顺式Pt(NH_3)_2Cl_2在Kβ及KL沸石上的分解过程及催化性能  

Decomposition and Dispersion of cisPt(NH_3)_2Cl_2 in K β and K L Zeolites

作　　者：郑坚[1] 董家禄[1] 须沁华[1] 

机构地区：[1]南京大学化学化工学院

出　　处：《分子催化》1998年第2期113-118,共6页Journal of Molecular Catalysis(China)

摘　　要：采用ＴＰＯ及ＴＧ－ＤＴＡ等方法，对顺式Ｐｔ（ＮＨ３）２Ｃｌ２在Ｋβ及ＫＬ沸石上的分解过程进行了研究，并与还原后铂粒子的分散状态及其对正己烷芳构化的催化性能相关联．发现Ｋβ沸石上较强的酸性及其孔道特点，使得顺铂中氨配体解离后较难离开沸石孔道，而发生自还原现象，因此导致铂粒子的聚集；在ＫＬ沸石上，可以避免自还原的发生．β沸石经碱金属离子交换后，其酸性强弱依次为Ｌｉβ＞Ｎａβ＞Ｋβ＞Ｒｂβ＞Ｃｓβ．沸石上酸性越强，则发生自还原的程度越大，因此所负载的铂粒子越大；表现在催化性能上。おPO and TGDTA methods were used to measure the decomposition of cisPt(NH_3)_2Cl_2 in K L and K β zeolites. The dispersion of Pt particles, as studied by TEM and H_2TPD, was related to the decomposition behavior, which further influenced the catalytic activity on nhexane pulse flow microreaction. The very weak acidity in K L zeolite, combined with the unique channel structure, avoided the occurring of autoreduction during calcination. While in K β zeolite, the existence of relatively strong acidic sites, combined with its characteristic structure, prevented the leaving of NH_3 formed during decomposition, autoreduction of Pt_2+ to Pt0 by NH_3 thus occurred to make Pt agglomerated to larger particles. In order to modify the acidity of K β zeolite, ion exchange with different alkali cations was carried out. The acidity of M β zeolites as determined by NH_3TPD decreased in the following order: Li β>Na β>K β>Rb β>Cs β. The decreasing in acidity improved both the dispersion of Pt particles and the aromatization activity. Pt particles in K L zeolite showed better dispersion and higher activity for nhexane aromatization because of the unique channel structrue of L zeolite.

关 键 词：顺铂 分解 分散度 沸石 芳构化 催化剂 铂催化剂 

分 类 号：O643.36[理学—物理化学]