(762i) TiO2 Promoted Gold-Based Catalysts for Propylene Epoxidation

Propylene oxide (PO) is a chemical intermediate of great value and in high demand. It is used to produce useful polymeric materials. A direct catalytic epoxidation of propylene with hydrogen and oxygen to PO represents an environmentally friendly process and can be fulfilled over gold-titanium based catalysts. Despite past studies, the gold- based catalysts suffer from low conversion and poor stability. Several factors govern the activity and stability the catalysts. Isolation of the titanium was found to significantly reduce the cracking of propylene to ethanal and carbon dioxide.[1-2] However, these sites could gradually deactivate due to the change of titanium oxidation state and coordination, leading to low selectivity and coke formation. In addition, gold nanoparticles appear to sinter at high temperature, resulting in low activity.

In this work, the geometric and electronic effects of gold-titanium based catalysts are studied in detail using a number of in situ characterization techniques, including in situ X-ray absorption spectroscopy and in situ Raman spectroscopy. The loading and location of titanium are precisely controlled by means of atomic layer deposition (ALD). Strategy has been developed to enhance the stability of the gold-based catalysts. The gold-based catalyst regenerated has been studied by applying different post-treatment of the spent catalysts.

References

[1] S. T. Oyama, Mechanisms in Homogeneous and Heterogeneous Epoxidation Catalysis. Elsevier, 2011.

[2] E. E. Stangland, B. Taylor, R. P. Andres, and W. N. Delgass, â??Direct Vapor Phase Propylene Epoxidation over Deposition-Precipitation Gold-Titania Catalysts in the Presence of H2/O2: Effects of Support, Neutralizing Agent, and Pretreatment,â? J. Phys. Chem. B, vol. 109, no. 6, pp. 2321â??2330, Feb. 2005.