| dc.description.abstract | ABSTRACT Homogeneous catalysis in which the catalyst, solvents and reactants are all in the same phase can yield high activity and selectivity and efficiently produce chemical products. However, the main problem with these kinds of reactions is separating and reusing precious metal catalyst; therefore, it needs to be performed in a convenient platform. To figure out this problem, a biphasic system can be suggested in which one phase sequesters the solid catalyst and the other phase delivers reactants to and remove products from the reaction media. But, there are some problems using these methods such as thermodynamics and solubility issues, mass transfer limitations, cross-contamination problems, environmental concerns and possibility for a continuous process. Thus, a biphasic ionic liquid (IL) /CO2 system is suggested, which may solve these problems. In this research, special properties of ionic liquids that can make them be the next class of alternative solvents is introduced, and subsequently the main issues in using them is discussed. Then, to overcome the abovementioned problems, a combined biphasic ionic liquid / CO2 system is managed to be used for homogeneous catalytic reactions. The main purpose of this project is running homogeneous catalytic reactions in biphasic IL/CO2 media and managing key parameters in kinetics, momentum and mass transfer, and phase behavior to control the reaction in an efficient zone. For this reason, two typical and large homogeneous catalytic reactions that are practiced in industry, hydroformylation and hydrogenation of 1-octene, have been selected. In order to investigate the effect of CO2 pressure on controlling the reaction over the mass transfer or kinetic zones, thorough studies have been arranged to determine the phase behavior and thermodynamic properties of compounds (reactants, products, and solvents) within the reaction conditions. It has also been revealed in this work that the momentum and mass transfer parameters (diffusivity and viscosity) of ionic liquids can be managed by either the structure of ionic liquids or the pressure of various compressed gases. Thus, the measured and correlated results of viscosities and diffusivities for pure and saturated of different types of ionic liquids with compressed CO2 and 1,1,1,2-tetrafluoroethane (R134a) are reported for further studies to choose the best media (ionic liquid/compressed gas) for reactions. Due to significant impacts of mass transfer on the reaction because of the high viscosity of ionic liquids, it is quite necessary to find mass transfer parameters for the reaction in the biphasic IL/CO2 system. At the first step in these studies, the phase equilibrium, volumetric, and interfacial properties of the catalytic media (ionic liquid phase) and the main substrate (1-octene) have been determined. Then, using the obtained information, the mass transfer coefficient is calculated. Finally, based on these experimental results, a robust, realistic, and efficient finite element method has been developed by Petera - Weatherley to model mass transfer between an ionic liquid droplet and 1-octene continuous system. At the end, further studies are recommended to find mass transfer parameters under compressed CO2 pressure and in presence of gas reactants on the reaction condition to superior understanding and managing the reaction characteristics. | |
