Novel Regioselective Nitration Of Chlorobenzene In Presence Of Lewis Acid Catalysts

It is imperative to develop a novel chlorobenzene nitration technology due to the environmental polution from traditional vitriol-nitric acid technology and imbalance requirement from downstream products of nitrochlorobenzene. This research is the project "Novel catalytic nitration technology with adjustable ratio of isomers" from Henan Kaipu Chemical Joint-Stock Ltd Com. and aims at developing a new regioselective catalytic nitration methodology with favorate ratio of o- and p- isomers to meet the different market reuirements, with environmental benignancy and promotion variety of downstream products.Firstly, caprolactam-based ionic liquid (IL) and trifluoromethanesulfonates were proposed for chlorobenzene regioselective nitration based on electrophilic substitution of chlorobenzene, which the former as IL catalyst was synthesized by caprolactam reacting with p-toluenesulfonic acid and the later as Lewis acid catalyst synthesized by triflic acid (TfOH) with ZrOCl₂ or Zn. Their structures were characterized by IR.Secondly, The GC9800 detection conditions were determined by using 1500mm×2mm stainless steel column, PEGA Stationary Liquid and TCD to analyse the nitration products of chlorobenzene. Nitrobenzene was used as internal standard and the internal standard curve of chlorobenzene, o-chloronitrobenzene and p-nitrochlorobenzene was obtained as well.And third, the catalytic activity and ortho-nitrochlorobenzene selectivity of two different catalysts such as caprolactam p-toluenesulfonic acid ionic liquid and trifluoromethanesulfonates were examined by single factor experiments. The result showed that Zr(OTf)₄ was found to be the most effective one among the two investigated. And the conversion of chlorobenzene was over 87.69% with 0.64:1 of ortho- to para- isomers distribution when 1,2-dichloroethane was used as solvent and 65-68% nitrate acid as nitration agent under the optimum conditions which were abtained by orthogonal test design: n(CB): n(NA): n(Zr(OTf)₄)=1:1.2:0.2, 86℃and 5h.Finally, under the optimum nitration conditions, the nitrition kinetics model in the 60℃-86℃of zirconium trifluoromethanesulfonate system was proposed and its parameters were obtained by multi-variables regression. The rate equation was derivated from experimental data shown as: where the reaction order and activation energy were 2 and -39.83kJ·mol^-1 respectively.