钙钛石型复合氧化物La_(1-x)Sr_xFeO_(3-λ)催化性能的研究——Ⅰ.固体结构以及缺陷性质与催化性能的关系

本文根据X光结构分析,发现La_(1-x)Sr_xFeO_(3-λ)当x自0变化至1时,样品晶格中均存在氧的无序缺陷,随着Sr~(2+)的掺入,样品晶格发生畸变,进而有晶型上的变化。TG研究表明,x>0.5的样品在高温下有大量晶格氧逸出。对于La_(1-x)(Ca,Sr)_xMO_(3±λ)(M=Mn,Fe,Co)三个体系的实验结果进行对比后认为,固体缺陷的产生受几何因素的影响,催化剂的活性与氧缺陷浓度及有序化程度有关。     

杂原子分子筛(Ⅱ)——B-Si Pentasil型沸石分子筛晶体结构的研究

应用多晶X射线衍射法测定了B-SiPentasil型沸石分子筛的晶体结构并经Rietveld法修正.其晶胞参数为:α=19.983(1)Å;b=19.973(1)Å;c=13.303(1)Å.空间群为D_2h¹⁶-P_nma.晶体的骨架结构与所报导的Si-AlZSM-5相似.结构测定的结果表明:硼原子进入了沸石分子筛的骨架.     

STUDY OF CATALYTIC BEHAVIOR OF PEROVSKITE-TYPE MIXED OXIDES La_(1-x)Sr_xFeO_(3-λ)(Ⅰ)——RELATIONS OF SOLID STRUCTURE AND DEFECT CHARACTER WITH CATALYTIC BEHAVIOR

According to X-ray structure analysis, it was found that there exist oxygen disordered defects in the crystal lattice of the samples without exception as x was changed from 0 to 1 in La_(1-x)Sr_xFeO_(3-x). With the doping of Sr~(2+), the crystal lattice was distorted extremely, even the crystal type varied. The results of TG showed a large amount of lattice oxygen released under high temperatures as x>0.5 in the samples. After comparison between the experiment results of the three systems La_(1-x)(Ca, Sr)_xMO_(3+x) (M=Mn, Fe and Co), it was concluded that the occurrence of solid defects is affected by the geometric factor and the catalytic activity is related to the concentration and the ordering extent of oxygen defects.     

杂原子(Si)等比取代骨架P和Al时AlPO4-5型分子筛结构的研究

应用多晶X-射线衍射法研究了SAPO-5型分子筛结构,并经Rictveld法修正。结构测定得出,平均每个晶胞3。13个Sj原子等比取代P和Al进入骨架,但仍保持APO-5型分子筛的对称性和几何构型。Sj在骨架中与P、Al基本上成无序排列,从而使分子筛骨架不带电荷,在[001]方向也失去极性。因此若Si原子等比取代骨架中的P和Al,对调节APO-5分子筛的催化性能不会有显著作用。