Facile modification of cobalt ferrite by SiO 2 and H‐ZSM‐5 support for hydrogen and filamentous carbon production from methane decomposition

Abstract

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.