High-efficiency co-liquefaction of brominated epoxy resin and low rank coal in supercritical water: Waste recycling and products upgrading

Abstract

With the acceleration of upgrading electronic information products, a large amount of electronic waste was generated. Brominated epoxy resins (BERs) are the main nonmetallic components of e-waste. The recycling of BERs has attracted people's attention due to their potential environmental risks. Low rank coal is difficult to efficiently utilize due to its high moisture content, oxygen content and low calorific value. This study developed an efficient co-liquefaction strategy for BERs and low rank coal by supercritical water (SCW) process. Under optimized conditions (temperature of 425 °C, reaction time of 60 min, solid-to-liquid ratio of 1:10 g/mL, and BERs-coal mass ratio of 1:4 g/g), the total conversion efficiency of co-liquefaction reached 56.76 %. When the temperature was 325–425 °C, there was a positive synergistic effect between BERs and low rank coal co-liquefaction, and the highest synergy efficiency of 11.13 % was reached at 400 °C. The introduction of BERs could significantly reduce the oxygenated compounds and the heteroatomic compounds in the liquefied oil products, improving the quality of oil products. The co-liquefaction promoted the production of phenolic chemicals and inhibited the cross-linking reaction of the decomposition products from low rank coal, and realized the synchronous conversion of BERs and low rank coal. The C-Br bond in the residue was significantly weakened after co-liquefaction. The oil products did not contain brominated organic compounds, also demonstrating the potential of the co-liquefaction process for debromination of BERs.