Sulfur removal in coal tar pitch by oxidation with hydrogen peroxide catalyzed by trichloroacetic acid and ultrasonic waves

Abstract

A procedure for the desulfurization of coal tar pitch (CTP) by oxidation with hydrogen peroxide (H2O2) was developed, in which trichloroacetic acid (TCA) was used as a catalyst combined with ultrasonic waves. For comparison, the effects of H2O2 combined with different catalysts on sulfur removal were also investigated. The oxidative system composed of H2O2 and TCA is highly effective for sulfur removal from CTP. The reaction conditions such as type of solvent used, temperature, and CTP-to-TCA ratio considerably influence sulfur removal when the same oxidant is used. The desulfurization efficiency for CTP with 0.9wt.% sulfur content reaches 91.1wt.% at a xylene-to-CTP volume ratio of 2.5, a CTP-to-TCA mass ratio of 0.5, an ultrasonic treatment duration of 60min, a reaction temperature of 70°C, and with an extraction liquid containing methanol and sodium hydroxyl. The experiment confirms that the addition of surface active agent has no beneficial effect on sulfur removal.