This work presents recent developments on improving the stability of high silica zeolites in aqueous phase under hydrothermal conditions. It is essential for zeolite catalyzed biomass conversion reactions to have robust catalysts. Their fragility was recently shown to correlate to the number of structural defects, e.g. silanol nests.1,2 Thus, removal of these defects yields a stabilized material more suitable for applications in aqueous phase. Proof of principle was conducted using large pore BEA zeolite incorporated with boron, capable of generating large numbers of silanol nests. The generated structural defects were then removed using a reactive silane, and the effectiveness was assessed with the help of cross-polarized (CP) 29Si-MAS-NMR. The stabilized material was tested under hydrothermal conditions, compared to the defect rich material and shown to retain significantly higher crystallinity. Additionally, the integrity of the microporous structure and macroscopic morphology in stabilized materials was retained as well. This was investigated using transmission electron microscopy (TEM) and N2-physisorption. Further evidence for the stabilizing effect of silylation was provided by FT-IR as well as TEM images of microtomed samples. Having established a method for improving the stability of zeolites in hot liquid water, application of this method was tested on Al-rich zeolites typically used in biomass-related dehydration reactions. Preliminary results are promising, showing retention of zeolitic parameters such as, crystallinity, microporosity, and Broensted acidity. The impact of the nature of the silylating agent will be discussed as well. 1. L. Zhang, K. Chen, B. Chen, J. L. White and D. E. Resasco, J. Am. Chem. Soc., 2015, DOI: 10.1021/jacs.5b07398. 2. A. Vjunov, M. A. Derewinski, J. L. Fulton, D. M. Camaioni and J. A. Lercher, J. Am. Chem. Soc., 2015, 137, 10374-10382.

Improving stability of zeolites in aqueous phase via selective structural defect removal

251st National Meeting (2016)

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