Microwave-assisted chemical looping gasification of plastics for H2-rich gas production

Abstract

Microwave-assisted heating coupled with chemical looping gasification was first proposed for the recycling of plastics into H2 rich gas, achieving a hydrogen conversion efficiency of up to 84.3 %. In the experiment, plastic was initially decomposed into hydrocarbon volatiles, followed by the gasification reactions in the presence of an oxygen carrier under vacuum conditions for 10 min. Subsequently, air was introduced for wax removal and oxygen carrier recovery for another 10 min. This study evaluated the chemical looping gasification performances of polypropylene using oxygen carriers NiaFebOx with different Ni/Fe molar ratios (0, 1:40, 1:20, 1:10, 3:20, and 1:5). NiFe20Ox showed the highest gas yield of 81.3 mmol/gPP with an H2 yield of 46.0 mmol/gPP. Among different microwave powers (590 W, 690 W, 790 W, 890 W, and 990 W), 890 W was identified as the ideal microwave power for maximum gas yield and H2 yield. Microwave-assisted heating exhibited high efficiency, achieving a heating rate of 450°C/min at 890 W, with the microwave oven consuming only 0.182 kWh of electrical power during the entire experiment. In the chemical looping gasification of various plastics (polypropylene, high-density polyethylene low-density polyethylene, polystyrene, and plastics mixture) over NiFe20Ox under 890 W microwave power, polypropylene yielded the highest gas and H2 production. This study provides a novel approach for efficiently recycling plastics, alleviating environmental pollution and contributing to energy sustainability.