CN104817426B - A kind of preparation method of ortho-chlorotolu'ene - Google Patents

Abstract

The present invention relates to a preparation method of o-chlorotoluene, specifically refers to using toluene as raw material, Cl as chlorine source, [BMIM]Cl–nZnCl ₂ (n=1, ₂ , 2.5, n is ZnCl ₂ and [BMIM] Cl molar ratio) acidic ionic liquid as catalyst, catalyzed toluene to prepare o-chlorotoluene; the present invention selects [BMIM]Cl–nZnCl ₂ (n=1, 2 or 2.5) acidic ionic liquid as the catalyst for chlorination, and Cl ₂ is chlorine Source, carry out selective chlorination reaction of toluene; This method can not only improve the selectivity of o-chlorotoluene in the product, but also the [BMIM]Cl- _nZnCl ionic liquid catalyst separated from the product can be reused, reducing production costs, An important method beneficial to the industrial production of o-chlorotoluene.

Description

A kind of preparation method of o-chlorotoluene

technical field

The present invention relates to a kind of preparation method of o-chlorotoluene, specifically refers to using toluene as raw material, Cl as chlorine source, [BMIM]Cl–nZnCl ₂ (n=1, ₂ , 2.5, n is ZnCl ₂ and [BMIM] The molar ratio of Cl) acidic ionic liquid is used as a catalyst to catalyze toluene to prepare o-chlorotoluene; it belongs to the technical field of toluene chlorination and also belongs to the technical field of ionic liquids.

Background technique

O-chlorotoluene is an important chemical raw material intermediate, widely used in pesticides, medicines, dyes and paints. It is also a medium-boiling organic solvent with good performance; at present, o-chlorotoluene is increasingly widely used in organic synthesis.

Using o-chlorotoluene as raw material and aluminum chloride as a catalyst, thiazole pesticides and fungicides can be directly synthesized; the condensation reaction product of o-chlorotoluene and dichloroalkane can be used as high-pressure grease and oil; Under the condition of sodium oxide alkaline hydrolysis to synthesize m-cresol and o-cresol, the yield can reach more than 80%; o-chlorotoluene can be further chlorinated under the condition of Lewis acid catalyst to prepare 2,6-dichlorotoluene, 2,4- Dichlorotoluene, etc.

At present, o-chlorotoluene is mainly prepared by using Lewis acid as a catalyst, chlorine gas as a chlorination agent, and catalyzing the selective chlorination of toluene; according to the reported literature, in the toluene chlorination process, the ratio of o-chlorotoluene to p-chlorotoluene Close to 1:1; in addition, the traditional Lewis acid cannot be separated from the chlorination product, resulting in a large amount of waste water, polluting the environment, and is not conducive to industrial production.

Therefore, it is very necessary to develop a process for o-chlorotoluene that is easy to industrialize, has low production cost, is easy to separate, and has a high reaction yield.

Contents of the invention

The present invention selects [BMIM]Cl-nZnCl ₂ (n=1, 2 or 2.5) acidic ionic liquid as the catalyzer of chlorination, Cl ₂ is chlorine source, carries out toluene selective chlorination reaction; The selectivity of chlorotoluene can reuse the [BMIM]Cl– _nZnCl ionic liquid catalyst separated from the product, which reduces production costs and is an important method that is beneficial to the industrial production of o-chlorotoluene.

A preparation method for o-chlorotoluene is characterized in that it is carried out in the following steps:

(1) Preparation of ionic liquid [BMIM]Cl-nZnCl ₂ : preparation method referenced literature: JSWilkes, JALevisky, RAWilson, CLHussey, Dialkylimidazolium chloroaluminate melts: a new class of room-temperature ionic liquids for electrochemistry, spectroscopy, and synthesis, Inorganic Chemistry. 1982, 21, 1263-1264.

Under the protection of nitrogen, stir 1.3mol of 1-methylimidazole and 1.4mol of n-chlorobutane in a 500mL three-necked flask with a condenser, and heat up to 80°C under reflux for 48h; use a separatory funnel to make The product was separated from the remaining unreacted liquid, and the product was washed with ethyl acetate for 3 times; the crude product was evaporated under vacuum at 60°C to remove residual ethyl acetate, and dried in vacuum at 70°C for 24h, and the obtained light yellow liquid was [ BMIM] Cl ionic liquid intermediate, stored in dry N ₂ atmosphere for future use.

In N ₂ atmosphere, add 34.92g (0.2mol) intermediate and 27.30g (0.2mol) ZnCl ₂ into the three-necked flask, stir to disperse evenly, and react at 120°C for 2h; change the amount of ZnCl ₂ to 54.60g (0.4mol) ) and 68.25g (0.5mol) to prepare [BMIM]Cl-2ZnCl ₂ , [BMIM]Cl-2.5ZnCl ₂ acidic ionic liquids.

(2) Toluene chlorination reaction step: Add 1.0 mol of toluene into a 250 mL four-neck flask, add a certain amount of [BMIM]Cl–nZnCl ₂ ionic liquid catalyst, and stir to make it evenly dispersed. Then feed the chlorine gas dried by concentrated sulfuric acid into the system, and react at a certain temperature for a certain period of time to obtain o-chlorotoluene. After the tail gas is condensed, it is absorbed by NaOH solution to remove unreacted Cl ₂ ; the reaction is carried out under light-shielding conditions. , separate the reaction product from the ionic liquid catalyst with a separatory funnel, and separate the ionic liquid for reuse.

Wherein, the [BMIM]Cl—nZnCl ₂ (n=1, 2, 2.5) ionic liquid catalyst added in the step (2) is added in an amount of 1% to 5% of the moles of toluene.

Wherein, step (2) chlorination reaction temperature is 30～90 ℃.

Wherein, the chlorination reaction time described in step (2) is 2 to 8 hours.

Wherein, the flow rate of chlorine gas dried by concentrated sulfuric acid is 50mL/min.

The advantages of the present invention are:

1. The present invention adopts chlorine gas as the chlorine source, and the source of raw materials is wide and the cost is low, so that the chlorination of toluene to prepare o-chlorotoluene is more conducive to industrialization.

2. The chlorination reaction condition that the present invention adopts is gentle, adopts gas-liquid continuous reaction, and reaction is easy to control, and raw material conversion rate is high, and the selectivity of o-chlorotoluene in the product is high.

3. The catalyst used in the present invention is easy to separate from the chlorinated product, and has good stability, which solves the shortcoming that the traditional Lewis acid catalyst is difficult to separate from the product, effectively reduces the production cost, and is beneficial to industrial production.

Description of drawings

Among the present invention, toluene chlorination product uses gas chromatograph to carry out quantitative analysis, and its model is GC7890-II.

Fig. 1 is the spectrogram of standard sample, and the preparation of standard sample is that internal standard isopropanol and raw material toluene, chlorination product are mixed in a certain proportion (reagents used are all commercially available analytical grades).

Fig. 2 is the spectrogram of toluene chlorination product, is under identical chromatographic condition, the analysis that toluene chlorination product is carried out. By comparing these two spectra, it can be seen that o-chlorotoluene was synthesized by ionic liquid catalyzed chlorination of toluene.

detailed description

The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto, and the data shown therein do not represent limitations to the scope of the present invention.

Example 1

(1) Preparation of ionic liquid [BMIM]Cl-2ZnCl ₂ : Under nitrogen protection, 1.3mol of 1-methylimidazole and 1.4mol of n-chlorobutane were stirred and mixed in a 500mL three-necked flask with a condenser , heated to 80°C under reflux and reacted for 48h; the product was separated from the remaining unreacted liquid with a separatory funnel, and the product was washed with ethyl acetate for 3 times; the crude product was rotary evaporated under vacuum at 60°C to remove residual ethyl acetate, Vacuum-dried at 70°C for 24h, the obtained pale yellow liquid was [BMIM]Cl ionic liquid intermediate, which was stored under a dry N ₂ atmosphere for future use.

In the N ₂ atmosphere, 34.92g (0.2mol) of the intermediate and 54.60g (0.4mol) of ZnCl ₂ were added to the three-necked flask, stirred to disperse evenly, and reacted at 120°C for 2h.

(2) Toluene chlorination reaction step Add 1.0mol toluene into a 250mL four-neck flask, add 0.03mol [BMIM]Cl-2ZnCl ₂ ionic liquid, stir to make it evenly dispersed, and then feed 50mL/min into the system through concentrated Sulfuric acid-dried chlorine gas was reacted at 70°C for 8 hours to obtain o-chlorotoluene, and the tail gas was absorbed by NaOH solution to remove unreacted Cl ₂ .

Change the amount of ZnCl2 to 27.30g ( _0.2mol ) and 68.25g (0.5mol) to prepare [BMIM]Cl _- ZnCl2, [BMIM]Cl- _2.5ZnCl2 acidic ionic liquids, and ionic liquids with different acid strengths can be obtained. The impact of toluene chlorination process, as shown in Table 1:

Table 1 Effects of ionic liquids with different acid strengths on the chlorination of toluene

Note: OCT is o-chlorotoluene, MCT is m-chlorotoluene, PCT is p-chlorotoluene, and DCT is dichlorotoluene.

As the ratio of ZnCl ₂ to the ionic liquid intermediate [BMIM]Cl increased from 1 to 2, 2.5, the conversion of toluene increased from 90.20% to 98.77%, 99.10%; the selectivity of the target product o-chlorotoluene increased from 68.97% to increased to 73.04%, then decreased to 69.73%.

As can be seen from Table 1, [BMIM]Cl- _nZnCl2 acidic ionic liquid has good catalytic activity to toluene chlorination, the conversion rate of toluene is high, and the selectivity of o-chlorotoluene is good. In addition, the increase of the acid strength of the ionic liquid is beneficial to the formation of the target product o-chlorotoluene, but it also leads to the increase of the by-product dichlorotoluene.

Example 2

Adopt the same method of embodiment 1 to prepare [BMIM]Cl- _2ZnCl ionic liquid, the process of toluene chlorination adopts the same method of embodiment 1, but change [BMIM]Cl-2ZnCl _The consumption of ionic liquid is 0.01mol, 0.05mol, can get [BMIM]Cl-2ZnCl _The influence of the consumption of ionic liquid on toluene chlorination process, as table 2:

Table 2 Effect of the amount of [BMIM]Cl-2ZnCl ₂ ionic liquid on the chlorination reaction of toluene

Table 2 shows the effect of catalyst dosage on toluene chlorination reaction. When [BMIM]Cl-2ZnCl ₂ ionic liquid was used as the catalyst, the conversion rate of toluene increased from 80.14% to 98.77% and 99.75% as the catalyst dosage increased from 1% to 3%, 99.75%; the selection of o-chlorotoluene Sex increased from 67.86% to 73.04%, then decreased to 68.58%.

As can be seen from Table 2, increasing the consumption of catalyzer is conducive to the raising of toluene chlorination reaction; But when catalyst consumption increases to 5% from 3%, because the increase of by-product dichlorotoluene, the selectivity of o-chlorotoluene is reduced . Therefore, from the point of view of industrialization, it is more appropriate to select 3% catalyst dosage.

Example 3

Adopt the same method of embodiment 1 to prepare [BMIM]Cl- _2ZnCl ionic liquid, the process of toluene chlorination adopts the same method of embodiment 1, but change reaction temperature to be 30 ℃, 50 ℃, 70 ℃, 90 ℃, The impact of different reaction temperatures on the toluene chlorination process can be obtained, as shown in Table 3:

Table 3 Effect of different reaction temperatures on the chlorination of toluene

Table 3 has reflected the influence of temperature of reaction on toluene chlorination reaction; As can be seen from table 3, along with temperature of reaction rising to 90 ℃ from 30 ℃, the transformation rate of toluene increases from 78.25% to 99.84%; The selectivity increases first and then decreases. At 70°C, the selectivity of o-chlorotoluene reaches a maximum value of 73.04%; the selectivity of dichlorotoluene increases from 1.89% to 7.17%; increase and the selectivity of o-chlorotoluene, but also promote the generation of dichlorotoluene.

Example 4

Adopt the same method of Example 1 to prepare [BMIM]Cl _- 2ZnCl2Ionic liquid, the process of toluene chlorination reaction adopts the same method of Example 1, but changing the reaction time is 2h, 4h, 6h, 8h, different reactions can be obtained The impact of time on the toluene chlorination process, as shown in Table 4:

Table 4 Effects of different reaction times on the chlorination of toluene

Table 4 reflects the influence of reaction time on toluene chlorination reaction. As can be seen from the table, with the prolongation of the reaction time, the conversion rate of toluene and the selectivity of o-chlorotoluene increased gradually. After 8 hours of reaction, the conversion rate of toluene reached 98.77%, and the selectivity of o-chlorotoluene reached 73.04%.

Example 5

Adopt the same method of embodiment 1 to prepare [BMIM]Cl- _2ZnCl ionic liquid, the process of toluene chlorination adopts the same method of embodiment 1, with [BMIM]Cl- _2ZnCl ionic liquid and chlorination product separation, use For the 2nd, 3rd, 4th, and 5th time, the influence of catalyst use times on the toluene chlorination process can be obtained, as shown in Table 5:

Table 5 Effect of catalyst usage times on toluene chlorination reaction

Table 5 reflects the impact of catalyst use times on the toluene chlorination reaction; as can be seen from Table 5, along with the increase of catalyst use times, the conversion rate of toluene and the selectivity of o-chlorotoluene all slowly decline, when the catalyst is used for the fifth time When in use, the conversion rate of toluene remained at 92.37%, and the selectivity of o-chlorotoluene remained at 70.11%, which indicated that [BMIM]Cl-2ZnCl ₂ ionic liquid catalyst had strong stability and good cycle performance.

Claims (2)

1. a kind of preparation method of ortho-chlorotolu'ene, it is characterised in that step is as follows：[BMIM] Cl-nZnCl are added into toluene₂From Sub- liquid catalyst, n=2, stirring makes it be uniformly dispersed；Then the chlorine dried through the concentrated sulfuric acid is passed through into system, certain At a temperature of reaction certain time obtain to absorb through NaOH solution after ortho-chlorotolu'ene, tail gas condensing and remove unreacted Cl₂；Reaction is being kept away Carried out under optical condition, after reaction terminates, reaction product is separated with ionic-liquid catalyst with separatory funnel, ionic liquid is isolated Body is reused；Described [BMIM] Cl-nZnCl₂Ionic-liquid catalyst addition is the 3% of toluene molar number；The chlorine It is 70 DEG C to change reaction temperature；The described chlorination reaction time is 8h.

2. a kind of preparation method of ortho-chlorotolu'ene as claimed in claim 1, it is characterised in that：The chlorine dried through the concentrated sulfuric acid Flow is 50mL/min.