Homogeneous oxidation using an oil-soluble oxidant,tert-amyl hydroperoxide(TAHP),for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts.Dibenzothio-phene(DBT),benzothiophene(BT) and 4,6-dimethyl-dibenzothiophene(DMDBT),which are the refractory sulfur compounds for hydrodesulfurization(HDS),were employed as model substrates for a simulated diesel fuel.Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated.The mass conversion of DBT reached near 100% at 90°C and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h.It was further found that the activities of the model substrates decreased in the or-der of DMDBT>DBT>BT.In the flow oxidation using TAHP as the oxidant,mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity(WHSV) from 40 h-1 to 10 h-1.A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds,i.e.4,6,8-trimethyl-2-nonylene,and 2-methylnaphthalene did not affect the oxidation of DBT.Car-bazole had nearly no effect on the conversion of DBT using TAHP,but had some influence on the one using tert-butyl hydroperoxide(TBHP).The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500 μg·g-1.In the flow oxidation using TAHP as the oxidant,the concentration of DBT in model fuels was reduced from 500 μg·g-1 to 7.2 μg·g-1 at WHSV of 10 h-1,and then reduced to 3.8 μg·g-1 by adsorption of Al2O3. Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide (TAHP), for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts.Dibenzothio-phene (DBT), benzothiophene (BT) and 4,6 -dimethyl-dibenzothiophene (DMDBT), which are the refractory sulfur compounds for hydrodesulfurization (HDS), were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached 100% at 90 ° C and a TAHP / DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT> DBT> BT.In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity (WHSV) from 40 h-1 to 10 h-1 .A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, ie4,6,8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide (TBHP). The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500 μg · g -1. The flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg · g -1 to 7.2 μg · g -1 at WHSV of 10 h -1 and then reduced to 3.8 μg · g -1 by adsorption of Al2O3.