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Synthesis and Characterization of Zirconium Silicalite-1
Ko, Yong Sig,Ahn, Wha Seung 한국화학공학회 1998 Korean Journal of Chemical Engineering Vol.15 No.4
Zirconium silicalite-1 (ZS-1) catalysts with MFI structure were prepared using a hydrothermal synthesis method. XRD, SEM, IR, ^(29)Si MAS NMR, UV-VIS DRS, physical adsorption of nitrogen, and elemental analysis were then performed to evaluate its physico-chemical properties, and evidences of Zr^(4+) incorporation into the zeolite framework were provided : The unit cell volume of zirconium silicalite-1 increased linearly with increases in zirconium content, and the characteristic framework i.r. spectra shifted to lower frequencies as Zr^(4+) was incorporated into the silicalite-1 lattice. For its catalytic reaction test, liquid phase 2-butanol oxidation using hydrogen peroxide as an oxidant was carried out. All of the zirconium silicalite-1 samples synthesized were active for the 2-butanol oxidation, but activities obtained using ZS-1 catalysts were lower than TS-1 catalyst. Zirconium in the zeolite framework was found to he the active site for the 2-butanol oxidation.
Hydrothermal synthesis and characterization of Fe(III)-substituted mordenites
Yong Sig Ko,장현태,안화승 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
Fe-substituted mordenites were synthesized hydrothermally, partially substituting iron atoms for the framework aluminum of mordenite. XRD, SEM, IR, UV-VIS DRS, ESR, XAS, and catalytic activity studies provided the evidence of Fe3+ present in the zeolite framework. The framework IR bands were shifted to lower frequencies as Fe3+ ions incorporated into the lattice, and a new Si-O-Fe bond vibration was located near 668 cm−1. The presence of a signal at g=4.3 in the ESR spectra was assigned to Fe3+ isomorphously substituted in the tetrahedral position. EXAFS at the Fe K-edge revealed that the Fe3+ ions were present in the zeolite framework in a four-fold coordination with an average Fe-O distance of 1.86 Å. In the UV-vis spectra, an absorption was observed at 375.7 nm which was assigned to the presence of Fe3+ in the zeolite framework. A toluene alkylation study reflected that the acidity strength of mordenite is weakened due to the presence of lattice iron species.
Influence of Synthesis Parameters on the Morphology and Particle Size Distribution of Zeolite L
Ko, Yong Sig,Ahn, Wha Seung 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.4
Zeolite L was synthesized hydrothermally from the substrate mixture of Na₂O-K₂O-Al₂O₃-SiO₂-H₂O system at temperatures of 373 443 K, and the influence of various synthesis parameters on the particle size distribution and surface morphology was investigated. The crystalline zeolite L samples obtained were characterized by means of X-ray powder diffraction, scanning electron microscopy. and particle size analysis. It was established that as the synthesis temperature increased, the average crystal size becomes larger with a broader particle size distribution. Particle size distribution and morphology of zeolite L was also affected by the silica source and the molar ratios of SiO₂/Al₂O₃, (K₂O+Na₂O)/SiO₂, Na₂O/(K₂O+Na₂O), and H₂O/(K₂O +Na₂O). The crystal size decreased significantly by stirring the gel during the synthesis or subjecting the substrate mixture to an aging treatment at room temperature before hydrothermal treatment. Different heating rates applied prior to subsequent isothermal crystallization at 443 K also significantly influence the particle size distribution and the morphology of zeolite L.