Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1997-04-08
1999-02-23
Wood, Elizabeth D.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502326, 502355, B01J 2338, B01J 2340
Patent
active
058743812
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/EP95/02836, filed Jul. 17, 1995 which designated the U.S.
FIELD OF THE INVENTION
The present invention relates to cobalt on alumina catalysts and to a process for making the same.
BACKGROUND OF THE INVENTION
In catalysts, cobalt is normally fixed on a carrier such as silica, aluminium silicate, alumina.
In these catalysts, the useful cobalt atoms are those which are exposed at the surface of the cobalt particles. The cobalt atoms which are not exposed (i.e not at the surface) will not participate in catalytic reaction.
Cobalt is an expensive metal and, in order to optimize its use as a catalyst, it is essential to increase as much as possible the (number of exposed cobalt atoms/ total number of cobalt atoms) ratio of the catalyst which, in turn, increases the cobalt surface area per gram of cobalt.
It is known from EP-A-13,275 to produce a supported coprecipitated cobalt-silica catalyst wherein a reaction mixture of cobalt ions, silicate ions and solid porous carrier particles is prepared and allowed to form a coprecipitate of cobalt and silicate ions onto the solid porous support particles. The obtained cobalt-silica catalyst has a BET total surface area ranging from 150 to 350 m.sup.2 /g and a cobalt surface area ranging from 5 to 20 m.sup.2 /g of cobalt.
It is also known from U.S. Pat. No. 4,591,579 to provide a process for the preparation of a transition metal-silicate catalyst in which an insoluble, basic compound of a transition metal (e.g. cobalt, nickel or copper) is precipitated with an alkaline precipitation agent from an aqueous solution of such a metal salt after which this compound is reacted with a silicate solution. In example 5, it is described such a catalyst wherein the cobalt surface area is 8.9 m.sup.2 /g of catalyst.
In `Stoichiometries of H.sub.2 and CO Adsorptions on cobalt`--Journal of Catalysis 85, page 63-77 (1984)--are disclosed on page 67, table 1, cobalt catalysts on different carriers. From the total maximum H.sub.2 uptake, it is possible to calculate the cobalt surface area per gram of catalyst and the cobalt surface area per gram of cobalt. It can be seen that, for cobalt on silica catalysts the cobalt surface area per gram of cobalt ranges between 6 and 65 m.sup.2 /g whereas for cobalt on transition alumina catalysts the cobalt surface area per gram of cobalt ranges between 15 and 26 m.sup.2 /g.
Thus, cobalt catalysts with a high cobalt surface area per gram of cobalt exist for cobalt on silica catalysts (and also for cobalt on carbon catalysts), but don't exist for cobalt on transition alumina catalysts.
Nevertheless, cobalt upon transition alumina catalysts present some distinct advantages towards other cobalt catalysts.
First of all, a cobalt on transition alumina catalyst is easier to shape by extrusion than a cobalt on silica catalyst and the mechanical strength of the resulting catalyst is higher.
In reactions where water is present (e.g. methanation, Fisher Tropsch), silica can be unstable. Alumina, however, is much more stable under such conditions.
There is therefore a need for a cobalt on transition alumina catalyst with a cobalt surface area per gram of cobalt higher than previously obtained.
Its is a first goal of the present invention to provide a cobalt on transition alumina catalyst with a cobalt surface area per gram of cobalt higher than previously.
It is a second goal of the present invention to provide a process for manufacturing such catalyst. calculate the metallic surface area is that obtained after pretreatment. During this pretreatment the sample is degassed and dried under vacuum at 120.degree. C. The pretreated sample is then reduced. Sample is heated to 425.degree. C. at a rate of 3.degree. C./min whilst hydrogen gas is passed through the sample at a flow rate of 250 ml/min. Still with the same hydrogen flow the sample is maintained at 425.degree. C. for 18 hours. Under vacuum the sample is heated up to 450.degree. C. over a 10 min time period. The sample is maintained a
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Database WPI, Section CH, Week 9315, Derwent Publications Ltd., London, GB; Class E12, AN 93-124391 & SU,A,728 222-Apr. 23, 1992, see abstract.
Bonne Raimond Laurentius
Lok Cornelis Martinus
Crosfield Limited
Wood Elizabeth D.
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