Co-production of carbon nanotubes and hydrogen from waste plastic gasification in a two-stage fluidized catalytic bed

This study aims to develop a two-stage fluidized catalytic bed reactor system for continuous coproduction of carbon nanotubes (CNTs) and hydrogen from waste plastics gasification. Ni/Al-SBA-15 and NieCu/CaOeSiO(2) catalysts have been synthesized and granulated for CNTs synthesis and hydrogen production in the first- and second-stage reactor, respectively. The operating parameters, including reaction temperature and equivalence ratio (ER), were investigated to confirm the feasibility for CNTs and hydrogen production of this system. The Ni/Al-SBA-15 added in the first-stage reactor enhanced the waste plastics degradation to produce CH4 and C-2-C-5 hydrocarbons with increasing temperature, which could be used as the source for CNTs synthesis. Lowering the ER promoted the catalytic thermal cracking and reforming of hydrocarbons that contributed to the CNTs and hydrogen production. Nevertheless, the H-2 production rate showed a significant increase to 857.6 mmol/h-g catalyst with the assistance of NieCu/CaOeSiO(2) in the second-stage reactor. The produced smallermolecule hydrocarbons from the second-stage reactor with higher temperatures could benefit the coproduction of CNTs and hydrogen. The two-stage fluidized catalytic bed gasification system exhibited an optimal performance of high fraction CNTs and H-2 when temperatures of first- and second-stage reactor were controlled at 600 and 800 degrees C, respectively, with 0.1 ER. (C) 2020 Elsevier Ltd. All rights reserved.