Ammonia Decomposition in the Presence of Co–Al2O3/SiO2 Catalysts: Effect of Cobalt Reduction Methods

Abstract

The focus on green energy requires the search for environmentally friendly energy storage systems. The choice of ammonia as a potential container for hydrogen is attributed to the high energy content in it and the absence of carbon and nitrogen oxide emissions during decomposition. In this study, Co–Al₂O₃/SiO₂ ammonia decomposition catalysts activated by the different methods, namely, cyclic reduction–carburization–reduction (RCR) and reduction–oxidation–reduction (ROR) procedures, have been tested and compared with a catalyst subjected to the conventional reduction of cobalt with hydrogen (R). The samples have been characterized by H₂-TPR, TEM, and XRD using synchrotron radiation; the studies have shown the invariance of the structural properties of the catalysts during reaction. Since the activity and effective activation energy values of the studied catalysts are similar, catalyst R characterized by the simplest synthesis procedure has been chosen for a long-term test, where it has exhibited high on-stream stability.