Platinum Metal-Free Catalysts for Selective Soft Oxidative Methane → Ethylene Coupling. Scope and Mechanistic Observations

Matthias Peter, Tobin J Marks

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Using abundant soft oxidants, a high methane-to-ethylene conversion might be achievable due to the low thermodynamic driving force for over-oxidation. Here we report on the oxidative coupling of methane by gaseous S2 (SOCM). The catalytic properties of Pd/Fe3O4 are compared with those of Fe3O4, and it is found that high ethylene selectivities can be achieved without noble metals; conversion and selectivity on Fe3O4 are stable for at least 48 h at SOCM conditions. SOCM data for 10 oxides are compared, and ethylene selectivities as high as 33% are found; the C2H4/C2H6 ratios of 9-12 observed at the highest S2 conversions are significantly higher than the C2H4/C2H6 ratios usually found in the CH4 coupling with O2. Complementary in-detail analytical studies show that, on Mg, Zr, Sm, W, and La catalysts, which strongly coke during the reaction, lower ethylene selectivities are observed than on Fe, Ti, and Cr catalysts, which only coke to a minor extent. Further catalyst-dependent changes during SOCM in surface area, surface composition, and partial conversion to oxysulfides and sulfides are discussed. Evidence concerning the reaction mechanism is obtained taking into account the selectivity for the different reaction products versus the contact time. CH4 coupling proceeds non-oxidatively with the evolution of H2 on some catalysts, and evidence is presented that C2H4 and C2H2 formation occur via C2H6 and C2H4 dehydrogenation, respectively.

Original languageEnglish
Pages (from-to)15234-15240
Number of pages7
JournalJournal of the American Chemical Society
Volume137
Issue number48
DOIs
Publication statusPublished - Dec 9 2015

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Platinum metals
Methane
Platinum
Coke
Ethylene
Metals
Catalysts
Oxidative Coupling
Ethylene Oxide
Sulfides
Thermodynamics
Oxidants
Dehydrogenation
Precious metals
Reaction products
Surface structure
Oxidation
Oxides
ethylene

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Platinum Metal-Free Catalysts for Selective Soft Oxidative Methane → Ethylene Coupling. Scope and Mechanistic Observations. / Peter, Matthias; Marks, Tobin J.

In: Journal of the American Chemical Society, Vol. 137, No. 48, 09.12.2015, p. 15234-15240.

Research output: Contribution to journalArticle

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