<p>In this study, four different heteropoly acids (HPAs) were doped into Sb-Mn-Ce/TiO₂ catalysts via an in-situ deposition method. The catalytic activity and sulfur resistance of the catalysts were evaluated, and the mechanisms behind their sulfur resistance were analyzed. The results indicate that doping with phosphotungstic acid (HPW) can effectively enhance the sulfur resistance of Sb-Mn-Ce/TiO₂ catalyst, enabling it to maintain high activity for a long time even in a flue gas environment with high SO₂ concentration: after 300&#xa0;min of exposure at 150 ℃ and 100&#xa0;ppm SO₂, the NO_x conversion rate of Sb-Mn-Ce/TiO₂-HPW still remains above 80%, which is superior to that of the unmodified catalyst and other HPAs-modified samples. In contrast, the other three heteropoly acids-phosphomolybdic acid (HPMo), silicotungstic acid (HSiW), and silicomolybdic acid (HSiMo)-lowered the sulfur resistance of the catalysts. HPW has enhanced the sulfur resistance of the Sb-Mn-Ce/TiO₂ catalyst through various mechanisms, including: 1. Increasing the average pore size of the catalyst. 2. Enhancing surface acidity and NH₃ adsorption ability of the catalyst. 3. Enhancing the redox performance of the catalyst.</p> Graphical abstract <p></p>