Efficient Closed-Loop Recycling of Polyurethane Plastic Over Binuclear Metal Catalysts Through Microwave Catalysis

Abstract

AbstractIn this study, several binuclear metals(II) complexes M2L(NO3)2 (M2=Co2, Ni2, Cu2, Zn2) with advanced catalytic activity were synthesized through a simple, low-cost, and one-step method, characterized by high-resolution mass spectrometry and X-ray single-crystal diffraction analysis. Results indicate the sequence of catalytic activity follows the Lewis acid strength of divalent metal ions and electronegativity order: Zn2(II) > Cu2(II) > Ni2(II) > Co2(II), among which Zn2L(NO3)2 catalyst exhibits superior polyurethane alcoholysis performance and reaches up to 48.52 gpu·h-1·gcat-1, which the mechanism of alcoholysis was explained by theoretical calculation. Significantly, the energy consumption of microwave catalysis can greatly save about 33.9% compared with conventional thermal catalysis under the same reaction conditions, demonstrating an energy-efficient catalytic depolymerization method. Besides, the polyol obtained from polyurethane depolymerization can be re-polymerized to polyurethane plastic, allowing the circular utilization of polyurethane plastic waste. Therefore, this work presents an energy-efficient and viable solution for polyurethane waste sustainable management.

Keywords: Keywords: Polyurethane, Microwave, Alcoholysis, Polyol, Regeneration