Catalyst Deactivation Modes of PdO/γ-Al₂O₃ Catalysts for Lean Methane Oxidation

Journal Article · Thu Jul 10 00:00:00 EDT 2025 · Johnson Matthey Technology Review

DOI:https://doi.org/10.1595/205651326X17521441507328· OSTI ID:2588281

Chen, Haiying ^[1]; Lugo-Jose, Yuliana ^[2]; Fedeyko, Joseph M. ^[2]; Toops, Todd ^[1]; Allard, Jr., Lawrence ^[1]; Lin, Yan-Ru ^[1]; Fiddler, Jacqueline ^[3]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
2. Johnson Matthey Inc., Wayne, PA (United States)
3. CONSOL Energy Inc., Canonsburg, PA (United States)

PdO/γ-Al₂O₃ catalysts are one of the most active catalytic components for the complete oxidation of methane. Under reaction conditions, especially in a wet feed, the catalysts suffer severe performance degradation. This study establishes a series of testing protocols to systematically investigate the causes of catalyst deactivation under methane oxidation reaction conditions. Four distinct catalyst deactivation modes are identified. Two of the deactivation modes are directly related to H₂O, either from the feed gas or as a part of the reaction products, with one (Mode 2) being attributed to the formation of surface hydroxyl groups and the other (Mode 3) to the competitive adsorption of H₂O on the catalysts. The impact of the two deactivation modes is acute and severe but reversible. In contrast, the other two deactivation modes are gradual and persistent but irreversible. Both modes are induced by CH₄ oxidation reaction, with the impact of a wet feed (Mode 4) being substantially more severe than that of a dry feed (Mode 1). The major cause of the irreversible catalyst deactivation is attributed to surface reconstruction of PdO nanoparticles, which behaves as a passivation layer lowering the number of coordinately unsaturated Pd sites for CH₄ activation. Although the passivation layer is relatively stable against thermal or hydrothermal treatment, it is not completely inert. Formation and partial regeneration of the passivation layer is a highly dynamic process and heavily depends on the reaction temperature: a lower reaction temperature (≤ 450 ℃) can lead to quicker catalyst deactivation; but a higher reaction temperature (between 500 – 550 ℃) can result in a greater extent of catalyst deactivation.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• Grant/Contract Number: AC05-00OR22725; AR0001532
• OSTI ID: 2588281
• Journal Information: Johnson Matthey Technology Review, Journal Name: Johnson Matthey Technology Review Journal Issue: 1 Vol. 70; ISSN 2056-5135
• Publisher: Johnson Matthey
• Country of Publication: United States
• Language: English

Related Subjects

PdO/γ-Al2O3
catalyst deactivation
irreversible deactivation
methane oxidation
surface reconstruction
water inhibition