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

Abstract

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.