Preparation method of lactide and reaction device

Abstract

The invention relates to a lactide preparation method and a reaction device. The preparation method comprises the following steps: (1) carrying out the following reactions in a reactive rectification tower I: carrying out a preliminary polymerization reaction on lactic acid to obtain a first lactic acid oligomer; (2) coupling the following reactions into a reactive rectification tower II: carrying out an oligomerization reaction on the first lactic acid oligomer to obtain a second lactic acid oligomer, and carrying out a first depolymerization reaction on the second lactic acid oligomer to obtain a lactide initial product; and (3) enabling tower kettle liquid of the reactive rectification tower II to enter a reactive rectification tower III, and carrying out a second depolymerization reaction to obtain lactide. Compared with the existing industrial mainstream known technology, the process and equipment of the lactic acid two-step method are greatly simplified, the equipment investment and the production cost are remarkably reduced, and the outstanding economical advantage is achieved.

Description

technical field

[0001] The invention relates to the technical field of lactide, in particular to a method for preparing lactide and a reaction device. Background technique

[0002] Polylactic acid (PLA), also known as polylactide, is a typical biodegradable polymer material prepared by chemical synthesis from renewable plant resources. In recent years, the demand for PLA in the global market has increased rapidly. It is expected that the demand will double every 3-5 years in the next few years, and it is expected that the supply will be in short supply for a long time. The global plastic ban and garbage sorting have brought a huge potential market for degradable plastics, especially disposable plastic products.

[0003] At present, the industrial production of PLA generally adopts the lactide ring-opening polymerization method. Lactide is the key intermediate for the synthesis of PLA, and its synthesis process and key equipment are the key directions of research in the indu...

Examples

Embodiment 1

[0145] This embodiment provides a kind of preparation method of lactide, and the preparation method is specifically as follows:

[0146] (1) The following reactions are coupled to the reactive distillation tower I for: dehydration of lactic acid, preliminary polymerization of lactic acid, purification of water and hydrolysis of defocused oil;

[0147] (2) The following reaction is coupled to the reactive distillation column II: the first lactic acid oligomer obtained by the preliminary polymerization reaction is subjected to an oligomerization reaction to obtain a second lactic acid oligomer, and the second lactic acid oligomer is reduced The polymer undergoes a first depolymerization reaction;

[0148] (3) making the bottom liquid of the reactive distillation tower II enter the reactive distillation tower III, and carry out the second depolymerization reaction in the depolymerization reaction section of the reactive distillation tower III;

[0149] (4) The lactide obtained i...

Embodiment 2

[0161] This embodiment provides a lactide preparation method and reaction device, the reaction device is the same as in Example 1, the only difference is that the following operating conditions are different:

[0162] Operating conditions: The pressure of reactive distillation column I is normal pressure, the temperature at the top of the tower is 100°C, the temperature on the trays is controlled by heat transfer oil heat exchange tubes, the temperature of the upper 10 trays is 150-160°C, and the temperature of the lower 10 trays is The temperature is 160~170℃; the reflux ratio is 1:1. Reactive distillation column feed 20kg / h.

[0163] The pressure of the reactive distillation column II is 1kPaA, the temperature on the tray is controlled by heat transfer oil heat exchange tubes, and is controlled at 170°C from top to bottom, and the temperature of the reboiler in the tower kettle is 190°C.

[0164] Reaction result: the Mw of the lactic acid oligomer in the bottom liquid of th...

Embodiment 3

[0166] This embodiment provides a method for preparing lactide and a reaction device. The reaction device is the same as that in Embodiment 1, the only difference being that the temperature of the reboiler in the first depolymerization reaction section, that is, the reactive distillation column II, is controlled at 200°C.

[0167] Reaction result: the conversion rate of the first depolymerization reaction of the lactic acid oligomers in the reactive distillation column II is 10%. The yield of the second depolymerization reaction in the reactive distillation column III is 64.2%, the optical purity of crude lactide is 97.3%, the content of lactic acid is 0.46%, and the total content of 2-5 lactic acid polymerization products is 1.05%.

[0168]As can be seen from the above results, the step-by-step depolymerization method of the present invention can be used to regulate the lactic acid content of crude lactide, the content of lactic acid and lactic acid oligomers in the crude lact...

technical field

[0001] The invention relates to the technical field of lactide, in particular to a method for preparing lactide and a reaction device. Background technique

[0002] Polylactic acid (PLA), also known as polylactide, is a typical biodegradable polymer material prepared by chemical synthesis from renewable plant resources. In recent years, the demand for PLA in the global market has increased rapidly. It is expected that the demand will double every 3-5 years in the next few years, and it is expected that the supply will be in short supply for a long time. The global plastic ban and garbage sorting have brought a huge potential market for degradable plastics, especially disposable plastic products.

[0003] At present, the industrial production of PLA generally adopts the lactide ring-opening polymerization method. Lactide is the key intermediate for the synthesis of PLA, and its synthesis process and key equipment are the key directions of research in the indu...

Examples

Embodiment 1

[0145] This embodiment provides a kind of preparation method of lactide, and the preparation method is specifically as follows:

[0146] (1) The following reactions are coupled to the reactive distillation tower I for: dehydration of lactic acid, preliminary polymerization of lactic acid, purification of water and hydrolysis of defocused oil;

[0147] (2) The following reaction is coupled to the reactive distillation column II: the first lactic acid oligomer obtained by the preliminary polymerization reaction is subjected to an oligomerization reaction to obtain a second lactic acid oligomer, and the second lactic acid oligomer is reduced The polymer undergoes a first depolymerization reaction;

[0148] (3) making the bottom liquid of the reactive distillation tower II enter the reactive distillation tower III, and carry out the second depolymerization reaction in the depolymerization reaction section of the reactive distillation tower III;

[0149] (4) The lactide obtained i...

Embodiment 2

[0161] This embodiment provides a lactide preparation method and reaction device, the reaction device is the same as in Example 1, the only difference is that the following operating conditions are different:

[0162] Operating conditions: The pressure of reactive distillation column I is normal pressure, the temperature at the top of the tower is 100°C, the temperature on the trays is controlled by heat transfer oil heat exchange tubes, the temperature of the upper 10 trays is 150-160°C, and the temperature of the lower 10 trays is The temperature is 160~170℃; the reflux ratio is 1:1. Reactive distillation column feed 20kg / h.

[0163] The pressure of the reactive distillation column II is 1kPaA, the temperature on the tray is controlled by heat transfer oil heat exchange tubes, and is controlled at 170°C from top to bottom, and the temperature of the reboiler in the tower kettle is 190°C.

[0164] Reaction result: the Mw of the lactic acid oligomer in the bottom liquid of th...

Embodiment 3

[0166] This embodiment provides a method for preparing lactide and a reaction device. The reaction device is the same as that in Embodiment 1, the only difference being that the temperature of the reboiler in the first depolymerization reaction section, that is, the reactive distillation column II, is controlled at 200°C.

[0167] Reaction result: the conversion rate of the first depolymerization reaction of the lactic acid oligomers in the reactive distillation column II is 10%. The yield of the second depolymerization reaction in the reactive distillation column III is 64.2%, the optical purity of crude lactide is 97.3%, the content of lactic acid is 0.46%, and the total content of 2-5 lactic acid polymerization products is 1.05%.

[0168]As can be seen from the above results, the step-by-step depolymerization method of the present invention can be used to regulate the lactic acid content of crude lactide, the content of lactic acid and lactic acid oligomers in the crude lact...

Images