Methane oxidation over Pt on .gamma.-alumina: kinetics and structure sensitivity

K. Otto

doi:10.1021/la00090a018

Structure sensitivity of methane oxidation over platinum and palladium

Journal of Catalysis ◽

10.1016/0021-9517(90)90282-o ◽

1990 ◽

Vol 122 (2) ◽

pp. 280-294 ◽

Cited By ~ 297

Author(s):

R HICKS

Keyword(s):

Methane Oxidation ◽

Structure Sensitivity

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ChemInform Abstract: Structure Sensitivity of Methane Oxidation Over Platinum and Palladium.

ChemInform ◽

10.1002/chin.199028047 ◽

1990 ◽

Vol 21 (28) ◽

Author(s):

R. F. HICKS ◽

H. QI ◽

M. L. YOUNG ◽

R. G. LEE

Keyword(s):

Methane Oxidation ◽

Structure Sensitivity ◽

Abstract Structure

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Structure sensitivity of methane oxidation on Pt/SiO2 of widely varying dispersity

Reaction Kinetics and Catalysis Letters ◽

10.1007/bf02061715 ◽

1988 ◽

Vol 37 (1) ◽

pp. 89-93 ◽

Cited By ~ 8

Author(s):

M. Kobayashi ◽

T. Kanno ◽

A. Konishi ◽

H. Takeda

Keyword(s):

Methane Oxidation ◽

Structure Sensitivity

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Site occupancy in gamma alumina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165732 ◽

1996 ◽

Vol 54 ◽

pp. 654-655

Author(s):

C. A. Bateman ◽

A.Z. Ringwelski ◽

R.W. Broach

Keyword(s):

Spinel Structure ◽

Site Occupancy ◽

Unit Cell ◽

Neutron Diffraction Data ◽

Gamma Alumina ◽

Tetrahedral Sites ◽

Powder Neutron Diffraction ◽

Cation Sites ◽

Powder Neutron Diffraction Data ◽

Insufficient Number

Gamma (γ) alumina is referred to as a defect spinel because it has a tetragonally distorted spinel structure (AB2O4) and an insufficient number of cations to fill all cation sites. In the spinel structure, the oxygen lattice is cubic close packed with A- and B-site cations in tetrahedral and octahedral coordination, respectively. The 2l⅓ Al atoms per unit cell of γ alumina can distribute themselves across 16 octahedral and 8 tetrahedral sites.The literature differs on where the 2⅔ cation vacancies per unit cell are located. Wilson and McConnell proposed that the vacancies in γ alumina, as first formed by calcining boehmite, are predominantly on the tetrahedral lattice but, with further heat treatment, move to occupy random positions on both octahedral and tetrahedral lattices. One study using NMR showed that the vacancies lay exclusively on the tetrahedral lattice, independent of the calcination temperature. A more-recent study using Rietveld refinement of powder neutron diffraction data suggested that both octahedral and tetrahedral lattices were partially occupied.

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Methane Oxidation on a Coverage Layer Study

GeoCongress 2008 ◽

10.1061/40970(309)12 ◽

2008 ◽

Author(s):

Juliana L. Rose ◽

Pedro Paulo F. Gouvêa ◽

Cláudio F. Mahler

Keyword(s):

Methane Oxidation

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Ultra-Low Amounts of Palladium (0.005-0.05 Wt% Pd) Supported on Titania: Remarkable Low-Temperature Activity for NO Reduction with CO and Structure-Function Property Relationships in Methane Oxidation

10.26434/chemrxiv.13489380.v1 ◽

2020 ◽

Author(s):

Konstantin Khivantsev ◽

Libor Kovarik ◽

Nicholas R. Jaegers ◽

János Szanyi ◽

Yong Wang

Keyword(s):

Nitric Oxide ◽

Carbon Monoxide ◽

Methane Oxidation ◽

Steam Reforming ◽

Methane Steam Reforming ◽

Oxide Reduction ◽

Water Steam ◽

Methane Steam ◽

Anatase Titania ◽

Nitric Oxide Reduction

Atomically dispersed Pd +2 cations with ultra-dilute loading of palladium (0.005-0.05 wt%) were anchored on anatase titania and characterized with FTIR, microscopy and catalytic tests. CO infrared adsorption produces a sharp, narrow mono-carbonyl Pd(II)-CO band at ~2,130 cm-1 indicating formation of highly uniform and stable Pd+2 ions on anatase titania. The 0.05 wt% Pd/TiO2 sample was evaluated for methane combustion under dry and wet (industrially relevant) conditions in the presence and absence of carbon monoxide. Notably, we find the isolated palladium atoms respond dynamically upon oxygen concentration modulation (switching-on and switching off). When oxygen is removed from the wet methane stream, palladium ions are reduced to metallic state by methane and catalyze methane steam reforming instead of complete methane oxidation. Re-admission of oxygen restores Pd+2 cations and switches off methane steam reforming activity. Moreover, 0.05 wt% Pd/TiO2 is a competent CO oxidation catalyst in the presence of water steam with 90% CO conversion and TOF ~ 4,000 hr-1 at 260 ⁰C. More importantly, we find that diluting 0.05 wt% Pd/titania sample with titania to ultra-low 0.005 wt% palladium loading produces a remarkably active material for nitric oxide reduction with carbon monoxide under industrially relevant conditions with >90% conversion of nitric oxide at 180 ⁰C (~460 ppm NO and 150 L/g*hr flow rate in the presence of >2% water steam) and TOF ~6,000 hr-1. Pd thus outperforms state-of-the-art rhodium containing catalysts with (15-20 times higher rhodium loading; rhodium is ~ 3 times more expensive than palladium). Furthermore, palladium catalysts are more selective towards nitrogen and produce significantly less ammonia relative to the more traditional rhodium catalysts due to lower Pd amount nd lower water-gas-shift activity. Our study is the first example of utilizing ultra-low (0.05 wt% and less) noble metal (Pd) amounts to produce heterogeneous catalysts with extraordinary activity for nitric oxide reduction. This opens up a pathway to study other Pd, Pt and Rh containing materials with ultra-low loadings of expensive noble metals dispersed on titania or titania-coated oxides for industrially relevant nitric oxide abatement.

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