Kinetic and safety assessment for salicylic acid nitration by nitric acid/acetic acid system

Batch salicylic acid nitration by nitric acid/acetic acid mixture under isothermal, isoperibolic and adiabatic conditions

“…Initial runs with a salicylic acid concentration up to 18 times higher than those used in previous studies have revealed that the system was still homogeneous and that the above described model [4] well predicts its behaviours (data not shown). Good results have been obtained also in the modelling of isothermal nitration processes of salicylic acid (Fig.…”

“…Nitric acid/acetic acid mixtures have been demonstrated to be a suitable system for the nitration of salicylic acid showing interesting features in terms of yield and achievement of an easier separation of the product from the solution. In a previous investigation [4] the authors have shown that runaway phenomena can occur during the nitration process of salicylic acid by means of nitric acid/acetic acid mixtures as a result of polynitration reactions which take place when the thermal control of the process is lost. In particular, successive nitration of 5-nitrosalicylic acid and of its side and by-product (3-nitrosalicylic acid and 2-nitrophenol) leads to the formation of explosive picric acid [5].…”

“…In particular, successive nitration of 5-nitrosalicylic acid and of its side and by-product (3-nitrosalicylic acid and 2-nitrophenol) leads to the formation of explosive picric acid [5]. The reaction network through which the system evolves has been completely characterized from the thermokinetic point of view, although the previous study [4] has been carried out on diluted systems in which the substrate concentration was even two orders of magnitude lower than that which could be of interest in real applications. Since one of the most interesting features of nitric acid/acetic acid mixtures is represented by the capability of the product 5-nitrosalicylic acid to separate from the reacting solution by precipitating, an extension of the study to assess the behaviour of more concentrated systems is of great importance.…”

“…Even though previous studies have demonstrated that the mixture of salicylic acid with nitric and acetic acid can give rise to runaway phenomena, no data are available for more concentrated heterogeneous systems. The present work thus aims to upgrade the model developed during previous investigations [4] to make it capable of simulating the nitration process starting …”

“…A good agreement was observed among the experimental data and those calculated by the model. It is worthwhile stressing that the kinetic parameters used in the model were those previously estimated [4] and reported in Table 1 without any adjustment. Similar results have been found by submitting to nitration (for initial conditions see Table 6) 3-nitrosalicylic acid (Figs.…”