Title of article :
Synthesis, characterization, and catalytic properties of zeolites IM-5 and NU-88
Author/Authors :
Song-Ho Lee، نويسنده , , Dong-Koo Lee، نويسنده , , Chae-Ho Shin، نويسنده , , Yong-Ki Park، نويسنده , , Paul A. Wright، نويسنده , , Won Mook Lee، نويسنده , , Suk Bong Hong، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2003
Pages :
20
From page :
151
To page :
170
Abstract :
The synthesis, characterization, and catalytic properties of two high-silica zeolites IM-5 and NU-88, whose structures still remain unresolved, are presented. When the 1,5-bis(N-methylpyrrolidinium)pentane and 1,6-bis(N-methylpyrrolidinium)hexane cations are used as organic structure-directing agents, respectively, crystallization of pure IM-5 and NU-88 was possible only from synthesis mixtures with a narrow range of SiO2/Al2O3 and NaOH/SiO2 ratios. The overall characterization results of this study strongly suggest that IM-5 is a new multidimensional large-pore zeolite, whereas NU-88 is a nanocrystalline material that could be an intergrowth of several hypothetical polymorphs in the beta family of zeolites. Despite its nanocrystalline nature, however, no detectable extraframework Al species were found to exist in H–NU-88, revealing excellent thermal stability. H–IM-5 and H–NU-88 both exhibit a very high 1-butene conversion compared to H–ZSM-35 over the period of time studied here, whereas the opposite holds for the formation of isobutene. This reveals that their pore topologies are large enough to allow undesired side reactions such as 1-butene dimerization followed by cracking to light olefins. They also show the initial n-octane cracking activity comparable to that on H–ZSM-5. However, a notable decrease in n-octane conversion on these two zeolites with increasing time on stream is observed. When the isomerization and cracking activities of all zeolites employed in this study are correlated with their coke-forming propensities, it can be concluded that both materials present a shape-selective character falling within the category of multidimensional, large-pore zeolites.
Keywords :
Vanadia catalysts , Sulfuric acid catalyst , Pyrosulfate melts , In situ Raman spectra , Vanadium oxosulfato complexes , Molten salt catalysts , SO2 oxidation
Journal title :
Journal of Catalysis
Serial Year :
2003
Journal title :
Journal of Catalysis
Record number :
1222629
Link To Document :
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