Method of preparing ZSM-5 using variable temperature without organic template
View Patent ↗Disclosed is a method of preparing ZSM-5 having substantially 100% crystallinity by using variable temperatures in the absence of an organic template, characterized in that a reaction mixture having a molar composition of M 2 O/SiO 2 (M: alkali metal ion) of 0.07-0.14, H 2 O/SiO 2 of 15-42 and SiO 2 /Al 2 O 3 of 20-100 is nucleated at relatively high temperatures (180-210° C.) and then crystallized at relatively low temperatures (130-170° C.), thus easily controlling a crystal size and a particle size distribution of the ZSM-5.
1. A method of preparing ZSM-5, comprising the following steps of:
mixing a silica source, an alkali metal oxide source, an alumina source and water, to prepare a reaction mixture having a molar composition of M 2 O/SiO 2 (M: alkali metal ion) of 0.07-0.14, H 2 O/SiO 2 of 15-42 and SiO 2 /Al 2 O 3 of 20-100;
maintaining the reaction mixture at 180-210° C. for a reaction time controlled in a range of 2-20 hours according to an intended crystal size and a particle size distribution of the ZSM-5, to obtain a nucleated reaction mixture; and
maintaining the nucleated reaction mixture at 130-170° C. for 10-200 hours to form crystals of the ZSM-5.
2. The method as defined in claim 1 , wherein the alkali metal oxide source is alkali metal hydroxide.
3. The method as defined in claim 1 , wherein the alkali metal is sodium.
4. The method as defined in claim 1 , wherein a molar ratio of the M 2 O/SiO 2 is in the range of 0.09-0.14 when the molar ratio of the SiO 2 /Al 2 O 3 is 29 or higher.
5. The method as defined in claim 1 , wherein the molar ratio of the M 2 O/SiO 2 is in the range of 0.07-0.1 when the molar ratio of the SiO 2 /Al 2 O 3 is less than 29.
6. The method as defined in claim 1 , wherein the alumina source is sodium aluminate or aluminum hydroxide.
7. The method as defined in claim 1 , wherein the silica source is selected from the group consisting of colloidal silica, sodium silicate, white carbon and boehmite.
8. The method as defined in claim 1 , wherein the ZSM-5 has an average crystal size of 1-6 μm.
9. The method as defined in claim 8 , wherein the ZSM-5 has an average crystal size of 2-3 μm.
10. The method as defined in claim 4 , wherein the ZSM-5 has a hexagonal crystal morphology.
11. The method as defined in claim 5 , wherein the ZSM-5 has a spiral crystal morphology.
12. The method as defined in claim 5 , wherein the nucleating step is performed for 10-20 hours when the molar ratio of the SiO 2 /Al 2 O 3 is not more than 22.
13. The method as defined in claim 12 , wherein the crystallizing step is performed for 96-200 hours.
14. The method as defined in claim 1 , wherein the crystallizing step is performed until crystallinity reaches substantially 100%.
15. A method of preparing ZSM-5, comprising the following steps of:
admixing a silica source, an alkali metal oxide source and water, to prepare a first aqueous solution;
separately admixing an alumina source, an alkali metal oxide source and water, to prepare a second aqueous solution;
mixing the first aqueous solution with the second aqueous solution while being optionally added with water, to prepare a reaction mixture having a molar composition of M 2 O/SiO 2 of 0.07-0.14, H 2 O/SiO 2 of 15-42 and SiO 2 /Al 2 O 3 of 20-100;
maintaining the reaction mixture at 180-210° C. for a reaction time controlled in the range of 2-20 hours according to an intended crystal size and a particle size distribution of the ZSM-5, to obtain a nucleated reaction mixture; and
maintaining the nucleated reaction mixture at 130-170° C. for 10-200 hours to form crystals of the ZSM-5.
16. The method as defined in claim 15 , wherein the silica source in the first aqueous solution amounts to 21.5-26.7 wt %, and the alumina source in the second aqueous solution amounts to 0.9-4.4 wt %.
17. The method as defined in claim 15 , wherein the alkali metal oxide source is alkali metal hydroxide.
18. A method of preparing ZSM-5, comprising the following steps of:
admixing a silica source, an alkali metal oxide source and water, to prepare a first aqueous solution;
separately admixing an alumina source and water, to prepare a second aqueous solution;
mixing the first aqueous solution with the second aqueous solution while being optionally added with water, to prepare a reaction mixture having a molar composition of M 2 O/SiO 2 of 0.07-0.14, H 2 O/SiO 2 of 15-42 and SiO 2 /Al 2 O 3 of 20-100;
maintaining the reaction mixture at 180-210° C. for a reaction time controlled in the range of 2-20 hours according to an intended crystal size and a particle size distribution of the ZSM-5, to obtain a nucleated reaction mixture; and
maintaining the nucleated reaction mixture at 130-170° C. for 10-200 hours to form crystals of the ZSM-5.
19. The method as defined in claim 18 , wherein the silica source in the first aqueous solution amounts to 21.5-26.7 wt %, and the alumina source in the second aqueous solution amounts to 0.9-4.4 wt %.
20. The method as defined in claim 18 , wherein the alkali metal oxide source is alkali metal hydroxide.