Modified zeolites that include hafnium-containing organometallic moieties and methods for making such
Disclosed herein are modified zeolites and methods for making modified zeolites. In one or more embodiments disclosed herein, a modified zeolite may include a microporous framework including a plurality of micropores having diameters of less than or equal to 2 nm. The microporous framework may include at least silicon atoms and oxygen atoms. The modified zeolite may further include organometallic moieties each bonded to a nitrogen atom of a secondary amine functional group comprising a nitrogen atom and a hydrogen atom. The organometallic moieties may comprise a hafnium atom that is bonded to the nitrogen atom of the secondary amine functional group. The nitrogen atom of the secondary amine function group may bridge the hafnium atom of the organometallic moiety and a silicon atom of the microporous framework.
1. A method for making a modified zeolite, the method comprising:
reacting an organometallic chemical with an amine functionalized zeolite, wherein the amine functionalized zeolite comprises a microporous framework comprising a plurality of micropores having diameters of less than or equal to 2 nm, wherein the microporous framework comprises at least silicon atoms and oxygen atoms, and wherein the amine functionalized zeolite comprises isolated terminal primary amine functionalities bonded to silicon atoms of the microporous framework;
wherein the reacting of the organometallic chemical with the amine functionalized zeolite forms the modified zeolite comprising organometallic moieties each bonded to a nitrogen atom of the modified zeolite, wherein the organometallic moieties comprises a portion of the organometallic chemical; and
wherein the organometallic chemical comprises hafnium.
2. The method of claim 1 , wherein the average pore size of the modified zeolite is greater than 2 nm.
3. The method of claim 1 , further comprising contacting a dehydroxylated zeolite with ammonia to from the amine functionalized zeolite, wherein the dehydroxylated zeolite comprises isolated terminal silanol functionalities comprising hydroxyl groups bonded to silicon atoms of the microporous framework, and wherein the contacting of the dehydroxylated zeolite with the ammonia forms the amine functionalized zeolite.
4. The method of claim 3 , further comprising dehydroxylating an initial zeolite to from the dehydroxylated zeolite, wherein the initial zeolite primarily comprises vicinal silanol functionalities, and wherein dehydroxylating the initial zeolite forms the isolated terminal silanol functionalities.
5. The method of claim 4 , wherein the dehydroxylation temperature is 800° C. or less, and wherein the contacting of the dehydroxylated zeolite with ammonia is at a temperature of less than 800° C.
6. The method of claim 1 , wherein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:
R 1 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group;
R 2 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group;
R 3 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group; and
R 4 is chosen from any of an alkyl group, a hydride group, a hydroxyl group, an alkoxy group, an allyl group, a cyclopentadienyl group, an amino group, an amido group, an imido group, a nitrido group, a carbene group, a carbyne group, a halide group, a benzyl group, a phenyl group, an acetyl group, or an oxide group.
7. The method of claim 1 , wherein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:
R 1 is an alkyl group;
R 2 is an alkyl group;
R 3 is an alkyl group; and
R 4 is an alkyl group.
8. The method of claim 1 , wherein the organometallic chemical comprises tetrakis(neopentyl) hafnium.
9. The method of claim 1 , wherein the organometallic moieties of the modified zeolite comprise hafnium.
10. The method of claim 1 , wherein the microporous framework further comprises aluminum atoms.
11. The method of claim 1 , wherein a hafnium atom of the organometallic moiety is bonded to the nitrogen atom of the modified zeolite.
12. The method of claim 1 , wherein the modified zeolite comprises a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm.
13. The method of claim 12 , wherein the modified zeolite is a ZSM-5 zeolite.
14. The method of claim 12 , wherein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:
R 1 is an alkyl group;
R 2 is an alkyl group;
R 3 is an alkyl group; and
R 4 is an alkyl group.
15. The method of claim 12 , wherein the microporous framework further comprises aluminum atoms.
16. The method of claim 12 , wherein the organometallic moieties of the modified zeolite comprise hafnium.
17. The method of claim 1 , wherein the modified zeolite is a ZSM-5 zeolite.
18. The method of claim 17 , wherein the organometallic chemical comprises HfR 1 R 2 R 3 R 4 , wherein:
R 1 is an alkyl group;
R 2 is an alkyl group;
R 3 is an alkyl group; and
R 4 is an alkyl group.
19. The method of claim 17 , wherein the organometallic chemical comprises tetrakis(neopentyl) hafnium.
20. The method of claim 17 , wherein the organometallic moieties of the modified zeolite comprise hafnium.