Transition-Metal-Free Zeolite Composites for Tandem Catalytic Conversion of Methane to Light Olefins

The methanol-to-olefins (MTO) reaction is considered one of the most important reactions in C1 chemistry, offering a route to produce basic petrochemicals from non-oil resources such as natural gas and coal. Direct conversion of methane, the primary component of natural gas, to olefins via methanol as an intermediate is of significant industrial interest. Recent studies demonstrate that methanol can be efficiently synthesized from methane using transition-metal-free aluminosilicate Ferrierite (FER) zeolite with nitrous oxide (N₂O) as the oxidant. Herein, a tandem catalytic system based on the composite FER and one more acidic zeolite is reported to achieve continuous conversion of methane to olefins. The topology and acidity of acidic zeolites critically influenced product distribution and hydrocarbon formation rates. When small-pore zeolites are used as acidic zeolites, complete conversion of methanol to olefins is successfully achieved. Reaction conditions for methane-to-olefins conversion are optimized using  silicoaluminophosphate (SAPO-34) as a representative acidic zeolite. The mass ratio of FER to SAPO-34 determined catalytic performance, with conversion of methane to light olefins achieving thermodynamic feasibility at 325-400 °C. Enhanced intimacy between FER and SAPO-34 particles promoted methane (CH₄) conversion. This work establishes an efficient strategy for high-selectivity light olefin production from methane over integrated transition-metal-free zeolite catalysts.