Thermo-catalytic conversion of waste plastics into surrogate fuels over spherical activated carbon of long-life durability

Abstract

Recovery of value-added fuels or chemicals from waste plastics by pyrolysis is a promising way to eliminate the waste plastics accumulation and alleviate the energy crisis, while developing efficient catalysts of high durability remains a challenge. Herein, activated carbon spheres of various surface chemistry were fabricated and subsequently used in ex-situ catalytic pyrolysis of low-density polyethylene to produce jet fuel and gasoline-ranged hydrocarbons. Experiment results indicate that with the increase of activation time and temperature, the acidity of activated carbon increased slightly owning to the oxygen-containing functional groups increased, and the specific surface area reached the maximum value (707 m2/g) at the activation condition of 800℃ for 60 min. The enlarged specific surface area promotes the C-C bond cleavage that releases more small gases at the expense of liquid yield, and the increase in density of oxygen-containing functional groups and acidity boosts the formation of aromatic hydrocarbons in liquid. When the activated carbon spheres were activated at 800℃ for 80 min, 100% of the hydrocarbons in the liquid belonged to jet fuel and gasoline, and their selectivity was 81.70 area.% and 96.25 area.%, respectively. More importantly, the catalyst exhibits excellent catalytic activity after four reactivation cycles, where the quality of the liquid product is similar to or even better than that achieved by the fresh catalyst. Furthermore, the catalyst still showed excellent performance in the catalytic pyrolysis of waste plastic mixture.