NOx abatement has been an indispensable part of environmental catalysis for decades. Selective catalytic reduction with ammonia using V2O5/TiO2 is an important technology for removing NOx emitted from industrial facilities. However, it has been a huge challenge for the catalyst to operate at low temperatures, because ammonium bisulfate (ABS) forms and causes deactivation by blocking the pores of the catalyst. Here, we report that physically mixed H-Y zeolite effectively protects vanadium active sites by trapping ABS in micropores. The mixed catalysts operate stably at a low temperature of 220 °C, which is below the dew point of ABS. The sulfur resistance of this system is fully maintained during repeated aging/regeneration cycles because the trapped ABS easily decomposes at 350 °C. Further investigations reveal that the pore structure and the amount of framework Al determined the trapping ability of various zeolites.
We have explored the origin of unusual first-order-type electronic and structural transitions in IrTe2, based on the first-principles total energy density functional theory analysis. We have clarified that the structural transition occurs through the interplay among the charge density wavelike lattice modulation with q1/5=(1/5,0,1/5), in-plane dimer ordering, and the uniform lattice deformation. The Ir-Ir dimer formation via a molecular-orbital version of the Jahn-Teller distortion in the Ir-Ir zigzag stripe is found to play the most important role in producing the charge disproportionation state. Angle-resolved photoemission spectroscopy reveals the characteristic features of structural transition, which are in good agreement with the density functional theory bands obtained by the band-unfolding technique.
Selective catalytic reduction of NO x with NH 3 (NH 3 − SCR) in Cu-SSZ-13 has been proposed to have a unique homogeneouslike mechanism governed by the spatial proximity of mobile Cu ions. Among factors that determine the proximity, the effect of ion density on the SCR reaction is well established; however, it has not been verified how the different mobility of the Cu ion influences the SCR reaction. Herein, we try to reveal the mobility-dependent SCR reaction by controlling the Cu species with different ion mobilities in Cu-SSZ-13. Since the reaction kinetics is governed by the diffusion of Cu ions, the Cu ion mobility determines the reactivity of the Cu-SSZ-13. In terms of this correlation, enhanced ion mobility leads to improved NH 3 −SCR activity. These findings help understand the behavior of Cu ions in Cu-SSZ-13 under a catalytic reaction and provide insights to design rational catalysts by tuning the ion mobility.
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