New method for preparing p-chlorotoluene through selective chlorination of toluene

Abstract

The invention provides a new method for preparing p-chlorotoluene through selective chlorination of toluene. The new method comprises the steps as follows: 1) mixing alkylimidazolium chloride ionic liquid with lewis acid to obtain lewis acid type ionic liquid, wherein R1 and R2 are C1 to C8 alkyl group, and MCln is lewis acid such as ferric trichloride, aluminium trichloride and antimony trichloride; 2) taking the lewis acid type ionic liquid as catalyst to be added in toluene solution, introducing chlorine gas in dark, controlling the temperature at 0-50 DEG C in the whole chlorination process, and controlling the chlorine introduction amount so as to enable the conversion percent of the toluene to be larger than 85%; and (3), cooling, and then filtering the ionic liquid to obtain the toluene monochloride mixture solution. After being applied for toluene ring chlorination as the catalyst, the advantages of small catalyst use amount, high selectivity to p-chlorotoluene, easy separation, and applicability are provided.

Description

technical field [0001] The invention belongs to the technical field of chemistry and relates to a new method for preparing p-chlorotoluene by selective chlorination of toluene. Background technique [0002] Using chlorine gas as a chlorination agent to chlorinate toluene to co-produce o-chlorotoluene and p-chlorotoluene is a commonly used method in industry. Due to the low activity of toluene, the reaction usually needs to be catalyzed by adding a catalyst. [0003] When chlorine gas is used as the chlorination agent to carry out ring chlorination of toluene, Lewis acid is often used as a catalyst. 3 , AlCl 3 , SbCl 3 , SbCl 5 , SnCl 4 etc. Iron powder can also be used. However, when toluene ring chlorination is carried out only with Lewis acid as catalyst, p-chlorotoluene / o-chlorotoluene only reaches 1:3. After adding different sulfur-containing organic substances as auxiliary agents, the para-selectivity can be improved [US 4647709, US 5105036]. The disadvantage of t...

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Problems solved by technology

The disadvantage of this method is that the amount of ionic liquid used as a solvent is too large, the cost is high, and it is difficult to recover, purify and apply mechanically [Organic Chemistry 2011, 31(2), 227-230]

[0006] In the prior art, the disadvantage of the catalytic method of Lewis acid plus organic sulfur additive is that the organic sulfur additive has changed, it is difficult to recycle and apply mechanically, and the selectivity of p-chlorotoluene is not high enough

The disadvantages of molecular sieve and molecular sieve plus additive catalytic method are large amount of molecular sieve, easy to collapse, difficult to recycle and apply

The disadvantage of the alkylimidazolium chloride salt ionic liquid method is that the amount of alkylimidazolium chloride salt ionic liquid is large, it is difficult to purify and apply mechanically, and the selectivity of p-chlorotoluene is not high enough.

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