Thesis (M.Sc.)--Chulalongkorn University, 2005

In this work, the oxidation of sulfur model compounds catalyzed with vanadium containing catalysts were studied. The sulfur compounds studied are: benzothiophene, dibenzothiophene, 4,6-dimethyldibenzothiophene that are typical refractory sulfur compounds in diesel fuels. The catalysts [W6O19]2-, [V(VW11 )O40]4-, [PVM11O40]4-, [PVMo10O40]4- and (VO)2P2O7 were prepared and characterized by FT-IR, UV-Vis and XRD. The experimental results show that vanadium containing catalysts catalyze the conversion of sulfur compounds to sulfone and the reactivity order of the catalyst is: [V(VW11)O40]4- > [W6O19]2- > [PVW11O40]4- ~ [PVMo10O40]4- > (VO)2P2O7. Parameters affecting the reaction were investigated: solvent, amount of catalyst, amount of oxidizing agent, addition of acetic acid and temperature. When the mole ration of [AcOH]/H2O2] was increased up to 1.5, the oxidiation activity was increased. Apparent activation energies of dibenzothiophene, 4.6 dimethyldibenzothiophene and benzothiophene oxidation were 52.83, 57.35 and 62.73 kJ/mol, respectively, which related to the reactivity of dibenzothiophene > 4,6- dimethyldibenzothiophene > benzothiophene. The removal of oxidized sulfur by combining extraction and adsorption became more effective. The results show that the catalysts can reduce the sulfur content of diesel fuels from 0.575 wt% to 0.055 wt%.