| 于飞,马江丽,任德志,赖慧龙,殷雪梅,赵云昆,常仕英.铁基分子筛活性位点的制备控制及对NH3-SCR活性的影响[J].分子催化,2022,36(4):321-329 |
| 铁基分子筛活性位点的制备控制及对NH3-SCR活性的影响 |
| Effect of Iron Sites and Synthesis Procedure of Fe-beta Catalysts on NH3-SCR Performance |
| 投稿时间：2022-05-14 修订日期：2022-06-22 |
| DOI：10.16084/j.issn1001-3555.2022.04.003 |
| 中文关键词: 铁活性位点 SCR活性 Fe-beta分子筛 汽车尾气 |
| 英文关键词:iron sites NH3-SCR properties Fe-beta molecular catalyst automotive exhaust |
| 基金项目:国家重点研发计划(No.2021YFB35033200); 云南省重大科技项目(No. 202102AB080007); 云南省基础研究计划(No.2019FD138) |
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| 中文摘要: |
| 采用离子交换法, 通过不同制备条件制备Fe-beta分子筛, 并探讨不同制备条件对催化剂活性位点和NH3-SCR活性的影响. 通过UV-Vis分析, 将不同位置的吸收峰归属于不同的铁活性位点, 300 nm以下的高能谱区可以归属于孤立的Fe3+位点, 300~400 nm间归属于低聚的FexOy簇, 而400 nm以上为Fe2O3大颗粒聚合物. 对比不同催化剂的SCR活性发现, 孤立的Fe3+和低聚态的Fe3+是主要的活性位点, 这两种物种的所占比例高低直接影响了催化剂的活性. 而大尺度的Fe2O3为非活性位点, 应尽量控制并降低其所占比例. 另外低聚态的Fe3+所占比例越高, N2O的生成量越高, N2的选择性越差. 因此, 在制备过程中, 除了控制大尺度的Fe2O3含量外, 还要尽量降低低聚态的Fe3+的含量, 以增加N2的选择性. 采用离子交换法制备Fe-beta催化剂, pH、交换温度、前驱体种类、硅铝比、煅烧条件等制备条件会对Fe-beta的活性位点造成影响, 从而导致活性差异. 根据实际应用需求, 调控制备条件, 可有效控制活性物种的分布, 制备出具有高效NH3-SCR活性的铁基分子筛催化剂. |
| 英文摘要: |
| Fe-Beta molecular sieves were prepared by ion exchange method under different synthesis conditions, and effects of preparation on NH3-SCR properties were investigated. The adsorption peaks were assigned to different active sites with the UV-Vis analysis. The spectral below 300 nm, spectral between 300~400 nm and spectral above 400 nm were assigned to isolated Fe3+, oligomeric FexOy clusters and large-scale Fe2O3 clusters, respectively. Based on the investigation of effects on the NH3-SCR activity, the isolated Fe3+and oligomeric Fe3+ species were the main active sites, which directly affects the activity with different proportion. While the large-scale Fe2O3 was an inactive site, and its proportion should be controlled and reduced. In addition, the higher proportion of oligomeric Fe3+, the higher N2O generated and the worse N2 selectivity. Therefore, except for controlling the content of large-scale Fe2O3, the content of oligomeric Fe3+ should be reduced to increase the selectivity of N2 during the preparation. The synthesis conditions such as pH, temperature, precursor type, Si/Al and the calcination condition would affect the active sites of Fe-beta during the ion exchange, resulting in differences in activity. Regulating the synthesis conditions can effectively control the distribution of active species based on different catalyst activity requirement. |
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