Green Nitration For Synthesis Of Nitrobenzene And Mononitrotoluene

Nitrated aromatics are important chemical products and intermediates, which are widely used in modern scientific field. However, there are problems associated with the conventional nitration of aromatics by mixed acid and these include poor atomic economy and serious environmental pollution. In recent years, the new clean nitration of aromatics has become a kind of very important and attractive research area.In this thesis, the green nitration of benzene and toluene by N2O5 to form nitrobenzene and mononitrotoluene, respectively, has been studied. The effects of the reaction conditions on the conversion of aromatics and the selectivity of nitrated aromatics, reaction kinetics and mechanism of nitration have been investigated.The nitration reaction of benzene and N2O5 catalyzed by several zeolites was carried out in a batch reactor. The effects of temperature, time and solvent on the nitration reaction were investigated. The optimal reaction conditions were found. The maximal conversion of benzene and selectivity of nitrobenzene were obtained over NaY zeolite in the CH2Cl2 solution at 15℃for 4 h and they were 99% for the conversion and 100% for the selectivity. The catalysts were characterized by Py-IR and NH3-TPD and the effect of the acid species on the surface of zeolites on the nitration reaction was investigated.The nitration reaction of toluene and N2O5 to form mononitrotoluene without the catalysts was also carried out. The optimal reaction conditions for the synthesis of mononitrotoluene were 15℃for the reaction temperature, 0.5h for reaction time, CH2Cl2 as solvent and 1.2:1 for the molar ratio of N2O5 to toluene. The conversion of toluene and the selectivity of mononitrotoluene at mentioned-above conditions were 98.6% and 97.7%, respectively.Kinetics of the nitration reaction of benzene over NaY zeolite and non-catalytic nitration of toluene were studied and the kinetics equations were obtained. They were as follows.For the nitration of benzene over NaY zeolite: r = 1.65×101 0 e75290/RT ?cbenzeneFor the nitration of toluene without the catalysts: r = 2.44×10 2 e25940/RT ?ctoluene.The existence of NO2+ in the solution which consists of N2O5/CH2Cl2 with and without catalysts was testified by low-temperature Raman spectrum. The reaction activity of the -H, -CH3 and -NO2 substituted aromatics obtained from the experimental data mentioned-above were toluene>>benzene>>nitrobenzene. Therefore, it is reasonable to assume that the nitration reaction of benzene and toluene with N2O5 was consistent with mechanism of electrophilic substitution.