Structure and reactivity of single site Ti catalysts for propylene epoxidation

Z. Lu; Xiaoyang Liu; Bin Zhang; Zhuoran Gan; S. Tang; Lu Ma; Tianpin Wu; George J. Nelson; Yong Qin; C. Heath Turner; Yu Lei

doi:10.1016/j.jcat.2019.07.051

Structure and reactivity of single site Ti catalysts for propylene epoxidation

Z. Lu, Xiaoyang Liu, Bin Zhang, Zhuoran Gan, S. Tang, Lu Ma, Tianpin Wu, George J. Nelson, Yong Qin, C. Heath Turner, Yu Lei

Research output: Contribution to journal › Article › peer-review

43 Scopus citations

Abstract

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 Ti–O 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 Ti–O coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single Ti–SiO₂ sites scale linearly as a function of the coordination number. Also, the predicted Ti–O bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.

Original language	English
Pages (from-to)	419-428
Number of pages	10
Journal	Journal of Catalysis
Volume	377
DOIs	https://doi.org/10.1016/j.jcat.2019.07.051
State	Published - Sep 2019
Externally published	Yes

Funding

This work is sponsored by the National Science Foundation (Grant # CBET-1511820 and CBET-1510485). Z. G. gratefully acknowledged the fellowship from the Alabama State funded Graduate Research Scholars Program (GRSP). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Computer resources are provided by the Alabama Supercomputer Center. This work is sponsored by the National Science Foundation (Grant # CBET-1511820 and CBET-1510485 ). Z. G. gratefully acknowledged the fellowship from the Alabama State funded Graduate Research Scholars Program (GRSP). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 . Computer resources are provided by the Alabama Supercomputer Center .

Funders	Funder number
DOE Office of Science
National Science Foundation	CBET-1511820, 1511820, CBET-1510485
National Science Foundation
U.S. Department of Energy
Office of Science
Argonne National Laboratory	DE-AC02-06CH11357
Argonne National Laboratory

Keywords

Atomic layer deposition
Coordination number
Gold
Single-atom catalysis
Titania

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10.1016/j.jcat.2019.07.051

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title = "Structure and reactivity of single site Ti catalysts for propylene epoxidation",

abstract = "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 Ti–O 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 Ti–O coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single Ti–SiO2 sites scale linearly as a function of the coordination number. Also, the predicted Ti–O bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.",

keywords = "Atomic layer deposition, Coordination number, Gold, Single-atom catalysis, Titania",

author = "Z. Lu and Xiaoyang Liu and Bin Zhang and Zhuoran Gan and S. Tang and Lu Ma and Tianpin Wu and Nelson, {George J.} and Yong Qin and Turner, {C. Heath} and Yu Lei",

note = "Publisher Copyright: {\textcopyright} 2019 Elsevier Inc.",

year = "2019",

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doi = "10.1016/j.jcat.2019.07.051",

language = "English",

volume = "377",

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AU - Lu, Z.

AU - Liu, Xiaoyang

AU - Zhang, Bin

AU - Gan, Zhuoran

AU - Tang, S.

AU - Ma, Lu

AU - Wu, Tianpin

AU - Nelson, George J.

AU - Qin, Yong

AU - Turner, C. Heath

AU - Lei, Yu

PY - 2019/9

Y1 - 2019/9

N2 - 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 Ti–O 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 Ti–O coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single Ti–SiO2 sites scale linearly as a function of the coordination number. Also, the predicted Ti–O bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.

AB - 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 Ti–O 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 Ti–O coordination number and bond length. Using a cluster model, density functional theory (DFT) calculations indicate that the partial charges of single Ti–SiO2 sites scale linearly as a function of the coordination number. Also, the predicted Ti–O bond lengths follow the same trend as found in the experiments, providing additional support for the observed experimental activity relationships.

KW - Atomic layer deposition

KW - Coordination number

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KW - Single-atom catalysis

KW - Titania

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ER -

Structure and reactivity of single site Ti catalysts for propylene epoxidation

Abstract

Funding

Keywords

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