Reduction of Pre-reduced Catalyst

Pre-reduced catalysts can be reduced much more quickly than oxidized catalyst because only about 10% of the catalyst is re-oxidized during stabilizatiom The procedure, therefore, only takes about one day. Early difficulties when prereduced catalysts were unstable and could overheat on exposure to air have been overcome and the catalyst is now very stable. It is wise, however, to take sensible precautions while loading a converter because of the large quantities of catalyst involved. 

The proportion of pre-reduced catalyst used depends on the time allowed for reduction and how easily the by-product aqueous ammonia can be used. Operating costs are balanced with the higher price of the catalyst. Using prereduced catalyst in only the top section of a reactor simplifies the early stages of reduction and speeds up commissioning. A full charge of pre-reduced catalyst allows much earlier production of ammonia but is more expensive. Although water evolution from pre-reduced catalyst is normally low, it is still usual to reduce only one bed at a time. 

---