College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China; Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials, Chongqing University, Chongqing, 400044, China.
Department of General Planning, China Metallurgical Industry Planning and Research Institute, Beijing 100013, PR China.
J Colloid Interface Sci. 2022 Sep 15;622:549-561. doi: 10.1016/j.jcis.2022.04.121. Epub 2022 Apr 27.
Due to the accumulation of heavy metal compounds produced by the sintering process in steel industry, the catalysts used for low-temperature selective catalytic reduction of NO with NH (NH-SCR) might be seriously deactivated. In this work, the deactivation effect of PbCl, Pb(NO), and PbSO on Mn-Ce activated carbon supported catalyst for low-temperature NH-SCR of NO was investigated and compared. Poisoned catalysts were provided by impregnating fresh catalysts with Pb(NO), PbSO and PbCl aqueous solutions, respectively. Deactivation could be observed on the poisoned samples, and the deactivation degree was following PbCl > PbSO > Pb(NO). The catalytic activities of all samples were tested, and the physicochemical properties of fresh and poisoned catalysts were assessed. PbCl caused the most severe deactivation of the catalyst, owing to its poor redox property and surface acidity. Cl could also react with Mn active sites to form -O-Mn-Cl bonds, resulting in additional acid sites, although these newly generated sites were not reactive in NH-SCR reaction process. PbSO exhibited moderate poisoning effect due to the addition of SO, which created new Brønsted acid sites, facilitating the NH adsorption and NO reduction. Pb(NO) had the least poisoning impact on the catalyst due to the NO, promoting the NH activation. The in situ DRIFTS results revealed that NH-SCR reaction over all samples was governed by Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism, and did not change due to the lead poisoning. Finally, a possible mechanistic model for different lead salts poisoning over Mn-Ce/AC catalyst was proposed.
由于钢铁行业烧结过程中重金属化合物的积累，用于低温选择性催化还原 NO 的 NH（NH-SCR）的催化剂可能会严重失活。在这项工作中，研究并比较了 PbCl、Pb(NO) 和 PbSO 对 Mn-Ce 活性炭负载催化剂低温 NH-SCR 中 NO 的失活作用。用 Pb(NO)、PbSO 和 PbCl 水溶液分别浸渍新鲜催化剂，得到中毒催化剂。在中毒样品上观察到失活，可以观察到失活程度为 PbCl > PbSO > Pb(NO)。测试了所有样品的催化活性，并评估了新鲜和中毒催化剂的物理化学性质。由于其较差的氧化还原性能和表面酸度，PbCl 导致催化剂失活最严重。Cl 还可以与 Mn 活性位反应形成-O-Mn-Cl 键，导致额外的酸位，尽管这些新生成的位在 NH-SCR 反应过程中没有反应性。由于 SO 的添加，PbSO 表现出适度的中毒效应，这会产生新的 Brønsted 酸位，有利于 NH 吸附和 NO 还原。由于 NO 的存在促进了 NH 的活化，Pb(NO) 对催化剂的中毒影响最小。原位 DRIFTS 结果表明，所有样品上的 NH-SCR 反应均受 Eley-Rideal (E-R) 和 Langmuir-Hinshelwood (L-H) 机制控制，并且由于铅中毒而没有改变。最后，提出了一种关于不同铅盐在 Mn-Ce/AC 催化剂上中毒的可能机理模型。
