含氮FAU分子筛的制备、表征及碱催化反应性能

Preparation,Characterization and Basic Catalytic Properties of Nitrogen-incorporated FAU Zeolites

利用脱水氮化法制备了含氮HY分子筛,氮化后分子筛的结晶度和比表面积均得到较好保持.由于氮原子的电负性低于氧原子,因此氮原子取代氧原子进入HY分子筛的骨架后,使其Lewis碱性得到增强.利用氨气吸附红外光谱、二氧化碳吸附红外光谱及二氧化碳程序升温脱附等方法对氮化前后的分子筛进行表征.结果表明,氮化后HY分子筛的L酸中心数量有所降低,B酸中心数量有所增加,同时生成新的碱性中心.由于新碱性中心的引入,含氮HY分子筛在Knoevenagel缩合碱性探针反应中表现出良好的活性.

Dehydration-nitridation method was employed to prepare nitrogen-incorporated HY zeolites.High crystallinity and specific surface area of parent HY were well preserved in nitrogen-incorporated HY zeolites.The base strength of HY framework was enhanced due to the replacement of oxygen by nitrogen with lower electronegativity.The acidity and basicity of nitrogen-incorporated HY zeolite were characterized by IR spectra using NH3 and CO2 as probe molecules and temperature-programmed desorption of CO2.The results show that the amounts of L-acid sites decrease while the amount of B-acid sites and base sites increase after nitridation.Moreover,new base sites with moderate strength are created after nitridation.Compared to parent HY zeolite,the nitridized sample exhibits improved basic catalytic performance in Knoevenagel condensation reaction.