Methods of regenerating aromatization catalysts
Methods for treating or rejuvenating a spent catalyst are disclosed. Such methods can employ a step of halogenating the spent catalyst, followed by decoking the halogenated spent catalyst.
1. A method of treating a spent catalyst comprising a transition metal and a catalyst support, the method comprising:
(1) contacting the spent catalyst with a halogen-containing stream to produce a halogenated spent catalyst, wherein the halogen-containing stream comprises from about 250 to about 5000 ppmv of a chlorine-containing compound and from about 250 to about 5000 ppmv of a fluorine-containing compound;
(2) contacting the halogenated spent catalyst with a purging stream consisting essentially of an inert gas; and
(3) contacting the halogenated spent catalyst with a decoking gas stream comprising oxygen.
2. The method of claim 1 , wherein the halogen-containing stream comprises Cl 2 , F 2 , and nitrogen, and is substantially free of oxygen-containing compounds.
3. The method of claim 2 , wherein:
step (1) is conducted at a halogenation temperature in a range from about 120° C. to about 320° C.; and
a molar ratio of Cl:F in the halogen-containing stream is in a range from about 0.2:1 to about 10:1.
4. The method of claim 1 , wherein the spent catalyst comprises:
platinum on a KL-zeolite;
a support matrix comprising alumina, silica, a mixed oxide thereof, or a mixture thereof;
from about 0.025 wt. % to about 5 wt. % chlorine; and
from about 0.025 wt. % to about 5 wt. % fluorine.
5. The method of claim 1 , wherein:
step (2) is conducted at a purging temperature in a range from about 150° C. to about 400° C.; and
the purging stream consists essentially of nitrogen.
6. The method of claim 1 , wherein:
step (3) is conducted at a peak decoking temperature in a range from about 300° C. to about 500° C.; and
the decoking gas stream in step (3) comprises air or a mixture of nitrogen and oxygen.
7. The method of claim 1 , further comprising a pre-drying step prior to step (1), the pre-drying step comprising contacting the spent catalyst with a pre-drying gas stream consisting essentially of an inert gas.
8. The method of claim 1 , further comprising a re-coking pretreatment step prior to step (1), the re-coking pretreatment step comprising contacting the spent catalyst with a pretreatment stream comprising molecular hydrogen and a hydrocarbon feed comprising C 6 -C 8 alkanes and/or cycloalkanes.
9. The method of claim 1 , further comprising a partial decoking step prior to step (1), the partial decoking step comprising contacting the spent catalyst with a partial decoking gas stream comprising oxygen at a partial decoking temperature in a range from about 150° C. to about 250° C.
10. The method of claim 1 , further comprising a reducing step after step (3), the reducing step comprising contacting the de-coked catalyst with a reducing gas stream comprising molecular hydrogen.
11. The method of claim 10 , wherein the reducing gas stream comprises at least about 25 mole % molecular hydrogen.
12. A reforming process comprising:
(a) contacting a hydrocarbon feed with an aromatization catalyst comprising a transition metal and a catalyst support under reforming conditions in a reactor system to produce an aromatic product;
(b) performing step (a) for a time period sufficient to form a spent aromatization catalyst;
(c) contacting the spent aromatization catalyst with a halogen-containing stream to produce a halogenated spent catalyst, wherein the halogen-containing stream comprises from about 250 to about 5000 ppmv of a chlorine-containing compound and from about 250 to about 5000 ppmv of a fluorine-containing compound;
(d) contacting the halogenated spent catalyst with a purging stream consisting essentially of an inert gas; and
(e) contacting the halogenated spent catalyst with a decoking gas stream comprising oxygen.
13. The process of claim 12 , wherein the reforming process is an in situ process.
14. The process of claim 12 , wherein steps (c)-(e) are performed in a vessel external to the reactor system.
15. A method of treating a spent catalyst comprising a transition metal and a catalyst support, the method comprising:
(1) contacting the spent catalyst with a halogen-containing stream comprising chlorine and fluorine to produce a halogenated spent catalyst;
(2) contacting the halogenated spent catalyst with a purging stream consisting essentially of an inert gas; and
(3) contacting the halogenated spent catalyst with a decoking gas stream comprising oxygen.
16. The method of claim 15 , wherein the spent catalyst comprises:
platinum on a KL-zeolite;
from about 0.1 wt. % to about 10 wt. % platinum;
a support matrix comprising alumina, silica, a mixed oxide thereof, or a mixture thereof;
from about 0.025 wt. % to about 5 wt. % chlorine; and
from about 0.025 wt. % to about 5 wt. % fluorine.
17. The method of claim 16 , further comprising a hydrocarbon treatment step prior to step (3), the hydrocarbon treatment step comprising contacting the halogenated spent catalyst with a hydrocarbon treatment stream comprising a hydrocarbon feed comprising C 6 -C 8 alkanes and/or cycloalkanes.
18. The method of claim 16 , wherein:
the halogen-containing stream comprises Cl 2 , F 2 , and nitrogen, and is substantially free of oxygen-containing compounds; and
a molar ratio of Cl:F in the halogen-containing stream is in a range from about 0.2:1 to about 10:1.
19. The method of claim 16 , wherein:
step (2) is conducted at a purging temperature in a range from about 150° C. to about 400° C.; and
the purging stream consists essentially of nitrogen.
20. The method of claim 16 , wherein:
step (3) is conducted at a peak decoking temperature in a range from about 300° C. to about 500° C.; and
the decoking gas stream in step (3) comprises air or a mixture of nitrogen and oxygen.