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SAPO‐34 Framework Contraction on Adsorption of Ammonia: A Neutron Scattering Study
Author(s) -
Silverwood Ian P.
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201900230
Subject(s) - quasielastic neutron scattering , chemistry , scattering , neutron scattering , neutron diffraction , ammonia , anisotropy , small angle neutron scattering , adsorption , analytical chemistry (journal) , molecular physics , crystallography , materials science , crystal structure , optics , physics , organic chemistry
Neutron scattering data was recorded from SAPO‐34 using the OSIRIS instrument before and after repeated ammonia adsorption at pressures up to 8 bar. Coherent scattering from the zeolite framework provides the neutron powder diffraction pattern and gave evidence for anisotropic contraction on ammonia dosing. Incoherent quasielastic scattering from the hydrogen of the ammonia showed that mobile ammonia was present in the framework. The quasielastic data was fitted to a model where the ammonia was confined within the chabazite cage in the c direction of the crystal lattice, with diffusion solely occurring through the perpendicular 8‐membered rings. The calculated diffusion constant reached a maximum of 6.3×10 −8 m 2 s −1 at 5 bar.