Effects of Nickel Species on Ni/Al2O3 Catalysts in Carbon Nanotube and Hydrogen Production by Waste Plastic Gasification: Bench- and Pilot-Scale Tests

Upcycling waste plastics into carbon nanotubes (CNTs) and hydrogen is attractive for its efficient disposal. Although Ni-based catalysts are typically used in both hydrogen production and CNT synthesis, few studies have investigated the catalytic active site for the co-production of CNTs and hydrogen by waste plastic gasification. To evaluate the effect of nickel species distribution of the Ni/Al2O3 catalyst, it was prepared by an impregnation method using different calcination atmospheres to determine their feasibility for the co-production of CNTs and hydrogen. For comparison, various Ni/Al2O3 catalysts for CNT growth were examined by CH4 thermal chemical vapor deposition (CVD). Ni/Al2O3 calcined under a reductive H2 atmosphere (H–Ni/Al2O3) gave smaller nickel nanoparticles containing metallic nickel species, which showed optimal performance for CNT and hydrogen co-production by waste plastic gasification. In addition, the quality of the CNTs was higher using this process compared to the CNTs synthesize...