CS_2中毒法研究Pt-Al_2O_3系催化剂活性中心的性质

本文对金属催化剂活性中心性质提出了新的表征方法,即用活性频率量度活性中心的强度,用原子组合数的概念描述原子组成活性中心的方式,在此基础上提出了活性频率和活性中心原子组合数的计算公式与新的测定方法。 从测出的活性频率和活性中心原于组合数的数据,发现了Pt-Al_2O_3催化剂具有两种活性中心即α和β中心。α中心CS_2的吸附能力比β中心强,但β中心对环己烷的脱氢活性比α中心强。同时证明了不管在α中心或在β中心上环己烷的脱氢反应都是在双位中心上进行的。 本文还考察了锡和铼对铂催化剂性能的影响,实验表明锡和铼都能从结构效应和电子效应方面影响铂的催化性能。

Study of the Nature of Active Sites on the Catalysts of Pt-Al_2O_3 System by CS_2 Poisoning Method

A series of Pt-Al2O3 catalysts were investigated by the CS2 poisoning method. For characterizing the nature of active site, a new expression was suggested: the activity frequency was used to relate the strength of active site and the concept of number of multiplet active atoms was introduced for describing the mode of active site forming, based upon which the calculating formulas and the method of measurement were proposed.From the data obtained relating to activity frequency and the number of multiplet active atoms, it has been found that there are two types of active sites on Pt surface, designated asα- and β-site. On a-site the adsorption of CS2 is stronger than on β-site, but for the cyclohexane dehydrogenation, the β-site is more active than a-site. However it is demonstrated whether on a-site or (B)-site the dehydrogenation of cyclohexane are all proceed by the way of dual site mechanism.The role of Sn and Re all can exert influence on the catalytic properties of Pt by both structural and electronic effect.