Lan Jin

A structured catalyst based on cobalt phthalocyanine/calcined Mg–Al hydrotalcite film for the oxidation of mercaptan

A structured catalyst has been fabricated by immobilizing cobalt phthalocyanine tetrasulfonate (CoPcS) on a mixed metal oxide (denoted as MMO) film, which exhibits excellent activity, stability and recyclability for mercaptan sweetening. Scanning electron microscopy (SEM) images show that the structured catalyst is composed of MMO nanoflakes whose ab-plane is perpendicular to the Al substrate, with desired mechanical strength and high adhesion to the substrate. In addition, in situ IR spectra and carbon dioxide temperature programmed desorption (CO2-TPD) reveal that the moderate basic site is overwhelming in the CoPcS/MMO structured catalyst, while the strong basic site predominates in the corresponding CoPcS/MMO powder catalyst. It was found that the structured catalyst exhibits high conversion (85.7%) for the oxidation of mercaptan to disulphide, markedly higher than that of the corresponding powder catalyst (38.7%), as a result of the high exposure of active species as well as the synergistic effect between the oxidation center (CoPcS) and the moderate basic site. In addition, the structured catalyst shows superior catalysis-regeneration performance, which facilitates its repeatable and cyclic usage over a long period. Therefore, this work provides a facile and effective method for the fabrication of structured catalyst with high catalytic activity and stability, as well as recyclability, which can be used as an eco-friendly catalyst for the sweetening process in the petroleum refining industry.

An optical sensor based on H-acid/layered double hydroxide composite film for the selective detection of mercury ion

A novel optical chemosensor was fabricated based on 1-amino-8-naphthol-3,6-disulfonic acid sodium (H-acid) intercalated layered double hydroxide (LDH) film via the electrophoretic deposition (EPD) method. The film of H-acid/LDH with the thickness of 1 μm possesses a well c-orientation of the LDH microcrystals confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fluorescence detection for Hg(II) in aqueous solution was performed by using the H-acid/LDH film sensor at pH 7.0, with a linear response range in 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) and a detection limit of 6.3 × 10(-8) mol L(-1). Furthermore, it exhibits excellent selectivity for Hg(II) over a large number of competitive cations including alkali, alkaline earth, heavy metal and transitional metals. The specific fluorescence response of the optical sensor is attributed to the coordination between Hg(II) and sulfonic group in the H-acid immobilized in the LDH matrix, which was verified by NMR spectroscopy and UV-vis spectra. In addition, density functional theory (DFT) calculation further confirms that the coordination occurs between one Hg(2+) and two O atoms in the sulfonic group, which is responsible for the significant fluorescence quenching of the H-acid/LDH film. The results indicate that the H-acid/LDH composite film can be potentially used as a chemosensor for the detection of Hg(2+) in the environmental and biomedical field.