Measuring Local Exothermic Effects During the Oxidative Coupling of Methane Using <i>Operando</i> Luminescence Thermometry

Oxidative coupling of methane (OCM) into ethylene is a very promising process for the valorization of methane. However, the high operating temperatures, severe exothermicity, and poor selectivity at high conversion rates have hindered its industrialization. Measurements of local catalyst temperatures, let alone research into the determining experimental parameters, are still scarce. Here, we use operando luminescence thermometry (LT) to measure local catalyst temperatures during the OCM reaction. This analytical technique reveals catalyst temperatures exceeding the oven temperature under inert conditions by almost 250°C. We observe a dependence of the local catalyst temperature on the amount of heat generated by the OCM process, and we show that the heat transfer and resulting catalyst temperature in the reactor are strongly influenced by experimental conditions and reactor/catalyst dimensions. This work showcases the opportunities of LT to measure catalyst temperatures and get more insight into high-temperature catalytic processes and their heat management, leading to crucial insights for the further optimization of chemical processes, such as OCM.