Abstract
The use of different calorimetric techniques for process design and scale up is well consolidated, allowing the definition of the kinetic and thermodynamic of the process and the evaluation of several parameters useful to optimization and process safety. During a calorimetric analysis temperature (or a temperature difference) is measured; from experimental data it is for example possible to calculate the heat flow and the heat evolved by the reaction and consequently the conversion and the reaction rate constant just if kinetics of the reaction is known. To overcome these limitations and to obtain additional information about the reaction, it is possible to couple to a calorimeter different type of sensors such as densitometers, refractometers, electrochemical, chromatographic and spectrophotometric probes (Schwedt, 1997). Some of these sensors are able to log data on line during the process and so to monitor the reaction at the same time of the calorimetric analysis. For safety aims, it is important to choose a sensor whose time for the analysis is comparable to the reaction time in order to have an accurate profile of the monitored parameter during the reaction (Moritz, 1989).
In a previous study (Parisi, 2002; Ampelli et al. 2003) an Ultra Violet - Visible spectrophotometer was integrated to a reaction calorimeter to analyse the kinetic of a specific reaction. In this work a similar UV - Vis probe has been coupled to an isoperibolic reaction calorimeter in order to study the feasibility of the application of an Early Warning Detection System (EDWS) to a spectrophotometric signal. The innovation of this integration of techniques is the analysis of the spectrophotometric signals with a reactor stability criterion based on divergence theory in order to check if this method of monitoring allows detecting runaway reactions at an early stage of the process, when it is still possible to take protective measures.
