Direct experimental detection of hydrogen radicals in non-oxidative methane catalytic reaction

Hao, Jihua; Schwach, Pierre; Li, Lulu; Guo, Xiaoguang; Weng, Junben; Zhang, Hailei; Shen, H. F.; Fang, Guangzhan; Huang, Xin; Pan, Xiulian; Xiao, Chunlei; Yang, Xueming; Bao, Xinhe

doi:10.1016/j.jechem.2020.04.001

Cited by 18 publications

(9 citation statements)

References 44 publications

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“…Different types of catalysts can be used for this process, including metal‐exchanged zeolites and metal‐modified oxides [1d, 2] . Several recent reports pinpointed exceptional performance of iron‐modified silica catalysts in this process, which displayed markedly different activity and product distribution patterns as compared to non‐catalyzed methane pyrolysis under the same conditions (Table S1) [2c–m] . Nonetheless, the mechanistic understanding that is essential to derive the rationale for tuning the product distribution and enhancing the catalyst lifetime is still elusive.…”

Section: Figurementioning

confidence: 99%

“…[ 1d , 2 ] Several recent reports pinpointed exceptional performance of iron‐modified silica catalysts in this process, which displayed markedly different activity and product distribution patterns as compared to non‐catalyzed methane pyrolysis under the same conditions (Table S1). [ 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j , 2k , 2l , 2m ] Nonetheless, the mechanistic understanding that is essential to derive the rationale for tuning the product distribution and enhancing the catalyst lifetime is still elusive. This is mainly caused by the complexity of the process, which likely involves contributions from both surface‐catalyzed and radical‐mediated gas‐phase pathways (Table S2).…”

mentioning

confidence: 99%

“…This is mainly caused by the complexity of the process, which likely involves contributions from both surface‐catalyzed and radical‐mediated gas‐phase pathways (Table S2). [ 2c , 2d , 2e , 2f , 2g , 2h , 3 ] In particular, for a silica‐confined single iron sites catalyst, Guo et al. [2c] proposed a reaction mechanism in which C−C bonds are formed via sequential homolytical bond dissociation reactions and stepwise chain growth.…”

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confidence: 99%

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Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

et al. 2021

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Radical‐mediated gas‐phase reactions play an important role in the conversion of methane under non‐oxidative conditions into olefins and aromatics over iron‐modified silica catalysts. Herein, we use operando photoelectron photoion coincidence spectroscopy to disentangle the elusive C2+ radical intermediates participating in the complex gas‐phase reaction network. Our experiments pinpoint different C2‐C5 radical species that allow for a stepwise growth of the hydrocarbon chains. Propargyl radicals (H2C−C≡C−H) are identified as essential precursors for the formation of aromatics, which then contribute to the formation of heavier hydrocarbon products via hydrogen abstraction–acetylene addition routes (HACA mechanism). These results provide comprehensive mechanistic insights that are relevant for the development of methane valorization processes.

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Section: Figurementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

et al. 2021

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“…In the last decade, various innovative catalytic technologies that can achieve methane conversion more efficiently and effectively by thermocatalysis, [29][30][31][32][33] electrocatalysis, [34][35][36] and photocatalysis [37][38][39] have been invented. Photoenergy, as an abundant and eco-friendly energy resource on Earth, has been utilized as an alternative, green, and sustainable driver for methane conversion and activation.…”

Section: Introductionmentioning

confidence: 99%

Research progress on methane conversion coupling photocatalysis and thermocatalysis

et al. 2021

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Conversion of methane into value-added chemicals is of significance for methane utilization and industrial demand of primary chemical products. The barrier associated with the nonpolar structure of methane and the high bond energy C-H bond (4.57 eV) makes it difficult to realize methane conversion and activation under mild conditions. The photothermal synergetic strategy by combining photon energy and thermo energy provides an advanced philosophy to achieve efficient methane conversion. In this review, we overview the current pioneering studies of photothermal methane indirect conversion and present the methane direct conversion by the way of photocatalysis and thermocatalysis to provide a fundamental understanding of methane activation. Finally, we end this review with a discussion on the remaining challenges and perspectives of methane direct conversion over single-atom catalysts via photothermal synergetic strategy.

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“…Methane is the main component of natural gas whose resource reserve is rich [25] and the storage and transportation solution is perfect. Thus it is the ideal fuel for reforming hydrogen production in small distributed hydrogen production scenarios.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Production via Partial Oxidation Reforming of Methane with Gliding Arc Discharge Plasma

Wang

Liu

et al. 2020

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Hydrogen production from partial oxidation reforming of methane in a gliding arc discharge (GAD) reactor is investigated. The effects of input power, the oxygen-carbon molar ratio (O/C), and residence time are studied, respectively. Products such as H 2 , CO, CO 2 , and C 2-C 4 hydrocarbons can be detected in the outlet gas. The experimental result shows that the input power of 36.4 W, the relitively low O/C of 0.705 and the 13.8 s residence time in this system will bring the highest H 2 energy yield. Compared to the decomposition of methane, partial oxidation of methane with air can maintain a stable discharge state and no carbon deposition on electrodes is observed during the reaction process. Optical emission spectroscopy (OES) is also employed to characterize this methane-air plasma. Based on the results of the experiment and OES, a possible mechanism of methane partial oxidation process was proposed, which points out that collisions of high-energy electrons and excited N 2 species (mainly N 2 (A)) with other species (such as O 2 , CH 4) in the plasma region are two main ways for the activation of this reforming system. Hydrogen is generated principally through the H-abstraction reaction and the H-coupling reaction.

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Direct experimental detection of hydrogen radicals in non-oxidative methane catalytic reaction

Cited by 18 publications

References 44 publications

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

Direct Evidence on the Mechanism of Methane Conversion under Non‐oxidative Conditions over Iron‐modified Silica: The Role of Propargyl Radicals Unveiled

Research progress on methane conversion coupling photocatalysis and thermocatalysis

Hydrogen Production via Partial Oxidation Reforming of Methane with Gliding Arc Discharge Plasma

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