Method for preparing 6-chloro-2-nitrotoluene through step-by-step chlorination

Abstract

The invention relates to the technical field of synthesis of 6-chloro-2-nitrotoluene, and particularly discloses a method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination, which comprises the following steps: connecting three chlorination kettles in series, and respectively marking by using a 1 # kettle, a 2 # kettle and a 3 # kettle; the method comprises the following steps: adding o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride into a 1 # kettle, heating to 55-60 DEG C, introducing chlorine for reaction, and closing the chlorine when the density of the 1 # kettle is 1.207-1.213 g / cm < 3 >; transferring the material in the 1 # kettle to a 2 # kettle through a bottom material transferring pipe, and simultaneously adding o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride into the 1 # kettle again; different catalysts are sequentially added in different stages of the o-nitrotoluene chlorination reaction, the temperature of each reaction kettle and the amount of the catalyst are adjusted, the reaction rates of the three kettles are balanced, the catalyst cost is low, the reaction conversion rate is high, the selectivity of 6-chloro-2-nitrotoluene is effectively improved, and the generation of polychlorides is reduced; the chlorine reaction rate is greatly improved, and the tail gas treatment cost and the raw material cost are reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of 6-chloro-2-nitrotoluene synthesis, and particularly relates to a method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination. BACKGROUND

[0002] Currently, the synthesis method of 6-chloro-2-nitrotoluene on the market is to place ortho-nitrotoluene and ferric chloride in a reaction kettle, and then chlorination is carried out at 50-60 DEG C. This method has a long reaction time, more polychloride is generated, and the utilization rate of chlorine gas is low. Patent document No. CN101985425A discloses a method for preparing 6-chloro-2-nitrotoluene, which comprises the following steps: ortho-nitrotoluene is put into a reaction kettle, stirring is started, a catalyst is put in, temperature is raised, and chlorine gas is passed in at a temperature of 25-85 DEG C. The reaction is stopped when the content of ortho-nitrotoluene is 8-12%, the mixture is cooled, and then discharged into a rectification section. This preparation method can effectively improve the ratio of 6-chloro-2-nitrotoluene and 4-chloro-2-nitrotoluene by properly selecting the catalyst without changing the existing mature process, so that the content of 6-chloro-2-nitrotoluene is about 65%, the production cost is reduced, energy is saved, and the method is suitable for industrial production.

[0003] However, ortho-nitrotoluene and antimony metal catalyst are put into the reaction kettle, the temperature is controlled, and chlorination is carried out. This method has a long reaction time. When the reaction is about to end, if the amount of chlorine gas is not changed, more polychloride will be generated. Therefore, the general operation is to reduce the chlorination rate, which will prolong the reaction time and cause low utilization rate of chlorine gas. Therefore, a method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination is needed to solve the above problems, so as to effectively improve the utilization rate of chlorine gas and shorten the reaction time without affecting the reaction conversion rate and selectivity. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination, which can effectively improve the utilization rate of chlorine gas and shorten the reaction time without affecting the reaction conversion rate and selectivity, so as to solve the problems in the background technology.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] A method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination, comprising the following steps:

[0007] S1, three chlorination kettles are connected in series, and are respectively marked as 1# kettle, 2# kettle and 3# kettle;

[0008] S2, in 1# pot into o-nitrotoluene and 1.5% -2.0% of anhydrous ferric chloride, temperature to 55-60℃, into chlorine gas reaction, to 1# pot to the density of 1.207-1.213g / cm 3 When the chlorine gas is closed;

[0009] S3, by the bottom of the material removal tube 1# pot material to 2# pot, while in 1# pot again into o-nitrotoluene and 1.5% -2.0% of anhydrous ferric chloride, 2# pot temperature to pot temperature 45-50℃, into chlorine gas reaction, to 2# pot, reaction to the density of 1.258-1.266g / cm 3 When the chlorine gas is closed;

[0010] S4, by the bottom of the material removal tube 2# pot material to 3# pot and add iodine, while 1# pot material to 2# pot, in 1# pot again into o-nitrotoluene and 1.5% -2.0% of anhydrous ferric chloride, control 3# pot temperature 40-45℃, into chlorine reaction, when 3# pot density reaches 1.298-1.301g / cm 3 When the chlorine gas is stopped;

[0011] S5, by the bottom of the material removal tube 3# pot material to the storage tank and carry out chromatographic analysis, repeat S4, to achieve the purpose of semi-continuous step chlorination.

[0012] Preferably, the bottom of the chlorination pot is provided with a gas distributor, which has a dense small hole ring pipe on one side close to the bottom of the pot, and the small holes on the ring pipe will evenly disperse the entering chlorine gas into a large number of fine bubbles, and three said chlorination pots have on-line density meters.

[0013] Preferably, the upper ends of the three said chlorination pots are connected in sequence through a chlorine gas pipeline, chlorine gas enters from 3# pot, passes through the chlorine gas pipeline into 2# pot, then into 1# pot, and finally enters the tail gas absorption system through the chlorine gas pipeline of 1# pot. The lower ends of the three said chlorination pots are connected in sequence through a material removal pipeline, o-nitrotoluene enters from 1# pot, passes through the material removal pipeline into 2# pot, then passes through the material removal pipeline into 3# pot, and finally is discharged through the chlorination liquid outlet of 3# pot.

[0014] Preferably, in step S2, when the chlorine gas is introduced into the 1# pot for reaction, the chlorine gas flow rate is 3%-4% of the mass of o-nitrotoluene per hour.

[0015] Preferably, in step S3, when o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride are again introduced into 1# pot, the temperature of 1# pot is controlled at 55-60℃, and when the chlorine gas is introduced for reaction, the chlorine gas flow rate is 6%-7% of the mass of o-nitrotoluene per hour.

[0016] Preferably, in step S4, the concentration of iodine added into the 3# kettle is 0.03%-0.05%, the flow rate of chlorine is 8%-10% of the mass of o-nitrotoluene per hour, the temperature of the 1# kettle is controlled at 55-60℃, and the temperature of the 2# kettle is controlled at 45-50℃.

[0017] Preferably, the capacity of the chlorination kettle is set to 2L, in semi-continuous reaction, the 1# kettle is fed with 1600g of o-nitrotoluene and 25.6g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid of the 1# kettle with a density of 1.208g / cm 3 ; the 3# kettle is fed with the chlorination liquid of the 2# kettle with a density of 1.259g / cm 3 ; and 0.8g of iodine is added. The temperatures of the 1# kettle, the 2# kettle and the 3# kettle are controlled at 60℃, 46℃ and 42℃ respectively, the flow rate of chlorine is kept at 134g per hour, and after 6.2 hours of reaction, the density of the 3# chlorination kettle is 1.298g / cm 3 . The discharged chlorination liquid is sampled and analyzed.

[0018] Preferably, the capacity of the chlorination kettle is set to 2L, in semi-continuous reaction, the 1# kettle is fed with 1600g of o-nitrotoluene and 25.6g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid of the 1# kettle with a density of 1.208g / cm 3 ; the 3# kettle is fed with the chlorination liquid of the 2# kettle with a density of 1.259g / cm 3 ; and 0.8g of iodine is added. The temperatures of the 1# kettle, the 2# kettle and the 3# kettle are controlled at 60℃, 46℃ and 42℃ respectively, the flow rate of chlorine is kept at 134g per hour, and after 6.2 hours of reaction, the density of the 3# chlorination kettle is 1.298g / cm 3 . The discharged chlorination liquid is sampled and analyzed.

[0019] Preferably, the capacity of the chlorination kettle is set to 2L, in semi-continuous reaction, the 1# kettle is fed with 1600g of o-nitrotoluene and 25.6g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid of the 1# kettle with a density of 1.208g / cm 3 ; the 3# kettle is fed with the chlorination liquid of the 2# kettle with a density of 1.259g / cm 3 ; and 0.8g of iodine is added. The temperatures of the 1# kettle, the 2# kettle and the 3# kettle are controlled at 60℃, 46℃ and 42℃ respectively, the flow rate of chlorine is kept at 134g per hour, and after 6.2 hours of reaction, the density of the 3# chlorination kettle is 1.298g / cm 3 . The discharged chlorination liquid is sampled and analyzed.

[0020] The method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination provided by the present application has the following advantages compared with the prior art:

[0021] 1. This invention balances the reaction rates of the three reactors by sequentially adding different catalysts at different stages of the chlorination reaction of o-nitrotoluene, adjusting the temperature and amount of catalyst in each reactor, and achieving low catalyst cost and high reaction conversion rate. This effectively improves the selectivity of 6-chloro-2-nitrotoluene and reduces the generation of polychlorinated compounds. The chlorine reaction rate is also significantly improved, reducing the cost of tail gas treatment and raw material costs.

[0022] 2. This invention improves the conversion rate of o-nitrotoluene while shortening the reaction time, increasing the selectivity of 6-chloro-2-nitrotoluene, and significantly improving the utilization rate of chlorine. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides, for example Figure 1 The stepwise chlorination method for preparing 6-chloro-2-nitrotoluene, as shown, includes the following steps:

[0026] S1. Connect the three chlorination reactors in series and label them as reactor #1, reactor #2 and reactor #3 respectively;

[0027] A gas distributor is installed at the bottom of the chlorination vessel. The gas distributor has a circular tube with dense small holes on one side near the bottom of the vessel. The small holes on the circular tube will allow chlorine gas to enter and be evenly dispersed into a large number of fine bubbles. All three chlorination vessels are equipped with online density meters.

[0028] The upper ends of the three chlorination reactors are connected in sequence via chlorine gas pipelines. Chlorine gas enters from reactor #3, passes through the chlorine gas pipeline to reactor #2, then to reactor #1, and finally enters the tail gas absorption system through the chlorine gas pipeline of reactor #1. The lower ends of the three chlorination reactors are connected in sequence via transfer pipelines. o-Nitrotoluene enters from reactor #1, passes through the transfer pipeline to reactor #2, then passes through the transfer pipeline to reactor #3, and finally exits through the chlorination liquid outlet of reactor #3.

[0029] S2. Add o-nitrotoluene and 1.5%-2.0% anhydrous ferric chloride to reactor #1, heat to 55-60℃, and introduce chlorine gas to react. Continue reacting in reactor #1 until the density reaches 1.207-1.213 g / cm³.3 When the chlorine gas is turned off;

[0030] When the 1# kettle is connected with chlorine gas, the flow rate of chlorine gas is 3%-4% of the mass of o-nitrotoluene per hour;

[0031] S3, the material in the 1# kettle is moved to the 2# kettle by the bottom material moving pipe, and o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride are added to the 1# kettle again, the temperature of the 2# kettle is raised to 45-50℃, and chlorine gas is connected for reaction, and when the density of the 2# kettle reaches 1.258-1.266 g / cm 3 When the chlorine gas is turned off;

[0032] When o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride are added to the 1# kettle again, the temperature of the 1# kettle is controlled at 55-60℃, and when the chlorine gas is connected for reaction, the flow rate of chlorine gas is 6%-7% of the mass of o-nitrotoluene per hour;

[0033] S4, the material in the 2# kettle is moved to the 3# kettle by the bottom material moving pipe and iodine is added, and the material in the 1# kettle is moved to the 2# kettle, o-nitrotoluene and 1.5%-2.0% of anhydrous ferric chloride are added to the 1# kettle again, the temperature of the 3# kettle is controlled at 40-45℃, and chlorine gas is connected for reaction, and when the density of the 3# kettle reaches 1.298-1.301 g / cm 3 When the chlorine gas is stopped;

[0034] The concentration of iodine added to the 3# kettle is 0.03%-0.05%, and when the chlorine gas is connected for reaction, the flow rate of chlorine gas is 8%-10% of the mass of o-nitrotoluene per hour, the temperature of the 1# kettle is controlled at 55-60℃, and the temperature of the 2# kettle is controlled at 45-50℃;

[0035] S5, the material in the 3# kettle is moved to the storage tank by the bottom material moving pipe and chromatographic analysis is performed, and S4 is repeatedly executed to achieve the purpose of semi-continuous step-by-step chlorination.

[0036] Since the ferric chloride catalyst generates less polychloride in the early stage of chlorination reaction, the selectivity of 6-chloro-2-nitrotoluene is high, but the reaction rate is slow in the later stage, and the amount of polychloride is greatly increased; the reaction rate of the ferric chloride and iodine compound is fast, and the amount of polychloride is also less in the later stage of reaction, but the selectivity of 6-chloro-2-nitrotoluene is lower, so a step-by-step chlorination process is designed, as shown in Figure 1 The three chlorination kettles with a gas distributor at the bottom are connected in series, each kettle has an online density instrument, the gas distributor is a circular ring pipe with dense small holes near the bottom of the kettle, which can uniformly disperse the entering chlorine gas into a large amount of fine bubbles, so that the chlorine gas can be more efficiently contacted and reacted with the material, and the three-kettle series can more effectively utilize the unreacted chlorine gas to participate in the reaction of the later kettle, the chlorine gas is connected from the 3# kettle, passes through the chlorine gas pipeline into the 2# kettle and then into the 1# kettle, and finally goes to the tail gas absorption system.

[0037] According to the above-mentioned method for preparing 6-chloro-2-nitrotoluene by step-by-step chlorination, the following specific examples are proposed:

[0038] Example 1

[0039] The capacity of the chlorination kettle is set to 2L. In semi-continuous reaction, the 1# chlorination kettle is fed with 1600g of o-nitrotoluene and 28.8g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid chlorinated by the 1# kettle to a density of 1.211 g / cm 3 ; the 3# kettle is fed with the chlorination liquid chlorinated by the 2# kettle to a density of 1.262 g / cm 3 , and 0.48g of iodine is added; the temperatures of the 1# kettle, the 2# kettle and the 3# kettle are controlled to be 60℃, 50℃ and 40℃ respectively, the chlorine feeding speed is maintained at 142g per hour, and after 6 hours of reaction, the density of the 3# chlorination kettle is 1.300 g / cm 3 . The discharged chlorination liquid is sampled and analyzed, and the results show that the o-nitrotoluene is 2.7%, the 6-chloro-2-nitrotoluene is 64.5%, the 4-chloro-2-nitrotoluene is 31.2%, and the polychloride is 1.3%.

[0040] Example 2

[0041] The capacity of the chlorination kettle is set to 2L. In semi-continuous reaction, the 1# chlorination kettle is fed with 1600g of o-nitrotoluene and 32g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid chlorinated by the 1# kettle to a density of 1.213 g / cm 3 ; the 3# kettle is fed with the chlorination liquid chlorinated by the 2# kettle to a density of 1.265 g / cm 3 , and 0.64g of iodine is added; the temperatures of the 1# kettle, the 2# kettle and the 3# kettle are controlled to be 58℃, 48℃ and 40℃ respectively, the chlorine feeding speed is maintained at 130g per hour, and after 6.5 hours of reaction, the density of the 3# chlorination kettle is 1.298 g / cm 3 . The discharged chlorination liquid is sampled and analyzed, and the results show that the o-nitrotoluene is 3.6%, the 6-chloro-2-nitrotoluene is 63.6%, the 4-chloro-2-nitrotoluene is 31.2%, and the polychloride is 1.1%.

[0042] Example 3

[0043] The capacity of the chlorination kettle is set to 2L. In semi-continuous reaction, the 1# kettle is fed with 1600g of o-nitrotoluene and 25.6g of anhydrous ferric chloride; the 2# kettle is fed with the chlorination liquid chlorinated by the 1# kettle to a density of 1.208 g / cm 3 ; the 3# kettle is fed with the chlorination liquid chlorinated by the 2# kettle to a density of 1.259 g / cm 3chlorination liquid was moved into and iodine 0.8 g was added; the temperatures of the 1st, 2nd and 3rd tanks were controlled to be 60℃, 46℃ and 42℃ respectively, the chlorine feeding speed was kept at 134 g per hour, and after 6.2 hours of reaction, the density of the 3rd chlorination tank was 1.298 g / cm 3 The discharged chlorination liquid was sampled and analyzed, and the results were as follows: o-nitrotoluene 3.2%, 6-chloro-2-nitrotoluene 63.2%, 4-chloro-2-nitrotoluene 32.3%, and polychloride 1.0%.

[0044] In order to verify that the method provided in the above examples can effectively improve the utilization rate of chlorine, the following comparative examples are provided:

[0045] Comparative Example 1

[0046] In a 2L chlorination tank with a gas distributor at the bottom, o-nitrotoluene 1600 g and anhydrous ferric chloride 28.8 g were added, the temperature in the tank was controlled to be 50-60℃, the chlorine feeding amount was 47 g per hour, and after 25 hours of reaction, the sample analysis results were as follows: o-nitrotoluene 6.3%, 6-chloro-2-nitrotoluene 59.5%, 4-chloro-2-nitrotoluene 28.7%, and polychloride 4.5%.

[0047] Comparative Example 2

[0048] In a 2L chlorination tank with a gas distributor at the bottom, o-nitrotoluene 1600 g, anhydrous ferric chloride 28.8 g and iodine 0.8 g were added, the temperature in the tank was controlled to be 40-60℃, the chlorine feeding amount was 96 g per hour, and after 9.5 hours of reaction, the sample analysis results were as follows: o-nitrotoluene 3.5%, 6-chloro-2-nitrotoluene 58.7%, 4-chloro-2-nitrotoluene 36.6%, and polychloride 1.2%.

[0049] The chlorine utilization rates of the samples of the above examples and comparative examples were calculated, and the calculation results are shown in the following table:

[0050]

[0051] From the above table data, it can be seen that the conversion rate of o-nitrotoluene in the examples of the present application is increased to 97.3%, the reaction time is shortened to 6.5 hours, the selectivity of 6-chloro-2-nitrotoluene is increased to 66.3, the chlorine utilization rate reaches 97.3%, and under the premise of improving the conversion rate of o-nitrotoluene, the reaction time is shortened, and the utilization rate of chlorine is greatly improved.

[0052] In summary, different catalysts are added in different stages of the chlorination reaction of o-nitrotoluene, the temperature of each reactor and the amount of catalyst are adjusted, the reaction rates of the three reactors are balanced, the catalyst cost is low, the reaction conversion rate is high, the selectivity of 6-chloro-2-nitrotoluene is effectively improved, the production of polychlorides is reduced, the reaction rate of chlorine is greatly improved, the cost of tail gas treatment and raw material cost is reduced, the reaction time is shortened under the premise of improving the conversion rate of o-nitrotoluene, the selectivity of 6-chloro-2-nitrotoluene is improved, and the utilization rate of chlorine is greatly improved.

[0053] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. shall be included in the protection scope of the present application.

Claims

1. A method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination, characterized in that: Includes the following steps: S1. Connect the three chlorination reactors in series and label them as reactor #1, reactor #2 and reactor #3 respectively; S2. Add o-nitrotoluene and 1.5%-2.0% anhydrous ferric chloride to reactor #1, heat to 55-60℃, and introduce chlorine gas to react. Continue reacting in reactor #1 until the density reaches 1.207-1.213 g / cm³. 3 Turn off the chlorine gas at that time; S3. Transfer the material from reactor #1 to reactor #2 via the bottom transfer pipe. Simultaneously, add o-nitrotoluene and 1.5%-2.0% anhydrous ferric chloride back into reactor #1. Heat reactor #2 to 45℃-50℃ and introduce chlorine gas to react. Continue reacting in reactor #2 until the density reaches 1.258-1.266 g / cm³. 3 Turn off the chlorine gas at that time; S4. Transfer the material from reactor #2 to reactor #3 via the bottom transfer pipe and add iodine. Simultaneously, transfer the material from reactor #1 to reactor #2. In reactor #1, add o-nitrotoluene and 1.5%-2.0% anhydrous ferric chloride again. Control the temperature of reactor #3 at 40-45℃ and purge the chlorine solution. When the density of reactor #3 reaches 1.298-1.301 g / cm³... 3 Stop chlorination at that time; S5. Transfer the material from reactor #3 to the storage tank via the bottom transfer pipe and perform chromatographic analysis. Repeat step S4 to achieve semi-continuous stepwise chlorination.

2. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 1, characterized in that: A gas distributor is installed at the bottom of the chlorination vessel. The gas distributor has a circular tube with densely packed small holes on one side near the bottom of the vessel. The small holes on the circular tube allow chlorine gas to enter and be evenly dispersed into a large number of fine bubbles. All three chlorination vessels are equipped with online density meters.

3. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 2, characterized in that: The upper ends of the three chlorination reactors are connected in sequence via chlorine gas pipelines. Chlorine gas enters from reactor #3, passes through the chlorine gas pipeline to reactor #2, then to reactor #1, and finally enters the tail gas absorption system through the chlorine gas pipeline of reactor #1. The lower ends of the three chlorination reactors are connected in sequence via transfer pipelines. o-Nitrotoluene enters from reactor #1, passes through the transfer pipeline to reactor #2, then passes through the transfer pipeline to reactor #3, and finally exits through the chlorination liquid outlet of reactor #3.

4. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 3, characterized in that: In step S2, when chlorine gas is introduced into reactor #1 of the chlorination reactor for reaction, the chlorine gas flow rate is 3%-4% of the mass of o-nitrotoluene feed per hour.

5. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 4, characterized in that: In step S3, when o-nitrotoluene and 1.5%-2.0% anhydrous ferric chloride are added to reactor #1 again, the temperature of reactor #1 is controlled at 55-60℃. When chlorine gas is introduced for reaction, the chlorine gas flow rate is 6%-7% of the mass of o-nitrotoluene feed per hour.

6. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 5, characterized in that: In step S4, the concentration of iodine added to reactor #3 is 0.03%-0.05%. When chlorine is introduced, the chlorine flow rate is 8%-10% of the feed mass of o-nitrotoluene per hour. The temperature of reactor #1 is controlled at 55-60℃, and the temperature of reactor #2 is controlled at 45℃-50℃.

7. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 1, characterized in that: The chlorination reactor has a capacity of 2L. In the semi-continuous reaction, reactor #1 is fed 1600g of o-nitrotoluene and 25.6g of anhydrous ferric chloride; reactor #2 is chlorinated from reactor #1 to a density of 1.208g / cm³. 3 The chlorination solution was transferred in; reactor #3 was chlorinated in reactor #2 until the density reached 1.259 g / cm³. 3 The chlorination solution was transferred in and 0.8g of iodine was added; the temperatures of reactors #1, #2, and #3 were controlled at 60℃, 46℃, and 42℃ respectively, with a chlorination rate of 134g per hour. After 6.2 hours of reaction, the density of reactor #3 was 1.298g / cm³. 3 Samples of the discharged chlorinated liquid were taken for analysis.

8. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 1, characterized in that: The capacity of the chlorination reactor is set to 2L. During the semi-continuous reaction, the feed to reactor #1 is 1600g of o-nitrotoluene and 32g of anhydrous ferric chloride; reactor #2 is chlorinated from reactor #1 until the density reaches 1.213g / cm³. 3 The chlorination solution was transferred in; reactor #3 was chlorinated in reactor #2 until the density reached 1.265 g / cm³. 3 The chlorination solution was transferred in and 0.64g of iodine was added; the temperatures of reactors #1, #2, and #3 were controlled at 58℃, 48℃, and 40℃ respectively, with a chlorination rate of 130g per hour. After 6.5 hours of reaction, the density of reactor #3 was 1.298g / cm³. 3 Samples of the discharged chlorinated liquid were taken for analysis.

9. The method for preparing 6-chloro-2-nitrotoluene by stepwise chlorination according to claim 1, characterized in that: The capacity of the chlorination reactor is set to 2L. During the semi-continuous reaction, the feed to chlorination reactor #1 is 1600g of o-nitrotoluene and 28.8g of anhydrous ferric chloride; reactor #2 is chlorinated from reactor #1 until the density reaches 1.211g / cm³. 3 The chlorination solution was transferred in; reactor #3 was chlorinated in reactor #2 until the density reached 1.262 g / cm³. 3 The chlorination solution was transferred in and 0.48g of iodine was added; the temperatures of reactors #1, #2, and #3 were controlled at 60℃, 50℃, and 40℃ respectively, with a chlorination rate of 142g per hour. After 6 hours of reaction, the density of reactor #3 was 1.300g / cm³. 3 Samples of the discharged chlorinated liquid were taken for analysis.

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