Quantifying Effects of Active Site Proximity on Rates of Methanol Dehydration to Dimethyl Ether over Chabazite Zeolites through Microkinetic Modeling.

Autor:	Marsden G; Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States., Kostetskyy P; Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States., Sekiya RS; Department of Chemical Engineering, University of Florida, 1030 Center, Drive P.O. Box 116005, Gainesville, Florida 32611, United States., Hoffman A; Department of Chemical Engineering, University of Florida, 1030 Center, Drive P.O. Box 116005, Gainesville, Florida 32611, United States., Lee S; Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907, United States., Gounder R; Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907, United States., Hibbitts D; Department of Chemical Engineering, University of Florida, 1030 Center, Drive P.O. Box 116005, Gainesville, Florida 32611, United States., Broadbelt LJ; Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
Jazyk:	angličtina
Zdroj:	ACS materials Au [ACS Mater Au] 2021 Dec 13; Vol. 2 (2), pp. 163-175. Date of Electronic Publication: 2021 Dec 13 (Print Publication: 2022).
DOI:	10.1021/acsmaterialsau.1c00057
Abstrakt:	Control of the spatial proximity of Brønsted acid sites within the zeolite framework can result in materials with properties that are distinct from materials synthesized through conventional crystallization methods or available from commercial sources. Recent experimental evidence has shown that turnover rates of different acid-catalyzed reactions increase with the fraction of proximal sites in chabazite (CHA) zeolites. The catalytic conversion of oxygenates is an important research area, and the dehydration of methanol to dimethyl ether (DME) is a well-studied reaction as part of methanol-to-olefin chemistry catalyzed by solid acids. Published experimental data have shown that DME formation rates (per acid site) increase systematically with the fraction of proximal acid sites in the six-membered ring of CHA. Here, we probe the effect of acid site proximity in CHA on methanol dehydration rates using electronic structure calculations and microkinetic modeling to identify the primary causes of this chemistry and their relationship to the local structure of the catalyst at the nanoscale. We report a density functional theory-parametrized microkinetic model of methanol dehydration to DME, catalyzed by acidic CHA zeolite with direct comparison to experimental data. Effects of proximal acid sites on reaction rates were captured quantitatively for a range of operating conditions and catalyst compositions, with a focus on total paired acid site concentration and reactant clustering to form higher nuclearity complexes. Next-nearest neighbor paired acid sites were identified as promoting the formation of methanol trimer clusters rather than the inhibiting tetramer or pentamer clusters, resulting in large increases in the rate for DME production due to the lower energy barriers present in the concerted methanol trimer reaction pathway. The model framework developed in this study can be extended to other zeolite materials and reaction chemistries toward the goal of rational design and development of next-generation catalytic materials and chemical processes. Competing Interests: The authors declare no competing financial interest. (© 2021 The Authors. Published by American Chemical Society.)
Databáze:	MEDLINE
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