CN101456788B - Method and equipment for preparing difluorochloroethane by photocatalysis - Google Patents

Abstract

The invention discloses a method for preparing difluoromonochloroethane by a photocatalytic reactor, comprising: mixing chlorine and difluoroethane and then entering a photocatalytic reactor to react to generate a crude difluoromonochloroethane; and then washing with water, washing with alkali, degassing, rectifying, and drying to obtain a finished difluoromonochloroethane. The photocatalytic reactor used in the reaction comprises a cylinder with a heat exchange jacket on the outer wall and an inner wall lined with an anti-corrosion material, wherein the top and bottom of the cylinder are provided with a material port, and the top of the cylinder is provided with a spray device, and the part below the spray device is assembled by connecting four sections up and down, and each tower section is provided with four ultraviolet lamps arranged up and down; three temperature measuring ports arranged up and down and a liquid difluoroethane feed port. The method of the invention has a high single-pass conversion rate, few by-products, and a selectivity of the reaction process higher than 95%. The photocatalytic reactor equipment occupies a small area, has a compact structure, and has less material backmixing.

Description

Method and equipment for preparing difluorochloroethane by photocatalysis

technical field

The invention relates to equipment and a production process for producing difluorochloroethane by photocatalysis. the

Background technique

Chlorodifluoroethane (CH ₃ CF ₂ Cl, commonly known as 142b) is a colorless, odorless, anesthetic gas with a boiling point of -0.96°C. It is combustible in air and can be used as a refrigerant and aerosol. Because of its small damage to the ozone layer, it is a substitute for Freon. The production process of difluoro-chloro-alkane is as follows:

That is, after difluoroethane is mixed with equimolar chlorine gas, it undergoes photocatalytic chemical reaction to generate the target difluorochloroethane and hydrogen chloride, and the mixed gas is removed from hydrogen chloride and purified to obtain a high-purity product. Since chlorine is a strong oxidizing agent, if the reaction time is long, more by-products will be produced in the reaction process, which will affect the yield of the target substance. Therefore, certain measures need to be taken to increase the single-pass conversion rate. The patent document with the publication number CN1556083A discloses a tank-type photocatalytic reactor for producing difluorochloroethane. It consists of multiple reactors in series to reduce the residence time of materials in the tank. Obviously, the back-mixing of materials in the tank photochemical reactor is serious and there are many by-products. Moreover, the equipment occupies a large area. If there is a problem with one equipment, all production must be stopped. Obviously not a good way. In addition, the current production process adopted in China often consumes high energy consumption, and the process has not been optimized reasonably. the

Contents of the invention

The invention provides a method for preparing difluoro-chloroethane with high single-pass conversion rate, few by-products, high selectivity of reaction process, convenient equipment maintenance and low failure rate. the

A kind of photocatalytic reactor prepares difluoro-chloroethane method, comprises the following steps:

(1) Liquid chlorine gas and difluoroethane are gasified in the gasifier and mixed in the mixer. The inner wall of the mixer is lined with polytetrafluoroethylene, and the upper part has porcelain filler;

(2) The mixed gas enters the photocatalytic reactor, the pressure inside the photocatalytic reactor is 0.1-0.12MPa, and the temperature is 80-100°C; in the entering gas, the molar flow ratio of chlorine gas and difluoroethane is 1:1;

The flow velocity of the mixed gas of chlorine and difluoroethane in the photocatalytic reactor is 0.085-0.09m/s, and the reaction time is 85-105s. the

(3) After the reaction gas is washed with water and alkali to absorb unreacted chlorine gas and hydrogen chloride generated by the reaction, the finished product is obtained after degassing, rectification and drying. the

In step (3), the concrete operation of the process of degassing, rectification, drying is:

A. The gas enters the gas cabinet after being washed with water and alkali to remove unreacted chlorine and hydrogen chloride generated by the reaction. The pressure of the gas cabinet is 104 ~ 106Kpa, and the water flow and lye flow are adjusted according to the production requirements. The concentration of lye is 20-25%

B. The gas in the gas cabinet enters the middle tank after being compressed and cooled. the

C. The unreacted difluoroethane is removed from the material in the degassing tower. The kettle temperature of No. 1 degassing tower is 55～60℃, the kettle pressure: 1.1-1.25Mpa, the top temperature: 50℃, the top pressure: 1.15Mpa. No. 2 degassing tower kettle temperature 45-55℃, kettle pressure: 0.9-0.95Mpa, top temperature 40-40.5, top pressure: 0.89-0.92Mpa

D. The top product is condensed and sent to the recovery tank, and then enters the photochemical reactor to participate in the reaction. The bottom product enters the rectification column. the

E. Rectification column kettle temperature 53-63℃, kettle pressure: 0.65-0.75Mpa, top temperature 49.5-50.5, top pressure: 0.7Mpa. the

F. The top product of the rectification tower is condensed and dried to become the finished difluorochloroethane, and the desiccant used for drying is molecular sieve. the

The invention also provides a photocatalytic reactor for preparing difluoro-chloroethane with small footprint, compact structure, less material back-mixing and high single-pass conversion rate. the

A photocatalytic reactor for preparing difluoro-chloroethane, comprising a cylinder with a heat exchange jacket on the outer wall and an anti-corrosion material on the inner wall, the top and bottom of the cylinder are provided with material ports, and the top of the cylinder is equipped with a spray The shower device, the lower part of the spray device is composed of four tower sections connected up and down, and each tower section is equipped with four ultraviolet lamps arranged up and down; three temperature measuring ports arranged up and down and a liquid difluoroethane inlet feed port. the

The liquid difluoroethane feed inlet is provided with a feed pipe whose end is a shower head and extends into the cylinder body. The material of the feed pipe whose end is a shower head is polytetrafluoroethylene. When it is high, the tower section will automatically spray liquid difluoroethane to cool down, which can not only absorb part of the reaction heat, but also make the temperature drop rapidly. And excess difluoroethane can improve the selectivity of the reaction. the

The spray device at the top of the cylinder is made of polytetrafluoroethylene. the

The anti-corrosion material lining the inner wall can be commonly used chemically inert materials such as lining polytetrafluoroethylene. the

The outer surface of the ultraviolet lamp is covered with a protective quartz glass tube, and the thickness of the quartz glass tube is 3-4mm. The quartz glass tube penetrates the cylinder body radially, one end of the quartz glass tube is closed and the other end is open, the ultraviolet lamp is put into or taken out of the quartz glass tube from the open end, and the contact part between the quartz glass tube and the cylinder body is sealed with gas and liquid, To ensure that the material does not leak. the

The wavelength of ultraviolet light selected by the ultraviolet lamp is 300-400nm, the center wavelength is 365nm, and the ultraviolet lamp is a single-ended lead wire. the

The four ultraviolet lamps on each tower section are arranged in parallel, and the ultraviolet lamps of any two tower sections among the four tower sections are not parallel to each other, and the included angle is 45 or 90 degrees. The staggered arrangement of ultraviolet lamps among the four tower sections is more conducive to the uniformity of light irradiation. the

The four tower sections mentioned above are connected by flanges between adjacent tower sections. the

The three temperature measuring ports arranged up and down in each tower section are basically located in the upper, middle and lower parts of the tower section, which is convenient for precise control of the reaction temperature of each part in the tower section. the

A small amount of liquid difluoroethane can be sprayed into each section of the photocatalytic reactor to prepare difluorochloroethane by using the photocatalytic reactor of the present invention, and the difluoroethane is both a cooling medium and a reactant. The cooling water in the jacket is an auxiliary means of temperature control. This method not only has a high heat utilization rate, but also improves the conversion rate of materials. The material after the compressor is used to preheat the difluoroethane, which improves the heat utilization efficiency. the

The method of the invention has high single-pass conversion rate, few by-products, selectivity of the reaction process higher than 95%, small footprint of photocatalytic reactor equipment, compact structure, and less back-mixing of materials. the

Description of drawings

Fig. 1 is a photocatalytic reactor structure schematic diagram of the present invention (only shows a tower section in the figure, and all the other three sections are omitted);

Fig. 2 is the top view structure schematic diagram of photocatalytic reactor of the present invention;

Fig. 3 is the flow chart that photocatalytic reactor of the present invention prepares difluoro-chloroethane, and among the figure label also with following:

1 photocatalytic reactor; 2 water washing tower; 3 alkali washing tower;

4 No. 1 degassing tower; 5 No. 2 degassing tower; 6 Rectification tower;

7 Difluoroethane storage tank; 8 Chlorine gas storage tank; 9 Mixer;

10 heat exchanger; 11 gas cabinet; 12 condensing cooler;

13 compressors. the

Fig. 4 is a schematic diagram of the photocatalytic reactor of the present invention when adjacent tower sections are matched. the

Detailed ways

Example 1

Referring to FIG. 1 , the photocatalytic reactor of the present invention includes a cylinder with a heat exchange jacket 20 on the outer wall and a polytetrafluoroethylene-lined inner wall. the

The top of the cylinder is provided with a material outlet 21, the bottom of the cylinder is provided with a material inlet 22, and the top of the cylinder is provided with a spray device 23 made of polytetrafluoroethylene. The part below the spray device 23 is assembled by connecting up and down with four tower sections (for convenience, Fig. 1 only draws a tower section, and the other three sections are omitted), in Fig. 1, the tower section 24 is provided with four ultraviolet lamps arranged up and down, and the ultraviolet lamp is covered with a protective quartz glass tube, as shown in Fig. The quartz glass tube 25, the quartz glass tube 26, the quartz glass tube 27 and the quartz glass tube 28 in. the

The reactor has four tower sections, each of which is 2m high, and the inner diameter of the reactor is 1m. the

The thickness of the quartz glass tube is 3mm. The quartz glass tube runs through the cylinder along the radial direction. One end of the quartz glass tube is closed and the other end is open. The ultraviolet lamp is put into or taken out of the quartz glass tube from the open end. The contact part between the quartz glass tube and the cylinder is sealed by gas and liquid to ensure the Do not leak. the

The wavelength of the ultraviolet light placed in the quartz glass tube 25, the quartz glass tube 26, the quartz glass tube 27 and the quartz glass tube 28 is 300-400nm, the central wavelength is 365nm, and the ultraviolet lamp is a single-ended lead wire. the

The tower section 24 is provided with three temperature measuring ports arranged up and down, namely the temperature measuring port 29, the temperature measuring port 30 and the temperature measuring port 31. The three temperature measuring ports are basically located at the upper, middle and lower parts of the tower section 24, which is convenient Precisely control the reaction temperature of each part in the tower section. the

The tower section 24 is provided with a liquid difluoroethane feed port, whose position height is basically the same as the temperature measuring port 30, since it is on the other side of the tower section 24 in Fig. 1, it is not shown in the figure. the

The liquid difluoroethane feed inlet is provided with a feed pipe with a shower nozzle at the end extending into the tower section 24, and the feed pipe with a shower nozzle at the end is made of polytetrafluoroethylene. When the reaction temperature of the tower section 24 is high , it will automatically spray liquid difluoroethane to cool down, which can not only absorb part of the reaction heat, but also make the temperature drop rapidly. And excess difluoroethane can improve the selectivity of the reaction. the

Referring to Figure 2, the ultraviolet lamps in each tower section are arranged in parallel, but the ultraviolet lamps of any two tower sections among the four tower sections are not parallel to each other, and the included angle is 45 or 90 degrees. The staggered arrangement of ultraviolet lamps among the four tower sections is more conducive to the uniformity of light irradiation. the

Referring to Figure 4, when the four tower sections are connected to each other, the adjacent tower sections are connected by flanges. the

Referring to Fig. 3, when utilizing photocatalytic reactor of the present invention to prepare difluoro-chloroethane, difluoroethane enters heat exchanger 10 after being discharged from difluoroethane storage tank 7, then enters mixer 9 and comes from chlorine storage tank After the chlorine gas of 8 is mixed, the mixed gas enters the photocatalytic reactor 1 for photocatalytic reaction. the

After the reaction, the mixed gas enters the gas cabinet 11 after being washed by the water washing tower 2 and the alkali washing tower 3, and then compressed by the compressor 13, and then enters the condensing cooler 12 to be cooled to become a liquid, and then enters the No. 1 degassing tower 4 and the No. 2 degassing tower No. degassing tower 5 removes difluoroethane, and the difluoroethane gas taken out of No. 1 degassing tower 4 and No. 2 degassing tower 5 tops returns to mixer 9 for recycling, and the product after degassing enters rectifying tower 6 Carry out rectification to obtain difluoro-chloroethane with higher purity. the

According to the above process to prepare difluoro-chloroethane, the molar ratio of chlorine and difluoroethane is 1:1. After gasification, it is mixed with a mixer, heated to 40°C and entered into a photocatalytic reactor for reaction. Chlorine and difluoro The flow rate of the mixed gas of ethane in the photochemical reactor is 0.09m/s, the reaction time is 85s, the pressure inside the photocatalytic reactor is 0.1MPa, and the temperature is 80°C; during the reaction, part of the liquid difluoroethane is sprayed into each tower section , The amount of material sprayed into the tower is 15% of the amount of difluoroethane entering the mixer. The flow rate of cold water sprayed into the top of the reactor is 2m ³ /h.

Samples were taken from the top of the photocatalytic reactor, washed with alkali, dried, and then analyzed by gas chromatography. The components were difluoromonochloroethane: 85.95%, difluoromonoalkane: 12.68%, unknown component 1: 0.74%, unknown Component 2: 0.5%, others: 0.13%, indicating that the method and reactor of the present invention have a high single-pass conversion rate and few by-products. the

The gas phase product at the top of the photocatalytic reactor is washed with water and alkali to remove unreacted chlorine and hydrogen chloride generated by the reaction, and then degassed, rectified and dried to obtain a finished product with a purity of more than 99.99%. the

Example 2:

Prepare difluoro-chloroethane according to the process and equipment of the embodiment. The molar ratio of chlorine gas and difluoroethane is 1:1. After gasification, it is mixed with a mixer, heated to 40°C and entered into a photocatalytic reactor for reaction. The flow rate of the mixed gas of chlorine and difluoroethane in the photochemical reactor is 0.085m/s, and the reaction time is 100s. Difluoroethane, the amount of material sprayed into the tower is 10% of the amount of difluoroethane entering the mixer. The flow rate of cold water sprayed into the top of the reactor is 2m ³ /h.

Samples were taken from the top of the photocatalytic reactor, washed with alkali, dried, and then analyzed by gas chromatography. The components were difluorochloroethane: 89.55%, difluorooxane: 8.08%, unknown component 1: 1.34%, Unknown component 2: 0.8%, others: 0.23%, indicating that the method and reactor of the present invention have a high single-pass conversion rate and few by-products. the

The gas phase product at the top of the photocatalytic reactor is washed with water and alkali to remove unreacted chlorine and hydrogen chloride generated by the reaction, and then degassed, rectified and dried to obtain a finished product with a purity of more than 99.99%. the

Example 3:

Prepare difluoro-chloroethane according to the process and equipment of the embodiment. The molar ratio of chlorine and difluoroethane is 1:1. After gasification, it is mixed with a mixer, heated to 55°C and entered into a photocatalytic reactor for reaction. The flow rate of the mixed gas of chlorine and difluoroethane in the photochemical reactor is 0.085m/s, and the reaction time is 90s. Difluoroethane, the amount of material sprayed into the tower is 10% of the amount of difluoroethane entering the mixer. The flow rate of cold water sprayed into the top of the reactor is 2m ³ /h.

Samples were taken from the top of the photocatalytic reactor, washed with alkali, dried, and then analyzed by gas chromatography. The components were difluoro-chloroethane: 85.95%, difluoro-alkane: 10.64%, unknown component 1: 1.74%, Unknown component 2: 1.67%, indicating that the method and reactor of the present invention have a high single-pass conversion rate and few by-products. the

The gas phase product at the top of the photocatalytic reactor is washed with water and alkali to remove unreacted chlorine and hydrogen chloride generated by the reaction, and then degassed, rectified and dried to obtain a finished product with a purity of more than 99.99%. the

Claims (7)

1. a photo catalysis reactor prepares difluoro monochlorethane method, may further comprise the steps:

(1) chlorine and C2H4F2 C2H4F2 are through mixing the laggard photo catalysis reactor of going into, and the molar flow ratio of chlorine and C2H4F2 C2H4F2 is 1: 1;

(2) chlorine and C2H4F2 C2H4F2 react in photo catalysis reactor and generate difluoro monochlorethane bullion; Described photo catalysis reactor; Comprise the cylindrical shell of outer wall belt heat exchange jacket, interior wall liner impregnating material, it is characterized in that: described cylinder top and bottom are provided with the material mouth, and the cylindrical shell inner top is provided with spray equipment; Spray equipment is saved to be communicated with up and down by four sections towers with the lower section and assembles, and each tower joint is equipped with four uv lamps arranging up and down; Three temperature-measuring ports and a liquid C2H4F2 C2H4F2 opening for feed of arranging up and down; The photo catalysis reactor internal pressure is 0.1MPa during reaction, 80 ℃ of temperature, and the liquid C2H4F2 C2H4F2 opening for feed of each tower joint sprays into the operative liquid C2H4F2 C2H4F2 again, and the inventory that sprays in the tower is 15% of the C2H4F2 C2H4F2 amount that gets into mixing tank;

(3) difluoro monochlorethane bullion obtains finished product difluoro monochlorethane after washing, alkali cleaning, the degassing, rectifying, drying.

2. a photo catalysis reactor prepares difluoro monochlorethane method, may further comprise the steps:

(1) chlorine and C2H4F2 C2H4F2 are through mixing the laggard photo catalysis reactor of going into, and the molar flow ratio of chlorine and C2H4F2 C2H4F2 is 1: 1;

(2) chlorine and C2H4F2 C2H4F2 react in photo catalysis reactor and generate difluoro monochlorethane bullion; Described photo catalysis reactor; Comprise the cylindrical shell of outer wall belt heat exchange jacket, interior wall liner impregnating material, it is characterized in that: described cylinder top and bottom are provided with the material mouth, and the cylindrical shell inner top is provided with spray equipment; Spray equipment is saved to be communicated with up and down by four sections towers with the lower section and assembles, and each tower joint is equipped with four uv lamps arranging up and down; Three temperature-measuring ports and a liquid C2H4F2 C2H4F2 opening for feed of arranging up and down; The photo catalysis reactor internal pressure is 0.12MPa during reaction, 100 ℃ of temperature, and the liquid C2H4F2 C2H4F2 opening for feed of each tower joint sprays into the operative liquid C2H4F2 C2H4F2 again, and the inventory that sprays in the tower is 10% of the C2H4F2 C2H4F2 amount that gets into mixing tank;

(3) difluoro monochlorethane bullion obtains finished product difluoro monochlorethane after washing, alkali cleaning, the degassing, rectifying, drying.

3. a photo catalysis reactor prepares difluoro monochlorethane method, may further comprise the steps:

(1) chlorine and C2H4F2 C2H4F2 are through mixing the laggard photo catalysis reactor of going into, and the molar flow ratio of chlorine and C2H4F2 C2H4F2 is 1: 1;

(2) chlorine and C2H4F2 C2H4F2 react in photo catalysis reactor and generate difluoro monochlorethane bullion; Described photo catalysis reactor; Comprise the cylindrical shell of outer wall belt heat exchange jacket, interior wall liner impregnating material, it is characterized in that: described cylinder top and bottom are provided with the material mouth, and the cylindrical shell inner top is provided with spray equipment; Spray equipment is saved to be communicated with up and down by four sections towers with the lower section and assembles, and each tower joint is equipped with four uv lamps arranging up and down; Three temperature-measuring ports and a liquid C2H4F2 C2H4F2 opening for feed of arranging up and down; The photo catalysis reactor internal pressure is 0.1MPa during reaction, 100 ℃ of temperature, and the liquid C2H4F2 C2H4F2 opening for feed of each tower joint sprays into the operative liquid C2H4F2 C2H4F2 again, and the inventory that sprays in the tower is 10% of the C2H4F2 C2H4F2 amount that gets into mixing tank;

(3) difluoro monochlorethane bullion obtains finished product difluoro monochlorethane after washing, alkali cleaning, the degassing, rectifying, drying.

4. photo catalysis reactor for preparing the difluoro monochlorethane; The cylindrical shell that comprises outer wall belt heat exchange jacket, interior wall liner impregnating material; It is characterized in that: described cylinder top and bottom are provided with the material mouth; The cylindrical shell inner top is provided with spray equipment, and spray equipment is saved to be communicated with up and down by four sections towers with the lower section and assembles, and each tower joint is equipped with four uv lamps arranging up and down; Three temperature-measuring ports and a liquid C2H4F2 C2H4F2 opening for feed of arranging up and down; Described liquid C2H4F2 C2H4F2 opening for feed place is provided with end and stretches in the cylindrical shell for the feed-pipe of seedpod of the lotus shower nozzle; The feed-pipe material is a tetrafluoroethylene, and the selected ultraviolet light wave wavelength of described uv lamp is 300～400nm.

5. photo catalysis reactor as claimed in claim 4 is characterized in that: the spray equipment material of described cylindrical shell inner top is a tetrafluoroethylene.

6. photo catalysis reactor as claimed in claim 4; It is characterized in that: described uv lamp outside is with the quartz glass tube that shields, silica glass tube thickness 3～4mm, and described quartz glass tube radially runs through cylindrical shell along cylindrical shell; The sealing of quartz glass tube one end, an end opening.

7. photo catalysis reactor as claimed in claim 4 is characterized in that: four uv lamps on each tower joint are arranged in parallel, in four towers joints any two towers joint uv lamp be not parallel to each other, angle is 45 or 90 degree.

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