(569ex) A Comparative Study of Parameters Estimation of Ammonia Synthesis Reaction Rates over Co/Ba/MgO Catalyst

The reaction mechanism of ammonia synthesis over catalytic materials is not well understood which led to numerous candidates of reaction rate equations with many potential parameters. A comprehensive assessment of ammonia synthesis reaction rate equations has been investigated [1].

This study aims to estimate the kinetic parameters for ammonia synthesis over a Co/BaO/MgO catalyst. It has been reported that the activity of ammonia synthesis is enhanced when the Co nanoparticles are encapsulated with BaO material [2]. A one-dimensional mathematical model is employed for a lab-scale ammonia synthesis converter. Two modified Langmuir-Hinshelwood (LH) rate equations 8-parameter and 4-parameter models are employed to describe the reaction rate over the based catalyst. The 4-parameter LH rate equation only considered the dissociation adsorption reaction step of nitrogen, while the 8-parameter LH rate considers the intermediate surface reaction steps of N, H, and NH groups. The kinetic parameters of ammonia synthesis over the Co/BaO/MgO catalyst are determined for both rate equations using an integral reactor model by least square regression with Tikhonov regularization. The parameters of LH rate equations are determined and compared with the experimental data at different regulation coefficients. Figure 1 shows that the fitting results of the 8-parameter model which shows an excellent agreement with experimental data.

References

[1] El-Shafie, M., Harada, H., Yajima, T., Tsuda, S., Inazu, K., & Kawajiri, Y. (2024). A comprehensive analysis of ammonia synthesis over a commercial iron-based catalyst using differential and integral reactor models. International Journal of Hydrogen Energy, 58, 1009-1019.

[2] Sato, K., Miyahara, S. I., Tsujimaru, K., Wada, Y., Toriyama, T., Yamamoto, T., ... & Nagaoka, K. (2021). Barium oxide encapsulating cobalt nanoparticles supported on magnesium oxide: active non-noble metal catalysts for ammonia synthesis under mild reaction conditions. ACS Catalysis, 11(21), 13050-13061.