Process for the preparation of 4-chloro-2,5-dimethoxynitrobenzene by one-pot chloronitration

Abstract

The application provides a method for preparing 4-chloro-2,5-dimethoxy nitrobenzene through one-pot chlorination and nitration reaction, wherein 1,4-dimethoxybenzene is oxidized to 2-chloro-1,4-dimethoxybenzene under the action of a catalyst and hydrogen peroxide through hydrochloric acid chlorination. Then, the product is further nitrated by a catalyst and nitric acid to obtain 4-chloro-2,5-dimethoxy nitrobenzene. The method can fuse the chlorination and nitration reaction, and catalytically prepare 4-chloro-2,5-dimethoxy nitrobenzene with high selectivity in one step, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a dye intermediate by one-pot chlorination and nitration reaction, in particular to a method for preparing 4-chloro-2,5-dimethoxy nitrobenzene by one-pot chlorination and nitration reaction. BACKGROUND

[0002] 4-chloro-2,5-dimethoxy aniline is an important intermediate for preparing a plurality of yellow azo organic pigments and ice-dye pigment varieties, and can also be used to prepare a plurality of red azo pigments. Due to the superior performance of its downstream azo pigments and the wide application field, it is an organic chemical raw material with increasing market demand year by year in recent years. It is the main raw material for synthesizing color phenol AS-IRG and color phenol AS-LC, and is an important fine chemical organic pigment intermediate. The downstream high-end pigment products extended from it are mainly used in the fields of coatings, printing ink, viscose fiber, fabric printing and dyeing (wallpaper, etc.), organic plastic coloring, etc., and have a wide range of uses in daily production and life.

[0003] Song Yuan et al. used hydroquinone as raw material, dimethyl sulfate as alkylating agent to obtain p-xylene dimethyl ether, then chlorinated under the condition of dichlorosulfuryl as chlorinating agent, and then nitrified without separation to obtain 2,5-dimethoxy-4-chloronitrobenzene with nitric acid as nitrating agent. The yield and purity of 2,5-dimethoxy-4-chloronitrobenzene were used to judge the effect of chlorination and nitration. The obtained 2,5-dimethoxy-4-chloronitrobenzene was subjected to catalytic hydrogenation to obtain the target compound-2,5-dimethoxy-4-chloroaniline. The synthetic route is shown in formula 1, and the total yield is 64%.

[0004]

[0005] Chinese patent document CN202010959397.2 provides a method for preparing 2,5-dimethoxy chlorobenzene. Phenol is dissolved in a solvent and put into a high-pressure reaction kettle, a catalyst composed of copper salt and other metal salt hydrochloride is added, pure oxygen is replaced three times, and then oxygen is filled to 1-1.5 MPa, and stirred at room temperature-50℃, the process maintains the oxygen pressure unchanged, after the reaction is completed, the oxygen is exhausted, dry HCl gas is introduced into the reaction kettle, the HCl gas pressure is maintained at 0.1-1 MPa during the reaction, after the reaction is completed, filtration, desolventizing and vacuum rectification are carried out to obtain 2-chloro-p-hydroquinone; 2-chloro-p-hydroquinone is added to the high-pressure reaction kettle and dissolved, 0.1-1 MPa chloromethane gas is introduced under alkaline conditions, the pressure is maintained, and the reaction is carried out at 50-120℃ until the raw material is completely consumed, and after desolventizing, the product 2,5-dimethoxy chlorobenzene is obtained by vacuum rectification. The reaction process is shown in formula 2, and the overall yield is 70%.

[0006] However, the reaction process is too complex.

[0007] SUMMARY

[0008] The present application aims to improve the prior art and provide a one-pot chlorination and nitration reaction method for preparing 4-chloro-2,5-dimethoxy nitrobenzene.

[0009] The one-pot chlorination and nitration reaction method for preparing 4-chloro-2,5-dimethoxy nitrobenzene comprises the following steps: A. Preparation of activated carbon supported silver chloride catalyst: dissolving a soluble silver salt in water to form a solution, adding activated carbon to the solution, stirring until uniform, then adding a chloride salt and stirring to react; after the reaction is completed, drying the water to obtain the activated carbon supported silver chloride catalyst; the mass of silver chloride in the catalyst accounts for 0.1%-5% of the total mass of the catalyst; B. adding a substrate 1,4-dimethoxybenzene, hydrochloric acid, the activated carbon supported silver chloride catalyst prepared in step A, and hydrogen peroxide to a reaction container, and carrying out chlorination at a certain temperature for a period of time; after the chlorination, adding nitric acid to the reaction system and continuing the nitration at the same temperature for a period of time, then separating the phases, distilling, and purifying to obtain the product 4-chloro-2,5-dimethoxy nitrobenzene.

[0010] Preferably, the chloride salt in step A is sodium chloride or potassium chloride; and the soluble silver salt is silver nitrate or silver acetate. Preferably, the molar amount of the chloride salt added in step A is 1.5-2 times the molar amount of the soluble silver salt; the stirring reaction is carried out at room temperature for 2-3 hours. The drying temperature is 100-120°C, and the drying time is 10-12 hours.

[0011] Preferably, the chlorination reaction temperature in step B is 60°C-70°C; the reaction time is 10h-20h; the molar ratio of the substrate 1,4-dimethoxybenzene to hydrogen peroxide is 1:(2-3); the molar ratio of the substrate 1,4-dimethoxybenzene to hydrochloric acid is 1:(1.2-1.7); and the mass of the catalyst added is 1%-10% of the mass of the substrate 1,4-dimethoxybenzene.

[0012] Preferably, the nitration reaction temperature is 60°C-70°C; the reaction time is 5-10h; and the molar amount of nitric acid added is 1.2-1.5 times the molar amount of 1,4-dimethoxybenzene.

[0013] The principle of the present application is shown in formula 3

[0014]

[0015] Beneficial effects:

[0016] The application is a method for preparing 4-chloro-2,5-dimethoxy nitrobenzene by one-pot chlorination and nitration. The method selects appropriate amount of hydrochloric acid as a chlorine source, which is oxidized to chlorine gas under the dual action of catalyst and hydrogen peroxide, and then the chlorine atom is selectively added to the benzene ring. The selectivity is controlled by controlling the reaction temperature and the amount of catalyst. Nitration of 2-chloro-1,4-dimethoxybenzene is achieved by adding nitric acid to the reaction system. The reaction process does not use chlorine gas and mixed acid, only slightly excess hydrochloric acid and nitric acid, which greatly reduces the danger and emission of such process. The process is simple, efficient, mild, high selective, low dangerous, low equipment requirement and low cost, which is suitable for industrial production. DETAILED DESCRIPTION

[0017] Embodiment 1: Preparation of catalyst A. Dissolve 0.1 g of silver nitrate in 100 ml of water, and then add 77 g of activated carbon and stir until uniform to obtain a mixed solution A. Add 0.0467 g of sodium chloride (molar ratio of sodium chloride to silver nitrate is 1.5:1) to the mixed solution A, continue to stir for two hours to obtain a mixed solution B, and then dry the mixed solution B in an oven at 120℃ for 12 h to obtain a silver chloride catalyst A, and the mass of silver chloride in the catalyst accounts for 0.1% of the total mass.

[0018] Embodiment 2: Preparation of catalyst B. The amount of silver nitrate is changed to 5 g, the amount of sodium chloride is changed to 3.2 g (molar ratio of sodium chloride to silver nitrate is 2:1), the drying temperature is changed to 100℃, and the time is changed to 10 h, and the rest is according to embodiment 1. A silver chloride catalyst B is obtained, and the mass of silver chloride in the catalyst accounts for 5% of the total mass.

[0019] Embodiment 3: Preparation of catalyst C. The amount of silver nitrate is changed to 1 g, the amount of sodium chloride is changed to 0.47 g (molar ratio of sodium chloride to silver nitrate is 1.5:1), and the stirring reaction time is changed to 3 h, and the rest is according to embodiment 1. A silver chloride catalyst C is obtained, and the mass of silver chloride in the catalyst accounts for 1% of the total mass.

[0020] Embodiment 4: Preparation of catalyst D. The silver nitrate is changed to 6.5 g of silver acetate, and the sodium chloride is changed to 3 g of potassium chloride, and the rest is according to embodiment 2. A silver chloride catalyst C is obtained, and the mass of silver chloride in the catalyst accounts for 5% of the total mass.

[0021] Embodiment 5:

[0022] In a reaction vessel was added 139 g (1 mol) of 1,4-dimethoxybenzene, 120 g (1.2 mol) of hydrochloric acid (36.5%), 227 g (2 mol) of hydrogen peroxide (30%), and 2 g of catalyst B (catalyst was added in an amount of 1.4% by mass of the substrate). The reaction vessel was sealed and placed at 60°C for 10 hours. After the reaction was completed, 120 g (1.2 mol) of nitric acid (65%) was added to the system and nitrated at 60°C for 10 hours. After the reaction was completed, the catalyst was separated by centrifugation. The liquid phase was neutralized with sodium carbonate to remove excess hydrochloric acid and nitric acid, and extracted with ethyl acetate three times, and the organic phase was combined. After the solvent was distilled off under reduced pressure, 161 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 74%.

[0023] Embodiment 6:

[0024] The amount of catalyst added was changed to 13.9 g (catalyst was added in an amount of 10% by mass of the substrate), and the catalyst was changed to catalyst A prepared in Embodiment 1, and the rest was performed as described in Embodiment 5. After the solvent was distilled off under reduced pressure, 150 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 69%.

[0025] Embodiment 7:

[0026] The amount of catalyst added was changed to 1.39 g (catalyst was added in an amount of 1% by mass of the substrate), and the rest was performed as described in Embodiment 5. After the solvent was distilled off under reduced pressure, 143 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 66%.

[0027] Embodiment 8:

[0028] The chlorination and nitration reaction temperature was changed to 65°C, and the rest was performed as described in Embodiment 5. After the solvent was distilled off under reduced pressure, 155 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 71%.

[0029] Embodiment 9:

[0030] The chlorination and nitration reaction temperature was changed to 70°C, and the rest was performed as described in Embodiment 5. After the solvent was distilled off under reduced pressure, 143 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 66%.

[0031] Embodiment 10:

[0032] The amount of hydrogen peroxide (30%) added was changed to 340 g (3 mol), and the rest was performed as described in Embodiment 5. After the solvent was distilled off under reduced pressure, 157 g of 4-chloro-2,5-dimethoxy nitrobenzene was obtained in a yield of 72%.

[0033] Embodiment 11:

[0034] The amount of hydrochloric acid (36.5%) was changed to 170 g (1.7 mol) and the rest of the operations were performed as described in Example 5. After evaporating the solvent under reduced pressure, 4-chloro-2,5-dimethoxynitrobenzene was obtained in a yield of 67% (146 g).

[0035] Example 12:

[0036] The reaction time was changed to 5 h and the rest of the operations were performed as described in Example 5. After evaporating the solvent under reduced pressure, 4-chloro-2,5-dimethoxynitrobenzene was obtained in a yield of 68% (149 g).

[0037] Example 13:

[0038] The amount of nitric acid was changed to 150 g (1.5 mol) and the rest of the operations were performed as described in Example 5. After evaporating the solvent under reduced pressure, 4-chloro-2,5-dimethoxynitrobenzene was obtained in a yield of 74% (159 g).

[0039] Example 14:

[0040] The catalyst was changed to catalyst C and the rest of the operations were performed as described in Example 5. After evaporating the solvent under reduced pressure, 4-chloro-2,5-dimethoxynitrobenzene was obtained in a yield of 71% (155 g).

[0041] Example 15:

[0042] The reaction time was changed to 20 h and the rest of the operations were performed as described in Example 5. After evaporating the solvent under reduced pressure, 4-chloro-2,5-dimethoxynitrobenzene was obtained in a yield of 74% (161 g).

[0043] Example 16:

[0044] The catalyst after the reaction in Example 5 was separated by centrifugation and reused. The process flow was the same as in Example 5 and the sample was analyzed by gas chromatography. The results are shown in Table 1.

[0045] Table 1: Catalyst reuse situation:

[0046] Number of recoveries 4-chloro-2,5-dimethoxy-nitrobenzene yield 1 74％ 2 73％ 3 73％ 4 72％ 5 71％

Claims

1. A method for preparing 4-chloro-2,5-dimethoxynitrobenzene by one-pot chlorination and nitration, comprising the following steps: A. Preparation of activated carbon supported silver chloride catalyst: dissolving a soluble silver salt in water to form a solution, adding activated carbon to the solution, stirring until uniform, adding a chloride salt, and stirring to react; after the reaction is completed, drying the water to obtain the activated carbon supported silver chloride catalyst; the mass of silver chloride in the catalyst accounts for 0.1%-5% of the total mass of the catalyst; the chloride salt is sodium chloride or potassium chloride; B. adding a substrate 1,4-dimethoxybenzene, hydrochloric acid, the activated carbon supported silver chloride catalyst prepared in step A, and hydrogen peroxide into a reaction vessel, and chlorinating at a certain temperature for a period of time; after the chlorination, adding nitric acid to the reaction system, and continuing to nitrate for a period of time; separating the phases, distilling, and purifying to obtain the product 4-chloro-2,5-dimethoxynitrobenzene.

2. The method of claim 1, wherein: The soluble silver salt in step A is silver nitrate or silver acetate.

3. The method of claim 1, wherein: The molar amount of the chloride salt added in step A is 1.5-2 times the molar amount of the soluble silver salt; the stirring time is 2-3 hours, the drying temperature is 100-120℃, and the drying time is 10-12 hours.

4. The method of claim 1, wherein The chlorination temperature in step B is 60℃-70℃; the reaction time is 10h-20h; the molar ratio of the substrate 1,4-dimethoxybenzene to hydrogen peroxide is 1:(2-3); the molar ratio of the substrate 1,4-dimethoxybenzene to hydrochloric acid is 1:(1.2-1.7); and the mass of the catalyst added is 1%-10% of the mass of the substrate 1,4-dimethoxybenzene.

5. The method of claim 1, wherein The nitration temperature is 60℃-70℃; the reaction time is 5-10h; and the molar amount of nitric acid added is 1.2-1.5 times the molar amount of 1,4-dimethoxybenzene.

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