Preparation method of 2, 4, 6-trichlorophenol

Abstract

The invention relates to a preparation method of 2, 4, 6-trichlorophenol, which comprises the following steps: taking phenol as a raw material, taking tetrachloroethylene and water according to a certain ratio as a directional catalyst and an inhibitor, chlorinating to generate a crude product of 2, 4, 6-trichlorophenol, and separating and purifying through a rectifying tower to obtain a target product. Tetrachloroethylene and water serve as catalysts and have a positioning function, the problem of flash points is avoided, the safety in the preparation process is high, the conversion rate of 2, 4, 6-trichlorophenol is improved, meanwhile, generation of 2, 3, 6-trichlorophenol, 2, 4, 5-trichlorophenol and other parachlorophenols generated by side reactions is inhibited, and the total yield of 2, 4, 6-trichlorophenol is 98% or above. The purity of 2, 4, 6-trichlorophenol obtained after purification through the rectifying tower is 99.5% or above, and 2, 3, 6 / 2, 5, 6-trichlorophenol is smaller than or equal to 0.1%, so that market requirements can be met.

Description

Technical Field

[0001] The invention relates to the technical field of 2,4,6-trichlorophenol, and in particular to a method for preparing 2,4,6-trichlorophenol. Background Art

[0002] 2,4,6-Trichlorophenol is used as a fuel intermediate, pesticide, preservative, and also as a solvent for polyester fibers. It is an important intermediate for the synthesis of fungicides prochloraz and herbicides.

[0003] The synthesis methods of 2,4,6-trichlorophenol are:

[0004] (1) Phenol direct chlorination method: Phenol is used as the raw material, without adding any solvent or catalyst, and is obtained by deep chlorination.

[0005] (2) Mixed phenol chlorination method: Mixed phenols produced in the production of other chlorophenols are chlorinated without adding any solvent or catalyst to obtain

[0006] (3) Chinese patent CN: 104311396A discloses a method for synthesizing 2,4,6-trichlorophenol, which uses phenol as a raw material and mercaptoethylamine as a catalyst to synthesize trichlorophenol.

[0007] Compared with the above ①②, the selectivity of the target product 2,4,6-trichlorophenol synthesized by chlorination without adding catalyst for phenol or mixed phenol is less than 92%, and the content of other trichlorophenols in the product exceeds 0.4%, which cannot meet the requirements of downstream customers. The content of 2,3,6 / 2,4,5-trichlorophenol in 2,4,6-trichlorophenol, the main intermediate of prochloraz, is required to be less than 0.1%. Therefore, the 2,4,6-trichlorophenol produced by scheme ① / ② has no market.

[0008] In Chinese patent CN:104311396A, a directional catalyst mercaptoethylamine is added. Although the conversion rate of 2,4,6-trichlorophenol is improved, the catalyst mercaptoethylamine has a low flash point and is highly dangerous. In addition, the content of 2,3,6 / 2,4,5-trichlorophenol in the product exceeds 0.2%, which cannot meet the market demand. Summary of the invention

[0009] The purpose of the present invention is to solve the above problems and provide a method for preparing 2,4,6-trichlorophenol.

[0010] The technical solution of the present invention is: a method for preparing 2,4,6-trichlorophenol, comprising the following steps:

[0011] ① Add phenol, tetrachloroethylene and water into the chlorination kettle, the weight ratio of phenol: tetrachloroethylene: water is 5:0.4-1.25:0.4-1;

[0012] ② Add chlorine to the reactor, adjust the chlorine feeding speed, slowly raise the temperature to T1, and react to generate crude 2,4,6-trichlorophenol; control the chlorine feeding time t1, and keep the temperature for t2 after the reaction is completed;

[0013] ③ The chlorination kettle is heated to T2, and tetrachloroethylene and water are removed under slight negative pressure for recycling to obtain crude 2,4,6-trichlorophenol; tetrachloroethylene and water serve as catalysts and have positioning functions, and there is no flash point problem. The preparation process is highly safe, and the conversion rate of 2,4,6-trichlorophenol is improved. At the same time, the production of 2,3,6-trichlorophenol, 2,4,5-trichlorophenol and other para-chlorophenol produced by side reactions is suppressed, and the total yield of 2,4,6-trichlorophenol is above 98%.

[0014] ④ The crude trichlorophenol from which tetrachloroethylene and water have been removed is transferred from the chlorination kettle to the distillation tower for distillation to obtain the finished product 2,4,6-trichlorophenol. The purity of the finished product 2,4,6-trichlorophenol after distillation and purification is ≥99.5%, and the purity of 2,3,6 / 2,5,6-trichlorophenol is ≤0.1%, which meets the market requirements.

[0015] Preferably, the slight negative pressure in step ③ is an absolute pressure of 90-95 KPa, which provides pressure conditions for removing tetrachloroethylene and water, and slight negative pressure is easier to remove.

[0016] Preferably, the chlorination kettle is a 6000L enamel chlorination kettle.

[0017] Preferably, in step ②, 4000 kg of phenol, 400-800 kg of water, and 400-1000 kg of tetrachloroethylene are added to the reactor, and the matching chlorine feeding rate is 50-150 kg / h. The reaction degree is controlled by controlling the speed of chlorine feeding into the reactor, thereby controlling the temperature in the reactor to be stable within a reasonable range.

[0018] Preferably, in step ②, the chlorine-passing time is 10 hours ≤ t1 ≤ 12 hours, and the heat preservation time is 70 minutes ≤ t2 ≤ 90 minutes.

[0019] Preferably, in step ②, the temperature after the reaction is heated is 60° C.≤T1≤80° C., and in step ③, the chlorination kettle is heated to 100° C.≤T2≤120° C. Combined with the above-mentioned slightly negative pressure state, tetrachloroethylene and water are more easily removed.

[0020] Preferably, in step ④, the top pressure of the distillation tower is controlled at 2-4 KPa, the top temperature is controlled at 120-130°C, and the bottom temperature is controlled at 140-150°C.

[0021] The beneficial effects of the present invention are as follows: a method for preparing 2,4,6-trichlorophenol, using phenol as a raw material, using tetrachloroethylene and water as a directional catalyst and inhibitor in a certain ratio, chlorinating to generate a crude product of 2,4,6-trichlorophenol, and then separating and purifying it through a distillation tower to obtain a target product. Tetrachloroethylene and water both serve as catalysts and have positioning functions, there is no flash point problem, the preparation process is highly safe, the conversion rate of 2,4,6-trichlorophenol is improved, and the production of 2,3,6-trichlorophenol, 2,4,5-trichlorophenol and other para-chlorophenol produced by side reactions is suppressed, and the total yield of 2,4,6-trichlorophenol is above 98%. After purification by a distillation tower, the purity of 2,4,6-trichlorophenol is above 99.5%, and 2,3,6 / 2,5,6-trichlorophenol is ≤0.1%. DETAILED DESCRIPTION

[0022] Embodiment 1: A method for preparing 2,4,6-trichlorophenol, comprising the following steps

[0023] ① Add phenol, tetrachloroethylene and water to a 6000L enamel chlorination kettle. Add 4000kg of phenol, 800kg of water and 400kg of tetrachloroethylene to the reactor. Tetrachloroethylene and water serve as catalysts and have positioning functions. There is no flash point problem. The preparation process is highly safe and improves the conversion rate of 2,4,6-trichlorophenol. At the same time, the production of 2,3,6-trichlorophenol, 2,4,5-trichlorophenol and other para-chlorophenol produced by side reactions is suppressed.

[0024] ② Add chlorine to the reactor, adjust the chlorine flow rate to 50-150kg / h, slowly heat up to 70-75°C, and generate crude 2,4,6-trichlorophenol; control the chlorine flow time to 10 hours, and keep the temperature for 70 minutes after the chlorine flow to the end of the reaction;

[0025] ③ The chlorination kettle is heated to 100°C≤T2≤120°C, and tetrachloroethylene and water are removed under slight negative pressure and recycled. The slight negative pressure is 90-95KPa absolute pressure to obtain crude 2,4,6-trichlorophenol. Samples are taken from the chlorination kettle for testing. The crude 2,4,6-trichlorophenol content is 98.1%, 2,3,6-trichlorophenol content is 0.05%, 2,5,6-trichlorophenol-trichlorophenol content is 0.05%, 2,4,5-trichlorophenol content is 0.01%, and polychlorophenol content is 1.79%.

[0026] ④ The crude trichlorophenol from which tetrachloroethylene and water have been removed is transferred from the chlorination kettle to the distillation tower for distillation, and the top pressure of the distillation tower is controlled at 2-4KPa, the top temperature is controlled at 120-130℃, and the bottom temperature is controlled at 140-150℃; the finished product 2,4,6-trichlorophenol is collected. The distillation finished product is sampled and tested, and the content of 2,4,6-trichlorophenol is 99.9%, the content of 2,5,6-trichlorophenol is 0.03%, the content of 2,6-dichlorophenol is 0.02%, and the content of polychlorophenol is 0.02%.

[0027] Embodiment 2: A method for preparing 2,4,6-trichlorophenol, comprising the following steps:

[0028] ① Add phenol, tetrachloroethylene and water to a 6000L enamel chlorination kettle. Add 4000kg of phenol, 400kg of water and 1000kg of tetrachloroethylene to the reactor. Tetrachloroethylene and water serve as catalysts and have positioning functions. There is no flash point problem. The preparation process is highly safe and improves the conversion rate of 2,4,6-trichlorophenol. At the same time, the production of 2,3,6-trichlorophenol, 2,4,5-trichlorophenol and other para-chlorophenol produced by side reactions is suppressed.

[0029] ② Add chlorine to the reactor, adjust the chlorine flow rate to 50-150kg / h, slowly heat up to 76°C, and generate crude 2,4,6-trichlorophenol; control the chlorine flow time to 11 hours, and keep the temperature for 80 minutes after the chlorine flow to the end of the reaction;

[0030] ③ The chlorination kettle is heated to 100°C≤T2≤120°C, and tetrachloroethylene and water are removed under slight negative pressure for recovery, with the slight negative pressure being 90-95KPa absolute pressure, to obtain crude 2,4,6-trichlorophenol; samples are taken from the chlorination kettle for testing, and the content of 2,4,6-trichlorophenol is 98.5%, the content of 2,3,6-trichlorophenol is 0.03%, the content of 2,5,6-trichlorophenol is 0.03%, the content of 2,4,-dichlorophenol is 0.08%, and the content of polychlorophenol is 1.28%.

[0031] ④ The crude trichlorophenol from which tetrachloroethylene and water have been removed is transferred from the chlorination kettle to the distillation tower for distillation, and the top pressure of the distillation tower is controlled at 2-4KPa, the top temperature is controlled at 120-130℃, and the bottom temperature is controlled at 140-150℃; the finished product 2,4,6-trichlorophenol is collected. The distillation finished product is sampled and tested, and the content of 2,4,6-trichlorophenol is 99.76%, 2,3,6-trichlorophenol is 0.06%, 2,3,5-trichlorophenol is 0.06%, 2,6-dichlorophenol is 0.03%, and polychlorophenol is 0.04%.

[0032] Embodiment 3: A method for preparing 2,4,6-trichlorophenol, comprising the following steps

[0033] ① Add phenol, tetrachloroethylene and water to a 6000L enamel chlorination kettle. Add 4000kg of phenol, 700kg of water and 700kg of tetrachloroethylene to the reactor. Tetrachloroethylene and water serve as catalysts and have positioning functions. There is no flash point problem. The preparation process is highly safe and improves the conversion rate of 2,4,6-trichlorophenol. At the same time, the production of 2,3,6-trichlorophenol, 2,4,5-trichlorophenol and other para-chlorophenol produced by side reactions is suppressed.

[0034] ② Add chlorine to the reactor, adjust the chlorine flow rate to 50-150kg / h, slowly heat up to 76°C, and generate crude 2,4,6-trichlorophenol; control the chlorine flow time to 11 hours, and keep the temperature for 75 minutes after the chlorine flow to the end of the reaction;

[0035] ③ The chlorination kettle is heated to 100°C≤T2≤120°C, and tetrachloroethylene and water are removed under slight negative pressure and recycled. The slight negative pressure is 90-95KPa absolute pressure to obtain crude 2,4,6-trichlorophenol. Samples are taken from the chlorination kettle for testing, and the content of 2,4,6-trichlorophenol is 98.8%, the content of 2,3,6-trichlorophenol is 0.03%, the content of 2,5,6-trichlorophenol is 0.03%, the content of 2,4, -dichlorophenol is 0.06%, the content of 2,6-dichlorophenol is 0.06%, and the content of polychlorophenol is 1.02%.

[0036] ④ The crude trichlorophenol from which tetrachloroethylene and water have been removed is transferred from the chlorination kettle to a distillation tower for distillation, and the top pressure of the distillation tower is controlled at 2-4KPa, the top temperature is controlled at 120-130°C, and the bottom temperature is controlled at 140-150°C; the finished product 2,4,6-trichlorophenol is collected. The distillation finished product is sampled and tested, and the content of 2,4,6-trichlorophenol is 99.83%, 2,3,6-trichlorophenol is 0.04%, 2,3,5-trichlorophenol is 0.04%, 2,6-dichlorophenol is 0.01%, and polychlorophenol is 0.04%.

Claims

1. A method for preparing 2,4,6-trichlorophenol, comprising the following steps: ① Add phenol, tetrachloroethylene and water into the chlorination kettle, the weight ratio of phenol: tetrachloroethylene: water is 5:0.4-1.25:0.4-1; ② Add chlorine to the reactor, adjust the chlorine feeding speed, slowly raise the temperature to T1, and react to generate crude 2,4,6-trichlorophenol; control the chlorine feeding time t1, and keep the temperature for t2 after the reaction is completed; ③ The chlorination kettle is heated to T2, and the tetrachloroethylene and water are removed under slight negative pressure for recycling to obtain crude 2,4,6-trichlorophenol; ④ The crude trichlorophenol from which tetrachloroethylene and water have been removed is transferred from the chlorination kettle to the distillation tower for distillation to obtain the finished product 2,4,6-trichlorophenol.

2. A method for preparing 2,4,6-trichlorophenol according to claim 1, characterized in that: The slight negative pressure in step ③ is an absolute pressure of 90-95KPa.

3. A method for preparing 2,4,6-trichlorophenol according to claim 1, characterized in that: The chlorination kettle is an enamel chlorination kettle.

4. A method for preparing 2,4,6-trichlorophenol according to claim 1, characterized in that: The chlorine feeding rate in step ② is 50-150kg / h.

5. A method for preparing 2,4,6-trichlorophenol according to claim 4, characterized in that: In the step ②, the chlorine-passing time is 10 hours≤t1≤12 hours, and the heat preservation time is 70 minutes≤t2≤90 minutes.

6. A method for preparing 2,4,6-trichlorophenol according to claim 5, characterized in that: In the step ②, the temperature after the reaction is heated is 60°C≤T1≤80°C, and in the step ③, the chlorination kettle is heated to 100°C≤T2≤120°C.

7. A method for preparing 2,4,6-trichlorophenol according to claim 1, characterized in that: In the step ④, the top pressure of the distillation tower is controlled at 2-4 KPa, the top temperature is controlled at 120-130°C, and the bottom temperature is controlled at 140-150°C.