Oxidative Dehydrogenation of Methane When Using TiO2- or WO3-Doped Sm2O3 in the Presence of Active Oxygen Excited with UV-LED

Shigeru Sugiyama,Naohiro Shimoda,Masahiro Katoh,Ikumi Okitsu,Yuki Kato,Akihiro Furube,Wataru Ninomiya,Yasunori Hayashi

doi:10.3390/catal10050559

Shigeru Sugiyama, Naohiro Shimoda + Show 6 more

Open Access

https://doi.org/10.3390/catal10050559

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Abstract

There are active oxygen species that contribute to oxidative coupling or the partial oxidation during the oxidative dehydrogenation of methane when using solid oxide catalysts, and those species have not been definitively identified. In the present study, we clarify which of the active oxygen species affect the oxidative dehydrogenation of methane by employing photo-catalysts such as TiO2 or WO3, which generate active oxygen from UV-LED irradiation conditions under an oxygen flow. These photo-catalysts were studied in combination with Sm2O3, which is a methane oxidation coupling catalyst. For this purpose, we constructed a reaction system that could directly irradiate UV-LED to a solid catalyst via a normal fixed-bed continuous-flow reactor operated at atmospheric pressure. Binary catalysts prepared from TiO2 or WO3 were either supported on or kneaded with Sm2O3 in the present study. UV-LED irradiation clearly improved the partial oxidation from methane to CO and/or slightly improved the oxidative coupling route from methane to ethylene when binary catalysts consisting of Sm2O3 and TiO2 are used, while negligible UV-LED effects were detected when using Sm2O3 and WO3. These results indicate that with UV-LED irradiation the active oxygen of O2− from TiO2 certainly contributes to the activation of methane during the oxidative dehydrogenation of methane when using Sm2O3, while the active oxygen of H2O2 from WO3 under the same conditions afforded only negligible effects on the activation of methane.

Highlights

The conversion of methane to high value-added chemicals is an important issue in the field of catalyst research
Stability many researchers are studying the direct of methane use methane gas chemicals because thesuch desired product requires onlymonoxide a one‐step [5], catalytic reaction
This study involved both mixed- and supported-catalysts that consisted of Sm2 O3 together with

Summary

Introduction

The conversion of methane to high value-added chemicals is an important issue in the field of catalyst research. Research on the catalytic reaction of methane has been actively conducted due to progress in the production technology of natural gas, which consists mainly of methane gas [1,2,3]. Methane has the potential for conversion to a variety of important chemicals, its application as a raw material in catalytic reactions has been limited due to chemical stability. Catalysts 2020, 10, x FOR PEER REVIEW Catalysts 10, x FOR. Theproblem, direct conversion of methane is considered the conversion most efficient way To 2020, overcome thePEER stability many researchers are studying the direct of methane use methane gas chemicals because thesuch desired product requires onlymonoxide a one‐step [5], catalytic reaction. The direct conversion of methane is considered the most efficient way to the oxidative[7]

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