(465a) Mechanism for Selective Fructose Etherification on Hierarchical Sn-SPP Zeolite Conference: AIChE Annual MeetingYear: 2017Proceeding: 2017 AIChE Annual MeetingGroup: Catalysis and Reaction Engineering DivisionSession: Catalysis with Microporous and Mesoporous Materials III Time: Wednesday, November 1, 2017 - 8:00am-8:18am Authors: Josephson, T. R., University of Minnesota Ren, L., University of Minnesota Guo, Q., University of Minnesota Pahari, S., University of Minnesota DeJaco, R. F., University of Minnesota Tsapatsis, M., University of Minnesota Siepmann, J. I., University of Minnesota Vlachos, D. G., University of Delaware Caratzoulas, S., University of Delaware Isomerization of glucose to fructose is a key reaction for enabling the conversion of sugars into a wide range of biorenewable chemicals through furanic intermediates. The highest glucose to fructose yields on Sn-Beta are 33%1, but a new catalyst, Sn-SPP can achieve a record 65% yield2, even in excess of the glucose/fructose equilibrium (50%). Sn-SPP catalyzes a new reaction: fructose etherification (formally a ketalization) to ethyl fructoside, which reverts to fructose after water is added post-reaction (see Scheme 1). After these initial experimental results, many fundamental questions were unanswered, including how the structure of the active site enables this chemistry, why Sn-SPP performs ketalization while Sn-Beta does not, and why fructose ketalization is catalyzed but not glucose acetalization. Scheme 1 - Reaction scheme for improving fructose yields from glucose using tandem reactions with fructose etherification. We answered these questions using periodic DFT calculations and Monte Carlo simulations. A screening algorithm identified the most thermodynamically stable active site geometries; Sn-SPP has a closed Sn site with three nearby silanol groups, while Sn-Beta has a hydrolyzed open Sn site with a single, more distant silanol group. Identification of the most favorable ketalization mechanism revealed that the silanols in Sn-SPP facilitate ketalization through key H-bonding interactions at the transition state, particularly via a Sn-O-Si-OH moiety. However, the silanol in the Sn-Beta active site is not positioned to stabilize the TS, giving a larger barrier and indicating why Sn-Beta is not active for this chemistry. Analyzing glucose acetalization revealed differences in stability of the key oxonium intermediate at the respective transition states, indicating the reason for the remarkable selectivity of this process for fructose ketalization over glucose acetalization. 1. Moliner, M.; Roman-Leshkov, Y.; Davis, M. E. E.; Román-Leshkov, Y.; Davis, M. E. E. Proc Natl Acad Sci U S A 2010, 107 (14), 61646168. 2. Ren, L.; Guo, Q.; Kumar, P.; Orazov, M.; Xu, D.; Alhassan, S. M.; Mkhoyan, K. A.; Davis, M. E.; Tsapatsis, M. Angew. Chemie - Int. Ed. 2015, 54 (37), 1084810851. Topics: Catalysis Computational Molecular Engineering Reaction Mechanism