Axial-time mapping: A diagnostic method to reveal concealed long-term catalyst deactivation mechanism in CO<sub>2</sub> hydrogenation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42127194.
- Also identified by DOI 10.1126/sciadv.aec8813 and PMC identifier 13170667.
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Abstract
An axial-time mapping (ATM) with dual time axes-catalyst-reactant contact time (<i>t</i><sub>c</sub>) and time on stream (TOS)-is developed to clarify long-term deactivation mechanisms of iron catalysts in CO<sub>2</sub> hydrogenation. Treating <i>t</i><sub>c</sub> and TOS as spatially distributed variables, ex situ datasets reconstruct axial phase gradients and performance shifts. Short <i>t</i><sub>c</sub> at the reactor inlet promotes carburization to χ-Fe<sub>5</sub>C<sub>2</sub> and Fe<sub>7</sub>C<sub>3</sub> in a CO-rich environment, whereas longer <i>t</i><sub>c</sub> downstream-where H<sub>2</sub>O accumulates-favors reoxidation to Fe<sub>3</sub>O<sub>4</sub>. Over time, residual Fe<sub>3</sub>O<sub>4</sub> is further carburized, enriching carbide phases, suppressing CO<sub>2</sub> activation, and enabling unconverted CO<sub>2</sub> to bypass the upper bed, thereby reducing the effective <i>t</i><sub>c</sub>. This leads to downstream migration of the CO formation zone and spatial separation of active and inactive regions. The <i>t</i><sub>c</sub>-TOS-resolved approach provides a sensitive and practical diagnostic tool for detecting and mitigating deactivation under industrial conditions. The ATM framework offers a generalizable strategy for probing phase evolution and deactivation pathways in complex heterogeneous catalytic systems.