Low-OSDA SSZ-39 Zeolite Upgrades Methane to Ethylene and Propylene

Abstract

The catalytic upgrading of methane to light olefins, particularly ethylene and propylene, under mild conditions remains a challenge due to the high stability of C–H bonds and the risk of overoxidation. A stable tandem process that integrates sequential C–H activation and C–C coupling is required to enable low-carbon chemical manufacturing. Here we demonstrate such a process over an aluminosilicate AEI zeolite (SSZ-39) synthesized via interzeolite conversion of ferrierite (FER). The synthesis operates over a wide OSDA/SiO2 ratio range with low sensitivity to the organic structure-directing agent concentration, reducing both the costly template consumption and the associated energy footprint. Combined experimental and spectroscopic studies show that methane is selectively oxidized to surface methoxy species under mild conditions, which subsequently convert to light olefins on strong acid sites within the confined AEI channels. The catalyst exhibits stable performance over multiple cycles with sustained olefin selectivity. This work establishes a cost-effective and environmentally benign strategy for direct natural gas valorization, bypassing traditional syngas chemistry and contributing to the mitigation of carbon emissions while producing valuable chemical feedstocks.