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Abstract
Temporal Analysis of Products (TAP) investigation on Natural Gas-fueled Vehicle (NGV) catalysts provides information related to the nature of reaction steps involved over noble metals and at the metal-support interface. The determination of accurate kinetic parameters for methane adsorption from single pulse experiments and subsequent investigation of sequential surface reactions from alternative CH4/O2 pulse experiments is the first step toward the establishment of relevant structure/activity relationships which can highlight the importance of the metal/support interface on freshly-prepared and aged single palladium based catalysts.
Keywords: CH4 adsorption; NGV catalyst; TAP reactor; metal/support interface; palladium.
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Figures
Figure 1
Temporal responses from single TAP…
Figure 1
Temporal responses from single TAP experiments at 400°C (A) and 550°C (B) on… Figure 1 Temporal responses from single TAP experiments at 400°C (A) and 550°C (B) on fresh-2.5 wt.% Pd/Al2O3 pre-reduced at 550°C. Temporal responses recorded at 400°C (C) and 550°C (D) on pre-activated samples in pure oxygen at 450°C [Reproduced with permission from reference Granger and Pietrzyk (2014)].
Figure 2
Comparison of the normalized CH …
Figure 2
Comparison of the normalized CH 4 (red) and Ar (blue) flow curves F … Figure 2 Comparison of the normalized CH4 (red) and Ar (blue) flow curves FiMi1∕2 vs. t/Mi1∕2 at 400°C (A) and 550°C (C) on fresh-2.5 wt.Pd/Al2O3 pre-reduced in 72 mbar H2 at 550°C for 30 min, and at 400°C (B) and 550°C (D) on pre-activated samples in pure oxygen at 450°C for 50 min—Fi stands for the pulse intensity normalized multiplied by Mi the molar weight of the compound I–Ar curve in blue and methane curve in red.
Figure 3
MS responses during single TAP…
Figure 3
MS responses during single TAP experiments at 400°C (A) and 550°C (B) on… Figure 3 MS responses during single TAP experiments at 400°C (A) and 550°C (B) on aged-2.5 wt.% Pd/Al2O3 pre-reduced in 72 mbar H2 at 550°C for 30 min. MS responses recorded at 400°C (C) and 550°C (D) on pre-activated samples in pure oxygen at 450°C for 50 min. Corrected data from QMS tuned to m/z = 15 (CH4), 44 (CO2), 28 (CO, CO2), and 2 (H2, CH4).
Figure 4
Comparison of the normalized CH …
Figure 4
Comparison of the normalized CH 4 (red) and Ar (blue) flow curves F … Figure 4 Comparison of the normalized CH4 (red) and Ar (blue) flow curves FiMi1∕2 vs. t/Mi1∕2 recorded at 400°C (A) and 550°C (C) on aged-2.5 wt.Pd/Al2O3 pre-reduced in 72 mbar H2 at 550°C for 30 min and at 400°C (B) and 500°C (D) on pre-activated samples in pure oxygen at 450°C for 50 min—Fi stands for the pulse intensity normalized multiplied by Mi the molar weight of the compound i.
Figure 5
Alternative pulses of CH 4 …
Figure 5
Alternative pulses of CH 4 and O 2 at 550°C on fresh 2.5… Figure 5 Alternative pulses of CH4 and O2 at 550°C on fresh 2.5 wt.% Pd/Al2O3 pre-reduced in H2 at 450°C prior to AP experiments.
Figure 6
Alternative pulse of O 2 …
Figure 6
Alternative pulse of O 2 and CH 4 at 550°C on fresh 2.5… Figure 6 Alternative pulse of O2 and CH4 at 550°C on fresh 2.5 wt.% Pd/Al2O3 pre-reduced in H2 at 450°C prior to AP experiments.
Figure 7
Alternatives pulses of CH 4 …
Figure 7
Alternatives pulses of CH 4 and O 2 at 550°C on aged-2.5 wt.%Pd/Al … Figure 7 Alternatives pulses of CH4and O2 at 550°C on aged-2.5 wt.%Pd/Al2O3 pre-reduced in H2 at 450°C prior to AP experiments.
Figure 8
Alternatives pulses of O 2 …
Figure 8
Alternatives pulses of O 2 and CH 4 at 550°C on aged-2.5 wt.%… Figure 8 Alternatives pulses of O2 and CH4 at 550°C on aged-2.5 wt.% Pd/Al2O3 pre-reduced in H2 at 450°C prior to AP experiments. All figures (8) See this image and copyright information in PMC
References
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