Tighter Confinement Increases Selectivity of d-Glucose Isomerization Toward l-Sorbose in Titanium Zeolites

Michael J. Cordon; Juan Carlos Vega-Vila; Alyssa Casper; Zige Huang; Rajamani Gounder

doi:10.1002/anie.202005207

Tighter Confinement Increases Selectivity of d-Glucose Isomerization Toward l-Sorbose in Titanium Zeolites

Michael J. Cordon, Juan Carlos Vega-Vila, Alyssa Casper, Zige Huang, Rajamani Gounder

Chemical Process Scale Up

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

Abstract

Aqueous-phase isomerization of d-glucose to d-fructose and l-sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti-MCM-41, TiO₂-SiO₂) and increase to detectable values when Ti sites are confined within the smaller 12-membered ring (12-MR) micropores of Ti-Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10-MR pores (Ti-MFI, Ti-CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8-MR pores of Ti-CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l-sorbose over d-fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti-MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.

Original language	English
Pages (from-to)	19102-19107
Number of pages	6
Journal	Angewandte Chemie - International Edition
Volume	59
Issue number	43
DOIs	https://doi.org/10.1002/anie.202005207
State	Published - Oct 19 2020

Funding

We acknowledge the financial support provided by the Purdue Process Safety and Assurance Center (P2SAC). We also acknowledge experimental assistance from Garrett M. Mitchell in the collection of TEM images, and from Laura Wilcox, Claire Nimlos, Trevor Lardinois and Elizabeth Bickel for measurement of XRD patterns, DRUV spectra, gas adsorption–desorption isotherms, and elemental analysis data. We acknowledge the financial support provided by the Purdue Process Safety and Assurance Center (P2SAC). We also acknowledge experimental assistance from Garrett M. Mitchell in the collection of TEM images, and from Laura Wilcox, Claire Nimlos, Trevor Lardinois and Elizabeth Bickel for measurement of XRD patterns, DRUV spectra, gas adsorption?desorption isotherms, and elemental analysis data.

Funders	Funder number
Laura Wilcox
Purdue Process Safety and Assurance Center	P2SAC

Keywords

Lewis acidic sites
confinement
glucose
sorbose
zeolites

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10.1002/anie.202005207

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title = "Tighter Confinement Increases Selectivity of d-Glucose Isomerization Toward l-Sorbose in Titanium Zeolites",

abstract = "Aqueous-phase isomerization of d-glucose to d-fructose and l-sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti-MCM-41, TiO2-SiO2) and increase to detectable values when Ti sites are confined within the smaller 12-membered ring (12-MR) micropores of Ti-Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10-MR pores (Ti-MFI, Ti-CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8-MR pores of Ti-CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l-sorbose over d-fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti-MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.",

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author = "Cordon, {Michael J.} and Vega-Vila, {Juan Carlos} and Alyssa Casper and Zige Huang and Rajamani Gounder",

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AU - Huang, Zige

AU - Gounder, Rajamani

PY - 2020/10/19

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N2 - Aqueous-phase isomerization of d-glucose to d-fructose and l-sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti-MCM-41, TiO2-SiO2) and increase to detectable values when Ti sites are confined within the smaller 12-membered ring (12-MR) micropores of Ti-Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10-MR pores (Ti-MFI, Ti-CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8-MR pores of Ti-CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l-sorbose over d-fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti-MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.

AB - Aqueous-phase isomerization of d-glucose to d-fructose and l-sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti-MCM-41, TiO2-SiO2) and increase to detectable values when Ti sites are confined within the smaller 12-membered ring (12-MR) micropores of Ti-Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10-MR pores (Ti-MFI, Ti-CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8-MR pores of Ti-CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l-sorbose over d-fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti-MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.

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KW - zeolites

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Tighter Confinement Increases Selectivity of d-Glucose Isomerization Toward l-Sorbose in Titanium Zeolites

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