Study On The Mn-Ce/TiO₂Low-temperature SCR Catalysts: Denitration Performance And Preparation Method Of Honeycombed Catalyst

NO_x is one of the main air pollutants and selective catalytic reductionis an effective method to remove NO_x in the flue gas from stationarysources. Because of the low energy consumption and operating cost to thelow-temperature SCR process, in recent years, it has attracted more andmore interests. Based on the review of the current situation oflow-temperature SCR technology, the main obstacle of this technology islow SCR activity at low temperature, poor SO₂resistance of catalysts,preparation method of honeycombed catalysts and low SCR activity. Inorder to solve those problems, the low-temperature SCR reaction wassystematically investigated by modified Mn-Ce/TiO₂catalysts in thisdissertation.Firstly, several metals were chosen to be doped into Mn-Ce/TiO₂catalyst. From activity tests and characterization results, it was found thatCe doping could mostly enhance the low-temperature activity of thecatalyst, NO conversions were about100%at100℃,Co/Ti=0.08⁰.1/1（molar ratio） was best matching, the oxygen storage capacity and thesurface acidity of the Mn-Ce/TiO₂catalyst were improved by the Co dopedin, which was beneficial to the adsoroption of NH3and its activation.Furthermore, the effects of SO₂on the low-temperature SCR activityof Mn-Ce/TiO₂and Mn-Ce-Co/TiO₂catalysts were investigated detailedly,which catalysts composite by Co/Ti=0.1（molar ratio） in these various Mn-Ce-Co/TiO₂catalysts has best sulfur poison resistance. Reactiontemperature is from140to150℃, NH₃/NO=1.05is the best reactioncondition of this low-temperature SCR Mn-Ce-Co/TiO₂catalysts, and theeffect of GHSV is insignificant. This catalyst was detected by BET, SEM,XRD, XPS and TPD, it illustrated that Co doping could effectively inhibitthe sulfation of catalyst active phase and decrease the stability of theformed manganese and titanium sulfate species. The deactivatedMn-Ce-Co/TiO₂catalyst samples were regenerated by different treatmentsand it was found that water-washing was a good regeneration technology,catalyst activity from52%recover to90%.Secondly, the molding preparation process of honeycombed catalystsand molding auxiliary selection was researched and this Mn-Ce/TiO₂honeycomb catalyst’s denitration activity and sulfur resistance had beentested. The preparation technology of honeycomb catalyst mainly includedpreparation of plastic mud group （ingredients, kneading, practice mud,standed）, preparation of honeycomb catalyst idiozome （extrusion molding）,drying process and calcination of this honeycomb catalyst idiozome;Molding auxiliary mainly contained water（mass ratio8%）, binder（methylcellulose3%）, lubricants, crowded agent （glycerin, salad oil12%）,and0.3mm system glass fiber15%.Results from SCR activity test of Mn-Ce/TiO₂honeycombed catalystshowed that it had good low temperature activity, widely activetemperature window, good adaptability in catalytic reaction, and alsoweakly effect of airspeed to catalytic activity. In addition, the catalystsulfur poisoning resistance test showed that Mn-Ce/TiO₂honeycombcatalyst had a fine sulfur poisoning resistance performance, with SO₂concentration about0.007%and0.012%, after reaction after24hours, therate of denitration still keep at94%and92%.Finally, the catalytic reduction selectivity and vulcanization poisoning _regeneration technology of Mn-Ce/TiO₂honeycombed catalyst wereanalysed, the results showed that this catalyst selectivity of low temperaturewas good, when in low temperature period below150℃, producing rate ofN2O in NH₃-SCR reaction was low, remain below4%; Mn-Ce/TiO₂honeycombed catalyst vulcanization poisoning activity recoveryregeneration research results showed that the best effect regeneration waswater scrubbing recovery technology and its catalytic activity may restoreto90%.Research in this paper produced a new type of granularMn-Ce-Co/TiO₂composite oxide catalyst reaction in low temperaturewhich had high SCR activity and good sulfur poison resistance. It lay agood foundation for preparation of the low temperature SCR technologyindustrialization catalysts. In addition, the integral Mn-Ce/TiO₂honeycomblow temperature SCR catalyst production process and auxiliary selectionresearch showed good denitration performance, strong sulfur resistance,convenient and effective regeneration technology and it provided areference for the preparation of honeycombed low temperature SCRcatalyst and performance research in future.