Analysis on Ammonia Synthesis over Wustite-Based Iron Catalyst

Abstract

Abstract: Wiistite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to
reductionunder a wide range of conditions. The reaction kinetics of ammonia synthesis can
be illustrated perfectly by boththe classical Temkin-Pyzhev and modified Temkin equations
with optimized α of 0.5. The pre-exponent factors andactivation energies at the pressures
of 8.0 and 15.0MPa are respectively ko = 1.09 × 1015, 7.35 × 1014 Pa0.5.s-1,and E =
156.6, 155.5kJ@mol-1 derived from the classical Temkin-Phyzhev equation, as well as ko =
2.45 × 1014,1.83 × 1014pa0.5.s-1, and E = 147.7, 147.2kJ.mol-1 derived from the modified
Temkin equation. Although thedegree of reduction under isothermal condition is primarily
dependent upon temperature, low pressure seems to beimperative for reduction under high
temperature and low space velocity to be considered as a high activity catalyst.The
reduction behavior with dry feed gas can be illustrated perfectly by the shrinking-sphere-
particle model, bywhich the reduction-rate constants of 4248exp (-71680/RT) and 644exp (-
87260/RT) were obtained for the powder(0.045-0.054 mm) and irregular shape (nominal
diameter 3.17 mm) catalysts respectively. The significant effect ofparticle size on
reduction rate was observed, therefore, it is important to take into account the influence
of particlesize on reduction for the optimization of reduction process in industry.

Key words: wustite-based catalyst, ammonia synthesis, catalytic activity, reduction behavior, kinetics

摘要： Wiistite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to
reductionunder a wide range of conditions. The reaction kinetics of ammonia synthesis can
be illustrated perfectly by boththe classical Temkin-Pyzhev and modified Temkin equations
with optimized α of 0.5. The pre-exponent factors andactivation energies at the pressures
of 8.0 and 15.0MPa are respectively ko = 1.09 × 1015, 7.35 × 1014 Pa0.5.s-1,and E =
156.6, 155.5kJ@mol-1 derived from the classical Temkin-Phyzhev equation, as well as ko =
2.45 × 1014,1.83 × 1014pa0.5.s-1, and E = 147.7, 147.2kJ.mol-1 derived from the modified
Temkin equation. Although thedegree of reduction under isothermal condition is primarily
dependent upon temperature, low pressure seems to beimperative for reduction under high
temperature and low space velocity to be considered as a high activity catalyst.The
reduction behavior with dry feed gas can be illustrated perfectly by the shrinking-sphere-
particle model, bywhich the reduction-rate constants of 4248exp (-71680/RT) and 644exp (-
87260/RT) were obtained for the powder(0.045-0.054 mm) and irregular shape (nominal
diameter 3.17 mm) catalysts respectively. The significant effect ofparticle size on
reduction rate was observed, therefore, it is important to take into account the influence
of particlesize on reduction for the optimization of reduction process in industry.

关键词: wustite-based catalyst;ammonia synthesis;catalytic activity;reduction behavior;kinetics

LI Xiaonian, LIU Huazhang, CEN Yaqing, HU Zhangneng. Analysis on Ammonia Synthesis over Wustite-Based Iron Catalyst[J]. .

李小年, 刘化章, 岑亚青, 胡樟能. 维氏体铁基氨合成催化剂动力学分析[J]. CIESC Journal.

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