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Methane oxidation hysteresis over Pt/Al2O3

Paper ID Volume ID Publish Year Pages File Format Full-Text
39677 45831 2014 7 PDF Available
Title
Methane oxidation hysteresis over Pt/Al2O3
Abstract

•Pt/Al2O3 was evaluated for CH4 oxidation as a function of temperature and O2 level.•Increasing O2 levels led to decreasing performance.•Hysteresis, in terms of ramping the temperature upward and downward, was observed.•This hysteresis effect can be used to maintain high conversions at lower temperatures.•Switching between high and low O2 levels can also be used to maintain high conversions.

With growing, accessible natural gas reserves, there is renewed interest in natural gas engines for the wider automotive market. A potential issue, if legislated, is controlling (reducing) the un-combusted CH4 emissions. The key challenge in catalytic CH4 oxidation is the high temperature required, relative to other hydrocarbon species. In this context, a monolith-supported Pt/Al2O3 catalyst was evaluated for CH4 combustion under fuel lean and fuel rich mixtures using temperature programmed reaction (TPRxn) and step-change temperature and oxygen level experiments. The experiments included performance evaluation during both ignition (increasing temperature) and extinction (decreasing temperature after ignition). Conversion hysteresis was observed, with the conversions during extinction higher than those during ignition under fuel lean or stoichiometric combustion reaction conditions. Results obtained demonstrate that this hysteresis effect can be used to achieve high CH4 oxidation conversions at temperatures lower than that required for ignition, admittedly first through using high temperatures to obtain ignition, then lowering the temperature to take advantage of the hysteresis. Results also suggest that changing O2 levels can lead to similar benefits. With the assumption that lean conditions and lower exhaust temperatures are associated with improved fuel economy, while higher exhaust temperatures and fuel rich conditions lead to higher CH4 oxidation rates over the catalyst, the findings presented clearly demonstrate the potential to achieve both via a cyclic operating approach, with the frequency on the order of 10 s of minutes. Data obtained when cycling between temperatures above and below the ignition point and between excess O2 and stoichiometric O2 levels proved this hypothesis.

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Keywords
Methane oxidation; Low temperature oxidation; Hysteresis
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Methane oxidation hysteresis over Pt/Al2O3
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 478, 20 May 2014, Pages 91–97
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
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