The Interaction of NH4HSO4 with Vanadium-Titanium Catalysts Modified with Molybdenum and Tungsten

With the wide application of selective catalytic reduction (SCR) systems in power plants for the control of NOx emission in China, a serious problem of catalyst deactivation due to the channel blockage by NH4HSO4 has drawn extensive attention. In this work, a combined experimental and simulation method was utilized to study the interaction between NH4HSO4 and a vanadium-titanium-based catalyst. Initially, the adsorption characteristics of NH4HSO4 onto TiO2, V2O5/TiO2, V2O5 -WO3/TiO2, and V2O5-MoO3/TiO2 were simulated following density functional theory. The simulation revealed that during reaction, the NH4HSO4 loaded onto TiO(2 )can be dissociated into NH4+ and SO42-. The existence of V2O5, WO3, and MoO3 can form a protective layer to inhibit the adsorption of NH(4)HSO(4)onto TiO2, to promote the reduction of sulfur-containing compounds, and to accelerate the reaction of NH4+ with NO. Thermogravimetric analysis also showed the positive effect of V, W, and Mo on NH4HSO4 decomposition. Fixed-bed experiments were then conducted to compare the performance of the studied catalysts and the effect of NH4HSO4 on their performance. It was proven that the V-5Mo/TiO2 catalyst showed better performance at low temperatures. On the V-5Mo/TiO2 catalyst, similar to 78 wt % NH4+ in NH4HSO4 was attached onto Lewis acid sites, which can accelerate the reduction reaction of NO by NH4+. Meanwhile, SO42- can comparatively be easily decomposed at lower temperatures.