Unsupported transition metal sulfide catalysts for deep hydrodesulfurization of hydrocarbon fuels

Abstract

The requirement of clean fuels has resulted in a continuing worldwide effort to dramatically reduce the sulfur levels. This is driving the need for more active hydrodesulfurization (HDS) catalysts. The purpose of this research is to study the potential of unsupported Mo based sulfide catalysts prepared from hydrothermal method. The unsupported catalysts exhibited the excellent activity for the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Activity and surface area of catalysts depend strongly upon the preparation temperature and pressure. Organic solvent added in catalyst preparation helps to improve the dispersion of the precursor molecules. The unpromoted and promoted (Co or Ni) Mo sulfide catalysts have different properties and activity. Addition of promoter decreased surface area and pore volume. TPR analysis suggested that promoter decrease metal sulfur bond strength. HRTEM and XRD results showed that the growth of catalyst particle was suppressed when promoter was added. The promoter increased HDS activity of MoS[subscript 2] and changed the contribution of the direct-desulfurization and of hydrogenation pathways. The main effect of the promoter was to increase the rate of C-S bond cleavage. The liquid-phase adsorption of DBT and 4,6-DMDBT was used to study the adsorption capacity and mechanism over the synthesized catalysts. The results showed that the promoters not only increase active site number, but also enhance activity of active sites of the Mo sulfide.