A method for synthesizing LO+ grade dipropylene glycol

Abstract

The application relates to a synthesis method of LO+ grade dipropylene glycol and belongs to the technical field of LO+ grade dipropylene glycol synthesis. 200g of 1,2-propylene glycol and 100g of propylene oxide are stirred at 60-80r / min for 10-15min to obtain pre-reaction materials; 3g of a biomass charcoal-based solid acid catalyst is added into the pre-reaction materials, added into a 500mL mechanical stirring reaction kettle, then the reaction kettle is sealed, nitrogen is introduced to remove air in the reaction kettle and make the pressure of the reaction kettle reach 0.3MPa, heating and stirring are started, the temperature is slowly increased to 120 DEG C, a small amount of nitrogen is discharged by gradually opening the vent valve during the temperature increasing process, so that the pressure of the reaction kettle is always kept at 0.3MPa, dipropylene glycol is prepared through ring-opening condensation reaction, and LO+ grade dipropylene glycol is obtained after the dipropylene glycol is separated and purified. In the method, the biomass charcoal-based solid acid catalyst exhibits high catalytic activity, so that the reaction has high conversion rate, the catalyst can be recycled after separation and recovery, the post-reaction treatment is simple, and the environment is friendly.

Description

Technical Field

[0001] This invention belongs to the field of LO+ grade dipropylene glycol synthesis technology, specifically relating to a method for synthesizing LO+ grade dipropylene glycol. Background Technology

[0002] Dipropylene glycol (also known as dipropylene glycol, dipropylene glycol, etc., abbreviated as DPG) is an odorless, colorless, slightly viscous liquid with a spicy and sweet taste at room temperature. It is water-soluble and hygroscopic, soluble in water and toluene, miscible with methanol and ether, non-corrosive, has very little skin irritation, and very low toxicity. Furthermore, dipropylene glycol has excellent solubility, making it an ideal solvent for daily chemical fragrances.

[0003] However, in recent years, with the gradual improvement of consumption levels and the development of the luxury goods industry such as cosmetics and perfumes, the market demand for high-quality dipropylene glycol has also been gradually increasing. Currently, however, the domestic supply capacity of dipropylene glycol is weak and insufficient to meet market demand, especially since the demand for high-quality dipropylene glycol products largely relies on imports. Furthermore, due to severe overcapacity in 1,2-propanediol production, there is a risk of obstructed sales, inventory backlog, and even production stoppages. At the same time, the price of 1,2-propanediol has decreased, leading to a significant decline in the profits of domestic 1,2-propanediol producers. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing LO+ grade dipropylene glycol in order to solve the above-mentioned problems.

[0005] The present invention achieves the above objectives through the following technical solutions:

[0006] This invention provides a method for synthesizing LO+ grade dipropylene glycol, comprising the following steps:

[0007] (a) Stir 200g of 1,2-propanediol and 100g of propylene oxide at 60-80r / min for 10-15min to obtain a pre-reaction mixture;

[0008] (II) Add 3g of biomass-based carbon-based solid acid catalyst to the pre-reaction material, then add it to a 500mL mechanically stirred reactor. Seal the reactor, purge with nitrogen to remove air and bring the reactor pressure to 0.3MPa. Start heating and stirring, slowly raising the temperature to 120℃. During heating, gradually open the vent valve to release a small amount of nitrogen to ensure the reactor pressure remains at 0.3MPa. Dipropylene glycol is prepared through a ring-opening condensation reaction. After separation and purification, LO+ grade dipropylene glycol is obtained. The residual liquid from separation is placed in a centrifuge at 2000r / min for 5min, and the supernatant is removed. Then, deionized water is added for ultrasonic washing, followed by centrifugation to remove the supernatant. This process is repeated three times to recover the biomass-based carbon-based solid acid catalyst, which is then dried and reused.

[0009] As a further optimization of the present invention, the molar ratio of 1,2-propanediol to propylene oxide is (1-6):1; the ring-opening condensation reaction temperature is 80-150℃; the ring-opening condensation reaction pressure is 0.1-0.8MPa; and the ring-opening condensation reaction time is 0.5-6h.

[0010] As a further optimization of the present invention, the specific steps for the separation and purification of dipropylene glycol are as follows: first, dipropylene glycol is distilled at atmospheric pressure for 25-30 minutes, and then distilled again under reduced pressure to 1.3-2.0 kPa (10-15 mmHg) for 30-40 minutes to obtain LO+ grade dipropylene glycol.

[0011] As a further optimization of the present invention, the preparation process of the biomass carbon-based solid acid catalyst is as follows:

[0012] (i) The dried biochar raw material alfalfa straw is ground into solid powder, the obtained solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed, and carbonized at a heating rate of 10℃ / min under inert gas protection to obtain alfalfa straw carbon material.

[0013] (ii) Take 4g of alfalfa straw char material and 60ml of sulfonating agent and add them to a round bottom flask. Stir vigorously. After the sulfonation reaction is completed, wash the obtained solid char material repeatedly with hot deionized water until the pH of the filtrate is the same as the pH of the original deionized water. Dry in a vacuum drying oven at 80℃ for 4h to obtain a biomass char-based solid acid catalyst.

[0014] As a further optimization of the present invention, the inert gas is one of nitrogen, argon, and helium.

[0015] As a further optimization of the present invention, the carbonization temperature is 300-600℃; the carbonization time is 1-8h.

[0016] As a further optimization of the present invention, the sulfonating agent is one of concentrated sulfuric acid, chlorosulfonic acid, benzenesulfonic acid, p-methylbenzenesulfonic acid, and p-aminobenzenesulfonic acid.

[0017] As a further optimization of the present invention, the sulfonation temperature is 140-180℃; the sulfonation time is 2-10h.

[0018] The beneficial effects of this invention are as follows: This invention uses 1,2-propanediol and propylene oxide as raw materials, and obtains LO+ grade dipropylene glycol product under the action of biomass carbon-based solid acid catalyst. In this method, the biomass carbon-based solid acid catalyst exhibits high catalytic activity, resulting in a high conversion rate of the reaction. Moreover, the catalyst can be reused after separation and recovery, and the post-reaction treatment is simple and environmentally friendly. Detailed Implementation

[0019] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0020] I. Materials

[0021] Unless otherwise specified, all methods used in this invention are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products.

[0022] The biomass-based solid acid catalyst in Comparative Example 3 was prepared using the biomass-based solid acid catalyst obtained in Chinese Invention Patent CN115254143B.

[0023] II. Methods

[0024] Example 1

[0025] Dry alfalfa straw, the raw material for biochar, is ground into solid powder. The resulting solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed. Under nitrogen protection, the temperature is raised to 400℃ at a heating rate of 10℃ / min, and then held at that temperature for 4 hours for carbonization to obtain alfalfa straw char material.

[0026] Take 4g of alfalfa straw char material and 60ml of concentrated sulfuric acid and add them to a round-bottom flask. Then stir vigorously at 180℃ for 4h. After the sulfonation reaction is completed, wash the obtained solid char material repeatedly with hot deionized water until the pH of the filtrate is the same as the pH of the original deionized water. Dry it in a vacuum drying oven at 80℃ for 4h to obtain a biomass char-based solid acid catalyst.

[0027] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 60r / min for 10min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0028] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air and bring the reactor pressure to 0.3MPa. Heating and stirring were started, and the temperature was slowly increased to 120℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure remained at 0.3MPa. Dipropylene glycol was prepared through a ring-opening condensation reaction (ring-opening condensation reaction temperature: 120℃, pressure: 0.3MPa, time: 2h). After the reaction was completed, dipropylene glycol was distilled at atmospheric pressure for 25min, and then distilled again under reduced pressure to 1.3kPa (10mmHg) for 30min to obtain LO+ grade dipropylene glycol.

[0029] Example 2

[0030] Dry alfalfa straw, the raw material for biochar, is ground into solid powder. The resulting solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed. Under nitrogen protection, the temperature is raised to 300℃ at a heating rate of 10℃ / min, and then held at that temperature for 1 hour to carbonize, thus obtaining alfalfa straw char material.

[0031] 4g of alfalfa straw char material and 60ml of concentrated sulfuric acid were added to a round-bottom flask and then stirred vigorously at 160℃ for 6h. After the sulfonation reaction was completed, the obtained solid char material was repeatedly washed with hot deionized water until the pH of the filtrate was the same as that of the original deionized water. After drying in a vacuum drying oven at 80℃ for 4h, a biomass char-based solid acid catalyst was obtained.

[0032] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 70r / min for 12min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0033] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air and bring the reactor pressure to 0.4MPa. Heating and stirring were started, and the temperature was slowly increased to 120℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure remained at 0.4MPa. Dipropylene glycol was prepared through a ring-opening condensation reaction (ring-opening condensation reaction temperature: 120℃, pressure: 0.4MPa, time: 3h). After the reaction was completed, dipropylene glycol was distilled at atmospheric pressure for 26min, and then subjected to a second distillation at reduced pressure to 1.6kPa (12mmHg) for 35min to obtain LO+ grade dipropylene glycol.

[0034] Example 3

[0035] Dry alfalfa straw, the raw material for biochar, is ground into solid powder. The resulting solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed. Under nitrogen protection, the temperature is raised to 600℃ at a heating rate of 10℃ / min, and then held at that temperature for 8 hours for carbonization to obtain alfalfa straw char material.

[0036] 4g of alfalfa straw char material and 60ml of concentrated sulfuric acid were added to a round-bottom flask and then stirred vigorously at 140℃ for 10h. After the sulfonation reaction was completed, the obtained solid char material was repeatedly washed with hot deionized water until the pH of the filtrate was the same as that of the original deionized water. After drying in a vacuum drying oven at 80℃ for 4h, a biomass char-based solid acid catalyst was obtained.

[0037] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 80r / min for 15min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0038] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air from the reactor and bring the reactor pressure to 0.3MPa. Heating and stirring were started, and the temperature was slowly increased to 110℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure was always maintained at 0.3MPa. Dipropylene glycol was prepared by ring-opening condensation reaction (ring-opening condensation reaction temperature: 110℃, pressure: 0.3MPa, time: 4h). Dipropylene glycol was distilled at atmospheric pressure for 30min, and then distilled again under reduced pressure to 2.0kPa (15mmHg) for 40min to obtain LO+ grade dipropylene glycol.

[0039] Comparative Example 1

[0040] Dry rapeseed straw, the raw material for biochar, is ground into solid powder. The resulting solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed. Under nitrogen protection, the temperature is raised to 400℃ at a heating rate of 10℃ / min, and then held at that temperature for 4 hours for carbonization to obtain rapeseed straw char material.

[0041] Take 4g of rapeseed straw char material and 60ml of concentrated sulfuric acid and add them to a round bottom flask. Then stir vigorously at 180℃ for 4h. After the sulfonation reaction is completed, wash the obtained solid char material repeatedly with hot deionized water until the pH of the filtrate is the same as the pH of the original deionized water. After drying in a vacuum drying oven at 80℃ for 4h, a biomass char-based solid acid catalyst is obtained.

[0042] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 60r / min for 10min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0043] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air and bring the reactor pressure to 0.3MPa. Heating and stirring were started, and the temperature was slowly increased to 120℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure remained at 0.3MPa. Dipropylene glycol was prepared through a ring-opening condensation reaction (ring-opening condensation reaction temperature: 120℃, pressure: 0.3MPa, time: 2h). After the reaction was completed, dipropylene glycol was distilled at atmospheric pressure for 25min, and then distilled again under reduced pressure to 1.3kPa (10mmHg) for 30min to obtain LO+ grade dipropylene glycol.

[0044] Comparative Example 2

[0045] Dry alfalfa straw, the raw material for biochar, is ground into solid powder. The resulting solid powder is transferred to a quartz boat, placed in a muffle furnace and sealed. Under nitrogen protection, the temperature is raised to 400℃ at a heating rate of 10℃ / min, and then held at that temperature for 4 hours for carbonization to obtain alfalfa straw char material.

[0046] Take 4g of alfalfa straw char material and 60ml of concentrated sulfuric acid and add them to a round-bottom flask. Then stir vigorously at 180℃ for 4h. After the sulfonation reaction is completed, wash the obtained solid char material repeatedly with hot deionized water until the pH of the filtrate is the same as the pH of the original deionized water. Dry it in a vacuum drying oven at 80℃ for 4h to obtain a biomass char-based solid acid catalyst.

[0047] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 60r / min for 10min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0048] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air and bring the reactor pressure to 0.3MPa. Heating and stirring were started, and the temperature was slowly increased to 120℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure remained at 0.3MPa. Dipropylene glycol was prepared through a ring-opening condensation reaction (ring-opening condensation reaction temperature: 120℃, pressure: 0.3MPa, time: 2h). After the reaction was completed, the dipropylene glycol was distilled at atmospheric pressure for 25min to obtain LO+ grade dipropylene glycol.

[0049] Comparative Example 3

[0050] 200g of 1,2-propanediol and 100g of propylene oxide were stirred at 60r / min for 10min (the molar ratio of 1,2-propanediol to propylene oxide was 3:1) to obtain the pre-reaction material;

[0051] 3g of biomass-based solid acid catalyst was added to the pre-reactant and then to a 500mL mechanically stirred reactor. The reactor was then sealed, and nitrogen gas was introduced to remove air and bring the reactor pressure to 0.3MPa. Heating and stirring were started, and the temperature was slowly increased to 120℃. During the heating process, a small amount of nitrogen gas was gradually released through the vent valve to ensure that the reactor pressure remained at 0.3MPa. Dipropylene glycol was prepared through a ring-opening condensation reaction (ring-opening condensation reaction temperature: 120℃, pressure: 0.3MPa, time: 2h). After the reaction was completed, dipropylene glycol was distilled at atmospheric pressure for 25min, and then distilled again under reduced pressure to 1.3kPa (10mmHg) for 30min to obtain LO+ grade dipropylene glycol.

[0052] Performance testing

[0053] (I) The LO+ grade dipropylene glycol prepared by the methods of Examples 1-3 and Comparative Examples 1-3 was placed at -10℃ for 12 hours. The crystallization of the LO+ grade dipropylene glycol was observed under a microscope. The color of the dipropylene glycol was detected by the platinum-cobalt colorimetric method. The purity of the LO+ grade dipropylene glycol was analyzed by gas chromatography. The test results are shown in the table below:

[0054] project Crystallization rate % chromaticity purity% Example 1 0 6 99.92 Example 2 1 7 99.91 Example 3 0 7 99.76 Comparative Example 1 3 9 99.29 Comparative Example 2 8 10 99.35 Comparative Example 3 4 9 99.12

[0055] As can be seen from the table above, the LO+ grade dipropylene glycol prepared by the methods of Examples 1-3 is superior to that of Comparative Examples 1-3 in terms of low-temperature crystallization rate, color and purity. In summary, the LO+ grade dipropylene glycol prepared by the methods of Examples 1-3 meets the standard grade.

[0056] (II) The biomass-based solid acid catalysts obtained by centrifugation in Example 1 and Comparative Example 1 were recycled and analyzed by gas chromatography. The gas chromatography results are shown in the table below:

[0057]

[0058] As can be seen from the table above, after the biomass carbon-based solid acid catalyst prepared by the method in Example 1 is recycled 5 times, the total selectivity of dipropylene glycol and tripropylene glycol can still be maintained at over 97%, which shows good recycling performance.

[0059] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A process for the synthesis of LO+ grade dipropylene glycol, characterized in that, The method comprises the following steps: (1) 200 g of 1,2-propylene glycol and 100 g of propylene oxide are stirred at 60-80 r / min for 10-15 min to obtain a pre-reaction material; (2) 3 g of the biomass charcoal-based solid acid catalyst is added to the pre-reaction material in a 500 mL mechanical stirring reaction kettle, the reaction kettle is then sealed, nitrogen is introduced to remove air in the reaction kettle and make the pressure of the reaction kettle reach 0.3 MPa, heating and stirring are started, and the temperature is slowly raised to 120 DEG C; during the temperature rising process, a small amount of nitrogen is discharged through the vent valve to ensure that the pressure of the reaction kettle is always kept at 0.3 MPa; after the ring-opening condensation reaction, dipropylene glycol is prepared, and LO+ grade dipropylene glycol is obtained after separation and purification of the dipropylene glycol; the residual liquid produced in the separation is put into a centrifuge, the speed is set to 2000 r / min, and centrifugation is performed for 5 min to remove the supernatant; then, deionized water is added for ultrasonic washing, the supernatant is removed by centrifugation, and the biomass charcoal-based solid acid catalyst is recovered after repeated three times, and is dried for repeated use; The preparation process of the biomass charcoal-based solid acid catalyst is as follows: (1) The dried biomass charcoal raw material alfalfa straw is ground into a solid powder, the obtained solid powder is transferred into a quartz boat, and the quartz boat is sealed and placed in a muffle furnace for carbonization under the protection of inert gas at a temperature rising rate of 10 DEG C / min to obtain alfalfa straw charcoal material; (2) 4 g of the alfalfa straw charcoal material and 60 ml of a sulfonating agent are added to a round-bottom flask, and stirred vigorously; after the sulfonation reaction is completed, the obtained solid charcoal material is repeatedly washed with hot deionized water until the pH of the filtrate is the same as that of the original deionized water; and the biomass charcoal-based solid acid catalyst is obtained after drying at 80 DEG C in a vacuum drying box for 4 h.

2. The process for the synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, The ring-opening condensation reaction temperature is 80-150 DEG C; the ring-opening condensation reaction pressure is 0.1-0.8 MPa; and the ring-opening condensation reaction time is 0.5-6 h.

3. The process for synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, The specific steps for separation and purification of the dipropylene glycol are as follows: the dipropylene glycol is first subjected to atmospheric distillation for 25-30 min, and then subjected to secondary distillation under reduced pressure to 1.3-2.0 kPa (10-15 mmHg) for 30-40 min to obtain LO+ grade dipropylene glycol.

4. The process for synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, The inert gas is one of nitrogen, argon and helium.

5. The process for synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, In the carbonization process, the carbonization temperature is 300-600 DEG C, and the carbonization time is 1-8 h. ​ 6. The process for synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, The sulfonating agent is one of concentrated sulfuric acid, chlorosulfonic acid, benzene sulfonic acid, p-toluenesulfonic acid and p-aminobenzenesulfonic acid.

7. The process for synthesis of LO+ grade dipropylene glycol as claimed in claim 1 wherein, In the sulfonation reaction, the sulfonation temperature is 140-180 DEG C, and the sulfonation time is 2-10 h. ​

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