Jia Lingfeng, Zhang Li, Liu Bing, Cheng Huifang, Li Huiquan, Zhao Zhen, Zhu Wenshuai, Song Weiyu, Liu Jian, Liu Jixing
School of Chemistry and Chemical Engineering, Institution for Energy Research, Jiangsu University, Zhenjiang 212013, P. R. China.
State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), Beijing 102249, P. R. China.
Environ Sci Technol. 2024 Aug 13. doi: 10.1021/acs.est.4c04101.
Hitherto, sulfur poisoning and hydrothermal aging have still been the challenges faced in practical applications of the Cu-SSZ-13 catalyst for the selective catalytic reduction (SCR) of NO from diesel engine exhaust. Here, we elaborately design and conduct an in-depth investigation of the synthetic effects of hydrothermal aging and SO poisoning on pristine Cu-SSZ-13 and Cu-SSZ-13@CeZrO core@shell structure catalysts (Cu@CZ). It has been discovered that Cu@CZ susceptible to 750 °C with 5 vol % HO followed by 200 ppm SO with 5 vol % HO (Cu@CZ-A-S) could still maintain nearly 100% NO conversion across the significantly wider temperature region of 200-425 °C, which is remarkably broader than that of the Cu-SSZ-13-A-S (300-400 °C) counterpart. The experimental results show that the hydrothermal aging process results in the migration of highly active Cu species within the cage of Cu-SSZ-13 to the CZ surface, forming CuO/CZ with abundant interfaces, which significantly enhances the adsorption and subsequent activation of NO, leading to the generation of reactive NO and HONO intermediates. Moreover, density functional theory (DFT) calculations reveal that the H of the HONO* species can function as Brønsted acid sites, effectively adsorbing NH to generate the active NHNO* intermediate, which readily decomposes into N and HO. Furthermore, this pathway is the rate-determining step with an energy barrier of 0.93 eV, notably lower than that of the "standard SCR" pathway (1.42 eV). Therefore, the formation of the new CuO/CZ interface profoundly boosts the low-temperature NH-SCR activity and improves the coresistance of the Cu@CZ catalyst to sulfur poisoning and hydrothermal aging.
迄今为止，硫中毒和水热老化仍然是Cu-SSZ-13催化剂用于柴油发动机尾气中NO选择性催化还原（SCR）实际应用时所面临的挑战。在此，我们精心设计并深入研究了水热老化和SO中毒对原始Cu-SSZ-13和Cu-SSZ-13@CeZrO核壳结构催化剂（Cu@CZ）的综合影响。研究发现，在5 vol% H₂O条件下经750 °C水热老化处理，随后在5 vol% H₂O条件下暴露于200 ppm SO₂后的Cu@CZ（Cu@CZ-A-S），在200 - 425 °C这一显著更宽的温度范围内仍能保持近100%的NO转化率，这比Cu-SSZ-13-A-S（300 - 400 °C）对应物的温度范围明显更宽。实验结果表明，水热老化过程导致Cu-SSZ-13笼内高活性Cu物种迁移至CZ表面，形成具有丰富界面的CuO/CZ，这显著增强了NO的吸附及后续活化，导致生成活性NO和HONO中间体。此外，密度泛函理论（DFT）计算表明，HONO物种的H可作为布朗斯特酸位点，有效吸附NH₃生成活性NH₃NO中间体，该中间体易于分解为N₂和H₂O。此外，此途径是能量垒为0.93 eV的速率决定步骤，明显低于“标准SCR”途径（1.42 eV）。因此，新的CuO/CZ界面的形成极大地提高了低温NH₃-SCR活性，并改善了Cu@CZ催化剂对硫中毒和水热老化的抗性。
