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Effect of micropores diffusion on kinetics of CH4 decomposition over a wood-derived carbon catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
42959 45949 2009 6 PDF Available
Title
Effect of micropores diffusion on kinetics of CH4 decomposition over a wood-derived carbon catalyst
Abstract

In order to optimise hydrogen production from biomass gasification, catalytic conversion of methane contained in a surrogate biomass syngas (CH4 14%; CO 19%; CO2 14%; H2 16%; H2O 30%; N2 7%) is investigated over a fixed bed of porous wood char as a function of temperature (800–1000 °C) and space time (1.6–6.2 min g L−1). Determination of Thiele modulus evidences a change of kinetic regime from chemically- to diffusion-controlled when the temperature increases; this finding is particularly relevant when porous chars having an average pore width of 1 nm are used as catalysts. Mass diffusion transfers are accounted for by a model introducing an internal effectiveness factor. Knudsen diffusion in micropores is shown to limit the conversion rate of methane per unit mass of catalyst, and explains why such a rate is not proportional to the BET surface area, especially when the latter is higher than typically 300 m2/g. It is concluded that diffusion limitations in micropores should be taken into account, otherwise underestimated activation energy and intrinsic kinetic constant are obtained in some experimental conditions.

Graphical abstractIn order to optimise hydrogen production from biomass gasification, catalytic conversion of methane contained in a surrogate biomass syngas (CH4 14%; CO 19%; CO2 14%; H2 16%; H2O 30%; N2 7%) is investigated over a fixed bed of porous wood char as a function of temperature (800–1000 °C) and space time (1.6–6.2 min g L−1). Determination of Thiele modulus evidences a change of kinetic regime from chemically- to Knudsen diffusion-controlled when the temperature increases. Mass diffusion transfers are accounted for by a model introducing an internal effectiveness factor.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Hydrogen production; Biomass; Methane decomposition; Carbon; Catalysis; Effective diffusivity
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Effect of micropores diffusion on kinetics of CH4 decomposition over a wood-derived carbon catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 360, Issue 2, 1 June 2009, Pages 120–125
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
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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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