(647a) Characterization of Tungsten and Zirconia Decorated Multi-Walled Carbon Nanotubes

Solid acid catalysts have found a wide range of applications, ranging from cracking of heavy polyols into smaller chains all the way to dehydration reactions that are useful in biomass conversion. The focus of this research is to develop strong solid acid catalysts supported on multi-walled carbon nanotubes (MWCNT) suitable for biomass processing applications. Previous work from our group has shown that zirconia supported on MWCNT is a hydrothermally stable catalyst and it is not altered when exposed to hot liquid water. Furthermore, this system has been sulfated to increase the catalytic acidity. However, it has been demonstrated that the sulfur species is not extraordinarily stable in aqueous media. Due to this fact, we have begun investigating the tungsten modified zirconia analogue that is expected to be more hydrothermally stable while maintaining comparable acidity. We plan a comparison between the sulfur and tungsten modified zirconia supported on MWCNT. The current work focuses on optimizing the synthesis of tungsten modified zirconia supported on MWCNT, investigating the particle size of the oxides when annealed at different temperatures with XRD and TEM, and conducting X-ray absorption spectroscopy on these materials. We are working towards kinetically characterizing the catalysts with a 2-butanol dehydration reaction. XRD and TEM indicate the zirconia particles are in the 2nm size range and the tungsten oxide particles are in the 6nm size range. XAS has shown shifts in the W L_3­ edge upon annealing at different temperatures, indicating a change in the oxidation state of the tungsten. We expect to correlate average oxidation found in the X-ray absorption studies with increased activity in the probe reaction, enabling us to understand catalytic activity in terms of electronic structure.