核壳型Ce-OMS-2@CeO_(2)催化剂的构建及其低温抗硫抗水SCR脱硝研究

Architecture of core-shell Ce-OMS-2@CeO_(2) catalyst and its SCR activity and SO_(2)+H_(2)O tolerance performance at low-temperature

本研究制备了核壳型和负载型的Ce-OMS-2复合物(Ce-OMS-2@CeO_(2)和CeO_(2)/Ce-OMS-2),并对其结构和性能进行了表征和测试。结果表明,核壳型Ce-OMS-2@CeO_(2)材料由于其介孔结构的保持能够明显提升反应气体NO的传质和吸附,提升脱硝效率。同时,核壳型Ce-OMS-2@CeO_(2)催化剂显著降低了硫酸氢铵(ABS)的分解温度,使得催化剂表面活性组分不易被ABS沉积覆盖,从而维持Ce-OMS-2@CeO_(2)高效的抗硫抗水脱硝性能。因此,核壳型Ce-OMS-2@CeO_(2)催化剂表现出优异的SCR脱硝性能和抗硫抗水性能(在无SO_(2)下,100-200℃NO转化率为~100%;在有SO_(2)下,NO转化率≥~80%可维持在4 h以上)。本工作为开发高效稳定的Mn基低温SCR脱硝催化剂提供了一种有效策略。

It is a challenge to develop highly sulfur dioxide and water(SO_(2)+H_(2)O)resistance for the low-temperature selective catalytic reduction(SCR)catalysts of nitrogen oxide(NO_(x))in the non-electric-power industry.In this paper,core-shell and loaded type of Ce-OMS-2 complexes(Ce-OMS-2@CeO_(2) and CeO_(2)/Ce-OMS-2)were successfully prepared.Their textural properties were characterized and catalytic performance were carried out.The results showed that the core-shell Ce-OMS-2@CeO_(2) material could maintain the mesoporous structure and significantly improve the mass transfer and adsorption of the reaction gas NO,thus improving the SCR efficiency.On the contrary,for the loaded CeO_(2)/Ce-OMS-2 catalyst,large amounts of CeO_(2) deposited on the surface of Ce-OMS-2 and blocked the mesoporous structure.Furthermore,SO_(2) reacted with CeO_(2)/Ce-OMS-2 to form lots of metal sulfate(manganese sulfate or cerium sulfate),which led to the deactivation of the active Mn sites.Therefore,the CeO_(2)/Ce-OMS-2 catalyst exhibited the low SCR activity and poor SO_(2)+H_(2)O tolerance during the SCR reaction.We also clarify the reason for the anti-sulfur of core-shell Ce-OMS-2@CeO_(2) catalyst.In the presence of SO_(2) and H_(2)O,SO_(2) could easily react with NH3 and H_(2)O to produce ammonium bisulfate(NH4HSO4,ABS)on the surface of the Ce-OMS-2 and CeO_(2)/Ce-OMS-2 catalysts.Then ABS can be physically deposited on the surface of the catalysts,thus blocking the active Mn sites to participate in the SCR reaction.Interesting,for the core-shell Ce-OMS-2@CeO_(2) catalyst,the formed ABS could significantly be decomposed at low temperature,leading to the exposure of surface active Mn sites of the catalyst.Herein,it could maintain the efficient SCR performance over the Ce-OMS-2@CeO_(2) catalyst.A dynamic balance of ABS formation and decomposition was achieved over Ce-OMS-2@CeO_(2) even at low temperatures,which hindered the SO_(2) poisoning during the NH3-SCR reaction.As expected,the core-shell Ce-OMS-2@CeO_(2) catalyst showed excellent SCR performance and SO_(2)+H_(2)O resistance(100%NO conversion in the temperature range of 100-200℃ without SO_(2),~80% NO conversion for 4 h in the presence of SO_(2)).This work provides an effective strategy for the development of efficient and stable Mn-based low-temperature SCR catalysts.