Eduard Serra

Emulsion polymerization of vinyl acetate: safe optimization of a hazardous complex process.

Fast and exothermic discontinuous emulsion polymerization processes are particularly difficult to optimize from both safety and productivity point of view because of the occurrence of side undesired reactions (e.g. chain transfer to monomer, backbiting, propagation of tertiary radicals, termination by disproportion, etc.) and the hazards of boiling phenomena and stable foam formation under atmospheric pressure. Moreover, the relevant number of loading, heating and cooling steps, required before starting the monomer addition (that is, the desired reaction), makes a strict product quality reproducibility very difficult to obtain. Under these operating conditions, it is necessary to employ a suitable combined theoretical and experimental procedure able to detect the optimum process dosing time at both the laboratory and the industrial scale. In this work, it is shown how to use the topological criterion theory together with proper adiabatic calorimeter and RC1 experimental data to safely optimize the synthesis of polyvinyl acetate through the radical emulsion polymerization of vinyl acetate by the means of an indirectly cooled isoperibolic semibatch reactor.

Sensitivity analysis of the 2-methylpyridine N-oxidation kinetic model

A sensitivity analysis of a previously developed global kinetic model, of the N-oxidation of 2-methylpyridine, involving seven kinetic and equilibrium constants, has been performed. It has been identified how individual constants influence the power evolution profile. The conditions, which ensure measurements sensitive to all constants, are outlined. A readily applicable, simple methodology has been developed to achieve accurate evaluation of the kinetic constants involved.

Maximum temperature attainable by runaway of synthesis reaction in semibatch processes

Abstract A new scenario for the calculation of the adiabatic temperature increase for semi-batch processes is presented. In the safety assessment of chemical reactions it is necessary to determine the value of the Maximum Temperature attainable by runaway of the Synthesis Reaction for the worst case. We demonstrate that the batch scenario is not always the most dangerous way to carry out a reaction. In addition, an improvement in the calculation of the MTSR is presented in order to obtain more realistic scenarios.

A comparison of calorimetric measurements by using different reaction calorimeters

For a great number of European safety groups, reaction calorimetry is the key technique for analysis of the main reaction in the risk assessment of chemical processes. A comparison of calorimetric studies of model reactions, the N-oxidation of two substituted pyridines with hydrogen peroxide, made by several European groups, can open the door to standardization of the methodologies used. However, the intrinsic experimental complexity of the model reactions, which included dosing at high temperature, a multiphase system and evaporation, and the different evaluation criteria, produced a considerable dispersion between the results obtained by the various groups.

Nonparametric Kinetic Methods

As all classic methods for kinetic analysis of data from thermal analysis experiments, the nonparametric kinetics method, NPK, assumes that the general expression for the reaction rate of a simple reaction is

The estimation of reaction enthalpy for complex molecules using benson groups : Comparison of different strategies

{\dot{\alpha } = g(\alpha ) \cdot f(T)}

Aplicación del método NPK a la determinación de la cinética de descomposición del triperòxido de triciclohexilideno

(16.1) where g(α) symbolizes the kinetic model of the process and f(T) accounts for the temperature dependence of the reaction.