Bifunctional strategies exploiting the selective and catalytic decomposition of formaldehyde by Y2O3 improve the lifetime of CHA zeotypes and zeolites for methanol-to-olefins catalysis 4-fold, as quantified by total turnovers, without disrupting the inherently high selectivity to light olefins. The improvement in catalyst lifetime increases with increasing proximity between H+ sites of the zeotype/zeolite and the surface of the rare earth metal oxide. This proximity effect demonstrates crucial transport of formaldehyde between and within zeotypic/zeolitic domains on catalyst lifetime. These results provide mechanistic insights revealing formaldehyde as an accelerant for the initiation and termination of chain carriers and exemplify a strategy for designing improved methanol-to-olefins catalysts by optimizing (bi)functionality and reaction-transport dynamical phenomena. (Chemical Equation Presented).
Bibliographical noteFunding Information:
We gratefully acknowledge financial support for this research from The Dow Chemical Company and the National Science Foundation (CBET 1055846) and thank Dr. Dean M. Millar and Dr. Yu Liu (The Dow Chemical Company) for preparation of HSAPO-34, HSSZ-13, and Y2O3 samples.
© 2017 American Chemical Society.
- bifunctional catalysis
- rare earth metal oxide
- yttrium oxide