MnTiO<sub>3</sub>-driven low-temperature oxidative coupling of methane over TiO<sub>2</sub>-doped Mn<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>WO<sub>4</sub>/SiO<sub>2</sub> catalyst.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28630917.
- Also identified by DOI 10.1126/sciadv.1603180 and PMC identifier 5466374.
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Abstract
Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C<sub>2</sub> products). Among the catalysts reported previously, Mn<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>WO<sub>4</sub>/SiO<sub>2</sub> showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO<sub>2</sub>-doped Mn<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>WO<sub>4</sub>/SiO<sub>2</sub> catalyst by using Ti-MWW zeolite as TiO<sub>2</sub> dopant as well as SiO<sub>2</sub> support, enabling OCM with 26% conversion and 76% C<sub>2</sub>-C<sub>3</sub> selectivity at 720°C because of MnTiO<sub>3</sub> formation. MnTiO<sub>3</sub> triggers the low-temperature Mn<sup>2+</sup>↔Mn<sup>3+</sup> cycle for O<sub>2</sub> activation while working synergistically with Na<sub>2</sub>WO<sub>4</sub> to selectively convert methane to C<sub>2</sub>-C<sub>3</sub>. We also prepared a practical Mn<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub>-Na<sub>2</sub>WO<sub>4</sub>/SiO<sub>2</sub> catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO<sub>3</sub>-Na<sub>2</sub>WO<sub>4</sub>/SiO<sub>2</sub>, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO<sub>3</sub>-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process.