Screening non-noble metal oxides to boost the low-temperature combustion of polyethylene waste in air

Abstract

Globally, the efficient utilization of polymer wastes is one of the most important issues for current sustainable development topics. Herein, a green and efficient low-temperature combustion approach is proposed to deal with polymer wastes and recover heat energy, simultaneously alleviating the environment and energy crisis. Non-noble metal oxides (Al2O3, Fe2O3, NiO2, ZrO2, La2O3 and CeO2) were prepared, characterized and screened to boost the low-temperature combustion of polyethylene waste at 300 °C in air. The mass change, heat release and COx formation were studied in details and employed to evaluate the combustion rate and efficiency. It was found that CeO2 significantly enhanced the combustion rate and efficiency, which was respectively 2 and 7 times that of non-catalytic case. An interesting phenomenon was observed that the catalytic performance of CeO2 in polyethylene low-temperature combustion was significantly improved by the 7-day storage in the room environment or water treatment. XPS analysis confirmed the co-existence of Ce3+ and Ce4+ in CeO2, and the 7-day storage and water treatment promoted the amount of Ce3+, which facilitated the formation of the oxygen vacancies. That may be the reason why CeO2 exhibited excellent catalytic performance in polyethylene low-temperature combustion.