CN107325046B - Liquid phase chlorination production process and device for tetrachloro-2-cyanopyridine - Google Patents
Liquid phase chlorination production process and device for tetrachloro-2-cyanopyridine Download PDFInfo
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Abstract
The invention relates to a production process of tetrachloro-2-cyanopyridine, which is characterized in that liquid 2-cyanopyridine is preheated and then enters a gas-liquid reinforced pre-reactor to be pre-reacted with chlorine under the action of a pre-reaction catalyst; after the reaction, the gas-phase material enters an absorption device to be absorbed after being washed. The liquid phase material after pre-reaction enters a gas-liquid reinforced main reactor and is subjected to chlorination reaction with chlorine under the action of a main reaction catalyst. And introducing the liquid-phase material discharged from the main reactor into an evaporator for separation to finally obtain tetrachloro-2-cyanopyridine solid. The process shortens the production flow of tetrachloro-2-cyanopyridine, and improves the safety and operability of the production process; the utilization rate of chlorine is improved, and the load of tail gas treatment is reduced; the chlorination reaction temperature is reduced, so that the problem that the catalyst is easy to coke is solved, and the service life of the catalyst is prolonged; the yield and the content of the product are improved, the difficulty of product purification is reduced, the reaction temperature is low, and the energy consumption is low; is green and environment-friendly.
Description
Technical Field
The invention relates to a reaction process and a device for liquid phase chlorination of tetrachloro-2-cyanopyridine, belonging to the technical field of fine chemical engineering.
Background
Pyridine chlorides have high biological activity and are widely used as pesticides, medicines and dye synthesis intermediates. The tetrachloro-2-cyanopyridine is used as raw material to develop and synthesize a series of pesticides such as insecticides and herbicides, which generally have the advantages of small dosage, high selectivity, low toxicity, small residual quantity, short residual period and the like and have important significance for soil sustainable utilization, agricultural development and environmental protection. In recent years, the development, application range and demand of downstream products using tetrachloro-2-cyanopyridine as a raw material have rapidly increased.
At present, the production method of tetrachloro-2-cyanopyridine mainly uses 2-cyanopyridine and chlorine as raw materials and produces the tetrachloro-2-cyanopyridine through gas phase chlorination reaction under the action of a catalyst. European patent EP182111 discloses a method for preparing tetrachloro-2-cyanopyridine by reacting 2-cyanopyridine as a raw material with chlorine in a fluidized bed reactor filled with activated carbon, wherein the reaction temperature of the method is up to 500 ℃, the reaction in the fluidized bed is not easy to control, the high-temperature polymerization phenomenon is easy to occur, the generated polymer can be adhered to the surface of the catalyst, so that the coking of the surface of the catalyst is caused, the activity of the catalyst is reduced, and the service life of the catalyst is greatly shortened. The Chinese patent CN 100579964C uses activated carbon soaked in ferric chloride hydrochloric acid solution as a catalyst and the Chinese patent CN 102875461A uses coconut shell activated carbon loaded rare earth metal chloride as a catalyst, and both use 2-cyanopyridine and chlorine as raw materials to synthesize tetrachloro-2-cyanopyridine through gas phase chlorination, wherein the gas phase chlorination reaction temperature is as high as 240-320 ℃, the catalyst is easy to inactivate, the service life is short, and the yield of the product is low. Meanwhile, the reaction heat of the gas phase chlorination reaction is large, the reactor is easy to fly warm, the process safety is poor, and accidents such as leakage and the like are easy to happen.
Disclosure of Invention
Aiming at the problems of the existing gas phase chlorination process, the invention provides a new process and a new device which can overcome the defects of the gas phase chlorination method, namely a new liquid phase chlorination process is adopted.
In order to realize the technical purpose, the invention provides a liquid phase chlorination reaction process of tetrachloro-2-cyanopyridine, which comprises the following steps:
(1) Preheating liquid 2-cyanopyridine, feeding the preheated liquid 2-cyanopyridine into a gas-liquid reinforced pre-reactor, and pre-reacting the preheated liquid 2-cyanopyridine with chlorine under the action of a pre-reaction catalyst; after the reaction, the gas-phase material enters an absorption device to be absorbed after being washed;
(2) The liquid phase material after the pre-reaction enters a gas-liquid reinforced main reactor and is subjected to chlorination reaction with chlorine under the action of a main reaction catalyst;
(3) The liquid phase material after the main reaction enters an evaporator for separation to obtain tetrachloro-2-cyanopyridine solid, and the unreacted raw material and the by-product return to the pre-reactor for continuous reaction.
The pre-reactor in the step (1) or the main reactor in the step (2) comprises a microbubble generator and a gas-liquid intensified reaction tower.
The preheating temperature in the step (1) is 30-170 ℃.
The average residence time of the pre-reaction in the pre-reactor in the step (1) is 8 to 12h; the reaction temperature is controlled to be 170 to 200 ℃; the reaction pressure is 0.3 to 1 atm.
The chlorination reaction temperature in the step (2) is 200-240 ℃; the reaction pressure is 1.2 to 3.0 atm; the reaction time is 8 to 12h.
The pre-reaction catalyst described in step (1) is FeCl supported 5% 3 The activated carbon of (1); the main reaction catalyst described in step (2) is FeCl supported with 5% by weight 3 The activated carbon of (1).
The chlorine gas in the step (1) comes from gas-phase materials discharged from the main reactor.
The washing in the step (1) is carried out by washing with liquid 2-cyanopyridine at the temperature of 30-160 ℃ in a washing tower.
The absorption in the step (1) is absorption in an absorption tower by alkali liquor.
The evaporator in the step (3) is a wiped film evaporator.
The technical purpose of the invention is also to provide a reactor for the reaction process, which comprises a liquid phase raw material inlet, a gas phase raw material inlet, a product outlet, a pre-reactor, a main reactor, an evaporator, a washing tower and an absorption tower;
the pre-reactor comprises a first gas-liquid reinforced reaction tower, a first micro-bubble generator and a first circulating pump; the first gas-liquid intensified reactor comprises a first circulating outlet, a first gas-phase outlet and a first liquid-phase outlet;
the liquid phase raw material inlet is connected with the first gas-liquid intensified reaction tower; the first gas phase outlet is respectively connected with the first micro-bubble generator and the washing tower through a tee joint; the first circulating outlet is connected with the first microbubble generator through a first circulating pump; the outlet of the first microbubble generator is connected with the first gas-liquid intensified reaction tower; a pre-reaction catalyst is arranged in the first microbubble generator;
the main reactor comprises a second gas-liquid intensified reaction tower, a second microbubble generator and a second circulating pump; the second gas-liquid intensified reactor comprises a second circulating outlet, a second gas-phase outlet and a second liquid-phase outlet;
the gas-phase raw material inlet is respectively connected with the second gas-liquid intensified reaction tower and the second microbubble generator through a tee; the first liquid phase outlet is connected with a second gas-liquid intensified reaction tower through a pump; the second gas phase outlet is respectively connected with the first micro-bubble reactor and the second micro-bubble reactor through a tee joint; the second circulating outlet is connected with a second microbubble generator through a second circulating pump; the outlet of the second microbubble generator is connected with the second gas-liquid intensified reaction tower; a main reaction catalyst is arranged in the second micro-bubble generator; the second liquid phase outlet is connected with an evaporator;
a light component outlet of the evaporator is connected with the first gas-liquid intensified reaction tower, and a heavy component outlet of the evaporator is connected with the product outlet;
and the gas phase outlet of the washing tower is connected with the absorption tower.
The evaporator is a wiped film evaporator.
A catalyst is arranged in the first micro-bubble reactor through a catalyst cage; and a catalyst is arranged in the second micro-bubble reactor through a catalyst cage.
The process and the device have the advantages that:
1. the two-stage series connection of the gas-liquid reinforced reaction tower replaces a gas-solid fluidized bed or a fixed bed reactor in the prior art, so that the production flow of tetrachloro-2-cyanopyridine is shortened, and the safety and operability of the production process are improved;
2. the utilization rate of chlorine is improved, and the load of tail gas treatment is reduced;
3. the chlorination reaction temperature is reduced, so that the problem that the catalyst is easy to coke is solved, and the service life of the catalyst is prolonged;
4. the yield and the content of the product are improved, and the difficulty of product purification is reduced;
5. high reaction temperature, low energy consumption and environmental protection.
Drawings
FIG. 1 is a schematic view of an apparatus for liquid phase chlorination of tetrachloro-2-cyanopyridine according to the present invention.
Wherein R-1 is a first gas-liquid intensified reaction tower, R-2 is a second gas-liquid intensified reaction tower, C-1 is a first micro-bubble generator, C-2 is a second micro-bubble generator, P-1 is a first circulating pump, P-2 is a pump, P-3 is a second circulating pump, T-1 is a washing tower, T-2 is an absorption tower, and E-1 is a wiped film evaporator.
10 11, 12, 13, 14, 15, 21 and 24 are gas phase pipelines; 1,2,3,4,5,6,7,8,9, 16, 17, 18, 19, 20, 22, 23 are liquid phase conduits.
Detailed Description
Example 1
20kg of FeCl loaded with 5% (wt) was charged in the first microbubble generator (C-1) and the second microbubble generator (C-2), respectively 3 The activated carbon of (2) is used as a pre-reaction catalyst and a main reaction catalyst. After the liquid 2-cyanopyridine is preheated to 30 ℃, the liquid 2-cyanopyridine is fed into a first gas-liquid intensified reaction tower (R-1) through a pipeline 1at a rate of 125kg/h to be fully mixed with chlorine, a gas-liquid mixture is fed into a first micro-bubble generator (C-1) through a pipeline 16 and a first circulating pump (P-1) to be pre-reacted in the first micro-bubble generator (C-1), and part of gas-phase materials can also be fed into the first micro-bubble generator (C-1) through a pipeline 15 to complete the circulation of the gas-phase materials. The material from the first micro-bubble generator (C-1) enters a first gas-liquid intensified reaction tower (R-1) through a pipeline 18 and is fully mixed with chlorine. The first gas-liquid intensified reaction tower (R-1), the first circulating pump (P-1) and the first micro-bubble generator (C-1) form a pre-reactor for chlorination reaction, the first gas-liquid intensified reaction tower (R-1) is responsible for fully mixing materials and chlorine, and the first micro-bubble generator (C-1) is fixed with a catalyst for chlorination reaction. The average retention time of the materials in the first gas-liquid intensified reaction tower (R-1) is about 12h, the gas phase pressure of the first gas-liquid intensified reaction tower (R-1) is maintained to be 0.8atm, the reaction temperature in the pre-reactor is maintained to be 170 ℃, and the flow of the adjusting pipeline 16 controls the conversion rate of the 2-cyanopyridine in the first gas-liquid intensified reaction tower (R-1) to be more than 40 percent. The material discharged from the first gas-liquid intensified reaction tower (R-1) enters the second gas-liquid intensified reaction tower (R-2) through a pipeline 2 and a pump (P-2)The gas-liquid intensified reaction tower (R-2) is fully mixed with chlorine, the second gas-liquid intensified reaction tower (R-2), the second circulating pump (P-2) and the second micro-bubble generator (C-2) form a main reactor of chlorination reaction, materials enter the second micro-bubble generator (C-2) through the pipeline 4 and the second circulating pump (P-3) to be chlorinated, the second gas-liquid intensified reaction tower (R-2) is responsible for fully mixing the materials with high-concentration chlorine, the second micro-bubble generator (C-2) is fixed with a catalyst to be chlorinated, and partial gas phase materials can enter the second micro-bubble generator (C-2) through the pipeline 13 to complete circulation of the gas phase materials. Fresh chlorine enters a second gas-liquid intensified reaction tower (R-2) and a second micro-bubble generator (C-2) from a pipeline 10 and a pipeline 11 respectively, and part of the chlorine discharged from the second gas-liquid intensified reaction tower (R-2) enters a first gas-liquid intensified reaction tower (R-1). The average retention time of the materials in the second gas-liquid intensified reaction tower (R-2) is about 8h, the gas phase pressure of the second gas-liquid intensified reaction tower (R-2) is maintained to be 1.4atm, the reaction temperature in the main reactor is maintained to be 200 ℃, and the flow of the adjusting pipeline 4 controls the yield of the tetrachloro-2-cyanopyridine in the second gas-liquid intensified reaction tower (R-2) to be more than 80 percent. The fully reacted material enters a wiped film evaporator (E-1) through a pipeline 7 for separation, and the unconverted light component enters the first gas-liquid intensified reaction tower (R-1) again through a pipeline 9 and a pipeline 1. The gas phase feed discharged from the first gas-liquid intensified reaction column (R-1) through the line 14 is introduced into the washing column (T-1), and 2-cyanopyridine feed at 160 ℃ is used as a washing liquid to be introduced from the top of the washing column (T-1). The gas phase material discharged from the washing column (T-1) contained less than 0.01% of 2-cyanopyridine and less than 1% of chlorine, and was fed into the absorption column (T-2) through the line 21, to absorb the acid gas by 30% by weight of sodium hydroxide solution.
Example 2
The first micro-bubble generator (C-1) and the second micro-bubble generator (C-2) are respectively filled with 18 kg loaded with 5% (wt) FeCl 3 The activated carbon of (2) is used as a pre-reaction catalyst and a main reaction catalyst. Preheating liquid 2-cyanopyridine to 70 ℃, then entering a first gas-liquid intensified reaction tower (R-1) through a pipeline 1at a rate of 130kg/h to be fully mixed with chlorine, and passing a gas-liquid mixture throughThe pipeline 16 and the first circulating pump (P-1) enter the first micro-bubble generator (C-1) to carry out pre-reaction in the first micro-bubble generator (C-1), and part of the gas-phase material can also enter the first micro-bubble generator (C-1) through the pipeline 15 to complete the circulation of the gas-phase material. The material from the first micro-bubble generator (C-1) enters a first gas-liquid intensified reaction tower (R-1) through a pipeline 18 and is fully mixed with chlorine. The first gas-liquid intensified reaction tower (R-1), the first circulating pump (P-1) and the first micro-bubble generator (C-1) form a pre-reactor for chlorination reaction, the first gas-liquid intensified reaction tower (R-1) is responsible for fully mixing materials and chlorine, and the first micro-bubble generator (C-1) is fixed with a catalyst for chlorination reaction. The average residence time of the materials in the first gas-liquid intensified reaction tower (R-1) is about 10h, the gas phase pressure of the first gas-liquid intensified reaction tower (R-1) is maintained to be 1atm, the reaction temperature in the pre-reactor is maintained to be 180 ℃, and the flow of the adjusting pipeline 16 controls the conversion rate of the 2-cyanopyridine in the first gas-liquid intensified reaction tower (R-1) to be more than 60%. The material discharged from the first gas-liquid intensified reaction tower (R-1) enters the second gas-liquid intensified reaction tower (R-2) through the pipeline 2 and the pump (P-2) to be fully mixed with chlorine, the second gas-liquid intensified reaction tower (R-2), the second circulating pump (P-2) and the second micro-bubble generator (C-2) form a main reactor of chlorination reaction, the material enters the second micro-bubble generator (C-2) through the pipeline 4 and the second circulating pump (P-3) to be chlorinated, the second gas-liquid intensified reaction tower (R-2) is responsible for fully mixing the material with high-concentration chlorine, the second micro-bubble generator (C-2) is fixed with a catalyst to be responsible for chlorination reaction, and part of gas-phase material can enter the second micro-bubble generator (C-2) through the pipeline 13 to complete circulation of the gas-phase material. Fresh chlorine enters a second gas-liquid intensified reaction tower (R-2) and a second micro-bubble generator (C-2) from a pipeline 10 and a pipeline 11 respectively, and part of the chlorine discharged from the second gas-liquid intensified reaction tower (R-2) enters a first gas-liquid intensified reaction tower (R-1). The average residence time of the materials in the second gas-liquid intensified reaction tower (R-2) is about 8h, the gas phase pressure of the second gas-liquid intensified reaction tower (R-2) is maintained to be 2.0 atm, the reaction temperature in the main reactor is maintained to be 210 ℃, and the flow of the adjusting pipeline 4 is controlled to be the second gas-liquid intensified reaction towerThe yield of tetrachloro-2-cyanopyridine in the reaction column (R-2) is more than 85%. The fully reacted material enters a wiped film evaporator (E-1) through a pipeline 7 for separation, and the unconverted light component enters the first gas-liquid intensified reaction tower (R-1) again through a pipeline 9 and a pipeline 1. The gas phase feed discharged from the first gas-liquid intensified reaction column (R-1) through the line 14 is introduced into the washing column (T-1), and 2-cyanopyridine feed at 30 ℃ is used as a washing liquid to be introduced from the top of the washing column (T-1). The gas phase material discharged from the washing column (T-1) contained less than 0.01% of 2-cyanopyridine and less than 1% of chlorine, and was fed into the absorption column (T-2) through the line 21, to absorb the acid gas by 30% by weight of sodium hydroxide solution.
Example 3
The first micro-bubble generator (C-1) and the second micro-bubble generator (C-2) are respectively filled with 25kg loaded with 5% (wt) FeCl 3 The activated carbon of (2) is used as a pre-reaction catalyst and a main reaction catalyst. After the liquid 2-cyanopyridine is preheated to 110 ℃, the liquid 2-cyanopyridine is fed into a first gas-liquid intensified reaction tower (R-1) through a pipeline 1at a rate of 130kg/h to be fully mixed with chlorine, a gas-liquid mixture is fed into a first micro-bubble generator (C-1) through a pipeline 16 and a first circulating pump (P-1) to be pre-reacted in the first micro-bubble generator (C-1), and part of gas-phase materials can also be fed into the first micro-bubble generator (C-1) through a pipeline 15 to complete the circulation of the gas-phase materials. The material from the first micro-bubble generator (C-1) is fully mixed with chlorine gas in the first gas-liquid intensified reaction tower (R-1) through the pipeline 18. The first gas-liquid intensified reaction tower (R-1), the first circulating pump (P-1) and the first micro-bubble generator (C-1) form a pre-reactor for chlorination reaction, the first gas-liquid intensified reaction tower (R-1) is responsible for fully mixing materials and chlorine, and the first micro-bubble generator (C-1) is fixed with a catalyst for chlorination reaction. The average residence time of the materials in the first gas-liquid intensified reaction tower (R-1) is about 9h, the gas phase pressure of the first gas-liquid intensified reaction tower (R-1) is maintained to be 0.9atm, the reaction temperature in the pre-reactor is maintained to be 190 ℃, and the flow of the adjusting pipeline 16 controls the conversion rate of the 2-cyanopyridine in the first gas-liquid intensified reaction tower (R-1) to be more than 50 percent. The material discharged from the first gas-liquid intensified reaction tower (R-1) enters through a pipeline 2 and a pump (P-2)The chlorine gas enters a second gas-liquid intensified reaction tower (R-2) to be fully mixed with the chlorine gas, the second gas-liquid intensified reaction tower (R-2), a second circulating pump (P-2) and a second micro-bubble generator (C-2) form a main reactor of chlorination reaction, materials enter the second micro-bubble generator (C-2) through a pipeline 4 and the second circulating pump (P-3) to be subjected to chlorination reaction, the second gas-liquid intensified reaction tower (R-2) is responsible for fully mixing the materials with the high-concentration chlorine gas, a catalyst is fixed on the second micro-bubble generator (C-2) to be responsible for chlorination reaction, and part of gas-phase materials can enter the second micro-bubble generator (C-2) through a pipeline 13 to complete circulation of the gas-phase materials. Fresh chlorine enters a second gas-liquid intensified reaction tower (R-2) and a second micro-bubble generator (C-2) from a pipeline 10 and a pipeline 11 respectively, and chlorine discharged from the second gas-liquid intensified reaction tower (R-2) partially enters a first gas-liquid intensified reaction tower (R-1). The average retention time of the materials in the second gas-liquid intensified reaction tower (R-2) is about 12h, the gas phase pressure of the second gas-liquid intensified reaction tower (R-2) is maintained to be 2.5atm, the reaction temperature in the main reactor is maintained to be 220 ℃, and the flow of the adjusting pipeline 4 is controlled to ensure that the yield of the tetrachloro-2-cyanopyridine in the second gas-liquid intensified reaction tower (R-2) is more than 88 percent. The fully reacted material enters a wiped film evaporator (E-1) through a pipeline 7 for separation, and the unconverted light component enters the first gas-liquid intensified reaction tower (R-1) again through a pipeline 9 and a pipeline 1. The gas phase material discharged from the first gas-liquid intensified reaction column (R-1) through the line 14 is introduced into a washing column (T-1), and 2-cyanopyridine material at 60 ℃ is used as a washing liquid to be introduced from the top of the washing column (T-1). The gas phase material discharged from the washing column (T-1) contained less than 0.01% of 2-cyanopyridine and less than 1% of chlorine, and was fed into the absorption column (T-2) through the line 21, to absorb the acid gas by 30% by weight of sodium hydroxide solution.
Example 4
30kg of FeCl loaded with 5% (wt) was charged in the first microbubble generator (C-1) and the second microbubble generator (C-2), respectively 3 The activated carbon of (2) is used as a pre-reaction catalyst and a main reaction catalyst. Preheating liquid 2-cyanopyridine to 150 ℃, then feeding the preheated liquid 2-cyanopyridine into a first gas-liquid intensified reaction tower R-1 through a pipeline 1at a rate of 150kg/h to be fully mixed with chlorine gas, and mixing the gas and the liquidThe material enters a first micro-bubble generator (C-1) through a pipeline 16 and a first circulating pump (P-1), pre-reaction is carried out in the first micro-bubble generator (C-1), and part of gas-phase material can also enter the first micro-bubble generator (C-1) through a pipeline 15 to complete circulation of the gas-phase material. The material from the first micro-bubble generator (C-1) enters the first gas-liquid intensified reaction tower (R-1) through the pipeline 18 to be fully mixed with chlorine. The first gas-liquid intensified reaction tower (R-1), the first circulating pump (P-1) and the first micro-bubble generator (C-1) form a pre-reactor for chlorination reaction, the first gas-liquid intensified reaction tower (R-1) is responsible for fully mixing materials and chlorine, and the first micro-bubble generator (C-1) is fixed with a catalyst for chlorination reaction. The average residence time of the materials in the first gas-liquid intensified reaction tower (R-1) is about 9h, the gas phase pressure of the first gas-liquid intensified reaction tower (R-1) is maintained to be 0.5atm, the reaction temperature in the pre-reactor is maintained to be 200 ℃, and the flow of the adjusting pipeline 16 controls the conversion rate of the 2-cyanopyridine in the first gas-liquid intensified reaction tower (R-1) to be more than 50 percent. The material discharged from the first gas-liquid intensified reaction tower (R-1) enters the second gas-liquid intensified reaction tower (R-2) through the pipeline 2 and the pump (P-2) to be fully mixed with chlorine, the second gas-liquid intensified reaction tower (R-2), the second circulating pump (P-2) and the second micro-bubble generator (C-2) form a main reactor of chlorination reaction, the material enters the second micro-bubble generator (C-2) through the pipeline 4 and the second circulating pump (P-3) to be chlorinated, the second gas-liquid intensified reaction tower (R-2) is responsible for fully mixing the material with high-concentration chlorine, the second micro-bubble generator (C-2) is fixed with a catalyst to be responsible for chlorination reaction, and part of gas-phase material can enter the second micro-bubble generator (C-2) through the pipeline 13 to complete circulation of the gas-phase material. Fresh chlorine enters a second gas-liquid intensified reaction tower (R-2) and a second micro-bubble generator (C-2) from a pipeline 10 and a pipeline 11 respectively, and part of the chlorine discharged from the second gas-liquid intensified reaction tower (R-2) enters a first gas-liquid intensified reaction tower (R-1). The average residence time of the materials in the second gas-liquid intensified reaction tower (R-2) is about 10h, the gas phase pressure of the second gas-liquid intensified reaction tower (R-2) is maintained to be 1.2atm, the reaction temperature in the main reactor is maintained to be 230 ℃, and the flow of the adjusting pipeline 4 is controlled to be second gas-liquidThe yield of tetrachloro-2-cyanopyridine in the enhanced reaction tower (R-2) is more than 85 percent. The fully reacted material enters a wiped film evaporator (E-1) through a pipeline 7 for separation, and the unconverted light component enters the first gas-liquid intensified reaction tower (R-1) again through a pipeline 9 and a pipeline 1. The gas phase feed discharged from the first gas-liquid intensified reaction column (R-1) through the line 14 is introduced into the washing column (T-1), and 2-cyanopyridine feed at 80 ℃ is used as a washing liquid to be introduced from the top of the washing column (T-1). The gas phase material discharged from the washing column (T-1) contained less than 0.01% of 2-cyanopyridine and less than 1% of chlorine, and was fed into the absorption column (T-2) through the line 21, to absorb the acid gas by 30% by weight of sodium hydroxide solution.
Example 5
22kg of FeCl loaded with 5% (wt) was charged in the first microbubble generator (C-1) and the second microbubble generator (C-2), respectively 3 The activated carbon of (2) is used as a pre-reaction catalyst and a main reaction catalyst. After the liquid 2-cyanopyridine is preheated to 170 ℃, the liquid 2-cyanopyridine is fed into a first gas-liquid intensified reaction tower R-1 through a pipeline 1at a rate of 125kg/h to be fully mixed with chlorine, a gas-liquid mixture is fed into a first micro-bubble generator (C-1) through a pipeline 16 and a first circulating pump (P-1) to be subjected to chlorination reaction in the first micro-bubble generator (C-1), and part of gas-phase materials can also be fed into the first micro-bubble generator (C-1) through a pipeline 15 to complete circulation of the gas-phase materials. The material from the first micro-bubble generator (C-1) enters the first gas-liquid intensified reaction tower (R-1) through the pipeline 18 to be fully mixed with chlorine. The first gas-liquid intensified reaction tower (R-1), the first circulating pump (P-1) and the first micro-bubble generator (C-1) form a pre-reactor for chlorination reaction, the first gas-liquid intensified reaction tower (R-1) is responsible for fully mixing materials and chlorine, and the first micro-bubble generator (C-1) is fixed with a catalyst for chlorination reaction. The average residence time of the materials in the first gas-liquid intensified reaction tower (R-1) is about 8h, the gas phase pressure of the first gas-liquid intensified reaction tower (R-1) is maintained to be 0.3atm, the reaction temperature in the pre-reactor is maintained to be 180 ℃, and the flow of the adjusting pipeline 16 controls the conversion rate of the 2-cyanopyridine in the first gas-liquid intensified reaction tower (R-1) to be more than 40%. The material discharged from the first gas-liquid intensified reaction tower (R-1) passes through a pipeline 2 and a pump (R)P-2) enters a second gas-liquid intensified reaction tower (R-2) to be fully mixed with chlorine, the second gas-liquid intensified reaction tower (R-2), a second circulating pump (P-2) and a second micro-bubble generator (C-2) form a main reactor of chlorination reaction, materials enter the C-2 through a pipeline 4 and the second circulating pump (P-3) to be subjected to chlorination reaction, the second gas-liquid intensified reaction tower (R-2) is responsible for fully mixing the materials with high-concentration chlorine, a catalyst is fixed on the C-2 to be responsible for chlorination reaction, and part of gas-phase materials can enter the C-2 through a pipeline 13 to complete circulation of the gas-phase materials. Fresh chlorine enters a second gas-liquid intensified reaction tower (R-2) and a second micro-bubble generator (C-2) from a pipeline 10 and a pipeline 11 respectively, and part of the chlorine discharged from the second gas-liquid intensified reaction tower (R-2) enters a first gas-liquid intensified reaction tower (R-1). The average retention time of the materials in the second gas-liquid intensified reaction tower (R-2) is about 10h, the gas phase pressure of the second gas-liquid intensified reaction tower (R-2) is maintained to be 3.0 atm, the reaction temperature in the main reactor is maintained to be 240 ℃, and the flow of the adjusting pipeline 4 is controlled to ensure that the yield of the tetrachloro-2-cyanopyridine in the second gas-liquid intensified reaction tower (R-2) is more than 85 percent. The fully reacted material enters a wiped film evaporator (E-1) through a pipeline 7 for separation, and the unconverted light component enters the first gas-liquid intensified reaction tower (R-1) again through a pipeline 9 and a pipeline 1. The gas phase feed discharged from the first gas-liquid intensified reaction column (R-1) through the line 14 is introduced into the washing column (T-1), and the 2-cyanopyridine feed at 100 ℃ is used as a washing liquid to be introduced from the top of the washing column (T-1). The gas phase material discharged from the washing column (T-1) contains less than 0.01% of 2-cyanopyridine and less than 1% of chlorine, and the gas phase material is introduced into an absorption column T-2 through a pipe 21, and 30 wt% of sodium hydroxide solution is used for absorbing acid gas.
Claims (3)
1. A liquid phase method production process of tetrachloro-2-cyanopyridine is characterized by comprising the following steps:
(1) Preheating liquid 2-cyanopyridine, feeding the preheated liquid 2-cyanopyridine into a gas-liquid reinforced pre-reactor, and pre-reacting the preheated liquid 2-cyanopyridine with chlorine under the action of a pre-reaction catalyst; after the reaction, the gas-phase material enters an absorption device to be absorbed after being washed;
(2) The liquid phase material after pre-reaction enters a gas-liquid reinforced main reactor and is subjected to chlorination reaction with chlorine under the action of a main reaction catalyst;
(3) The liquid phase material after the main reaction enters an evaporator for separation to obtain tetrachloro-2-cyanopyridine solid, and the unreacted raw material and the by-product return to the pre-reactor for continuous reaction;
the pre-reactor in the step (1) or the main reactor in the step (2) comprises a micro-bubble generator and a gas-liquid intensified reaction tower; the evaporator in the step (3) is a wiped film evaporator;
the preheating temperature in the step (1) is 30-170 ℃;
the average residence time of the pre-reaction in the pre-reactor in the step (1) is 8-12 h; the reaction temperature is controlled to be 170-200 ℃; the reaction pressure is 0.3-1 atm;
the washing in the step (1) is washing with liquid 2-cyanopyridine at 30-160 ℃ in a washing tower;
the chlorination reaction temperature in the step (2) is 200-240 ℃; the reaction pressure is 1.2-3 atm; the reaction time is 8-12 h;
the reactor used for the process comprises a liquid phase raw material inlet, a gas phase raw material inlet, a product outlet, a pre-reactor, a main reactor, an evaporator, a washing tower and an absorption tower;
the pre-reactor comprises a first gas-liquid intensified reaction tower, a first micro-bubble generator and a first circulating pump; the first gas-liquid intensified reactor comprises a first circulating outlet, a first gas-phase outlet and a first liquid-phase outlet;
the liquid phase raw material inlet is connected with the first gas-liquid intensified reaction tower; the first gas phase outlet is respectively connected with the first micro-bubble generator and the washing tower through a tee joint; the first circulating outlet is connected with the first microbubble generator through a first circulating pump; the outlet of the first micro-bubble generator is connected with the first gas-liquid reinforced reaction tower; a pre-reaction catalyst is arranged in the first microbubble generator;
the main reactor comprises a second gas-liquid intensified reaction tower, a second microbubble generator and a second circulating pump; the second gas-liquid intensified reactor comprises a second circulating outlet, a second gas-phase outlet and a second liquid-phase outlet;
the gas-phase raw material inlet is respectively connected with the second gas-liquid intensified reaction tower and the second microbubble generator through a tee; the first liquid phase outlet is connected with a second gas-liquid intensified reaction tower through a pump; the second gas phase outlet is respectively connected with the first micro-bubble reactor and the second micro-bubble reactor through a tee joint; the second circulating outlet is connected with a second microbubble generator through a second circulating pump; the outlet of the second microbubble generator is connected with the second gas-liquid intensified reaction tower; a main reaction catalyst is arranged in the second microbubble generator; the second liquid phase outlet is connected with an evaporator;
a light component outlet of the evaporator is connected with the first gas-liquid intensified reaction tower, and a heavy component outlet of the evaporator is connected with the product outlet;
the gas phase outlet of the washing tower is connected with the absorption tower;
the pre-reaction catalyst described in step (1) is FeCl supported with 5% by weight 3 The activated carbon of (1); the main reaction catalyst described in step (2) is FeCl supported with 5% by weight 3 The activated carbon of (1).
2. The process of claim 1, wherein the chlorine gas in step (1) is derived from the gaseous feed withdrawn from the main reactor.
3. The process according to claim 1, wherein the absorption in step (1) is absorption in an absorption column with lye.
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