Deep purification process of high-purity glycerol

Abstract

The invention relates to the technical field of glycerol purification, in particular to a high-purity glycerol deep purification process which comprises the following steps: adding methanol and phosphoric acid into crude glycerol to prepare pretreated glycerol; adding a composite alkali solution into the pretreated glycerol, standing and layering to obtain a clear liquid phase, adding activated carbon and stirring, and injecting filtrate into an ion exchange column after centrifugal separation; distilling the liquid flowing out of the ion exchange column to obtain semi-treated glycerol; and sequentially carrying out reduced pressure distillation and activated carbon deodorization and decolorization treatment on the semi-treated glycerol to obtain the high-purity glycerol. According to the method, methanol and phosphoric acid are firstly used for treatment, separation of glycerol is facilitated, salt is sufficiently separated out by adding a composite alkali solution, impurities in crude glycerol can be well adsorbed and removed by matching with added activated carbon, and non-electrolytic substances of the crude glycerol are adsorbed and fixed under the assistance of ion exchange resin, so that further purification is realized; finally, methanol and water are removed through distillation / reduced pressure distillation, and the purity of the obtained glycerol can reach 99.9%.

Description

Technical Field

[0001] The present invention relates to the technical field of glycerol purification, in particular to a high-purity glycerol deep purification process. Background Art

[0002] Glycerol, commonly known as glycerin, is an important chemical product commonly used in lubricants, softeners, pharmaceuticals, daily cosmetics, and organic synthesis. With the rapid globalization of the biomass energy industry, my country's biodiesel industry is growing rapidly. The production of biodiesel produces a large amount of crude glycerin as a byproduct. Recovering and refining glycerin can alleviate my country's glycerin supply and demand imbalance and reduce biodiesel costs.

[0003] Crude glycerin contains approximately 10-15% water, small amounts of inorganic salts, organic soaps, fatty acids and lipids, polymerized glycerol, and certain unidentified odorous impurities. This complex composition, coupled with glycerin's high boiling point and heat sensitivity, makes traditional multi-effect evaporation and distillation purification processes not only complex and costly, but also prone to oxidation and deterioration of the glycerin under prolonged high-temperature conditions, impacting its quality. To address this issue, a process for deep purification of high-purity glycerin was proposed. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a high-purity glycerol deep purification process, which produces high-purity glycerol through methanol dilution, composite alkaline solution desalination, double adsorption and other processes.

[0005] To achieve the above object, the present invention provides the following technical solution: a high-purity glycerol deep purification process, comprising the following steps: (1) Methanol is added to the crude glycerol for dilution, and then the pH is adjusted to a weak acidic state using phosphoric acid. After the reaction is completed, the mixture is centrifuged to obtain pretreated glycerol; (2) Adding a composite alkali solution to the pretreated glycerol, adjusting the pH to a weak alkaline state, allowing the mixture to stand for stratification to obtain a clear liquid phase, adding activated carbon to the clear liquid phase and stirring, centrifuging after the reaction is complete, and injecting the filtrate into an ion exchange column; (3) distilling the liquid flowing out of the ion exchange column to remove methanol and obtain semi-treated glycerol; (4) The semi-treated glycerol is subjected to vacuum distillation and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0006] Preferably, in step (1), the mass ratio of methanol to crude glycerol is 1:(3-5); phosphoric acid is used to adjust the pH to between 5 and 6; and the reaction is carried out at 55-60° C. for 20-25 minutes.

[0007] Preferably, in step (2), the compound alkali solution is formed by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution; and the pH of the compound alkali solution is adjusted to be between 7 and 8.

[0008] Preferably, in step (2), the amount of activated carbon added is 0.8-1.2% of the mass of the clear liquid phase; and the reaction is carried out at room temperature for 40-60 minutes.

[0009] Preferably, in step (2), the preparation method of the ion exchange column is as follows: S1, weighing anion resin and cationic resin, adding distilled water and stirring to mix, to obtain a resin mixture liquid; S2, introducing the resin mixture liquid into a glass column, and washing with distilled water until neutral, to obtain.

[0010] Preferably, the anion resin is a strong base anion resin, and the cationic resin is a strong acid cationic resin.

[0011] Preferably, the mass ratio of the anion resin to the cationic resin is 1:(1.2-1.5).

[0012] Preferably, in step (3), the distillation temperature is 64-66°C under normal pressure.

[0013] Preferably, in step (4), the reduced pressure distillation process is: controlling the vacuum degree to 105-115 Pa and the temperature to 105-110°C.

[0014] The present invention provides a high-purity glycerol deep purification process, which has the following beneficial effects compared with the existing technology: In the present invention, methanol is used as a diluent and is treated with phosphoric acid, which helps to separate glycerol. Subsequently, a composite alkaline solution is added to allow salt to be fully precipitated. Combined with activated carbon added in the early stage, impurities in the crude glycerol can be effectively adsorbed and removed. Ion exchange resin is then used to adsorb and fix non-electrolytic substances such as aldehydes, pigments, and esters in the crude glycerol, thereby achieving further purification. Finally, distillation / reduced pressure distillation is used to remove methanol and water, and the resulting glycerol has a purity of up to 99.9%.

[0015] The present invention adopts a composite alkaline solution, which has a significantly better removal effect on some impurities in crude glycerol compared with a single alkaline treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a process flow chart for deep purification of high-purity glycerol according to the present invention. DETAILED DESCRIPTION

[0017] The following examples illustrate the implementation methods of the present application in detail, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0018] Example 1

[0019] The method for making an ion exchange column is as follows: S1. Weigh a strong base anion resin and a strong acid cation resin in a mass ratio of 1:1.2, add distilled water and stir to obtain a resin mixture liquid.

[0020] S2. Introduce the resin mixture liquid into a glass column and wash it with distilled water until it becomes neutral.

[0021] Example 2

[0022] The method for making an ion exchange column is as follows: S1. Weigh a strong base anion resin and a strong acid cation resin in a mass ratio of 1:1.5, add distilled water and stir to obtain a resin mixture liquid.

[0023] S2. Introduce the resin mixture liquid into a glass column and wash it with distilled water until it becomes neutral.

[0024] Example 3

[0025] A high-purity glycerol deep purification process comprises the following steps: (1) Methanol was added to the crude glycerol for dilution, and then the pH was adjusted to 5 with phosphoric acid. After reacting at 55°C for 25 minutes, the mixture was centrifuged to obtain pretreated glycerol. The mass ratio of methanol to crude glycerol was 1:3.

[0026] The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0027] (2) Adding a composite alkali solution to the pretreated glycerol, adjusting the pH to 7, allowing the mixture to stand for stratification to obtain a clear liquid phase, adding activated carbon accounting for 0.8% of the mass of the clear liquid phase to the clear liquid phase and stirring, reacting at room temperature for 40 minutes, and then centrifuging and injecting the filtrate into an ion exchange column; The composite alkali solution is prepared by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution.

[0028] (3) The liquid flowing out of the ion exchange column is distilled at 66°C under normal pressure to remove methanol and obtain semi-treated glycerol.

[0029] (4) The semi-treated glycerol is subjected to reduced pressure distillation (the vacuum degree is controlled at 105 Pa and the temperature is 110°C) and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0030] In this embodiment, the ion exchange column in Example 1 was used.

[0031] Example 4

[0032] A high-purity glycerol deep purification process comprises the following steps: Methanol was added to the crude glycerol for dilution, and then the pH was adjusted to 6 with phosphoric acid. After reacting at 60°C for 20 minutes, the mixture was centrifuged to obtain pretreated glycerol. The mass ratio of methanol to crude glycerol was 1:5.

[0033] The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0034] (2) Adding a composite alkali solution to the pretreated glycerol, adjusting the pH to 8, allowing the mixture to stand for stratification to obtain a clear liquid phase, adding activated carbon accounting for 1.2% of the mass of the clear liquid phase to the clear liquid phase and stirring, reacting at room temperature for 60 minutes, and then centrifuging and injecting the filtrate into an ion exchange column; The composite alkali solution is prepared by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution.

[0035] (3) The liquid flowing out of the ion exchange column is distilled at 64°C under normal pressure to remove methanol and obtain semi-treated glycerol.

[0036] (4) The semi-treated glycerol is subjected to reduced pressure distillation (the vacuum degree is controlled at 115 Pa and the temperature is 105°C) and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0037] In this embodiment, the ion exchange column in Example 2 was used.

[0038] Example 5

[0039] A high-purity glycerol deep purification process comprises the following steps: Methanol was added to the crude glycerol for dilution, and then the pH was adjusted to 6 with phosphoric acid. After reacting at 60°C for 20 minutes, the mixture was centrifuged to obtain pretreated glycerol. The mass ratio of methanol to crude glycerol was 1:4.

[0040] The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0041] (2) Adding a composite alkali solution to the pretreated glycerol, adjusting the pH to 8, allowing the mixture to stand for stratification to obtain a clear liquid phase, adding activated carbon accounting for 1.0% of the mass of the clear liquid phase to the clear liquid phase and stirring, reacting at room temperature for 50 minutes, and then centrifuging and injecting the filtrate into an ion exchange column; The composite alkali solution is prepared by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution.

[0042] (3) The liquid flowing out of the ion exchange column is distilled at 65°C under normal pressure to remove methanol and obtain semi-treated glycerol.

[0043] (4) The semi-treated glycerol is subjected to reduced pressure distillation (the vacuum degree is controlled at 110 Pa and the temperature is 110°C) and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0044] In this embodiment, the ion exchange column in Example 1 was used.

[0045] Comparative Example 1 A high-purity glycerol deep purification process comprises the following steps: Add the composite alkali solution to the crude glycerol, adjust the pH to 8, let it stand for stratification to obtain a clear liquid phase, add 1.0% of the weight of the clear liquid phase to the activated carbon, stir, react at room temperature for 50 minutes, then centrifuge and inject the filtrate into an ion exchange column; The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0046] The composite alkali solution is prepared by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution.

[0047] (2) The liquid flowing out of the ion exchange column is subjected to vacuum distillation (controlling the vacuum degree at 110 Pa and the temperature at 110°C) and activated carbon deodorization and decolorization treatment in sequence to produce high-purity glycerin.

[0048] In this embodiment, the ion exchange column in Example 1 was used.

[0049] Comparative Example 2 A high-purity glycerol deep purification process comprises the following steps: Methanol was added to the crude glycerol for dilution, and then the pH was adjusted to 6 with phosphoric acid. After reacting at 60°C for 20 minutes, the mixture was centrifuged to obtain pretreated glycerol. The mass ratio of methanol to crude glycerol was 1:4.

[0050] The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0051] (2) Add saturated calcium hydroxide solution to the pretreated glycerol, adjust the pH to 8, let it stand for stratification to obtain a clear liquid phase, add activated carbon accounting for 1.0% of the mass of the clear liquid phase to the clear liquid phase and stir, react at room temperature for 50 minutes, then centrifuge and inject the filtrate into an ion exchange column; (3) The liquid flowing out of the ion exchange column is distilled at 65°C under normal pressure to remove methanol and obtain semi-treated glycerol.

[0052] (4) The semi-treated glycerol is subjected to reduced pressure distillation (the vacuum degree is controlled at 110 Pa and the temperature is 110°C) and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0053] In this embodiment, the ion exchange column in Example 1 was used.

[0054] Comparative Example 3 A high-purity glycerol deep purification process comprises the following steps: (1) Methanol was added to the crude glycerol for dilution, and then the pH was adjusted to 6 with phosphoric acid. After reacting at 60°C for 20 minutes, the mixture was centrifuged to obtain pretreated glycerol. The mass ratio of methanol to crude glycerol was 1:4.

[0055] The main components of crude glycerin include: 85.5wt% glycerin, 13.8% water, 0.1% soap, and the remainder is other impurities.

[0056] (2) Add 2 mol / L sodium hydroxide solution to the pretreated glycerol, adjust the pH to 8, let it stand for stratification to obtain a clear liquid phase, add activated carbon accounting for 1.0% of the mass of the clear liquid phase to the clear liquid phase and stir, react at room temperature for 50 minutes, then centrifuge and inject the filtrate into an ion exchange column; (3) The liquid flowing out of the ion exchange column is distilled at 65°C under normal pressure to remove methanol and obtain semi-treated glycerol.

[0057] (4) The semi-treated glycerol is subjected to reduced pressure distillation (the vacuum degree is controlled at 110 Pa and the temperature is 110°C) and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

[0058] In this embodiment, the ion exchange column in Example 1 was used.

[0059] Ingredient testing 1. According to the test method for glycerol impurities (GC) in the Chinese Pharmacopoeia Volume IV (2020 Edition), the high-purity glycerol in Examples 3-5 and Comparative Examples 1-3 was tested. The specific test results are shown in the table below.

[0060] Table 1 Index analysis While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-purity glycerol deep purification process, characterized in that: The following steps are involved: (1) Methanol is added to the crude glycerol for dilution, and then the pH is adjusted to a weak acidic state using phosphoric acid. After the reaction is completed, the mixture is centrifuged to obtain pretreated glycerol; (2) Adding a composite alkali solution to the pretreated glycerol, adjusting the pH to a weak alkaline state, allowing the mixture to stand for stratification to obtain a clear liquid phase, adding activated carbon to the clear liquid phase and stirring, centrifuging after the reaction is completed, and injecting the filtrate into an ion exchange column; (3) distilling the liquid flowing out of the ion exchange column to remove methanol and obtain semi-treated glycerol; (4) The semi-treated glycerol is subjected to vacuum distillation and activated carbon deodorization and decolorization treatment in sequence to obtain high-purity glycerol.

2. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (1), the mass ratio of methanol to crude glycerol is 1:(3-5); phosphoric acid is used to adjust the pH to between 5 and 6; and the reaction is carried out at 55-60° C. for 20-25 minutes.

3. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (2), the composite alkali solution is formed by introducing a 2 mol / L equivalent sodium hydroxide solution into a saturated calcium hydroxide solution; and the pH of the composite alkali solution is adjusted to be between 7 and 8.

4. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (2), the amount of activated carbon added is 0.8-1.2% of the mass of the clear liquid phase; and the reaction is carried out at room temperature for 40-60 minutes.

5. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (2), the preparation method of the ion exchange column is as follows: S1. Weigh anionic resin and cationic resin, add distilled water and stir to obtain a resin mixture liquid; S2. Introduce the resin mixture liquid into a glass column and wash it with distilled water until it becomes neutral.

6. The high-purity glycerol deep purification process according to claim 5, characterized in that: The anion resin is a strong base anion resin, and the cationic resin is a strong acid cationic resin.

7. The high-purity glycerol deep purification process according to claim 5, characterized in that: The mass ratio of the anion resin to the cationic resin is 1:(1.2-1.5).

8. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (3), the distillation temperature is 64-66°C under normal pressure.

9. The high-purity glycerol deep purification process according to claim 1, characterized in that: In step (4), the reduced pressure distillation process is as follows: controlling the vacuum degree to 105-115 Pa and the temperature to 105-110°C.

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