Glycolysis of Polyethylene Terephthalate by BiOCl Nanoplates: Synergy of Surface Hydroxy Groups, Facets, and Lewis Acid Sites.

Accumulation of waste plastics on the earth's surface is a global challenge. There is a possibility of turning this challenge into an opportunity by plastic upcycling. In this work, the potential of bismuth oxychloride (BiOCl) as a heterogeneous catalyst for the glycolysis of polyethylene terephthalate (PET) is reported. Among the catalysts prepared, Bi-Co nanoplates showed the highest PET conversion and bis(2-hydroxyethyl) terephthalate (BHET) yield. Main reasons for the enhanced catalytic activity are the presence of more surface hydroxyl groups, exposed 001 crystal facets, and abundant Lewis acidic sites (Bi³⁺). Further, the Response Surface Methodology (RSM) was used to assess the effectiveness of the synthesized catalyst. The regression model developed shows that the PET conversion and BHET yield are significantly affected by the amount of ethylene glycol, the reaction time, the reaction temperature, and the amount of catalyst. The BHET yield reaches 70.25% using Bi-Co catalyst under optimal conditions. The fundamental glycolysis mechanism and elements governing product selectivity toward BHET are established. A techno-economic analysis showed that BiOCl nanoplates are the ideal candidates for the large-scale glycolysis of PET. This work presents the immense potential of BiOX for thermal catalytic processes.