Zeolite-based catalysts for oxidative upgrading of methane: design and control of active sites

Oxidative upgrading of methane into carbon monoxide, methanol, lower hydrocarbons (such as ethane and ethylene), and other oxygenates has been achieved at relatively low temperatures over zeolite-based catalysts. The high tunability afforded by the framework structures of zeolites offers a unique and precious opportunity for the design of active species, resulting in outstanding catalytic performance. Thus, we categorize the various reported active species in zeolite-based catalysts into three groups in terms of their origin, viz., active species originated from intra-framework heteroatoms, active species introduced by ion-exchange, and active species prepared by impregnation. We present an overview of the performance, structure, and catalysis of each category and comment on the general outlook.