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Pt/L沸石催化剂对正己烷芳构化有很高的活性及选择性,关于其机理众说不一.Der-ouane等人把它的这种优越性能归因于L沸石具有特殊孔道结构,可使极小的Pt颗粒稳定地存在.但是,当他们研究非孔性材料Mg(Al)O载Pt后,却意外地发现其催化正己烷芳构化性能与Pt/L相当.至今为止,人们对Pt/L催化剂中沸石载体的作用还没有一致的认识. 最近我们研究了Pt(NH_3)_2Cl_2/Kβ沸石的分解还原行为,发现在300℃分解时发生自还原,即在非还原气氛中,Pt～(2+)离子可被解离的配体NH_3预先还原而生成Pt～0原子,从而导致Pt颗粒在H_2还原过程中聚结长大.本文采用TPR,CO-FTIR和~(129)Xe NMR等方法检测沸石中的Pt物种.结果首次表明,在Pt(NH_3)_2Cl_2/KL沸石的分解过程中由于未曾发生自还原现象,因而获得高分散的Pt颗粒并且具有很好的芳构化性能
Pt / L zeolite catalysts have very high activity and selectivity for the aromatization of n-hexane with different mechanisms, and Der-ouane et al. Attributed this superiority to the fact that zeolite L has a special pore structure, So that very small Pt particles exist stably.However, when they study the non-porous material Mg (Al) O carried Pt, but unexpectedly found its catalytic n-hexane aromatization performance comparable with Pt / L. So far, people The role of zeolite supports in Pt / L catalysts has not been uniformly recognized.Recently, we investigated the decomposition and reduction behavior of Pt (NH 3) _ 2 Cl 2 / Kβ zeolites and found that they were self-reduced when decomposed at 300 ℃, The Pt ~ (2+) ion can be pre-reduced by the NH3, which is dissociated to form Pt ~ 0 atom, resulting in the coalescence and growth of Pt particles during the H2 reduction.In this paper, TPR, CO- Xe NMR detection of Pt species in zeolite.The results showed for the first time that highly dispersed Pt particles were obtained due to the absence of self-reduction during the decomposition of Pt (NH_3) _2Cl_2 / KL zeolite and had good aromatization performance