(345g) K-Promoted Ru Catalysts For Ammonia Decomposition Discovered Using High-Throughput Experimentation
Hydrogen storage is difficult and the current sources of hydrogen generation involve the use of carbonaceous substances such as methanol and methane, which give off undesired CO emissions. Ammonia has emerged as the leading alternative because of its high hydrogen storage capacity (17.7 %) and energy density (3000 Wh/kg). and the catalytic decomposition produces clean CO free hydrogen. The only byproduct of the decomposition is environmentally benign nitrogen. The reaction is endothermic and the reaction temperature is based on the catalyst used. Therefore, the most effective catalysts are those that maximize the decomposition efficiency at the lowest possible temperatures.
We have screened nearly twenty single metals and several bimetallic catalysts as a function of catalyst loading, inlet composition, and temperature (order of 400 experiments) using an HTE reactor system coupled with an FTIR analysis system capable of screening 16 catalytic materials in parallel. It was found that Ru is the best catalyst amongst all the single metal and bimetallic combinations we have tested so far. Furthermore, it is also found that addition of 12%K to a 4%Ru catalyst leads to an increase of ~35% in ammonia decomposition efficiency at 350C. Response surface experimental design has further led to substantial improvements of the Ru catalyst with promotion, especially at lower temperatures. It has also been found that the promoting effect is not limited to K but extends to some other alkaline metals like Na, Rb. In addition, we have studied a number of synthesis variables, including the effects of support, solvent used, calcination temperature and time. It has been found that solvent and support could have an important effect on activity.