分子筛晶粒外表面催化活性作用

小晶粒分子筛具有与一般分子筛不同的动力学行为.半径为100至300nm左右的晶粒有明显较大比例的外表面积.用表观速率常数和对比效率因子.可描述小晶粒分子筛的等温一级反应动力学行为.由于外表面的活性贡献,小晶粒分子筛能有更好的表观活性.晶粒半径大于10~3nm后,其外表面积比例可忽略.小晶粒分子筛的外表面积可能比一般分子筛明显要高.

CATALYTIC ACTIVITY OF MOLECULAR SIEVE CRYSTALLITES ON EXTERIOR SURFACE

Small molecular sieve crystallites have different kinetic behavior as compared to the large ones. The study shows that crystallites with radii of 100-300 nm have a significant part of outer surface area. The curvature or structure factor have an important effect on the exterior surface area of the crystallites. Hence small crystallites practically have a large outer surface area. Apparent kinetics constant and relative effectiveness factor are included in the model developed for first-order reaction. Small crystallites have significantly higher effectiveness than that of large ones. The catalytic activity on the exterior surface for crystallites of radii over 10000nm can be negligible.