Deep oxidation of aqueous organics over a silicon carbide-activated carbon supported platinum–ruthenium bimetallic catalyst

Abstract

In previous work, we developed a highly active bimetallic platinum-ruthenium catalyst supported on a very high surface area activated carbon substrate. In fixed bed reactors, this catalyst proved capable of the continuous long-term deep oxidation of a variety of aqueous organic contaminants associated with spacecraft wastewater streams at 121°C. This work was extended to the mineralization of more typical environmental contaminants, including halocarbons and aromatics. The primary weakness of this catalyst was the tendency toward relatively high rates of chemical decomposition. To overcome this limitation, methods were developed for the production of a silicon carbide coating over the surface of the activated carbon, yielding a reasonable trade-off between increasing resilience and decreasing surface area. Here we report the catalytic decomposition of dissolved organic contaminants at 130°C using this silicon carbide/activated carbon supported bimetallic catalyst.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…In spite of a reduction of the SiC-coated catalyst surface areas, their oxidation rate constants in the oxidation of an aqueous acetic acid solution were comparable irrespective to the following β-SiC coating sequence and significantly higher than that measured for the uncoated RP-121 catalyst. 527 In recent years, microwave (MW) irradiation has been successfully employed in a series of SiC-supported catalysts for the treatment and decomposition of various cyclic pollutants and aromatic polycyclic dyes in water. Indeed, the ability of SiC matrix to adsorb and convert electromagnetic microwaves into heat acting as a responsive susceptor has improved the decomposition performance of a series of transition-metalbased catalysts applied as effective water remediation tools.…”

“…As far as the use of SiC in this further branch of environmental catalysis is concerned, the first contribution which appeared in the literature is due to the USA team of Atwater et al, who proposed to improve the resilience of a highly active bimetallic platinum–ruthenium catalyst on AC (RP-121), employed for the deep oxidation of organic pollutants, by means of a silicon carbide coating upon reaction with gaseous silicon monoxide under an inert carrier gas stream. , They clearly demonstrated that the conversion of surface regions of AC support into β-SiC increased significantly the catalyst resistance to oxidation by O 2 -saturated water under the operative conditions. Remarkably, the β-SiC coating was operated on the AC-based catalyst before and after impregnation with the bimetallic noble metal mixture.…”

“…Remarkably, the β-SiC coating was operated on the AC-based catalyst before and after impregnation with the bimetallic noble metal mixture. In spite of a reduction of the SiC-coated catalyst surface areas, their oxidation rate constants in the oxidation of an aqueous acetic acid solution were comparable irrespective to the following β-SiC coating sequence and significantly higher than that measured for the uncoated RP-121 catalyst …”