Fluctuating Storage of the Active Phase in a Mn-Na₂ WO₄ /SiO₂ Catalyst for the Oxidative Coupling of Methane

Structural dynamics of a Mn-Na₂ WO₄ /SiO₂ catalyst were detected directly under reaction conditions during the oxidative coupling of methane via in situ XRD and operando Raman spectroscopy. A new concept of fluctuating storage and release of an active phase in heterogeneous catalysis is proposed that involves the transient generation of active sodium oxide species via a reversible reaction of Na₂ WO₄ with Mn₇ SiO₁₂ . The process is enabled by phase transitions and melting at the high reaction temperatures that are typically applied.