活性炭负载钌催化剂上氨合成反应动力学研究

在固定床反应器中对Ba-Ru-K/AC催化剂在相应的工业条件下［温度(350~450) ℃，压力10 MPa，V(H₂)∶V(N₂)=1.0、1.5、2.0、2.5和3.0，空速(60 000~180 000) h^－1］,进行了系列动力学测试。采用改进的Temkin动力学方程对实验数据进行拟合，考虑到H₂和NH₃的吸附对催化剂作用的阻碍效应，优化得到动力学模型参数n、α、w₁和w₂分别为1、0.15、0.5和1.4。结果表明，在Temkin方程中加入H₂和NH₃的吸附项能够获得可靠的动力学模型，用Arrhenius和Van’t Hoff方程对动力学和热力学参数k、K_H2和K_NH3进行线性拟合，得到氨合成反应的活化能为90.2 kJ·mol^－1，远低于铁基催化剂，说明Ru上N₂的解离吸附活化能垒远低于传统磁铁矿基催化剂和维氏体基催化剂。H₂的吸附热为76.2 kJ·mol^－1，证明Ba-Ru-K/AC催化剂上H₂的吸附较强烈，对N₂的吸附有强烈的抑制作用。改进的Temkin动力学方程能应用于使用Ru/C催化剂的氨合成反应器的设计和操作。

Kinetics study on ammonia synthesis over AC-supported Ru catalyst

Kinetics tests for ammonia synthesis over a Ba-Ru-K/AC catalyst were carried out under simulated industrial reaction condition［T=（350-450） ℃, p=10 MPa, V(H₂)∶V(N₂)=1.0, 1.5, 2.0, 2.5 and 3.0, GHSV=(60 000~180 000) h^－1］ in a fixed-bed reactor. The experimental data was fitted with modified Temkin kinetic equation considering the suppressant effect of H₂ and NH₃ adsorption on N2 adsorption, and optimized kinetic model parameters of n,α, w₁ and w₂ were 1, 0.15, 0.5 and 1.4, respectively. The results indicated that a dependable kinetic model could be obtained by modifying the Temkin equation by considering the H₂ and NH₃ adsorption factors. Activation energy for the ammonia synthesis reaction was obtained as 90.2 kJ·mol^－1 after linear fitting the kinetic and thermodynamic parameters k, K_H2 and K_NH3with the Arrhenius and Van't Hoff equation, which was much lower than that over iron-based catalyst, which indicated that the activation energy barrier of N₂ dissociative adsorption on Ru was far lower than that on either the conventional magnetite-based catalyst or wustite-based catalyst; the hydrogen adsorption heat was 76.2 kJ·mol^－1, indicating that the adsorption of hydrogen on the Ba-Ru-K/AC catalyst was so strong that it inhibitied the dissociative adsorption of nitrogen. The modified Temkin equation was applicable to the design and operation of ammonia synthesis reactor using Ru/C catalyst.