Compositions – Gaseous compositions – Carbon-oxide and hydrogen containing
Patent
1996-01-24
1999-11-23
Griffin, Walter D.
Compositions
Gaseous compositions
Carbon-oxide and hydrogen containing
502337, 502325, 502349, C07C 102
Patent
active
059894571
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalyst for the production of synthesis gas in the form of CO and H.sub.2 from CO.sub.2 and CH.sub.4 and/or other light hydrocarbons.
2. Description of the Related Art
The combustion of fossil fuels in the form of coal, petroleum or natural gas or of secondary fuels produced therefrom which is effected predominantly in the industrialized countries is leading to an increased concentration of CO.sub.2 in the atmosphere. Since CO.sub.2 is one of the so-called greenhouse gases, even relatively slight increases in concentration lead to traumatic changes which have their effect throughout the world. An increase of the average temperature in the atmosphere has already been observed and a further increase is expected in the coming years, resulting in more frequent and more violent natural catastrophes (for instance periods of drought, flood, storm). Therefore, increased efforts are required to at least reduce the tempo of the further increase in the concentration of CO.sub.2. It is being attempted to achieve this primarily by decreasing the consumption of energy. To achieve this, some countries have thought, for instance, of introducing an energy tax, the amount of which is based on the amount of CO.sub.2 liberated upon the consumption of energy. Another possible manner of reducing the liberation of CO.sub.2 is to reuse this gas for instance, for the production of other products.
Synthesis gas (CO+H.sub.2) is used in a number of chemical processes. Such synthesis gas can be produced in different ways. The method most used consists of the reforming of methane. This leads to a product having an H.sub.2 /CO ratio of 3 in accordance with the reaction:
The H.sub.2 /CO ratio can be shifted further to even higher values by increasing the amount of H.sub.2 O relative to the amount of CH.sub.4, followed by a CO-shift reaction:
A synthesis gas produced in this manner is particularly suitable for the synthesis of methanol, which in its turn can be further converted into other petrochemical products.
The partial oxidation of methane with oxygen represents another method for the production of synthesis gas and is characterized by a H.sub.2 /CO ratio of 2:
Such a synthesis gas is particularly suitable for the Fischer-Tropsch synthesis, which requires an H.sub.2 /CO ratio of about 1.7-2.5.
The production of oxoalcohols is another important field of use of synthesis gas. Oxoalcohols are produced by hydroforming .alpha.-olefins in accordance with the reaction: .fwdarw.CH.sub.3 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CHO
The aldehyde is then hydrogenated to form the desired alcohol. In this production process an H.sub.2 /CO ratio of about 1 is required. One possibility for producing such a synthesis gas is afforded by the gasification of coal.
Another possibility of producing such a synthesis gas having an H.sub.2 /CO ratio of 1 is the reaction of CO.sub.2 with CH.sub.2 :
It is known to effect this reaction at, for instance, 500.degree. C. under increased pressure in the presence of a catalyst. Since such processes have not acquired any practical importance up to now, there are relatively few publications on this subject (for instance, Chem. Eng. Science 1988, No. 11, pages 3049-3062, and Chem. Eng. Science 1989, No. 12, pages 2825-2829). As suitable catalysts the metals Ni, Pt, Rh and Pd are mentioned, these elements being applied in each case to a support material which consists of Al.sub.2 O.sub.3 or SiO.sub.2. The effectiveness in principle of such catalysts can easily be shown in a laboratory test. However, they are unsuitable for commercial use. This is due to the fact that undesired side reactions are also promoted by the action of the catalyst, namely:
These side reactions are undesired, since they lead to the formation of free carbon which deposits on the catalyst (coking) and reduces the activity thereof more and more (deactivation). The coking can, to be sure, be reduced by a drastic increase in the amount of CO.sub.2 beyond
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Mercera Patrick Dennis L.
Ross Julian Richard H.
Seshan Kulathu-Iyer
Xue Erzeng
Griffin Walter D.
Mannesmann Aktiengesellschaft & K.T.I. Group B.V.
Preisch Nadine
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