| MCM-41 has been successfully synthesized using microwave interval heating method. And the influence of stirring temperature, microwave heating time and microwave interval time have been investigated. It showed that raising stirring temperature(30-60℃) and prolonging microwave heating time(30-40min) could increase the structural order of the samples, but the influence of microwave interval time upon the samples was unobvious. With comparing the samples synthesized by microwave method with the samples synthesized by hydrothermal method and room-temperature method, we found that the sample synthesized by hydrothermal method had the biggest pore diameter(3.1nm), the smallest BET surface(709 m2·g-1), and the best stability; Reversely, the sample synthesized by room-temperature method had the smallest pore diameter(2.5nm), the biggest BET surface(826 m2·g-1) and the worst stability; and the pore diameter of the sample synthesized by microwave method was approximately 2.8nm, and its BET surface was 782 m2·g-1, and the stability was between that of the samples synthesized by hydrothermal method and room-temperature method. After post-hydrothermal heating in pure water, the sample had better stability. The stability of the sample could also been improved by post-microwave heating in pure water, but the effect was not as good as the former. And we also could improve the stability by introducing Ti and Y into the sample. And the result showed that the introduction of little Ti (Ti/Si≤0.02) did not change the mesoporous structure, and when Ti/Si=0.1, the sample still had hexagonal mesoporous structure; The mesoporous structure of sample modified by Y has been destroyed and collapsed completely as Y/Si≥0.05. The influent factors of synthesizing MCM-48 under hydrothermal condition have been worked. As the value of NaOH/TEOS increasing, the mesoporous structure of the sample changed from MCM-50 to MCM-48 (NaOH/TEOS=0.6, MCM-48). And the mesoporous structure of the sample changed from MCM-41 to MCM-48, with prolonging the synthesized time(synthesized time≥ 48h, MCM-48). We also worked on synthesizing MCM-48 by microwave heating. With mixing cationic-anionic template agent (CTAB-C12H25NaSO3), we successfully synthesized MCM-48 under microwave irradiation. As the addition of C12H25NaSO3 increasing, the mesoporous structure of the samples changed from MCM-41 to MCM-48(C12H25NaSO3/TEOS ≥ 0.02, MCM-48), but the effect of microwave time was unobvious. It could been synthesized MCM-48, as NaOH/TEOS≤0.8, and we also synthesize MCM-48 as CTAB/TEOS=0.2-0.5. But it was difficult to synthesize MCM-48, as employing signal surfactant (CTAB) or mixing cationic-neutral surfactant (CTAB-TX-100) as template.
|
PDF Full Text Request