Absence of evidence is not evidence of absence: Multiple steady states in ammonia synthesis

Abstract

Using a chemical reaction network (CRN) Theory approach, three well-accepted mechanisms of ammonia synthesis over iron catalyst taking place within an isothermal Continuous Flow Stirred Tank Reactor (CFSTR) are analyzed. Together with its deficiency analysis, the CRN Theory provides a suitable framework to assert whether a particular reaction network has the capacity to support multiple steady states using the reaction mechanism structure alone. Through deficiency analysis, we argued that the presence of two surface catalytic sites during absorption-desorption of nitrogen (microscale) is causative of bistability (macroscale) in two of the three ammonia synthesis mechanisms here considered.