Mechanistic Studies of Continuous Partial Methane Oxidation on Cu-Zeolites Using Kinetic and Spectroscopic Methods

Over the past few decades, a significant amount of research effort has focused on investigating the active site requirements and reaction mechanisms for partial methane oxidation (PMO) to methanol over copper-exchanged zeolites during stoichiometric and stepwise chemical looping routes. More recently, research efforts have expanded to include investigating the PMO reaction in a continuous catalytic regime, primarily focusing on determining the influence of catalyst composition on Cu speciation and structure and, in turn, on PMO rate and selectivity. The structures of candidate Cu active sites are commonly studied using a combination of ex situ and in situ spectroscopic approaches. In this perspective, we critically examine the prior literature on catalytic PMO over Cu-zeolites to identify key knowledge gaps that remain in our understanding as motivation for future research efforts. We identify opportunities for future research to address these gaps by adapting analogous interrogation techniques that have been successfully used to elucidate the active site requirements and mechanistic details of another catalytic redox reaction cycle on Cu-zeolites, the selective catalytic reduction (SCR) of nitrogen oxides (NOx). This concept paper summarizes opportunities for future research to provide molecular-level insights into the active site structures and reaction kinetics and mechanisms of continuous catalytic partial methane oxidation to methanol on copper-exchanged zeolites. image