Pilot-Scale Test of a V2O5-WO3/TiO2-Coated Type of Honeycomb DeNOx Catalyst and Its Deactivation Mechanism

A V2O5-WO3/TiO2-coated type of honeycomb catalyst was tested in a pilot-scale plant for DeNO(x) of the flue gas from a coal-fired glass kiln at temperatures of 250-310 degrees C for a cumulative period of 2500 h. The catalyst exhibited a two-stage deactivation feature: a gradual activity reduction in the first 1100 h followed by an accelerated deactivation in the remaining period. SEM-EDS analysis of the spent samples revealed that cumulation of Na2SO4 contained in the flue gas on the surface and in the subsurface layer of the coated active component is the main cause of deactivation which leads to the decline of mass transfer of NH3 from the gas phase to catalyst. Furthermore, the NH3-TPD patterns suggested that Na+ worked to lower the weak Bronsted acidity of the catalyst, whereas SO42- led to competitive adsorption of NH3 to formation of stable ammonium sulfate species below 300 degrees C.