Oxidative desulfurization of middle distillate using ozone

Mixed gases of 1.83 vol% ozone in oxygen and 0.81 vol% ozone in air were prepared using an ozone generator in which oxygen and air were used as feed gases. Hydrodesulfulized light gas oil (HLGO), which contained 150 ppm dibenzothiophene (DBT) and 145 ppm 4,6-dimethyldibenzothiophene (4,6-DMDBT), was oxidized at 50 degrees C under atomospheric pressure by one of the feed gases bubbled through the oil in a batch reactor. Ozone is a highly reactive oxidant, and DBTs in HLGO were converted quantitatively to DBT sulfones. it was found that il,6-DMDBT was more readily oxidized than DBT. This indicated that methyl-substituted DBTs were converted more readily to DBT sulfones than DBT. The conversion of DBT slightly increased with addition of formic acid to HLGO. Further, in the reaction with 0.81 vol% ozone/air mixed gas, DBT conversion, which was similar to that with 1.83 vol% ozone/oxygen mixed gas was obtained when the reaction time was doubled. After such oxidation, heteroatom was oxidized, and eduction of gum containing a considerable amount (6.0%) was observed. The result of elemental analysis indicated that practically all of the heteroatom of the feed light gas oil was found in it.