An experimental investigation of promoted iron-based oxide for high-temperature water-gas shift reaction catalysts at membrane reactor conditions and an experimental and computational study of solvent effects in toluene chlorination.

摘要

This dissertation consists of two parts. Part A, "An experimental investigation of promoted iron based oxide for high temperature water gas shift reaction (WGSR) catalysts in membrane reactor conditions" which includes in Chapter 1 and Chapter 2. Trade off between rate of the reaction and conversion of WGSR can be avoided by operating this reaction in a membrane reactor. A microkinetic model was proposed and simulation results show that better reducibility may improve the performance of iron oxide based catalysts by reducing the CO2 inhibition effect. Unpromoted iron oxide deactivated quickly during reaction. CeO2 promotion does not affect the iron oxide reducibility or the CO2 inhibition for WGSR relative to unsupported iron oxide. Low copper loading iron chromium oxide forms a Fe-Cr-Cu-O solid solution, increases the reducibility of the iron oxide based catalyst and alleviates CO2 inhibition at membrane reactor conditions. Excess copper leads to a separate CuO phase which is be reduced to metallic copper during the reaction. A copper loading of ca. 5% wt is believed to be the optimal copper loading for this study.; Part B is "An Experimental and Computational Study of Solvent Effects in Toluene Chlorination" which includes chapter 3. The rate of the uncatalyzed chlorination of toluene by molecular chlorine was studied without added solvent and in acetic acid solution. During competitive reaction in acetic acid, the chlorination of C7H8 proceeded at a rate equal to that of C7D8. The rate of reaction was estimated to be smaller by a factor of 10-4, when no solvent was added. Calculations using density functional theory suggest that the reaction is bimolecular and does not involve an arenium cation as an intermediate when low-dielectric solvents are used. The carbon-hydrogen bond is broken late in the reaction process, consistent with the observed kinetic isotope effect. The difference between the reaction rate without solvent and that in acetic acid can be attributed to the stabilization of the activated complex in acetic acid solution. The computational results suggest that in other solvents, with higher dielectric constants, the accepted reaction pathway involving an arenium cation is likely to predominate.