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Kinetics of the partial oxidation of methane to formaldehyde on silica catalyst
Author(s) -
Arena Francesco,
Frusteri Francesco,
Parmaliana Adolfo
Publication year - 2000
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690461119
Subject(s) - chemistry , catalysis , formaldehyde , kinetics , chemisorption , order of reaction , activation energy , reaction rate , methane , chemical kinetics , partial oxidation , rate determining step , reaction rate constant , inorganic chemistry , organic chemistry , physics , quantum mechanics
Abstract The kinetics of the partial oxidation of methane to formaldehyde (MPO) on a “precipitated” silica catalyst in the 500–800°C range was investigated. The influence of temperature and reaction mixture composition on the density of reduced sites of the catalyst under steady state was evaluated by in situ reaction temperature oxygen chemisorption measurements. The kinetics of the MPO on silica is pseudo first and zero‐order on P CH 4and P o 2, respectively, while the density of reduced sites depends upon the square root of the P CH 4/P O 2ratio. The rate‐determining step is the activation of C–H bond of CH 4 molecules (E red = 142 kJ·mol −1 ), while oxygen replenishment is a nonactivated reaction step (E ox ≈20 kJ·mol −1 ). A Langmuir‐Hinshelwood kinetic model, accounting for a two‐site‐dissociative activation mechanism of both CH 4 and O 2 , thoroughly describes the steady state of the silica surface and the reaction kinetics of the MPO in the 500–800°C range.