The meso-/microporous lamellar zeolites couple the catalytic features of micropores within the lamellae and the improved access and transport consequence of external surfaces and mesopores in a single material, possessing the capacity of processing large molecules. The synthesis and catalytic behavior investigation of lamellar zeolites has become the subject of intense research. This talk highlights the quantification of acid site locations and catalytic characterizations of these acid sites in different locations of lamellar pillared MFI and pillared MWW zeolites. The concentrations of external surface, pore mouth and internal surface Brønsted acid sites in these zeolites were quantified by a combined dimethyl ether (DME) titration and methanol dehydration in the presence of 2,6-di-tert-butylpyridine (DTBP) or triphenylphosphine (TPP), respectively. DME can access to all Brønsted acid sites in PMFI and PMWW zeolites and thus determine the total number of acid sites. DTBP cannot access to acid sites in micropores, but on the external surface and at the pore mouth regions. In contrast, TPP can only access to acid sites on external surface. The degree of decrease in methanol dehydration rate in the presence of DTBP or TPP indicates the fraction of the sum of external surface and pore mouth acid sites and the sole fraction of external surface acid sites, respectively. The study shows that PMFI contains ~32% external surface, ~6% pore mouth acid sites, and ~62% internal acid sites; while PMWW consists of ~33% external surface, ~31% pore mouth acid sites and ~36% internal acid sites. The individual external surface or pore mouth acid site performed distinctively in alkylation of mesitylene by benzyl alcohol and inulin hydrolysis reactions.

Quantification of external surface, pore mouth and internal acid sites and catalytic properties in lamellar pillared MFI and pillared MWW zeolites

254th National Meeting (2017)

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