METHOD AND DEVICE FOR SEPARATION AND PURIFICATION OF GLYCOLIC ACID BY RECTIFICATION-CRYSTALLIZATION COUPLING PROCESS AND USE

Abstract

The present disclosure belongs to the technical field of separation and purification of glycolic acid, and in particular, to a method and device for separation and purification of glycolic acid by a rectification-crystallization coupling process and use. Bio-based platform compound molecules are used as raw materials to synthesize the glycolic acid, and the obtained crude glycolic acid is separated and purified using the rectification-crystallization coupling process to obtain high-purity glycolic acid. The method initiates system separation and purification under a new glycolic acid synthesis route, which has the difficulty that the glycolic acid is easy to polymerize during concentration, so there are technical barriers to equipment design of vacuum rectification and adjustment of process parameters. In addition, during crystallization, there are technical barriers to equipment design of a crystallization kettle and adjustment of process parameters.

Claims

1. A method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process, the method comprising: synthesizing glycolic acid using bio-based platform compound molecules as raw materials; and separating and purifying the obtained crude glycolic acid using the rectification-crystallization coupling process to obtain high-purity glycolic acid.

2. The method according to claim 1, further comprising the following steps: step I, preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials: transforming the platform compound molecules with a supported catalyst to synthesize the crude glycolic acid; step II, conducting rectification concentration on the obtained crude glycolic acid: concentrating a crude glycolic acid solution to be greater than or equal to 70 wt. % in a rectification column using vacuum rectification technology; and step III, conducting cooling crystallization and filtration on the concentrated solution to obtain high-purity glycolic acid crystals: crystallizing the glycolic acid in a crystallization kettle coupled in series with the rectification column, and filtering and separating the crystallized glycolic acid to obtain the high-purity glycolic acid.

3. The method according to claim 2, wherein preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials in step I further comprises: reacting at 80° C. for 10 h with a platinum on carbon (Pt/C) catalyst and using ethylene glycol bio-based platform compound molecules as the raw materials to obtain the crude glycolic acid solution.

4. The method according to claim 1, wherein the bio-based platform compound molecules in step I comprise one or a mixture of two or more selected from the group consisting of ethylene glycol, glyoxal, and oxalic acid diol aldehyde compounds, glycerol and butanediol polyol aldehyde compounds, and cellulose.

5. The method according to claim 1, wherein the crude glycolic acid in step I comprises one or a mixture of two or more selected from the group consisting of glycolic acid, glycolaldehyde, ethylene glycol, glyoxal, glyoxylic acid, oxalic acid, formic acid, sorbitol, propylene glycol, butanediol, cellulose, glycerol, and lactic acid polyol aldehyde compounds.

6. The method according to claim 1, wherein conducting rectification concentration on the obtained crude glycolic acid in step II further comprises: concentrating a crude glycolic acid solution with a mass fraction of 35 wt. % to be greater than or equal to 70 wt. % by vacuum rectification at 20° C. to 250° C. under 0-10 MPa; and the rectification column has a feed temperature of 30° C., a plate number of 25, a reflux ratio of 0.32, a bottom temperature of 60° C., and an absolute pressure of 0.29 MPa; and methods for the rectification concentration comprise one or more of ordinary distillation, atmospheric rectification, vacuum rectification, and molecular rectification in series.

7. The method according to claim 1, wherein methods for crystallization in step III comprise one or more of cooling crystallization, evaporative crystallization, sublimation crystallization, and recrystallization in series; and a process of conducting cooling crystallization and filtration on the concentrated solution to obtain high-purity glycolic acid crystals further comprises: crystallizing the obtained concentrated solution of the glycolic acid in the crystallization kettle, the cooling crystallization and the recrystallization are conducted at −20° C. to 40° C. under a cooling rate of 0.1-20° C./min and a stirring rate of 100-1,500 r/min during cooling, a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution is 0.01-20%; and the evaporative crystallization and the sublimation crystallization are conducted at −20° C. to 200° C.

8. A glycolic acid, obtained by the method according to claim 1.

9. The glycolic acid according to claim 8, wherein the method further comprises the following steps: step I, preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials: transforming the platform compound molecules with a supported catalyst to synthesize the crude glycolic acid; step II, conducting rectification concentration on the obtained crude glycolic acid: concentrating a crude glycolic acid solution to be greater than or equal to 70 wt. % in a rectification column using vacuum rectification technology; and step III, conducting cooling crystallization and filtration on the concentrated solution to obtain high-purity glycolic acid crystals: crystallizing the glycolic acid in a crystallization kettle coupled in series with the rectification column, and filtering and separating the crystallized glycolic acid to obtain the high-purity glycolic acid.

10. The glycolic acid according to claim 8, wherein preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials in step I further comprises: reacting at 80° C. for 10 h with a platinum on carbon (Pt/C) catalyst and using ethylene glycol bio-based platform compound molecules as the raw materials to obtain the crude glycolic acid solution.

11. The glycolic acid according to claim 8, wherein the bio-based platform compound molecules in step I comprise one or a mixture of two or more selected from the group consisting of ethylene glycol, glyoxal, and oxalic acid diol aldehyde compounds, glycerol and butanediol polyol aldehyde compounds, and cellulose.

12. The glycolic acid according to claim 8, wherein the crude glycolic acid in step I comprises one or a mixture of two or more selected from the group consisting of glycolic acid, glycolaldehyde, ethylene glycol, glyoxal, glyoxylic acid, oxalic acid, formic acid, sorbitol, propylene glycol, butanediol, cellulose, glycerol, and lactic acid polyol aldehyde compounds.

13. The glycolic acid according to claim 8, wherein conducting rectification concentration on the obtained crude glycolic acid in step II further comprises: concentrating a crude glycolic acid solution with a mass fraction of 35 wt. % to be greater than or equal to 70 wt. % by vacuum rectification at 20° C. to 250° C. under 0-10 MPa; and the rectification column has a feed temperature of 30° C., a plate number of 25, a reflux ratio of 0.32, a bottom temperature of 60° C., and an absolute pressure of 0.29 MPa; and methods for the rectification concentration comprise one or more of ordinary distillation, atmospheric rectification, vacuum rectification, and molecular rectification in series.

14. The glycolic acid according to claim 8, wherein crystallization in step III comprise one or more of cooling crystallization, evaporative crystallization, sublimation crystallization, and recrystallization in series; and a process of conducting cooling crystallization and filtration on the concentrated solution to obtain high-purity glycolic acid crystals further comprises: crystallizing the obtained concentrated solution of the glycolic acid in the crystallization kettle, the cooling crystallization and the recrystallization are conducted at −20° C. to 40° C. under a cooling rate of 0.1-20° C./min and a stirring rate of 100-1,500 r/min during cooling, a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution is 0.01-20%; and the evaporative crystallization and the sublimation crystallization are conducted at −20° C. to 200° C.

15. A device for separation and purification by rectification and crystallization coupling implementing the method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process according to claim 1, the device comprising: a vacuum rectification column and a crystallization kettle; a rectification column plate is welded inside the vacuum rectification column comprising an upper part connected to a condenser through a tubing and a lower part connected to a reboiler and the crystallization kettle through tubings; and a crystallization kettle temperature controller and a condensed water circulator are arranged at an upper part of the crystallization kettle; and a mechanical stirring device is arranged inside the crystallization kettle.

16. The device according to claim 15, wherein the method further comprises the following steps: step I, preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials: transforming the platform compound molecules with a supported catalyst to synthesize the crude glycolic acid; step II, conducting rectification concentration on the obtained crude glycolic acid: concentrating a crude glycolic acid solution to be greater than or equal to 70 wt. % in a rectification column using vacuum rectification technology; and step III, conducting cooling crystallization and filtration on the concentrated solution to obtain high-purity glycolic acid crystals: crystallizing the glycolic acid in a crystallization kettle coupled in series with the rectification column, and filtering and separating the crystallized glycolic acid to obtain the high-purity glycolic acid.

17. The device according to claim 15, wherein a process of preparing the crude glycolic acid using the bio-based platform compound molecules as the raw materials in step I further comprises: reacting at 80° C. for 10 h with a platinum on carbon (Pt/C) catalyst and using ethylene glycol bio-based platform compound molecules as the raw materials to obtain the crude glycolic acid solution.

18. The device according to claim 15, wherein the bio-based platform compound molecules in step I comprise one or a mixture of two or more selected from the group consisting of ethylene glycol, glyoxal, and oxalic acid diol aldehyde compounds, glycerol and butanediol polyol aldehyde compounds, and cellulose.

19. The device according to claim 15, wherein the crude glycolic acid in step I comprises one or a mixture of two or more selected from the group consisting of glycolic acid, glycolaldehyde, ethylene glycol, glyoxal, glyoxylic acid, oxalic acid, formic acid, sorbitol, propylene glycol, butanediol, cellulose, glycerol, and lactic acid polyol aldehyde compounds.

20. The device according to claim 15, wherein conducting rectification concentration on the obtained crude glycolic acid in step II further comprises: concentrating a crude glycolic acid solution with a mass fraction of 35 wt. % to be greater than or equal to 70 wt. % by vacuum rectification at 20° C. to 250° C. under 0-10 MPa; and the rectification column has a feed temperature of 30° C., a plate number of 25, a reflux ratio of 0.32, a bottom temperature of 60° C., and an absolute pressure of 0.29 MPa; and methods for the rectification concentration comprise one or more of ordinary distillation, atmospheric rectification, vacuum rectification, and molecular rectification in series.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings incorporated into the specification and constituting part of the specification illustrate the examples of the present disclosure, and serve, together with the specification, to explain the principles of the present disclosure.

[0035] FIG. 1 is a flow chart of a method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process provided by an example of the present disclosure; and

[0036] FIG. 2 is a schematic structural diagram of a device for separation and purification by rectification and crystallization coupling provided by an example of the present disclosure.

[0037] Reference numerals: A, vacuum rectification column; B, crystallization kettle; 1, rectification column plate; 2, condenser; 3, reboiler; 4, crystallization kettle temperature controller; 5, condensed water circulator; and 6, mechanical stirring device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To enable the objectives, features, and advantages mentioned above of the present disclosure to be more apparent and easily understood, specific implementations of the present disclosure will be described in detail below in conjunction with the drawings. The following describes many details in order to provide a thorough understanding of the present disclosure. However, the present disclosure can be implemented in many other ways other than those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present disclosure, and thus the present disclosure is not limited to the specific implementations disclosed below.

[0039] All technical and scientific terms used in the present disclosure have the same meaning as commonly understood by those skilled in the technical field of the present disclosure. The terms used in the specification of the present disclosure are only for the purpose of describing specific examples, rather than to limit the present disclosure. The term “and/or” used herein includes any and all combinations of one or more of the associated listed items.

[0040] As shown in FIG. 1, the present disclosure provides a method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process, including the following steps.

[0041] S101, crude glycolic acid is prepared using bio-based platform compound molecules as raw materials. Specifically, the platform compound molecules are subjected to green transformation with a supported catalyst to synthesize the crude glycolic acid. For example, a reaction is conducted at 80° C. for 10 h with a Pt/C catalyst and using ethylene glycol bio-based platform compound molecules as the raw materials to obtain a crude glycolic acid solution.

[0042] S102, the obtained crude glycolic acid is subjected to rectification concentration to be greater than or equal to 70 wt. %. Specifically, the crude glycolic acid solution is concentrated in a rectification column using vacuum rectification technology. For example, a crude glycolic acid solution with a mass fraction of 35 wt. % is subjected to vacuum rectification. The rectification column has a feed temperature of 30° C., a plate number of 25, a reflux ratio of 0.32, a bottom temperature of 60° C., and an absolute pressure of 0.29 MPa.

[0043] S103, cooling crystallization and filtration are conducted on the concentrated solution to obtain high-purity glycolic acid crystals. Specifically, the glycolic acid is crystallized in a crystallization kettle B coupled in series with the rectification column, and filtered and separated to obtain high-purity glycolic acid. For example, the obtained concentrated solution of the glycolic acid is crystallized in the crystallization kettle B at −15° C. under a cooling rate of 0.5° C./min and a stirring rate of 400 r/min, and 1 wt. % of glycolic acid seed crystals is added.

[0044] In an example of the present disclosure, as shown in FIG. 2, a device for separation and purification by rectification and crystallization coupling is further provided, composed of a vacuum rectification column A and a crystallization kettle B, and specifically including: a rectification column plate 1, a condenser 2, a reboiler 3, a crystallization kettle temperature controller 4, a condensed water circulator 5, and a mechanical stirring device 6. The crude glycolic acid is put into the rectification column plate 1. The glycolic acid crystals are taken out from the bottom of the crystallization kettle B. The rectification column plate 1 is welded inside the vacuum rectification column A including an upper part connected to the condenser 2 through a tubing and a lower part connected to the reboiler 3 and the crystallization kettle B through tubings. The crystallization kettle temperature controller 4 and the condensed water circulator 5 are arranged at an upper part of the crystallization kettle B. The mechanical stirring device 6 is arranged inside the crystallization kettle B.

[0045] The technical solutions of the present disclosure will be further described below in conjunction with specific examples.

Example 1

[0046] A method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process included the following steps.

[0047] Cellulose was subjected to one-step hydrothermal conversion with a tungsten/nickel catalyst at 200° C. under an initial hydrogen pressure of 6 MPa to obtain ethylene glycol, and the ethylene glycol was subjected to one-step hydrothermal conversion with a Pt catalyst supported on activated carbon (Pt/AC) at 80° C. under an initial oxygen pressure of 2 MPa to obtain crude glycolic acid.

[0048] The obtained crude glycolic acid was concentrated by vacuum rectification at a vacuum temperature of 50° C. under an absolute pressure of 0.5 MPa during vacuum, and the crude glycolic acid was concentrated to 70 wt. %.

[0049] Cooling crystallization was conducted on the obtained concentrated solution at −20° C. under a cooling rate of 0.5° C./min and a stirring rate of 800 r/min, and a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution was 2%.

[0050] Thus, the high-purity glycolic acid crystals were obtained.

Examples 2 to 10

[0051] According to the method for separation and purification of glycolic acid in Example 1, the temperature and pressure of the vacuum rectification used were adjusted, and the other parameters were the same. The glycolic acid was separated and purified. The yield and purity of the glycolic acid were recorded, as shown in Table 1.

TABLE-US-00001 TABLE 1 T, ° C. P, MPa Yield, % Purity, % Example 1 40 0.05 56.7 91.5 Example 2 40 0.1 70.5 93.9 Example 3 40 0.2 81.4 92.7 Example 4 40 0.5 60.6 95.8 Example 5 40 1.0 66.9 96.8 Example 6 30 0.1 59.9 93.4 Example 7 50 0.1 72.3 95.8 Example 8 60 0.1 76.9 96.5 Example 9 70 0.1 78.5 98.7 Example 10 80 0.1 89.4 99.1

Examples 11 to 20

[0052] According to the method for separation and purification of glycolic acid in Example 1, the cooling rate, crystallization temperature, and rotational speed of the cooling crystallization used were adjusted, and the other parameters were the same. The glycolic acid was separated and purified. The yield and purity of the glycolic acid were recorded, as shown in Table 2.

TABLE-US-00002 TABLE 2 t, ° C./min T, ° C. R, r/min Yield, % Purity, % Example 11 0.5 −5 500 56.8 93.5 Example 12 0.5 −5 500 69.4 96.7 Example 13 0.5 −5 500 68.9 94.9 Example 14 1 −5 500 75.9 95.6 Example 15 1 −5 500 78.4 97.2 Example 16 1 −20 800 84.2 98.3 Example 17 5 −20 800 85.5 96.1 Example 18 5 −20 800 87.3 93.6 Example 19 5 −20 800 89.1 94.7 Example 20 10 −20 800 88.4 95.2

Example 21

[0053] A method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process included the following steps.

[0054] Glycerol was subjected to one-step hydrothermal conversion with a Pt—Fe/CeO.sub.2 catalyst at 100° C. under an initial hydrogen pressure of 1 MPa to obtain crude glycolic acid.

[0055] The obtained crude glycolic acid was concentrated by vacuum rectification at a vacuum temperature of 50° C. under an absolute pressure of 0.5 MPa during vacuum, and the crude glycolic acid was concentrated to 70 wt. %.

[0056] Cooling crystallization was conducted on the obtained concentrated solution at −20° C. under a cooling rate of 0.5° C./min and a stirring rate of 800 r/min, and a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution was 2%.

[0057] Thus, the high-purity glycolic acid crystals were obtained.

Example 22

[0058] A method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process included the following steps. Methyl glycolate was hydrolyzed to obtain crude glycolic acid in one step.

[0059] The obtained crude glycolic acid was concentrated by vacuum rectification at a vacuum temperature of 50° C. under an absolute pressure of 0.5 MPa during vacuum, and the crude glycolic acid was concentrated to 70 wt. %.

[0060] Cooling crystallization was conducted on the obtained concentrated solution at −20° C. under a cooling rate of 0.5° C./min and a stirring rate of 800 r/min, and a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution was 2%.

[0061] Thus, the high-purity glycolic acid crystals were obtained.

Example 23

[0062] A method for separation and purification of bio-based glycolic acid by a rectification-crystallization coupling process included the following steps.

[0063] Ethylene glycol was subjected to one-step hydrothermal conversion with an Au/NaY catalyst at 95° C. under an initial hydrogen pressure of 1 MPa to obtain crude glycolic acid.

[0064] The obtained crude glycolic acid was concentrated by vacuum rectification at a vacuum temperature of 50° C. under an absolute pressure of 0.5 MPa during vacuum, and the crude glycolic acid was concentrated to 70 wt. %.

[0065] Cooling crystallization was conducted on the obtained concentrated solution at −20° C. under a cooling rate of 0.5° C./min and a stirring rate of 800 r/min, and a percentage of a mass of glycolic acid seed crystals added to that of the glycolic acid in the concentrated solution was 2%.

[0066] Thus, the high-purity glycolic acid crystals were obtained.

[0067] The vacuum rectification temperature and pressure were adjusted according to the glycolic acid of different synthetic sources of Examples 24 to 31, and the other parameters were the same. The glycolic acid was separated and purified. The yield and purity of the glycolic acid were recorded, as shown in Table 3.

TABLE-US-00003 TABLE 3 Raw materials for synthesizing glycolic acid T, ° C. P, MPa Yield, % Purity, % Example 24 Cellulose 50 0.1 58.3 92.3 Example 25 Glycerol 50 0.1 56.8 96.1 Example 26 Methyl 50 0.1 59.4 97.2 glycolate Example 27 Ethylene 50 0.1 56.1 95.3 glycol Example 28 Cellulose 70 0.05 70.4 97.1 Example 29 Glycerol 70 0.05 75.3 98.5 Example 30 Methyl 70 0.05 76.8 99.1 glycolate Example 31 Ethylene 70 0.05 79.1 94.5 glycol

[0068] The vacuum rectification temperature and pressure were adjusted according to the glycolic acid of different synthetic sources of Examples 32 to 39, and the other parameters were the same. The glycolic acid was separated and purified. The yield and purity of the glycolic acid were recorded, as shown in Table 4.

TABLE-US-00004 TABLE 4 Raw materials for synthesizing t, T, R, Yield, Purity, glycolic acid ° C./min ° C. r/min % % Example 32 Cellulose 1 −5 200 61.4 93.5 Example 33 Glycerol 1 −5 200 68.1 96.1 Example 34 Methyl 1 −5 200 64.9 92.7 glycolate Example 35 Ethylene 1 −5 200 69.6 98.2 glycol Example 36 Cellulose 5 −15 600 81.4 94.1 Example 37 Glycerol 5 −15 600 85.9 95.7 Example 38 Methyl 5 −15 600 84.8 93.1 glycolate Example 39 Ethylene 5 −15 600 89.2 94.9 glycol

[0069] Those skilled in the art can easily think of other implementation solutions of the present disclosure after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, purposes or adaptive changes of the present disclosure. Such variations, purposes or applicable changes follow the general principle of the present disclosure and include common knowledge or conventional technical means in the technical field which is not disclosed in the present disclosure. The specification and examples are merely considered as illustrative, and the real scope and spirit of the present disclosure are pointed out by the claims.

[0070] It should be noted that the present disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and can be modified and changed in many ways without departing from the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims.