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  • Co-production of carbon nan...
    Yang, Ren-Xuan; Wu, Shan-Luo; Chuang, Kui-Hao; Wey, Ming-Yen

    Renewable energy, October 2020, 2020-10-00, Volume: 159
    Journal Article

    This study aims to develop a two-stage fluidized catalytic bed reactor system for continuous co-production of carbon nanotubes (CNTs) and hydrogen from waste plastics gasification. Ni/Al-SBA-15 and Ni–Cu/CaO–SiO2 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 C2–C5 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 H2 production rate showed a significant increase to 857.6 mmol/h-g catalyst with the assistance of Ni–Cu/CaO–SiO2 in the second-stage reactor. The produced smaller-molecule hydrocarbons from the second-stage reactor with higher temperatures could benefit the co-production of CNTs and hydrogen. The two-stage fluidized catalytic bed gasification system exhibited an optimal performance of high fraction CNTs and H2 when temperatures of first- and second-stage reactor were controlled at 600 and 800 °C, respectively, with 0.1 ER. Display omitted •A two-stage fluidized catalytic bed is developed to produce carbon nanotubes and H2.•Ni/Al-SBA-15 and Ni–Cu/CaO–SiO2 were granulation to use in the pilot-scale system.•Ni/Al-SBA-15 and Ni–Cu/CaO–SiO2 highly enhanced carbon nanotubes and H2 production.•Operating parameters of the fluidized bed were evaluated for catalytic performance.•The system gave 857.6 mmol H2/h-g catalyst and carbon nanotubes fraction of 48.0%.