Hydrogen production from catalytic gasification of waste wood–plastic composite using Ni-based catalysts supported on low-cost materials

Abstract

In this study, the catalytic potential of low-cost materials (i.e. olivine, dolomite, and red mud (RM)) for H₂-rich gas generation through the air gasification of wood–plastic composite (WPC) was investigated. Among the low-cost materials, the use of RM resulted in the maximum H₂ selectivity (25.81 vol%) and gas yield (65.80 wt%). This is attributed to the effect of Fe₂O₃ content in RM, which induced the formation of oxygen vacancies, enhancing coking resistance, and stimulating water–gas shift reaction during the gasification process. Using RM, increasing the temperature from 700 to 800 °C enhanced the gas yield and H₂ selectivity due to the promotion of endothermic dry- and steam-methane reforming reactions. Increasing the equivalence ratio in the range of 0.2 to 0.3 decreased the H₂ selectivity while promoting the gas and CO₂ production because of strengthened oxidation reactions which is undesirable for H₂-rich gas production. Further, loading 10 wt% Ni and the addition of promoters increased the gas yield along with H₂ and CO selectivities, in particular, 5 wt% Ca-10 wt% Ni/RM catalyst showed the highest gas yield (77.72 wt%), and H₂ selectivity (37.49 vol%). This suggests that the combined effects of Ni and promoters enhanced the activity, selectivity, and stability of catalyst for H₂ production. Overall, air gasification using promoted Ni-based catalysts supported on low-cost materials like RM as a catalyst can provide a new technology to convert WPC into a more useful and high-energy density substance such as H₂-rich gas.