Features of Li-Mn-MgO catalysts and their relevance in the oxidative coupling of methane

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1170· OSTI ID:7084526

Mariscal, R; Soria, J; Pena, M A; Fierro, J L.G. ^[1]

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1. Instituto de Catalisis y Petroleoquimica, Madrid (Spain)

This work describes relevant structural features of the ternary Li-Mn-MgO system useful for the reaction of methane oxidative coupling. For a Mn-MgO catalyst, XRD, XPS, and ESR techniques revealed that manganese is incorporated into a Mg[sub 6]MnO[sub 8] phase in which the formal oxidation state of manganese is Mn[sup 4+]. Addition of Li[sub 2]CO[sub 3] in small amounts (0.48-1.60 wt.% Li) to the base Mn-MgO catalyst results in partial destruction of the Mg[sub 6]MnO[sub 8] phase. TPR and XPS data showed that the reduction of manganese is easier in the bulk Mg[sub 6]MnO[sub 8] compound than in the Mn-MgO catalyst and that it is inhibited by lithium. Moreover, the increase in Mn/Mg XPS intensity ratios in the lithium-doped counterparts indicates that lithium incorporation into the base Mn-MgO catalyst enhances manganese dispersion, in agreement with the increase of Mn[sup 4+]-Mn[sup 4+] distance derived from ESR spectra. 37 refs., 6 figs., 4 tabs.

• OSTI ID: 7084526
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 147:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030400 -- Natural Gas-- Products & By-Products
10 SYNTHETIC FUELS
100200 -- Synthetic Fuels-- Production-- (1990-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALKANES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ELECTRON SPECTROSCOPY
ELECTRON SPIN RESONANCE
HYDROCARBONS
LITHIUM COMPOUNDS
LITHIUM OXIDES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MAGNETIC RESONANCE
MANGANESE COMPOUNDS
MANGANESE OXIDES
METHANE
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
REDUCTION
RESONANCE
SCATTERING
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
VALENCE
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY