Unveiling the Promoting Effect of Niobium on Cu-KIT-6 Nanoporous Catalysts for the Selective Catalytic Reduction of NOx with High Resistance to Ammonium Bisulfate Poisoning

In this study, Nb modification was applied to promote the performance of selective catalytic reduction (SCR) of NO_x and NH₄HSO₄ (ABS) resistance of pure silica molecular sieve KIT-6-supported copper nanoporous catalysts. Experimental results revealed that the optimal Cu₅–NK sample possessed above 80% deNO_x efficiency with good N₂ selectivity in the temperature range of 260–400 °C and ABS deposition only reduced the SCR efficiency of the Cu₅–NK sample by 20% at 320 °C. Characterization results indicated that Nb modification would induce formation of strong interactions with Cu, which enlarged pore size, amplified dispersion of active Cu species, and enhanced redox ability and surface acidity. Importantly, the enlarged pore size could weaken the thermal stability of ABS and promote its decomposition, while more active Cu sites retained by strong Cu–Nb interactions could participate in the SCR reaction and easily consume NH₄⁺ from the deposited ABS on the catalyst. These were the main reasons for promoting SCR performances and ABS resistance of Cu-KIT-6 nanoporous catalysts by Nb modification. Such findings could pave a way for the development of highly efficient SCR catalysts with good ABS resistance for real application.