Monitoring Aging and Deactivation of Emission Abatement Catalysts for Selective Catalytic Reduction of NOx

Titania/vanadia, zeolite, and noble metal catalysts are utilized for selective catalytic reduction (SCR) of NOx using ammonia as the reductant in different temperature ranges. Studies of aging have been carried out to probe deactivation rates and mechanisms. Periodic laboratory testing of samples of NOx reduction catalysts from multi-layer reactors, such as those utilized at electric power plants, allows prediction of catalyst life-times. Testing has been carried out under protocol conditions with monolith, plate-type, and pelleted catalysts so that relative NO reduction rates can be compared, with or without the presence of SO2. The catalysts were analyzed by surface analysis techniques, including electron microscopy and X-ray photoelectron spectroscopy, to probe surface morphology, loss of active components, presence of poisons, and blocking of pores and active sites by ammonium bisulfate to determine the dominant mode(s) of gradual deactivation.