The catalytic oxidation of methane to useful products

The catalytic oxidation of methane to useful products

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ISSN 1018-5593
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Commission of the European Communities
energy
The catalytic oxidation of methane
to useful products Commission of the European Communities
energy
The catalytic oxidation of methane
to useful products
J.R.H. Ross, J.G. van Ommen, JA Roos, S.J. Korf
University of Twente
Department of Chemical Engineering
PO Box 217
7500 AE Enschede
The Netherlands
Contract No EN3C/0039-NL (GDF)
Final report
Research funded in part by
the Commission of
the European Communities
Non-nuclear energy R&D programme
'Optimization of the production and utilization of hydrocarbons'
Directorate-General |~
PA'-l. nrHC? ElSioih.
Science, Research and Development
U.C. EUR 13767 EN 1991 Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1991
ISBN 92-826-3217-2 Catalogue number: CD-NA-13767-EN-C
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1991
Printed in Belgium ABSTRACT
Work carried out at the University of Twente as part of a collaboration with the
Technical University of Eindhoven and the National Institute of Higher Education, Limerick,
has been concentrated on gaining an understanding of the factors influencing the behaviour
of various catalyst systems for the oxidative coupling of methane. Systems studied have
included /PbO/Al203, Li/MgO, various rare earth oxides and BaC03/CaO. Particular
attention was given to the Li/MgO system; not only was it shown that the active phase in
such catalysts was derived from Li2C03 species but it was demonstrated that the life-time of
such systems could be prolonged by adding C02 to the feed to the reactor. Considerable
improvements in yield can be achieved by paying attention to the reactor construction and
reaction conditions.
It has been shown that further considerable improvements in the Li/MgO catalyst system
can be achieved by adding various oxides to the formulation; the most promising of these
being Sn02 and CoO. The Li/Sn/MgO system is very stable and it can be used at relatively
low temperatures, when gas-phase processes are much less important. Detailed investigation
of the reaction network over the different catalyst systems has shown that the sequence:
CH4 -> qHg - C2H4 - COx
is predominant over the Li/MgO and doped Li/MgO systems. A parallel route to COx (i.e.
directly from CH4) is important over many of the other catalyst systems, and this is
responsible for lower selectivities over these systems. It is concluded that most attention in
the future should be given to developing stable low-temperature catalysts; under these
conditions, there is a higher chance of obtaining the high C^ yields needed for a commercial
application of oxidative methane coupling.
- Ill -AIMS OF THE RESEARCH
The aim of the research described in this report was to understand those factors
which determine the behaviour of catalytic systems for the oxidative coupling of methane. By
gaining an understanding of the effects of reaction conditions and of the mechanism of the
reaction, using various catalyst systems, it was hoped that it would be possible to design
better catalysts which might be usable in industrial application. Of particular importance in
this respect is the attainment of high activity, selectivity and catalyst stability.
V -TABLE OF CONTENTS
Page
III Abstract
V Aims of the Research
1 Section 1 General Introduction
9 Section 2 Effect of Gas Composition and Process Conditions
Section 3 The Selective Oxidation of Methane to Ethane
16
and Ethylene over Various Oxide Catalysts
20
Section 4 Lithium Doped Magnesium Oxide Catalysts
25 Section 5m Chemistry of Lithium Doped Magnesium
30 Oxide Catalysts
Section 6 Studies on Doped and Un-Doped Rare Earth Oxides
35
Section 7 The Effect of Promoters on the Behaviour of Sm203
Catalysts
37
Section 8 A Comparison of the Behaviours at Short Residence
Times of Ba/CaO, Li/MgO, Sm203 and La203 Catalysts
Section 9 The Effect of Additives on Lithium Doped Magnesium
40
Oxide Catalysts
Section 10 Comparison of the Reactivities of Ethane and Ethylene
48 in the Presence of Oxygen over Li/MgO and Sm203 Catalysts
Section 11 The Reaction Path over a Lithium-Doped Magnesium Oxide
Catalyst, Factors Affecting the Rate of Total Oxidation
54 of Ethane and Ethylene
Section 12 Kinetic and Mechanistic Aspects of the oxydative coupling
58 of Methane over a Li/MgO Catalyst
Section 13 A Study of the Kinetics of the Oxidative Coupling of
66
Methane over a Li/Sn/MgO Catalyst
74
Section 14 Main Conclusions of the Research
76
List of References
79
List of Figures
123
List of Tables
- VII