The Influence Of TiO₂-supports On The Catalytic Properties Of Catalyst For De-NO_x And The Study On Deactivation And Regeneration Of The Catalyst

Selective catalytic reduction (SCR) is the mainstay for nitrogen oxides (NOx) removal from flue gas. The most important part of the SCR system is the catalyst. Currently the most widely used catalyst for commercial nitrogen oxides (NOx) removal is V2O5-WO3/TiO2catalyst. In this work, nano-TiO2and industuial grade-TiO2were selected and made into1%V2O5-10%WO3/TiO2catalysts by impregnation method. And the influence of TiO2-supports on the catalytic properties of catalyts was studied. Based on the nano-catalyst, alkali oxide(Na2O and K2O) and potassium salts(KCl and K2SO4) were doped on the fresh catalyst by impregnation method to achieve the poisoned catalysts. The effect of alkali oxide and potassium salt on deactivation of catalyst was researched. Different regeneration liquids(water,0.5mol/L sulfuric acid,1mol/L ammonium sulfate) were used to regenerate the poisoned catalysts. The main conclusions are as follows:(1) The gas hourly space velocity(GHSV) that the nano-catalyst allowed(7.5～100×103h-1) was much higher than that the industuial grade-catalyst allowed. The NH3/NO molar ratio(≥1.0) almost had no effect on the NOx conversion of nano-catalyst, and a complete conversion of NOx was achieved with the NH3/NO molar ratio1.2(GHSV=7.5×3h-1) in the range of300～500℃. While the NOx conversion of the industuial grade-catalyst reduced significantly, as the GHSV(7.5～15×10h-1) increased or the NH3/NO molar ratio decreased. Under the same GHSV(7500h-1) and NH3/NO molar ratio(1.0), in the range of300～500℃the NOx conversion of nano-catalyst reached almost100%, while the maximum NOx conversion of industuial grade-catalyst was only85%at400℃. Besides, the nano-catalyst had broader and more stable De-NOx temperature window.(2)The effects of the molar ratio of Na/V, K/V(0.5,1,2,3, and4) on NOx conversion of Na2O and K2O-doped catalysts were researched. It was found that with the increace of the molar ratio of Na/V and K/V, NOx conversion of the catalysts decreased. While the molar ratio of Na/V and K/V got4, in the whole temperature range (200～500℃) the highest NOx conversion of the catalysts respectively were 22.45%(350℃) and16.46%(200℃). And deactivation extent caused by K2O was much stronger than that caused by Na20. Different regeneration liquids(water,0.5mol/L sulfuric acid.1mol/L ammonium sulfate) were used to regenerate the poisoned catalysts. Regeneration effect of ammonium sulfate was the best on both the poisoned catalysts. With the regeneration temperature30℃and the regeneration time30min, NOx conversion of the poisoned catalysts recovered completely above300℃, and below300℃there was partial recovery.(3)Both KCl and K2SO4could inactivate the catalyst. As the molar ratio of K/V(0.5,1.2.3, and4) rised. the activity of the catalysts reduced. And deactivation extent caused by KCl was much stronger than that caused by K2SO4. Washing with water, sulfuric acid, ammonium sulfate could reactivate the poisoned catalysts, but ammonium sulfate reached the best effect. The activity of the poisoned catalysts recovered completely above300℃, and below300℃there was partial recovery.