A method for preparing chloroacetyl chloride by gas phase

Abstract

This invention discloses a gas-phase method for preparing chloroacetyl chloride. Chlorine gas and vaporized acetyl chloride are introduced into a reaction tower, and chloroacetyl chloride is prepared under high-temperature conditions catalyzed by a solid superacid. The high-temperature conditions eliminate gas-liquid mass transfer resistance, significantly shortening the reaction time. The combination of high temperature and short residence time effectively suppresses the formation of byproducts such as dichloroacetyl chloride and trichloroacetyl chloride, improving product purity. This invention features a simple process that is easily implemented for continuous, industrial-scale production.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical synthesis technology, specifically relating to a gas-phase method for preparing chloroacetyl chloride. Background Technology

[0002] Chloroacetyl chloride is an important fine chemical intermediate in the pharmaceutical, pesticide, dye, and auxiliary industries. Industrially, it is often prepared by selective chlorination of acetyl chloride using chlorine gas as a raw material. Traditional production processes mostly employ a low-temperature liquid-phase chlorination route, with the reaction temperature typically controlled at 50-60℃, using liquid acetyl chloride to react with chlorine gas via bubbling. This process has significant drawbacks: the reaction is controlled by gas-liquid mass transfer resistance, resulting in a slow reaction rate and long production cycle; prolonged high-temperature residence can easily lead to deep chlorination, generating polychlorinated byproducts such as dichloroacetyl chloride and trichloroacetyl chloride, leading to decreased selectivity of the target product and increased separation and purification load; simultaneously, the heterogeneous liquid-phase reaction system is unevenly mixed, and excessively high local chlorine concentrations further exacerbate side reactions, restricting the improvement of product purity and yield.

[0003] To improve reaction efficiency and selectivity, existing technologies have attempted to improve them through catalytic modification and reactor optimization, but they have not yet broken away from the cryogenic liquid reverse chlorination system, and the core problems such as limited mass transfer and long cycle time have not been fundamentally solved.

[0004] Therefore, developing a new process for preparing chloroacetyl chloride that can overcome mass transfer limitations, accelerate reaction rates, and be adapted to continuous production has significant industrial value and application prospects. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a gas-phase method for preparing chloroacetyl chloride, overcoming the slow reaction rate and long reaction time of existing low-temperature liquid-phase chlorination processes. The method first vaporizes acetyl chloride at high temperature, then reacts it with chlorine gas in a homogeneous mixture under gas-phase conditions, fundamentally overcoming the limitations of gas-liquid mass transfer resistance, effectively suppressing polychlorination side reactions, and improving the selectivity and purity of chloroacetyl chloride.

[0006] This invention is achieved through the following technical solution: A gas-phase method for preparing chloroacetyl chloride includes the following steps: (1) Fix the solid superacid catalyst on the tray of the reaction tower and raise the temperature; (2) Chlorine gas and vaporized acetyl chloride are introduced into the reaction tower, and a chlorination reaction occurs on the tower plate with a fixed catalyst; (3) After the crude product is purified by distillation, the product chloroacetyl chloride is collected.

[0007] According to the gas-phase method for preparing chloroacetyl chloride, the reaction tower has an inner diameter of 0.6~0.8m, 25~30 trays, a tray spacing of 0.4~0.5m, and a tower height of 12~17m.

[0008] According to the gas-phase method for preparing chloroacetyl chloride, in step (1), the temperature is raised to 100~105℃.

[0009] According to the gas-phase method for preparing chloroacetyl chloride, in step (1), the solid superacid catalyst is a type I catalyst or / and a type II catalyst, and the type I catalyst is SO4. 2- / ZrO2 or SO4 2- / TiO2, a type II catalyst, is one of WO3 / ZrO2, WO3 / TiO2, WO3 / SnO2, MoO3 / ZrO2, MoO3 / TiO2 or MoO3 / SnO2.

[0010] According to the gas-phase method for preparing chloroacetyl chloride, the solid superacid catalyst accounts for 1-5% of the mass of acetyl chloride.

[0011] According to the gas-phase method for preparing chloroacetyl chloride, the solid superacid catalyst is uniformly spread on the trays of the reaction tower and pressed and fixed by a grid-type catalyst press plate, and the gas passes uniformly from bottom to top through the trays to undergo the chlorination reaction.

[0012] According to the gas-phase method for preparing chloroacetyl chloride, the molar ratio of acetyl chloride to chlorine in step (2) is 1:0.95~1.05.

[0013] According to the gas-phase method for preparing chloroacetyl chloride, the inlet pressure of acetyl chloride and chlorine gas in step (2) is 0.12~0.25 MPa.

[0014] According to the gas-phase method for preparing chloroacetyl chloride, in step (2), the residence time of acetyl chloride and chlorine gas in the reaction tower is 1~4h, and the residence time is determined by the inlet pressure and the number of trays.

[0015] Beneficial effects of this invention: This invention employs high-temperature gasification and gas-gas homogeneous reaction to eliminate gas-liquid mass transfer resistance, significantly increasing the reaction rate and shortening the reaction time. The combination of high temperature and short residence time effectively suppresses the formation of byproducts such as dichloroacetyl chloride and trichloroacetyl chloride, resulting in high selectivity and purity of the target product. The reaction system is uniformly mixed, avoiding excessively high local chlorine concentrations, minimizing side reactions, reducing post-treatment load, and making the process suitable for continuous production. Detailed Implementation

[0016] The specific details of this invention will be further explained below: The gas-phase method for preparing chloroacetyl chloride of the present invention uses a reaction tower with an inner diameter of 0.6~0.8m, 25~30 trays, a tray spacing of 0.4~0.5m, and a tower height of 12~17m.

[0017] Includes the following steps: 1) The solid superacid catalyst is evenly spread on the trays of the reaction tower and secured with grid-type catalyst clamps. The temperature is raised to 100-105℃, and the gas flows uniformly upwards through the trays to undergo the chlorination reaction. Solid superacid catalysts are classified into Class I and / or Class II catalysts. Class I catalysts are SO4. 2- / ZrO2 or SO4 2- / TiO2, a type II catalyst, is one of WO3 / ZrO2, WO3 / TiO2, WO3 / SnO2, MoO3 / ZrO2, MoO3 / TiO2 or MoO3 / SnO2; 2) Chlorine gas and vaporized acetyl chloride are introduced into a reaction tower, where a chlorination reaction occurs on a tray with a fixed catalyst. The solid superacid catalyst accounts for 1-5% of the mass of acetyl chloride, and the molar ratio of acetyl chloride to chlorine gas is 1:0.95-1.05. The residence time of acetyl chloride and chlorine gas in the reaction tower is 1-4 hours. After the crude product is purified by distillation, the product chloroacetyl chloride is collected.

[0018] The specific parameters of the present invention are described below: Example 1:

[0019] The reaction column was set to have 27 trays, using SO4. 2- 2 kg of ZrO2 catalyst was evenly spread on all trays. The reaction temperature was controlled at 106 ± 1℃. 100 kg of acetyl chloride and 91.2 kg of chlorine gas were simultaneously introduced at a pressure of 0.20~0.25 MPa. The residence time of acetyl chloride and chlorine gas on the trays was controlled at 1.5 h. After purification by distillation, the chloroacetyl chloride was collected in the product tank, and the unreacted acetyl chloride was recycled. Gas phase analysis showed that the composition before distillation was: 84.67% chloroacetyl chloride, 0.20% dichloroacetyl chloride, and 15.13% acetyl chloride, with a conversion rate of 79.58% and a yield of 79.45%.

[0020] Example 2:

[0021] The reaction column was set with 25 trays. 5 kg of MoO3 / ZrO2 catalyst was evenly distributed across all trays. The reaction temperature was controlled at 102±1℃. 100 kg of acetyl chloride and 94.8 kg of chlorine gas were simultaneously introduced at a pressure of 0.15~0.18 MPa. The residence time of acetyl chloride and chlorine gas on the trays was controlled at 2.5 h. After purification by distillation, the crude product was purified, and the chloroacetyl chloride was collected in the product tank, while the unreacted acetyl chloride was recycled. Gas phase analysis showed that the composition before distillation was: 75.79% chloroacetyl chloride, 1.19% dichloroacetyl chloride, 0.68% trichloroacetyl chloride, and 22.34% acetyl chloride. The conversion rate was 70.58%, and the product yield was 69.36%.

[0022] Example 3:

[0023] The reaction column was set to have 25 trays, using SO4. 2- Five kilograms of ZrO2 and WO3 / ZrO2 catalyst were evenly spread on all the trays, with a mass ratio of 2:1. The reaction temperature was controlled at 106±1℃. One hundred kilograms of acetyl chloride and ninety-three kilograms of chlorine gas were simultaneously introduced at a pressure of 0.18~0.22 MPa. The residence time of acetyl chloride and chlorine gas on the trays was controlled at 1.5 hours. After purification by distillation, the chloroacetyl chloride was collected in the product tank, and the unreacted acetyl chloride was recycled. Gas phase analysis showed that the composition before distillation was: 79.98% chloroacetyl chloride, 0.59% dichloroacetyl chloride, 0.59% trichloroacetyl chloride, and 19.11% acetyl chloride. The conversion rate was 74.58%, and the product yield was 73.95%.

[0024] Comparative Example 1: Chloroacetyl chloride was added to the reactor as a base material, and SO4 was added to the reactor. 2- Using ZrO2 catalyst, the stirring was turned on, and the circulating pump and steam heating were started, controlling the temperature at 70~80℃. The reactor was connected to the circulating pump via a buffer tank to form a closed circulation system. Acetyl chloride was injected into the reactor at a flow rate of 10.6±0.2 kg / h, and chlorine gas was simultaneously introduced, controlling the chlorine flow rate at 8.0±0.1 kg / h. After reacting for 1.5 hours, chloroacetyl chloride was transferred to a collection tank through the outlet. Gas phase analysis showed that the content of chloroacetyl chloride was 51.01%, dichloroacetyl chloride was 7.11%, trichloroacetyl chloride was 11.56%, and acetyl chloride was 30.33%, with a conversion rate of 80.16% and a product yield of 47.55%.

[0025] Comparative Example 2: The feeding time was changed to 1 hour, while other process conditions and operating steps remained the same as in Example 1. Gas chromatography analysis revealed that the content of chloroacetyl chloride was 67.88%, dichloroacetyl chloride was 0.08%, acetyl chloride was 32.04%, the conversion rate was 59.58%, and the product yield was 59.53%.

[0026] Comparative Example 3: The feeding time was changed to 4 hours, while other process conditions and operating steps remained the same as in Example 1. Gas chromatography analysis revealed that the content of chloroacetyl chloride was 30.45%, dichloroacetyl chloride was 18.58%, trichloroacetyl chloride was 50.89%, acetyl chloride was 0.08%, the conversion rate was 99.85%, and the product yield was 39.85%.

[0027] The parameters from Examples 1-3 and Comparative Examples 1-3 were tabulated to obtain the following table. , Comparative studies of Examples 1-3 revealed that the catalytic effect of Type I catalyst was superior to that of Type II catalyst. The reason for this is that in Type I catalyst, the surface of TiO2 modified with sulfate has an extremely high density of strong Brønsted acid centers. These strong protic acids can greatly reduce the energy barrier of acetylchloroenolization, rapidly generating enol intermediates, thereby accelerating the reaction with chlorine. In contrast, the acidic centers of Type II catalyst are mainly Lewis acids, and their Brønsted acid strength is weaker than that of the sulfation system.

[0028] Comparing Example 1 and the comparative example, it was found that while the conversion rate could be maintained well using a circulating reactor, the selectivity was reduced; shortening the feeding time improved the product selectivity, but the conversion rate was low; extending the feeding time almost completely converted the raw materials, but the selectivity was still low, and none of these methods offered any production advantages.

[0029] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing chloroacetyl chloride by gas phase, characterized in that, Includes the following steps: (1) Fix the solid superacid catalyst on the tray of the reaction tower and raise the temperature; (2) Chlorine gas and vaporized acetyl chloride are introduced into the reaction tower, and a chlorination reaction occurs on the tower plate with a fixed catalyst; (3) After the crude product is purified by distillation, the product chloroacetyl chloride is collected.

2. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, The reaction tower has an inner diameter of 0.6~0.8m, 25~30 trays, a tray spacing of 0.4~0.5m, and a tower height of 12~17m.

3. The synthesis method according to claim 1, characterized in that, In step (1), the temperature is raised to 100~108℃.

4. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, In step (1), the solid superacid catalyst is a type I catalyst and / or a type II catalyst, where the type I catalyst is SO4. 2- / ZrO2 or SO4 2- / TiO2, a type II catalyst, is one of WO3 / ZrO2, WO3 / TiO2, WO3 / SnO2, MoO3 / ZrO2, MoO3 / TiO2 or MoO3 / SnO2.

5. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, The solid superacid catalyst accounts for 1-5% of the mass of acetyl chloride.

6. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, The solid superacid catalyst is evenly spread on the trays of the reaction tower and is pressed and fixed by a grid-type catalyst press plate. The gas passes through the trays evenly from bottom to top to undergo the chlorination reaction.

7. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, In step (2), the molar ratio of acetyl chloride to chlorine is 1:0.95~1.

05.

8. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, In step (2), the inlet pressure of acetyl chloride and chlorine gas is 0.12~0.25MPa.

9. The method for preparing chloroacetyl chloride by gas phase method according to claim 1, characterized in that, In step (2), the residence time of acetyl chloride and chlorine gas in the reaction tower is 1 to 4 hours.