Method for producing p-chorotoluene by using element selenium as catalyst

Abstract

The invention provides a method for producing p-chorotoluene by using the element selenium as a catalyst, comprising the following steps of: using a selenium-containing organic compound as a catalyst, performing a liquid phase ring chlorination reaction between toluene and chlorine, followed by aeration after the reaction, removing residual chlorine and hydrogen chloride gas in the reaction solution, rectifying to obtain o-chlorotoluene, and carrying out melt crystallization on the enriched p-chorotoluene to obtain the high-purity p-chorotoluene. By the adoption of the method, the yield of p-chorotoluene is raised; the catalyst with a stable structure can be repeatedly applied; the technology and equipment are simple; the production cost is low; and there is no pollution to the environment.

Description

technical field

[0001] The invention belongs to the field of chemical industry, in particular to a method for producing p-chlorotoluene by using element selenium as a catalyst. Background technique

[0002] Chlorotoluene, including p-chlorotoluene and o-chlorotoluene, is an important class of organic chemical raw materials and is widely used in fine organic chemical products such as pesticides, medicines, and dyes. Among them, p-chlorotoluene is more widely used, and its price is much higher than that of o-chlorotoluene.

[0003] Chlorotoluene is generally produced by ring chlorination of toluene, but using common Lewis acid as a catalyst, most of the monochlorotoluene obtained by ring chlorination of toluene is o-chlorotoluene, and the content of p-chlorotoluene is only 30 %-40%. Because the use of p-chlorotoluene is far more than that of o-chlorotoluene, for this reason, a catalyst that can improve the ratio of ring chlorination reaction must be selected to improve the r...

Examples

Embodiment 1

[0028] Catalyst preparation and chlorination reaction

[0029] In a four-neck flask equipped with a reflux condenser, a chlorine pipe, stirring, and a thermometer, add 0.5 g of iron powder, 0.8 g of selenium powder, and 0.7 ml of benzyl chloride, and then add 400 ml of toluene. Chlorine gas was introduced at room temperature, and the temperature was controlled not to exceed 40°C. Chlorine gas feed rate is 150-160 ml / min, and the feed time is about 6 hours. At this time, iron powder and selenium powder are all dissolved, the conversion rate of toluene is between 60-70%, and there is a relatively large amount of chlorine in the reaction material system. oily substance produced. The catalyst prepared above was preserved for future use.

[0030] Take 40 ml of the above-mentioned homogeneously mixed catalyst, (it should be measured quickly after full stirring to avoid catalyst sedimentation), and add 400 ml of fresh toluene, and place it in a four-necked flask equipped with a ref...

Embodiment 2

[0037] Chlorination reaction

[0038] According to the experimental method of Example 1, an appropriate amount of one of antimony trichloride, ferric chloride, and zinc chloride is added in an amount of 0.05-0.1 g, and the chlorination reaction time can be shortened to 5 hours. After testing, its ratio to the ortho position is similar to that of Example 1, and the number of applications can reach 20-80 times.

[0039]

Embodiment 3

[0041] Industrial Catalyst Preparation and Chlorination

[0042] In a 3000L reactor equipped with a reflux condenser, a chlorine pipe, agitator and a thermometer, add 4.0Kg of iron powder, 6.4Kg of selenium powder and 6.5L of benzyl chloride, and then add 1600 L of toluene. A catalyst for toluene ring chlorination reaction is prepared by feeding chlorine gas. The preparation method is controlled as in Example 1.

[0043] 10,000 L of dry toluene was put into a reaction tower with a diameter of 1.3 m and a height of 12 m, and then 250 L of the above-mentioned catalyst was put in for chlorine reaction. The external circulation is cooled, the temperature is controlled not to exceed 55°C, and the end point of the reaction is detected by chromatography. The result is: the ortho ratio is 57:43, the conversion rate is greater than 99.0%, and the dichlorotoluene is less than 2.5%.

[0044] After the above-mentioned catalyst is aerated, the still residue of simple distillation can ...

technical field

[0001] The invention belongs to the field of chemical industry, in particular to a method for producing p-chlorotoluene by using element selenium as a catalyst. Background technique

[0002] Chlorotoluene, including p-chlorotoluene and o-chlorotoluene, is an important class of organic chemical raw materials and is widely used in fine organic chemical products such as pesticides, medicines, and dyes. Among them, p-chlorotoluene is more widely used, and its price is much higher than that of o-chlorotoluene.

[0003] Chlorotoluene is generally produced by ring chlorination of toluene, but using common Lewis acid as a catalyst, most of the monochlorotoluene obtained by ring chlorination of toluene is o-chlorotoluene, and the content of p-chlorotoluene is only 30 %-40%. Because the use of p-chlorotoluene is far more than that of o-chlorotoluene, for this reason, a catalyst that can improve the ratio of ring chlorination reaction must be selected to improve the r...

Examples

Embodiment 1

[0028] Catalyst preparation and chlorination reaction

[0029] In a four-neck flask equipped with a reflux condenser, a chlorine pipe, stirring, and a thermometer, add 0.5 g of iron powder, 0.8 g of selenium powder, and 0.7 ml of benzyl chloride, and then add 400 ml of toluene. Chlorine gas was introduced at room temperature, and the temperature was controlled not to exceed 40°C. Chlorine gas feed rate is 150-160 ml / min, and the feed time is about 6 hours. At this time, iron powder and selenium powder are all dissolved, the conversion rate of toluene is between 60-70%, and there is a relatively large amount of chlorine in the reaction material system. oily substance produced. The catalyst prepared above was preserved for future use.

[0030] Take 40 ml of the above-mentioned homogeneously mixed catalyst, (it should be measured quickly after full stirring to avoid catalyst sedimentation), and add 400 ml of fresh toluene, and place it in a four-necked flask equipped with a ref...

Embodiment 2

[0037] Chlorination reaction

[0038] According to the experimental method of Example 1, an appropriate amount of one of antimony trichloride, ferric chloride, and zinc chloride is added in an amount of 0.05-0.1 g, and the chlorination reaction time can be shortened to 5 hours. After testing, its ratio to the ortho position is similar to that of Example 1, and the number of applications can reach 20-80 times.

[0039]

Embodiment 3

[0041] Industrial Catalyst Preparation and Chlorination

[0042] In a 3000L reactor equipped with a reflux condenser, a chlorine pipe, agitator and a thermometer, add 4.0Kg of iron powder, 6.4Kg of selenium powder and 6.5L of benzyl chloride, and then add 1600 L of toluene. A catalyst for toluene ring chlorination reaction is prepared by feeding chlorine gas. The preparation method is controlled as in Example 1.

[0043] 10,000 L of dry toluene was put into a reaction tower with a diameter of 1.3 m and a height of 12 m, and then 250 L of the above-mentioned catalyst was put in for chlorine reaction. The external circulation is cooled, the temperature is controlled not to exceed 55°C, and the end point of the reaction is detected by chromatography. The result is: the ortho ratio is 57:43, the conversion rate is greater than 99.0%, and the dichlorotoluene is less than 2.5%.

[0044] After the above-mentioned catalyst is aerated, the still residue of simple distillation can ...