Irreversible Deactivation Mechanism of Propane Dehydrogenation Catalysts Unveiled by In Situ TEM: Roles of Al x Cr y O Solid Solutions

Alumina‐supported chromium oxide (CrO x /Al 2 O 3 ) catalyst is crucial for propane dehydrogenation (PDH) to propylene in industry. However, its severe deactivation compromises economic viability, and a comprehensive understanding of the deactivation mechanism remains elusive. Herein, an irreversible deactivation mechanism of a pilot‐scale CrO x /Al 2 O 3 catalyst by two stages under reaction conditions was revealed via in situ gas transmission electron microscopy (in situ gas TEM). During the early deactivation stage, CrO x particles gradually disperse and incorporate into the alumina lattice, forming Al x Cr y O solid solutions with low Cr content, which promote the growth of curved graphitic carbon. During the deep deactivation stage, the continuous migration of Cr species into the support ultimately results in the formation of Cr‐rich solid solutions. These Cr‐rich solid solutions can only partially revert to Cr‐poor solid solutions under “oxidative regeneration” condition, which appears to be a key cause of the irreversible deactivation. This work clarifies the deactivation mechanism for CrO x /Al 2 O 3 catalyst and provides critical insights for rational design of next‐generation catalysts and industrial operating conditions.