Abstract The effect of lead on the catalytic performance of Mn-Ce/TiO2 catalysts in the selective catalytic reduction (SCR) of NOx with ammonia at low temperature was investigated; with the help of nitrogen sorption, XRD, FT-IR spectroscopy, H2-TPR and NH3-TPD characterization, the causes of lead poisoning and acid regeneration were clarified. The results indicate that the doping of Pb in Mn-Ce/TiO2 leads to a significant decrease of the low-temperature SCR activity; with a Pb loading of 11%, the conversion of NO over Mn-Ce/TiO2 at 180°C decreases from original 100% on the fresh catalyst to 44% on the Pd-poisoned catalyst. The presence of Pb may reduce the content of active Mn4+ and Ce3+ species on the Mn-Ce/TiO2 catalyst, which suppresses the redox cycle of Mn4+ + Ce3+ ↔ Mn3+ + Ce4+; moreover, the decrease of surface acidity on the Mn-Ce/TiO2 catalyst by the doping of Pb is also disadvantageous to the adsorption and activation of NH3. The Pd-poisoned Mn-Ce/TiO2 can be regenerated by nitric acid treatment; after the regeneration, the catalytic activity of Mn-Ce/TiO2 in NH3-SCR of NO is almost completely recovered and even exceeds that of the fresh catalyst at 80–150°C. The nitric acid treatment can restore the redox capacity of Mn-Ce/TiO2, increase the surface area, and create new acid sites, which contribute to recovery of the activity of Pb-poisoned Mn-Ce/TiO2 catalyst in NH3-SCR.

中文翻译：

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低温下 NO NH3-SCR Mn-Ce/TiO2 催化剂的铅中毒及再生

摘要 研究了铅对Mn-Ce/TiO2催化剂低温氨选择性催化还原(SCR)催化性能的影响；借助氮吸附、XRD、FT-IR光谱、H2-TPR和NH3-TPD表征，阐明了铅中毒和酸再生的原因。结果表明，Mn-Ce/TiO2中Pb的掺杂导致低温SCR活性显着降低；在 Pb 负载为 11% 的情况下，在 180°C 下，Mn-Ce/TiO2 上的 NO 转化率从新鲜催化剂上的原始 100% 降低到 Pd 中毒催化剂上的 44%。Pb 的存在可能会降低 Mn-Ce/TiO2 催化剂上活性 Mn4+ 和 Ce3+ 物质的含量，从而抑制 Mn4+ + Ce3+ ↔ Mn3+ + Ce4+ 的氧化还原循环；而且，Pb的掺杂降低了Mn-Ce/TiO2催化剂的表面酸度，也不利于NH3的吸附和活化。Pd中毒的Mn-Ce/TiO2可以通过硝酸处理进行再生；再生后 Mn-Ce/TiO2 在 NO 的 NH3-SCR 中的催化活性几乎完全恢复，甚至在 80-150℃时超过了新鲜催化剂的催化活性。硝酸处理可以恢复Mn-Ce/TiO2的氧化还原能力，增加比表面积，并产生新的酸位点，有助于在NH3-SCR中恢复Pb中毒的Mn-Ce/TiO2催化剂的活性。Mn-Ce/TiO2 在 NO 的 NH3-SCR 中的催化活性几乎完全恢复，甚至在 80-150°C 时超过了新鲜催化剂的催化活性。硝酸处理可以恢复Mn-Ce/TiO2的氧化还原能力，增加比表面积，并产生新的酸位点，有助于在NH3-SCR中恢复Pb中毒的Mn-Ce/TiO2催化剂的活性。Mn-Ce/TiO2 在 NO 的 NH3-SCR 中的催化活性几乎完全恢复，甚至在 80-150°C 时超过了新鲜催化剂的催化活性。硝酸处理可以恢复Mn-Ce/TiO2的氧化还原能力，增加比表面积，并产生新的酸位点，有助于在NH3-SCR中恢复Pb中毒的Mn-Ce/TiO2催化剂的活性。