Novel cobalt-free oxygen permeable membrane

A series of cobalt-free and low cost perovskite oxygen permeable membranes based on BaCexFe1-xO3-delta (BCF) oxides was successfully synthesized and the membrane showed both high oxygen permeability and high stability under reductive atmosphere, which will be most suitable for constructing a membrane reactor for selective oxidation of light hydrocarbons to syngas or high value corresponding oxygenates.

Catalytic partial oxidation of gasoline to syngas in a dense membrane reactor

In our previous work, it was shown that LiLaNiO/gamma-Al2O3 was an excellent catalyst for partial oxidation of heptane to syngas in a fixed-bed reactor at high temperature and the selectivity of CO was about 93%. However, pure oxygen was used as the oxidant. We have developed a dense oxygen permeation membrane Ba0.5Sr0.5Co0.8Fe0.2O3 that can supply pure oxygen for the reaction. In this work, the membrane was combined with the catalyst LiLaNiO/gamma-Al2O3 in one rector for the partial oxidation of heptane that is typical component of gasoline. A good performance of the membrane reactor has been obtained, with 100% n-heptane conversion and >94% hydrogen selectivity at the optimized reaction conditions. (C) 2004 Elsevier B.V. All rights reserved.

Separation and identification of compounds in Rhizoma chuanxiong by comprehensive two-dimensional liquid chromatography coupled to mass spectrometry

A comprehensive two-dimensional liquid chromatographic separation system based on the combination of a CN column and an ODS column is developed for the separation of components in a traditional Chinese medicine (TCM) Rhizoma chuanxiong. Two columns are coupled by a two-position, eight-port valve equipped with two storage loops and controlled by a computer. The effluent is detected by both the diode array detector and atmospheric pressure chemical ionization (APCI) mass spectrometer. More than 52 components in the methanol extract of R. chuanxiong were resolved and 11 of them were preliminary identified according to their UV and mass spectra. (C) 2004 Elsevier B.V. All rights reserved.

Short columns with molecularly imprinted monolithic stationary phases for rapid separation of diastereomers and enantiomers

Three molecularly imprinted monolithic columns with different length but almost identical column volume had been prepared. It was observed that the separation factors of diastereomers and enantiomers were almost unaffected by column length. However, the short column with dimension of 38 mm x 8 mm W. showed much lower resistance to flow rate so that it could be operated at much higher flow rates. By combining stepwise gradient elution with elevated flow rate, the diastereomers of cinchonine and cinchonidine and the enantiomers of Cbz-DL-Trp and Fmoc-DL-Trp were successfully separated within 3 min on the short column with dimension of 38 mm. x 8 mm i.d.. Based on the above results, a cinchonine imprinted monolithic disk with dimension of 10 mm x 16 mm W. was further developed. The SEM image and the pore size distribution profile showed that large flow-through pores are present on the prepared monolith, which allowed mobile phase to flow through the disk with very low resistance. Chromatographic performances on the monolithic disk were almost unchanged compared with the long columns. A rapid separation of cinchonine and cinchonidine was achieved in 2.5 min at the flow rate of 9.0 ml/min. Furthermore, it was observed that there was almost no effect of the flow rate on the dynamic binding capacity at high flow rates. In addition, the effect of the loading concentration of analytes on the dynamic binding capacity, namely adsorption isotherm, was also investigated. A non-linear adsorption isotherm of cinchonine was observed on the molecularly imprinted monolith with cinchonine as template, which might be a main reason to result in the peak tailing of template molecule. (C) 2004 Elsevier B.V. All rights reserved.

Effect of sodium alginate concentration on membrane strength and permeating property of poly-l-arginine group microcapsule

A novel poly-l-arginine microcapsule was prepared due to its nutritional function and pharmacological efficacy. A high-voltage electrostatic droplet generator was used to make uniform microcapsules. The results show that the membrane strength and permeating property are both remarkably affected with the changes of sodium alginate concentration. With the sodium alginate concentration increasing, gel beads sizes increase from 233 mum to 350 mum, release ratio is also higher at the same time, but the membrane strength decreases.

Application of uniform design and genetic algorithm in optimization of reversed-phase chromatographic separation

An optimization method based on uniform design in conjunction with genetic algorithm is described. According to the proposed method, the uniform design technique was applied to the design of starting experiments, which can reduce the number of experiments compared with traditional simultaneous methods, such as simplex. And genetic algorithm was used in optimization procedure, which can improve the rapidity of optimal procedure. The hierarchical chromatographic response function was modified to evaluate the separation equality of a chromatogram. An iterative procedure was adopted to search for the optimal condition to improve the accuracy of predicted retention and the quality of the chromatogram. The optimization procedure was tested in optimization of the chromatographic separation of 11 alkaloids in reversed-phase ion pair chromatography and satisfactory optimal result was obtained. (C) 2003 Elsevier B.V. All rights reserved.

The separation of biomolecules using capillary electrochromatography

The unique properties of capillary electrochromatography such as high performance, high selectivity, minimum consumption of both reagents and samples, and good compatibility with mass spectrometry make this technique an attractive one for the analysis of biomolecules including peptides, proteins, carbohydrates, nucleosides and nucleoticles. Irreversible adsorption between the biomolecules and the charged packing surface leads to a lack of reproducibility and serious peak tailing, so various approaches have been taken to overcome this and to improve the technique for future challenges.

Degradation mechanism of polystyrene sulfonic acid membrane and application of its composite membranes in fuel cells

The lifetime behavior of a H-2/O-2 proton exchange membrane (PEM) fuel cell with polystyrene sulfonic acid (PSSA) membrane have been investigated in order to give an insight into the degradation mechanism of the PSSA membrane. The distribution of sulfur concentration in the cross section of the PSSA membrane was measured by energy dispersive analysis of X-ray, and the chemical composition of the PSSA membrane was characterized by infrared spectroscopy before and after the lifetime experiment. The degradation mechanism of the PSSA membrane is postulated as: the oxygen reduction at the cathode proceeds through some peroxide intermediates during the fuel cell operation, and these intermediates have strong oxidative ability and may chemically attack the tertiary hydrogen at the a carbon of the PSSA; the degradation of the PSSA membrane mainly takes place at the cathode side of the cell, and the loss of the aromatic rings and the SO3- groups simultaneously occurs from the PSSA membrane. A new kind of the PSSA-Nafion composite membrane, where the Nafion membrane is bonded with the PSSA membrane and located at the cathode of the cell, was designed to prevent oxidation degradation of the PSSA membrane in fuel cells. The performances of fuel cells with PSSA-Nafion101 and PSSA-recast Nafion composite membranes are demonstrated to be stable after 835 h and 240 h, respectively.