Using new types of catalysts, ammonia can be synthesized at lower pressures and temperatures. To unlock the potential of this mild condition ammonia synthesis, it is necessary to find an alternative to ammonia condensation (1) . A promising solution is ammonia absorption by metal halides, as these materials can efficiently and selectively remove ammonia down to ppm level, even at elevated temperatures (2). These halides are dispersed in porous carrier materials, such as silica gel, expanded natural graphite, and zeolite, to ensure mechanical stability of the porous bed and its stability over cycling.

In situ thermal and fast neutrons imaging at our instruments ANTARES and NECTAR at MLZ have been used to study ammonia absorption in thermochemical heat storage (THS) prototype reactors (3). The high energy thermal and fast neutron enable penetration through complex sample environments, while high neutron cross section of hydrogen enables imaging of hydrogen or hydrogenous substance like ammonia. Hence, these are suitable instruments for in situ radiography and tomography characterization, for investigating the uptake of ammonia by novel sorbent materials in real time. Additionally multimodal imaging combing X-ray or Gamma ray imaging can provide complementary information about sample morphology and further aid understanding of the process. The aim of this study is to investigate new ammonia sorbent materials using neutron imaging, to extract information about ammonia absorption in scaled up systems.

1. Smith, C., Hill, A. K. & Torrente-Murciano, L. Current and future role of Haber-Bosch ammonia in a carbon-free energy landscape. Energy Environ. Sci. 13, 331–344 (2020).
2. Malmali, M. et al. Better Absorbents for Ammonia Separation. ACS Sustain. Chem. Eng. 6, 6536–6546 (2018).
3. Berdiyeva, P. et al. In-situ neutron imaging study of NH3 absorption and desorption in SrCl2 within a heat storage prototype reactor. J. Energy Storage 29, 101388 (2020).