Performance And Kinetics Of The Selective Catalytic Reduction Of NO_x Over Novel Fe-Ce-Ti/TiO₂

The austere situation of NOx emissions is a huge pressure to sustainable development of our country, So NH3-SCR technology is very important to De-NOx field of coal-fired power plants in our country. The key to SCR technology is catalyst, compared to existing technology, low temperature SCR technology costs less power and money, so researching and developing low temperature SCR catalyst is a focus. Existing iron-cerium catalyst has high SCR activity at meddle-low temperature, but the activity temperature can not meet the requirements of low temperature SCR technology, so this paper dops another kind of titanium in it to explore a way to improve its low temperature SCR activity on the condition that titanium dosage is constant, and researches its De-NOx performance and reaction kinetics.Since the atomic number of titanium is near that of iron, titanium doping can induce the extranuclear electron of iron, so it can change the physical-chemical nature in the process to influence SCR performance of catalyst. The SCR activity tests of catalysts with different titanium loading amount are carried out to explore a way to improve its low temperature SCR activity and obtain the optimum loading amount of titanium; From the test results of BET, XPS, XRD, TPD, we find that cerium doping makes a larger specific surface area and pore volume but smaller bore diameter, active components in amorphous state highly disperse on the catalyst surface, the oxygen concentration and NH3adsorbance are higher at low temperature, all of which can promote SCR reaction.On this basis, this paper investigates the effects of calcined temperature, reaction temperature, oxygen concentration, NH3/NO and GHSV on the SCR De-NO, performance of iron-cerium-titanium catalyst systematically, we find that:the catalyst calcined at400℃has the best SCR activity, higher calcined temperature can lead to the crystallization of active components and parts of anatase TiO2change into rutile TiO2; the denitration efficiency can reach90%at175℃, indicating that low temperature activity is good, and the denitration efficiency is higher than95%between200℃and400℃; the denitration efficiency is very low without O2in the feeding gas, and when bubbling little amount of O2while the denitration efficiency rises rapidly, the denitration efficiency stays the same when oxygen concentration is over3%,indicating that O2is very important in SCR reaction; the denitration efficiency is highest when NH3/NO is1and GHSV is30000h-1.Furthermore, this paper studies the reaction kinetics of this novel iron-cerium-titanium catalyst considering the effects of NH3, NO and O2concentration on the reaction rate. We find that in the SCR reaction, the reaction order of NH3is0, the reaction order of NO is1, the reaction order of O2is0when the oxygen concentration is over3%While it becomes0.39when the oxygen concentration is less than3%. The reaction activation energy is28.6KJ·mol-1(while the activation energy of commercial catalyst is70～90KJ·mol-1and the iron-based catalyst is50～70KJ·mol-1) and the reaction rate constant is23248.4exp [-28559.1/(RgT)], after knowing the effects of NH3, NO and O2concentration to reaction rate.