Continuous loop production of diuron and systems

Abstract

This invention discloses a continuous cyclic production method and system for diuron, comprising: dehydration treatment: preparing aniline solution from recovered toluene, heating and refluxing for dehydration and later use; cold photoreaction: preparing phosgene solution and conducting a cold photoreaction, maintaining constant system pressure and timely removal of reaction heat during the reaction, and ensuring excess phosgene throughout the pressurized reaction; thermophotoreaction: conducting a thermophotoreaction with continuous light transmission, recovering byproduct hydrogen chloride and excess phosgene during the reaction, and performing dephotochemical treatment on the well-reacted solution; addition reaction: refluxing and dehydrating the material after the cold addition reaction, separating diuron, filtering out the mother liquor for toluene recovery, and recycling the recovered toluene for use in preparing aniline solution and the cold addition reaction. This application effectively improves reaction efficiency by increasing the phosgene concentration in the solution, rapidly removing reaction heat, inhibiting the formation of the diaddition product urea, and strictly controlling the moisture content in the reaction solution to effectively prevent hydrolysis of phosgene and products.

Description

Technical Field

[0001] This invention relates to the field of diuron technology, specifically to a continuous cycle production method and system for preparing diuron. Background Technology

[0002] Diuron (CAS: 330-54-1) is a classic substituted urea systemic herbicide. It was first developed and introduced by DuPont in the 1950s. Its mechanism of action is primarily through absorption by plant roots and leaves, specifically inhibiting electron transport in photosynthesis (PSII inhibitor), leading to weed death due to energy depletion. Diuron is broad-spectrum and highly effective, widely used in cotton, sugarcane, orchards, and non-cultivated land for the control of annual grasses and broadleaf weeds.

[0003] Diuron is produced by esterification of 3,4-dichloroaniline with phosgene to form a 3,4-dichlorophenyl isocyanate intermediate, which is then added to an aqueous dimethylamine solution to generate diuron. During the esterification reaction, 3,4-dichlorophenylformyl chloride is first generated at low temperature, and the byproduct hydrogen chloride reacts with 3,4-dichloroaniline to produce hydrochloride, forming a large amount of solid. During the thermophotochemical reaction, 3,4-dichlorophenylformyl chloride slowly decomposes to form an isocyanate intermediate, and the hydrochloride also slowly reacts to eventually form an isocyanate intermediate, resulting in a completely clear solution. Finally, after nitrogen purification, diuron is obtained through cold and thermal addition reactions with an aqueous dimethylamine solution.

[0004] Cold light esterification reaction:

[0005]

[0006] Thermo-photoesterification reaction:

[0007]

[0008] Addition reaction:

[0009]

[0010] Side reactions:

[0011]

[0012] In the production of diuron, the esterification reaction of 3,4-dichloroaniline with phosgene releases a large amount of heat. Furthermore, the intermediates 3,4-dichlorophenylformyl chloride and 3,4-dichloroaniline hydrochloride generated in the cold photocatalytic reaction have low solubility in toluene, resulting in a large amount of solids. This significant heat effect severely impacts the production efficiency of batch reactors. In batch production, 3,4-dichloroaniline is slowly added dropwise to the phosgene solution (a mixture of phosgene dissolved in toluene). This dropwise addition process takes more than 10 hours, and the solid formation limits the use of microchannel reactors. To control the formation of the byproduct urea, simultaneous photocatalytic addition is used to ensure a constant excess of phosgene, resulting in low phosgene utilization.

[0013] To improve phosgene utilization, patent CN104326942B discloses a method for continuous phosgene removal during the preparation of small-variety isocyanates. This method involves recovering phosgene solution via a phosgene-removing distillation column and feeding it into a reactor for further reaction. However, due to the limited phosgene pressure provided by the phosgene-generating device, the concentration of the phosgene solution is limited, making it impossible to pressurize the continuous cold phosgene reaction. Ultimately, the phosgene utilization rate remains low, resulting in low reaction efficiency.

[0014] To improve the production efficiency of the equipment, patent CN103360282B provides a method for multi-stage continuous production of isocyanates, but the raw material used is o-dichlorobenzene, the solvent is hexamethylenediamine, and the cold light reaction ends in 5-10 minutes, so the reaction efficiency is low.

[0015] Patent CN117551001A provides a method for producing isocyanates using two or more series reactors. In this method, a first phosgene is mixed with a substituted aniline in a mixer, and the resulting liquid enters the first reactor. A second phosgene is then introduced into the first reactor. This method fails to remove the heat of reaction and cannot effectively suppress the formation of the side reaction urea, resulting in low reaction efficiency.

[0016] In addition, patent CN102482205B discloses a method for partial solvent recycling during the preparation of isocyanates. This method involves partial solvent recycling through a distillation column under positive or negative pressure and controlling the moisture content in the solvent. However, it cannot achieve the recycling of phosgene or the suppression of the side reaction urea.

[0017] Therefore, how to improve phosgene utilization, suppress the production of by-product urea, and improve production efficiency are common technical problems faced by the industry. Summary of the Invention

[0018] This invention provides a continuous cyclic production method for diuron, which can improve phosgene utilization, suppress the production of by-product urea, and increase the production efficiency of the equipment. Extensive experimental research was conducted by technical personnel, who discovered that increasing the phosgene concentration in the feed solution and rapidly removing reaction heat effectively improves reaction efficiency, suppresses the formation of the diaddition product urea, and strictly controls the moisture content in the reaction solution to effectively prevent the hydrolysis of phosgene and the product.

[0019] This invention provides the following technical solution: a continuous cyclic preparation method for diuron, comprising:

[0020] S1: Dehydration treatment: Dissolve 3,4-dichloroaniline in partially recovered toluene to prepare an aniline solution, heat and reflux to dehydrate until the water content of the aniline solution is less than 200 ppm before use;

[0021] S2: Cold photocatalytic reaction: After replenishing the phosgene and toluene mixture recovered from isocyanate with phosgene, a photocatalytic esterification solution is prepared. The photocatalytic esterification solution and the aniline solution obtained in S1 are continuously introduced into the reactor in a certain proportion for cold photocatalytic reaction. The system maintains constant pressure and removes the heat of reaction in time. The by-product hydrogen chloride and excess phosgene generated during the reaction are recovered and reused. The cold photocatalytic esterification solution is continuously introduced into the thermophotocatalytic reaction.

[0022] S3: Thermophoto reaction: The cold photoesterified liquid obtained from S2 is continuously fed into the reactor, and a certain proportion of phosgene is continuously introduced to maintain a constant temperature for thermophoto reaction. At the same time, by-product hydrogen chloride and excess phosgene are recovered. The liquid after thermophoto reaction is continuously fed into the reaction de-photogenerating tower for de-photogenerating treatment.

[0023] In S2 and S3, the by-product hydrogen chloride and excess phosgene are recovered through a phosgene recovery tower. The lower half of the reaction dephosgene tower removes phosgene, while the upper half replenishes phosgene, achieving a continuous replenishment reaction. Toluene, hydrogen chloride, and phosgene are removed from the top of the reaction dephosgene tower. The tail gas is condensed to recover anhydrous toluene and phosgene. The liquid enters the phosgene recovery tower. After the phosgene recovery tower absorbs phosgene, the tail gas is recovered through a hydrogen chloride recovery system to recover hydrochloric acid. Anhydrous phosgene-containing toluene is used to replenish phosgene and prepare the phosgene-containing liquid used in S2.

[0024] S4: Cold addition reaction: After the S3 de-lighting treatment, the isocyanate toluene solution is continuously output. The isocyanate toluene solution, dimethylamine aqueous solution and the remaining recovered toluene are subjected to a cold addition reaction. The reacted material is then refluxed for dehydration, cooled for crystallization, centrifuged and dried to obtain diuron. The obtained filtrate is used for toluene recovery. Part of the recovered toluene is used in the dehydration treatment to produce aniline solution, and part is used in the cold addition reaction.

[0025] This continuous cycle production method for diuron effectively improves reaction efficiency by increasing the phosgene concentration in the feed solution, rapidly removing the heat of reaction, inhibiting the formation of the diaddition product urea, and strictly controlling the moisture in the reaction solution to effectively prevent the hydrolysis of phosgene and products.

[0026] As an optional embodiment of the continuous cyclic preparation method for diuron described in this invention, in S1, the mass percentage concentration of 3,4-dichloroaniline in the aniline solution in toluene solvent is controlled between 20% and 25%. In S2, the cold photoreaction pressure is controlled at 0.05-0.10 MPa, the temperature at 0-20°C, and the average residence time is controlled at 1-2 h. In S2, when replenishing phosgene, the feed molar ratio of phosgene to 3,4-dichloroaniline is 0.5-0.6:1, the phosgene concentration in the phosgene solution is controlled at 50-55%, and the feed molar ratio of phosgene to 3,4-dichloroaniline in the phosgene solution is 3.5-4:1. The thermophotoreaction is carried out at atmospheric pressure, the temperature is controlled at 60-70°C, the average residence time is controlled at 2-4 h, and the molar ratio of phosgene introduced during continuous light transmission to aniline in the thermophotoreaction is 0.5-0.6:1. In the upper section of the phosgene removal tower, the molar ratio of supplemental light input to aniline is 0.05-0.1:1. The concentration of 3,4-dichlorophenyl isocyanate in the tower bottom is controlled at 24%-26% to achieve equilibrium with the mass of toluene in the aniline solution. The temperature of the bottom liquid in the phosgene recovery tower is controlled at -20 to -10°C. In the cold addition reaction, the mass percentage of dimethylamine in the dimethylamine aqueous solution is 30%-40%.

[0027] As an optional scheme of the continuous cyclic preparation method for diuron as described in this invention, in S2, the cold photoreaction temperature is controlled at 0-20℃.

[0028] A system employing any of the above-mentioned continuous cyclic production methods for diuron includes a reflux dehydrator, a cold light circulation reactor, a back pressure valve, a continuous discharge valve, a thermo-light reactor, a reaction delighting tower, a condenser, a phosgene recovery tower, a jet mixer, a cold addition reactor, a thermo-addition reactor, a cooling crystallizer, a diuron centrifuge, and a toluene recovery tower. A reflux dehydrator is used to dissolve 3,4-dichloroaniline in partially recovered toluene to prepare an aniline solution, which is then heated and refluxed for dehydration until the water content of the aniline solution is less than 200 ppm before use. A cold photoluminescence circulating reactor is used for the cold photoluminescence reaction, with a back pressure valve located between the cold photoluminescence circulating reactor and the phosgene recovery tower to maintain a constant system pressure. A continuous discharge valve is located between the cold photoluminescence circulating reactor and the hot photoluminescence reactor to maintain a constant system liquid level. A hot photoluminescence reactor is used for the hot photoluminescence reaction. A reaction deluminescence tower is used for deluminescence treatment. A condenser is located between the reaction deluminescence tower and the phosgene recovery tower to condense and recover anhydrous toluene and phosgene, while the phosgene recovery tower is used for phosgene recovery. A jet mixer is used to prepare photomethyl liquid. A cold addition reactor is located between the reaction deluminescence tower and the hot addition reactor, where the cold addition reactor is used for the cold addition reaction, and the hot addition reactor is used for reflux dehydration. The hot addition reactor is connected to a cooling crystallizer, which is connected to a diuron centrifuge, which is connected to a toluene recovery tower. The cooling crystallization kettle is used for cooling crystallization, the diuron centrifuge is used for centrifugation, and the recovered toluene output from the toluene recovery tower is recycled to the reflux dehydrator and the cold addition reactor for the preparation of aniline solution and the cold addition reaction.

[0029] As an optional system for the continuous cyclic preparation method of diuron described in this invention, the upper section of the reaction decolorization tower adopts a high-load reactive distillation tower, controlling the total residence time of the feed liquid on the upper trays to be 15-30 min. The cold addition reaction temperature is controlled at 0-15℃. The average residence time of the cold addition reaction is controlled at 8-10 h. The cooling crystallization temperature is controlled at 40-60℃.

[0030] The present invention has the following beneficial effects:

[0031] 1. This continuous cycle production method for preparing diuron increases the phosgene concentration in the reaction system by pressurizing the cold phosgene circulation reaction and maintaining the pressure through a back pressure valve, thereby reducing phosgene overflow and improving reaction efficiency and phosgene utilization.

[0032] 2. This continuous cycle production method for diuron uses photomethyl liquid circulation absorption and supplemental lighting to control the amount of phosgene entering the cold light reaction, always maintaining an excess ratio of phosgene in the cold light reaction, effectively suppressing the generation of the side reaction urea.

[0033] 3. In this continuous cycle production method for preparing diuron, the heat of reaction is removed in a timely manner while being pressurized during the cold photocatalytic reaction, and the flow of solid slurry is overcome, thereby improving the production efficiency of the equipment.

[0034] 4. In this continuous circulation system for preparing diuron, the reactive distillation column achieves the function of a gradual heating stage in the intermittent thermo-photochemical reaction, while simultaneously performing phosgene removal. Furthermore, the removed phosgene is utilized promptly, further improving the utilization rate of phosgene. Together with the phosgene recovery tower, it forms a stable phosgene liquid recycling system, stably controlling the amount of phosgene used and the reaction ratio during the reaction process, increasing the total yield of diuron to 97%, and reducing the molar consumption of phosgene to below 1.3 mol equivalent. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the system for the continuous cyclic preparation of diuron in this invention. Detailed Implementation

[0036] 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. 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.

[0037] like Figure 1 As shown, the continuous circulation system for preparing diuron in this invention includes: a reflux dehydrator 1, an aniline liquid feed pump 2, a cold light circulation reactor 3, a back pressure valve 4, a continuous discharge valve 5, a thermo-light reactor 6, a reaction delighting tower feed pump 7, a reaction delighting tower 8, a condenser 9, a phosgene recovery tower 10, a photomethyl liquid feed pump 11, a jet mixer 12, a cold addition reactor 13, a thermo-addition reactor 14, an addition liquid discharge pump 15, a cooling crystallization vessel 16, a diuron centrifuge 17, and a toluene recovery tower 18.

[0038] The reflux dehydrator 1 is used to dissolve 3,4-dichloroaniline in a partially recovered toluene solution to prepare an aniline solution. The solution is then heated and refluxed for dehydration until the water content of the aniline solution is less than 200 ppm before it is ready for use. The aniline solution feed pump 2 is used to transport the aniline solution to the cold light circulation reactor 3. The cold light circulation reactor 3 is used for the cold light reaction. The cold light circulation reactor 3 is equipped with a heat exchanger and a circulation pump, which can remove the heat of reaction in a timely manner. The back pressure valve 4 is located between the cold light circulation reactor 3 and the phosgene recovery tower 10 to maintain a constant system pressure. The continuous discharge valve 5 is located between the cold light circulation reactor 3 and the hot light reactor 6 to maintain a constant system liquid level. The feed pump 7 of the reaction delighting tower is located between the thermophotoreactor 6 and the reaction delighting tower 8. The reaction delighting tower 8 is used for delighting treatment. The condenser 9 is located between the reaction delighting tower 8 and the phosgene recovery tower 10. It is used to condense and recover anhydrous toluene and phosgene. The phosgene liquid feed pump 11 is located between the phosgene recovery tower 10 and the jet mixer 12. The jet mixer 12 is used to mix the phosgene liquid and phosgene. The cold addition reactor 13 is located between the reaction delighting tower 8 and the thermal addition reactor 14. The cold addition reactor 13 is used for cold addition reaction. The thermal addition reactor 14 is used for reflux dehydration. The thermal addition reactor 14 is connected to the cooling crystallizer 16 through the addition liquid discharge pump 15. The cooling crystallizer 16 is connected to the diuron centrifuge 17. The diuron centrifuge 17 is connected to the toluene recovery tower 18. The recovered toluene output from the toluene recovery tower 18 is respectively sent to the reflux dehydrator 1 and the cold addition reactor 13.

[0039] use Figure 1 The continuous cyclic preparation system for diuron includes the following methods for preparing diuron:

[0040] 3,4-Dichloroaniline was dissolved in recycled toluene to prepare a 22% aniline-toluene solution, which was then refluxed and dehydrated in reflux dehydrator 1 until the water content was less than 200 ppm.

[0041] The recovered phosgene-toluene solution is concentrated in a jet mixer 12 to prepare a 55% phosgene-methyl phosgene solution. This solution is continuously pumped into the cold phosgene-toluene circulating reactor 3, and the reactor level is filled to the normal production level. The dehydrated aniline solution is then continuously pumped into the cold phosgene-toluene circulating reactor 3 for a cold phosgene-toluene reaction. The flow rate of the phosgene-methyl phosgene solution is adjusted to maintain the molar ratio of phosgene to aniline continuously entering the reactor. The reactor level is stabilized by a continuous discharge valve 5 interlocked with the liquid level, and the pressure inside the reactor is maintained by a back pressure valve 4.

[0042] The liquid from the cold photocatalytic reaction continuously enters the thermophotocatalytic reactor 6 and undergoes simultaneous photocatalytic reaction under normal pressure. The by-product hydrogen chloride and phosgene tail gas enter the phosgene recovery tower 10 to recover phosgene. The liquid after the thermophotocatalytic reaction is clarified is continuously fed into the reaction dephosphorization tower 8 for further thermophotocatalytic reaction and dephosphorization. Toluene, phosgene and by-product hydrogen chloride distilled off at the top of the tower are cooled by a condenser and then enter the phosgene recovery tower 10 to absorb phosgene.

[0043] The debled isocyanate toluene solution is continuously fed into cold addition reactor 13 for continuous cold addition reaction with 40% dimethylamine aqueous solution. The reacted material is then fed into hot addition reactor 14 for reflux dehydration, then transferred to cooling crystallization kettle 16 for cooling crystallization, and finally centrifuged and filtered by diuron centrifuge 17 and dried to obtain diuron product.

[0044] use Figure 1 The specific control parameters and results of the continuous cyclic preparation system for diuron are shown in Tables 1 and 2: These are specific examples of continuous diuron production under different reaction conditions.

[0045] Table 1:

[0046]

[0047] Table 2:

[0048]

[0049] It should be noted that, according to the applicant's literature review and experiments, the current yield of diuron in production is 95-96%, and the phosgene consumption is 1.5-1.6 mol equivalents. In production, the cold photocatalytic reaction uses a jacketed reactor for cooling, and to control the temperature from exceeding the limit, the aniline dropping time is as long as 15 hours, followed by several hours of heat preservation, totaling more than 18 hours. The thermocatalytic reaction takes 4-6 hours.

[0050] In Examples 1-5 of this application, the yields of Examples 4 and 5 are significantly lower than those of Examples 1-3, and Example 4 has a higher phosgene consumption. This is because in Example 4, phosgene overflows from the reaction solution at atmospheric pressure during the cold photocatalytic reaction, leading to incomplete cold photocatalytic reaction. More phosgene needs to be introduced during the thermophotocatalytic reaction stage, and the reaction time is delayed, affecting product yield and phosgene utilization. In Example 5, the cold photocatalytic reaction pressure is too high, making it difficult for the byproduct hydrogen chloride to overflow, resulting in excessive aniline hydrochloride, affecting the thermophotocatalytic reaction efficiency, and increasing the amount of urea generated by the side reaction, thus affecting product yield.

[0051] In Examples 6-10 of this application, the yields of Examples 9 and 10 are significantly lower than those of Examples 6-8, and Example 9 has a relatively high phosgene consumption. In Example 8, the reactive distillation column is not circulated with phosgene and is only used as a phosgene removal column. Due to the inherent problem of incomplete material reaction in fully mixed continuous reactions, the yield is slightly lower. Integrating the reactive distillation column and the phosgene removal column can achieve the effect of multi-stage reaction at minimal cost in a small-scale reaction process with gradually increasing temperature. In Example 9, the bottom liquid temperature of the phosgene recovery column is too high, the spray absorption efficiency is low, the amount of dissolved phosgene added is insufficient, and the concentration of phosgene-containing liquid is insufficient. To achieve the molar ratio of the cold-light reaction, a large amount of phosgene-containing liquid circulation is required, leading to increased phosgene loss, shortened reactor residence time, incomplete material reaction, increased phosgene consumption, and reduced product yield. In Example 10, the cold-light reaction time is too short, and too much unreacted aniline and aniline hydrochloride enters the hot-light reaction time, leading to an increase in the side reaction urea and a reduced product yield. The materials must react fully under cold-light conditions.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A continuous cyclic production method for diuron, characterized in that, include: S1: Dehydration treatment: Dissolve 3,4-dichloroaniline in partially recovered toluene to prepare an aniline solution, heat and reflux to dehydrate until the water content of the aniline solution is less than 200 ppm before use; S2: Cold photocatalytic reaction: After replenishing the phosgene and toluene mixture recovered from isocyanate with phosgene, a photocatalytic esterification solution is prepared. The photocatalytic esterification solution and the aniline solution obtained in S1 are continuously introduced into the reactor in a certain proportion for cold photocatalytic reaction. The system maintains constant pressure and removes the heat of reaction in time. The by-product hydrogen chloride and excess phosgene generated during the reaction are recovered and reused. The cold photocatalytic esterification solution is continuously introduced into the thermophotocatalytic reaction. S3: Thermophoto reaction: The cold photoesterified liquid obtained from S2 is continuously fed into the reactor, and a certain proportion of phosgene is continuously introduced to maintain a constant temperature for thermophoto reaction. At the same time, by-product hydrogen chloride and excess phosgene are recovered. The liquid after thermophoto reaction is continuously fed into the reaction de-photogenerating tower for de-photogenerating treatment. In S2 and S3, the by-product hydrogen chloride and excess phosgene are recovered through a phosgene recovery tower. The lower half of the reaction dephosgene tower removes phosgene, while the upper half replenishes phosgene, achieving a continuous replenishment reaction. Toluene, hydrogen chloride, and phosgene are removed from the top of the reaction dephosgene tower. The tail gas is condensed to recover anhydrous toluene and phosgene. The liquid enters the phosgene recovery tower. After the phosgene recovery tower absorbs phosgene, the tail gas is recovered through a hydrogen chloride recovery system to recover hydrochloric acid. Anhydrous toluene is used to replenish phosgene to prepare the phosgene liquid used in S2. S4: Cold addition reaction: After the S3 de-lighting treatment, the isocyanate toluene solution is continuously output. The isocyanate toluene solution, dimethylamine aqueous solution and the remaining recovered toluene are subjected to a cold addition reaction. The reacted material is then refluxed for dehydration, cooled for crystallization, centrifuged and dried to obtain diuron. The obtained filtrate is used for toluene recovery. Part of the recovered toluene is used in the dehydration treatment to produce aniline solution, and part is used in the cold addition reaction.

2. The production method for continuous cyclic preparation of diuron according to claim 1, characterized in that: The mass percentage concentration of 3,4-dichloroaniline in the aniline solution in S1 in toluene solvent is controlled between 20% and 25%.

3. The continuous cyclic production method for diuron according to claim 1 or 2, characterized in that: In S2, the cold light reaction pressure is controlled at 0.05-0.10 MPa, the temperature is controlled at 0-20℃, and the average reaction residence time is controlled at 1-2 h.

4. The continuous cyclic production method for diuron according to claim 1 or 2, characterized in that: In S2, when replenishing phosgene, the feed molar ratio of phosgene to 3,4-dichloroaniline is 0.5-0.6:1, the phosgene concentration in the phosgene solution is controlled at 50-55%, and the feed molar ratio of phosgene to 3,4-dichloroaniline in the phosgene solution is 3.5-4:

1.

5. The continuous cyclic production method for diuron according to claim 1 or 2, characterized in that: The thermo-photon reaction is carried out at atmospheric pressure, with the temperature controlled at 60-70℃ and the average residence time controlled at 2-4h. The molar ratio of phosgene to aniline during continuous light transmission in the thermo-photon reaction is 0.5-0.6:

1.

6. The continuous cyclic production method for diuron according to claim 1 or 2, characterized in that: The molar ratio of supplemental light intake to aniline in the upper half of the reaction delighting tower is 0.05-0.1:1, and the concentration of 3,4-dichlorophenyl isocyanate in the tower bottom is controlled at 24%-26%.

7. The continuous cyclic production method for diuron according to claim 1 or 2, characterized in that: The temperature of the liquid at the bottom of the phosgene recovery tower is controlled between -20 and -10℃.

8. The method for producing diuron in a continuous cycle according to claim 1 or 2, characterized in that: In the cold addition reaction, the mass percentage of dimethylamine in the aqueous solution of dimethylamine is 30%-40%.

9. A system for the continuous cyclic preparation of diuron, used to implement the production method for the continuous cyclic preparation of diuron as described in any one of claims 1-8, characterized in that: It includes a reflux dehydrator (1), a cold light circulation reactor (3), a back pressure valve (4), a continuous discharge valve (5), a thermo-light reactor (6), a reaction delight tower (8), a condenser (9), a phosgene recovery tower (10), a jet mixer (12), a cold addition reactor (13), a thermo addition reactor (14), a cooling crystallizer (16), a diuron centrifuge (17), and a toluene recovery tower (18). The reflux dehydrator (1) is used to dissolve 3,4-dichloroaniline in a partially recovered toluene solution to prepare an aniline solution, heat it to increase the temperature and reflux to dehydrate it until the water content of the aniline solution is less than 200 ppm and then it is ready for use. The cold light circulation reactor (3) is used for cold light reaction. The back pressure valve (4) is set between the cold light circulation reactor (3) and the phosgene recovery tower (10) to keep the system pressure constant. The continuous discharge valve (5) is set between the cold light circulation reactor (3) and the thermoluminescent reactor (6) to keep the system liquid level constant. The thermophotoreactor (6) is used to carry out thermophoto reactions; The reaction delighting tower (8) is used for delighting treatment; The condenser (9) is located between the reaction deluminescence tower (8) and the phosgene recovery tower (10) for condensing and recovering anhydrous toluene and phosgene, and the phosgene recovery tower (10) is used for phosgene recovery. The jet mixer (12) is used to prepare the light-sensitive liquid; The cold addition reactor (13) is located between the reaction delighting tower (8) and the thermal addition reactor (14). The cold addition reactor (13) is used for cold addition reaction, and the thermal addition reactor (14) is used for reflux dehydration. The thermal addition reactor (14) is connected to the cooling crystallization vessel (16), the cooling crystallization vessel (16) is connected to the diuron centrifuge (17), the diuron centrifuge (17) is connected to the toluene recovery tower (18), the cooling crystallization vessel (16) is used for cooling crystallization, the diuron centrifuge (17) is used for centrifugation, and the recovered toluene output from the toluene recovery tower (18) is recycled to the reflux dehydrator (1) and the cold addition reactor (13) for the preparation of aniline solution and cold addition reaction.

10. The system for continuous cyclic preparation of diuron according to claim 9, characterized in that: The upper section of the reaction delighting tower (8) adopts a reaction distillation tower with high liquid loading.

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