A301 catalyst for ammonia synthesis with Fe 1- x O as precursor was promoted by Al 2O 3, K 2O, CaO and other metallic oxides. The precursor Fe 1- x O is stable in kinetics under the existence of the precursors, althou...A301 catalyst for ammonia synthesis with Fe 1- x O as precursor was promoted by Al 2O 3, K 2O, CaO and other metallic oxides. The precursor Fe 1- x O is stable in kinetics under the existence of the precursors, although it is unstable in thermodynamics below 843 K. The reduced A301 catalyst has good heat resistance. The activity can be recovered completely in case of short period poison by carbon monoxide, but can not be recovered when the catalyst is poisoned by sulphur and its compounds. The purification of synthesis gas, especially desulphurization and deoxidation, is a key to ensure the stable performance and NH 3 production capacity of A301 catalyst.展开更多
Wuestite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions.The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the...Wuestite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions.The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the classical Temkin-Pyzhev and modified Tecmkin equations with optimized α of 0.5,The pre-exponent factors and activation energies at the pressures of 8.0 and 15.0MPa are respectively κ0=1.09×10^15,7.35×10^14Pa^0.5·s^-1,and E=156.6,155.5kJ·mol^-1 derived from the classical Temkin-Phyzhev equation,as well as k0=2.45×10^14 ,1.83×10^14Pa^0.5·s^-1，and E=147.7,147.2kJ·mol^-1 derived from the modified Temkin equation.Although the degree of reduction under isothermal condition is primarily dependent upon temperature,low pressure seems to be imperative 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,by which the reduction-rate constants of 4248exp(-71680/RT) and 644exp(-87260/RT) were obtained for the powder (0.045-0.054mm) and irregular shape(nominal diameter 3.17mm) catalysts respectively.The significant effect of particle size on reduction rate was observed,therefore,it is important to take into account the influence of particle size on reduction for the optimization of reduction process in industry.展开更多
文摘A301 catalyst for ammonia synthesis with Fe 1- x O as precursor was promoted by Al 2O 3, K 2O, CaO and other metallic oxides. The precursor Fe 1- x O is stable in kinetics under the existence of the precursors, although it is unstable in thermodynamics below 843 K. The reduced A301 catalyst has good heat resistance. The activity can be recovered completely in case of short period poison by carbon monoxide, but can not be recovered when the catalyst is poisoned by sulphur and its compounds. The purification of synthesis gas, especially desulphurization and deoxidation, is a key to ensure the stable performance and NH 3 production capacity of A301 catalyst.
基金Supported by the National Natural Science Foundation of China (No. 29706011), the Natural Science Foundation of Zhejiang Province for the distinguished young scholars (No. RC9702) and the Ninth-five Key Project of China (No. 96-550-02-01).
文摘Wuestite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions.The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the classical Temkin-Pyzhev and modified Tecmkin equations with optimized α of 0.5,The pre-exponent factors and activation energies at the pressures of 8.0 and 15.0MPa are respectively κ0=1.09×10^15,7.35×10^14Pa^0.5·s^-1,and E=156.6,155.5kJ·mol^-1 derived from the classical Temkin-Phyzhev equation,as well as k0=2.45×10^14 ,1.83×10^14Pa^0.5·s^-1，and E=147.7,147.2kJ·mol^-1 derived from the modified Temkin equation.Although the degree of reduction under isothermal condition is primarily dependent upon temperature,low pressure seems to be imperative 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,by which the reduction-rate constants of 4248exp(-71680/RT) and 644exp(-87260/RT) were obtained for the powder (0.045-0.054mm) and irregular shape(nominal diameter 3.17mm) catalysts respectively.The significant effect of particle size on reduction rate was observed,therefore,it is important to take into account the influence of particle size on reduction for the optimization of reduction process in industry.
