first extractant mixer 5 is connected to the top outlet of the extractant recovery distillation column 2. The outlet of the first extractant mixer 5 is connected to the first inlet of the extraction column 1. The second extractant mixer 4 has a first inlet and a second inlet. The first inlet of the second extractant mixer 4 receives supplemental second extractant, and the second inlet of the second extractant mixer 4 is connected to the top outlet of the raffinate recovery distillation column 3. The outlet of the second extractant mixer 4 is connected to the second inlet of the extraction column 1. The first extractant mixer 5 can uniformly mix the extractant mixture rich in the first extractant with the supplemental first extractant before returning it to the extraction column 1. This ensures the uniformity of the extractant components entering the extraction column 1, thereby ensuring the uniformity of extraction. Similarly, the second extractant mixer 4 can uniformly mix the extractant mixture rich in the second extractant with the supplemental second extractant.

[0032] In some preferred embodiments, the separation system further includes a splitter 6, the inlet of which is connected to the top outlet of the extractant recovery distillation column 2, the first outlet of which is connected to the first inlet of the extraction column 1, and the second outlet of which is connected to the second inlet of the extraction column 1.

[0033] In some preferred embodiments, the extraction column 1 has 8 to 30 trays, with the trays arranged sequentially from top to bottom. The third inlet of the extraction column 1 is located at trays 2 to 20. More preferably, the extraction column 1 has 10 to 18 trays, with the third inlet located at trays 6 to 10. The location of the third inlet affects the extraction separation effect and the required number of trays. This inlet configuration allows for optimal separation with the fewest possible trays, meaning the top outlet stream of the extraction column contains almost no glycerol, and the bottom outlet stream contains almost no glyceryl carbonate.

[0034] In some preferred embodiments, the extractant recovery distillation column 2 has 10-30 trays, with the trays arranged sequentially from top to bottom. The feed inlet of the extractant recovery distillation column 2 is located at trays 3-20. More preferably, the extractant recovery distillation column 2 has 12-19 trays, with the feed inlet located at trays 5-9. This arrangement aims to completely separate the extractant and glyceryl carbonate with as few trays and energy consumption as possible. Increasing the number of trays improves the purity of the top product, increases separation efficiency, and reduces the amount of reflux liquid required to achieve the same separation goal. However, an excessive number of trays increases equipment investment and operating costs. The feed location is mainly determined by the feed composition; a higher extractant concentration results in a higher feed location for better separation.

[0035] In some preferred embodiments, the number of trays in the raffinate extractant recovery distillation column 3 is 20-70; the tray sequence is defined as increasing sequentially from the top to the bottom of the column, with the feed inlet of the raffinate extractant recovery distillation column 3 located at trays 10-65; more preferably, the number of trays in the raffinate extractant recovery distillation column 3 is 30-60, with the feed inlet located at trays 15-30. This arrangement is intended to completely separate the extractant and glyceryl carbonate with as few trays and energy consumption as possible.

[0036] The extractant recovery distillation column 2 and the raffinate extractant recovery distillation column 3 are equipped with condensers at the top and reboilers at the bottom to complete the distillation separation.

[0037] The extraction tower 1, the extractant recovery distillation tower 2, and the raffinate extractant recovery distillation tower 3 described in this invention are plate towers or packed towers. If a packed tower is selected, the number of tower plates is calculated from the packing layer height and the equal plate height.

[0038] Based on the separation system described above, the present invention provides a separation process for a glycerol-glyceryl carbonate mixture, comprising: The glycerol-glyceryl carbonate mixture is fed into the third inlet of extraction tower 1. The first extractant and the second extractant enter the extraction tower 1 from the first inlet and the second inlet, respectively. The glycerol-glyceryl carbonate mixture is subjected to multi-stage extraction using the first extractant and the second extractant. The extract phase is collected from the top outlet of extraction tower 1, and the raffinate phase is collected from the bottom outlet of extraction tower 1. The extract phase is separated in extract phase extractant recovery distillation column 2, and the heavy distillate is glycerol carbonate, while the light distillate is an extractant mixture rich in the first extractant. The raffinate is separated in raffinate extractant recovery distillation column 3, and the heavy distillate is glycerol, while the light distillate is an extractant mixture rich in the second extractant.

[0039] The extract phase comprises a large amount of the first extractant, glyceryl carbonate, and a small amount of the second extractant. The raffinate phase comprises a large amount of the second extractant, glycerol, and a small amount of the first extractant. The extract phase is distilled to obtain a high concentration of glyceryl carbonate at the bottom of the column and an extractant mixture rich in the first extractant at the top. The raffinate phase is distilled to obtain a high concentration of glycerol at the bottom of the column and an extractant mixture rich in the second extractant at the top. To improve the utilization rate of the extractant and reduce costs, the extractant mixture rich in the first and second extractants can be recycled back to extraction column 1 for reuse.

[0040] Specifically, in some preferred embodiments, the extractant mixture rich in the first extractant is mixed with a supplement of the first extractant and then enters the extraction tower 1 from the first inlet of the extraction tower 1; the extractant mixture rich in the second extractant is mixed with a supplement of the second extractant and then enters the extraction tower 1 from the second inlet of the extraction tower 1.

[0041] In some preferred embodiments, the extractant mixture rich in the first extractant is split into two parts by a splitter 6. One part, after being mixed with a supplemented second extractant, enters the extraction column 1 through the second inlet. This part accounts for 5% to 50% of the total flow rate at the top of the extractant recovery distillation column 2, more preferably 15% to 30%, and is used to recycle a portion of the second extractant entering the extraction phase back to the second inlet for better extraction separation. However, since the mixture is predominantly composed of the first extractant, this proportion cannot be too high to prevent excessive first extractant from entering the extraction column through the second inlet, which could adversely affect the separation. The other part, split by the splitter 6, is mixed with a supplemented first extractant and enters the extraction column 1 through the first inlet.

[0042] In some preferred embodiments, the mass flow ratio of the first extractant entering the extraction tower 1 to the glycerol-glyceryl carbonate mixture feed is 1 to 6, more preferably 1 to 4. If this mass flow ratio is too small, the extraction and separation effect will be unsatisfactory; if it is too large, the utilization rate of the extractant and the efficiency of the process will decrease.

[0043] In some preferred embodiments, the mass flow ratio of the second extractant entering the extraction tower 1 to the glycerol-glyceryl carbonate mixture feed is 0.5~2, more preferably 0.5~1. If this mass flow ratio is too small, the extraction and separation effect will be unsatisfactory; if it is too large, the utilization rate of the extractant and the efficiency of the process will decrease.

[0044] In some preferred embodiments, the multi-stage extraction pressure of the extraction tower 1 is 0.5~3.5 atm, and the extraction temperature is 20~80 °C; more preferably, the multi-stage extraction pressure is 1~1.3 atm, and the extraction temperature is 25~35 °C. The extraction pressure has almost no effect on the separation effect, while the miscibility between components increases with increasing temperature. Therefore, increasing the temperature is detrimental to the extraction and separation effect, but excessively low temperatures require a cooling unit, which is not economical.

[0045] In some preferred embodiments, the pressure of the extractant recovery distillation column 2 is 0.1~2 atm, the bottom temperature is 150~300 ℃, the top temperature is 30~80 ℃, and the reflux ratio is 0.1~5; more preferably, the pressure is 0.1~1.2 atm, the bottom temperature is 180~250 ℃, the top temperature is 35~60 ℃, and the reflux ratio is 0.1~2. To reduce the risk of high-temperature decomposition of glycerol carbonate, the distillation operating pressure can be appropriately reduced to lower the bottom temperature; the top temperature mainly depends on the boiling point of the extractant. By setting the pressure, reflux ratio, and bottom temperature in this way, the concentration of glycerol carbonate collected from the bottom of the extractant recovery distillation column 2 can be not less than 99%, preferably greater than 99.5%, with fewer trays and lower energy consumption.

[0046] In some preferred embodiments, the pressure of the raffinate extractant recovery distillation column 3 is 0.1~2 atm, the bottom temperature is 150~300 ℃, the top temperature is 30~100 ℃, and the reflux ratio is 0.1~3; more preferably, the pressure is 0.1~1.1 atm, the bottom temperature is set to 160~280 ℃, the top temperature is set to 50~90 ℃, and the reflux ratio is 0.1~1. To reduce the risk of high-temperature decomposition of glycerol, the distillation operating pressure can be appropriately reduced to lower the bottom temperature; the top temperature mainly depends on the boiling point of the extractant. By setting the pressure, reflux ratio, and bottom temperature in this way, the concentration of the glycerol product collected from the bottom of the raffinate extractant recovery distillation column 3 can be achieved with fewer trays and lower energy consumption, with a concentration not less than 93%, preferably greater than 97%.

[0047] The multi-stage extraction and separation process of the glycerol-glyceryl carbonate mixture of the present invention can be used to separate glycerol-glyceryl carbonate mixtures containing 1% to 99% glyceryl carbonate; preferably, it can be used to separate mixtures containing 10% to 95% glyceryl carbonate.

[0048] Example 1 This embodiment 1 adopts Figure 1 The separation system shown includes: an extraction column 1, an extractant recovery distillation column 2, a raffinate extractant recovery distillation column 3, a first extractant mixer 5, and a second extractant mixer 4; the extraction column 1 has a first inlet, a second inlet, and a third inlet at its bottom, top, and middle sections, respectively; the third inlet of the extraction column 1 is used to receive a glycerol-glyceryl carbonate mixture; the first inlet of the extraction column 1 is used to receive a first extractant; and the second inlet of the extraction column 1 is used to receive a second extractant; the first extractant is 2-pentanone, and the second extractant is water.

[0049] The first extractant mixer 5 has a first inlet and a second inlet. The first inlet of the first extractant mixer 5 is used to receive the supplemented first extractant. The second inlet of the first extractant mixer 5 is connected to the top outlet of the extractant recovery distillation column 2. The outlet of the first extractant mixer 5 is connected to the first inlet of the extraction column 1. The second extractant mixer 4 has a first inlet and a second inlet. The first inlet of the second extractant mixer 4 is used to receive the supplemented second extractant. The second inlet of the second extractant mixer 4 is connected to the top outlet of the raffinate recovery distillation column 3. The outlet of the second extractant mixer 4 is connected to the second inlet of the extraction column 1.

[0050] The number of trays in extraction column 1 is 12; the feed position of the glycerol-glyceryl carbonate mixture is the 8th tray; the feed position of the first extractant is the 12th tray; the feed position of the second extractant is the 1st tray; (2) The number of trays in extraction phase extractant recovery distillation column 2 is 13; the feed position of the extraction phase is the 5th tray; the number of trays in raffinate phase extractant recovery distillation column 3 is 40; the feed position of the raffinate phase is the 20th tray.

[0051] The separation process in this embodiment includes: The glycerol-glyceryl carbonate mixture is fed into the third inlet of extraction tower 1. The first extractant and the second extractant enter the extraction tower 1 from the first inlet and the second inlet, respectively. The glycerol-glyceryl carbonate mixture is subjected to multi-stage extraction using the first extractant and the second extractant. The extract phase is collected from the top outlet of extraction tower 1, and the raffinate phase is collected from the bottom outlet of extraction tower 1. The extract phase is separated in extract phase extractant recovery distillation column 2, and the heavy distillate is glycerol carbonate, while the light distillate is an extractant mixture rich in the first extractant. The raffinate phase is separated by raffinate phase extractant recovery distillation column 3, and the heavy distillate is glycerol, while the light distillate is an extractant mixture rich in the second extractant. The extractant mixture rich in the first extractant is mixed with the replenished first extractant and then returned to the extraction tower 1 from the first inlet; The extractant mixture rich in the second extractant is mixed with the supplemented second extractant and then returned to the extraction tower 1 from the second inlet of the extraction tower 1.

[0052] The key process conditions are as follows: (1) The pressure of extraction tower 1 is atmospheric pressure 1 atm and the extraction temperature is 30℃; (2) The pressure of the extractant recovery distillation column 2 is 0.1 atm; the bottom temperature is set to 215 ℃ and the top temperature is set to 50 ℃; the reflux ratio is set to 0.1. (3) The pressure of the distillation column 3 for recovering the raffinate extractant is 1 atm; the top temperature is set to 57 ℃; the bottom temperature is set to 270 ℃; and the reflux ratio is set to 0.1. (4) The mass fraction of glycerol in the glycerol-glyceryl carbonate mixture to be separated is 16%, and the mass fraction of glyceryl carbonate is 84%. (5) The first extractant feed is 1.8 times the mass flow rate of the glycerol-glyceryl carbonate mixture, and the second extractant in the top feed of extraction tower 1 is 0.3 times the mass flow rate of the glycerol-glyceryl carbonate mixture.

[0053] Example 2: Splitting the extractant phase like Figure 2 As shown, the separation system in this embodiment is basically the same as the separation system corresponding to Embodiment 1, except that: the separation system further includes a splitter 6, the inlet of the splitter 6 is connected to the top outlet of the extractant recovery distillation column 2, the first outlet of the splitter 6 is connected to the second inlet of the first extractant mixer 5, and the second outlet of the splitter 6 is connected to the third inlet of the second extractant mixer 4.

[0054] The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 1, except that: the mixed extractant rich in the first extractant is taken from the top of the extractant recovery distillation column 2 and divided into two streams by the splitter 6 with a mass ratio of 1:4. One stream with a mass fraction of 20% is recycled back to the top feed of the extraction column 1, and the remaining 80% is recycled back to the bottom feed of the extraction column 1.

[0055] Example 3: Changing the initial feed rate of the second extractant, water. The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 2, except that the ratio of the second extractant water to the glycerol-glyceryl carbonate mixture feed mass flow rate is adjusted to 0.2.

[0056] Example 4: Changing the split mass ratio of the circulating flow stream The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 2, except that: the distillate from the top of the extractant recovery distillation column 2 is separated by the splitter 6, with a mass fraction of 25%, and recycled back to the top feed of the extraction column 1, while the remaining 75% is recycled back to the bottom feed of the extraction column 1.

[0057] Example 5: Changing the feed position of raw materials The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 2, except that the feed position of the glycerol-glyceryl carbonate mixture is adjusted to the first tray.

[0058] Example 6: Changing the mass ratio of glycerol to glyceryl carbonate in a glycerol-glyceryl carbonate mixture The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 2, except that the mass fraction of glycerol in the glycerol-glyceryl carbonate mixture is 44% and the mass fraction of glyceryl carbonate is 56%.

[0059] Example 7: Changing the mass ratio of glycerol to glyceryl carbonate in a glycerol-glyceryl carbonate mixture The separation process of the glycerol-glyceryl carbonate mixture in this embodiment is basically the same as that in Example 2, except that the mass fraction of glycerol in the glycerol-glyceryl carbonate mixture is 4% and the mass fraction of glyceryl carbonate is 96%.

[0060] The extraction and separation effects obtained in Examples 1-7 are shown in Table 1.

[0061] Table 1

[0062] As can be seen from Example 1, the process of the present invention can completely separate high-concentration glycerol carbonate mixtures. Comparing Examples 1 and 2, it can be seen that the product concentration and recovery rate obtained by splitting a portion of the extractant and recycling it back to the second inlet of the extraction tower (Example 2) are both superior. Examples 3 and 4 demonstrate that the process of the present invention can effectively separate glycerol-glycerol carbonate mixtures under the required parameter configurations. Example 5 shows that when the feed position of the glycerol-glycerol carbonate mixture is unfavorable (first plate), the concentration of glycerol carbonate obtained is lower. Examples 6 and 7 show that the process of the present invention is also applicable to the separation of glycerol-glycerol carbonate mixtures with low concentrations (Example 6) and higher concentrations (Example 7).

[0063] In summary, the separation process of glycerol carbonate and glycerol provided by this invention allows the first extractant and water to form a liquid-liquid two-phase system, avoiding the problem of miscibility between the extractant and glycerol and inability to separate layers due to excessively high concentrations of glycerol carbonate in the mixture. This process is applicable to a wide range of concentrations. The extraction tower is equipped with three inlets for feeding the mixture to be separated, the first extractant, and the second extractant, respectively. Glycerol and glycerol carbonate are completely separated through a single extraction tower, and the extractant is further separated by an extractant distillation tower, resulting in a high concentration of glycerol and glycerol carbonate with a yield close to 100%. This achieves a highly efficient and continuous separation effect, with a glycerol carbonate concentration as high as 99.6% and a yield of 99.9%.

[0064] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it; obviously, the listed embodiments are only a part of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

Claims

1. A continuous separation system for a glycerol-glyceryl carbonate mixture, characterized in that, include: Extraction column (1), extract phase extractant recovery distillation column (2) and raffinate phase extractant recovery distillation column (3); The extraction tower (1) has a first inlet, a second inlet, and a third inlet at its bottom, top, and middle sections, respectively. The third inlet of the extraction tower (1) is used to receive a glycerol-glyceryl carbonate mixture, the first inlet of the extraction tower (1) is used to receive a first extractant, and the second inlet of the extraction tower (1) is used to receive a second extractant. The first extractant is methyl isobutyl ketone, cyclohexanone, or 2-pentanone, and the second extractant is water. The top outlet of the extraction tower (1) is connected to the inlet of the extraction phase extractant recovery distillation tower (2), and the bottom outlet is connected to the inlet of the raffinate phase extractant recovery distillation tower (3).

2. The continuous separation system for the glycerol-glyceryl carbonate mixture according to claim 1, characterized in that, The top outlet of the extractant recovery distillation column (2) is connected to the first inlet of the extraction column (1); the top outlet of the raffinate extractant recovery distillation column (3) is connected to the second inlet of the extraction column (1).

3. The continuous separation system for the glycerol-glyceryl carbonate mixture according to claim 2, characterized in that, It also includes a first extractant mixer (5) and a second extractant mixer (4); the first extractant mixer (5) is provided with a first inlet and a second inlet, the first inlet of the first extractant mixer (5) is used to receive the supplemented first extractant, the second inlet of the first extractant mixer (5) is connected to the top outlet of the extractant recovery distillation column (2), and the outlet of the first extractant mixer (5) is connected to the first inlet of the extraction column (1); the second extractant mixer (4) is provided with a first inlet and a second inlet, the first inlet of the second extractant mixer (4) is used to receive the supplemented second extractant, the second inlet of the second extractant mixer (4) is connected to the top outlet of the raffinate extractant recovery distillation column (3), and the outlet of the second extractant mixer (4) is connected to the second inlet of the extraction column (1).

4. The continuous separation system for the glycerol-glyceryl carbonate mixture according to claim 2, characterized in that, It also includes a splitter (6), the inlet of which is connected to the top outlet of the extractant recovery distillation column (2), the first outlet of which is connected to the first inlet of the extraction column (1), and the second outlet of which is connected to the second inlet of the extraction column (1).

5. The continuous separation system for the glycerol-glyceryl carbonate mixture according to claim 1, characterized in that, The extraction tower (1) has 8 to 30 trays, the extraction phase extractant recovery distillation tower (2) has 10 to 30 trays, and the raffinate phase extractant recovery distillation tower (3) has 20 to 70 trays. The tray order of the extraction tower (1), the extraction phase extractant recovery distillation tower (2), and the raffinate phase extractant recovery distillation tower (3) is defined as increasing sequentially from the top to the bottom of the tower. The third inlet of the extraction tower (1) is located at the 2nd to 20th tray. The feed inlet of the extraction phase extractant recovery distillation tower (2) is located at the 3rd to 20th tray. The feed inlet of the raffinate phase extractant recovery distillation tower (3) is located at the 10th to 65th tray.

6. A continuous separation process for a glycerol-glyceryl carbonate mixture, characterized in that, The continuous separation system according to any one of claims 1 to 5 includes: The glycerol-glyceryl carbonate mixture is fed into the third inlet of the extraction tower (1). The first extractant and the second extractant enter the extraction tower (1) from the first inlet and the second inlet, respectively. The glycerol-glyceryl carbonate mixture is subjected to multi-stage countercurrent extraction using the first extractant and the second extractant. The extract phase is collected at the top outlet of the extraction tower (1), and the raffinate phase is collected at the bottom outlet of the extraction tower (1). The extract phase is separated by an extract phase extractant recovery distillation column (2), and the heavy distillate is glycerol carbonate, while the light distillate is an extractant mixture rich in the first extractant. The raffinate is separated by a raffinate extractant recovery distillation column (3), and the heavy distillate is glycerol, while the light distillate is an extractant mixture rich in the second extractant.

7. The continuous separation process for the glycerol-glyceryl carbonate mixture according to claim 6, characterized in that, The extractant mixture rich in the first extractant is mixed with the supplemented first extractant and then enters the extraction tower (1) through the first inlet; the extractant mixture rich in the second extractant is mixed with the supplemented second extractant and then enters the extraction tower (1) through the second inlet.

8. The continuous separation process for the glycerol-glyceryl carbonate mixture according to claim 7, characterized in that, The extractant mixture rich in the first extractant is divided into two parts by the splitter (6). One part is mixed with the supplemented first extractant and enters the extraction tower (1) from the first inlet of the extraction tower (1). The other part is mixed with the supplemented second extractant and enters the extraction tower (1) from the second inlet of the extraction tower (1).

9. The continuous separation process for the glycerol-glyceryl carbonate mixture according to claim 7, characterized in that, The mass flow ratio of the first extractant to the glycerol-glyceryl carbonate mixture fed into the extraction tower (1) is 1 to 6; the mass flow ratio of the second extractant to the glycerol-glyceryl carbonate mixture fed into the extraction tower (1) is 0.5 to 2.

10. The continuous separation process for the glycerol-glyceryl carbonate mixture according to claim 6, characterized in that, The multi-stage extraction pressure of the extraction column (1) is 0.5~3.5 atm, and the extraction temperature is 20~80 ℃; the extraction phase extractant recovery distillation column (2) has a column pressure of 0.1~2 atm, a bottom temperature of 150~300 ℃, a top temperature of 30~80 ℃, and a reflux ratio of 0.1~5; the raffinate extractant recovery distillation column (3) has a column pressure of 0.1~2 atm, a bottom temperature of 150~300 ℃, a top temperature of 30~100 ℃, and a reflux ratio of 0.1~3.

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