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Fe^(3+)位点,300~400 nm间归属于低聚的Fe_(x)O_(y)簇,而400 nm以上为Fe_(2)O_(3)大颗粒聚合物.对比不同催化剂的SCR活性发现,孤立的Fe^(3+)和低聚态的Fe^(3+)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Fe_(2)O_(3)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Fe^(3+)所占比例越高,N_(2)O的生成量越高,N_(2)的选择性越差.因此,在制备过程中,除了控制大尺度的Fe_(2)O_(3)含量外,还要尽量降低低聚态的Fe^(3+)的含量,以增加N_(2)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.
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 Fe^(3+),oligomeric Fe_(x)O_(y)clusters and large-scale Fe_(2)O_(3)clusters,respectively.Based on the investigation of effects on the NH3-SCR activity,the isolated Fe^(3+)and oligomeric Fe^(3+)species were the main active sites,which directly affects the activity with different proportion.While the large-scale Fe_(2)O_(3)was an inactive site,and its proportion should be controlled and reduced.In addition,the higher proportion of oligomeric Fe^(3+),the higher N_(2)O generated and the worse N_(2)selectivity.Therefore,except for controlling the content of large-scale Fe_(2)O_(3),the content of oligomeric Fe^(3+)should be reduced to increase the selectivity of N_(2)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.
作者
于飞
马江丽
任德志
赖慧龙
殷雪梅
赵云昆
常仕英
YU Fei;MA Jiang-li;REN De-zhi;LAI Hui-long;YIN Xue-mei;ZHAO Yun-kun;CHANG Shi-ying(Kunming Sino-Platinum Metals Catalyst Co,Ltd,Kunming 650106,China)
出处
《分子催化》
CAS
CSCD
北大核心
2022年第4期321-329,共9页
Journal of Molecular Catalysis(China)
基金
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)
作者简介
于飞(1987-),男,硕士研究生;通信联系人:常仕英,E-mail:shiying.chang@spmcatalyst.com
