MeAPO-5分子筛的合成及其在肉桂醇选择氧化反应中的催化性能

Synthesis and Catalytic Properties of MeAPO-5 Molecular Sieves for Selective Oxidation of Cinnamyl Alcohol

采用水热法合成了一系列杂原子磷铝分子筛MeAPO-5(Me=Co,Fe,Cu,Zn,Mn),并利用X射线衍射(XRD),热重-差热分析(TG-DTA),电感耦合等离子体原子发射光谱(ICP-AES)和漫反射紫外-可见光谱(DRUV-Vis)等技术对分子筛的结构,化学组成以及金属离子的存在状态进行了表征.结果表明,合成的纯相MeAPO-5分子筛具有较高的结晶度,金属杂原子种类显著影响其在MeAPO-5分子筛中的存在状态,取代度及合成样品的结晶度.Co2+,Fe3+,Zn2+和Mn2+较易进入分子筛骨架,而Cu2+较难进入.通过考察MeAPO-5分子筛在肉桂醇氧化反应中的催化性能,发现CoAPO-5分子筛具有良好的选择氧化催化性能,1,4-二氧六环是较好的溶剂,调变反应温度可以有效调控产物的选择性.

A series of metal ion-substituted aluminophosphate molecular sieves of MeAPO-5（Me=Co,Fe,Cu,Zn,Mn） were hydrothermally synthesized.The as-synthesized and calcined samples were characterized by X-ray diffraction（XRD）,diffuse reflectance（DR） UV-Vis spectroscopy,thermogravimetric-differential thermal analysis（TG-DTA）,and inductively coupled plasma-atomic emission spectroscopy（ICP-AES） techniques.The as-synthesized single-phase MeAPO-5 molecular sieves all had high crystallinities.The type of metal significantly influences the states and amounts of the incorporated metal species,as indicated by DR UV-Vis and ICP analysis results.Co^2＋,Zn^2＋,Fe^3＋,and Mn^2＋ can be incorporated into the framework through the substitution of Al^3＋,while Cu^2＋ substitution is difficult.Selective oxidation of cinnamyl alcohol with molecular oxygen over various MeAPO-5 molecular sieves was conducted to probe the effects of the nature and states of metal species on their catalytic performances.CoAPO-5 showed higher catalytic activity and selectivity than the other MeAPO-5 molecular sieves.1,4-Dioxane should be of the choice of solvent.A decrease in the reaction temperature favors the formation of cinnamaldehyde whereas an increase in the reaction temperature remarkably promotes the epoxidation of cinnamyl alcohol regardless of the occurrence of deep oxidation processes.