Oxidative dehydrogenation of propane over transition metal sulfides using sulfur as an alternative oxidant

Arinaga, Allison M.; Liu, Shanfu; Marks, Tobin J.

doi:10.1039/d0cy01039a

Cited by 12 publications

(31 citation statements)

References 41 publications

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“…However, to our knowledge, this is the first time that O 2 and S 2 have been directly compared for a light alkane partial oxidation reaction. The results support the hypothesis introduced in prior literature that S 2 can afford higher olefin selectivity by moderating the thermodynamic driving force towards overoxidation [5a,6–7] …”

Section: Figuresupporting

confidence: 90%

“…In this study, xV/Al 2 O 3 materials with V weight loadings of x=1.0 and 3.5 wt% were examined. Figure 1a shows the propylene selectivity as a function of conversion for these materials and for sulfided‐bulk ZrO 2 , the highest performing catalyst in prior SODHP studies [7] . It is clear that the xV/Al 2 O 3 materials are significantly more selective for propylene at comparable conversions and reaction temperatures.…”

Section: Figurementioning

confidence: 95%

“…One approach to address this issue that has been explored in the ODHP literature is to replace O 2 with a softer oxidant, such as CO 2 or N 2 O, in order to mitigate the overoxidation to CO x. [4] In addition to oxygen‐containing molecules, this laboratory has previously shown that S 2 can be used as an alternative oxidant in a number of light alkane partial oxidations such as methane coupling to ethylene, [5] the ODH of ethane, [6] and ODHP [7] . For ODHP, we investigated a number of bulk metal sulfide surfaces as catalysts for this sulfur‐ODHP (SODHP) reaction, finding that the activation energy for propylene formation decreases with falling metal‐sulfur bond energy.…”

Section: Figurementioning

confidence: 99%

“…For ODHP, we investigated a number of bulk metal sulfide surfaces as catalysts for this sulfur‐ODHP (SODHP) reaction, finding that the activation energy for propylene formation decreases with falling metal‐sulfur bond energy. These and other observations led to a proposed mechanism in which a surface S of the metal sulfide activates the C−H bond in propane [7] . Nevertheless, the surface area of bulk metal sulfides is relatively low, and the nature of the active sites is not well understood, complicating the determination of meaningful reaction rates and mechanistic understanding.…”

Section: Figurementioning

confidence: 99%

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Supported Vanadium Catalysts for Selective Sulfur‐Oxidative Dehydrogenation of Propane

et al. 2021

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The catalytic oxidative dehydrogenation of propane (ODHP) is a challenging reaction due to facile competing overoxidation to COx. The gaseous disulfur molecule, S2, is isoelectronic with O2 and has been shown to act as an alternative, “soft oxidant” for the analogous process (SODHP) over bulk metal sulfide catalysts. However, these bulk catalysts suffer from low surface areas and ill‐defined active sites – issues that might be addressed with a supported catalyst. Here we investigate supported V/Al2O3 materials for SODHP. We show that these catalysts are highly selective for propylene, far surpassing the yields of the prior bulk systems. Isolated sulfided vanadium species are found to be more active and selective than crystalline vanadium sulfide. Additionally, we compare the S2 and O2 oxidants over sulfided and calcined V/Al2O3 materials, respectively, and find that the propylene selectivity is enhanced using S2 as the oxidant. These results suggest that sulfur is a promising soft oxidant that can be used to achieve high propylene selectivities over supported metal sulfides.

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Section: Figuresupporting

confidence: 90%

Section: Figurementioning

confidence: 95%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Supported Vanadium Catalysts for Selective Sulfur‐Oxidative Dehydrogenation of Propane

et al. 2021

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“…Catalytic runs begin by exposing the Fe 3 O 4 precatalyst to flowing H 2 S (sulfurization) for several hours to produce the active catalyst. Catalytic experiments flow Ar over molten S 8 (melting point = 388 K; boiling point = 718 K) to transport gaseous S 2 and a CH 4 into the reactor described previously (29,34,41,42). Gaseous products are quantified by gas chromatography.…”

Section: Resultsmentioning

confidence: 99%

“Soft” oxidative coupling of methane to ethylene: Mechanistic insights from combined experiment and theory

Liu

Udyavara

Zhang

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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The oxidative coupling of methane to ethylene using gaseous disulfur (2CH4 + S2 → C2H4 + 2H2S) as an oxidant (SOCM) proceeds with promising selectivity. Here, we report detailed experimental and theoretical studies that examine the mechanism for the conversion of CH4 to C2H4 over an Fe3O4-derived FeS2 catalyst achieving a promising ethylene selectivity of 33%. We compare and contrast these results with those for the highly exothermic oxidative coupling of methane (OCM) using O2 (2CH4 + O2 → C2H4 + 2H2O). SOCM kinetic/mechanistic analysis, along with density functional theory results, indicate that ethylene is produced as a primary product of methane activation, proceeding predominantly via CH2 coupling over dimeric S–S moieties that bridge Fe surface sites, and to a lesser degree, on heavily sulfided mononuclear sites. In contrast to and unlike OCM, the overoxidized CS2 by-product forms predominantly via CH4 oxidation, rather than from C2 products, through a series of C–H activation and S-addition steps at adsorbed sulfur sites on the FeS2 surface. The experimental rates for methane conversion are first order in both CH4 and S2, consistent with the involvement of two S sites in the rate-determining methane C–H activation step, with a CD4/CH4 kinetic isotope effect of 1.78. The experimental apparent activation energy for methane conversion is 66 ± 8 kJ/mol, significantly lower than for CH4 oxidative coupling with O2. The computed methane activation barrier, rate orders, and kinetic isotope values are consistent with experiment. All evidence indicates that SOCM proceeds via a very different pathway than that of OCM.

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Alternative Oxidants for the Catalytic Oxidative Coupling of Methane

2021

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The catalytic oxidative coupling of methane (OCM) to C2 hydrocarbons with oxygen (O2‐OCM) has garnered renewed worldwide interest in the past decade due to the emergence of enormous new shale gas resources. However, the C2 selectivity of typical OCM processes is significantly challenged by overoxidation to COx products. Other gaseous reagents such as N2O, CO2, and S2 have been investigated to a far lesser extent as alternative, milder oxidants to replace O2. Although several authoritative review articles have summarized OCM research progress in depth, recent oxidative coupling developments using alternative oxidants (X‐OCM) have not been overviewed in detail. In this perspective, we review and analyze OCM research results reporting the implementation of N2O, CO2, S2, and other non‐O2 oxidants, highlighting the unique chemistries of these systems and their advantages/challenges compared to O2‐OCM. Current outlook and potential areas for future study are also discussed.

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Oxidative dehydrogenation of propane over transition metal sulfides using sulfur as an alternative oxidant

Abstract: The use of alternative oxidants for the oxidative dehydrogenation of propane (ODHP) is a promising strategy to suppress the facile overoxidation to COx that occurs with O2. Gaseous disulfur (S2)...

Cited by 12 publications

References 41 publications

Supported Vanadium Catalysts for Selective Sulfur‐Oxidative Dehydrogenation of Propane

Supported Vanadium Catalysts for Selective Sulfur‐Oxidative Dehydrogenation of Propane

“Soft” oxidative coupling of methane to ethylene: Mechanistic insights from combined experiment and theory

Alternative Oxidants for the Catalytic Oxidative Coupling of Methane

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