Facile modification of cobalt ferrite by SiO₂ and H-ZSM-5 support for hydrogen and filamentous carbon production from methane decomposition

In this work, new catalyst composed of cobalt ferrite CoFe₂O₄ supported on amorphous silica (SiO₂) and zeolite (H-ZSM-5) were prepared using impregnation method with loading ratio 1:1. The catalytic activity of the new 50 wt% CoFe₂O₄/SiO₂ and 50 wt% CoFe₂O₄/H-ZSM-5 catalysts were evaluated for direct methane decomposition to hydrogen production at fixed operating temperature of 800°C. The physiochemical properties of the fresh and spent catalysts were characterized by several techniques such as scanning electron microscope (SEM), X-ray diffractometer (XRD), Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy (XPS), thermogravimetric (TGA), and Raman spectroscopy. The CoFe₂O₄/H-ZSM-5 catalyst exhibited higher activity and stability than CoFe₂O₄/SiO₂ catalyst. Maximum methane conversion reached 37.35% and hydrogen formation rate of 76.48 × 10⁻⁵ mol H₂ g⁻¹ min⁻¹ at time on stream (TOS) of 300 min for CoFe₂O₄/H-ZSM-5, while its 5.80% with 15.82 × 10⁻⁵ mol H₂ g⁻¹ min⁻¹ at TOS of 30 min. The XRD, Raman, and XPS results confirm the presence of CoFe₂O₄ particles on the CoFe₂O₄/H-ZSM-5 catalyst surface, while the CoFe₂O₄ particles partially shield with SiO₂ in CoFe₂O₄/SiO₂ catalyst. SEM images of spent catalysts elucidated the formation of filamentous carbon which indirectly confirm the higher distribution of CoFe₂O₄ in CoFe₂O₄/H-ZSM-5 than that of CoFe₂O₄/SiO₂. The deposited carbon on spent CoFe₂O₄/H-ZSM-5 catalyst was evaluated using TGA, which was found to be ca. 50 wt%. Highlights: CoFe₂O₄/SiO₂ and CoFe₂O₄/H-ZSM-5 catalysts synthesized and characterized by various techniques. H-ZSM-5 and SiO₂ support material were found strongly affects the physiochemical properties and the methane decomposition activity of CoFe₂O₄ catalyst. CoFe₂O₄/H-ZSM-5 catalyst performance reached 37.4% and the hydrogen formation rate was 76.5 × 10⁻⁵ mol H₂ g⁻¹ min⁻¹. CoFe₂O₄/SiO₂ catalyst demonstrated a negligible activity toward methane cracking and producing hydrogen. The estimated deposited carbon on the spent catalysts were 1 wt% and 50 wt% for CoFe₂O₄/SiO₂ and CoFe₂O₄/H-ZSM-5, respectively.