Method and device for preparing 2-chloro-5-trichloromethylpyridine through fixed bed continuous gas phase catalytic chlorination
By using fixed-bed continuous gas phase catalysis method in 2-chloro-5-trichloromethylpyridine synthesis, the chlorination reaction was carried out in the fixed-bed reactor in two parts, and the chlorine gas and catalyst was premixed, which solved the problems of long synthesis cycle, low yield and low chlorine utilization in the prior art, and achieved an efficient and environmentally friendly chlorination reaction effect.
Patent Information
- Application Number
- CN202411876285.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-04-01
AI Technical Summary
In the prior art, the synthesis method of 2-chloro-5-trichloromethylpyridine has problems such as long cycles, low product yields, many side reactions, and low chlorine utilization, resulting in waste of resources and environmental pollution.
By using the fixed-bed continuous gas phase catalysis method, 2-chloro-5-methylpyridine is divided into two parts and premixed with chlorine and catalyst, and the chlorination reaction is carried out in the fixed-bed reactor, and a static mixer and a high-temperature catalyst are used to improve the reaction efficiency.
The yield of 2-chloro-5-trichloromethylpyridine is increased to more than 88%, the chlorination time is shortened to minute level, and the chlorine utilization rate is increased to 90%, reducing the cost of exhaust gas treatment and wastewater waste gas emissions.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of chemical pesticide preparation, and specifically relates to a method and a device for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination. Background Art
[0002] 2-Chloro-5-trichloromethylpyridine is an important organic chemical intermediate for the synthesis of pesticides and medicines. Its further derivation can also be used to synthesize the nitrogen heterocyclic pesticide intermediate 2,3-dichloro-5-trifluoromethylpyridine, further broadening its application range and value.
[0003] At present, the chlorination of pyridine is mainly carried out by direct chlorination of pyridine in industry, and the direct chlorination of pyridine is further divided into liquid phase chlorination of pyridine and gas phase chlorination of pyridine. The traditional synthesis of 2-chloro-5-trichloromethylpyridine mainly adopts the kettle liquid phase method, which produces chlorinated pyridine in a cycle of up to 40-90h, and the product yield is low, only 75%-80%. In addition, the kettle liquid phase method also has the problem of many side reactions, which not only reduces the purity of the target product, but also increases the difficulty of subsequent separation and purification. More seriously, the utilization rate of chlorine in the kettle liquid phase method during the chlorination process is extremely low, less than 60%. This not only causes a great waste of resources, but also brings the risk of environmental pollution.
[0004] Therefore, developing an efficient and environmentally friendly method for synthesizing 2-chloro-5-trichloromethylpyridine has become a technical problem that needs to be solved urgently. Summary of the invention
[0005] The purpose of the present invention is to provide a method and device for preparing 2-chloro-5-trichloromethylpyridine by continuous gas-phase catalytic chlorination in a fixed bed.
[0006] To achieve the above object, the technical solution adopted by the present invention is:
[0007] The invention discloses a method for preparing 2-chloro-5-trichloromethylpyridine by continuous gas-phase catalytic chlorination in a fixed bed. The raw material 2-chloro-5-methylpyridine is divided into two parts to participate in the reaction; one part of the 2-chloro-5-methylpyridine and chlorine are respectively introduced into a preheater for heating and mixed in a static mixer, and the other part of the 2-chloro-5-methylpyridine is mixed with a catalyst. The two mixtures are subjected to chlorination reaction in a fixed bed reactor to obtain 2-chloro-5-trichloromethylpyridine.
[0008] The gas generated by the chlorination reaction in the fixed bed reactor is all introduced into the quenching tower, and the liquid phase 2-chloro-5-trichloromethylpyridine in the quenching tower is collected.
[0009] The weight of 2-chloro-5-methylpyridine mixed with the catalyst accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction.
[0010] The gasification temperature of 2-chloro-5-methylpyridine after heating in a preheater is 60-200°C, the heating temperature of chlorine gas after heating in a preheater is 200-300°C, and the mixing temperature of 2-chloro-5-methylpyridine and the catalyst is 50-70°C.
[0011] The chlorination reaction temperature in the fixed bed reactor is controlled to be 300-500°C, preferably 350°C.
[0012] The residence time of the chlorination reaction in the fixed bed reactor is controlled to be 5-30s.
[0013] The amount of the catalyst used is 0.1% to 2% by weight of the 2-chloro-5-methylpyridine mixed with the catalyst.
[0014] The catalyst is one or more of phosphorus trichloride, thionyl chloride, azobisisobutyl cyanide, azobisisoheptanenitrile, benzoyl peroxide, and di-tert-butyl hydroperoxide.
[0015] The molar ratio of 2-chloro-5-methylpyridine to chlorine gas feed is 1:2.0-3.0, based on the total molar amount of 2-chloro-5-methylpyridine.
[0016] A device used in the method, comprising: a chlorine preheater (1), a 2-chloro-5-methylpyridine preheater (2), a static mixer (3), a fixed bed reactor (4), and a catalyst mixing tank (5);
[0017] The static mixer (3) is provided with a channel inlet I, a channel inlet II, and an outlet, wherein the channel inlet I is connected to the outlet of the 2-chloro-5-methylpyridine preheater (2), and the channel inlet II is connected to the outlet of the chlorine gas preheater (1);
[0018] The fixed bed reactor (4) is provided with an inlet A, an inlet B and an outlet, wherein the inlet A is connected to the outlet of the static mixer (3), the inlet B is connected to the outlet of the catalyst mixing tank (5), and the outlet outputs the product.
[0019] The fixed bed reactor (4) is 1 m long, and the reaction channel adopts a coil mode with an inner diameter of 25-40 mm.
[0020] Compared with the prior art, the advantages of the present invention are:
[0021] The present invention proposes a gas phase catalytic method for the first time, wherein a pyridine catalyst mixture and a pyridine chlorine mixture are introduced into a fixed bed reactor at the same time, the two mixtures are mixed more fully in the reactor, the catalyst can quickly initiate a reaction at a high temperature, the reaction cycle and the utilization rate of chlorine are improved, and at the same time, the gasification state reduces pipeline blockage.
[0022] The invention divides the raw material 2-chloro-5-methylpyridine into two parts, premixes them with chlorine and a catalyst respectively, and then a chlorination reaction occurs in a fixed bed reactor. A static mixer allows the gas phase 2-chloro-5-methyl and chlorine to be mixed more fully. The high temperature in the reactor causes the catalyst to be quickly gasified and initiates a reaction, thereby accelerating the chlorination reaction process. Gas phase catalysis increases the yield of 2-chloro-5-trichloromethylpyridine in the chlorination process to more than 88%, and the chlorination time is greatly shortened to the minute level. Due to the high completeness of the gas phase reaction, the utilization rate of chlorine can be increased to 90%, greatly reducing the cost of tail gas treatment and reducing the discharge of waste water and waste gas. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 The present invention is a process flow chart of 2-chloro-5-trichloromethylpyridine synthesis, wherein 1-chlorine preheater, 2-2-chloro-5-methylpyridine preheater, 3-static mixer, 4-fixed bed reactor, 5-catalyst mixing tank. DETAILED DESCRIPTION
[0024] The present invention is further described below in conjunction with embodiments.
[0025] The device used in the following embodiments of the present invention comprises: a chlorine gas preheater (1), a 2-chloro-5-methylpyridine preheater (2), a static mixer (3), a fixed bed reactor (4), and a catalyst mixing tank (5);
[0026] The static mixer (3) is provided with a channel inlet I, a channel inlet II, and an outlet, wherein the channel inlet I is connected to the outlet of the 2-chloro-5-methylpyridine preheater (2), and the channel inlet II is connected to the outlet of the chlorine gas preheater (1);
[0027] The fixed bed reactor (4) is provided with an inlet A, an inlet B and an outlet, wherein the inlet A is connected to the outlet of the static mixer (3), the inlet B is connected to the outlet of the catalyst mixing tank (5), and the outlet outputs the product.
[0028] The fixed bed reactor (4) is 1 m long, and the reaction channel adopts a coil mode with an inner diameter of 30 mm.
[0029] Example 1
[0030] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0031] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater and chlorine preheater at a ratio of 1:3.0 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0032] 2-chloro-5-methylpyridine and phosphorus trichloride are continuously added into a catalyst mixing tank 5 at a ratio of 1:0.001 (mass ratio) and mixed thoroughly at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction;
[0033] The above two mixtures are introduced into the fixed bed reactor 4 together, and catalytic reaction is carried out at 350° C. with a residence time of 20 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 90.5% and a chlorine utilization rate of 90%.
[0034] Example 2
[0035] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0036] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine preheater 1 at a ratio of 1:2.5 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0037] The raw materials 2-chloro-5-methylpyridine and azobisisobutyronitrile are continuously added into the catalyst mixing tank 5 at a ratio of 1:0.001 (mass ratio) and fully mixed at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction;
[0038] The above two mixtures are introduced into the fixed bed reactor 4 together, and catalytic reaction is carried out at 350° C. with a residence time of 17 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 92.8% and a chlorine utilization rate of 92%.
[0039] Example 3
[0040] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under nitrogen, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor to 350°C under nitrogen;
[0041] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine preheater 1 at a ratio of 1:2.3 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0042] The raw materials 2-chloro-5-methylpyridine and benzoyl peroxide are continuously added into the catalyst mixing tank 5 at a ratio of 1:0.01 (mass ratio) and fully mixed at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction;
[0043] The above two mixtures are introduced into the fixed bed reactor 4 together, and catalytic reaction is carried out at 350° C. with a residence time of 15 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 97.6% and a chlorine utilization rate of 93.4%.
[0044] Example 4
[0045] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0046] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine preheater 1 at a ratio of 1:2.2 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0047] The raw materials 2-chloro-5-methylpyridine and thionyl chloride are continuously added into a catalyst mixing tank 5 at a ratio of 1:0.015 (mass ratio) and fully mixed at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction; the above two mixtures are introduced into a fixed bed reactor 4 together, and a catalytic reaction is carried out at 350° C. with a residence time of 12 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 94.7%, and a chlorine utilization rate of 94.1%.
[0048] Example 5
[0049] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0050] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine preheater 1 at a ratio of 1:2.1 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0051] The raw materials 2-chloro-5-methylpyridine and di-tert-butyl hydroperoxide are continuously added into the catalyst mixing tank 5 at a ratio of 1:0.02 (mass ratio) and fully mixed at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction;
[0052] The above two mixtures are introduced into the fixed bed reactor 4 together, and catalytic reaction is carried out at 350° C. with a residence time of 10 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 89.7% and a chlorine utilization rate of 95.3%.
[0053] Example 6
[0054] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0055] 2-chloro-5-methylpyridine and chlorine are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine preheater 1 at a ratio of 1:3.0 mol, respectively, 2-chloro-5-methylpyridine is heated to 100° C., and chlorine is heated to 200° C., and the vaporized pyridine and chlorine are simultaneously introduced into the static mixer 3 for thorough mixing;
[0056] The raw materials 2-chloro-5-methylpyridine and phosphorus trichloride are continuously added into the catalyst mixing tank 5 at a ratio of 1:0.02 (mass ratio) and fully mixed at 60° C., wherein the amount of 2-chloro-5-methylpyridine accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction;
[0057] The above two mixtures were introduced into a fixed bed reactor together for catalytic reaction at 350° C. with a residence time of 10 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 90.5% and a chlorine utilization rate of 90.2%.
[0058] Comparative Example 1
[0059] All 2-chloro-5-methylpyridine is mixed with the catalyst and then reacted with chlorine in a fixed bed reactor, specifically:
[0060] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0061] The raw materials 2-chloro-5-methylpyridine and di-tert-butyl hydroperoxide were fully mixed at 60° C. in a ratio of 1:0.002 (mass ratio), based on the total weight of 2-chloro-5-methylpyridine involved in the reaction;
[0062] 2-chloro-5-methylpyridine, the catalyst mixture and chlorine gas are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and the chlorine preheater 1 in a ratio of 1:3.0 mol, respectively, the 2-chloro-5-methylpyridine mixture is heated to 100° C., and the chlorine gas is heated to 200° C., and the vaporized pyridine mixture and chlorine gas are simultaneously introduced into the static mixer 3 for thorough mixing;
[0063] The above mixture was introduced into a fixed bed reactor for catalytic reaction at 350° C. with a residence time of 10 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 83.5% and a chlorine utilization rate of 84%.
[0064] Comparative Example 2
[0065] All 2-chloro-5-methylpyridine and chlorine are preheated, gasified, mixed, and then reacted with a catalyst in a fixed bed reactor, specifically:
[0066] Preheat 2-chloro-5-methylpyridine preheater 2 to 100°C and chlorine preheater 1 to 200°C under nitrogen environment;
[0067] Di-tert-butyl hydroperoxide is added into a fixed bed reactor 4 and preheated to 350° C. under a nitrogen environment, wherein the weight of the di-tert-butyl hydroperoxide accounts for 0.2% of the total weight of the 2-chloro-5-methylpyridine involved in the reaction;
[0068] 2-chloro-5-methylpyridine and chlorine gas are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine gas preheater 1 at a ratio of 1:3.0 mol, respectively, and the 2-chloro-5-methylpyridine mixture is heated to 100° C. and the chlorine gas is heated to 200° C. The vaporized pyridine mixture and chlorine gas are simultaneously introduced into the static mixer 3 for thorough mixing;
[0069] The mixture was introduced into a fixed bed reactor for catalytic reaction at 350° C. with a residence time of 12 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 84.5% and a chlorine utilization rate of 87.3%.
[0070] Comparative Example 3
[0071] All 2-chloro-5-methylpyridine is mixed with the catalyst and then reacted with chlorine in a fixed bed reactor, specifically:
[0072] Preheat the 2-chloro-5-methylpyridine preheater 2 to 100°C under a nitrogen environment, preheat the chlorine preheater 1 to 200°C, and preheat the fixed bed reactor 4 to 350°C under a nitrogen environment;
[0073] The raw materials 2-chloro-5-methylpyridine and di-tert-butyl hydroperoxide were fully mixed at 60° C. in a ratio of 1:0.002 (mass ratio), based on the total weight of 2-chloro-5-methylpyridine involved in the reaction;
[0074] 2-chloro-5-methylpyridine, the catalyst mixture and chlorine gas are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and the chlorine preheater 1 in a ratio of 1:2.5 mol, respectively, the 2-chloro-5-methylpyridine mixture is heated to 100° C., and the chlorine gas is heated to 200° C., and the gasified pyridine mixture and chlorine gas are simultaneously introduced into the static mixer 3 for thorough mixing;
[0075] The above mixture was introduced into a fixed bed reactor for catalytic reaction at 350° C. with a residence time of 10 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 81.5% and a chlorine utilization rate of 84.7%.
[0076] Comparative Example 4
[0077] All 2-chloro-5-methylpyridine and chlorine are preheated, gasified, mixed, and then reacted with a catalyst in a fixed bed reactor, specifically:
[0078] Preheat 2-chloro-5-methylpyridine preheater 2 to 100°C and chlorine preheater 1 to 200°C under nitrogen environment;
[0079] Di-tert-butyl hydroperoxide is added into a fixed bed reactor 4 and preheated to 350° C. under a nitrogen environment, wherein the weight of the di-tert-butyl hydroperoxide accounts for 0.2% of the total weight of the 2-chloro-5-methylpyridine involved in the reaction;
[0080] 2-chloro-5-methylpyridine and chlorine gas are introduced into the preheated 2-chloro-5-methylpyridine preheater 2 and chlorine gas preheater 1 at a ratio of 1:2.5 mol, respectively, and the 2-chloro-5-methylpyridine mixture is heated to 100° C. and the chlorine gas is heated to 200° C. The vaporized pyridine mixture and chlorine gas are simultaneously introduced into the static mixer 3 for thorough mixing;
[0081] The mixture was introduced into a fixed bed reactor for catalytic reaction at 350° C. with a residence time of 10 seconds to obtain 2-chloro-5-trichloromethylpyridine with a content of 85.5% and a chlorine utilization rate of 88.1%.
[0082] As can be seen from the above-described embodiments and comparative examples, comparative example 1 is due to reacting all 2-chloro-5-picoline with catalyst in chlorine in fixed-bed reactor, and raw material and catalyst are easily catalyzed in advance in static mixer mixing process and side reaction occurs, resulting in reaction yield being lower, and by-product is more.Comparative example 2 is due to reacting all 2-chloro-5-picoline with chlorine in fixed-bed reactor after preheating gasification mixing, and catalyst is easily overflowed from fixed-bed channel outlet with mixed gas after being heated and gasified, and cannot be catalyzed continuously and uniformly, resulting in reaction residence time being longer, and reaction yield being lower.Therefore, raw material 2-chloro-5-picoline of the present invention is divided into two parts, and after being premixed with chlorine and catalyst respectively, chlorination reaction occurs in fixed-bed reactor again, and static mixer makes gas phase pyridine and chlorine mix more fully, and high temperature in reactor makes catalyst gasify quickly and initiate reaction, accelerates chlorination reaction process. Gas phase catalysis increases the yield of 2-chloro-5-trichloromethylpyridine in the chlorination process to more than 88%, and at the same time greatly shortens the chlorination time to minutes. Due to the high completeness of the gas phase reaction, the chlorine utilization rate can be increased to 90%, greatly reducing the cost of tail gas treatment and the emission of wastewater and exhaust gas.
Claims
1. A method for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination, characterized in that: The raw material 2-chloro-5-methylpyridine is divided into two parts to participate in the reaction; one part of the 2-chloro-5-methylpyridine and chlorine are respectively introduced into a preheater for heating and mixed in a static mixer, and the other part of the 2-chloro-5-methylpyridine is mixed with a catalyst, and the above two mixtures undergo chlorination reaction in a fixed bed reactor to obtain 2-chloro-5-trichloromethylpyridine.
2. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed bed continuous gas phase catalytic chlorination as claimed in claim 1, characterized in that: The gas generated by the chlorination reaction in the fixed bed reactor is all introduced into the quenching tower, and the liquid phase 2-chloro-5-trichloromethylpyridine in the quenching tower is collected.
3. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed bed continuous gas phase catalytic chlorination as claimed in claim 1, characterized in that: The weight of 2-chloro-5-methylpyridine mixed with the catalyst accounts for 10% of the total weight of 2-chloro-5-methylpyridine participating in the reaction.
4. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed bed continuous gas phase catalytic chlorination as claimed in claim 1, characterized in that: The gasification temperature of 2-chloro-5-methylpyridine is 60-200°C after being heated by a preheater, and the temperature of chlorine gas is 200-300°C after being heated by a preheater.
5. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination as claimed in claim 1, characterized in that: The chlorination reaction temperature in the fixed bed reactor is controlled to be 300-500°C, preferably 350°C.
6. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination as claimed in claim 1, characterized in that: The residence time of the chlorination reaction in the fixed bed reactor is controlled to be 5-30s.
7. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed bed continuous gas phase catalytic chlorination as claimed in claim 1, characterized in that: The amount of the catalyst used is 0.1% to 2% by weight of the 2-chloro-5-methylpyridine mixed with the catalyst.
8. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination as claimed in claim 7, characterized in that: The catalyst is one or more of phosphorus trichloride, thionyl chloride, azobisisobutyl cyanide, azobisisoheptanenitrile, benzoyl peroxide, and di-tert-butyl hydroperoxide.
9. The method for preparing 2-chloro-5-trichloromethylpyridine by fixed-bed continuous gas-phase catalytic chlorination as claimed in claim 1, characterized in that: The molar ratio of 2-chloro-5-methylpyridine to chlorine gas feed is 1:2.0-3.0, based on the total molar amount of 2-chloro-5-methylpyridine.
10. An apparatus used in the method according to claim 1, characterized in that: The device comprises: a chlorine gas preheater (1), a 2-chloro-5-methylpyridine preheater (2), a static mixer (3), a fixed bed reactor (4), and a catalyst mixing tank (5); The static mixer (3) is provided with a channel inlet I, a channel inlet II, and an outlet, wherein the channel inlet I is connected to the outlet of the 2-chloro-5-methylpyridine preheater (2), and the channel inlet II is connected to the outlet of the chlorine gas preheater (1); The fixed bed reactor (4) is provided with an inlet A, an inlet B and an outlet, wherein the inlet A is connected to the outlet of the static mixer (3), the inlet B is connected to the outlet of the catalyst mixing tank (5), and the outlet outputs the product.