Development of catalysts containing Ni, V, Ce for the selective oxidation of hydrogen sulfur to elemental sulfur

The Claus process, an old method for sulfur recovery, includes thermal oxidation and catalytic reaction steps. In this process high sulfur recovery can not be achieved because of equilibrium limitations in catalytic reaction step. However, in a single step selective catalytic oxidation of H2S, there is no equilibrium limitation. In this study, development of active and selective catalyst for selective oxidation of H2S to elemental sulfur was investigated.Catalysts containing Ni, V and Ce were synthesized by the complexation method (Ni-O, Ni-V, Ni-Ce) and by impregnation of both these metals into MCM-41 material (Ni@MCM-41, Ni-V@MCM-41, Ni-Ce@MCM-41, Ce-V@MCM-41). Equimolar ratio of metals was used for all mixed metal oxides and total metal concentration was kept as 15% wt in MCM-41 supported catalysts. Ce-V@MCM-41 catalysts at different metal concentrations (10% and 20%) were also prepared. Catalysts synthesized in this work were characterized by XRD, BET, Hg-porosimeter, SEM, EDS, TPR and XPS measurements. XRD patterns of Ni-V catalyst prepared by the complexation method showed Ni2V2O7 crystalline phase while there was no peak corresponding to Ni and V metals in Ni-V@MCM-41 catalyst. BET surface areas of the catalysts prepared by the complexation method between 7-45 m2/g. In the case of MCM-41 supported catalysts, surface areas were significantly increased (ten times higher than the catalysts prepared by the complexation method). In the last step of this study, catalytic activities of Ce-V@MCM-41 catalysts in the selective oxidation of H2S were tested in a fixed bed reactor at temperatures between 200-300 0C. Ce-V(15)@MCM-41 catalyst was found to be the most active catalyst at 250 0C. XRD patterns of Ce-V(15)@MCM-41 catalyst showed that there was no change in CeVO4 crystal form of this catalyst after the oxidation reaction.