A diethylene glycol refining method

Abstract

The present application relates to a diethylene glycol refining method, comprising the following steps: (1) making diethylene glycol flow through a fixed bed hydrogenation reactor, diethylene glycol is subjected to hydrogenation reaction in the fixed bed hydrogenation reactor to obtain hydrogenated material; (2) soaking ion exchange resin in diethylene glycol to obtain pretreated ion exchange resin; (3) loading the pretreated ion exchange resin obtained in step (2) into a fixed bed reactor, and making the hydrogenated material obtained in step (1) flow through the fixed bed reactor to obtain high-purity diethylene glycol. The present application has simple process, low energy consumption and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of chemical refining technology, specifically to a method for refining diethylene glycol. Background Technology

[0002] Diethylene glycol (commonly known as diethylene glycol) is a polyol with the chemical formula C4H. 10 O3 is a colorless, odorless, transparent, hygroscopic viscous liquid. It is non-corrosive, low in toxicity, and has a pungent, sweet taste. It has a strong solubility for hydrocarbons; diethylene glycol is miscible with water, ethanol, ethylene glycol, acetone, chloroform, furfural, etc., but immiscible with diethyl ether, carbon tetrachloride, carbon disulfide, straight-chain aliphatic hydrocarbons, and aromatic hydrocarbons. The presence of ether bonds and hydroxyl groups in its structure makes it miscible with many polar solvents, making it a good solvent for resins, oils, and printing inks. It is also used as a component in automotive brake fluids and antifreeze, and as a gas dehydrating agent, extractant, softener, lubricant, and dispersant. Furthermore, the unique structure of diethylene glycol gives it special physicochemical properties, making it an important organic synthesis intermediate for ethers and esters, and it has wide applications in the petrochemical, polymer, and pharmaceutical industries. Diethylene glycol is a byproduct of ethylene glycol production. The presence of trace amounts of carboxylic acids, aldehydes, and unsaturated compounds such as conjugated alkenes in diethylene glycol can cause substandard color and low UV transmittance in the 220–350 nm range. Using it as a raw material may also accelerate catalyst deactivation. Therefore, the removal of impurities from diethylene glycol is crucial.

[0003] CN115427146A discloses a method for pretreating ion exchange resins to remove aldehyde impurities. This method uses diethylene glycol and / or triethylene glycol and aldehydes as a raw material model. The ion exchange resin is first soaked in monoethylene glycol, and then a mixture of diethylene glycol and / or triethylene glycol and aldehydes is passed through the soaked ion exchange resin. This reduces the aldehyde concentration in the raw material from 5–200 ppm to 15 ppm. However, for raw materials containing high concentrations of aldehyde impurities, ion exchange resin alone cannot completely remove them; other methods are needed to achieve the desired effect. Furthermore, aldehydes can poison the resin, resulting in a short resin lifespan.

[0004] CN109704929A discloses a method for the hydrogenation purification of diethylene glycol. The crude diethylene glycol is sequentially passed through a first fixed-bed hydrogenation reactor packed with an activated supported catalyst, and then through second and third fixed-bed hydrogenation reactors packed with an activated composite catalyst. This three-step catalytic process significantly improves the UV transmittance of diethylene glycol, increasing it from 80% to 99% at 350 nm. While this method significantly improves the UV transmittance of the diethylene glycol product, the three-step hydrogenation process requires precise control of the reaction conditions in each reactor and suffers from high energy consumption. Furthermore, material transfer between multiple reactors can lead to contamination or side reactions, further affecting product purity.

[0005] CN106946667A discloses a diethylene glycol purification process. The process involves adding 3-4 wt% strong alkali and 3-4 wt% chloroethane to crude diethylene glycol, heating and stirring at 100°C, and then subjecting the liquid to vacuum distillation, collecting the fraction at 150°C-155°C. This yields high-purity diethylene glycol with low acidity, meeting the requirements of the precision electronics industry. However, the strong alkali and chloroethane used in this method cause serious environmental pollution.

[0006] Therefore, developing a simple, energy-efficient, environmentally friendly method for purifying diethylene glycol with high aldehyde content is of great application value in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a method for purifying diethylene glycol, which uses a hydrogenation catalytic coupling ion exchange resin decolorization method to effectively decolorize and remove impurities from diethylene glycol.

[0008] The technical solution adopted in this invention is:

[0009] A method for purifying diethylene glycol includes the following steps:

[0010] (1) Diethylene glycol is passed through a fixed-bed hydrogenation reactor, where it undergoes a hydrogenation reaction to obtain hydrogenated material.

[0011] (2) Immerse the ion exchange resin in diethylene glycol to obtain a pretreated ion exchange resin;

[0012] (3) The pretreated ion exchange resin obtained in step (2) is loaded into a fixed bed reactor, and the hydrogenated material obtained in step (1) flows through the fixed bed reactor to obtain high-purity diethylene glycol.

[0013] Furthermore, the diethylene glycol mentioned in step (1) has a purity of 80-99% and an aldehyde content of 200-5000 ppm.

[0014] Furthermore, in step (1), the fixed bed is filled with a high-performance Raney nickel catalyst.

[0015] Furthermore, in step (1), the hydrogenation reaction conditions include: a reaction pressure of 0.5–1 MPa, a reaction temperature of 60–160 °C, and a reaction space velocity of 1–20 h⁻¹. -1 The volume ratio of hydrogen to diethylene glycol in the feed is 300–8000:1.

[0016] Further, in step (2), the ion exchange resin is soaked at 20-50°C for 12-24 hours, and the mass ratio of diethylene glycol to ion exchange resin is 1-3:1.

[0017] Furthermore, in step (2), the ion exchange resin is an acidic cation exchange resin.

[0018] Furthermore, in step (3), the feed rate of diethylene glycol is 20–40 mL / h, the feed temperature is 40–60 °C, and the reaction space velocity is 1–5 h⁻¹. -1 .

[0019] Furthermore, in step (3), the fixed-bed reactor is an atmospheric pressure reactor.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention employs a hydrogenation catalytic coupling ion exchange resin decolorization method. First, aldehydes in diethylene glycol are converted into alcohols through a hydrogenation reaction. Then, alcohols and a small amount of residual aldehydes are removed through ion exchange resin. This method can reduce the aldehyde content in diethylene glycol from 1000 ppm to below 100 ppm. After purification, the product has a UV transmittance of 99% at 350 nm.

[0022] 2. Ion exchange resins have good adsorption effects on both alcohols and aldehydes. By converting some aldehydes into alcohols through hydrogenation and then removing them through resin adsorption, the pollution of aldehydes on the resin can be reduced and its service life can be improved. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with preferred embodiments.

[0024] This invention uses a UV spectrophotometer to detect the UV transmittance of diethylene glycol; uses gas chromatography to detect the purity of diethylene glycol; and uses UV spectrophotometry to determine the absorbance and calculate the aldehyde content of diethylene glycol.

[0025] Example 1

[0026] (1) Take 70g of Raney nickel catalyst and pack it into the first fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0027] (2) 85g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 30°C for 12 hours and then taken out and packed into the second fixed bed reactor. The inner diameter of the tube was 4.6cm, the height was 10.8cm, and the bed thickness was 7.3cm.

[0028] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The hydrogenation reaction is carried out in the first fixed-bed reactor. The reaction conditions in the first fixed-bed reactor are: reaction pressure 0.6 MPa, reaction temperature 80 °C, hydrogen flow rate 300 mL / min, and diethylene glycol liquid hourly space velocity 5 h⁻¹. -1 The diethylene glycol after hydrogenation is passed through a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor are: diethylene glycol feed temperature of 40°C, feed rate of 40 mL / h, and reaction space velocity of 2 h⁻¹. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0029] Example 2

[0030] (1) Take 70g of Raney nickel catalyst and pack it into the first fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0031] (2) 85g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 40°C for 18 hours and then taken out and packed into the second fixed bed reactor. The inner diameter of the tube was 4.2cm, the height was 6.5cm, and the bed thickness was 7.3cm.

[0032] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The hydrogenation reaction is carried out in the first fixed-bed reactor. The reaction conditions of the first fixed-bed reactor are: reaction pressure 1 MPa, reaction temperature 120℃, hydrogen flow rate 200 mL / min, and diethylene glycol liquid hourly space velocity 8 h⁻¹. -1 The diethylene glycol after hydrogenation is passed through a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor are: diethylene glycol feed temperature of 60°C, feed rate of 30 mL / h, and reaction space velocity of 3 h⁻¹. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0033] Example 3

[0034] (1) Take 70g of Raney nickel catalyst and pack it into the first fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0035] (2) 100g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 50°C for 24 hours and then taken out and packed into the second fixed bed reactor. The inner diameter of the tube was 3.2cm, the height was 6.5cm, and the bed thickness was 8.6cm.

[0036] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The hydrogenation reaction is carried out in the first fixed-bed reactor. The reaction conditions of the first fixed-bed reactor are: reaction pressure 1 MPa, reaction temperature 160℃, hydrogen flow rate 200 mL / min, and diethylene glycol liquid hourly velocity 1 h⁻¹. -1 The diethylene glycol after hydrogenation is passed through a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor are: diethylene glycol feed temperature of 60°C, feed rate of 20 mL / h, and reaction space velocity of 2 h⁻¹. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0037] Example 4

[0038] (1) Take 70g of Raney nickel catalyst and pack it into the first fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0039] (2) 75g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 20°C for 12 hours and then taken out and packed into the second fixed bed reactor. The inner diameter of the tube was 3.2cm, the height was 6.5cm, and the bed thickness was 6.4cm.

[0040] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The hydrogenation reaction is carried out in the first fixed-bed reactor. The reaction conditions in the first fixed-bed reactor are: reaction pressure 0.5 MPa, reaction temperature 60 °C, hydrogen flow rate 200 mL / min, and diethylene glycol liquid hourly space velocity 20 h⁻¹. -1 The diethylene glycol after hydrogenation is passed through a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor are: diethylene glycol feed temperature of 40°C, feed rate of 40 mL / h, and reaction space velocity of 5 h⁻¹. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0041] Example 5

[0042] (1) Take 70g of Raney nickel catalyst and pack it into the first fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0043] (2) 100g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 20°C for 24 hours and then taken out and packed into the second fixed bed reactor. The inner diameter of the tube was 3.2cm, the height was 6.5cm, and the bed thickness was 8.6cm.

[0044] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The hydrogenation reaction is carried out in the first fixed-bed reactor. The reaction conditions in the first fixed-bed reactor are: reaction pressure 0.8 MPa, reaction temperature 60 °C, hydrogen flow rate 200 mL / min, and diethylene glycol liquid hourly space velocity 10 h⁻¹. -1 The diethylene glycol after hydrogenation is passed through a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor are: diethylene glycol feed temperature of 60°C, feed rate of 40 mL / h, and reaction space velocity of 1 h⁻¹. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0045] Comparative Example 1

[0046] (1) Take 70g of Raney nickel catalyst and fill it into a fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0047] (2) Diethylene glycol liquid is passed through a fixed-bed reactor to carry out a hydrogenation reaction. The reaction conditions are: reaction pressure 0.6 MPa, reaction temperature 80℃, hydrogen flow rate 300 mL / min, and diethylene glycol liquid hourly space velocity 5 h⁻¹. -1 The diethylene glycol collected after the reaction was tested for purity and transmittance. The results are shown in Table 1.

[0048] Comparative Example 2

[0049] (1) 85g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 30°C for 12 hours and then taken out and packed into a fixed bed reactor with an inner diameter of 3.2cm, a height of 6.5cm and a bed thickness of 7.3cm.

[0050] (2) Diethylene glycol liquid is passed through a fixed-bed reactor under the following conditions: diethylene glycol feed temperature of 40℃, feed rate of 40mL / h, and reaction space velocity of 4h. -1 The pressure was at atmospheric pressure. The diethylene glycol after the reaction was collected, and its purity and transmittance were measured. The results are shown in Table 1.

[0051] Comparative Example 3

[0052] (1) 85g of ion exchange resin (Rohm and Haas Amberlyst 15) was soaked in diethylene glycol at 30°C for 12 hours and then taken out and packed into the first fixed bed reactor. The inner diameter of the tube was 3.2cm, the height was 6.5cm, and the bed thickness was 7.3cm.

[0053] (2) Take 70g of Raney nickel catalyst and pack it into the second fixed bed reactor. The inner diameter of the tube is 3.2cm, the height is 6.5cm, and the bed thickness is 4.3cm.

[0054] (3) Diethylene glycol liquid is passed sequentially through a first fixed-bed reactor and a second fixed-bed reactor. The reaction conditions in the first fixed-bed reactor are: diethylene glycol feed temperature of 40℃, feed rate of 40mL / h, and reaction space velocity of 1h. -1 The pressure was atmospheric pressure. The hydrogenation reaction was carried out in a second fixed-bed reactor. The reaction conditions in the second fixed-bed reactor were: reaction pressure 0.6 MPa, reaction temperature 80℃, hydrogen flow rate 300 mL / min, and diethylene glycol liquid hourly space velocity 5 h⁻¹. -1 The diethylene glycol collected after the reaction was tested for purity and transmittance. The results are shown in Table 1.

[0055] Table 1. Test results of diethylene glycol before and after purification

[0056]

[0057]

[0058] As shown in Table 1, the method of this invention can purify diethylene glycol with a high aldehyde content, yielding high-quality diethylene glycol with excellent color. Comparative Examples 1 and 2, using a single hydrogenation and resin adsorption method, produced diethylene glycol with a significantly lower color than that of this invention. Comparative Example 3, using a method of first adsorbing with resin followed by hydrogenation, showed better results than the single method, but the color of the resulting diethylene glycol product was still lower than that of this invention. The reason for this is that the resin adsorption method, where ion exchange resins can only specifically adsorb aldehydes, suffers from low adsorption capacity and insufficient efficiency. Its effect is inferior to the hydrogenation method, where aldehydes are reduced to alcohols via Raney nickel catalysis, followed by simultaneous adsorption of residual aldehydes and the generated alcohols using ion exchange resins.

[0059] While the specific embodiments of the present invention have been described in detail above, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims. Those skilled in the art can make appropriate modifications to these embodiments without departing from the technical concept and spirit of the present invention, and these modified embodiments are obviously also included within the scope of protection of the present invention.

Claims

1. A method for purifying diethylene glycol, characterized in that, Includes the following steps: (1) Diethylene glycol is passed through a fixed-bed hydrogenation reactor, where it undergoes a hydrogenation reaction to obtain hydrogenated material. (2) Immerse the ion exchange resin in diethylene glycol to obtain a pretreated ion exchange resin; (3) The pretreated ion exchange resin obtained in step (2) is loaded into a fixed bed reactor, and the hydrogenated material obtained in step (1) flows through the fixed bed reactor to obtain high-purity diethylene glycol.

2. The method for purifying diethylene glycol according to claim 1, characterized in that, The diethylene glycol mentioned in step (1) has a purity of 80-99% and an aldehyde content of 200-5000 ppm.

3. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (1), the fixed bed is filled with a high-performance Raney nickel catalyst.

4. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (1), the hydrogenation reaction conditions include: reaction pressure 0.5–1 MPa, reaction temperature 60–160 °C, and reaction space velocity 1–20 h⁻¹. -1 The volume ratio of hydrogen to diethylene glycol in the feed is 300–8000:

1.

5. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (2), the ion exchange resin is soaked at 20-50°C for 12-24 hours, and the mass ratio of diethylene glycol to ion exchange resin is 1-3:

1.

6. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (2), the ion exchange resin is an acidic cation exchange resin.

7. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (3), the feed rate of diethylene glycol is 20–40 mL / h, the feed temperature is 40–60 °C, and the reaction space velocity is 1–5 h⁻¹. -1 .

8. The method for purifying diethylene glycol according to claim 1, characterized in that, In step (3), the fixed-bed reactor is an atmospheric pressure reactor.

Images