摘要
离子交换法制备的Fe-ZSM-5和K-Fe-ZSM-5分子筛,经不同温度水热处理后作为催化剂应用于N2O为氧化剂的苯一步氧化制取苯酚反应中。实验中,采用XRD、N2-吸附仪、NH3-TPD、27Al MAS NMR、FT-IR、UV-vis和H2-TPR等方法对催化剂进行表征。结果显示:离子交换制备的Fe-ZSM-5分子筛,部分Fe离子以Fe2O3形式负载于分子筛的孔道中。经水热处理,分子筛骨架脱铝导致Brnsted酸性位减少,而Fe2O3离子发生迁移形成活性Fe离子位。在苯一步氧化制苯酚反应中,N2O分子吸附于Fe离子位生成α-O。活性评价结果显示,水热处理前后,催化剂分解N2O性能不变,但苯酚选择性随水热处理温度的升高而逐渐降低。此外,K离子的引入将导致催化剂选择性的降低。
Fe-ZSM-5 and K-Fe-ZSM-5 zeolites were prepared by ion-exchange, followed by hydrothermal treat- ment at different temperature. After characterization by means of XRD, nitrogen adsorption/desorption, NH3-TPD, 27 A1 MAS NMR, FT-IR, UV-vis and H2-TPR, the samples have been investigated as catalysts for the one step oxi- dation of benzene to phenol by N20 as oxidizing agent. The results show that part of Fe2O3 particles are loaded on the surface and the pore of the Fe-ZSM-5 zeolite by ion-exchange. After hydrothermal treatment, Fe-ZSM-5 zeoliteoccurs framework dealumination and Brφnsted acid sites is decreased; The amounts of Fe2O3 particles decrease and iron-ions can be migrates to form highly active Fe^3＋ sites. These result in that N20 molecules can be adsorbed on these highly active Fe3^＋ sites and decompound to α-O. Before and after hydrothermal treatment, N20 conversion is almost unchanged in one step oxidation of benzene to phenol. Phenol selectivity is gradually increased with increas- ing temperature of hydrothermal treatment. However, the phenol selectivity is decreased because kalium ion is in- troduced into Fe-ZSM-5 zeolite.
出处
《科学技术与工程》
北大核心
2013年第16期4607-4613,共7页
Science Technology and Engineering
