Influence of promoters to reduction rate

The reduction rate of iron catalyst is related with the type and content of promoters. Many researchers studied the inhibitory effect of promoter content on reductions, indicating that structural promoters, such as AI2O3 etc. have strong inhibitory effect on the reduction of Fc304. MgO, Ti02, Si02 etc. also inhibit the reduction rate. Electronic promoters such as K2O etc. can help to speed up the reduction rate of the catalyst. In addition, addition of CuO, NiO promotes the reduction of iron oxide, but these oxides will reduce ammonia sjmthesis activity. Therefore, it is commonly accepted that the promoters which can reduce the reduction rate can increase the activity of ammonia sjmthesis, and it also can improve the thermal stability and anti-poisoning ability. 

The solid solution formed with iron oxides impacts the reduction rate, for example, addition of 1%-10% CaO increases the reducibility, with the product of the reduction of CaO and a-Fe sponge. CaO and magnetite form CaxFe3 x04, which affects both the thermodjmamics and kinetics together, and Ca2Fe205 has the lowest rate of reduction (Fig. 5.21).  

Addition of MgO in wiistite decreases the reduction rate. The impact of addition MgO to magnetite is complex. Low content of oxide additives decreases reduction 

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