Effect of additives on sulfur resistance of catalytic filter material during denitrification and synergistic decomposition of 1,2-DCBz

Modified Mn-Ce/P84 catalytic filter material can be used to achieve high removal efficiency of NOx and 1,2-DCBz in bag-filtering dust precipitator synergistic removal of multiple pollutants. However, the presence of SO2 in the actual industrial flue gas has an adverse impact on the catalytic performance of the catalytic filter material. In this paper, a kind of Mn-Ce catalytic filter material was prepared by the impregnation method, which was modified by Fe, Cu, and Co, respectively. As a result, the sulfur resistance of the catalytic filter material was improved. The change of catalytic activity of the three kinds of modified catalytic filter material at different concentrations was compared in the SO2 flue gas fixed bed system. And the modified catalytic filter materials were characterized by SEM, BET, XPS, XRD, and H2-TPR. When the temperature was over 80 °C, different concentrations of SO2 were injected into the simulated flue gas to test the denitrification activity of the catalytic filter material. The results showed that under the low SO2 concentration of 150 ppm, the denitrification activity and 1,2-DCBz activity of Fe, Co, and Cu-modified filter material were increased, and the sulfur resistance of Fe was better under the flue gas conditions of 300 ppm and 450 ppm SO2. Under the condition of 450 ppm SO2 and 200 °C reaction, 93.4% denitrification efficiency and 96.1% 1,2-DCBz removal efficiency could be achieved by using modified Fe-Mn-Ce catalytic filter material.

Improved Sulfur Resistance of COMMERCIAl V2O5-WO3/TiO2 SCR Catalyst Modified by Ce and Cu

The accumulation of NH4HSO4 leads to the deactivation of commercial V2O5-WO3/TiO2 catalyst (VWTi) in practical application. The commercial catalyst is modified with 0.3 wt. % Ce and 0.05 wt. % Cu (donated as VWCeCuTi), and its sulfur resistance is noticeably improved. After loading 20 wt. % NH4HSO4, the NOx conversion of VWCeCuTi-S remains 40% at 250 °C, higher than that of VWTi-S (25%). Through a series of characterization analyses, it was found that the damaged surface areas and acid sites are the key factors for the deactivation of S-poisoned samples. However, surface-active oxygen and NO adsorption are increased by NH4HSO4 deposition, and the L–H mechanism is promoted over S-poisoned samples. Due to the interaction between V, Ce and Cu, the surface-active oxygen over VWCeCuTi-S is increased, and then NO adsorption is promoted. In addition, VWCeCuTi-S obtains a higher V5+ ratio and a better redox property than VWTi-S, which in turn accelerates the NH3-SCR reaction. More NO adsorption and encouraged reaction contribute to the better sulfur resistance of VWCeCuTi.

New Insights into the Decomposition Behavior of NH4HSO4 on the SiO2-Decorated SCR Catalyst and Its Enhanced SO2-Resistant Ability

This article illustrates the detailed decomposition behavior of NH₄HSO₄ on the TiO₂ and TiO₂-SiO₂ supports, along with the effect of SiO₂ addition on the sulfur resistance of the corresponding V₂O₅-based catalysts. For TiO₂ support, sulfate species selectively occupied its surface basic hydroxyl groups, while Si-OH groups functioned as the main sites for the accommodation of NH₄HSO₄ over the TiO₂-SiO₂ mixed support, enabling its surface sulfate species with higher thermal stability. Compared with NH₄ ⁺ on the TiO₂ surface, NH₄ ⁺ on the TiO₂-SiO₂ mixed support was much easier to be consumed during the heating process, hence causing some variations in the decomposition behavior of NH₄HSO₄. Finally, adding SiO₂ enhanced the SO₂ tolerance properties of the catalysts to a certain extent. When exposed to the SO₂-containing flue gas, the deposition of NH₄HSO₄ mainly caused serious deactivation of SiO₂-free catalyst, while the as-accumulated SO₄ ^2- also contributed to the declined activity of SiO₂-added catalyst. These results ensured the potential commercialization of TiO₂-SiO₂-based catalysts in the typical low-temperature selective catalytic reduction systems in the short run and pointed out a strategy to design new catalysts with superior activity and enhanced SO₂-tolerant ability.

NH3-SCR performance and the resistance to SO2 for Nb doped vanadium based catalyst at low temperatures

Niobium oxide as the promoter was doped in the V/WTi catalyst for the selective catalytic reduction (SCR) of NO. The results showed that the addition of Nb₂O₅ could improve the SCR activity at low temperatures and the 6wt.% additive was an appropriate dosage. The enhanced reaction activity of adsorbed ammonia species and the improved dispersion of vanadium oxide might be the reasons for the elevation of SCR activity at low temperatures. The resistances to SO₂ of 3V6Nb/WTi catalyst at different temperatures were investigated. FTIR spectrum and TG-FTIR result indicated that the deposition of ammonium sulfate species was the main deactivation reason at low temperatures, which still exhibited the reactivity with NO above 200°C on the catalyst surface. There was a synergistic effect among NH₃, H₂O and SO₂ that NH₃ and H₂O both accelerated the catalyst deactivation in the presence of SO₂ at 175°C. The thermal treatment at 400°C could regenerate the deactivated catalyst and get SCR activity recovered. The particle and monolith catalysts both kept stable NO_x conversion at 225°C with high concentration of H₂O and SO₂ during the long time tests.