Cd－ZSM－5沸石的结构稳定性和积炭－烧炭特性

用热分析方法研究了Ｃｄ改性ＺＳＭ－５沸石催化剂（Ｃｄ－ＺＳＭ－５）的结构稳定性和积炭－烧炭特性，发现上述性质和制备因素密切相关．结果表明，在５００℃以上氢气中，Ｃｄ（１１）被还原成金属Ｃｄ，并逐渐流失，其稳定性随制备方法而变，按交换法＞浸渍法＞混合法顺序下降。这种变化可与Ｃｄ状态（Ｃｄ２＋和ＣｄＯ）分布不同，以及它们的还原性不同相关联，Ｃｄ２＋离子与沸石间的强相互作用使其较之ＣｄＯ难以还原。改性沸石的积炭初速率是交换法＜混合法＜浸渍法，且随Ｃｄ增加而增加。以离子交换０．６％Ｃｄ样品的结构稳定性最好，积炭初速率也最低。Ｃｄ改性使烧炭活化能提高，烧炭活化能按交换法、浸渍法、混合法次序递增，且随Ｃｄ增加而增加。

Structure stability and coking─decoking behavior of Cd-ZSM-5 zeolite catalyst

Structure stability and coking-decoking behaviorof thd Cd-omodified ZSM-5 zeolite catalysts (Cd-ZSM-5) have been studied thermogravinetrically, and fond closely relative to preparation factors. The results show that Cd (II) species on thde catalyst is reduced to the metal form and lost gradually in flowing H2 at temperatures above 500℃. The stability of Cd (II) is changed with modifying methods, following the order ino-exchange (E) > impregnation (I) >mixing (M),which can be considered in correlation with the variations of distribution of two Cd (II ) species (Cd2+ and CdO) and of their reducibilities. Cd2+ is strongly interacted with the acidic OH groups of thd zeolite,resulting in a more difficult re-duction of Cd2+ than that of CdO.The initial coking rate of Cd-ZSM-5 is varide in the order E