FIGURE 2 Effect of temperature and residence time on the
conversion of CB. The mass
fraction of H2SO4 = 95%, molar ratio of
HNO3 to CB = 1.3, Q or = 0.4
mL/min, and Q ac = 0.9 mL/min
It is worth mentioning that DNCB is an undesirable byproduct, and to
obtain accurate kinetic data for the nitration of CB, the selectivity of
DNCB needs to be controlled to a low level. The selectivity of each CB
nitration product was investigated as a function of the reaction
temperature, as shown in Figure 3 . As the temperature and
residence time increased, NCB was further nitrated to form DNCB,
resulting in an increase in the selectivity of DNCB. However, at the low
temperature used in this work and with the short residence time, the
selectivity of DNCB remained below 1%. In addition, lowering the
temperature had a more obvious inhibitory effect than shortening the
residence time on the formation of DNCB. Therefore, the formation of
DNCB had a negligible effect on the accuracy of the primary CB nitration
kinetic data. When substituents are introduced on the benzene ring, the
nitration difficulty will change. For example, in the tertiary nitration
of CB, because the introduced nitro functional group is an
electron-withdrawing group, the electron cloud density of the benzene
ring decreases, and a certain steric hindrance is generated, making
nitration more difficult. Therefore, no 1-chloro-2,4,6-trinitrobenzene
was detected after reaction.