Dynamic Behavior of Sr species in Sr/La₂O₃ under Oxidative Coupling of Methane

Parviz Yazdani¹, Nadadur V. Srinath¹, Saashwath S. Tharakaraman¹, Lennert A. Dooghe¹, Aiman Sadaqa¹, Robin De Coen¹, Alessandro Longo², Hilde Poelman¹, Emiliano Fonda³, Guy B. Marin¹, Vladimir V. Galvita¹, Kevin M. Van Geem^1*, and Mark Saeys^1*

¹Laboratory for Chemical Technology, Ghent University, Technologiepark 125, B-9052 Ghent, Belgium.

²ESRF, The European Synchrotron, 71 Avenue des Martyrs, CS40220, Cedex 9, 38043 Grenoble, France.

³Synchrotron SOLEIL, L’Orme des Merisiers – St. Aubin-BP 48, Gif s/Yvette, 91192 France

* Corresponding author

Sr/La₂O₃-based catalyst systems feature multiple catalytically active sites, making them well-suited for reactions such as the industrially significant oxidative coupling of methane (OCM). Precisely because of this multi-site structure, understanding the nature of these active sites under OCM conditions remains a key challenge. In this study, we investigate the properties of Sr/La₂O₃ through extensive performance evaluation and characterization. In-situ EXAFS measurements at the La K edge under calcination environment reveal a modification in the La coordination upon Sr loading. The La-O bond distance decreases, and Sr is incorporated into the La second shell. The so-formed La-O-Sr defect structures will entail enhanced reducibility. Under OCM conditions at 800°C, however, Sr/La₂O₃ is not stable due to Sr species mobility within the solid solution. This mobility is influenced by the gas composition, making the latter a critical factor that can either enhance catalytic performance or contribute to catalyst deactivation.

Dr. Yazdani obtained his Ph.D. in Chemical Engineering at the National University of Singapore, one of the top universities worldwide, through a collaboration program with the “Institute Of Sustainability for Chemicals, Energy And Environment,” a well-known research group in heterogeneous catalysis. Throughout his doctoral studies, he designed heterogeneous catalysts with improved stability for the sustainable production of glycols from biomass.

He joined the Ghent University Laboratory for Chemical Technology (LCT) as a postdoctoral research fellow in 2019 and is now a senior scientist. He works on catalyst design for light olefins production via three chemistries: oxidative coupling of methane (OCM), CO₂ hydrogenation, and plastic pyrolysis. His research mainly focuses on gaining detailed insight into the catalyst properties and performance, thereby understanding the relations between structure, activity, and selectivity. He also possesses expertise in the scale-up of catalytic processes such as OCM and plastic pyrolysis.