A method for continuously producing dichloroacetic acid and dichloroacetyl chloride

Abstract

This invention pertains to the preparation technology of chemical intermediates and aims to provide a method for the continuous production of dichloroacetic acid and dichloroacetyl chloride. The method includes: continuously feeding sulfuric acid, water, and tetrachloroethylene into a continuous flow reactor, heating to carry out a continuous reaction; discharging gas from the top of the continuous flow reactor, and overflowing liquid from the top of the reactor; separating the gas and liquid phases to obtain the products dichloroacetic acid and / or dichloroacetyl chloride; controlling the ratio of dichloroacetic acid and dichloroacetyl chloride by adjusting the feed rates of sulfuric acid, water, and tetrachloroethylene. This invention utilizes a continuous flow reactor to allow the raw materials to contact in a continuous gas-liquid turbulent flow, ensuring thorough mixing, promoting the reaction, and improving the mass transfer effect between reactants. Compared with existing technologies, this invention significantly improves reaction efficiency, significantly reduces equipment costs, and enhances operational safety, enabling continuous production.

Description

Technical Field

[0001] This invention pertains to chemical intermediate production technology, specifically relating to a method for the continuous production of dichloroacetic acid and dichloroacetyl chloride. Background Technology

[0002] Dichloroacetic acid (DCA) and dichloroacetyl chloride (DCAC) are important chemical intermediates in organic synthesis and are widely used in medicine, pesticides, dyes and other fields.

[0003] The mainstream synthesis process of dichloroacetic acid revolves around chlorination. Industrially, the acetic acid-catalyzed chlorination method is used: acetic acid is used as a raw material, and chlorine gas is applied under the action of a catalyst to primarily produce monochloroacetic acid, with dichloroacetic acid as a byproduct. The dichloroacetic acid content can be increased by controlling the degree of chlorination, but this also easily generates trichloroacetic acid. The advantages are that the raw material acetic acid is inexpensive and readily available, and the process is mature. The disadvantages are that the degree of chlorination needs to be precisely controlled; insufficient chlorination mainly produces monochloroacetic acid, while excessive chlorination mainly produces trichloroacetic acid. Furthermore, chlorine gas is highly corrosive, requiring high-quality equipment. In addition, chlorination is considered a hazardous process in industry.

[0004] The industrial synthesis of dichloroacetyl chloride mainly includes the following two routes: (1) Dichloroacetic acid chlorination method: Dichloroacetic acid is used as raw material and reacts with chlorinating agents (such as phosphorus trichloride, phosphorus pentachloride, thionyl chloride) to produce dichloroacetyl chloride. The advantage is that the reaction conditions are mild, room temperature or slight heating is sufficient, and there is no need to use a high pressure vessel; the disadvantage is that the source of dichloroacetic acid is limited, and the chlorinating agent is corrosive, and the reaction will produce a large amount of sulfur and phosphorus-containing waste acid, which is difficult to purify and reuse. This method does not conform to the concept of modern green chemistry and has been gradually abandoned in industry. (2) Trichloroethylene oxidation method: The main method for producing dichloroacetyl chloride in industry at present. The advantage is that no waste acid is generated, and the raw materials are cheap and readily available; the disadvantage is that the reaction requires the use of oxygen oxidation and free radical initiators, which have strict requirements on the type and amount of initiator, poor reaction selectivity, and is prone to explosion, which is a dangerous process in industry.

[0005] Zhejiang Benli Technology Co., Ltd. has invented a method for synthesizing dichloroacetyl compounds (application number: 202511560466.1), which includes a method for synthesizing dichloroacetic acid and dichloroacetyl chloride. This method can prepare the target product with high yield and high selectivity, and solves the problems of low product purity and high cost in previous synthesis methods.

[0006] Our technicians discovered in subsequent research that: (1) Under high-temperature reaction conditions in a batch reactor, the boiling point of tetrachloroethylene is much lower than the reaction temperature, and hydrogen chloride gas is produced at the same time, which causes the system pressure to gradually increase as the reaction proceeds, so pressure-resistant reaction equipment must be used; (2) The high pressure characteristics make it difficult to use glass-lined material for the reactor, and the high corrosiveness of the reaction liquid requires the reactor to be made of special material, which significantly increases the difficulty of industrialization; (3) The system pressure causes tetrachloroethylene to exist mainly in liquid form at the reaction temperature, and liquid tetrachloroethylene is immiscible with sulfuric acid, which severely limits the mass transfer between reactants, resulting in low reaction efficiency.

[0007] Therefore, there is an urgent need to develop a safer, more efficient, and industrially feasible production process for dichloroacetic acid and dichloroacetyl chloride. Summary of the Invention

[0008] The technical problem this invention aims to solve is to overcome the shortcomings of existing processes and provide a method for the continuous production of dichloroacetic acid and dichloroacetyl chloride. This invention fundamentally reconstructs the reaction mechanism and mass transfer pathway, solving the problem of low reaction efficiency in previous processes. While improving the overall industrialization level, it also enhances process safety and environmental friendliness.

[0009] To solve the technical problem, the solution of the present invention is:

[0010] A method for the continuous production of dichloroacetic acid and dichloroacetyl chloride is provided, comprising: continuously feeding sulfuric acid, water, and tetrachloroethylene into a continuous flow reactor and heating them for a continuous reaction; discharging gas from the top of the continuous flow reactor and overflowing liquid from the top of the reactor; separating the gas and liquid phases to obtain the products dichloroacetic acid and / or dichloroacetyl chloride; controlling the ratio of products dichloroacetic acid and dichloroacetyl chloride by adjusting the feed rates of sulfuric acid, water, and tetrachloroethylene. The reaction liquid is separated by distillation to obtain concentrated sulfuric acid and dichloroacetic acid products, and the gas is separated by condensation to obtain dichloroacetyl chloride product, unreacted tetrachloroethylene, and non-condensable hydrogen chloride gas.

[0011] As a preferred embodiment of the present invention, the amount of sulfuric acid used in the raw materials entering the continuous flow reactor is calculated based on pure H2SO4, and the molar ratio of sulfuric acid to tetrachloroethylene is 1 to 100:1; the ratio of sulfuric acid to water is controlled so that the mass concentration of sulfuric acid in the reaction solution is greater than 80%.

[0012] As a preferred embodiment of the present invention, concentrated sulfuric acid is heated to 130-200 °C and then sent to the bottom of the reactor.

[0013] As a preferred embodiment of the present invention, liquid tetrachloroethylene is heated and vaporized, and the resulting tetrachloroethylene gas is sent to the bottom of the reactor.

[0014] As a preferred embodiment of the present invention, the water is the water contained in the concentrated sulfuric acid itself, or a set amount of water is added to the concentrated sulfuric acid according to a set dosage, heated and then sent into the reactor together; or, the water is separately measured according to a set ratio and sent into the reactor through an independent pipeline.

[0015] As a preferred embodiment of the present invention, the reaction temperature in the continuous reactor is controlled at 130-200°C; the reactor pressure is atmospheric pressure or slightly positive pressure, so that tetrachloroethylene is kept in a vaporized state.

[0016] As a preferred embodiment of the present invention, when the water in the system is completely consumed, the reaction produces dichloroacetyl chloride, or a mixture of dichloroacetyl chloride and dichloroacetic acid: that is, when the molar ratio of water to tetrachloroethylene is 1:1, the product is dichloroacetyl chloride; when the molar ratio of water to tetrachloroethylene is between 1:1 and 2:1, the product is dichloroacetyl chloride and dichloroacetic acid; when the water in the system is not completely consumed, that is, when the molar ratio of water to tetrachloroethylene is 2:1, the product is dichloroacetic acid.

[0017] As a preferred embodiment of the present invention, the continuous flow reactor is any one of the following: a tower reactor, including a gas distributor at the bottom, packing inside the tower, an external heating jacket, a bottom feed inlet, an upper discharge outlet and a top gas outlet; or a tubular reactor, including an internal static mixer, an external heating jacket, a bottom feed inlet, an upper discharge outlet and a top gas outlet.

[0018] As a preferred embodiment of the present invention, a distillation column is used to separate the liquid overflowing from the top of the continuous flow reactor. Concentrated sulfuric acid is discharged from the bottom of the distillation column and recycled. The top fraction of the distillation column is dichloroacetic acid. The gas discharged from the top of the continuous flow reactor is condensed in stages to obtain dichloroacetyl chloride and unreacted tetrachloroethylene, which are recycled as reaction raw materials. Hydrogen chloride gas is sent to a spray tower for absorption with water, and the residual gas is discharged as tail gas.

[0019] Compared with existing synthesis methods, the beneficial effects of this invention are:

[0020] This invention, based on the principle of process intensification, proposes a technical solution for preparing dichloroacetic acid and dichloroacetyl chloride using sulfuric acid, water, and tetrachloroethylene gas in a continuous flow reactor. Under normal or slightly positive pressure conditions, gaseous tetrachloroethylene is introduced into the bottom of the continuous flow reaction tower and further dispersed by a gas distributor. During its ascent, the tetrachloroethylene gas comes into continuous turbulent contact with high-temperature liquid sulfuric acid, ensuring thorough mixing and promoting the reaction. The bubbling effect of the hydrogen chloride gas produced during the ascent further enhances the mass transfer between reactants, significantly improving reaction efficiency while eliminating the need for mechanical stirring.

[0021] (1) Significantly improved reaction efficiency: In traditional batch reactors, tetrachloroethylene is mainly in a liquid state under pressure, which is immiscible with sulfuric acid and difficult to mix. This invention converts tetrachloroethylene into a gaseous state, changing the reaction system from a high-pressure liquid-liquid two-phase reaction to an atmospheric-pressure gas-liquid two-phase reaction. The tetrachloroethylene gas is dispersed by a gas distributor and further comes into continuous gas-liquid turbulent contact with sulfuric acid in the reactor. The gas and liquid are fully mixed to promote the reaction. In principle, the reaction mechanism and mass transfer path are reconstructed, solving the problem of low reaction efficiency in batch reactor processes.

[0022] (2) Significantly reduced equipment investment: In traditional batch reactors, the boiling point of tetrachloroethylene is much lower than the reaction temperature, and hydrogen chloride gas is produced at the same time. As the reaction proceeds, the system pressure gradually increases, requiring a pressure-resistant reactor, making it difficult to use glass-lined equipment; the high corrosivity means that the reaction must use special alloy materials, greatly increasing the difficulty of industrialization; the present invention adopts an atmospheric pressure or slightly positive pressure reaction mode, avoiding the risk of corrosion leakage and overpressure explosion caused by high pressure, reducing the requirements for equipment materials and pressure resistance, and significantly saving equipment investment.

[0023] (3) Improved operational safety: The gas distributor and internal components of the tower reactor of this invention enhance gas-liquid mixing, shorten the reaction time, and eliminate the need for dynamic equipment such as mechanical stirring, thereby improving the safety and stability of production operation.

[0024] (4) Achieve continuous production: This invention can achieve continuous production of dichloroacetic acid and dichloroacetyl chloride, significantly improve production efficiency, reduce production costs, and is more suitable for large-scale industrial production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the continuous production apparatus for dichloroacetic acid and dichloroacetyl chloride in this invention.

[0026] The attached diagram labels are as follows: 1. Tower reactor; 2. Gas distributor; 3. Sampling point; 4. Temperature sensor; 5. Sulfuric acid heating vessel; 6. Tetrachloroethylene vaporization tank; 7. Reaction liquid storage tank; 8. Distillation column; 9. Reboiler; 10. Sulfuric acid receiving tank; 11. Condenser; 12. Tetrachloroethylene receiving tank; 13. Dichloroacetic acid receiving tank; 14. Condenser; 15. Tetrachloroethylene receiving tank; 16. Dichloroacetyl chloride receiving tank; 17. Spray tower; 18. Online gas composition analyzer. Detailed Implementation

[0027] To more clearly illustrate the technical solution of the present invention, the following description is provided in conjunction with embodiments.

[0028] Part 1: Overview of the Technical Solution of the Invention (Taking a Tower Reactor as an Example)

[0029] Continuous production method of dichloroacetic acid / dichloroacetyl chloride

[0030] 1. Raw material pretreatment and feeding

[0031] The continuous production of dichloroacetic acid / dichloroacetyl chloride according to the present invention uses sulfuric acid, tetrachloroethylene, and water as raw materials. Heated concentrated sulfuric acid is pumped to the bottom of a tower reactor via pipeline. Liquid tetrachloroethylene is heated and vaporized to obtain tetrachloroethylene vapor, which is then piped to the bottom of the tower reactor. The water in the raw materials can be the water contained in the commercial concentrated sulfuric acid (or recycled sulfuric acid), or water can be added to the sulfuric acid according to a set dosage and fed into the tower reactor after heating. Alternatively, water can be selectively fed into the tower reactor via a separate pipeline according to a set ratio.

[0032] 2. Reaction

[0033] Heated sulfuric acid, water, and tetrachloroethylene vapor are continuously fed into the bottom of a tower reactor for continuous reaction. The temperature inside the tower is controlled at 130–200°C (preferably 160–180°C); the pressure inside the tower is atmospheric pressure or slightly positive pressure (to ensure that tetrachloroethylene remains in a vaporized state). The reaction liquid is drawn from the top of the reactor and sent to a distillation unit for separation to obtain concentrated sulfuric acid and dichloroacetic acid products. The gas discharged from the top of the reactor is condensed and separated to obtain unreacted tetrachloroethylene, dichloroacetyl chloride products, and hydrogen chloride gas as a byproduct.

[0034]

[0035] This invention, based on identical production equipment, allows for the control of the ratio of dichloroacetic acid and dichloroacetyl chloride obtained by adjusting the feed rates of sulfuric acid, water, and tetrachloroethylene, thereby yielding a final product that meets the requirements. Specifically: using pure sulfuric acid as the sulfuric acid, the molar ratio of sulfuric acid to tetrachloroethylene is maintained at 1–100:1; the ratio of sulfuric acid to water is controlled to ensure that the mass concentration of sulfuric acid in the reaction solution is greater than 80%; when water in the system is completely consumed, the reaction produces dichloroacetyl chloride, or a mixture of dichloroacetyl chloride and dichloroacetic acid: that is, when the molar ratio of water to tetrachloroethylene is 1:1, the main product is dichloroacetyl chloride; when the molar ratio of water to tetrachloroethylene is between 1:1 and 2:1, the products are dichloroacetyl chloride and dichloroacetic acid; when water in the system is not completely consumed, i.e., when the molar ratio of water to tetrachloroethylene is 2:1, the product is dichloroacetic acid.

[0036] The continuous production method of this invention allows for the recovery and reuse of some unreacted tetrachloroethylene and sulfuric acid, with a yield of over 95% based on tetrachloroethylene alone; all sulfuric acid is recycled. The resulting dichloroacetic acid and dichloroacetyl chloride are of high quality, with a content greater than 99%.

[0037] Part Two: Specific Implementation Examples and Comparative Analysis

[0038] Example 1

[0039] In this embodiment, the specific implementation steps for the continuous production of dichloroacetyl chloride are as follows:

[0040] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 170°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 23.9 kg / h and 0.6 kg / h, respectively.

[0041] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0042] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature at 160-170℃, thus allowing the hydrolysis reaction to proceed under normal pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 4:1:1.

[0043] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After the reaction liquid in the tank is cooled to 120°C, it is discharged from the bottom of the tank and sent to a distillation column for separation, recovering a small amount of tetrachloroethylene (0.18 kg / h) and concentrated sulfuric acid (23.3 kg / h).

[0044] 5. The light phase product is drawn from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.28 kg / h), dichloroacetyl chloride product (8.4 kg / h), and byproduct hydrogen chloride gas (2.1 kg / h). Analysis and calculations show that the yield of dichloroacetyl chloride product is 95.1%.

[0045] Example 2

[0046] In this embodiment, the specific implementation steps for the continuous production of dichloroacetyl chloride are as follows:

[0047] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 180°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 6.1 kg / h and 0.43 kg / h, respectively.

[0048] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0049] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature at 170-180℃, thus allowing the hydrolysis reaction to occur under normal pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 1:1:0.5.

[0050] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a raw material, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After the reaction liquid in the tank is cooled to 120°C, it is discharged from the bottom of the tank and sent to a distillation column for separation, recovering a small amount of tetrachloroethylene (0.30 kg / h) and concentrated sulfuric acid (5.9 kg / h).

[0051] 5. The light phase product is drawn from the top of the reactor and, after condensation and separation, yields unreacted tetrachloroethylene (4.6 kg / h), dichloroacetyl chloride product (4.3 kg / h), and byproduct hydrogen chloride gas (1.1 kg / h). Based on the recovered tetrachloroethylene, the yield of dichloroacetyl chloride product is 95.6%.

[0052] Example 3

[0053] In this embodiment, the specific implementation steps for the continuous production of dichloroacetyl chloride are as follows:

[0054] 1. 100% sulfuric acid (prepared using fuming sulfuric acid) and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 130°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 100% sulfuric acid and water are controlled at 603.1 kg / h and 0.87 kg / h, respectively.

[0055] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0056] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature at 130-140℃, thus allowing the hydrolysis reaction to occur under normal pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 100:1:0.8.

[0057] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After the reaction liquid in the tank is cooled to 120°C, it is discharged from the bottom of the tank and sent to a distillation column for separation, recovering a small amount of tetrachloroethylene (0.19 kg / h) and concentrated sulfuric acid (602.2 kg / h).

[0058] 5. The light phase product is drawn from the top of the reactor and, after condensation and separation, yields unreacted tetrachloroethylene (2.1 kg / h), dichloroacetyl chloride product (6.8 kg / h), and byproduct hydrogen chloride gas (1.7 kg / h). Analysis and calculations show that the yield of dichloroacetyl chloride product is 95.2%.

[0059] Example 4

[0060] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid and dichloroacetyl chloride are as follows:

[0061] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 180°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled to be 6.03 kg / h and 1.07 kg / h, respectively.

[0062] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0063] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature at 170-180℃, thus allowing the hydrolysis reaction to proceed under normal pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 1:1:1.1.

[0064] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.21 kg / h), dichloroacetic acid (0.74 kg / h), and concentrated sulfuric acid (5.8 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 9.5%.

[0065] 5. The light phase product is drawn off from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.17 kg / h), byproduct hydrogen chloride gas (2.3 kg / h), and product dichloroacetyl chloride (7.6 kg / h), with a yield of 85.9%.

[0066] Example 5

[0067] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid and dichloroacetyl chloride are as follows:

[0068] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 170°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 72.4 kg / h and 0.18 kg / h, respectively.

[0069] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0070] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 160-170℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed material entering the tower reactor is 12:1:1.5.

[0071] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After the reaction liquid in the tank is cooled to 120°C, it is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.27 kg / h), dichloroacetic acid (3.8 kg / h), and concentrated sulfuric acid (70.5 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 47.7%.

[0072] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.26 kg / h), byproduct hydrogen chloride gas (4.1 kg / h), and product dichloroacetyl chloride (4.2 kg / h, yield 47.5%).

[0073] Example 6

[0074] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid and dichloroacetyl chloride are as follows:

[0075] 1. 100% pure sulfuric acid (prepared using fuming sulfuric acid) and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 140°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 100% sulfuric acid and water are controlled at 591.1 kg / h and 2.06 kg / h, respectively.

[0076] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0077] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature at 140-150℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure (or slightly positive pressure). The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 100:1:1.9.

[0078] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.18 kg / h), dichloroacetic acid (6.7 kg / h), and concentrated sulfuric acid (590.2 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 85.4%.

[0079] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.19 kg / h), hydrogen chloride gas (4.1 kg / h), and dichloroacetyl chloride (0.86 kg / h, 10.0%).

[0080] Example 7

[0081] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0082] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 200°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 12.1 kg / h and 1.9 kg / h, respectively.

[0083] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0084] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 190-200℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed entering the tower reactor is 2:1:2.

[0085] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.1 kg / h), dichloroacetic acid (7.5 kg / h), and concentrated sulfuric acid (11.7 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 96.8%.

[0086] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.21 kg / h) and byproduct hydrogen chloride gas (4.3 kg / h).

[0087] Example 8

[0088] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0089] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 190°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 60.3 kg / h and 2.1 kg / h, respectively.

[0090] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0091] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 180-190℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed material entering the tower reactor is 10:1:3.

[0092] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.23 kg / h), dichloroacetic acid (7.4 kg / h), and concentrated sulfuric acid (59 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 95.4%.

[0093] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.28 kg / h) and byproduct hydrogen chloride gas (4.2 kg / h).

[0094] Example 9

[0095] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0096] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 180°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 120.6 kg / h and 3.0 kg / h, respectively.

[0097] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0098] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 180-190℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed entering the tower reactor is 20:1:5.

[0099] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.11 kg / h), dichloroacetic acid (7.6 kg / h), and concentrated sulfuric acid (120.1 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 97.3%.

[0100] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.13 kg / h) and byproduct hydrogen chloride gas (4.3 kg / h).

[0101] Example 10

[0102] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0103] 1. 98% sulfur and water are precisely metered and added through two inlets at the top of the liquid heating tank; the sulfuric acid solution in the tank is heated to 160°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 301.6 kg / h and 4.8 kg / h, respectively.

[0104] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0105] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 160-170℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed entering the tower reactor is 50:1:10.

[0106] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.1 kg / h), dichloroacetic acid (7.6 kg / h), and concentrated sulfuric acid (304.5 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 97.8%.

[0107] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.09 kg / h) and byproduct hydrogen chloride gas (4.3 kg / h).

[0108] Example 11

[0109] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0110] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 150°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 603.1 kg / h and 9.7 kg / h, respectively.

[0111] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0112] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 150-160℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed entering the tower reactor is 100:1:20.

[0113] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After the reaction liquid in the tank is cooled to 120°C, it is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.21 kg / h), dichloroacetic acid (7.4 kg / h), and concentrated sulfuric acid (609.6 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 95.4%.

[0114] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.24 kg / h) and byproduct hydrogen chloride gas (4.2 kg / h).

[0115] Example 12

[0116] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0117] 1. 98% sulfuric acid is precisely metered and added through the feed inlet at the top of the heating tank; the sulfuric acid solution in the tank is heated to 170°C through the heating jacket, and then metered and pumped to the bottom of the tower reactor at a flow rate of 24.1 kg / h; at the same time, water is directly pumped into the bottom of the reaction tower using a feed pump, and the water feed rate is controlled at 1.7 kg / h.

[0118] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0119] 3. Tetrachloroethylene gas, 98% concentrated sulfuric acid, and water are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. Temperature is controlled by heat transfer oil in the outer jacket of the tower reactor, maintaining the reaction temperature within the tower at 160-170℃, thus allowing the hydrolysis reaction to proceed under atmospheric pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the feed to the tower reactor is 4:1:2.

[0120] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.13 kg / h), dichloroacetic acid (7.5 kg / h), and concentrated sulfuric acid (23.4 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 96.7%.

[0121] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.2 kg / h) and byproduct hydrogen chloride gas (4.3 kg / h).

[0122] Example 13

[0123] In this embodiment, the specific implementation steps for the continuous production of dichloroacetic acid are as follows:

[0124] 1. 98% sulfuric acid and water are precisely metered and added through two inlets at the top of the liquid heating tank. The sulfuric acid solution in the tank is heated to 180°C using a heating jacket, and then pumped to the bottom of the tower reactor using a flow meter. In this embodiment, the feed rates of 98% sulfuric acid and water are controlled at 60.3 kg / h and 2.1 kg / h, respectively.

[0125] 2. Liquid tetrachloroethylene is heated and vaporized in a tetrachloroethylene vaporization tank to form tetrachloroethylene gas at 160°C. This gas is then metered and sent to the bottom of the tower reactor. In this embodiment, the tetrachloroethylene feed rate is controlled at 10 kg / h.

[0126] 3. Tetrachloroethylene gas and concentrated sulfuric acid are fed from the bottom of the tower reactor and thoroughly mixed and contacted within the tower via a gas distributor. The temperature inside the tower is maintained at 180-190℃ by heat transfer oil control in the outer jacket of the tower reactor. The pressure interlock device at the top of the reaction tower is adjusted to maintain the pressure at 2-3 kPa (a slight positive pressure; at this temperature and pressure, tetrachloroethylene is in a slightly gaseous state, and the tower pressure fluctuates slightly due to the gas produced by the reaction), thus allowing the hydrolysis reaction to proceed under a slightly positive pressure. The molar ratio of sulfuric acid, tetrachloroethylene, and water in the raw materials entering the tower reactor is 10:1:3.

[0127] 4. As the reaction proceeds, the reaction liquid overflows from bottom to top in the tower reactor, and tetrachloroethylene, as a reactant, is gradually consumed along the height of the tower. The reaction liquid flows out through the overflow port at the top of the tower and enters the reaction liquid storage tank. After being cooled to 120°C, the reaction liquid in the tank is discharged from the bottom of the tank and sent to a distillation column for separation, recovering small amounts of tetrachloroethylene (0.21 kg / h), dichloroacetic acid (7.5 kg / h), and concentrated sulfuric acid (59.1 kg / h). Analytical calculations show that the yield of dichloroacetic acid is 95.3%.

[0128] 5. The light phase product is drawn out from the top of the reactor and separated by condensation to obtain unreacted tetrachloroethylene (0.26 kg / h) and byproduct hydrogen chloride gas (4.2 kg / h).

[0129] Comparative Example

[0130] In this embodiment, a batch reactor is used (due to excessively high pressure in batch reactors, the reaction scale is reduced proportionally for safety reasons). The specific implementation steps for dichloroacetic acid are as follows:

[0131] 1. In a high-pressure autoclave, add 2.4 kg of 98% sulfuric acid, 0.17 kg of water and 1 kg of tetrachloroethylene (the molar ratio of sulfuric acid, tetrachloroethylene and water is 4:1:2).

[0132] 2. Set the internal temperature to 160℃ to start heating and stirring the reaction. As the reaction proceeds, the pressure inside the reactor gradually increases.

[0133] 3. The heat preservation time is 5 hours, and the pressure rises to a maximum of 2.9 MPa; the temperature is then lowered after the reaction is completed.

[0134] 4. After the reaction is complete, cool down, open the pressure relief valve, release the gas produced in the reaction, and absorb it with water.

[0135] 5. The reaction solution was distilled under reduced pressure to recover 70g of tetrachloroethylene and separate 696g of dichloroacetic acid, with a yield of 89%.

[0136] From the perspective of batch reaction, the reaction effect is worse than that of tower reaction. The main reason is that the pressure gradually increases during the reaction. When the pressure is higher than 0.4 MPa, tetrachloroethylene is liquid at 160°C and is immiscible with sulfuric acid. The stirring and mass transfer effect is poor, and the reaction efficiency is reduced. At the same time, the pressure of batch reaction is much higher than that of atmospheric pressure tower reaction, which increases the reaction risk.

[0137] It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of this invention. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations.

Claims

1. A method for continuous production of dichloroacetic acid and dichloroacetyl chloride, characterized in that, include: Sulfuric acid, water, and tetrachloroethylene are continuously fed into a continuous flow reactor and heated for continuous reaction. Gas is discharged from the top of the continuous flow reactor, and liquid overflows from the top of the reactor. The gas and liquid phases are separated to obtain the products dichloroacetic acid and / or dichloroacetyl chloride. The ratio of products dichloroacetic acid and dichloroacetyl chloride is controlled by adjusting the feed rates of sulfuric acid, water, and tetrachloroethylene.

2. The method according to claim 1, characterized in that, The amount of sulfuric acid used in the feed entering the continuous flow reactor is calculated based on pure H2SO4. The molar ratio of sulfuric acid to tetrachloroethylene is 1 to 100:

1. The ratio of sulfuric acid to water is controlled so that the mass concentration of sulfuric acid in the reaction solution is greater than 80%.

3. The method according to claim 1, characterized in that, Concentrated sulfuric acid is heated to 130–200 °C and then sent to the bottom of the reactor.

4. The method according to claim 1, characterized in that, Liquid tetrachloroethylene is heated and vaporized, and the resulting tetrachloroethylene gas is sent to the bottom of the reactor.

5. The method according to claim 1, characterized in that, The water is either the water content of concentrated sulfuric acid itself, or a set amount of water is added to concentrated sulfuric acid according to a set dosage, heated, and then fed into the reactor together; or the water is separately metered according to a set ratio and fed into the reactor through an independent pipeline.

6. The method according to claim 1, characterized in that, The reaction temperature in the continuous reactor is controlled at 130–200°C; the reactor pressure is at atmospheric pressure or slightly positive pressure to keep tetrachloroethylene in a vaporized state.

7. The method according to claim 1, characterized in that, When all the water in the system is consumed, the reaction produces dichloroacetyl chloride, or a mixture of dichloroacetyl chloride and dichloroacetic acid; when the water in the system is not completely consumed, the product is dichloroacetic acid.

8. The method according to claim 1, characterized in that, The sulfuric acid obtained after product separation is recovered and recycled.

9. The method according to claim 1, characterized in that, The continuous flow reactor is any one of the following: a tower reactor, including a bottom gas distributor, internal packing, an external heating jacket, a bottom feed inlet, an upper discharge outlet, and a top gas outlet; or a tubular reactor, including an internal static mixer, an external heating jacket, a bottom feed inlet, an upper discharge outlet, and a top gas outlet.

10. The method according to claim 1, characterized in that, A distillation column is used to separate the liquid overflowing from the top of the continuous flow reactor. Concentrated sulfuric acid is discharged from the bottom of the distillation column and recycled. The top fraction of the distillation column is dichloroacetic acid. The gas discharged from the top of the continuous flow reactor is condensed in stages to obtain dichloroacetyl chloride and unreacted tetrachloroethylene, which are recycled as raw materials. Hydrogen chloride gas is sent to a spray tower for absorption with water, and the residual gas is discharged as tail gas.

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