The gas-phase decomposition of nitromethane over metal ion-exchanged sodium Y zeolite and sodium X zeolite

Abstract

The major products formed in the gas decomposition of nitromethane at 573 K over nickel(II)-, uranyl(VI)-, or zinc(II)-exchanged sodium Y zeolite are ammonia, carbon dioxide, and water, much of which is isolated on cooling as the ammonium bicarbonate: ammonium carbamate double salt, along with significant amounts of molecular nitrogen and carbon monoxide. Much less carbonate double salt is isolated when using the copper(II)-exchanged sodium Y zeolite where molecular nitrogen, carbon monoxide, and carbon dioxide are the major products with a smaller amount of water. An even smaller amount of carbonate double salt is isolated when the decomposition occurs over the sodium Y zeolite, the major product being carbon monoxide with smaller amounts of molecular nitrogen, carbon dioxide, and water and minor amounts of molecular hydrogen, methane, and nitrous oxide. The decomposition of nitromethane over cadmium(II)-, lanthanum(III)-, and cobalt(II)-exchanged sodium X zeolite leads to the isolation of the carbonate double salt in amounts comparable to those formed using the nickel(II)-, zinc(II)-, or uranyl(V)-exchanged sodium Y zeolite, though the zinc(II)- or nickel(II)- exchanged sodium X zeolite leads to isolation of significantly less carbonate double salt and the sodium X zeolite to hardly any. The mechanism of the metal-exchanged zeolite-catalyzed decomposition of nitromethane is considered in terms of two major pathways for decomposition. Using the same conditions for the catalytic conversion of nitromethane to products, nitroethane is recovered unchanged.