摘要
采用二次合成法制备了含氮MCM-41分子筛,系统考察了氨气流速、氮化温度和氮化时间等因素对分子筛氮含量的影响,并通过X射线衍射、N2吸附、透射电镜、X射线光电子能谱和29Si MAS NMR等方法探测了氮化后分子筛的物理化学特性.结果表明,氨气流速和氮化温度是影响分子筛氮含量的主要因素.氨气流速为400ml/min时,950℃下经12h氮化后的MCM-41分子筛氮含量(质量分数)可达26·0%,并较好地保持了原有分子筛的骨架结构.由于氮化温度相对较低,对分子筛的结构破坏较小,而氮含量高、氮化后的MCM-41分子筛对Knoevenagal缩合反应具有很高的碱催化活性.
MCM-41 with high nitrogen content was prepared by nitridation of MCM-41 with NH3 at high flow rate and low temperature. The highest nitrogen content （mass fraction） of about 26.0% was achieved in NH3 with a flow rate of 400 ml/min at 950 ℃ for 12 h. The NH3 flow rate and nitridation temperature were the key factors that influenced the nitrogen content of the nitrided MCM-41 samples, whereas the silicon source and alkali source had little effect. The nitrogen content of the nitrided samples was stable when the nitridation time was over 12 h. X-ray diffraction, N2 adsorption, transmission electron microscopy, X-ray photoelectron spectroscopy, and 29Si MAS NMR results indicated that the mesopore framework of parent MCM-41 was well preserved after nitridation. Moreover, nitrogen was incorporated into the framework of MCM-41. The nitrided MCM-41 with high nitrogen content exhibited high basic catalytic activity for Knoevenagal condensation of malononitrile and henzaldehyde owing to the slight damage of nitridation at low temperature to the framework of MCM-41.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第6期495-500,共6页
基金
国家重点基础研究发展计划(973计划)(2003CB615801)
国家自然科学基金重点基金(20233030)资助项目
