Total Oxidation of Methane Over Sulfur Poisoning Resistant Pt/ZrO2 Catalyst: Effect of Pt2+–Pt4+ and Pt2+–Zr4+ Dipoles at Metal-Support Interface

Water, which is an intrinsic part of the exhaust gas of combustion engines, strongly inhibits the methane oxidation reaction over palladium oxide-based catalysts under lean conditions and leads to severe catalyst deactivation. In this combined experimental and modeling work, we approach this challenge with kinetic measurements in flow reactors and a microkinetic model, respectively. We propose a mechanism that takes the instantaneous impact of water on the noble metal particles into account. The dual site microkinetic model is based on the mean-field approximation and consists of 39 reversible surface reactions among 23 surface species, 15 related to Pd-sites, and eight associated with the oxide. A variable number of available catalytically active sites is used to describe light-off activity tests as well as spatially resolved concentration profiles. The total oxidation of methane is studied at atmospheric pressure, with space velocities of 160,000 h−1 in the temperature range of 500–800 K for mixtures of methane in the presence of excess oxygen and up to 15% water, which are typical conditions occurring in the exhaust of lean-operated natural gas engines. The new approach presented is also of interest for modeling catalytic reactors showing a dynamic behavior of the catalytically active particles in general.

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Dynamic study of methane interaction with active sites involved in the total oxidation of methane over Pd/Al2O3 catalyst.

Reaction Kinetics and the Development and Operation of Catalytic Processes, Proceedings of the 3rd International Symposium - Studies in Surface Science and Catalysis ◽

10.1016/s0167-2991(01)81980-7 ◽

2001 ◽

pp. 333-340

Author(s):

S. Fessi ◽

A. Ghorbel ◽

A. Rives ◽

R. Hubaut

Keyword(s):

Active Sites ◽

Dynamic Study ◽

Total Oxidation ◽

Oxidation Of Methane ◽

Al2o3 Catalyst

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Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Catalysts ◽

10.3390/catal10060613 ◽

2020 ◽

Vol 10 (6) ◽

pp. 613

Author(s):

Hussein Mahdi S. Al-Aani ◽

Mihaela M. Trandafir ◽

Ioana Fechete ◽

Lucia N. Leonat ◽

Mihaela Badea ◽

...

Keyword(s):

Electron Microscopy ◽

Transition Metal ◽

Mixed Oxide ◽

Mixed Oxides ◽

Catalytic Performance ◽

Atomic Ratio ◽

Total Oxidation ◽

X Ray ◽

Oxidation Of Methane ◽

Al2o3 Catalyst

To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

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