Application of positron annihilation to the characterization of zeolites
Application of positron annihilation to the characterization of zeolites
复制标题
正电子湮灭在沸石表征中的应用
DOI：
10.1021/j100219a035
复制
发表时间：
1982
期刊：
影响因子：
--
通讯作者：
Y. Ujihira
中科院分区：
文献类型：
--
作者：
H. Nakanishi;Y. Ujihira
通过改变排液温度，对合成沸石13X、SK-40、NH/sub -4 /-X和NH/sub -4 /-Y的正电子湮灭寿命和多普勒展宽进行了测量，以研究沸石笼的性质。正电子湮灭的四个组成部分，从寿命谱推导出来，从作者的测量结果和对沸石的其他研究中得到解释。随着水分子解吸的进行，o- p在笼中的寿命变长。发现沸石中某些活性基团与o-Ps相互作用，降低了o-Ps的寿命。沸石中的沸石酸不仅可以作为氧化剂，还可以作为Ps形成的抑制剂。试图用正电子寿命技术估计勃朗斯特酸的数量。最长的寿命为50 ns，表明o-Ps湮灭在自由直径为60 a的孔洞中，这种现象似乎不规则地存在于faujasite沸石中。发现o-Ps在这个大腔中被氧化。
Positron annihilation lifetime and Doppler-broadening measurements were carried out for synthetic zeolite 13X, SK-40, NH/sub 4/-X, and NH/sub 4/-Y by varying the evacuation temperature in order to study the character of the zeolite cages. Four components of the positron annihilation, derived from the lifetime spectra, were interpreted from the results of the authors' measurements and other studies on zeolites. The o-Ps lifetimes in the cages became longer as the desorption of water molecules proceeded. It was found that some active groups in zeolites interacted with o-Ps and reduced the o-Ps lifetime after all the water molecules had detected. Bronsted acid in the zeolite acted not only as an oxidizer but also as an inhibitor of Ps formation. An attempt was made to estimate the amount of Bronsted acids by the positron lifetime technique. The longest lifetime of 50 ns indicates o-Ps annihilation in a pore with 60 A free diameter, which seems to exist irregularly in the faujasite zeolites. It was found that o-Ps was oxidized in this large cavity.