Structure and reactivity of Pt cluster and Pt-based bimetallic cluster supported on KL zeoliteKL 제올라이트에 담지된 백금 이원 금속 클러스터의 구조와 반응성에 관한 연구

Cited 0 time in webofscience Cited 0 time in scopus
  • Hit : 480
  • Download : 0
Zeolite is a crystalline aluminosilicate containing nanopores with a different size depending on the channel interconnection. The zeolite is a best for encapsulating nanometer size cluster of either metal oxide or metal inside its pore. Recently, KL zeolite has attracted much attention due to its superior activity and selectivity of n-hexane dehydrocyclization, compared to conventional platinum catalysts. The previous works on the Pt cluster in KL zeolite suggests that a 1,6 ring closer of n-hexane occurs preferentially on the cluster surface and the nature of KL zeolite play an important role in the determination of an activity and selectivity. The investigation with X-ray absorption fine structure (XAFS) showed that Pt cluster consisted of ca. 5 - 6 atoms, the smallest cluster size so far obtained inside the zeolite cage. However, a slight increase of the Pt cluster size caused a loss of catalytic activity, which originates from either a high platinum content more than 1 wt% or a sulfur induced cluster growth. In the present work, Pt clusters inside the KL zeolite channel were prepared in a quasi-static manner in order to avoid the pore blockage. The $Pt(NH_3)_4^{2+}$-exchanged precursor was activated in flowing oxygen at 593 K and subsequently reduced in hydrogen flow at 573 K. The resulting sample contained a numerous number of Pt clusters inside the KL zeolite channel without a pore blockage. The results from xenon and $CCl_4$ adsorption measurement, hydrogen chemisorption, XAFS and n-hexane dehydrocyclization showed that most Pt clusters were accessible for n-hexane to convert into benzene. The results of curve fitting of XAFS under controlled atmospheres, hydrogen and helium, suggested that the both intrinsic of platinum and metal-support interaction are responsible for the change of cluster morphology upon hydrogen chemisorption. It is noteworthy that the chemisorption of hydrogen on platinum cluster depleted the hole density from $5d_{5/2}$ ba...
Advisors
Ryoo, Ryongresearcher유룡researcher
Description
한국과학기술원 : 화학과,
Publisher
한국과학기술원
Issue Date
1997
Identifier
112613/325007 / 000945410
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 1997.2, [ xi, 135 p. ]

Keywords

PtPd; PtNi; PtSn; Pt cluster; KL zeolite; Bimetallic catalyst; 크세논핵자기공명분광법; X선 흡광법; 이원금속촉매; 백금클러스터; KL 제올라이트; 129Xe NMR; XAFS

URI
http://hdl.handle.net/10203/31459
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=112613&flag=dissertation
Appears in Collection
CH-Theses_Ph.D.(박사논문)
Files in This Item
There are no files associated with this item.

qr_code

  • mendeley

    citeulike


rss_1.0 rss_2.0 atom_1.0