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The Study on Location and Adsorbate Interaction for Vanadium Species in $VO^{2+}-SAPO-5$ by Electron Spin Resonance and Electron Spin Echo Modulation Spectroscopies
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  • The Study on Location and Adsorbate Interaction for Vanadium Species in $VO^{2+}-SAPO-5$ by Electron Spin Resonance and Electron Spin Echo Modulation Spectroscopies
  • The Study on Location and Adsorbate Interaction for Vanadium Species in $VO^{2+}-SAPO-5$ by Electron Spin Resonance and Electron Spin Echo Modulation Spectroscopies
저자명
Back. Gern-Ho,Park. Sung-Gun,Lee. Chul-Wee
간행물명
Journal of the Korean magnetic resonance society
권/호정보
2005년|9권 2호|pp.138-154 (17 pages)
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한국자기공명학회
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정기간행물|ENG|
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이 논문은 한국과학기술정보연구원과 논문 연계를 통해 무료로 제공되는 원문입니다.
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기타언어초록

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2;at;600^{circ}C$ for 5 h, thus suggesting oxidation of $V^{4+};to;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.