Ruthenium catalyst on carbon nanofiber support layers for use in silicon-based structured microreactors. Part II: Catalytic reduction of bromate contaminants in aqueous phase

Abstract

Catalyst layers were synthesized inside a structured channel of silicon based microreactor and used to remove bromate contaminants in water. It is demonstrated that Ru/CNF based catalyst is active for bromate reduction, resulting in turn over frequencies (TOFs) higher than conventional powdered catalyst, i.e. activated carbon (AC). This enhanced catalytic performance can be attributed to improve mass transfer properties of entangled CNF layers with macroporous (open) structure, which offer enhanced accessibility to all the Ru active sites in contrast to the poor accessibility of active sites in the case of AC support material.Although promising catalytic activity of Ru/CNF catalyst was observed for bromate reduction, a continuing deactivation was observed during 5h time on stream operation. A variety of characterization techniques including TEM, XPS, TPR, ICP probed that in addition to catalyst sintering, formation of catalytically inactive Ru(OH)x phase on catalyst surface was an important reason of this deactivation. Use of higher alcohols proved to be beneficial for achieving stability of Ru/CNF catalyst for bromate reduction, however with reduced levels of overall activity.