Ethylene production by direct conversion of methane over isolated single active centers

Toraman, Hilal Ezgi; Alexopoulos, Konstantinos; Oh, Su Cheun; Cheng, Sichao; Liu, Dongxia; Vlachos, Dionisios G.

doi:10.1016/j.cej.2021.130493

Cited by 25 publications

(21 citation statements)

References 73 publications

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“…On the basis of these results, they suggested a mechanism in which methane activation starts with the formation of CH 3 • radicals, and continues with further dehydrocoupling and cyclization in the gas-phase. However, a DFT-based mechanistic analysis from Vlachos et al in 2021 suggested that ethylene formation on isolated iron sites of Fe@SiO 2 catalyst is much more favorable than gas phase dehydrocoupling of methyl radicals desorbed from iron sites . On the other side, a newly published research study from van Bokhoven, Hemberger, and colleagues presents strong spectroscopic evidence for the role of radical-mediated gas-phase reactions during high-temperature (945–1400 °C) conversion of methane into olefins and aromatics over iron modified silica catalysts .…”

Section: Radical Chemistry In Zeolite Catalysismentioning

confidence: 99%

“…However, a DFT-based mechanistic analysis from Vlachos et al in 2021 suggested that ethylene formation on isolated iron sites of Fe@SiO 2 catalyst is much more favorable than gas phase dehydrocoupling of methyl radicals desorbed from iron sites. 325 study from van Bokhoven, Hemberger, and colleagues presents strong spectroscopic evidence for the role of radical-mediated gas-phase reactions during high-temperature (945−1400 °C) conversion of methane into olefins and aromatics over iron modified silica catalysts. 220 In this study, they investigated the gas-phase products at the reactor outlet using imaging photoelectron photoioncoincidence (iPEPICO) spectroscopy thanks to synchrotron radiation.…”

Section: Methane Dehydroaromatization (Mda)mentioning

confidence: 99%

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First-Generation Organic Reaction Intermediates in Zeolite Chemistry and Catalysis

Gong

Çağlayan

et al. 2022

Chem. Rev.

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Zeolite chemistry and catalysis are expected to play a decisive role in the next decade(s) to build a more decentralized renewable feedstock-dependent sustainable society owing to the increased scrutiny over carbon emissions. Therefore, the lack of fundamental and mechanistic understanding of these processes is a critical “technical bottleneck” that must be eliminated to maximize economic value and minimize waste. We have identified, considering this objective, that the chemistry related to the first-generation reaction intermediates (i.e., carbocations, radicals, carbenes, ketenes, and carbanions) in zeolite chemistry and catalysis is highly underdeveloped or undervalued compared to other catalysis streams (e.g., homogeneous catalysis). This limitation can often be attributed to the technological restrictions to detect such “short-lived and highly reactive” intermediates at the interface (gas–solid/solid–liquid); however, the recent rise of sophisticated spectroscopic/analytical techniques (including under in situ/operando conditions) and modern data analysis methods collectively compete to unravel the impact of these organic intermediates. This comprehensive review summarizes the state-of-the-art first-generation organic reaction intermediates in zeolite chemistry and catalysis and evaluates their existing challenges and future prospects, to contribute significantly to the “circular carbon economy” initiatives.

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Section: Radical Chemistry In Zeolite Catalysismentioning

confidence: 99%

Section: Methane Dehydroaromatization (Mda)mentioning

confidence: 99%

First-Generation Organic Reaction Intermediates in Zeolite Chemistry and Catalysis

Gong

Çağlayan

et al. 2022

Chem. Rev.

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“…A high selectivity towards ethylene (>50%) at relatively high conversion (>30%) has been exclusively reported 233 by DICP in Dalian. A mechanism has been proposed, 234 where the true active site is an iron carbide, on which ethylene is formed through the methyl group formation and recombination.…”

Section: Light Olefin Synthesis From Hydrocarbonsmentioning

confidence: 99%

Light olefin synthesis from a diversity of renewable and fossil feedstocks: state-of the-art and outlook

et al. 2022

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“…The DNMC at the studied conditions involved a complex heterogeneous–homogeneous reaction network ( Guo et al, 2014 ; Toraman et al, 2021 ). The mechanistic investigation into the Fe/SiO 2 catalyst revealed that the silica lattice-confined Fe sites initiated CH 4 dehydrogenation to generate methyl and hydrogen species, enabling a series of subsequent surface and gas-phase reactions to form dehydrogenated and cyclized large hydrocarbon products.…”

Section: Resultsmentioning

confidence: 99%

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Cheng

Sakbodin

et al. 2022

Front. Chem.

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Direct non-oxidative methane conversion (DNMC) converts methane (CH4) in one step to olefin and aromatic hydrocarbons and hydrogen (H2) co-product. Membrane reactors comprising methane activation catalysts and H2-permeable membranes can enhance methane conversion by in situ H2 removal via Le Chatelier's principle. Rigorous description of H2 kinetic effects on both membrane and catalyst materials in the membrane reactor, however, has been rarely studied. In this work, we report the impact of hydrogen activation by hydrogen-permeable SrCe0.8Zr0.2O3−δ (SCZO) perovskite oxide material on DNMC over an iron/silica catalyst. The SCZO oxide has mixed ionic and electronic conductivity and is capable of H2 activation into protons and electrons for H2 permeation. In the fixed-bed reactor packed with a mixture of SCZO oxide and iron/silica catalyst, stable and high methane conversion and low coke selectivity in DNMC was achieved by co-feeding of H2 in methane stream. The characterizations show that SCZO activates H2 to favor “soft coke” formation on the catalyst. The SCZO could absorb H2in situ to lower its local concentration to mitigate the reverse reaction of DNMC in the tested conditions. The co-existence of H2 co-feed, SCZO oxide, and DNMC catalyst in the present study mimics the conditions of DNMC in the H2-permeable SCZO membrane reactor. The findings in this work offer the mechanistic understanding of and guidance for the design of H2-permeable membrane reactors for DNMC and other alkane dehydrogenation reactions.

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Ethylene production by direct conversion of methane over isolated single active centers

Cited by 25 publications

References 73 publications

First-Generation Organic Reaction Intermediates in Zeolite Chemistry and Catalysis

First-Generation Organic Reaction Intermediates in Zeolite Chemistry and Catalysis

Light olefin synthesis from a diversity of renewable and fossil feedstocks: state-of the-art and outlook

Understanding the Impact of Hydrogen Activation by SrCe0.8Zr0.2O3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

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