(501f) Investigating the Effect of Si/Al Ratio on the Catalytic Activity of Two-Dimensional MFI Nanosheets in Friedel-Crafts Alkylations Employing Bulky Reactants

Authors: 
Korde, A., Georgia Institute of Techonology
Min, B., Georgia Institute of Technology
Nair, S., Georgia Institute of Technology
Jones, C. W., Georgia Institute of Technology
Zeolite catalysts with pronounced two-dimensional (2D) morphologies, specifically 2D MFI nanosheets with varying Si/Al ratio, are synthesized using a diquaternary ammonium structure-directing agent. The resulting materials are composed of multilamellar stacks of MFI nanosheets, each nanosheet having a thickness of ~2 nm. Zeolites with such morphology are hypothesized to offer accessibility advantages in catalytic reactions involving large, bulky molecules. The catalytic performance of the 2D MFI nanosheet materials with different Si/Al ratios is compared using the liquid phase Friedel-Crafts alkylation of benzene with benzyl alcohol. The turnover frequency (TOF) of the catalysts was evaluated with and without the addition of a bulky poison, 2,6 di-tert-butylpyridine (DTBP), to deactivate the external acid sites. Without the addition of DTBP, the turnover frequency (TOF) of the catalysts decreases with decreasing Si/Al ratio, whereas the TOF is extremely low when the external acid sites are poisoned using DTBP. Thus, in the case of bulky reactants, the reaction is mainly catalyzed on the external acid sites and additional acid sites created within the micropores by decreasing the Si/Al ratio do not contribute to the reaction in a significant way since they are not easily accessible.
Topics: