Oxidation of Thiophenes over Silica Gel in Hydrogen Peroxide/Formic Acid System

Abstract

Thiophene (C 4H 4S) and 3-methylthiophene(3-MC 4S) are typical thiophenenic sulfur compounds that exist in fluid catalytic cracking (FCC) gasoline. Oxidation of C 4H 4S and 3-MC 4H 4S were conducted in hydrogen peroxide (H 2O 2) and formic acid system over a series of silica gel loaded with metal oxide. The silica gel loaded with copper and cobalt (1:1) oxide was found very active for the model compound oxidation using H 2O 2/formic acid, while the silica gel unloaded with metal oxide was less active. The sulfur removal rate of thiophenes was different as solvent was changed. And the conversation of C 4H 4S and 3-MC 4H 4S was improved at higher temperature, but reduced when olefin was added. The sulfur removal rate of model sulfur compounds was enhanced when the phase transfer catalyst emulsifier polyethylene glycol octyl phenyl ether or tetrabutylammonium bromide(TBAB) was added. The sulfur removal rate of simulated gasoline containing 524μg·ml −1 sulfur reached 90%. Interestingly, in a H 2O 2 and formic acid system with the addition of TBAB, a bromine substitution trend appeared in the oxidation of thiophenes, suggesting the influence of TBAB.