CN112898266B - Device and method for industrially preparing L-lactide - Google Patents
Device and method for industrially preparing L-lactide Download PDFInfo
- Publication number
- CN112898266B CN112898266B CN202110128273.4A CN202110128273A CN112898266B CN 112898266 B CN112898266 B CN 112898266B CN 202110128273 A CN202110128273 A CN 202110128273A CN 112898266 B CN112898266 B CN 112898266B
- Authority
- CN
- China
- Prior art keywords
- cracking
- dehydration
- cyclization
- prepolymer
- prepolymerization
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/24—Stationary reactors without moving elements inside
- B01J19/2415—Tubular reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/24—Stationary reactors without moving elements inside
- B01J19/247—Suited for forming thin films
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D319/00—Heterocyclic compounds containing six-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D319/10—1,4-Dioxanes; Hydrogenated 1,4-dioxanes
- C07D319/12—1,4-Dioxanes; Hydrogenated 1,4-dioxanes not condensed with other rings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00002—Chemical plants
- B01J2219/00004—Scale aspects
- B01J2219/00006—Large-scale industrial plants
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
The invention relates to a device for industrially preparing L-lactide, which comprises a multistage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are connected in sequence. The invention also provides a method for industrially preparing the L-lactide, which comprises the steps of multistage dehydration prepolymerization, precracking and cracking cyclization which are sequentially carried out. The device and the method provided by the invention can realize continuous production of the L-lactide, have the advantages of short reaction time, low required temperature, high production efficiency and high product purity, and are easy for subsequent separation and purification.
Description
Technical Field
The invention relates to the technical field of chemical production, in particular to a device and a method for industrially preparing L-lactide.
Background
The poly-L-lactic acid is a polymer with excellent performance, biocompatibility and biodegradability, is a non-toxic and non-irritant synthetic polymer material, and is mainly used in degradable packaging materials, disposable tableware, preservative films, surgical devices and the like.
Poly L-lactic acid can be synthesized by two ways, one is a direct polymerization method, i.e. L-lactic acid monomer is directly condensed to obtain L-lactic acid polymer under the action of catalyst, the method is generally difficult to prepare polymer with high relative molecular mass; the other is a ring-opening polymerization method, namely, firstly synthesizing lactide by dehydrating and cyclizing an L-lactic acid monomer, purifying the lactide, and then carrying out ring-opening polymerization reaction to obtain poly L-lactic acid. The method can obtain high molecular weight products with millions of molecular weights through ion polymerization or coordination polymerization, thereby becoming the preferred method for preparing the poly-L-lactic acid at present. The synthesis of lactide generally adopts a two-step method, namely L-lactic acid is dehydrated and polycondensed to obtain an L-lactic acid oligomer, and the L-lactide is synthesized through the cyclization reaction of the oligomer, so that the L-lactide becomes an important intermediate for preparing the degradable material poly L-lactic acid.
At present, L-lactic acid is mostly adopted as a raw material in the synthesis method of L-lactide. The steps for preparing the lactide by the L-lactic acid monomer are complex, the efficiency is low, and meanwhile, the problems of too long dehydration time, too high depolymerization temperature of the L-lactic acid oligomer, high system viscosity, serious reactant oxidation and the like in prepolymerization also exist, so that the yield of the L-lactide is not high, the racemization phenomenon is serious, the difficulty is increased for the subsequent refining of the L-lactide, the purification cost of the L-lactide is too high, the production cost of the poly L-lactic acid is high, and the large-area popularization and use are difficult to obtain.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, solves the technical problems of difficult dehydration, low cracking cyclization yield, low speed, low purity and the like of high-viscosity materials by adopting an optimized device and process, obviously improves the production efficiency, the product yield and the quality of the L-lactide, and has industrial value.
In a first aspect, the invention provides an apparatus for the industrial production of L-lactide.
Specifically, the device provided by the invention comprises a multistage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are connected in sequence;
in the multistage dehydration prepolymerization unit, the previous stage dehydration prepolymerization unit comprises a dehydration prepolymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration prepolymerization heater; a gas discharge port at the top of the gas-prepolymer separation chamber is connected with a condenser, preferably passes through a lactic acid rectifying tower and then is connected with the condenser, lactic acid obtained by rectifying the lactic acid rectifying tower returns to the dehydration prepolymerization heater for continuous reaction, and a product obtained by condensing the condenser is recycled; a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit;
in the multistage dehydration prepolymerization unit, the dehydration prepolymerization unit at the rear level comprises a dehydration prepolymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration prepolymerization heater; a gas discharge port at the top of the gas-prepolymer separation chamber is directly connected with a condenser, and a condensed product returns to a dehydration prepolymerization heater in the previous-level dehydration prepolymerization unit for continuous reaction; a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit or the pre-cracking unit;
the pre-cracking unit comprises a pre-cracking reactor which is used for fully mixing the prepolymer with a catalyst and rapidly heating to the temperature required by the cracking cyclization reaction;
the cracking and cyclization unit comprises a cracking and cyclization heater and a gas-substrate separation chamber connected with a discharge port of the cracking and cyclization heater; and a gas discharge port at the top of the gas-substrate separation chamber is connected with a lactide condenser and is condensed to obtain liquid lactide.
The device provided by the invention adopts a multistage dehydration prepolymerization unit, can remarkably improve the dehydration polymerization effect of lactic acid, which is a high-viscosity material, and particularly improves the quality of a final product and reduces the content of impurities. According to the invention, the lactic acid rectifying tower is arranged in the dehydration prepolymerization unit at the prior level, so that the lactic acid taken away by a large amount of water vapor can be recovered, and the recovered lactic acid can be recycled; and because a large amount of water is removed in the dehydration prepolymerization unit at the previous level, only a small amount of water vapor is formed in the dehydration prepolymerization unit at the later level, and the gas product can be directly condensed and recycled without lactic acid rectification. The device provided by the invention is also provided with the pre-cracking unit before the cracking and cyclization unit, so that the prepolymer and the catalyst can be efficiently mixed, uniformly and rapidly heated, and the subsequent cracking and cyclization reaction is facilitated.
In some embodiments of the present invention, the gas outlet at the top of the gas phase-prepolymer separation chamber is first passed through a lactic acid rectification column and then connected to a condenser. In actual production, the lactic acid obtained by rectification in the lactic acid rectification tower can return to the gas-prepolymer separation chamber first, and then is pumped into the falling film heater by the circulating pump to continue reaction.
In some embodiments of the present invention, the multistage dehydrating prepolymerization unit comprises 2 to 6 stages, preferably 3 to 4 stages of dehydrating prepolymerization units.
In some embodiments of the invention, the multistage dehydrating prepolymerization unit comprises a 4-stage dehydrating prepolymerization unit; wherein:
the first-stage and second-stage dehydration pre-polymerization units respectively comprise a dehydration pre-polymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration pre-polymerization heater; a gas discharge hole at the top of the gas-prepolymer separation chamber passes through a lactic acid rectifying tower and then is connected with a condenser, lactic acid obtained by rectifying in the lactic acid rectifying tower returns to the dehydration prepolymerization heater for continuous reaction, and liquid obtained by condensing in the condenser is recycled; a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit;
the third stage and the fourth stage dehydration pre-polymerization units respectively comprise a dehydration pre-polymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration pre-polymerization heater; a gas discharge port at the top of the gas-prepolymer separation chamber is directly connected with a condenser, and a condensed product returns to a dehydration prepolymerization heater in the first-stage and/or second-stage dehydration prepolymerization unit for continuous reaction; and a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit or the pre-cracking unit.
In some embodiments of the present invention, the dehydration prepolymerization heater is a reactor capable of realizing film distribution heating, preferably a falling film reactor with multiple sets of tubes inside. The reactor structure preferably adopted by the invention can play a role in uniformly distributing the film on the high-viscosity material of lactic acid, improving the reaction efficiency, shortening the reaction time and generating less by-products.
In some embodiments of the present invention, in each stage of the dehydrating and pre-polymerizing unit, the circulating pump at the bottom of the gas-phase pre-polymer separation chamber also returns the pre-polymer which does not reach the target molecular weight to the dehydrating and pre-polymerizing heater for further reaction, so as to realize the full utilization of the materials.
In some embodiments of the present invention, in the previous stage of the dehydration prepolymerization unit, the condensate can be recycled by concentrating, etc. to enrich the lactic acid contained therein, and then returned to the dehydration prepolymerization heater for further reaction.
In some embodiments of the present invention, in the post-stage dehydration prepolymerization unit, the gas outlet at the top of the condenser is also connected with a catcher, and the product obtained by catching is recycled to realize the full utilization of the materials.
In some embodiments of the invention, the cracking and cyclization heater is also a reactor capable of realizing film distribution heating, and is preferably a falling film reactor with a plurality of sets of tubes arranged inside.
In some embodiments of the present invention, in the cracking and cyclization unit, a circulation pump at the bottom of the gas-substrate separation chamber returns incompletely reacted prepolymer to the cracking and cyclization heater for continuous reaction, so as to realize full utilization of materials.
In some embodiments of the present invention, in the cracking and cyclization unit, a residue lead-out channel is further disposed at the bottom of the gas-substrate separation chamber, and residues in the substrate are extracted outwards by a substrate extraction pump, so as to avoid enrichment of residues or impurities during the cracking and cyclization process.
In some embodiments of the invention, in the cracking and cyclization unit, a gas outlet at the top of the lactide condenser is also connected with a trap, and the trapped product is recovered to realize full utilization of materials.
In a second aspect, the present invention provides a method for the industrial production of L-lactide.
Specifically, the method provided by the invention comprises the steps of multistage dehydration prepolymerization, pre-cracking and cracking cyclization which are sequentially carried out;
in the multi-stage dehydration prepolymerization process, the previous stage dehydration prepolymerization comprises a dehydration prepolymerization reaction and a separation of products obtained by the reaction; condensing the separated gas product, preferably condensing the residual gas product after rectifying lactic acid, recovering the rectified lactic acid, continuing to perform dehydration prepolymerization reaction, and recycling the condensed product; the prepolymer obtained by separation enters the next level of dehydration prepolymerization;
in the multi-stage dehydration prepolymerization process, the dehydration prepolymerization at the later stage comprises a dehydration prepolymerization reaction and separation of products obtained by the reaction; directly condensing the gas product obtained by separation, and returning the product obtained by condensation to the previous-level dehydration prepolymerization for continuing the dehydration prepolymerization reaction; the prepolymer obtained by separation enters the next-level dehydration prepolymerization or pre-cracking;
the pre-cracking comprises the steps of fully mixing the prepolymer with a catalyst and quickly heating to the temperature required by the cracking cyclization reaction;
the cracking cyclization comprises the steps of carrying out cracking cyclization reaction on the pre-cracked material and separating a product obtained by the reaction; and condensing the gas product obtained by separation to obtain liquid lactide.
The invention adopts a multi-stage dehydration prepolymerization mode, can obviously improve the dehydration polymerization effect of the high-viscosity material lactic acid, especially the quality of the final product, and reduce the impurity content. In the prior dehydration prepolymerization process, the lactic acid taken away from a large amount of water vapor is recycled, so that the content of the L-lactic acid in condensed water collected by dehydration prepolymerization is greatly reduced from about 25 percent to below 0.5 percent; and because a large amount of water is removed in the dehydration and prepolymerization process of the prior grade, only a small amount of water vapor is formed in the dehydration and prepolymerization process of the later grade, and the lactic acid rectification is not needed, and the gas product can be directly condensed and recycled. The method provided by the invention carries out pre-cracking before cracking and cyclization, can efficiently mix the prepolymer with the catalyst, uniformly and quickly heat the prepolymer, can improve the cracking and cyclization rate and improve the quality of the L-lactide.
In some embodiments of the invention, the separated gaseous product may be directly condensed to give a lactic acid-containing condensate. The condensate can be returned to the concentration working section for concentration, and then returned to the dehydration prepolymerization working section for dehydration prepolymerization reaction.
In some embodiments of the present invention, the separated gas product is subjected to lactic acid rectification and then the remaining gas product is condensed, and the resulting condensate can be returned to the concentration section. The lactic acid obtained by the lactic acid rectification can be directly subjected to dehydration prepolymerization reaction.
In some embodiments of the present invention, the multistage dehydration prepolymerization comprises 2 to 6 stages, preferably 3 to 4 stages.
In some embodiments of the invention, the multi-stage dehydrating prepolymerization comprises a 4-stage dehydrating prepolymerization; wherein:
the first-stage and second-stage dehydration prepolymerization respectively comprise a dehydration prepolymerization reaction and a separation of products obtained by the reaction; rectifying the separated gas product by using lactic acid, condensing the residual gas product, recovering the rectified lactic acid, continuing to perform a dehydration prepolymerization reaction, and recovering and utilizing the condensed product; the prepolymer obtained by separation enters the next level of dehydration prepolymerization;
the third-stage and the fourth-stage dehydration prepolymerization respectively comprise a dehydration prepolymerization reaction and separation of products obtained by the reaction; directly condensing the gas product obtained by separation, and returning the product obtained by condensation to the first-stage and/or second-stage dehydration prepolymerization for continuing dehydration prepolymerization reaction; and the prepolymer obtained by separation enters the next grade of dehydration prepolymerization or pre-cracking.
In some embodiments of the present invention, during each stage of the dehydrating and pre-polymerizing process, the pre-polymer which is obtained by separation and does not reach the target molecular weight is recovered, and the dehydrating and pre-polymerizing reaction is continued to be performed, so as to fully utilize the materials.
In some embodiments of the present invention, during the pre-stage dehydration and pre-polymerization, the condensate may be recycled by concentration or the like, so as to enrich the lactic acid contained therein, and then return to continue the dehydration and pre-polymerization reaction.
In some embodiments of the present invention, during the dehydration prepolymerization process of the subsequent stage, the gaseous substances remained in the condensation process are collected and returned to the previous stage to continue the dehydration prepolymerization process, so as to realize the full utilization of the materials.
In some embodiments of the invention, the dehydration prepolymerization reaction is carried out in a falling film reactor with a plurality of sets of tubes, and the dehydration prepolymerization reaction capacity for materials is 2-20 kg/(m)2H) being exposed to the atmosphere. Preferably, in the multistage dehydration prepolymerization process, the material processing speed of the later stage is slower than that of the previous stage. The reaction capacity of the material in the invention specifically refers to the mass of the material which is heated and reacted in unit time (per hour) and unit area (per square meter).The invention unexpectedly discovers that the parameters are controlled within the range, so that the materials in the dehydration prepolymerization process have excellent film-forming effect and shorter heating time, the reaction efficiency is high, and the racemization of the raw material (L-lactic acid) is reduced, thereby improving the quality and the yield of the final product.
In some embodiments of the present invention, the temperature of the material in the multistage dehydration and prepolymerization process is 130-190 ℃, preferably 150-175 ℃. Preferably, in the multistage dehydration prepolymerization process, the temperature of the material at the later stage is not lower than that of the material at the previous stage; and/or the vacuum level of the subsequent level is not lower than the vacuum level of the previous level.
In some embodiments of the present invention, the weight average molecular weight of the prepolymer obtained by the multistage dehydration and prepolymerization is 1500-3000 Da. Preferably, in the multistage dehydration prepolymerization process, the molecular weight of the prepolymer obtained in the later stage is greater than that of the prepolymer obtained in the previous stage.
In some embodiments of the present invention, the multistage dehydration prepolymerization is a 4-stage dehydration prepolymerization, wherein the weight average molecular weight of the prepolymer obtained in the first stage is 100-300 Da, the weight average molecular weight of the prepolymer obtained in the second stage is 800-1000 Da, the weight average molecular weight of the prepolymer obtained in the third stage is 1200-1700 Da, and the weight average molecular weight of the prepolymer obtained in the fourth stage is 2000-2800 Da.
In some embodiments of the present invention, the catalyst used in the multistage dehydration prepolymerization is selected from stannous octoate, stannous oxide, and a mixture of one or more of L-stannous lactate; preferably, the dosage of the catalyst is 0.01-0.1% of the mass of the L-lactic acid, and more preferably 0.02-0.05%.
In some embodiments of the present invention, the catalyst used for the lytic cyclization is selected from a mixture of one or more of stannous octoate, stannous oxide, and stannous L-lactate; preferably, the catalyst is used in an amount of 0.01 to 0.3%, more preferably 0.05 to 0.2% based on the mass of the prepolymer.
In some embodiments of the invention, the rapid temperature rise rate in the pre-cracking process is 1-5 ℃ per second. By adopting the rapid heating mode, the high efficiency of the cracking and cyclization process and the good product quality can be ensured.
In some embodiments of the invention, the cracking and cyclization reaction is carried out in a falling-film reactor comprising a plurality of sets of tubes, and the cracking and cyclization reaction capacity of the material is 2-10 kg/(m)2˙h)。
In some embodiments of the invention, the temperature of the feed during the lytic cyclization process is 180 ℃ to 220 ℃, preferably 190 ℃ to 210 ℃.
In some embodiments of the present invention, the vacuum degree in the cracking and cyclization process is 100-2000pa, preferably 500-1500 pa.
In some embodiments of the invention, the gas product obtained by separation after the cracking cyclization reaction is condensed at 85-110 ℃ to obtain liquid L-lactide.
In some embodiments of the present invention, during the cracking and cyclization process, the incompletely reacted prepolymer obtained by separation is also recovered, and the cracking and cyclization reaction is continued to achieve full utilization of materials.
In some embodiments of the present invention, during the cracking and cyclization process, a residue in the separated substrate is extracted outwards, preferably, the residue is extracted outwards by 1 to 10%, preferably 3 to 5% of the mass of the prepolymer, so as to avoid enrichment of the residue or impurities during the cracking and cyclization process.
In some embodiments of the present invention, during the cracking and cyclization process, the gaseous substances remained in the condensation process are collected and returned to the dehydration and prepolymerization process, so as to realize the full utilization of materials.
The method provided by the invention can be used for preparing L-lactide by using the device provided by the first aspect.
Compared with the prior art, the device and the method provided by the invention have the advantages of short reaction time of dehydration, prepolymerization and cracking, low temperature and high production efficiency; continuous dehydration and continuous cracking cyclization can be realized, and L-lactide can be continuously obtained, so that the method is suitable for industrial continuous production; the prepared L-lactide product has high purity, is easy for subsequent separation and purification and has high yield.
Drawings
FIG. 1 is a schematic diagram showing the structure of the first stage dehydrating prepolymerization unit in example 1, the first or second stage dehydrating prepolymerization unit in example 2, or the first or second stage dehydrating prepolymerization unit in example 3;
FIG. 2 is a schematic diagram showing the structure of the second stage dehydrating prepolymerization unit in example 1, the third stage dehydrating prepolymerization unit in example 2, or the third or fourth stage dehydrating prepolymerization unit in example 3;
in fig. 1 and 2, 1, a falling film heater; 2. a gas-prepolymer separation chamber; 3. a circulation pump; 4. a lactic acid rectification column; 5. a condenser; 6. a condensate collection tank; 7. a vacuum unit; 8. a trap;
FIG. 3 is a schematic diagram of the structures of a pre-cleavage unit and a cleavage cyclization unit in example 1, example 2 or example 3; wherein, a pre-cracking reactor; b. a falling film heater; c. a gas phase-substrate separation chamber; d. a condenser; e. a lactide liquid collection tank; f. a lactide storage tank; g. a trap; h. a vacuum unit; i. a circulation pump; j. a substrate extraction pump.
Detailed Description
The following description of the embodiments of the present invention is provided by way of specific examples, and those skilled in the art will readily appreciate the advantages and effects of the present invention from the description herein. The details of the apparatus and the control section in the present specification may be modified or changed variously without departing from the spirit of the present invention based on the fundamental principle of the present invention.
Example 1
The embodiment provides a device for industrially preparing lactide, which comprises a two-stage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are connected in sequence;
the first stage dehydrating prepolymerization unit (as shown in FIG. 1) comprises: a falling film heater 1 and a gas phase-prepolymer separation chamber 2 connected with a discharge port of the falling film heater; a discharge port at the bottom of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3, the prepolymer is pumped to a second-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas phase-prepolymer separation chamber 2 is sequentially connected with a lactic acid rectifying tower 4 provided with a lactic acid feed port, a condenser 5 and a condensate collecting tank 6, lactic acid obtained by rectifying in the lactic acid rectifying tower 4 returns to the gas phase-prepolymer separation chamber 2 and is pumped into the falling film heater 1 by a circulating pump 3 for continuous reaction, and a product obtained by condensing in the condenser 5 can also return to the falling film heater 1 for continuous reaction after being concentrated; the first-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the second stage dehydrating prepolymerization unit (as shown in FIG. 2) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; the bottom discharge port of the gas phase-prepolymer separation chamber 2 is connected with a circulating pump 3 to pump the prepolymer to a cracking cyclization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas-prepolymer separation chamber 2 is sequentially connected with a condenser 5, a condensate collecting tank 6 and a catcher 8, and a product obtained by condensing the condenser 5 can be returned to a falling film heater 1 in a first-stage dehydration prepolymerization unit for continuous dehydration prepolymerization reaction; the second-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the pre-cracking unit (shown in figure 3) comprises a pre-cracking reactor a for mixing and heating materials; fully mixing and heating the catalyst and the prepolymer in a pre-cracking reactor a, and conveying the mixture to a feeding port at the top end of a falling film heater b;
the lytic cyclization unit (as shown in FIG. 3) comprises: a falling film heater b and a gas phase-substrate separation chamber c connected with a discharge port of the falling film heater b; a discharge port at the top of the gas-substrate separation chamber c is connected with a condenser d; liquid lactide obtained by condensation of the condenser d is input into a lactide storage tank f for storage through a lactide liquid collecting groove e, a discharge hole in the top of the condenser d is also connected with a catcher g, and materials recovered by the catcher g can return to a dehydration prepolymerization unit; the system is provided with a vacuum unit h; and a bottom discharge hole of the gas phase-substrate separation chamber c can be connected with a circulating pump i to return the insufficiently cracked materials to the falling film heater b for further reaction, and can also be connected with a substrate extraction pump j to discharge residues generated in the cracking and cyclization process.
Example 2
The embodiment provides a device for industrially preparing lactide, which comprises a three-stage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are sequentially connected;
the first stage dehydrating prepolymerization unit (as shown in FIG. 1) comprises: a falling film heater 1 and a gas phase-prepolymer separation chamber 2 connected with a discharge port of the falling film heater; a discharge port at the bottom of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3, the prepolymer is pumped to a second-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas phase-prepolymer separation chamber 2 is sequentially connected with a lactic acid rectifying tower 4 provided with a lactic acid feed port, a condenser 5 and a condensate collecting tank 6, lactic acid obtained by rectifying in the lactic acid rectifying tower 4 returns to the gas phase-prepolymer separation chamber 2 and is pumped into the falling film heater 1 by a circulating pump 3 for continuous reaction, and a product obtained by condensing in the condenser 5 can also return to the falling film heater 1 for continuous reaction after being concentrated; the first-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the second stage dehydrating prepolymerization unit (as shown in FIG. 1) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; a discharge port at the bottom of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3, the prepolymer is pumped to a third-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas phase-prepolymer separation chamber 2 is sequentially connected with a lactic acid rectifying tower 4, a condenser 5 and a condensate collecting tank 6, lactic acid obtained by rectifying in the lactic acid rectifying tower 4 returns to the falling film heater 1 for continuous reaction, and a product obtained by condensing in the condenser 5 also returns to the falling film heater 1 for continuous reaction after being concentrated; the second-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the third stage dehydrating prepolymerization unit (as shown in FIG. 2) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; the bottom discharge port of the gas phase-prepolymer separation chamber 2 is connected with a circulating pump 3 to pump the prepolymer to a cracking cyclization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas-prepolymer separation chamber 2 is sequentially connected with a condenser 5, a condensate collecting tank 6 and a catcher 8, and a product obtained by condensing the condenser 5 can be returned to the falling film heater 1 in the first-stage or second-stage dehydration prepolymerization unit for continuous dehydration prepolymerization reaction; the third-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the structures of the pre-cleavage unit and the cleavage cyclization unit are the same as those of example 1.
Example 3
The embodiment provides a device for industrially preparing lactide, which comprises a four-stage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are connected in sequence;
the first stage dehydrating prepolymerization unit (as shown in FIG. 1) comprises: a falling film heater 1 and a gas phase-prepolymer separation chamber 2 connected with a discharge port of the falling film heater; a discharge port at the bottom of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3, the prepolymer is pumped to a second-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas phase-prepolymer separation chamber 2 is sequentially connected with a lactic acid rectifying tower 4 provided with a lactic acid feed port, a condenser 5 and a condensate collecting tank 6, lactic acid obtained by rectifying in the lactic acid rectifying tower 4 returns to the gas phase-prepolymer separation chamber 2 and is pumped into the falling film heater 1 by a circulating pump 3 for continuous reaction, and a product obtained by condensing in the condenser 5 can also return to the falling film heater 1 for continuous reaction after being concentrated; the first-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the second stage dehydrating prepolymerization unit (as shown in FIG. 1) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; a discharge port at the bottom of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3, the prepolymer is pumped to a third-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas phase-prepolymer separation chamber 2 is sequentially connected with a lactic acid rectifying tower 4, a condenser 5 and a condensate collecting tank 6, lactic acid obtained by rectifying in the lactic acid rectifying tower 4 returns to the falling film heater 1 for continuous reaction, and a product obtained by condensing in the condenser 5 can also return to the falling film heater 1 for continuous reaction after being concentrated; the second-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the third stage dehydrating prepolymerization unit (as shown in FIG. 2) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; the bottom discharge port of the gas-prepolymer separation chamber 2 is connected with a circulating pump 3 to pump the prepolymer to a fourth-stage dehydration prepolymerization unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas-prepolymer separation chamber 2 is sequentially connected with a condenser 5, a condensate collecting tank 6 and a catcher 8, and a product obtained by condensing the condenser 5 can be returned to the falling film heater 1 in the first-stage or second-stage dehydration prepolymerization unit for continuous dehydration prepolymerization reaction; the third-stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the fourth stage of the dehydrating prepolymerization unit (as shown in FIG. 2) comprises: a falling film heater 1 provided with a higher prepolymer feeding port and a gas phase-prepolymer separation chamber 2 connected with a discharging port thereof; the bottom discharge port of the gas phase-prepolymer separation chamber 2 is connected with a circulating pump 3 to pump the prepolymer to a pre-cracking unit, and the prepolymer which does not reach the target molecular weight is pumped back to the falling film heater 1 for further reaction; a discharge port at the top of the gas-prepolymer separation chamber 2 is sequentially connected with a condenser 5, a condensate collecting tank 6 and a catcher 8, and a product obtained by condensing the condenser 5 can be returned to the falling film heater 1 in the first-stage or second-stage dehydration prepolymerization unit for continuous dehydration prepolymerization reaction; the fourth stage dehydration prepolymerization unit is provided with a vacuum unit 7;
the structures of the pre-cleavage unit and the cleavage cyclization unit are the same as those of example 1.
Example 4
Pumping heat stable-grade L-lactic acid with average acidity of 93.56% (w/w) into a first-stage dehydration pre-polymerization falling-film reactor according to the average flow rate of 637.02kg/h, controlling the material temperature of 152-, when the molecular weight of the prepolymer in the third-stage falling-film reactor reaches 1500-1700Da, starting a delivery pump at the bottom of the third-stage falling-film reactor to deliver materials to the fourth-stage falling-film reactor, controlling the temperature of the materials in the falling-film reactor of the fourth-stage dehydration prepolymer to be 170-172 ℃ and the vacuum degree to be 1000-1200Pa, and when the molecular weight of the prepolymer in the fourth-stage falling-film reactor reaches 2300-2500Da, starting a delivery pump at the bottom of the fourth-stage falling-film reactor to pump the average 476.01kg/h to deliver the materials to the pre-cracking reactor, and simultaneously starting a catalyst flow pump to ensure that the interlocking proportion of the flow of the catalyst and the flow of the prepolymer entering the pre-cracking reactor is 0.06-0.07 percent. The outlet temperature of the pre-pyrolysis reactor was controlled at 193-195 ℃. When the liquid levels of the separation chamber of the continuous cracking and cyclization device and the inlet of the cracking circulating pump are displayed, starting the circulating pump to start the circulating mode of the pump, and controlling the material temperature of the continuous cracking and cyclization device to be 193-195 ℃. Meanwhile, the condenser at the top end of the separation chamber of the continuous cracking and cyclization device is started to cool water, and the temperature is controlled to be 106-108 ℃. The vacuum degree of the separation chamber is controlled to be 900-1100 Pa. After the continuous operation of the materials is stable, the flow detection is carried out: the average flow rate of crude L-lactide was 450.19kg/h, and the average flow rate of cleavage residue was 16.62 kg/h.
15288.60kg of L-lactic acid with the acidity of 93.56% (w/w) is consumed accumulatively for 24 hours, 3834.30kg of condensed water is discharged after dehydration, and the condensed water contains 0.45% (w/w) of L-lactic acid through detection; the conversion of L-lactic acid into prepolymer was calculated to be 99.879%.
11424.30kg of accumulated feed is fed into the 24-hour cracking and cyclization reaction system, 220.80kg of L-lactic acid, oligomer and the like are discharged from a cracking catcher, and 398.91kg of cracking substrate is discharged; the total mass of the collected crude L-lactide is 10804.59kg, the total lactide content is 97.59 percent through detection, and the L-lactide content reaches 92.85 percent.
Example 5
Pumping heat stable-grade L-lactic acid with the average acidity of 95.85% (w/w) into a first-stage dehydration pre-polymerization falling-film reactor according to the average flow rate of 628.06kg/h, controlling the material temperature of the first-stage falling-film reactor to be 146-, when the molecular weight of the prepolymer in the third-stage falling-film reactor reaches 1300-1500Da, starting a delivery pump at the bottom of the third-stage falling-film reactor to deliver materials to the fourth-stage falling-film reactor, controlling the temperature of the materials in the falling-film reactor of the fourth-stage dehydration prepolymer to be 171-173 ℃, and starting a vacuum degree of 800-1000Pa, when the molecular weight of the prepolymer in the fourth-stage falling-film reactor reaches 2400-2600Da, starting a delivery pump at the bottom of the fourth-stage falling-film reactor to pump the average 480.89kg/h into the pre-cracking reactor to deliver the materials, and simultaneously starting a catalyst flow pump to ensure that the interlocking proportion of the flow of the catalyst and the flow of the prepolymer entering the pre-cracking reactor is 0.09%. The outlet temperature of the pre-pyrolysis reactor was controlled at 200-202 ℃. When the liquid levels of the separation chamber of the continuous cracking and cyclization device and the inlet of the cracking circulating pump are displayed, starting the circulating pump to start the circulating mode of the pump, and controlling the material temperature of the continuous cracking and cyclization device to be 200-202 ℃. Meanwhile, a condenser at the top end of a separation chamber of the continuous cracking and cyclization device is started to cool water, and the temperature is controlled to be 105 ℃. The vacuum degree of the vacuum pump is controlled to 950-1150 pa. After the continuous operation of the materials is stable, the flow detection is carried out: the average flow rate of L-lactide was 456.96kg/h and the flow rate of cleavage residue was 15.32 kg/h.
15073.55kg of L-lactic acid with the acidity of 95.85% (w/w) is consumed accumulatively for 24 hours, 3502.13kg of condensed water is discharged after dehydration, and the condensed water contains 0.49% (w/w) of L-lactic acid through detection; the conversion of L-lactic acid into prepolymer was calculated to be 99.881%.
11541.42kg of accumulated feed is generated in 24-hour cracking and cyclization, 206.64kg of L-lactic acid and oligomer are discharged from a cracking trap, and 367.68kg of cracking substrate is discharged; the total mass of the collected crude L-lactide is 10967.10kg, the total lactide content is 97.79 percent through detection, and the L-lactide content reaches 93.15 percent.
Example 6
Pumping heat stable-grade L-lactic acid with the average acidity of 98.15% (w/w) into a first-stage dehydration pre-polymerization falling-film reactor according to the average flow rate of 616.40kg/h, controlling the material temperature of 154-, the vacuum degree is 1100-. The outlet temperature of the pre-pyrolysis reactor was controlled at 202-204 ℃. When the liquid levels of the separation chamber of the continuous cracking and cyclization device and the inlet of the cracking circulating pump are displayed, starting the circulating pump to start the circulating mode of the pump, and controlling the material temperature of the continuous cracking and cyclization device to be 202-204 ℃. Meanwhile, a condenser at the top end of a separation chamber of the continuous cracking and cyclization device is started to cool water, and the temperature is controlled to be 101 ℃. The vacuum degree of the vacuum pump is controlled to be 800-100 pa. After the continuous operation of the materials is stable, the flow detection is carried out: the average flow rate of L-lactide was 459.52kg/h and the flow rate of cleavage residue was 14.33 kg/h.
14793.71kg of L-lactic acid with acidity of 98.15% (w/w) is consumed accumulatively for 24 hours, 3163.22kg of condensed water is discharged after dehydration, and the condensed water contains 0.49% (w/w) of L-lactic acid through detection; the conversion of L-lactic acid into prepolymer was calculated to be 99.893%.
11600.49kg of accumulated feed is generated in 24-hour cracking and cyclization, 228.02kg of L-lactic acid and oligomer are discharged from a cracking trap, and 343.92kg of cracking substrate is discharged; the total mass of the collected crude L-lactide is 11028.55kg, the total lactide content is 97.95 percent through detection, and the L-lactide content reaches 91.65 percent.
Example 7
Pumping heat stable-grade L-lactic acid with the average acidity of 99.68% (w/w) into a first-stage dehydration pre-polymerization falling-film reactor according to the average flow of 595.91kg/h, controlling the material temperature of 156-, when the molecular weight of the prepolymer in the third-stage falling-film reactor reaches 1500-1700Da, starting a delivery pump at the bottom of the third-stage falling-film reactor to deliver materials to the fourth-stage falling-film reactor, controlling the temperature of the materials in the falling-film reactor of the fourth-stage dehydration prepolymer to be 173-175 ℃ and the vacuum degree to be 900-1100Pa, and when the molecular weight of the prepolymer in the fourth-stage falling-film reactor reaches 2600-2800Da, starting a delivery pump at the bottom of the fourth-stage falling-film reactor to pump the average 474.65kg/h to deliver the materials to the pre-cracking reactor, and simultaneously starting a catalyst flow pump to ensure that the interlocking proportion of the catalyst flow and the prepolymer flow entering the pre-cracking reactor is 0.18 percent. The outlet temperature of the pre-pyrolysis reactor was controlled at 205-. When the liquid levels of the separation chamber of the continuous cracking and cyclization device and the inlet of the cracking circulating pump are displayed, starting the circulating pump to start the circulating mode of the pump, and controlling the material temperature of the continuous cracking and cyclization device to be 205-. Meanwhile, a condenser at the top end of a separation chamber of the continuous cracking and cyclization device is started to cool water, and the temperature is controlled to be 98 ℃. The vacuum degree of the vacuum pump is controlled to be 600-800 Pa. After the continuous operation of the materials is stable, the flow detection is carried out: the average flow rate of L-lactide was 452.40kg/h, and the flow rate of cleavage residue was 13.65 kg/h.
14301.77kg of L-lactic acid with the acidity of 99.68% (w/w) is consumed accumulatively for 24 hours, 2890.15kg of condensed water is discharged after dehydration, and the detected content of the condensed water is 0.47% (w/w) of the L-lactic acid; the conversion of L-lactic acid into prepolymer was calculated to be 99.905%.
11391.62kg of accumulated feed is generated in 24-hour cracking and cyclization, 206.41kg of L-lactic acid and oligomer are discharged from a cracking trap, and 327.60kg of cracking substrate is discharged; the total mass of the collected crude L-lactide is 10857.61kg, the total lactide content is 97.79 percent through detection, and the L-lactide content reaches 91.36 percent.
The methods described in examples 4-7 can all be used to prepare lactide using the apparatus provided in example 3.
While the invention has been described in detail in the foregoing by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that certain modifications and combinations thereof are possible in light of the above teachings. Accordingly, such modifications and combinations are intended to be included within the scope of this invention as claimed.
Claims (20)
1. The device for industrially preparing the L-lactide is characterized by comprising a multistage dehydration prepolymerization unit, a pre-cracking unit and a cracking cyclization unit which are sequentially connected;
the multistage dehydration prepolymerization unit comprises a 4-stage dehydration prepolymerization unit; wherein:
the first-stage and second-stage dehydration pre-polymerization units respectively comprise a dehydration pre-polymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration pre-polymerization heater; a gas discharge hole at the top of the gas-prepolymer separation chamber passes through a lactic acid rectifying tower and then is connected with a condenser, lactic acid obtained by rectifying in the lactic acid rectifying tower returns to the dehydration prepolymerization heater for continuous reaction, and a product obtained by condensing in the condenser is recycled; a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit;
the third stage and the fourth stage dehydration pre-polymerization units respectively comprise a dehydration pre-polymerization heater and a gas-prepolymer separation chamber connected with a discharge port of the dehydration pre-polymerization heater; a gas discharge port at the top of the gas-prepolymer separation chamber is directly connected with a condenser, and a condensed product returns to a dehydration prepolymerization heater in the first-stage and/or second-stage dehydration prepolymerization unit for continuous reaction; a prepolymer discharge port at the bottom of the gas-prepolymer separation chamber is connected with a feed channel of a next-stage dehydration prepolymerization unit or the pre-cracking unit;
the pre-cracking unit comprises a pre-cracking reactor which is used for fully mixing the prepolymer with a catalyst and rapidly heating to the temperature required by the cracking cyclization reaction;
the cracking and cyclization unit comprises a cracking and cyclization heater and a gas-substrate separation chamber connected with a discharge port of the cracking and cyclization heater; a gas discharge port at the top of the gas-substrate separation chamber is connected with a lactide condenser and is condensed to obtain liquid lactide;
the dehydration pre-polymerization heater and/or the cracking cyclization heater are/is internally provided with a plurality of groups of falling film reactors with tubes, so that film distribution heating can be realized; the dehydration prepolymerization reaction is carried out in a falling film reactor with a plurality of groups of tubes, and the dehydration prepolymerization reaction capacity of the material is 2-20 kg/(m)2H), the dehydration prepolymerization reaction capability of the material refers to the mass of the material heated to react in unit time and unit area; cracking cyclization reaction is carried out in a falling film reactor with a plurality of groups of tubes, and the cracking cyclization reaction capacity of the material is 2-10 kg/(m)2H), the cracking and cyclization reaction capability of the material refers to the mass of the material which is heated to react in unit time and unit area;
in the multistage dehydration prepolymerization process, the material processing speed of the later grade is slower than that of the previous grade, the material temperature of the later grade is not lower than that of the previous grade, and the vacuum degree of the later grade is not lower than that of the previous grade.
2. The apparatus of claim 1, wherein in each stage of the dehydration prepolymerization unit, the circulating pump at the bottom of the gas-prepolymer separation chamber returns the prepolymer which does not reach the target molecular weight to the dehydration prepolymerization heater for further reaction;
and/or, in the dehydration prepolymerization unit of the later stage, a gas outlet at the top of the condenser is also connected with the catcher.
3. The device according to claim 1, wherein in the cracking and cyclization unit, a circulating pump at the bottom of the gas-substrate separation chamber returns incompletely reacted prepolymer to the cracking and cyclization heater for further reaction;
and/or in the cracking and cyclization unit, the bottom of the gas-substrate separation chamber is also provided with a residue outlet channel, and residues in the substrate are extracted outwards through a substrate extraction pump;
and/or in the cracking and cyclization unit, a gas outlet at the top of the lactide condenser is also connected with a trap.
4. The method for industrially preparing the L-lactide is characterized by comprising the steps of multistage dehydration prepolymerization, pre-cracking and cracking cyclization which are sequentially carried out;
the multistage dehydration prepolymerization comprises 4-stage dehydration prepolymerization; wherein:
the first-stage and second-stage dehydration prepolymerization respectively comprise a dehydration prepolymerization reaction and a separation of products obtained by the reaction; rectifying the separated gas product by using lactic acid, condensing the residual gas product, recovering the rectified lactic acid, continuing to perform a dehydration prepolymerization reaction, and recovering and utilizing the condensed product; the prepolymer obtained by separation enters the next level of dehydration prepolymerization;
the third-stage and the fourth-stage dehydration prepolymerization respectively comprise a dehydration prepolymerization reaction and separation of products obtained by the reaction; directly condensing the gas product obtained by separation, and returning the product obtained by condensation to the first-stage and/or second-stage dehydration prepolymerization for continuing dehydration prepolymerization reaction; the prepolymer obtained by separation enters the next-level dehydration prepolymerization or pre-cracking;
the pre-cracking comprises the steps of fully mixing the prepolymer with a catalyst and quickly heating to the temperature required by the cracking cyclization reaction;
the cracking cyclization comprises the steps of carrying out cracking cyclization reaction on the pre-cracked material and separating a product obtained by the reaction; condensing the gas product obtained by separation to obtain liquid lactide;
the dehydration pre-polymerization heater and/or the cracking cyclization heater is a falling film reactor with a plurality of groups of tubes arranged inside, and can realize film distribution and heating; the dehydration prepolymerization reaction is carried out in a falling film reactor with a plurality of groups of tubes, and the dehydration prepolymerization reaction capacity of the material is 2-20 kg/(m)2H), the dehydration prepolymerization reaction capability of the material refers to the mass of the material heated to react in unit time and unit area;
in the multistage dehydration prepolymerization process, the material processing speed of the later grade is slower than that of the previous grade, the material temperature of the later grade is not lower than that of the previous grade, and the vacuum degree of the later grade is not lower than that of the previous grade;
in the multistage dehydration and prepolymerization process, the weight average molecular weight of the prepolymer obtained in the first stage is 100-300 Da, the weight average molecular weight of the prepolymer obtained in the second stage is 800-1000 Da, the weight average molecular weight of the prepolymer obtained in the third stage is 1200-1700 Da, and the weight average molecular weight of the prepolymer obtained in the fourth stage is 2000-2800 Da.
5. The method as claimed in claim 4, wherein in each stage of the dehydration prepolymerization process, the prepolymer which is separated and does not reach the target molecular weight is returned to a dehydration prepolymerization heater for further dehydration prepolymerization reaction;
and/or, in the course of dehydration prepolymerization of subsequent stage, collecting the residual gaseous material in the course of condensation and returning it to previous stage to make dehydration prepolymerization.
6. The method as claimed in claim 4, wherein the temperature of the material in the multistage dehydration prepolymerization process is 130-190 ℃.
7. The method of claim 6, wherein the temperature of the material in the multistage dehydration prepolymerization process is 150 ℃ to 175 ℃.
8. The method as claimed in claim 4, wherein the catalyst used in the multistage dehydration prepolymerization is selected from stannous octoate and stannous oxide, or a mixture of two.
9. The method as claimed in claim 8, wherein the catalyst is used in the multistage dehydration prepolymerization in an amount of 0.01 to 0.1% by mass of the L-lactic acid.
10. The method as claimed in claim 9, wherein the catalyst is used in the multistage dehydration prepolymerization in an amount of 0.02 to 0.05% by mass of the L-lactic acid.
11. The method as claimed in claim 4, wherein the catalyst used for the cracking cyclization is selected from stannous octoate and stannous oxide or a mixture of two of the stannous octoate and the stannous oxide.
12. The process of claim 11, wherein the amount of the catalyst used for the cleavage cyclization is 0.01 to 0.3% of the mass of the prepolymer.
13. The process according to claim 12, wherein the amount of catalyst used for the cleavage cyclization is 0.05 to 0.2% of the mass of the prepolymer.
14. The method according to claim 4, wherein the rapid temperature rise speed in the pre-cracking process is 1-5 ℃/s.
15. The method according to claim 4, wherein the cracking and cyclization reaction is carried out in a falling film reactor comprising a plurality of sets of tubes, and the cracking and cyclization reaction capacity of the material is 2-10 kg/(m & lt/& gt)2˙h)；
And/or the temperature of the materials in the cracking and cyclization process is 180-220 ℃;
and/or the vacuum degree in the cracking cyclization process is 100-2000 pa;
and/or condensing a gas product obtained by separation after the cracking cyclization reaction at 85-110 ℃ to obtain liquid L-lactide.
16. The method of claim 15, wherein the temperature of the feed during the lytic cyclization process is between 190 ℃ and 210 ℃;
and/or the vacuum degree in the cracking and cyclization process is 500-1500 pa.
17. The method according to claim 4, wherein during the cracking and cyclization process, the incompletely reacted prepolymer obtained by separation is recovered and the cracking and cyclization reaction is continued;
and/or, in the cracking and cyclization process, residues in the separated substrate are extracted outwards;
and/or, in the cracking and cyclization process, collecting gaseous substances remained in the condensation process and returning the gaseous substances to the dehydration and prepolymerization process.
18. The method of claim 17, wherein during said cleavage cyclization, a residue of said separated substrate is withdrawn from said reaction vessel in an amount of 1-10% based on the mass of said prepolymer.
19. The method of claim 18, wherein during said cleavage cyclization, a residue of said separated substrate is withdrawn from said reaction vessel in an amount of 3 to 5% of the mass of said prepolymer.
20. The method according to any one of claims 4 to 19, wherein the device according to any one of claims 1 to 3 is used for producing L-lactide.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111330337.5A CN114160064B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
| CN202110128273.4A CN112898266B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110128273.4A CN112898266B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111330337.5A Division CN114160064B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112898266A CN112898266A (en) | 2021-06-04 |
| CN112898266B true CN112898266B (en) | 2021-11-19 |
Family
ID=76121621
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111330337.5A Active CN114160064B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
| CN202110128273.4A Active CN112898266B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111330337.5A Active CN114160064B (en) | 2021-01-29 | 2021-01-29 | Device and method for industrially preparing L-lactide |
Country Status (1)
| Country | Link |
|---|---|
| CN (2) | CN114160064B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113582964B (en) * | 2021-08-23 | 2022-04-12 | 扬州惠通科技股份有限公司 | Lactide continuous production system and production method |
| CN116063270A (en) * | 2021-10-31 | 2023-05-05 | 中国石油化工股份有限公司 | Method and system for continuously preparing lactide through step control |
| CN114471438B (en) * | 2022-02-18 | 2023-08-25 | 华陆工程科技有限责任公司 | Reaction device and method for industrially preparing lactide |
| CN115872970A (en) * | 2022-12-08 | 2023-03-31 | 青岛普力机电工程有限公司 | Method for continuously producing lactide with high purity from lactic acid raw material |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106831700A (en) * | 2017-03-28 | 2017-06-13 | 南京大学 | A kind of method of full green sealing circulation technology production optical voidness L/D lactides |
| CN111153886A (en) * | 2020-01-16 | 2020-05-15 | 南京大学 | Method and device for synthesizing lactide with high yield and rapidness |
| CN211384959U (en) * | 2019-11-26 | 2020-09-01 | 南京华基塔业有限公司 | Reaction system for preparing lactide from lactic acid |
| CN211384958U (en) * | 2019-11-26 | 2020-09-01 | 南京华基塔业有限公司 | Intelligent reaction system for preparing lactide from lactic acid |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5521278A (en) * | 1994-08-18 | 1996-05-28 | Ecological Chemical Products | Integrated process for the manufacture of lactide |
| US7858730B2 (en) * | 2007-07-12 | 2010-12-28 | Eastman Chemical Company | Multi-level tubular reactor with dual headers |
| KR101486213B1 (en) * | 2013-11-26 | 2015-01-26 | 한국화학연구원 | Manufacturing method for lactide using a tube bundle falling film reactor and an agitated thin film reactor |
| KR102198137B1 (en) * | 2014-01-16 | 2021-01-04 | 한국화학연구원 | A method for preparation of lactide using metal sulfite as a depolymerization catalyst |
| CN111039918A (en) * | 2019-12-24 | 2020-04-21 | 安徽丰原发酵技术工程研究有限公司 | Method for preparing D-lactide by one-step gas phase reaction |
| CN111424059B (en) * | 2020-06-08 | 2020-09-08 | 中粮营养健康研究院有限公司 | Method and system for producing high-yield, high-gloss pure lactide by using biological fermentation technology to prepare lactic acid |
-
2021
- 2021-01-29 CN CN202111330337.5A patent/CN114160064B/en active Active
- 2021-01-29 CN CN202110128273.4A patent/CN112898266B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106831700A (en) * | 2017-03-28 | 2017-06-13 | 南京大学 | A kind of method of full green sealing circulation technology production optical voidness L/D lactides |
| CN211384959U (en) * | 2019-11-26 | 2020-09-01 | 南京华基塔业有限公司 | Reaction system for preparing lactide from lactic acid |
| CN211384958U (en) * | 2019-11-26 | 2020-09-01 | 南京华基塔业有限公司 | Intelligent reaction system for preparing lactide from lactic acid |
| CN111153886A (en) * | 2020-01-16 | 2020-05-15 | 南京大学 | Method and device for synthesizing lactide with high yield and rapidness |
Non-Patent Citations (1)
| Title |
|---|
| JD公司丙交酯生产线项目投资决策分析;李建涛;《中国优秀硕士学位论文全文数据库（电子期刊） 经济与管理科学辑》;20180615;第2018卷(第6期);第29-30页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114160064B (en) | 2024-01-26 |
| CN112898266A (en) | 2021-06-04 |
| CN114160064A (en) | 2022-03-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112898266B (en) | Device and method for industrially preparing L-lactide | |
| CN110498787B (en) | Lactide purification system and purification method | |
| KR101801176B1 (en) | Method for the manufacture of a polyhydroxy-carboxylic acid | |
| JP4427571B2 (en) | Apparatus and method for polymer synthesis | |
| TWI477494B (en) | Cleaning device for separating dilactide from material mixtures, polymerisation device, method for separating dilactide from material mixtures and also use | |
| EP2406246B1 (en) | Methods for producing lactide with recycle of meso-lactide | |
| US20210188799A1 (en) | Synthesis method and device for rapidly producing lactide at high yield | |
| CN111424059B (en) | Method and system for producing high-yield, high-gloss pure lactide by using biological fermentation technology to prepare lactic acid | |
| KR101486213B1 (en) | Manufacturing method for lactide using a tube bundle falling film reactor and an agitated thin film reactor | |
| CN114471438A (en) | Reaction device and method for industrial preparation of lactide | |
| CN112958030A (en) | System and method for efficiently synthesizing glycolide | |
| CN215250525U (en) | Glycolide continuous production device | |
| WO2013159347A1 (en) | Method for continuously producing high-content high-optical-purity lactate | |
| CN116272665A (en) | Process system for continuously and efficiently producing polymer grade lactide | |
| CN111116776A (en) | Method for improving gas-phase external circulation heat removal capacity of polymerization kettle | |
| CN114716655B (en) | Process for preparing lactide-glycolide copolymer | |
| TWI837905B (en) | A method and system for the continuous preparation of lactide under step control | |
| CN114349733B (en) | Method for continuously preparing high-gloss pure L, L-lactide | |
| CN116063271B (en) | Method for preparing lactide from high molecular weight lactic acid oligomer | |
| CN115246810B (en) | Glycolide continuous production device and application thereof | |
| CN204874355U (en) | Device of preparation lactide | |
| WO2023071865A1 (en) | Method and system for continuously preparing lactide by step control | |
| CN214553590U (en) | System for high-efficient synthetic glycolide | |
| CN116041313A (en) | Method and device for continuously preparing lactide | |
| CN112679465B (en) | Method for preparing lactide by coupling reaction rectification |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |