A simple and general scale-up procedure, based on boundary and temperature diagram safety criteria for exothermic semibatch reactors (SBRs), has been developed. Such a procedure is based on a few graphical correlations that allow end users, dealing with homogeneous as well as heterogeneous SBRs (with or without autocatalytic behavior), an easy selection of safe operating conditions at the laboratory scale and for their scale-up to the industrial one, maximizing at the same time the industrial reactor productivity.

In this work, a simple and general method has been developed that, on the basis of an easy-to-measure quantity referred to as the ψ number, allows for ongoing detection of the displacement of the SBR operating regime from safe target conditions, without any information about the reaction kinetics. Such a feature is of particular importance because, when dealing with reaction processes in the fine-chemicals and pharmaceuticals industries, the estimation of the kinetic parameters of the reactions involved is often not practicable, because of the huge variety of productions encountered and the simultaneous occurrence of mass-transfer phenomena in heterogeneous systems. Moreover, the method in question has been confirmed to be useful for the early detection of low-reactivity or non-ignition regimes of the SBR, to prevent the dangerous accumulation phenomena resulting in a thermal loss of control of the main reaction and a further triggering of pressure-generating decomposition events. Finally, the criterion was validated by analyzing the available data from an industrial SBR in which the water emulsion polymerization of acrylic monomers was performed

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In this work, a procedure based on the use of boundary and temperature diagrams for selecting safe and productive operating conditions of homogeneous semibatch reactors is presented and the influence of the reaction kinetics on the shape and extension of such diagrams is discussed. It has been found that using correlations developed for (1,1) reaction order kinetics can lead to both unsafe or not necessary low production operating conditions, especially with reference to the reaction order of the dosed coreactant. Moreover, the dependence of the shape and extension of such diagrams on the chemical kinetics has been found to be completely different when homogeneous or heterogeneous reacting systems are considered. A number of ready-to-use boundary and temperature diagrams is presented, together with some rules of thumb for their use, allowing for the easy selection of safe and productive operating conditions for homogeneous semibatch reactors.

In this work a simple and general procedure, for optimally scaling-up exothermic semibatch processes, has been applied to the analysis of a nitration reaction performed in the agrochemical industry for the production of an important class of herbicides. Such a reaction is performed in indirectly cooled semibatch reactors in which the species to be nitrated is added to a mixture of sulfuric and nitric acid, forming an heterogeneous (liquid-liquid) system. Adiabatic calorimetric experiments performed in an ARC equipment showed that the reaction in question belongs to the most critical class of exothermic reaction processes, for which maximum attainable temperature due to synthesis reaction (MTSR) is, at the same time, higher than system decomposition temperature and lower than boiling temperature of the reaction mass. It has been verified, through reaction calorimetry experiments (performed in an RC1 equipment), that the optimization -scale-up procedure previously developed allows, with a minimum calculation and experimental effort, both for a selection, at laboratory scale, of operating conditions characterized by a rapid coreactant consumption and for their safe scale-up, maximizing industrial reactor productivity.