Selective upcycling of brominated epoxy resin by subcritical water ammonia process with waste copper-based catalyst: Production of high purity methyl pyrimidine/phenols and copper recovery

• We report a selective SWA upcycling of TBBPAER with waste copper-based catalyst. • 61.32 % of TBBPAER could be selectively upcycled at 300 °C for 15 min. • High value-added methylpyridine with a 90 % of purity could be obtained. • 80.0 % of the copper could be recovered from waste copper-based catalyst. • The SWA reaction mechanism of TBBPAER and waste copper-based catalyst was proposed. Tetrabromobisphenol A epoxy resin (TBBPAER) is the main non-metallic component of electronic waste. The scale of electronic waste production and the accompanying TBBPAER waste disposal problems represent a great opportunity for chemical upcycling. But the chemical upcycling of TBBPAER faces great challenges due to its high bromine content and thermally stability. In this study, a subcritical water ammonia (SWA) process combined with waste copper-based catalyst (WCC) selectively converted TBBPAER in high yields (63.46 % at 300°C for 15 min and 73.66 % for 60 min) to low molecular-weight liquid products including high value-added methyl pyrimidine and phenols. The electron transfer among multivalent copper species contained in the WCC promoted the production of free radicals OH, O 2 − , NH 2 , and :NH, which resulted in the efficient conversion of TBBPAER and a 99.29 % of debromination ratio. The molecular chain of TBBPAER was snipped by OH and NH 2 to produce tetrabromobisphenol A groups (TAG) and ternary carbon groups (TCG). The further degradation of TAG resulted in the producing of phenol chemicals with a purity of 91.8 % (GC peak area%). The further cyclization of TCG induced by :NH produced methyl pyrimidine with a purity of 91.9 % (GC peak area%). The formation of copper ammonia complex led to the leaching/recovery of 86.6 % of copper from the WCC. The SWA-WCC approach demonstrated how TBBPAER waste could be a viable feedstock for the producing of high value-added methyl pyrimidine and phenol chemicals. This study provided a novel sustainable strategy for synchronous treatment/upcycling of the two different wastes of TBBPAER and WCC. The leaching toxicity test of Cu and Zn for the solid residue after the co-treatment showed that their leaching concentrations were much lower than the hazardous waste standard.