Heterogeneous catalysis is important for the development of atom and energy efficient chemical transformations. The design of processes that are highly selective, energy efficient and environmentally benign requires detailed knowledge of the reaction kinetics, thorough evaluation of catalytic materials and rapid optimization of the reaction conditions. Microreactors enable precise control of reaction parameters (e.g. temperature, pressure), and the reaction conditions can be continuously varied and monitored in flow systems during catalytic processes, greatly accelerating reaction kinetic studies and process optimization. Hierarchically porous monolithic columns are anticipated to produce high surface areas that also highly accessible. Monoliths of silver supported on silica (Ag/SiO2) and cobalt oxide (Ag/Co3O4) have been synthesized and evaluated as heterogeneous catalysts for the continuous hydrogenation of Eosin, monitored by continuous UV-vis analysis of the effluent. The Eosin is found to adsorb strongly on the silver and hydrogenation of the Eosin by borohydride is observed. The activity of both Ag/SiO2 and Ag/Co3O4 columns is observed to decrease by approximately 60% over a period of 12 to 18 hours. From AAS analysis of the effluent from aqueous solutions and hexane, and from SEM characterization of the catalysts, it was found that this decrease in activity resulted from some loss of silver from the column and due to coarsening of the silver particles. The loss of silver is believed to result from both loss of whole particles and from dissolution of the silver.

Monolithic flow microreactors using silver supported on hierarchically porous silica and cobalt oxide: Activity and stability

249th National Meeting (2015)

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