Low Temperature Selective Catalytic Reduction(SCR) Of NO_x On Cerium-based Catalysts

NO_xis the main air pollutant of coal-fired power plants, which is one ofthe important reasons to cause pollution such as acid rain, photochemical smogand so on. Selective catalytic reduction process is the major technology forreducing NO_xemissions from coal-fired power plants. However, thecommerical vanaidia-based catalyst is active within a narrow temperaturewindow of300-400℃, easily to be deactived by SO₂in the flue gas. And theformation of N₂O and toxicity of vanadia cause secondary pollution. Therefore,it is of great importance to develop a new environmental-friendly catalyst forlow temperature SCR with high activity.CeO₂is an inexpensive and versatile light rare earth oxide. Due to its goodsulfur-resistance, excellent heat stability, high chemical activity, good oxidationand delivery capacity, CeO₂can change the dispersion of the active componenton the carrier and enhance the catalytic performance.This article focused on catalyst activity evaluation and SO₂poisoningexperiment of cerium-based catalysts, by use of the catalyst prepared withdifferent calcination temperatures, precursors and carriers.Thus it tried to findout catalyst structure characterized by BET, XRD, H₂-TPR, NH₃-TPD,XPS-findings that assisted to reveal mechanism of catalytic reaction and sulfurresistance in the hopes of a reference for the industrialization application of thenew SCR catalysts.The prerequisite of multi-phase-catalyzed reaction was chemisorptionprocesses. Thus, chemisorption property and reaction mechanism of NO in thelow temperature SCR catalysts were studied using quantum chemistrycalculation to expound their function in the reaction, finally the microscopicprocess and the mechanism were revealed.Reacrch showed the catalyst which used cerous nitrate as the Ce precursor,prepared at350℃for6h,with sol-gel method had high catalytic activity and good SO₂resistance.Al₂O₃as a catalyst carrier had high dispersion degree ofactive components,strong binding energy of adsorption and made chargetransfer between the catalyst and NO which played an important role inadsorption process.As a result,SCR reaction mechanism and poison mechanismof SO₂resistance were investigated to provide possible guidances for industrialapplication.