COx-free hydrogen production from ammonia at low temperature using Co/SiC catalyst: Effect of promoter

Abstract

Cobalt catalysts (5 wt%) using β-SiC as a support and modified with different alkaline (K and Cs), alkaline-earth (Ca and Mg) and rare-earth (La and Ce) metals were prepared, characterized, and examined in the hydrogen production from ammonia decomposition at low temperatures. Porous SiC has been proved to be a suitable support for promoted cobalt catalysts, which are highly active for the target decomposition reaction. Catalysts modified with small amount (1 wt%) of K and La remarkably enhanced the catalytic activity whereas the addition of Cs, Mg, Ca or Ce to cobalt catalyst decreased the ammonia conversion with respect to the unpromoted catalyst. The total basic sites and electron-donor properties of the K metal modified the electronic structure of cobalt active sites increasing the ammonia conversion at low temperatures. However, an excess of K promoter resulted in a decrease in the hydrogen production due to the blockage of the active sites. Therefore, the catalyst containing 1 wt% K and 5 wt% Co resulted in an excellent H2 production associated with an ammonia conversion close to 100% at 450 °C. Moreover, the selected catalyst provided suitable performance stability after one day of reaction.