Catalytic wet oxidation of ethylene glycol: kinetics of reaction on a Mn–Ce–O catalyst

Abstract

Wet oxidation (WO) is an ambitious key technology looking for the treatment of different industrial effluents, safeguarding environmental problems. Ethylene glycol (EG) has been found to be a refractory compound. Different heterogeneous catalysts in slurry conditions using a high-pressure batch reactor at 160–220 °C and 15–25 bar of oxygen partial pressure were studied for enhancing WO efficiency. The activity of commercial catalysts (Pt/Al 2O 3, CuO–ZnO/Al 2O 3, CuO– MnO x / Al 2 O 3 , Fe 2 O 3 – MnO x and CuO– MnO x ) was compared with the one related to various catalysts prepared in our laboratory (Ag–Ce–O, Mn–Ce–O and Ce–O). The Mn–Ce–O catalyst showed very high activity in terms of total oxidation of EG as well as total organic carbon reductions (up to 99.3%). Formic acid was identified as the only intermediate compound and the pH evolution was related with its formation/oxidation. Kinetic studies revealed activation energies of 31.8 and 45.0 kJ/mol concerning the two step mechanism of EG degradation by means of Mn–Ce–O. The catalyst stability was observed in terms of metal leaching and carbon adsorption, and its texture and morphology were analyzed by SEM, TEM, EDXS and SAED. Whiskers of MnOOH and/or β - MnO 2 were detected.