Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1998-03-17
2000-02-22
Bell, Mark L.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502328, 502330, 502332, 502338, 502304, 502316, 502319, 502321, 502340, 502355, 585407, 585410, 585411, 585418, 585420, 585421, 585433, 585654, 585659, 585661, 585662, 585663, B01J 2300, B01J 2358, C07C 1500, C07C 200, C07C 5333
Patent
active
060280271
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an improved process for preparing catalysts comprising iron and potassium and preferably cerium and, if desired, further elements, which catalysts are suitable for dehydrogenating hydrocarbons to give the corresponding olefinically unsaturated hydrocarbons, in particular for dehydrogenating ethylbenzene to give styrene.
Such catalysts and their preparation are described, for example, in U.S. Pat. No. 3,904,552 (1), the European Patents 177 832 (2), 181 999 (3), 195 252 (4), 296 285 (5), 297 685 (6), 297 657 (7) and 502 510 (8) and DE-A 28 15 812 (9), 28 15 874 (10), 36 43 382 (11) and 38 21 431 (12).
Apart from iron and potassium, the known catalysts generally contain promoters, ie. elements which, at least after the preparation process, are generally present in the form of their oxides. Promoters described are, for example, Mo, Ce (1), W (4), Mg (2, 3), V, Cr (9), Ti (8) and other elements. In the preparation process, these constituents are processed together with the iron and potassium compounds in the form of oxides or decomposable compounds to give pastes which contain the constituents of the future catalyst in the form of precursors and form oxides on subsequent heating (calcination). It is possible to add further auxiliaries, eg. organic compounds or graphite, which are burned on subsequent heating, for example to improve the shapability of the paste or to favorably influence the hardness and porosity of the finished catalyst.
After intimate mixing, for example dry mixing of the constituents or a spray-dried powder produced therefrom, if desired with addition of water, shaped bodies are produced which are then dried and calcined at from about 300 to 1100.degree. C. and thus converted into the finished catlaysts (1, 4, 9). According to (12), a defined compound, viz. a potassium ferrite of the formula K.sub.2 Fe.sub.22 O.sub.34, is also effective as catalyst.
Reference (5) discloses, in particular, a process having two calcination steps in which methylcellulose or graphite is added to the raw composition, these being burned out at from 250.degree. C. to 600.degree. C., after which, in a further step at from 700 to 800.degree. C., the remaining carbonates too are converted into the corresponding oxides.
However, the known catalysts are still far removed from being able to give an ideal result, ie. they still form undesired byproducts and also appear to be capable of improvement in terms of the specific output (possible space-time yield) and their life under industrial conditions (mechanical stability).
It is an object of the present invention to provide a process by means of which it is possible to prepare catalysts of the type indicated in the introduction which are improved in terms of activity and selectivity and also the mechanical stability.
We have found that this object is achieved by the process of the present invention which gives catalysts having higher porosity, higher activity and better selectivity than the known catalysts.
It has been found that it is possible to prepare improved catalysts comprising iron and potassium and, if desired, further elements, which catalysts are suitable for dehydrogenating hydrocarbons, in particular for dehydrogenating ethylbenzene to give styrene, by preparing a finely divided, preferably aqueous, mixture of an iron compound with a potassium compound and, if desired, compounds of further elements, drying the mixture if appropriate, heating (calcining) it in a first step so that agglomerates having a diameter of from 5 to 50 .mu.m and formed from smaller individual particles are obtained and, in a second step, preferably after shaping, heating (calcining) it at from 300 to 1000.degree. C.
Iron, potassium and, if desired, promoters are mixed with one another in the form of oxides or of substances which are converted into oxides on heating.
As iron compound, preference is given to using Fe.sub.2 O.sub.3 (haematite), FeOOH (goethite), Fe.sub.3 O.sub.4 or another synthetic or naturally occurring oxidic iron compound.
As potassium compound,
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Baier Michael
Buchele Wolfgang
Hofstadt Otto
Neth Norbert
Petersen Hermann
BASF - Aktiengesellschaft
Bell Mark L.
Hailey Patricia L.
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