Coking kinetics on the catalyst during alkylation of fcc off-gas with benzene to ethylbenzene

The production of ethylbenzene from the alkylation of dilute ethylene in fee off-gases with benzene has been commercialized in China over a newly developed catalyst composed of ZSM-5/ZSM-11 co-crystallized zeolite. The duration of an operation cycle of the commercial catalyst could be as long as 180 days. The conversion of ethylene could attain higher than 95%, while the amount of coke deposited on the catalyst was only about 10 wt.%. Thermogravimetry (TG) was used to study the coking behavior of the catalyst during the alkylation of fee off-gas with benzene to ethylbenzene. Based on effects of reaction time, reaction temperature, reactants and products on coking during the alkylation process, it is found that the coking rate during the alkylation procedure follows the order: ethylbenzene > ethylene > propylene > benzene for single component, and benzene-ethylene > benzene-propylene for bi-components under the same reaction condition. Furthermore, the coking kinetic equations for benzene-ethylene, benzene-propylene and ethylbenzene were established. (C) 2003 Elsevier B.V. All rights reserved.

Red-light-emitting iridium complexes with hole-transporting 9-arylcarbazole moieties for electrophosphorescence efficiency/color purity trade-off optimizationE

The synthesis, structures, photophysics, electrochemistry and electrophosphorescent properties of new red phosphorescent cyclometalated iridium(III) isoquinoline complexes, bearing 9-arylcarbazolyl chromophores, are reported. The functional properties of these red phosphors correlate well with the results of density functional theory calculations

Red-Light-Emitting Iridium Complexes with Hole-Transporting 9-Arylcarbazole Moieties for Electrophosphorescence Efficiency/ Color Purity Trade-off Optimization

The synthesis, structures, photophysics, electrochemistry and electrophosphorescent properties of new red phosphorescent cyclometalated iridium(III) isoquinoline complexes, bearing 9-arylcarbazolyl chromophores, are reported. The functional properties of these red phosphors correlate well with the results of density functional theory calculations. The highest occupied molecular orbital levels of these complexes are raised by the integration of a carbazole unit to the iridium isoquinoline core so that the hole-transporting ability is improved in the resulting complexes relative to those with I-phenylisoquinoline ligands. All of the complexes are highly thermally stable and emit an intense red light at room temperature with relatively short lifetimes that are beneficial for highly efficient organic light-emitting diodes (OLEDs).

Screening and Structural Characterization of alpha-Glucosidase Inhibitors from Hawthorn Leaf Flavonoids Extract by Ultrafiltration LC-DAD-MSn and SORI-CID FTICR MS

In vitro a-glucosidase inhibition assays and ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray ionization tandem mass spectrometry (ultrafiltration LC-DAD-ESI-MSn) were combined to screen a-glucosidase inhibitors from hawthorn leaf flavonoids extract (HLFE). As a result, four compounds were identified as alpha-glucosidase inhibitors in the HLFE, and their structures were confirmed to be quercetin-3-O-rha-(1-4)-glc-rha and C-glycosylflavones (vitexin-2 ''-O-glucoside, vitexin-2 ''-O-rhamnoside and vitexin) by high-resolution sustained off resonance irradiation collision-induced dissociation (SORI-CID) data obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS).

Micropatterning of polymeric semiconductor by selective lift-off method using epoxy mold

A simple and efficient method for patterning polymeric semiconductors for applications in the field of organic electronics is proposed. The entire polymer layer, except for the desired pattern, is selectively lifted off from a flat poly(dimethylsiloxane) (PDMS) stamp surface by an epoxy mold with a relief pattern. This is advantageous because the elastic deformation of the PDMS stamp around protrusions of a patterned stamp under pressure can assist the plastic deformation of a polymer film along the pattern edges, yielding large area and high quality patterns, and the PDMS surface has low surface energy, which allows the easy removal of the polymer film.

Highly efficient single-emitting-layer white organic light-emitting diodes with reduced efficiency roll-off

By codoping blue and orange phosphorescent dyes into a single host material, a highly efficient white organic light-emitting diode (WOLED) with Commission Internationale de L'Eclairage coordinates of (0.38, 0.43) at 12 V is demonstrated. Remarkably, this WOLED achieves reduced current efficiency roll-off, which slightly decreases from its maximum value of 37.3-31.0 cd/A at 1000 cd/m(2). The device operational mechanism is subsequently investigated in order to unveil the origin of the high performance.

Achieving highly efficient white organic light-emitting diodes with reduced efficiency roll-off

A highly efficient and colour-stable three-wavelength white organic light-emitting diode with the structure of indium tin oxide (ITO)/MoO3/N,N'-diphenyl-N,N'-bis (1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB)/4,4'-N,N'-dicarbazole-biphenyl (CBP): bis(2,4-diphenylquinolyl-N,C-2') iridium( acetylacetonate) (PPQ)(2)Ir(acac)/NPB/p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph):2-methyl-9,10-di(2-naphthyl) anthracene (MADN)/tris (8-hydroxyquinoline) aluminum (AlQ): 10-(2-Benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T)/AlQ/LiF/Al is fabricated and characterized. A current efficiency of 12.3 cdA(-1) at an illumination-relevant brightness of 1000 cd m(-2) is obtained, which rolls off slightly to 10.3 cdA(-1) at a rather high brightness of 10 000 cd m(-2). We attribute this great reduction in the efficiency roll-off to the wise management of singlet and triplet excitons between emissive layers as well as the superior charge injection and diffusion balance in the device.

Surface-enhanced Raman scattering of 4-aminothiophenol self-assembled monolayers in sandwich structure with nanoparticle shape dependence: Off-surface plasmon resonance condition

A universal metal-molecule-metal sandwich architecture by the self-assembly of Ag nanoparticles (NPs) and Au NPs of various shapes interconnected with 4-aminothiophenol (4-ATP) molecules was presented. These Ag NPs/4-ATP/Au NPs sandwich structures were characterized by surface enhanced Raman scattering (SERS) using an off-surface plasmon resonance condition. Enhancement factors (EF) on the order of 10(8) for 9b(b(2)) vibration mode were observed for the 4-ATP self-assembled monolayers (SAMs) in such sandwich structures. The factors are 2 orders of magnitude larger than that on the monolayer of Au NPs of various shapes under similar condition. More importantly, remarkable increase in the intensity of b(2) vibrational modes, which is characteristic of the charge transfer (CT) behavior between metal NPs and 4-ATP molecules, was observed in these sandwich structures under 1064 nm excitation. The obtained EF on these sandwich structure for 9b(b(2)) is larger than that for 7a vibration mode by a factor of similar to 10(2), demonstrating the importance of the contribution of the CT mechanism and the CT behavior of metal contacts, which play a significant role in metal-molecule-metal nanosystems.

Layer-by-layer electrodeposition of redox polymers and enzymes on screen-printed carbon electrodes for the preparation of reagentless biosensors

Layer-by-layer electrodeposition of redox polymer/enzyme composition films on screen-printed carbon electrodes for fabrication of reagentless enzyme biosensors has been proposed and the resulting films were found to be very stable and rigid.

Electrooxidative polymerization of phenothiazine derivatives on screen-printed carbon electrode and its application to determine NADH in flow injection analysis system

The electrooxidation polymerization of phenothiazine derivatives, including azure A and toluidine blue 0, has been studied at screen-printed carbon electrodes in neutral phosphate buffer. Both compounds yield strongly adsorbed electroactive polymer with reversible behavior and formal potentials closed to 0.04 V at pH 6.9. The modified electrodes exhibited good stability and electrocatalysis for NADH oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 500 mV lower than that of the bare electrodes. Further, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5-100 muM.

The modification of screen-printed carbon electrodes with amino group and its application to construct a H2O2 biosensor

Electrooxidation of thionine on screen-printed carbon electrode gives rise to the modification of the surface with amino groups for the covalent immobilization of enzymes such as horseradish peroxidase (HRP). The biosensor was constructed using multilayer enzymes which covalently immobilized onto the surface of amino groups modified screen-printed carbon electrode using glutaraldehyde as a bifunctional reagent. The multilayer assemble of HRP has been characterized with the cyclic voltammetry and the faradaic impedance spectroscopy. The H2O2 biosensor exhibited a fast response (2 s) and low detection limit (0.5 muM).

Electropolymerization of azure B on a screen-printed carbon electrode and its application to the determination of NADH in a flow injection analysis system

The electrooxidation polymerization of azure B on screen-printed carbon electrodes in neutral phosphate buffer was studied. The poly(azure B) modified electrodes exhibited excellent electrocatalysis and stability for dihydronicotinamide adenine dinucleotide (NADH) oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 400 mV lower than that at the bare electrodes. Different techniques, including cyclic voltammetry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy have been employed to characterize the poly (azure B) film. Furthermore, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5 muM to 100 muM.

Multilayer films of carbon nanotubes and redox polymer on screen-printed carbon electrodes for electrocatalysis of ascorbic acid

Multilayer films containing multiwall carbon nanotubes and redox polymer were successfully fabricated on a screen-printed carbon electrode using layer-by-layer (LBL) assembled method. UV-vis spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and electrochemical method were used to characterize the assembled multilayer films. The multilayer films modified electrodes exhibited good electrocatalytic activity towards the oxidation of ascorbic acid (AA). Compared with the bare electrode, the oxidation peak potential negatively shifted about 350 mV (versus Ag/AgCl). Furthermore, the modified screen-printed carbon electrodes (SPCEs) could be used for the determination of ascorbic acid in real samples.