Mechanisms of Desulfurization by Nanomaterials

Abstract

A variety of materials are used as catalyst and adsorbent during the desulfurization of petroleum products, and nanomaterials also find its application in this field. In different desulfurization process, the behavior of nanomaterials towards desulfurization is different. In the case of hydrodesulfurization process, the catalyst used are CoMo or NiMo sulfides supported on various supports. The catalysts bear anion vacancy or coordinatively unsaturated sites, where the sulfur compounds adsorb and react with hydrogen, to set free sulfur as H2S. The structure of the catalyst deeply influences its HDS activity; rim and edge model proposed suggests that the rim and edge sites of the catalysts sheets stacked together are more active for HDS of larger molecules. The activity of the catalysts enhances with reducing its crystalline structure. The catalysts used in oxidative desulfurization (ODS) include supported and unsupported metal oxides, polyoxmetalates, and transition metals as cations. During ODS reactions, the catalysts either act as an oxygen carrier, by converting into peroxo species or then enhance the dissociation of the oxidant to boost up the selective oxidation of the sulfur compounds. In adsorptive desulfurization, the adsorbent materials selectively retain the sulfur compounds by π-complexation or physical adsorption. In some cases, the adsorbents assist in cracking of sulfur compounds during the adsorption process.