TiOx-supported Na-Mn-W oxides for the oxidative coupling of methane

Divakar R. Aireddy; Amitava Roy; David A. Cullen; Kunlun Ding

doi:10.1016/j.cattod.2022.12.008

TiO_x-supported Na-Mn-W oxides for the oxidative coupling of methane

Divakar R. Aireddy, Amitava Roy, David A. Cullen, Kunlun Ding

Materials MicroAnalysis

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C₂₊ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WO_x and MnO_x sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnO_x species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnO_x/Na₂WO₄/SiO₂, with a synergistic effect between MnO_x and WO_x sites. Advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaO_x and MnO_x species have strong interactions with the acidic WO_x and TiO_x species, which might contribute to the high selectivity toward C₂₊ products and suppressed CO_x formation.

Original language	English
Article number	113977
Journal	Catalysis Today
Volume	416
DOIs	https://doi.org/10.1016/j.cattod.2022.12.008
State	Published - Apr 1 2023

Funding

We thank Dr. Spivey for the access to infrared instrument, and Dr. Dooley for the access to nitrogen sorption instrument. K.D. acknowledges the American Chemical Society Petroleum Research Fund. Electron microscopy studies were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. X-ray diffraction and scanning electron microscopy were performed at the Shared Instrumentation Facility at Louisiana State University. We thank Dr. Spivey for the access to infrared instrument, and Dr. Dooley for the access to nitrogen sorption instrument. K.D. acknowledges the American Chemical Society Petroleum Research Fund. Electron microscopy studies were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. X-ray diffraction and scanning electron microscopy were performed at the Shared Instrumentation Facility at Louisiana State University.

Keywords

Na-Mn-W oxides
Oxidative coupling of methane
Synergistic effect
Titanate

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10.1016/j.cattod.2022.12.008

Cite this

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title = "TiOx-supported Na-Mn-W oxides for the oxidative coupling of methane",

abstract = "Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WOx and MnOx sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnOx species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnOx/Na2WO4/SiO2, with a synergistic effect between MnOx and WOx sites. Advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaOx and MnOx species have strong interactions with the acidic WOx and TiOx species, which might contribute to the high selectivity toward C2+ products and suppressed COx formation.",

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AU - Roy, Amitava

AU - Cullen, David A.

AU - Ding, Kunlun

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N2 - Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WOx and MnOx sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnOx species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnOx/Na2WO4/SiO2, with a synergistic effect between MnOx and WOx sites. Advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaOx and MnOx species have strong interactions with the acidic WOx and TiOx species, which might contribute to the high selectivity toward C2+ products and suppressed COx formation.

AB - Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WOx and MnOx sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnOx species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnOx/Na2WO4/SiO2, with a synergistic effect between MnOx and WOx sites. Advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaOx and MnOx species have strong interactions with the acidic WOx and TiOx species, which might contribute to the high selectivity toward C2+ products and suppressed COx formation.

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