Nano-Assembled Mordenite Zeolite with Tunable Morphology for Carbonylation of Dimethyl Ether

Morphology dependent catalytic performance has been reported pervasively in heterogeneous catalysis, especially on nano-materials. Microporous zeolites with different shapes and sizes tend to exhibit distinct features in reactions, mainly resulting from varied diffusion limitations. Nano-sized zeolites are considered as great catalyst candidates because of a shorter diffusion path. However, design and fabrication of zeolite with nano dimensions and desired morphology are still challenging. Here, we elucidate the pathway(s) of mordenite (MOR) zeolite growth, which involves both particle attachment and layer-by-layer mechanisms. Then, we report a facile method to tune the morphology of MOR by adding cetyltrimethylammonium bromide (CTAB) during conventional hydrothermal synthesis. By combining TG-DTG, ICP-OES, acidic sites quantification, and a DFT study, we disclose that CTAB functions as a growth modifier as well as a pore filler during crystallization. As a result, the nanosheets-assembled, bundles-like, and flowers-like MOR are successfully synthesized, respectively. More importantly, the obtained MOR samples with CTAB addition show enhanced activity in carbonylation of dimethyl ether because of improved mass transfer efficiency. The results of this study offer a commercially available strategy to achieve required structural outcomes and optimize performance for microporous zeolites.