Publication
The combination of reaction calorimetry and supercritical fluids as reactants and/or solvent holds great potential for the optimization of chemical processes using high pressure near-critical and/or supercritical mixtures. The very specific properties of supercritical fluids and fluid mixtures have been under investigation already from the nineteenth century and some are quite well understood. But there is still a lack of knowledge in macroscopic properties and raw data for pure fluids and fluid mixtures. This cumulates with the difficulty to apply simple equations of state for the prediction of phase behavior and the calculation of the thermodynamic and the derived transport properties. As a whole, the relatively poor engineering information about supercritical fluids is one of the major reasons that explains the slow industrial development of supercritical processing. The work presented here concerns the complete development of the new "supercritical reaction calorimetry field", which is in fact the application of reaction calorimetry to supercritical fluids media. As far as we know we are pioneers in this domain as only relatively small scale calorimeters have been successfully used with SCFs and only scarcely. The fact is that the use of reaction calorimetry provides essential information for scale-up purposes. Moreover it allows additional in-line equipment to be used, in order to get complementary information. This renders the reaction calorimeter much lesser specialized and potentially attractive as a tool for industrial application developments. In order to correctly position this project in the scale of laboratory and industrial researches, the first chapter is dedicated to the review of SCFs and SCF mixtures properties, their potential as volatile organic solvent relievers and their actual industrial applications. As a result there is still a great need in engineering data for pure SCFs and their mixtures, although their unique properties make them suitable for several processes, mostly driven by environmental considerations. Classical reaction calorimetry is also shortly discussed with the determination of the technical challenge that arose from the use of a supercritical fluid, as it basically occupies all the available space. Thus we point out that both cover and flange should be separately controlled and adjusted to the inner temperature in order to avoid side heat transfer from the reaction media to those elements. Moreover, the regulation parameters for the jacket and the additional cover and flange should be optimized. This has proved to be difficult as these parameters have been shown to depend strongly on the supercritical carbon dioxide pairs, density and temperature. Nevertheless satisfactory pairs of P, I parameters for all three parts of the reactor have been found using the Ziegler-Nichols approach for the jacket and a pure trial-and-error approach for the two others. The heat transfer with SCFs should be carefully taken i