Results of VPCAR Pilot Scale and System Level Tests for the Selective Oxidation of Ammonia to Nitrogen and Water

The cost of delivering the payloads to space increases dramatically with distance and therefore missions to deep space place a strong emphasis on reducing launch weight and eliminating resupply requirements. The Vapor Phase Catalytic Ammonia Removal (VPCAR) system, which is being developed for water purification, is an example of this focus because it has no resupply requirements. A key step in the VPCAR system is the catalytic oxidation of ammonia and volatile hydrocarbons to benign compounds such as carbon dioxide, water, and nitrogen. Currently, platinum-based commercial oxidation catalysts are being used for these reactions. However, conventional platinum catalysts can convert ammonia (NH₃) to NO and NO₂ (collectively referred to as NO_X), which are more hazardous than ammonia.

In this SBIR Phase II project TDA Research (TDA) and Hamilton Sundstrand Space Systems International (HSSSI) developed ammonia oxidation catalysts that are selective for nitrogen and water and we are using these to optimize the oxidation reactor design. We have identified selective catalysts and we also carried out kinetic analyses of the most active materials. TDA then designed and constructed a pilot scale oxidation reactor that operates at the reduced pressures expected in the VPCAR system. In this paper, we summarize the results obtained in tests of catalysts prepared by both TDA and HSSSI.