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RISS 인기검색어
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- 저자 : Musselwhite, Nathan (검색결과 2 건)
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Musselwhite, Nathan,Na, Kyungsu,Sabyrov, Kairat,Alayoglu, Selim,Somorjai, Gabor A. American Chemical Society 2015 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.137 No.32
<P>Several types of mesoporous aluminosilicates were synthesized and evaluated in the catalytic isomerization of <I>n</I>-hexane, both with and without Pt nanoparticles loaded into the mesopores. The materials investigated included mesoporous MFI and BEA type zeolites, MCF-17 mesoporous silica, and an aluminum modified MCF-17. The acidity of the materials was investigated through pyridine adsorption and Fourier Transform-Infrared Spectroscopy (FT-IR). It was found that the strong Brönsted acid sites in the micropores of the zeolite catalysts facilitated the cracking of hexane. However, the medium strength acid sites on the Al modified MCF-17 mesoporous silica greatly enhanced the isomerization reaction. Through the loading of different amounts of Pt into the mesopores of the Al modified MCF-17, the relationship between the metal nanoparticles and acidic sites on the support was revealed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2015/jacsat.2015.137.issue-32/jacs.5b04808/production/images/medium/ja-2015-04808g_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja5b04808'>ACS Electronic Supporting Info</A></P>
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Yang, Euiseob,Jang, Eun Jeong,Lee, Jun Gyeong,Yoon, Sinmyung,Lee, Jaekyoung,Musselwhite, Nathan,Somorjai, Gabor A.,Kwak, Ja Hun,An, Kwangjin The Royal Society of Chemistry 2018 Catalysis science & technology Vol.8 No.13
<P>Acidic halogen-modified (Cl and F) porous alumina supports with well-defined macropores and mesopores were designed to prepare alumina-supported Pt nanoparticle (NP) catalysts (Pt/Cl-Al2O3, Pt/F-Al2O3, and Pt/Al2O3). The catalysts were then used for <I>n</I>-hexane reforming in a tubular fixed bed reactor with a hexane : H2 ratio of 1 : 4.3 at ambient pressure and various temperatures (240-400 °C). Although the reaction rates for all catalysts were maximised at 360 °C, Pt/Cl-Al2O3 exhibited the highest rate (at 8.66 × 10<SUP>−8</SUP> mol s<SUP>−1</SUP>). Regarding product selectivity, Pt/Cl-Al2O3 and Pt/F-Al2O3 yielded a higher number of olefin products and fewer cracking products than Pt/Al2O3. Temperature programmed desorption (TPD) with ethanol and <I>in situ</I> diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) with CO and pyridine adsorption were used to characterise the alumina support surface acidity. Compared with γ-Al2O3, the TPD results indicated that the Cl-Al2O3 and F-Al2O3 surface acidities were enhanced by surface modification. The <I>in situ</I> DRIFTS experiments confirmed that the relative ratio of Lewis to Brønsted acid sites of Cl-Al2O3 (0.64) was higher than those of F-Al2O3 (0.54) and unmodified Al2O3 (0.56). Additionally, the DRIFTS spectra confirmed that the Pt NPs were preferentially deposited onto the Lewis acid sites of the supports, and the CO adsorption spectra revealed that Pt NPs with (111) facets were preferentially deposited onto the Lewis acid sites. The surface acidity studies indicated that the enhanced Lewis acidity of Cl-Al2O3 induced high reaction rates at all temperatures, resulting in skeletal rearrangements of hydrocarbons toward branched isomers at high temperature <I>via</I> a conventional bifunctional mechanism.</P>
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