Production process and production system of glycolide

Abstract

The invention provides a production process and a production system of glycolide, and the production process of glycolide comprises the following steps: generating crude glycolide steam through a cracking cyclization reaction of glycollic acid or glycollate oligomer and a catalyst, and enabling the crude glycolide steam to enter a quench tower from the bottom of the quench tower, the crude glycolide steam is in vapor-liquid countercurrent contact with quenching spray liquid which is continuously sprayed downwards in the quenching tower, so that the crude glycolide steam is quickly cooled and condensed, the adopted quenching spray liquid comprises a material flow B1 which is shunted by a crude glycolide material flow A in a pressurizing process, and meanwhile, the invention provides a corresponding glycolide production system. According to the production process and the production system of the glycolide, disclosed by the invention, the retention time of the glycolide in a high-temperature region is finally short, the amount of the glycolide entrained in a vapor phase is less, self-polymerization of the glycolide can be greatly reduced, the pressure drop is low, and the possibility of blockage is low.

Description

Technical Field

[0001] The invention belongs to the field of biodegradable materials, and in particular relates to a production process and a production system of glycolide. Background Art

[0002] Polyglycolic acid, also known as polyglycolic acid (PGA), is a biodegradable aliphatic polymer that can be hydrolyzed under the catalysis of enzymes or acids and bases in microorganisms or organisms to eventually form carbon dioxide and water. It is a biodegradable material with great development potential. Glycolide is a cyclic dimer of glycolic acid. Ring-opening polymerization of glycolide is a relatively mature method for preparing polyglycolic acid, which can obtain polyglycolic acid with a higher relative molecular mass.

[0003] The production of glycolide uses glycolic acid or glycolic acid esters as the reactants to prepare glycolic acid oligomers through condensation polymerization, and then the glycolic acid oligomers are cracked into rings to produce glycolide. The crude glycolide produced by the ring-forming reactor contains impurities such as water, glycolic acid and oligomers in addition to glycolide, and needs to be purified and refined before it can be used.

[0004] The purification methods of glycolide mainly include solvent absorption method, gas-assisted evaporation method, recrystallization method, etc., and the recrystallization method is used more frequently: after the cracking is completed, the crude glycolide enters the dissolution kettle to cool to room temperature, and then the recrystallization solvent is added to the dissolution kettle for purification. In the above production process, glycolide is evaporated from the cyclization reactor under high temperature and high vacuum, and the hot liquid glycolide directly enters the dissolution kettle for cooling, or enters the dissolution kettle for cooling after condensation. This process inevitably has a high-temperature residence period, and glycolide is prone to self-polymerization at high temperature to generate low molecular weight polymers, which ultimately leads to a decrease in the quality and / or yield of glycolide. Summary of the invention

[0005] Aiming at the problem that the crude glycolide product in the prior art is easy to self-polymerize during the cooling process in the glycolide production process, the present invention provides a glycolide production process and a production system thereof. The production process adopts glycolide vapor bottom feeding, glycolide flow out of the bottom, spraying liquid top spraying, and flowing out of the bottom together. During the spraying process of the spraying liquid, the high-temperature glycolide vapor is converted into a relatively low-temperature liquid flow. The crude glycolide product can be quickly obtained, and the time that glycolide stays at a high temperature is reduced, thereby reducing the self-polymerization of glycolide.

[0006] In one aspect, a process for producing glycolide of the present invention comprises the following steps:

[0007] 1) generating crude glycolide vapor through a cracking ring reaction of glycolic acid or glycolate oligomers and a catalyst;

[0008] 2) the crude glycolide vapor enters the interior of the quenching tower from the bottom of the quenching tower to undergo a spray cooling process; during the spray cooling process, the crude glycolide vapor is in vapor-liquid countercurrent contact with the quenching spray liquid continuously sprayed downward from the interior of the quenching tower to obtain rapidly condensed and cooled crude glycolide; the temperature at the top of the quenching tower is 30-105° C., and the temperature at the bottom of the tower is 70-120° C.;

[0009] 3) The crude glycolide after condensation and cooling is accumulated at the bottom of the quench tower to form a crude glycolide logistics A, and the crude glycolide logistics A is divided into logistics B1 and logistics B2 through a pressurization process; the logistics B1 is cooled again to form a quench solvent B1, and the quench solvent B1 is recycled into the quench spray liquid described in step 2); the logistics B2 is purified by a refining unit to obtain high-purity glycolide.

[0010] In the above-mentioned glycolide production process, the crude glycolide vapor generated by the cracking ring reaction enters the bottom of the quenching tower, and the vapor-liquid two phases are countercurrently contacted in the tower, and the crude glycolide vapor is quickly condensed and cooled. The glycolide stays in the high temperature zone for a short time, which can greatly reduce the self-polymerization of glycolide. In the step 3), the crude glycolide stream A is divided into stream B1 and stream B2 through the pressurization process; the stream B1 is cooled again to form a quenching solvent B1, which is circulated back to the quenching tower and sprayed downward as the quenching spray liquid; the other stream B2 is refined and purified in the glycolide refining unit.

[0011] Furthermore, in the production process of glycolide described in the present invention, the quenching spray liquid also includes a quenching solvent C other than the quenching solvent B1, and the temperature of the quenching solvent C is 30-130°C; the temperature of the top of the quenching tower is 30-100°C, and the temperature of the bottom of the tower is 70-115°C.

[0012] Furthermore, the quenching solvent C in the glycolide production process of the present invention includes one or more of alcohols, esters, ketones, ethers or hydrocarbon organic substances with a boiling point of 120 to 300° C. Preferably, the quenching solvent C may include one or more of methyl glycolate, 1,4-butanediol, ethylene glycol and C6 to C9 alcohols.

[0013] Furthermore, the quenching spray liquid in the glycolide production process of the present invention also includes a quenching solvent C, which reduces the amount of crude glycolide flow from the circulating cooler that needs to be circulated back to the quenching tower for spraying, thereby reducing the load of the circulating cooler.

[0014] Furthermore, the steam discharged from the top of the quench tower in the glycolide production process of the present invention is condensed to obtain light organic matter D, and the quench solvent C also contains the light organic matter D.

[0015] Furthermore, the steam discharged from the top of the quench tower in the glycolide production process of the present invention is a vapor phase flow containing trace amounts of glycolide, which enters the condenser and continues to condense into light organic matter D and tail gas. Among them, the light organic matter D can be recycled back to the quench solvent C and used as a quench spray liquid in the spray cooling process; and the tail gas is generally recycled.

[0016] Furthermore, in the production process of glycolide described in the present invention, the spray cooling process comprises two or more spray layers for spraying;

[0017] The quenching spray liquid of the upper spray layer of the spray layer is the quenching solvent C, and the quenching spray liquid of the lower spray layer of the spray layer is the quenching solvent B1; or, the quenching spray liquid of the spray layer is a mixture of the quenching solvent C and the quenching solvent B1.

[0018] Furthermore, in the glycolide production process of the present invention, the weight ratio of the quenching solvent C to the liquid vapor of the crude glycolide vapor is 0.3-10, and the weight ratio of the quenching spray liquid to the liquid vapor of the crude glycolide vapor is 5-35.

[0019] Furthermore, in the glycolide production process of the present invention, the quenching spray liquid located in the upper spray layer is the quenching solvent C, and the quenching spray liquid located in the lower spray layer is the quenching solvent B1; the quenching solvent C is divided into 1 to 5 spray layers for spraying downward, and the quenching solvent B1 is divided into 1 to 10 spray layers for spraying downward.

[0020] Furthermore, in the glycolide production process of the present invention, the upper spray liquid is the quenching solvent C, and the lower spray liquid is the quenching solvent B1. Since the temperature of the quenching solvent C entering the quenching tower is lower than the temperature of the quenching solvent B1 entering the quenching tower, it not only reduces the amount of crude glycolide flow from the circulating cooler that needs to be circulated back to the quenching tower for spraying, thereby reducing the load of the circulating cooler, but also has a better condensation and cooling effect on the vapor phase rising to the upper part of the quenching tower, thereby further reducing the amount of glycolide entrained in the vapor phase.

[0021] Furthermore, the quenching tower in the glycolide production process of the present invention can generally be an empty tower, a packed tower or a plate tower. Preferably, the quenching tower is an empty tower.

[0022] The spray cooling process of the present invention may also be set to only one spray layer, and the quenching spray liquid of the spray layer may be only the quenching solvent B1, or a mixture of the quenching solvent B1 and the quenching solvent C.

[0023] Furthermore, in the glycolide production process of the present invention, the absolute pressure of the cracking ring reaction in step 1) is 100-5000 Pa, the temperature of the crude glycolide vapor is 180-300° C., and the internal absolute pressure of the quenching tower is 100-5000 Pa.

[0024] The glycolide production process of the present invention has low pressure drop and is not easy to be blocked. The residence time of glycolide in the high temperature zone is short, and the self-polymerization of glycolide can be greatly reduced.

[0025] The cracking and cyclization reaction of the present invention generates not only the crude glycolide vapor but also a melt after the depolymerization and cyclization reaction, and the melt is discharged through a melt flow pipeline.

[0026] In another aspect, the present invention provides a glycolide production system, comprising: a ring-forming reactor, a quenching tower and a refining unit, and a logistics pipeline connecting the various devices;

[0027] The exhaust port of the loop reactor is connected to the bottom of the quench tower through a logistics pipeline, and the bottom discharge port of the quench tower is coupled and connected to the refining unit;

[0028] A spray structure is provided inside the quenching tower, and the spray structure includes a first spray structure, and the first spray structure is provided with one or more spray layers;

[0029] A booster device is connected between the bottom discharge port of the quench tower and the feed port of the refining unit. The booster device is connected to a circulating cooler, and the circulating cooler is connected to the first spray structure through a logistics pipeline.

[0030] In the present invention, a booster device is provided between the quenching tower and the feed inlet of the refining unit, or a booster device and a circulating cooler are provided between the quenching tower and the feed inlet of the refining unit; the circulating cooler is connected to the first spray structure through a logistics pipeline.

[0031] Furthermore, in the glycolide production system of the present invention, the spray structure further comprises a second spray structure, and the second spray structure is provided with a spray layer having a number greater than or equal to 1;

[0032] The second spray structure is located above the first spray structure;

[0033] The production system also includes: a solvent supply unit, a condenser, an organic matter recovery unit and a tail gas recovery and processing unit;

[0034] The solvent supply unit is connected to the second spray structure through a logistics pipeline, and a heat exchanger is provided between the solvent supply unit and the quenching tower;

[0035] The condenser is coupled to the top discharge port of the quench tower, the organic matter recovery unit is connected to the liquid outlet of the condenser through a logistics pipeline, and the tail gas recovery and processing unit is connected to the non-condensable gas outlet of the condenser through a logistics pipeline;

[0036] The discharge port of the organic matter recovery unit is communicated with the heat exchanger through a logistics pipeline.

[0037] Furthermore, in the glycolide production system of the present invention, a filtering device is provided before and / or after the boosting device;

[0038] The ring-forming reactor further comprises a defoaming structure, and the defoaming structure is arranged at the exhaust port of the ring-forming reactor, or the defoaming structure is arranged inside the ring-forming reactor;

[0039] The quenching tower is an empty tower, a packed tower or a plate tower, and the shell of the quenching tower is provided with a heat preservation device.

[0040] Furthermore, a filtering device is provided before and / or after the boosting device in the glycolide production system of the present invention to remove oligomers and / or other solid substances contained in the crude glycolide flow. Preferably, the shell of the quenching tower is provided with a heat preservation device to prevent the glycolide from solidifying.

[0041] Furthermore, the defoaming structure in the glycolide production system of the present invention is used to remove low molecular weight polymers entrained in the crude glycolide vapor.

[0042] Furthermore, when the quench tower in the glycolide production system of the present invention is an empty tower, the spray layer of the spray structure can be a spray pipeline structure layer, and the number of spray structure layers is preferably set to 1 to 10 layers of downward spraying, including 1 spray layer and 10 spray layers. More preferably, the number of the spray layers is 3 to 8 layers of downward spraying.

[0043] Furthermore, when the quenching tower in the glycolide production system of the present invention is a packed tower or a plate tower, the spray structure layer may be a plate, and the theoretical number of plates is preferably 1-10.

[0044] In another aspect, the above-mentioned system for producing glycolide of the present invention is used in the above-mentioned process for producing glycolide.

[0045] The present invention has the following beneficial effects:

[0046] In the glycolide production process and production system of the present invention, the vapor-liquid two phases are countercurrently contacted inside the quench tower, and the crude glycolide vapor is quickly cooled, so that the residence time of glycolide in the high temperature zone is short, the amount of glycolide entrained in the vapor phase is less, the self-polymerization of glycolide can be greatly reduced, and the pressure drop is low and it is not easy to block. In addition, the quench spray liquid of the present invention can also include a quench solvent of alcohols, esters, ketones, ethers or hydrocarbon organic matter with a boiling point of 120 to 300° C., which reduces the amount of crude glycolide flow from the circulating cooler that needs to be circulated back to the quench tower for spraying, and reduces the load of the circulating cooler. Further, the upper quench spray liquid is the quench solvent, and the lower quench spray liquid is a part of the crude glycolide flow that has been pressurized and cooled. The quench solvent has a better condensation and cooling effect on the vapor phase rising to the upper part of the quench tower, and further reduces the amount of glycolide entrained in the vapor phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of a glycolide production system provided by an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of a glycolide production system provided by another embodiment of the present invention;

[0049] Figure 3 A schematic diagram of a glycolide production system provided by another embodiment of the present invention;

[0050] 1a, loop reactor, 2a, quench tower, 3a, circulating cooler, 4a, booster equipment, 5a, condenser, 6a, refining unit, 7a, solvent supply unit, 8a, organic matter recovery unit, 9a, tail gas recovery and treatment unit, 10a, heat exchanger;

[0051] 1. Raw material logistics pipeline, 2. Steam logistics pipeline, 3. Melt logistics pipeline, 4. Vapor phase recovery logistics pipeline, 5. 、 Crude glycolide logistics pipeline, 6, purification logistics pipeline, 7 、 Circulating spray liquid logistics pipeline, 7B 、 Rapid cooling solvent logistics pipeline, 8. Light organic matter logistics pipeline, 9. Exhaust gas logistics pipeline. DETAILED DESCRIPTION

[0052] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described in detail with reference to the accompanying drawings. 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. If the specific conditions are not specified in the specific implementation methods, they shall be carried out according to the conventional conditions or the conditions recommended by the manufacturer.

[0053] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims. The terms used in the present disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure.

[0054] The present invention is further described in detail below in conjunction with specific embodiments.

[0055] Example 1

[0056] A production process of glycolide of the present invention, the specific steps of the production process include:

[0057] 1) Crude glycolide vapor is generated by cracking and cyclizing glycolic acid or glycolate oligomers and a catalyst; the absolute pressure of the cracking and cyclizing reaction is 100-5000 Pa, and the temperature of the crude glycolide vapor is 180-300°C.

[0058] 2) The crude glycolide vapor enters the interior of the quenching tower from the bottom of the quenching tower and undergoes a spray cooling process; during the spray cooling process, the crude glycolide vapor and the quenching spray liquid continuously sprayed downward from the interior of the quenching tower undergo vapor-liquid countercurrent contact to obtain rapidly condensed and cooled crude glycolide; the temperature at the top of the quenching tower is 30-105°C, and the temperature at the bottom of the tower is 70-120°C; the internal absolute pressure of the quenching tower is 100-5000Pa.

[0059] 3) The crude glycolide after condensation and cooling is gathered at the bottom of the quench tower to form a crude glycolide logistics A, and the crude glycolide logistics A is separated into logistics B1 and logistics B2 through a pressurization process; logistics B1 is cooled again to form a quench solvent B1, and the quench solvent B1 is recycled to the quench spray liquid in step 2); logistics B2 is purified by a refining unit to obtain high-purity glycolide.

[0060] The spray cooling process includes one or more spray layers for spraying; the quenching spray liquid of the spray layer is the quenching solvent B1, and the weight ratio of the quenching solvent B1 to the crude glycolide vapor is 3 to 35. Exemplarily, 1 to 10 spray layers are set to spray downward; more preferably, 3 to 8 spray layers are set to spray downward.

[0061] Example 2

[0062] A production process of glycolide of the present invention comprises the following steps:

[0063] 1) Crude glycolide vapor is generated by cracking and cyclizing glycolic acid or glycolate oligomers and a catalyst; the absolute pressure of the cracking and cyclizing reaction is 100-5000 Pa, and the temperature of the crude glycolide vapor is 180-300°C.

[0064] 2) The crude glycolide vapor enters the interior of the quenching tower from the bottom of the quenching tower and undergoes a spray cooling process; during the spray cooling process, the crude glycolide vapor and the quenching spray liquid continuously sprayed downward from the interior of the quenching tower undergo vapor-liquid countercurrent contact to obtain rapidly condensed and cooled crude glycolide; the internal absolute pressure of the quenching tower is 100 to 5000 Pa.

[0065] 3) The crude glycolide after condensation and cooling is gathered at the bottom of the quench tower to form a crude glycolide logistics A, and the crude glycolide logistics A is separated into logistics B1 and logistics B2 through a pressurization process; logistics B1 is cooled again to form a quench solvent B1, and the quench solvent B1 is recycled to the quench spray liquid in step 2); logistics B2 is purified by a refining unit to obtain high-purity glycolide.

[0066] In step 2), the quenching spray liquid also includes a quenching solvent C other than the quenching solvent B1, and the temperature of the quenching solvent C is 30-130°C; the temperature of the top of the quenching tower is 30-100°C, and the temperature of the bottom of the tower is 70-115°C; the quenching solvent C includes one or more organic substances selected from alcohols, esters, ketones, ethers or hydrocarbons with a boiling point of 120-300°C.

[0067] The steam discharged from the top of the quench tower is condensed to obtain light organic matter D; the quench solvent C also contains light organic matter D.

[0068] In the above-mentioned spray cooling process, the steam discharged from the top of the quench tower is a vapor phase flow containing trace amounts of glycolide, which enters the condenser and continues to condense into light organic matter D and tail gas. Among them, the light organic matter D can be recycled back to the quenching solvent C and used as a quenching spray liquid in the spray cooling process; and the tail gas is generally recycled. Exemplarily, 0 to 99% of the light organic matter D is recycled back to the quenching solvent C.

[0069] The spray cooling process includes one or more spray layers for spraying, and the quenching spray liquid of the spray layer is a mixture of quenching solvent C and quenching solvent B1. The weight ratio of the quenching solvent C to the liquid vapor of the crude glycolide vapor is 0.3 to 10, and the weight ratio of the quenching spray liquid to the liquid vapor of the crude glycolide vapor is 5 to 35. Exemplarily, 1 to 10 spray layers are set to spray downward. More preferably, 3 to 8 spray layers are set to spray downward.

[0070] Example 3

[0071] A production process of glycolide of the present invention comprises the following steps:

[0072] 1) Crude glycolide vapor is generated by cracking and cyclizing glycolic acid or glycolate oligomers and a catalyst; the absolute pressure of the cracking and cyclizing reaction is 100-5000 Pa, and the temperature of the crude glycolide vapor is 180-300°C.

[0073] 2) The crude glycolide vapor enters the interior of the quenching tower from the bottom of the quenching tower and undergoes a spray cooling process; during the spray cooling process, the crude glycolide vapor and the quenching spray liquid continuously sprayed downward from the interior of the quenching tower undergo vapor-liquid countercurrent contact to obtain rapidly condensed and cooled crude glycolide; the internal absolute pressure of the quenching tower is 100 to 5000 Pa.

[0074] 3) The crude glycolide after condensation and cooling is gathered at the bottom of the quench tower to form a crude glycolide logistics A, and the crude glycolide logistics A is separated into logistics B1 and logistics B2 through a pressurization process; logistics B1 is cooled again to form a quench solvent B1, and the quench solvent B1 is recycled to the quench spray liquid in step 2); logistics B2 is purified by a refining unit to obtain high-purity glycolide.

[0075] In step 2), the quenching spray liquid also includes a quenching solvent C other than the quenching solvent B1, and the temperature of the quenching solvent C is 30-130°C; the temperature of the top of the quenching tower is 30-100°C, and the temperature of the bottom of the tower is 70-115°C; the quenching solvent C includes one or more organic substances selected from alcohols, esters, ketones, ethers or hydrocarbons with a boiling point of 120-300°C.

[0076] The steam discharged from the top of the quench tower is condensed to obtain light organic matter D; the quench solvent C also contains light organic matter D.

[0077] In the above-mentioned spray cooling process, the steam discharged from the top of the quench tower is a vapor phase flow containing trace amounts of glycolide, which enters the condenser and continues to condense into light organic matter D and tail gas. Among them, the light organic matter D can be recycled back to the quenching solvent C and used as a quenching spray liquid in the spray cooling process; and the tail gas is generally recycled. Exemplarily, 0 to 99% of the light organic matter D is recycled back to the quenching solvent C.

[0078] The spray cooling process includes two or more spray layers for spraying, the quenching spray liquid of the upper spray layer of the spray layer is the quenching solvent C, and the quenching spray liquid of the lower spray layer of the spray layer is the quenching solvent B1. The weight ratio of the quenching solvent C to the liquid vapor of the crude glycolide vapor is 0.3-10, and the weight ratio of the quenching spray liquid to the liquid vapor of the crude glycolide vapor is 5-35. Preferably, the upper spray layer is provided with 1 to 5 layers for downward spraying, and the lower spray layer is provided with 1 to 10 layers for downward spraying. More preferably, the upper spray layer is provided with 1 to 3 layers for downward spraying, and the lower spray layer is provided with 2 to 8 layers for downward spraying.

[0079] Example 4

[0080] like Figure 1 As shown, a glycolide production system of the present invention is used for the glycolide production process of the above-mentioned embodiment 1, and the production system includes: a ring-forming reactor 1a, a quenching tower 2a and a refining unit 6a, and a logistics pipeline connecting the various devices. The exhaust port of the ring-forming reactor 1a is connected to the bottom of the quenching tower 2a through a logistics pipeline, and the bottom discharge port of the quenching tower 2a is coupled and connected to the refining unit 6a; the interior of the quenching tower 2a is provided with a spray structure, and the spray structure includes a first spray structure, and the first spray structure is provided with a number of spray layers greater than or equal to 1. A booster device 4a is connected between the quenching tower 2a and the feed port of the refining unit 6a, and the booster device 4a is connected to the circulating cooler 3a, and the circulating cooler 3a is connected to the first spray structure through a circulating logistics pipeline; the refining unit 6a is a distillation unit or a recrystallization unit.

[0081] The production system further includes: a condenser 5a, an organic matter recovery unit 8a and a tail gas recovery and treatment unit 9a.

[0082] The condenser 5a is coupled to the top discharge port of the quench tower 2a, and the organic matter recovery unit 8a and the tail gas recovery and treatment unit 9a are respectively connected to the condenser 5a through logistics pipelines.

[0083] A filtering device is arranged before and / or after the pressure increasing device 4a to remove oligomers and / or other solid substances contained in the crude glycolide stream.

[0084] The shell of the quench tower 2a is provided with a heat-insulating device to prevent glycolide from solidifying.

[0085] The ring-forming reactor 1a further comprises a defoaming structure, which is arranged at the exhaust port of the ring-forming reactor 1a, or arranged inside the ring-forming reactor 1a, and is used to remove low molecular weight polymers entrained in the crude glycolide vapor.

[0086] The quenching tower 2a is an empty tower, a packed tower or a plate tower.

[0087] Example 5

[0088] like Figure 2 As shown, another glycolide production system of the present invention is used for the glycolide production process of the above-mentioned embodiment 2. The only difference between this embodiment 5 and embodiment 4 is that the production system also includes: a solvent supply unit 7a, the solvent supply unit 7a is connected to the quenching tower 2a and is provided with a heat exchanger 10a, the solvent supply unit 7a is connected to the first spray structure through a logistics pipeline, and the discharge port of the organic matter recovery unit 8a is connected to the heat exchanger 10a through a logistics pipeline.

[0089] Example 6

[0090] like Figure 3As shown, another glycolide production system of the present invention is used for the glycolide production process of the above-mentioned embodiment 3. The only difference between this embodiment 6 and embodiment 5 is that the production system also includes: a second spray structure, the second spray structure is located above the first spray structure, the second spray structure is provided with a number greater than or equal to 1 spray layer, and the discharge ports of the solvent supply unit 7a and the organic matter recovery unit 8a are connected to the second spray structure through a logistics pipeline.

[0091] Example 7

[0092] like Figure 1 As shown, a glycolide production process and production system of the present invention, glycolic acid or glycolate oligomers enter the ring-forming reactor 1a through the raw material flow pipeline 1, contact with the catalyst, and undergo cracking and ring-forming reaction at a temperature of 180-300°C and an absolute pressure of 100-5000Pa to generate crude glycolide vapor and a melt after depolymerization and ring-forming reaction, and the melt after depolymerization and ring-forming reaction is discharged through the melt flow pipeline 3.

[0093] The crude glycolide vapor is a steam flow containing glycolide and other by-products. The crude glycolide vapor enters the interior of the quench tower 2a from the bottom of the quench tower 2a through the steam flow pipeline 2. The quench spray liquid is a quench solvent B1 and is connected to the upper part of the quench tower 2a through the circulating spray liquid flow pipeline 7, thereby spraying the crude glycolide vapor. The internal temperature of the quench tower 2a is 30-120°C, the temperature of the top of the tower is 30-105°C, and the temperature of the bottom of the tower is 70-120°C; the internal absolute pressure of the quench tower 2a is 100-5000Pa. The quench spray liquid inside the quench tower 2a is in liquid-vapor countercurrent contact with the crude glycolide vapor to obtain rapidly condensed and cooled crude glycolide; the condensed and cooled crude glycolide is gathered at the bottom of the quench tower 2a to form a crude glycolide flow A with a relatively high concentration.

[0094] The crude glycolide logistics A is transported to the boosting device 4a through the cooling logistics pipeline 5 and is pressurized to be divided into logistics B1 and logistics B2. Logistics B1 and logistics B2 enter the circulating cooler 3a for cooling; logistics B1 forms a quenching solvent B1, which is circulated back to the quenching tower 2a through the circulating spray liquid logistics pipeline 7, is connected with the first spray structure of the spray structure, enters the quenching spray liquid, and undergoes a spray cooling process; logistics B2 enters the refining unit 6a through the purification logistics pipeline 6. The refining unit 6a is a recrystallization unit, and high-purity glycolide is obtained after purification.

[0095] The steam remaining at the top of the quench tower 2a during the spray cooling process enters the condenser 5a through the vapor recovery logistics pipeline 4, and is divided into light organic matter D and tail gas after condensation, and enters the organic recovery unit 8a and the tail gas logistics pipeline 9 respectively to enter the tail gas recovery treatment unit 9a for treatment.

[0096] A filtering device is provided between the quenching tower 2a and the pressure-boosting device 4a, and / or between the pressure-boosting device 4a and the circulating cooler 3a, so as to remove oligomers and / or other solid substances contained in the crude glycolide flow.

[0097] The ring-forming reactor 1a further includes a defoaming structure, which is arranged at the exhaust port of the ring-forming reactor 1a, or arranged inside the ring-forming reactor 1a.

[0098] The quenching tower 2a is an empty tower, and the spray layer of the first spray structure is a spray pipeline structure layer, which is 8 in number, forming 8 spray layers. The shell of the quenching tower 2a is provided with a heat preservation device.

[0099] Example 8

[0100] like Figure 3 , the only difference between this embodiment 8 and embodiment 7 is that the production system of glycolide also includes: a second spray structure and a solvent supply unit, the solvent supply unit is connected to the second spray structure through a logistics pipeline, and a heat exchanger 10a is provided between the solvent supply unit and the quenching tower 2a. The second spray structure is located above the first spray structure. The spray structure layer of the second spray structure of the spray structure is a spray pipeline structure layer, the number is 2, forming two layers of spray layers. The spray structure layer of the first spray structure of the spray structure is a spray pipeline structure layer, the number is 4, forming four layers of spray layers.

[0101] The discharge port of the organic matter recovery unit 8a is connected to the solvent supply unit through a logistics pipeline.

[0102] Example 9

[0103] like Figure 1 As shown, a glycolide production process and production system of the present invention, 35kg / hr crude glycolide steam generated by the ring reactor 1a, the crude glycolide steam temperature is about 230°C, is directly introduced into the quenching tower 2a through the steam flow pipeline 2 at the bottom of the quenching tower 2a, the quenching spray liquid used in the quenching tower 2a is the quenching solvent B1 and is connected to the upper part of the quenching tower 2a through the circulating spray liquid flow pipeline 7, the total amount of the quenching spray liquid is about 832kg / hr, and is divided into 3 layers of spray layers to The temperature of the quench spray liquid entering the quench tower 2a is about 75°C. The quench tower 2a is an empty tower. The crude glycolide vapor contacts the sprayed quench spray liquid in countercurrent. The crude glycolide logistics A formed by cooling and condensation is collected at the bottom of the quench tower 2a. The crude glycolide logistics A is pressurized by the booster 4a and divided into logistics B1 and logistics B2. Logistics B2 is sent to the subsequent glycolide refining unit 6a for refining and purification. Logistics B1 is cooled and then circulated back to the quench tower through the circulating spray liquid logistics pipeline 7 for continued spraying. The absolute pressure in the quench tower is 400Pa, the top temperature is 75.7°C, and the bottom temperature is 90.4°C.

[0104] The purification of refining unit 6a includes two-stage crystallization kettles. Part of the crude glycolide flow B2 flowing out from the bottom of the quenching tower 2a is introduced into the first crystallization kettle at a temperature of 30°C, staying for 60 minutes, and then introduced into the second crystallization kettle at a temperature of -2°C, staying for 15 minutes. The solid-liquid mixture of the second crystallization kettle is then centrifuged and washed, and the solid is retained and dried at a temperature of 60°C and an absolute pressure of ≤500Pa for 2 hours to obtain refined glycolide.

[0105] The glycolide production process of Example 9 significantly reduces the self-polymerization of glycolide, and the glycolide production system can operate continuously and stably for more than 8 weeks.

[0106] Example 10

[0107] like Figure 3 As shown, the difference between this embodiment 10 and embodiment 9 is that the quenching spray liquid used in the quenching tower 2a also includes ethyl glycolate, the total amount of ethyl glycolate is about 15.6 kg / hr, the temperature of the quenching solvent ethyl glycolate is about 50°C, there are two spray layers, located at the upper spray layer; the quenching spray liquid used in the lower spray layer is quenching solvent B1 and is connected to the upper part of the quenching tower 2a through the circulating spray liquid logistics pipeline 7, the liquid-vapor weight ratio of quenching solvent B1 to crude glycolide vapor is 24.65, the temperature of quenching solvent B1 is about 80°C, and it is divided into one spray layer for downward spraying. The internal absolute pressure of the quenching tower 2a is 400 Pa, the tower top temperature is 75.2°C, and the tower bottom temperature is 88.3°C.

[0108] The glycolide production process of Example 10 significantly reduces the self-polymerization of glycolide, and the glycolide production system can operate continuously and stably for more than 8 weeks.

[0109] In the glycolide production process and production system proposed in the above-mentioned embodiments 1 to 10 of the present invention, the vapor and liquid phases are in countercurrent contact in the tower, the crude glycolide vapor is quickly cooled, and the amount of glycolide entrained in the final vapor phase is less; and the pressure drop is low, it is not easy to block, and the residence time of glycolide in the high temperature zone is short, which can greatly reduce the self-polymerization of glycolide. The upper layer spray liquid is a quenching solvent, which reduces the amount of crude glycolide flow from the circulating cooler that needs to be circulated back to the quenching tower for spraying, and reduces the load of the circulating cooler.

[0110] The present invention is described by the above specific embodiments, and those skilled in the art should understand that various changes and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. The parts not described in detail in the present specification are well-known technologies to those skilled in the art. In addition, various modifications can be made to the present invention for specific situations or specific circumstances without departing from the scope of the present use. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all implementation methods falling within the scope of the claims of the present invention.

Claims

1. A process for producing glycolide, characterized in that: The specific steps of the production process of glycolide include: 1) generating crude glycolide vapor through a cracking ring reaction of glycolic acid or glycolate oligomers and a catalyst; 2) the crude glycolide vapor enters the interior of the quenching tower from the bottom of the quenching tower to undergo a spray cooling process; during the spray cooling process, the crude glycolide vapor is in vapor-liquid countercurrent contact with the quenching spray liquid continuously sprayed downward from the interior of the quenching tower to obtain rapidly condensed and cooled crude glycolide; the temperature at the top of the quenching tower is 30-105° C., and the temperature at the bottom of the tower is 70-120° C.; 3) The crude glycolide after condensation and cooling is accumulated at the bottom of the quench tower to form a crude glycolide logistics A, and the crude glycolide logistics A is divided into logistics B1 and logistics B2 through a pressurization process; the logistics B1 is cooled again to form a quench solvent B1, and the quench solvent B1 is recycled into the quench spray liquid described in step 2); the logistics B2 is purified by a refining unit to obtain high-purity glycolide.

2. The process for producing glycolide according to claim 1, characterized in that: The quenching spray liquid further includes a quenching solvent C in addition to the quenching solvent B1, and the temperature of the quenching solvent C is 30-130°C; the temperature of the top of the quenching tower is 30-100°C, and the temperature of the bottom of the tower is 70-115°C; The quenching solvent C includes one or more organic substances selected from alcohols, esters, ketones, ethers or hydrocarbons with a boiling point of 120 to 300°C.

3. The process for producing glycolide according to claim 2, characterized in that: The steam discharged from the top of the quench tower is condensed to obtain light organic matter D; the quench solvent C also contains the light organic matter D.

4. The process for producing glycolide according to any one of claims 2 and 3, characterized in that: The spray cooling process includes two or more spray layers for spraying; The quenching spray liquid of the upper spray layer of the spray layer is the quenching solvent C, and the quenching spray liquid of the lower spray layer of the spray layer is the quenching solvent B1; or, the quenching spray liquid of the spray layer is a mixture of the quenching solvent C and the quenching solvent B1.

5. The process for producing glycolide according to claim 4, characterized in that: The weight ratio of the quenching solvent C to the liquid vapor of the crude glycolide vapor is 0.3-10, and the weight ratio of the quenching spray liquid to the liquid vapor of the crude glycolide vapor is 5-35.

6. The process for producing glycolide according to claim 5, characterized in that: The quenching spray liquid of the upper spray layer of the spray layer is the quenching solvent C, and the quenching solvent C is divided into 1 to 5 spray layers for spraying downward; the quenching spray liquid of the lower spray layer of the spray layer is the quenching solvent B1, and the quenching solvent B1 is divided into 1 to 10 spray layers for spraying downward.

7. The process for producing glycolide according to claim 1, characterized in that: The absolute pressure of the cracking ring reaction in step 1) is 100-5000 Pa, the temperature of the crude glycolide vapor is 180-300° C.; the internal absolute pressure of the quenching tower is 100-5000 Pa.

8. A system for producing glycolide, characterized in that: include: Loop reactor, quench tower and refining unit, as well as logistics pipelines connecting various equipment; The exhaust port of the loop reactor is connected to the bottom of the quench tower through a logistics pipeline, and the bottom discharge port of the quench tower is coupled and connected to the refining unit; A spray structure is provided inside the quenching tower, and the spray structure includes a first spray structure, and the first spray structure is provided with a spray layer greater than or equal to 1; A booster device is connected between the bottom discharge port of the quench tower and the feed port of the refining unit. The booster device is connected to a circulating cooler, and the circulating cooler is connected to the first spray structure through a logistics pipeline.

9. The production system according to claim 8, characterized in that: The spray structure further includes a second spray structure, wherein the second spray structure is provided with a spray layer having a number greater than or equal to 1; The second spray structure is located above the first spray structure; The production system also includes: a solvent supply unit, a condenser, an organic matter recovery unit and a tail gas recovery and processing unit; The solvent supply unit is connected to the second spray structure through a logistics pipeline, and a heat exchanger is provided between the solvent supply unit and the quenching tower; The condenser is coupled to the top discharge port of the quench tower, the organic matter recovery unit is connected to the liquid outlet of the condenser through a logistics pipeline, and the tail gas recovery and processing unit is connected to the non-condensable gas outlet of the condenser through a logistics pipeline; The discharge port of the organic matter recovery unit is communicated with the heat exchanger through a logistics pipeline.

10. The production system according to claim 9, characterized in that: A filtering device is arranged before and / or after the boosting device; The ring-forming reactor further comprises a defoaming structure, and the defoaming structure is arranged at the exhaust port of the ring-forming reactor, or the defoaming structure is arranged inside the ring-forming reactor; The quenching tower is an empty tower, a packed tower or a plate tower, and the shell of the quenching tower is provided with a heat preservation device.

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