The influence of pre-treatment gas mixture upon the ammonia synthesis activity of Co-Re catalysts

Abstract

Abstract CoRe4 catalysts highly active for ammonia synthesis at ambient pressure and 400 °C can be prepared without an ammonolysis stage. Pre-treatments under 3:1 H2:N2 and 3:1 H2:Ar atmospheres are shown to influence catalytic performance with the latter treatment leading to an induction period prior to development of activity upon switching to an ammonia synthesis feedstream providing indirect evidence for formation of an active nitride phase. The difference in behaviour between the two pre-treatment atmospheres is manifested in temperature programmed isotopic exchange experiments where H2:Ar treated material is inactive and its H2:N2 treated counterpart active.