Solar pyrolysis of waste plastics with photothermal catalysts for high-value products

The photothermal catalytic pyrolysis of low-density polyethylene (LDPE) plastics has been investigated with bifunctional photo-thermo catalysts in a novel photothermal reaction system. Six kinds of catalysts were introduced and explored in an in-situ fixed-bed reactor under 500 °C heated by solar simulator. The results indicated that the hydrogen production and jet fuel selectivity of Ni-Ti-Al catalyst were 34 mol/kg and 80% respectively, which were significantly higher than 7 mol/kg and 38% of Ti-Al. Catalysts loaded with Ni exhibited strong selectivity for aromatic hydrocarbon, achieving 49.51% for Ni-Al and 53.46% for Ni-Ti-Al especially. In addition, Ni-Ti-Al led to high-quality filamentous carbon tubes in smaller diameter, which presented high thermal stability and graphitization. Bifunctional catalyst, especially Ni-Ti-Al possesses obvious photothermal catalytic performance, which is ascribed to relaxations of photogenerated inter- and intra-band electrons of plasmonic metal Ni and excellent carriers transfer capability of non-plasmonic semiconductor TiO2. The production of hydrogen and jet fuel from plastic by photothermal catalytic pyrolysis provides an environmentally friendly way for high-value-recycling of large amount of the waste plastics.