In this study, we investigate the effect of thermal treatment/calcination on the stability and activity of a Na-Mn-W/SiO₂ catalyst for the oxidative coupling of methane reaction. The catalyst performance and characterisation measurements suggest that the W species are directly involved in the catalyst active site responsible for CH₄ conversion. Under operating conditions, the active components, present in the form of Na-W-O-Mn molten state, are highly mobile and volatile. By varying the parameters of the calcination protocol, it was shown that these molten components can be partially stabilised, resulting in a catalyst with lower activity (due to loss of surface area) but higher stability even for long duration OCM reaction experiments.