CN211190194U - Reaction system for lactic acid oligomerization - Google Patents
Reaction system for lactic acid oligomerization Download PDFInfo
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- CN211190194U CN211190194U CN201922073359.2U CN201922073359U CN211190194U CN 211190194 U CN211190194 U CN 211190194U CN 201922073359 U CN201922073359 U CN 201922073359U CN 211190194 U CN211190194 U CN 211190194U
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Abstract
The utility model provides an oligomeric reaction system of lactic acid. The reaction system comprises: the lactic acid oligomerization reaction kettle and the reaction rectifying tower are connected in sequence; the reaction rectifying tower comprises a tower kettle reboiler, a rectifying section and a deep oligomerization dehydration reaction section, wherein the rectifying section and the deep oligomerization dehydration reaction section are arranged from top to bottom; a first feeding hole is formed in a tower section between the rectifying section and the deep oligomerization dehydration reaction section and is used for introducing a product of the lactic acid oligomerization reaction kettle into the reaction rectifying tower; and a tower kettle of the reaction rectifying tower is provided with a first discharge port, a product discharged from the first discharge port is heated by the tower kettle reboiler, one part of the product returns to the deep oligomerization dehydration reaction section again, and the other part of the product is directly collected. The utility model provides a reaction system has optimized the reaction route through unifying rectification and the oligomeric dehydration reaction of degree of depth and has unified the integration, has improved reaction separation efficiency, has realized the effect of enough in time desorption with the hydroenergy in the reaction system, avoids the existence of water to dilute reaction material.
Description
Technical Field
The utility model relates to a lactic acid is oligomeric to react the preparation field, particularly, relates to an oligomeric reaction system of lactic acid.
Background
The production and exploitation of lactide has gained increasing attention in recent years, mainly because the ring-opening polymerization of lactide is an efficient method for preparing high molecular weight polylactic acid. Polylactic acid is a biodegradable material with a great development prospect, and is an excellent medical high polymer material because the final products decomposed in the natural environment are carbon dioxide and water, so that the polylactic acid is nontoxic and harmless to the environment, and has the advantages of good biocompatibility and biodegradability, excellent mechanical property, easiness in processing and forming and the like. The ring-opening polymerization reaction of lactide is an effective method for preparing high-molecular-weight polylactic acid, and the molecular weight of the polylactic acid of a polymerization product can reach millions.
The existing lactide generation process comprises the following steps:
(1) oligomerization reaction: the lactic acid is subjected to multistage esterification reaction under certain temperature and pressure conditions, and is dehydrated and polycondensed into oligomer;
LACID(MIXED)-->P15(MIXED)+H2O(MIXED)
lactic acid oligomer
(oligomers are mixtures of components with a degree of polymerization of 1 to 30(P1-P30) with gradually increasing boiling points, in which the mixture is replaced by P15)
(2) And (3) synthesis reaction: under certain temperature and pressure conditions, the oligomer is thermally decomposed and broken to form lactide.
P15(MIXED)-->7DLL(MIXED)+LACID(MIXED)
Oligomer lactide lactic acid
Wherein, the oligomerization reaction process of the first step is lactic acid intermolecular dehydration, and because the oligomerization reaction is a reversible reaction, the existence of water can dilute reaction materials and influence the reaction rate, thereby influencing the normal operation of the reaction process.
In view of this, the present invention is especially provided.
SUMMERY OF THE UTILITY MODEL
A first object of the utility model is to provide an oligomeric reaction system of lactic acid, this reaction system is through unifying rectification and the oligomeric dehydration of degree of depth reaction integrated, reaction route has been optimized, reaction separation efficiency has been improved, the effect of the timely desorption of water in the reaction system has been realized, the existence of avoiding water dilutes reaction material, influence the reaction process, and then the quality and the yield of oligomeric product have been improved, save equipment cost has also been played in addition, the area's of saving equipment effect, kill two birds with one stone.
The second objective of the present invention is to provide a reaction method for performing lactic acid oligomerization by using the above reaction system, wherein the quality of the lactic acid oligomer product obtained by the reaction is good and the yield is high.
In order to realize the above purpose of the utility model, the following technical scheme is adopted:
the utility model provides an oligomeric reaction system of lactic acid, include: the lactic acid oligomerization reaction kettle and the reaction rectifying tower are connected in sequence;
the reaction rectifying tower comprises a tower kettle reboiler, a rectifying section and a deep oligomerization dehydration reaction section, wherein the rectifying section and the deep oligomerization dehydration reaction section are arranged from top to bottom and are formed by randomly combining a plurality of tower plates and fillers;
a first feeding hole is formed in a tower section between the rectifying section and the deep oligomerization dehydration reaction section and is used for introducing a product of the lactic acid oligomerization reaction kettle into the reaction rectifying tower;
and a tower kettle of the reaction rectifying tower is provided with a first discharge port, and after a product discharged from the first discharge port is heated by the tower kettle reboiler, one part of the product returns to the deep oligomerization dehydration reaction section again, and the other part of the product is directly collected.
In the prior art, the oligomerization reaction process is lactic acid intermolecular dehydration, the reaction is reversible, the reaction rate is influenced by the presence of water, reaction materials are diluted, and the reaction process is restricted because the water in the oligomerization reaction system cannot be removed in time; meanwhile, more residual water is left in the materials, so that the efficiency of the synthesis reaction kettle is reduced, and therefore, water in a reaction system needs to be quickly extracted, and the reaction equilibrium is carried out towards the polymerization direction.
The utility model discloses a solve above-mentioned technical problem, specially set up the oligomeric dehydration reaction section of degree of depth in the reaction rectifying column, not only compensatied the oligomeric reation kettle incomplete problem of reaction of lactic acid, after oligomeric reaction in the reaction rectifying column, in time got rid of moisture through the rectification section in addition, avoided the existence of water to dilute the reaction material, the problem of influence reaction process takes place, and then improved the quality and the yield of oligomeric product.
The utility model discloses an among the lactic acid oligomerization reaction process, the product that obtains is the oligomer between the degree of polymerization 1-30, so-called degree of polymerization is the important index of weighing polymer molecule size, refers to and uses the repeating unit number as the benchmark, the average value of the repeating unit number that contains on the polymer macromolecular chain promptly, the utility model discloses a repeating unit is exactly the lactic acid molecule.
For convenience of the present invention, the symbol P indicates P1-P30, i.e., P15 indicates polymerization between 15 lactic acid molecules, i.e., polymerization between 1 and 30 polymerization degrees.
The bottoms of reactive distillation columns are mostly oligomers with high density such as P29 and P30 in polymerization degree, and a bottom reboiler is arranged in the bottoms to prevent solidification.
After being heated by a reboiler at the tower bottom, one part of products returns to the reaction rectifying tower for further rectifying reaction, and the other part of products is directly extracted as products and is directly used as raw materials for synthesizing lactide after certain post-treatment steps.
Preferably, as a further implementable scheme, the tower kettle reboiler is a falling film reboiler, a second feed inlet is formed in the top of the falling film reboiler, a second discharge outlet is formed in the bottom of the falling film reboiler, the second feed inlet is communicated with the first discharge outlet, one part of substances discharged from the second discharge outlet is introduced into the deep oligomerization and dehydration reaction section to continue oligomerization, the other part of the substances is directly collected, and the substances are further reacted and synthesized as the raw material of the lactide after subsequent post-treatment steps.
The utility model discloses a so select the type of tower cauldron reboiler for falling liquid film formula reboiler, because this type's reboiler compares with ordinary reboiler type, and the film is formed on the pipe wall, and heat exchange efficiency is very high, and the hold-up time is short, is difficult to the coking, and the material of having avoided the tower cauldron takes place the polymerization and has the accessory substance to generate. And because of the falling film reboiler, the material needs to be fed from the top and discharged from the bottom of the reboiler to improve the evaporation efficiency.
Preferably, as a further implementable scheme, a raw material inlet and a reaction product outlet are arranged on the lactic acid oligomerization reaction kettle, the raw material inlet comprises a lactic acid inlet, and the reaction product outlet is arranged at the bottom of the lactic acid oligomerization reaction kettle;
and the reaction product outlet is communicated with the first feed inlet on the reaction rectifying tower.
The utility model discloses an oligomerization at lactic acid oligomerization reation kettle, can realize the polymerization formation oligomer between the lactic acid.
The generated oligomer is mainly gathered at the bottom of the lactic acid oligomerization reaction kettle with high density, so that the reaction product outlet is arranged at the bottom of the kettle, and the lactic acid inlet is arranged on the side wall of the kettle.
Preferably, as a further implementable scheme, a first conveying pump is arranged on a pipeline for communicating the second feeding hole with the first discharging hole so as to facilitate conveying.
Likewise, as a further practical solution, a second delivery pump is provided on the conduit where the reaction product outlet communicates with the first feed port, also for convenience of delivery.
The specific type of the transfer pump is not limited, the vacuum pump can also meet the process requirements according to the specific requirements, the cost is low, and the occupied area is small.
Preferably, as a further implementable scheme, a pipeline connecting the reaction product outlet and the first feed inlet is further provided with a circulating pipeline for returning a part of substances discharged from the reaction product outlet to the lactic acid oligomerization reaction kettle, and the circulating pipeline is provided with a heat exchanger.
The heat exchanger is arranged on the circulating pipeline, the reaction temperature of the lactic acid oligomerization reaction kettle is controlled in a material circulation mode, the heating of materials can be realized by introducing steam when the temperature is lower, the cooling of the materials can be realized by introducing condensed water when the temperature is higher, the heat exchanger is arranged on the circulating pipeline, and the effect of controlling the reaction temperature in the kettle of the lactic acid oligomerization reaction kettle can be mainly played.
The utility model discloses in, the type of heat exchanger does not have specific restriction, can be for floating head heat exchanger, fixed tube sheet heat exchanger, U-shaped tube sheet heat exchanger, plate heat exchanger etc..
The tubular heat exchanger is preferred, the material passes through a tube pass, and the heat exchange medium passes through a shell pass, because the structure of the heat exchanger is simpler and more compact, and the manufacturing cost is lower.
Preferably, as a further implementable aspect, the lactic acid oligomerization reaction kettle is a jacketed stirred reaction kettle. The temperature of the oligomerization reaction is about 140 ℃, so the reaction kettle needs to be heated by introducing steam into a jacket.
In addition, in order to enhance the progress of the oligomerization reaction, a stirrer may be disposed in the reaction vessel, and the stirrer may be a propeller stirrer, an anchor stirrer, a turbine stirrer, or the like, wherein the propeller stirrer has the simplest structure, and the propeller stirrer may be classified into a flat propeller stirrer and a slanted propeller stirrer according to the shape of the blades. The flat paddle type stirrer generates radial force, the inclined paddle type stirrer generates axial force, and the paddle type stirrer is suitable for stirring low-viscosity liquid, suspension liquid and dissolved liquid.
The paddle stirrer of the utility model is preferably a paddle stirrer with three flat paddles, because the relative stirring of the stirrer with the structure is more uniform.
Preferably, as a further practicable scheme, the top of the reactive distillation column is provided with an overhead condenser for refluxing condensation of water, lactic acid and oligomers distilled from the top of the column to enhance the distillation reaction operation.
The utility model also provides a lactic acid oligomerization method, including the following step:
(A) the lactic acid enters the lactic acid oligomerization reaction kettle to react to generate oligomer;
(B) and (4) feeding the oligomer into a reaction rectifying tower for deep dehydration and oligomerization, and rectifying to obtain a final product.
Preferably, as a further implementable scheme, in the step (A), the reaction temperature is between 100 ℃ and 200 ℃, preferably 130 ℃ and 150 ℃, more preferably the reaction temperature is 140 ℃, and the pressure is 0.05 MPa.
Preferably, as a further implementable scheme, in the step (B), the temperature of the rectification reaction is controlled between 100 and 200 ℃, more preferably between 130 and 170 ℃, preferably 150 ℃, and the pressure is negative pressure, and the specific degree of the negative pressure is not limited at all as long as the negative pressure is negative pressure.
Adopt the utility model discloses the oligomer product that lactic acid oligomerization method preparation obtained is of good quality, the yield is high, has avoided the influence of moisture to oligomerization result, has fully realized the quick discharge of the produced water among the reaction sequence.
Compared with the prior art, the beneficial effects of the utility model reside in that:
(1) the lactic acid oligomerization reaction system of the utility model integrates rectification and oligomerization reaction, optimizes the reaction route, improves the reaction separation efficiency, and further improves the quality and yield of products;
(2) the reaction system for oligomerization of lactic acid has simple structure and less three wastes, realizes the full recycling of raw materials and occupies small area;
(3) the utility model realizes the function of controlling the reaction temperature in the lactic acid oligomerization reaction kettle by arranging the circulating pipeline and the heat exchanger;
(4) the tower kettle reboiler is a falling film reboiler, so that the heat exchange efficiency is improved, and the by-product generation caused by the polymerization of the substances in the tower kettle is avoided;
(5) the utility model discloses a reaction system has realized the effect with the timely desorption of water in the reaction system, avoids the existence of water to dilute the reaction material, and the problem that influences the reaction process takes place, and then has improved the quality and the yield of oligomeric product.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 is a schematic structural diagram of a reaction system for oligomerization of lactic acid according to an embodiment of the present invention.
Description of the drawings:
a 100-lactic acid oligomerization reaction kettle; a 110-lactic acid inlet;
130-a reaction product outlet; 140-a second delivery pump;
150-a circulation conduit; 160-heat exchanger.
200-a reactive distillation column; 210-a rectification section;
220-deep oligomerization dehydration reaction section; 230-a first feed port;
240-first discharge hole; 250-column kettle reboiler;
251-a second feed port; 252-a second discharge port;
260-a first delivery pump;
270-overhead condenser.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings and detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In order to clarify the technical solution of the present invention, the following description is made in the form of specific embodiments.
Examples
Referring to fig. 1, the reaction system for oligomerization of lactic acid according to an embodiment of the present invention includes two main apparatus bodies, namely, an oligomerization reaction kettle 100 and a reaction rectification column 200, which are connected in sequence, wherein the reaction rectification column 200 includes a reboiler 250, a condenser 270 at the top of the column, and a rectification section 210 and a deep oligomerization dehydration reaction section 220 which are arranged from top to bottom;
wherein, the lactic acid oligomerization reaction kettle 100 is provided with a raw material inlet and a reaction product outlet 130, and the raw material inlet is a lactic acid inlet 110.
The first material outlet 240 is arranged at the bottom of the reaction rectifying tower 200, and the first material inlet 230 is arranged on the tower sections of the rectifying section 210 and the deep oligomerization dehydration reaction section 220.
The reaction product outlet 130 on the lactic acid oligomerization reaction kettle 100 is communicated with the first feed inlet 230 on the reactive distillation column 200, and for the convenience of transportation, a second transfer pump 140 is further disposed on the communicated pipeline for providing power to transport oligomers generated by the lactic acid oligomerization reaction kettle 100 to the reactive distillation column 200 for further reaction and separation.
In addition, a branch of a circulation pipeline 150 is connected to a pipeline through which the reaction product outlet 130 on the lactic acid oligomerization reaction kettle 100 is communicated with the first feed inlet 230, a heat exchanger 160 is arranged on the circulation pipeline 150, the heat exchanger 160 is a tube type heat exchanger, the material passes through a tube pass, a heat exchange medium passes through a shell pass, and the material after heat exchange is introduced into the lactic acid oligomerization reaction kettle again through the arrangement of the circulation pipeline 150 and the heat exchanger 160, so as to realize temperature control of the lactic acid oligomerization reaction kettle.
In short, a part of the oligomers generated from the lactic acid oligomerization reaction kettle 100 is returned to the kettle again through the circulation pipeline 150, and the other part enters the reactive distillation column 200 for further reactive distillation.
The lactic acid oligomerization reaction kettle 100 is a stirring reaction kettle with a jacket, steam is introduced into the jacket to control the reaction temperature to be 140 ℃, the pressure to be 0.05MPa, and a paddle type stirrer with three flat paddles is selected as the stirrer to improve the stirring force of the reaction.
In addition, the still reboiler 250 included in the other main equipment reaction rectification column 200 is a falling film reboiler, which has high efficiency and avoids the generation of byproducts. The top of the falling film reboiler is provided with a second feed inlet 251, the bottom of the falling film reboiler is provided with a second discharge outlet 252, and the second feed inlet 251 is communicated with the first discharge outlet 240 on the reaction rectifying tower, so that a part of the product discharged from the first discharge outlet 240 is returned to the deep oligomerization and dehydration reaction section 220 after being heated by the tower kettle reboiler 250, and the other part is directly collected.
A first delivery pump 260 is further disposed on a pipeline connecting the second feed opening 251 and the first discharge opening 240 for convenient transportation.
The material from the reactive distillation column 200 mainly contains oligomers, unreacted raw materials, water, etc., and after entering the reactive distillation column, volatile components of water, lactic acid and a small amount of oligomers gradually accumulate at the top of the column, while the bottom is oligomers having a relatively high density of P1 to P30.
The rectifying section 210 and the deep oligomerization and dehydration reaction section 220 of the reactive rectifying tower 200 are mainly composed of trays and fillers, and the types of the fillers can be Raschig rings, pall rings, step rings and the like. The deep oligomerization reaction section 220 is mainly composed of trays, and may not be added with a filler.
Although the pressure drop of the packing per se is relatively low, the packing has the defect of easy fouling, so that the tower section which is easy to foul is preferably in a tower plate mode.
The top of the reactive distillation column 200 is provided with a top condenser, the components of the top of the column mainly comprise water, lactic acid and a small amount of oligomers, one part of the components flows back to the reactive distillation column 200 through the top condenser 270, and the other part of the components flows out from the top condenser 270 and is recycled.
The distillation reaction temperature in the reactive distillation column 200 is 150 ℃ and the pressure is negative pressure.
In the above-described embodiment, the type of the heat exchanger 160 may also be a floating head heat exchanger, a fixed tube-plate heat exchanger, a U-shaped tube-plate heat exchanger, a plate heat exchanger, or the like.
In the above embodiment, the heating manner of the lactic acid oligomerization reaction kettle 100 may also be a manner of arranging heating pipes on the outer wall of the reaction kettle instead of the jacket, and the type of the stirrer is not limited to three flat paddles, and may be a single flat paddle, two flat paddles, etc., and the type of the stirrer may also be a propeller stirrer, an anchor stirrer, a turbine stirrer, etc.
In the above embodiment, the number of the pump bodies is not specifically required, and the pump bodies may be arranged at corresponding positions as required.
In the above embodiment, the rectifying section 210 and the deep oligomerization and dehydration reaction section 220 of the reactive rectifying tower 200 are only a preferable configuration, and may be increased or decreased according to the actual rectifying effect, for example, it is also feasible to additionally add some rectifying sections.
In the above embodiment, the reaction temperature in the lactic acid oligomerization reaction vessel 100 may be 130 ℃, 135 ℃, 145 ℃, 150 ℃ or the like, and the reaction pressure may be 0.03MPa, 0.04MPa, 0.06MPa, 0.07MPa or the like.
Similarly, the temperature in the reactive distillation column 200 may be 130 ℃, 135 ℃, 145 ℃, 150 ℃ or the like.
In addition, the height, diameter, number of plates, and division of the column section of the reactive distillation column 200 can be adjusted according to actual needs.
The working process and principle of the oligomeric reaction system of lactic acid of the present invention are briefly described as follows:
firstly, after nitrogen purges pipelines of the lactic acid oligomerization reaction kettle 100, the reaction rectifying tower 200 and the interior of the reaction kettle, lactic acid raw materials are introduced into the lactic acid oligomerization reaction kettle 100 according to a proportion, stirring is carried out while a stirring device of the lactic acid oligomerization reaction kettle is started, the reaction temperature is controlled at 140 ℃, the reaction pressure is 0.05MPa, and oligomers are gradually gathered at the bottom of the kettle along with the progress of the reaction.
One part of the oligomers generated at the bottom of the reaction kettle is conveyed into the reaction rectifying tower 200 through a pipeline, the other part of the oligomers is circulated through a circulating pipeline 150, a heat exchanger 160 is arranged on the circulating pipeline 150, and the reaction temperature in the lactic acid oligomerization reaction kettle is controlled by heating and cooling the oligomers flowing through the circulating pipeline 150.
The generated oligomer and unreacted raw materials enter the deep oligomerization dehydration reaction section 220 from the middle section of the reaction rectifying tower 200 through a pipeline to carry out deep oligomerization dehydration reaction. The operation pressure of the reactive distillation column 200 is negative pressure, and the temperature at the bottom of the column is about 150 ℃.
After deep oligomerization and dehydration reaction, the generated oligomers P1-P30 with high boiling point gradually gather at the bottom of the tower, volatile components of lactic acid, a small amount of oligomers and water are separated to the top of the tower through a rectifying section 210, one part of the volatile components of lactic acid, a small amount of oligomers and water are refluxed through a top condenser 270, the other part of the volatile components of lactic acid, a small amount of oligomers and water are discharged through the top condenser 270, and the volatile components of lactic acid, the.
In addition, unreacted raw materials and other substances are still in the oligomer at the bottom of the tower after the deep oligomerization dehydration reaction, and after part of the oligomer passes through a tower kettle reboiler 250 of the tower kettle, the oligomer is subjected to cyclic deep reaction rectification at the tower kettle, and the other part of oligomer is extracted and post-treated to be used as a subsequent synthetic raw material of lactide.
The tower reboiler 250 is a falling film reboiler, and the material enters from the top of the tower reboiler 250 and returns to the reactive distillation column 200 from the bottom of the tower reboiler 250 after being evaporated.
For the convenience of control, a valve is correspondingly arranged on a pipeline of the reaction process system, the type of the valve can be a ball valve, a butterfly valve and the like, and an electromagnetic valve can also be adopted as an important control point.
The above steps are repeated circularly to make the whole reaction system run smoothly.
By adopting the lactic acid oligomerization reaction mode of the utility model, the conversion rate of raw materials is increased by 10-20% compared with the prior art, and the yield of oligomers is correspondingly improved compared with the prior art, thereby achieving the effects of reducing energy consumption and improving the conversion rate of raw materials and the yield of products.
Compare with the oligomeric reaction system of prior art's lactic acid, the utility model discloses a reaction system equipment subassembly is few, area is little, the energy consumption is low, with low costs, the reaction is controllable, and the raw materials conversion rate is high, provides the more strong oligomeric reaction system of lactic acid of operability for follow-up preparation lactide, is worth extensively popularizing and applying.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (8)
1. A reaction system for oligomerization of lactic acid, comprising: the lactic acid oligomerization reaction kettle and the reaction rectifying tower are connected in sequence;
the reaction rectifying tower comprises a tower kettle reboiler, a rectifying section and a deep oligomerization dehydration reaction section, wherein the rectifying section and the deep oligomerization dehydration reaction section are arranged from top to bottom and are formed by randomly combining a plurality of tower plates and fillers;
a first feeding hole is formed in a tower section between the rectifying section and the deep oligomerization dehydration reaction section and is used for introducing a product of the lactic acid oligomerization reaction kettle into the reaction rectifying tower;
and a tower kettle of the reaction rectifying tower is provided with a first discharge port, and after a product discharged from the first discharge port is heated by the tower kettle reboiler, one part of the product returns to the deep oligomerization dehydration reaction section again, and the other part of the product is directly collected.
2. The reaction system of claim 1, wherein the tower reboiler is a falling film reboiler, the top of the falling film reboiler is provided with a second inlet, the bottom of the falling film reboiler is provided with a second outlet, the second inlet is communicated with the first outlet, and a part of the substances from the second outlet is introduced into the deep oligomerization and dehydration reaction section, and the other part is directly collected.
3. The reaction system of claim 2, wherein a first transfer pump is disposed on a pipe where the second feed port communicates with the first discharge port.
4. The reaction system of claim 1, wherein a raw material inlet and a reaction product outlet are arranged on the lactic acid oligomerization reaction kettle, the raw material inlet comprises a lactic acid inlet, and the reaction product outlet is arranged at the bottom of the lactic acid oligomerization reaction kettle;
and the reaction product outlet is communicated with the first feed inlet on the reaction rectifying tower.
5. The reaction system of claim 4 wherein a second transfer pump is provided in the conduit communicating the reaction product outlet with the first feed inlet.
6. The reaction system as claimed in claim 5, wherein a circulation pipeline is further disposed on the pipeline connecting the reaction product outlet and the first feeding hole, for returning a part of the substance from the reaction product outlet to the lactic acid oligomerization reaction kettle, and a heat exchanger is disposed on the circulation pipeline.
7. The reaction system of any one of claims 1 to 6, wherein the lactic acid oligomerization reaction kettle is a jacketed stirred reaction kettle.
8. The reaction system according to any one of claims 1 to 6, wherein an overhead condenser is provided at the top of the reactive distillation column for condensing and refluxing water, lactic acid and oligomers distilled from the top of the column.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112876453A (en) * | 2021-01-29 | 2021-06-01 | 南京华基塔业有限公司 | Reaction system and method for preparing lactide from lactic acid |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112876453A (en) * | 2021-01-29 | 2021-06-01 | 南京华基塔业有限公司 | Reaction system and method for preparing lactide from lactic acid |
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