Mesoporous Oxide Supported Catalysts for Low Temperature Oxidation of Dissolved Organics in Spacecraft Wastewater Streams

Abstract

Novel mesoporous bimetallic oxidation catalysts are described, which are currently under development for the deep oxidation (mineralization) of aqueous organic contaminants in wastewater produced on-board manned spacecraft, and lunar and planetary habitats. The goal of the ongoing development program is to produce catalysts capable of organic contaminant mineralization near ambient temperature. Such a development will significantly reduce Equivalent System Mass (ESM) for the ISS Water Processor Assembly (WPA), which must operate at 135°C to convert organic carbon to CO 2 and carboxylic acids. Improvements in catalyst performance were achieved due to the unique structural characteristics of mesoporous materials, which include a three-dimensional network of partially ordered interconnected mesopores (5-25 nm). This structure results in high surface area, high pore volume, and reduced distances for reactants and byproducts to diffuse to and from interior catalyst sites, as compared to the tortuous diffusion path in conventional, high surface area microporous (1-2 nm) supports. Mesocellular Foams (MCFs) composed of silica-zirconia solid solutions, chemically impregnated with platinum and ruthenium, were found to produce the most active catalyst. This catalyst proved capable of mineralization of acetic acid, a refractory organic, at ambient temperature.