A 'Smart' Hollandite DeNO_x Catalyst: Self-Protection against Alkali Poisoning

摘要

Global warming, caused by an increase in atmospheric CO2 concentrations, and limited fossil-fuel resources have stimulated the search for environmentally sustainable energy sources with zero or low CO2 emission. The use of biomass as a CO2-neutral fuel has drawn widespread attention, since biomass as part of the global carbon ecocycle is an increasingly important energy resource. An associated issue, which is often encountered in the control of NO_x emissions from the alkali-rich stack gas of power plants (co-)fuelled by biomass, is the severe deactivation of conventional V2O5-WO3/TiO2 catalysts in the selective catalytic reduction of NO by NH3 (NH3-SCR). This deactivation is predominately caused by the strong interaction of alkali-metal ions with catalytically active sites. For example, Zheng et al. proposed a deactivation mechanism by proton exchange at catalytically active Br0nsted acid sites with alkali-metal ions. The exchange reactions occur readily at normal NH3-SCR operating temperatures because alkali species, such as KC1 and K2SO4, are mobile in view of their low Tamman temperatures (T_(Tam)).