Structure and reactivity of single site Ti catalysts for propylene epoxidation
2019
Lu, Zheng | Liu, Xiaoyang | Zhang, Bin | Gan, Zhuoran | Tang, Siwen | Ma, Lu | Wu, Tianpin | Nelson, George J. | Qin, Yong | Turner, C Heath | Lei, Yu
Propylene epoxidation using molecular oxygen and hydrogen mixture on Au-based catalysts has attracted attention because of high propylene oxide selectivity and the use of an inexpensive and environmental friendly oxidant. Single-site titanium on metal oxide supports plays an important role in achieving high reactivity and selectivity in propylene epoxidation. Here we used TiO2 atomic layer deposition (ALD) to synthesize single-site titanium imbedded in the SiO2 framework for propylene epoxidation. High temperature calcination was used as post-treatment to control the titania structure and TiO coordination number. Using UV–vis spectroscopy and X-ray absorption spectroscopy, we successfully established that under similar propylene conversion the selectivity to propylene oxide (PO) is strongly correlated to the TiO coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single TiSiO2 sites scale linearly as a function of the coordination number. Also, the predicted TiO bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.
اظهر المزيد [+] اقل [-]الكلمات المفتاحية الخاصة بالمكنز الزراعي (أجروفوك)
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