Correlations of thermo-physical properties used for process optimization via simulation-models are built mainly on data determined at atmospheric pressure which has to be extrapolated for high-pressure applications. Main intention for this work is therefore to supplement the fragmentary substance data base in literature at pressures of up to 3000 bar with main focus on the pressure dependence of heat capacities. For implementing this new topic the first step of this work is to evaluate different measurement methods for heat capacities regarding their applicability and precision in a special high-pressure Tian-Calvet calorimeter: the Transitiometer. Following the method evaluation, thermo-physical properties of several gases and fluids in their temperature and more important their pressure dependence are determined. Results are compared to available literature data or equations of state, mainly PC-SAFT. Additional topics of this work are the investigation of polymer degradation as function of time and temperature, fitting of correlations and PC-SAFT parameters to measured heat capacities as well as the implementation of correlations in a deterministic simulation-model of an industrial process.weiterlesen