TY - JOUR
T1 - Poisoning of vanadia based SCR catalysts by potassium:influence of catalyst composition and potassium mobility
AU - Olsen, Brian Kjærgaard
AU - Kügler, Frauke
AU - Jensen, Anker Degn
PY - 2016
Y1 - 2016
N2 - The deactivation of V2O5–(WO3)/TiO2 catalysts for selective catalytic reduction (SCR) of NOx upon exposure to aerosols of KCl or K2SO4, at different temperatures, has been studied. All samples exposed for more than 240 hours lost a substantial fraction of their initial activity although lower exposure temperatures slowdown the deactivation. K2SO4 causes a lower rate of deactivation compared to KCl. This may be related to a faster transfer of potassium from the solid KCl matrix to the catalyst, however, it cannot be ruled out toalso be caused by a significantly larger particle size of the K2SO4 aerosol (mass based distribution mode:1.3 μm) compared to that of the KCl aerosol (mass based distribution mode: 0.12 μm). The relative activities of exposed catalysts indicate that promotion with WO3 accelerates the deactivation, likely due to theenhanced Brønsted acidity which appears to promote the transport of potassium. Using a newly developed experimental protocol consisting of two-layer pellets of SCR catalysts, where one side is impregnated with KCl or K2SO4, the potassium transport in such systems, which is assumed to take place through reactionand diffusion over acid sites, was investigated. SEM-WDS measurements on pellets heat treated at 350 °Cshow that potassium bound in KCl readily leaves its counter ion and thus moves faster into the catalystcompared to potassium from K2SO4, which is in agreement with results from the aerosol exposures.
AB - The deactivation of V2O5–(WO3)/TiO2 catalysts for selective catalytic reduction (SCR) of NOx upon exposure to aerosols of KCl or K2SO4, at different temperatures, has been studied. All samples exposed for more than 240 hours lost a substantial fraction of their initial activity although lower exposure temperatures slowdown the deactivation. K2SO4 causes a lower rate of deactivation compared to KCl. This may be related to a faster transfer of potassium from the solid KCl matrix to the catalyst, however, it cannot be ruled out toalso be caused by a significantly larger particle size of the K2SO4 aerosol (mass based distribution mode:1.3 μm) compared to that of the KCl aerosol (mass based distribution mode: 0.12 μm). The relative activities of exposed catalysts indicate that promotion with WO3 accelerates the deactivation, likely due to theenhanced Brønsted acidity which appears to promote the transport of potassium. Using a newly developed experimental protocol consisting of two-layer pellets of SCR catalysts, where one side is impregnated with KCl or K2SO4, the potassium transport in such systems, which is assumed to take place through reactionand diffusion over acid sites, was investigated. SEM-WDS measurements on pellets heat treated at 350 °Cshow that potassium bound in KCl readily leaves its counter ion and thus moves faster into the catalystcompared to potassium from K2SO4, which is in agreement with results from the aerosol exposures.
U2 - 10.1039/c5cy01409c
DO - 10.1039/c5cy01409c
M3 - Journal article
SN - 2044-4753
VL - 6
SP - 2249
EP - 2260
JO - Catalysis Science & Technology
JF - Catalysis Science & Technology
ER -