Abstract
The industrial production of mononitrobenzene (MNB) is currently achieved with high yields by liquid phase nitration of benzene (Bz). However, the environmental footprint of this process is highly dependent on the minimization of reaction by-products, such as nitrophenols, whose elimination and disposal procedures are subjected to very strict regulations. The mechanisms behind their formation are still not completely understood and would benefit from detailed information about their distribution in the reaction mixture. This work reports predictive models for the distribution ratio (??) of the by-products 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP) in a bi-phasic organic-aqueous system representative of industrial nitrators.
Equilibrium concentrations of DNP and TNP were measured at 30 °C for different initial conditions, namely: composition of the aqueous (H2SO4 + water) and organic (Bz + MNB) phases, their weight ratio, and the concentration of nitrophenols. Multivariate linear regression (MLR) models were built with a sub-set of the experimental data and confirmed by external validation, exhibiting high fit quality (??2 and ??2 > 0.900) and 22 prediction capability (??Pred,DNP = 0.936; ??Pred,TNP = 0.962). The most significant predictor was the equilibrium concentration of sulphuric acid in the aqueous phase, followed by benzene concentration in the organic phase. The distribution ratios of DNP and TNP decrease with the increase of these concentrations. A higher affinity of DNP with the organic phase was confirmed by ??DNP ˜ 2??TNP.
