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

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• 作者：A. Dufour ; A. Celzard ; B. Ouartassi ; F. Broust ; V. Fierro ; A. Zoulalian
• 关键词：Hydrogen production ; Biomass ; Methane decomposition ; Carbon ; Catalysis ; Effective diffusivity
• 刊名：Applied Catalysis A: General
• 出版年：2009
• 出版时间：1 June 2009
• 年：2009
• 卷：360
• 期：2
• 页码：120-125
• 全文大小：234 K

文摘

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.