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Title: The origin of selectivity in the conversion of glucose to fructose and mannose in Sn-BEA and Na-exchanged Sn-BEA zeolites

Abstract

We investigate the isomerization and epimerization of glucose to fructose and mannose in Sn-BEA andNa-exchanged Sn-BEA using density-functional theory calculations on periodic BEA crystals. We comparereaction pathways both in the absence and presence of water molecules in the vicinity of the active siteand find that water effectively determines the selectivity in Na-Sn-BEA. We identify two competingepimerization pathways, one involving direct 1,2-carbon shift and the other involving 1,2-hydride shiftvia fructose. In Sn-BEA, the isomerization to fructose is the kinetically dominant pathway, while mannoseis formed via the indirect 1,2-hydride shift epimerization pathway. In Na-Sn-BEA, the kinetically domi-nant pathway is epimerization to mannose via the direct 1,2-carbon shift pathway (Bilik mechanism)only in the presence of water solvent in the vicinity of the active site, whereas isomerization is preferredin the absence of water. We argue that polar water molecules that coordinate around the Na cation screenstrong electrostatic interactions between Na+and the glucose backbone that are responsible for thestrong inhibition of the 1,2-carbon shift mechanism in the absence of water. In Sn-BEA, the presenceof water does not influence the selectivity. Our calculations resolve for the first time the role of waterand Na cations in the catalytic activity of Sn-BEA, and rationalize the experimental data.

Authors:
 [1];  [1];  [1];  [2]
  1. University of Delaware, Newark, DE (United States). Catalysis Center for Energy Innovation; University of Delaware, Newark, DE (United States). Department of Chemical and Biomolecular Engineering
  2. University of Delaware, Newark, DE (United States). Catalysis Center for Energy Innovation
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory, Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC).; Energy Frontier Research Centers (EFRC) (United States). Catalysis Center for Energy Innovation (CCEI)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
OSTI Identifier:
1463646
DOE Contract Number:  
SC0001004; AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 355; Journal Issue: C; Journal ID: ISSN 0021-9517
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Li, Sha, Josephson, Tyler, Vlachos, Dionisios G., and Caratzoulas, Stavros. The origin of selectivity in the conversion of glucose to fructose and mannose in Sn-BEA and Na-exchanged Sn-BEA zeolites. United States: N. p., 2017. Web. doi:10.1016/j.jcat.2017.09.001.
Li, Sha, Josephson, Tyler, Vlachos, Dionisios G., & Caratzoulas, Stavros. The origin of selectivity in the conversion of glucose to fructose and mannose in Sn-BEA and Na-exchanged Sn-BEA zeolites. United States. doi:10.1016/j.jcat.2017.09.001.
Li, Sha, Josephson, Tyler, Vlachos, Dionisios G., and Caratzoulas, Stavros. Wed . "The origin of selectivity in the conversion of glucose to fructose and mannose in Sn-BEA and Na-exchanged Sn-BEA zeolites". United States. doi:10.1016/j.jcat.2017.09.001.
@article{osti_1463646,
title = {The origin of selectivity in the conversion of glucose to fructose and mannose in Sn-BEA and Na-exchanged Sn-BEA zeolites},
author = {Li, Sha and Josephson, Tyler and Vlachos, Dionisios G. and Caratzoulas, Stavros},
abstractNote = {We investigate the isomerization and epimerization of glucose to fructose and mannose in Sn-BEA andNa-exchanged Sn-BEA using density-functional theory calculations on periodic BEA crystals. We comparereaction pathways both in the absence and presence of water molecules in the vicinity of the active siteand find that water effectively determines the selectivity in Na-Sn-BEA. We identify two competingepimerization pathways, one involving direct 1,2-carbon shift and the other involving 1,2-hydride shiftvia fructose. In Sn-BEA, the isomerization to fructose is the kinetically dominant pathway, while mannoseis formed via the indirect 1,2-hydride shift epimerization pathway. In Na-Sn-BEA, the kinetically domi-nant pathway is epimerization to mannose via the direct 1,2-carbon shift pathway (Bilik mechanism)only in the presence of water solvent in the vicinity of the active site, whereas isomerization is preferredin the absence of water. We argue that polar water molecules that coordinate around the Na cation screenstrong electrostatic interactions between Na+and the glucose backbone that are responsible for thestrong inhibition of the 1,2-carbon shift mechanism in the absence of water. In Sn-BEA, the presenceof water does not influence the selectivity. Our calculations resolve for the first time the role of waterand Na cations in the catalytic activity of Sn-BEA, and rationalize the experimental data.},
doi = {10.1016/j.jcat.2017.09.001},
journal = {Journal of Catalysis},
issn = {0021-9517},
number = C,
volume = 355,
place = {United States},
year = {2017},
month = {11}
}