Abstract
<jats:p>Sorption‑enhanced ammonia synthesis (SEAS) requires solid sorbents with high capacity, fast kinetics, and reliable models at elevated temperature and pressure. Here, zeolites and supported metal halides are compared systematically for high‑temperature NH3 sorption for SEAS process design. Commercial zeolites (3A, 4A, 13X, LiLSX) were screened by quasi‑continuous pulse chemisorption (ambient pressure, 50–350 °C), combining capacity determination with TPD‑based site analysis. The most promising candidate LiLSX, still adsorbing NH3 at more than 300 °C, was then benchmarked against supported MnCl2‑based sorbents in a high‑pressure magnetic suspension balance (200–400 °C, up to 12 bar ammonia partial pressure). Morphology and salt distribution were characterized by SEM/EDX. Equilibria were modeled with Langmuir, Toth, Sips and dual‑site Langmuir (DSL) isotherms. NH3 adsorption kinetics on LiLSX were fitted using driving force, stretched exponential (SE) and double SE (DSE) rate expressions. Only LiLSX showed appreciable NH3 uptake above 200 °C in pulse chemisorption and remains active at 300 °C and 0.1 bar ammonia partial pressure. TPD signal and isotherm modeling confirm adsorption on two site types. At SEAS‑relevant conditions, LiLSX attained on average ~40 % higher NH3 capacity than MnCl2(30 wt.%)/AC. LiLSX sustained a quasi‑stable working capacity over 90 adsorption–desorption cycles at 300–350 °C without detectable structural damage. Among all kinetic models tested, the DSE approach best captures LiLSX NH3 uptake behavior and reflects two characteristic time scales aligned with the dual‑site equilibrium description. The presented methodology and model parameters directly support the design and simulation of SEAS reactors.</jats:p>