| Autor: |
Limsangkass, Wimonrat, Praserthdam, Piyasan, Phatanasri, Suphot, Panpranot, Joongjai, Chaemchuen, Somboon, Jareewatchara, Wuttithep, Kunjara Na Ayudhya, Sirachaya, Suriye, Kongkiat |
| Zdroj: |
Reaction Kinetics, Mechanisms and Catalysis; October 2014, Vol. 113 Issue: 1 p225-240, 16p |
| Abstrakt: |
Silica-supported tungsten catalysts with various tungsten oxide loadings were physically mixed with micro- or nano-sized SiO2excess supports and investigated in the metathesis of ethylene and trans-2-butene to propylene. Adding nano-sized SiO2excess support led to higher trans-2-butene conversion and propylene yield than those of micro-one and also removed the induction period. It was indicated from FT-Raman spectra and in situ UV–vis spectra that silica-supported tungsten catalysts mixed with nano-sized SiO2excess support had the higher ratio of isolated surface tetrahedral tungsten oxide species to WO3crystal and could be well-dispersed than micro-one. The characterization results of the separated nano-sized SiO2excess support from the spent catalyst by in situ Raman spectroscopy clearly exhibited the presence of isolated surface tetrahedral tungsten oxide species, the active site precursor of metathesis reaction, on the separated nano-sized SiO2excess support, confirming the thermal spreading of tungsten from the original catalysts to the nano-sized SiO2and creating more isolated surface tetrahedral tungsten oxide species. |
| Databáze: |
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