Ammonia decomposition kinetics over LiOH-promoted, α-Al2O3-supported Ru catalyst

Abstract

A LiOH-promoted Ru-based catalyst was recently reported to have a high TOF of 17.7 s−1 at 623 K, compared to 2.7 s−1 for an un-promoted Ru-based catalyst, and has been reproduced for this study to develop further understanding of the catalyst activity under a range of conditions. The kinetic values were calculated using a Temkin-Pyzhev-like power law rate expression model. Reaction orders, pre-exponential factors (A) and activation energies (E) were calculated for two temperature ranges, 623–748 K, and 748–873 K. The TOF of this catalyst at 623 K is not similar to that previously reported, being only 1.6 s−1 in this study. A follow-up CFD analysis supports the fact that the kinetic model effectively describes performance of the catalyst at a range of temperatures and pressures, and can be used in the future on similar catalysts. H2 partial pressure has an inhibitory effect on the rate of decomposition of NH3 at all temperatures, not just near or below 673 K as previously proposed in the literature, however equilibrium decomposition is still possible with sufficient catalyst loading.