POISONING /DEACTIVATION OF V_2O_5/TiO_2 SCR CATALYST IN COAL AND BIOMASS-FIRED SYSTMES

摘要

This paper summarizes SCR catalyst deactivation results from experiments with both lab-synthesized vanadia-based catalyst and samples from slipstreams of commercial systems using both coal and biomass-coal blends as fuels. The laboratory results indicate that Na and Ca (among others materials) poison SCR catalysts when they contact the surface intimately, with Na a stronger poison than Ca. Surface sulfation, on the other hand, increases catalytic activity. In situ FTIR spectroscopy combined with XPS analyses indicate that sulfate dose not form on vanadia sites but on titania sites, and sulfation enhances NH_3 adsorption on Bronsted acid sties but not on Lewis acid sites. NO reduction activities from both fresh and sulfated vanadia catalyst indicate that the activity increase by increasing the amount of active sites without changing the activation energy. Activity studies of commercial monolith catalysts with various exposure time indicated that fouling and plugging instead of poisoning are the main deactivation mechanism of vanadia catalyst.