Synergetic effects of Al addition on the performance of CoFe2O4 catalyst for hydrogen production and filamentous carbon formation from direct cracking of methane

Abstract

Improving methane catalytic decomposition process was deemed an effective approach for hydrogen production. Here, a novel catalyst AlxCo1-xFe2O4 with a variable aluminum content was synthesized via a co-precipitation route for the direct cracking of methane. The catalytic activity of AlxCo1-xFe2O4 was performed in a fixed bed reactor at temperature of 800°C and 20 mL/min of fed gas. A sequence of characterizations, including SEM, BET, XRD, XPS, Raman and TGA for fresh and spent catalysts, was exploited to examine the influence of Alx content on the morphology, porosity, structure, chemical composition, and cation distribution of AlxCo1-xFe2O4. As the Alx content increased in AlxCo1-xFe2O4 their morphology became more fractal and decreased in particle size, lattice parameter, lattice size, while their pore surface increased. Further cation re-distributions from octahedral to tetrahedral sites as Fe3+ and Al3+ relocated in the Tetrahedral site and Oxygen lattice decreased as observed from Raman and XPS results. Catalytic activity studies showed that Alx content of 0.6 in AlxCo1-xFe2O4 lead maximum methane conversion up to ∼ 91.10 % and hydrogen formation rate of 1.780 ×10-3 mol H2 g-1 s-1. The catalytic activity behavior was explained in correlation with the characteristics of spent catalysts.