The effect of potassium promoter on the activity of wustite-based ammoniasynthesis catalyst

Ammonia synthesis reaction from N۲ and H۲ is composed of several steps. The main role ofammonia synthesis catalyst is to dissociate the N۲ bond, because of its high bond energy. It is theheart of the ammonia plant and has a direct effect on the economic benefits of the whole plant,and is thus called an economic catalyst[۱]. Wustite-based ammonia synthesis catalyst (WASC) isthe new generation ammonia synthesis catalyst that is more highly active than magnetite-basedcatalyst[۲]. It was typically produced by a high-temperature fusion method in which a high-grademagnetite and iron/graphite and promoters are melted followed by cooling, crushing, andsieving. An electrical furnace will be used for melting material above ۱۸۰۰ °C. The usualpromoters such as Al, Ca, K, Mg, and Si were used for improving activity, heat resistance, andantitoxic performances[۳]. The most important promoter that is effective in the activity (NH۳ %)of wustite catalyst is potassium (K) which is named an electronic promoter. It is donated anelectron to the anti-bonding N۲ bond that is facilitated the dissociation of N۲ in the ratedeterminingstep. In this research, some samples of WASC were prepared with various contentof K (۰.۵-۲ %), and their activity of them was measured. It was shown that about ۱ % K isenough for activity. It was concluded that the high amount of K promoter does not result in highactivity.

کلیدواژه ها:

wustite ، ammonia synthesis ، potassium ، promoter