281522 Synthesis of 14-Membered Ring Aluminosilicate Zeolites and Their Applications As Solid Acid Catalysts
Zeolites have widely been utilized as catalysts in petrochemical industry and as adsorbents in separation and purification. Last two decades, zeolites possessing extra-large-pore with more than 12-membered ring (12-MR) has been developed and received a great attention because their pore sizes are favorable for the diffusion of bulkier molecules. However, such extra-large-pore zeolites have not been applied in catalysts due to their poor hydrothermal stabilities. Recently, 14-membered ring aluminosilicate zeolites with CFI, SFH and SFN-types have been synthesized using highly elaborated organic structure-directing agents (OSDAs). However, their catalytic performances have not fully been investigated. Herein, we report the synthesis of 14-membered ring aluminosilicate zeolites with CFI, SFH and SFN-types and their applications as solid acid catalysts.
CIT-5(CFI), SSZ-53(SFH), SSZ-59(SFN) zeolites were synthesized according to the previous reports with slight modifications. Aluminosilicate-type CIT-5 was synthesized using N(16)-methylsparteinium hydroxide as OSDA. The mother gel was hydrothermally treated 175 ºC for 7 days. Borosilicate-type SSZ-53 and SSZ-59 were synthesized using N, N, N-trimethyl-phenylcyclohexyl methyl ammonium hydroxide and N-methyl-N-[(1-phenylcyclopentyl)methyl]heptamethyleneiminium hydroxide as OSDA, respectively. CIT-5 was obtained by calcination of the NH3+-type sample. Aluminosilicate-type SSZ-53 and SSZ-59 were obtained through the post-treatment of the borosilicate ones using Al(NO3)3.
It was confirmed by the XRD patterns that the zeolites having pure CFI, SFH, SFN structures were formed. The Si/Al atomic ratios of CIT-5, SSZ-53 and SSZ-59 were estimated at 44, 50, and 55, respectively. The catalytic performances of the prepared three catalysts and Beta with 12-MR as a control in the acylation of 2-methoxynaphthalene (2-MN) with acetic anhydride were investigated. The conversion of 2-MN over CIT-5 was low because of its weak acid strength compared to other three zeolites. SSZ-53 and SSZ-59 showed similar conversions of 2-MN to Beta (ca. 94%). When SSZ-53 and SSZ-59 were used as catalyst, the yield of 1-acetyl-2-methoxynaphthalene (1,2-AMN) was higher than 2-acetyl-6-methoxynaphthalene (2,6-AMN). On the other hand, Beta gave the higher yield of 2,6-AMN than 1,2-AMN. These results imply that 14-MR is favorable to forming the bulky product, 1,2-AMN.
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