Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1990-05-10
1993-04-06
Shine, W. J.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
B01J 3502
Patent
active
052003833
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the production of catalytically active mixed phases in powder form, from precursors which contain the elements of the mixed phases, with thermal and mechanical treatment.
Numerous methods are known for the preparation of catalytically active mixed phases of, for example, ternary or quaternary oxides as a basis for the production of catalysts. The manufacturing methods depend on the structure of the desired phase. Usually these manufacturing methods are based on solid reactions in which individual oxides are mixed with one another and then subjected to a heat treatment. Other methods are based on precipitation processes in which the mixed phase is precipitated from a suspension or solution of precursors. In these methods metal salts or organometallic compounds are usually subjected to a precipitation, dried, and crushed, a cure is performed, then they are again dried, shaped and finally again subjected to a heat treatment. Such methods do not in all cases result in pure mixed phases, even when special attention is given to the conduct of the method as regards the temperatures and pressures to be used. In these cases binary oxides are bound into the desired mixed phase as impurities, so that, among other things, catalytic properties are substantially diminished. However, all these previously known methods are based on a great number of process steps entailing complex apparatus and correspondingly high installation costs.
The invention is addressed to the problem of substantially simplifying the method for the production of catalytically active mixed phases in powder form, and of preparing the desired mixed phases without impurities, with less complex apparatus and lower installation cost, preferably at atmospheric pressure and at a lower temperature level.
Setting out from a method of the kind mentioned above, this problem is solved in accordance with the invention in that the precursor contained in a solution or suspension is brought onto heated surfaces of moving heat carrying bodies, and precipitated and dissociated or, more specifically, decomposed on the latter by evaporating the solvent, the mixed phase formed on the heat carrying bodies is removed, and the solid mixed phase is then crushed. On account of this method of procedure, a constantly self-renewing, wettable heat carrying surface is to be made available at a temperature level corresponding to the evaporation temperatures of the suspension or solution, which enables the process to be arranged in a continuous series of the individual stages.
In further development of the invention, the surface of the heat carrying bodies is heated to a higher temperature level exceeding the evaporation temperature of their solvent. In this manner it becomes possible not only to precipitate and dissociate or decompose the precursor, but at the same time to perform the calcination of the mixed phase, thus reducing the amount of time required for the production of the mixed phase in powder form.
The economy of the method for the production of catalytically active mixed phases can be further improved by continuously removing the volatile component of the solvent or suspension, separating it from this entrained solid matter, and feeding it to the portion of the mixed phase that is directly withdrawn from the process.
In a preferred development of the invention, within a reactor whose circumference is circular in cross section or in the shape of a polygon approaching a circle, the mixed phase is removed from the surfaces of the heat carrying bodies by the relative movement within the bed of the bodies, and furthermore the mixed phase is simultaneously ground as well as separated continuously or discontinuously from the circuit of the heat carrying bodies. By this procedure the individual steps of the process are performed within a moving bed of the heat carrying bodies, and the temperature of the bodies can be adapted to the optimum for the individual steps of the process. It is thus possible to avoid exceeding or falling below th
REFERENCES:
patent: 3966639 (1976-06-01), Callahan et al.
patent: 4170570 (1979-10-01), Zagata et al.
Kotter Michael
Weyland Friedrich
Kraftanlagen Aktiengesellschaft
Shine W. J.
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