Effects of Using Carbon-Coated Alumina as Support for Ba-Promoted Ru Catalyst in Ammonia Synthesis

Ru catalysts using alumina (Al2O3) as support are inferior in ammonia synthesis. In the present study, we coated alumina with carbon to enhance the activity of Ba-promoted Ru/Al2O3 catalyst. The support obtained in sucrose pyrolysis is herein denoted as sC-Al2O3 while that through acetylene decomposition as gC-Al2O3. It is observed that sC-Al2O3 is with carbon homogeneously dispersed on the surface. In the case of gC-Al2O3, the dispersion of surface carbon is inhomogeneous. Enhanced catalyst activity and stability in ammonia synthesis are observed over the Ba-promoted Ru catalyst that is supported on gC-Al2O3. The phenomenon is attributed to a combination of surface hydrogen enrichment, lowering of nitrogen desorption temperature, and hydrogen desorption through a favorable H-2-formation pathway. This research provides a new approach for the design of high-performance catalysts not only for ammonia synthesis but also for catalytic reactions where the tuning of hydrogen adsorption and desorption is critical.