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Boron Sites in Borosilicate Zeolites at Various Stages of Hydration Studied by Solid State NMR Spectroscopy

Hwang, Son-Jong and Chen, Cong-Yan and Zones, Stacey I. (2004) Boron Sites in Borosilicate Zeolites at Various Stages of Hydration Studied by Solid State NMR Spectroscopy. Journal of Physical Chemistry B, 108 (48). pp. 18535-18546. ISSN 1520-6106. doi:10.1021/jp0476904.

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The local structures of framework boron atoms in borosilicate zeolites B-β, B-SSZ-33 and B-SSZ-42 have been studied in the course of hydration/dehydration by employing solid-state NMR methods. In particular, characterization of trigonal boron sites has been studied in great detail. ^(11)B MAS NMR spectra showed that boron trigonally coordinated to the framework (B(OSi)_3, denoted as B[3]) can be readily transformed to a defective trigonal boron site (B(OSi)_2(OH), denoted as B[3]-I) as a result of hydration. The presence of B[3]-I sites was proven by utilizing a number of different NMR methods including ^(11)B MAS NMR at two different fields (11.7 and 19.6 T), ^(11)B MQMAS, ^(11)B CPMAS, and ^(11)B 2D HETCOR experiments. The B[3]-I species can be converted into B[3] upon dehydroxylation, but its presence can also be sustained even after very high-temperature treatment (at least up to 500 °C). The formation of deboronated species, B(OH)_3, in distorted form was detected even under a mild hydration treatment. HETCOR NMR revealed that hydroxyl protons with chemical shifts at 2.4 and 3.3 ppm in ^1H NMR are correlated with B[3] and B[3]-I sites, respectively. The presence of a new hydroxyl proton at 3.8 ppm in ^1H NMR that showed selective correlation with B[3]-I in HETCOR NMR was also identified.

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Hwang, Son-Jong0000-0002-3210-466X
Additional Information:© 2004 American Chemical Society. Received 27 May 2004. Published online 9 November 2004. Published in print 1 December 2004. We thank ChevronTexaco Energy Technology Co. for supporting this work. Acquisition of NMR spectra at 19.6 T was made possible by help from Drs. Hyungtae Kwak and Z. Gan at the NHMFL in Florida. Their contribution is greatly acknowledged. Helpful discussion from Prof. Mark E. Davis at California Institute of Technology is also acknowledged. The NMR facility at Caltech was supported by the National Science Foundation under Grant 9724240 and partially supported by the MRSEC Program of the National Science Foundation under Award DMR-0080065
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ChevronTexaco Energy Technology Co.UNSPECIFIED
National High Magnetic Field LaboratoryUNSPECIFIED
Issue or Number:48
Record Number:CaltechAUTHORS:20170706-091619866
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Official Citation:Boron Sites in Borosilicate Zeolites at Various Stages of Hydration Studied by Solid State NMR Spectroscopy Son-Jong Hwang, Cong-Yan Chen, and Stacey I. Zones The Journal of Physical Chemistry B 2004 108 (48), 18535-18546 DOI: 10.1021/jp0476904
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78798
Deposited By: Ruth Sustaita
Deposited On:06 Jul 2017 22:05
Last Modified:15 Nov 2021 17:43

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