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RISS 인기검색어
- 검색키워드
- 저자 : Tarach, Karolina (검색결과 2 건)
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Gó,ra-Marek, Kinga,Tarach, Karolina,Choi, Minkee American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.23
<P>This work was aimed to evidence that substituted pyridine, 2,6-di-<I>tert</I>-butylpyridine, is a suitable probe for the quantitative investigation of the external acidity in hierarchically structured zeolites. The 2,6-di-<I>tert</I>-butylpyridine was too large to enter the micropores, even in wide pore zeolites, and nearly no sites in nonmesoporous zeolites were available. Accessibility studies of acid sites in zeolites TNU-9 and BEA involving quantitative IR measurements with hindered 2,6-di-<I>tert</I>-butylpyridine as a probe were performed. The extinction coefficients of the 1615 cm<SUP>–1</SUP> diagnostic bands of 2,6-di-<I>tert</I>-butylpyridine interacting with Brønsted acid sites were determined. Lewis acid sites were not detected with the probe. The accessibility factor (AF) for the 2,6-di-<I>tert</I>-butylpyridine probe molecule was defined as the number of sites detected by adsorption of the dTBPy (external sites) divided by the total amount of acid sites in the studied zeolites as quantified by pyridine sorption. Upon desilication resulting in the fabrication of the secondary mesopores, the enhanced accessibility of the protonic sites was observed. In comparison to the mesoporous zeolites with the secondary system of mesopores generated by alkaline leaching, considerably higher accessibility of protonic sites was evidenced in both ultrathin ZSM-5 and delaminated ITQ-2 zeolite.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-23/jp501928k/production/images/medium/jp-2014-01928k_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp501928k'>ACS Electronic Supporting Info</A></P>
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Gó,ra-Marek, Kinga,Brylewska, Kamila,Tarach, Karolina A.,Choi, Minkee The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.17
<P>This work was attempted in order to provide a new and well-established approach for the quantification of Fe<SUP>2+</SUP> sites in zeolites. The experimental procedure was based on carbon monoxide and nitrogen monoxide sorption in Fe-exchanged ZSM-5 zeolites with different pore hierarchies, which was followed by IR spectroscopy. The values of the absorption coefficients of the respective monocarbonyl Fe<SUP>2+</SUP>(CO) and mononitrosyl Fe<SUP>2+</SUP>(NO) IR bands were obtained. In turn, the concentrations of Fe(<SMALL>II</SMALL>) moieties of various kinds were calculated and discussed with regard to the composition (Si/Al and Fe/Al ratios) of the zeolites studied.</P> <P>Graphic Abstract</P><P>This work was attempted in order to provide a new and well-established approach for the quantification of Fe<SUP>2+</SUP> sites in zeolites. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5dt00424a'> </P>
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