Cooperative Surface Passivation and Hierarchical Structuring of Zeolite Beta Catalysts

Abstract

We report a method to prepare core-shell zeolite beta (*BEA) with an aluminous core and an epitaxial Si-rich shell. This method capitalizes on the inherent defects in *BEA crystals to simultaneously passivate acid sites on external surfaces and increase intracrystalline mesoporosity through facile post-hydrothermal synthesis modification in alkaline media. This process creates more hydrophobic materials by reducing silanol defects and enriching the shell in silica via a combination of dealumination and the relocation of silica from the core to the shell during intracrystalline mesopore formation. The catalytic consequences of *BEA core-shells relative to conventional analogues were tested using the biomass conversion of levulinic acid and n-butanol to n-butyl levulinate as a benchmark reaction. Our findings reveal that siliceous shells and intracrystalline mesopores synergistically enhance the performance of *BEA catalysts.

Silicalite-1 Layer Secures the Bifunctional Nature of a CO2 Hydrogenation Catalyst

“…Zeolitic core–shell structures often provide versatile beneficial functions for catalysis, , for instance, shape selectivity, , bifunctionality, and sintering resistance. , Rimer et al have developed abundant types of core–shell and egg-shell zeolite catalysts that showed enhanced performance in hydrocarbon processing as well as biomass conversion. , Very recently, the core–shell zeolite has also been reported for CO 2 conversion, primarily for the regulation of the selectivity of aromatic products. , Herein, we report that such a core–shell zeolite structure was able to overcome the challenges aforementioned during CO 2 hydrogenation, where the construction of the shell, referring to coating a layer of silicalite-1 (S-1) over a pristine zeolite H-ZSM-5 crystal, was realized by a facile secondary growth. Such an S-1 shell was found to be able to secure the bifunctional nature of a typical CO 2 hydrogenation catalyst, i.e ., In 2 O 3 /H-ZSM-5, by which the activity for the synthesis of C 2 + hydrocarbons under both nanoscale (in a manner of PM) and microscale (in a manner of GM) proximity was well-improved.…”

“… 44 , 45 Rimer et al have developed abundant types of core–shell and egg-shell zeolite catalysts that showed enhanced performance in hydrocarbon processing as well as biomass conversion. 46 , 47 Very recently, the core–shell zeolite has also been reported for CO 2 conversion, primarily for the regulation of the selectivity of aromatic products. 17 , 48 Herein, we report that such a core–shell zeolite structure was able to overcome the challenges aforementioned during CO 2 hydrogenation, where the construction of the shell, referring to coating a layer of silicalite-1 (S-1) over a pristine zeolite H-ZSM-5 crystal, was realized by a facile secondary growth.…”

Surface barriers to mass transfer in nanoporous materials for catalysis and separations

“…109,110 They also applied cooperative surface passivation and hierarchical structuring to improve the catalytic activity of zeolite beta catalysts. 111 Now over a decade ago, Ryoo and colleagues first synthesized singleunit-cell nanosheets, demonstrating higher catalytic activity and better stability than conventional microporous zeolites. 112,113 Their remarkable materials aimed to improve the overall mass transfer performance but, at the time, no analysis of the external surface permeability was performed.…”