CN116139791A - Control method of glycolide production process - Google Patents
Control method of glycolide production process Download PDFInfo
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- CN116139791A CN116139791A CN202111389335.3A CN202111389335A CN116139791A CN 116139791 A CN116139791 A CN 116139791A CN 202111389335 A CN202111389335 A CN 202111389335A CN 116139791 A CN116139791 A CN 116139791A
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Abstract
The invention discloses a control method of glycolide production technology, which comprises the following steps: the mass of the reaction mass passing through the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to be 3-1290 kg/(hour square meter).
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a control method of glycolide production technology.
Background
Glycolide is a cyclic dimer of glycolic acid, and a technique for producing high molecular weight polyglycolic acid by ring-opening polymerization of glycolide has been attracting attention. Glycolic acid or glycolates are used as reaction materials, glycolic acid oligomer is prepared through polycondensation, and then depolymerization of the glycolic acid oligomer into ring reaction is carried out to generate gas-phase glycolide, and the gas-phase glycolide is obtained through cooling and collection. In the preparation process, the heat control of the reaction system is particularly important. If the heat of the reaction system is too high, on one hand, the reaction energy consumption is high, and on the other hand, the materials in the reactor are easy to coke, so that the blockage is caused, the reacted residues cannot be discharged from the reactor, the cleaning difficulty is high, and the obtained glycolide product is yellow, and the yield is low; however, if the heat of the reaction system is too low, the degree of depolymerization cyclization reaction is affected, the reaction speed is slowed down, so that the final reaction degree is low, the yield of the obtained glycolide product is low, the impurity content is high, the difficulty of the subsequent glycolide purification process is increased, and the energy consumption of purification is also obviously increased.
Thus, there is an urgent need in the art to develop a production process for efficiently and stably producing glycolide to achieve low carbonization of glycolide.
Disclosure of Invention
The invention aims to provide a control method for glycolide production to efficiently and stably prepare glycolide.
In a first aspect of the present invention, there is provided a method of controlling a glycolide production process comprising depolymerizing glycolic acid or a glycolate polymer to give glycolide by a cyclization reaction, the method comprising the steps of: the parameter a is set to 3-1290 kg/(hr square meter) and represents the mass of the reaction mass per unit time through the unit heat exchange area in the reactor.
In another embodiment, the parameter a is 3-860 kg/(hr square meter).
In another embodiment, the parameter a is 12-451 kg/(hr square meter), preferably 18-215 kg/(hr square meter).
In another embodiment, when the glycolide production process is a batch production process based on one reactor, the throughput of the reaction mass per unit time is the product of the parameter a and the heat exchange area of the reactor.
In another embodiment, when the glycolide production process is a continuous production process based on one reactor, the feed rate of the reaction mass is the product of the parameter a and the heat exchange area of the reactor.
In another embodiment, where the glycolide production process is a continuous production process based on more than two reactors in series, the feed rate of the reaction material to the first reactor is the product of the arithmetic mean of the parameters a of each reactor and the sum of the heat transfer areas of each reactor.
In another embodiment, the heat transfer coefficient K of the reactor is from 100 to 3600 watts/(square meter. Deg.C).
In another embodiment, the heat transfer temperature difference of the reactor is 5-100 ℃.
In a second aspect of the present invention, there is provided a process for producing glycolide, the process comprising the steps of:
(i) Feeding the melted reaction material into the reactor for depolymerization; the reaction material contains glycollic acid or glycollate polymer; and
(ii) The reaction materials are depolymerized into glycolide by heating;
setting a parameter a to be 3-1290 kg/(hr square meter), wherein the parameter a represents the mass of a reaction material passing through a unit heat exchange area in a reactor in unit time;
when the batch production process is based on one reactor, the throughput of the reaction materials in unit time is the product of the parameter a and the heat exchange area of the reactor; or (b)
In a continuous production process based on one reactor, the feeding rate of the reaction material is the product of the parameter a and the heat exchange area of the reactor; or (b)
In a continuous production process based on more than two reactors connected in series, the feed rate of the reaction mass of the first reactor is the product of the arithmetic mean value of the parameters a of the reactors and the sum of the heat exchange areas of the reactors.
In another embodiment, the glycolic acid or glycolate polymer has a weight average molecular weight of no less than 1000; and/or
The reaction mass in step (i) also contains a catalyst; and/or
The temperature in the reactor in the step (ii) is 220-300 ℃ and the pressure is less than or equal to 50kPa; and/or
The method further comprises the steps of: collecting and purifying the glycolide obtained in the step (ii).
Accordingly, the invention provides a production process for efficiently and stably preparing glycolide so as to realize low carbonization of glycolide.
Drawings
FIG. 1 shows a reaction system model of two reactors in series; wherein the solid line box represents the reactor 100.
FIG. 2 shows a reaction system model of two parallel reactors; wherein the solid boxes represent reactors 101, 102, respectively.
Detailed Description
The inventor has conducted extensive and intensive studies and has found that glycolide can be efficiently and stably produced by a method for controlling the quality of a reaction material corresponding to a unit heat exchange area in a reactor per unit time. On this basis, the present invention has been completed.
The invention provides a control method of glycolide production process, based on controlling the heat of the reaction system, mainly comprising the steps of depolymerizing glycolic acid (or glycolate) polymer into a ring, controlling the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely parameter a, to be 3-1290 kg/(h.m) 2 ) Thereby controlling the amount of heat obtained per unit mass of the reaction mass.
The reactor used in the present invention may be conventional in the art, such as, but not limited to, commercially available conventional reactors, the type of reactor being, for example, but not limited to, stirred reactors, falling film reactors, scraped film reactors, and the like.
The inventors found that if the parameter a is less than 3 kg/(h.m) 2 ) Coking is easy to occur in the reactor, so that the loss of reaction materials is caused, the yield of glycolide is reduced, the obtained glycolide product is yellow, the residual materials in the reactor are difficult to remove, and the reactor needs to be cleaned specially, so that time and labor are wasted; if the parameter a is greater than 1290 kg/(h.m) 2 ) The reaction degree of the reaction materials in the reactor is low, so that the yield of the final glycolide is low, the purity of the obtained glycolide product is low, and the subsequent purification is difficult.
In one embodiment of the invention, the mass of the reaction mass per unit heat exchange area in the reactor per unit time, i.e.the parameter a, is from 3 to 860 kg/(h.m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the Preferably, the mass of the reaction material corresponding to the unit heat exchange area in the reactor in the unit time, namely the parameter a, is 12-451 kg/(h.m) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the More preferably, the mass of the reaction mass corresponding to the unit heat exchange area in the reactor in the unit time, namely the parameter a, is 18-215 kg/(h.m) 2 )。
The weight average molecular weight of the glycolic acid (or glycolate) polymer is not less than 1000; preferably, the weight average molecular weight is not less than 2000 and not more than 200000; further, the glycolic acid (or glycolate) polymer has a weight average molecular weight of not less than 3000 and not more than 100000; more preferably, the glycolic acid (or glycolate) polymer has a weight average molecular weight of no less than 5000 and no greater than 60000.
The reaction material used in the above method is not limited to the glycolic acid oligomer, and may be polyglycolic acid having a molecular weight (weight average molecular weight) of more than 200000, for example, waste polyglycolic acid material having a weight average molecular weight of about 200000 or more, and glycolide may be produced as the reaction material by the above method after the recovery treatment, thereby realizing the reuse of the waste polyglycolic acid material.
The heat transfer coefficient K of the reactor used in the invention can be 100-3600W/(m) 2 Temperature of 150-3000W/(m), for example, but not limited to 2 ·℃)、500-2000W/(m 2 ·℃)、300-1500W/(m 2 DEG C), and the like.
The heat transfer temperature difference of the reactor used in the present invention is controlled to 5-100 ℃, for example, but not limited to, 20-70 ℃, 30-50 ℃, 10-40 ℃, 60-90 ℃, 25-80 ℃, etc.
The control method provided by the invention is suitable for both batch production process of glycolide and continuous production process of glycolide.
As used herein, "batch production process" refers to the process in which the reaction mass is processed in a defined processing sequence and operating conditions during production, with the product being output in a limited amount.
As used herein, a "continuous production process" refers to a process in which the reaction mass is continuously passed through a set of specialized equipment, each equipment operating at steady state and performing only one specific processing task, and the product is output in a continuous flow.
Further, the "batch production process" and the "continuous production process" of the present invention have the following characteristics, respectively:
when the control method is used for the batch production process, the V value (namely V=Sxa) can be calculated according to the heat exchange area S of the used reactor by setting the parameter a, namely the processing amount of the reactor to the reaction materials in unit time (namely 1 h), so that the calculated V value is used for feeding. For example, but not limited to, in a gap-type production process, the parameter a is set to 20 kg/(h.m) 2 ) The heat exchange area S of the reactor used was about 15m 2 The processing amount of the reaction materials in the unit time (namely 1 h) in the production process of the reactor is about 300kg, the reaction materials are put into the reactor at one time, the reactor is heated, the temperature in the reactor is controlled to be 220-300 ℃, the absolute pressure is controlled to be less than or equal to 50kPa, the gas-phase glycolide generated in the reaction process is collected, and the production is stopped when the reaction time reaches the set time, thus the batch production is completed once.
When the control method is used for the continuous production process, the V value (namely V=Sxa) can be calculated by setting the parameter a and according to the heat exchange area S of the used reactor, namely the average mass feeding rate of the reaction materials into the reactor. For example, but not limited to, in a continuous production process, the set parameter a is 20 kg/(h.m) 2 ) The heat exchange area S of the reactor used was about 15m 2 The average mass feeding rate V of the reaction materials in the production process of the reactor is about 300kg/h, the melted reaction materials are pumped into the reactor, the temperature of the heat exchange surface in the reactor is set to be about 220-300 ℃, the absolute pressure in the reactor is controlled to be less than or equal to 50kPa, the gas-phase glycolide generated in the reaction process is collected, the time for the reaction materials to completely pass through the heat exchange surface in the reactor is about 0.2-12h, the reaction materials collected at the bottom of the reactor are discharged at the set average mass discharging rate L of the reaction materials, wherein the setting of the value L is based on the control of the stability of the material liquid level parameter at the bottom of the reactor, so that a stable continuous production process is established.
In one embodiment of the present invention, the present invention providesThe control method of (2) is used for continuous production process, and the parameter a of each reactor is respectively set first i (i is an integer not less than 1), and then calculating each reactor parameter a i The arithmetic average value of the above is used to obtain the parameter a, and the average mass feed rate V of the reaction materials of the first reactor in the reaction system is calculated according to the total heat exchange area S of the multiple reactors 1 (V 1 =s×a), based on the calculated V 1 Pumping molten reaction material into a first reactor, controlling the temperature of heat exchange surface in the first reactor to 220-300 deg.C, controlling absolute pressure in the reactor to be less than or equal to 50kPa, collecting gas-phase glycolide produced in the course of reaction, discharging material collected in the bottom portion of first reactor and making it enter into a second reactor to make reaction, and so on until the reaction material passes through the last reactor, in the course of the above-mentioned processes, the total time for the reaction material to pass through heat exchange surface in each reactor is about 0.2-12 hr, collecting gas-phase glycolide produced in each reactor, and the average mass discharge rate L of reaction material of first reactor is described 1 Average mass feed rate V of the reaction mass for each subsequent reactor j (j is an integer greater than or equal to 2) and the average mass discharge rate L of the corresponding reaction materials j And (j is an integer more than or equal to 2) so as to control the material liquid level parameters at the bottom of each reactor to be stable, thereby establishing a stable continuous production process.
When more than 2 reactors are used in the glycolide production process of the present invention, the parameter a for the entire depolymerization cyclization reaction system needs to be set instead of for a certain reactor in the system.
In one embodiment of the invention, more than 2 reactors (see figure 1) are arranged in series in the depolymerization and cyclization reaction system, the reaction conditions (such as temperature, pressure and the like) in each reactor can be the same or different, and the parameters a of each reactor can be respectively and independently set i Then by calculating the respective reactor parameters a i The arithmetic mean of (a) gives the parameter a for the entire depolymerization to ring reaction system.
In one embodiment of the present invention, there are more than 2 reactors (see fig. 2) arranged in parallel in the depolymerization loop reaction system, and the reaction conditions (e.g., temperature, pressure, etc.) in each reactor may be the same or different, and each reactor in parallel and the parallel line in which it is located should be considered as a single reaction system. The reactor 101 and the parallel line 201 in fig. 2 form a separate reaction system, and the reactor 102 and the parallel line 202 in fig. 2 form another separate reaction system.
The invention also provides a preparation method of glycolide, which comprises the following steps:
firstly, setting the mass (i.e. parameter a) of a reaction material passing through a unit heat exchange area in a reactor in unit time, and then enabling the melted reaction material to enter the reactor for depolymerization; the reaction material contains glycollic acid (or glycollate) polymer;
secondly, carrying out thermal depolymerization on the reaction materials to obtain gas-phase glycolide;
and thirdly, collecting the generated gas-phase glycolide.
The above-mentioned first step sets the parameter a according to the control method of glycolide production process provided by the present invention, and determines the amount of molten reaction mass charged in the reactor or determines the mass feed rate of the molten reaction mass into the reactor.
The reaction mass in the first step also contains a catalyst; in one embodiment of the invention, the catalyst is added in an amount of no more than 5wt% of the mass of the molten glycolic acid (or glycolate) polymer; the catalyst may be selected from at least one of tin compounds, antimony compounds, or zinc compounds, such as, but not limited to, stannous octoate, stannous chloride, tin lactate, antimony trioxide, and diethyl zinc or zinc acetate dihydrate.
In one embodiment of the present invention, the reaction material in the above first step may be a glycolic acid (or glycolate) polymer having a weight average molecular weight of not less than 1000; for example, but not limited to, the weight average molecular weight is not less than 2000 and not more than 200000; further, the glycolic acid (or glycolate) polymer has a weight average molecular weight of not less than 3000 and not more than 100000; more preferably, the glycolic acid (or glycolate) polymer has a weight average molecular weight of no less than 5000 and no greater than 60000.
The reaction material in the first step may be polyglycolic acid having a molecular weight (weight average molecular weight) of more than 200000, for example, waste polyglycolic acid material having a weight average molecular weight of about 200000 or more, and glycolide may be produced as the reaction material by the above method after the recovery treatment, thereby realizing the reuse of the waste polyglycolic acid material.
In one embodiment of the present invention, the temperature in the reactor is 220 to 300℃and the absolute pressure is 50kPa or less in the depolymerization reaction stage of the glycolic acid (or glycolate) polymer in the second step.
In one embodiment of the present invention, in the third step, the produced gas-phase glycolide may be condensed and collected in a conventional condenser.
In one embodiment of the present invention, the collected glycolide may also be purified by means such as, but not limited to, recrystallization or continuous crystallization.
The technical parameter a provided by the invention can provide relevant technical references for technicians carrying out the industrialized production of glycolide, and the glycolide is prepared based on the method provided by the invention, so that the technical problems of easiness in coking of materials, equipment blockage, low product yield, insufficient reaction, low purity of the obtained product and the like caused by poor control of the heat of a reaction system and the amount of treated materials can be effectively solved.
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
In this document, all features, such as values, amounts, and concentrations, are for brevity and convenience only, as defined in the numerical or percent range. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
The above-mentioned features of the invention, or of the embodiments, may be combined in any desired manner. All of the features disclosed in this specification may be used in combination with any combination of features, provided that the combination of features is not inconsistent and all such combinations are contemplated as falling within the scope of the present specification. The various features disclosed in the specification may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, the disclosed features are merely general examples of equivalent or similar features.
The invention has the main advantages that:
1. the method provided by the invention uses the melted glycolic acid (or glycolate) oligomer as a reaction material, does not need to use an organic solvent, belongs to a low-carbonization environment-friendly production process, can realize the efficient utilization of heat in a reaction system by selecting and setting a proper parameter a (namely the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time), greatly reduces the energy consumption, can realize low-carbonization continuous stable glycolide production, is suitable for industrial popularization and application, and is beneficial to promoting the realization of industrial carbon neutralization targets.
2. The method provided by the invention provides a new idea for the control mode of the existing glycolide production process, has good flexibility, and is suitable for both batch production process of glycolide and continuous production process of glycolide. The method can be used for designing a new glycolide production line, and can also be used for modifying the existing glycolide production line so as to improve the production efficiency of glycolide and realize a green low-carbonization production mode.
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. The experimental procedures, which do not address the specific conditions in the examples below, are generally carried out under conventional conditions or under conditions recommended by the manufacturer. All percentages, ratios, proportions, or parts are by weight unless otherwise indicated. The units in weight volume percent are well known to those skilled in the art and refer, for example, to the weight of solute in 100 milliliters of solution. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred methods and materials described herein are presented for illustrative purposes only.
In the following examples, quantitative analysis can be performed with respect to the purity of glycolide products by gas chromatography, which is carried out with the following model: island body fluid; chromatographic column model: TC-17 (. Phi.0.25 mm. Times.30 m.times.2 μm); the temperature of the gasification chamber is 295 ℃; chromatographic column temperature rising process: after holding at 60 ℃ for 3 minutes, heating to 280 ℃ at a heating rate of 20 ℃/min, and holding for 3 minutes; the monitor was a hydrogen flame detector with a temperature of 300 ℃.
Examples 1-1 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 25 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 5kg/h, a molten reaction mass comprising a glycolic acid polymer having a weight average molecular weight of about 10000 and stannous octoate, wherein the added amount of stannous octoate is about 0.3% of the mass of the glycolic acid polymer, was introduced into the reactor at a feed rate of about 5kg/h, the temperature of the heat exchange surface in the reactor was set to about 220℃and the heat transfer temperature difference of the reactor was about 70℃and the heat transfer coefficient K was about 100W/(m) 2 The absolute pressure in the reactor is set to be about 100Pa, and the reaction materials flow downwards along the heat exchange surface of the reactor and undergo heat generation depolymerization to form a ring reactionThe gas phase glycolide is pumped out of the reactor, condensed by an external condenser and collected in a storage tank, in the process, the time for the reaction material to completely pass through a heat exchange surface in the reactor is about 0.5h, and the reaction material collected at the bottom of the reactor is discharged at a set average mass discharge rate L of the reaction material, wherein the value L is set based on the control of the stability of the material level parameter at the bottom of the reactor, so that a stable continuous production flow is established.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 4.81kg/h, yield of glycolide at about 96.2%, purity of glycolide as measured by gas chromatography at about 95.9%, and color of glycolide as assessed by a colorimetric card as good, white yellowish.
Examples 1 to 2 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 25 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 5kg/h, a molten reaction mass comprising a glycolic acid polymer having a weight average molecular weight of about 5000 and antimony trioxide, wherein the amount of antimony trioxide added was about 1.0% of the mass of the glycolic acid polymer, was introduced into the reactor at a feed rate of about 5kg/h, the temperature of the heat transfer surface within the reactor was set to about 260℃and the heat transfer difference of the reactor was about 50℃and the heat transfer coefficient K was about 100W/(m) 2 In the process, the absolute pressure in the reactor is set to be about 1kPa, the reaction material flows downwards along the heat exchange surface of the reactor, the reaction material undergoes heat generation depolymerization into ring reaction to generate gas-phase glycolide, the generated gas-phase glycolide is pumped out of the reactor, condensed by an external condenser and then collected into a storage tank, the time for the reaction material to completely pass through the heat exchange surface in the reactor is about 2 hours, the reaction material collected at the bottom of the reactor is discharged at a set average mass discharge rate L of the reaction material, wherein the value L is set based on the stability of the material level parameter controlling the bottom of the reactor, so as to establish stable continuousAnd (3) a formula production flow.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 4.57kg/h, yield of glycolide at about 91.4%, purity of glycolide as measured by gas chromatography at about 95.7%, and chromaticity of glycolide as assessed by a colorimetric card as good, white band light yellow.
Examples 1 to 3 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 25 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 5kg/h, a molten reaction mass comprising glycolic acid polymer having a weight average molecular weight of about 3000 and diethyl zinc, wherein the amount of diethyl zinc added was about 2.0% of the mass of glycolic acid polymer, was introduced into the reactor at a feed rate of about 5kg/h, the temperature of the heat exchange surface within the reactor was set to about 235℃and the heat transfer temperature difference of the reactor was about 30℃and the heat transfer coefficient K was about 100W/(m) 2 The absolute pressure in the reactor is set to be about 15kPa, the reaction material flows downwards along the heat exchange surface of the reactor, the reaction material undergoes heat generation depolymerization into ring reaction to generate gas-phase glycolide, the generated gas-phase glycolide is pumped out of the reactor, condensed by an external condenser and then collected into a storage tank, in the process, the time for the reaction material to completely pass through the heat exchange surface in the reactor is 1h, the reaction material collected at the bottom of the reactor is discharged at a set average mass discharge rate L of the reaction material, wherein the value of L is set based on the stability of the material level parameter controlling the bottom of the reactor, so that a stable continuous production flow is established.
The reactor was able to run stably throughout the process of this example, collecting glycolide at about 4.13kg/h, yield of glycolide at about 82.6%, purity of glycolide at about 94.6% as measured by gas chromatography, and color of glycolide as assessed by a colorimetric card as good, white yellowish.
Examples 1 to 4 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 25 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 5kg/h, a molten reaction mass comprising glycolic acid polymer having a weight average molecular weight of about 20000 and tin lactate, wherein the tin lactate was added in an amount of about 5.0% by mass of the glycolic acid polymer, was introduced into the reactor at a feed rate of about 5kg/h, the temperature of the heat exchange surface in the reactor was set to about 300℃and the heat transfer temperature difference of the reactor was about 5℃and the heat transfer coefficient K was about 100W/(m) 2 The absolute pressure in the reactor is set to be about 50kPa, the reaction material flows downwards along the heat exchange surface of the reactor, the reaction material undergoes heat generation depolymerization into ring reaction to generate gas-phase glycolide, the generated gas-phase glycolide is pumped out of the reactor, condensed by an external condenser and then collected into a storage tank, in the process, the time for the reaction material to completely pass through the heat exchange surface in the reactor is about 4 hours, the reaction material collected at the bottom of the reactor is discharged at a set average mass discharge rate L of the reaction material, wherein the value of L is set based on the stability of the material liquid level parameter controlling the bottom of the falling film reactor, so that a stable continuous production flow is established.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 3.63kg/h, yield of glycolide at about 2.6%, purity of glycolide at about 87.5% as measured by gas chromatography, and chromaticity of glycolide as assessed by a colorimetric card as good, white band light yellow.
Example 2 (continuous production Process)
The heat exchange area is selected to be about 2m 2 The reactor of (2) was set to 3 kg/(h.m) by setting the mass of the reaction material corresponding to the unit heat exchange area in the reactor per unit time, i.e., the parameter a 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 6kg/h, and the molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 60000 and stannous octoate, antimony trioxide, each added in an amount of stannous octoate, antimony trioxide, respectivelyAbout 0.6% and 0.4% of the mass of the glycolic acid polymer was introduced into the reactor at a feed rate of about 6kg/h, the temperature of the heat exchange surface in the reactor was set to about 240℃and the heat transfer temperature difference of the reactor was about 5℃and the heat transfer coefficient K was about 100W/(m) 2 The absolute pressure in the reactor is set to be about 200Pa, the reaction material flows downwards along the heat exchange surface of the reactor, the reaction material undergoes heat generation depolymerization into ring reaction to generate gas-phase glycolide, the generated gas-phase glycolide is pumped out of the reactor, condensed by an external condenser and then collected into a storage tank, in the process, the time for the reaction material to completely pass through the heat exchange surface in the reactor is about 0.2h, the reaction material collected at the bottom of the reactor is discharged at a set average mass discharge rate L of the reaction material, wherein the value L is set based on the stability of the material liquid level parameter controlling the bottom of the reactor, so that a stable continuous production flow is established.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 5.6kg/h, yield of glycolide at about 93.3%, purity of glycolide at about 89.2% as measured by gas chromatography, and color of glycolide as assessed by a colorimetric card as medium, light yellow.
Comparative example 1 (continuous production process)
The heat exchange area is selected to be about 2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 2.2 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the falling film reactor was estimated to be about 4.4kg/h, and the other conditions were the same as in example 2.
In the comparative example, coking occurs on a part of heat exchange surfaces in the reactor, so that part of reaction materials are trapped on the corresponding heat exchange surfaces, the reaction must be stopped, a stable continuous production flow cannot be established, the heat exchange surfaces in the reactor, which are subjected to coking, need to be cleaned, and otherwise, the reactor cannot be used continuously.
In this comparative example, glycolide was collected to be about 2.3kg/h, the yield of glycolide was about 52.3%, the purity of glycolide was measured by gas chromatography to be about 84.7%, and the chromaticity of glycolide was evaluated by using a colorimetric card to be a good product, yellow.
Example 3 (continuous production Process)
The heat exchange area is selected to be about 2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to be 12 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was estimated to be about 24kg/h, and a molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 100000 and stannous octoate, wherein the added amount of stannous octoate is about 0.8% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 24kg/h, the time for the reaction mass to completely pass through the heat exchange surface in the reactor was about 1h, and the other conditions were the same as in example 2.
The reactor was able to run stably throughout the process of this example, collecting glycolide at about 22.9kg/h, yield of glycolide at about 95.4%, purity of glycolide at about 92.7% as measured by gas chromatography, and chromaticity of glycolide as assessed by a colorimetric card as good, white, yellowish.
Example 4 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 18 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 3.6kg/h, and a molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 140000 and stannous octoate, wherein the added amount of stannous octoate is about 1.4% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 3.6kg/h, the time for the reaction mass to pass completely through the heat exchange surface in the reactor was about 8h, and the other conditions were the same as in example 2.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 3.28kg/h, yield of glycolide at about 91.1%, purity of glycolide as measured by gas chromatography at about 95.8%, and color of glycolide as assessed by a colorimetric card as good, white yellowish.
Example 5 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) was set to 215 kg/(h.m) by setting the mass of the reaction material corresponding to the unit heat exchange area in the reactor per unit time, i.e., the parameter a 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 43kg/h, and the molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 200000 and stannous octoate, wherein the added amount of stannous octoate is about 3.5% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 43kg/h, the heat transfer temperature difference of the reactor was about 20℃and the heat transfer coefficient K was about 1000W/(m) 2 The reaction mass was passed completely through the heat exchange surface in the reactor for about 12 hours at a temperature of about c, the remaining conditions being the same as in example 2.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 35.8kg/h, yield of glycolide at about 83.2%, purity of glycolide as measured by gas chromatography at about 95.5%, and color of glycolide as assessed by a colorimetric card as good, white yellowish.
Example 6 (continuous production Process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) was set to 451 kg/(h.m) of the mass of the reaction material corresponding to the unit heat exchange area in the reactor per unit time, i.e., the parameter a 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 90.2kg/h, and the molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 80000 and stannous octoate, wherein the added amount of stannous octoate is about 2.2% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 90.2kg/h, the heat transfer temperature difference of the reactor was about 35℃and the heat transfer coefficient K was about 1000W/(m) 2 The reaction mass was passed completely through the heat exchange surface in the reactor for about 0.5h at a temperature of about deg.c, the remaining conditions being the same as in example 2.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 65.1kg/h, yield of glycolide at about 72.2%, purity of glycolide as measured by gas chromatography at about 90.1%, and color of glycolide as assessed by a colorimetric card as good, white yellowish.
Example 7 (continuous production Process)
The heat exchange area is selected to be about 0.20m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 860 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 172kg/h, and the molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 2000 and stannous octoate, wherein the added amount of stannous octoate is about 0.5% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 172kg/h, the heat transfer temperature difference of the reactor was about 70℃and the heat transfer coefficient K was about 2500W/(m) 2 The reaction mass was passed completely through the heat exchange surface in the reactor for about 1h at the same conditions as in example 2.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 114.7kg/h, yield of glycolide at about 66.7%, purity of glycolide as measured by gas chromatography at about 85.3%, and color of glycolide as assessed by a colorimetric card as medium, light yellow.
Example 8 (continuous production Process)
The heat exchange area is selected to be about 0.20m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 1290 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was calculated to be about 258kg/h, and the molten reaction mass (comprising glycolic acid polymer having a weight average molecular weight of about 1000 and stannous octoate, wherein the added amount of stannous octoate is about 0.2% of the mass of the glycolic acid polymer) was introduced into the reactor at a feed rate of about 172kg/h, the heat transfer temperature difference of the reactor was about 100℃and the heat transfer coefficient K was about 3600W/(m) 2 The reaction mass was passed completely through the heat exchange surface in the reactor for about 0.5h at a temperature of about deg.c, the remaining conditions being the same as in example 2.
Throughout the process of this example, the reactor was able to run stably, collecting glycolide at about 162.3kg/h, yield of glycolide at about 62.9%, purity of glycolide at about 80.2% as measured by gas chromatography, and color of glycolide as judged to be acceptable, yellow by colorimetric card.
Comparative example 2 (continuous production process)
The heat exchange area is selected to be about 0.2m 2 The reactor of (2) is characterized in that the mass of the reaction material corresponding to the unit heat exchange area in the reactor in unit time, namely the parameter a, is set to 1300 kg/(h.m) 2 ) The average mass feed rate V of the reaction mass of the reactor was estimated to be about 260kg/h, and the other conditions were the same as in example 8.
Throughout the process of this comparative example, although the reactor was able to run stably, the glycolide collected was only about 50.8kg/h, the yield of glycolide was about 19.5%, the purity of glycolide was only about 62.2% as measured by gas chromatography, and the chromaticity of glycolide was evaluated as non-conforming, dark yellow by using a colorimetric card.
Example 9 (continuous production Process)
The depolymerization and cyclization reaction system in this example employs 3 reactors in series (the heat exchange area of each of the three reactors is about 0.2m 2 And the heat transfer coefficients K are about 200W/(m) 2 Temperature of the first reactor), parameter a) of the first reactor 1 Set to 20 kg/(h.m) 2 ) Parameter a of the second reactor 2 Set to 30 kg/(h.m) 2 ) Parameter a of the third reactor 3 Set to 46 kg/(h.m) 2 ) Based on the selected a 1 、a 2 And a 3 The arithmetic average value of the three parameters was calculated to be 32 kg/(h.m) 2 ) The obtained parameter a is 32 kg/(h.m) 2 ) While the three reactors have a total heat exchange area S of about 0.6m 2 From this, the average mass feed rate V of the reaction mass of the first reactor in the reaction system can be deduced 1 About 19.2kg/h based on the calculated V 1 Values will melt the reaction mass (comprising glycolic acid oligomer and stannous octoate having a weight average molecular weight of about 18000, whichThe stannous octoate is added in an amount of about 0.03 percent of the mass of the glycolic acid oligomer, the stannous octoate is introduced into a first reactor, the temperature of a heat exchange surface in the first reactor is controlled to be about 265 ℃, the heat transfer temperature difference of the first reactor is controlled to be about 35 ℃, the absolute pressure is controlled to be about 250Pa, the reaction material flows downwards along the heat exchange surface of the reactor and undergoes the heat generation depolymerization cyclization reaction to generate gas-phase glycolide, the generated gas-phase glycolide is pumped out of the reactor, condensed by an external condenser and then is collected into a storage tank, the time for the reaction material to completely pass through the heat exchange surface in the first reactor is about 0.1h, and the material gathered at the bottom of the first reactor is discharged at the average mass discharge rate L of the reaction material 1 Discharging the reaction mixture from the first reactor at an average mass feed rate V 2 Is introduced into a second reactor, the temperature of the heat exchange surface in the second reactor is controlled to be about 270 ℃, the heat transfer temperature difference of the second reactor is controlled to be about 20 ℃, the absolute pressure is controlled to be about 200Pa, the gas-phase glycolide generated in the reaction process is collected, the time for the reaction material to completely pass through the heat exchange surface in the second reactor is about 0.5h, and the material collected at the bottom of the second reactor is discharged at the average mass discharge rate L of the reaction material 2 Discharging the reaction mixture from the second reactor at an average mass feed rate V 3 Is led into a third reactor, the temperature of the heat exchange surface in the third reactor is controlled to be about 280 ℃, the heat transfer temperature difference of the third reactor is controlled to be about 10 ℃, the absolute pressure is controlled to be about 100Pa, the gas-phase glycolide generated in the reaction process is collected, the time for the reactant material to completely pass through the heat exchange surface in the third reactor is about 0.2h, and the material collected at the bottom of the third reactor is discharged at the average mass discharge rate L of the reactant material 3 Discharging the third falling-film reactor, wherein in the process, the parameter L 1 、V 2 、L 2 、V 3 L and 3 based on the control of the stability of the material level parameters at the bottom of each reactor, a stable continuous production flow is established.
The whole process of this example was carried out stably in each reactor, and the glycolide was collected at about 17.6kg/h, the yield of glycolide was about 91.7%, the purity of glycolide was about 95.7% as measured by gas chromatography, and the chromaticity of glycolide was evaluated by using a colorimetric card, and the result was evaluated as a good product, and the white band was pale yellow.
The foregoing description is only illustrative of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, which is defined broadly in the appended claims, and any person skilled in the art to which the invention pertains will readily appreciate that many modifications, including those that fall within the metes and bounds of the claims, or equivalence of such metes and bounds thereof.
Claims (10)
1. A method for controlling a glycolide production process comprising depolymerizing glycolic acid or a glycolide polymer to glycolide by a cyclization reaction, the method comprising the steps of: the parameter a is set to 3-1290 kg/(hr square meter) and represents the mass of the reaction mass per unit time through the unit heat exchange area in the reactor.
2. The control method according to claim 1, wherein the parameter a is 3-860 kg/(hr-square meter).
3. A control method according to claim 1, characterized in that the parameter a is 12-451 kg/(hr-square meter), preferably 18-215 kg/(hr-square meter).
4. The control method according to claim 1, wherein when the glycolide production process is a batch production process based on one reactor, the throughput of the reaction mass per unit time is the product of the parameter a and the heat exchange area of the reactor.
5. The control method according to claim 1, wherein when the glycolide production process is a continuous production process based on one reactor, the feed rate of the reaction mass is the product of the parameter a and the heat exchange area of the reactor.
6. The control method according to claim 1, wherein when the glycolide production process is a continuous production process based on two or more reactors connected in series, the feed rate of the reaction material of the first reactor is the product of the arithmetic average value of the parameter a of each reactor and the sum of the heat exchange areas of each reactor.
7. The control method according to claim 1, wherein the heat transfer coefficient K of the reactor is 100 to 3600 watts/(square meter. Deg.c).
8. The control method according to claim 1, wherein the heat transfer temperature difference of the reactor is 5 to 100 ℃.
9. A process for the preparation of glycolide, said process comprising the steps of:
(i) Feeding the melted reaction material into the reactor for depolymerization; the reaction material contains glycollic acid or glycollate polymer;
(ii) The reaction materials are depolymerized into glycolide by heating;
the method is characterized in that a parameter a is set to 3-1290 kg/(hour square meter), wherein the parameter a represents the mass of a reaction material passing through a unit heat exchange area in a reactor in unit time;
when the batch production process is based on one reactor, the throughput of the reaction materials in unit time is the product of the parameter a and the heat exchange area of the reactor; or (b)
In a continuous production process based on one reactor, the feeding rate of the reaction material is the product of the parameter a and the heat exchange area of the reactor; or (b)
In a continuous production process based on more than two reactors connected in series, the feed rate of the reaction mass of the first reactor is the product of the arithmetic mean value of the parameters a of the reactors and the sum of the heat exchange areas of the reactors.
10. The method of making according to claim 9 wherein the glycolic acid or glycolate polymer has a weight average molecular weight of not less than 1000; and/or
The reaction mass in step (i) also contains a catalyst; and/or
The temperature in the reactor in the step (ii) is 220-300 ℃ and the pressure is less than or equal to 50kPa; and/or;
the method further comprises the steps of: collecting and purifying the glycolide obtained in the step (ii).
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