Thermal regeneration characteristics of titanium isopropoxide-modified TiO 2 for the removal of environmentally hazardous NO x in iron ore sintering process

The deactivation and thermal regeneration characteristics of a V 2 O 5 -WO 3 /TiO 2 catalyst modified with titanium isopropoxide (TTIP) were investigated after it was applied for 2,400 h at 240 °C in a selective catalytic reduction (SCR) pilot plant to purify the exhaust gas from an iron ore sintering process in steelworks. Evolved gas analysis/mass spectrometry (EGA/MS) analysis was adopted to determine the temperature for thermal regeneration, and thermal treatment was performed at the determined temperature for 3 h in a N 2 atmosphere. The catalysts (Fresh catalyst: N-Cat, used catalyst: U-Cat, and thermally regenerated catalyst: R-Cat-X (X is thermal regeneration temperature)) were analyzed by elemental analyzer, X-ray fluorescence (XRF, component analysis), Brunauer-Emmett-Teller (BET, specific surface area and porosity), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS, surface micro-structure and components), X-ray diffraction (XRD, crystalline structure), and Fourier-transform infrared (FT-IR, surface functional group). Thermal regeneration of catalyst was evaluated by NO x removal efficiency, depending on the regeneration temperature. It was found that the deactivation of the catalyst occurred due to the reduction of specific surface area and porosity by ammonium (bi)sulfate (AS or ABS). The NO x removal efficiency of the R-Cat-400 and the R-Cat-500 reached to 98.5% and 99.1%, respectively. Due to the breakdown of AS and ABS during the thermal regeneration, those results were quite similar to those of the N-Cat. Although the NO x removal efficiency of the R-Cat-500 was higher than that of the R-Cat-400, the temperature for thermal regeneration needs to be determined under consideration of the emission of high concentration of SO 2 emitted during thermal regeneration.