Investigation of NO Reduction by H2 on Pd Monolith with Transient and Isotopic Exchange Techniques: I. H2/D2 Exchange with H2O and NH3

Isotope exchange of hydrogen atoms in water, ammonia, and hydrogen with deuterium, as well as adsorption of ammonia and water on an alumina-supported Pd monolith, were studied with transient step-response experiments. The investigation provided new insights into reaction mechanisms. Deuterium underwent an exchange reaction with hydrogen in ammonia and water. The step-response experiments yielded information about the surface reaction mechanisms, indicating adsorption-assisted desorption of hydrogen, decomposition of ammonia, and stepwise formation of deuterated water and ammonia. Detailed reaction pathways explaining isotope exchange of the hydrogen atoms in water, ammonia, and hydrogen with deuterium were proposed. The work forms the basis for the understanding of reaction mechanisms between nitrogen oxide and hydrogen, where ammonia is formed on Pd as a by-product.