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Study on Mo(V) Species, Location and Adsorbates Interactions in MoH-SAPO-34 by Employing ESR and Electron Spin-Echo Modulation Spectroscopies
Study on Mo(V) Species, Location and Adsorbates Interactions in MoH-SAPO-34 by Employing ESR and Electron Spin-Echo Modulation Spectroscopies
Journal of the Korean Chemical Society. 2002. Feb, 46(1): 26-36
  • Published : February 20, 2002
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Back, Gern-Ho
Jang, Chang-Ki
Ru, Chang-Kuk
Cho, Young-Hwan
So, Hyun-Soo
Kevan, Larry

Abstract
A solid-state reaction of $MoO_3$ with as-synthesized H-SAPO-34 generated paramagnetic Mo(V) species. The dehydration resulted in weak Mo(V) species, and subsequent activation resulted in the formation of Mo(V) species such as $Mo(V)_{5c}$ and $Mo(V)_{6c}$ that are characterized by ESR. The data of ESR and ESEM show the oxomolybdenum species, to be $(MoO_2)^+$ or $(MoO)^{3+}$. The $(MoO_2)^+$ species seems to be more probable. Since H-SAPO-34 has a low framework negative charge, $(MoO)^{3+}$ with a high positive charge can not be easily stabilized. A solution reaction between the solution of silico-molybdic acid and calcined H-SAPO-34 resulted in only $(MoO_2)^+$ species. A rhombic ESR signal is observed on adsorption of $D_2O$, $CD_3OH$, $CH_3Ch_2OD$ and $ND_3$. The Location and coordination structure of Mo(V) species has been determined by three-pulse electron spin-echo modulation data and their simulations. After the adsorption of methanol, ethylene, ammonia, and water for MoH-SAPO-34, three molecules, one molecule, one and one molecule, respectively, are directly coordinated to $(MoO_2)^+)$.
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