Yaojun Sun

Excellent photocatalytic degradation activities of ordered mesoporous anatase TiO2-SiO2 nanocomposites to various organic contaminants.

Ordered 2-D hexagonal mesoporous TiO(2)-SiO(2) nanocomposites consisted of anatase TiO(2) nanocrystals and amorphous SiO(2) nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO(2)-20SiO(2)-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of SiOH groups and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from TiOH groups, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO(2)-10SiO(2)-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO(2)-SiO(2) nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants.

Synthesis and structural characterization of B-Al-ZSM-5 zeolite from boron–silicon porous glass in the vapor phase

Abstract B-Al-ZSM-5 zeolite was synthesized on granules of boron–silicon porous glass in a vapor mixture of ethylamine and water at 180°C. The as-synthesized zeolite obtained by vapor–solid reaction and the calcined B-Al-ZSM-5 zeolites were characterized with 11 B, 29 Si, 27 Al, 13 C MAS NMR, XRD, IR, and TG/DTG/DTA. The various states of the species of BO, AlO, and SiO in both the amorphous porous glass and the as-synthesized zeolite were inspected in detail with 11 B, 29 Si and 27 Al MAS NMR. The complete incorporation of BO, AlO, and SiO into the framework of the zeolite was confirmed. The possible position of the template in the zeolite was investigated with 13 C MAS NMR. The unit cell of the zeolite contracts with the incorporation of boron atoms into the framework. The crystallinity of the as-synthesized zeolite is about 93% with orthorhombic symmetry both before and after calcination. After calcination, the crystallinity of the zeolite decreases due to B removal. The number of ethylamine molecules located at different positions of the zeolite channels is discussed in relation to TG/DTG/DTA data.

Characterization and reactivity of Ni,Mo-supported MCM-41 catalysts for hydrodesulfurization

The adorption isotherms of MCM-41 molecular sieve and catalysts exhibit two regions in their reversible parts and also two hysteresis loops. The first hysteresis at relative pressure below 0.4 is assigned to the capillary condensation in the mesoporous channels, and it is sensitive to the filling or blockage in the channels. The adsorption isotherms together with XRD results can be used to characterize the dispersion of nickel and molybdenum oxides on MCM-41. MCM-41 supported Ni and Mo catalysts are in general more active than similar NaY supported catalysts, but they are more strongly dependent on the dispersion of metal oxides owing to the unidimensional channel system, of MCM-41.

Crystallization of zeolite ZSM-39 studied by 13C and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy

13 C CP MAS NMR, 29Si MAS NMR and XRD have been used to study the crystallization of zeolite ZSM-39 in the tetramethylethylenediamine (TMEDA)–SiO2–H2O system. With the formation of the precursor from SiO2 species surrounding TMEDA followed by nucleation, the 13C chemical shift of the —C2H4— group moves progressively to higher field. This indicates that one molecule of TMEDA is shared by two neighbours of the [51264] cage and that the —C2H4— group of TMEDA interacts strongly with oxygen atoms located at the 6-ring window between the two cages.

H3PW12O40 AND ITS CESIUM SALTS AS PENTANE ISOMERIZATION CATALYSTS AT AMBIENT TEMPERATURE

H3PW12O40 and its acidic cesium salts are catalytically active for pentane isomerization at ambient temperature. The influence of activation temperature and Cs content of the catalysts on their activity and selectivity have been investigated and discussed in relation to textural properties and surface acidity. H3PW12O40 and Cs2.25H0.75PW12O40 are superacidic as evaluated by measuring the rate constants of pentane isomerization at 35°C. Their acid strengths are in the range of H0=−13∼−12.4.

The adsorption isotherms, IR and29Si MAS NMR spectra of modified MCM-41 molecular sieves

RECENTLY a new family of mesoporous molecular sieves, M41S, was reported by researchers atMobil R&D Corporation.As a member of the family, MCM-41, which exhibits a hexagonalarray of uniform channel mesopores, has been synthesized. The channel size can be variedfrom approximately 1.5 nm to greater than 10 nm by choosing different surfactants, auxiliarychemicals (1,3,5-trimethylbenzene) in the reactant,and by changing the reaction condi-tions. The wall thickness of this kind of molecular sieve is in the range of 0.3 to 1.3 nm esti-...

STUDIES ON TEMPLATE MOLECULES: LOCATION, ORIENTATION, PROTONATION AND INTERACTION WITH FRAMEWORK IN HIGH SILICA ZEOLITES

Template molecule of TMEDA (tetramethylethylenediamine) trapped in the channel or the cage of high silica zeolites of mordenite,ZSM-5, ZSM-35, ZSM-39, and CF-3 were characterized by 13 C CP MAS and HPDEC MAS n.m.r. spectra, IR spectra, TG/DTA and chemical analysis. Linear relations between 13 C chemical shift (δ) for -CH 3 and -C 2 H 4 - groups of TMEDA, and the free diameter (1) of the channel or the cage have been determined. It was found that an obvious difference in relative intensity of 13 C CP and HPDEC resonance, line narrowness, and great division from the δ-l linear relations can be used to deduce the position, the orientation of template molecule in the channel or the cage of the zeolites, and its interaction with framework.