Tar induced deactivation and regeneration of a commercial V2O5-MoO3/TiO2 catalyst during selective catalytic reduction of NO with NH3

Abstract

Tar species on catalyst’s surface promote the deposition of NH4HSO4/(NH4)2SO4 leading to the complete deactivation of V2O5-MoO3/TiO2 catalyst utilized in a glass kiln. The proposed pyrolysis method in this work effectively removes the poisoning substances. TG-IR and TG-MS results indicate that the pyrolysis products are mainly CO2 and SO2 representing the pyrolysis of tar species and NH4HSO4/(NH4)2SO4. The heating rate and pyrolysis temperature are the critical factors to keep a superior mechanical property. The axial and transverse compressive strength remained 1.77 MPa and 0.53 Mpa falling only by 4.8% and 13.1% respectively through the optimized treatment at 420 °C for 2 h with heating rate of 3 K min−1. The characterizations indicated that the surface area, pore volume and acid property were apparently restored after the heat treatment. As a result, the regenerated powder catalyst showed 100% NO conversion and more than 94% N2 selectivity at 250 – 300 °C and the regenerated honeycomb catalyst exhibited 91.6% NO conversion at 260 °C. The TPR and XPS results indicated changes of the redox behavior, which contracted the temperature range of excellent performance. Typically, the redox cycles shifting to high temperatures narrowed this temperature range, while the excessive oxidation ability decreased the N2 selectivity. The schematic of tar induced deactivation and regeneration was proposed. Overall, the tar induced deactivated catalyst was successfully regenerated by proper pyrolysis and can be reutilized in the original glass kiln at 260 °C.