Kinetic studies of ammonia synthesis over a barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide

The kinetic studies of ammonia synthesis over a barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide were performed. The commercial iron catalyst was used for comparison purposes. Measurements were carried out under conditions close to the industrial ones, i.e. at the temperature of 400, 440, 480 degrees C, pressure of 9.0 MPa and various NH3 concentrations in the inlet gas. The cobalt catalyst displayed higher catalytic activity in the entire tested range of temperature and ammonia concentrations in comparison to the iron catalyst. The catalytic behaviour in ammonia synthesis process was analysed with a power-law rate equation and the reaction orders with respect to H-2 and NH3 were determined. There was no difference in the values of the reaction order with respect to H-2 for both the catalysts indicating that NH3 synthesis reaction rate is not inhibited by hydrogen. In contrast, the reaction order with respect to NH3 varied on the catalyst. The cobalt-based catalyst had a less negative value of the reaction order with respect to NH3 revealing a lower inhibition by product itself (NH3) compared to the iron catalyst. Due to its high activity the cobalt-based catalyst may be considered as a valuable alternative to the iron catalyst for ammonia synthesis process. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.