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US Navy submarines have used Hopcalite catalyst (MnO2, CuO) for over 30 years to oxidize carbon monoxide, hydrogen, and many trace organic species. During that time, the material has been manufactured by the same company, and the performance of fresh Hopcalite has never shown significant variation. Recently, a new lot of Hopcalite was tested and found to be 300% more active toward one specific refrigerant than measured in previous lots. In life support applications, unexpectedly high activity can generate hazardous products that endanger crew and equipment. This paper will describe and interpret the tests performed by the Naval Research Laboratory and Naval Surface Warfare Center to investigate different Hopcalite samples.

The United States Navy uses the catalyst HOPCALITE for removal of carbon monoxide and hydrogen from the enclosed atmosphere of its submarines. At temperatures higher than those required for CO and H2, HOPCALITE also catalyses the oxidation of many organic substances. In some cases, these reactions produce toxic byproducts and/or catalyst poisoning. The activity of HOPCALITE varies greatly toward seemingly similar species. This work presents a model for predicting the activity of HOPCALITE with a linear equation using simple physical and chemical properties of the reacting species. Many parameters were evaluated. The model uses only three parameters to fit the observed reactivities of 51 chemicals. A final correlation coefficient (r2) of 0.80 is achieved.

Replacing ozone depleting refrigerants on U.S. Navy submarines has created new design challenges as they interface with the atmosphere control machinery. The environmentally friendly nature of new HFC's and HCFC's is in part due to their higher reactivity. Unfortunately that reactivity causes excessive decomposition resulting in toxic gas production when processed in the catalytic oxidizer, the U.S. Navy Submarine CO and H2 Catalytic Burner. The catalyst/air stream is heated to induce the decomposition of H2, CO and trace organics. An effort is underway to lower the burner temperature to minimize refrigerant decomposition. This paper discusses test results of varying catalyst temperatures when trace contaminants, representative of the submarine atmosphere, are oxidized on the burner's catalyst. The effects of water vapor and catalyst age on oxidation efficiencies are also reported. Both bench scale and full scale burner test results are discussed.

Alternate refrigerant HFC-134a has been found to be substantially more reactive than CFC-12 in the US Navy submarine catalytic burner. The burner operates at 316°C and uses a manganese dioxide/copper monoxide catalyst, Hopcalite. The reaction of HFC-134a produced hazardous quantities of HF in the outlet air in excess of the established submarine exposure limits. No other hazardous products, such as carbonyl fluoride, were detected.