Research On Low-temperature Mn-based DeNOx Catalyst

NOx has become China's first large acidic gas pollutants.NOx can cause human respiratory system disease,photochemical smog,acid rain and haze.At present,the method of removing NOx which is the most commonly used is NH₃-SCR,and the key is the development of deNOx catalyst.The focus of this paper is to develop a kind of low temperature deNOx catalyst which is used for coal fired boiler exhaust.In this paper,the inlet gases were composed of 500 ppm NO,500 ppm NH₃,3%volume fraction of oxygen,and the rest was N₂,and the airspeed was 20000h^-1.First we used?-Al₂O₃ as carrier,and found that the best loading proportion is 10%.wt MnO₂ and the calcination temperature is 500?.Ce-doped manganese-based catalysts increased low-temperature deNOx activity.When Mn:Ce=4:1?molar ratio?,the deNOx efficiency was the best relatively.Also we found that with ZrO₂ doping into carrier more and more,the low-temperature deNOx activity is better and better.When the carrier was ZrO₂,the catalyst had the best low-temperature deNOx activity of all.The deNOx efficiency could reach100%when the temperature was 90?,and the deNOx efficiency could up to 90%between 80?and 220?and had the highest NOx conversion rate which is99.9%.Stability experiments showed that the Mn-Ce/ZrO₂ catalyst has good activity stability,but its anti-SO₂ performance was poor.Ce-ZrO₂ carrier is a three-way catalyst which is commonly used.In this paper,we made Ce-ZrO₂?Ce-TiO₂?Ce-SiO₂?Ce-Al₂O₃ carrier using the co-precipitation method,and then loaded 10%.wt MnO₂ using the impregnation method.We found that the Mn/Ce0.5Zr0.5 catalyst has the best low-temperature deNOx activity.The deNOx efficiency could up to 90%between 90?and 210?and had the highest NOx conversion rate which is 99.4%.It had the nearly same low-temperature deNOx activity as the Mn-Ce/ZrO₂ catalyst.Stability experiments showed that the Mn/Ce0.5Zr0.5 catalyst has good activity stability too,and its anti-SO₂performance was better than Mn-Ce/ZrO₂ catalyst.In this paper,we made 3mm cylindrical deNOx catalysts and investigated the influence of the preparation process on the performance of the catalysts.When the glue solvent was 0.07 nitric acid?the mass ratio between the glue solvent and the special pseudo boehmite?,the catalyst had the best low-temperature deNOx activity,but its deNOx activity was lower than the powdery catalyst.After the ZrO₂ added to the carrier,the average side crush strength of the catalyst had increased,but the low temperature deNOx ability only enhanced to a limited extent,we also need to modify the forming catalysts in the following work.