After achieving an optimum
loading, further addition of the promoter has a detrimental
effect inhibiting reduction and carbidization, decreasing the CO
conversion, and shifting the product selectivity to shorter hydrocarbons
[4,13]. Similar effects have been reported for potassium
[14]. Ngantsoue-Hoc et al. [12] have shown that not only the promoter
loading defines its effectiveness but also the reaction conditions
and CO conversion levels