Method for preparation of mesoporous zeolites
Provided is a preparation method for a mesoporous zeolite, particularly a method for preparing mesoporous zeolite through a simple process without using costly materials such as an organic amine template or a surfactant. The method includes 1) forming a synthetic zeolite gel by mixing a silica precursor, an aluminum precursor and water and aging the resulted mixture; 2) carrying out zeolite synthesis by subjecting the synthetic zeolite gel to a hydrothermal reaction; 3) cooling the synthesized zeolite from the above step 2), then adding a basic solution thereto and allowing them to react, thereby obtaining a mesoporous zeolite slurry; and 4) washing the mesoporous zeolite slurry with water, drying and firing it, thereby obtaining a mesoporous zeolite.
1. A method for preparing a mesoporous zeolite comprising:
1) forming a synthetic zeolite gel by mixing a silica precursor, an aluminum precursor and water and aging the resulted mixture;
2) carrying out zeolite synthesis by subjecting the synthetic zeolite gel to a hydrothermal reaction;
3) cooling the synthesized zeolite from the above step 2), then adding a basic solution wherein the amount of a base in the form of the basic solution is 0.05-0.5 moles per mole of the silica precursor thereto and allowing them to react, thereby obtaining a mesoporous zeolite slurry; and
4) washing the mesoporous zeolite slurry with water, drying and firing it, thereby obtaining a mesoporous zeolite.
2. The method according to claim 1 , further comprising a step of adjusting pH to 11.0-12.0 by adding an acid, after mixing the silica precursor, the aluminum precursor and water, and before aging the mixture in the above step 1).
3. The method according to claim 2 , wherein the acid is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid and formic acid.
4. The method according to claim 1 , further comprising adding and mixing a sodium precursor and a zeolite seed in the above step 1).
5. The method according to claim 4 , wherein the sodium precursor is at least one selected from the group consisting of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfate.
6. The method according to claim 1 , wherein the silica precursor is at least one selected from the group consisting of tetraethylorthosilicate, silica sol, silica gel, sodium silicate and fumed silica, and the aluminum precursor is at least one selected from the group consisting of aluminum alkoxide, sodium aluminate, aluminum sulfate, aluminum chloride, boehmite and aluminum hydroxide.
7. The method according to claim 1 , wherein the molar ratio of the silicon precursor to the aluminum precursor (Si/Al) is 20-60.
8. The method according to claim 1 , wherein the aging process in the above step 1) is conducted at 20-120° C. for 1-24 hours.
9. The method according to claim 1 , wherein the hydrothermal reaction of the zeolite synthetic gel in the above step 2) is conducted at a temperature range of 100-200° C. for the reaction period of 1-7 hours.
10. The method according to claim 1 , wherein the above step 3) is carried out by cooling the zeolite to 100° C. or less, adding thereto a basic solution, stirring together and reacting it at 20-100° C.
11. The method according to claim 1 , wherein the basic solution is prepared from at least one base selected from the group consisting of NaOH, KOH, CsOH, LiOH, Ca(OH) 2 and Na 2 CO 3 .
12. The method according to claim 1 , wherein the Si/Al molar ratio in the zeolite in the above step 3), which is synthesized from the step 2), is 20-60.
13. The method according to claim 1 , wherein the average mesopore size of the mesoporous zeolite obtained from the above step 4) is in the range of 5-50 nm and volume thereof is 0.1-1.0 cc/g.