High resolution transmission electron microscope observation of industrialhigh performance Ziegler catalysts

High resolution transmission electron microscopy (HRTEM) was used to direct ly observe the distribution of crystalline regions in Ziegler catalysts pre pared by mechanical plus chemical routes (internal donor; Cat-A: ethylbenzo ate, Cat-B: dibutylphthalate, Cat-C: none) and by an entirely chemical rout e (internal donor; Cat-D: dibutylphthalate). A comparison of Cat-A, Cat-B, and their precursors (ground products of an original MgCl2 with a donor) in dicates that MgCl2 crystals are significantly destroyed by the co-grinding procedure regardless of the kinds of internal donor, and further destructio n preferentially occurs in Cat-B compared with that in Cat-A. The crystalli ne lattice of the original MgCl2 is destroyed from the surface into the int erior region in the catalysts prepared by the former method. The destructio n of the crystals is found to be severe in the following order: Cat-C great er than or equal to Cat-B > Cat-A in the surface area, Cat-C > Cat-B > Cat- A in the central area. On the other hand, Cat-D shows the different distrib utions of crystalline regions, which are predominantly present in the near- surface area, but absent in the central area. These results suggest that th e distribution of MgCl2 crystalline regions exhibit a strong correlation wi th the catalyst preparation procedures and, hence, the catalyst performance .