O-chlorobenzyl chloride synthesis process
By using a composite catalyst and a staged heating method, the reaction control problem in the synthesis of o-chlorobenzyl chloride was solved, achieving highly selective and low-energy synthesis of o-chlorobenzyl chloride, and improving product purity and yield.
Patent Information
- Application Number
- CN202511635885.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-10
- Publication Date
- 2026-02-06
AI Technical Summary
The existing synthesis process of o-chlorobenzyl chloride is characterized by slow reaction start-up, high risk of runaway, poor selectivity, high energy consumption, and numerous byproducts, resulting in low product purity and insufficient yield.
A composite catalyst, including an azo initiator and benzoyl peroxide, and a free radical stabilizer are added. Combined with segmented heating and a blue light source, the concentration and temperature of the free radicals in the reaction are controlled to achieve segmented and controllable initiation.
It improves reaction selectivity, reduces energy consumption and chlorine consumption, reduces by-product formation, and improves product purity and yield.
Smart Images
Figure CN121471052A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of chemical production, and particularly relates to a synthesis process of o-chlorobenzyl chloride. BACKGROUND
[0002] O-chlorobenzyl chloride is an important fine chemical product, and is widely used in the industries of medicine, pesticide and dye. A series of intermediates or products with high value can be synthesized by using o-chlorobenzyl chloride as raw material. At present, the light chlorination method and the catalyst chlorination method are mainly used in industry. The catalyst chlorination method usually uses a single initiator (such as benzoyl peroxide or azo initiator). However, the method has the following problems: (1) slow reaction start: high-temperature initiator (such as benzoyl peroxide) needs a higher temperature to effectively decompose, and the reaction induction period is long; (2) risk of reaction out of control: low-temperature initiator (such as azo initiator) rapidly decomposes at high temperature and cannot maintain a stable free radical concentration; (3) poor selectivity: the reaction at a single temperature cannot effectively control the occurrence of side reactions, resulting in low product purity and affecting product quality; and (4) high energy consumption: a high temperature needs to be maintained for a long time, and the energy consumption is high, and the reaction conditions are not convenient to control. The light catalytic chlorination process has gradually matured, but it also has some shortcomings, such as weak reaction selectivity of o-chlorotoluene to o-chlorobenzyl chloride, low conversion rate, high reflux ratio required for separating o-chlorotoluene from the chlorination liquid, long reaction time leading to high content of by-products, further reducing the reaction selectivity, affecting the subsequent rectification and purification, low yield of o-chlorobenzyl chloride, and high reaction consumption. In addition, the long reaction time increases the consumption of chlorine gas, leads to high content of by-products, further reduces the reaction selectivity, affects the subsequent rectification and purification, and cannot meet the yield demand.
[0003] In the research process of the two methods, it is found that a composite catalyst can be used for o-chlorobenzyl chloride synthesis reaction on the basis of the current light chlorination production process. The catalyst itself has the characteristics of high activation performance, no interference with the reaction and small use amount, the light chlorination process has the characteristics of environmental protection and energy saving, and the two are combined by using their respective advantages. However, because the two initiators decompose at the same time at the beginning of the reaction, it is impossible to realize segmented controllable initiation, and the reaction is prone to be out of control due to the too high free radical concentration. SUMMARY
[0004] (1) Technical problem to be solved The purpose of the present application is to provide a synthesis process of o-chlorobenzyl chloride, and to develop a synthesis process of o-chlorobenzyl chloride which can realize segmented controllable initiation, improve reaction selectivity, reduce energy consumption, reduce chlorine gas consumption and generate multi-chlorine impurities.
[0005] (2) Technical scheme In order to achieve the above purpose, on the one hand, the present application provides a synthesis process of o-chlorobenzyl chloride, comprising the following steps: S1. Catalyst system preparation: At 18~24℃, an azo initiator is compounded with benzoyl peroxide at a molar ratio of 1:1~5, a free radical stabilizer is added to obtain a composite catalyst, and low-purity o-chlorotoluene is added for dissolution, mixed uniformly to obtain a catalyst solution; S2. Mixing of reactants: The catalyst solution and high-purity o-chlorotoluene are added to a photocatalytic tower reactor for mixing to obtain a reaction liquid; S3. Stepwise warming chlorination reaction: The reaction liquid is subjected to stepwise warming chlorination at -0.095~(-0.098) MPa: First stage: warmed to 60~80℃, kept for 2 hours, and low-temperature initiation was carried out by slowly passing in chlorine; Second stage: warmed to 100~120℃ at a warming rate of 10℃ / h~20℃ / h; Third stage: maintained at 100~120℃, and chlorination reaction was continued by passing in chlorine for 7~10 hours; S4. Product separation: Unreacted o-chlorotoluene was recovered from the top of the tower, and o-chlorobenzyl chloride crude product was obtained from the bottom of the tower; S5. Refining and purification: The o-chlorobenzyl chloride crude product was refined by vacuum distillation to obtain high-purity o-chlorobenzyl chloride product.
[0006] Further, the azo initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisdimethylvaleronitrile, dimethyl azobisvalerate, diethyl azobisvalerate, etc.; preferably azobisisobutyronitrile.
[0007] Further, the free radical stabilizer is one or more of 2,6-di-tert-butyl-p-cresol, hydroquinone, p-methoxyphenol, nitrobenzene; preferably 2,6-di-tert-butyl-p-cresol; the addition amount of the free radical stabilizer is 0.5%~3% of the total mass of the composite catalyst.
[0008] Further, the addition amount of the composite catalyst in S1 is 0.3%~3% of the mass of high-purity o-chlorotoluene.
[0009] Further, the benzoyl peroxide is prepared by mixing benzoyl peroxide powder with molten paraffin, high-speed stirring to emulsify into microspheres, sieving 20~50μm after cooling and solidification.
[0010] Further, the low-purity o-chlorotoluene in S1 is o-chlorotoluene with a purity less than 98% separated from the top of the rectifying column, and the mass ratio of the composite catalyst to low-purity o-chlorotoluene is 1:2~8.
[0011] Further, the high-purity o-chlorotoluene in S2 has a purity ≥98%.
[0012] Further, the light source in the preferred photocatalytic tower type reaction device in S2 is a blue light lamp with a wavelength of 400-460 nm.
[0013] Further, the first stage chlorine gas flow rate is 20-60 kg / h, and the third stage chlorine gas flow rate is 120-200 kg / h.
[0014] On the basis of the photochlorination production process, a composite catalyst is used for the synthesis reaction of o-chlorobenzyl chloride. Although the reaction energy consumption and the generation of by-products can be greatly reduced, the decomposition of the catalyst is also accelerated by photo catalysis. Therefore, the blue light lamp is used as the light source in the present application. Compared with the traditional ultraviolet light, the energy consumption and equipment maintenance cost of long-term operation are significantly reduced, the blue light photon energy is more moderate, the reaction selectivity is better, the chlorine molecules are preferentially activated, and the destructive effect on the reactants and products is greatly reduced, which helps to reduce by-products, improve product purity and yield.
[0015] In addition, in order to avoid the decomposition of the azo initiator and benzoyl peroxide at the beginning of the reaction, leading to too high initial concentration of free radicals, too violent reaction start, and poor reaction selectivity control, and possible exacerbation of over-chlorination and other side reactions, the present application uses paraffin to wrap benzoyl peroxide and adds a free radical stabilizer when preparing the composite catalyst. The paraffin wrapped benzoyl peroxide can achieve physical isolation, so that only azo initiators produce free radicals at low temperatures. However, the decomposition of azo initiators at high temperatures is self-accelerating, which makes the initial free radical generation speed too fast, and a large number of free radicals will attack o-chlorotoluene at the same time, and the reaction heat is released instantaneously. Therefore, the addition of an appropriate amount of free radical stabilizer can consume part of the free radicals generated by the azo initiator, avoid the instantaneous over-concentration of free radicals, and prevent the reaction from running out of control and flying temperature. At high temperatures, the free radical stabilizer is consumed, the paraffin is melted to release benzoyl peroxide, and stable free radicals are provided for the high-temperature stage, so that the reaction can continue. While using the azo initiator and benzoyl peroxide compound catalyst, the present application adopts a segmented temperature rise to realize segmented initiation, and further improves the controllability of the reaction.
[0016] In summary, due to the use of the above technical solutions, the present application has the following advantages: 1. By compounding azo initiators and benzoyl peroxide, and adding a free radical stabilizer, the azo initiator dominates the start at the low temperature stage (60-80℃), and the benzoyl peroxide dominates the maintenance at the high temperature stage (100-120℃), and the controllability of the reaction is significantly improved.
[0017] 2. The free radical stabilizer consumes the high concentration of instantaneous free radicals generated by the initial stage of azo initiator, prevents the reaction from running out of control and flying temperature, and the physical isolation of benzoyl peroxide by paraffin wrapping technology avoids the initial free radical concentration being too high, further improves the effect of segmented initiation.
[0018] 3. The blue light source is used as the photocatalytic initiator, and the composite catalyst is used to carry out the synthesis reaction of o-chlorobenzyl chloride, which not only reduces the energy consumption, but also reduces the use amount of catalyst, avoids the generation of by-products, and further improves the product purity. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The o-chlorobenzyl chloride synthesis process flowchart of the present application is shown in the figure. Figure 2 The spectrum of the unreacted o-chlorotoluene recovered from the top of the tower is shown in the figure. DETAILED DESCRIPTION
[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0021] Embodiment 1: The present embodiment discloses an o-chlorobenzyl chloride synthesis process, comprising the following steps: S1. Catalyst system preparation: at 20℃, 82g of azobis isobutyronitrile is compounded with 363g of benzoyl peroxide, 8.9g of 2,6-di-tert-butyl-p-cresol is added to obtain a composite catalyst, and then 2kg of low-purity o-chlorotoluene is added for dissolution, and the mixture is stirred uniformly to obtain a catalyst solution; S2. Mixing of reaction materials: the catalyst solution and 151kg of high-purity o-chlorotoluene are added to a photocatalytic tower type reaction device for mixing to obtain a reaction liquid; S3. Stepwise heating chlorination reaction: under-0.095MPa, the blue light source is turned on, the wavelength is set to 450nm, and the reaction liquid is subjected to stepwise heating chlorination: First stage: heating to 70℃ at a rate of 15℃ / h, maintaining for 2 hours, slowly passing in chlorine gas, and controlling the flow rate at 45kg / h for low-temperature initiation; Second stage: heating to 110℃ at a rate of 15℃ / h; Third stage: maintaining at 110℃, continuing to pass in chlorine gas with a flow rate controlled at 150kg / h for 8 hours of chlorination reaction; S4. Product separation: unreacted o-chlorotoluene is recovered from the top of the tower, and o-chlorobenzyl chloride crude product is obtained from the bottom of the tower; S5. Purification: the crude o-chlorobenzyl chloride is refined by vacuum distillation to obtain high-purity o-chlorobenzyl chloride product.
[0022] It should be noted that, as Figure 1 The process flow chart of synthesizing o-chlorobenzyl chloride is shown in the figure, low-purity o-chlorotoluene is added in the preparation stage of the catalyst system to dissolve the catalyst, the catalyst system is stirred and mixed uniformly, and then is added to the photocatalytic reaction device, the raw material o-chlorotoluene is added, the blue light source is turned on, and the chlorination reaction is carried out by stage heating.
[0023] It should be noted that, as Figure 2 The spectrum of recovering unreacted o-chlorotoluene at the top of the tower is shown in the figure.
[0024] The azo initiator is azobisisobutyronitrile.
[0025] The radical stabilizer is 2,6-di-tert-butyl-p-cresol; the addition amount of the radical stabilizer is 2% of the total mass of the composite catalyst.
[0026] The addition amount of the composite catalyst in S1 is 0.3% of the mass of high-purity o-chlorotoluene.
[0027] The benzoyl peroxide is prepared by mixing benzoyl peroxide powder and molten paraffin, high-speed stirring and emulsification to form microspheres, sieving 20-50 μm after cooling and solidification.
[0028] The low-purity o-chlorotoluene in S1 is o-chlorotoluene with a purity of 88% separated from the top of the distillation column, and the mass ratio of the composite catalyst to the low-purity o-chlorotoluene is 1:4.4.
[0029] The high-purity o-chlorotoluene in S2 has a purity of 98%.
[0030] The light source in the photocatalytic tower type reaction device in S2 is preferably a blue light lamp with a wavelength of 450 nm.
[0031] The first stage chlorine gas flow rate in S3 is 45 kg / h, and the third stage chlorine gas flow rate is 150 kg / h.
[0032] Example 2: The present embodiment discloses a synthesis process of o-chlorobenzyl chloride, comprising the following steps: S1. Catalyst system preparation: at 20°C, 164g azobisisobutyronitrile is compounded with 242g benzoyl peroxide, 2.1g 2,6-di-tert-butyl-p-cresol is added to obtain a composite catalyst, and 820g low-purity o-chlorotoluene is added for dissolution, and the mixture is stirred and mixed uniformly to obtain a catalyst solution; S2. Mixing of reaction materials: the catalyst solution and 27kg high-purity o-chlorotoluene are added to the photocatalytic tower type reaction device for mixing to obtain a reaction liquid; S3. Stepwise temperature rising chlorination reaction: under-0.095 MPa, turn on the blue light source, set the wavelength to 450 nm, and perform stepwise temperature rising chlorination on the reaction solution: First stage: temperature rising to 70℃ at a rate of 15℃ / h, keep for 2 hours, slowly introduce chlorine gas, and control the flow rate at 45 kg / h for low-temperature initiation; Second stage: temperature rising to 110℃ at a rate of 15℃ / h; Third stage: maintain 110℃, continue to introduce chlorine gas, control the flow rate at 150 kg / h, and perform chlorination reaction for 8 hours; S4. Product separation: recover unreacted o-chlorotoluene at the top of the column, and obtain o-chlorobenzyl chloride crude product at the bottom of the column; S5. Refining and purification: perform vacuum distillation refining on the o-chlorobenzyl chloride crude product to obtain high-purity o-chlorobenzyl chloride product.
[0033] Example 3: This example discloses a synthesis process of o-chlorobenzyl chloride, which comprises the following steps: S1. Catalyst system preparation: at 20℃, compound 41g of azobisisobutyronitrile with 303g of benzoyl peroxide, add 10.6g of 2,6-di-tert-butyl-p-cresol to obtain a composite catalyst, then add 2.8kg of low-purity o-chlorotoluene for dissolution, stir and mix uniformly to obtain a catalyst solution; S2. Mixing of reaction materials: mix the catalyst solution with 12kg of high-purity o-chlorotoluene in a photocatalytic column reactor to obtain a reaction solution; S3. Stepwise temperature rising chlorination reaction: under-0.095 MPa, turn on the blue light source, set the wavelength to 450 nm, and perform stepwise temperature rising chlorination on the reaction solution: First stage: temperature rising to 70℃ at a rate of 15℃ / h, keep for 2 hours, slowly introduce chlorine gas, and control the flow rate at 45 kg / h for low-temperature initiation; Second stage: temperature rising to 110℃ at a rate of 15℃ / h; Third stage: maintain 110℃, continue to introduce chlorine gas, control the flow rate at 150 kg / h, and perform chlorination reaction for 8 hours; S4. Product separation: recover unreacted o-chlorotoluene at the top of the column, and obtain o-chlorobenzyl chloride crude product at the bottom of the column; S5. Refining and purification: perform vacuum distillation refining on the o-chlorobenzyl chloride crude product to obtain high-purity o-chlorobenzyl chloride product.
[0034] Examples 4-9: Examples 4-9 are based on Example 1, except that the synthesis process of o-chlorobenzyl chloride is different from Example 1 in the temperature and chlorine flow rate in step S3 of stepwise temperature rising chlorination reaction. The difference points are shown in Table 1.
[0035]
[0036] Other components and preparation methods are the same as in Example 1.
[0037] Comparative Example 1: This comparative example is based on Example 1, except that in this comparative example, the light source in the preferred photocatalytic tower reactor in S2 is ultraviolet light with a wavelength of 400-460 nm.
[0038] Other components and preparation methods are the same as in Example 1.
[0039] Comparative Example 2: This comparative example is based on Example 1, except that in this comparative example, the benzoyl peroxide is not wrapped in paraffin wax.
[0040] Other components and preparation methods are the same as in Example 1.
[0041] Comparative Example 3: This comparative example is based on Example 1, except that in this comparative example, no free radical stabilizer is added.
[0042] Other components and preparation methods are the same as in Example 1.
[0043] Comparative Example 4: This comparative example is based on Example 1, except that in this comparative example, no azobisisobutyronitrile is added.
[0044] Other components and preparation methods are the same as in Example 1.
[0045] Comparative Example 5: This comparative example is based on Example 1, except that in this comparative example, no benzoyl peroxide is added.
[0046] Other components and preparation methods are the same as in Example 1.
[0047] Comparative Example 6: This comparative example is based on Example 1, except that in this comparative example, the blue light lamp light source is not turned on.
[0048] Other components and preparation methods are the same as in Example 1.
[0049] Comparative Example 7: This comparative example is based on Example 1, except that in this comparative example, no composite catalyst is added.
[0050] Other components and preparation methods are the same as in Example 1.
[0051] Test verification: Test 1: The conversion rate of o-chlorotoluene, the yield of o-chlorobenzyl chloride, and the content of by-product o-chlorodichlorobenzyl in Examples 1, 4-9 were analyzed and calculated, the purity of o-chlorobenzyl chloride was detected by gas chromatography, and the influence of the stepwise temperature chlorination reaction on the synthesis of o-chlorobenzyl chloride was analyzed.
[0052]
[0053] As shown in Table 2, the effect of the staged temperature rising chlorination reaction on the synthesis of o-chlorobenzyl chloride, from the data in the table, the conversion rate of o-chlorotoluene, the yield and purity of o-chlorobenzyl chloride under the condition of staged temperature rising are higher, and the content of by-product o-chlorodichlorobenzene is lower, which is because the initial temperature is lower, only free radicals are generated by the decomposition of azobisisobutyronitrile, so that the initial free radical concentration is controlled, excessive chlorination is effectively inhibited, the content of by-product o-chlorodichlorobenzene is significantly reduced, through the high temperature in the later stage, the free radicals are maintained by benzoyl peroxide, the conversion rate of o-chlorotoluene is improved, and then the final yield and purity of o-chlorobenzyl chloride are higher.
[0054] Test two: the effect of other factors on the synthesis of o-chlorobenzyl chloride: the conversion rate of o-chlorotoluene, the yield of o-chlorobenzyl chloride, and the content of by-product o-chlorodichlorobenzene in examples 1-3 and comparative examples 1-7 are analyzed and calculated, and the purity of o-chlorobenzyl chloride is detected by gas chromatography.
[0055]
[0056] As shown in Table 3, the conversion rate of o-chlorotoluene, the yield and purity of o-chlorobenzyl chloride, and the content of o-chlorodichlorobenzene, combined with the data in Table 2 and Table 3, it can be known that example 1 is the best scheme of the present application. From the data in the table, it can be known that the combination of the photochlorination production process and the composite catalyst for the synthesis of o-chlorobenzyl chloride can greatly improve the synthesis effect of o-chlorobenzyl chloride, but the combination of the two processes is easy to cause the free radical concentration of the reaction liquid to be too high, the product o-chlorobenzyl chloride continues to be chlorinated, the by-product increases, and the yield and purity of o-chlorobenzyl chloride decrease. Therefore, a blue light source needs to be used, the benzoyl peroxide wrapped by paraffin needs to be used, and a free radical stabilizer needs to be additionally added, so as to control the concentration of free radicals, thereby improving the conversion rate of o-chlorotoluene, the yield and purity of o-chlorobenzyl chloride, and reducing the generation of by-product o-chlorodichlorobenzene.
[0057] The above only describes the preferred embodiments of the present application and should not be used to limit the protection scope of the present application, any modifications, equivalent replacements and improvements made by any person skilled in the art within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims
1. A process for synthesizing o-chlorobenzyl chloride, characterized in that, Includes the following steps: S1. Catalyst system preparation: At 18~24℃, azo initiators and benzoyl peroxide were compounded at a molar ratio of 1:1~5, and a free radical stabilizer was added to obtain a composite catalyst. Low-purity o-chlorotoluene was then added to dissolve the catalyst and mixed evenly to obtain a catalyst solution. S2. Mixing of reactants: The catalyst solution and high-purity o-chlorotoluene are added to the photocatalytic tower reactor and mixed to obtain the reaction solution; S3. Segmented heating chlorination reaction: The reaction solution is subjected to segmented heating chlorination at -0.095~(-0.098) MPa: First stage: Heat to 60~80℃, keep warm for 2 hours, and slowly introduce chlorine gas to initiate low-temperature ignition; Second stage: Increase the temperature to 100~120℃ at a heating rate of 10℃ / h~20℃ / h; Third stage: Maintain 100~120℃ and continue to introduce chlorine gas to carry out the chlorination reaction for 7~10 hours; S4. Product separation: Unreacted o-chlorotoluene is recovered from the top of the column, and crude o-chlorobenzyl chloride is obtained from the bottom of the column; S5. Refining and purification: The crude o-chlorobenzyl chloride product is purified by vacuum distillation to obtain a high-purity o-chlorobenzyl chloride product.
2. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The azo initiator is one or more of azobisisobutyronitrile, azobisisovalerate, azodimethylvalerate, dimethyl azobisisobutyrate, diethyl azobisisobutyrate, etc.; preferably azobisisobutyronitrile.
3. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The free radical stabilizer is one or more of 2,6-di-tert-butyl-p-cresol, hydroquinone, p-methoxyphenol, and nitrobenzene; preferably 2,6-di-tert-butyl-p-cresol; the amount of the free radical stabilizer added is 0.5% to 3% of the total mass of the composite catalyst.
4. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The amount of composite catalyst added in S1 is 0.3% to 3% of the mass of high-purity o-chlorotoluene.
5. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The benzoyl peroxide is prepared by mixing benzoyl peroxide powder with molten paraffin, emulsifying it at high speed to form microspheres, cooling and solidifying it, and then sieving it to a size of 20~50μm.
6. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The low-purity o-chlorotoluene in S1 is o-chlorotoluene with a purity of less than 98% separated from the top of the distillation column, and the mass ratio of the composite catalyst to the low-purity o-chlorotoluene is 1:2~8.
7. The synthesis process of o-chlorobenzyl chloride according to claim 1, characterized in that, The high-purity o-chlorotoluene in S2 has a purity ≥98%.
8. The process for synthesizing o-chlorobenzyl chloride according to claim 1, characterized in that, In the preferred photocatalytic tower reactor of S2, the light source is a blue lamp with a wavelength of 400nm~460nm.
9. The process for synthesizing o-chlorobenzyl chloride according to claim 1, characterized in that, In S3, the chlorine flow rate in the first stage is 20~60 kg / h, and the chlorine flow rate in the third stage is 120~200 kg / h.