Weiyang Dong

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.

CFD modeling of a UV-LED photocatalytic odor abatement process in a continuous reactor

This paper presents a model study of a UV light-emitting-diode (UV-LED) based photocatalytic odor abatement process. It integrated computational fluid dynamics (CFD) modeling of the gas flow in the reactor with LED-array radiation field calculation and Langmuir-Hinshelwood reaction kinetics. It was applied to simulate the photocatalytic degradation of dimethyl sulfide (DMS) in a UV-LED reactor based on experimentally determined chemical kinetic parameters. A non-linear power law relating reaction rate to irradiation intensity was adopted. The model could predict the steady state DMS concentration profiles by calculating the advection, diffusion and Langmuir-Hinshelwood reaction kinetics. By affecting the radiation intensity and uniformity, the position of the LED array relative to the catalyst appeared to be a critical parameter determining DMS removal efficiency. Too small distances might yield low quantum efficiency and consequently poor abatement performance. This study provided an example of LED-based photocatalytic process modeling and gave insights into the optimization of light source design for photocatalytic applications.

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.

Preparation of an MFI-type zeolite membrane on a porous glass disc by substrate self-transformation

An MFI-type zeolite membrane containing boron has been prepared on the surface of a boron–silicon porous glass disc by substrate self-transformation in the vapor of ethylamine (EA) and H2O; both XRD and SEM show that the zeolite crystals on the surface of the porous glass disc were in random orientation; the thickness of the membrane layer was ca. 10–20 μm; permeation of O2 and N2, and the chemical composition of the membrane were measured.

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-...