| Previous theoretical work predicted the possibility of enhancing three-phase packed-bed reactor performance by operating in the pulsing-flow regime. In this work, the beneficial effects of pulsing-flow upon reaction outcome were investigated both experimentally and theoretically. In addition, hydrodynamic studies were performed to improve the understanding of the pulsing-flow regime.; A laboratory-scale trickle-bed reactor was employed to study the effects of flow regime upon the hydrogenation of phenylacetylene over a Pt/Al 2O3 catalyst under isothermal conditions. With properly designed experiments, the reaction performance in pulsing-flow and trickling-flow was compared directly. Results indicated that, holding all other parameters constant, pulsing-flow was superior to trickling-flow.; The intrinsic kinetics of the reaction system were investigated in a stirred semibatch slurry reactor, and experimental data were fitted to rate expressions by least-squares analysis. Resulting activation energies compared well with values reported in the literature. The rate expressions determined in this work provide a useful tool for reactor and catalyst design.; Attempts were made to extend the benefits of the pulsing-flow regime to systems operating at average gas and liquid flow rates corresponding to the trickling-flow regime by using the induced-pulsing feed strategy. While experiments performed under mild gas limiting conditions did not demonstrate a benefit from this mode of operation, a theoretical model of the reactor, utilizing the intrinsic kinetics determined in the present work and capable of reproducing experimental results under trickling, pulsing and induced-pulsing flow conditions, predicted improvement in reactor performance owing to induced-pulsing operation under liquid-limited conditions.; Hydrodynamic investigations of multiple air-water packed-column systems indicated that pulses arise from convective disturbances in either unstable trickling-flow (at relatively low gas and liquid flows) or dispersed-bubbling flow (at high gas and liquid flow rates). Based upon experimental observations, models for predicting the transition from trickling- to pulsing-flow regime and pulsing- to dispersed-bubbling flow were developed.; Overall, the present work provides an improved understanding of the pulsing-flow regime in trickle-bed reactors, and how it may be utilized to improve existing and future reactor designs. |
