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A kinetics study for the oxidative coupling of methane on a Mn/Na2WO4/SiO2 catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
40876 45869 2012 13 PDF Available
Title
A kinetics study for the oxidative coupling of methane on a Mn/Na2WO4/SiO2 catalyst
Abstract

This paper presents an experimental kinetic study for the oxidative coupling of methane (OCM) over a Mn/Na2WO4/SiO2 catalyst prepared by incipient wetness impregnation. Because the catalyst is a reducible metal oxide, the stability of the catalyst has been assessed by Thermo Gravimetric Analysis (TGA). These experiments show that the catalyst has to be pre-treated with oxygen in order to obtain high C2 selectivity (around 85%) and that a low oxygen partial pressure during the OCM reactions is already sufficient to maintain the catalyst stable in the oxidized state.The catalyst has subsequently been tested in a micro-catalytic fixed bed reactor. The overall reaction orders and rate constants of the primary reactions were determined by measuring the intrinsic reaction rates at different methane and oxygen inlet concentrations. It was found that the reaction order in oxygen for the coupling reaction is 0.38, while the reaction order in oxygen for ethylene oxidation approaches unity, indicating that low oxygen concentration levels are beneficial for obtaining a high C2 selectivity (up to 80–90%). Such a low oxygen concentration can be obtained with distributive feeding in a membrane reactor.Based on the experiments and least-squares minimization, a simplified reaction mechanism is proposed, where the dependency of the ethane (coupling) and carbon dioxide (oxidation) production rates and the secondary ethylene production and C2 oxidation rates can be described with power-law type reaction rate expressions.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (63 K)Download as PowerPoint slideHighlights► Mn/Na2WO4/SiO2 catalyst for OCM was prepared and investigated. ► The catalyst has excellent long-term stability and moderate catalytic activity. ► A possible reaction path has been proposed for OCM. ► The effect of both homogeneous and heterogeneous reactions has been evaluated. ► Kinetic expressions have been derived to be used for modeling of chemical reactors.

Keywords
Methane oxidative coupling; Catalysis; Kinetics; Mn/Na2WO4/SiO2
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A kinetics study for the oxidative coupling of methane on a Mn/Na2WO4/SiO2 catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 433–434, 8 August 2012, Pages 96–108
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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Price after discount Only $4.95
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