Byongjin Lee

Infrared study of H/D isotope exchange reaction of alkanes and Brønsted acidic hydroxyl groups on FER zeolite

H/D isotope exchange between n-alkanes and the acidic OD groups in ferrierite was observed by infrared spectroscopy. The real activation energies were estimated by adding the heats of adsorption to the apparent activation energies, resulting in almost the same value for all n-alkanes. The transition state for the reaction is discussed.

Synthesis and Property of Mesoporous Tantalum Oxides

Some mesoporous Ta2O5 were synthesized and characterized by N2 adsorption isotherms, TEM and XRD. Although the one prepared by the ligand-assisted templating (LAT) method was neither thermally nor mechanically stable, its hydrophobicity was found to be utilized for efficient intercalation of large dye molecules from aqueous solution. On the other hand, the thick wall of the mesoporous Ta2O5 synthesized by neutral surfactant templating (NST) method partly maintained mesopores even after calcination at crystallization temperature (1023 K). By the mixing of Ta and Nb sources (1:1), homogeneous (Nb, Ta)2O5 was prepared. The amorphous thick wall of as-prepared mesoporous (Nb, Ta)2O5 was crystallized by calcination at 923 K, while maintaining the mesopores in single crystal particles.

FT-IR study of H216O and H218O adsorption on H-ferrierite

Abstract The adsorption structure of water on H-ferrierite at room temperature was investigated with Fourier transform infrared spectroscopy using H 2 16 O and H 2 18 O . From the isotope shifts, three bands from 3000 to 1500 cm −1 were conclusively assigned to the so-called A, B, C triplet of the hydrogen-bonded complex of water and the Bronsted acid hydroxyl groups on zeolites. The shifts of other bands also confirmed that the structure of adsorbed water molecules on H-ferrierite is the hydrogen-bonded one.

Preparation of ordered mesoporous NbTa mixed oxide with crystallized wall

Abstract An ordered 2D-hexagonal mesoporous Nb and Ta (Nb:Ta=l:l) mixed oxide was successfully crystallized. A new strategy for preserving mesoporous structure after the crystallization of the walls was performed by re-filling a templating material to the mesopores before crystallization for suppressing the destruction of mesoporous structure. Transmission electron microscopy and electron diffraction analyses revealed the formation of crystallized mesoporous NbTa mixed oxide with single crystal phases in periodical mesoporous structure (denoted NbTa-TIT-2) at ca. 100-nm range.

Single crystal particles of a mesoporous mixed transition metal oxide with a wormhole structure

A new type of mesoporous mixed transition metal oxide of Nb and Ta (NbTa-TIT-1) has been prepared through a two-step calcination, which consists of single crystal particles with wormhole mesoporous structure.

Preparation of crack-free, transparent, nanoporous niobium oxide film with crystalline structure by evaporation-induced self-assembly (EISA) process

Nanoporous niobium oxide thin film with wormhole pore structure is prepared by combining a dip-coating method and an evaporation-induced self-assembly (EISA) technique. The template of nanopore and inorganic source used are commercially available neutral block copolymer P85, HO(CH2CH2O)26(CH2CH(CH3)O)39(CH2-CH2O)26H, and niobium pentachloride. The crystallized nanoporous niobium oxide film is successfully fabricated by a two-step calcination process: the first calcination process removes the template and forms a nanoporous film with amorphous framework, and the second calcinations step crystallizes the framework with random pore originated from the voids among the single crystalline domains. Scanning electron microscopy (SEM) reveals that the obtained material is a crack-free nanoporous film with the thickness of c.a. 200–300 nm. The crystal oxide framework and nanoporous structure is characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis in details.

Effect of cations addition for the highly ordered mesoporous niobium oxide

Abstract Wormhole-like mesoporous niobium oxide was prepared by neutral templating route. Addition of trace amount of cations (Li + , Na + , K + , Mg 2+ , Ca 2+ , or Ba 2+ ) promoted structural regularity to 3-dimensionally (3D) ordered mesoporous niobium oxide. The 3D ordered mesoporous niobium oxide showed 5 and 3 nm of pore diameter and wall thickness, respectively. X-ray diffraction (XRD) and electron diffraction (ED) patterns verified 3D hexagonal structure of the mesoporous niobium oxide similarly to the mesoporous silica, SBA-2 and SBA-12, with P6 3 /mmc mesoporous structure.

07-P-15 - Synthesis and characterization of the mesoporous material of single crystal particles

Publisher Summary This chapter discusses the synthesis and characterization of the mesoporous material of single crystal particles. Mesoporous structure is constructed in the single-crystal particles of niobium and tantalum-mixed oxide. Transmission electron microscopy (TEM) and electron diffraction indicate single-crystal phase with the mean pore size of 10 nm. The crystallized mesoporous material show mechanical and hydrothermal stability.