In situ recoating of catalyst beds
A process for coating internals in a reactor, except for the coating of electrically heatable, at least partly open-cell foams, with a catalytically active material or a precursor thereof, in which an aerosol which contains the catalytically active material or the precursor thereof as a disperse phase is provided and the aerosol is passed through the reactor at a rate in the range from 0.1 to 4 m/s, which is established so that the disperse phase of the aerosol is deposited on the internals in the reactor.
1. A process for coating internals which have previously been introduced into a reactor, except for the coating of electrically heatable, at least partly open-cell foams, with a catalytically active solid material or a precursor thereof, in which an aerosol which contains the catalytically active material or the precursor thereof as a disperse phase is provided and the aerosol is passed through the reactor at a rate in the range of from 0.1 to 4 m/s, which is established so that the disperse phase of the aerosol is deposited on the internals in the reactor and wherein the reactor is employed for carrying out oxidation or dehydrogenation reactions and the oxidation or dehydrogenation reactions are the synthesis of maleic anhydride, phthalic anhydride, acrolein, (meth)acrylic acid, or ethylene oxide.
2. A process as claimed in claim 1 , wherein the aerosol is passed through the reactor at a velocity in the range from 0.2 to 4 m/s.
3. A process as claimed in claim 2 , wherein the aerosol is passed through the reactor and the velocity in the range from 0.2 to 2 m/s.
4. A process as claimed in claim 3 , wherein the disperse phase of the aerosol has a particle size of from 0.5 to 5 μm.
5. A process as claimed in claim 1 , wherein the disperse phase of the aerosol has a particle size of from 0.1 to 10 μm.
6. A process as claimed in claim 5 , wherein the disperse phase of the aerosol has a particle size of from 0.5 to 5 μm.
7. A process as claimed in claim 1 , wherein the aerosol is produced by dry comminution of a solid catalyst or of a precursor of a solid catalyst, to a particle size of from 0.1 to 10 μm metering and dispersing in an inert gas stream.
8. A process as claimed in claim 7 , wherein the solid catalyst has a particle size of from 0.2 to 5 μm and the inert gas stream is a nitrogen stream.
9. A process as claimed in claim 1 , wherein the aerosol is produced by comminuting, by means of nozzles, a liquid which may have been heated or a liquid mixture, or a solution, suspension or emulsion which may have been superheated.
10. A process as claimed in claim 1 , wherein the internals are formed from moldings which are movable relative to one another and are present in the form of a fixed bed, fluidized bed or moving bed.
11. A process as claimed in claim 1 , wherein the internals are present in the form of a consolidated, porous system.
12. A process as claimed in claim 11 , wherein the consolidated, porous system is woven fabric, knitted fabric, braid or foam; except for electrically heatable foams.
13. A process as claimed in of claim 1 , which comprises internals having ordered flow channels.
14. A process as claimed in claim 13 , wherein the internals are stacked packings or monoliths.
15. A process as claimed in claim 1 , wherein the internals are pipes through which a heating medium is passed.
16. A process as claimed in claim 15 , wherein the pipes are ribbed pipes.
17. A process as claimed in claim 1 , wherein the disperse phase deposited on the internals in the reactor is subjected to further process steps.
18. A process as claimed in claim 17 , wherein the disperse phase deposited on the internals in the reactor is further fixed, activated and/or calcined.
19. A process as claimed in claim 1 , wherein the coating is an initial coating.
20. A process as claimed in claim 1 , wherein the coating comprises a reactivation of catalyst material on the surface of internals in a reactor.
21. A process for coating internals which have previously been introduced into a reactor, except for the coating of electrically heatable, at least partly open-cell foams, with a catalytically active material or a precursor thereof, in which an aerosol which contains the catalytically active material or the precursor thereof as a disperse phase is provided and the aerosol is passed through the reactor at a rate in the range from 0.1 to 4 m/s, which is established so that the disperse phase of the aerosol is deposited on the internals in the reactor and wherein the reactor is employed for carrying out oxidation or dehydrogenation reactions and the oxidation or dehydrogenation reactions are the synthesis of maleic anhydride, phthalic anhydride, or ethylene oxide.