A density functional theory study of propylene epoxidation on RuO2(110) surface

Atmaca, Deniz Onay; Düzenli, Derya; Özbek, M. Oluş; Önal, Işık

doi:10.1016/j.apsusc.2016.05.090

Cited by 17 publications

(19 citation statements)

References 51 publications

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“…In fact, the experimental result demonstrated that the pure RuO 2 has very low PO formation selectivity (only 3.9% at the 1.1% C 3 H 6 conversion) . It might be pointed out that the previous theoretical work indicated that the RuO 2 would have the ∼50% selectivity for PO formation when using atop adsorbed oxygen (O t –Ru) as the active species . However, the AHS processes might be more intrinsic in determining the whole PO formation selectivity.…”

Section: Resultsmentioning

confidence: 96%

“…12 It might be pointed out that the previous theoretical work indicated that the RuO 2 would have the ∼50% selectivity for PO formation when using atop adsorbed oxygen (O t −Ru) as the active species. 28 However, the AHS processes might be more intrinsic in determining the whole PO formation selectivity. On the other hand, as the PO formation selectivity is also very low catalyzed by pure Cu 2 O (only 1.4% at the 1.4% C 3 H 6 conversion), 12 namely, the O 2 * (O*) bound to the Cu site directly is still not the active species.…”

Section: Modelsmentioning

confidence: 99%

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Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

Xiao

Wang

2020

J. Phys. Chem. C

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The copper-catalyzed propylene epoxidation reaction is an important process to produce PO (propylene oxide), and the addition of Ru can enhance its selectivity significantly, so it is worthy to explore the physical nature behind the Ru promotion effect from a theoretical aspect. In the present work, the reaction of propylene-selective oxidation over Ru-doped Cu 2 O(111) (named Ru@Cu 2 O(111)) was studied by density functional theory calculations systematically. It is found that the addition of Ru has the ability to promote O−O bond activation, which might be beneficial to the propylene reaction. Our results show that when O* (O 2 *) bound to the unsaturated surface copper (Cu CUS ) atom connected to Ru(O*−Cu CUS −Ru), it shows the ability to inhibit the dehydrogenation reaction and to promote the epoxidation process, thereby leading to the high selectivity toward the PO formation compared to pure Cu 2 O(111). On the other hand, the too strong binding of O 2 * (O*) (usually binds to the Ru sites) is not beneficial for the PO formation because it is less active in the kinetic aspect, indicating that the active site toward the PO formation might be the Cu CUS adjacent to the Ru ions (Cu CUS −Ru), rather than the Ru site or the Cu CUS site that is far from the Ru site like that of pure Cu 2 O. The promotion effect of Ru is to affect the catalytic activity of the Cu site through the electronic effect by acting as the ligand, instead of acting as the active site to take part in the propylene epoxidation directly. Moreover, it was found that different oxygen species [lattice oxygen (O SUF ), adsorbed atomic oxygen (O*), or adsorbed molecular oxygen (O 2 *)] show different catalytic effects for propylene epoxidation, which follows the trend O* ≈ O 2 * > O SUF . Finally, the possible factors controlling the Ru promotion effect have been analyzed, and the stronger binding to OH hinders the dehydrogenation process and stronger binding to CH 3 CH 2 O is beneficial to the PO formation over Ru@Cu 2 O(111). It is hoped that the present results may be applied to other promoters of transition metals such as Rh or alkali metal such as Na and hence is useful for further development of promising catalysts for propylene epoxidation.

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Section: Resultsmentioning

confidence: 96%

Section: Modelsmentioning

confidence: 99%

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

Xiao

Wang

2020

J. Phys. Chem. C

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“…Figure gives some possible structures. Some authors further distinguish between OME and OMME, OMP1 and OMMP1, and OMP2 and OMMP2 on account of how they bind to the surface, which is especially relevant on less densely packed surfaces, such as 110. Analogously, OOMP1 and OOMMP1 and OOMP2 and OOMMP2 can be distinguished …”

Section: Experimental Propylene Epoxidation On Silver-based Catalystsmentioning

confidence: 99%

“…The consensus in the scientific community is that, for PO selectivity, the oxametallacycle (OMC) is the prerequisite reaction intermediate. − In the following section, the formation and different desorption possibilities of oxametallacycle intermediates are discussed. DFT studies have been used extensively to both discover the reaction mechanism and to evaluate the energetics and kinetics of its individual steps.…”

Section: Experimental Propylene Epoxidation On Silver-based Catalystsmentioning

confidence: 99%

Propylene Epoxidation using Molecular Oxygen over Copper- and Silver-Based Catalysts: A Review

et al. 2020

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Propylene oxide (PO) is a versatile chemical, mainly used in the synthesis of polyurethane plastics. Propylene epoxidation using molecular oxygen could replace the tedious current synthesis protocols, which use expensive H 2 O 2 or organic peroxides as oxidants. This review focuses on the propylene epoxidation reaction using molecular oxygen in the gas phase over copper-and silver-based catalysts. Silver is a proven and industrially used ethylene epoxidation catalyst. However, it initiates allylic hydrogen stripping (AHS) in propylene epoxidation, shifting the selectivity toward unwanted acrolein and total oxidation. Nevertheless, silver has been extensively studied to determine if AHS could be mitigated by targeted active site design and various doping strategies. Copper-based catalysts have been less extensively studied but have been experimentally proved as well as theoretically confirmed that their PO selectivity is on par with that of silver. In this review, different catalyst modification strategies have been analyzed and the achieved improvements discussed. Theoretical approaches aimed at understanding the mechanism and predicting catalytic performance on the basis of electronic states (density functional theory calculations) are also reviewed. We conclude with a future outlook on how the current state of the art knowledge of active site modification and reaction engineering approaches could leverage the PO selectivity toward industrial requirements, thus enabling a breakthrough in gas-phase propylene epoxidation using O 2 .

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“…Previous studies have shown that the facile water splitting reaction driven by RuO 2 or IrO 2 surfaces results in the O- or OH-covered surfaces, depending on the environment. ,,,,, Both experimental , and theoretical − studies indicated that in the presence of oxygen, the oxygen-covered (also called “oxygen-rich” or “ o -rich”) RuO 2 or IrO 2 surfaces might form. Crihan et al observed via STM the existence of fully occupied o -rich RuO 2 (110) surface at room temperature.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Study on CO Removing Mechanism on Pt-Decorated Oxygen-Rich Anode Surfaces (Pt₂/o-MO₂(110), M = Ru and Ir) in DMFC

Liu

Chang

et al. 2017

J. Phys. Chem. C

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Direct methanol fuel cell (DMFC) is an efficient power source. However, the DMFC anodes are easily toxified by CO or other hydrocarbons, which terminates the methanol oxidation reaction (MOR). The most commonly used high performance catalyst on DMFC anodes is Pt or bimetallic PtRu. In this work, we apply density functional theory (DFT) to investigate the adsorption of CO and H2O on pristine Pt2/MO2(110) and the oxygen-rich Pt2/o-MO2(110) surfaces (M = Ru and Ir). We find that the application of the oxygen-rich surfaces significantly reduces the adsorption energies of CO and H2O molecules as well as the major reaction barrier (CO + OH → CO2) in the water–gas–shift-like (WGS-like) reactions forming CO2. Our detailed analyses on the electronic interaction between the catalysts and adsorbates indicate that Pt2/o-MO2(110) may be a promising DMFC anode material, which reduces the poison problem, and that it may be the actual experimental system that is responsible for the observed efficient CO removal.

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A density functional theory study of propylene epoxidation on RuO2(110) surface

Cited by 17 publications

References 51 publications

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

Propylene Epoxidation using Molecular Oxygen over Copper- and Silver-Based Catalysts: A Review

First-Principles Study on CO Removing Mechanism on Pt-Decorated Oxygen-Rich Anode Surfaces (Pt₂/o-MO₂(110), M = Ru and Ir) in DMFC

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A density functional theory study of propylene epoxidation on RuO2(110) surface

Cited by 17 publications

References 51 publications

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu2O(111)

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu2O(111)

Propylene Epoxidation using Molecular Oxygen over Copper- and Silver-Based Catalysts: A Review

First-Principles Study on CO Removing Mechanism on Pt-Decorated Oxygen-Rich Anode Surfaces (Pt2/o-MO2(110), M = Ru and Ir) in DMFC

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Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

Theoretical Investigation into the Key Role of Ru in the Epoxidation of Propylene over Cu₂O(111)

First-Principles Study on CO Removing Mechanism on Pt-Decorated Oxygen-Rich Anode Surfaces (Pt₂/o-MO₂(110), M = Ru and Ir) in DMFC