MAl-CO3 based layered double hydroxides for catalytic depolymerization of poly (ethylene terephthalate) and poly(bisphenol A carbonate) waste materials

The study emphasizes upon the sustainable way to design an efficient, stable, ecofriendly and recyclable catalyst approach for PET and PC waste glycolysis into value added products. The metal-based catalytic materials promote various mechanisms of glycolysis reaction. The easily produced, extensive, low-priced, green and highly active catalytic materials have been evaluated for the chemical degradation/ recycling of plastic into monomers and valuable chemicals. In this study, the layered double hydroxides (LDHs) composed of different metals ions (M = Zn, Mn, Pb, Cd, Mg, Ni, Co, Ca, Cu) as MAl-CO3 have been synthesized because of the potential applications of these anionic synthetic clay materials with their specific properties including tailored acidic and basic sites, adsorbent-specific behaviour, anion exchangeability, tuneable metal composition, biocompatibility, layered structure and catalytic properties. The structural parameters and characterization of LDHs synthesis were confirmed on the basis of the results obtained by XRD, SEM-EDX and FTIR analysis of these synthesized clays. Besides, Catalytic depolymerization of PET and PC waste was accomplished using MAl-CO3 based layered double hydroxides (LDHs) and ethylene glycol into BHET and bisphenol A. The characterization of isolated products[bis(2-hydroxyethyl terephthalate) (BHET) and bisphenol A (BPA)] was carried out using NMR, mass spectrophotometry, FTIR and Thin layer chromatography analysis. The catalytic performance of LDHs combinations was observed as Zn > Mn > Li, Pb > Cd > Mg > Ni > Co > Ca > Cu for PET while only ZnAl-CO3 LDH displayed catalytic activity for PC degradation yielding BHET (79.34%) and BPA (89.07%) respectively.