Hydrogen production for mobile application

Hydrogen production for mobile application: NH₃ cracking over ZrON

Ammonia can be employed as a carrier gas as an alternative to methanol. The large-scale production of Ammonia is well understood and can be operated in less costly places where hydrogen gas is available. The subsequent production of hydrogen by decomposition of ammonia is also well understood. In principle, the process only yields hydrogen and hydrogen gases. However, most catalysts used in this process have a major drawback as there produce significant amounts of hydrazine. Hydrazine is a fuel cell poison similar to carbon monoxide and therefore must be removed in subsequent gas purification unit. There is therefore a need to develop alternative novel catalysts for decomposition of ammonia with low or no production of hydrazine. Hence the limited selectivity of common metal catalysts in production of hydrogen from ammonia originates from the presence of neighboring active sites that leads or facilitates the formation of hydrazine.

The aim of the current work was in two fold. One was the structural and catalytic investigation of novel Cu/ ZrO₂/CeO₂ catalysts prepared by co-precipitation and its application in energy. The surface area was further increased through employing porous polymer beads as template for the preparation of the solid catalysts. Samples with different Cu loadings were examined for the steam reforming of methanol and their catalytic properties are discussed, including long-term stability as well as CO production. In addition, the reaction mechanism was studied and kinetically analyzed in order to determine the rate constants and the activation energies for the model reactions.

The second aim was to attempt and tailor the selectivity of improved catalysts by seeking novel materials that avoid neighboring active sites. Additionally, this will not only reduce the production of hydrazine but will provide nitrogen atoms from the catalyst bulk for the formation of dinitrogen molecules. For this work, Nitrogen-conducting zirconium oxynitrides were chosen as the promising new ammonia decomposition catalysts that would avoid the presence of neighboring metal sites.