Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.

In this paper after a literature surveyin which we describe previous development of the theory and the experimental work to prove the theorieswe discuss the so-called safety diagram and practical values of the relevant parameters in laboratory and plant equipment. We explore when operating conditions are inherently safe and prove that the findings of the safety diagram also apply to batch reactors. We explain the safety diagram data can also be applied to reactions with orders different from 1 for each component and to multiple reactions. All criteria in the literature, developed to determine safe operating conditions to prevent runaway in semibatch and batch reactors, are based on the knowledge of the kinetics of the reactions concerned. In fine chemical industries, however, usually it is impossible to determine kinetics due to economic and time constraints. Previous work on so-called safety diagrams, therefore, has been extended to the full range of all practical cooling number values as they occur in plant reactor operations. From the results obtained two diagrams are presented for the minimum value of the so-called exothermicity, below which no runaway will occur, as well as for the minimum reactivity, above which no runaways are possible, both as a function of the cooling number:  one diagram is for the reactions taking place in the dispersed phase, and the other is for those in the continuous phase. With these diagrams inherently safe operating conditions can be determined for high reactor productivities. It is demonstrated that the data obtained can be used also for a multiple-reaction scheme, except for autocatalytic reactions. Further it is discussed how the necessary information can be obtained by reactor tests in the plant, by experiments in standard laboratory equipment, and from the literature. A rapid procedure is developed which leads to safe operating conditions without costly and time-consuming kinetic studies.

Aromatic nitration by mixed acid was selected as a specific case of heterogeneous liquid-liquid reaction. An extensive experimental programme was followed using adiabatic and heat flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments was carried out to study the influence of different initial and operating conditions, such as temperature, stirring speed, feed rate and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate was developed. In this paper, the mathematical modelling, implementation and experimental validation for mononitrations of benzene, toluene and chlorobenzene in the mass transfer controlled regime of fast liquid-liquid reactions are presented and discussed.