Method for producing metal-doped zeolites and use thereof for the catalytic conversion of nitrogen oxides
View Patent ↗The present invention provides a process for the preparation of metal-doped zeolites comprising the steps of i) provision of a dry mixture of a) a zeolite, b) a compound of a catalytically active metal, ii) intimate grinding of the mixture, iii) heating of the mixture in a reactor, iv) cooling to room temperature and obtaining the metal-doped zeolite, wherein the internal pressure in the reactor during the heating is kept in a pressure range from 0 to −200 millibar. The invention further relates to the use of a metal-doped zeolite prepared by means of the process according to the invention for the conversion of NO x and N 2 O into harmless products.
1. Process for the preparation of metal-doped zeolites comprising the steps of:
i) provision of a dry mixture of
a) a zeolite, and
b) a compound of a catalytically active metal,
ii) intimate grinding of the mixture,
iii) heating of the mixture in a reactor to a defined temperature between 300° C. and 800° C.
iv) maintenance of the mixture at the defined temperature between 300° C. and 800° C., and
v) cooling to room temperature and obtaining the metal-doped zeolite, characterized in that the internal pressure in the reactor during the heating is kept in a negative pressure range from below 0 to −200 millibar.
2. Process according to claim 1 , characterized in that the internal pressure in the reactor is maintained in a negative pressure range from −10 to −50 millibar.
3. Process according to claim 1 , characterized in that the catalytically active metal is selected from the group consisting of Cu, Co, Rh, Pd, Ir, Pt, Ru, Fe, Ni, and V.
4. Process according to claim 1 , characterized in that in step i) a nitrogen containing compound selected from the group consisting of an ammonium salt, solid urea, and a solid urea derivative is added.
5. Process according to claim 1 , characterized in that the heating period is b 60 min to 5 h.
6. Process according to claim 1 , characterized in that the temperature is maintained for 8 to 20 h.
7. Process according to claim 6 , characterized in that the catalytically active metal compound is added in a quantity of 0.5 to 10 wt.-% relative to the total dry mixture.
8. Process according to claim 7 , characterized in that silicon-rich zeolites with a SiO 2 :Al 2 O 3 ratio of >2.5 are used.
9. Process according to claim 8 , characterized in that ZSM-5, Y, BETA or mordenite type zeolites are used.
10. Process according to claim 9 , characterized in that the zeolites are present wholly or partly in their ammonium form.
11. Process according to claim 1 , characterized in that the temperature is between 400° C. to 600° C.
12. Process according to claim 6 , characterized in that the temperature is maintained for 10 to 16 h.
13. Process according to claim 8 , characterized in that silicon-rich zeolites with a SiO 2 :Al 2 O 3 ratio of >10 are used.