Pd/NiSMM上正己烷异构化的反应机理

Isomerization Mechanism of n-Hexane on Pd/NiSMM

通过对正已烷在Pd/NiSMM催化剂上的异构化反应产物分布的分析,以及与负载钯的氢型丝光沸石催化剂(Pd/HM)反应行为的比较,认为在Pd/NiSMM上烷烃异构化反应遵循既有双功能催化机理又有酸催化机理的综合催化反应机理。正构烷烃先按双功能催化机理生成单侧链异构烷烃,再在酸性中心作用下生成多侧链异构烷烃。双功能催化反应中所需要的Bronsted酸中心主要是在还原过程中产生的。镍的还原在提供了主要的金属催化功能的同时产生了大量的质子酸。钯的作用主要是促进镍的还原。我们发现Pd/NiSMM催化剂上的金属催化功能有余而酸性催化功能不足,因而设法增强其酸催化功能是改进该催化剂的方向。

The mechanisms of n-hexane isomerization on palladium-loaded NiSMM were studied. It was found that n-hexane isomerization on Pd/NiSMM follows a combination of bifunctional catalytic mechanism and acidic catalytic mechanism, n-Hexane is first converted to single-branched isohexanes by bifunctional mechanism, and then the latter is converted to isohexane with more than two side chains under the action of acidic sites. Bronsted acidic sites required in bifunctional mechanism are mainly formed during reduction of the catalyst. Reduction of nickel ions provides both metal with catalytic function and Bronsted acid. The main function of palladium is to promote the reduction of nickel ions.