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

CoRe4 catalysts highly active for ammonia synthesis at ambient pressure and 400 degrees C can be prepared without an ammonolysis stage. Pre-treatments under 3:1 H-2:N-2 and 3:1 H-2: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. The difference in behaviour between the two pre-treatment atmospheres is manifested in temperature programmed nitrogen isotopic exchange experiments where H-2:Ar treated material is inactive and its H-2:N-2 treated counterpart is active. (C) 2015 The Authors. Published by Elsevier B.V.