Development of a novel monolith froth reactor for three-phase catalytic reactions.

摘要

The monolith froth reactor has been developed utilizing two-phase flow in a monolith catalyst. Bubble-train flow, consisting of trains of gas bubbles and liquid slugs, is produced within the monolith channels by feeding a two-phase froth into the bottom of the monolith. This feed method is suitable for a commercial scale reactor. Because the liquid film which develops between the gas phase and the surface of the catalyst is extremely thin, bubble-train flow within a monolith can provide reaction rates that are near intrinsic values.; Catalytic oxidation of aqueous phenol over copper oxide supported on {dollar}gamma{dollar}-alumina was used as a model reaction for investigating reactor performance. Generation of a froth was confirmed by visual inspection; the average bubble size was approximately that which would be predicted by a force balance. The effect of externally controllable process variables (liquid and gas flow rates, temperature, pressure, and reactant concentrations) on the rate of oxidation was investigated. Reaction rate and conversion were found to increase as temperature or pressure increased and to decrease as gas flow rate increased. Reaction rate exhibited a maximum with respect to liquid flow rate, while conversion decreased with increasing liquid flow rate. The activation energy calculated from the apparent reaction rate was 67 kJ/mol. This value is similar to reported intrinsic values, suggesting that mass transfer limitations in the monolith froth reactor were minimal.; The effects of reactor operating conditions on reaction rate were evaluated using a simple mass transfer model. For bubble-train flow, reaction rates in the thin film region and in the liquid slug region were found to respond similarly to changes in operating conditions. Using the model, reaction rate was found to increase with an increase in liquid flow rate, temperature, pressure or oxygen concentration. Reaction rate also increased with a decrease in gas flow rate. The thickness of the liquid film and the uniformity of flow in the monolith channels was found to have the greatest affect on the reaction rate. The model suggests that mass transfer limitations are negligible.