SEPARATING THE EFFECT OF HUMIDITY FROM TIME-ON-STREAM AGING IN AG/Α-AL₂O₃ CATALYSTS: A DRY-WET-DRY HYSTERESIS PROTOCOL
Keywords:
Keywords: Ag/α-Al₂O₃; water vapor; ethylene epoxidation; stability; hysteresis; deactivation.Abstract
Abstract: Water vapor can alter oxygen states on Ag, promoter balance, and hydroxylation of the support in Ag/α-Al₂O₃ catalysts. A simple before/after-humidity comparison does not distinguish the effect of humidity from natural time-on-stream aging; non-steady-state experiments may provide stronger mechanistic evidence than a single steady-state endpoint [5]. Two scientific contributions are proposed. The first is a Dry-Wet-Dry protocol that combines wet exposure, return to dry conditions, and a time-matched parallel dry control. The second is classification of changes into reversible surface-state effects and persistent structural changes by combining a recovery coefficient with structural diagnostics. The framework treats water tolerance as a time-dependent catalyst state rather than a single selectivity value.
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