Roles of Ce0.8Zr0.2O2 Catalysts in Boosting the Efficient Combustion of Waste Plastics

Abstract

Because of superior oxygen storage and release capability, Ce-based catalysts were widely used in the oxidation reaction, while seldomly mentioned in waste plastics combustion. Herein, Ce_0.8Zr_0.2O₂ catalysts were prepared by the complexed hydrothermal method (CeZr(C)), oxalic acid gel method (CeZr(O)), and hydrothermal method (CeZr(N)); and then, used in PE (polyethylene) combustion. Compared with PE noncatalytic combustion that exhibited an initial combustion temperature of 269 °C, CeZr(C) slightly reduced the initial combustion temperature to 263 °C, while CeZr(N) and CeZr(O) significantly reduced the initial combustion temperature to 245 and 251 °C, respectively. It was deduced that the activity of CeZr(N) and CeZr(O) in PE catalytic combustion was significantly higher than that of CeZr(C). Based on the systematic characterization, two reaction mechanisms were proposed to explain the excellent performance of CeZr(O) and CeZr(N) in PE combustion: (1) Because of the abundant surface area and O₂ adsorption, CeZr(O) enhanced the activation of molecular oxygen and the formation of active oxygen, which was easier to attack C─C/C─H bond and initiate PE combustion than molecular oxygen. (2) Because of the strong acidity, CeZr(N) enhanced the activation of C─C/C─H bond in polymer molecules, which benefited the attack of molecular oxygen, and reduced the reaction temperature.