Nam Ho Heo

Molten-salt method for the synthesis of zeolitic materials: I. Zeolite formation in alkaline molten-salt system

Abstract The molten-salt method has been applied for the zeolitization of fly ash and other mineral wastes. Fly ash was converted into zeolitic materials by a simple thermal treatment at molten states of some salt mixtures without any addition of water. Various combinations of salt mixtures were employed for the zeolitization of fly ash, using NaOH, KOH, or NH 4 F as mineralizer, and NaNO 3 , KNO 3 , or NH 4 NO 3 as stabilizer. The resultant zeolitic materials were composed of sodalite and cancrinite as major crystalline phases. This molten-salt method was also confirmed for the facile zeolitization of kaolinite, montmorillonite, and natural zeolite waste. The main zeolite species synthesized by the molten-salt method were dependent on the types of salt mixture and raw material used. The molten-salt method developed in this study could open a new and alternative approach for the mass treatment of these mineral wastes at low cost, as well as for the improvement of the purity and alkalinity of zeolitic materials.

Molten-salt method for the synthesis of zeolitic materials. II. Characterization of zeolitic materials

Characterization of zeolitic materials synthesized by the newly developed molten-salt method was carried out. Their physicochemical properties were investigated and compared to those of zeolitic materials prepared by the conventional hydrothermal method. The molten-salt method exhibited much less elemental loss during the zeolitization process. The product yield based on the reaction weight was about twice as high in the molten-salt method as in the hydrothermal method. The molten-salt method resulted in zeolitic materials with higher purity, larger contents of alkali metals, lower pH values, and lower cation exchange capacity (higher Si/Al ratio). Salt occlusion also took place in the cavities of the resulting zeolites during the zeolitization of fly ash by the molten-salt method. It seems, therefore, apparent that the high temperature and dry conditions in the molten-salt method lead to zeolitic materials which are somewhat different from hydrothermally synthesized zeolitic materials.

A Cationic Cesium Continuum in Zeolite X

A cesium continuum that fills the channels and cavities of zeolite X has been prepared, and its structure has been determined by single-crystal x-ray crystallography. The three-dimensional continuum is cationic to balance the negative charge of the zeolite framework. Its valence electrons, only 0.3 per Cs+ ion, are widely delocalized over 95 percent of the cesium ions in the crystal. The continuum has a unit cell formula of (Cs122)86+ and contains Cs13 and Cs14 clusters (one per supercage) arranged like the atoms in diamond, with one Cs2 appendix (in the sodalite cavity) per cluster.

Palladium-Catalyzed Diastereoselective Synthesis of Isoindolinones

Abstract: 2-Bromobenzaldehyde reacts diastereoselectively with chiral alkanolamines under carbon monoxide in the presence of a catalytic amount of bis(triphenylphosphine)palladium(II) chloride to afford the corresponding tricyclic isoindolinones in moderate to good yields.

The crystalline-state photochromism, thermochromism and X-ray structural characterization of a new spiroxazine

Abstract A new spiroxazine 4 was found to be photochromic and thermochromic both in solution and in the crystalline state. X-ray crystallography was used to determine that the molecules of the spiroxazine were arranged in a monoclinic (C2) crystallographic system. Intermolecular hydrogen bonds, together with interlayer, aromatic π–π stacking interactions, stabilize the molecular conformation and packing in the crystal structure.

Crystal Structure of a photoconductive dithiosquarylium dye: 2,4-Bis(1,3,3-trimethyl-2-indolinylidenemethyl) cyclobutenediylium-1,3-dithiolate

Abstract The crystal structure of a new dithiosquarylium dye (DTSQ), viz, 2,4-bis(1,3,3-trimethyl-2-indolinylidenemethyl) cyclobutenediylium-1,3-dithiolate, has been determined by X-ray crystallography. A crystal was grown from chloroform/ethylacetate (8:1/v:v) and found to exist in the monoclinic space group P2 1 /n (no. 14). The molecule is roughly planar and adopts the trans conformation.

Synthesis and X-ray structural characterization of new spiroxazine

Abstract A novel spiroxazine containing a mesogenic group has been prepared. The colourless spiroxazine exhibit photochromism through ring opening of the oxazine ring. The crystal structure was determined by X-ray crystallography and the crystal was found to exist in the triclinic space group P1 (No. 1).

Crystal structure of cesium zeolite A prepared by complete aqueous exchange

Abstract The complete exchange of zeolite 4A with Cs + has been achieved by the reaction of a single crystal of hydrated NH 4 + -A with a modest excess of CsOH slush. Its structure was determined by X-ray crystallographic methods. Up to one additional molecule of CsOH is taken up per sodalite cavity. To avoid close Cs + -Cs + contacts through 6-rings, four Cs + ions per large cavity are found nearly opposite 4-rings rather than opposite 6-rings as is usually seen. The hydroxide ion is presumed to be between the two Cs + ions found in each sodalite cavity.

Facile palladium-catalysed synthesis of 1-aryl-1H-indazoles from 2-bromobenzaldehydes and arylhydrazines

2-Bromobenzaldehydes react with arylhydrazines in toluene at 100 [degree]C in the presence of a catalytic amount of a palladium catalyst and phosphorus chelating ligands such as 1,1[prime or minute]-bis(diphenylphosphino)ferrocene and 1,3-bis(diphenylphosphino)propane along with NaO-t-Bu to afford 1-aryl-1H-indazoles in good yields.

Microporous Semicrystalline Silica Materials

A new family of microporous semicrystalline silica materials (MSSMs) were developed at room temperature from acidic mixtures of alkyl-substituted silane and tetramethylalkoxysilane. Hydrolyzed alkyl-substituted silica precursors, having hydrophilic silanol groups and hydrophobic alkyl groups, presumably act not only as templates but also as sol stabilizers for continuous pore engineering of silica materials in the micropore region. Depending on the substituted alkyl (SUA) groups in initial sols, MSSMs have distinct broad x-ray diffraction peaks in low 2θ range of 2° to 12°, distinguishable thermal behavior of SUA groups, highly flexible processability, and discrete micropore size with good thermal stability of micropores after the removal of SUA groups. These designer microporous silicas are expected to be useful for molecular sieving applications.