To reveal the nature of SO₃ poisoning of Cu/SAPO-34 selective catalytic reduction (SCR) catalysts, CHA structure, copper species, and NO_x conversion were probed. The Cu/SAPO-34 catalyst was treated with different ratios of SO₃ to SO_x (0, 6, 13, and 20%) at 250 °C. The breakage of SiO(H)Al bonds takes place and leads to aluminum sulfate formation upon SO_x sulfation. More isolated Cu²⁺ transform to copper sulfate with an increment of the SO₃/SO_x ratio. Catalysts poisoned with SO_x show lower NO_x conversion at 150–300 °C, the reason for which is a reduced number of isolated Cu²⁺ sites, as their turnover frequencies (TOFs) are identical. The loss of isolated Cu²⁺ and SiO(H)Al bonds is responsible for the inferior activity above 300 °C. The presence of SO₃ cannot be ignored because of the irreversible reaction with Cu/SAPO-34 when diesel oxidation catalysts are applied upstream of the SCR.

为了揭示Cu / SAPO-34选择性催化还原（SCR）催化剂的SO ₃中毒性质，对CHA结构，铜种类和NO _x转化率进行了研究。在250°C下以不同比例的SO ₃与SO _x（0、6、13和20％）处理Cu / SAPO-34催化剂。发生Si O（H）Al键断裂，并导致SO _x硫酸化形成硫酸铝。随着SO ₃ / SO _x比的增加，更多的孤立的Cu ²⁺转化为硫酸铜。被SO _x毒化的催化剂显示出较低的NO _x在150–300°C时发生转化，其原因是孤立的Cu ²⁺位点数量减少，因为它们的周转频率（TOF）相同。分离出的Cu ²⁺和Si O（H）Al键的丧失是造成高于300°C的劣活性的原因。当在SCR的上游使用柴油氧化催化剂时，由于与Cu / SAPO-34发生不可逆反应，因此不能忽略SO ₃的存在。