A study of the interactions of molten sodium nitrate-potassium nitrate 50 mol percent mixture with water vapor and carbon dioxide in the air

ABSTRACT:
Chemical energy storage and/or transmission systems based on the reversible dissociation of sulfur trioxide depend on catalysts capable of operating for extended periods of time at temperatures near 1,089 OK (1,500 OF) without losing activity or subliming. Based on a review of catalysts

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currently used for production of sulfuric acid, none of the off-the-shelf catalysts will satisfy these requirements. A total of 50 new catalysts using 21 different active metals and a wide variety of catalyst carriers and preparation methods were prepared and tested for activity in SOx reactions using differential isothermal reactors and pulsed microreactors. The most active catalyst, a 1 percent platinum on alumina catalyst, was subjected to a 6-month accelerated life test at 1,144 oK (1,600 OF). Samples were periodically withdrawn to measure remaining activity. The main degradation mechanism was identified as loss of carrier surface area by sintering and platinum active metal by volatilization. The temperature to which the catalyst was exposed during the life test had been increased to 1,144 oK in order to accelerate aging phenomena and in order to demonstrate margin. Based on tests in the differential isothermal reactor, activity remaining after 6 months at 1,144 oK was approximately half of that of fresh catalyst. A kinetic rate equation for the decomposition of undiluted S03 on a Pt catalyst at 1,005 to 1,135 oK was derived from experimental data. A computer model was developed for the sizing of S03 decomposition reactors based on desired conversion and ten other input variables.

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