HEAT-BALANCE REACTION CALORIMETRY AND ITS APPLICATIONS IN ETHYLENE POLYMERIZATIONS

Reaction calorimetry is a powerful tool for the determination of polym erization rate, monomer conversion, heat transfer properties and visco sities for batch and semi-batch polymerizations. Reaction calorimetry makes it possible to study these phenomena simultaneously, and to see if there are interactions between them. In particular, for batch polym erizations, a reaction calorimeter opens up new possibilities for stud ying the polymerization process. The aim of this thesis was to design and construct a reaction calorimeter for studying polymerizations, inc luding data acquisition and instrument control. After construction of the device, a thermal model for the calorimeter was developed, firstly to ensure good estimates of fundamental parameters and secondly to gu arantee accurate characterizations of the device. Also of interest was the application of the calorimeter knowledge to metallocene polymeriz ations. The viscosity of the reaction mixture was found to increase dr amatically during the metallocene catalysed ethylene slurry polymeriza tion, but it could be controlled through the selection of an appropria te reaction mixture medium. The apparent viscosity of the reaction mix ture increased due to the growing amount of solid polymer in the suspe nsion and, as a result, the value of the heat transfer coefficient dec reased. The porous polymer particles produced also have very strong ef fects on macro scale mass transfer when Et[Ind]2ZrCl2 provides the cat alyst. The mass transfer between gas and liquid phases was the rate-de termining step for the ethylene polymerization when the apparent visco sity of the reaction medium was above 15 mPas. The rapid decrease in t he polymerization rate was not detected when very small amounts of cat alyst were used. When the initial polymerization rate was below 0.19 m mol/s, it took a long time before sufficient amount of the solid polym er was produced to have an influence on the mass transfer between gas and liquid phases. Using low catalyst concentrations the polymerizatio n rate was decreased due to catalyst deactivation, and the effect of m ass transfer resistance was not seen.