Fe-AlPO4-5 分子筛的共振拉曼光谱  

Resonance Raman Spectrum of Fe-AlPO_4-5 Zeolite

作　　者：孙科举[1,2] 李微雪[1] 冯兆池[1] 李灿[1] 

机构地区：[1]中国科学院大连化学物理研究所催化基础国家重点实验室,辽宁大连116023 [2]中国科学院研究生院,北京100049

出　　处：《物理化学学报》2009年第4期606-610,共5页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(20621063,20772123和20733008)资助项目

摘　　要：利用周期性密度泛函的方法,将过渡金属杂原子取代的硅基分子筛的共振拉曼计算结果成功推广到磷铝分子筛体系中.根据对Fe-ZSM-5共振拉曼光谱特点的推广和对Fe-AlPO4-5振动光谱的理论计算结果,预测在Fe-AlPO4-5的共振拉曼光谱的1190、1130、1000-1050和600cm-1位置附近将出现四条显著的谱带.实验的Fe-AlPO4-5的共振拉曼光谱中确实观察到四条与骨架Fe物种相关的谱带分别位于1210、1130、1050和630cm-1处,与预测结果一致.另外发现含铁磷铝分子筛的共振振动频率要高于相应的含铁硅基分子筛体系的振动频率,这种频率的差异主要是氧在不同分子筛体系中受力的力常数不同引起的.另外磷氧四面体和铝氧四面体之间的电荷吸引作用对振动频率也有较大的影响.Resonance Raman spectrum results from the study of silica zeolites that contain transition metals by density functional theory （DFT） calculations were extended successfully to an aluminum phosphate zeolite system. Based on the study of the resonance Raman spectrum of Fe-ZSM-5 and DFT calculations of Fe-AlPO4-5,we predicted the presence of four vibrational bands at 1190,1130,1000-1050 and 600 cm-1 in the resonance Raman spectrum of Fe-AlPO4-5. Experimentally those four bands were found at 1210,1130,1050,and 630 cm-1 in the Raman spectrum of Fe-AlPO4-5,excited by a 244 nm laser,and were assigned to the framework Fe species. The resonance Raman spectrum of Fe-AlPO4-5 is similar to that of the Fe-ZSM-5 zeolite since both zeolites have similar tetrahedrally coordinated Fe species in the framework. However,the vibrational frequencies of Fe-AlPO4-5 are higher than those of Fe-ZSM-5 because of the higher force constant of oxygen in Al—O—P than in Si—O—Si. Furthermore,the effect of the electrostatic attraction between the PO4 tetrahedron and the AlO4 tetrahedron is found to be important to the vibrational frequencies.

关 键 词：密度泛函理论 Fe-AlPO4-5 共振拉曼光谱 

分 类 号：O641.1[理学—物理化学]