Oxidation of thiophenes over silica gel using hydrogen peroxide and formic acid

Thiophene (C4H4S) and 3-methylthiophene (3-MC4H4S) are typical thiophenenic sulfur compounds that exist in gasoline from the fluid catalytic cracking (FCC) process. C4H4S and 3-MC4H4S were oxidized on silica gel by hydrogen peroxide (H2O2) and formic acid. The silica gel loaded with copper and cobalt (1:1) was very active catalyst for the oxidation of these sulfur compounds, while the silica gel unloaded with metal was less active. Oxidation of these sulfur compounds was taken place under mild reaction conditions and high conversion was achieved by increasing the reaction time. The sulfur removal rate of C4H4S and 3-MC4H4S was enhanced when the emulsifier OP or tetrabutylammonium bromide (TBAB) was added. It is interesting to find that a bromine substitution appeared as TBAB was added in the oxidation system.