Analysis of the Reaction Mechanism and Catalytic Activity of Metal-Substituted Beta Zeolite for the Isomerization of Glucose to Fructose
Journal
ACS CATALYSIS
Journal Volume
4
Journal Issue
5
Pages
1537
Date Issued
2014
Author(s)
Abstract
Glucose-fructose isomerization mediated by Sn-BEA is investigated using an extended QM/MM model containing 208 tetrahedral atoms. The isomerization mechanism consists of a sequence of ring-opening, isomerization, and ring-closing processes, consistent with the previously reported experimental observations. In agreement with the experimentally observed kinetic isotope effect, the rate-determining step is found to involve a hydride shift from the C2 carbon to the C1 carbon. The apparent activation energy for the rate-limiting step is 22.3 kcal/mol at 343 K. The difference in the reaction barriers for the partially hydrolyzed and the fully coordinated Sn sites was investigated using energy decomposition analysis. It is found that the higher activity of the partially hydrolyzed site comes from the extra flexibility provided by the defect in the lattice. The effect of substituting Sn in the active site by Ti, Zr, V, Nb, Si, and Ge was examined, and it was found that Sn and Zr are metals that result in the lowest reaction barrier for glucose isomerization. By using energy decomposition analysis, two physical properties are shown to contribute to the magnitude of the reaction barrier: the polarizability of the metal atom in the active site and the Brønsted basicity of the oxygen atom bound to the metal atom. © 2014 American Chemical Society.
Subjects
quantum mechanics-molecular mechanics; zeolite; catalysis; glucose isomerization; reaction mechanism; energy decomposition analysis
catalysis; energy decomposition analysis; glucose isomerization; quantum mechanics-molecular mechanics; reaction mechanism; zeolite
Other Subjects
catalysis; energy decomposition analysis; glucose isomerization; quantum mechanics-molecular mechanics; reaction mechanism; zeolite
Publisher
AMER CHEMICAL SOC
Type
journal article