Stabilization of various CO + H2 catalysts,studied by in situ mössbauer spectroscopy

The carbon formed during the reaction of CO + H₂ on iron catalysts plays an essential role in determining the catalytic activity, product selectivity and deactivation. Different forms of carbon can be distinguished in the reaction: (i) reactive or mobile carbon, already identified for iron and ruthenium catalysts; (ii) immobile carbon which is responsible for methane formation, and (iii) bulk, inactive carbide which makes the catalysts deactivated.Various possibilities are available for stabilizing the catalytically active metallic component. One of the important factors is the particle size. The smaller the iron particle, the less amount of inactive carbon is formed. Other factors such as the type of support (e.g. zeolite) which maintains the iron in highly dispersed state, or the use of second metal or non-reducible promoter by which high dispersion of iron can be ensured and stabilized, favourably affect the activity and selectivity of the catalysts, as well. In the present paper examples are presented for the above mentioned cases.