Ba-Modulated Perovskites Enable Sustainable in Situ Steam Decoking via Lattice Oxygen Activation and Oxygen Vacancy Engineering

Abstract

Abstract

Coke deposition in furnace tubes is a critical challenge in steam cracking units, as it results in increased energy consumption, frequent shutdowns, and significant carbon emissions, thereby hindering the sustainable development of the ethylene industry. Furthermore, efficient in situ removal and conversion of highly graphitised coke remain difficult due to its structural inertness. In this work, we developed a series of Ca/Ba y Sr 1– y Fe 0.1 Mn 0.9 O 3 perovskite catalysts (termed CSFM- y or BSFM- y ) via modulation of A-sites with alkaline earth metals for sustainable in situ steam decoking. Comprehensive structural characterisation and density functional theory calculations indicated that substitution with larger radius Ba cations regulates the dynamic balance between the alkalinity of lattice oxygen and the Lewis acidity of unsaturated sites induced by oxygen vacancies, alters the Mn–O bond environment, and promotes the activation of surface lattice oxygen by water molecules to form highly mobile lattice-oxygen hydroxyl radicals, · O lat H, thereby continuously replenishing the oxygen vacancies in the catalyst. The abundant oxygen vacancies and enhanced hybridisation between O 2p and transition-metal 3d orbitals in BSFM-0.9 further facilitate water activation and regulate the electronic interactions between oxygen intermediates and the catalyst surface, promoting the diffusion and transfer of hydroxyl radicals, · OH, and adsorbed oxide species, *O 2–, to graphitic carbon. As a result, BSFM-0.9 achieved a graphitic carbon conversion of 74.1% within 120 min and complete coke removal within 60 min. Importantly, BSFM-0.9 also demonstrated strong potential as an active material for catalytic decoking coatings, enabling continuous in situ decoking and reducing the need for energy-intensive shutdown processes. This work provides mechanistic insights into alkaline earth metal-regulated perovskite catalysts and establishes a sustainable catalytic strategy for energy-efficient and low-emission industrial decoking.