Catalytic Decomposition of Gaseous Byproducts from Primary Solid Waste Treatment Technologies

Waste Management Systems (WMSs) designed for use aboard long-term spacecraft missions and within Lunar and planetary habitations must reduce volume and recover useful resources from solid wastes, as well as impart chemical and microbial stability to stored wastes. Many WMS processes produce high concentrations of toxic emissions that can periodically overwhelm Trace Contaminant Control Systems (TCCSs) designed to handle nominal atmospheric contaminants. A prototype Catalytic Oxidation System (COS) has been developed for this contingency, and when mated to different WMS processes, will treat these toxic emissions on an as-needed basis. The COS reactor utilizes a platinum and ruthenium bimetallic catalyst supported on mesoporous zirconia that is highly active and oxidizes at relatively low temperature a wide variety of volatile organic compounds (VOCs) and inorganic toxic emissions produced by WMS processes. Furthermore, the COS catalyst has demonstrated stable long-term operation and resistance to catalyst poisoning. Contaminants utilized as COS challenges represent a wide range of chemical species including polynuclear aromatic hydrocarbons (benzo-a-pyrene and naphthalene), aromatic hydrocarbons (benzene), organic acids (acetic acid), ketones (acetone), esters (diethyl phthalate), refractory hydrocarbons (methane), hydrogen sulfide, and carbon monoxide. The COS prototype, in which emissions are pumped into the catalytic reactor and VOC oxidation performance is evaluated using an integrated Total Hydrocarbon Analyzer (THA), was designed to easily adapt to a variety of WMS processes. In addition, the COS catalyst has successfully oxidized a complex, high concentration VOC stream generated by a laboratory scale pyrolysis reactor previously used in a NASA funded waste management program and by the Microwave Solid Waste Stabilization and Water Recovery Prototype. The future development of the COS technology will increase the range of technologies applicable to WMS and allow improvement of materials loop closure in Advanced Life Support.