Mechanism for catalytic cracking of coal tar over fresh and reduced LaNi1-xFexO3 perovskite

Abstract

Efficient removal of tar at gas outlet is a challenge during COREX ironmaking process. The differences between fresh and reduced LaNi1-xFexO3 perovskite were investigated via catalytic cracking of coal tar at 700 °C. The total gas yield of fresh catalysts is generally higher than that of reduced ones. The reduced catalyst produced more tar and carbon deposition. While the fresh LaNi0.8Fe0.2O3 gave the highest total gas yield (34.8 mmol/gcoal) and H2 yield (20.9 mmol/gcoal), and the lowest tar production (0.05%) and carbon deposition (10.9%). The perovskite structure was destroyed after reduction and the metal in perovskite was reduced to load on the catalyst surface. Partial oxidation which produces CO and H2 mainly occurs in the catalysis of reduced perovskite. Complete oxidation which generates CO2 and water is the major catalytic route for fresh perovskite. Oxygen in perovskite will transfer from the bulk to the surface. Water in the product supplements oxygen for the perovskite to construct an oxygen transition cycle which can maintain the catalyst activity. Tar is decomposed by the oxygen in fresh perovskite structure. The high nickel content in perovskite could promote the oxidation of tar.