The Effect of ppm-Level Na Impurity on the Structure of SiO2-Supported Mo Catalysts Prepared in a Clean Room |
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| Authors: | Chun W-J Asakura K Ishii H Liu T Iwasawa Y |
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| Affiliation: | (1) Department of Chemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan;(2) Catalysis Research Center, Hokkaido University, Kita-ku, Sapporo, 060-0811, Japan;(3) NTT System Electronic Laboratory, Morino-sato, Atsugi, Kanagawa, 243-0198, Japan;(4) Merck-Kanto, Advanced Chemicals Ltd, Ching Chien Rd, Kuan Yin Industrial Park, Taoyuan, Taiwan, ROC |
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| Abstract: | To investigate the effect of alkali impurity in Mo/SiO2 on the MoO
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structure on SiO2 surfaces SiO2-supported Mo oxides were prepared with various amounts of Na ions in a class-1 clean bench with a laminar flow in a class-1000 clean room. The Na concentrations were varied in the range 0-5000 ppm, while the Mo loading on SiO2 was maintained at 0.7 wt%. The Mo-Na/SiO2 samples obtained were characterized by diffuse reflectance UV-visible and Raman spectroscopy. Three types of Mo species were identified: octahedral monooxo Mo monomer species, Na2Mo2O7 and MoO3. At less than 100 ppm Na both octahedral Mo monomers and MoO3 species were formed on SiO2. The MoO3 species was transformed to Na2Mo2O7 at 2000 ppm Na, where the Na ions interact directly with the Mo species on the surface. The octahedral monooxo Mo monomer species seems not to be influenced significantly by Na impurity. |
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| Keywords: | alkali impurities in Mo/SiO2 characterization by UV-visible Raman spectroscopy |
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