Influence of TiO₂-supports on the catalytic properties of catalyts for De-NO_x in flue gas

Nano-TiO₂ and industrial grade-TiO₂ were selected and used as supports of catalysts for De-NO_x in flue gas. V₂O₅ and WO₃ were impregnated onto supports TiO₂ to obtain the active components 1%V₂O₅-10%WO₃/ TiO₂ of the commercial catalysts, which were used for the removal of NO_x in flue gas. The allowed gas hourly space velocity(GHSV) of the catalyst supported on nano-TiO₂ is much higher than that of the catalyst supported on industrial grade-TiO₂. The NH₃/NO molar ratio(≥1.0) almost has no effect on the NO_x conversion of catalyst supported on nano-TiO₂, and a complete conversion of NO_x can be achieved with the NH₃/NO molar ratio=1.2 in the range of 300~350°C. While the NO_x conversion of the catalyst supported on industrial grade-TiO₂ reduces significantly with the GHSV increase or the NH₃/NO molar ratio decrease. Under the same GHSV(7500 h?1) and NH₃/NO molar ratio (1.0), the NO_x conversion of catalyst supported on nano-TiO₂ reaches almost 100%, while the maximum NO_x conversion of catalyst supported on industrial grade-TiO₂ is only 85% at 400°C. Besides, the catalyst supported on nano-TiO₂ has broader De-NO_x temperature window. The supports and catalysts were characterized by scanning electron microscope (SEM), N₂ adsorption/desorption, X-ray diffraction (XRD), temperature-programmed desorption for ammonia(NH₃-TPD), and particle size analysis. The results show that the specific surface area, pore volume and surface acidity of the catalyst supported on nano-TiO₂ are far larger than those of the catalyst supported on industrial grade-TiO₂.