Raman studies of peroxide formation, decomposition, and reduction on Ba/MgO

Abstract

Ba/MgO is an active catalyst for the oxidative coupling of methane to form ethane and ethylene. It has been proposed that activation of methane occurs via reaction with peroxide species present at the surface of the catalyst. In the present work, Raman spectroscopy has been used to investigate the formation, decomposition, and reduction of BaO₂ on 4 mol% Ba/MgO. The presence of BaO₂ is evidenced by the presence of a band at 842 cm⁻¹. The peroxide forms above 300°C but is stable to decomposition at temperatures up to 500°C. Reduction of BaO₂ to BaO proceeds via Ba(OH)₂. BaCO₃ forms when either BaO or BaO₂ is exposed to CO₂. Once formed, BaCO₃ is stable to decomposition in He or O₂ at temperatures up to 500°C. Only BaCO₃ is observed when a mixture of CH₄ and O₂ is passed over the catalyst at 500°C.