Cascade upcycling polystyrene waste into ethylbenzene over Fe2N @ C

Thermochemical conversion is one of the most effective ways to upcycle organic solid wastes into fuels and/or value-added chemicals. In this study, the tandem hydropyrolysis/hydrocracking of polystyrene (PS) to produce ethylbenzene was studied using metal nitrides as catalysts. Fe, N co-doped carbon-based catalyst (Fe2N @ C) with core-shell structure was synthesized. The experimental results showed that carbon doping significantly improved the catalytic performance of iron nitride. The yield of ethylbenzene obtained from Fe2N @ C catalysis was 81 wt%, which is much higher than that of Fe2N (63.3 wt%) and commercial iron nitride (FeN, 4.9 wt%) under the hydropyrolysis temperature of 480 ℃, hydrocracking temperature of 280 ℃, and low H2 pressure of 0.2 MPa. The high catalytic activity of Fe2N @ C is ascribed to the synergy of metal-based selective hydrogenation and acid site-mediated C-C bond activation. This work provides a flexible and efficient catalytic technology for the high-value utilization of polystyrene waste.