论文部分内容阅读
金属——载体型催化剂在石油化工过程中有着广泛的应用,被载活性组分金属的分散度往往直接影响催化剂的反应性能。据报导金属分散度与反应活性的关联大致可分为四类:(1)比活性与晶粒大小无关;(2)比活性随晶粒大小增加而降低;(3)比活性随晶粒大小增加而增加;(4)对一定大小的晶粒比活性有一极大值。除第(1)种类型外,其余类型反应活性都与金属分散度有关,由此可见,对金属分散度及其测定方法进行研究是极为重要的。用以考察金属分散度的方法很多,如化学吸附法、色谱法、电子显微镜、磁学方法及X光线宽化法和X线小角度散射(简称SAXS)等。其中(SAXS)法由于具有制样简单,结晶态和无定形态粒子都可测定等优点,所以成为测定金属分散度的重要手段。
Metal-supported catalysts have a wide range of applications in petrochemical processes. The dispersion of the supported active metals often has a direct impact on the reactivity of the catalysts. It has been reported that the relationship between metal dispersion and reactivity can be divided into four categories: (1) specific activity has nothing to do with grain size; (2) specific activity decreases with grain size; (3) specific activity varies with grain size Increase and increase; (4) to a certain size of grain specific activity has a maximum value. With the exception of type (1), the remaining types of reactivity are related to the degree of metal dispersion. Thus, it is important to study the degree of metal dispersion and its determination. There are many ways to study the dispersion of metal, such as chemical adsorption, chromatography, electron microscopy, magnetic methods and X-ray broadening method and X-ray small angle scattering (SAXS) and so on. The (SAXS) method is an important method to determine the metal dispersion because of its advantages such as simple sample preparation, determination of crystalline and amorphous particles.