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Tracking the Active Catalyst for Iron‐Based Ammonia Decomposition by In Situ Synchrotron Diffraction Studies
Author(s) -
Tseng JoChi,
Gu Dong,
Pistidda Claudio,
Horstmann Christian,
Dornheim Martin,
Ternieden Jan,
Weidenthaler Claudia
Publication year - 2018
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201800398
Subject(s) - catalysis , materials science , nitride , synchrotron , iron nitride , decomposition , ammonia production , iron oxide , chemical engineering , inorganic chemistry , chemistry , nanotechnology , metallurgy , organic chemistry , physics , layer (electronics) , nuclear physics , engineering
Iron‐based catalysts for NH 3 decomposition have been studied by a combination of catalytic tests and in situ synchrotron diffraction experiments performed in an inert sapphire plug‐flow cell. In contrast to steel‐based reaction cells, sapphire or quartz glass cells show no blind activity. Starting from iron oxide precursors, iron nitrides form during the activation cycle. Nitrides remain as main crystalline phases and govern the conversion of NH 3 decomposition in the subsequent cycles. In this work structural and compositional changes of the nitrides were monitored in situ during heating and cooling cycles. The state of the catalyst under reaction conditions was analyzed by high resolution in situ synchrotron diffraction experiments. The analyses enable establishing reaction pathways and correlation of structural features with catalytic conversions. The most active phases are iron nitrides with high mobility and solubility for nitrogen atoms, such as Fe 3 N x . Phase changes from Fe 3 N x to γ‐FeN x were observed above 700 °C. The formation of γ‐FeN x seems to suppress the catalytic conversion. Moreover, the positive influence of a mesostructured support/catalyst composite on the catalytic conversion and catalyst stability were studied in detail.