(708c) Ammonia Adsorption in Pure-Silica Zeolites at High Temperatures and Pressures

Ammonia is an industrially relevant chemical with applications such as fertilizer synthesis and energy storage.¹ Conventionally, ammonia is synthesized by the Haber–Bosh process at pressures (p) of 100–250 bar and temperatures (T) of 650–750 K.² However, the increasing demand coupled with the drive toward small-scale ammonia manufacturing requires ammonia separation with energy-efficient and at extreme conditions. Although sorbents with strong adsorption sites are suitable for this application, a crucial parameter to consider is the regeneration of the sorbent.

Hence, we studied ammonia adsorption in pure-silica zeolites (PSZ) and self-pillared pentasil (SPP) hierarchical zeolite at high temperatures and pressures. We performed NpT-Gibbs ensemble Monte Carlo (GEMC) simulations to obtain ammonia isotherms under the experimental (T = 323–473 K, p = 0–16 bar) and process conditions (T = 523–673 K, p = 32–1024 bar). Our findings indicate that PSZ exhibits high ammonia working adsorption capacity compared to previously reported commercial adsorbents. We found good agreements between experimental and simulation ammonia isotherms and predicted high pressure swing adsorption (PSA) capacity for PSZ and SPP even at T = 673 K. Our work demonstrates that PSZ and SPP sorbents are suitable for ammonia adsorption processes such as gas separation at process conditions and sorption-enhanced reactor design.

References

1. Erisman, J. W.; Sutton, M. A.; Galloway, J.; Klimont, Z.; Winiwarter, W.How a century of ammonia synthesis changed the world (2008). Geosci., 1, 636– 639
2. Haber, F., & van Oordt, G. (1905). Über die Bildung von Ammoniak den Elementen. Anorg. Allg. Chem., 44, 341–378.